On Tue, Sep 15 2020 at 9:08pm -0400,
Ming Lei <ming.lei@xxxxxxxxxx> wrote:
> On Tue, Sep 15, 2020 at 01:23:57PM -0400, Mike Snitzer wrote:
> > blk_queue_split() has become compulsory from .submit_bio -- regardless
> > of whether it is recursing. Update DM core to always call
> > blk_queue_split().
> >
> > dm_queue_split() is removed because __split_and_process_bio() handles
> > splitting as needed.
> >
> > Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> > ---
> > drivers/md/dm.c | 45 +--------------------------------------------
> > 1 file changed, 1 insertion(+), 44 deletions(-)
> >
> > diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> > index fb0255d25e4b..0bae9f26dc8e 100644
> > --- a/drivers/md/dm.c
> > +++ b/drivers/md/dm.c
> > @@ -1530,22 +1530,6 @@ static int __send_write_zeroes(struct clone_info *ci, struct dm_target *ti)
> > return __send_changing_extent_only(ci, ti, get_num_write_zeroes_bios(ti));
> > }
> >
> > -static bool is_abnormal_io(struct bio *bio)
> > -{
> > - bool r = false;
> > -
> > - switch (bio_op(bio)) {
> > - case REQ_OP_DISCARD:
> > - case REQ_OP_SECURE_ERASE:
> > - case REQ_OP_WRITE_SAME:
> > - case REQ_OP_WRITE_ZEROES:
> > - r = true;
> > - break;
> > - }
> > -
> > - return r;
> > -}
> > -
> > static bool __process_abnormal_io(struct clone_info *ci, struct dm_target *ti,
> > int *result)
> > {
> > @@ -1723,23 +1707,6 @@ static blk_qc_t __process_bio(struct mapped_device *md, struct dm_table *map,
> > return ret;
> > }
> >
> > -static void dm_queue_split(struct mapped_device *md, struct dm_target *ti, struct bio **bio)
> > -{
> > - unsigned len, sector_count;
> > -
> > - sector_count = bio_sectors(*bio);
> > - len = min_t(sector_t, max_io_len((*bio)->bi_iter.bi_sector, ti), sector_count);
> > -
> > - if (sector_count > len) {
> > - struct bio *split = bio_split(*bio, len, GFP_NOIO, &md->queue->bio_split);
> > -
> > - bio_chain(split, *bio);
> > - trace_block_split(md->queue, split, (*bio)->bi_iter.bi_sector);
> > - submit_bio_noacct(*bio);
> > - *bio = split;
> > - }
> > -}
> > -
> > static blk_qc_t dm_process_bio(struct mapped_device *md,
> > struct dm_table *map, struct bio *bio)
> > {
> > @@ -1759,17 +1726,7 @@ static blk_qc_t dm_process_bio(struct mapped_device *md,
> > }
> > }
> >
> > - /*
> > - * If in ->queue_bio we need to use blk_queue_split(), otherwise
> > - * queue_limits for abnormal requests (e.g. discard, writesame, etc)
> > - * won't be imposed.
> > - */
> > - if (current->bio_list) {
> > - if (is_abnormal_io(bio))
> > - blk_queue_split(&bio);
> > - else
> > - dm_queue_split(md, ti, &bio);
> > - }
> > + blk_queue_split(&bio);
>
> In max_io_len(), target boundary is taken into account when figuring out
> the max io len. However, this info won't be used any more after
> switching to blk_queue_split(). Is that one potential problem?
Thanks for your review. But no, as the patch header says:
"dm_queue_split() is removed because __split_and_process_bio() handles
splitting as needed."
(__split_and_process_non_flush calls max_io_len, as does
__process_abnormal_io by calling __send_changing_extent_only)
SO the blk_queue_split() bio will be further split if needed (due to
DM target boundary, etc).
Mike
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