From: Miao Xie <miaox@cn.fujitsu.com>
Date: Thu, 11 Apr 2013 10:30:16 +0000 (+0000)
Subject: Btrfs: use a lock to protect incompat/compat flag of the super block
X-Git-Tag: v3.10-rc1~31^2~57
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ceda08642459e31673d24d7968d864390d2ce5fa;p=pandora-kernel.git

Btrfs: use a lock to protect incompat/compat flag of the super block

The following case will make the incompat/compat flag of the super block
be recovered.
 Task1					|Task2
 flags = btrfs_super_incompat_flags();	|
					|flags = btrfs_super_incompat_flags();
 flags |= new_flag1;			|
					|flags |= new_flag2;
 btrfs_set_super_incompat_flags(flags);	|
					|btrfs_set_super_incompat_flags(flags);
the new_flag1 is recovered.

In order to avoid this problem, we introduce a lock named super_lock into
the btrfs_fs_info structure. If we want to update incompat/compat flags
of the super block, we must hold it.

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