On Thu, Oct 13, 2016 at 1:24 PM, Jens Axboe <axboe@xxxxxxxxx> wrote: > On 10/13/2016 02:19 PM, Dan Williams wrote: >> >> On Thu, Oct 13, 2016 at 1:09 PM, Jens Axboe <axboe@xxxxxxxxx> wrote: >>> >>> On 10/13/2016 02:06 PM, Dan Williams wrote: >>>> >>>> >>>> On Thu, Oct 13, 2016 at 12:53 PM, Adam Manzanares >>>> <adam.manzanares@xxxxxxxx> wrote: >>>>> >>>>> >>>>> Patch adds an association between iocontext ioprio and the ioprio of a >>>>> request. This value is set in blk_rq_set_prio which takes the request >>>>> and >>>>> the ioc as arguments. If the ioc is valid in blk_rq_set_prio then the >>>>> iopriority of the request is set as the iopriority of the ioc. In >>>>> init_request_from_bio a check is made to see if the ioprio of the bio >>>>> is >>>>> valid and if so then the request prio comes from the bio. >>>>> >>>>> Signed-off-by: Adam Manzananares <adam.manzanares@xxxxxxx> >>>>> --- >>>>> block/blk-core.c | 4 +++- >>>>> include/linux/blkdev.h | 14 ++++++++++++++ >>>>> 2 files changed, 17 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/block/blk-core.c b/block/blk-core.c >>>>> index 14d7c07..361b1b9 100644 >>>>> --- a/block/blk-core.c >>>>> +++ b/block/blk-core.c >>>>> @@ -1153,6 +1153,7 @@ static struct request *__get_request(struct >>>>> request_list *rl, int op, >>>>> >>>>> blk_rq_init(q, rq); >>>>> blk_rq_set_rl(rq, rl); >>>>> + blk_rq_set_prio(rq, ioc); >>>>> req_set_op_attrs(rq, op, op_flags | REQ_ALLOCED); >>>>> >>>>> /* init elvpriv */ >>>>> @@ -1656,7 +1657,8 @@ void init_request_from_bio(struct request *req, >>>>> struct bio *bio) >>>>> >>>>> req->errors = 0; >>>>> req->__sector = bio->bi_iter.bi_sector; >>>>> - req->ioprio = bio_prio(bio); >>>>> + if (ioprio_valid(bio_prio(bio))) >>>>> + req->ioprio = bio_prio(bio); >>>> >>>> >>>> >>>> Should we use ioprio_best() here? If req->ioprio and bio_prio() >>>> disagree one side has explicitly asked for a higher priority. >>> >>> >>> >>> It's a good question - but if priority has been set in the bio, it makes >>> sense that that would take priority over the general setting for the >>> task/io context. So I think the patch is correct as-is. >> >> >> Assuming you always trust the kernel to know the right priority... > > > If it set it in the bio, it better know what it's doing. Besides, > there's nothing stopping the caller from checking the task priority when > it sets it. If we do ioprio_best(), then we are effectively preventing > anyone from submitting a bio with a lower priority than the task has > generally set. Ah, that makes sense. Move the ioprio_best() decision out to whatever code is setting bio_prio() to allow for cases where the kernel knows best. -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
