On 02/27/2017 09:59 AM, Omar Sandoval wrote:
> On Mon, Feb 27, 2017 at 05:36:21PM +0200, Sagi Grimberg wrote:
>> Otherwise we won't be able to retrieve the request from
>> the tag.
>>
>> Signed-off-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
>> ---
>> block/blk-mq.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index d84c66fb37b7..9611cd9920e9 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -312,6 +312,7 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q, int rw,
>> ret = -EWOULDBLOCK;
>> goto out_queue_exit;
>> }
>> + alloc_data.hctx->tags->rqs[rq->tag] = rq;
>>
>> return rq;
>>
>> --
>> 2.7.4
>
> This one I think is a little bit cleaner if we just push that assignment
> into __blk_mq_alloc_request() like this (again, compile tested only):
>
> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> index 98c7b061781e..7267c9c23529 100644
> --- a/block/blk-mq-sched.c
> +++ b/block/blk-mq-sched.c
> @@ -135,8 +135,6 @@ struct request *blk_mq_sched_get_request(struct request_queue *q,
> rq = __blk_mq_alloc_request(data, op);
> } else {
> rq = __blk_mq_alloc_request(data, op);
> - if (rq)
> - data->hctx->tags->rqs[rq->tag] = rq;
> }
>
> if (rq) {
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 9e6b064e5339..b4cf9dfa926b 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -234,6 +234,7 @@ struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data,
> }
> rq->tag = tag;
> rq->internal_tag = -1;
> + data->hctx->tags->rqs[rq->tag] = rq;
> }
>
> blk_mq_rq_ctx_init(data->q, data->ctx, rq, op);
Agree, let's keep that in one place, if we can.
> Looking a little closer at the caller, though, this is kind of weird:
>
> struct request *nvme_alloc_request(struct request_queue *q,
> struct nvme_command *cmd, unsigned int flags, int qid)
> {
> unsigned op = nvme_is_write(cmd) ? REQ_OP_DRV_OUT : REQ_OP_DRV_IN;
> struct request *req;
>
> if (qid == NVME_QID_ANY) {
> req = blk_mq_alloc_request(q, op, flags);
> } else {
> req = blk_mq_alloc_request_hctx(q, op, flags,
> qid ? qid - 1 : 0);
> }
> if (IS_ERR(req))
> return req;
>
> req->cmd_flags |= REQ_FAILFAST_DRIVER;
> nvme_req(req)->cmd = cmd;
>
> return req;
> }
>
> In the "any" case, we allocate a request with a scheduler tag and go
> through the scheduler as usual. In the hctx case, we're getting a
> request with a driver tag, meaning we go through the
> blk_mq_sched_bypass_insert() path when we run the request.
>
> There's nothing really wrong about that, it just seems weird. Not sure
> if it's weird enough to act on :)
That's just broken, we need to fix that up. _hctx() request alloc
should return scheduler request as well.
Omar, care to rework patch #1 and incorporate a fix for the hctx
alloc? Then I'll fix up patch #2, adding the carry-over of the
reserved flag. We'll just rebase for-linus, it's not a stable
branch.
--
Jens Axboe
