cifs: fix missing unlock in cifs_file_copychunk_range()

BugLink: https://bugs.launchpad.net/bugs/2036450

xfstests generic/013 and generic/476 reported WARNING as follows:

  WARNING: lock held when returning to user space!
  6.1.0-rc5+ #4 Not tainted
  ------------------------------------------------
  fsstress/504233 is leaving the kernel with locks still held!
  2 locks held by fsstress/504233:
   #0: ffff888054c38850 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at:
                        lock_two_nondirectories+0xcf/0xf0
   #1: ffff8880b8fec750 (&sb->s_type->i_mutex_key#21/4){+.+.}-{3:3}, at:
                        lock_two_nondirectories+0xb7/0xf0

This will lead to deadlock and hungtask.

Fix this by releasing locks when failed to write out on a file range in
cifs_file_copychunk_range().

Fixes: 3e3761f ("smb3: use filemap_write_and_wait_range instead of filemap_write_and_wait")
Cc: [email protected] # 6.0
Reviewed-by: Paulo Alcantara (SUSE) <[email protected]>
Signed-off-by: ChenXiaoSong <[email protected]>
Signed-off-by: Steve French <[email protected]>
(cherry picked from commit 5024878)
Signed-off-by: Tim Gardner <[email protected]>

Author: ChenXiaoSong

fs/cifs/cifsfs.c

@@ -1274,7 +1274,7 @@ ssize_t cifs_file_copychunk_range(unsigned int xid,
 	rc = filemap_write_and_wait_range(src_inode->i_mapping, off,
 					  off + len - 1);
 	if (rc)
-		goto out;
+		goto unlock;
 
 	/* should we flush first and last page first */
 	truncate_inode_pages(&target_inode->i_data, 0);
@@ -1290,6 +1290,8 @@ ssize_t cifs_file_copychunk_range(unsigned int xid,
 	 * that target is updated on the server
 	 */
 	CIFS_I(target_inode)->time = 0;
+
+unlock:
 	/* although unlocking in the reverse order from locking is not
 	 * strictly necessary here it is a little cleaner to be consistent
 	 */