From patchwork Sun May 8 09:36:40 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Baolin Wang X-Patchwork-Id: 12842297 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B3E68C433F5 for ; Sun, 8 May 2022 09:38:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:List-Subscribe:List-Help: List-Post:List-Archive:List-Unsubscribe:List-Id:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=nFKwTSXAkmwqcxrtu+Y8QPPqe3Gj31dIdFdm5vd6OLw=; b=gwNoxnQm2pSajq GpJFqbINDCqoKfhCqIsY6HwOKEAk4TZhhpTGH+eZGcjL4AVh60PwUGo6k49LkO768rLiUGQfUexAy ttZqcP8GluURHVJ/eap6IGWxSU7uQSGevlckctLTPJ91v1bA0tkX4SRxWWzjcBqfxuvbAbI9GOZQJ Cp6bjx4p2yeVQxSz1BJHhVK3i0uGfZPUxi5sSC7OcW1DVF3DOgexRRBVEWXA/EPXXHY5Kq/088/a2 hBLEEtnDYMFR2fAUI0V7ke9eeBt3TFu1lOgjI7KbaG9LOgMbEgpmei16GRSLh9RaT+u3nhkMxOZSY 8TOhHaYTYLpeW8/k38bA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nndLq-009fGS-Om; Sun, 08 May 2022 09:37:18 +0000 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nndLY-009f90-Ec for linux-arm-kernel@lists.infradead.org; Sun, 08 May 2022 09:37:02 +0000 X-Alimail-AntiSpam: AC=PASS; BC=-1|-1; BR=01201311R151e4; CH=green; DM=||false|; DS=||; FP=0|-1|-1|-1|0|-1|-1|-1; HT=e01e04394; MF=baolin.wang@linux.alibaba.com; NM=1; PH=DS; RN=31; SR=0; TI=SMTPD_---0VCZu2JX_1652002614; Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VCZu2JX_1652002614) by smtp.aliyun-inc.com(127.0.0.1); Sun, 08 May 2022 17:36:55 +0800 From: Baolin Wang To: akpm@linux-foundation.org, mike.kravetz@oracle.com, catalin.marinas@arm.com, will@kernel.org Cc: tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, arnd@arndb.de, baolin.wang@linux.alibaba.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 2/3] mm: rmap: Fix CONT-PTE/PMD size hugetlb issue when migration Date: Sun, 8 May 2022 17:36:40 +0800 Message-Id: <1ec8a987be1a5400e077260a300d0079564b1472.1652002221.git.baolin.wang@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: References: In-Reply-To: References: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220508_023700_697067_ECF3F321 X-CRM114-Status: GOOD ( 16.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On some architectures (like ARM64), it can support CONT-PTE/PMD size hugetlb, which means it can support not only PMD/PUD size hugetlb: 2M and 1G, but also CONT-PTE/PMD size: 64K and 32M if a 4K page size specified. When migrating a hugetlb page, we will get the relevant page table entry by huge_pte_offset() only once to nuke it and remap it with a migration pte entry. This is correct for PMD or PUD size hugetlb, since they always contain only one pmd entry or pud entry in the page table. However this is incorrect for CONT-PTE and CONT-PMD size hugetlb, since they can contain several continuous pte or pmd entry with same page table attributes. So we will nuke or remap only one pte or pmd entry for this CONT-PTE/PMD size hugetlb page, which is not expected for hugetlb migration. The problem is we can still continue to modify the subpages' data of a hugetlb page during migrating a hugetlb page, which can cause a serious data consistent issue, since we did not nuke the page table entry and set a migration pte for the subpages of a hugetlb page. To fix this issue, we should change to use huge_ptep_clear_flush() to nuke a hugetlb page table, and remap it with set_huge_pte_at() and set_huge_swap_pte_at() when migrating a hugetlb page, which already considered the CONT-PTE or CONT-PMD size hugetlb. Signed-off-by: Baolin Wang Reported-by: kernel test robot Reported-by: kernel test robot Reviewed-by: Muchun Song Reviewed-by: Mike Kravetz --- mm/rmap.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 6fdd198..7cf2408 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1924,13 +1924,15 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, break; } } + + /* Nuke the hugetlb page table entry */ + pteval = huge_ptep_clear_flush(vma, address, pvmw.pte); } else { flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); + /* Nuke the page table entry. */ + pteval = ptep_clear_flush(vma, address, pvmw.pte); } - /* Nuke the page table entry. */ - pteval = ptep_clear_flush(vma, address, pvmw.pte); - /* Set the dirty flag on the folio now the pte is gone. */ if (pte_dirty(pteval)) folio_mark_dirty(folio); @@ -2015,7 +2017,10 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, pte_t swp_pte; if (arch_unmap_one(mm, vma, address, pteval) < 0) { - set_pte_at(mm, address, pvmw.pte, pteval); + if (folio_test_hugetlb(folio)) + set_huge_pte_at(mm, address, pvmw.pte, pteval); + else + set_pte_at(mm, address, pvmw.pte, pteval); ret = false; page_vma_mapped_walk_done(&pvmw); break; @@ -2024,7 +2029,10 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, !anon_exclusive, subpage); if (anon_exclusive && page_try_share_anon_rmap(subpage)) { - set_pte_at(mm, address, pvmw.pte, pteval); + if (folio_test_hugetlb(folio)) + set_huge_pte_at(mm, address, pvmw.pte, pteval); + else + set_pte_at(mm, address, pvmw.pte, pteval); ret = false; page_vma_mapped_walk_done(&pvmw); break; @@ -2050,7 +2058,11 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, swp_pte = pte_swp_mksoft_dirty(swp_pte); if (pte_uffd_wp(pteval)) swp_pte = pte_swp_mkuffd_wp(swp_pte); - set_pte_at(mm, address, pvmw.pte, swp_pte); + if (folio_test_hugetlb(folio)) + set_huge_swap_pte_at(mm, address, pvmw.pte, + swp_pte, vma_mmu_pagesize(vma)); + else + set_pte_at(mm, address, pvmw.pte, swp_pte); trace_set_migration_pte(address, pte_val(swp_pte), compound_order(&folio->page)); /*