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Date:   Fri, 14 Jun 2019 09:43:43 -0400
From:   Josef Bacik <josef@toxicpanda.com>
To:     Tejun Heo <tj@kernel.org>
Cc:     dsterba@suse.com, clm@fb.com, josef@toxicpanda.com,
        axboe@kernel.dk, jack@suse.cz, linux-btrfs@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
        kernel-team@fb.com
Subject: Re: [PATCH 3/8] blkcg: implement REQ_CGROUP_PUNT
Message-ID: <20190614134342.rtm4iwxgzbsueyfg@MacBook-Pro-91.local>
References: <20190614003350.1178444-1-tj@kernel.org>
 <20190614003350.1178444-4-tj@kernel.org>
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On Thu, Jun 13, 2019 at 05:33:45PM -0700, Tejun Heo wrote:
> When a shared kthread needs to issue a bio for a cgroup, doing so
> synchronously can lead to priority inversions as the kthread can be
> trapped waiting for that cgroup.  This patch implements
> REQ_CGROUP_PUNT flag which makes submit_bio() punt the actual issuing
> to a dedicated per-blkcg work item to avoid such priority inversions.
> 
> This will be used to fix priority inversions in btrfs compression and
> should be generally useful as we grow filesystem support for
> comprehensive IO control.
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Chris Mason <clm@fb.com>

Reviewed-by: Josef Bacik <josef@toxicpanda.com>

Thanks,

Josef