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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 8EAF5C2D0DB for ; Thu, 30 Jan 2020 21:57:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 614C720708 for ; Thu, 30 Jan 2020 21:57:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726225AbgA3V5Q (ORCPT ); Thu, 30 Jan 2020 16:57:16 -0500 Received: from mga18.intel.com ([134.134.136.126]:18902 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725835AbgA3V5Q (ORCPT ); Thu, 30 Jan 2020 16:57:16 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Jan 2020 13:57:15 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,382,1574150400"; d="scan'208";a="233109286" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by orsmga006.jf.intel.com with ESMTP; 30 Jan 2020 13:57:12 -0800 Date: Fri, 31 Jan 2020 05:57:27 +0800 From: Wei Yang To: Russell King - ARM Linux admin Cc: Wei Yang , Dmitry Osipenko , akpm@linux-foundation.org, dan.j.williams@intel.com, aneesh.kumar@linux.ibm.com, kirill@shutemov.name, yang.shi@linux.alibaba.com, thellstrom@vmware.com, Thierry Reding , Jon Hunter , linux-kernel@vger.kernel.org, linux-mm@kvack.org, "linux-tegra@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH 3/5] mm/mremap: use pmd_addr_end to calculate next in move_page_tables() Message-ID: <20200130215727.GA11373@richard> Reply-To: Wei Yang References: <20200117232254.2792-1-richardw.yang@linux.intel.com> <20200117232254.2792-4-richardw.yang@linux.intel.com> <7147774a-14e9-4ff3-1548-4565f0d214d5@gmail.com> <20200129094738.GE25745@shell.armlinux.org.uk> <20200129215745.GA20736@richard> <20200129232441.GI25745@shell.armlinux.org.uk> <20200130013000.GA5137@richard> <20200130141505.GK25745@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200130141505.GK25745@shell.armlinux.org.uk> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 30, 2020 at 02:15:05PM +0000, Russell King - ARM Linux admin wrote: >On Thu, Jan 30, 2020 at 09:30:00AM +0800, Wei Yang wrote: >> On Wed, Jan 29, 2020 at 11:24:41PM +0000, Russell King - ARM Linux admin wrote: >> >On Thu, Jan 30, 2020 at 05:57:45AM +0800, Wei Yang wrote: >> >> On Wed, Jan 29, 2020 at 09:47:38AM +0000, Russell King - ARM Linux admin wrote: >> >> >On Sun, Jan 26, 2020 at 05:47:57PM +0300, Dmitry Osipenko wrote: >> >> >> 18.01.2020 02:22, Wei Yang пишет: >> >> >> > Use the general helper instead of do it by hand. >> >> >> > >> >> >> > Signed-off-by: Wei Yang >> >> >> > --- >> >> >> > mm/mremap.c | 7 ++----- >> >> >> > 1 file changed, 2 insertions(+), 5 deletions(-) >> >> >> > >> >> >> > diff --git a/mm/mremap.c b/mm/mremap.c >> >> >> > index c2af8ba4ba43..a258914f3ee1 100644 >> >> >> > --- a/mm/mremap.c >> >> >> > +++ b/mm/mremap.c >> >> >> > @@ -253,11 +253,8 @@ unsigned long move_page_tables(struct vm_area_struct *vma, >> >> >> > >> >> >> > for (; old_addr < old_end; old_addr += extent, new_addr += extent) { >> >> >> > cond_resched(); >> >> >> > - next = (old_addr + PMD_SIZE) & PMD_MASK; >> >> >> > - /* even if next overflowed, extent below will be ok */ >> >> >> > + next = pmd_addr_end(old_addr, old_end); >> >> >> > extent = next - old_addr; >> >> >> > - if (extent > old_end - old_addr) >> >> >> > - extent = old_end - old_addr; >> >> >> > old_pmd = get_old_pmd(vma->vm_mm, old_addr); >> >> >> > if (!old_pmd) >> >> >> > continue; >> >> >> > @@ -301,7 +298,7 @@ unsigned long move_page_tables(struct vm_area_struct *vma, >> >> >> > >> >> >> > if (pte_alloc(new_vma->vm_mm, new_pmd)) >> >> >> > break; >> >> >> > - next = (new_addr + PMD_SIZE) & PMD_MASK; >> >> >> > + next = pmd_addr_end(new_addr, new_addr + len); >> >> >> > if (extent > next - new_addr) >> >> >> > extent = next - new_addr; >> >> >> > move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma, >> >> >> > >> >> >> >> >> >> Hello Wei, >> >> >> >> >> >> Starting with next-20200122, I'm seeing the following in KMSG on NVIDIA >> >> >> Tegra (ARM32): >> >> >> >> >> >> BUG: Bad rss-counter state mm:(ptrval) type:MM_ANONPAGES val:190 >> >> >> >> >> >> and eventually kernel hangs. >> >> >> >> >> >> Git's bisection points to this patch and reverting it helps. Please fix, >> >> >> thanks in advance. >> >> > >> >> >The above is definitely wrong - pXX_addr_end() are designed to be used >> >> >with an address index within the pXX table table and the address index >> >> >of either the last entry in the same pXX table or the beginning of the >> >> >_next_ pXX table. Arbitary end address indicies are not allowed. >> >> > >> >> >> >> #define pmd_addr_end(addr, end) \ >> >> ({ unsigned long __boundary = ((addr) + PMD_SIZE) & PMD_MASK; \ >> >> (__boundary - 1 < (end) - 1)? __boundary: (end); \ >> >> }) >> >> >> >> If my understanding is correct, the definition here align the addr to next PMD >> >> boundary or end. >> >> >> >> I don't see the possibility to across another PMD. Do I miss something? >> > >> >Look at the definition of p*_addr_end() that are used when page tables >> >are rolled up. >> > >> >> Sorry, I don't get your point. >> >> What's the meaning of "roll up" here? >> >> Would you mind giving me an example? I see pmd_addr_end() is not used in many >> places in core kernel. By glancing those usages, all the places use it like >> pmd_addr_end(addr, end). Seems no specially handing on the end address. >> >> Or you mean the case when pmd_addr_end() is defined to return "end" directly? > >Not all hardware has five levels of page tables. When hardware does not >have five levels, it is common to "roll up" some of the page tables into >others. > >There are generic ways to implement this, which include using: > >include/asm-generic/pgtable-nop4d.h >include/asm-generic/pgtable-nopud.h >include/asm-generic/pgtable-nopmd.h > >and then there's architecture ways to implement this. 32-bit ARM takes >its implementation for PMD not from the generic version, which >post-dates 32-bit ARM, but from how page table roll-up was implemented >back at the time when the current ARM scheme was devised. The generic >scheme is unsuitable for 32-bit ARM since we do more than just roll-up >page tables, but this is irrelevent for this discussion. > >All three of the generic implementations, and 32-bit ARM, define the >pXX_addr_end() macros thusly: > >include/asm-generic/pgtable-nop4d.h:#define p4d_addr_end(addr, end) (end) >include/asm-generic/pgtable-nopmd.h:#define pmd_addr_end(addr, end) (end) >include/asm-generic/pgtable-nopud.h:#define pud_addr_end(addr, end) (end) >arch/arm/include/asm/pgtable-2level.h:#define pmd_addr_end(addr,end) (end) > >since, as I stated, pXX_addr_end() expects its "end" argument to be >the address index of the next entry in the immediately upper page >table level, or the address index of the last entry we wish to >process, which ever is smaller. > >If it's larger than the address index of the next entry in the >immediately upper page table level, then the effect of all these >macros will be to walk off the end of the current level of page >table. > >To see how they _should_ be used, see the loops in free_pgd_range() >and the free_pXX_range() functions called from there and below. > >In all cases when the pXX_addr_end() macro was introduced, what I state >above holds true - and I believe still holds true today, until this >patch that has reportedly caused issues. > Thanks for your patience in explaining this for me. I got your point. This is my fault in understanding the code. >-- >RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ >FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up >According to speedtest.net: 11.9Mbps down 500kbps up -- Wei Yang Help you, Help me