From: Andrea Righi <righi.andrea@gmail.com>
To: Josef Bacik <josef@toxicpanda.com>
Cc: Paolo Valente <paolo.valente@linaro.org>,
Tejun Heo <tj@kernel.org>, Li Zefan <lizefan@huawei.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Jens Axboe <axboe@kernel.dk>, Vivek Goyal <vgoyal@redhat.com>,
Dennis Zhou <dennis@kernel.org>,
cgroups@vger.kernel.org, linux-block@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] blkcg: prevent priority inversion problem during sync()
Date: Sat, 9 Feb 2019 14:52:31 +0100 [thread overview]
Message-ID: <20190209135231.GA1910@xps-13> (raw)
In-Reply-To: <20190209120633.GA2506@xps-13>
On Sat, Feb 09, 2019 at 01:06:33PM +0100, Andrea Righi wrote:
...
> +/**
> + * blkcg_wb_waiters_on_bdi - check for writeback waiters on a block device
> + * @bdi: block device to check
> + *
> + * Return true if any other blkcg is waiting for writeback on the target block
> + * device, false otherwise.
> + */
> +bool blkcg_wb_waiters_on_bdi(struct backing_dev_info *bdi)
> +{
> + struct blkcg *blkcg, *curr_blkcg;
> + bool ret = false;
> +
> + if (unlikely(!bdi))
> + return false;
> +
> + rcu_read_lock();
> + curr_blkcg = css_to_blkcg(task_css(current, io_cgrp_id));
Sorry, the logic is messed up here. We shouldn't get curr_blkcg from the
current task, because during writeback throttling the context is
obviously not the current task.
I'll post a new patch soon.
> + list_for_each_entry_rcu(blkcg, &bdi->cgwb_waiters, cgwb_wait_node)
> + if (blkcg != curr_blkcg) {
> + ret = true;
> + break;
> + }
> + rcu_read_unlock();
> +
> + return ret;
> +}
-Andrea
prev parent reply other threads:[~2019-02-09 13:52 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-09 12:06 [RFC PATCH] blkcg: prevent priority inversion problem during sync() Andrea Righi
2019-02-09 13:52 ` Andrea Righi [this message]
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