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author | Dmitry Monakhov <dmonakhov@openvz.org> | 2010-01-27 19:44:36 (GMT) |
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committer | Jens Axboe <jens.axboe@oracle.com> | 2010-01-28 14:08:29 (GMT) |
commit | 1d6165851cd8e3f919d446cd6da35dee44e8837e (patch) | |
tree | a9d68cfc0e838490d12963aa917ef78a54ae2073 /fs | |
parent | c84a301d4a4b1cc382a6549b4e7881ce5b796d63 (diff) | |
download | linux-fsl-qoriq-1d6165851cd8e3f919d446cd6da35dee44e8837e.tar.xz |
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>
Diffstat (limited to 'fs')
-rw-r--r-- | fs/bio.c | 7 |
1 files changed, 6 insertions, 1 deletions
@@ -542,13 +542,18 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page if (page == prev->bv_page && offset == prev->bv_offset + prev->bv_len) { + unsigned int prev_bv_len = prev->bv_len; prev->bv_len += len; if (q->merge_bvec_fn) { struct bvec_merge_data bvm = { + /* prev_bvec is already charged in + bi_size, discharge it in order to + simulate merging updated prev_bvec + as new bvec. */ .bi_bdev = bio->bi_bdev, .bi_sector = bio->bi_sector, - .bi_size = bio->bi_size, + .bi_size = bio->bi_size - prev_bv_len, .bi_rw = bio->bi_rw, }; |