[PATCH dlm/next 8/8] md-cluster: use DLM_LSFL_SOFTIRQ for dlm_new_lockspace()

[Alexander Aring <aahringo@redhat.com>]

Recently the DLM subsystem introduced the flag DLM_LSFL_SOFTIRQ for
dlm_new_lockspace() to signal the capability to handle DLM ast/bast
callbacks in softirq context to avoid an additional context switch due
the DLM callback workqueue.

The md-cluster implementation only does synchronized calls above the
async DLM API. That synchronized API should may be also offered by DLM,
however it is very simple as md-cluster callbacks only does a complete()
call for their wait_for_completion() wait that is occurred after the
async DLM API call. This patch activates the recently introduced
DLM_LSFL_SOFTIRQ flag that allows that the DLM callbacks are executed in
a softirq context that md-cluster can handle. It is reducing a
unnecessary context workqueue switch and should speed up DLM in some
circumstance.

In future other DLM users e.g. gfs2 will also take usage of this flag to
avoid the additional context switch due the DLM callback workqueue. In
far future hopefully we can remove this kernel lockspace flag only and
remove the callback workqueue at all.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
---
 drivers/md/md-cluster.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
index 8e36a0feec09..eb9bbf12c8d8 100644
--- a/drivers/md/md-cluster.c
+++ b/drivers/md/md-cluster.c
@@ -887,7 +887,7 @@ static int join(struct mddev *mddev, int nodes)
 	memset(str, 0, 64);
 	sprintf(str, "%pU", mddev->uuid);
 	ret = dlm_new_lockspace(str, mddev->bitmap_info.cluster_name,
-				0, LVB_SIZE, &md_ls_ops, mddev,
+				DLM_LSFL_SOFTIRQ, LVB_SIZE, &md_ls_ops, mddev,
 				&ops_rv, &cinfo->lockspace);
 	if (ret)
 		goto err;
-- 
2.43.0