On Fri 22-05-15 17:13:38, Tejun Heo wrote:
> A blkg (blkcg_gq) can be congested and decongested independently from
> other blkgs on the same request_queue. Accordingly, for cgroup
> writeback support, the congestion status at bdi (backing_dev_info)
> should be split and updated separately from matching blkg's.
>
> This patch prepares by adding blkg->wb_congested and associating a
> blkg with its matching per-blkcg bdi_writeback_congested on creation.
>
> v2: Updated to associate bdi_writeback_congested instead of
> bdi_writeback.
>
> Signed-off-by: Tejun Heo <t...@kernel.org>
> Cc: Jens Axboe <ax...@kernel.dk>
> Cc: Jan Kara <j...@suse.cz>
> Cc: Vivek Goyal <vgo...@redhat.com>
Looks good to me. You can add:
Reviewed-by: Jan Kara <j...@suse.com>
> ---
> block/blk-cgroup.c | 17 +++++++++++++++--
> include/linux/blk-cgroup.h | 6 ++++++
> 2 files changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
> index 979cfdb..31610ae 100644
> --- a/block/blk-cgroup.c
> +++ b/block/blk-cgroup.c
> @@ -182,6 +182,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
> struct blkcg_gq *new_blkg)
> {
> struct blkcg_gq *blkg;
> + struct bdi_writeback_congested *wb_congested;
> int i, ret;
>
> WARN_ON_ONCE(!rcu_read_lock_held());
> @@ -193,22 +194,30 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
> goto err_free_blkg;
> }
>
> + wb_congested = wb_congested_get_create(&q->backing_dev_info,
> + blkcg->css.id, GFP_ATOMIC);
> + if (!wb_congested) {
> + ret = -ENOMEM;
> + goto err_put_css;
> + }
> +
> /* allocate */
> if (!new_blkg) {
> new_blkg = blkg_alloc(blkcg, q, GFP_ATOMIC);
> if (unlikely(!new_blkg)) {
> ret = -ENOMEM;
> - goto err_put_css;
> + goto err_put_congested;
> }
> }
> blkg = new_blkg;
> + blkg->wb_congested = wb_congested;
>
> /* link parent */
> if (blkcg_parent(blkcg)) {
> blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
> if (WARN_ON_ONCE(!blkg->parent)) {
> ret = -EINVAL;
> - goto err_put_css;
> + goto err_put_congested;
> }
> blkg_get(blkg->parent);
> }
> @@ -245,6 +254,8 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
> blkg_put(blkg);
> return ERR_PTR(ret);
>
> +err_put_congested:
> + wb_congested_put(wb_congested);
> err_put_css:
> css_put(&blkcg->css);
> err_free_blkg:
> @@ -391,6 +402,8 @@ void __blkg_release_rcu(struct rcu_head *rcu_head)
> if (blkg->parent)
> blkg_put(blkg->parent);
>
> + wb_congested_put(blkg->wb_congested);
> +
> blkg_free(blkg);
> }
> EXPORT_SYMBOL_GPL(__blkg_release_rcu);
> diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
> index 3033eb1..07a32b8 100644
> --- a/include/linux/blk-cgroup.h
> +++ b/include/linux/blk-cgroup.h
> @@ -99,6 +99,12 @@ struct blkcg_gq {
> struct hlist_node blkcg_node;
> struct blkcg *blkcg;
>
> + /*
> + * Each blkg gets congested separately and the congestion state is
> + * propagated to the matching bdi_writeback_congested.
> + */
> + struct bdi_writeback_congested *wb_congested;
> +
> /* all non-root blkcg_gq's are guaranteed to have access to parent */
> struct blkcg_gq *parent;
>
> --
> 2.4.0
>
--
Jan Kara <j...@suse.cz>
SUSE Labs, CR
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