The extent map cache can become stale when extents are moved or
defragmented, causing subsequent operations to see outdated extent flags.
This triggers a BUG_ON in ocfs2_refcount_cal_cow_clusters().
The problem occurs when:
1. copy_file_range() creates a reflinked extent with OCFS2_EXT_REFCOUNTED
2. ioctl(FITRIM) triggers ocfs2_move_extents()
3. __ocfs2_move_extents_range() reads and caches the extent (flags=0x2)
4. ocfs2_move_extent()/ocfs2_defrag_extent() calls __ocfs2_move_extent()
which clears OCFS2_EXT_REFCOUNTED flag on disk (flags=0x0)
5. The extent map cache is not invalidated after the move
6. Later write() operations read stale cached flags (0x2) but disk has
updated flags (0x0), causing a mismatch
7. BUG_ON(!(rec->e_flags & OCFS2_EXT_REFCOUNTED)) triggers
Fix by clearing the extent map cache after each extent move/defrag
operation in __ocfs2_move_extents_range(). This ensures subsequent
operations read fresh extent data from disk.
Link: https://lore.kernel.org/all/20251009142917.517229-1-kartikey406@gmail.com/T/
Link: https://lkml.kernel.org/r/20251009154903.522339-1-kartikey406@gmail.com
Fixes: 53069d4e76 ("Ocfs2/move_extents: move/defrag extents within a certain range.")
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Reported-by: syzbot+6fdd8fa3380730a4b22c@syzkaller.appspotmail.com
Tested-by: syzbot+6fdd8fa3380730a4b22c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?id=2959889e1f6e216585ce522f7e8bc002b46ad9e7
Reviewed-by: Mark Fasheh <mark@fasheh.com>
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
78a63493f8