ksmbd: use F_SETLK when unlocking a file

ksmbd seems to be trying to use a cmd value of 0 when unlocking a file.
That activity requires a type of F_UNLCK with a cmd of F_SETLK. For
local POSIX locking, it doesn't matter much since vfs_lock_file ignores
@cmd, but filesystems that define their own ->lock operation expect to
see it set sanely.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/smb2pdu.c

@@ -6753,7 +6753,7 @@ static int smb2_set_flock_flags(struct file_lock *flock, int flags)
 	case SMB2_LOCKFLAG_UNLOCK:
 		ksmbd_debug(SMB, "received unlock request\n");
 		flock->fl_type = F_UNLCK;
-		cmd = 0;
+		cmd = F_SETLK;
 		break;
 	}
 
@@ -7131,7 +7131,7 @@ int smb2_lock(struct ksmbd_work *work)
 		rlock->fl_start = smb_lock->start;
 		rlock->fl_end = smb_lock->end;
 
-		rc = vfs_lock_file(filp, 0, rlock, NULL);
+		rc = vfs_lock_file(filp, F_SETLK, rlock, NULL);
 		if (rc)
 			pr_err("rollback unlock fail : %d\n", rc);