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Commit 9ca170a3c0cbb0d5251cef6f5a3300fa436ba8ec

Authored by Mikulas Patocka
Committed by Alasdair G Kergon
1 parent c26655ca3c
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

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>

Showing 1 changed file with 4 additions and 1 deletions Side-by-side Diff

drivers/md/dm-kcopyd.c
Diff comments   View file @ 9ca170a
... ... @@ -450,7 +450,10 @@
450 450 {
451 451 struct dm_kcopyd_client *kc = job->kc;
452 452 atomic_inc(&kc->nr_jobs);
453   - push(&kc->pages_jobs, job);
  453 + if (unlikely(!job->source.count))
  454 + push(&kc->complete_jobs, job);
  455 + else
  456 + push(&kc->pages_jobs, job);
454 457 wake(kc);
455 458 }
456 459