cifs: fix missing unlock in cifs_file_copychunk_range()

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: 3e3761f1 ("smb3: use filemap_write_and_wait_range instead of filemap_write_and_wait")
Cc: stable@vger.kernel.org # 6.0
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: ChenXiaoSong <chenxiaosong2@huawei.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifsfs.c

@@ -1281,7 +1281,7 @@ 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);
@@ -1297,6 +1297,8 @@ 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
 	 */