+ ocfs2-clear-extent-cache-after-moving-defragmenting-extents.patch added to mm-hotfixes-unstable branch

+ ocfs2-clear-extent-cache-after-moving-defragmenting-extents.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: ocfs2: clear extent cache after moving/defragmenting extents
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     ocfs2-clear-extent-cache-after-moving-defragmenting-extents.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ocfs2-clear-extent-cache-after-moving-defragmenting-extents.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Deepanshu Kartikey <kartikey406@gmail.com>
Subject: ocfs2: clear extent cache after moving/defragmenting extents
Date: Thu, 9 Oct 2025 21:19:03 +0530

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defragmented, causing subsequent operations to see outdated extent flags.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
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>
---

 fs/ocfs2/move_extents.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/fs/ocfs2/move_extents.c~ocfs2-clear-extent-cache-after-moving-defragmenting-extents
+++ a/fs/ocfs2/move_extents.c
@@ -867,6 +867,11 @@ static int __ocfs2_move_extents_range(st
 			mlog_errno(ret);
 			goto out;
 		}
+		/*
+		 * Invalidate extent cache after moving/defragging to prevent
+		 * stale cached data with outdated extent flags.
+		 */
+		ocfs2_extent_map_trunc(inode, cpos);
 
 		context->clusters_moved += alloc_size;
 next:
_

Patches currently in -mm which might be from kartikey406@gmail.com are

hugetlbfs-check-for-shareable-lock-before-calling-huge_pmd_unshare.patch
ocfs2-clear-extent-cache-after-moving-defragmenting-extents.patch