[089/200] md: set mddev readonly flag on blkdev BLKROSET ioctl

[Greg KH]

2.6.34-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Williams <dan.j.williams@xxxxxxxxx>

commit e2218350465e7e0931676b4849b594c978437bce upstream.

When the user sets the block device to readwrite then the mddev should
follow suit.  Otherwise, the BUG_ON in md_write_start() will be set to
trigger.

The reverse direction, setting mddev->ro to match a set readonly
request, can be ignored because the blkdev level readonly flag precludes
the need to have mddev->ro set correctly.  Nevermind the fact that
setting mddev->ro to 1 may fail if the array is in use.

Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: NeilBrown <neilb@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/md/md.c |   29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5517,6 +5517,7 @@ static int md_ioctl(struct block_device
 	int err = 0;
 	void __user *argp = (void __user *)arg;
 	mddev_t *mddev = NULL;
+	int ro;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
@@ -5652,6 +5653,34 @@ static int md_ioctl(struct block_device
 			err = do_md_stop(mddev, 1, 1);
 			goto done_unlock;
 
+		case BLKROSET:
+			if (get_user(ro, (int __user *)(arg))) {
+				err = -EFAULT;
+				goto done_unlock;
+			}
+			err = -EINVAL;
+
+			/* if the bdev is going readonly the value of mddev->ro
+			 * does not matter, no writes are coming
+			 */
+			if (ro)
+				goto done_unlock;
+
+			/* are we are already prepared for writes? */
+			if (mddev->ro != 1)
+				goto done_unlock;
+
+			/* transitioning to readauto need only happen for
+			 * arrays that call md_write_start
+			 */
+			if (mddev->pers) {
+				err = restart_array(mddev);
+				if (err == 0) {
+					mddev->ro = 2;
+					set_disk_ro(mddev->gendisk, 0);
+				}
+			}
+			goto done_unlock;
 	}
 
 	/*


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