On 7/27/20 4:07 PM, Sagi Grimberg wrote:
> Drivers that may have to quiesce a large amount of request queues at once
> (e.g. controller or adapter reset). These drivers would benefit from an
> async quiesce interface such that the can trigger quiesce asynchronously
> and wait for all in parallel.
>
> This leaves the synchronization responsibility to the driver, but adds
> a convenient interface to quiesce async and wait in a single pass.
>
> Signed-off-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
> ---
> block/blk-mq.c | 46 ++++++++++++++++++++++++++++++++++++++++++
> include/linux/blk-mq.h | 4 ++++
> 2 files changed, 50 insertions(+)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index abcf590f6238..d913924117d2 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -209,6 +209,52 @@ void blk_mq_quiesce_queue_nowait(struct request_queue *q)
> }
> EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
>
> +void blk_mq_quiesce_queue_async(struct request_queue *q)
> +{
> + struct blk_mq_hw_ctx *hctx;
> + unsigned int i;
> + int rcu = false;
> +
> + blk_mq_quiesce_queue_nowait(q);
> +
> + queue_for_each_hw_ctx(q, hctx, i) {
> + hctx->rcu_sync = kmalloc(sizeof(*hctx->rcu_sync), GFP_KERNEL);
> + if (!hctx->rcu_sync) {
> + /* fallback to serial rcu sync */
> + if (hctx->flags & BLK_MQ_F_BLOCKING)
> + synchronize_srcu(hctx->srcu);
> + else
> + rcu = true;
> + } else {
> + init_completion(&hctx->rcu_sync->completion);
> + init_rcu_head(&hctx->rcu_sync->head);
> + if (hctx->flags & BLK_MQ_F_BLOCKING)
> + call_srcu(hctx->srcu, &hctx->rcu_sync->head,
> + wakeme_after_rcu);
> + else
> + call_rcu(&hctx->rcu_sync->head,
> + wakeme_after_rcu);
> + }
> + }
> + if (rcu)
> + synchronize_rcu();
> +}
> +EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_async);
This won't always be async, and that might matter to some users. I think
it'd be better to put the fallback path into the _wait() part instead,
since the caller should expect that to be blocking/waiting as the name
implies.
Nit picking, but...
--
Jens Axboe
