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 <neil@brown.name>
Link: https://lore.kernel.org/20250608230952.20539-5-neil@brown.name
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: neilbrown

fs/exportfs/expfs.c

@@ -549,15 +549,13 @@ exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
 			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.