From: Andrew Morton <akpm@linux-foundation.org>
To: Jingbo Xu <jefflexu@linux.alibaba.com>
Cc: shr@devkernel.io, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, joseph.qi@linux.alibaba.com
Subject: Re: [PATCH] mm: fix arithmetic for bdi min_ratio and max_ratio
Date: Mon, 18 Dec 2023 10:21:17 -0800 [thread overview]
Message-ID: <20231218102117.c91ab02353ff76b952f3ec9e@linux-foundation.org> (raw)
In-Reply-To: <20231218031640.77983-1-jefflexu@linux.alibaba.com>
On Mon, 18 Dec 2023 11:16:40 +0800 Jingbo Xu <jefflexu@linux.alibaba.com> wrote:
> bdi->[min|max]_ratio are both part per million. Fix the wrong
> arithmetic when setting bdi's min_ratio and max_ratio.
>
> Fixes: efc3e6ad53ea ("mm: split off __bdi_set_max_ratio() function")
> Fixes: 8021fb3232f2 ("mm: split off __bdi_set_min_ratio() function")
As we have two Fixes:, it would be better to have two patches please.
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -692,7 +692,6 @@ static int __bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ra
>
> if (min_ratio > 100 * BDI_RATIO_SCALE)
> return -EINVAL;
> - min_ratio *= BDI_RATIO_SCALE;
>
> spin_lock_bh(&bdi_lock);
> if (min_ratio > bdi->max_ratio) {
> @@ -729,7 +728,8 @@ static int __bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ra
> ret = -EINVAL;
> } else {
> bdi->max_ratio = max_ratio;
> - bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100;
> + bdi->max_prop_frac = div64_u64(FPROP_FRAC_BASE * max_ratio,
> + 100UL * BDI_RATIO_SCALE);
> }
> spin_unlock_bh(&bdi_lock);
Does this change have any observable runtime effects? If so, what are they?
next prev parent reply other threads:[~2023-12-18 18:21 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-18 3:16 Jingbo Xu
2023-12-18 3:29 ` Jingbo Xu
2023-12-18 18:21 ` Andrew Morton [this message]
2023-12-19 2:03 ` Jingbo Xu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20231218102117.c91ab02353ff76b952f3ec9e@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=jefflexu@linux.alibaba.com \
--cc=joseph.qi@linux.alibaba.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=shr@devkernel.io \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox