grace-period ending & NLM

[bfields@fieldses.org (J. Bruce Fields)]

We have two grace periods, one for NLM and one for NFSv4+, and don't
permit normal locking until both are over.

As far as I can tell nfsdcltrack doesn't understand statd/NSM state; it
only concerns itself with NFSv4+.  It can end the NFSv4 grace period
early, but that still leaves the server returning GRACE errors until NSM
exits its grace period.

The server has never had any smarts to end the NSM grace period early,
even though there are common cases (e.g., no clients at all) where it
easily could.  We could fix that.

But one quick thing we can do to limit the impact of the NLM grace
period is just to note that NLM locks have never conflicted with NFSv4
opens, so NFSv4 opens don't really need to be waiting.

Am I missing anything?

--b.

commit d2ab7fe05cd0
Author: J. Bruce Fields <bfields@redhat.com>
Date:   Thu Aug 6 12:47:02 2015 -0400

    lockd: NLM grace period shouldn't block NFSv4 opens
    
    NLM locks don't conflict with NFSv4 share reservations, so we're not
    going to learn anything new by watiting for them.
    
    They do conflict with NFSv4 locks and with delegations.
    
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
index 530914b5c455..d678bcc3cbcb 100644
--- a/fs/lockd/svc.c
+++ b/fs/lockd/svc.c
@@ -591,6 +591,7 @@ static int lockd_init_net(struct net *net)
 
 	INIT_DELAYED_WORK(&ln->grace_period_end, grace_ender);
 	INIT_LIST_HEAD(&ln->lockd_manager.list);
+	ln->lockd_manager.block_opens = false;
 	spin_lock_init(&ln->nsm_clnt_lock);
 	return 0;
 }
diff --git a/fs/nfs_common/grace.c b/fs/nfs_common/grace.c
index ae6e58ea4de5..fd8c9a5bcac4 100644
--- a/fs/nfs_common/grace.c
+++ b/fs/nfs_common/grace.c
@@ -63,14 +63,33 @@ EXPORT_SYMBOL_GPL(locks_end_grace);
  * lock reclaims.
  */
 int
-locks_in_grace(struct net *net)
+__state_in_grace(struct net *net, bool open)
 {
 	struct list_head *grace_list = net_generic(net, grace_net_id);
+	struct lock_manager *lm;
 
-	return !list_empty(grace_list);
+	if (!open)
+		return !list_empty(grace_list);
+
+	list_for_each_entry(lm, grace_list, list) {
+		if (lm->block_opens)
+			return true;
+	}
+	return false;
+}
+
+int locks_in_grace(struct net *net)
+{
+	return __state_in_grace(net, 0);
 }
 EXPORT_SYMBOL_GPL(locks_in_grace);
 
+int opens_in_grace(struct net *net)
+{
+	return __state_in_grace(net, 1);
+}
+EXPORT_SYMBOL_GPL(opens_in_grace);
+
 static int __net_init
 grace_init_net(struct net *net)
 {
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index e779d7db24b0..b9681ee0ed19 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -415,10 +415,10 @@ nfsd4_open(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 	/* Openowner is now set, so sequence id will get bumped.  Now we need
 	 * these checks before we do any creates: */
 	status = nfserr_grace;
-	if (locks_in_grace(net) && open->op_claim_type != NFS4_OPEN_CLAIM_PREVIOUS)
+	if (opens_in_grace(net) && open->op_claim_type != NFS4_OPEN_CLAIM_PREVIOUS)
 		goto out;
 	status = nfserr_no_grace;
-	if (!locks_in_grace(net) && open->op_claim_type == NFS4_OPEN_CLAIM_PREVIOUS)
+	if (!opens_in_grace(net) && open->op_claim_type == NFS4_OPEN_CLAIM_PREVIOUS)
 		goto out;
 
 	switch (open->op_claim_type) {
@@ -827,7 +827,7 @@ nfsd4_remove(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 {
 	__be32 status;
 
-	if (locks_in_grace(SVC_NET(rqstp)))
+	if (opens_in_grace(SVC_NET(rqstp)))
 		return nfserr_grace;
 	status = nfsd_unlink(rqstp, &cstate->current_fh, 0,
 			     remove->rm_name, remove->rm_namelen);
@@ -846,7 +846,7 @@ nfsd4_rename(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 
 	if (!cstate->save_fh.fh_dentry)
 		return status;
-	if (locks_in_grace(SVC_NET(rqstp)) &&
+	if (opens_in_grace(SVC_NET(rqstp)) &&
 		!(cstate->save_fh.fh_export->ex_flags & NFSEXP_NOSUBTREECHECK))
 		return nfserr_grace;
 	status = nfsd_rename(rqstp, &cstate->save_fh, rename->rn_sname,
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index c94859122e6f..97fe7c8c6a8e 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4052,7 +4052,8 @@ nfs4_open_delegation(struct svc_fh *fh, struct nfsd4_open *open,
 		case NFS4_OPEN_CLAIM_FH:
 			/*
 			 * Let's not give out any delegations till everyone's
-			 * had the chance to reclaim theirs....
+			 * had the chance to reclaim theirs, *and* until
+			 * NLM locks have all been reclaimed:
 			 */
 			if (locks_in_grace(clp->net))
 				goto out_no_deleg;
@@ -4426,7 +4427,7 @@ check_special_stateids(struct net *net, svc_fh *current_fh, stateid_t *stateid,
 {
 	if (ONE_STATEID(stateid) && (flags & RD_STATE))
 		return nfs_ok;
-	else if (locks_in_grace(net)) {
+	else if (opens_in_grace(net)) {
 		/* Answer in remaining cases depends on existence of
 		 * conflicting state; so we must wait out the grace period. */
 		return nfserr_grace;
@@ -4445,7 +4446,7 @@ check_special_stateids(struct net *net, svc_fh *current_fh, stateid_t *stateid,
 static inline int
 grace_disallows_io(struct net *net, struct inode *inode)
 {
-	return locks_in_grace(net) && mandatory_lock(inode);
+	return opens_in_grace(net) && mandatory_lock(inode);
 }
 
 /* Returns true iff a is later than b: */
@@ -6564,6 +6565,7 @@ nfs4_state_start_net(struct net *net)
 		return ret;
 	nn->boot_time = get_seconds();
 	nn->grace_ended = false;
+	nn->nfsd4_manager.block_opens = true;
 	locks_start_grace(net, &nn->nfsd4_manager);
 	nfsd4_client_tracking_init(net);
 	printk(KERN_INFO "NFSD: starting %ld-second grace period (net %p)\n",
diff --git a/include/linux/fs.h b/include/linux/fs.h
index cc008c338f5a..9a9d314f7b27 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -942,12 +942,18 @@ struct lock_manager_operations {
 
 struct lock_manager {
 	struct list_head list;
+	/*
+	 * NFSv4 and up also want opens blocked during the grace period;
+	 * NLM doesn't care:
+	 */
+	bool block_opens;
 };
 
 struct net;
 void locks_start_grace(struct net *, struct lock_manager *);
 void locks_end_grace(struct lock_manager *);
 int locks_in_grace(struct net *);
+int opens_in_grace(struct net *);
 
 /* that will die - we need it for nfs_lock_info */
 #include <linux/nfs_fs_i.h>