md: Constify attribute_group structs

The attribute_group structs are never modified, they're only passed to
sysfs_create_group() and sysfs_remove_group(). Make them const to allow
the compiler to put them in read-only memory.
Signed-off-by: NRikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: NSong Liu <song@kernel.org>

drivers/md/md-bitmap.c

@@ -2616,7 +2616,7 @@ static struct attribute *md_bitmap_attrs[] = {
 	&max_backlog_used.attr,
 	NULL
 };
-struct attribute_group md_bitmap_group = {
+const struct attribute_group md_bitmap_group = {
 	.name = "bitmap",
 	.attrs = md_bitmap_attrs,
 };

drivers/md/md.c

@@ -785,7 +785,7 @@ static struct mddev *mddev_alloc(dev_t unit)
 	return ERR_PTR(error);
 }
 
-static struct attribute_group md_redundancy_group;
+static const struct attribute_group md_redundancy_group;
 
 void mddev_unlock(struct mddev *mddev)
 {
@@ -802,7 +802,7 @@ void mddev_unlock(struct mddev *mddev)
 		 * test it under the same mutex to ensure its correct value
 		 * is seen.
 		 */
-		struct attribute_group *to_remove = mddev->to_remove;
+		const struct attribute_group *to_remove = mddev->to_remove;
 		mddev->to_remove = NULL;
 		mddev->sysfs_active = 1;
 		mutex_unlock(&mddev->reconfig_mutex);
@@ -5500,7 +5500,7 @@ static struct attribute *md_redundancy_attrs[] = {
 	&md_degraded.attr,
 	NULL,
 };
-static struct attribute_group md_redundancy_group = {
+static const struct attribute_group md_redundancy_group = {
 	.name = NULL,
 	.attrs = md_redundancy_attrs,
 };

drivers/md/md.h

@@ -481,7 +481,7 @@ struct mddev {
 	atomic_t			max_corr_read_errors; /* max read retries */
 	struct list_head		all_mddevs;
 
-	struct attribute_group		*to_remove;
+	const struct attribute_group	*to_remove;
 
 	struct bio_set			bio_set;
 	struct bio_set			sync_set; /* for sync operations like
@@ -613,7 +613,7 @@ struct md_sysfs_entry {
 	ssize_t (*show)(struct mddev *, char *);
 	ssize_t (*store)(struct mddev *, const char *, size_t);
 };
-extern struct attribute_group md_bitmap_group;
+extern const struct attribute_group md_bitmap_group;
 
 static inline struct kernfs_node *sysfs_get_dirent_safe(struct kernfs_node *sd, char *name)
 {

drivers/md/raid5.c

@@ -6940,7 +6940,7 @@ static struct attribute *raid5_attrs[] =  {
 	&ppl_write_hint.attr,
 	NULL,
 };
-static struct attribute_group raid5_attrs_group = {
+static const struct attribute_group raid5_attrs_group = {
 	.name = NULL,
 	.attrs = raid5_attrs,
 };