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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>
This commit is contained in:
Mike Snitzer 2015-05-22 09:14:03 -04:00 committed by Jens Axboe
parent b04a5636a6
commit 326e1dbb57
12 changed files with 27 additions and 66 deletions
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4
block/bio-integrity.c
View File

@ -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;
}

35
block/bio.c
View File

@ -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;
}
@ -1808,26 +1821,6 @@ 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

2
drivers/md/bcache/io.c
View File

@ -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);

6
drivers/md/dm-cache-target.c
View File

@ -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);
}
/*----------------------------------------------------------------*/

2
drivers/md/dm-raid1.c
View File

@ -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;
}

1
drivers/md/dm-snap.c
View File

@ -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();

9
drivers/md/dm-thin.c
View File

@ -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);

2
drivers/md/dm-verity.c
View File

@ -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)

2
fs/btrfs/disk-io.c
View File

@ -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)

14
fs/btrfs/volumes.c
View File

@ -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->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,

2
fs/btrfs/volumes.h
View File

@ -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;

12
include/linux/bio.h
View File

@ -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 *);
@ -658,17 +657,6 @@ static inline struct bio *bio_list_get(struct bio_list *bl)
return 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_set is used to allow other portions of the IO system to
* allocate their own private memory pools for bio and iovec structures.