NFS: Don't revalidate the directory permissions on a lookup failure

There should be no reason to expect the directory permissions to change
just because the directory contents changed or a negative lookup timed
out. So let's avoid doing a full call to nfs_mark_for_revalidate() in
that case.
Furthermore, if this is a negative dentry, and we haven't actually done
a new lookup, then we have no reason yet to believe the directory has
changed at all. So let's remove the gratuitous directory inode
invalidation altogether when called from
nfs_lookup_revalidate_negative().

Reported-by: Geert Jansen <gerardu@amazon.com>
Fixes: 5ceb9d7 ("NFS: Refactor nfs_lookup_revalidate()")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Author: Trond Myklebust

fs/nfs/dir.c

@@ -1401,6 +1401,15 @@ int nfs_lookup_verify_inode(struct inode *inode, unsigned int flags)
 	goto out;
 }
 
+static void nfs_mark_dir_for_revalidate(struct inode *inode)
+{
+	struct nfs_inode *nfsi = NFS_I(inode);
+
+	spin_lock(&inode->i_lock);
+	nfsi->cache_validity |= NFS_INO_REVAL_PAGECACHE;
+	spin_unlock(&inode->i_lock);
+}
+
 /*
  * We judge how long we want to trust negative
  * dentries by looking at the parent inode mtime.
@@ -1435,7 +1444,6 @@ nfs_lookup_revalidate_done(struct inode *dir, struct dentry *dentry,
 			__func__, dentry);
 		return 1;
 	case 0:
-		nfs_mark_for_revalidate(dir);
 		if (inode && S_ISDIR(inode->i_mode)) {
 			/* Purge readdir caches. */
 			nfs_zap_caches(inode);
@@ -1525,6 +1533,13 @@ nfs_lookup_revalidate_dentry(struct inode *dir, struct dentry *dentry,
 	nfs_free_fattr(fattr);
 	nfs_free_fhandle(fhandle);
 	nfs4_label_free(label);
+
+	/*
+	 * If the lookup failed despite the dentry change attribute being
+	 * a match, then we should revalidate the directory cache.
+	 */
+	if (!ret && nfs_verify_change_attribute(dir, dentry->d_time))
+		nfs_mark_dir_for_revalidate(dir);
 	return nfs_lookup_revalidate_done(dir, dentry, inode, ret);
 }
 
@@ -1567,7 +1582,7 @@ nfs_do_lookup_revalidate(struct inode *dir, struct dentry *dentry,
 		error = nfs_lookup_verify_inode(inode, flags);
 		if (error) {
 			if (error == -ESTALE)
-				nfs_zap_caches(dir);
+				nfs_mark_dir_for_revalidate(dir);
 			goto out_bad;
 		}
 		nfs_advise_use_readdirplus(dir);
@@ -2064,7 +2079,6 @@ nfs_add_or_obtain(struct dentry *dentry, struct nfs_fh *fhandle,
 	dput(parent);
 	return d;
 out_error:
-	nfs_mark_for_revalidate(dir);
 	d = ERR_PTR(error);
 	goto out;
 }