From: Miao Xie <miaox@cn.fujitsu.com>
Date: Thu, 20 Feb 2014 10:08:51 +0000 (+0800)
Subject: Btrfs: use ACCESS_ONCE to prevent the optimize accesses to ->last_trans_log_full_commit
X-Git-Tag: v3.15-rc1~96^2~78
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5c902ba6223f6a6575054226931fafc51314a25f;p=pandora-kernel.git

Btrfs: use ACCESS_ONCE to prevent the optimize accesses to ->last_trans_log_full_commit

->last_trans_log_full_commit may be changed by the other tasks without lock,
so we need prevent the compiler from the optimize access just like
	tmp = fs_info->last_trans_log_full_commit
	if (tmp == ...)
		...

	<do something>

	if (tmp == ...)
		...

In fact, we need get the new value of ->last_trans_log_full_commit during
the second access. Fix it by ACCESS_ONCE().

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