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Mon, 16 Dec 2024 09:37:52 +0100 Message-ID: Date: Mon, 16 Dec 2024 19:07:45 +1030 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] btrfs: avoid opencoded 64-bit div/mod operation To: Arnd Bergmann , Chris Mason , Josef Bacik , David Sterba , Anand Jain Cc: Arnd Bergmann , Qu Wenruo , Johannes Thumshirn , Boris Burkov , Naohiro Aota , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org References: <20241216083248.1816638-1-arnd@kernel.org> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCZxF1YAUJEP5a sQAKCRDCPZHzoSX+qF+mB/9gXu9C3BV0omDZBDWevJHxpWpOwQ8DxZEbk9b9LcrQlWdhFhyn xi+l5lRziV9ZGyYXp7N35a9t7GQJndMCFUWYoEa+1NCuxDs6bslfrCaGEGG/+wd6oIPb85xo naxnQ+SQtYLUFbU77WkUPaaIU8hH2BAfn9ZSDX9lIxheQE8ZYGGmo4wYpnN7/hSXALD7+oun tZljjGNT1o+/B8WVZtw/YZuCuHgZeaFdhcV2jsz7+iGb+LsqzHuznrXqbyUQgQT9kn8ZYFNW 7tf+LNxXuwedzRag4fxtR+5GVvJ41Oh/eygp8VqiMAtnFYaSlb9sjia1Mh+m+OBFeuXjgGlG VvQFzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCZxF1gQUJEP5a0gAK CRDCPZHzoSX+qHGpB/kB8A7M7KGL5qzat+jBRoLwB0Y3Zax0QWuANVdZM3eJDlKJKJ4HKzjo B2Pcn4JXL2apSan2uJftaMbNQbwotvabLXkE7cPpnppnBq7iovmBw++/d8zQjLQLWInQ5kNq Vmi36kmq8o5c0f97QVjMryHlmSlEZ2Wwc1kURAe4lsRG2dNeAd4CAqmTw0cMIrR6R/Dpt3ma +8oGXJOmwWuDFKNV4G2XLKcghqrtcRf2zAGNogg3KulCykHHripG3kPKsb7fYVcSQtlt5R6v HZStaZBzw4PcDiaAF3pPDBd+0fIKS6BlpeNRSFG94RYrt84Qw77JWDOAZsyNfEIEE0J6LSR/ In-Reply-To: <20241216083248.1816638-1-arnd@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:7bemtGciY5P/jAHqXkVt/PZ+Bs2Ujc7n2pNW8RISo5qGIkVwrN+ zajiPZzTePtr2FtAQhpAvSL4ILIa+isH85zr9zOUK2itUtl8UiBsG5j91XsXfoFXzVVnOel 0ECIsIKVdZUWNH2I7uuOnLOduOcb7lpK3vNnqBXZmQFEY8TG4WHb3jBPKHmYuwoyJgACtU5 hG7AbXewACfXBk7tGvb6A== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:OhJPsoBUczw=;JUrKA7cTwWqoXTSnOCFv08Gm+W9 f7WO0ThjOom9fV1w22HsqBRJLT/2+NhcKjSZ2gbk/p2kO5jmgTWPyHfNjMv/4iHe+ObqcCsTo lMjTrXb3RK5ocCidCmLQ9Y+fo9/P+T5D0rmK2askasnQ/Scw3Di2i7VaA80GHOKKN8wSwMvSe DR2cnMeI0jV0yvcIvoNEzps5ZpNxF5yGIueS44Q9cOMwnGSuGMz2R3nr3DocGK2OosuU6lFvj mLcc9wjD7dGHSQ99FlW4+8Tg6nYXupQLDX0gpvTqiT82f8kaBoplD7+nJ2gGieYFGbtIqRIyg l6sNeEZQdpqIXFNe+OOoTFFYS0hn8wfOmnW1HsH+67MgVp/qUwReqik78KSNXPqgTJdz8hYEA qCg24YTaSut2ZcAup/CIyu8Fag2fmioR7onYOvFA/OYCVJ9KnWCc6wS9boQFvsTQqfhjk2z3Z sRWAxq0wdYtcB+WBNTnniqFOHwpCzxAQ3mAYW/YC4O1zjDFwrfgFT+afMHTkhVMxrVRiK8AzS Aobrtcq0Pzkb73zVK2FRsUSxstqabJa5zGxMPGjGMddhnlkGonNR6k9XZxXKhQBCSdaPuiC/i /QjXZ+RSWDdlTgppEEu4HE8/IZZIncokil0gUkunbBIV+Y8TZC0IIshJr9SPGj3OFP8kRVcCl qy+8GyMPj9uoRm+NT+/4Gxc8k/3iA3ZWfbb4d4pOH05RkSz9McGET8qjULA3ooB+VSREqFver wcR1h/N1mG6GdW3SBFQxf7LJI0d5P73TyLrjIhF45H1XGDcwMCihmn1wYlHZ56Utp/NvzKrbE nES+/O0Wos4miWXnbNfNr/Uez6L2V+IcB+LFVlsaSw2kIHhSLpfGolqSNnP18HFEt1JFoEydX 6sC2V2ViVNoAhyA3+KctYmi384d1A+NjPPmjewiLzzQnj1o8BRirXbvBLmULhMVo0mJFqc0p2 bOX+MnMKY0hk+Fd9a86Aws9g7cHOdzLwtaF+eaCrHzPITJpl5A8+FvjlNBQuDJNk5oa41ADi0 1xphE4NrzHW7GMyW34zVulhPiQ/TRUlkRWVs/DR/N/V/zDKla/+2nXlb4XJVfBXdFZ4szzaHx dXAOl/HDhXHJaLz3oahWgezETZRsWS =E5=9C=A8 2024/12/16 19:02, Arnd Bergmann =E5=86=99=E9=81=93: > From: Arnd Bergmann > > Dividing 64-bit numbers causes a link failure on 32-bit builds: > > arm-linux-gnueabi-ld: fs/btrfs/sysfs.o: in function `btrfs_read_policy_s= tore': > sysfs.c:(.text+0x3ce0): undefined reference to `__aeabi_ldivmod' > > Use an explicit call to div_u64_rem() here to work around this. It would > be possible to optimize this further, but this is not a performance > critical operation. > > Fixes: 185fa5c7ac5a ("btrfs: introduce RAID1 round-robin read balancing"= ) > Signed-off-by: Arnd Bergmann > --- > fs/btrfs/sysfs.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c > index 50bc4b6cb821..67bc8fa4d6ab 100644 > --- a/fs/btrfs/sysfs.c > +++ b/fs/btrfs/sysfs.c > @@ -1433,7 +1433,9 @@ static ssize_t btrfs_read_policy_store(struct kobj= ect *kobj, > #ifdef CONFIG_BTRFS_EXPERIMENTAL > if (index =3D=3D BTRFS_READ_POLICY_RR) { > if (value !=3D -1) { > - if ((value % fs_devices->fs_info->sectorsize) !=3D 0) { > + u32 rem; > + div_u64_rem(value, fs_devices->fs_info->sectorsize, &rem); The original check is already bad, it's just a IS_ALIGNED(). So a much simpler solution is: + if (!IS_ALIGNED(value, fs_info->sectorsize)) { Thanks, Qu > + if (rem) { > btrfs_err(fs_devices->fs_info, > "read_policy: min_contiguous_read %lld should be multiples of the sect= orsize %u", > value, fs_devices->fs_info->sectorsize);