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authorMike Snitzer <snitzer@redhat.com>2015-05-22 09:14:03 -0400
committerJens Axboe <axboe@fb.com>2015-05-22 08:58:55 -0600
commit326e1dbb57368087a36607aaebe9795b8d5453e5 (patch)
treebbc17b38188d4f2d45d255f1254d63494d37e1e4 /drivers/md/dm-snap.c
parentb04a5636a665f5529fdf69ee7e5512156196f31c (diff)
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>
Diffstat (limited to 'drivers/md/dm-snap.c')
-rw-r--r--drivers/md/dm-snap.c1
1 files changed, 0 insertions, 1 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 8bfeae218531..7c82d3ccce87 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();