Hello. I think there seems to be a problem that the request
complete processing will be omitted due to the follow routine.
Please give me a advice or opinion if I get a mistake or missing something.
Thank you.
>
>When a request complete then send ipi to original cpu which issued request.
>If cpu offline during this process, send_ipi might fail.
>However, there is currently no code to handle this error case.
>This may cause in missing request complete.
>Therefore, if send_ipi fails due to cpu offline, the request complete
>has to be processed directly from the cpu where it is running.
>
>
>
>Signed-off-by: Manjong Lee <mj0123.lee@xxxxxxxxxxx>
>Signed-off-by: Changheun Lee <nanich.lee@xxxxxxxxxxx>
>Signed-off-by: Junho Kim <junho89.kim@xxxxxxxxxxx>
>---
> block/blk-mq.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
>diff --git a/block/blk-mq.c b/block/blk-mq.c
>index 3c1e6b6d991d..f2ce79708c5e 100644
>--- a/block/blk-mq.c
>+++ b/block/blk-mq.c
>@@ -1064,17 +1064,22 @@ static inline bool blk_mq_complete_need_ipi(struct request *rq)
> return cpu_online(rq->mq_ctx->cpu);
> }
>
>-static void blk_mq_complete_send_ipi(struct request *rq)
>+static int blk_mq_complete_send_ipi(struct request *rq)
> {
> struct llist_head *list;
> unsigned int cpu;
>+ int ret = 0;
>
> cpu = rq->mq_ctx->cpu;
> list = &per_cpu(blk_cpu_done, cpu);
> if (llist_add(&rq->ipi_list, list)) {
> INIT_CSD(&rq->csd, __blk_mq_complete_request_remote, rq);
>- smp_call_function_single_async(cpu, &rq->csd);
>+ ret = smp_call_function_single_async(cpu, &rq->csd);
>+ if (ret)
>+ llist_del_all(list);
> }
>+
>+ return ret;
> }
>
> static void blk_mq_raise_softirq(struct request *rq)
>@@ -1099,10 +1104,9 @@ bool blk_mq_complete_request_remote(struct request *rq)
> if (rq->cmd_flags & REQ_POLLED)
> return false;
>
>- if (blk_mq_complete_need_ipi(rq)) {
>- blk_mq_complete_send_ipi(rq);
>- return true;
>- }
>+ if (blk_mq_complete_need_ipi(rq))
>+ if (!blk_mq_complete_send_ipi(rq))
>+ return true;
>
> if (rq->q->nr_hw_queues == 1) {
> blk_mq_raise_softirq(rq);
>--
>2.32.0
>
