On 12/5/18 12:43 AM, Jianchao Wang wrote:
> We don't allow direct dispatch of anything but regular reads/writes
> and insert all of non-read-write requests. However, this is not
> correct for 'bypass_insert == true' case where inserting is ignored
> and BLK_STS_RESOURCE is returned. The caller will fail forever.
>
> Fix it with inserting the non-read-write request to hctx dispatch
> list to avoid to involve merge and io scheduler when bypass_insert
> is true.
>
> Signed-off-by: Jianchao Wang <jianchao.w.wang@xxxxxxxxxx>
> ---
> block/blk-mq.c | 19 +++++++++++++++++--
> 1 file changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 9005505..153af90 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1822,6 +1822,7 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
> {
> struct request_queue *q = rq->q;
> bool run_queue = true;
> + bool force = false;
>
> /*
> * RCU or SRCU read lock is needed before checking quiesced flag.
> @@ -1836,9 +1837,19 @@ static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
> goto insert;
> }
>
> - if (!blk_rq_can_direct_dispatch(rq) || (q->elevator && !bypass_insert))
> + if (q->elevator && !bypass_insert)
> goto insert;
>
> + if (!blk_rq_can_direct_dispatch(rq)) {
> + /*
> + * For 'bypass_insert == true' case, insert request into hctx
> + * dispatch list.
> + */
> + if (bypass_insert)
> + force = true;
> + goto insert;
> + }
Just do force = bypass_insert, no need for the if.
--
Jens Axboe
