NFSv4: Allow attribute caching with 'noac' mounts if client holds a delegation

If the server has given us a delegation on a file, we _know_ that we can
cache the attribute information even when the user has specified 'noac'.

Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/file.c

@@ -161,13 +161,16 @@ static int nfs_revalidate_file_size(struct inode *inode, struct file *filp)
 	struct nfs_server *server = NFS_SERVER(inode);
 	struct nfs_inode *nfsi = NFS_I(inode);
 
-	if (server->flags & NFS_MOUNT_NOAC)
-		goto force_reval;
+	if (nfs_have_delegated_attributes(inode))
+		goto out_noreval;
+
 	if (filp->f_flags & O_DIRECT)
 		goto force_reval;
-	if (nfsi->npages != 0)
-		return 0;
-	if (!(nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE) && !nfs_attribute_timeout(inode))
+	if (nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE)
+		goto force_reval;
+	if (nfs_attribute_timeout(inode))
+		goto force_reval;
+out_noreval:
 	return 0;
 force_reval:
 	return __nfs_revalidate_inode(server, inode);

fs/nfs/inode.c

@@ -742,9 +742,14 @@ int nfs_attribute_timeout(struct inode *inode)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
 
+	return !time_in_range_open(jiffies, nfsi->read_cache_jiffies, nfsi->read_cache_jiffies + nfsi->attrtimeo);
+}
+
+static int nfs_attribute_cache_expired(struct inode *inode)
+{
 	if (nfs_have_delegated_attributes(inode))
 		return 0;
-	return !time_in_range_open(jiffies, nfsi->read_cache_jiffies, nfsi->read_cache_jiffies + nfsi->attrtimeo);
+	return nfs_attribute_timeout(inode);
 }
 
 /**
@@ -757,7 +762,7 @@ int nfs_attribute_timeout(struct inode *inode)
 int nfs_revalidate_inode(struct nfs_server *server, struct inode *inode)
 {
 	if (!(NFS_I(inode)->cache_validity & NFS_INO_INVALID_ATTR)
-			&& !nfs_attribute_timeout(inode))
+			&& !nfs_attribute_cache_expired(inode))
 		return NFS_STALE(inode) ? -ESTALE : 0;
 	return __nfs_revalidate_inode(server, inode);
 }
@@ -794,7 +799,8 @@ int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping)
 	int ret = 0;
 
 	if ((nfsi->cache_validity & NFS_INO_REVAL_PAGECACHE)
-			|| nfs_attribute_timeout(inode) || NFS_STALE(inode)) {
+			|| nfs_attribute_cache_expired(inode)
+			|| NFS_STALE(inode)) {
 		ret = __nfs_revalidate_inode(NFS_SERVER(inode), inode);
 		if (ret < 0)
 			goto out;