[09/39] md: Fix unfortunate interaction with evms

[Greg KH <gregkh@suse.de>]

2.6.31-stable review patch.  If anyone has any objections, please let us know.

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

From: NeilBrown <neilb@suse.de>

commit cbd1998377504df005302ac90d49db72a48552a6 upstream.

evms configures md arrays by:
  open device
  send ioctl
  close device

for each different ioctl needed.
Since 2.6.29, the device can disappear after the 'close'
unless a significant configuration has happened to the device.
The change made by "SET_ARRAY_INFO" can too minor to stop the device
from disappearing, but important enough that losing the change is bad.

So: make sure SET_ARRAY_INFO sets mddev->ctime, and keep the device
active as long as ctime is non-zero (it gets zeroed with lots of other
things when the array is stopped).

This is suitable for -stable kernels since 2.6.29.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 drivers/md/md.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -276,7 +276,9 @@ static void mddev_put(mddev_t *mddev)
 	if (!atomic_dec_and_lock(&mddev->active, &all_mddevs_lock))
 		return;
 	if (!mddev->raid_disks && list_empty(&mddev->disks) &&
-	    !mddev->hold_active) {
+	    mddev->ctime == 0 && !mddev->hold_active) {
+		/* Array is not configured at all, and not held active,
+		 * so destroy it */
 		list_del(&mddev->all_mddevs);
 		if (mddev->gendisk) {
 			/* we did a probe so need to clean up.
@@ -5040,6 +5042,10 @@ static int set_array_info(mddev_t * mdde
 		mddev->minor_version = info->minor_version;
 		mddev->patch_version = info->patch_version;
 		mddev->persistent = !info->not_persistent;
+		/* ensure mddev_put doesn't delete this now that there
+		 * is some minimal configuration.
+		 */
+		mddev->ctime         = get_seconds();
 		return 0;
 	}
 	mddev->major_version = MD_MAJOR_VERSION;