| Message ID | 20230621132208.1142318-1-ming.lei@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | blk-mq: don't insert passthrough request into sw queue | expand |
On Wed, 21 Jun 2023 21:22:08 +0800, Ming Lei wrote: > In case of real io scheduler, q->elevator is set, so blk_mq_run_hw_queue() > may just check if scheduler queue has request to dispatch, see > __blk_mq_sched_dispatch_requests(). Then IO hang may be caused because > all passthorugh requests may stay in sw queue. > > And any passthrough request should have been inserted to hctx->dispatch > always. > > [...] Applied, thanks! [1/1] blk-mq: don't insert passthrough request into sw queue commit: 2293cae703cda162684ae966db6b1b4a11b5e88f Best regards,
On 6/21/23 06:22, Ming Lei wrote: > percpu_ref_get(&this_hctx->queue->q_usage_counter); > /* passthrough requests should never be issued to the I/O scheduler */ > - if (this_hctx->queue->elevator && !is_passthrough) { > + if (is_passthrough) { > + spin_lock(&this_hctx->lock); > + list_splice_tail_init(&list, &this_hctx->dispatch); > + spin_unlock(&this_hctx->lock); > + blk_mq_run_hw_queue(this_hctx, from_sched); > + } else if (this_hctx->queue->elevator) { > this_hctx->queue->elevator->type->ops.insert_requests(this_hctx, > &list, 0); > blk_mq_run_hw_queue(this_hctx, from_sched); The code change in this patch looks fine to me. However, with this patch applied the code and the source code comment just above the modified are now out of sync :-( Bart.
diff --git a/block/blk-mq.c b/block/blk-mq.c index 4c02c28b4835..1628873d7587 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2750,7 +2750,12 @@ static void blk_mq_dispatch_plug_list(struct blk_plug *plug, bool from_sched) percpu_ref_get(&this_hctx->queue->q_usage_counter); /* passthrough requests should never be issued to the I/O scheduler */ - if (this_hctx->queue->elevator && !is_passthrough) { + if (is_passthrough) { + spin_lock(&this_hctx->lock); + list_splice_tail_init(&list, &this_hctx->dispatch); + spin_unlock(&this_hctx->lock); + blk_mq_run_hw_queue(this_hctx, from_sched); + } else if (this_hctx->queue->elevator) { this_hctx->queue->elevator->type->ops.insert_requests(this_hctx, &list, 0); blk_mq_run_hw_queue(this_hctx, from_sched);
In case of real io scheduler, q->elevator is set, so blk_mq_run_hw_queue() may just check if scheduler queue has request to dispatch, see __blk_mq_sched_dispatch_requests(). Then IO hang may be caused because all passthorugh requests may stay in sw queue. And any passthrough request should have been inserted to hctx->dispatch always. Reported-by: Guangwu Zhang <guazhang@redhat.com> Fixes: d97217e7f024 ("blk-mq: don't queue plugged passthrough requests into scheduler") Signed-off-by: Ming Lei <ming.lei@redhat.com> --- block/blk-mq.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)