+ calc_size = max_t(u64, calc_size, BTRFS_STRIPE_LEN);
+
+ do_div(calc_size, BTRFS_STRIPE_LEN);
+ calc_size *= BTRFS_STRIPE_LEN;
+
+ return calc_size;
+}
+
+static struct map_lookup *__shrink_map_lookup_stripes(struct map_lookup *map,
+ int num_stripes)
+{
+ struct map_lookup *new;
+ size_t len = map_lookup_size(num_stripes);
+
+ BUG_ON(map->num_stripes < num_stripes);
+
+ if (map->num_stripes == num_stripes)
+ return map;
+
+ new = kmalloc(len, GFP_NOFS);
+ if (!new) {
+ /* just change map->num_stripes */
+ map->num_stripes = num_stripes;
+ return map;
+ }
+
+ memcpy(new, map, len);
+ new->num_stripes = num_stripes;
+ kfree(map);
+ return new;
+}
+
+/*
+ * helper to allocate device space from btrfs_device_info, in which we stored
+ * max free space information of every device. It is used when we can not
+ * allocate chunks by default size.
+ *
+ * By this helper, we can allocate a new chunk as larger as possible.
+ */
+static int __btrfs_alloc_tiny_space(struct btrfs_trans_handle *trans,
+ struct btrfs_fs_devices *fs_devices,
+ struct btrfs_device_info *devices,
+ int nr_device, u64 type,
+ struct map_lookup **map_lookup,
+ int min_stripes, u64 *stripe_size)
+{
+ int i, index, sort_again = 0;
+ int min_devices = min_stripes;
+ u64 max_avail, min_free;
+ struct map_lookup *map = *map_lookup;
+ int ret;
+
+ if (nr_device < min_stripes)
+ return -ENOSPC;
+
+ btrfs_descending_sort_devices(devices, nr_device);
+
+ max_avail = devices[0].max_avail;
+ if (!max_avail)
+ return -ENOSPC;
+
+ for (i = 0; i < nr_device; i++) {
+ /*
+ * if dev_offset = 0, it means the free space of this device
+ * is less than what we need, and we didn't search max avail
+ * extent on this device, so do it now.
+ */
+ if (!devices[i].dev_offset) {
+ ret = find_free_dev_extent(trans, devices[i].dev,
+ max_avail,
+ &devices[i].dev_offset,
+ &devices[i].max_avail);
+ if (ret != 0 && ret != -ENOSPC)
+ return ret;
+ sort_again = 1;
+ }
+ }
+
+ /* we update the max avail free extent of each devices, sort again */
+ if (sort_again)
+ btrfs_descending_sort_devices(devices, nr_device);
+
+ if (type & BTRFS_BLOCK_GROUP_DUP)
+ min_devices = 1;
+
+ if (!devices[min_devices - 1].max_avail)
+ return -ENOSPC;
+
+ max_avail = devices[min_devices - 1].max_avail;
+ if (type & BTRFS_BLOCK_GROUP_DUP)
+ do_div(max_avail, 2);
+
+ max_avail = __btrfs_calc_stripe_size(fs_devices, max_avail, type,
+ min_stripes, 1);
+ if (type & BTRFS_BLOCK_GROUP_DUP)
+ min_free = max_avail * 2;
+ else
+ min_free = max_avail;
+
+ if (min_free > devices[min_devices - 1].max_avail)
+ return -ENOSPC;
+
+ map = __shrink_map_lookup_stripes(map, min_stripes);
+ *stripe_size = max_avail;
+
+ index = 0;
+ for (i = 0; i < min_stripes; i++) {
+ map->stripes[i].dev = devices[index].dev;
+ map->stripes[i].physical = devices[index].dev_offset;
+ if (type & BTRFS_BLOCK_GROUP_DUP) {
+ i++;
+ map->stripes[i].dev = devices[index].dev;
+ map->stripes[i].physical = devices[index].dev_offset +
+ max_avail;
+ }
+ index++;
+ }
+ *map_lookup = map;
+
+ return 0;
+}