[PATCH 26/30] mm/memory-failure: Stop setting the folio error flag

[PATCH 26/30] mm/memory-failure: Stop setting the folio error flag

[Matthew Wilcox (Oracle)]

Nobody checks the error flag any more, so setting it accomplishes
nothing.  Remove the obsolete parts of this comment; it hasn't
been true since errseq_t was used to track writeback errors in 2017.

Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: linux-mm@kvack.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/memory-failure.c | 29 -----------------------------
 1 file changed, 29 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index ec30611ec5ad..e065dd9be21e 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1092,7 +1092,6 @@ static int me_pagecache_dirty(struct page_state *ps, struct page *p)
 {
 	struct address_space *mapping = page_mapping(p);
 
-	SetPageError(p);
 	/* TBD: print more information about the file. */
 	if (mapping) {
 		/*
@@ -1100,34 +1099,6 @@ static int me_pagecache_dirty(struct page_state *ps, struct page *p)
 		 * 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 between 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);
 	}
-- 
2.43.0

[PATCH 30/30] mm: Remove PG_error

[Matthew Wilcox (Oracle)]

The PG_error bit is now unused; delete it and free up a bit in
page->flags.

Cc: linux-mm@kvack.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/proc/page.c                         | 1 -
 include/linux/page-flags.h             | 6 +-----
 include/trace/events/mmflags.h         | 1 -
 include/uapi/linux/kernel-page-flags.h | 2 +-
 mm/migrate.c                           | 2 --
 5 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/fs/proc/page.c b/fs/proc/page.c
index 2fb64bdb64eb..05eb6617668a 100644
--- a/fs/proc/page.c
+++ b/fs/proc/page.c
@@ -186,7 +186,6 @@ u64 stable_page_flags(const struct page *page)
 #endif
 
 	u |= kpf_copy_bit(k, KPF_LOCKED,	PG_locked);
-	u |= kpf_copy_bit(k, KPF_ERROR,		PG_error);
 	u |= kpf_copy_bit(k, KPF_DIRTY,		PG_dirty);
 	u |= kpf_copy_bit(k, KPF_UPTODATE,	PG_uptodate);
 	u |= kpf_copy_bit(k, KPF_WRITEBACK,	PG_writeback);
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index a9a6e0f7367e..931820c8ea95 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -71,8 +71,6 @@
  * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
  * file-backed pagecache (see mm/vmscan.c).
  *
- * PG_error is set to indicate that an I/O error occurred on this page.
- *
  * PG_arch_1 is an architecture specific page state bit.  The generic code
  * guarantees that this bit is cleared for a page when it first is entered into
  * the page cache.
@@ -108,7 +106,6 @@ enum pageflags {
 	PG_waiters,		/* Page has waiters, check its waitqueue. Must be bit #7 and in the same byte as "PG_locked" */
 	PG_active,
 	PG_workingset,
-	PG_error,
 	PG_owner_priv_1,	/* Owner use. If pagecache, fs may use*/
 	PG_arch_1,
 	PG_reserved,
@@ -188,7 +185,7 @@ enum pageflags {
 	 */
 
 	/* At least one page in this folio has the hwpoison flag set */
-	PG_has_hwpoisoned = PG_error,
+	PG_has_hwpoisoned = PG_active,
 	PG_large_rmappable = PG_workingset, /* anon or file-backed */
 };
 
@@ -511,7 +508,6 @@ static inline int TestClearPage##uname(struct page *page) { return 0; }
 
 __PAGEFLAG(Locked, locked, PF_NO_TAIL)
 FOLIO_FLAG(waiters, FOLIO_HEAD_PAGE)
-PAGEFLAG(Error, error, PF_NO_TAIL) TESTCLEARFLAG(Error, error, PF_NO_TAIL)
 PAGEFLAG(Referenced, referenced, PF_HEAD)
 	TESTCLEARFLAG(Referenced, referenced, PF_HEAD)
 	__SETPAGEFLAG(Referenced, referenced, PF_HEAD)
diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index e46d6e82765e..4f2a18a11970 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -100,7 +100,6 @@
 #define __def_pageflag_names						\
 	DEF_PAGEFLAG_NAME(locked),					\
 	DEF_PAGEFLAG_NAME(waiters),					\
-	DEF_PAGEFLAG_NAME(error),					\
 	DEF_PAGEFLAG_NAME(referenced),					\
 	DEF_PAGEFLAG_NAME(uptodate),					\
 	DEF_PAGEFLAG_NAME(dirty),					\
diff --git a/include/uapi/linux/kernel-page-flags.h b/include/uapi/linux/kernel-page-flags.h
index 6f2f2720f3ac..ff8032227876 100644
--- a/include/uapi/linux/kernel-page-flags.h
+++ b/include/uapi/linux/kernel-page-flags.h
@@ -7,7 +7,7 @@
  */
 
 #define KPF_LOCKED		0
-#define KPF_ERROR		1
+#define KPF_ERROR		1	/* Now unused */
 #define KPF_REFERENCED		2
 #define KPF_UPTODATE		3
 #define KPF_DIRTY		4
diff --git a/mm/migrate.c b/mm/migrate.c
index 2594a00279f1..c0acb52ac4e4 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -561,8 +561,6 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio)
 {
 	int cpupid;
 
-	if (folio_test_error(folio))
-		folio_set_error(newfolio);
 	if (folio_test_referenced(folio))
 		folio_set_referenced(newfolio);
 	if (folio_test_uptodate(folio))
-- 
2.43.0