[PATCH v2] f2fs: return symlink writeback errors

[Wenjie Qi]

F2FS writes long symlink data with page_symlink() and then flushes the
symlink mapping to reduce the chance of exposing a broken symlink.

That flush result is currently ignored. If the writeback fails, symlink()
still returns success even though the symlink is not durable and the same
operation can already surface -EIO through syncfs().

Return the writeback error to userspace and skip the dirsync flush once the
symlink data flush has failed.

Fixes: d0cae97cb600 ("f2fs: flush symlink path to avoid broken symlink after POR")
Cc: stable@xxxxxxxxxx
Signed-off-by: Wenjie Qi <qiwenjie@xxxxxxxxxx>
---
Changes since v1:
- fix the Fixes tag to point to the real introducing commit

Reproducer:
- enable FAULT_WRITE_IO on the mounted F2FS filesystem
- create a long symlink so the target is written through page_symlink()
- old kernel: symlink() returns 0, syncfs() returns -EIO, and the symlink is
  absent after remount
- new kernel: symlink() returns -EIO

 fs/f2fs/namei.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
index 7ffdf23cea5e..a8db3928c8b5 100644
--- a/fs/f2fs/namei.c
+++ b/fs/f2fs/namei.c
@@ -707,15 +707,16 @@ static int f2fs_symlink(struct mnt_idmap *idmap, struct inode *dir,
 	 * performance regression.
 	 */
 	if (!err) {
-		filemap_write_and_wait_range(inode->i_mapping, 0,
-							disk_link.len - 1);
+		err = filemap_write_and_wait_range(inode->i_mapping, 0,
+						   disk_link.len - 1);
 
-		if (IS_DIRSYNC(dir))
+		if (!err && IS_DIRSYNC(dir))
 			f2fs_sync_fs(sbi->sb, 1);
-	} else {
-		f2fs_unlink(dir, dentry);
 	}
 
+	if (err)
+		f2fs_unlink(dir, dentry);
+
 	f2fs_balance_fs(sbi, true);
 	goto out_free_encrypted_link;
 
-- 
2.43.0