FAILED: patch "[PATCH] f2fs: fix to avoid potential deadloop in" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-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 <[email protected]>.

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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x ce366bfa821ec81dd45bde547ee31e659306cc61
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090958-plastic-payee-9f0a@gregkh' --subject-prefix 'PATCH 5.15.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 <[email protected]>
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

index 968e5ed38816..86c2e67e43b6 100644
@@ -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);

From: Chao Yu <[email protected]>

[ Upstream commit ce366bfa821ec81dd45bde547ee31e659306cc61 ]

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

---
 fs/f2fs/node.c | 5 +++++
 1 file changed, 5 insertions(+)

index e5a06a65a5398..34a590d500819 100644
@@ -1847,6 +1847,11 @@ 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_page->index);
 		lock_page(last_page);
+		if (unlikely(last_page->mapping != NODE_MAPPING(sbi))) {
+			f2fs_put_page(last_page, 1);
+			ret = -EAGAIN;
+			goto out;
+		}
 		f2fs_wait_on_page_writeback(last_page, NODE, true, true);
 		set_page_dirty(last_page);
 		unlock_page(last_page);

2.53.0