Commit 9ca170a3 authored Dec 10, 2009 by Mikulas Patocka Committed by Alasdair G Kergon Dec 10, 2009

dm kcopyd: accept zero size jobs



dm-kcopyd: accept zero-size jobs

This patch changes dm-kcopyd so that it accepts zero-size jobs and completes
them immediatelly via its completion thread.

It is needed for multisnapshots snapshot resizing. When we are writing to
a chunk beyond origin end, no copying is done. To simplify the code, we submit
an empty request to kcopyd and let kcopyd complete it. If we didn't submit
a request to kcopyd and called the completion routine immediatelly, it would
violate the principle that completion is called only from one thread and
it would need additional locking.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

parent c26655ca

drivers/md/dm-kcopyd.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -450,6 +450,9 @@ static void dispatch_job(struct kcopyd_job *job)
		{
		struct dm_kcopyd_client *kc = job->kc;
		atomic_inc(&kc->nr_jobs);
		if (unlikely(!job->source.count))
		push(&kc->complete_jobs, job);
		else
		push(&kc->pages_jobs, job);
		wake(kc);
		}