[dm-devel] [PATCH 7/7] dm kcopyd: add simple copy offload support

[Mikulas Patocka]

On Tue, 17 Aug 2021, SelvaKumar S wrote:

> Introduce copy_jobs to use copy-offload, if supported by underlying devices
> otherwise fall back to existing method.

dm-kcopyd is usually used on the dm-linear target. And this patchset 
doesn't support passing copy requests through the linear target - so this 
patch doesn't seem useful.

Mikulas

> run_copy_jobs() calls block layer copy offload API, if both source and
> destination request queue are same and support copy offload.
> On successful completion, destination regions copied count is made zero,
> failed regions are processed via existing method.
> 
> Signed-off-by: SelvaKumar S <selvakuma.s1 at samsung.com>
> Signed-off-by: Nitesh Shetty <nj.shetty at samsung.com>
> ---
>  drivers/md/dm-kcopyd.c | 56 +++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 50 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c
> index 37b03ab7e5c9..d9ee105a6127 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;
>  };
> @@ -579,6 +581,43 @@ 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;
> +
> +	struct request_queue *src_q, *dest_q;
> +
> +	for (i = 0; i < job->num_dests; i++) {
> +		srange.src = job->source.sector;
> +		srange.len = job->source.count;
> +
> +		src_q = bdev_get_queue(job->source.bdev);
> +		dest_q = bdev_get_queue(job->dests[i].bdev);
> +
> +		if (src_q != dest_q && !src_q->limits.copy_offload)
> +			break;
> +
> +		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;
> @@ -659,6 +698,7 @@ static void do_work(struct work_struct *work)
>  	spin_unlock_irq(&kc->job_lock);
>  
>  	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);
> @@ -676,6 +716,8 @@ 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
> @@ -916,6 +958,7 @@ 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;
> @@ -971,6 +1014,7 @@ void dm_kcopyd_client_destroy(struct dm_kcopyd_client *kc)
>  
>  	BUG_ON(!list_empty(&kc->callback_jobs));
>  	BUG_ON(!list_empty(&kc->complete_jobs));
> +	WARN_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
> 
> 
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