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([2601:647:4000:d7:9d55:11e:7174:3ec6]) by smtp.gmail.com with ESMTPSA id g7sm349470pjs.48.2020.05.29.15.27.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 29 May 2020 15:27:33 -0700 (PDT) Subject: Re: [PATCH v2] blkdev: Replace blksize_bits() with ilog2() To: Matthew Wilcox , Kaitao Cheng Cc: axboe@kernel.dk, hch@lst.de, sth@linux.ibm.com, viro@zeniv.linux.org.uk, clm@fb.com, jaegeuk@kernel.org, hch@infradead.org, mark@fasheh.com, dhowells@redhat.com, balbi@kernel.org, damien.lemoal@wdc.com, ming.lei@redhat.com, martin.petersen@oracle.com, satyat@google.com, chaitanya.kulkarni@wdc.com, houtao1@huawei.com, asml.silence@gmail.com, ajay.joshi@wdc.com, linux-kernel@vger.kernel.org, songmuchun@bytedance.com, hoeppner@linux.ibm.com, heiko.carstens@de.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com, linux-s390@vger.kernel.org, sagi@grimberg.me, linux-nvme@lists.infradead.org, gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, josef@toxicpanda.com, dsterba@suse.com, linux-btrfs@vger.kernel.org, chao@kernel.org, linux-f2fs-devel@lists.sourceforge.net, darrick.wong@oracle.com, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, jlbec@evilplan.org, joseph.qi@linux.alibaba.com, ocfs2-devel@oss.oracle.com, deepa.kernel@gmail.com References: <20200529141100.37519-1-pilgrimtao@gmail.com> <20200529202713.GC19604@bombadil.infradead.org> From: Bart Van Assche Autocrypt: addr=bvanassche@acm.org; prefer-encrypt=mutual; keydata= mQENBFSOu4oBCADcRWxVUvkkvRmmwTwIjIJvZOu6wNm+dz5AF4z0FHW2KNZL3oheO3P8UZWr LQOrCfRcK8e/sIs2Y2D3Lg/SL7qqbMehGEYcJptu6mKkywBfoYbtBkVoJ/jQsi2H0vBiiCOy fmxMHIPcYxaJdXxrOG2UO4B60Y/BzE6OrPDT44w4cZA9DH5xialliWU447Bts8TJNa3lZKS1 AvW1ZklbvJfAJJAwzDih35LxU2fcWbmhPa7EO2DCv/LM1B10GBB/oQB5kvlq4aA2PSIWkqz4 3SI5kCPSsygD6wKnbRsvNn2mIACva6VHdm62A7xel5dJRfpQjXj2snd1F/YNoNc66UUTABEB AAG0JEJhcnQgVmFuIEFzc2NoZSA8YnZhbmFzc2NoZUBhY20ub3JnPokBOQQTAQIAIwUCVI67 igIbAwcLCQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEHFcPTXFzhAJ8QkH/1AdXblKL65M Y1Zk1bYKnkAb4a98LxCPm/pJBilvci6boefwlBDZ2NZuuYWYgyrehMB5H+q+Kq4P0IBbTqTa jTPAANn62A6jwJ0FnCn6YaM9TZQjM1F7LoDX3v+oAkaoXuq0dQ4hnxQNu792bi6QyVdZUvKc macVFVgfK9n04mL7RzjO3f+X4midKt/s+G+IPr4DGlrq+WH27eDbpUR3aYRk8EgbgGKvQFdD CEBFJi+5ZKOArmJVBSk21RHDpqyz6Vit3rjep7c1SN8s7NhVi9cjkKmMDM7KYhXkWc10lKx2 RTkFI30rkDm4U+JpdAd2+tP3tjGf9AyGGinpzE2XY1K5AQ0EVI67igEIAKiSyd0nECrgz+H5 PcFDGYQpGDMTl8MOPCKw/F3diXPuj2eql4xSbAdbUCJzk2ETif5s3twT2ER8cUTEVOaCEUY3 eOiaFgQ+nGLx4BXqqGewikPJCe+UBjFnH1m2/IFn4T9jPZkV8xlkKmDUqMK5EV9n3eQLkn5g lco+FepTtmbkSCCjd91EfThVbNYpVQ5ZjdBCXN66CKyJDMJ85HVr5rmXG/nqriTh6cv1l1Js T7AFvvPjUPknS6d+BETMhTkbGzoyS+sywEsQAgA+BMCxBH4LvUmHYhpS+W6CiZ3ZMxjO8Hgc ++w1mLeRUvda3i4/U8wDT3SWuHcB3DWlcppECLkAEQEAAYkBHwQYAQIACQUCVI67igIbDAAK CRBxXD01xc4QCZ4dB/0QrnEasxjM0PGeXK5hcZMT9Eo998alUfn5XU0RQDYdwp6/kMEXMdmT oH0F0xB3SQ8WVSXA9rrc4EBvZruWQ+5/zjVrhhfUAx12CzL4oQ9Ro2k45daYaonKTANYG22y //x8dLe2Fv1By4SKGhmzwH87uXxbTJAUxiWIi1np0z3/RDnoVyfmfbbL1DY7zf2hYXLLzsJR mSsED/1nlJ9Oq5fALdNEPgDyPUerqHxcmIub+pF0AzJoYHK5punqpqfGmqPbjxrJLPJfHVKy goMj5DlBMoYqEgpbwdUYkH6QdizJJCur4icy8GUNbisFYABeoJ91pnD4IGei3MTdvINSZI5e Message-ID: Date: Fri, 29 May 2020 15:27:30 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200529202713.GC19604@bombadil.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-05-29 13:27, Matthew Wilcox wrote: > On Fri, May 29, 2020 at 10:11:00PM +0800, Kaitao Cheng wrote: >> There is a function named ilog2() exist which can replace blksize. >> The generated code will be shorter and more efficient on some >> architecture, such as arm64. And ilog2() can be optimized according >> to different architecture. > > We'd get the same benefit from a smaller patch with just: > > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -1502,15 +1502,9 @@ static inline int blk_rq_aligned(struct request_queue *q, unsigned long addr, > return !(addr & alignment) && !(len & alignment); > } > > -/* assumes size > 256 */ > static inline unsigned int blksize_bits(unsigned int size) > { > - unsigned int bits = 8; > - do { > - bits++; > - size >>= 1; > - } while (size > 256); > - return bits; > + return ilog2(size); > } > > static inline unsigned int block_size(struct block_device *bdev) Hi Matthew, I had suggested to change all blksize_bits() calls into ilog2() calls because I think that a single function to calculate the logarithm base 2 is sufficient. Thanks, Bart.