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=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, 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 BD695C4338F for ; Mon, 16 Aug 2021 13:35:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 660C460F46 for ; Mon, 16 Aug 2021 13:35:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 660C460F46 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 0A26A6B0072; Mon, 16 Aug 2021 09:35:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 029FC6B0073; Mon, 16 Aug 2021 09:35:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E34576B0074; Mon, 16 Aug 2021 09:35:26 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0122.hostedemail.com [216.40.44.122]) by kanga.kvack.org (Postfix) with ESMTP id C79386B0072 for ; Mon, 16 Aug 2021 09:35:26 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 621EC21230 for ; Mon, 16 Aug 2021 13:35:26 +0000 (UTC) X-FDA: 78481040652.01.7A35CF5 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf12.hostedemail.com (Postfix) with ESMTP id E1E901004145 for ; Mon, 16 Aug 2021 13:35:25 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 9F70D60E90; Mon, 16 Aug 2021 13:35:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1629120925; bh=V2djZ0s5eeYtPknbm6mCjf0Kvlgls1rw9uu907bgUCs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fGJUSESwqddkOhbxJBKFSBoQkKCT63dyH7dKHeiKg2jInhttWHaz787y2iKM/ZITx eyfEHk59i49OYPoU5+TuSPZlQBYcZXK/HlzRjhQuWECbXIOHEhqZ/DGtVpdSU75GQy PrfpV+r9wqXD1kG6v0Dz90X4heFDYvKfjrM6JVnQ= Date: Mon, 16 Aug 2021 15:35:22 +0200 From: Greg Kroah-Hartman To: Chen Huang Cc: Roman Gushchin , Muchun Song , Wang Hai , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, Andrew Morton , Alexei Starovoitov Subject: Re: [PATCH 5.10.y 01/11] mm: memcontrol: Use helpers to read page's memcg data Message-ID: References: <20210816072147.3481782-1-chenhuang5@huawei.com> <20210816072147.3481782-2-chenhuang5@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=linuxfoundation.org header.s=korg header.b=fGJUSESw; spf=pass (imf12.hostedemail.com: domain of gregkh@linuxfoundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org; dmarc=pass (policy=none) header.from=linuxfoundation.org X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: E1E901004145 X-Stat-Signature: dimbcushttrxd6sj1ryajai5bbeoicn5 X-HE-Tag: 1629120925-615628 Content-Transfer-Encoding: quoted-printable 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: On Mon, Aug 16, 2021 at 09:21:11PM +0800, Chen Huang wrote: >=20 >=20 > =E5=9C=A8 2021/8/16 16:34, Greg Kroah-Hartman =E5=86=99=E9=81=93: > > On Mon, Aug 16, 2021 at 07:21:37AM +0000, Chen Huang wrote: > >> From: Roman Gushchin > >=20 > > What is the git commit id of this patch in Linus's tree? > >=20 > >> > >> 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: Page= Kmemcg > >> flag is defined as a page type (like buddy, offline, etc), so it tak= es a > >> bit from a page->mapped counter. Pages with a type set can't be map= ped 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 pa= ge > >> 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 forma= lizes > >> accesses to the page->mem_cgroup and page->obj_cgroups using new hel= pers, > >> 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 po= inter, > >> 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 fo= r > >> storing additional bits of information. In fact, we already do this= for > >> slab pages, where the last bit indicates that a pointer has an attac= hed > >> 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 doe= s > >> check the lowest bit, and if set, returns NULL. page_memcg() contai= ns 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.c= om > >> > >> Conflicts: > >> mm/memcontrol.c > >=20 > > The "Conflicts:" lines should be removed. > >=20 > > Please fix up the patch series and resubmit. But note, this seems > > really intrusive, are you sure these are all needed? > >=20 >=20 > OK=EF=BC=8CI will resend the patchset. > Roman Gushchin's patchset formalize accesses to the page->mem_cgroup an= d > 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 c= group > pointer. That's the problem I met. And Muchun Song's patchset fix this. > So I think these are all needed. What in-tree driver causes this to happen and under what workload? > > What UIO driver are you using that is showing problems like this? > >=20 >=20 > The UIO driver is my own driver, and it's creation likes this: > First, we register a device > pdev =3D platform_device_register_simple("uio_driver,0, NULL, 0); > and use uio_info to describe the UIO driver, the page is alloced and us= ed > for uio_vma_fault > info->mem[0].addr =3D (phys_addr_t) kzalloc(PAGE_SIZE, GFP_ATOMIC); That is not a physical address, and is not what the uio api is for at all. Please do not abuse it that way. > then we register the UIO driver. > uio_register_device(&pdev->dev, info) So no in-tree drivers are having problems with the existing code, only fake ones? thanks, greg k-h