[PATCH] loop: clear read-only flag in loop_clr_fd.

[Tao Ma <tm@tao.ma>]

From: Tao Ma <boyu.mt@taobao.com>

In 75f1dc0, we check bdev_read_only() from blkdev_get().
But the loop_clr_fd doesn't clear the read only flag.
What cause a error if we changing a loop device from
read only to writable.

A simple test to reproduce the error reported by Milan[1]:
touch /x1.img
losetup -r /dev/loop0 /x1.img
losetup -d /dev/loop0
losetup /dev/loop0 /x1.img
/dev/loop0: Permission denied

1: http://marc.info/?l=linux-kernel&m=129756258222642&w=2

Reported-by: Milan Broz <mbroz@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
---
 drivers/block/loop.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 44e18c0..0d24579 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1036,8 +1036,10 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
 	memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
 	memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
 	memset(lo->lo_file_name, 0, LO_NAME_SIZE);
-	if (bdev)
+	if (bdev) {
+		set_device_ro(bdev, 0);
 		invalidate_bdev(bdev);
+	}
 	set_capacity(lo->lo_disk, 0);
 	loop_sysfs_exit(lo);
 	if (bdev) {
-- 
1.6.3.GIT