From: Bart Van Assche <bvanassche@acm.org>
To: Dennis Zhou <dennis@kernel.org>, Jens Axboe <axboe@kernel.dk>,
Tejun Heo <tj@kernel.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,
Ming Lei <ming.lei@redhat.com>
Subject: Re: [PATCH] blkcg: handle dying request_queue when associating a blkg
Date: Tue, 11 Dec 2018 15:16:13 -0800 [thread overview]
Message-ID: <1544570173.185366.397.camel@acm.org> (raw)
In-Reply-To: <20181211230308.66276-1-dennis@kernel.org>
On Tue, 2018-12-11 at 18:03 -0500, Dennis Zhou wrote:
+AD4 diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
+AD4 index 6bd0619a7d6e..c30661ddc873 100644
+AD4 --- a/block/blk-cgroup.c
+AD4 +-+-+- b/block/blk-cgroup.c
+AD4 +AEAAQA -202,6 +-202,12 +AEAAQA static struct blkcg+AF8-gq +ACo-blkg+AF8-create(struct blkcg +ACo-blkcg,
+AD4 WARN+AF8-ON+AF8-ONCE(+ACE-rcu+AF8-read+AF8-lock+AF8-held())+ADs
+AD4 lockdep+AF8-assert+AF8-held(+ACY-q-+AD4-queue+AF8-lock)+ADs
+AD4
+AD4 +- /+ACo request+AF8-queue is dying, do not create/recreate a blkg +ACo-/
+AD4 +- if (blk+AF8-queue+AF8-dying(q)) +AHs
+AD4 +- ret +AD0 -ENODEV+ADs
+AD4 +- goto err+AF8-free+AF8-blkg+ADs
+AD4 +- +AH0
+AD4 +-
+AD4 /+ACo blkg holds a reference to blkcg +ACo-/
+AD4 if (+ACE-css+AF8-tryget+AF8-online(+ACY-blkcg-+AD4-css)) +AHs
+AD4 ret +AD0 -ENODEV+ADs
What prevents that the queue state changes after blk+AF8-queue+AF8-dying() has returned
and before blkg+AF8-create() returns? Are you sure you don't need to protect this
code with a blk+AF8-queue+AF8-enter() / blk+AF8-queue+AF8-exit() pair?
Bart.
WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <bvanassche@acm.org>
To: Dennis Zhou <dennis@kernel.org>, Jens Axboe <axboe@kernel.dk>,
Tejun Heo <tj@kernel.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,
Ming Lei <ming.lei@redhat.com>
Subject: Re: [PATCH] blkcg: handle dying request_queue when associating a blkg
Date: Tue, 11 Dec 2018 15:16:13 -0800 [thread overview]
Message-ID: <1544570173.185366.397.camel@acm.org> (raw)
In-Reply-To: <20181211230308.66276-1-dennis@kernel.org>
On Tue, 2018-12-11 at 18:03 -0500, Dennis Zhou wrote:
> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
> index 6bd0619a7d6e..c30661ddc873 100644
> --- a/block/blk-cgroup.c
> +++ b/block/blk-cgroup.c
> @@ -202,6 +202,12 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
> WARN_ON_ONCE(!rcu_read_lock_held());
> lockdep_assert_held(&q->queue_lock);
>
> + /* request_queue is dying, do not create/recreate a blkg */
> + if (blk_queue_dying(q)) {
> + ret = -ENODEV;
> + goto err_free_blkg;
> + }
> +
> /* blkg holds a reference to blkcg */
> if (!css_tryget_online(&blkcg->css)) {
> ret = -ENODEV;
What prevents that the queue state changes after blk_queue_dying() has returned
and before blkg_create() returns? Are you sure you don't need to protect this
code with a blk_queue_enter() / blk_queue_exit() pair?
Bart.
next prev parent reply other threads:[~2018-12-11 23:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-11 23:03 [PATCH] blkcg: handle dying request_queue when associating a blkg Dennis Zhou
2018-12-11 23:16 ` Bart Van Assche [this message]
2018-12-11 23:16 ` Bart Van Assche
2018-12-12 4:06 ` Dennis Zhou
2018-12-12 23:54 ` Bart Van Assche
2018-12-12 23:54 ` Bart Van Assche
2018-12-13 15:47 ` Dennis Zhou
2018-12-13 0:43 ` Jens Axboe
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