From: Li Zefan <lizf@cn.fujitsu.com>
Date: Thu, 8 Dec 2011 01:08:40 +0000 (-0500)
Subject: Btrfs: check if the to-be-added device is writable
X-Git-Tag: v3.2-rc5~28^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a5d16333612718569ffd26064270e535cb9c3928;p=pandora-kernel.git

Btrfs: check if the to-be-added device is writable

If we call ioctl(BTRFS_IOC_ADD_DEV) directly, we'll succeed in adding
a readonly device to a btrfs filesystem, and btrfs will write to
that device, emitting kernel errors:

[ 3109.833692] lost page write due to I/O error on loop2
[ 3109.833720] lost page write due to I/O error on loop2
...

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
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