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Message-ID: <67fde182.050a0220.3483fc.0043.GAE@google.com>
Date: Mon, 14 Apr 2025 21:33:06 -0700
From: syzbot <syzbot+8bb6fd945af4e0ad9299@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] Re: [syzbot] [mm?] WARNING in move_to_new_folio
For archival purposes, forwarding an incoming command email to
linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com.
***
Subject: Re: [syzbot] [mm?] WARNING in move_to_new_folio
Author: shivankg@....com
On 4/14/2025 3:14 AM, syzbot wrote:
> syzbot has bisected this issue to:
>
> commit 7ee3647243e5c4a9d74d4c7ec621eac75c6d37ea
> Author: Matthew Wilcox (Oracle) <willy@...radead.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@...kaller.appspotmail.com
> Fixes: 7ee3647243e5 ("migrate: Remove call to ->writepage")
>
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
#syz test
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
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