rbd: remove buggy rollback functionality

This doesn't interact with resizing well, since it doesn't set the
size of the device to the size at the snapshot. It's also an expensive
operation to be synchronous. Rollback can still be done with the
userspace rbd tool.
Signed-off-by: Josh Durgin <josh.durgin@dreamhost.com>

Documentation/ABI/testing/sysfs-bus-rbd

@@ -57,13 +57,6 @@ create_snap
 
 	 $ echo <snap-name> > /sys/bus/rbd/devices/<dev-id>/snap_create
 
-rollback_snap
-
-	Rolls back data to the specified snapshot. This goes over the entire
-	list of rados blocks and sends a rollback command to each.
-
-	 $ echo <snap-name> > /sys/bus/rbd/devices/<dev-id>/snap_rollback
-
 snap_*
 
 	A directory per each snapshot

drivers/block/rbd.c

@@ -183,10 +183,6 @@ static LIST_HEAD(rbd_client_list);      /* clients */
 
 static int __rbd_init_snaps_header(struct rbd_device *rbd_dev);
 static void rbd_dev_release(struct device *dev);
-static ssize_t rbd_snap_rollback(struct device *dev,
-				 struct device_attribute *attr,
-				 const char *buf,
-				 size_t size);
 static ssize_t rbd_snap_add(struct device *dev,
 			    struct device_attribute *attr,
 			    const char *buf,
@@ -1359,32 +1355,6 @@ static int rbd_req_sync_notify(struct rbd_device *dev,
 	return ret;
 }
 
-/*
- * Request sync osd rollback
- */
-static int rbd_req_sync_rollback_obj(struct rbd_device *dev,
-				     u64 snapid,
-				     const char *obj)
-{
-	struct ceph_osd_req_op *ops;
-	int ret = rbd_create_rw_ops(&ops, 1, CEPH_OSD_OP_ROLLBACK, 0);
-	if (ret < 0)
-		return ret;
-
-	ops[0].snap.snapid = snapid;
-
-	ret = rbd_req_sync_op(dev, NULL,
-			       CEPH_NOSNAP,
-			       0,
-			       CEPH_OSD_FLAG_WRITE | CEPH_OSD_FLAG_ONDISK,
-			       ops,
-			       1, obj, 0, 0, NULL, NULL, NULL);
-
-	rbd_destroy_ops(ops);
-
-	return ret;
-}
-
 /*
  * Request sync osd read
  */
@@ -1891,7 +1861,6 @@ static DEVICE_ATTR(name, S_IRUGO, rbd_name_show, NULL);
 static DEVICE_ATTR(refresh, S_IWUSR, NULL, rbd_image_refresh);
 static DEVICE_ATTR(current_snap, S_IRUGO, rbd_snap_show, NULL);
 static DEVICE_ATTR(create_snap, S_IWUSR, NULL, rbd_snap_add);
-static DEVICE_ATTR(rollback_snap, S_IWUSR, NULL, rbd_snap_rollback);
 
 static struct attribute *rbd_attrs[] = {
 	&dev_attr_size.attr,
@@ -1902,7 +1871,6 @@ static struct attribute *rbd_attrs[] = {
 	&dev_attr_current_snap.attr,
 	&dev_attr_refresh.attr,
 	&dev_attr_create_snap.attr,
-	&dev_attr_rollback_snap.attr,
 	NULL
 };
 
@@ -2433,64 +2401,6 @@ static ssize_t rbd_snap_add(struct device *dev,
 	return ret;
 }
 
-static ssize_t rbd_snap_rollback(struct device *dev,
-				 struct device_attribute *attr,
-				 const char *buf,
-				 size_t count)
-{
-	struct rbd_device *rbd_dev = dev_to_rbd(dev);
-	int ret;
-	u64 snapid;
-	u64 cur_ofs;
-	char *seg_name = NULL;
-	char *snap_name = kmalloc(count + 1, GFP_KERNEL);
-	ret = -ENOMEM;
-	if (!snap_name)
-		return ret;
-
-	/* parse snaps add command */
-	snprintf(snap_name, count, "%s", buf);
-	seg_name = kmalloc(RBD_MAX_SEG_NAME_LEN + 1, GFP_NOIO);
-	if (!seg_name)
-		goto done;
-
-	mutex_lock_nested(&ctl_mutex, SINGLE_DEPTH_NESTING);
-
-	ret = snap_by_name(&rbd_dev->header, snap_name, &snapid, NULL);
-	if (ret < 0)
-		goto done_unlock;
-
-	dout("snapid=%lld\n", snapid);
-
-	cur_ofs = 0;
-	while (cur_ofs < rbd_dev->header.image_size) {
-		cur_ofs += rbd_get_segment(&rbd_dev->header,
-					   rbd_dev->obj,
-					   cur_ofs, (u64)-1,
-					   seg_name, NULL);
-		dout("seg_name=%s\n", seg_name);
-
-		ret = rbd_req_sync_rollback_obj(rbd_dev, snapid, seg_name);
-		if (ret < 0)
-			pr_warning("could not roll back obj %s err=%d\n",
-				   seg_name, ret);
-	}
-
-	ret = __rbd_update_snaps(rbd_dev);
-	if (ret < 0)
-		goto done_unlock;
-
-	ret = count;
-
-done_unlock:
-	mutex_unlock(&ctl_mutex);
-done:
-	kfree(seg_name);
-	kfree(snap_name);
-
-	return ret;
-}
-
 static struct bus_attribute rbd_bus_attrs[] = {
 	__ATTR(add, S_IWUSR, NULL, rbd_add),
 	__ATTR(remove, S_IWUSR, NULL, rbd_remove),