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Tue, 19 Dec 2023 10:42:48 +0800 From: Jingbo Xu To: shr@devkernel.io, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, joseph.qi@linux.alibaba.com, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org Subject: [PATCH v2 1/2] mm: fix arithmetic for bdi min_ratio Date: Tue, 19 Dec 2023 10:42:45 +0800 Message-Id: <20231219024246.65654-2-jefflexu@linux.alibaba.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20231219024246.65654-1-jefflexu@linux.alibaba.com> References: <20231219024246.65654-1-jefflexu@linux.alibaba.com> MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: B154320002 X-Stat-Signature: tsfhwj6ussxj95p4sn839qk7a8x38khk X-HE-Tag: 1702953771-914984 X-HE-Meta: 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 6laTcVyU HFFRZKovu+YEF04aFCLKd6X9YmN7nLiL3VVVqWOt5RNnZuakLniaOt3ljazEy195DYTNOdmJMBQUbyVdIp7x8Al1+qt3KZi9fEPcDIZWINXW78OacmiQy1s6l9ug2Gl+ym+KfUJFGnFZ7Dh19+z2oMZOBiOINvueGde9o 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: Since now bdi->min_ratio is part per million, fix the wrong arithmetic. Otherwise it will fail with -EINVAL when setting a reasonable min_ratio, as it tries to set min_ratio to (min_ratio * BDI_RATIO_SCALE) in percentage unit, which exceeds 100% anyway. # cat /sys/class/bdi/253\:0/min_ratio 0 # cat /sys/class/bdi/253\:0/max_ratio 100 # echo 1 > /sys/class/bdi/253\:0/min_ratio -bash: echo: write error: Invalid argument Fixes: 8021fb3232f2 ("mm: split off __bdi_set_min_ratio() function") Reported-by: Joseph Qi Signed-off-by: Jingbo Xu --- mm/page-writeback.c | 1 - 1 file changed, 1 deletion(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index ee2fd6a6af40..2140382dd768 100644 --- 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) { From patchwork Tue Dec 19 02:42:46 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jingbo Xu X-Patchwork-Id: 13497802 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id DCB8AC35274 for ; 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s=arc-20220608; d=hostedemail.com; t=1702953773; a=rsa-sha256; cv=none; b=xgXvEmQwENtGZYmRjv9YHB9g00sx07nY8MjYPClrHyg8UaZdfzsR5xjweNNP9DNsykevHA /c+fMCxaaajoiOCgMqWgh00IZYrWgpQUoTVYHG7elq3g0VI1z6gAPKZpeLrrYEG6m5v45I kgU2dfTsxaUEU2j27wQmdfUx1v6KNmI= X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R491e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046049;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0Vyp79GX_1702953768; Received: from localhost(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0Vyp79GX_1702953768) by smtp.aliyun-inc.com; Tue, 19 Dec 2023 10:42:49 +0800 From: Jingbo Xu To: shr@devkernel.io, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, joseph.qi@linux.alibaba.com, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org Subject: [PATCH v2 2/2] mm: fix arithmetic for max_prop_frac when setting max_ratio Date: Tue, 19 Dec 2023 10:42:46 +0800 Message-Id: <20231219024246.65654-3-jefflexu@linux.alibaba.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20231219024246.65654-1-jefflexu@linux.alibaba.com> References: <20231219024246.65654-1-jefflexu@linux.alibaba.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: DE0FB1C001C X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 7c5g4uhe8fnmqjdsiackc1stfdu9u515 X-HE-Tag: 1702953772-409458 X-HE-Meta: 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 Tj84luv3 XMjn0AMkb/txdJGfaqF+tPvc1RHjGZg6p99kXy2fLF0m54m3YDyR7BaIK4jwN5vdx1uZIfXKokQGSCft9SFD+Da3mt0Bqxz9lM19KMWaKveIPK37Mfztng6cGLPoxo2OIxcg+s3vs8KFINRKQSwfSzaKFm2WZXDuvWQ4k X-Bogosity: Ham, tests=bogofilter, spamicity=0.000042, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 --- 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..dda59b368c01 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 = div64_u64(FPROP_FRAC_BASE * max_ratio, + 100 * BDI_RATIO_SCALE); } spin_unlock_bh(&bdi_lock);