Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964799AbbERUkv (ORCPT ); Mon, 18 May 2015 16:40:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41398 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932864AbbERUkr (ORCPT ); Mon, 18 May 2015 16:40:47 -0400 Date: Mon, 18 May 2015 16:40:17 -0400 From: Mike Snitzer To: Jan Kara , hch@infradead.org, Jens Axboe Cc: Chris Mason , dm-devel@redhat.com, linux-kernel@vger.kernel.org Subject: [PATCH for-4.2 v2 01/14] block: remove management of bi_remaining when restoring original bi_end_io Message-ID: <20150518204017.GA17202@redhat.com> References: <1431637512-64245-1-git-send-email-snitzer@redhat.com> <1431637512-64245-2-git-send-email-snitzer@redhat.com> <20150518072237.GE26351@quack.suse.cz> <20150518131358.GA13998@redhat.com> <20150518153644.GA10187@quack.suse.cz> <20150518155948.GE13998@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150518155948.GE13998@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 11165 Lines: 341 Commit c4cf5261 ("bio: skip atomic inc/dec of ->bi_remaining for non-chains") regressed all existing callers that followed this pattern: 1) saving a bio's original bi_end_io 2) wiring up an intermediate bi_end_io 3) restoring the original bi_end_io from intermediate bi_end_io 4) calling bio_endio() to execute the restored original bi_end_io The regression was due to BIO_CHAIN only ever getting set if bio_inc_remaining() is called. For the above pattern it isn't set until step 3 above (step 2 would've needed to establish BIO_CHAIN). As such the first bio_endio(), in step 2 above, never decremented __bi_remaining before calling the intermediate bi_end_io -- leaving __bi_remaining with the value 1 instead of 0. When bio_inc_remaining() occurred during step 3 it brought it to a value of 2. When the second bio_endio() was called, in step 4 above, it should've called the original bi_end_io but it didn't because there was an extra reference that wasn't dropped (due to atomic operations being optimized away since BIO_CHAIN wasn't set upfront). Fix this issue by removing the __bi_remaining management complexity for all callers that use the above pattern -- bio_chain() is the only interface that _needs_ to be concerned with __bi_remaining. For the above pattern callers just expect the bi_end_io they set to get called! Remove bio_endio_nodec() and also remove all bio_inc_remaining() calls that aren't associated with the bio_chain() interface. changes in v2: Care is now taken to clear the BIO_CHAIN flag once ->__bi_remaining drops to 0. Also, the bio_inc_remaining() interface has moved local to bio.c. Fixes: c4cf5261 ("bio: skip atomic inc/dec of ->bi_remaining for non-chains") Signed-off-by: Mike Snitzer --- block/bio-integrity.c | 4 ++-- block/bio.c | 35 ++++++++++++++--------------------- drivers/md/bcache/io.c | 2 +- drivers/md/dm-cache-target.c | 6 ------ drivers/md/dm-raid1.c | 2 -- drivers/md/dm-snap.c | 1 - drivers/md/dm-thin.c | 9 +++------ drivers/md/dm-verity.c | 2 +- fs/btrfs/disk-io.c | 2 +- fs/btrfs/volumes.c | 16 +++++----------- fs/btrfs/volumes.h | 2 -- include/linux/bio.h | 12 ------------ 12 files changed, 27 insertions(+), 66 deletions(-) diff --git a/block/bio-integrity.c b/block/bio-integrity.c index 5cbd5d9..0436c21 100644 --- a/block/bio-integrity.c +++ b/block/bio-integrity.c @@ -361,7 +361,7 @@ static void bio_integrity_verify_fn(struct work_struct *work) /* Restore original bio completion handler */ bio->bi_end_io = bip->bip_end_io; - bio_endio_nodec(bio, error); + bio_endio(bio, error); } /** @@ -388,7 +388,7 @@ void bio_integrity_endio(struct bio *bio, int error) */ if (error) { bio->bi_end_io = bip->bip_end_io; - bio_endio_nodec(bio, error); + bio_endio(bio, error); return; } diff --git a/block/bio.c b/block/bio.c index c2ff8a8..259197d 100644 --- a/block/bio.c +++ b/block/bio.c @@ -303,6 +303,17 @@ static void bio_chain_endio(struct bio *bio, int error) bio_put(bio); } +/* + * Increment chain count for the bio. Make sure the CHAIN flag update + * is visible before the raised count. + */ +static inline void bio_inc_remaining(struct bio *bio) +{ + bio->bi_flags |= (1 << BIO_CHAIN); + smp_mb__before_atomic(); + atomic_inc(&bio->__bi_remaining); +} + /** * bio_chain - chain bio completions * @bio: the target bio @@ -1756,8 +1767,10 @@ static inline bool bio_remaining_done(struct bio *bio) BUG_ON(atomic_read(&bio->__bi_remaining) <= 0); - if (atomic_dec_and_test(&bio->__bi_remaining)) + if (atomic_dec_and_test(&bio->__bi_remaining)) { + clear_bit(BIO_CHAIN, &bio->bi_flags); return true; + } return false; } @@ -1809,26 +1822,6 @@ void bio_endio(struct bio *bio, int error) EXPORT_SYMBOL(bio_endio); /** - * bio_endio_nodec - end I/O on a bio, without decrementing bi_remaining - * @bio: bio - * @error: error, if any - * - * For code that has saved and restored bi_end_io; thing hard before using this - * function, probably you should've cloned the entire bio. - **/ -void bio_endio_nodec(struct bio *bio, int error) -{ - /* - * If it's not flagged as a chain, we are not going to dec the count - */ - if (bio_flagged(bio, BIO_CHAIN)) - bio_inc_remaining(bio); - - bio_endio(bio, error); -} -EXPORT_SYMBOL(bio_endio_nodec); - -/** * bio_split - split a bio * @bio: bio to split * @sectors: number of sectors to split from the front of @bio diff --git a/drivers/md/bcache/io.c b/drivers/md/bcache/io.c index fa028fa..cb64e64a 100644 --- a/drivers/md/bcache/io.c +++ b/drivers/md/bcache/io.c @@ -55,7 +55,7 @@ static void bch_bio_submit_split_done(struct closure *cl) s->bio->bi_end_io = s->bi_end_io; s->bio->bi_private = s->bi_private; - bio_endio_nodec(s->bio, 0); + bio_endio(s->bio, 0); closure_debug_destroy(&s->cl); mempool_free(s, s->p->bio_split_hook); diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 705eb7b..41b2594 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -86,12 +86,6 @@ static void dm_unhook_bio(struct dm_hook_info *h, struct bio *bio) { bio->bi_end_io = h->bi_end_io; bio->bi_private = h->bi_private; - - /* - * Must bump bi_remaining to allow bio to complete with - * restored bi_end_io. - */ - bio_inc_remaining(bio); } /*----------------------------------------------------------------*/ diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c index d6a1c09..743fa9b 100644 --- a/drivers/md/dm-raid1.c +++ b/drivers/md/dm-raid1.c @@ -1254,8 +1254,6 @@ static int mirror_end_io(struct dm_target *ti, struct bio *bio, int error) dm_bio_restore(bd, bio); bio_record->details.bi_bdev = NULL; - bio_inc_remaining(bio); - queue_bio(ms, bio, rw); return DM_ENDIO_INCOMPLETE; } diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index 8bfeae2..7c82d3c 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -1478,7 +1478,6 @@ out: if (full_bio) { full_bio->bi_end_io = pe->full_bio_end_io; full_bio->bi_private = pe->full_bio_private; - bio_inc_remaining(full_bio); } increment_pending_exceptions_done_count(); diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 342dbda..e852602c 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -793,10 +793,9 @@ static void inc_remap_and_issue_cell(struct thin_c *tc, static void process_prepared_mapping_fail(struct dm_thin_new_mapping *m) { - if (m->bio) { + if (m->bio) m->bio->bi_end_io = m->saved_bi_end_io; - bio_inc_remaining(m->bio); - } + cell_error(m->tc->pool, m->cell); list_del(&m->list); mempool_free(m, m->tc->pool->mapping_pool); @@ -810,10 +809,8 @@ static void process_prepared_mapping(struct dm_thin_new_mapping *m) int r; bio = m->bio; - if (bio) { + if (bio) bio->bi_end_io = m->saved_bi_end_io; - bio_inc_remaining(bio); - } if (m->err) { cell_error(pool, m->cell); diff --git a/drivers/md/dm-verity.c b/drivers/md/dm-verity.c index 66616db..bb9c6a0 100644 --- a/drivers/md/dm-verity.c +++ b/drivers/md/dm-verity.c @@ -459,7 +459,7 @@ static void verity_finish_io(struct dm_verity_io *io, int error) bio->bi_end_io = io->orig_bi_end_io; bio->bi_private = io->orig_bi_private; - bio_endio_nodec(bio, error); + bio_endio(bio, error); } static void verity_work(struct work_struct *w) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 2ef9a4b..fbdbee4 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1745,7 +1745,7 @@ static void end_workqueue_fn(struct btrfs_work *work) bio->bi_private = end_io_wq->private; bio->bi_end_io = end_io_wq->end_io; kmem_cache_free(btrfs_end_io_wq_cache, end_io_wq); - bio_endio_nodec(bio, error); + bio_endio(bio, error); } static int cleaner_kthread(void *arg) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 8e8d1d1..dac77d4 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -5585,10 +5585,10 @@ int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree, static inline void btrfs_end_bbio(struct btrfs_bio *bbio, struct bio *bio, int err) { - if (likely(bbio->flags & BTRFS_BIO_ORIG_BIO_SUBMITTED)) - bio_endio_nodec(bio, err); - else - bio_endio(bio, err); + bio->bi_private = bbio->private; + bio->bi_end_io = bbio->end_io; + bio_endio(bio, err); + btrfs_put_bbio(bbio); } @@ -5632,8 +5632,6 @@ static void btrfs_end_bio(struct bio *bio, int err) bio = bbio->orig_bio; } - bio->bi_private = bbio->private; - bio->bi_end_io = bbio->end_io; btrfs_io_bio(bio)->mirror_num = bbio->mirror_num; /* only send an error to the higher layers if it is * beyond the tolerance of the btrfs bio @@ -5815,8 +5813,6 @@ static void bbio_error(struct btrfs_bio *bbio, struct bio *bio, u64 logical) /* Shoud be the original bio. */ WARN_ON(bio != bbio->orig_bio); - bio->bi_private = bbio->private; - bio->bi_end_io = bbio->end_io; btrfs_io_bio(bio)->mirror_num = bbio->mirror_num; bio->bi_iter.bi_sector = logical >> 9; @@ -5897,10 +5893,8 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio, if (dev_nr < total_devs - 1) { bio = btrfs_bio_clone(first_bio, GFP_NOFS); BUG_ON(!bio); /* -ENOMEM */ - } else { + } else bio = first_bio; - bbio->flags |= BTRFS_BIO_ORIG_BIO_SUBMITTED; - } submit_stripe_bio(root, bbio, bio, bbio->stripes[dev_nr].physical, dev_nr, rw, diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index ebc3133..cedae03 100644 --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -292,8 +292,6 @@ struct btrfs_bio_stripe { struct btrfs_bio; typedef void (btrfs_bio_end_io_t) (struct btrfs_bio *bio, int err); -#define BTRFS_BIO_ORIG_BIO_SUBMITTED (1 << 0) - struct btrfs_bio { atomic_t refs; atomic_t stripes_pending; diff --git a/include/linux/bio.h b/include/linux/bio.h index 7486ea1..f0291cf 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -427,7 +427,6 @@ static inline struct bio *bio_clone_kmalloc(struct bio *bio, gfp_t gfp_mask) } extern void bio_endio(struct bio *, int); -extern void bio_endio_nodec(struct bio *, int); struct request_queue; extern int bio_phys_segments(struct request_queue *, struct bio *); @@ -659,17 +658,6 @@ static inline struct bio *bio_list_get(struct bio_list *bl) } /* - * Increment chain count for the bio. Make sure the CHAIN flag update - * is visible before the raised count. - */ -static inline void bio_inc_remaining(struct bio *bio) -{ - bio->bi_flags |= (1 << BIO_CHAIN); - smp_mb__before_atomic(); - atomic_inc(&bio->__bi_remaining); -} - -/* * bio_set is used to allow other portions of the IO system to * allocate their own private memory pools for bio and iovec structures. * These memory pools in turn all allocate from the bio_slab -- 2.3.2 (Apple Git-55) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/