BTRFS_DELAYED_BACKGROUND
BTRFS_DELAYED_BACKGROUND / 2)
if (atomic_read(&delayed_root->items) < BTRFS_DELAYED_BACKGROUND)
if ((atomic_read(&delayed_root->items) < BTRFS_DELAYED_BACKGROUND) ||
BTRFS_DELAYED_BACKGROUND || seq % BTRFS_DELAYED_BATCH == 0))