On Wed, 14 Dec 2016, Eric Wheeler wrote: > Since dm-crypt queues writes (and sometimes reads) to a different kernel > thread (workqueue), the bios will dispatch from tasks with different > io_context->ioprio settings than the submitting task, thus giving > incorrect ioprio hints to the io scheduler. The motivation of this patch is for ioprio-driven writebackup/bypass hinting inside bcache when bcache is under dm-crypt which Jens is picking up for 4.10: https://lkml.org/lkml/2016/12/6/607 Without assigning the ioprio before queuing to the en/decrypt queues, bcache isn't notified of the priority---and presumably neither is the IO scheduler. The ioprio aware schedulers like CFQ and BFQ also benefit with more knowledge about the bio's when passing through dm-crypt. It would be great if this can be accepted for 4.10, too. -- Eric Wheeler > > By assigning the ioprio to the bio before queuing to a workqueue, the > original submitting task's io_context->ioprio setting can be retained > through the life of the bio. We only set the bio's ioprio in dm-crypt > if not already set (by somewhere else, higher in the stack). > > Signed-off-by: Eric Wheeler <dm-devel@xxxxxxxxxxxxxxxxxx> > Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx> > Cc: Alasdair Kergon <agk@xxxxxxxxxx> > Cc: Mike Snitzer <snitzer@xxxxxxxxxx> > Cc: Shaohua Li <shli@xxxxxxxxxx> > Cc: Jens Axboe <axboe@xxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > --- > block/bio.c | 1 + > drivers/md/dm-crypt.c | 11 +++++++++-- > include/linux/bio.h | 23 +++++++++++++++++++++++ > 3 files changed, 33 insertions(+), 2 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index db85c57..1a529ff 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -584,6 +584,7 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src) > bio->bi_iter = bio_src->bi_iter; > bio->bi_io_vec = bio_src->bi_io_vec; > > + bio_set_prio(bio, bio_prio(bio_src)); > bio_clone_blkcg_association(bio, bio_src); > } > EXPORT_SYMBOL(__bio_clone_fast); > diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c > index 9b99ee9..ea7e102 100644 > --- a/drivers/md/dm-crypt.c > +++ b/drivers/md/dm-crypt.c > @@ -1133,6 +1133,7 @@ static void clone_init(struct dm_crypt_io *io, struct bio *clone) > clone->bi_private = io; > clone->bi_end_io = crypt_endio; > clone->bi_bdev = cc->dev->bdev; > + bio_set_prio(clone, bio_prio(io->base_bio)); > bio_set_op_attrs(clone, bio_op(io->base_bio), bio_flags(io->base_bio)); > } > > @@ -2070,10 +2071,16 @@ static int crypt_map(struct dm_target *ti, struct bio *bio) > io->ctx.req = (struct skcipher_request *)(io + 1); > > if (bio_data_dir(io->base_bio) == READ) { > - if (kcryptd_io_read(io, GFP_NOWAIT)) > + if (kcryptd_io_read(io, GFP_NOWAIT)) { > + if (!ioprio_valid(bio_prio(io->base_bio))) > + bio_set_task_prio(io->base_bio, current); > kcryptd_queue_read(io); > - } else > + } > + } else { > + if (!ioprio_valid(bio_prio(io->base_bio))) > + bio_set_task_prio(io->base_bio, current); > kcryptd_queue_crypt(io); > + } > > return DM_MAPIO_SUBMITTED; > } > diff --git a/include/linux/bio.h b/include/linux/bio.h > index 97cb48f..0b4f8bb 100644 > --- a/include/linux/bio.h > +++ b/include/linux/bio.h > @@ -62,6 +62,29 @@ > #define bio_sectors(bio) ((bio)->bi_iter.bi_size >> 9) > #define bio_end_sector(bio) ((bio)->bi_iter.bi_sector + bio_sectors((bio))) > > +/* Set the bio's ioprio to that of the task's io_context->ioprio, if any. > + * Always returns io_context->ioprio (or 0 if none); bio can be NULL. > + */ > +static inline unsigned short bio_set_task_prio( > + struct bio *bio, struct task_struct *task) > +{ > + struct io_context *ioc; > + unsigned short ioprio = 0; > + > + ioc = get_task_io_context(current, GFP_NOIO, NUMA_NO_NODE); > + if (ioc) { > + if (ioprio_valid(ioc->ioprio)) { > + ioprio = ioc->ioprio; > + put_io_context(ioc); > + } > + > + if (bio != NULL && ioprio_valid(ioprio)) > + bio_set_prio(bio, ioc->ioprio); > + } > + > + return ioprio; > +} > + > /* > * Check whether this bio carries any data or not. A NULL bio is allowed. > */ > -- > 1.8.3.1 > > > -- > dm-devel mailing list > dm-devel@xxxxxxxxxx > https://www.redhat.com/mailman/listinfo/dm-devel > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
