[PATCH V5 0/2] JFS: Implement migrate_folio for jfs_metapage_aops

[PATCH V5 0/2] JFS: Implement migrate_folio for jfs_metapage_aops

[Shivank Garg]

This patch addresses a warning that occurs during memory compaction due
to JFS's missing migrate_folio operation. The warning was introduced by
commit 7ee3647243e5 ("migrate: Remove call to ->writepage") which added
explicit warnings when filesystem don't implement migrate_folio.

The syzbot reported following [1]:
  jfs_metapage_aops does not implement migrate_folio
  WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline]
  WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
  Modules linked in:
  CPU: 1 UID: 0 PID: 5861 Comm: syz-executor280 Not tainted 6.15.0-rc1-next-20250411-syzkaller #0 PREEMPT(full) 
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
  RIP: 0010:fallback_migrate_folio mm/migrate.c:953 [inline]
  RIP: 0010:move_to_new_folio+0x70e/0x840 mm/migrate.c:1007

To fix this issue, this series implement metapage_migrate_folio() for JFS
which handles both single and multiple metapages per page configurations.

While most filesystems leverage existing migration implementations like
filemap_migrate_folio(), buffer_migrate_folio_norefs() or buffer_migrate_folio()
(which internally used folio_expected_refs()), JFS's metapage architecture
requires special handling of its private data during migration. To support this,
this series introduce the folio_expected_ref_count(), which calculates
external references to a folio from page/swap cache, private data, and page
table mappings.
This standardized implementation replaces the previous ad-hoc
folio_expected_refs() function and enables JFS to accurately determine whether
a folio has unexpected references before attempting migration.

[1]: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299

Changelogs:
V5 (current):
- Add folio_expected_ref_count() for refcount calculation
- Add details about need of folio_expected_ref_count() for JFS

V4:
- https://lore.kernel.org/all/20250422114000.15003-1-shivankg@amd.com
- Make folio_expected_refs() inline and rename to folio_migration_expected_refs()

V3:
- https://lore.kernel.org/all/20250417060630.197278-1-shivankg@amd.com
- Fix typos

V1/V2:
- https://lore.kernel.org/all/20250413172356.561544-1-shivankg@amd.com
- Implement metapage_migrate_folio() similar to buffer_migrate_folio() but
  specialized to move JFS metapage data

#syz test: https://github.com/shivankgarg98/linux.git 69a58d5260

Shivank Garg (2):
  mm: Add folio_expected_ref_count() for reference count calculation
  jfs: implement migrate_folio for jfs_metapage_aops

 fs/jfs/jfs_metapage.c | 94 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/mm.h    | 55 +++++++++++++++++++++++++
 mm/migrate.c          | 22 ++--------
 3 files changed, 153 insertions(+), 18 deletions(-)

-- 
2.34.1

[PATCH V5 1/2] mm: Add folio_expected_ref_count() for reference count calculation

[Shivank Garg]

Implement folio_expected_ref_count() to calculate expected folio
reference counts from:
- Page/swap cache (1 per page)
- Private data (1)
- Page table mappings (1 per map)

While originally needed for page migration operations, this improved
implementation standardizes reference counting by consolidating all
refcount contributors into a single, reusable function that can benefit
any subsystem needing to detect unexpected references to folios.

The folio_expected_ref_count() returns the sum of these external
references without including any reference the caller itself might hold.
Callers comparing against the actual folio_ref_count() must account for
their own references separately.

Suggested-by: Matthew Wilcox <willy@infradead.org>
Co-developed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Shivank Garg <shivankg@amd.com>
---
 include/linux/mm.h | 55 ++++++++++++++++++++++++++++++++++++++++++++++
 mm/migrate.c       | 22 ++++---------------
 2 files changed, 59 insertions(+), 18 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 68d3dd14b323..1db540bb9381 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2115,6 +2115,61 @@ static inline bool folio_maybe_mapped_shared(struct folio *folio)
 	return folio_test_large_maybe_mapped_shared(folio);
 }
 
+/**
+ * folio_expected_ref_count - calculate the expected folio refcount
+ * @folio: the folio
+ *
+ * Calculate the expected folio refcount, taking references from the pagecache,
+ * swapcache, PG_private and page table mappings into account. Useful in
+ * combination with folio_ref_count() to detect unexpected references (e.g.,
+ * GUP or other temporary references).
+ *
+ * Does currently not consider references from the LRU cache. If the folio
+ * was isolated from the LRU (which is the case during migration or split),
+ * the LRU cache does not apply.
+ *
+ * Calling this function on an unmapped folio -- !folio_mapped() -- that is
+ * locked will return a stable result.
+ *
+ * Calling this function on a mapped folio will not result in a stable result,
+ * because nothing stops additional page table mappings from coming (e.g.,
+ * fork()) or going (e.g., munmap()).
+ *
+ * Calling this function without the folio lock will also not result in a
+ * stable result: for example, the folio might get dropped from the swapcache
+ * concurrently.
+ *
+ * However, even when called without the folio lock or on a mapped folio,
+ * this function can be used to detect unexpected references early (for example,
+ * if it makes sense to even lock the folio and unmap it).
+ *
+ * The caller must add any reference (e.g., from folio_try_get()) it might be
+ * holding itself to the result.
+ *
+ * Returns the expected folio refcount.
+ */
+static inline int folio_expected_ref_count(const struct folio *folio)
+{
+	const int order = folio_order(folio);
+	int ref_count = 0;
+
+	if (WARN_ON_ONCE(folio_test_slab(folio)))
+		return 0;
+
+	if (folio_test_anon(folio)) {
+		/* One reference per page from the swapcache. */
+		ref_count += folio_test_swapcache(folio) << order;
+	} else if (!((unsigned long)folio->mapping & PAGE_MAPPING_FLAGS)) {
+		/* One reference per page from the pagecache. */
+		ref_count += !!folio->mapping << order;
+		/* One reference from PG_private. */
+		ref_count += folio_test_private(folio);
+	}
+
+	/* One reference per page table mapping. */
+	return ref_count + folio_mapcount(folio);
+}
+
 #ifndef HAVE_ARCH_MAKE_FOLIO_ACCESSIBLE
 static inline int arch_make_folio_accessible(struct folio *folio)
 {
diff --git a/mm/migrate.c b/mm/migrate.c
index c80591514e66..67f2bf1eb51e 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -445,20 +445,6 @@ void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
 }
 #endif
 
-static int folio_expected_refs(struct address_space *mapping,
-		struct folio *folio)
-{
-	int refs = 1;
-	if (!mapping)
-		return refs;
-
-	refs += folio_nr_pages(folio);
-	if (folio_test_private(folio))
-		refs++;
-
-	return refs;
-}
-
 /*
  * Replace the folio in the mapping.
  *
@@ -601,7 +587,7 @@ static int __folio_migrate_mapping(struct address_space *mapping,
 int folio_migrate_mapping(struct address_space *mapping,
 		struct folio *newfolio, struct folio *folio, int extra_count)
 {
-	int expected_count = folio_expected_refs(mapping, folio) + extra_count;
+	int expected_count = folio_expected_ref_count(folio) + extra_count + 1;
 
 	if (folio_ref_count(folio) != expected_count)
 		return -EAGAIN;
@@ -618,7 +604,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
 				   struct folio *dst, struct folio *src)
 {
 	XA_STATE(xas, &mapping->i_pages, folio_index(src));
-	int rc, expected_count = folio_expected_refs(mapping, src);
+	int rc, expected_count = folio_expected_ref_count(src) + 1;
 
 	if (folio_ref_count(src) != expected_count)
 		return -EAGAIN;
@@ -749,7 +735,7 @@ static int __migrate_folio(struct address_space *mapping, struct folio *dst,
 			   struct folio *src, void *src_private,
 			   enum migrate_mode mode)
 {
-	int rc, expected_count = folio_expected_refs(mapping, src);
+	int rc, expected_count = folio_expected_ref_count(src) + 1;
 
 	/* Check whether src does not have extra refs before we do more work */
 	if (folio_ref_count(src) != expected_count)
@@ -837,7 +823,7 @@ static int __buffer_migrate_folio(struct address_space *mapping,
 		return migrate_folio(mapping, dst, src, mode);
 
 	/* Check whether page does not have extra refs before we do more work */
-	expected_count = folio_expected_refs(mapping, src);
+	expected_count = folio_expected_ref_count(src) + 1;
 	if (folio_ref_count(src) != expected_count)
 		return -EAGAIN;
 
-- 
2.34.1

[PATCH V5 2/2] jfs: implement migrate_folio for jfs_metapage_aops

[Shivank Garg]

Add the missing migrate_folio operation to jfs_metapage_aops to fix
warnings during memory compaction. These warnings were introduced by
commit 7ee3647243e5 ("migrate: Remove call to ->writepage") which
added explicit warnings when filesystems don't implement migrate_folio.

System reports following warnings:
  jfs_metapage_aops does not implement migrate_folio
  WARNING: CPU: 0 PID: 6870 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline]
  WARNING: CPU: 0 PID: 6870 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007

Implement metapage_migrate_folio() which handles both single and multiple
metapages per page configurations.

Fixes: 35474d52c605 ("jfs: Convert metapage_writepage to metapage_write_folio")
Reported-by: syzbot+8bb6fd945af4e0ad9299@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/67faff52.050a0220.379d84.001b.GAE@google.com
Tested-by: syzbot+8bb6fd945af4e0ad9299@syzkaller.appspotmail.com
Signed-off-by: Shivank Garg <shivankg@amd.com>
---

The commit
e7021e2fe0b4 ("x86/efi: Make efi_enter/leave_mm() use the use_/unuse_temporary_mm() machinery")
is introducing some regression on linux-next, blocking me from testing JFS issue.
https://lore.kernel.org/all/SJ1PR11MB6129E62E3B372932C6B7477FB9BD2@SJ1PR11MB6129.namprd11.prod.outlook.com/

After reverting the above series, the syzcaller did not report any issue with my patch.
Syzbot Test link: https://lore.kernel.org/all/6811f0a8.050a0220.39e3a1.0d08.GAE@google.com/
---
 fs/jfs/jfs_metapage.c | 94 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 94 insertions(+)

diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
index df575a873ec6..f863ba521533 100644
--- a/fs/jfs/jfs_metapage.c
+++ b/fs/jfs/jfs_metapage.c
@@ -15,6 +15,7 @@
 #include <linux/mempool.h>
 #include <linux/seq_file.h>
 #include <linux/writeback.h>
+#include <linux/migrate.h>
 #include "jfs_incore.h"
 #include "jfs_superblock.h"
 #include "jfs_filsys.h"
@@ -151,6 +152,54 @@ static inline void dec_io(struct folio *folio, blk_status_t status,
 		handler(folio, anchor->status);
 }
 
+static int __metapage_migrate_folio(struct address_space *mapping, struct folio *dst,
+				    struct folio *src, enum migrate_mode mode)
+{
+	struct meta_anchor *src_anchor = src->private;
+	struct metapage *mps[MPS_PER_PAGE] = {0};
+	struct metapage *mp;
+	int i, rc;
+
+	for (i = 0; i < MPS_PER_PAGE; i++) {
+		mp = src_anchor->mp[i];
+		if (mp && metapage_locked(mp))
+			return -EAGAIN;
+	}
+
+	rc = filemap_migrate_folio(mapping, dst, src, mode);
+	if (rc != MIGRATEPAGE_SUCCESS)
+		return rc;
+
+	for (i = 0; i < MPS_PER_PAGE; i++) {
+		mp = src_anchor->mp[i];
+		if (!mp)
+			continue;
+		if (unlikely(insert_metapage(dst, mp))) {
+			/* If error, roll-back previosly inserted pages */
+			for (int j = 0 ; j < i; j++) {
+				if (mps[j])
+					remove_metapage(dst, mps[j]);
+			}
+			return -EAGAIN;
+		}
+		mps[i] = mp;
+	}
+
+	/* Update the metapage and remove it from src */
+	for (i = 0; i < MPS_PER_PAGE; i++) {
+		mp = mps[i];
+		if (mp) {
+			int page_offset = mp->data - folio_address(src);
+
+			mp->data = folio_address(dst) + page_offset;
+			mp->folio = dst;
+			remove_metapage(src, mp);
+		}
+	}
+
+	return MIGRATEPAGE_SUCCESS;
+}
+
 #else
 static inline struct metapage *folio_to_mp(struct folio *folio, int offset)
 {
@@ -175,6 +224,32 @@ static inline void remove_metapage(struct folio *folio, struct metapage *mp)
 #define inc_io(folio) do {} while(0)
 #define dec_io(folio, status, handler) handler(folio, status)
 
+static int __metapage_migrate_folio(struct address_space *mapping, struct folio *dst,
+				    struct folio *src, enum migrate_mode mode)
+{
+	struct metapage *mp;
+	int page_offset;
+	int rc;
+
+	mp = folio_to_mp(src, 0);
+	if (mp && metapage_locked(mp))
+		return -EAGAIN;
+
+	rc = filemap_migrate_folio(mapping, dst, src, mode);
+	if (rc != MIGRATEPAGE_SUCCESS)
+		return rc;
+
+	if (unlikely(insert_metapage(dst, mp)))
+		return -EAGAIN;
+
+	page_offset = mp->data - folio_address(src);
+	mp->data = folio_address(dst) + page_offset;
+	mp->folio = dst;
+	remove_metapage(src, mp);
+
+	return MIGRATEPAGE_SUCCESS;
+}
+
 #endif
 
 static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
@@ -554,6 +629,24 @@ static bool metapage_release_folio(struct folio *folio, gfp_t gfp_mask)
 	return ret;
 }
 
+/**
+ * metapage_migrate_folio - Migration function for JFS metapages
+ */
+static int metapage_migrate_folio(struct address_space *mapping, struct folio *dst,
+				  struct folio *src, enum migrate_mode mode)
+{
+	int expected_count;
+
+	if (!src->private)
+		return filemap_migrate_folio(mapping, dst, src, mode);
+
+	/* Check whether page does not have extra refs before we do more work */
+	expected_count = folio_expected_ref_count(src) + 1;
+	if (folio_ref_count(src) != expected_count)
+		return -EAGAIN;
+	return __metapage_migrate_folio(mapping, dst, src, mode);
+}
+
 static void metapage_invalidate_folio(struct folio *folio, size_t offset,
 				    size_t length)
 {
@@ -570,6 +663,7 @@ const struct address_space_operations jfs_metapage_aops = {
 	.release_folio	= metapage_release_folio,
 	.invalidate_folio = metapage_invalidate_folio,
 	.dirty_folio	= filemap_dirty_folio,
+	.migrate_folio	= metapage_migrate_folio,
 };
 
 struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
-- 
2.34.1

Re: [syzbot] [mm?] WARNING in move_to_new_folio

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+8bb6fd945af4e0ad9299@syzkaller.appspotmail.com
Tested-by: syzbot+8bb6fd945af4e0ad9299@syzkaller.appspotmail.com

Tested on:

commit:         69a58d52 Revert "x86/mm: Add 'mm' argument to unuse_te..
git tree:       https://github.com/shivankgarg98/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=137a68d4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f002bbe3fe2ccafa
dashboard link: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299
compiler:       Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.

Re: [PATCH V5 0/2] JFS: Implement migrate_folio for jfs_metapage_aops

[Andrew Morton]

On Wed, 30 Apr 2025 10:01:49 +0000 Shivank Garg <shivankg@amd.com> wrote:

> This patch addresses a warning that occurs during memory compaction due
> to JFS's missing migrate_folio operation. The warning was introduced by
> commit 7ee3647243e5 ("migrate: Remove call to ->writepage") which added
> explicit warnings when filesystem don't implement migrate_folio.
> 
> The syzbot reported following [1]:
>   jfs_metapage_aops does not implement migrate_folio
>   WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline]
>   WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
>   Modules linked in:
>   CPU: 1 UID: 0 PID: 5861 Comm: syz-executor280 Not tainted 6.15.0-rc1-next-20250411-syzkaller #0 PREEMPT(full) 
>   Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
>   RIP: 0010:fallback_migrate_folio mm/migrate.c:953 [inline]
>   RIP: 0010:move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
> 
> To fix this issue, this series implement metapage_migrate_folio() for JFS
> which handles both single and multiple metapages per page configurations.

Thanks, I'll add these to mm.git for some testing while discussion
proceeds.

Do we think these patches should be backported into -stable kernels?

Or maybe we should simply remove the warning from -stable kernels then
re-add it when we're confident that all in-tree filesystems are good?

Re: [PATCH V5 0/2] JFS: Implement migrate_folio for jfs_metapage_aops

[Matthew Wilcox]

On Wed, Apr 30, 2025 at 02:21:35PM -0700, Andrew Morton wrote:
> On Wed, 30 Apr 2025 10:01:49 +0000 Shivank Garg <shivankg@amd.com> wrote:
> > This patch addresses a warning that occurs during memory compaction due
> > to JFS's missing migrate_folio operation. The warning was introduced by
> > commit 7ee3647243e5 ("migrate: Remove call to ->writepage") which added
> > explicit warnings when filesystem don't implement migrate_folio.
> 
> Do we think these patches should be backported into -stable kernels?
> 
> Or maybe we should simply remove the warning from -stable kernels then
> re-add it when we're confident that all in-tree filesystems are good?

7ee3647243e5 is not yet in Linus' tree, let alone in -stable.

[PATCH V4 0/2] JFS: Implement migrate_folio for jfs_metapage_aops

[Shivank Garg]

This patch addresses a warning that occurs during memory compaction due
to JFS's missing migrate_folio operation. The warning was introduced by
commit 7ee3647243e5 ("migrate: Remove call to ->writepage") which added
explicit warnings when filesystem don't implement migrate_folio.

The syzbot reported following [1]:
  jfs_metapage_aops does not implement migrate_folio
  WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline]
  WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
  Modules linked in:
  CPU: 1 UID: 0 PID: 5861 Comm: syz-executor280 Not tainted 6.15.0-rc1-next-20250411-syzkaller #0 PREEMPT(full) 
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
  RIP: 0010:fallback_migrate_folio mm/migrate.c:953 [inline]
  RIP: 0010:move_to_new_folio+0x70e/0x840 mm/migrate.c:1007

This implement metapage_migrate_folio which handles both single and multiple
metapages per page configurations.

[1]: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299

Previous Versions:
V1/V2:
https://lore.kernel.org/all/20250413172356.561544-1-shivankg@amd.com
V3:
https://lore.kernel.org/all/20250417060630.197278-1-shivankg@amd.com

#syz test: https://github.com/AMDESE/linux-mm.git f17a3b8bc


Shivank Garg (2):
  mm: export folio_expected_refs for JFS migration handler
  jfs: implement migrate_folio for jfs_metapage_aops

 fs/jfs/jfs_metapage.c   | 94 +++++++++++++++++++++++++++++++++++++++++
 include/linux/migrate.h |  1 +
 mm/migrate.c            |  3 +-
 3 files changed, 97 insertions(+), 1 deletion(-)

-- 
2.34.1

Re: [syzbot] [mm?] WARNING in move_to_new_folio

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

 legacy bootconsole [earlyser0] disabled
[    2.023888][    T0] Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar
[    2.025496][    T0] ... MAX_LOCKDEP_SUBCLASSES:  8
[    2.026234][    T0] ... MAX_LOCK_DEPTH:          48
[    2.027545][    T0] ... MAX_LOCKDEP_KEYS:        8192
[    2.028529][    T0] ... CLASHASH_SIZE:          4096
[    2.045554][    T0] ... MAX_LOCKDEP_ENTRIES:     1048576
[    2.047369][    T0] ... MAX_LOCKDEP_CHAINS:      1048576
[    2.049406][    T0] ... CHAINHASH_SIZE:          524288
[    2.051376][    T0]  memory used by lock dependency info: 106625 kB
[    2.053638][    T0]  memory used for stack traces: 8320 kB
[    2.055715][    T0]  per task-struct memory footprint: 1920 bytes
[    2.058123][    T0] mempolicy: Enabling automatic NUMA balancing. Configure with numa_balancing= or the kernel.numa_balancing sysctl
[    2.062523][    T0] ACPI: Core revision 20241212
[    2.064822][    T0] APIC: Switch to symmetric I/O mode setup
[    2.066614][    T0] x2apic enabled
[    2.071611][    T0] APIC: Switched APIC routing to: physical x2apic
[    2.080202][    T0] ..TIMER: vector=0x30 apic1=0 pin1=0 apic2=-1 pin2=-1
[    2.082132][    T0] clocksource: tsc-early: mask: 0xffffffffffffffff max_cycles: 0x1fb63109b96, max_idle_ns: 440795265316 ns
[    2.094615][    T0] Calibrating delay loop (skipped) preset value.. 4399.99 BogoMIPS (lpj=21999980)
[    2.097159][    T0] Last level iTLB entries: 4KB 64, 2MB 8, 4MB 8
[    2.098499][    T0] Last level dTLB entries: 4KB 64, 2MB 32, 4MB 32, 1GB 4
[    2.099918][    T0] Spectre V1 : Mitigation: usercopy/swapgs barriers and __user pointer sanitization
[    2.102698][    T0] Spectre V2 : Spectre BHI mitigation: SW BHB clearing on syscall and VM exit
[    2.104484][    T0] Spectre V2 : Mitigation: IBRS
[    2.105540][    T0] Spectre V2 : Spectre v2 / SpectreRSB: Filling RSB on context switch and VMEXIT
[    2.109513][    T0] RETBleed: Mitigation: IBRS
[    2.111317][    T0] Spectre V2 : mitigation: Enabling conditional Indirect Branch Prediction Barrier
[    2.113299][    T0] Spectre V2 : User space: Mitigation: STIBP via prctl
[    2.114649][    T0] Speculative Store Bypass: Mitigation: Speculative Store Bypass disabled via prctl
[    2.117580][    T0] MDS: Mitigation: Clear CPU buffers
[    2.118495][    T0] TAA: Mitigation: Clear CPU buffers
[    2.120451][    T0] MMIO Stale Data: Vulnerable: Clear CPU buffers attempted, no microcode
[    2.123857][    T0] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[    2.124558][    T0] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[    2.126861][    T0] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[    2.129671][    T0] x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
[    2.134556][    T0] x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'standard' format.
[    2.558992][    T0] Freeing SMP alternatives memory: 132K
[    2.560524][    T0] pid_max: default: 32768 minimum: 301
[    2.562227][    T0] LSM: initializing lsm=lockdown,capability,landlock,yama,safesetid,tomoyo,apparmor,bpf,ima,evm
[    2.565143][    T0] landlock: Up and running.
[    2.566184][    T0] Yama: becoming mindful.
[    2.567752][    T0] TOMOYO Linux initialized
[    2.570977][    T0] AppArmor: AppArmor initialized
[    2.575204][    T0] LSM support for eBPF active
[    2.584242][    T0] Dentry cache hash table entries: 1048576 (order: 11, 8388608 bytes, vmalloc hugepage)
[    2.588245][    T0] Inode-cache hash table entries: 524288 (order: 10, 4194304 bytes, vmalloc hugepage)
[    2.594675][    T0] Mount-cache hash table entries: 16384 (order: 5, 131072 bytes, vmalloc)
[    2.598390][    T0] Mountpoint-cache hash table entries: 16384 (order: 5, 131072 bytes, vmalloc)
[    2.606995][    T0] Running RCU synchronous self tests
[    2.609248][    T0] Running RCU synchronous self tests
[    2.733732][    T1] smpboot: CPU0: Intel(R) Xeon(R) CPU @ 2.20GHz (family: 0x6, model: 0x4f, stepping: 0x0)
[    2.734535][    T9] ------------[ cut here ]------------
[    2.734535][    T9] WARNING: CPU: 0 PID: 9 at arch/x86/mm/tlb.c:919 switch_mm_irqs_off+0x686/0x810
[    2.734535][    T9] Modules linked in:
[    2.734535][    T9] CPU:serialport: Connected to syzkaller.us-central1-c.ci-upstream-linux-next-kasan-gce-root-test-job-parallel-0 port 1 (session ID: 8b8c42debbe22e4907102c6ca34b474bf814b5a2c14fd2264a6785197a17a5b8, active connections: 1).
 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted 6.15.0-rc2-next-20250417-syzkaller-04782-gf17a3b8bcabd #0 PREEMPT(full) 
[    2.734535][    T9] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
[    2.734535][    T9] Workqueue: events once_deferred
[    2.734535][    T9] RIP: 0010:switch_mm_irqs_off+0x686/0x810
[    2.734535][    T9] Code: 90 41 f7 c5 00 08 00 00 0f 84 ee fa ff ff 90 0f 0b 90 e9 e5 fa ff ff 90 0f 0b 90 e9 76 fe ff ff 90 0f 0b 90 e9 cc fb ff ff 90 <0f> 0b 90 4d 39 f4 0f 85 eb fb ff ff e9 31 fc ff ff 90 0f 0b 90 e9
[    2.734535][    T9] RSP: 0000:ffffc900000e75c0 EFLAGS: 00010056
[    2.734535][    T9] RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff816f9cdd
[    2.734535][    T9] RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88801b070940
[    2.734535][    T9] RBP: ffffc900000e7690 R08: ffff88801b070947 R09: 1ffff1100360e128
[    2.734535][    T9] R10: dffffc0000000000 R11: ffffed100360e129 R12: ffffffff8ee49240
[    2.734535][    T9] R13: ffff88801b070940 R14: ffffffff8ee49240 R15: 0000000000000000
[    2.734535][    T9] FS:  0000000000000000(0000) GS:ffff888124fa0000(0000) knlGS:0000000000000000
[    2.734535][    T9] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.734535][    T9] CR2: ffff88823ffff000 CR3: 000000001b078000 CR4: 00000000003506f0
[    2.734535][    T9] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    2.734535][    T9] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    2.734535][    T9] Call Trace:
[    2.734535][    T9]  <TASK>
[    2.734535][    T9]  ? __pfx_switch_mm_irqs_off+0x10/0x10
[    2.734535][    T9]  unuse_temporary_mm+0x160/0x270
[    2.734535][    T9]  ? __pfx_unuse_temporary_mm+0x10/0x10
[    2.734535][    T9]  ? __text_poke+0x6bb/0xb40
[    2.734535][    T9]  ? __text_poke+0x6bb/0xb40
[    2.734535][    T9]  ? serial8250_isa_init_ports+0x6b/0x110
[    2.734535][    T9]  __text_poke+0x7b6/0xb40
[    2.734535][    T9]  ? serial8250_isa_init_ports+0x6b/0x110
[    2.734535][    T9]  ? __pfx_text_poke_memcpy+0x10/0x10
[    2.734535][    T9]  ? __pfx___text_poke+0x10/0x10
[    2.734535][    T9]  ? __pfx___mutex_trylock_common+0x10/0x10
[    2.734535][    T9]  ? __pfx___might_resched+0x10/0x10
[    2.734535][    T9]  ? rcu_is_watching+0x15/0xb0
[    2.734535][    T9]  smp_text_poke_batch_finish+0x3e7/0x12c0
[    2.734535][    T9]  ? arch_jump_label_transform_apply+0x17/0x30
[    2.734535][    T9]  ? __pfx___mutex_lock+0x10/0x10
[    2.734535][    T9]  ? __pfx_smp_text_poke_batch_finish+0x10/0x10
[    2.734535][    T9]  ? arch_jump_label_transform_queue+0x9b/0x100
[    2.734535][    T9]  ? __jump_label_update+0x387/0x3b0
[    2.734535][    T9]  arch_jump_label_transform_apply+0x1c/0x30
[    2.734535][    T9]  static_key_disable_cpuslocked+0xd2/0x1c0
[    2.734535][    T9]  static_key_disable+0x1a/0x20
[    2.734535][    T9]  once_deferred+0x70/0xb0
[    2.734535][    T9]  ? process_scheduled_works+0x9cb/0x18e0
[    2.734535][    T9]  process_scheduled_works+0xac3/0x18e0
[    2.734535][    T9]  ? __pfx_process_scheduled_works+0x10/0x10
[    2.734535][    T9]  ? assign_work+0x367/0x3d0
[    2.734535][    T9]  worker_thread+0x870/0xd50
[    2.734535][    T9]  ? __kthread_parkme+0x1a8/0x200
[    2.734535][    T9]  ? __pfx_worker_thread+0x10/0x10
[    2.734535][    T9]  kthread+0x7b7/0x940
[    2.734535][    T9]  ? __pfx_worker_thread+0x10/0x10
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ? _raw_spin_unlock_irq+0x23/0x50
[    2.734535][    T9]  ? lockdep_hardirqs_on+0x9d/0x150
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ret_from_fork+0x4b/0x80
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ret_from_fork_asm+0x1a/0x30
[    2.734535][    T9]  </TASK>
[    2.734535][    T9] Kernel panic - not syncing: kernel: panic_on_warn set ...
[    2.734535][    T9] CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted 6.15.0-rc2-next-20250417-syzkaller-04782-gf17a3b8bcabd #0 PREEMPT(full) 
[    2.734535][    T9] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
[    2.734535][    T9] Workqueue: events once_deferred
[    2.734535][    T9] Call Trace:
[    2.734535][    T9]  <TASK>
[    2.734535][    T9]  dump_stack_lvl+0x241/0x360
[    2.734535][    T9]  ? __pfx_dump_stack_lvl+0x10/0x10
[    2.734535][    T9]  ? __pfx__printk+0x10/0x10
[    2.734535][    T9]  ? vscnprintf+0x5d/0x90
[    2.734535][    T9]  panic+0x349/0x880
[    2.734535][    T9]  ? __warn+0x174/0x4d0
[    2.734535][    T9]  ? __pfx_panic+0x10/0x10
[    2.734535][    T9]  ? ret_from_fork_asm+0x1a/0x30
[    2.734535][    T9]  __warn+0x344/0x4d0
[    2.734535][    T9]  ? switch_mm_irqs_off+0x686/0x810
[    2.734535][    T9]  report_bug+0x2b3/0x500
[    2.734535][    T9]  ? switch_mm_irqs_off+0x686/0x810
[    2.734535][    T9]  ? switch_mm_irqs_off+0x686/0x810
[    2.734535][    T9]  ? switch_mm_irqs_off+0x688/0x810
[    2.734535][    T9]  handle_bug+0x89/0x170
[    2.734535][    T9]  exc_invalid_op+0x1a/0x50
[    2.734535][    T9]  asm_exc_invalid_op+0x1a/0x20
[    2.734535][    T9] RIP: 0010:switch_mm_irqs_off+0x686/0x810
[    2.734535][    T9] Code: 90 41 f7 c5 00 08 00 00 0f 84 ee fa ff ff 90 0f 0b 90 e9 e5 fa ff ff 90 0f 0b 90 e9 76 fe ff ff 90 0f 0b 90 e9 cc fb ff ff 90 <0f> 0b 90 4d 39 f4 0f 85 eb fb ff ff e9 31 fc ff ff 90 0f 0b 90 e9
[    2.734535][    T9] RSP: 0000:ffffc900000e75c0 EFLAGS: 00010056
[    2.734535][    T9] RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff816f9cdd
[    2.734535][    T9] RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88801b070940
[    2.734535][    T9] RBP: ffffc900000e7690 R08: ffff88801b070947 R09: 1ffff1100360e128
[    2.734535][    T9] R10: dffffc0000000000 R11: ffffed100360e129 R12: ffffffff8ee49240
[    2.734535][    T9] R13: ffff88801b070940 R14: ffffffff8ee49240 R15: 0000000000000000
[    2.734535][    T9]  ? switch_mm_irqs_off+0x26d/0x810
[    2.734535][    T9]  ? __pfx_switch_mm_irqs_off+0x10/0x10
[    2.734535][    T9]  unuse_temporary_mm+0x160/0x270
[    2.734535][    T9]  ? __pfx_unuse_temporary_mm+0x10/0x10
[    2.734535][    T9]  ? __text_poke+0x6bb/0xb40
[    2.734535][    T9]  ? __text_poke+0x6bb/0xb40
[    2.734535][    T9]  ? serial8250_isa_init_ports+0x6b/0x110
[    2.734535][    T9]  __text_poke+0x7b6/0xb40
[    2.734535][    T9]  ? serial8250_isa_init_ports+0x6b/0x110
[    2.734535][    T9]  ? __pfx_text_poke_memcpy+0x10/0x10
[    2.734535][    T9]  ? __pfx___text_poke+0x10/0x10
[    2.734535][    T9]  ? __pfx___mutex_trylock_common+0x10/0x10
[    2.734535][    T9]  ? __pfx___might_resched+0x10/0x10
[    2.734535][    T9]  ? rcu_is_watching+0x15/0xb0
[    2.734535][    T9]  smp_text_poke_batch_finish+0x3e7/0x12c0
[    2.734535][    T9]  ? arch_jump_label_transform_apply+0x17/0x30
[    2.734535][    T9]  ? __pfx___mutex_lock+0x10/0x10
[    2.734535][    T9]  ? __pfx_smp_text_poke_batch_finish+0x10/0x10
[    2.734535][    T9]  ? arch_jump_label_transform_queue+0x9b/0x100
[    2.734535][    T9]  ? __jump_label_update+0x387/0x3b0
[    2.734535][    T9]  arch_jump_label_transform_apply+0x1c/0x30
[    2.734535][    T9]  static_key_disable_cpuslocked+0xd2/0x1c0
[    2.734535][    T9]  static_key_disable+0x1a/0x20
[    2.734535][    T9]  once_deferred+0x70/0xb0
[    2.734535][    T9]  ? process_scheduled_works+0x9cb/0x18e0
[    2.734535][    T9]  process_scheduled_works+0xac3/0x18e0
[    2.734535][    T9]  ? __pfx_process_scheduled_works+0x10/0x10
[    2.734535][    T9]  ? assign_work+0x367/0x3d0
[    2.734535][    T9]  worker_thread+0x870/0xd50
[    2.734535][    T9]  ? __kthread_parkme+0x1a8/0x200
[    2.734535][    T9]  ? __pfx_worker_thread+0x10/0x10
[    2.734535][    T9]  kthread+0x7b7/0x940
[    2.734535][    T9]  ? __pfx_worker_thread+0x10/0x10
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ? _raw_spin_unlock_irq+0x23/0x50
[    2.734535][    T9]  ? lockdep_hardirqs_on+0x9d/0x150
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ret_from_fork+0x4b/0x80
[    2.734535][    T9]  ? __pfx_kthread+0x10/0x10
[    2.734535][    T9]  ret_from_fork_asm+0x1a/0x30
[    2.734535][    T9]  </TASK>
[    2.734535][    T9] Rebooting in 86400 seconds..


syzkaller build log:
go env (err=<nil>)
GO111MODULE='auto'
GOARCH='amd64'
GOBIN=''
GOCACHE='/syzkaller/.cache/go-build'
GOENV='/syzkaller/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/syzkaller/jobs-2/linux/gopath/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/syzkaller/jobs-2/linux/gopath'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/syzkaller/jobs-2/linux/gopath/pkg/mod/golang.org/toolchain@v0.0.1-go1.23.7.linux-amd64'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/syzkaller/jobs-2/linux/gopath/pkg/mod/golang.org/toolchain@v0.0.1-go1.23.7.linux-amd64/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.23.7'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/syzkaller/.config/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/syzkaller/jobs-2/linux/gopath/src/github.com/google/syzkaller/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build1748814211=/tmp/go-build -gno-record-gcc-switches'

git status (err=<nil>)
HEAD detached at 0bd6db4180
nothing to commit, working tree clean


tput: No value for $TERM and no -T specified
tput: No value for $TERM and no -T specified
Makefile:31: run command via tools/syz-env for best compatibility, see:
Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
go list -f '{{.Stale}}' ./sys/syz-sysgen | grep -q false || go install ./sys/syz-sysgen
make .descriptions
tput: No value for $TERM and no -T specified
tput: No value for $TERM and no -T specified
Makefile:31: run command via tools/syz-env for best compatibility, see:
Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
bin/syz-sysgen
touch .descriptions
GOOS=linux GOARCH=amd64 go build "-ldflags=-s -w -X github.com/google/syzkaller/prog.GitRevision=0bd6db418098e2d98a2edf948b41410d3d9f9e70 -X 'github.com/google/syzkaller/prog.gitRevisionDate=20250411-130225'" -o ./bin/linux_amd64/syz-execprog github.com/google/syzkaller/tools/syz-execprog
mkdir -p ./bin/linux_amd64
g++ -o ./bin/linux_amd64/syz-executor executor/executor.cc \
	-m64 -O2 -pthread -Wall -Werror -Wparentheses -Wunused-const-variable -Wframe-larger-than=16384 -Wno-stringop-overflow -Wno-array-bounds -Wno-format-overflow -Wno-unused-but-set-variable -Wno-unused-command-line-argument -static-pie -std=c++17 -I. -Iexecutor/_include   -DGOOS_linux=1 -DGOARCH_amd64=1 \
	-DHOSTGOOS_linux=1 -DGIT_REVISION=\"0bd6db418098e2d98a2edf948b41410d3d9f9e70\"
/usr/bin/ld: /tmp/ccfRLisG.o: in function `Connection::Connect(char const*, char const*)':
executor.cc:(.text._ZN10Connection7ConnectEPKcS1_[_ZN10Connection7ConnectEPKcS1_]+0x104): warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking


Error text is too large and was truncated, full error text is at:
https://syzkaller.appspot.com/x/error.txt?x=1143c568580000


Tested on:

commit:         f17a3b8b jfs: implement migrate_folio for jfs_metapage..
git tree:       https://github.com/AMDESE/linux-mm.git
kernel config:  https://syzkaller.appspot.com/x/.config?x=796b05042c1188b
dashboard link: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299
compiler:       Debian clang version 15.0.6, Debian LLD 15.0.6

Note: no patches were applied.

[PATCH V3 0/2] JFS: Implement migrate_folio for jfs_metapage_aops

[Shivank Garg]

This patch addresses a warning that occurs during memory compaction due
to JFS's missing migrate_folio operation. The warning was introduced by
commit 7ee3647 ("migrate: Remove call to ->writepage") which added
explicit warnings when filesystem don't implement migrate_folio.

The syzbot reported following [1]:
  jfs_metapage_aops does not implement migrate_folio
  WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline]
  WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
  Modules linked in:
  CPU: 1 UID: 0 PID: 5861 Comm: syz-executor280 Not tainted 6.15.0-rc1-next-20250411-syzkaller #0 PREEMPT(full) 
  Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
  RIP: 0010:fallback_migrate_folio mm/migrate.c:953 [inline]
  RIP: 0010:move_to_new_folio+0x70e/0x840 mm/migrate.c:1007

This Implement metapage_migrate_folio which handles both single and multiple
metapages per page configurations.

[1]: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299

V1/V2:
https://lore.kernel.org/all/20250413172356.561544-1-shivankg@amd.com

#syz test: https://github.com/AMDESE/linux-mm.git 07246f14ea

Best Regards,
Shivank

Shivank Garg (2):
  mm: export folio_expected_refs for JFS migration handler
  jfs: implement migrate_folio for jfs_metapage_aops

 fs/jfs/jfs_metapage.c   | 94 +++++++++++++++++++++++++++++++++++++++++
 include/linux/migrate.h |  1 +
 mm/migrate.c            |  3 +-
 3 files changed, 97 insertions(+), 1 deletion(-)

-- 
2.34.1

Re: [syzbot] [mm?] WARNING in move_to_new_folio

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

tes for 255 objects at 0xffff88823be00000-0xffff88823c000000
[    1.925837][    T0] Console: colour VGA+ 80x25
[    1.926854][    T0] printk: legacy console [ttyS0] enabled
[    1.926854][    T0] printk: legacy console [ttyS0] enabled
[    1.928807][    T0] printk: legacy bootconsole [earlyser0] disabled
[    1.928807][    T0] printk: legacy bootconsole [earlyser0] disabled
[    1.931060][    T0] Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar
[    1.932421][    T0] ... MAX_LOCKDEP_SUBCLASSES:  8
[    1.933470][    T0] ... MAX_LOCK_DEPTH:          48
[    1.934392][    T0] ... MAX_LOCKDEP_KEYS:        8192
[    1.935279][    T0] ... CLASSHASH_SIZE:          4096
[    1.936068][    T0] ... MAX_LOCKDEP_ENTRIES:     1048576
[    1.937188][    T0] ... MAX_LOCKDEP_CHAINS:      1048576
[    1.938022][    T0] ... CHAINHASH_SIZE:          524288
[    1.938854][    T0]  memory used by lock dependency info: 106625 kB
[    1.940170][    T0]  memory used for stack traces: 8320 kB
[    1.941640][    T0]  per task-struct memory footprint: 1920 bytes
[    1.942814][    T0] mempolicy: Enabling automatic NUMA balancing. Configure with numa_balancing= or the kernel.numa_balancing sysctl
[    1.945209][    T0] ACPI: Core revision 20241212
[    1.946927][    T0] APIC: Switch to symmetric I/O mode setup
[    1.948578][    T0] x2apic enabled
[    1.953337][    T0] APIC: Switched APIC routing to: physical x2apic
[    1.960868][    T0] ..TIMER: vector=0x30 apic1=0 pin1=0 apic2=-1 pin2=-1
[    1.963220][    T0] clocksource: tsc-early: mask: 0xffffffffffffffff max_cycles: 0x1fb6f76ef03, max_idle_ns: 440795255960 ns
[    1.965573][    T0] Calibrating delay loop (skipped) preset value.. 4400.41 BogoMIPS (lpj=22002080)
[    1.976248][    T0] Last level iTLB entries: 4KB 64, 2MB 8, 4MB 8
[    1.977543][    T0] Last level dTLB entries: 4KB 64, 2MB 32, 4MB 32, 1GB 4
[    1.978831][    T0] Spectre V1 : Mitigation: usercopy/swapgs barriers and __user pointer sanitization
[    1.981126][    T0] Spectre V2 : Spectre BHI mitigation: SW BHB clearing on syscall and VM exit
[    1.983233][    T0] Spectre V2 : Mitigation: IBRS
[    1.983963][    T0] Spectre V2 : Spectre v2 / SpectreRSB: Filling RSB on context switch and VMEXIT
[    1.985668][    T0] RETBleed: Mitigation: IBRS
[    1.986468][    T0] Spectre V2 : mitigation: Enabling conditional Indirect Branch Prediction Barrier
[    1.987833][    T0] Spectre V2 : User space: Mitigation: STIBP via prctl
[    1.989023][    T0] Speculative Store Bypass: Mitigation: Speculative Store Bypass disabled via prctl
[    1.990381][    T0] MDS: Mitigation: Clear CPU buffers
[    1.991105][    T0] TAA: Mitigation: Clear CPU buffers
[    1.992276][    T0] MMIO Stale Data: Vulnerable: Clear CPU buffers attempted, no microcode
[    1.993752][    T0] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
[    1.994963][    T0] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
[    1.995572][    T0] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
[    1.996652][    T0] x86/fpu: xstate_offset[2]:  576, xstate_sizes[2]:  256
[    1.997837][    T0] x86/fpu: Enabled xstate features 0x7, context size is 832 bytes, using 'standard' format.
[    2.295143][    T0] Freeing SMP alternatives memory: 132K
[    2.295587][    T0] pid_max: default: 32768 minimum: 301
[    2.297541][    T0] LSM: initializing lsm=lockdown,capability,landlock,yama,safesetid,tomoyo,apparmor,bpf,ima,evm
[    2.300386][    T0] landlock: Up and running.
[    2.301189][    T0] Yama: becoming mindful.
[    2.302225][    T0] TOMOYO Linux initialized
[    2.303858][    T0] AppArmor: AppArmor initialized
[    2.307123][    T0] LSM support for eBPF active
[    2.314189][    T0] Dentry cache hash table entries: 1048576 (order: 11, 8388608 bytes, vmalloc hugepage)
[    2.318576][    T0] Inode-cache hash table entries: 524288 (order: 10, 4194304 bytes, vmalloc hugepage)
[    2.320554][    T0] Mount-cache hash table entries: 16384 (order: 5, 131072 bytes, vmalloc)
[    2.322439][    T0] Mountpoint-cache hash table entries: 16384 (order: 5, 131072 bytes, vmalloc)
[    2.330329][    T0] Running RCU synchronous self tests
[    2.331252][    T0] Running RCU synchronous self tests
[    2.453357][    T1] smpboot: CPU0: Intel(R) Xeon(R) CPU @ 2.20GHz (family: 0x6, model: 0x4f, stepping: 0x0)
[    2.455556][    T9] ------------[ cut here ]------------
[    2.455556][    T9] WARNING: CPU: 0 PID: 9 at arch/x86/mm/tlb.c:919 switch_mm_irqs_off+0x686/0x810
[    2.455556][    T9] Modules linked in:
[    2.455556][    T9] CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted 6.15.0-rc2-next-20250416-syzkaller-04531-g07246f14ea38 #0 PREEMPT(full) 
[    2.455556][    T9] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
[    2.455556][    T9] Workqueue: events once_deferred
[    2.455556][    T9] RIP: 0010:switch_mm_irqs_off+0x686/0x810
[    2.455556][    T9] Code: 90 41 f7 c5 00 08 00 00 0f 84 ee fa ff ff 90 0f 0b 90 e9 e5 fa ff ff 90 0f 0b 90 e9 76 fe ff ff 90 0f 0b 90 e9 cc fb ff ff 90 <0f> 0b 90 4d 39 f4 0f 85 eb fb ff ff e9 31 fc ff ff 90 0f 0b 90 e9
[    2.455556][    T9] RSP: 0000:ffffc900000e7680 EFLAGS: 00010056
[    2.455556][    T9] RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff816ffd4d
[    2.455556][    T9] RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88801b070940
[    2.455556][    T9] RBP: ffffc900000e7750 R08: ffff88801b070947 R09: 1ffff1100360e128
[    2.455556][    T9] R10: dffffc0000000000 R11: ffffed100360e129 R12: ffffffff8ee492c0
[    2.455556][    T9] R13: ffff88801b070940 R14: ffffffff8ee492c0 R15: 0000000000000000
[    2.455556][    T9] FS:  0000000000000000(0000) GS:ffff888124f9c000(0000) knlGS:0000000000000000
[    2.455556][    T9] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.455556][    T9] CR2: ffff88823ffff000 CR3: 000000001b078000 CR4: 00000000003506f0
[    2.455556][    T9] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    2.455556][    T9] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    2.455556][    T9] Call Trace:
[    2.455556][    T9]  <TASK>
[    2.455556][    T9]  ? __pfx_switch_mm_irqs_off+0x10/0x10
[    2.455556][    T9]  ? __text_poke+0x6bb/0xb40
[    2.455556][    T9]  ? kasan_check_range+0x28f/0x2a0
[    2.455556][    T9]  ? serial8250_isa_init_ports+0x6b/0x110
[    2.455556][    T9]  unuse_temporary_mm+0x9f/0x100
[    2.455556][    T9]  __text_poke+0x7b6/0xb40
[    2.455556][    T9]  ? serial8250_isa_init_ports+0x6b/0x110
[    2.455556][    T9]  ? __pfx_text_poke_memcpy+0x10/0x10
[    2.455556][    T9]  ? __pfx___text_poke+0x10/0x10
[    2.455556][    T9]  ? __pfx___mutex_trylock_common+0x10/0x10
[    2.455556][    T9]  ? __pfx___might_resched+0x10/0x10
[    2.455556][    T9]  ? rcu_is_watching+0x15/0xb0
[    2.455556][    T9]  smp_text_poke_batch_finish+0x3e7/0x12c0
[    2.455556][    T9]  ? arch_jump_label_transform_apply+0x17/0x30
[    2.455556][    T9]  ? __pfx___mutex_lock+0x10/0x10
[    2.455556][    T9]  ? __pfx_smp_text_poke_batch_finish+0x10/0x10
[    2.455556][    T9]  ? arch_jump_label_transform_queue+0x9b/0x100
[    2.455556][    T9]  ? __jump_label_update+0x387/0x3b0
[    2.455556][    T9]  arch_jump_label_transform_apply+0x1c/0x30
[    2.455556][    T9]  static_key_disable_cpuslocked+0xd2/0x1c0
[    2.455556][    T9]  static_key_disable+0x1a/0x20
[    2.455556][    T9]  once_deferred+0x70/0xb0
[    2.455556][    T9]  ? process_scheduled_works+0x9cb/0x18e0
[    2.455556][    T9]  process_scheduled_works+0xac3/0x18e0
[    2.455556][    T9]  ? __pfx_process_scheduled_works+0x10/0x10
[    2.455556][    T9]  ? assign_work+0x367/0x3d0
[    2.455556][    T9]  worker_thread+0x870/0xd50
[    2.455556][    T9]  ? __kthread_parkme+0x1a8/0x200
[    2.455556][    T9]  ? __pfx_worker_thread+0x10/0x10
[    2.455556][    T9]  kthread+0x7b7/0x940
[    2.455556][    T9]  ? __pfx_worker_thread+0x10/0x10
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ? _raw_spin_unlock_irq+0x23/0x50
[    2.455556][    T9]  ? lockdep_hardirqs_on+0x9d/0x150
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ret_from_fork+0x4b/0x80
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ret_from_fork_asm+0x1a/0x30
[    2.455556][    T9]  </TASK>
[    2.455556][    T9] Kernel panic - not syncing: kernel: panic_on_warn set ...
[    2.455556][    T9] CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted 6.15.0-rc2-next-20250416-syzkaller-04531-g07246f14ea38 #0 PREEMPT(full) 
[    2.455556][    T9] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
[    2.455556][    T9] Workqueue: events once_deferred
[    2.455556][    T9] Call Trace:
[    2.455556][    T9]  <TASK>
[    2.455556][    T9]  dump_stack_lvl+0x241/0x360
[    2.455556][    T9]  ? __pfx_dump_stack_lvl+0x10/0x10
[    2.455556][    T9]  ? __pfx__printk+0x10/0x10
[    2.455556][    T9]  ? vscnprintf+0x5d/0x90
[    2.455556][    T9]  panic+0x349/0x880
[    2.455556][    T9]  ? __warn+0x174/0x4d0
[    2.455556][    T9]  ? __pfx_panic+0x10/0x10
[    2.455556][    T9]  ? ret_from_fork_asm+0x1a/0x30
[    2.455556][    T9]  __warn+0x344/0x4d0
[    2.455556][    T9]  ? switch_mm_irqs_off+0x686/0x810
[    2.455556][    T9]  report_bug+0x2b3/0x500
[    2.455556][    T9]  ? switch_mm_irqs_off+0x686/0x810
[    2.455556][    T9]  ? switch_mm_irqs_off+0x686/0x810
[    2.455556][    T9]  ? switch_mm_irqs_off+0x688/0x810
[    2.455556][    T9]  handle_bug+0x89/0x170
[    2.455556][    T9]  exc_invalid_op+0x1a/0x50
[    2.455556][    T9]  asm_exc_invalid_op+0x1a/0x20
[    2.455556][    T9] RIP: 0010:switch_mm_irqs_off+0x686/0x810
[    2.455556][    T9] Code: 90 41 f7 c5 00 08 00 00 0f 84 ee fa ff ff 90 0f 0b 90 e9 e5 fa ff ff 90 0f 0b 90 e9 76 fe ff ff 90 0f 0b 90 e9 cc fb ff ff 90 <0f> 0b 90 4d 39 f4 0f 85 eb fb ff ff e9 31 fc ff ff 90 0f 0b 90 e9
[    2.455556][    T9] RSP: 0000:ffffc900000e7680 EFLAGS: 00010056
[    2.455556][    T9] RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff816ffd4d
[    2.455556][    T9] RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88801b070940
[    2.455556][    T9] RBP: ffffc900000e7750 R08: ffff88801b070947 R09: 1ffff1100360e128
[    2.455556][    T9] R10: dffffc0000000000 R11: ffffed100360e129 R12: ffffffff8ee492c0
[    2.455556][    T9] R13: ffff88801b070940 R14: ffffffff8ee492c0 R15: 0000000000000000
[    2.455556][    T9]  ? switch_mm_irqs_off+0x26d/0x810
[    2.455556][    T9]  ? __pfx_switch_mm_irqs_off+0x10/0x10
[    2.455556][    T9]  ? __text_poke+0x6bb/0xb40
[    2.455556][    T9]  ? kasan_check_range+0x28f/0x2a0
[    2.455556][    T9]  ? serial8250_isa_init_ports+0x6b/0x110
[    2.455556][    T9]  unuse_temporary_mm+0x9f/0x100
[    2.455556][    T9]  __text_poke+0x7b6/0xb40
[    2.455556][    T9]  ? serial8250_isa_init_ports+0x6b/0x110
[    2.455556][    T9]  ? __pfx_text_poke_memcpy+0x10/0x10
[    2.455556][    T9]  ? __pfx___text_poke+0x10/0x10
[    2.455556][    T9]  ? __pfx___mutex_trylock_common+0x10/0x10
[    2.455556][    T9]  ? __pfx___might_resched+0x10/0x10
[    2.455556][    T9]  ? rcu_is_watching+0x15/0xb0
[    2.455556][    T9]  smp_text_poke_batch_finish+0x3e7/0x12c0
[    2.455556][    T9]  ? arch_jump_label_transform_apply+0x17/0x30
[    2.455556][    T9]  ? __pfx___mutex_lock+0x10/0x10
[    2.455556][    T9]  ? __pfx_smp_text_poke_batch_finish+0x10/0x10
[    2.455556][    T9]  ? arch_jump_label_transform_queue+0x9b/0x100
[    2.455556][    T9]  ? __jump_label_update+0x387/0x3b0
[    2.455556][    T9]  arch_jump_label_transform_apply+0x1c/0x30
[    2.455556][    T9]  static_key_disable_cpuslocked+0xd2/0x1c0
[    2.455556][    T9]  static_key_disable+0x1a/0x20
[    2.455556][    T9]  once_deferred+0x70/0xb0
[    2.455556][    T9]  ? process_scheduled_works+0x9cb/0x18e0
[    2.455556][    T9]  process_scheduled_works+0xac3/0x18e0
[    2.455556][    T9]  ? __pfx_process_scheduled_works+0x10/0x10
[    2.455556][    T9]  ? assign_work+0x367/0x3d0
[    2.455556][    T9]  worker_thread+0x870/0xd50
[    2.455556][    T9]  ? __kthread_parkme+0x1a8/0x200
[    2.455556][    T9]  ? __pfx_worker_thread+0x10/0x10
[    2.455556][    T9]  kthread+0x7b7/0x940
[    2.455556][    T9]  ? __pfx_worker_thread+0x10/0x10
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ? _raw_spin_unlock_irq+0x23/0x50
[    2.455556][    T9]  ? lockdep_hardirqs_on+0x9d/0x150
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ret_from_fork+0x4b/0x80
[    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
[    2.455556][    T9]  ret_from_fork_asm+0x1a/0x30
[    2.455556][    T9]  </TASK>
[    2.455556][    T9] Rebooting in 86400 seconds..


syzkaller build log:
go env (err=<nil>)
GO111MODULE='auto'
GOARCH='amd64'
GOBIN=''
GOCACHE='/syzkaller/.cache/go-build'
GOENV='/syzkaller/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/syzkaller/jobs/linux/gopath/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/syzkaller/jobs/linux/gopath'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/syzkaller/jobs/linux/gopath/pkg/mod/golang.org/toolchain@v0.0.1-go1.23.7.linux-amd64'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/syzkaller/jobs/linux/gopath/pkg/mod/golang.org/toolchain@v0.0.1-go1.23.7.linux-amd64/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.23.7'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/syzkaller/.config/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/syzkaller/jobs/linux/gopath/src/github.com/google/syzkaller/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build1450323150=/tmp/go-build -gno-record-gcc-switches'

git status (err=<nil>)
HEAD detached at 0bd6db4180
nothing to commit, working tree clean


tput: No value for $TERM and no -T specified
tput: No value for $TERM and no -T specified
Makefile:31: run command via tools/syz-env for best compatibility, see:
Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
go list -f '{{.Stale}}' ./sys/syz-sysgen | grep -q false || go install ./sys/syz-sysgen
make .descriptions
tput: No value for $TERM and no -T specified
tput: No value for $TERM and no -T specified
Makefile:31: run command via tools/syz-env for best compatibility, see:
Makefile:32: https://github.com/google/syzkaller/blob/master/docs/contributing.md#using-syz-env
bin/syz-sysgen
touch .descriptions
GOOS=linux GOARCH=amd64 go build "-ldflags=-s -w -X github.com/google/syzkaller/prog.GitRevision=0bd6db418098e2d98a2edf948b41410d3d9f9e70 -X 'github.com/google/syzkaller/prog.gitRevisionDate=20250411-130225'" -o ./bin/linux_amd64/syz-execprog github.com/google/syzkaller/tools/syz-execprog
mkdir -p ./bin/linux_amd64
g++ -o ./bin/linux_amd64/syz-executor executor/executor.cc \
	-m64 -O2 -pthread -Wall -Werror -Wparentheses -Wunused-const-variable -Wframe-larger-than=16384 -Wno-stringop-overflow -Wno-array-bounds -Wno-format-overflow -Wno-unused-but-set-variable -Wno-unused-command-line-argument -static-pie -std=c++17 -I. -Iexecutor/_include   -DGOOS_linux=1 -DGOARCH_amd64=1 \
	-DHOSTGOOS_linux=1 -DGIT_REVISION=\"0bd6db418098e2d98a2edf948b41410d3d9f9e70\"
/usr/bin/ld: /tmp/ccXxW6Eo.o: in function `Connection::Connect(char const*, char const*)':
executor.cc:(.text._ZN10Connection7ConnectEPKcS1_[_ZN10Connection7ConnectEPKcS1_]+0x104): warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking


Error text is too large and was truncated, full error text is at:
https://syzkaller.appspot.com/x/error.txt?x=14fe3a3f980000


Tested on:

commit:         07246f14 jfs: implement migrate_folio for jfs_metapage..
git tree:       https://github.com/AMDESE/linux-mm.git
kernel config:  https://syzkaller.appspot.com/x/.config?x=361d80851af850ed
dashboard link: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.

Re: [syzbot] [mm?] WARNING in move_to_new_folio

[Shivank Garg]

On 4/17/2025 2:17 PM, syzbot wrote:
> Hello,
> 
> syzbot tried to test the proposed patch but the build/boot failed:
> 
...
> [    2.455556][    T9] ------------[ cut here ]------------
> [    2.455556][    T9] WARNING: CPU: 0 PID: 9 at arch/x86/mm/tlb.c:919 switch_mm_irqs_off+0x686/0x810
> [    2.455556][    T9] Modules linked in:
> [    2.455556][    T9] CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted 6.15.0-rc2-next-20250416-syzkaller-04531-g07246f14ea38 #0 PREEMPT(full) 
> [    2.455556][    T9] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
> [    2.455556][    T9] Workqueue: events once_deferred
> [    2.455556][    T9] RIP: 0010:switch_mm_irqs_off+0x686/0x810
> [    2.455556][    T9] Code: 90 41 f7 c5 00 08 00 00 0f 84 ee fa ff ff 90 0f 0b 90 e9 e5 fa ff ff 90 0f 0b 90 e9 76 fe ff ff 90 0f 0b 90 e9 cc fb ff ff 90 <0f> 0b 90 4d 39 f4 0f 85 eb fb ff ff e9 31 fc ff ff 90 0f 0b 90 e9
> [    2.455556][    T9] RSP: 0000:ffffc900000e7680 EFLAGS: 00010056
> [    2.455556][    T9] RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff816ffd4d
> [    2.455556][    T9] RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88801b070940
> [    2.455556][    T9] RBP: ffffc900000e7750 R08: ffff88801b070947 R09: 1ffff1100360e128
> [    2.455556][    T9] R10: dffffc0000000000 R11: ffffed100360e129 R12: ffffffff8ee492c0
> [    2.455556][    T9] R13: ffff88801b070940 R14: ffffffff8ee492c0 R15: 0000000000000000
> [    2.455556][    T9] FS:  0000000000000000(0000) GS:ffff888124f9c000(0000) knlGS:0000000000000000
> [    2.455556][    T9] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    2.455556][    T9] CR2: ffff88823ffff000 CR3: 000000001b078000 CR4: 00000000003506f0
> [    2.455556][    T9] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [    2.455556][    T9] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [    2.455556][    T9] Call Trace:
> [    2.455556][    T9]  <TASK>
> [    2.455556][    T9]  ? __pfx_switch_mm_irqs_off+0x10/0x10
> [    2.455556][    T9]  ? __text_poke+0x6bb/0xb40
> [    2.455556][    T9]  ? kasan_check_range+0x28f/0x2a0
> [    2.455556][    T9]  ? serial8250_isa_init_ports+0x6b/0x110
> [    2.455556][    T9]  unuse_temporary_mm+0x9f/0x100
> [    2.455556][    T9]  __text_poke+0x7b6/0xb40
> [    2.455556][    T9]  ? serial8250_isa_init_ports+0x6b/0x110
> [    2.455556][    T9]  ? __pfx_text_poke_memcpy+0x10/0x10
> [    2.455556][    T9]  ? __pfx___text_poke+0x10/0x10
> [    2.455556][    T9]  ? __pfx___mutex_trylock_common+0x10/0x10
> [    2.455556][    T9]  ? __pfx___might_resched+0x10/0x10
> [    2.455556][    T9]  ? rcu_is_watching+0x15/0xb0
> [    2.455556][    T9]  smp_text_poke_batch_finish+0x3e7/0x12c0
> [    2.455556][    T9]  ? arch_jump_label_transform_apply+0x17/0x30
> [    2.455556][    T9]  ? __pfx___mutex_lock+0x10/0x10
> [    2.455556][    T9]  ? __pfx_smp_text_poke_batch_finish+0x10/0x10
> [    2.455556][    T9]  ? arch_jump_label_transform_queue+0x9b/0x100
> [    2.455556][    T9]  ? __jump_label_update+0x387/0x3b0
> [    2.455556][    T9]  arch_jump_label_transform_apply+0x1c/0x30
> [    2.455556][    T9]  static_key_disable_cpuslocked+0xd2/0x1c0
> [    2.455556][    T9]  static_key_disable+0x1a/0x20
> [    2.455556][    T9]  once_deferred+0x70/0xb0
> [    2.455556][    T9]  ? process_scheduled_works+0x9cb/0x18e0
> [    2.455556][    T9]  process_scheduled_works+0xac3/0x18e0
> [    2.455556][    T9]  ? __pfx_process_scheduled_works+0x10/0x10
> [    2.455556][    T9]  ? assign_work+0x367/0x3d0
> [    2.455556][    T9]  worker_thread+0x870/0xd50
> [    2.455556][    T9]  ? __kthread_parkme+0x1a8/0x200
> [    2.455556][    T9]  ? __pfx_worker_thread+0x10/0x10
> [    2.455556][    T9]  kthread+0x7b7/0x940
> [    2.455556][    T9]  ? __pfx_worker_thread+0x10/0x10
> [    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
> [    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
> [    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
> [    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
> [    2.455556][    T9]  ? _raw_spin_unlock_irq+0x23/0x50
> [    2.455556][    T9]  ? lockdep_hardirqs_on+0x9d/0x150
> [    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
> [    2.455556][    T9]  ret_from_fork+0x4b/0x80
> [    2.455556][    T9]  ? __pfx_kthread+0x10/0x10
> [    2.455556][    T9]  ret_from_fork_asm+0x1a/0x30
> [    2.455556][    T9]  </TASK>
> [    2.455556][    T9] Kernel panic - not syncing: kernel: panic_on_warn set ...

This is some unrelated regression issue. Also, reported here:
https://lore.kernel.org/all/SJ1PR11MB6129E62E3B372932C6B7477FB9BD2@SJ1PR11MB6129.namprd11.prod.outlook.com
https://lore.kernel.org/all/67fce34b.050a0220.3483fc.0026.GAE@google.com


Thanks,
Shivank

[syzbot] [mm?] WARNING in move_to_new_folio

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    01c6df60d5d4 Add linux-next specific files for 20250411
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=107b77e4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=db03cefa26ecf825
dashboard link: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/928246b3f3d5/disk-01c6df60.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/79a68c4e1134/vmlinux-01c6df60.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9caf8c293819/bzImage-01c6df60.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8bb6fd945af4e0ad9299@syzkaller.appspotmail.com

------------[ cut here ]------------
jfs_metapage_aops does not implement migrate_folio
WARNING: CPU: 0 PID: 6870 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline]
WARNING: CPU: 0 PID: 6870 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
Modules linked in:
CPU: 0 UID: 0 PID: 6870 Comm: syz.3.196 Not tainted 6.15.0-rc1-next-20250411-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:fallback_migrate_folio mm/migrate.c:953 [inline]
RIP: 0010:move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
Code: b8 00 00 00 00 00 fc ff df 41 80 7c 05 00 00 74 08 4c 89 e7 e8 73 2d fe ff 49 8b 34 24 48 c7 c7 00 8b 57 8c e8 d3 0b 53 ff 90 <0f> 0b 90 90 e9 0a fd ff ff e8 74 f6 93 ff 90 0f 0b 90 eb a7 e8 69
RSP: 0018:ffffc900045aeb30 EFLAGS: 00010246
RAX: d74fd979f2566d00 RBX: 0000000000000000 RCX: 0000000000080000
RDX: ffffc9000e489000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: ffffea0000c98800 R08: ffffffff81829232 R09: 1ffff110170c4852
R10: dffffc0000000000 R11: ffffed10170c4853 R12: ffff8880612710a8
R13: 1ffff1100c24e215 R14: ffffffff8c839248 R15: ffff888061270f88
FS:  00007f855ea5e6c0(0000) GS:ffff888124f80000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000008 CR3: 000000003477c000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 migrate_folio_move mm/migrate.c:1312 [inline]
 migrate_folios_move mm/migrate.c:1664 [inline]
 migrate_pages_batch+0x1e86/0x30b0 mm/migrate.c:1911
 migrate_pages_sync mm/migrate.c:1968 [inline]
 migrate_pages+0x24f8/0x3470 mm/migrate.c:2050
 compact_zone+0x365d/0x4dd0 mm/compaction.c:2689
 compact_node mm/compaction.c:2958 [inline]
 compact_nodes mm/compaction.c:2980 [inline]
 sysctl_compaction_handler+0x498/0x9a0 mm/compaction.c:3031
 proc_sys_call_handler+0x54b/0x820 fs/proc/proc_sysctl.c:601
 iter_file_splice_write+0xbdf/0x1530 fs/splice.c:738
 do_splice_from fs/splice.c:935 [inline]
 direct_splice_actor+0x11b/0x220 fs/splice.c:1158
 splice_direct_to_actor+0x595/0xc90 fs/splice.c:1102
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0x281/0x3d0 fs/splice.c:1227
 do_sendfile+0x582/0x8d0 fs/read_write.c:1368
 __do_sys_sendfile64 fs/read_write.c:1423 [inline]
 __se_sys_sendfile64+0x102/0x1e0 fs/read_write.c:1415
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f855db8d169
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f855ea5e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f855dda6080 RCX: 00007f855db8d169
RDX: 00002000000000c0 RSI: 0000000000000006 RDI: 0000000000000007
RBP: 00007f855dc0e990 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000009 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f855dda6080 R15: 00007ffe70b954f8
 </TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

Re: [syzbot] [mm?] WARNING in move_to_new_folio

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    01c6df60d5d4 Add linux-next specific files for 20250411
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=111db870580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=db03cefa26ecf825
dashboard link: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10afca3f980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=116f5c04580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/928246b3f3d5/disk-01c6df60.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/79a68c4e1134/vmlinux-01c6df60.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9caf8c293819/bzImage-01c6df60.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/9e5bb76a4272/mount_3.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=14ebd398580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8bb6fd945af4e0ad9299@syzkaller.appspotmail.com

------------[ cut here ]------------
jfs_metapage_aops does not implement migrate_folio
WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline]
WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
Modules linked in:
CPU: 1 UID: 0 PID: 5861 Comm: syz-executor280 Not tainted 6.15.0-rc1-next-20250411-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:fallback_migrate_folio mm/migrate.c:953 [inline]
RIP: 0010:move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
Code: b8 00 00 00 00 00 fc ff df 41 80 7c 05 00 00 74 08 4c 89 e7 e8 73 2d fe ff 49 8b 34 24 48 c7 c7 00 8b 57 8c e8 d3 0b 53 ff 90 <0f> 0b 90 90 e9 0a fd ff ff e8 74 f6 93 ff 90 0f 0b 90 eb a7 e8 69
RSP: 0018:ffffc90003f16b30 EFLAGS: 00010246
RAX: b07441ff5c2b4f00 RBX: 0000000000000000 RCX: ffff88803508bc00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffea00008cc8c0 R08: ffffffff81829232 R09: fffffbfff1d7ab08
R10: dffffc0000000000 R11: fffffbfff1d7ab08 R12: ffff888075b9d130
R13: 1ffff1100eb73a26 R14: ffffffff8c839248 R15: ffff888075b9d010
FS:  0000555581ea4380(0000) GS:ffff888125080000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb8bd341e36 CR3: 000000003002a000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 migrate_folio_move mm/migrate.c:1312 [inline]
 migrate_folios_move mm/migrate.c:1664 [inline]
 migrate_pages_batch+0x1e86/0x30b0 mm/migrate.c:1911
 migrate_pages_sync mm/migrate.c:1941 [inline]
 migrate_pages+0x1e13/0x3470 mm/migrate.c:2050
 compact_zone+0x365d/0x4dd0 mm/compaction.c:2689
 compact_node mm/compaction.c:2958 [inline]
 compact_nodes mm/compaction.c:2980 [inline]
 sysctl_compaction_handler+0x498/0x9a0 mm/compaction.c:3031
 proc_sys_call_handler+0x54b/0x820 fs/proc/proc_sysctl.c:601
 iter_file_splice_write+0xbdf/0x1530 fs/splice.c:738
 do_splice_from fs/splice.c:935 [inline]
 direct_splice_actor+0x11b/0x220 fs/splice.c:1158
 splice_direct_to_actor+0x595/0xc90 fs/splice.c:1102
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0x281/0x3d0 fs/splice.c:1227
 do_sendfile+0x582/0x8d0 fs/read_write.c:1368
 __do_sys_sendfile64 fs/read_write.c:1423 [inline]
 __se_sys_sendfile64+0x102/0x1e0 fs/read_write.c:1415
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0011f6cc49
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 17 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffeb8797248 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f0011f6cc49
RDX: 0000200000000180 RSI: 0000000000000003 RDI: 0000000000000004
RBP: 00000000000f4240 R08: 0000555581ea5378 R09: 0000555581ea5378
R10: 000000000000000a R11: 0000000000000246 R12: 00000000000161d0
R13: 00007ffeb8797280 R14: 00007ffeb879726c R15: 00007f0011fb503b
 </TASK>


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

Re: [syzbot] [mm?] WARNING in move_to_new_folio

[syzbot]

syzbot has bisected this issue to:

commit 7ee3647243e5c4a9d74d4c7ec621eac75c6d37ea
Author: Matthew Wilcox (Oracle) <willy@infradead.org>
Date:   Wed Apr 2 14:59:57 2025 +0000

    migrate: Remove call to ->writepage

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15be8fe4580000
start commit:   01c6df60d5d4 Add linux-next specific files for 20250411
git tree:       linux-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=17be8fe4580000
console output: https://syzkaller.appspot.com/x/log.txt?x=13be8fe4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=db03cefa26ecf825
dashboard link: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10afca3f980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=116f5c04580000

Reported-by: syzbot+8bb6fd945af4e0ad9299@syzkaller.appspotmail.com
Fixes: 7ee3647243e5 ("migrate: Remove call to ->writepage")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Re: [syzbot] [mm?] WARNING in move_to_new_folio

[Shivank Garg]

[-- Attachment #1: Type: text/plain, Size: 1243 bytes --]


#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 01c6df60d5d4

Best Regards,
Shivank

On 4/14/2025 3:14 AM, syzbot wrote:
> syzbot has bisected this issue to:
> 
> commit 7ee3647243e5c4a9d74d4c7ec621eac75c6d37ea
> Author: Matthew Wilcox (Oracle) <willy@infradead.org>
> Date:   Wed Apr 2 14:59:57 2025 +0000
> 
>     migrate: Remove call to ->writepage
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15be8fe4580000
> start commit:   01c6df60d5d4 Add linux-next specific files for 20250411
> git tree:       linux-next
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=17be8fe4580000
> console output: https://syzkaller.appspot.com/x/log.txt?x=13be8fe4580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=db03cefa26ecf825
> dashboard link: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10afca3f980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=116f5c04580000
> 
> Reported-by: syzbot+8bb6fd945af4e0ad9299@syzkaller.appspotmail.com
> Fixes: 7ee3647243e5 ("migrate: Remove call to ->writepage")
> 
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[-- Attachment #2: 0001-jfs-implement-migrate_folio-for-jfs_metapage_aops.patch --]
[-- Type: text/plain, Size: 6141 bytes --]

From 0cd57d102a07f453d4a722215ce8ae34ff81c0a1 Mon Sep 17 00:00:00 2001
From: Shivank Garg <shivankg@amd.com>
Date: Sun, 13 Apr 2025 16:40:53 +0000
Subject: [PATCH] jfs: implement migrate_folio for jfs_metapage_aops

Add the missing migrate_folio operation to jfs_metapage_aops to fix
warnings during memory compaction. These warnings were introduced by
commit 7ee3647243e5 ("migrate: Remove call to ->writepage") which
added explicit warnings when filesystems don't implement migrate_folio.

System reports following warnings:
  jfs_metapage_aops does not implement migrate_folio
  WARNING: CPU: 0 PID: 6870 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline]
  WARNING: CPU: 0 PID: 6870 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007

Implement metapage_migrate_folio which handles both single and multiple
metapages per page configurations.

Fixes: 35474d52c605 ("jfs: Convert metapage_writepage to metapage_write_folio")
Reported-by: syzbot+8bb6fd945af4e0ad9299@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/67faff52.050a0220.379d84.001b.GAE@google.com
Signed-off-by: Shivank Garg <shivankg@amd.com>
---
 fs/jfs/jfs_metapage.c   | 94 +++++++++++++++++++++++++++++++++++++++++
 include/linux/migrate.h |  1 +
 mm/migrate.c            |  3 +-
 3 files changed, 97 insertions(+), 1 deletion(-)

diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
index df575a873ec6..50759a846e22 100644
--- a/fs/jfs/jfs_metapage.c
+++ b/fs/jfs/jfs_metapage.c
@@ -15,6 +15,7 @@
 #include <linux/mempool.h>
 #include <linux/seq_file.h>
 #include <linux/writeback.h>
+#include <linux/migrate.h>
 #include "jfs_incore.h"
 #include "jfs_superblock.h"
 #include "jfs_filsys.h"
@@ -151,6 +152,54 @@ static inline void dec_io(struct folio *folio, blk_status_t status,
 		handler(folio, anchor->status);
 }
 
+static int __metapage_migrate_folio(struct address_space *mapping, struct folio *dst,
+				    struct folio *src, enum migrate_mode mode)
+{
+	struct meta_anchor *src_anchor = src->private;
+	struct metapage *mps[MPS_PER_PAGE] = {0};
+	struct metapage *mp;
+	int i, rc;
+
+	for (i = 0; i < MPS_PER_PAGE; i++) {
+		mp = src_anchor->mp[i];
+		if (mp && metapage_locked(mp))
+			return -EAGAIN;
+	}
+
+	rc = filemap_migrate_folio(mapping, dst, src, mode);
+	if (rc != MIGRATEPAGE_SUCCESS)
+		return rc;
+
+	for (i = 0; i < MPS_PER_PAGE; i++) {
+		mp = src_anchor->mp[i];
+		if (!mp)
+			continue;
+		if (unlikely(insert_metapage(dst, mp))) {
+			/* If error, roll-back previosly inserted pages */
+			for (int j = 0 ; j < i; j++) {
+				if (mps[j])
+					remove_metapage(dst, mps[j]);
+			}
+			return -EAGAIN;
+		}
+		mps[i] = mp;
+	}
+
+	/* Update the metapage and remove it from src */
+	for (int i = 0; i < MPS_PER_PAGE; i++) {
+		mp = mps[i];
+		if (mp) {
+			int page_offset = mp->data - folio_address(src);
+
+			mp->data = folio_address(dst) + page_offset;
+			mp->folio = dst;
+			remove_metapage(src, mp);
+		}
+	}
+
+	return MIGRATEPAGE_SUCCESS;
+}
+
 #else
 static inline struct metapage *folio_to_mp(struct folio *folio, int offset)
 {
@@ -175,6 +224,32 @@ static inline void remove_metapage(struct folio *folio, struct metapage *mp)
 #define inc_io(folio) do {} while(0)
 #define dec_io(folio, status, handler) handler(folio, status)
 
+static int __metapage_migrate_folio(struct address_space *mapping, struct folio *dst,
+				    struct folio *src, enum migrate_mode mode)
+{
+	struct metapage *mp;
+	int page_offset;
+	int rc;
+
+	mp = folio_to_mp(src, 0);
+	if (mp && metapage_locked(mp))
+		return -EAGAIN;
+
+	rc = filemap_migrate_folio(mapping, dst, src, mode);
+	if (rc != MIGRATEPAGE_SUCCESS)
+		return rc;
+
+	if (unlikely(insert_metapage(src, mp)))
+		return -EAGAIN;
+
+	page_offset = mp->data - folio_address(src);
+	mp->data = folio_address(dst) + page_offset;
+	mp->folio = dst;
+	remove_metapage(src, mp);
+
+	return MIGRATEPAGE_SUCCESS;
+}
+
 #endif
 
 static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
@@ -554,6 +629,24 @@ static bool metapage_release_folio(struct folio *folio, gfp_t gfp_mask)
 	return ret;
 }
 
+/**
+ * metapage_migrate_folio - Migration function for JFS metapages
+ */
+static int metapage_migrate_folio(struct address_space *mapping, struct folio *dst,
+				  struct folio *src, enum migrate_mode mode)
+{
+	int expected_count;
+
+	if (!src->private)
+		return filemap_migrate_folio(mapping, dst, src, mode);
+
+	/* Check whether page does not have extra refs before we do more work */
+	expected_count = folio_expected_refs(mapping, src);
+	if (folio_ref_count(src) != expected_count)
+		return -EAGAIN;
+	return __metapage_migrate_folio(mapping, dst, src, mode);
+}
+
 static void metapage_invalidate_folio(struct folio *folio, size_t offset,
 				    size_t length)
 {
@@ -570,6 +663,7 @@ const struct address_space_operations jfs_metapage_aops = {
 	.release_folio	= metapage_release_folio,
 	.invalidate_folio = metapage_invalidate_folio,
 	.dirty_folio	= filemap_dirty_folio,
+	.migrate_folio	= metapage_migrate_folio,
 };
 
 struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index aaa2114498d6..cb31c5b1eb6a 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -60,6 +60,7 @@ struct movable_operations {
 /* Defined in mm/debug.c: */
 extern const char *migrate_reason_names[MR_TYPES];
 
+int folio_expected_refs(struct address_space *mapping, struct folio *folio);
 #ifdef CONFIG_MIGRATION
 
 void putback_movable_pages(struct list_head *l);
diff --git a/mm/migrate.c b/mm/migrate.c
index 6e2488e5dbe4..0f01b8a87dec 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -445,7 +445,7 @@ void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd)
 }
 #endif
 
-static int folio_expected_refs(struct address_space *mapping,
+int folio_expected_refs(struct address_space *mapping,
 		struct folio *folio)
 {
 	int refs = 1;
@@ -458,6 +458,7 @@ static int folio_expected_refs(struct address_space *mapping,
 
 	return refs;
 }
+EXPORT_SYMBOL_GPL(folio_expected_refs);
 
 /*
  * Replace the folio in the mapping.
-- 
2.34.1

Re: [syzbot] [mm?] WARNING in move_to_new_folio

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
unregister_netdevice: waiting for DEV to become free

unregister_netdevice: waiting for batadv0 to become free. Usage count = 3


Tested on:

commit:         01c6df60 Add linux-next specific files for 20250411
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1142f0cc580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=db03cefa26ecf825
dashboard link: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=107a60cc580000