[PATCH] md: delay starting md threads until array is completely setup

When an array is started we start one or two threads (two if there is a
reshape or recovery that needs to be completed).

We currently start these *before* the array is completely set up and in
particular before queue->queuedata is set.  If the thread actually starts
very quickly on another CPU, we can end up dereferencing queue->queuedata
and oops.

This patch also makes sure we don't try to start a recovery if a reshape is
being restarted.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/md.c

@@ -3095,7 +3095,6 @@ static int do_md_run(mddev_t * mddev)
 		}
 
 	set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);
-	md_wakeup_thread(mddev->thread);
 
 	if (mddev->sb_dirty)
 		md_update_sb(mddev);
@@ -3116,7 +3115,7 @@ static int do_md_run(mddev_t * mddev)
 	 * start recovery here.  If we leave it to md_check_recovery,
 	 * it will remove the drives and not do the right thing
 	 */
-	if (mddev->degraded) {
+	if (mddev->degraded && !mddev->sync_thread) {
 		struct list_head *rtmp;
 		int spares = 0;
 		ITERATE_RDEV(mddev,rdev,rtmp)
@@ -3137,10 +3136,11 @@ static int do_md_run(mddev_t * mddev)
 				       mdname(mddev));
 				/* leave the spares where they are, it shouldn't hurt */
 				mddev->recovery = 0;
-			} else
-				md_wakeup_thread(mddev->sync_thread);
+			}
 		}
 	}
+	md_wakeup_thread(mddev->thread);
+	md_wakeup_thread(mddev->sync_thread); /* possibly kick off a reshape */
 
 	mddev->changed = 1;
 	md_new_event(mddev);

drivers/md/raid5.c

@@ -3246,9 +3246,6 @@ static int run(mddev_t *mddev)
 		set_bit(MD_RECOVERY_RUNNING, &mddev->recovery);
 		mddev->sync_thread = md_register_thread(md_do_sync, mddev,
 							"%s_reshape");
-		/* FIXME if md_register_thread fails?? */
-		md_wakeup_thread(mddev->sync_thread);
-
 	}
 
 	/* read-ahead size must cover two whole stripes, which is