md: restore ability of spare drives to spin down.

neilbrown · neilbrown · commit 1176568de7e0 · 2010-05-07T21:10:57.000+10:00
Some time ago we stopped the clean/active metadata updates from being written to a 'spare' device in most cases so that it could spin down and say spun down. Device failure/removal etc are still recorded on spares. However commit 51d5668 broke this 50% of the time, depending on whether the event count is even or odd. The change log entry said: This means that the alignment between 'odd/even' and 'clean/dirty' might take a little longer to attain, how ever the code makes no attempt to create that alignment, so it could take arbitrarily long. So when we find that clean/dirty is not aligned with odd/even, force a second metadata-update immediately. There are already cases where a second metadata-update is needed immediately (e.g. when a device fails during the metadata update). We just piggy-back on that. Reported-by: Joe Bryant <tenminjoe@yahoo.com> Signed-off-by: NeilBrown <neilb@suse.de> Cc: stable@kernel.org
diff --git a/drivers/md/md.c b/drivers/md/md.c
@@ -2109,12 +2109,18 @@ static void md_update_sb(mddev_t * mddev, int force_change)
 		if (!mddev->in_sync || mddev->recovery_cp != MaxSector) { /* not clean */
 			/* .. if the array isn't clean, an 'even' event must also go
 			 * to spares. */
-			if ((mddev->events&1)==0)
+			if ((mddev->events&1)==0) {
 				nospares = 0;
+				sync_req = 2; /* force a second update to get the
+					       * even/odd in sync */
+			}
 		} else {
 			/* otherwise an 'odd' event must go to spares */
-			if ((mddev->events&1))
+			if ((mddev->events&1)) {
 				nospares = 0;
+				sync_req = 2; /* force a second update to get the
+					       * even/odd in sync */
+			}
 		}
 	}
 
