On Mon, Apr 19, 2021 at 04:41:02PM +0900, Johannes Thumshirn wrote:
> +void btrfs_reclaim_bgs_work(struct work_struct *work)
> +{
> + struct btrfs_fs_info *fs_info =
> + container_of(work, struct btrfs_fs_info, reclaim_bgs_work);
> + struct btrfs_block_group *bg;
> + struct btrfs_space_info *space_info;
> + int ret;
> +
> + if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags))
> + return;
> +
> + if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE))
> + return;
> +
> + mutex_lock(&fs_info->reclaim_bgs_lock);
> + spin_lock(&fs_info->unused_bgs_lock);
> + while (!list_empty(&fs_info->reclaim_bgs)) {
> + bg = list_first_entry(&fs_info->reclaim_bgs,
> + struct btrfs_block_group,
> + bg_list);
> + list_del_init(&bg->bg_list);
> +
> + space_info = bg->space_info;
> + spin_unlock(&fs_info->unused_bgs_lock);
> +
> + /* Don't want to race with allocators so take the groups_sem */
> + down_write(&space_info->groups_sem);
> +
> + spin_lock(&bg->lock);
> + if (bg->reserved || bg->pinned || bg->ro) {
> + /*
> + * We want to bail if we made new allocations or have
> + * outstanding allocations in this block group. We do
> + * the ro check in case balance is currently acting on
> + * this block group.
> + */
> + spin_unlock(&bg->lock);
> + up_write(&space_info->groups_sem);
> + goto next;
> + }
> + spin_unlock(&bg->lock);
> +
> + /* Get out fast, in case we're unmounting the FS. */
> + if (btrfs_fs_closing(fs_info)) {
> + up_write(&space_info->groups_sem);
> + goto next;
> + }
> +
> + ret = inc_block_group_ro(bg, 0);
> + up_write(&space_info->groups_sem);
> + if (ret < 0)
> + goto next;
> +
> + btrfs_info(fs_info, "reclaiming chunk %llu", bg->start);
This could state the bg usage ratio, bg->used / bg->length .
> + trace_btrfs_reclaim_block_group(bg);
> + ret = btrfs_relocate_chunk(fs_info, bg->start);
> + if (ret)
> + btrfs_err(fs_info, "error relocating chunk %llu",
> + bg->start);
> +
> +next:
> + btrfs_put_block_group(bg);
> + spin_lock(&fs_info->unused_bgs_lock);
> + }
> + spin_unlock(&fs_info->unused_bgs_lock);
> + mutex_unlock(&fs_info->reclaim_bgs_lock);
> + btrfs_exclop_finish(fs_info);
> +}
