NFS: Fix dcache revalidation bugs

We don't need to force a dentry lookup just because we're making changes to
the directory.

Don't update nfsi->cache_change_attribute in nfs_end_data_update: that
overrides the NFSv3/v4 weak consistency checking that tells us our update
was the only one, and that tells us the dcache is still valid.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/dir.c

@@ -650,15 +650,11 @@ static int nfs_fsync_dir(struct file *filp, struct dentry *dentry, int datasync)
  */
 static int nfs_check_verifier(struct inode *dir, struct dentry *dentry)
 {
-	unsigned long verf;
-
 	if (IS_ROOT(dentry))
 		return 1;
-	verf = dentry->d_time;
-	if (nfs_caches_unstable(dir)
-			|| verf != NFS_I(dir)->cache_change_attribute)
-		return 0;
+	if (dentry->d_time == NFS_I(dir)->cache_change_attribute)
 		return 1;
+	return 0;
 }
 
 static inline void nfs_set_verifier(struct dentry * dentry, unsigned long verf)

fs/nfs/inode.c

@@ -785,7 +785,6 @@ void nfs_end_data_update(struct inode *inode)
 		nfsi->cache_validity |= NFS_INO_INVALID_DATA;
 		spin_unlock(&inode->i_lock);
 	}
-	nfsi->cache_change_attribute = jiffies;
 	atomic_dec(&nfsi->data_updates);
 }