NFSv4: Return unreferenced delegations more promptly

If the client is not using a delegation, the right thing to do is to return
it as soon as possible. This helps reduce the amount of state the server
has to track, as well as reducing the potential for conflicts with other
clients.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 00c350c031b4..e75f2f8c5245 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -43,6 +43,27 @@ static void nfs_free_delegation(struct nfs_delegation *delegation)
 		put_rpccred(cred);
 }
 
+void nfs_mark_delegation_referenced(struct nfs_delegation *delegation)
+{
+	set_bit(NFS_DELEGATION_REFERENCED, &delegation->flags);
+}
+
+int nfs_have_delegation(struct inode *inode, int flags)
+{
+	struct nfs_delegation *delegation;
+	int ret = 0;
+
+	flags &= FMODE_READ|FMODE_WRITE;
+	rcu_read_lock();
+	delegation = rcu_dereference(NFS_I(inode)->delegation);
+	if (delegation != NULL && (delegation->type & flags) == flags) {
+		nfs_mark_delegation_referenced(delegation);
+		ret = 1;
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
 static int nfs_delegation_claim_locks(struct nfs_open_context *ctx, struct nfs4_state *state)
 {
 	struct inode *inode = state->inode;
@@ -188,6 +209,7 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
 	delegation->change_attr = nfsi->change_attr;
 	delegation->cred = get_rpccred(cred);
 	delegation->inode = inode;
+	delegation->flags = 1<<NFS_DELEGATION_REFERENCED;
 	spin_lock_init(&delegation->lock);
 
 	spin_lock(&clp->cl_lock);
@@ -382,6 +404,26 @@ void nfs_handle_cb_pathdown(struct nfs_client *clp)
 	nfs_client_mark_return_all_delegations(clp);
 }
 
+static void nfs_client_mark_return_unreferenced_delegations(struct nfs_client *clp)
+{
+	struct nfs_delegation *delegation;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(delegation, &clp->cl_delegations, super_list) {
+		if (test_and_clear_bit(NFS_DELEGATION_REFERENCED, &delegation->flags))
+			continue;
+		set_bit(NFS_DELEGATION_RETURN, &delegation->flags);
+		set_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state);
+	}
+	rcu_read_unlock();
+}
+
+void nfs_expire_unreferenced_delegations(struct nfs_client *clp)
+{
+	nfs_client_mark_return_unreferenced_delegations(clp);
+	nfs_delegation_run_state_manager(clp);
+}
+
 /*
  * Asynchronous delegation recall!
  */