NFS: Add a module option to disable directory delegations

When this option is disabled then the client will not request directory
delegations or check if we have one during the revalidation paths.

Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Author: Anna Schumaker

fs/nfs/delegation.c

@@ -30,6 +30,11 @@
 static unsigned nfs_delegation_watermark = NFS_DEFAULT_DELEGATION_WATERMARK;
 module_param_named(delegation_watermark, nfs_delegation_watermark, uint, 0644);
 
+bool directory_delegations = true;
+module_param(directory_delegations, bool, 0644);
+MODULE_PARM_DESC(directory_delegations,
+		 "Enable the use of directory delegations, defaults to on.");
+
 static struct hlist_head *nfs_delegation_hash(struct nfs_server *server,
 		const struct nfs_fh *fhandle)
 {
@@ -143,6 +148,8 @@ static int nfs4_do_check_delegation(struct inode *inode, fmode_t type,
  */
 int nfs4_have_delegation(struct inode *inode, fmode_t type, int flags)
 {
+	if (S_ISDIR(inode->i_mode) && !directory_delegations)
+		nfs_inode_evict_delegation(inode);
 	return nfs4_do_check_delegation(inode, type, flags, true);
 }
 

fs/nfs/delegation.h

@@ -124,6 +124,8 @@ static inline int nfs_have_delegated_mtime(struct inode *inode)
 						 NFS_DELEGATION_FLAG_TIME);
 }
 
+extern bool directory_delegations;
+
 static inline void nfs_request_directory_delegation(struct inode *inode)
 {
 	if (S_ISDIR(inode->i_mode))

fs/nfs/nfs4proc.c

@@ -4473,6 +4473,8 @@ static int nfs4_get_referral(struct rpc_clnt *client, struct inode *dir,
 #if IS_ENABLED(CONFIG_NFS_V4_1)
 static bool should_request_dir_deleg(struct inode *inode)
 {
+	if (!directory_delegations)
+		return false;
 	if (!inode)
 		return false;
 	if (!S_ISDIR(inode->i_mode))