md: clean up irregularity with raid autodetect

When a raid1 array is stopped, all components currently get added to the list
for auto-detection.  However we should really only add components that were
found by autodetection in the first place.  So add a flag to record that
information, and use it.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/md/md.c

@@ -1503,7 +1503,8 @@ static void export_rdev(mdk_rdev_t * rdev)
 	free_disk_sb(rdev);
 	list_del_init(&rdev->same_set);
 #ifndef MODULE
-	md_autodetect_dev(rdev->bdev->bd_dev);
+	if (test_bit(AutoDetected, &rdev->flags))
+		md_autodetect_dev(rdev->bdev->bd_dev);
 #endif
 	unlock_rdev(rdev);
 	kobject_put(&rdev->kobj);
@@ -6025,6 +6026,7 @@ static void autostart_arrays(int part)
 			MD_BUG();
 			continue;
 		}
+		set_bit(AutoDetected, &rdev->flags);
 		list_add(&rdev->same_set, &pending_raid_disks);
 		i_passed++;
 	}

include/linux/raid/md_k.h

@@ -83,6 +83,7 @@ struct mdk_rdev_s
 #define	BarriersNotsupp	5		/* BIO_RW_BARRIER is not supported */
 #define	AllReserved	6		/* If whole device is reserved for
 					 * one array */
+#define	AutoDetected	7		/* added by auto-detect */
 
 	int desc_nr;			/* descriptor index in the superblock */
 	int raid_disk;			/* role of device in array */