From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [PATCH 3/4] dm: fix missing bio_split() pattern code in __split_and_process_bio() Date: Mon, 21 Jan 2019 11:02:04 -0500 Message-ID: <20190121160204.GA32117@redhat.com> References: <20190119180506.1300-1-snitzer@redhat.com> <20190119180506.1300-4-snitzer@redhat.com> <20190121032153.GA24610@ming.t460p> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20190121032153.GA24610@ming.t460p> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Ming Lei Cc: axboe@kernel.dk, linux-block@vger.kernel.org, dm-devel@redhat.com, NeilBrown List-Id: dm-devel.ids On Sun, Jan 20 2019 at 10:21P -0500, Ming Lei wrote: > On Sat, Jan 19, 2019 at 01:05:05PM -0500, Mike Snitzer wrote: > > Use the same BIO_QUEUE_ENTERED pattern that was established by commit > > cd4a4ae4683dc ("block: don't use blocking queue entered for recursive > > bio submits") by setting BIO_QUEUE_ENTERED after bio_split() and before > > recursing via generic_make_request(). > > > > Also add trace_block_split() because it provides useful context about > > bio splits in blktrace. > > > > Depends-on: cd4a4ae4683dc ("block: don't use blocking queue entered for recursive bio submits") > > Fixes: 18a25da84354 ("dm: ensure bio submission follows a depth-first tree walk") > > Cc: stable@vger.kernel.org # 4.16+ > > Signed-off-by: Mike Snitzer > > --- > > drivers/md/dm.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/drivers/md/dm.c b/drivers/md/dm.c > > index fbadda68e23b..6e29c2d99b99 100644 > > --- a/drivers/md/dm.c > > +++ b/drivers/md/dm.c > > @@ -1654,7 +1654,9 @@ static blk_qc_t __split_and_process_bio(struct mapped_device *md, > > sectors[op_stat_group(bio_op(bio))], ci.sector_count); > > part_stat_unlock(); > > > > + bio_set_flag(bio, BIO_QUEUE_ENTERED); > > bio_chain(b, bio); > > + trace_block_split(md->queue, b, bio->bi_iter.bi_sector); > > ret = generic_make_request(bio); > > break; > > } > > In theory, BIO_QUEUE_ENTERED is only required when __split_and_process_bio() is > called from generic_make_request(). However, it may be called from dm_wq_work(), > this way might cause trouble on operation to q->q_usage_counter. Good point, I've tweaked this patch to clear BIO_QUEUE_ENTERED in dm_make_request(). And to Neil's point: yes, these changes really do need to made common since it appears all bio_split() callers do go on to call generic_make_request(). Anyway, here is the updated patch that is now staged in linux-next: From: Mike Snitzer Date: Fri, 18 Jan 2019 01:21:11 -0500 Subject: [PATCH v2] dm: fix missing bio_split() pattern code in __split_and_process_bio() Use the same BIO_QUEUE_ENTERED pattern that was established by commit cd4a4ae4683dc ("block: don't use blocking queue entered for recursive bio submits") by setting BIO_QUEUE_ENTERED after bio_split() and before recursing via generic_make_request(). Also add trace_block_split() because it provides useful context about bio splits in blktrace. Depends-on: cd4a4ae4683dc ("block: don't use blocking queue entered for recursive bio submits") Fixes: 18a25da84354 ("dm: ensure bio submission follows a depth-first tree walk") Cc: stable@vger.kernel.org # 4.16+ Signed-off-by: Mike Snitzer --- drivers/md/dm.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index fbadda68e23b..25884f833a32 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1654,7 +1654,9 @@ static blk_qc_t __split_and_process_bio(struct mapped_device *md, sectors[op_stat_group(bio_op(bio))], ci.sector_count); part_stat_unlock(); + bio_set_flag(bio, BIO_QUEUE_ENTERED); bio_chain(b, bio); + trace_block_split(md->queue, b, bio->bi_iter.bi_sector); ret = generic_make_request(bio); break; } @@ -1734,6 +1736,13 @@ static blk_qc_t dm_make_request(struct request_queue *q, struct bio *bio) map = dm_get_live_table(md, &srcu_idx); + /* + * Clear the bio-reentered-generic_make_request() flag, + * will be set again as needed if bio needs to be split. + */ + if (bio_flagged(bio, BIO_QUEUE_ENTERED)) + bio_clear_flag(bio, BIO_QUEUE_ENTERED); + /* if we're suspended, we have to queue this io for later */ if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags))) { dm_put_live_table(md, srcu_idx); -- 2.15.0