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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C6E8C433EF for ; Wed, 4 May 2022 02:48:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343551AbiEDCwV (ORCPT ); Tue, 3 May 2022 22:52:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231154AbiEDCwT (ORCPT ); Tue, 3 May 2022 22:52:19 -0400 Received: from out30-44.freemail.mail.aliyun.com (out30-44.freemail.mail.aliyun.com [115.124.30.44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6D78820BFB for ; Tue, 3 May 2022 19:48:43 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R511e4;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=6;SR=0;TI=SMTPD_---0VCA2Nsv_1651632519; Received: from 30.32.81.226(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VCA2Nsv_1651632519) by smtp.aliyun-inc.com(127.0.0.1); Wed, 04 May 2022 10:48:40 +0800 Message-ID: Date: Wed, 4 May 2022 10:49:23 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH v2 3/3] mm: rmap: Use flush_cache_range() to flush cache for hugetlb pages To: Mike Kravetz , akpm@linux-foundation.org Cc: almasrymina@google.com, songmuchun@bytedance.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <0b986dc4-5843-3e2d-c2df-5a2e9f13e6ab@oracle.com> From: Baolin Wang In-Reply-To: <0b986dc4-5843-3e2d-c2df-5a2e9f13e6ab@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/4/2022 4:17 AM, Mike Kravetz wrote: > On 4/27/22 03:52, Baolin Wang wrote: >> Now we will use flush_cache_page() to flush cache for anonymous hugetlb >> pages when unmapping or migrating a hugetlb page mapping, but the >> flush_cache_page() only handles a PAGE_SIZE range on some architectures >> (like arm32, arc and so on), which will cause potential cache issues. >> Thus change to use flush_cache_range() to cover the whole size of a >> hugetlb page. >> >> Signed-off-by: Baolin Wang >> --- >> mm/rmap.c | 90 ++++++++++++++++++++++++++++++++++----------------------------- >> 1 file changed, 48 insertions(+), 42 deletions(-) >> >> diff --git a/mm/rmap.c b/mm/rmap.c >> index 4f0d115..6fdd198 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -1528,13 +1528,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, >> anon_exclusive = folio_test_anon(folio) && >> PageAnonExclusive(subpage); >> >> - if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) { >> - /* >> - * To call huge_pmd_unshare, i_mmap_rwsem must be >> - * held in write mode. Caller needs to explicitly >> - * do this outside rmap routines. >> - */ >> - VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); >> + if (folio_test_hugetlb(folio)) { >> /* >> * huge_pmd_unshare may unmap an entire PMD page. >> * There is no way of knowing exactly which PMDs may >> @@ -1544,22 +1538,31 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, >> */ >> flush_cache_range(vma, range.start, range.end); >> >> - if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) { >> - flush_tlb_range(vma, range.start, range.end); >> - mmu_notifier_invalidate_range(mm, range.start, >> - range.end); >> - >> + if (!folio_test_anon(folio)) { >> /* >> - * The ref count of the PMD page was dropped >> - * which is part of the way map counting >> - * is done for shared PMDs. Return 'true' >> - * here. When there is no other sharing, >> - * huge_pmd_unshare returns false and we will >> - * unmap the actual page and drop map count >> - * to zero. >> + * To call huge_pmd_unshare, i_mmap_rwsem must be >> + * held in write mode. Caller needs to explicitly >> + * do this outside rmap routines. >> */ >> - page_vma_mapped_walk_done(&pvmw); >> - break; >> + VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); >> + >> + if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) { >> + flush_tlb_range(vma, range.start, range.end); >> + mmu_notifier_invalidate_range(mm, range.start, >> + range.end); >> + >> + /* >> + * The ref count of the PMD page was dropped >> + * which is part of the way map counting >> + * is done for shared PMDs. Return 'true' >> + * here. When there is no other sharing, >> + * huge_pmd_unshare returns false and we will >> + * unmap the actual page and drop map count >> + * to zero. >> + */ >> + page_vma_mapped_walk_done(&pvmw); >> + break; >> + } >> } >> } else { >> flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); >> @@ -1885,13 +1888,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, >> anon_exclusive = folio_test_anon(folio) && >> PageAnonExclusive(subpage); >> >> - if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) { >> - /* >> - * To call huge_pmd_unshare, i_mmap_rwsem must be >> - * held in write mode. Caller needs to explicitly >> - * do this outside rmap routines. >> - */ >> - VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); >> + if (folio_test_hugetlb(folio)) { >> /* >> * huge_pmd_unshare may unmap an entire PMD page. >> * There is no way of knowing exactly which PMDs may >> @@ -1901,22 +1898,31 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, >> */ >> flush_cache_range(vma, range.start, range.end); >> >> - if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) { >> - flush_tlb_range(vma, range.start, range.end); >> - mmu_notifier_invalidate_range(mm, range.start, >> - range.end); >> - >> + if (!folio_test_anon(folio)) { >> /* >> - * The ref count of the PMD page was dropped >> - * which is part of the way map counting >> - * is done for shared PMDs. Return 'true' >> - * here. When there is no other sharing, >> - * huge_pmd_unshare returns false and we will >> - * unmap the actual page and drop map count >> - * to zero. >> + * To call huge_pmd_unshare, i_mmap_rwsem must be >> + * held in write mode. Caller needs to explicitly >> + * do this outside rmap routines. >> */ >> - page_vma_mapped_walk_done(&pvmw); >> - break; >> + VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); >> + >> + if (huge_pmd_unshare(mm, vma, &address, pvmw.pte)) { >> + flush_tlb_range(vma, range.start, range.end); >> + mmu_notifier_invalidate_range(mm, range.start, >> + range.end); >> + >> + /* >> + * The ref count of the PMD page was dropped >> + * which is part of the way map counting >> + * is done for shared PMDs. Return 'true' >> + * here. When there is no other sharing, >> + * huge_pmd_unshare returns false and we will >> + * unmap the actual page and drop map count >> + * to zero. >> + */ >> + page_vma_mapped_walk_done(&pvmw); >> + break; >> + } >> } >> } else { >> flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); > > Thanks, > The code looks fine. It is unfortunate that we need so many levels of > indenting and exceed 80 columns. But, that is OK. I'll do a cleanup to make it more readable with factoring the hugetlb case into a new function after the fix series[1]. [1] https://lore.kernel.org/linux-arm-kernel/20220503120343.6264e126@thinkpad/T/ > > Reviewed-by: Mike Kravetz > > I see you have a followup series to address the call to ptep_clear_flush() > for hugetlb pages not unmapped via huge_pmd_share and will take a look at > that soon. Thanks.