From: Jens Axboe <axboe@kernel.dk>
To: Tejun Heo <tj@kernel.org>
Cc: Roman Gushchin <guro@fb.com>,
linux-block@vger.kernel.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@fb.com,
Josef Bacik <jbacik@fb.com>
Subject: Re: [PATCH block/for-5.4-fixes] blkcg: make blkcg_print_stat() print stats only for online blkgs
Date: Wed, 6 Nov 2019 17:08:59 -0700 [thread overview]
Message-ID: <1ef277bb-8591-6029-2e9b-319820b3460c@kernel.dk> (raw)
In-Reply-To: <20191105160951.GS3622521@devbig004.ftw2.facebook.com>
On 11/5/19 9:09 AM, Tejun Heo wrote:
> blkcg_print_stat() iterates blkgs under RCU and doesn't test whether
> the blkg is online. This can call into pd_stat_fn() on a pd which is
> still being initialized leading to an oops.
>
> The heaviest operation - recursively summing up rwstat counters - is
> already done while holding the queue_lock. Expand queue_lock to cover
> the other operations and skip the blkg if it isn't online yet. The
> online state is protected by both blkcg and queue locks, so this
> guarantees that only online blkgs are processed.
Applied, thanks Tejun.
--
Jens Axboe
prev parent reply other threads:[~2019-11-07 0:09 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-05 16:09 Tejun Heo
2019-11-07 0:08 ` Jens Axboe [this message]
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