[PATCH] md: allow a linear array to have drives added while active

Signed-off-by: Neil Brown <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/md/linear.c

···
 	return ret;
 }
 
-static int linear_run (mddev_t *mddev)
+static linear_conf_t *linear_conf(mddev_t *mddev, int raid_disks)
 {
 	linear_conf_t *conf;
 	dev_info_t **table;
···
 	sector_t curr_offset;
 	struct list_head *tmp;
 
-	conf = kzalloc (sizeof (*conf) + mddev->raid_disks*sizeof(dev_info_t),
+	conf = kzalloc (sizeof (*conf) + raid_disks*sizeof(dev_info_t),
 			GFP_KERNEL);
 	if (!conf)
-		goto out;
+		return NULL;
+
 	mddev->private = conf;
 
 	cnt = 0;
-	mddev->array_size = 0;
+	conf->array_size = 0;
 
 	ITERATE_RDEV(mddev,rdev,tmp) {
 		int j = rdev->raid_disk;
 		dev_info_t *disk = conf->disks + j;
 
-		if (j < 0 || j > mddev->raid_disks || disk->rdev) {
+		if (j < 0 || j > raid_disks || disk->rdev) {
 			printk("linear: disk numbering problem. Aborting!\n");
 			goto out;
 		}
···
 			blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 
 		disk->size = rdev->size;
-		mddev->array_size += rdev->size;
+		conf->array_size += rdev->size;
 
 		cnt++;
 	}
-	if (cnt != mddev->raid_disks) {
+	if (cnt != raid_disks) {
 		printk("linear: not enough drives present. Aborting!\n");
 		goto out;
 	}
···
 		unsigned round;
 		unsigned long base;
 
-		sz = mddev->array_size >> conf->preshift;
+		sz = conf->array_size >> conf->preshift;
 		sz += 1; /* force round-up */
 		base = conf->hash_spacing >> conf->preshift;
 		round = sector_div(sz, base);
···
 
 	BUG_ON(table - conf->hash_table > nb_zone);
 
+	return conf;
+
+out:
+	kfree(conf);
+	return NULL;
+}
+
+static int linear_run (mddev_t *mddev)
+{
+	linear_conf_t *conf;
+
+	conf = linear_conf(mddev, mddev->raid_disks);
+
+	if (!conf)
+		return 1;
+	mddev->private = conf;
+	mddev->array_size = conf->array_size;
+
 	blk_queue_merge_bvec(mddev->queue, linear_mergeable_bvec);
 	mddev->queue->unplug_fn = linear_unplug;
 	mddev->queue->issue_flush_fn = linear_issue_flush;
 	return 0;
+}
 
-out:
-	kfree(conf);
-	return 1;
+static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
+{
+	/* Adding a drive to a linear array allows the array to grow.
+	 * It is permitted if the new drive has a matching superblock
+	 * already on it, with raid_disk equal to raid_disks.
+	 * It is achieved by creating a new linear_private_data structure
+	 * and swapping it in in-place of the current one.
+	 * The current one is never freed until the array is stopped.
+	 * This avoids races.
+	 */
+	linear_conf_t *newconf;
+
+	if (rdev->raid_disk != mddev->raid_disks)
+		return -EINVAL;
+
+	newconf = linear_conf(mddev,mddev->raid_disks+1);
+
+	if (!newconf)
+		return -ENOMEM;
+
+	newconf->prev = mddev_to_conf(mddev);
+	mddev->private = newconf;
+	mddev->raid_disks++;
+	mddev->array_size = newconf->array_size;
+	set_capacity(mddev->gendisk, mddev->array_size << 1);
+	return 0;
 }
 
 static int linear_stop (mddev_t *mddev)
···
 	linear_conf_t *conf = mddev_to_conf(mddev);
   
 	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
-	kfree(conf->hash_table);
-	kfree(conf);
+	do {
+		linear_conf_t *t = conf->prev;
+		kfree(conf->hash_table);
+		kfree(conf);
+		conf = t;
+	} while (conf);
 
 	return 0;
 }
···
 	.run		= linear_run,
 	.stop		= linear_stop,
 	.status		= linear_status,
+	.hot_add_disk	= linear_add,
 };
 
 static int __init linear_init (void)

drivers/md/md.c

···
 
 		if (desc->state & (1<<MD_DISK_FAULTY))
 			set_bit(Faulty, &rdev->flags);
-		else if (desc->state & (1<<MD_DISK_SYNC) &&
-			 desc->raid_disk < mddev->raid_disks) {
+		else if (desc->state & (1<<MD_DISK_SYNC) /* &&
+			    desc->raid_disk < mddev->raid_disks */) {
 			set_bit(In_sync, &rdev->flags);
 			rdev->raid_disk = desc->raid_disk;
 		}
···
 
 		rdev->raid_disk = -1;
 		err = bind_rdev_to_array(rdev, mddev);
+		if (!err && !mddev->pers->hot_remove_disk) {
+			/* If there is hot_add_disk but no hot_remove_disk
+			 * then added disks for geometry changes,
+			 * and should be added immediately.
+			 */
+			super_types[mddev->major_version].
+				validate_super(mddev, rdev);
+			err = mddev->pers->hot_add_disk(mddev, rdev);
+			if (err)
+				unbind_rdev_from_array(rdev);
+		}
 		if (err)
 			export_rdev(rdev);
 

include/linux/raid/linear.h

···
 
 struct linear_private_data
 {
+	struct linear_private_data *prev;	/* earlier version */
 	dev_info_t		**hash_table;
 	sector_t		hash_spacing;
+	sector_t		array_size;
 	int			preshift; /* shift before dividing by hash_spacing */
 	dev_info_t		disks[0];
 };