[PATCH] md: split off some md attributes in sysfs to a separate group

Some, but not all, md array support data redundancy and hence support checking
and restoring that redundancy (resync, rebuild).

Some attributes apply specifically to functions involving this redundancy, and
so should only appear for md arrays for which they are meaningful.  i.e.  they
should not appear for raid0, linear, multpath, faulty.

This patch separates these into a distinct group and creates the group only if
the personality supports sync_request.
Signed-off-by: Neil Brown <neilb@suse.de>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/md.c

@@ -1807,10 +1807,19 @@ md_mismatches = __ATTR_RO(mismatch_cnt);
 static struct attribute *md_default_attrs[] = {
 	&md_level.attr,
 	&md_raid_disks.attr,
+	NULL,
+};
+
+static struct attribute *md_redundancy_attrs[] = {
 	&md_scan_mode.attr,
 	&md_mismatches.attr,
 	NULL,
 };
+static struct attribute_group md_redundancy_group = {
+	.name = NULL,
+	.attrs = md_redundancy_attrs,
+};
+
 
 static ssize_t
 md_attr_show(struct kobject *kobj, struct attribute *attr, char *page)
@@ -2047,6 +2056,8 @@ static int do_md_run(mddev_t * mddev)
 		bitmap_destroy(mddev);
 		return err;
 	}
+	if (mddev->pers->sync_request)
+		sysfs_create_group(&mddev->kobj, &md_redundancy_group);
  	atomic_set(&mddev->writes_pending,0);
 	mddev->safemode = 0;
 	mddev->safemode_timer.function = md_safemode_timeout;
@@ -2155,6 +2166,9 @@ static int do_md_stop(mddev_t * mddev, int ro)
 				set_disk_ro(disk, 0);
 			blk_queue_make_request(mddev->queue, md_fail_request);
 			mddev->pers->stop(mddev);
+			if (mddev->pers->sync_request)
+				sysfs_remove_group(&mddev->kobj, &md_redundancy_group);
+
 			module_put(mddev->pers->owner);
 			mddev->pers = NULL;
 			if (mddev->ro)