FAILED: patch "[PATCH] f2fs: fix to avoid potential deadloop in" failed to apply to 6.6-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x ce366bfa821ec81dd45bde547ee31e659306cc61
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026090957-spectacle-juniper-fbdf@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ce366bfa821ec81dd45bde547ee31e659306cc61 Mon Sep 17 00:00:00 2001
From: Chao Yu <chao@kernel.org>
Date: Mon, 24 Aug 2026 21:17:29 +0800
Subject: [PATCH] f2fs: fix to avoid potential deadloop in
 f2fs_fsync_node_pages()

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>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

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);