From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [PATCH v2 4/4] dm: unconditionally call blk_queue_split() in dm_process_bio() Date: Tue, 15 Sep 2020 21:28:14 -0400 Message-ID: <20200916012813.GA23236@redhat.com> References: <20200915172357.83215-1-snitzer@redhat.com> <20200915172357.83215-5-snitzer@redhat.com> <20200916010817.GB791425@T590> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20200916010817.GB791425@T590> Sender: linux-block-owner@vger.kernel.org To: Ming Lei Cc: Jens Axboe , Vijayendra Suman , dm-devel@redhat.com, linux-block@vger.kernel.org List-Id: dm-devel.ids On Tue, Sep 15 2020 at 9:08pm -0400, Ming Lei 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 > > --- > > 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