From: Dennis Zhou <dennisszhou@gmail.com>
To: Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Josef Bacik <josef@toxicpanda.com>
Cc: kernel-team@fb.com, linux-block@vger.kernel.org,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
"Dennis Zhou (Facebook)" <dennisszhou@gmail.com>
Subject: [PATCH 13/15] blkcg: change blkg reference counting to use percpu_ref
Date: Thu, 30 Aug 2018 21:53:54 -0400 [thread overview]
Message-ID: <20180831015356.69796-14-dennisszhou@gmail.com> (raw)
In-Reply-To: <20180831015356.69796-1-dennisszhou@gmail.com>
From: "Dennis Zhou (Facebook)" <dennisszhou@gmail.com>
Now that every bio is associated with a blkg, this puts the use of
blkg_get, blkg_try_get, and blkg_put on the hot path. This switches over
the refcnt in blkg to use percpu_ref.
Signed-off-by: Dennis Zhou <dennisszhou@gmail.com>
---
block/blk-cgroup.c | 56 +++++++++++++++++++++-----------------
include/linux/blk-cgroup.h | 14 +++-------
2 files changed, 35 insertions(+), 35 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index f678cd555814..bbea4b44bd8f 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -84,6 +84,30 @@ static void blkg_free(struct blkcg_gq *blkg)
kfree(blkg);
}
+/*
+ * A group is RCU protected, but having an rcu lock does not mean that one
+ * can access all the fields of blkg and assume these are valid. For
+ * example, don't try to follow throtl_data and request queue links.
+ *
+ * Having a reference to blkg under an rcu allows accesses to only values
+ * local to groups like group stats and group rate limits.
+ */
+static void __blkg_release(struct percpu_ref *ref)
+{
+ struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt);
+
+ percpu_ref_exit(&blkg->refcnt);
+
+ /* release the blkcg and parent blkg refs this blkg has been holding */
+ css_put(&blkg->blkcg->css);
+ if (blkg->parent)
+ blkg_put(blkg->parent);
+
+ wb_congested_put(blkg->wb_congested);
+
+ blkg_free(blkg);
+}
+
/**
* blkg_alloc - allocate a blkg
* @blkcg: block cgroup the new blkg is associated with
@@ -110,7 +134,6 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
blkg->q = q;
INIT_LIST_HEAD(&blkg->q_node);
blkg->blkcg = blkcg;
- atomic_set(&blkg->refcnt, 1);
/* root blkg uses @q->root_rl, init rl only for !root blkgs */
if (blkcg != &blkcg_root) {
@@ -217,6 +240,10 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
blkg_get(blkg->parent);
}
+ ret = percpu_ref_init(&blkg->refcnt, __blkg_release, 0, GFP_KERNEL);
+ if (ret)
+ goto err_cancel_ref;
+
/* invoke per-policy init */
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];
@@ -249,6 +276,8 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
blkg_put(blkg);
return ERR_PTR(ret);
+err_cancel_ref:
+ percpu_ref_exit(&blkg->refcnt);
err_put_congested:
wb_congested_put(wb_congested);
err_put_css:
@@ -378,7 +407,7 @@ static void blkg_destroy(struct blkcg_gq *blkg)
* Put the reference taken at the time of creation so that when all
* queues are gone, group can be destroyed.
*/
- blkg_put(blkg);
+ percpu_ref_kill(&blkg->refcnt);
}
/**
@@ -405,29 +434,6 @@ static void blkg_destroy_all(struct request_queue *q)
q->root_rl.blkg = NULL;
}
-/*
- * A group is RCU protected, but having an rcu lock does not mean that one
- * can access all the fields of blkg and assume these are valid. For
- * example, don't try to follow throtl_data and request queue links.
- *
- * Having a reference to blkg under an rcu allows accesses to only values
- * local to groups like group stats and group rate limits.
- */
-void __blkg_release_rcu(struct rcu_head *rcu_head)
-{
- struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head);
-
- /* release the blkcg and parent blkg refs this blkg has been holding */
- css_put(&blkg->blkcg->css);
- if (blkg->parent)
- blkg_put(blkg->parent);
-
- wb_congested_put(blkg->wb_congested);
-
- blkg_free(blkg);
-}
-EXPORT_SYMBOL_GPL(__blkg_release_rcu);
-
/*
* The next function used by blk_queue_for_each_rl(). It's a bit tricky
* because the root blkg uses @q->root_rl instead of its own rl.
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 97cb82029b18..b60d063fb0d7 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -126,7 +126,7 @@ struct blkcg_gq {
struct request_list rl;
/* reference count */
- atomic_t refcnt;
+ struct percpu_ref refcnt;
/* is this blkg online? protected by both blkcg and q locks */
bool online;
@@ -455,8 +455,7 @@ static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)
*/
static inline void blkg_get(struct blkcg_gq *blkg)
{
- WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0);
- atomic_inc(&blkg->refcnt);
+ percpu_ref_get(&blkg->refcnt);
}
/**
@@ -468,23 +467,18 @@ static inline void blkg_get(struct blkcg_gq *blkg)
*/
static inline struct blkcg_gq *blkg_try_get(struct blkcg_gq *blkg)
{
- if (atomic_inc_not_zero(&blkg->refcnt))
+ if (percpu_ref_tryget(&blkg->refcnt))
return blkg;
return NULL;
}
-
-void __blkg_release_rcu(struct rcu_head *rcu);
-
/**
* blkg_put - put a blkg reference
* @blkg: blkg to put
*/
static inline void blkg_put(struct blkcg_gq *blkg)
{
- WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0);
- if (atomic_dec_and_test(&blkg->refcnt))
- call_rcu(&blkg->rcu_head, __blkg_release_rcu);
+ percpu_ref_put(&blkg->refcnt);
}
/**
--
2.17.1
next prev parent reply other threads:[~2018-08-31 1:54 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-31 1:53 [PATCH 00/15] blkcg ref count refactor/cleanup + blkcg avg_lat Dennis Zhou
2018-08-31 1:53 ` [PATCH 01/15] Revert "blk-throttle: fix race between blkcg_bio_issue_check() and cgroup_rmdir()" Dennis Zhou
2018-08-31 1:53 ` [PATCH 02/15] blkcg: delay blkg destruction until after writeback has finished Dennis Zhou
2018-08-31 15:27 ` Josef Bacik
2018-08-31 20:19 ` Dennis Zhou
2018-08-31 1:53 ` [PATCH 03/15] blkcg: use tryget logic when associating a blkg with a bio Dennis Zhou
2018-08-31 15:30 ` Josef Bacik
2018-08-31 20:20 ` Dennis Zhou
2018-08-31 1:53 ` [PATCH 04/15] blkcg: fix ref count issue with bio_blkcg using task_css Dennis Zhou
2018-08-31 15:35 ` Josef Bacik
2018-08-31 23:04 ` Tejun Heo
2018-09-06 15:21 ` Dennis Zhou
2018-08-31 1:53 ` [PATCH 05/15] blkcg: update blkg_lookup_create to do locking Dennis Zhou
2018-08-31 15:37 ` Josef Bacik
2018-08-31 23:09 ` Tejun Heo
2018-08-31 1:53 ` [PATCH 06/15] blkcg: always associate a bio with a blkg Dennis Zhou
2018-08-31 9:01 ` kbuild test robot
2018-08-31 10:02 ` kbuild test robot
2018-08-31 23:16 ` Tejun Heo
2018-09-06 20:41 ` Dennis Zhou
2018-09-07 3:03 ` [LKP] [blkcg] c02c58dab2: WARNING:at_block/blk-throttle.c:#blk_throtl_bio kernel test robot
2018-08-31 1:53 ` [PATCH 07/15] blkcg: consolidate bio_issue_init and blkg association Dennis Zhou
2018-08-31 9:19 ` kbuild test robot
2018-08-31 11:11 ` kbuild test robot
2018-08-31 15:42 ` Josef Bacik
2018-09-06 20:43 ` Dennis Zhou
2018-08-31 23:45 ` Tejun Heo
2018-08-31 1:53 ` [PATCH 08/15] blkcg: associate a blkg for pages being evicted by swap Dennis Zhou
2018-08-31 15:44 ` Josef Bacik
2018-08-31 23:47 ` Tejun Heo
2018-08-31 1:53 ` [PATCH 09/15] blkcg: associate writeback bios with a blkg Dennis Zhou
2018-08-31 15:45 ` Josef Bacik
2018-08-31 23:53 ` Tejun Heo
2018-08-31 1:53 ` [PATCH 10/15] blkcg: remove bio->bi_css and instead use bio->bi_blkg Dennis Zhou
2018-08-31 15:46 ` Josef Bacik
2018-09-01 0:13 ` Tejun Heo
2018-08-31 1:53 ` [PATCH 11/15] blkcg: remove additional reference to the css Dennis Zhou
2018-09-01 0:26 ` Tejun Heo
2018-09-06 20:45 ` Dennis Zhou
2018-08-31 1:53 ` [PATCH 12/15] blkcg: cleanup and make blk_get_rl use blkg_lookup_create Dennis Zhou
2018-09-01 0:29 ` Tejun Heo
2018-09-11 2:37 ` [LKP] [blkcg] 22f657e287: general_protection_fault:#[##] kernel test robot
2018-08-31 1:53 ` Dennis Zhou [this message]
2018-08-31 15:49 ` [PATCH 13/15] blkcg: change blkg reference counting to use percpu_ref Josef Bacik
2018-09-01 0:31 ` Tejun Heo
2018-09-06 20:46 ` Dennis Zhou
2018-09-07 3:08 ` [LKP] [blkcg] 6ef69a3a0b: WARNING:suspicious_RCU_usage kernel test robot
2018-08-31 1:53 ` [PATCH 14/15] blkcg: rename blkg_try_get to blkg_tryget Dennis Zhou
2018-08-31 15:50 ` Josef Bacik
2018-09-01 0:32 ` Tejun Heo
2018-08-31 1:53 ` [PATCH 15/15] blkcg: add average latency tracking to blk-cgroup Dennis Zhou
2018-08-31 10:22 ` kbuild test robot
2018-08-31 11:38 ` kbuild test robot
2018-09-01 0:35 ` [PATCH 00/15] blkcg ref count refactor/cleanup + blkcg avg_lat Tejun Heo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180831015356.69796-14-dennisszhou@gmail.com \
--to=dennisszhou@gmail.com \
--cc=axboe@kernel.dk \
--cc=cgroups@vger.kernel.org \
--cc=hannes@cmpxchg.org \
--cc=josef@toxicpanda.com \
--cc=kernel-team@fb.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).