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=-14.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 95D52C4338F for ; Mon, 16 Aug 2021 13:33:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7EDBD6056B for ; Mon, 16 Aug 2021 13:33:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238529AbhHPNdd (ORCPT ); Mon, 16 Aug 2021 09:33:33 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:8427 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239015AbhHPNVr (ORCPT ); Mon, 16 Aug 2021 09:21:47 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4GpF7W6nfBz87Wk; Mon, 16 Aug 2021 21:17:11 +0800 (CST) Received: from dggema756-chm.china.huawei.com (10.1.198.198) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Mon, 16 Aug 2021 21:21:13 +0800 Received: from [10.174.177.134] (10.174.177.134) by dggema756-chm.china.huawei.com (10.1.198.198) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Mon, 16 Aug 2021 21:21:12 +0800 Subject: Re: [PATCH 5.10.y 01/11] mm: memcontrol: Use helpers to read page's memcg data To: Greg Kroah-Hartman CC: Roman Gushchin , Muchun Song , "Wang Hai" , , , , Andrew Morton , Alexei Starovoitov References: <20210816072147.3481782-1-chenhuang5@huawei.com> <20210816072147.3481782-2-chenhuang5@huawei.com> From: Chen Huang Message-ID: Date: Mon, 16 Aug 2021 21:21:11 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="gbk" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.134] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggema756-chm.china.huawei.com (10.1.198.198) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ÔÚ 2021/8/16 16:34, Greg Kroah-Hartman дµÀ: > On Mon, Aug 16, 2021 at 07:21:37AM +0000, Chen Huang wrote: >> From: Roman Gushchin > > What is the git commit id of this patch in Linus's tree? > >> >> Patch series "mm: allow mapping accounted kernel pages to userspace", v6. >> >> Currently a non-slab kernel page which has been charged to a memory cgroup >> can't be mapped to userspace. The underlying reason is simple: PageKmemcg >> flag is defined as a page type (like buddy, offline, etc), so it takes a >> bit from a page->mapped counter. Pages with a type set can't be mapped to >> userspace. >> >> But in general the kmemcg flag has nothing to do with mapping to >> userspace. It only means that the page has been accounted by the page >> allocator, so it has to be properly uncharged on release. >> >> Some bpf maps are mapping the vmalloc-based memory to userspace, and their >> memory can't be accounted because of this implementation detail. >> >> This patchset removes this limitation by moving the PageKmemcg flag into >> one of the free bits of the page->mem_cgroup pointer. Also it formalizes >> accesses to the page->mem_cgroup and page->obj_cgroups using new helpers, >> adds several checks and removes a couple of obsolete functions. As the >> result the code became more robust with fewer open-coded bit tricks. >> >> This patch (of 4): >> >> Currently there are many open-coded reads of the page->mem_cgroup pointer, >> as well as a couple of read helpers, which are barely used. >> >> It creates an obstacle on a way to reuse some bits of the pointer for >> storing additional bits of information. In fact, we already do this for >> slab pages, where the last bit indicates that a pointer has an attached >> vector of objcg pointers instead of a regular memcg pointer. >> >> This commits uses 2 existing helpers and introduces a new helper to >> converts all read sides to calls of these helpers: >> struct mem_cgroup *page_memcg(struct page *page); >> struct mem_cgroup *page_memcg_rcu(struct page *page); >> struct mem_cgroup *page_memcg_check(struct page *page); >> >> page_memcg_check() is intended to be used in cases when the page can be a >> slab page and have a memcg pointer pointing at objcg vector. It does >> check the lowest bit, and if set, returns NULL. page_memcg() contains a >> VM_BUG_ON_PAGE() check for the page not being a slab page. >> >> To make sure nobody uses a direct access, struct page's >> mem_cgroup/obj_cgroups is converted to unsigned long memcg_data. >> >> Signed-off-by: Roman Gushchin >> Signed-off-by: Andrew Morton >> Signed-off-by: Alexei Starovoitov >> Reviewed-by: Shakeel Butt >> Acked-by: Johannes Weiner >> Acked-by: Michal Hocko >> Link: https://lkml.kernel.org/r/20201027001657.3398190-1-guro@fb.com >> Link: https://lkml.kernel.org/r/20201027001657.3398190-2-guro@fb.com >> Link: https://lore.kernel.org/bpf/20201201215900.3569844-2-guro@fb.com >> >> Conflicts: >> mm/memcontrol.c > > The "Conflicts:" lines should be removed. > > Please fix up the patch series and resubmit. But note, this seems > really intrusive, are you sure these are all needed? > OK£¬I will resend the patchset. Roman Gushchin's patchset formalize accesses to the page->mem_cgroup and page->obj_cgroups. But for LRU pages and most other raw memcg, they may pin to a memcg cgroup pointer, which should always point to an object cgroup pointer. That's the problem I met. And Muchun Song's patchset fix this. So I think these are all needed. > What UIO driver are you using that is showing problems like this? > The UIO driver is my own driver, and it's creation likes this: First, we register a device pdev = platform_device_register_simple("uio_driver,0, NULL, 0); and use uio_info to describe the UIO driver, the page is alloced and used for uio_vma_fault info->mem[0].addr = (phys_addr_t) kzalloc(PAGE_SIZE, GFP_ATOMIC); then we register the UIO driver. uio_register_device(&pdev->dev, info) Thanks! > thanks, > > greg k-h > > . >