block: fix bio_add_page for non trivial merge_bvec_fn case
We have to properly decrease bi_size in order to merge_bvec_fn return
right result. Otherwise this result in false merge rejects for two
absolutely valid bio_vecs. This may cause significant performance
penalty for example fs_block_size == 1k and block device is raid0 with
small chunk_size = 8k. Then it is impossible to merge 7-th fs-block in
to bio which already has 6 fs-blocks.
Cc: <stable@kernel.org>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
1 file changed