NFS: Only look at the change attribute cache state in nfs_weak_revalidate()

Just like in nfs_check_verifier(), we want to use
nfs_mapping_need_revalidate_inode() to check our knowledge of the
change attribute is up to date.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/dir.c

@@ -1273,8 +1273,8 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
  */
 static int nfs_weak_revalidate(struct dentry *dentry, unsigned int flags)
 {
-	int error;
 	struct inode *inode = d_inode(dentry);
+	int error = 0;
 
 	/*
 	 * I believe we can only get a negative dentry here in the case of a
@@ -1293,7 +1293,8 @@ static int nfs_weak_revalidate(struct dentry *dentry, unsigned int flags)
 		return 0;
 	}
 
-	error = nfs_revalidate_inode(NFS_SERVER(inode), inode);
+	if (nfs_mapping_need_revalidate_inode(inode))
+		error = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
 	dfprintk(LOOKUPCACHE, "NFS: %s: inode %lu is %s\n",
 			__func__, inode->i_ino, error ? "invalid" : "valid");
 	return !error;