[PATCH 23/49] writeback, blkcg: associate each blkcg_gq with the corresponding bdi_writeback_congested

Tejun Heo
2015-04-06T20:17:16Z

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 <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Vivek Goyal <vgoyal@redhat.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;

--
2.1.0