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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id C9DC1C41535 for ; Tue, 19 Dec 2023 08:42:21 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 622758D000F; Tue, 19 Dec 2023 03:42:21 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5D1C38D0005; Tue, 19 Dec 2023 03:42:21 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4E7FD8D000F; Tue, 19 Dec 2023 03:42:21 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 3E6EF8D0005 for ; Tue, 19 Dec 2023 03:42:21 -0500 (EST) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 02FE6120748 for ; 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s=arc-20220608; d=hostedemail.com; t=1702975339; a=rsa-sha256; cv=none; b=J3PxwQIfU04lqYiTiO0D6IQ6u3JaSNpqC5wkOelKoD+daNCf4wDEO7jOwlGXq1eBWylOc9 oSlfGwvQGeKqU5s3dxubyPWARcRyFL+KPgNMfny04RUHjmLG3JQomNo/oNSMgguRL0Cyos wvw25YMuWuGulcoSETpLuO4XTkxRgjc= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=none; spf=pass (imf20.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8E4F31FB; Tue, 19 Dec 2023 00:43:02 -0800 (PST) Received: from [10.57.75.230] (unknown [10.57.75.230]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 02A783F738; Tue, 19 Dec 2023 00:42:16 -0800 (PST) Message-ID: <8b6c9485-568c-41e4-8ef9-0ac6c33754ea@arm.com> Date: Tue, 19 Dec 2023 08:42:16 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 15/39] mm/huge_memory: batch rmap operations in __split_huge_pmd_locked() Content-Language: en-GB To: David Hildenbrand , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , "Matthew Wilcox (Oracle)" , Hugh Dickins , Yin Fengwei , Mike Kravetz , Muchun Song , Peter Xu References: <20231211155652.131054-1-david@redhat.com> <20231211155652.131054-16-david@redhat.com> <652f143e-1547-4ded-892f-1216ce689c9b@redhat.com> From: Ryan Roberts In-Reply-To: <652f143e-1547-4ded-892f-1216ce689c9b@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: w6fqbmztu97pgqi4mig656yxc1sf3iuy X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 26E2E1C0005 X-Rspam-User: X-HE-Tag: 1702975338-754467 X-HE-Meta: U2FsdGVkX1+6lnaPuIMNc94YEX31HeuRvcJSkxpCTAAeqymoADVlgIDSbM5e7Dd4WOHXd0Nr3+kv3bZ8l4q5ClzNcLAVxKsPWZKArESjGaGzuULb97GJaCK8idtqGTukKfI/riN8UpVDkfMBgUOy5aJn2LDDcLO9Wl9n+bWgPfwBxfPfO55u9oMNcTCFK1N4bf37xg1p99p4oYyk0yXAwltxAL60PKqmG4InaHrCW4GeGzMjqP+g95peOt1lC/ZhgmSlsWY/i0SlDTGqGfB+sRD/mSGaqHR/0abOS/ywE1hcqqg5hyWzJi3R5fCMTdNHv/illq7GBQ7dRyVnVeihi4VJbYRdczqRqFsSLvjYvgfo6Zv14Rz/Gb0g3gQIsY01ofgbrPz934LkmmIXlae/rUg1Vv/cAC8YsURdf01ayE6PmCIT9HhD+Qm0NEn5MbSqt3CcjCUZ0knyx1Lrlzl/I0+bV0AbkUukTWkNFi1g9bfaJ5OZpYu5YdjTVaBVm8zHaXRS8QwfOoANZ7uR3a+kWj0+Xq4y2whCVnAVU2/TwQA2X06Dt2Wia1t2iiwN8SCbcq5Oh95TUxEf6Fjz0eaPKGww2KleX9UJwXN64TGsGLfCT0pxpoHxEmNglhHrWzXW9P4zH3qotD8X4+dMals59C35Fbc8MQz+NcwRZxB9kSCz9w8AMZyHGEIQ7By1JijaA45i+bEwVaSCUwflJSXcVHAmmf5DV/jKkmUB4u8RM4+WsH8Ct6ZWTVWHB4MIH3DUtYyvDgmRymJY8CjZldlSN0GX9ssQf4a6lYUR64cvO6UZGaQMH5lEfzfvbuNBcah9UzBByvpFCfFaDzVtIxCDJNyRqFpdtVh2c9fcVskqwoHa/GkbVAweDXZnFoAjV9HfMQ6Jo2PaqScy1Gi8yjjsY9lfcfB+GlRk6Ak5m81CbqHsK8aMhg3pWPsMoHgYHtJeV71vQ9e12953YB7AkI2 TyqWGFNn asJAipx4yymbmbX+dhiq5AyNwjijHqasM8mqoq7HC+jwbbm7hKH7URnmvmlBonyaPWcZq8qfMjD/4qwSIVaoPkDwq3k6Q7c8vLAdv1t/IrzY04fB0PJpgX+hHgCiZQivY5BhC0PeVPw44MXKgMjRzDy+k7PpGUYlmGxQMYd+CG4J2ZvzmrtvRxjeyYrj/rYi2hfOEDT0qxEGVTqiCT1sibKJn4A== 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: List-Subscribe: List-Unsubscribe: On 18/12/2023 17:03, David Hildenbrand wrote: > On 18.12.23 17:22, Ryan Roberts wrote: >> On 11/12/2023 15:56, David Hildenbrand wrote: >>> Let's use folio_add_anon_rmap_ptes(), batching the rmap operations. >>> >>> While at it, use more folio operations (but only in the code branch we're >>> touching), use VM_WARN_ON_FOLIO(), and pass RMAP_EXCLUSIVE instead of >>> manually setting PageAnonExclusive. >>> >>> We should never see non-anon pages on that branch: otherwise, the >>> existing page_add_anon_rmap() call would have been flawed already. >>> >>> Signed-off-by: David Hildenbrand >>> --- >>>   mm/huge_memory.c | 23 +++++++++++++++-------- >>>   1 file changed, 15 insertions(+), 8 deletions(-) >>> >>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>> index 1f5634b2f374..82ad68fe0d12 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -2398,6 +2398,7 @@ static void __split_huge_pmd_locked(struct >>> vm_area_struct *vma, pmd_t *pmd, >>>           unsigned long haddr, bool freeze) >>>   { >>>       struct mm_struct *mm = vma->vm_mm; >>> +    struct folio *folio; >>>       struct page *page; >>>       pgtable_t pgtable; >>>       pmd_t old_pmd, _pmd; >>> @@ -2493,16 +2494,18 @@ static void __split_huge_pmd_locked(struct >>> vm_area_struct *vma, pmd_t *pmd, >>>           uffd_wp = pmd_swp_uffd_wp(old_pmd); >>>       } else { >>>           page = pmd_page(old_pmd); >>> +        folio = page_folio(page); >>>           if (pmd_dirty(old_pmd)) { >>>               dirty = true; >>> -            SetPageDirty(page); >>> +            folio_set_dirty(folio); >>>           } >>>           write = pmd_write(old_pmd); >>>           young = pmd_young(old_pmd); >>>           soft_dirty = pmd_soft_dirty(old_pmd); >>>           uffd_wp = pmd_uffd_wp(old_pmd); >>>   -        VM_BUG_ON_PAGE(!page_count(page), page); >>> +        VM_WARN_ON_FOLIO(!folio_ref_count(folio), folio); >>> +        VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); >> >> Is this warning really correct? file-backed memory can be PMD-mapped with >> CONFIG_READ_ONLY_THP_FOR_FS, so presumably it can also have the need to be >> remapped as pte? Although I guess if we did have a file-backed folio, it >> definitely wouldn't be correct to call page_add_anon_rmap() / >> folio_add_anon_rmap_ptes()... > > Yes, see the patch description where I spell that out. Oh god, how did I miss that... sorry! > > PTE-remapping a file-back folio will simply zap the PMD and refault from the > page cache after creating a page table. Yep, that makes sense. > > So this is anon-only code. >