On Thu, Nov 04, 2021 at 05:41:35AM -0600, Jens Axboe wrote:
> >> if (!submit_bio_checks(bio) || !blk_crypto_bio_prep(&bio))
> >> - goto queue_exit;
> >> + return;
> >
> > This is broken, we really ant the submit checks under freeze
> > protection to make sure the parameters can't be changed underneath
> > us.
>
> Which parameters are you worried about in submit_bio_checks()? I don't
> immediately see anything that would make me worry about it.
Mostly checks if certain operations are supported or not, as
revalidation could clear those.
> > This looks weird, as blk_try_enter_queue is already called by
> > bio_queue_enter.
>
> It's just for avoiding a pointless call into bio_queue_enter(), which
> isn't needed it blk_try_enter_queue() is successful. The latter is short
> and small and can be inlined, while bio_queue_enter() is a lot bigger.
If this is so impotant let's operated with an inlined bio_queue_enter
that calls out of line into slow path instead of open coding it
like this.
> >> } else {
> >> struct blk_mq_alloc_data data = {
> >> .q = q,
> >> @@ -2528,6 +2534,11 @@ void blk_mq_submit_bio(struct bio *bio)
> >> .cmd_flags = bio->bi_opf,
> >> };
> >>
> >> + if (unlikely(!blk_mq_queue_enter(q, bio)))
> >> + return;
> >> +
> >> + rq_qos_throttle(q, bio);
> >> +
> >
> > At some point the code in this !cached branch really needs to move
> > into a helper..
>
> Like in the next patch?
No, I mean the !cached case which is a lot more convoluted.
