[PATCH] f2fs: fix to avoid potential deadloop in f2fs_fsync_node_pages()

[PATCH] f2fs: fix to avoid potential deadloop in f2fs_fsync_node_pages()

[Chao Yu]

There is potential deadloop in race condition:

Thread A				Thread B
- fsync
 - f2fs_do_sync_file
  - f2fs_fsync_node_pages
   - last_fsync_dnode
    - folio_get(last_folio)
					- f2fs_setattr
					 - f2fs_truncate
					  - f2fs_truncate_blocks
					   - f2fs_do_truncate_blocks
					    - f2fs_truncate_inode_blocks
					     - truncate_dnode
					      - truncate_node
					       - invalidate_mapping_pages
					        - folio->mapping = NULL
   - is_node_folio alwasy return false
   - atomic && !marked is always true,
     then goto retry

Cc: stable@kernel.org
Fixes: 608514deba38 ("f2fs: set fsync mark only for the last dnode")
Signed-off-by: Chao Yu <chao@kernel.org>
---
 fs/f2fs/node.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 968e5ed38816..86c2e67e43b6 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -2016,6 +2016,11 @@ int f2fs_fsync_node_pages(struct f2fs_sb_info *sbi, struct inode *inode,
 		f2fs_debug(sbi, "Retry to write fsync mark: ino=%u, idx=%lx",
 			   ino, last_folio->index);
 		folio_lock(last_folio);
+		if (unlikely(!is_node_folio(last_folio))) {
+			f2fs_folio_put(last_folio, true);
+			ret = -EAGAIN;
+			goto out;
+		}
 		f2fs_folio_wait_writeback(last_folio, NODE, true, true);
 		folio_mark_dirty(last_folio);
 		folio_unlock(last_folio);
-- 
2.49.0

Re: [f2fs-dev] [PATCH] f2fs: fix to avoid potential deadloop in f2fs_fsync_node_pages()

[patchwork-bot+f2fs]

Hello:

This patch was applied to jaegeuk/f2fs.git (dev)
by Jaegeuk Kim <jaegeuk@kernel.org>:

On Mon, 24 Aug 2026 21:17:29 +0800 you wrote:
> There is potential deadloop in race condition:
> 
> Thread A				Thread B
> - fsync
>  - f2fs_do_sync_file
>   - f2fs_fsync_node_pages
>    - last_fsync_dnode
>     - folio_get(last_folio)
> 					- f2fs_setattr
> 					 - f2fs_truncate
> 					  - f2fs_truncate_blocks
> 					   - f2fs_do_truncate_blocks
> 					    - f2fs_truncate_inode_blocks
> 					     - truncate_dnode
> 					      - truncate_node
> 					       - invalidate_mapping_pages
> 					        - folio->mapping = NULL
>    - is_node_folio alwasy return false
>    - atomic && !marked is always true,
>      then goto retry
> 
> [...]

Here is the summary with links:
  - [f2fs-dev] f2fs: fix to avoid potential deadloop in f2fs_fsync_node_pages()
    https://git.kernel.org/jaegeuk/f2fs/c/ce366bfa821e

You are awesome, thank you!
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