From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 345F5C4338F for ; Fri, 6 Aug 2021 19:39:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0A53961167 for ; Fri, 6 Aug 2021 19:39:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232347AbhHFTjy convert rfc822-to-8bit (ORCPT ); Fri, 6 Aug 2021 15:39:54 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:7803 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229748AbhHFTjx (ORCPT ); Fri, 6 Aug 2021 15:39:53 -0400 Received: from dggemv711-chm.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4GhG5B0hd9zYlFQ; Sat, 7 Aug 2021 03:39:26 +0800 (CST) Received: from dggpemm000001.china.huawei.com (7.185.36.245) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Sat, 7 Aug 2021 03:39:35 +0800 Received: from dggemi761-chm.china.huawei.com (10.1.198.147) by dggpemm000001.china.huawei.com (7.185.36.245) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Sat, 7 Aug 2021 03:39:34 +0800 Received: from dggemi761-chm.china.huawei.com ([10.9.49.202]) by dggemi761-chm.china.huawei.com ([10.9.49.202]) with mapi id 15.01.2176.012; Sat, 7 Aug 2021 03:39:34 +0800 From: "Song Bao Hua (Barry Song)" To: Greg KH CC: "andriy.shevchenko@linux.intel.com" , "yury.norov@gmail.com" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "dave.hansen@intel.com" , "linux@rasmusvillemoes.dk" , "rafael@kernel.org" , "rdunlap@infradead.org" , "agordeev@linux.ibm.com" , "sbrivio@redhat.com" , "jianpeng.ma@intel.com" , "valentin.schneider@arm.com" , "peterz@infradead.org" , "bristot@redhat.com" , "guodong.xu@linaro.org" , tangchengchang , "Zengtao (B)" , yangyicong , "tim.c.chen@linux.intel.com" , Linuxarm , "tiantao (H)" , "Jonathan Cameron" Subject: RE: [PATCH v9 1/5] cpumask: introduce cpumap_print_list/bitmask_to_buf to support large bitmask and list Thread-Topic: [PATCH v9 1/5] cpumask: introduce cpumap_print_list/bitmask_to_buf to support large bitmask and list Thread-Index: AQHXirK6LfP8uGs3C0uIGivdv2MjYqtl8KiAgADt/kA= Date: Fri, 6 Aug 2021 19:39:34 +0000 Message-ID: References: <20210806110251.560-1-song.bao.hua@hisilicon.com> <20210806110251.560-2-song.bao.hua@hisilicon.com> In-Reply-To: Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.126.202.213] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: Greg KH [mailto:gregkh@linuxfoundation.org] > Sent: Saturday, August 7, 2021 1:22 AM > To: Song Bao Hua (Barry Song) > Cc: andriy.shevchenko@linux.intel.com; yury.norov@gmail.com; > linux-kernel@vger.kernel.org; akpm@linux-foundation.org; > dave.hansen@intel.com; linux@rasmusvillemoes.dk; rafael@kernel.org; > rdunlap@infradead.org; agordeev@linux.ibm.com; sbrivio@redhat.com; > jianpeng.ma@intel.com; valentin.schneider@arm.com; peterz@infradead.org; > bristot@redhat.com; guodong.xu@linaro.org; tangchengchang > ; Zengtao (B) ; > yangyicong ; tim.c.chen@linux.intel.com; Linuxarm > ; tiantao (H) ; Jonathan Cameron > > Subject: Re: [PATCH v9 1/5] cpumask: introduce > cpumap_print_list/bitmask_to_buf to support large bitmask and list > > On Fri, Aug 06, 2021 at 11:02:47PM +1200, Barry Song wrote: > > From: Tian Tao > > > > The existing cpumap_print_to_pagebuf() is used by cpu topology and other > > drivers to export hexadecimal bitmask and decimal list to userspace by > > sysfs ABI. > > > > Right now, those drivers are using a normal attribute for this kind of > > ABIs. A normal attribute typically has show entry as below: > > > > static ssize_t example_dev_show(struct device *dev, > > struct device_attribute *attr, char *buf) > > { > > ... > > return cpumap_print_to_pagebuf(true, buf, &pmu_mmdc->cpu); > > } > > show entry of attribute has no offset and count parameters and this > > means the file is limited to one page only. > > > > cpumap_print_to_pagebuf() API works terribly well for this kind of > > normal attribute with buf parameter and without offset, count: > > > > static inline ssize_t > > cpumap_print_to_pagebuf(bool list, char *buf, const struct cpumask *mask) > > { > > return bitmap_print_to_pagebuf(list, buf, cpumask_bits(mask), > > nr_cpu_ids); > > } > > > > The problem is once we have many cpus, we have a chance to make bitmask > > or list more than one page. Especially for list, it could be as complex > > as 0,3,5,7,9,...... We have no simple way to know it exact size. > > > > It turns out bin_attribute is a way to break this limit. bin_attribute > > has show entry as below: > > static ssize_t > > example_bin_attribute_show(struct file *filp, struct kobject *kobj, > > struct bin_attribute *attr, char *buf, > > loff_t offset, size_t count) > > { > > ... > > } > > > > With the new offset and count parameters, this makes sysfs ABI be able > > to support file size more than one page. For example, offset could be > > >= 4096. > > > > This patch introduces cpumap_print_bitmask/list_to_buf() and their bitmap > > infrastructure bitmap_print_bitmask/list_to_buf() so that those drivers > > can move to bin_attribute to support large bitmask and list. At the same > > time, we have to pass those corresponding parameters such as offset, count > > from bin_attribute to this new API. > > > > Signed-off-by: Tian Tao > > Cc: Andrew Morton > > Cc: Andy Shevchenko > > Cc: Randy Dunlap > > Cc: Stefano Brivio > > Cc: Alexander Gordeev > > Cc: "Ma, Jianpeng" > > Cc: Yury Norov > > Cc: Valentin Schneider > > Cc: Peter Zijlstra > > Cc: Daniel Bristot de Oliveira > > Reviewed-by: Jonathan Cameron > > Signed-off-by: Barry Song > > --- > > include/linux/bitmap.h | 6 +++ > > include/linux/cpumask.h | 38 +++++++++++++++ > > lib/bitmap.c | 103 ++++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 147 insertions(+) > > > > diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h > > index a36cfcec4e77..37f36dad18bd 100644 > > --- a/include/linux/bitmap.h > > +++ b/include/linux/bitmap.h > > @@ -227,6 +227,12 @@ unsigned int bitmap_ord_to_pos(const unsigned long > *bitmap, unsigned int ord, un > > int bitmap_print_to_pagebuf(bool list, char *buf, > > const unsigned long *maskp, int nmaskbits); > > > > +extern int bitmap_print_bitmask_to_buf(char *buf, const unsigned long > *maskp, > > + int nmaskbits, loff_t off, size_t count); > > + > > +extern int bitmap_print_list_to_buf(char *buf, const unsigned long *maskp, > > + int nmaskbits, loff_t off, size_t count); > > + > > Why are you adding bitmap_print_list_to_buf() when no one uses it in > this patch series? > > Did I miss it somewhere? Yes. It is used in every patch except the last one from Yury which is only extending comment. drivers/base/topology.c: +static ssize_t name##_list_read(struct file *file, struct kobject *kobj, \ + struct bin_attribute *attr, char *buf, \ + loff_t off, size_t count) \ +{ \ + struct device *dev = kobj_to_dev(kobj); \ + \ + return cpumap_print_list_to_buf(buf, topology_##mask(dev->id), \ + off, count); \ } drivers/base/node.c: +static inline ssize_t cpulist_read(struct file *file, struct kobject *kobj, + struct bin_attribute *attr, char *buf, + loff_t off, size_t count) { - ... + cpumask_and(mask, cpumask_of_node(node_dev->dev.id), cpu_online_mask); + n = cpumap_print_list_to_buf(buf, mask, off, count); + free_cpumask_var(mask); > > thanks, > > greg k-h Thanks Barry