exportfs: use lookup_one_unlocked()

rather than locking the directory and using lookup_one(), just use
lookup_one_unlocked(). This keeps locking code centralised.

Signed-off-by: NeilBrown <[e-mail]>
Link: https://lore.kernel.org/[e-mail]
Reviewed-by: Chuck Lever <[e-mail]>
Reviewed-by: Jeff Layton <[e-mail]>
Signed-off-by: Christian Brauner <[e-mail]>

fs/exportfs/expfs.c

···
 			goto err_result;
 		}
 
-		inode_lock(target_dir->d_inode);
-		nresult = lookup_one(mnt_idmap(mnt), &QSTR(nbuf), target_dir);
+		nresult = lookup_one_unlocked(mnt_idmap(mnt), &QSTR(nbuf), target_dir);
 		if (!IS_ERR(nresult)) {
 			if (unlikely(nresult->d_inode != result->d_inode)) {
 				dput(nresult);
 				nresult = ERR_PTR(-ESTALE);
 			}
 		}
-		inode_unlock(target_dir->d_inode);
 		/*
 		 * At this point we are done with the parent, but it's pinned
 		 * by the child dentry anyway.