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Thu, 4 Jan 2024 17:41:01 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id kuyQJq3tlmWQcQAAD6G6ig (envelope-from ); Thu, 04 Jan 2024 17:41:01 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 0C27EA07EF; Thu, 4 Jan 2024 18:41:01 +0100 (CET) Date: Thu, 4 Jan 2024 18:41:01 +0100 From: Jan Kara To: Jingbo Xu Cc: shr@devkernel.io, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, joseph.qi@linux.alibaba.com, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, willy@infradead.org Subject: Re: [PATCH v3 2/2] mm: fix arithmetic for max_prop_frac when setting max_ratio Message-ID: <20240104174101.oax6zbdhy4v5u4bf@quack3> References: <20231219142508.86265-1-jefflexu@linux.alibaba.com> <20231219142508.86265-3-jefflexu@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231219142508.86265-3-jefflexu@linux.alibaba.com> X-Rspamd-Queue-Id: AE0D5180008 X-Rspam-User: X-Stat-Signature: ru7gih7ezmynymieocz57bmhhxwfm7e3 X-Rspamd-Server: rspam03 X-HE-Tag: 1704390063-226987 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue 19-12-23 22:25:08, Jingbo Xu wrote: > Since now bdi->max_ratio is part per million, fix the wrong arithmetic > for max_prop_frac when setting max_ratio. Otherwise the miscalculated > max_prop_frac will affect the incrementing of writeout completion count > when max_ratio is not 100%. > > Fixes: efc3e6ad53ea ("mm: split off __bdi_set_max_ratio() function") > Signed-off-by: Jingbo Xu Good catch. Feel free to add: Reviewed-by: Jan Kara Honza > --- > mm/page-writeback.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index 2140382dd768..05e5c425b3ff 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -728,7 +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 = (FPROP_FRAC_BASE * max_ratio) / > + (100 * BDI_RATIO_SCALE); > } > spin_unlock_bh(&bdi_lock); > > -- > 2.19.1.6.gb485710b > > -- Jan Kara SUSE Labs, CR