Btrfs: resize all devices when we dont assign a specific, device id

index 7624212..4f0748ef 100644
@@ -1311,12 +1311,51 @@ out_ra:
 	return ret;
 }
 
+static struct btrfs_device *get_avail_device(struct btrfs_root *root, u64 devid)
+{
+	struct btrfs_key key;
+	struct btrfs_path *path;
+	struct btrfs_dev_item *dev_item;
+	struct btrfs_device *device = NULL;
+	int ret;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return ERR_PTR(-ENOMEM);
+
+	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
+	key.offset = devid;
+	key.type = BTRFS_DEV_ITEM_KEY;
+
+	ret = btrfs_search_slot(NULL, root->fs_info->chunk_root, &key,
+				path, 0, 0);
+	if (ret < 0) {
+		device = ERR_PTR(ret);
+		goto out;
+	}
+	btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+	if (key.objectid != BTRFS_DEV_ITEMS_OBJECTID ||
+	    key.type != BTRFS_DEV_ITEM_KEY) {
+		device = NULL;
+		goto out;
+	}
+	dev_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				  struct btrfs_dev_item);
+	devid = btrfs_device_id(path->nodes[0], dev_item);
+
+	device = btrfs_find_device(root->fs_info, devid, NULL, NULL);
+out:
+	btrfs_free_path(path);
+	return device;
+}
+
 static noinline int btrfs_ioctl_resize(struct file *file,
 					void __user *arg)
 {
-	u64 new_size;
+	u64 new_size = 0;
 	u64 old_size;
-	u64 devid = 1;
+	u64 orig_new_size = 0;
+	u64 devid = -1ULL;
 	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
 	struct btrfs_ioctl_vol_args *vol_args;
 	struct btrfs_trans_handle *trans;

@@ -1325,6 +1364,8 @@ static noinline int btrfs_ioctl_resize(struct file *file,
 	char *devstr = NULL;
 	int ret = 0;
 	int mod = 0;
+	int scan_all = 1;
+	int use_max = 0;
 
 	if (root->fs_info->sb->s_flags & MS_RDONLY)
 		return -EROFS;

@@ -1361,8 +1402,31 @@ static noinline int btrfs_ioctl_resize(struct file *file,
 		devid = simple_strtoull(devstr, &end, 10);
 		printk(KERN_INFO "btrfs: resizing devid %llu\n",
 		       (unsigned long long)devid);
+		scan_all = 0;
 	}
-	device = btrfs_find_device(root->fs_info, devid, NULL, NULL);
+
+	if (!strcmp(sizestr, "max")) {
+		use_max = 1;
+	} else {
+		if (sizestr[0] == '-') {
+			mod = -1;
+			sizestr++;
+		} else if (sizestr[0] == '+') {
+			mod = 1;
+			sizestr++;
+		}
+		orig_new_size = memparse(sizestr, NULL);
+		if (orig_new_size == 0) {
+			ret = -EINVAL;
+			goto out_free;
+		}
+	}
+
+	if (devid < -1ULL)
+		device = btrfs_find_device(root->fs_info, devid, NULL, NULL);
+	else
+		device = get_avail_device(root, 0);
+again:
 	if (!device) {
 		printk(KERN_INFO "btrfs: resizer unable to find device %llu\n",
 		       (unsigned long long)devid);

@@ -1377,22 +1441,10 @@ static noinline int btrfs_ioctl_resize(struct file *file,
 		goto out_free;
 	}
 
-	if (!strcmp(sizestr, "max"))
+	if (use_max)
 		new_size = device->bdev->bd_inode->i_size;
-	else {
-		if (sizestr[0] == '-') {
-			mod = -1;
-			sizestr++;
-		} else if (sizestr[0] == '+') {
-			mod = 1;
-			sizestr++;
-		}
-		new_size = memparse(sizestr, NULL);
-		if (new_size == 0) {
-			ret = -EINVAL;
-			goto out_free;
-		}
-	}
+	else
+		new_size = orig_new_size;
 
 	if (device->is_tgtdev_for_dev_replace) {
 		ret = -EINVAL;

@@ -1439,6 +1491,20 @@ static noinline int btrfs_ioctl_resize(struct file *file,
 		ret = btrfs_shrink_device(device, new_size);
 	} /* equal, nothing need to do */
 
+	if (ret)
+		goto out_free;
+
+	if (scan_all) {
+		/* next available device */
+		device = get_avail_device(root, device->devid + 1);
+		if (!device)
+			goto out_free;
+		if (IS_ERR(device)) {
+			ret = PTR_ERR(device);
+			goto out_free;
+		}
+		goto again;
+	}
 out_free:
 	kfree(vol_args);
 out: