From: David Teigland <teigland@redhat.com>
Date: Wed, 8 Sep 2010 18:47:38 -0400
Subject: [fs] dlm: no node callback when try 1cb lock req fails
Message-id: <20100908184738.GA14358@redhat.com>
Patchwork-id: 28181
O-Subject: [RHEL5.6 PATCH] dlm: Don't send callback to node making lock
	request when "try 1cb" fails
Bugzilla: 504188
RH-Acked-by: Steven Whitehouse <swhiteho@redhat.com>
RH-Acked-by: Robert S Peterson <rpeterso@redhat.com>

bz 504188

dlm: Don't send callback to node making lock request when "try 1cb" fails

upstream: queued for 2.6.37

When converting a lock, an lkb is in the granted state and also being used
to request a new state. In the case that the conversion was a "try 1cb"
type which has failed, and if the new state was incompatible with the old
state, a callback was being generated to the requesting node. This is
incorrect as callbacks should only be sent to all the other nodes holding
blocking locks. The requesting node should receive the normal (failed)
response to its "try 1cb" conversion request only.

This was discovered while debugging a performance problem on GFS2, however
this fix also speeds up GFS as well. In the GFS2 case the performance gain
is over 10x for cases of write activity to an inode whose glock is cached
on another, idle (wrt that glock) node.

(comment added, dct)

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Tested-by: Abhijith Das <adas@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

diff --git a/fs/dlm/lock.c b/fs/dlm/lock.c
index cd2b2cf..edea42b 100644
--- a/fs/dlm/lock.c
+++ b/fs/dlm/lock.c
@@ -1807,6 +1807,9 @@ static void send_bast_queue(struct dlm_rsb *r, struct list_head *head,
 	struct dlm_lkb *gr;
 
 	list_for_each_entry(gr, head, lkb_statequeue) {
+		/* skip self when sending basts to convertqueue */
+		if (gr == lkb)
+			continue;
 		if (gr->lkb_bastaddr && modes_require_bast(gr, lkb)) {
 			queue_bast(r, gr, lkb->lkb_rqmode);
 			gr->lkb_highbast = lkb->lkb_rqmode;