[PATCH] [0/19] HWPOISON: Intro

[PATCH] [0/19] HWPOISON: Intro

[Andi Kleen]

[AK: This is a version with the correct file list
and some fixes.  Please disregard the version I posted yesterday]

New version of the hwpoison patchkit. Various changes.
Believed to address all earlier review comments.

Active error truncate is enabled per file system now, so it adds
a new VFS operation "error_remove_page" for this.
This prevents any truncation on metadata pages, on those
it just does invalidate.

Also various bug fixes, most of them from Fengguang.

Please see the individual patches for changelog.

Should be good to go now.

Passes the hwpoison specific parts of the mce-test test suite
(git://git.kernel.org/pub/scm/utils/cpu/mce/mce-test.git)

Also available as git tree from 
git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6.git hwpoison

Andrew, Please consider for merging.

Thanks,
-Andi

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---

Upcoming Intel CPUs have support for recovering from some memory errors
(``MCA recovery''). This requires the OS to declare a page "poisoned", 
kill the processes associated with it and avoid using it in the future. 

This patchkit implements the necessary infrastructure in the VM.

To quote the overview comment:

 * High level machine check handler. Handles pages reported by the
 * hardware as being corrupted usually due to a 2bit ECC memory or cache
 * failure.
 *
 * This focusses on pages detected as corrupted in the background.
 * When the current CPU tries to consume corruption the currently
 * running process can just be killed directly instead. This implies
 * that if the error cannot be handled for some reason it's safe to
 * just ignore it because no corruption has been consumed yet. Instead
 * when that happens another machine check will happen.
 *
 * Handles page cache pages in various states. The tricky part
 * here is that we can access any page asynchronous to other VM
 * users, because memory failures could happen anytime and anywhere,
 * possibly violating some of their assumptions. This is why this code
 * has to be extremely careful. Generally it tries to use normal locking
 * rules, as in get the standard locks, even if that means the
 * error handling takes potentially a long time.
 *
 * Some of the operations here are somewhat inefficient and have non
 * linear algorithmic complexity, because the data structures have not
 * been optimized for this case. This is in particular the case
 * for the mapping from a vma to a process. Since this case is expected
 * to be rare we hope we can get away with this.

The code consists of a the high level handler in mm/memory-failure.c, 
a new page poison bit and various checks in the VM to handle poisoned
pages.

The main target right now is KVM guests, but it works for all kinds
of applications.

For the KVM use there was need for a new signal type so that
KVM can inject the machine check into the guest with the proper
address. This in theory allows other applications to handle
memory failures too. The expection is that near all applications
won't do that, but some very specialized ones might. 

This is not fully complete yet, in particular there are still ways
to access poison through various ways (crash dump, /proc/kcore etc.)
that need to be plugged too.


-Andi

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[PATCH] [1/19] HWPOISON: Add page flag for poisoned pages

[Andi Kleen]

Hardware poisoned pages need special handling in the VM and shouldn't be 
touched again. This requires a new page flag. Define it here.

The page flags wars seem to be over, so it shouldn't be a problem
to get a new one.

v2: Add TestSetHWPoison (suggested by Johannes Weiner)

Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/linux/page-flags.h |   17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

Index: linux/include/linux/page-flags.h
===================================================================
--- linux.orig/include/linux/page-flags.h
+++ linux/include/linux/page-flags.h
@@ -51,6 +51,9 @@
  * PG_buddy is set to indicate that the page is free and in the buddy system
  * (see mm/page_alloc.c).
  *
+ * PG_hwpoison indicates that a page got corrupted in hardware and contains
+ * data with incorrect ECC bits that triggered a machine check. Accessing is
+ * not safe since it may cause another machine check. Don't touch!
  */
 
 /*
@@ -102,6 +105,9 @@ enum pageflags {
 #ifdef CONFIG_IA64_UNCACHED_ALLOCATOR
 	PG_uncached,		/* Page has been mapped as uncached */
 #endif
+#ifdef CONFIG_MEMORY_FAILURE
+	PG_hwpoison,		/* hardware poisoned page. Don't touch */
+#endif
 	__NR_PAGEFLAGS,
 
 	/* Filesystems */
@@ -263,6 +269,15 @@ PAGEFLAG(Uncached, uncached)
 PAGEFLAG_FALSE(Uncached)
 #endif
 
+#ifdef CONFIG_MEMORY_FAILURE
+PAGEFLAG(HWPoison, hwpoison)
+TESTSETFLAG(HWPoison, hwpoison)
+#define __PG_HWPOISON (1UL << PG_hwpoison)
+#else
+PAGEFLAG_FALSE(HWPoison)
+#define __PG_HWPOISON 0
+#endif
+
 static inline int PageUptodate(struct page *page)
 {
 	int ret = test_bit(PG_uptodate, &(page)->flags);
@@ -387,7 +402,7 @@ static inline void __ClearPageTail(struc
 	 1 << PG_private | 1 << PG_private_2 | \
 	 1 << PG_buddy	 | 1 << PG_writeback | 1 << PG_reserved | \
 	 1 << PG_slab	 | 1 << PG_swapcache | 1 << PG_active | \
-	 1 << PG_unevictable | __PG_MLOCKED)
+	 1 << PG_unevictable | __PG_MLOCKED | __PG_HWPOISON)
 
 /*
  * Flags checked when a page is prepped for return by the page allocator.

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[PATCH] [2/19] HWPOISON: Export some rmap vma locking to outside world

[Andi Kleen]

Needed for later patch that walks rmap entries on its own.

This used to be very frowned upon, but memory-failure.c does
some rather specialized rmap walking and rmap has been stable
for quite some time, so I think it's ok now to export it.

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/linux/rmap.h |    6 ++++++
 mm/rmap.c            |    4 ++--
 2 files changed, 8 insertions(+), 2 deletions(-)

Index: linux/include/linux/rmap.h
===================================================================
--- linux.orig/include/linux/rmap.h
+++ linux/include/linux/rmap.h
@@ -112,6 +112,12 @@ int page_mkclean(struct page *);
  */
 int try_to_munlock(struct page *);
 
+/*
+ * Called by memory-failure.c to kill processes.
+ */
+struct anon_vma *page_lock_anon_vma(struct page *page);
+void page_unlock_anon_vma(struct anon_vma *anon_vma);
+
 #else	/* !CONFIG_MMU */
 
 #define anon_vma_init()		do {} while (0)
Index: linux/mm/rmap.c
===================================================================
--- linux.orig/mm/rmap.c
+++ linux/mm/rmap.c
@@ -191,7 +191,7 @@ void __init anon_vma_init(void)
  * Getting a lock on a stable anon_vma from a page off the LRU is
  * tricky: page_lock_anon_vma rely on RCU to guard against the races.
  */
-static struct anon_vma *page_lock_anon_vma(struct page *page)
+struct anon_vma *page_lock_anon_vma(struct page *page)
 {
 	struct anon_vma *anon_vma;
 	unsigned long anon_mapping;
@@ -211,7 +211,7 @@ out:
 	return NULL;
 }
 
-static void page_unlock_anon_vma(struct anon_vma *anon_vma)
+void page_unlock_anon_vma(struct anon_vma *anon_vma)
 {
 	spin_unlock(&anon_vma->lock);
 	rcu_read_unlock();

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[PATCH] [3/19] HWPOISON: Add support for poison swap entries v2

[Andi Kleen]

Memory migration uses special swap entry types to trigger special actions on 
page faults. Extend this mechanism to also support poisoned swap entries, to 
trigger poison handling on page faults. This allows follow-on patches to 
prevent processes from faulting in poisoned pages again.

v2: Fix overflow in MAX_SWAPFILES (Fengguang Wu)
v3: Better overflow fix (Hidehiro Kawai)

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/linux/swap.h    |   34 ++++++++++++++++++++++++++++------
 include/linux/swapops.h |   38 ++++++++++++++++++++++++++++++++++++++
 mm/swapfile.c           |    4 ++--
 3 files changed, 68 insertions(+), 8 deletions(-)

Index: linux/include/linux/swap.h
===================================================================
--- linux.orig/include/linux/swap.h
+++ linux/include/linux/swap.h
@@ -34,16 +34,38 @@ static inline int current_is_kswapd(void
  * the type/offset into the pte as 5/27 as well.
  */
 #define MAX_SWAPFILES_SHIFT	5
-#ifndef CONFIG_MIGRATION
-#define MAX_SWAPFILES		(1 << MAX_SWAPFILES_SHIFT)
+
+/*
+ * Use some of the swap files numbers for other purposes. This
+ * is a convenient way to hook into the VM to trigger special
+ * actions on faults.
+ */
+
+/*
+ * NUMA node memory migration support
+ */
+#ifdef CONFIG_MIGRATION
+#define SWP_MIGRATION_NUM 2
+#define SWP_MIGRATION_READ	(MAX_SWAPFILES + SWP_HWPOISON_NUM)
+#define SWP_MIGRATION_WRITE	(MAX_SWAPFILES + SWP_HWPOISON_NUM + 1)
 #else
-/* Use last two entries for page migration swap entries */
-#define MAX_SWAPFILES		((1 << MAX_SWAPFILES_SHIFT)-2)
-#define SWP_MIGRATION_READ	MAX_SWAPFILES
-#define SWP_MIGRATION_WRITE	(MAX_SWAPFILES + 1)
+#define SWP_MIGRATION_NUM 0
 #endif
 
 /*
+ * Handling of hardware poisoned pages with memory corruption.
+ */
+#ifdef CONFIG_MEMORY_FAILURE
+#define SWP_HWPOISON_NUM 1
+#define SWP_HWPOISON		MAX_SWAPFILES
+#else
+#define SWP_HWPOISON_NUM 0
+#endif
+
+#define MAX_SWAPFILES \
+	((1 << MAX_SWAPFILES_SHIFT) - SWP_MIGRATION_NUM - SWP_HWPOISON_NUM)
+
+/*
  * Magic header for a swap area. The first part of the union is
  * what the swap magic looks like for the old (limited to 128MB)
  * swap area format, the second part of the union adds - in the
Index: linux/include/linux/swapops.h
===================================================================
--- linux.orig/include/linux/swapops.h
+++ linux/include/linux/swapops.h
@@ -131,3 +131,41 @@ static inline int is_write_migration_ent
 
 #endif
 
+#ifdef CONFIG_MEMORY_FAILURE
+/*
+ * Support for hardware poisoned pages
+ */
+static inline swp_entry_t make_hwpoison_entry(struct page *page)
+{
+	BUG_ON(!PageLocked(page));
+	return swp_entry(SWP_HWPOISON, page_to_pfn(page));
+}
+
+static inline int is_hwpoison_entry(swp_entry_t entry)
+{
+	return swp_type(entry) == SWP_HWPOISON;
+}
+#else
+
+static inline swp_entry_t make_hwpoison_entry(struct page *page)
+{
+	return swp_entry(0, 0);
+}
+
+static inline int is_hwpoison_entry(swp_entry_t swp)
+{
+	return 0;
+}
+#endif
+
+#if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION)
+static inline int non_swap_entry(swp_entry_t entry)
+{
+	return swp_type(entry) >= MAX_SWAPFILES;
+}
+#else
+static inline int non_swap_entry(swp_entry_t entry)
+{
+	return 0;
+}
+#endif
Index: linux/mm/swapfile.c
===================================================================
--- linux.orig/mm/swapfile.c
+++ linux/mm/swapfile.c
@@ -697,7 +697,7 @@ int free_swap_and_cache(swp_entry_t entr
 	struct swap_info_struct *p;
 	struct page *page = NULL;
 
-	if (is_migration_entry(entry))
+	if (non_swap_entry(entry))
 		return 1;
 
 	p = swap_info_get(entry);
@@ -2083,7 +2083,7 @@ static int __swap_duplicate(swp_entry_t
 	int count;
 	bool has_cache;
 
-	if (is_migration_entry(entry))
+	if (non_swap_entry(entry))
 		return -EINVAL;
 
 	type = swp_type(entry);

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[PATCH] [4/19] HWPOISON: Add new SIGBUS error codes for hardware poison signals

[Andi Kleen]

Add new SIGBUS codes for reporting machine checks as signals. When 
the hardware detects an uncorrected ECC error it can trigger these
signals.

This is needed for telling KVM's qemu about machine checks that happen to
guests, so that it can inject them, but might be also useful for other programs.
I find it useful in my test programs.

This patch merely defines the new types.

- Define two new si_codes for SIGBUS.  BUS_MCEERR_AO and BUS_MCEERR_AR
* BUS_MCEERR_AO is for "Action Optional" machine checks, which means that some
corruption has been detected in the background, but nothing has been consumed
so far. The program can ignore those if it wants (but most programs would
already get killed)
* BUS_MCEERR_AR is for "Action Required" machine checks. This happens
when corrupted data is consumed or the application ran into an area
which has been known to be corrupted earlier. These require immediate
action and cannot just returned to. Most programs would kill themselves.
- They report the address of the corruption in the user address space
in si_addr.
- Define a new si_addr_lsb field that reports the extent of the corruption
to user space. That's currently always a (small) page. The user application
cannot tell where in this page the corruption happened.

AK: I plan to write a man page update before anyone asks.

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/asm-generic/siginfo.h |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Index: linux/include/asm-generic/siginfo.h
===================================================================
--- linux.orig/include/asm-generic/siginfo.h
+++ linux/include/asm-generic/siginfo.h
@@ -82,6 +82,7 @@ typedef struct siginfo {
 #ifdef __ARCH_SI_TRAPNO
 			int _trapno;	/* TRAP # which caused the signal */
 #endif
+			short _addr_lsb; /* LSB of the reported address */
 		} _sigfault;
 
 		/* SIGPOLL */
@@ -112,6 +113,7 @@ typedef struct siginfo {
 #ifdef __ARCH_SI_TRAPNO
 #define si_trapno	_sifields._sigfault._trapno
 #endif
+#define si_addr_lsb	_sifields._sigfault._addr_lsb
 #define si_band		_sifields._sigpoll._band
 #define si_fd		_sifields._sigpoll._fd
 
@@ -192,7 +194,11 @@ typedef struct siginfo {
 #define BUS_ADRALN	(__SI_FAULT|1)	/* invalid address alignment */
 #define BUS_ADRERR	(__SI_FAULT|2)	/* non-existant physical address */
 #define BUS_OBJERR	(__SI_FAULT|3)	/* object specific hardware error */
-#define NSIGBUS		3
+/* hardware memory error consumed on a machine check: action required */
+#define BUS_MCEERR_AR	(__SI_FAULT|4)
+/* hardware memory error detected in process but not consumed: action optional*/
+#define BUS_MCEERR_AO	(__SI_FAULT|5)
+#define NSIGBUS		5
 
 /*
  * SIGTRAP si_codes

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[PATCH] [5/19] HWPOISON: Add basic support for poisoned pages in fault handler v3

[Andi Kleen]

- Add a new VM_FAULT_HWPOISON error code to handle_mm_fault. Right now
architectures have to explicitely enable poison page support, so
this is forward compatible to all architectures. They only need
to add it when they enable poison page support.
- Add poison page handling in swap in fault code

v2: Add missing delayacct_clear_flag (Hidehiro Kawai)
v3: Really use delayacct_clear_flag (Hidehiro Kawai)

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/linux/mm.h |    3 ++-
 mm/memory.c        |   18 +++++++++++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

Index: linux/mm/memory.c
===================================================================
--- linux.orig/mm/memory.c
+++ linux/mm/memory.c
@@ -1319,7 +1319,8 @@ int __get_user_pages(struct task_struct
 				if (ret & VM_FAULT_ERROR) {
 					if (ret & VM_FAULT_OOM)
 						return i ? i : -ENOMEM;
-					else if (ret & VM_FAULT_SIGBUS)
+					if (ret &
+					    (VM_FAULT_HWPOISON|VM_FAULT_SIGBUS))
 						return i ? i : -EFAULT;
 					BUG();
 				}
@@ -2511,8 +2512,15 @@ static int do_swap_page(struct mm_struct
 		goto out;
 
 	entry = pte_to_swp_entry(orig_pte);
-	if (is_migration_entry(entry)) {
-		migration_entry_wait(mm, pmd, address);
+	if (unlikely(non_swap_entry(entry))) {
+		if (is_migration_entry(entry)) {
+			migration_entry_wait(mm, pmd, address);
+		} else if (is_hwpoison_entry(entry)) {
+			ret = VM_FAULT_HWPOISON;
+		} else {
+			print_bad_pte(vma, address, pte, NULL);
+			ret = VM_FAULT_OOM;
+		}
 		goto out;
 	}
 	delayacct_set_flag(DELAYACCT_PF_SWAPIN);
@@ -2536,6 +2544,10 @@ static int do_swap_page(struct mm_struct
 		/* Had to read the page from swap area: Major fault */
 		ret = VM_FAULT_MAJOR;
 		count_vm_event(PGMAJFAULT);
+	} else if (PageHWPoison(page)) {
+		ret = VM_FAULT_HWPOISON;
+		delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
+		goto out;
 	}
 
 	lock_page(page);
Index: linux/include/linux/mm.h
===================================================================
--- linux.orig/include/linux/mm.h
+++ linux/include/linux/mm.h
@@ -700,11 +700,12 @@ static inline int page_mapped(struct pag
 #define VM_FAULT_SIGBUS	0x0002
 #define VM_FAULT_MAJOR	0x0004
 #define VM_FAULT_WRITE	0x0008	/* Special case for get_user_pages */
+#define VM_FAULT_HWPOISON 0x0010	/* Hit poisoned page */
 
 #define VM_FAULT_NOPAGE	0x0100	/* ->fault installed the pte, not return page */
 #define VM_FAULT_LOCKED	0x0200	/* ->fault locked the returned page */
 
-#define VM_FAULT_ERROR	(VM_FAULT_OOM | VM_FAULT_SIGBUS)
+#define VM_FAULT_ERROR	(VM_FAULT_OOM | VM_FAULT_SIGBUS | VM_FAULT_HWPOISON)
 
 /*
  * Can be called by the pagefault handler when it gets a VM_FAULT_OOM.

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[PATCH] [6/19] HWPOISON: Add various poison checks in mm/memory.c v2

[Andi Kleen]

Bail out early when hardware poisoned pages are found in page fault handling.
Since they are poisoned they should not be mapped freshly into processes,
because that would cause another (potentially deadly) machine check

This is generally handled in the same way as OOM, just a different
error code is returned to the architecture code.

v2: Do a page unlock if needed (Fengguang Wu)

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 mm/memory.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: linux/mm/memory.c
===================================================================
--- linux.orig/mm/memory.c
+++ linux/mm/memory.c
@@ -2711,6 +2711,12 @@ static int __do_fault(struct mm_struct *
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
 		return ret;
 
+	if (unlikely(PageHWPoison(vmf.page))) {
+		if (ret & VM_FAULT_LOCKED)
+			unlock_page(vmf.page);
+		return VM_FAULT_HWPOISON;
+	}
+
 	/*
 	 * For consistency in subsequent calls, make the faulted page always
 	 * locked.

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[PATCH] [7/19] HWPOISON: x86: Add VM_FAULT_HWPOISON handling to x86 page fault handler v2

[Andi Kleen]

Add VM_FAULT_HWPOISON handling to the x86 page fault handler. This is 
very similar to VM_FAULT_OOM, the only difference is that a different
si_code is passed to user space and the new addr_lsb field is initialized.

v2: Make the printk more verbose/unique

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 arch/x86/mm/fault.c |   19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

Index: linux/arch/x86/mm/fault.c
===================================================================
--- linux.orig/arch/x86/mm/fault.c
+++ linux/arch/x86/mm/fault.c
@@ -167,6 +167,7 @@ force_sig_info_fault(int si_signo, int s
 	info.si_errno	= 0;
 	info.si_code	= si_code;
 	info.si_addr	= (void __user *)address;
+	info.si_addr_lsb = si_code == BUS_MCEERR_AR ? PAGE_SHIFT : 0;
 
 	force_sig_info(si_signo, &info, tsk);
 }
@@ -799,10 +800,12 @@ out_of_memory(struct pt_regs *regs, unsi
 }
 
 static void
-do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address)
+do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
+	  unsigned int fault)
 {
 	struct task_struct *tsk = current;
 	struct mm_struct *mm = tsk->mm;
+	int code = BUS_ADRERR;
 
 	up_read(&mm->mmap_sem);
 
@@ -818,7 +821,15 @@ do_sigbus(struct pt_regs *regs, unsigned
 	tsk->thread.error_code	= error_code;
 	tsk->thread.trap_no	= 14;
 
-	force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
+#ifdef CONFIG_MEMORY_FAILURE
+	if (fault & VM_FAULT_HWPOISON) {
+		printk(KERN_ERR
+	"MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
+			tsk->comm, tsk->pid, address);
+		code = BUS_MCEERR_AR;
+	}
+#endif
+	force_sig_info_fault(SIGBUS, code, address, tsk);
 }
 
 static noinline void
@@ -828,8 +839,8 @@ mm_fault_error(struct pt_regs *regs, uns
 	if (fault & VM_FAULT_OOM) {
 		out_of_memory(regs, error_code, address);
 	} else {
-		if (fault & VM_FAULT_SIGBUS)
-			do_sigbus(regs, error_code, address);
+		if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON))
+			do_sigbus(regs, error_code, address, fault);
 		else
 			BUG();
 	}

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[PATCH] [8/19] HWPOISON: Use bitmask/action code for try_to_unmap behaviour

[Andi Kleen]

try_to_unmap currently has multiple modi (migration, munlock, normal unmap)
which are selected by magic flag variables. The logic is not very straight
forward, because each of these flag change multiple behaviours (e.g.
migration turns off aging, not only sets up migration ptes etc.)
Also the different flags interact in magic ways.

A later patch in this series adds another mode to try_to_unmap, so 
this becomes quickly unmanageable.

Replace the different flags with a action code (migration, munlock, munmap)
and some additional flags as modifiers (ignore mlock, ignore aging).
This makes the logic more straight forward and allows easier extension
to new behaviours. Change all the caller to declare what they want to 
do.

This patch is supposed to be a nop in behaviour. If anyone can prove 
it is not that would be a bug.

Cc: Lee.Schermerhorn@hp.com
Cc: npiggin@suse.de

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/linux/rmap.h |   13 ++++++++++++-
 mm/migrate.c         |    2 +-
 mm/rmap.c            |   40 ++++++++++++++++++++++------------------
 mm/vmscan.c          |    2 +-
 4 files changed, 36 insertions(+), 21 deletions(-)

Index: linux/include/linux/rmap.h
===================================================================
--- linux.orig/include/linux/rmap.h
+++ linux/include/linux/rmap.h
@@ -85,7 +85,18 @@ static inline void page_dup_rmap(struct
  */
 int page_referenced(struct page *, int is_locked,
 			struct mem_cgroup *cnt, unsigned long *vm_flags);
-int try_to_unmap(struct page *, int ignore_refs);
+enum ttu_flags {
+	TTU_UNMAP = 0,			/* unmap mode */
+	TTU_MIGRATION = 1,		/* migration mode */
+	TTU_MUNLOCK = 2,		/* munlock mode */
+	TTU_ACTION_MASK = 0xff,
+
+	TTU_IGNORE_MLOCK = (1 << 8),	/* ignore mlock */
+	TTU_IGNORE_ACCESS = (1 << 9),	/* don't age */
+};
+#define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
+
+int try_to_unmap(struct page *, enum ttu_flags flags);
 
 /*
  * Called from mm/filemap_xip.c to unmap empty zero page
Index: linux/mm/rmap.c
===================================================================
--- linux.orig/mm/rmap.c
+++ linux/mm/rmap.c
@@ -773,7 +773,7 @@ void page_remove_rmap(struct page *page)
  * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
  */
 static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
-				int migration)
+				enum ttu_flags flags)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	unsigned long address;
@@ -795,11 +795,13 @@ static int try_to_unmap_one(struct page
 	 * If it's recently referenced (perhaps page_referenced
 	 * skipped over this mm) then we should reactivate it.
 	 */
-	if (!migration) {
+	if (!(flags & TTU_IGNORE_MLOCK)) {
 		if (vma->vm_flags & VM_LOCKED) {
 			ret = SWAP_MLOCK;
 			goto out_unmap;
 		}
+	}
+	if (!(flags & TTU_IGNORE_ACCESS)) {
 		if (ptep_clear_flush_young_notify(vma, address, pte)) {
 			ret = SWAP_FAIL;
 			goto out_unmap;
@@ -839,12 +841,12 @@ static int try_to_unmap_one(struct page
 			 * pte. do_swap_page() will wait until the migration
 			 * pte is removed and then restart fault handling.
 			 */
-			BUG_ON(!migration);
+			BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION);
 			entry = make_migration_entry(page, pte_write(pteval));
 		}
 		set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
 		BUG_ON(pte_file(*pte));
-	} else if (PAGE_MIGRATION && migration) {
+	} else if (PAGE_MIGRATION && (TTU_ACTION(flags) == TTU_MIGRATION)) {
 		/* Establish migration entry for a file page */
 		swp_entry_t entry;
 		entry = make_migration_entry(page, pte_write(pteval));
@@ -1013,12 +1015,13 @@ static int try_to_mlock_page(struct page
  * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
  * 'LOCKED.
  */
-static int try_to_unmap_anon(struct page *page, int unlock, int migration)
+static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
 {
 	struct anon_vma *anon_vma;
 	struct vm_area_struct *vma;
 	unsigned int mlocked = 0;
 	int ret = SWAP_AGAIN;
+	int unlock = TTU_ACTION(flags) == TTU_MUNLOCK;
 
 	if (MLOCK_PAGES && unlikely(unlock))
 		ret = SWAP_SUCCESS;	/* default for try_to_munlock() */
@@ -1034,7 +1037,7 @@ static int try_to_unmap_anon(struct page
 				continue;  /* must visit all unlocked vmas */
 			ret = SWAP_MLOCK;  /* saw at least one mlocked vma */
 		} else {
-			ret = try_to_unmap_one(page, vma, migration);
+			ret = try_to_unmap_one(page, vma, flags);
 			if (ret == SWAP_FAIL || !page_mapped(page))
 				break;
 		}
@@ -1058,8 +1061,7 @@ static int try_to_unmap_anon(struct page
 /**
  * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
  * @page: the page to unmap/unlock
- * @unlock:  request for unlock rather than unmap [unlikely]
- * @migration:  unmapping for migration - ignored if @unlock
+ * @flags: action and flags
  *
  * Find all the mappings of a page using the mapping pointer and the vma chains
  * contained in the address_space struct it points to.
@@ -1071,7 +1073,7 @@ static int try_to_unmap_anon(struct page
  * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
  * 'LOCKED.
  */
-static int try_to_unmap_file(struct page *page, int unlock, int migration)
+static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
 {
 	struct address_space *mapping = page->mapping;
 	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
@@ -1083,6 +1085,7 @@ static int try_to_unmap_file(struct page
 	unsigned long max_nl_size = 0;
 	unsigned int mapcount;
 	unsigned int mlocked = 0;
+	int unlock = TTU_ACTION(flags) == TTU_MUNLOCK;
 
 	if (MLOCK_PAGES && unlikely(unlock))
 		ret = SWAP_SUCCESS;	/* default for try_to_munlock() */
@@ -1095,7 +1098,7 @@ static int try_to_unmap_file(struct page
 				continue;	/* must visit all vmas */
 			ret = SWAP_MLOCK;
 		} else {
-			ret = try_to_unmap_one(page, vma, migration);
+			ret = try_to_unmap_one(page, vma, flags);
 			if (ret == SWAP_FAIL || !page_mapped(page))
 				goto out;
 		}
@@ -1120,7 +1123,8 @@ static int try_to_unmap_file(struct page
 			ret = SWAP_MLOCK;	/* leave mlocked == 0 */
 			goto out;		/* no need to look further */
 		}
-		if (!MLOCK_PAGES && !migration && (vma->vm_flags & VM_LOCKED))
+		if (!MLOCK_PAGES && !(flags & TTU_IGNORE_MLOCK) &&
+			(vma->vm_flags & VM_LOCKED))
 			continue;
 		cursor = (unsigned long) vma->vm_private_data;
 		if (cursor > max_nl_cursor)
@@ -1154,7 +1158,7 @@ static int try_to_unmap_file(struct page
 	do {
 		list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
 						shared.vm_set.list) {
-			if (!MLOCK_PAGES && !migration &&
+			if (!MLOCK_PAGES && !(flags & TTU_IGNORE_MLOCK) &&
 			    (vma->vm_flags & VM_LOCKED))
 				continue;
 			cursor = (unsigned long) vma->vm_private_data;
@@ -1194,7 +1198,7 @@ out:
 /**
  * try_to_unmap - try to remove all page table mappings to a page
  * @page: the page to get unmapped
- * @migration: migration flag
+ * @flags: action and flags
  *
  * Tries to remove all the page table entries which are mapping this
  * page, used in the pageout path.  Caller must hold the page lock.
@@ -1205,16 +1209,16 @@ out:
  * SWAP_FAIL	- the page is unswappable
  * SWAP_MLOCK	- page is mlocked.
  */
-int try_to_unmap(struct page *page, int migration)
+int try_to_unmap(struct page *page, enum ttu_flags flags)
 {
 	int ret;
 
 	BUG_ON(!PageLocked(page));
 
 	if (PageAnon(page))
-		ret = try_to_unmap_anon(page, 0, migration);
+		ret = try_to_unmap_anon(page, flags);
 	else
-		ret = try_to_unmap_file(page, 0, migration);
+		ret = try_to_unmap_file(page, flags);
 	if (ret != SWAP_MLOCK && !page_mapped(page))
 		ret = SWAP_SUCCESS;
 	return ret;
@@ -1239,8 +1243,8 @@ int try_to_munlock(struct page *page)
 	VM_BUG_ON(!PageLocked(page) || PageLRU(page));
 
 	if (PageAnon(page))
-		return try_to_unmap_anon(page, 1, 0);
+		return try_to_unmap_anon(page, TTU_MUNLOCK);
 	else
-		return try_to_unmap_file(page, 1, 0);
+		return try_to_unmap_file(page, TTU_MUNLOCK);
 }
 
Index: linux/mm/vmscan.c
===================================================================
--- linux.orig/mm/vmscan.c
+++ linux/mm/vmscan.c
@@ -654,7 +654,7 @@ static unsigned long shrink_page_list(st
 		 * processes. Try to unmap it here.
 		 */
 		if (page_mapped(page) && mapping) {
-			switch (try_to_unmap(page, 0)) {
+			switch (try_to_unmap(page, TTU_UNMAP)) {
 			case SWAP_FAIL:
 				goto activate_locked;
 			case SWAP_AGAIN:
Index: linux/mm/migrate.c
===================================================================
--- linux.orig/mm/migrate.c
+++ linux/mm/migrate.c
@@ -669,7 +669,7 @@ static int unmap_and_move(new_page_t get
 	}
 
 	/* Establish migration ptes or remove ptes */
-	try_to_unmap(page, 1);
+	try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS);
 
 	if (!page_mapped(page))
 		rc = move_to_new_page(newpage, page);

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[PATCH] [9/19] HWPOISON: Handle hardware poisoned pages in try_to_unmap

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

When a page has the poison bit set replace the PTE with a poison entry.
This causes the right error handling to be done later when a process runs
into it.

v2: add a new flag to not do that (needed for the memory-failure handler
later) (Fengguang)
v3: remove unnecessary is_migration_entry() test (Fengguang, Minchan)

Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/linux/rmap.h |    1 +
 mm/rmap.c            |    9 ++++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

Index: linux/mm/rmap.c
===================================================================
--- linux.orig/mm/rmap.c
+++ linux/mm/rmap.c
@@ -819,7 +819,14 @@ static int try_to_unmap_one(struct page
 	/* Update high watermark before we lower rss */
 	update_hiwater_rss(mm);
 
-	if (PageAnon(page)) {
+	if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
+		if (PageAnon(page))
+			dec_mm_counter(mm, anon_rss);
+		else
+			dec_mm_counter(mm, file_rss);
+		set_pte_at(mm, address, pte,
+				swp_entry_to_pte(make_hwpoison_entry(page)));
+	} else if (PageAnon(page)) {
 		swp_entry_t entry = { .val = page_private(page) };
 
 		if (PageSwapCache(page)) {
Index: linux/include/linux/rmap.h
===================================================================
--- linux.orig/include/linux/rmap.h
+++ linux/include/linux/rmap.h
@@ -93,6 +93,7 @@ enum ttu_flags {
 
 	TTU_IGNORE_MLOCK = (1 << 8),	/* ignore mlock */
 	TTU_IGNORE_ACCESS = (1 << 9),	/* don't age */
+	TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
 };
 #define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)
 

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[PATCH] [10/19] HWPOISON: check and isolate corrupted free pages v2

[Andi Kleen]

From: Wu Fengguang <fengguang.wu@intel.com>

If memory corruption hits the free buddy pages, we can safely ignore them.
No one will access them until page allocation time, then prep_new_page()
will automatically check and isolate PG_hwpoison page for us (for 0-order
allocation).

This patch expands prep_new_page() to check every component page in a high
order page allocation, in order to completely stop PG_hwpoison pages from
being recirculated.

Note that the common case -- only allocating a single page, doesn't
do any more work than before. Allocating > order 0 does a bit more work,
but that's relatively uncommon.

This simple implementation may drop some innocent neighbor pages, hopefully
it is not a big problem because the event should be rare enough.

This patch adds some runtime costs to high order page users.

[AK: Improved description]

v2: Andi Kleen:
Port to -mm code
Move check into separate function.
Don't dump stack in bad_pages for hwpoisoned pages.
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 mm/page_alloc.c |   20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

Index: linux/mm/page_alloc.c
===================================================================
--- linux.orig/mm/page_alloc.c
+++ linux/mm/page_alloc.c
@@ -234,6 +234,12 @@ static void bad_page(struct page *page)
 	static unsigned long nr_shown;
 	static unsigned long nr_unshown;
 
+	/* Don't complain about poisoned pages */
+	if (PageHWPoison(page)) {
+		__ClearPageBuddy(page);
+		return;
+	}
+
 	/*
 	 * Allow a burst of 60 reports, then keep quiet for that minute;
 	 * or allow a steady drip of one report per second.
@@ -646,7 +652,7 @@ static inline void expand(struct zone *z
 /*
  * This page is about to be returned from the page allocator
  */
-static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
+static inline int check_new_page(struct page *page)
 {
 	if (unlikely(page_mapcount(page) |
 		(page->mapping != NULL)  |
@@ -655,6 +661,18 @@ static int prep_new_page(struct page *pa
 		bad_page(page);
 		return 1;
 	}
+	return 0;
+}
+
+static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
+{
+	int i;
+
+	for (i = 0; i < (1 << order); i++) {
+		struct page *p = page + i;
+		if (unlikely(check_new_page(p)))
+			return 1;
+	}
 
 	set_page_private(page, 0);
 	set_page_refcounted(page);

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[PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Andi Kleen]

From: Nick Piggin <npiggin@suse.de>

Extract out truncate_inode_page() out of the truncate path so that
it can be used by memory-failure.c

[AK: description, headers, fix typos]
v2: Some white space changes from Fengguang Wu 

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/linux/mm.h |    2 ++
 mm/truncate.c      |   29 +++++++++++++++--------------
 2 files changed, 17 insertions(+), 14 deletions(-)

Index: linux/mm/truncate.c
===================================================================
--- linux.orig/mm/truncate.c
+++ linux/mm/truncate.c
@@ -93,11 +93,11 @@ EXPORT_SYMBOL(cancel_dirty_page);
  * its lock, b) when a concurrent invalidate_mapping_pages got there first and
  * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
  */
-static void
+static int
 truncate_complete_page(struct address_space *mapping, struct page *page)
 {
 	if (page->mapping != mapping)
-		return;
+		return -EIO;
 
 	if (page_has_private(page))
 		do_invalidatepage(page, 0);
@@ -108,6 +108,7 @@ truncate_complete_page(struct address_sp
 	remove_from_page_cache(page);
 	ClearPageMappedToDisk(page);
 	page_cache_release(page);	/* pagecache ref */
+	return 0;
 }
 
 /*
@@ -135,6 +136,16 @@ invalidate_complete_page(struct address_
 	return ret;
 }
 
+int truncate_inode_page(struct address_space *mapping, struct page *page)
+{
+	if (page_mapped(page)) {
+		unmap_mapping_range(mapping,
+				   (loff_t)page->index << PAGE_CACHE_SHIFT,
+				   PAGE_CACHE_SIZE, 0);
+	}
+	return truncate_complete_page(mapping, page);
+}
+
 /**
  * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
  * @mapping: mapping to truncate
@@ -196,12 +207,7 @@ void truncate_inode_pages_range(struct a
 				unlock_page(page);
 				continue;
 			}
-			if (page_mapped(page)) {
-				unmap_mapping_range(mapping,
-				  (loff_t)page_index<<PAGE_CACHE_SHIFT,
-				  PAGE_CACHE_SIZE, 0);
-			}
-			truncate_complete_page(mapping, page);
+			truncate_inode_page(mapping, page);
 			unlock_page(page);
 		}
 		pagevec_release(&pvec);
@@ -238,15 +244,10 @@ void truncate_inode_pages_range(struct a
 				break;
 			lock_page(page);
 			wait_on_page_writeback(page);
-			if (page_mapped(page)) {
-				unmap_mapping_range(mapping,
-				  (loff_t)page->index<<PAGE_CACHE_SHIFT,
-				  PAGE_CACHE_SIZE, 0);
-			}
+			truncate_inode_page(mapping, page);
 			if (page->index > next)
 				next = page->index;
 			next++;
-			truncate_complete_page(mapping, page);
 			unlock_page(page);
 		}
 		pagevec_release(&pvec);
Index: linux/include/linux/mm.h
===================================================================
--- linux.orig/include/linux/mm.h
+++ linux/include/linux/mm.h
@@ -809,6 +809,8 @@ static inline void unmap_shared_mapping_
 extern int vmtruncate(struct inode * inode, loff_t offset);
 extern int vmtruncate_range(struct inode * inode, loff_t offset, loff_t end);
 
+int truncate_inode_page(struct address_space *mapping, struct page *page);
+
 #ifdef CONFIG_MMU
 extern int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long address, unsigned int flags);

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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Nick Piggin]

On Wed, Aug 05, 2009 at 11:36:38AM +0200, Andi Kleen wrote:
> 
> From: Nick Piggin <npiggin@suse.de>
> 
> Extract out truncate_inode_page() out of the truncate path so that
> it can be used by memory-failure.c
> 
> [AK: description, headers, fix typos]
> v2: Some white space changes from Fengguang Wu 
> 
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> 
> ---
>  include/linux/mm.h |    2 ++
>  mm/truncate.c      |   29 +++++++++++++++--------------
>  2 files changed, 17 insertions(+), 14 deletions(-)
> 
> Index: linux/mm/truncate.c
> ===================================================================
> --- linux.orig/mm/truncate.c
> +++ linux/mm/truncate.c
> @@ -93,11 +93,11 @@ EXPORT_SYMBOL(cancel_dirty_page);
>   * its lock, b) when a concurrent invalidate_mapping_pages got there first and
>   * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
>   */
> -static void
> +static int
>  truncate_complete_page(struct address_space *mapping, struct page *page)
>  {
>  	if (page->mapping != mapping)
> -		return;
> +		return -EIO;

Hmm, at this point, the page must have been removed from pagecache,
so I don't know if you need to pass an error back?

  
>  	if (page_has_private(page))
>  		do_invalidatepage(page, 0);
> @@ -108,6 +108,7 @@ truncate_complete_page(struct address_sp
>  	remove_from_page_cache(page);
>  	ClearPageMappedToDisk(page);
>  	page_cache_release(page);	/* pagecache ref */
> +	return 0;
>  }
>  
>  /*
> @@ -135,6 +136,16 @@ invalidate_complete_page(struct address_
>  	return ret;
>  }
>  
> +int truncate_inode_page(struct address_space *mapping, struct page *page)
> +{
> +	if (page_mapped(page)) {
> +		unmap_mapping_range(mapping,
> +				   (loff_t)page->index << PAGE_CACHE_SHIFT,
> +				   PAGE_CACHE_SIZE, 0);
> +	}
> +	return truncate_complete_page(mapping, page);
> +}
> +
>  /**
>   * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
>   * @mapping: mapping to truncate
> @@ -196,12 +207,7 @@ void truncate_inode_pages_range(struct a
>  				unlock_page(page);
>  				continue;
>  			}
> -			if (page_mapped(page)) {
> -				unmap_mapping_range(mapping,
> -				  (loff_t)page_index<<PAGE_CACHE_SHIFT,
> -				  PAGE_CACHE_SIZE, 0);
> -			}
> -			truncate_complete_page(mapping, page);
> +			truncate_inode_page(mapping, page);
>  			unlock_page(page);
>  		}
>  		pagevec_release(&pvec);
> @@ -238,15 +244,10 @@ void truncate_inode_pages_range(struct a
>  				break;
>  			lock_page(page);
>  			wait_on_page_writeback(page);
> -			if (page_mapped(page)) {
> -				unmap_mapping_range(mapping,
> -				  (loff_t)page->index<<PAGE_CACHE_SHIFT,
> -				  PAGE_CACHE_SIZE, 0);
> -			}
> +			truncate_inode_page(mapping, page);
>  			if (page->index > next)
>  				next = page->index;
>  			next++;
> -			truncate_complete_page(mapping, page);
>  			unlock_page(page);
>  		}
>  		pagevec_release(&pvec);
> Index: linux/include/linux/mm.h
> ===================================================================
> --- linux.orig/include/linux/mm.h
> +++ linux/include/linux/mm.h
> @@ -809,6 +809,8 @@ static inline void unmap_shared_mapping_
>  extern int vmtruncate(struct inode * inode, loff_t offset);
>  extern int vmtruncate_range(struct inode * inode, loff_t offset, loff_t end);
>  
> +int truncate_inode_page(struct address_space *mapping, struct page *page);
> +
>  #ifdef CONFIG_MMU
>  extern int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>  			unsigned long address, unsigned int flags);

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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Wu Fengguang]

On Wed, Aug 05, 2009 at 06:20:08PM +0800, Nick Piggin wrote:
> On Wed, Aug 05, 2009 at 11:36:38AM +0200, Andi Kleen wrote:
> > 
> > From: Nick Piggin <npiggin@suse.de>
> > 
> > Extract out truncate_inode_page() out of the truncate path so that
> > it can be used by memory-failure.c
> > 
> > [AK: description, headers, fix typos]
> > v2: Some white space changes from Fengguang Wu 
> > 
> > Signed-off-by: Andi Kleen <ak@linux.intel.com>
> > 
> > ---
> >  include/linux/mm.h |    2 ++
> >  mm/truncate.c      |   29 +++++++++++++++--------------
> >  2 files changed, 17 insertions(+), 14 deletions(-)
> > 
> > Index: linux/mm/truncate.c
> > ===================================================================
> > --- linux.orig/mm/truncate.c
> > +++ linux/mm/truncate.c
> > @@ -93,11 +93,11 @@ EXPORT_SYMBOL(cancel_dirty_page);
> >   * its lock, b) when a concurrent invalidate_mapping_pages got there first and
> >   * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
> >   */
> > -static void
> > +static int
> >  truncate_complete_page(struct address_space *mapping, struct page *page)
> >  {
> >  	if (page->mapping != mapping)
> > -		return;
> > +		return -EIO;
> 
> Hmm, at this point, the page must have been removed from pagecache,
> so I don't know if you need to pass an error back?

Me think so too. When called from hwpoison, the page count and lock
have both be taken, so at least _in this case_,

        (page->mapping != mapping)

can be equally written as

        (page->mapping == NULL)

But anyway, the return value is now ignored in upper layer :)

Thanks,
Fengguang

>   
> >  	if (page_has_private(page))
> >  		do_invalidatepage(page, 0);
> > @@ -108,6 +108,7 @@ truncate_complete_page(struct address_sp
> >  	remove_from_page_cache(page);
> >  	ClearPageMappedToDisk(page);
> >  	page_cache_release(page);	/* pagecache ref */
> > +	return 0;
> >  }
> >  
> >  /*
> > @@ -135,6 +136,16 @@ invalidate_complete_page(struct address_
> >  	return ret;
> >  }
> >  
> > +int truncate_inode_page(struct address_space *mapping, struct page *page)
> > +{
> > +	if (page_mapped(page)) {
> > +		unmap_mapping_range(mapping,
> > +				   (loff_t)page->index << PAGE_CACHE_SHIFT,
> > +				   PAGE_CACHE_SIZE, 0);
> > +	}
> > +	return truncate_complete_page(mapping, page);
> > +}
> > +
> >  /**
> >   * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
> >   * @mapping: mapping to truncate
> > @@ -196,12 +207,7 @@ void truncate_inode_pages_range(struct a
> >  				unlock_page(page);
> >  				continue;
> >  			}
> > -			if (page_mapped(page)) {
> > -				unmap_mapping_range(mapping,
> > -				  (loff_t)page_index<<PAGE_CACHE_SHIFT,
> > -				  PAGE_CACHE_SIZE, 0);
> > -			}
> > -			truncate_complete_page(mapping, page);
> > +			truncate_inode_page(mapping, page);
> >  			unlock_page(page);
> >  		}
> >  		pagevec_release(&pvec);
> > @@ -238,15 +244,10 @@ void truncate_inode_pages_range(struct a
> >  				break;
> >  			lock_page(page);
> >  			wait_on_page_writeback(page);
> > -			if (page_mapped(page)) {
> > -				unmap_mapping_range(mapping,
> > -				  (loff_t)page->index<<PAGE_CACHE_SHIFT,
> > -				  PAGE_CACHE_SIZE, 0);
> > -			}
> > +			truncate_inode_page(mapping, page);
> >  			if (page->index > next)
> >  				next = page->index;
> >  			next++;
> > -			truncate_complete_page(mapping, page);
> >  			unlock_page(page);
> >  		}
> >  		pagevec_release(&pvec);
> > Index: linux/include/linux/mm.h
> > ===================================================================
> > --- linux.orig/include/linux/mm.h
> > +++ linux/include/linux/mm.h
> > @@ -809,6 +809,8 @@ static inline void unmap_shared_mapping_
> >  extern int vmtruncate(struct inode * inode, loff_t offset);
> >  extern int vmtruncate_range(struct inode * inode, loff_t offset, loff_t end);
> >  
> > +int truncate_inode_page(struct address_space *mapping, struct page *page);
> > +
> >  #ifdef CONFIG_MMU
> >  extern int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> >  			unsigned long address, unsigned int flags);

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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Andi Kleen]

On Wed, Aug 05, 2009 at 12:20:08PM +0200, Nick Piggin wrote:
> >  truncate_complete_page(struct address_space *mapping, struct page *page)
> >  {
> >  	if (page->mapping != mapping)
> > -		return;
> > +		return -EIO;
> 
> Hmm, at this point, the page must have been removed from pagecache,
> so I don't know if you need to pass an error back?

It could be reused, which would be bad for us?

The final check is the page error count in the end anyways.

-Andi

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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Nick Piggin]

On Wed, Aug 05, 2009 at 03:46:08PM +0200, Andi Kleen wrote:
> On Wed, Aug 05, 2009 at 12:20:08PM +0200, Nick Piggin wrote:
> > >  truncate_complete_page(struct address_space *mapping, struct page *page)
> > >  {
> > >  	if (page->mapping != mapping)
> > > -		return;
> > > +		return -EIO;
> > 
> > Hmm, at this point, the page must have been removed from pagecache,
> > so I don't know if you need to pass an error back?
> 
> It could be reused, which would be bad for us?
 
I haven't brought up the caller at this point, but IIRC you had
the page locked and mapping confirmed at this point anyway so
it would never be an error for your code.

Probably it would be nice to just force callers to verify the page.
Normally IMO it is much nicer and clearer to do it at the time the
page gets locked, unless there is good reason otherwise.

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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Andi Kleen]

> I haven't brought up the caller at this point, but IIRC you had
> the page locked and mapping confirmed at this point anyway so
> it would never be an error for your code.
> 
> Probably it would be nice to just force callers to verify the page.
> Normally IMO it is much nicer and clearer to do it at the time the
> page gets locked, unless there is good reason otherwise.

Ok. I think I'll just keep it as it is for now.

The only reason I added the error code was to make truncate_inode_page
fit into .error_remove_page, but then latter I did another wrapper
so it could be removed again. But it won't hurt to have it either.

-Andi


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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Nick Piggin]

On Wed, Aug 05, 2009 at 04:10:01PM +0200, Andi Kleen wrote:
> > I haven't brought up the caller at this point, but IIRC you had
> > the page locked and mapping confirmed at this point anyway so
> > it would never be an error for your code.
> > 
> > Probably it would be nice to just force callers to verify the page.
> > Normally IMO it is much nicer and clearer to do it at the time the
> > page gets locked, unless there is good reason otherwise.
> 
> Ok. I think I'll just keep it as it is for now.
> 
> The only reason I added the error code was to make truncate_inode_page
> fit into .error_remove_page, but then latter I did another wrapper
> so it could be removed again. But it won't hurt to have it either.

OK, it's more of a cleanup/nit.

One question I had for the others (Andrew? other mm guys?) what is the
feelings of merging this feature? Leaving aside exact implementation
and just considering the high level design and cost/benefit. Last time
there were some people objecting, so I wonder the situation now? So
does anybody need more convincing? :)

Also I will just cc linux-arch. It would be interesting to know whether
powerpc, ia64, or s390 or others would be interested to use this feature?

Thanks,
Nick

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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Andi Kleen]

> One question I had for the others (Andrew? other mm guys?) what is the
> feelings of merging this feature? Leaving aside exact implementation
> and just considering the high level design and cost/benefit. Last time
> there were some people objecting, so I wonder the situation now? So
> does anybody need more convincing? :)

The main objection last time was that it was a bit too late in the 
release schedule.

I can't remember anyone really questioning the basic feature itself.

> Also I will just cc linux-arch. It would be interesting to know whether
> powerpc, ia64, or s390 or others would be interested to use this feature?

ia64 is interested (but no code so far) I talked to DaveM and he seems to be 
interested for sparc too.  I would expect other server architectures to 
eventually use it as they get around to writing the necessary architecture 
specific glue.

-Andi

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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Nick Piggin]

On Wed, Aug 05, 2009 at 04:41:12PM +0200, Andi Kleen wrote:
> > One question I had for the others (Andrew? other mm guys?) what is the
> > feelings of merging this feature? Leaving aside exact implementation
> > and just considering the high level design and cost/benefit. Last time
> > there were some people objecting, so I wonder the situation now? So
> > does anybody need more convincing? :)
> 
> The main objection last time was that it was a bit too late in the 
> release schedule.
> 
> I can't remember anyone really questioning the basic feature itself.

I can't exactly remember. Maybe it was in a thread with Alan and/or
Arjan ;) I don't think the feature itself was questioned as much as
cost/benefit. Maybe I was wrong...

I just want to see everyone is happy with the basic idea ;)


> > Also I will just cc linux-arch. It would be interesting to know whether
> > powerpc, ia64, or s390 or others would be interested to use this feature?
> 
> ia64 is interested (but no code so far) I talked to DaveM and he seems to be 
> interested for sparc too.  I would expect other server architectures to 
> eventually use it as they get around to writing the necessary architecture 
> specific glue.

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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Matthew Wilcox]

On Wed, Aug 05, 2009 at 04:41:12PM +0200, Andi Kleen wrote:
> > One question I had for the others (Andrew? other mm guys?) what is the
> > feelings of merging this feature? Leaving aside exact implementation
> > and just considering the high level design and cost/benefit. Last time
> > there were some people objecting, so I wonder the situation now? So
> > does anybody need more convincing? :)
> 
> The main objection last time was that it was a bit too late in the 
> release schedule.
> 
> I can't remember anyone really questioning the basic feature itself.
> 
> > Also I will just cc linux-arch. It would be interesting to know whether
> > powerpc, ia64, or s390 or others would be interested to use this feature?
> 
> ia64 is interested (but no code so far) I talked to DaveM and he seems to be 
> interested for sparc too.  I would expect other server architectures to 
> eventually use it as they get around to writing the necessary architecture 
> specific glue.

parisc could certainly implement this.  Don't know if there's interest.

-- 
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"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."

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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Martin Schwidefsky]

On Wed, 5 Aug 2009 16:16:42 +0200
Nick Piggin <npiggin@suse.de> wrote:

> On Wed, Aug 05, 2009 at 04:10:01PM +0200, Andi Kleen wrote:
> > > I haven't brought up the caller at this point, but IIRC you had
> > > the page locked and mapping confirmed at this point anyway so
> > > it would never be an error for your code.
> > > 
> > > Probably it would be nice to just force callers to verify the page.
> > > Normally IMO it is much nicer and clearer to do it at the time the
> > > page gets locked, unless there is good reason otherwise.
> > 
> > Ok. I think I'll just keep it as it is for now.
> > 
> > The only reason I added the error code was to make truncate_inode_page
> > fit into .error_remove_page, but then latter I did another wrapper
> > so it could be removed again. But it won't hurt to have it either.
> 
> OK, it's more of a cleanup/nit.
> 
> One question I had for the others (Andrew? other mm guys?) what is the
> feelings of merging this feature? Leaving aside exact implementation
> and just considering the high level design and cost/benefit. Last time
> there were some people objecting, so I wonder the situation now? So
> does anybody need more convincing? :)
> 
> Also I will just cc linux-arch. It would be interesting to know whether
> powerpc, ia64, or s390 or others would be interested to use this feature?

This is not relevant for s390, as current machines do transparent memory
sparing if a memory module goes bad. Really old machines reported bad
memory to the OS by means of a machine check (storage error uncorrected
and storage error corrected). I have never seen this happen, the level
below the OS deals with these errors for us.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Andi Kleen]

> This is not relevant for s390, as current machines do transparent memory
> sparing if a memory module goes bad. Really old machines reported bad
> memory to the OS by means of a machine check (storage error uncorrected
> and storage error corrected). I have never seen this happen, the level
> below the OS deals with these errors for us.

Ok fine. It's for the poorer cousins then who can't afford memory mirroring.

-Andi

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Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

[Wu Fengguang]

On Wed, Aug 05, 2009 at 10:01:45PM +0800, Nick Piggin wrote:
> On Wed, Aug 05, 2009 at 03:46:08PM +0200, Andi Kleen wrote:
> > On Wed, Aug 05, 2009 at 12:20:08PM +0200, Nick Piggin wrote:
> > > >  truncate_complete_page(struct address_space *mapping, struct page *page)
> > > >  {
> > > >  	if (page->mapping != mapping)
> > > > -		return;
> > > > +		return -EIO;
> > > 
> > > Hmm, at this point, the page must have been removed from pagecache,
> > > so I don't know if you need to pass an error back?
> > 
> > It could be reused, which would be bad for us?
>  
> I haven't brought up the caller at this point, but IIRC you had
> the page locked and mapping confirmed at this point anyway so
> it would never be an error for your code.

Right, that 'if' will always evaluate to false for the hwpoison case.
Because that 'mapping' was taken from 'page->mapping' inside page lock
and they will just remain the same values.

> Probably it would be nice to just force callers to verify the page.
> Normally IMO it is much nicer and clearer to do it at the time the
> page gets locked, unless there is good reason otherwise.

Yes we do checked page->mapping after taking page lock.

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[PATCH] [12/19] HWPOISON: Add invalidate_inode_page

[Andi Kleen]

From: Wu Fengguang <fengguang.wu@intel.com>

Add a simple way to invalidate a single page
This is just a refactoring of the truncate.c code.
Originally from Fengguang, modified by Andi Kleen.

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/linux/mm.h |    2 ++
 mm/truncate.c      |   26 ++++++++++++++++++++------
 2 files changed, 22 insertions(+), 6 deletions(-)

Index: linux/include/linux/mm.h
===================================================================
--- linux.orig/include/linux/mm.h
+++ linux/include/linux/mm.h
@@ -811,6 +811,8 @@ extern int vmtruncate_range(struct inode
 
 int truncate_inode_page(struct address_space *mapping, struct page *page);
 
+int invalidate_inode_page(struct page *page);
+
 #ifdef CONFIG_MMU
 extern int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long address, unsigned int flags);
Index: linux/mm/truncate.c
===================================================================
--- linux.orig/mm/truncate.c
+++ linux/mm/truncate.c
@@ -146,6 +146,24 @@ int truncate_inode_page(struct address_s
 	return truncate_complete_page(mapping, page);
 }
 
+/*
+ * Safely invalidate one page from its pagecache mapping.
+ * It only drops clean, unused pages. The page must be locked.
+ *
+ * Returns 1 if the page is successfully invalidated, otherwise 0.
+ */
+int invalidate_inode_page(struct page *page)
+{
+	struct address_space *mapping = page_mapping(page);
+	if (!mapping)
+		return 0;
+	if (PageDirty(page) || PageWriteback(page))
+		return 0;
+	if (page_mapped(page))
+		return 0;
+	return invalidate_complete_page(mapping, page);
+}
+
 /**
  * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
  * @mapping: mapping to truncate
@@ -312,12 +330,8 @@ unsigned long invalidate_mapping_pages(s
 			if (lock_failed)
 				continue;
 
-			if (PageDirty(page) || PageWriteback(page))
-				goto unlock;
-			if (page_mapped(page))
-				goto unlock;
-			ret += invalidate_complete_page(mapping, page);
-unlock:
+			ret += invalidate_inode_page(page);
+
 			unlock_page(page);
 			if (next > end)
 				break;

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[PATCH] [13/19] HWPOISON: Define a new error_remove_page address space op for async truncation

[Andi Kleen]

Truncating metadata pages is not safe right now before
we haven't audited all file systems.

To enable truncation only for data address space define
a new address_space callback error_remove_page.

This is used for memory_failure.c memory error handling.

This can be then set to truncate_inode_page()

This patch just defines the new operation and adds documentation.

Callers and users come in followon patches.

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 Documentation/filesystems/vfs.txt |    7 +++++++
 include/linux/fs.h                |    1 +
 include/linux/mm.h                |    1 +
 mm/truncate.c                     |   17 +++++++++++++++++
 4 files changed, 26 insertions(+)

Index: linux/include/linux/fs.h
===================================================================
--- linux.orig/include/linux/fs.h
+++ linux/include/linux/fs.h
@@ -595,6 +595,7 @@ struct address_space_operations {
 	int (*launder_page) (struct page *);
 	int (*is_partially_uptodate) (struct page *, read_descriptor_t *,
 					unsigned long);
+	int (*error_remove_page)(struct address_space *, struct page *);
 };
 
 /*
Index: linux/Documentation/filesystems/vfs.txt
===================================================================
--- linux.orig/Documentation/filesystems/vfs.txt
+++ linux/Documentation/filesystems/vfs.txt
@@ -536,6 +536,7 @@ struct address_space_operations {
 	/* migrate the contents of a page to the specified target */
 	int (*migratepage) (struct page *, struct page *);
 	int (*launder_page) (struct page *);
+	int (*error_remove_page) (struct mapping *mapping, struct page *page);
 };
 
   writepage: called by the VM to write a dirty page to backing store.
@@ -694,6 +695,12 @@ struct address_space_operations {
   	prevent redirtying the page, it is kept locked during the whole
 	operation.
 
+  error_remove_page: normally set to generic_error_remove_page if truncation
+	is ok for this address space. Used for memory failure handling.
+	Setting this implies you deal with pages going away under you,
+	unless you have them locked or reference counts increased.
+
+
 The File Object
 ===============
 
Index: linux/mm/truncate.c
===================================================================
--- linux.orig/mm/truncate.c
+++ linux/mm/truncate.c
@@ -147,6 +147,23 @@ int truncate_inode_page(struct address_s
 }
 
 /*
+ * Used to get rid of pages on hardware memory corruption.
+ */
+int generic_error_remove_page(struct address_space *mapping, struct page *page)
+{
+	if (!mapping)
+		return -EINVAL;
+	/*
+	 * Only punch for normal data pages for now.
+	 * Handling other types like directories would need more auditing.
+	 */
+	if (!S_ISREG(mapping->host->i_mode))
+		return -EIO;
+	return truncate_inode_page(mapping, page);
+}
+EXPORT_SYMBOL(generic_error_remove_page);
+
+/*
  * Safely invalidate one page from its pagecache mapping.
  * It only drops clean, unused pages. The page must be locked.
  *
Index: linux/include/linux/mm.h
===================================================================
--- linux.orig/include/linux/mm.h
+++ linux/include/linux/mm.h
@@ -810,6 +810,7 @@ extern int vmtruncate(struct inode * ino
 extern int vmtruncate_range(struct inode * inode, loff_t offset, loff_t end);
 
 int truncate_inode_page(struct address_space *mapping, struct page *page);
+int generic_error_remove_page(struct address_space *mapping, struct page *page);
 
 int invalidate_inode_page(struct page *page);
 

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[PATCH] [14/19] HWPOISON: Add PR_MCE_KILL prctl to control early kill behaviour per process

[Andi Kleen]

This allows processes to override their early/late kill
behaviour on hardware memory errors.

Typically applications which are memory error aware is
better of with early kill (see the error as soon
as possible), all others with late kill (only
see the error when the error is really impacting execution)

There's a global sysctl, but this way an application
can set its specific policy.

We're using two bits, one to signify that the process
stated its intention and that 

I also made the prctl future proof by enforcing
the unused arguments are 0.

The state is inherited to children for now. I've
been considering to reset it on exec, but not done for
now (TBD).

Note this makes us officially run out of process flags
on 32bit, but the next patch can easily add another field.

Manpage patch will be supplied separately.

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/linux/prctl.h |    2 ++
 include/linux/sched.h |    2 ++
 kernel/sys.c          |   22 ++++++++++++++++++++++
 3 files changed, 26 insertions(+)

Index: linux/include/linux/sched.h
===================================================================
--- linux.orig/include/linux/sched.h
+++ linux/include/linux/sched.h
@@ -1674,6 +1674,7 @@ extern cputime_t task_gtime(struct task_
 #define PF_EXITPIDONE	0x00000008	/* pi exit done on shut down */
 #define PF_VCPU		0x00000010	/* I'm a virtual CPU */
 #define PF_FORKNOEXEC	0x00000040	/* forked but didn't exec */
+#define PF_MCE_PROCESS  0x00000080      /* process policy on mce errors */
 #define PF_SUPERPRIV	0x00000100	/* used super-user privileges */
 #define PF_DUMPCORE	0x00000200	/* dumped core */
 #define PF_SIGNALED	0x00000400	/* killed by a signal */
@@ -1693,6 +1694,7 @@ extern cputime_t task_gtime(struct task_
 #define PF_SPREAD_PAGE	0x01000000	/* Spread page cache over cpuset */
 #define PF_SPREAD_SLAB	0x02000000	/* Spread some slab caches over cpuset */
 #define PF_THREAD_BOUND	0x04000000	/* Thread bound to specific cpu */
+#define PF_MCE_EARLY    0x08000000      /* Early kill for mce process policy */
 #define PF_MEMPOLICY	0x10000000	/* Non-default NUMA mempolicy */
 #define PF_MUTEX_TESTER	0x20000000	/* Thread belongs to the rt mutex tester */
 #define PF_FREEZER_SKIP	0x40000000	/* Freezer should not count it as freezeable */
Index: linux/kernel/sys.c
===================================================================
--- linux.orig/kernel/sys.c
+++ linux/kernel/sys.c
@@ -1528,6 +1528,28 @@ SYSCALL_DEFINE5(prctl, int, option, unsi
 				current->timer_slack_ns = arg2;
 			error = 0;
 			break;
+		case PR_MCE_KILL:
+			if (arg4 | arg5)
+				return -EINVAL;
+			switch (arg2) {
+			case 0:
+				if (arg3 != 0)
+					return -EINVAL;
+				current->flags &= ~PF_MCE_PROCESS;
+				break;
+			case 1:
+				current->flags |= PF_MCE_PROCESS;
+				if (arg3 != 0)
+					current->flags |= PF_MCE_EARLY;
+				else
+					current->flags &= ~PF_MCE_EARLY;
+				break;
+			default:
+				return -EINVAL;
+			}
+			error = 0;
+			break;
+
 		default:
 			error = -EINVAL;
 			break;
Index: linux/include/linux/prctl.h
===================================================================
--- linux.orig/include/linux/prctl.h
+++ linux/include/linux/prctl.h
@@ -88,4 +88,6 @@
 #define PR_TASK_PERF_COUNTERS_DISABLE		31
 #define PR_TASK_PERF_COUNTERS_ENABLE		32
 
+#define PR_MCE_KILL	33
+
 #endif /* _LINUX_PRCTL_H */

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[PATCH] [15/19] HWPOISON: The high level memory error handler in the VM v7

[Andi Kleen]

Add the high level memory handler that poisons pages
that got corrupted by hardware (typically by a two bit flip in a DIMM
or a cache) on the Linux level. The goal is to prevent everyone
from accessing these pages in the future.

This done at the VM level by marking a page hwpoisoned
and doing the appropriate action based on the type of page
it is.

The code that does this is portable and lives in mm/memory-failure.c

To quote the overview comment:

 * High level machine check handler. Handles pages reported by the
 * hardware as being corrupted usually due to a 2bit ECC memory or cache
 * failure.
 *
 * This focuses on pages detected as corrupted in the background.
 * When the current CPU tries to consume corruption the currently
 * running process can just be killed directly instead. This implies
 * that if the error cannot be handled for some reason it's safe to
 * just ignore it because no corruption has been consumed yet. Instead
 * when that happens another machine check will happen.
 *
 * Handles page cache pages in various states. The tricky part
 * here is that we can access any page asynchronous to other VM
 * users, because memory failures could happen anytime and anywhere,
 * possibly violating some of their assumptions. This is why this code
 * has to be extremely careful. Generally it tries to use normal locking
 * rules, as in get the standard locks, even if that means the
 * error handling takes potentially a long time.
 *
 * Some of the operations here are somewhat inefficient and have non
 * linear algorithmic complexity, because the data structures have not
 * been optimized for this case. This is in particular the case
 * for the mapping from a vma to a process. Since this case is expected
 * to be rare we hope we can get away with this.

There are in principle two strategies to kill processes on poison:
- just unmap the data and wait for an actual reference before 
killing
- kill as soon as corruption is detected.
Both have advantages and disadvantages and should be used 
in different situations. Right now both are implemented and can
be switched with a new sysctl vm.memory_failure_early_kill
The default is early kill.

The patch does some rmap data structure walking on its own to collect
processes to kill. This is unusual because normally all rmap data structure
knowledge is in rmap.c only. I put it here for now to keep 
everything together and rmap knowledge has been seeping out anyways

v2: Fix anon vma unlock crash (noticed by Johannes Weiner <hannes@cmpxchg.org>)
Handle pages on free list correctly (also noticed by Johannes)
Fix inverted try_to_release_page check (found by Chris Mason)
Add documentation for the new sysctl.
Various other cleanups/comment fixes.
v3: Use blockable signal for AO SIGBUS for better qemu handling.
Numerous fixes from Fengguang Wu: 
New code layout for the table (redone by AK)
Move the hwpoison bit setting before the lock (Fengguang Wu)
Some code cleanups (Fengguang Wu, AK)
Add missing lru_drain (Fengguang Wu)
Do more checks for valid mappings (inspired by patch from Fengguang)
Handle free pages and fixes for clean pages (Fengguang)
Removed swap cache handling for now, needs more work
Better mapping checks to avoid races (Fengguang)
Fix swapcache (Fengguang)
Handle private2 pages too (Fengguang)
v4: Various fixes based on review comments from Nick Piggin
Document locking order.
Improved comments.
Slightly improved description
Remove bogus hunk.
Wait properly for writeback pages (Nick Piggin)
v5: Improve various comments
Handle page_address_in_vma() failure better by SIGKILL and also
	make message debugging only
Clean up printks
Remove redundant PageWriteback check (Nick Piggin)
Add missing clear_page_mlock
Reformat state table to be <80 columns again
Use truncate helper instead of manual truncate in me_pagecache_*
Check for metadata buffer pages and reject them.
A few cleanups.
v6:
Fix a printk broken in the last round of cleanups.
More minor cleanups and fixes based on comments from Fengguang Wu.
Rename /proc/meminfo Header to "HardwareCorrupted"
Add a printk for the failed mapping case (Fengguang Wu)
Better clean page check (Fengguang Wu)
v7:
Use lru_add_drain_all
Use isolate_lru result in final status
[Merge with Fengguang's version. Only cherry picked changes.]
Fix bad pfn handling in action_result  (Fengguang)
Reverse tasklist lock locking order (Nick Piggin)
Check if VMA has really page mapped (Fengguang)
Add a missing page->mapping test (Fengguang)
Account all bad pages (Fengguang)
Misc comment fixes (Fengguang, Andi)
Add sysctl to force panic on memory failure
Only truncate if address space has it enabled, otherwise invalidate
Now selectable in Kconfig by the user.
Allow elevated reference count and return status
Misc changes

Cc: npiggin@suse.de
Cc: riel@redhat.com
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>

---
 Documentation/sysctl/vm.txt |   41 ++
 fs/proc/meminfo.c           |    9 
 include/linux/mm.h          |    7 
 include/linux/rmap.h        |    1 
 kernel/sysctl.c             |   25 +
 mm/Kconfig                  |    9 
 mm/Makefile                 |    1 
 mm/filemap.c                |    4 
 mm/memory-failure.c         |  828 ++++++++++++++++++++++++++++++++++++++++++++
 mm/rmap.c                   |    7 
 10 files changed, 929 insertions(+), 3 deletions(-)

Index: linux/mm/Makefile
===================================================================
--- linux.orig/mm/Makefile
+++ linux/mm/Makefile
@@ -40,5 +40,6 @@ obj-$(CONFIG_SMP) += allocpercpu.o
 endif
 obj-$(CONFIG_QUICKLIST) += quicklist.o
 obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o page_cgroup.o
+obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o
 obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
 obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o
Index: linux/mm/memory-failure.c
===================================================================
--- /dev/null
+++ linux/mm/memory-failure.c
@@ -0,0 +1,828 @@
+/*
+ * Copyright (C) 2008, 2009 Intel Corporation
+ * Authors: Andi Kleen, Fengguang Wu
+ *
+ * This software may be redistributed and/or modified under the terms of
+ * the GNU General Public License ("GPL") version 2 only as published by the
+ * Free Software Foundation.
+ *
+ * High level machine check handler. Handles pages reported by the
+ * hardware as being corrupted usually due to a 2bit ECC memory or cache
+ * failure.
+ *
+ * Handles page cache pages in various states.	The tricky part
+ * here is that we can access any page asynchronous to other VM
+ * users, because memory failures could happen anytime and anywhere,
+ * possibly violating some of their assumptions. This is why this code
+ * has to be extremely careful. Generally it tries to use normal locking
+ * rules, as in get the standard locks, even if that means the
+ * error handling takes potentially a long time.
+ *
+ * The operation to map back from RMAP chains to processes has to walk
+ * the complete process list and has non linear complexity with the number
+ * mappings. In short it can be quite slow. But since memory corruptions
+ * are rare we hope to get away with this.
+ */
+
+/*
+ * Notebook:
+ * - hugetlb needs more code
+ * - kcore/oldmem/vmcore/mem/kmem check for hwpoison pages
+ * - pass bad pages to kdump next kernel
+ */
+#define DEBUG 1
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/page-flags.h>
+#include <linux/sched.h>
+#include <linux/rmap.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/backing-dev.h>
+#include "internal.h"
+
+/* For better testing 1; Change default later to 0 */
+int sysctl_memory_failure_early_kill __read_mostly = 1;
+
+int sysctl_memory_failure_recovery __read_mostly = 1;
+
+atomic_long_t mce_bad_pages __read_mostly = ATOMIC_LONG_INIT(0);
+
+/*
+ * Send all the processes who have the page mapped an ``action optional''
+ * signal.
+ */
+static int kill_proc_ao(struct task_struct *t, unsigned long addr, int trapno,
+			unsigned long pfn)
+{
+	struct siginfo si;
+	int ret;
+
+	printk(KERN_ERR
+		"MCE %#lx: Killing %s:%d early due to hardware memory corruption\n",
+		pfn, t->comm, t->pid);
+	si.si_signo = SIGBUS;
+	si.si_errno = 0;
+	si.si_code = BUS_MCEERR_AO;
+	si.si_addr = (void *)addr;
+#ifdef __ARCH_SI_TRAPNO
+	si.si_trapno = trapno;
+#endif
+	si.si_addr_lsb = PAGE_SHIFT;
+	/*
+	 * Don't use force here, it's convenient if the signal
+	 * can be temporarily blocked.
+	 * This could cause a loop when the user sets SIGBUS
+	 * to SIG_IGN, but hopefully noone will do that?
+	 */
+	ret = send_sig_info(SIGBUS, &si, t);  /* synchronous? */
+	if (ret < 0)
+		printk(KERN_INFO "MCE: Error sending signal to %s:%d: %d\n",
+		       t->comm, t->pid, ret);
+	return ret;
+}
+
+/*
+ * Kill all processes that have a poisoned page mapped and then isolate
+ * the page.
+ *
+ * General strategy:
+ * Find all processes having the page mapped and kill them.
+ * But we keep a page reference around so that the page is not
+ * actually freed yet.
+ * Then stash the page away
+ *
+ * There's no convenient way to get back to mapped processes
+ * from the VMAs. So do a brute-force search over all
+ * running processes.
+ *
+ * Remember that machine checks are not common (or rather
+ * if they are common you have other problems), so this shouldn't
+ * be a performance issue.
+ *
+ * Also there are some races possible while we get from the
+ * error detection to actually handle it.
+ */
+
+struct to_kill {
+	struct list_head nd;
+	struct task_struct *tsk;
+	unsigned long addr;
+	unsigned addr_valid:1;
+};
+
+/*
+ * Failure handling: if we can't find or can't kill a process there's
+ * not much we can do.	We just print a message and ignore otherwise.
+ */
+
+/*
+ * Schedule a process for later kill.
+ * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
+ * TBD would GFP_NOIO be enough?
+ */
+static void add_to_kill(struct task_struct *tsk, struct page *p,
+		       struct vm_area_struct *vma,
+		       struct list_head *to_kill,
+		       struct to_kill **tkc)
+{
+	struct to_kill *tk;
+
+	if (*tkc) {
+		tk = *tkc;
+		*tkc = NULL;
+	} else {
+		tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC);
+		if (!tk) {
+			printk(KERN_ERR
+		"MCE: Out of memory while machine check handling\n");
+			return;
+		}
+	}
+	tk->addr = page_address_in_vma(p, vma);
+	tk->addr_valid = 1;
+
+	/*
+	 * In theory we don't have to kill when the page was
+	 * munmaped. But it could be also a mremap. Since that's
+	 * likely very rare kill anyways just out of paranoia, but use
+	 * a SIGKILL because the error is not contained anymore.
+	 */
+	if (tk->addr == -EFAULT) {
+		pr_debug("MCE: Unable to find user space address %lx in %s\n",
+			page_to_pfn(p), tsk->comm);
+		tk->addr_valid = 0;
+	}
+	get_task_struct(tsk);
+	tk->tsk = tsk;
+	list_add_tail(&tk->nd, to_kill);
+}
+
+/*
+ * Kill the processes that have been collected earlier.
+ *
+ * Only do anything when DOIT is set, otherwise just free the list
+ * (this is used for clean pages which do not need killing)
+ * Also when FAIL is set do a force kill because something went
+ * wrong earlier.
+ */
+static void kill_procs_ao(struct list_head *to_kill, int doit, int trapno,
+			  int fail, unsigned long pfn)
+{
+	struct to_kill *tk, *next;
+
+	list_for_each_entry_safe (tk, next, to_kill, nd) {
+		if (doit) {
+			/*
+			 * In case something went wrong with munmaping
+			 * make sure the process doesn't catch the
+			 * signal and then access the memory. Just kill it.
+			 * the signal handlers
+			 */
+			if (fail || tk->addr_valid == 0) {
+				printk(KERN_ERR
+		"MCE %#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n",
+					pfn, tk->tsk->comm, tk->tsk->pid);
+				force_sig(SIGKILL, tk->tsk);
+			}
+
+			/*
+			 * In theory the process could have mapped
+			 * something else on the address in-between. We could
+			 * check for that, but we need to tell the
+			 * process anyways.
+			 */
+			else if (kill_proc_ao(tk->tsk, tk->addr, trapno,
+					      pfn) < 0)
+				printk(KERN_ERR
+		"MCE %#lx: Cannot send advisory machine check signal to %s:%d\n",
+					pfn, tk->tsk->comm, tk->tsk->pid);
+		}
+		put_task_struct(tk->tsk);
+		kfree(tk);
+	}
+}
+
+static int task_early_kill(struct task_struct *tsk)
+{
+	if (!tsk->mm)
+		return 0;
+	if (tsk->flags & PF_MCE_PROCESS)
+		return !!(tsk->flags & PF_MCE_EARLY);
+	return sysctl_memory_failure_early_kill;
+}
+
+/*
+ * Collect processes when the error hit an anonymous page.
+ */
+static void collect_procs_anon(struct page *page, struct list_head *to_kill,
+			      struct to_kill **tkc)
+{
+	struct vm_area_struct *vma;
+	struct task_struct *tsk;
+	struct anon_vma *av;
+
+	read_lock(&tasklist_lock);
+	av = page_lock_anon_vma(page);
+	if (av == NULL)	/* Not actually mapped anymore */
+		goto out;
+	for_each_process (tsk) {
+		if (!task_early_kill(tsk))
+			continue;
+		list_for_each_entry (vma, &av->head, anon_vma_node) {
+			if (!page_mapped_in_vma(page, vma))
+				continue;
+			if (vma->vm_mm == tsk->mm)
+				add_to_kill(tsk, page, vma, to_kill, tkc);
+		}
+	}
+	page_unlock_anon_vma(av);
+out:
+	read_unlock(&tasklist_lock);
+}
+
+/*
+ * Collect processes when the error hit a file mapped page.
+ */
+static void collect_procs_file(struct page *page, struct list_head *to_kill,
+			      struct to_kill **tkc)
+{
+	struct vm_area_struct *vma;
+	struct task_struct *tsk;
+	struct prio_tree_iter iter;
+	struct address_space *mapping = page->mapping;
+
+	/*
+	 * A note on the locking order between the two locks.
+	 * We don't rely on this particular order.
+	 * If you have some other code that needs a different order
+	 * feel free to switch them around. Or add a reverse link
+	 * from mm_struct to task_struct, then this could be all
+	 * done without taking tasklist_lock and looping over all tasks.
+	 */
+
+	read_lock(&tasklist_lock);
+	spin_lock(&mapping->i_mmap_lock);
+	for_each_process(tsk) {
+		pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+
+		if (!task_early_kill(tsk))
+			continue;
+
+		vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff,
+				      pgoff) {
+			/*
+			 * Send early kill signal to tasks where a vma covers
+			 * the page but the corrupted page is not necessarily
+			 * mapped it in its pte.
+			 * Assume applications who requested early kill want
+			 * to be informed of all such data corruptions.
+			 */
+			if (vma->vm_mm == tsk->mm)
+				add_to_kill(tsk, page, vma, to_kill, tkc);
+		}
+	}
+	spin_unlock(&mapping->i_mmap_lock);
+	read_unlock(&tasklist_lock);
+}
+
+/*
+ * Collect the processes who have the corrupted page mapped to kill.
+ * This is done in two steps for locking reasons.
+ * First preallocate one tokill structure outside the spin locks,
+ * so that we can kill at least one process reasonably reliable.
+ */
+static void collect_procs(struct page *page, struct list_head *tokill)
+{
+	struct to_kill *tk;
+
+	if (!page->mapping)
+		return;
+
+	tk = kmalloc(sizeof(struct to_kill), GFP_NOIO);
+	if (!tk)
+		return;
+	if (PageAnon(page))
+		collect_procs_anon(page, tokill, &tk);
+	else
+		collect_procs_file(page, tokill, &tk);
+	kfree(tk);
+}
+
+/*
+ * Error handlers for various types of pages.
+ */
+
+enum outcome {
+	FAILED,		/* Error handling failed */
+	DELAYED,	/* Will be handled later */
+	IGNORED,	/* Error safely ignored */
+	RECOVERED,	/* Successfully recovered */
+};
+
+static const char *action_name[] = {
+	[FAILED] = "Failed",
+	[DELAYED] = "Delayed",
+	[IGNORED] = "Ignored",
+	[RECOVERED] = "Recovered",
+};
+
+/*
+ * Error hit kernel page.
+ * Do nothing, try to be lucky and not touch this instead. For a few cases we
+ * could be more sophisticated.
+ */
+static int me_kernel(struct page *p, unsigned long pfn)
+{
+	return DELAYED;
+}
+
+/*
+ * Already poisoned page.
+ */
+static int me_ignore(struct page *p, unsigned long pfn)
+{
+	return IGNORED;
+}
+
+/*
+ * Page in unknown state. Do nothing.
+ */
+static int me_unknown(struct page *p, unsigned long pfn)
+{
+	printk(KERN_ERR "MCE %#lx: Unknown page state\n", pfn);
+	return FAILED;
+}
+
+/*
+ * Free memory
+ */
+static int me_free(struct page *p, unsigned long pfn)
+{
+	return DELAYED;
+}
+
+/*
+ * Clean (or cleaned) page cache page.
+ */
+static int me_pagecache_clean(struct page *p, unsigned long pfn)
+{
+	int err;
+	int ret = FAILED;
+	struct address_space *mapping;
+
+	if (!isolate_lru_page(p))
+		page_cache_release(p);
+
+	/*
+	 * Now truncate the page in the page cache. This is really
+	 * more like a "temporary hole punch"
+	 * Don't do this for block devices when someone else
+	 * has a reference, because it could be file system metadata
+	 * and that's not safe to truncate.
+	 */
+	mapping = page_mapping(p);
+	if (!mapping) {
+		/*
+		 * Page has been teared down in the meanwhile
+		 */
+		return FAILED;
+	}
+
+	/*
+	 * Truncation is a bit tricky. Enable it per file system for now.
+	 *
+	 * Open: to take i_mutex or not for this? Right now we don't.
+	 */
+	if (mapping->a_ops->error_remove_page) {
+		err = mapping->a_ops->error_remove_page(mapping, p);
+		if (err != 0) {
+			printk(KERN_INFO "MCE %#lx: Failed to punch page: %d\n",
+					pfn, err);
+		} else if (page_has_private(p) &&
+				!try_to_release_page(p, GFP_NOIO)) {
+			pr_debug("MCE %#lx: failed to release buffers\n", pfn);
+		} else {
+			ret = RECOVERED;
+		}
+	} else {
+		/*
+		 * If the file system doesn't support it just invalidate
+		 * This fails on dirty or anything with private pages
+		 */
+		if (invalidate_inode_page(p))
+			ret = RECOVERED;
+		else
+			printk(KERN_INFO "MCE %#lx: Failed to invalidate\n",
+				pfn);
+	}
+	return ret;
+}
+
+/*
+ * Dirty cache page page
+ * Issues: when the error hit a hole page the error is not properly
+ * propagated.
+ */
+static int me_pagecache_dirty(struct page *p, unsigned long pfn)
+{
+	struct address_space *mapping = page_mapping(p);
+
+	SetPageError(p);
+	/* TBD: print more information about the file. */
+	if (mapping) {
+		/*
+		 * IO error will be reported by write(), fsync(), etc.
+		 * who check the mapping.
+		 * This way the application knows that something went
+		 * wrong with its dirty file data.
+		 *
+		 * There's one open issue:
+		 *
+		 * The EIO will be only reported on the next IO
+		 * operation and then cleared through the IO map.
+		 * Normally Linux has two mechanisms to pass IO error
+		 * first through the AS_EIO flag in the address space
+		 * and then through the PageError flag in the page.
+		 * Since we drop pages on memory failure handling the
+		 * only mechanism open to use is through AS_AIO.
+		 *
+		 * This has the disadvantage that it gets cleared on
+		 * the first operation that returns an error, while
+		 * the PageError bit is more sticky and only cleared
+		 * when the page is reread or dropped.  If an
+		 * application assumes it will always get error on
+		 * fsync, but does other operations on the fd before
+		 * and the page is dropped inbetween then the error
+		 * will not be properly reported.
+		 *
+		 * This can already happen even without hwpoisoned
+		 * pages: first on metadata IO errors (which only
+		 * report through AS_EIO) or when the page is dropped
+		 * at the wrong time.
+		 *
+		 * So right now we assume that the application DTRT on
+		 * the first EIO, but we're not worse than other parts
+		 * of the kernel.
+		 */
+		mapping_set_error(mapping, EIO);
+	}
+
+	return me_pagecache_clean(p, pfn);
+}
+
+/*
+ * Clean and dirty swap cache.
+ *
+ * Dirty swap cache page is tricky to handle. The page could live both in page
+ * cache and swap cache(ie. page is freshly swapped in). So it could be
+ * referenced concurrently by 2 types of PTEs:
+ * normal PTEs and swap PTEs. We try to handle them consistently by calling
+ * try_to_unmap(TTU_IGNORE_HWPOISON) to convert the normal PTEs to swap PTEs,
+ * and then
+ *      - clear dirty bit to prevent IO
+ *      - remove from LRU
+ *      - but keep in the swap cache, so that when we return to it on
+ *        a later page fault, we know the application is accessing
+ *        corrupted data and shall be killed (we installed simple
+ *        interception code in do_swap_page to catch it).
+ *
+ * Clean swap cache pages can be directly isolated. A later page fault will
+ * bring in the known good data from disk.
+ */
+static int me_swapcache_dirty(struct page *p, unsigned long pfn)
+{
+	int ret = FAILED;
+
+	ClearPageDirty(p);
+	/* Trigger EIO in shmem: */
+	ClearPageUptodate(p);
+
+	if (!isolate_lru_page(p)) {
+		page_cache_release(p);
+		ret = DELAYED;
+	}
+
+	return ret;
+}
+
+static int me_swapcache_clean(struct page *p, unsigned long pfn)
+{
+	int ret = FAILED;
+
+	if (!isolate_lru_page(p)) {
+		page_cache_release(p);
+		ret = RECOVERED;
+	}
+	delete_from_swap_cache(p);
+	return ret;
+}
+
+/*
+ * Huge pages. Needs work.
+ * Issues:
+ * No rmap support so we cannot find the original mapper. In theory could walk
+ * all MMs and look for the mappings, but that would be non atomic and racy.
+ * Need rmap for hugepages for this. Alternatively we could employ a heuristic,
+ * like just walking the current process and hoping it has it mapped (that
+ * should be usually true for the common "shared database cache" case)
+ * Should handle free huge pages and dequeue them too, but this needs to
+ * handle huge page accounting correctly.
+ */
+static int me_huge_page(struct page *p, unsigned long pfn)
+{
+	return FAILED;
+}
+
+/*
+ * Various page states we can handle.
+ *
+ * A page state is defined by its current page->flags bits.
+ * The table matches them in order and calls the right handler.
+ *
+ * This is quite tricky because we can access page at any time
+ * in its live cycle, so all accesses have to be extremly careful.
+ *
+ * This is not complete. More states could be added.
+ * For any missing state don't attempt recovery.
+ */
+
+#define dirty		(1UL << PG_dirty)
+#define sc		(1UL << PG_swapcache)
+#define unevict		(1UL << PG_unevictable)
+#define mlock		(1UL << PG_mlocked)
+#define writeback	(1UL << PG_writeback)
+#define lru		(1UL << PG_lru)
+#define swapbacked	(1UL << PG_swapbacked)
+#define head		(1UL << PG_head)
+#define tail		(1UL << PG_tail)
+#define compound	(1UL << PG_compound)
+#define slab		(1UL << PG_slab)
+#define buddy		(1UL << PG_buddy)
+#define reserved	(1UL << PG_reserved)
+
+static struct page_state {
+	unsigned long mask;
+	unsigned long res;
+	char *msg;
+	int (*action)(struct page *p, unsigned long pfn);
+} error_states[] = {
+	{ reserved,	reserved,	"reserved kernel",	me_ignore },
+	{ buddy,	buddy,		"free kernel",	me_free },
+
+	/*
+	 * Could in theory check if slab page is free or if we can drop
+	 * currently unused objects without touching them. But just
+	 * treat it as standard kernel for now.
+	 */
+	{ slab,		slab,		"kernel slab",	me_kernel },
+
+#ifdef CONFIG_PAGEFLAGS_EXTENDED
+	{ head,		head,		"huge",		me_huge_page },
+	{ tail,		tail,		"huge",		me_huge_page },
+#else
+	{ compound,	compound,	"huge",		me_huge_page },
+#endif
+
+	{ sc|dirty,	sc|dirty,	"swapcache",	me_swapcache_dirty },
+	{ sc|dirty,	sc,		"swapcache",	me_swapcache_clean },
+
+#ifdef CONFIG_UNEVICTABLE_LRU
+	{ unevict|dirty, unevict|dirty,	"unevictable LRU", me_pagecache_dirty},
+	{ unevict,	unevict,	"unevictable LRU", me_pagecache_clean},
+#endif
+
+#ifdef CONFIG_HAVE_MLOCKED_PAGE_BIT
+	{ mlock|dirty,	mlock|dirty,	"mlocked LRU",	me_pagecache_dirty },
+	{ mlock,	mlock,		"mlocked LRU",	me_pagecache_clean },
+#endif
+
+	{ lru|dirty,	lru|dirty,	"LRU",		me_pagecache_dirty },
+	{ lru|dirty,	lru,		"clean LRU",	me_pagecache_clean },
+	{ swapbacked,	swapbacked,	"anonymous",	me_pagecache_clean },
+
+	/*
+	 * Catchall entry: must be at end.
+	 */
+	{ 0,		0,		"unknown page state",	me_unknown },
+};
+
+#undef lru
+
+static void action_result(unsigned long pfn, char *msg, int result)
+{
+	struct page *page = NULL;
+	if (pfn_valid(pfn))
+		page = pfn_to_page(pfn);
+
+	printk(KERN_ERR "MCE %#lx: %s%s page recovery: %s\n",
+		pfn,
+		page && PageDirty(page) ? "dirty " : "",
+		msg, action_name[result]);
+}
+
+static int page_action(struct page_state *ps, struct page *p,
+			unsigned long pfn, int ref)
+{
+	int result;
+
+	result = ps->action(p, pfn);
+	action_result(pfn, ps->msg, result);
+	if (page_count(p) != 1 + ref)
+		printk(KERN_ERR
+		       "MCE %#lx: %s page still referenced by %d users\n",
+		       pfn, ps->msg, page_count(p) - 1);
+
+	/* Could do more checks here if page looks ok */
+	/*
+	 * Could adjust zone counters here to correct for the missing page.
+	 */
+
+	return result == RECOVERED ? 0 : -EBUSY;
+}
+
+#define N_UNMAP_TRIES 5
+
+/*
+ * Do all that is necessary to remove user space mappings. Unmap
+ * the pages and send SIGBUS to the processes if the data was dirty.
+ */
+static void hwpoison_user_mappings(struct page *p, unsigned long pfn,
+				  int trapno)
+{
+	enum ttu_flags ttu = TTU_UNMAP | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS;
+	struct address_space *mapping;
+	LIST_HEAD(tokill);
+	int ret;
+	int i;
+	int kill = 1;
+
+	if (PageReserved(p) || PageCompound(p) || PageSlab(p))
+		return;
+
+	if (!PageLRU(p))
+		lru_add_drain_all();
+
+	/*
+	 * This check implies we don't kill processes if their pages
+	 * are in the swap cache early. Those are always late kills.
+	 */
+	if (!page_mapped(p))
+		return;
+
+	if (PageSwapCache(p)) {
+		printk(KERN_ERR
+		       "MCE %#lx: keeping poisoned page in swap cache\n", pfn);
+		ttu |= TTU_IGNORE_HWPOISON;
+	}
+
+	/*
+	 * Propagate the dirty bit from PTEs to struct page first, because we
+	 * need this to decide if we should kill or just drop the page.
+	 */
+	mapping = page_mapping(p);
+	if (!PageDirty(p) && mapping && mapping_cap_writeback_dirty(mapping)) {
+		if (page_mkclean(p)) {
+			SetPageDirty(p);
+		} else {
+			kill = 0;
+			ttu |= TTU_IGNORE_HWPOISON;
+			printk(KERN_INFO
+	"MCE %#lx: corrupted page was clean: dropped without side effects\n",
+				pfn);
+		}
+	}
+
+	/*
+	 * First collect all the processes that have the page
+	 * mapped in dirty form.  This has to be done before try_to_unmap,
+	 * because ttu takes the rmap data structures down.
+	 *
+	 * Error handling: We ignore errors here because
+	 * there's nothing that can be done.
+	 */
+	if (kill)
+		collect_procs(p, &tokill);
+
+	/*
+	 * try_to_unmap can fail temporarily due to races.
+	 * Try a few times (RED-PEN better strategy?)
+	 */
+	for (i = 0; i < N_UNMAP_TRIES; i++) {
+		ret = try_to_unmap(p, ttu);
+		if (ret == SWAP_SUCCESS)
+			break;
+		pr_debug("MCE %#lx: try_to_unmap retry needed %d\n", pfn,  ret);
+	}
+
+	if (ret != SWAP_SUCCESS)
+		printk(KERN_ERR "MCE %#lx: failed to unmap page (mapcount=%d)\n",
+				pfn, page_mapcount(p));
+
+	/*
+	 * Now that the dirty bit has been propagated to the
+	 * struct page and all unmaps done we can decide if
+	 * killing is needed or not.  Only kill when the page
+	 * was dirty, otherwise the tokill list is merely
+	 * freed.  When there was a problem unmapping earlier
+	 * use a more force-full uncatchable kill to prevent
+	 * any accesses to the poisoned memory.
+	 */
+	kill_procs_ao(&tokill, !!PageDirty(p), trapno,
+		      ret != SWAP_SUCCESS, pfn);
+}
+
+int __memory_failure(unsigned long pfn, int trapno, int ref)
+{
+	struct page_state *ps;
+	struct page *p;
+	int res;
+
+	if (!sysctl_memory_failure_recovery)
+		panic("Memory failure from trap %d on page %lx", trapno, pfn);
+
+	if (!pfn_valid(pfn)) {
+		action_result(pfn, "memory outside kernel control", IGNORED);
+		return -EIO;
+	}
+
+	p = pfn_to_page(pfn);
+	if (TestSetPageHWPoison(p)) {
+		action_result(pfn, "already hardware poisoned", IGNORED);
+		return 0;
+	}
+
+	atomic_long_add(1, &mce_bad_pages);
+
+	/*
+	 * We need/can do nothing about count=0 pages.
+	 * 1) it's a free page, and therefore in safe hand:
+	 *    prep_new_page() will be the gate keeper.
+	 * 2) it's part of a non-compound high order page.
+	 *    Implies some kernel user: cannot stop them from
+	 *    R/W the page; let's pray that the page has been
+	 *    used and will be freed some time later.
+	 * In fact it's dangerous to directly bump up page count from 0,
+	 * that may make page_freeze_refs()/page_unfreeze_refs() mismatch.
+	 */
+	if (!get_page_unless_zero(compound_head(p))) {
+		action_result(pfn, "free or high order kernel", IGNORED);
+		return PageBuddy(compound_head(p)) ? 0 : -EBUSY;
+	}
+
+	/*
+	 * Lock the page and wait for writeback to finish.
+	 * It's very difficult to mess with pages currently under IO
+	 * and in many cases impossible, so we just avoid it here.
+	 */
+	lock_page_nosync(p);
+	wait_on_page_writeback(p);
+
+	/*
+	 * Now take care of user space mappings.
+	 */
+	hwpoison_user_mappings(p, pfn, trapno);
+
+	/*
+	 * Torn down by someone else?
+	 */
+	if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {
+		action_result(pfn, "already truncated LRU", IGNORED);
+		res = 0;
+		goto out;
+	}
+
+	res = -EBUSY;
+	for (ps = error_states;; ps++) {
+		if ((p->flags & ps->mask) == ps->res) {
+			res = page_action(ps, p, pfn, ref);
+			break;
+		}
+	}
+out:
+	unlock_page(p);
+	return res;
+}
+EXPORT_SYMBOL_GPL(__memory_failure);
+
+/**
+ * memory_failure - Handle memory failure of a page.
+ * @pfn: Page Number of the corrupted page
+ * @trapno: Trap number reported in the signal to user space.
+ *
+ * This function is called by the low level machine check code
+ * of an architecture when it detects hardware memory corruption
+ * of a page. It tries its best to recover, which includes
+ * dropping pages, killing processes etc.
+ *
+ * The function is primarily of use for corruptions that
+ * happen outside the current execution context (e.g. when
+ * detected by a background scrubber)
+ *
+ * Must run in process context (e.g. a work queue) with interrupts
+ * enabled and no spinlocks hold.
+ */
+void memory_failure(unsigned long pfn, int trapno)
+{
+	__memory_failure(pfn, trapno, 0);
+}
Index: linux/include/linux/mm.h
===================================================================
--- linux.orig/include/linux/mm.h
+++ linux/include/linux/mm.h
@@ -1324,5 +1324,12 @@ void vmemmap_populate_print_last(void);
 extern int account_locked_memory(struct mm_struct *mm, struct rlimit *rlim,
 				 size_t size);
 extern void refund_locked_memory(struct mm_struct *mm, size_t size);
+
+extern void memory_failure(unsigned long pfn, int trapno);
+extern int __memory_failure(unsigned long pfn, int trapno, int ref);
+extern int sysctl_memory_failure_early_kill;
+extern int sysctl_memory_failure_recovery;
+extern atomic_long_t mce_bad_pages;
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */
Index: linux/kernel/sysctl.c
===================================================================
--- linux.orig/kernel/sysctl.c
+++ linux/kernel/sysctl.c
@@ -1356,6 +1356,31 @@ static struct ctl_table vm_table[] = {
 		.mode		= 0644,
 		.proc_handler	= &scan_unevictable_handler,
 	},
+#ifdef CONFIG_MEMORY_FAILURE
+	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "memory_failure_early_kill",
+		.data		= &sysctl_memory_failure_early_kill,
+		.maxlen		= sizeof(sysctl_memory_failure_early_kill),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_minmax,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &zero,
+		.extra2		= &one,
+	},
+	{
+		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "memory_failure_recovery",
+		.data		= &sysctl_memory_failure_recovery,
+		.maxlen		= sizeof(sysctl_memory_failure_recovery),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_minmax,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &zero,
+		.extra2		= &one,
+	},
+#endif
+
 /*
  * NOTE: do not add new entries to this table unless you have read
  * Documentation/sysctl/ctl_unnumbered.txt
Index: linux/fs/proc/meminfo.c
===================================================================
--- linux.orig/fs/proc/meminfo.c
+++ linux/fs/proc/meminfo.c
@@ -95,7 +95,11 @@ static int meminfo_proc_show(struct seq_
 		"Committed_AS:   %8lu kB\n"
 		"VmallocTotal:   %8lu kB\n"
 		"VmallocUsed:    %8lu kB\n"
-		"VmallocChunk:   %8lu kB\n",
+		"VmallocChunk:   %8lu kB\n"
+#ifdef CONFIG_MEMORY_FAILURE
+		"HardwareCorrupted: %8lu kB\n"
+#endif
+		,
 		K(i.totalram),
 		K(i.freeram),
 		K(i.bufferram),
@@ -140,6 +144,9 @@ static int meminfo_proc_show(struct seq_
 		(unsigned long)VMALLOC_TOTAL >> 10,
 		vmi.used >> 10,
 		vmi.largest_chunk >> 10
+#ifdef CONFIG_MEMORY_FAILURE
+		,atomic_long_read(&mce_bad_pages) << (PAGE_SHIFT - 10)
+#endif
 		);
 
 	hugetlb_report_meminfo(m);
Index: linux/mm/Kconfig
===================================================================
--- linux.orig/mm/Kconfig
+++ linux/mm/Kconfig
@@ -233,6 +233,15 @@ config DEFAULT_MMAP_MIN_ADDR
 	  /proc/sys/vm/mmap_min_addr tunable.
 
 
+config MEMORY_FAILURE
+	depends on MMU
+	depends on X86_MCE
+	bool "Enable memory failure recovery"
+	help
+	  Enables code to recover from some memory failures on systems
+	  with MCA recovery. This allows a system to continue running
+	  even when some of its memory has uncorrected errors.
+
 config NOMMU_INITIAL_TRIM_EXCESS
 	int "Turn on mmap() excess space trimming before booting"
 	depends on !MMU
Index: linux/Documentation/sysctl/vm.txt
===================================================================
--- linux.orig/Documentation/sysctl/vm.txt
+++ linux/Documentation/sysctl/vm.txt
@@ -32,6 +32,8 @@ Currently, these files are in /proc/sys/
 - legacy_va_layout
 - lowmem_reserve_ratio
 - max_map_count
+- memory_failure_early_kill
+- memory_failure_recovery
 - min_free_kbytes
 - min_slab_ratio
 - min_unmapped_ratio
@@ -53,7 +55,6 @@ Currently, these files are in /proc/sys/
 - vfs_cache_pressure
 - zone_reclaim_mode
 
-
 ==============================================================
 
 block_dump
@@ -275,6 +276,44 @@ e.g., up to one or two maps per allocati
 
 The default value is 65536.
 
+=============================================================
+
+memory_failure_early_kill:
+
+Control how to kill processes when uncorrected memory error (typically
+a 2bit error in a memory module) is detected in the background by hardware
+that cannot be handled by the kernel. In some cases (like the page
+still having a valid copy on disk) the kernel will handle the failure
+transparently without affecting any applications. But if there is
+no other uptodate copy of the data it will kill to prevent any data
+corruptions from propagating.
+
+1: Kill all processes that have the corrupted and not reloadable page mapped
+as soon as the corruption is detected.  Note this is not supported
+for a few types of pages, like kernel internally allocated data or
+the swap cache, but works for the majority of user pages.
+
+0: Only unmap the corrupted page from all processes and only kill a process
+who tries to access it.
+
+The kill is done using a catchable SIGBUS with BUS_MCEERR_AO, so processes can
+handle this if they want to.
+
+This is only active on architectures/platforms with advanced machine
+check handling and depends on the hardware capabilities.
+
+Applications can override this setting individually with the PR_MCE_KILL prctl
+
+==============================================================
+
+memory_failure_recovery
+
+Enable memory failure recovery (when supported by the platform)
+
+1: Attempt recovery.
+
+0: Always panic on a memory failure.
+
 ==============================================================
 
 min_free_kbytes:
Index: linux/mm/filemap.c
===================================================================
--- linux.orig/mm/filemap.c
+++ linux/mm/filemap.c
@@ -105,6 +105,10 @@
  *
  *  ->task->proc_lock
  *    ->dcache_lock		(proc_pid_lookup)
+ *
+ *  (code doesn't rely on that order, so you could switch it around)
+ *  ->tasklist_lock             (memory_failure, collect_procs_ao)
+ *    ->i_mmap_lock
  */
 
 /*
Index: linux/mm/rmap.c
===================================================================
--- linux.orig/mm/rmap.c
+++ linux/mm/rmap.c
@@ -36,6 +36,11 @@
  *                 mapping->tree_lock (widely used, in set_page_dirty,
  *                           in arch-dependent flush_dcache_mmap_lock,
  *                           within inode_lock in __sync_single_inode)
+ *
+ * (code doesn't rely on that order so it could be switched around)
+ * ->tasklist_lock
+ *   anon_vma->lock      (memory_failure, collect_procs_anon)
+ *     pte map lock
  */
 
 #include <linux/mm.h>
@@ -311,7 +316,7 @@ pte_t *page_check_address(struct page *p
  * if the page is not mapped into the page tables of this VMA.  Only
  * valid for normal file or anonymous VMAs.
  */
-static int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
+int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
 {
 	unsigned long address;
 	pte_t *pte;
Index: linux/include/linux/rmap.h
===================================================================
--- linux.orig/include/linux/rmap.h
+++ linux/include/linux/rmap.h
@@ -129,6 +129,7 @@ int try_to_munlock(struct page *);
  */
 struct anon_vma *page_lock_anon_vma(struct page *page);
 void page_unlock_anon_vma(struct anon_vma *anon_vma);
+int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 
 #else	/* !CONFIG_MMU */
 

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[PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Andi Kleen]

Enable removing of corrupted pages through truncation
for a bunch of file systems: ext*, xfs, gfs2, ocfs2, ntfs
These should cover most server needs.

I chose the set of migration aware file systems for this
for now, assuming they have been especially audited.
But in general it should be safe for all file systems
on the data area that support read/write and truncate.

Caveat: the hardware error handler does not take i_mutex
for now before calling the truncate function. Is that ok?

Cc: tytso@mit.edu
Cc: hch@infradead.org
Cc: mfasheh@suse.com
Cc: aia21@cantab.net
Cc: hugh.dickins@tiscali.co.uk
Cc: swhiteho@redhat.com
Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 fs/ext2/inode.c             |    2 ++
 fs/ext3/inode.c             |    3 +++
 fs/ext4/inode.c             |    4 ++++
 fs/gfs2/aops.c              |    3 +++
 fs/ntfs/aops.c              |    2 ++
 fs/ocfs2/aops.c             |    1 +
 fs/xfs/linux-2.6/xfs_aops.c |    1 +
 mm/shmem.c                  |    1 +
 8 files changed, 17 insertions(+)

Index: linux/fs/gfs2/aops.c
===================================================================
--- linux.orig/fs/gfs2/aops.c
+++ linux/fs/gfs2/aops.c
@@ -1135,6 +1135,7 @@ static const struct address_space_operat
 	.direct_IO = gfs2_direct_IO,
 	.migratepage = buffer_migrate_page,
 	.is_partially_uptodate = block_is_partially_uptodate,
+	.error_remove_page = generic_error_remove_page,
 };
 
 static const struct address_space_operations gfs2_ordered_aops = {
@@ -1151,6 +1152,7 @@ static const struct address_space_operat
 	.direct_IO = gfs2_direct_IO,
 	.migratepage = buffer_migrate_page,
 	.is_partially_uptodate = block_is_partially_uptodate,
+	.error_remove_page = generic_error_remove_page,
 };
 
 static const struct address_space_operations gfs2_jdata_aops = {
@@ -1166,6 +1168,7 @@ static const struct address_space_operat
 	.invalidatepage = gfs2_invalidatepage,
 	.releasepage = gfs2_releasepage,
 	.is_partially_uptodate = block_is_partially_uptodate,
+	.error_remove_page = generic_error_remove_page,
 };
 
 void gfs2_set_aops(struct inode *inode)
Index: linux/fs/ntfs/aops.c
===================================================================
--- linux.orig/fs/ntfs/aops.c
+++ linux/fs/ntfs/aops.c
@@ -1550,6 +1550,7 @@ const struct address_space_operations nt
 	.migratepage	= buffer_migrate_page,	/* Move a page cache page from
 						   one physical page to an
 						   other. */
+	.error_remove_page = generic_error_remove_page,
 };
 
 /**
@@ -1569,6 +1570,7 @@ const struct address_space_operations nt
 	.migratepage	= buffer_migrate_page,	/* Move a page cache page from
 						   one physical page to an
 						   other. */
+	.error_remove_page = generic_error_remove_page,
 };
 
 #ifdef NTFS_RW
Index: linux/fs/ocfs2/aops.c
===================================================================
--- linux.orig/fs/ocfs2/aops.c
+++ linux/fs/ocfs2/aops.c
@@ -1968,4 +1968,5 @@ const struct address_space_operations oc
 	.releasepage		= ocfs2_releasepage,
 	.migratepage		= buffer_migrate_page,
 	.is_partially_uptodate	= block_is_partially_uptodate,
+	.error_remove_page	= generic_error_remove_page,
 };
Index: linux/fs/xfs/linux-2.6/xfs_aops.c
===================================================================
--- linux.orig/fs/xfs/linux-2.6/xfs_aops.c
+++ linux/fs/xfs/linux-2.6/xfs_aops.c
@@ -1636,4 +1636,5 @@ const struct address_space_operations xf
 	.direct_IO		= xfs_vm_direct_IO,
 	.migratepage		= buffer_migrate_page,
 	.is_partially_uptodate  = block_is_partially_uptodate,
+	.error_remove_page	= generic_error_remove_page,
 };
Index: linux/mm/shmem.c
===================================================================
--- linux.orig/mm/shmem.c
+++ linux/mm/shmem.c
@@ -2421,6 +2421,7 @@ static const struct address_space_operat
 	.write_end	= shmem_write_end,
 #endif
 	.migratepage	= migrate_page,
+	.error_remove_page = generic_error_remove_page,
 };
 
 static const struct file_operations shmem_file_operations = {
Index: linux/fs/ext2/inode.c
===================================================================
--- linux.orig/fs/ext2/inode.c
+++ linux/fs/ext2/inode.c
@@ -819,6 +819,7 @@ const struct address_space_operations ex
 	.writepages		= ext2_writepages,
 	.migratepage		= buffer_migrate_page,
 	.is_partially_uptodate	= block_is_partially_uptodate,
+	.error_remove_page	= generic_error_remove_page,
 };
 
 const struct address_space_operations ext2_aops_xip = {
@@ -837,6 +838,7 @@ const struct address_space_operations ex
 	.direct_IO		= ext2_direct_IO,
 	.writepages		= ext2_writepages,
 	.migratepage		= buffer_migrate_page,
+	.error_remove_page	= generic_error_remove_page,
 };
 
 /*
Index: linux/fs/ext3/inode.c
===================================================================
--- linux.orig/fs/ext3/inode.c
+++ linux/fs/ext3/inode.c
@@ -1819,6 +1819,7 @@ static const struct address_space_operat
 	.direct_IO		= ext3_direct_IO,
 	.migratepage		= buffer_migrate_page,
 	.is_partially_uptodate  = block_is_partially_uptodate,
+	.error_remove_page	= generic_error_remove_page,
 };
 
 static const struct address_space_operations ext3_writeback_aops = {
@@ -1834,6 +1835,7 @@ static const struct address_space_operat
 	.direct_IO		= ext3_direct_IO,
 	.migratepage		= buffer_migrate_page,
 	.is_partially_uptodate  = block_is_partially_uptodate,
+	.error_remove_page	= generic_error_remove_page,
 };
 
 static const struct address_space_operations ext3_journalled_aops = {
@@ -1848,6 +1850,7 @@ static const struct address_space_operat
 	.invalidatepage		= ext3_invalidatepage,
 	.releasepage		= ext3_releasepage,
 	.is_partially_uptodate  = block_is_partially_uptodate,
+	.error_remove_page	= generic_error_remove_page,
 };
 
 void ext3_set_aops(struct inode *inode)
Index: linux/fs/ext4/inode.c
===================================================================
--- linux.orig/fs/ext4/inode.c
+++ linux/fs/ext4/inode.c
@@ -3373,6 +3373,7 @@ static const struct address_space_operat
 	.direct_IO		= ext4_direct_IO,
 	.migratepage		= buffer_migrate_page,
 	.is_partially_uptodate  = block_is_partially_uptodate,
+	.error_remove_page	= generic_error_remove_page,
 };
 
 static const struct address_space_operations ext4_writeback_aops = {
@@ -3388,6 +3389,7 @@ static const struct address_space_operat
 	.direct_IO		= ext4_direct_IO,
 	.migratepage		= buffer_migrate_page,
 	.is_partially_uptodate  = block_is_partially_uptodate,
+	.error_remove_page	= generic_error_remove_page,
 };
 
 static const struct address_space_operations ext4_journalled_aops = {
@@ -3402,6 +3404,7 @@ static const struct address_space_operat
 	.invalidatepage		= ext4_invalidatepage,
 	.releasepage		= ext4_releasepage,
 	.is_partially_uptodate  = block_is_partially_uptodate,
+	.error_remove_page	= generic_error_remove_page,
 };
 
 static const struct address_space_operations ext4_da_aops = {
@@ -3418,6 +3421,7 @@ static const struct address_space_operat
 	.direct_IO		= ext4_direct_IO,
 	.migratepage		= buffer_migrate_page,
 	.is_partially_uptodate  = block_is_partially_uptodate,
+	.error_remove_page	= generic_error_remove_page,
 };
 
 void ext4_set_aops(struct inode *inode)

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Christoph Hellwig]

On Wed, Aug 05, 2009 at 11:36:43AM +0200, Andi Kleen wrote:
> 
> Enable removing of corrupted pages through truncation
> for a bunch of file systems: ext*, xfs, gfs2, ocfs2, ntfs
> These should cover most server needs.
> 
> I chose the set of migration aware file systems for this
> for now, assuming they have been especially audited.
> But in general it should be safe for all file systems
> on the data area that support read/write and truncate.
> 
> Caveat: the hardware error handler does not take i_mutex
> for now before calling the truncate function. Is that ok?

It will probably need locking, e.g. the iolock in XFS.  I'll
need to take a look at the actual implementation of
generic_error_remove_page to make sense of this.

Is there any way for us to test this functionality without introducing
real hardware problems?


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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Wu Fengguang]

On Wed, Aug 05, 2009 at 07:12:31PM +0800, Christoph Hellwig wrote:
> On Wed, Aug 05, 2009 at 11:36:43AM +0200, Andi Kleen wrote:
> > 
> > Enable removing of corrupted pages through truncation
> > for a bunch of file systems: ext*, xfs, gfs2, ocfs2, ntfs
> > These should cover most server needs.
> > 
> > I chose the set of migration aware file systems for this
> > for now, assuming they have been especially audited.
> > But in general it should be safe for all file systems
> > on the data area that support read/write and truncate.
> > 
> > Caveat: the hardware error handler does not take i_mutex
> > for now before calling the truncate function. Is that ok?
> 
> It will probably need locking, e.g. the iolock in XFS.  I'll
> need to take a look at the actual implementation of
> generic_error_remove_page to make sense of this.

In patch 13, it simply calls truncate_inode_page() for S_ISREG inodes.

Nick suggests call truncate_inode_page() with i_mutex. Sure we can
do mutex_trylock(i_mutex), but we'd appreciate it if some fs gurus
can demonstrate some bad consequences of not doing so, thanks!

> Is there any way for us to test this functionality without introducing
> real hardware problems?

We have some additional patches (ugly but works for now) that export
interfaces for injecting hwpoison to selected types pages. It can
guarantee only data/metadata pages of selected fs will be poisoned.
Based on which we can do all kinds of stress testing in user space.

Thanks,
Fengguang

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Andi Kleen]

On Wed, Aug 05, 2009 at 07:12:31AM -0400, Christoph Hellwig wrote:
> On Wed, Aug 05, 2009 at 11:36:43AM +0200, Andi Kleen wrote:
> > 
> > Enable removing of corrupted pages through truncation
> > for a bunch of file systems: ext*, xfs, gfs2, ocfs2, ntfs
> > These should cover most server needs.
> > 
> > I chose the set of migration aware file systems for this
> > for now, assuming they have been especially audited.
> > But in general it should be safe for all file systems
> > on the data area that support read/write and truncate.
> > 
> > Caveat: the hardware error handler does not take i_mutex
> > for now before calling the truncate function. Is that ok?
> 
> It will probably need locking, e.g. the iolock in XFS.  I'll
> need to take a look at the actual implementation of
> generic_error_remove_page to make sense of this.

Thanks for the review.

It just calls the lower end of the truncate path.

http://git.kernel.org/?p=linux/kernel/git/ak/linux-mce-2.6.git;a=commitdiff;h=b5d3322870b0f6e369809674d2c73857fd6ef480

and

http://git.kernel.org/?p=linux/kernel/git/ak/linux-mce-2.6.git;a=commitdiff;h=4c2df4fa9e4687bde815883fabc602ccc5961272

Is that ok? It should be roughly the same as normal truncate does,
except it doesn't take i_mutex currently.

We're careful to not do it for non regular inodes.

> 
> Is there any way for us to test this functionality without introducing
> real hardware problems?

Yes, there are three different injectors to chose from :)

The easiest one is usually the madvise(MADV_POISON) injector.

Just map a suitable page and

There's a test program in 

http://git.kernel.org/?p=utils/cpu/mce/mce-test.git;a=blob;f=tsrc/tinjpage.c;h=954e1edab765d1c141f693ae9767ba9d5491c1aa;hb=HEAD

that can be extended for new tests.

-Andi

-- 
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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Hidehiro Kawai]

Hi,

Andi Kleen wrote:

> Index: linux/fs/ext3/inode.c
> ===================================================================
> --- linux.orig/fs/ext3/inode.c
> +++ linux/fs/ext3/inode.c
> @@ -1819,6 +1819,7 @@ static const struct address_space_operat
>  	.direct_IO		= ext3_direct_IO,
>  	.migratepage		= buffer_migrate_page,
>  	.is_partially_uptodate  = block_is_partially_uptodate,
> +	.error_remove_page	= generic_error_remove_page,
>  };

(I'm sorry if I'm missing the point.)

If my understanding is correct, the following scenario can happen:

1. An uncorrected error on a dirty page cache page is detected by
   memory scrubbing
2. Kernel unmaps and truncates the page to recover from the error
3. An application reads data from the file location corresponding
   to the truncated page
   ==> Old or garbage data will be read into a new page cache page
4. The application modifies the data and write back it to the disk
5. The file will corrurpt!

(Yes, the application is wrong to not do the right thing, i.e. fsync,
 but it's not user's fault!)

A similar data corruption can be caused by a write I/O error,
because dirty flag is cleared even if the page couldn't be written
to the disk.

However, we have a way to avoid this kind of data corruption at
least for ext3.  If we mount an ext3 filesystem with data=ordered
and data_err=abort, all I/O errors on file data block belonging to
the committing transaction are checked.  When I/O error is found,
abort journaling and remount the filesystem with read-only to
prevent further updates.  This kind of feature is very important
for mission critical systems.

If we merge this patch, we would face the data corruption problem
again.

I think there are three options,

(1) drop this patch
(2) merge this patch with new panic_on_dirty_page_cache_corruption
    sysctl
(3) implement a more sophisticated error_remove_page function
  
>  static const struct address_space_operations ext3_writeback_aops = {
> @@ -1834,6 +1835,7 @@ static const struct address_space_operat
>  	.direct_IO		= ext3_direct_IO,
>  	.migratepage		= buffer_migrate_page,
>  	.is_partially_uptodate  = block_is_partially_uptodate,
> +	.error_remove_page	= generic_error_remove_page,
>  };

The writeback case would be OK. It's not much different from the I/O
error case.

>  static const struct address_space_operations ext3_journalled_aops = {
> @@ -1848,6 +1850,7 @@ static const struct address_space_operat
>  	.invalidatepage		= ext3_invalidatepage,
>  	.releasepage		= ext3_releasepage,
>  	.is_partially_uptodate  = block_is_partially_uptodate,
> +	.error_remove_page	= generic_error_remove_page,
>  };
>  
>  void ext3_set_aops(struct inode *inode)

I'm not sure about the journalled case.  I'm going to take a look at
it later.

Best regards,
-- 
Hidehiro Kawai
Hitachi, Systems Development Laboratory
Linux Technology Center

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Wu Fengguang]

Hi Hidehiro,

On Mon, Aug 10, 2009 at 02:36:01PM +0800, Hidehiro Kawai wrote:
> Hi,
> 
> Andi Kleen wrote:
> 
> > Index: linux/fs/ext3/inode.c
> > ===================================================================
> > --- linux.orig/fs/ext3/inode.c
> > +++ linux/fs/ext3/inode.c
> > @@ -1819,6 +1819,7 @@ static const struct address_space_operat
> >  	.direct_IO		= ext3_direct_IO,
> >  	.migratepage		= buffer_migrate_page,
> >  	.is_partially_uptodate  = block_is_partially_uptodate,
> > +	.error_remove_page	= generic_error_remove_page,
> >  };
> 
> (I'm sorry if I'm missing the point.)
> 
> If my understanding is correct, the following scenario can happen:
> 
> 1. An uncorrected error on a dirty page cache page is detected by
>    memory scrubbing
> 2. Kernel unmaps and truncates the page to recover from the error
> 3. An application reads data from the file location corresponding
>    to the truncated page
>    ==> Old or garbage data will be read into a new page cache page
> 4. The application modifies the data and write back it to the disk
> 5. The file will corrurpt!
> 
> (Yes, the application is wrong to not do the right thing, i.e. fsync,
>  but it's not user's fault!)

Right. Note that the data has already been corrupted and the above
scenario can be called as re-corruption. We set AS_EIO to trigger some
IO reporting mechanism so that it won't corrupt *silently*.

> A similar data corruption can be caused by a write I/O error,
> because dirty flag is cleared even if the page couldn't be written
> to the disk.

Yes.

> However, we have a way to avoid this kind of data corruption at
> least for ext3.  If we mount an ext3 filesystem with data=ordered
> and data_err=abort, all I/O errors on file data block belonging to
> the committing transaction are checked.  When I/O error is found,
> abort journaling and remount the filesystem with read-only to
> prevent further updates.  This kind of feature is very important
> for mission critical systems.

Agreed. We also set PG_error, which should be enough to trigger such
remount?

> If we merge this patch, we would face the data corruption problem
> again.
> 
> I think there are three options,
> 
> (1) drop this patch
> (2) merge this patch with new panic_on_dirty_page_cache_corruption
>     sysctl
> (3) implement a more sophisticated error_remove_page function

In fact we proposed a patch for preventing the re-corruption case, see

        http://lkml.org/lkml/2009/6/11/294

However it is hard to answer the (policy) question "How sticky should
the EIO bit remain?".

> >  static const struct address_space_operations ext3_writeback_aops = {
> > @@ -1834,6 +1835,7 @@ static const struct address_space_operat
> >  	.direct_IO		= ext3_direct_IO,
> >  	.migratepage		= buffer_migrate_page,
> >  	.is_partially_uptodate  = block_is_partially_uptodate,
> > +	.error_remove_page	= generic_error_remove_page,
> >  };
> 
> The writeback case would be OK. It's not much different from the I/O
> error case.
> 
> >  static const struct address_space_operations ext3_journalled_aops = {
> > @@ -1848,6 +1850,7 @@ static const struct address_space_operat
> >  	.invalidatepage		= ext3_invalidatepage,
> >  	.releasepage		= ext3_releasepage,
> >  	.is_partially_uptodate  = block_is_partially_uptodate,
> > +	.error_remove_page	= generic_error_remove_page,
> >  };
> >  
> >  void ext3_set_aops(struct inode *inode)
> 
> I'm not sure about the journalled case.  I'm going to take a look at
> it later.

Thanks,
Fengguang

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Hidehiro Kawai]

Wu Fengguang wrote:

>>However, we have a way to avoid this kind of data corruption at
>>least for ext3.  If we mount an ext3 filesystem with data=ordered
>>and data_err=abort, all I/O errors on file data block belonging to
>>the committing transaction are checked.  When I/O error is found,
>>abort journaling and remount the filesystem with read-only to
>>prevent further updates.  This kind of feature is very important
>>for mission critical systems.
> 
> Agreed. We also set PG_error, which should be enough to trigger such
> remount?

ext3 doesn't check PG_error.  Maybe we need to do:

1. trylock_buffer()
2. if step 1. succeeds, then clear_buffer_dirty(),
   clear_buffer_uptodate(), and set_buffer_write_io_error()

Note that we can't truncate the corrupted page until the error
check is done by kjournald.
 
>>If we merge this patch, we would face the data corruption problem
>>again.
>>
>>I think there are three options,
>>
>>(1) drop this patch
>>(2) merge this patch with new panic_on_dirty_page_cache_corruption
>>    sysctl
>>(3) implement a more sophisticated error_remove_page function
> 
> In fact we proposed a patch for preventing the re-corruption case, see
> 
>         http://lkml.org/lkml/2009/6/11/294
> 
> However it is hard to answer the (policy) question "How sticky should
> the EIO bit remain?".

It's a good approach!  This approach may also solve my concern,
the re-corruption issue caused by transient IO errors.

But I also think it needs a bit more consideration.  For example,
if the application has the valid data in the user space buffer,
it would try to re-write it after detecting an IO error from the
previous write.  In this case, we should clear the sticky error flag.
 
Thanks,
-- 
Hidehiro Kawai
Hitachi, Systems Development Laboratory
Linux Technology Center

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Andi Kleen]

On Tue, Aug 11, 2009 at 12:48:36PM +0900, Hidehiro Kawai wrote:
> Wu Fengguang wrote:
> 
> >>However, we have a way to avoid this kind of data corruption at
> >>least for ext3.  If we mount an ext3 filesystem with data=ordered
> >>and data_err=abort, all I/O errors on file data block belonging to
> >>the committing transaction are checked.  When I/O error is found,
> >>abort journaling and remount the filesystem with read-only to
> >>prevent further updates.  This kind of feature is very important
> >>for mission critical systems.
> > 
> > Agreed. We also set PG_error, which should be enough to trigger such
> > remount?
> 
> ext3 doesn't check PG_error.  Maybe we need to do:

When we truncate the page it's gone so there's no page to set PG_error 
on.

-Andi
-- 
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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Wu Fengguang]

On Tue, Aug 11, 2009 at 11:48:36AM +0800, Hidehiro Kawai wrote:
> Wu Fengguang wrote:
> > In fact we proposed a patch for preventing the re-corruption case, see
> > 
> >         http://lkml.org/lkml/2009/6/11/294
> > 
> > However it is hard to answer the (policy) question "How sticky should
> > the EIO bit remain?".
> 
> It's a good approach!  This approach may also solve my concern,
> the re-corruption issue caused by transient IO errors.
> 
> But I also think it needs a bit more consideration.  For example,
> if the application has the valid data in the user space buffer,
> it would try to re-write it after detecting an IO error from the
> previous write.  In this case, we should clear the sticky error flag.

Yes, and maybe more than that. The IO error issue really deserves an
independent work, which will inevitably involve lots of discussions
with lots of people.

For the data re-corruption problem, "vm.memory_failure_recovery = 0"
should be the most clean workaround for now. Can we settle with that?
Our goal for this initial hwpoison implementation is to achieve good
coverage (not necessarily every possible case :).

Thanks,
Fengguang

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Andi Kleen]

Hi,

> If my understanding is correct, the following scenario can happen:

Yes it can happen.

> 
> 1. An uncorrected error on a dirty page cache page is detected by
>    memory scrubbing
> 2. Kernel unmaps and truncates the page to recover from the error
> 3. An application reads data from the file location corresponding
>    to the truncated page
>    ==> Old or garbage data will be read into a new page cache page

The problem currently is that the error is not sticky enough and
doesn't stay around long enough. It gets reported once,
but not in later IO operations.

However it's a generic problem not unique to hwpoison. Me 
and Fengguang went through the error propagation as our test program
triggered the problem and we looked like it was really a generic problem,
not unique to hardware poison (e.g. the IO error handling 
on metadata has exactly the same problem)

And redesigning VFS IO error reporting was a bit of of scope for hwpoison.
So we decided to not be better than a normal IO error here for now.

An application that handles current IO errors correctly will
also also handle hwpoison IO errors correctly. And application
that doesn't handle current IO errors correctly will also
not necessarily handle hwpoison correctly (it's not better and not worse)
So the hwpoison errors are pretty much the same as the normal IO
errors.

The normal error path probably needs some improvements, in particular
the address space EIO error error likely needs to be more sticky
than it is today.

An application has to handle the error on the first strike.

That is something that could be improved in the VFS -- although I fear
any improvements here could also break compatibility. I don't think
it's a blocker on hwpoison for now. It needs more design
effort and thinking (e.g. likely the address space IO error
bit should be separated into multiple bits)

Perhaps you're interested in working on this?

> 4. The application modifies the data and write back it to the disk
> 5. The file will corrurpt!
> 
> (Yes, the application is wrong to not do the right thing, i.e. fsync,
>  but it's not user's fault!)
> 
> A similar data corruption can be caused by a write I/O error,
> because dirty flag is cleared even if the page couldn't be written
> to the disk.
> 
> However, we have a way to avoid this kind of data corruption at
> least for ext3.  If we mount an ext3 filesystem with data=ordered
> and data_err=abort, all I/O errors on file data block belonging to
> the committing transaction are checked.  When I/O error is found,
> abort journaling and remount the filesystem with read-only to
> prevent further updates.  This kind of feature is very important
> for mission critical systems.

Well it sounds like a potentially useful enhancement to ext3 (or ext4).

One issue is that the default is not ordered anymore since
Linus changed the default.

I'm sure other enhancements for IO errors could be done too.
Some of the file systems also handle them still quite poorly (e.g. btrfs)

But again I don't think it's a blocker for hwpoison.

> I think there are three options,
> 
> (1) drop this patch
> (2) merge this patch with new panic_on_dirty_page_cache_corruption
>     sysctl
> (3) implement a more sophisticated error_remove_page function

(4) accept that hwpoison error handling is not better and not worse than normal
IO error handling.

We opted for (4).


-Andi
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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Hidehiro Kawai]

Andi Kleen wrote:

>>1. An uncorrected error on a dirty page cache page is detected by
>>   memory scrubbing
>>2. Kernel unmaps and truncates the page to recover from the error
>>3. An application reads data from the file location corresponding
>>   to the truncated page
>>   ==> Old or garbage data will be read into a new page cache page
> 
> The problem currently is that the error is not sticky enough and
> doesn't stay around long enough. It gets reported once,
> but not in later IO operations.
> 
> However it's a generic problem not unique to hwpoison. Me 

Yes, it's a generic problem, and introducing a sticky error flag
is one of the approach to solve the problem.  I think it is a good
approach because it doesn't depend on individual filesystems.

> And application
> that doesn't handle current IO errors correctly will also
> not necessarily handle hwpoison correctly (it's not better and not worse)

This is my main concern.  I'd like to prevent re-corruption even if
applications don't have good manners.

As for usual I/O error, ext3/4 can now do it by using data=ordered and
data_err=abort mount options.  Moreover, if you mount the ext3/4
filesystem with the additional errors=panic option, kernel gets
panic on write error instead of read-only remount.  Customers
who regard data integrity is very important require these features.

But this patch (PATCH 16/19) introduce this problem again, because
it doesn't provide a way to shut out further writes to the fs.
Of course, we can do it by setting tolerant level to 0 or
memory_failure_recovery to 0.  But it would be overkill.
That is why I suggested this:
>>(2) merge this patch with new panic_on_dirty_page_cache_corruption
>>    sysctl


> That is something that could be improved in the VFS -- although I fear
> any improvements here could also break compatibility. I don't think
> it's a blocker on hwpoison for now. It needs more design
> effort and thinking (e.g. likely the address space IO error
> bit should be separated into multiple bits)
> 
> Perhaps you're interested in working on this?

Yes.  Transient IO errors have a potential for causing re-corruption
problem.  Now ext3/4 provide ways to prevent it, but not the other
filesystems.  We would need a generic way.
 
>>4. The application modifies the data and write back it to the disk
>>5. The file will corrurpt!
>>
>>(Yes, the application is wrong to not do the right thing, i.e. fsync,
>> but it's not user's fault!)
>>
>>A similar data corruption can be caused by a write I/O error,
>>because dirty flag is cleared even if the page couldn't be written
>>to the disk.
>>
>>However, we have a way to avoid this kind of data corruption at
>>least for ext3.  If we mount an ext3 filesystem with data=ordered
>>and data_err=abort, all I/O errors on file data block belonging to
>>the committing transaction are checked.  When I/O error is found,
>>abort journaling and remount the filesystem with read-only to
>>prevent further updates.  This kind of feature is very important
>>for mission critical systems.
> 
> Well it sounds like a potentially useful enhancement to ext3 (or ext4).
> 
> One issue is that the default is not ordered anymore since
> Linus changed the default.

Yes, but what is important is whether the system provides
such feature or not.

> I'm sure other enhancements for IO errors could be done too.
> Some of the file systems also handle them still quite poorly (e.g. btrfs)
> 
> But again I don't think it's a blocker for hwpoison.

Unfortunately, it can be a blocker.  As I stated, we can block the
possible re-corruption caused by transient IO errors on ext3/4
filesystems.  But applying this patch (PATCH 16/19), re-corruption
can happen even if we use data=ordered, data_err=abort and
errors=panic mount options.

So...

>>I think there are three options,
>>
>>(1) drop this patch
>>(2) merge this patch with new panic_on_dirty_page_cache_corruption
>>    sysctl
>>(3) implement a more sophisticated error_remove_page function
> 
> (4) accept that hwpoison error handling is not better and not worse than normal
> IO error handling.
> 
> We opted for (4).

Could you consider adopting (2) or (3)?  Fengguang's sticky EIO
approach (http://lkml.org/lkml/2009/6/11/294) is also OK.
I hope HWPOISON patches are merged into 2.6.32.  So (2) is the
best answer for me, because it's simple and less intrusive.

Thanks,
-- 
Hidehiro Kawai
Hitachi, Systems Development Laboratory
Linux Technology Center

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Andi Kleen]

On Tue, Aug 11, 2009 at 12:50:59PM +0900, Hidehiro Kawai wrote:
> > And application
> > that doesn't handle current IO errors correctly will also
> > not necessarily handle hwpoison correctly (it's not better and not worse)
> 
> This is my main concern.  I'd like to prevent re-corruption even if
> applications don't have good manners.

I don't think there's much we can do if the application doesn't
check for IO errors properly. What would you do if it doesn't
check for IO errors at all? If it checks for IO errors it simply
has to check for them on all IO operations -- if they do 
they will detect hwpoison errors correctly too.

> As for usual I/O error, ext3/4 can now do it by using data=ordered and
> data_err=abort mount options.  Moreover, if you mount the ext3/4
> filesystem with the additional errors=panic option, kernel gets
> panic on write error instead of read-only remount.  Customers
> who regard data integrity is very important require these features.

Well they can also set vm.memory_failure_recovery = 0 then if they don't
care about their uptime. 

> That is why I suggested this:
> >>(2) merge this patch with new panic_on_dirty_page_cache_corruption

You probably mean panic_on_non_anonymous_dirty_page_cache
Normally anonymous memory is dirty.

> >>    sysctl

It's unclear to me this special mode is really desirable.
Does it bring enough value to the user to justify the complexity
of another exotic option?  The case is relatively exotic,
as in dirty write cache that is mapped to a file.

Try to explain it in documentation and you see how ridiculous it sounds; u
it simply doesn't have clean semantics

("In case you have applications with broken error IO handling on
your mission critical system ...") 

> > I'm sure other enhancements for IO errors could be done too.
> > Some of the file systems also handle them still quite poorly (e.g. btrfs)
> > 
> > But again I don't think it's a blocker for hwpoison.
> 
> Unfortunately, it can be a blocker.  As I stated, we can block the
> possible re-corruption caused by transient IO errors on ext3/4
> filesystems.  But applying this patch (PATCH 16/19), re-corruption
> can happen even if we use data=ordered, data_err=abort and
> errors=panic mount options.

We don't corrupt data on disk. Applications
that don't check for IO errors correctly may see stale data
from the same file on disk though.

This can happen in all the cases you listed above except for panic-on-error.

If you want panic-on-error behaviour simply set vm.memory_failure_recovery = 0


> > (4) accept that hwpoison error handling is not better and not worse than normal
> > IO error handling.
> > 
> > We opted for (4).
> 
> Could you consider adopting (2) or (3)?  Fengguang's sticky EIO
> approach (http://lkml.org/lkml/2009/6/11/294) is also OK.

I believe redesigned IO error handling does not belong in the 
core hwpoison patchkit. It's big enough as it is and I consider it frozen
unless fatal bugs are found -- and frankly this is not a fatal 
error in my estimation.

If you want to have improved IO error handling feel free to
submit it separately. I agree this area could use some work.
But it probably needs more design work first.

-Andi

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Hidehiro Kawai]

Andi Kleen wrote:

> On Tue, Aug 11, 2009 at 12:50:59PM +0900, Hidehiro Kawai wrote:
> 
>>>And application
>>>that doesn't handle current IO errors correctly will also
>>>not necessarily handle hwpoison correctly (it's not better and not worse)
>>
>>This is my main concern.  I'd like to prevent re-corruption even if
>>applications don't have good manners.
> 
> I don't think there's much we can do if the application doesn't
> check for IO errors properly. What would you do if it doesn't
> check for IO errors at all? If it checks for IO errors it simply
> has to check for them on all IO operations -- if they do 
> they will detect hwpoison errors correctly too.

I believe it's not uncommon for applications to do buffered write
and then exit without fsync().  And I think it's difficult to
preclude such applications and commands from the system perfectly.
 
>>That is why I suggested this:
>>
>>>>(2) merge this patch with new panic_on_dirty_page_cache_corruption
>>>>    sysctl
> 
> You probably mean panic_on_non_anonymous_dirty_page_cache
> Normally anonymous memory is dirty.

Yes, and sorry for my ambiguous description.  I used the word "cache"
to intend to not include anonymous pages.
 
> It's unclear to me this special mode is really desirable.
> Does it bring enough value to the user to justify the complexity
> of another exotic option?  The case is relatively exotic,
> as in dirty write cache that is mapped to a file.
> 
> Try to explain it in documentation and you see how ridiculous it sounds; u
> it simply doesn't have clean semantics
> 
> ("In case you have applications with broken error IO handling on
> your mission critical system ...") 

Generally, dropping unwritten dirty page caches is considered to be
risky.  So the "panic on IO error" policy has been used as usual
practice for some systems.  I just suggested that we adopted
this policy into machine check errors. 

vm.memory_failure_recovery satisfies my minimal requirement.
It's OK at this stage, but I'd like to improve this in the future.

Another option is to introduce "ignore all" policy instead of
panicking at the beginig of memory_failure().  Perhaps it finally
causes SRAR machine check, and then kernel will panic or a process
will be killed.  Anyway, this is a topic for the next stage.
 
>>>(4) accept that hwpoison error handling is not better and not worse than normal
>>>IO error handling.
>>>
>>>We opted for (4).
>>
>>Could you consider adopting (2) or (3)?  Fengguang's sticky EIO
>>approach (http://lkml.org/lkml/2009/6/11/294) is also OK.
> 
> I believe redesigned IO error handling does not belong in the 
> core hwpoison patchkit.

I agree.
 
> If you want to have improved IO error handling feel free to
> submit it separately. I agree this area could use some work.
> But it probably needs more design work first.

Well, this patch set itself looks good to me.
I also looked into the other patches, I couldn't find any
problems (although I'm not good judge of reviewing).

Reviewed-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>

Thanks,
-- 
Hidehiro Kawai
Hitachi, Systems Development Laboratory
Linux Technology Center



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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Andi Kleen]

On Wed, Aug 12, 2009 at 11:49:56AM +0900, Hidehiro Kawai wrote:
> > I don't think there's much we can do if the application doesn't
> > check for IO errors properly. What would you do if it doesn't
> > check for IO errors at all? If it checks for IO errors it simply
> > has to check for them on all IO operations -- if they do 
> > they will detect hwpoison errors correctly too.
> 
> I believe it's not uncommon for applications to do buffered write
> and then exit without fsync().  And I think it's difficult to
> preclude such applications and commands from the system perfectly.

That's true, but for anything mission critical you would expect them
to use some transactional mechanism, either with O_SYNC or fsync().
Otherwise they always risk data loss anyways.

> > It's unclear to me this special mode is really desirable.
> > Does it bring enough value to the user to justify the complexity
> > of another exotic option?  The case is relatively exotic,
> > as in dirty write cache that is mapped to a file.
> > 
> > Try to explain it in documentation and you see how ridiculous it sounds; u
> > it simply doesn't have clean semantics
> > 
> > ("In case you have applications with broken error IO handling on
> > your mission critical system ...") 
> 
> Generally, dropping unwritten dirty page caches is considered to be
> risky.  So the "panic on IO error" policy has been used as usual
> practice for some systems.  I just suggested that we adopted
> this policy into machine check errors. 

Hmm, what we could possibly do -- as followon patches -- would be to
let error_remove_page check the per file system panic-on-io-error
super block setting for dirty pages and panic in this case too.  
Unfortunately this setting is currently per file system, not generic,
so it would need to be a fs specific check (or the flag would need
to be moved into a generic fs superblock field first)

I think that would be relatively clean semantics wise. Would you be 
interested in working on patches for that? 

> Another option is to introduce "ignore all" policy instead of
> panicking at the beginig of memory_failure().  Perhaps it finally
> causes SRAR machine check, and then kernel will panic or a process
> will be killed.  Anyway, this is a topic for the next stage.

The problem is memory_failure() would then need to start distingushing
between AR=1 and AR=0 which it doesn't today.

It could be done, but would need some more work. 

> > If you want to have improved IO error handling feel free to
> > submit it separately. I agree this area could use some work.
> > But it probably needs more design work first.
> 
> Well, this patch set itself looks good to me.
> I also looked into the other patches, I couldn't find any
> problems (although I'm not good judge of reviewing).
> 
> Reviewed-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>

Thanks for your review and your comments.

-Andi
-- 
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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Hidehiro Kawai]

Andi Kleen wrote:

>>Generally, dropping unwritten dirty page caches is considered to be
>>risky.  So the "panic on IO error" policy has been used as usual
>>practice for some systems.  I just suggested that we adopted
>>this policy into machine check errors. 
> 
> Hmm, what we could possibly do -- as followon patches -- would be to
> let error_remove_page check the per file system panic-on-io-error
> super block setting for dirty pages and panic in this case too.  
> Unfortunately this setting is currently per file system, not generic,
> so it would need to be a fs specific check (or the flag would need
> to be moved into a generic fs superblock field first)

A generic setting would be better, so I suggested
panic_on_dirty_page_cache_corruption flag which would be checked
before invoking error_remove_page().  If we check per-filesystem
settings, we might want to notify EIO to the filesystem.
 
> I think that would be relatively clean semantics wise. Would you be 
> interested in working on patches for that? 

Yes. :-)
I will work on this as soon as I come back from summer vacation.

>>Another option is to introduce "ignore all" policy instead of
>>panicking at the beginig of memory_failure().  Perhaps it finally
>>causes SRAR machine check, and then kernel will panic or a process
>>will be killed.  Anyway, this is a topic for the next stage.
> 
> The problem is memory_failure() would then need to start distingushing
> between AR=1 and AR=0 which it doesn't today.
> 
> It could be done, but would need some more work. 

It's my understanding that memory_failure() are never called in
AR=1 case.  Is it wrong?
 
Thanks,
-- 
Hidehiro Kawai
Hitachi, Systems Development Laboratory
Linux Technology Center

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Andi Kleen]

On Wed, Aug 12, 2009 at 06:52:14PM +0900, Hidehiro Kawai wrote:
> Andi Kleen wrote:
> 
> >>Generally, dropping unwritten dirty page caches is considered to be
> >>risky.  So the "panic on IO error" policy has been used as usual
> >>practice for some systems.  I just suggested that we adopted
> >>this policy into machine check errors. 
> > 
> > Hmm, what we could possibly do -- as followon patches -- would be to
> > let error_remove_page check the per file system panic-on-io-error
> > super block setting for dirty pages and panic in this case too.  
> > Unfortunately this setting is currently per file system, not generic,
> > so it would need to be a fs specific check (or the flag would need
> > to be moved into a generic fs superblock field first)
> 
> A generic setting would be better, so I suggested
> panic_on_dirty_page_cache_corruption flag which would be checked
> before invoking error_remove_page().  If we check per-filesystem
> settings, we might want to notify EIO to the filesystem.

You mean remounting ro if that is set?
That makes sense, but I'm not sure how complicated it would be.
I still would prefer to unify it with the file system settings.

> > The problem is memory_failure() would then need to start distingushing
> > between AR=1 and AR=0 which it doesn't today.
> > 
> > It could be done, but would need some more work. 
> 
> It's my understanding that memory_failure() are never called in
> AR=1 case.  Is it wrong?

Today yes, but we don't want to hardcode that assumption. e.g. for IA64
they will definitely need the equivalent of AR=1 handling.

-Andi

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Nick Piggin]

On Tue, Aug 11, 2009 at 09:17:56AM +0200, Andi Kleen wrote:
> On Tue, Aug 11, 2009 at 12:50:59PM +0900, Hidehiro Kawai wrote:
> > > And application
> > > that doesn't handle current IO errors correctly will also
> > > not necessarily handle hwpoison correctly (it's not better and not worse)
> > 
> > This is my main concern.  I'd like to prevent re-corruption even if
> > applications don't have good manners.
> 
> I don't think there's much we can do if the application doesn't
> check for IO errors properly. What would you do if it doesn't
> check for IO errors at all? If it checks for IO errors it simply
> has to check for them on all IO operations -- if they do 
> they will detect hwpoison errors correctly too.

But will quite possibly do the wrong thing: ie. try to re-sync the
same page again, or try to write the page to a new location, etc.

This is the whole problem with -EIO semantics I brought up.
 

> > That is why I suggested this:
> > >>(2) merge this patch with new panic_on_dirty_page_cache_corruption
> 
> You probably mean panic_on_non_anonymous_dirty_page_cache
> Normally anonymous memory is dirty.
> 
> > >>    sysctl
> 
> It's unclear to me this special mode is really desirable.
> Does it bring enough value to the user to justify the complexity
> of another exotic option?  The case is relatively exotic,
> as in dirty write cache that is mapped to a file.
> 
> Try to explain it in documentation and you see how ridiculous it sounds; u
> it simply doesn't have clean semantics
> 
> ("In case you have applications with broken error IO handling on
> your mission critical system ...") 

Not broken error handling. It is very simple: if the application is
assuming EIO is an error with dirty data being sent to disk, rather
than an error with the data itself (which I think may be a common
assumption). Then it could have a problem.

If a database for example tries to write the data to another location
in response to EIO and then record it in a list of failed IOs before
halting the database. Then if it restarts it might try to again try
writing out these failed IOs (eg. give the administrator a chance to
fix IO devices). Completely made up scenario but it is not outlandish
and it would cause bad data corruption.

A mission critical server will *definitely* want to panic on dirty
page corruption, IMO, because by definition they should be able to
tolerate panic. But if they do not know about this change to -EIO
semantics, then it is quite possible to cause problems.

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Andi Kleen]

> page corruption, IMO, because by definition they should be able to
> tolerate panic. But if they do not know about this change to -EIO
> semantics, then it is quite possible to cause problems.

There's no change really. You already have this problem with
any metadata error, which can cause similar trouble.
If the application handles those correctly it will also 
handle hwpoison correctly.

-Andi

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Nick Piggin]

On Wed, Aug 12, 2009 at 10:23:31AM +0200, Andi Kleen wrote:
> > page corruption, IMO, because by definition they should be able to
> > tolerate panic. But if they do not know about this change to -EIO
> > semantics, then it is quite possible to cause problems.
> 
> There's no change really. You already have this problem with
> any metadata error, which can cause similar trouble.
> If the application handles those correctly it will also 
> handle hwpoison correctly.

What do you mean metadata error?

To be clear, we're talking about safety given by a panic on any
memory error, versus safety of this hwpoison code (specifically
which removes dirty pagecache pages as -EIO).

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Andi Kleen]

On Wed, Aug 12, 2009 at 10:46:13AM +0200, Nick Piggin wrote:
> On Wed, Aug 12, 2009 at 10:23:31AM +0200, Andi Kleen wrote:
> > > page corruption, IMO, because by definition they should be able to
> > > tolerate panic. But if they do not know about this change to -EIO
> > > semantics, then it is quite possible to cause problems.
> > 
> > There's no change really. You already have this problem with
> > any metadata error, which can cause similar trouble.
> > If the application handles those correctly it will also 
> > handle hwpoison correctly.
> 
> What do you mean metadata error?

e.g. when there's an write error on the indirect block or any
other fs metadata. This can also cause you to lose data. The error 
reporting also works through the address space like with hwpoison,
so it only gets reported once.

I'm not really against fixing that (make the error more sticky
as Fengguang puts it), but I don't think it needs to be mixed
with hwpoison.

-Andi
-- 
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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Nick Piggin]

On Wed, Aug 12, 2009 at 10:57:27AM +0200, Andi Kleen wrote:
> On Wed, Aug 12, 2009 at 10:46:13AM +0200, Nick Piggin wrote:
> > On Wed, Aug 12, 2009 at 10:23:31AM +0200, Andi Kleen wrote:
> > > > page corruption, IMO, because by definition they should be able to
> > > > tolerate panic. But if they do not know about this change to -EIO
> > > > semantics, then it is quite possible to cause problems.
> > > 
> > > There's no change really. You already have this problem with
> > > any metadata error, which can cause similar trouble.
> > > If the application handles those correctly it will also 
> > > handle hwpoison correctly.
> > 
> > What do you mean metadata error?
> 
> e.g. when there's an write error on the indirect block or any
> other fs metadata. This can also cause you to lose data. The error 
> reporting also works through the address space like with hwpoison,
> so it only gets reported once.

Well, this is also a filesystem issue, but anyway the data typically
does not get thrown out. So a subsequent fsync should be able to
retry.

But if the filesystem can't handle such errors and loses the original
data when there is an IO error in newly dirty metadata, then it's
a problem in the filesystem really isn't it?


> I'm not really against fixing that (make the error more sticky
> as Fengguang puts it), but I don't think it needs to be mixed
> with hwpoison.

I don't know if making it sticky realy "fixes" it. The problem is
different semantics of what EIO means. My example illustrates this.

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Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for migration aware file systems

[Wu Fengguang]

On Wed, Aug 12, 2009 at 05:05:18PM +0800, Nick Piggin wrote:
> On Wed, Aug 12, 2009 at 10:57:27AM +0200, Andi Kleen wrote:
> > On Wed, Aug 12, 2009 at 10:46:13AM +0200, Nick Piggin wrote:
> > > On Wed, Aug 12, 2009 at 10:23:31AM +0200, Andi Kleen wrote:
> > > > > page corruption, IMO, because by definition they should be able to
> > > > > tolerate panic. But if they do not know about this change to -EIO
> > > > > semantics, then it is quite possible to cause problems.
> > > > 
> > > > There's no change really. You already have this problem with
> > > > any metadata error, which can cause similar trouble.
> > > > If the application handles those correctly it will also 
> > > > handle hwpoison correctly.
> > > 
> > > What do you mean metadata error?
> > 
> > e.g. when there's an write error on the indirect block or any
> > other fs metadata. This can also cause you to lose data. The error 
> > reporting also works through the address space like with hwpoison,
> > so it only gets reported once.
> 
> Well, this is also a filesystem issue, but anyway the data typically
> does not get thrown out. So a subsequent fsync should be able to
> retry.

Right. In normal EIO, the data in page cache is still good and
accessible.

> But if the filesystem can't handle such errors and loses the original
> data when there is an IO error in newly dirty metadata, then it's
> a problem in the filesystem really isn't it?

Right, and the fs should report EIO on future sync attempts as long as
the problem sticks.

> > I'm not really against fixing that (make the error more sticky
> > as Fengguang puts it), but I don't think it needs to be mixed
> > with hwpoison.
> 
> I don't know if making it sticky realy "fixes" it. The problem is
> different semantics of what EIO means. My example illustrates this.

Case 1: (re)sync on EIO: sticky EIO will help.

Case 2: read out the data from page cache and rewrite it somewhere.
Sticky EIO is not enough, because here the application assumes the
dirty page is still accessible. In this case, patch
http://lkml.org/lkml/2009/6/11/294 will help. It effectively freezes
the radix tree, so that no new pages will be loaded to replace the 
corrupted data and fake a 'good' one.

Thanks,
Fengguang

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[PATCH] [17/19] HWPOISON: Enable error_remove_page for NFS

[Andi Kleen]

Enable hardware memory error handling for NFS

Truncation of data pages at runtime should be safe in NFS,
even when it doesn't support migration so far.

Cc: Trond.Myklebust@netapp.com

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 fs/nfs/file.c |    1 +
 1 file changed, 1 insertion(+)

Index: linux/fs/nfs/file.c
===================================================================
--- linux.orig/fs/nfs/file.c
+++ linux/fs/nfs/file.c
@@ -480,6 +480,7 @@ const struct address_space_operations nf
 	.releasepage = nfs_release_page,
 	.direct_IO = nfs_direct_IO,
 	.launder_page = nfs_launder_page,
+	.error_remove_page = generic_error_remove_page,
 };
 
 /*

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[PATCH] [18/19] HWPOISON: Add madvise() based injector for hardware poisoned pages v3

[Andi Kleen]

Impact: optional, useful for debugging

Add a new madvice sub command to inject poison for some
pages in a process' address space.  This is useful for
testing the poison page handling.

Open issues:

- This patch allows root to tie up arbitary amounts of memory.
Should this be disabled inside containers?
- There's a small race window between getting the page and injecting.
The patch drops the ref count because otherwise memory_failure
complains about dangling references. In theory with a multi threaded
injector one could inject poison for a process foreign page this way.
Not a serious issue right now.

v2: Use write flag for get_user_pages to make sure to always get
a fresh page
v3: Don't request write mapping (Fengguang Wu)

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 include/asm-generic/mman-common.h |    1 +
 mm/madvise.c                      |   34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

Index: linux/mm/madvise.c
===================================================================
--- linux.orig/mm/madvise.c
+++ linux/mm/madvise.c
@@ -207,6 +207,36 @@ static long madvise_remove(struct vm_are
 	return error;
 }
 
+#ifdef CONFIG_MEMORY_FAILURE
+/*
+ * Error injection support for memory error handling.
+ */
+static int madvise_hwpoison(unsigned long start, unsigned long end)
+{
+	int ret = -EIO;
+	/*
+	 * RED-PEN
+	 * This allows to tie up arbitary amounts of memory.
+	 * Might be a good idea to disable it inside containers even for root.
+	 */
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	for (; start < end; start += PAGE_SIZE) {
+		struct page *p;
+		int ret = get_user_pages(current, current->mm, start, 1,
+						0, 0, &p, NULL);
+		if (ret != 1)
+			return ret;
+		printk(KERN_INFO "Injecting memory failure for page %lx at %lx\n",
+		       page_to_pfn(p), start);
+		/* Ignore return value for now */
+		__memory_failure(page_to_pfn(p), 0, 1);
+		put_page(p);
+	}
+	return ret;
+}
+#endif
+
 static long
 madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
 		unsigned long start, unsigned long end, int behavior)
@@ -307,6 +337,10 @@ SYSCALL_DEFINE3(madvise, unsigned long,
 	int write;
 	size_t len;
 
+#ifdef CONFIG_MEMORY_FAILURE
+	if (behavior == MADV_HWPOISON)
+		return madvise_hwpoison(start, start+len_in);
+#endif
 	if (!madvise_behavior_valid(behavior))
 		return error;
 
Index: linux/include/asm-generic/mman-common.h
===================================================================
--- linux.orig/include/asm-generic/mman-common.h
+++ linux/include/asm-generic/mman-common.h
@@ -34,6 +34,7 @@
 #define MADV_REMOVE	9		/* remove these pages & resources */
 #define MADV_DONTFORK	10		/* don't inherit across fork */
 #define MADV_DOFORK	11		/* do inherit across fork */
+#define MADV_HWPOISON	12		/* poison a page for testing */
 
 /* compatibility flags */
 #define MAP_FILE	0

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[PATCH] [19/19] HWPOISON: Add simple debugfs interface to inject hwpoison on arbitary PFNs

[Andi Kleen]

Useful for some testing scenarios, although specific testing is often
done better through MADV_POISON

This can be done with the x86 level MCE injector too, but this interface
allows it to do independently from low level x86 changes.

Open issues: 

Should be disabled for cgroups.

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---
 mm/Kconfig           |    6 +++++-
 mm/Makefile          |    1 +
 mm/hwpoison-inject.c |   40 ++++++++++++++++++++++++++++++++++++++++
 mm/madvise.c         |    2 +-
 4 files changed, 47 insertions(+), 2 deletions(-)

Index: linux/mm/hwpoison-inject.c
===================================================================
--- /dev/null
+++ linux/mm/hwpoison-inject.c
@@ -0,0 +1,40 @@
+/* Inject a hwpoison memory failure on a arbitary pfn */
+#include <linux/module.h>
+#include <linux/debugfs.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+
+static struct dentry *hwpoison_dir, *corrupt_pfn;
+
+static int hwpoison_inject(void *data, u64 val)
+{
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	printk(KERN_INFO "Injecting memory failure at pfn %Lx\n", val);
+	return __memory_failure(val, 18, 0);
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(hwpoison_fops, NULL, hwpoison_inject, "%lli\n");
+
+static void pfn_inject_exit(void)
+{
+	if (hwpoison_dir)
+		debugfs_remove_recursive(hwpoison_dir);
+}
+
+static int pfn_inject_init(void)
+{
+	hwpoison_dir = debugfs_create_dir("hwpoison", NULL);
+	if (hwpoison_dir == NULL)
+		return -ENOMEM;
+	corrupt_pfn = debugfs_create_file("corrupt-pfn", 0600, hwpoison_dir,
+					  NULL, &hwpoison_fops);
+	if (corrupt_pfn == NULL) {
+		pfn_inject_exit();
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+module_init(pfn_inject_init);
+module_exit(pfn_inject_exit);
Index: linux/mm/Kconfig
===================================================================
--- linux.orig/mm/Kconfig
+++ linux/mm/Kconfig
@@ -236,12 +236,16 @@ config DEFAULT_MMAP_MIN_ADDR
 config MEMORY_FAILURE
 	depends on MMU
 	depends on X86_MCE
-	bool "Enable memory failure recovery"
+	bool "Enable recovery from hardware memory errors"
 	help
 	  Enables code to recover from some memory failures on systems
 	  with MCA recovery. This allows a system to continue running
 	  even when some of its memory has uncorrected errors.
 
+config HWPOISON_INJECT
+	tristate "Poison pages injector"
+	depends on MEMORY_FAILURE && DEBUG_KERNEL
+
 config NOMMU_INITIAL_TRIM_EXCESS
 	int "Turn on mmap() excess space trimming before booting"
 	depends on !MMU
Index: linux/mm/Makefile
===================================================================
--- linux.orig/mm/Makefile
+++ linux/mm/Makefile
@@ -41,5 +41,6 @@ endif
 obj-$(CONFIG_QUICKLIST) += quicklist.o
 obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o page_cgroup.o
 obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o
+obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o
 obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
 obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o
Index: linux/mm/madvise.c
===================================================================
--- linux.orig/mm/madvise.c
+++ linux/mm/madvise.c
@@ -213,7 +213,7 @@ static long madvise_remove(struct vm_are
  */
 static int madvise_hwpoison(unsigned long start, unsigned long end)
 {
-	int ret = -EIO;
+	int ret = 0;
 	/*
 	 * RED-PEN
 	 * This allows to tie up arbitary amounts of memory.

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