[PATCH] ntfs: avoid self-deadlock during inode eviction

[Hyunchul Lee]

An attribute-list update performed while allocating clusters can drop the
last reference to the temporary attribute inode. Evicting that inode
drops its reference to the base inode and can invoke ntfs_drop_big_inode()
for the base inode from within the base inode's own writeback path.

If the base inode is unlinked, ntfs_drop_big_inode() calls
truncate_setsize(), which waits for the inode's folio writeback to
complete. The same writeback worker is responsible for completing that
writeback, so it waits for itself indefinitely.

Prevent this self-deadlock by grabbing a reference to the base inode at the
beginning of ntfs_writepages() and releasing it at the end of the function.
This defers eviction until all bios have been submitted, allowing the wait
for folio writeback to complete safely.

Signed-off-by: Hyunchul Lee <hyc.lee@xxxxxxxxx>
---
 fs/ntfs/aops.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index 1fbf832ad165..88e5b2def66c 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -251,6 +251,8 @@ static int ntfs_writepages(struct address_space *mapping,
 		.wbc		= wbc,
 		.ops		= &ntfs_writeback_ops,
 	};
+	bool need_iput = false;
+	int ret;
 
 	if (NVolShutdown(ni->vol))
 		return -EIO;
@@ -267,7 +269,20 @@ static int ntfs_writepages(struct address_space *mapping,
 		return -EOPNOTSUPP;
 	}
 
-	return iomap_writepages(&wpc);
+	/*
+	 * Prevent eviction in writeback to avoid deadlock in
+	 * ntfs_drop_big_inode().
+	 */
+	if ((ni->type == AT_DATA || ni->type == AT_INDEX_ALLOCATION) &&
+	    igrab(inode))
+		need_iput = true;
+
+	ret = iomap_writepages(&wpc);
+
+	if (need_iput)
+		iput(inode);
+
+	return ret;
 }
 
 static int ntfs_swap_activate(struct swap_info_struct *sis,

---
base-commit: ec050fc4cf17d341e08c8e25dd9dd6af37bb2e67
change-id: 20260702-fix-deadlock-inode-eviction-086ee99bd59d

Best regards,
-- 
Thanks,
Hyunchul