NFSD: only call fh_unlock() once in nfsd_link()

On non-error paths, nfsd_link() calls fh_unlock() twice.  This is safe
because fh_unlock() records that the unlock has been done and doesn't
repeat it.
However it makes the code a little confusing and interferes with changes
that are planned for directory locking.

So rearrange the code to ensure fh_unlock() is called exactly once if
fh_lock() was called.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/vfs.c

@@ -1541,9 +1541,10 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
 	dirp = d_inode(ddir);
 
 	dnew = lookup_one_len(name, ddir, len);
-	host_err = PTR_ERR(dnew);
-	if (IS_ERR(dnew))
-		goto out_nfserr;
+	if (IS_ERR(dnew)) {
+		err = nfserrno(PTR_ERR(dnew));
+		goto out_unlock;
+	}
 
 	dold = tfhp->fh_dentry;
 
@@ -1562,17 +1563,17 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
 		else
 			err = nfserrno(host_err);
 	}
-out_dput:
 	dput(dnew);
-out_unlock:
-	fh_unlock(ffhp);
+out_drop_write:
 	fh_drop_write(tfhp);
 out:
 	return err;
 
-out_nfserr:
-	err = nfserrno(host_err);
-	goto out_unlock;
+out_dput:
+	dput(dnew);
+out_unlock:
+	fh_unlock(ffhp);
+	goto out_drop_write;
 }
 
 static void