NFS: nfs_lookup doesn't need to revalidate the parent directory's inode

 nfs_lookup() used to consult a lookup cache before trying an actual wire
 lookup operation.  The lookup cache would be invalid, of course, if the
 parent directory's mtime had changed, so nfs_lookup performed an inode
 revalidation on the parent.

 Since nfs_lookup() doesn't use a cache anymore, the revalidation is no
 longer necessary.  There are cases where it will generate a lot of
 unnecessary GETATTR traffic.

 See http://bugzilla.linux-nfs.org/show_bug.cgi?id=9

 Test-plan:
 Use lndir and "rm -rf" and watch for excess GETATTR traffic or application
 level errors.
Signed-off-by: NChuck Lever <cel@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/dir.c

@@ -853,12 +853,6 @@ static struct dentry *nfs_lookup(struct inode *dir, struct dentry * dentry, stru
 	dentry->d_op = NFS_PROTO(dir)->dentry_ops;
 
 	lock_kernel();
-	/* Revalidate parent directory attribute cache */
-	error = nfs_revalidate_inode(NFS_SERVER(dir), dir);
-	if (error < 0) {
-		res = ERR_PTR(error);
-		goto out_unlock;
-	}
 
 	/* If we're doing an exclusive create, optimize away the lookup */
 	if (nfs_is_exclusive_create(dir, nd))