From: Miao Xie <miaox@cn.fujitsu.com>
Date: Thu, 27 Feb 2014 05:58:04 +0000 (+0800)
Subject: Btrfs: fix wrong lock range and write size in check_can_nocow()
X-Git-Tag: v3.15-rc1~96^2~50
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c933956ddf80bc455d33cbcf39d35d935daf45a9;p=pandora-kernel.git

Btrfs: fix wrong lock range and write size in check_can_nocow()

The write range may not be sector-aligned, for example:

       |--------|--------|	<- write range, sector-unaligned, size: 2blocks
  |--------|--------|--------|  <- correct lock range, size: 3blocks

But according to the old code, we used the size of write range to calculate
the lock range directly, not considered the offset, we would get a wrong lock
range:

       |--------|--------|	<- write range, sector-unaligned, size: 2blocks
  |--------|--------|		<- wrong lock range, size: 2blocks

And besides that, the old code also had the same problem when calculating
the real write size. Correct them.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
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