[PATCH 5/5] NFS: Add a module option to disable directory delegations

[Anna Schumaker <anna@kernel.org>]

From: Anna Schumaker <anna.schumaker@oracle.com>

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>
---
 fs/nfs/delegation.c | 7 +++++++
 fs/nfs/delegation.h | 2 ++
 fs/nfs/nfs4proc.c   | 2 ++
 3 files changed, 11 insertions(+)

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index b4c192f00e94..2248e3ad089a 100644
--- a/fs/nfs/delegation.c
+++ b/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);
 }
 
diff --git a/fs/nfs/delegation.h b/fs/nfs/delegation.h
index 8968f62bf438..46d866adb5c2 100644
--- a/fs/nfs/delegation.h
+++ b/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))
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index fa176db362c7..33b64d000c40 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4463,6 +4463,8 @@ 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))
-- 
2.51.2