From: Jens Axboe <axboe@kernel.dk>
To: Tejun Heo <tj@kernel.org>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com, cgroups@vger.kernel.org
Subject: Re: [PATCH v2 block/for-next] blk-iocost: fix divide-by-zero in transfer_surpluses()
Date: Fri, 11 Sep 2020 16:43:18 -0600 [thread overview]
Message-ID: <59987f54-47fc-766f-0667-5a90daca0b1a@kernel.dk> (raw)
In-Reply-To: <20200911224049.GA865564@mtj.thefacebook.com>
On 9/11/20 4:40 PM, Tejun Heo wrote:
> Conceptually, root_iocg->hweight_donating must be less than WEIGHT_ONE but
> all hweight calculations round up and thus it may end up >= WEIGHT_ONE
> triggering divide-by-zero and other issues. Bound the value to avoid
> surprises.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Fixes: e08d02aa5fc9 ("blk-iocost: implement Andy's method for donation weight updates")
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> ---
> Jens, I was flipping between doing max_t(, 1) over the whole divider and
> doing min_t(, WEIGHT_ONE - 1) for hweight_donating. I thought that I as
> testing after the last change but it obviously wasn't and the previous patch
> doesn't compile due to missing type argument. Can you please apply this
> patch instead? I can send an incremental patch if that'd be better. My
> apologies.
Sure, I replaced it. BTW, you had two signed-off-by's in there.
--
Jens Axboe
next prev parent reply other threads:[~2020-09-11 22:43 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-11 17:07 [PATCH block/for-next] blk-iocost: fix divide-by-zero in transfer_surpluses() Tejun Heo
2020-09-11 17:10 ` Jens Axboe
2020-09-11 22:40 ` [PATCH v2 " Tejun Heo
2020-09-11 22:43 ` Jens Axboe [this message]
2020-09-11 22:44 ` Tejun Heo
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