block: remove management of bi_remaining when restoring original bi_end_io

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.

Also, the bio_inc_remaining() interface has been moved local to bio.c.

Fixes: c4cf5261 ("bio: skip atomic inc/dec of ->bi_remaining for non-chains")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index 5cbd5d9..0436c21 100644 (file)
--- 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 (file)
--- 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..cb64e64 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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..e852602 100644 (file)
--- 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 (file)
--- 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 e08a926..0bccf18 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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