NFS: Request a directory delegation on ACCESS, CREATE, and UNLINK

This patch adds a new flag: NFS_INO_REQ_DIR_DELEG to signal that a
directory wants to request a directory delegation the next time it does
a GETATTR. I have the client request a directory delegation when doing
an access, create, or unlink call since these calls indicate that a user
is working with a directory.

Signed-off-by: Anna Schumaker <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/delegation.c

···
 	delegation->inode = NULL;
 	rcu_assign_pointer(nfsi->delegation, NULL);
 	spin_unlock(&delegation->lock);
+	clear_bit(NFS_INO_REQ_DIR_DELEG, &nfsi->flags);
 	return delegation;
 }
 

fs/nfs/delegation.h

···
 						 NFS_DELEGATION_FLAG_TIME);
 }
 
+static inline void nfs_request_directory_delegation(struct inode *inode)
+{
+	if (S_ISDIR(inode->i_mode))
+		set_bit(NFS_INO_REQ_DIR_DELEG, &NFS_I(inode)->flags);
+}
+
 int nfs4_delegation_hash_alloc(struct nfs_server *server);
 
 #endif

fs/nfs/nfs4proc.c

···
 	return status;
 }
 
+#if IS_ENABLED(CONFIG_NFS_V4_1)
+static bool should_request_dir_deleg(struct inode *inode)
+{
+	if (!inode)
+		return false;
+	if (!S_ISDIR(inode->i_mode))
+		return false;
+	if (!nfs_server_capable(inode, NFS_CAP_DIR_DELEG))
+		return false;
+	if (!test_and_clear_bit(NFS_INO_REQ_DIR_DELEG, &(NFS_I(inode)->flags)))
+		return false;
+	if (nfs4_have_delegation(inode, FMODE_READ, 0))
+		return false;
+	return true;
+}
+#else
+static bool should_request_dir_deleg(struct inode *inode)
+{
+	return false;
+}
+#endif /* CONFIG_NFS_V4_1 */
+
 static int _nfs4_proc_getattr(struct nfs_server *server, struct nfs_fh *fhandle,
 				struct nfs_fattr *fattr, struct inode *inode)
 {
···
 		.rpc_argp = &args,
 		.rpc_resp = &res,
 	};
+	struct nfs4_gdd_res gdd_res;
 	unsigned short task_flags = 0;
+	int status;
 
 	if (nfs4_has_session(server->nfs_client))
 		task_flags = RPC_TASK_MOVEABLE;
···
 	if (inode && (server->flags & NFS_MOUNT_SOFTREVAL))
 		task_flags |= RPC_TASK_TIMEOUT;
 
+	args.get_dir_deleg = should_request_dir_deleg(inode);
+	if (args.get_dir_deleg)
+		res.gdd_res = &gdd_res;
+
 	nfs4_bitmap_copy_adjust(bitmask, nfs4_bitmask(server, fattr->label), inode, 0);
 	nfs_fattr_init(fattr);
 	nfs4_init_sequence(&args.seq_args, &res.seq_res, 0, 0);
-	return nfs4_do_call_sync(server->client, server, &msg,
-			&args.seq_args, &res.seq_res, task_flags);
+
+	status = nfs4_do_call_sync(server->client, server, &msg,
+				   &args.seq_args, &res.seq_res, task_flags);
+	if (args.get_dir_deleg) {
+		if (status == -EOPNOTSUPP) {
+			server->caps &= ~NFS_CAP_DIR_DELEG;
+		} else if (status == 0 && gdd_res.status == GDD4_OK) {
+			status = nfs_inode_set_delegation(inode, current_cred(),
+							  FMODE_READ, &gdd_res.deleg,
+							  0, NFS4_OPEN_DELEGATE_READ);
+		}
+	}
+	return status;
 }
 
 int nfs4_proc_getattr(struct nfs_server *server, struct nfs_fh *fhandle,
···
 	do {
 		err = _nfs4_proc_getattr(server, fhandle, fattr, inode);
 		trace_nfs4_getattr(server, fhandle, fattr, err);
-		err = nfs4_handle_exception(server, err,
-				&exception);
+		if (err == -EOPNOTSUPP)
+			exception.retry = true;
+		else
+			err = nfs4_handle_exception(server, err, &exception);
 	} while (exception.retry);
 	return err;
 }
···
 	int status = 0;
 
 	if (!nfs4_have_delegation(inode, FMODE_READ, 0)) {
+		nfs_request_directory_delegation(inode);
 		res.fattr = nfs_alloc_fattr();
 		if (res.fattr == NULL)
 			return -ENOMEM;
···
 
 	ilabel = nfs4_label_init_security(dir, dentry, sattr, &l);
 
+	nfs_request_directory_delegation(dir);
+
 	if (!(server->attr_bitmask[2] & FATTR4_WORD2_MODE_UMASK))
 		sattr->ia_mode &= ~current_umask();
 	state = nfs4_do_open(dir, ctx, flags, sattr, ilabel, NULL);
···
 	nfs4_init_sequence(&args->seq_args, &res->seq_res, 1, 0);
 
 	nfs_fattr_init(res->dir_attr);
+	nfs_request_directory_delegation(d_inode(dentry->d_parent));
 
 	if (inode) {
 		nfs4_inode_return_delegation(inode);
···
 	.minor_version = 1,
 	.init_caps = NFS_CAP_READDIRPLUS
 		| NFS_CAP_ATOMIC_OPEN
+		| NFS_CAP_DIR_DELEG
 		| NFS_CAP_POSIX_LOCK
 		| NFS_CAP_STATEID_NFSV41
 		| NFS_CAP_ATOMIC_OPEN_V1
···
 	.minor_version = 2,
 	.init_caps = NFS_CAP_READDIRPLUS
 		| NFS_CAP_ATOMIC_OPEN
+		| NFS_CAP_DIR_DELEG
 		| NFS_CAP_POSIX_LOCK
 		| NFS_CAP_STATEID_NFSV41
 		| NFS_CAP_ATOMIC_OPEN_V1

include/linux/nfs_fs.h

···
 #define NFS_INO_LAYOUTCOMMITTING (10)		/* layoutcommit inflight */
 #define NFS_INO_LAYOUTSTATS	(11)		/* layoutstats inflight */
 #define NFS_INO_ODIRECT		(12)		/* I/O setting is O_DIRECT */
+#define NFS_INO_REQ_DIR_DELEG	(13)		/* Request a directory delegation */
 
 static inline struct nfs_inode *NFS_I(const struct inode *inode)
 {

include/linux/nfs_fs_sb.h

···
 #define NFS_CAP_REBOOT_LAYOUTRETURN	(1U << 8)
 #define NFS_CAP_OFFLOAD_STATUS	(1U << 9)
 #define NFS_CAP_ZERO_RANGE	(1U << 10)
+#define NFS_CAP_DIR_DELEG	(1U << 11)
 #define NFS_CAP_OPEN_XOR	(1U << 12)
 #define NFS_CAP_DELEGTIME	(1U << 13)
 #define NFS_CAP_POSIX_LOCK	(1U << 14)