[RFC PATCH v5 4/4] dm kcopyd: add simple copy offload support

SelvaKumar S
2021-02-20T02:03:00Z

Introduce copy_jobs to use copy-offload if it is natively
supported (by underlying device) or else fall back to original method.

run_copy_jobs() calls block layer copy offload api with
BLKDEV_COPY_NOEMULATION. On successful completion, if only one destination
device was present, then jobs is queued for completion. If multiple
destinations were present, the completed destination is zeroed and
pushed to pages_jobs to process copy offload for other destinations. In
case of copy_offload failure, remaining destinations are processed via
regular copying mechanism.

Signed-off-by: SelvaKumar S <selvakuma.s1@samsung.com>
---
drivers/md/dm-kcopyd.c | 49 ++++++++++++++++++++++++++++++++++++------
1 file changed, 43 insertions(+), 6 deletions(-)

diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c
index 1bbe4a34ef4c..2442c4870e97 100644
--- a/drivers/md/dm-kcopyd.c
+++ b/drivers/md/dm-kcopyd.c
@@ -74,18 +74,20 @@ struct dm_kcopyd_client {
atomic_t nr_jobs;

/*
- * We maintain four lists of jobs:
+ * We maintain five lists of jobs:
*
- * i) jobs waiting for pages
- * ii) jobs that have pages, and are waiting for the io to be issued.
- * iii) jobs that don't need to do any IO and just run a callback
- * iv) jobs that have completed.
+ * i) jobs waiting to try copy offload
+ * ii) jobs waiting for pages
+ * iii) jobs that have pages, and are waiting for the io to be issued.
+ * iv) jobs that don't need to do any IO and just run a callback
+ * v) jobs that have completed.
*
- * All four of these are protected by job_lock.
+ * All five of these are protected by job_lock.
*/
spinlock_t job_lock;
struct list_head callback_jobs;
struct list_head complete_jobs;
+ struct list_head copy_jobs;
struct list_head io_jobs;
struct list_head pages_jobs;
};
@@ -581,6 +583,36 @@ static int run_io_job(struct kcopyd_job *job)
return r;
}

+static int run_copy_job(struct kcopyd_job *job)
+{
+ int r, i, count = 0;
+ unsigned long flags = 0;
+ struct range_entry srange;
+
+ flags |= BLKDEV_COPY_NOEMULATION;
+ for (i = 0; i < job->num_dests; i++) {
+ srange.src = job->source.sector;
+ srange.len = job->source.count;
+
+ r = blkdev_issue_copy(job->source.bdev, 1, &srange,
+ job->dests[i].bdev, job->dests[i].sector, GFP_KERNEL, flags);
+ if (r)
+ break;
+
+ job->dests[i].count = 0;
+ count++;
+ }
+
+ if (count == job->num_dests) {
+ push(&job->kc->complete_jobs, job);
+ } else {
+ push(&job->kc->pages_jobs, job);
+ r = 0;
+ }
+
+ return r;
+}
+
static int run_pages_job(struct kcopyd_job *job)
{
int r;
@@ -662,6 +694,7 @@ static void do_work(struct work_struct *work)
spin_unlock_irqrestore(&kc->job_lock, flags);

blk_start_plug(&plug);
+ process_jobs(&kc->copy_jobs, kc, run_copy_job);
process_jobs(&kc->complete_jobs, kc, run_complete_job);
process_jobs(&kc->pages_jobs, kc, run_pages_job);
process_jobs(&kc->io_jobs, kc, run_io_job);
@@ -679,6 +712,8 @@ static void dispatch_job(struct kcopyd_job *job)
atomic_inc(&kc->nr_jobs);
if (unlikely(!job->source.count))
push(&kc->callback_jobs, job);
+ else if (job->source.bdev->bd_disk == job->dests[0].bdev->bd_disk)
+ push(&kc->copy_jobs, job);
else if (job->pages == &zero_page_list)
push(&kc->io_jobs, job);
else
@@ -919,6 +954,7 @@ struct dm_kcopyd_client *dm_kcopyd_client_create(struct dm_kcopyd_throttle *thro
spin_lock_init(&kc->job_lock);
INIT_LIST_HEAD(&kc->callback_jobs);
INIT_LIST_HEAD(&kc->complete_jobs);
+ INIT_LIST_HEAD(&kc->copy_jobs);
INIT_LIST_HEAD(&kc->io_jobs);
INIT_LIST_HEAD(&kc->pages_jobs);
kc->throttle = throttle;
@@ -974,6 +1010,7 @@ void dm_kcopyd_client_destroy(struct dm_kcopyd_client *kc)

BUG_ON(!list_empty(&kc->callback_jobs));
BUG_ON(!list_empty(&kc->complete_jobs));
+ BUG_ON(!list_empty(&kc->copy_jobs));
BUG_ON(!list_empty(&kc->io_jobs));
BUG_ON(!list_empty(&kc->pages_jobs));
destroy_workqueue(kc->kcopyd_wq);
--
2.25.1