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To:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, josef@toxicpanda.com,
        Tejun Heo <tj@kernel.org>, cgroups@vger.kernel.org
References: <cover.1560510935.git.asml.silence@gmail.com>
From:   Pavel Begunkov <asml.silence@gmail.com>
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Subject: Re: [RESEND RFC PATCH 0/2] Fix misuse of blk_rq_stats in
 blk-iolatency
Message-ID: <276a02f3-3b1a-0580-54fb-497f85103ae3@gmail.com>
Date:   Mon, 30 Sep 2019 11:29:21 +0300
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From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
 linux-kernel@vger.kernel.org, josef@toxicpanda.com, Tejun Heo
 <tj@kernel.org>, cgroups@vger.kernel.org
Message-ID: <276a02f3-3b1a-0580-54fb-497f85103ae3@gmail.com>
Subject: Re: [RESEND RFC PATCH 0/2] Fix misuse of blk_rq_stats in
 blk-iolatency
References: <cover.1560510935.git.asml.silence@gmail.com>
In-Reply-To: <cover.1560510935.git.asml.silence@gmail.com>

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Hi,

I claim, that there is a bug, that hopefully doesn't show itself apart
from a minor disabled optimisation. It's _too_ easy to misuse, and if
somebody try to reuse, this could lead to quite interesting issues.

Could somebody at last take a look?
Thanks

On 25/07/2019 00:35, Pavel Begunkov (Silence) wrote:
> From: Pavel Begunkov <asml.silence@gmail.com>
>=20
> There are implicit assumptions about struct blk_rq_stats, which make
> it's very easy to misuse. The first patch fixes consequences, and the
> second employs type-system to prevent recurrences.
>=20
> Acked-by: Josef Bacik <josef@toxicpanda.com>
>=20
> Pavel Begunkov (2):
>   blk-iolatency: Fix zero mean in previous stats
>   blk-stats: Introduce explicit stat staging buffers
>=20
>  block/blk-iolatency.c     | 60 ++++++++++++++++++++++++++++++---------=

>  block/blk-stat.c          | 48 +++++++++++++++++++++++--------
>  block/blk-stat.h          |  9 ++++--
>  include/linux/blk_types.h |  6 ++++
>  4 files changed, 94 insertions(+), 29 deletions(-)
>=20

--=20
Yours sincerely,
Pavel Begunkov


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