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From: Greg KH on 1 Jul 2010 14:50
2.6.32-stable review patch. If anyone has any objections, please let us know.

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

From: Dan Williams <dan.j.williams(a)intel.com>

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(a)intel.com>
Signed-off-by: NeilBrown <neilb(a)suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>

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

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5334,6 +5334,7 @@ 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;
@@ -5469,6 +5470,34 @@ 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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