From: Dmitry Monakhov <dmonakhov@openvz.org>
Date: Wed, 27 Jan 2010 19:44:36 +0000 (+0300)
Subject: block: fix bio_add_page for non trivial merge_bvec_fn case
X-Git-Tag: v2.6.33-rc7~37^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1d6165851cd8e3f919d446cd6da35dee44e8837e;p=pandora-kernel.git

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>
---

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