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 062A3C369D5 for ; Mon, 28 Apr 2025 12:50:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DE9466B0032; Mon, 28 Apr 2025 08:50:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D988C6B0099; Mon, 28 Apr 2025 08:50:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C10D96B00AF; Mon, 28 Apr 2025 08:50:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 9EA0A6B0032 for ; Mon, 28 Apr 2025 08:50:31 -0400 (EDT) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 7E5FC57C78 for ; Mon, 28 Apr 2025 12:50:31 +0000 (UTC) X-FDA: 83383436262.24.47BA66C Received: from out-171.mta0.migadu.com (out-171.mta0.migadu.com [91.218.175.171]) by imf08.hostedemail.com (Postfix) with ESMTP id 7FFC0160002 for ; Mon, 28 Apr 2025 12:50:29 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="IVDg/78T"; spf=pass (imf08.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.171 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1745844629; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=tmoFP7mWK1xDtxpxC3gMfuoxF1w2bYb3YT1RZ1atP8s=; b=GJbzlBpeUC4gVrvUMttWofMwmIx2J6OviC7UiVOWvIPvABacY4Ndd2g/20g46EfkgLbJPT 6lO2h3Fnc279u/ZLzydf3Un3OfmoFbIHLGEt69h4rp+VFlk3z6XdAvsyNMRKIqgCXDnRCL /bqzK9vNR3Rzv0yIdi+Za0DZoQ5fKeA= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="IVDg/78T"; spf=pass (imf08.hostedemail.com: domain of lance.yang@linux.dev designates 91.218.175.171 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1745844629; a=rsa-sha256; cv=none; b=r2Z8K31GxdmQ+/QhOiTmFKXGa8ZVwFPhzVrmtxfTZcDVoN3nLcNkB9VE1cxmrqn9q1QNhj TrojoBweTtmnS8+oEo5uUZGrRoah8mveHggL7b7vmeYp7WlDUcodn4tGm1XW0xQhKYXEXb iu0KNO/lm+TV2/Eh+YjQWCPB2ZBm9uU= Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1745844626; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=tmoFP7mWK1xDtxpxC3gMfuoxF1w2bYb3YT1RZ1atP8s=; b=IVDg/78TnwGssY/I/XW2WmOiRAnxxN48wxv1DWSOCn3YYb121+/64IkBo8+FUsCQdf9s0r O4aEsbZgKEok2xAK7cR2Jra+qNt2wSy6aLTx/92JqIYlczVAdJnhq0Wp4jK84B+ExiHoYm jE+4B/I/DSK0Aikia6yGoAONLSl/tRw= Date: Mon, 28 Apr 2025 20:50:11 +0800 MIME-Version: 1.0 Subject: Re: [PATCH 6/7] mm: Batch around can_change_pte_writable() Content-Language: en-US To: Dev Jain , akpm@linux-foundation.org Cc: ryan.roberts@arm.com, david@redhat.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, anshuman.khandual@arm.com, peterx@redhat.com, joey.gouly@arm.com, ioworker0@gmail.com, baohua@kernel.org, kevin.brodsky@arm.com, quic_zhenhuah@quicinc.com, christophe.leroy@csgroup.eu, yangyicong@hisilicon.com, linux-arm-kernel@lists.infradead.org, namit@vmware.com, hughd@google.com, yang@os.amperecomputing.com, ziy@nvidia.com References: <20250428120414.12101-1-dev.jain@arm.com> <20250428120414.12101-7-dev.jain@arm.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <20250428120414.12101-7-dev.jain@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 61ewwb1dfmxwzpj6qzg6qou9uix4zkej X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 7FFC0160002 X-Rspam-User: X-HE-Tag: 1745844629-204719 X-HE-Meta: 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 KluBlRnQ Gs31rUVOKXVgKN59JiNPVHYI6GVE2IUFT7+BVaR1BOfgnLlCMsGl9xU/WtoQ2RM6fb13GEW4dJ19XA3nu/yxqy4odW49FUb/nUHjXZvd0+/n6h+APoT7R1xbglHrUf2VBnsPdZw6ac8qqiEmHpNfupDPOTUpgAoIvKZ860DPc8SgutThM9OCYEviQGirIJcEsmy8tORwYSDITG1HiUqyqtq8nGlUyeiO3T56xoE1Hej6J3oHG9g4qPDTqZeD8x/owUoNtqxh95kPJjDZe2Ygy6YAfMObv0z7YktMP 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: Hey Dev, On 2025/4/28 20:04, Dev Jain wrote: > In preparation for patch 7, we need to properly batch around > can_change_pte_writable(). We batch around pte_needs_soft_dirty_wp() by > the corresponding fpb flag, we batch around the page-anon exclusive check > using folio_maybe_mapped_shared(); modify_prot_start_ptes() collects the > dirty and access bits across the batch, therefore batching across > pte_dirty(): this is correct since the dirty bit on the PTE really > is just an indication that the folio got written to, so even if > the PTE is not actually dirty (but one of the PTEs in the batch is), > the wp-fault optimization can be made. > > Signed-off-by: Dev Jain > --- > include/linux/mm.h | 4 ++-- > mm/gup.c | 2 +- > mm/huge_memory.c | 4 ++-- > mm/memory.c | 6 +++--- > mm/mprotect.c | 9 ++++++--- > 5 files changed, 14 insertions(+), 11 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 5eb0d77c4438..ffa02e15863f 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2710,8 +2710,8 @@ int get_cmdline(struct task_struct *task, char *buffer, int buflen); > #define MM_CP_UFFD_WP_ALL (MM_CP_UFFD_WP | \ > MM_CP_UFFD_WP_RESOLVE) > > -bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, > - pte_t pte); > +bool can_change_ptes_writable(struct vm_area_struct *vma, unsigned long addr, > + pte_t pte, struct folio *folio, unsigned int nr); > extern long change_protection(struct mmu_gather *tlb, > struct vm_area_struct *vma, unsigned long start, > unsigned long end, unsigned long cp_flags); > diff --git a/mm/gup.c b/mm/gup.c > index 84461d384ae2..6a605fc5f2cb 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -614,7 +614,7 @@ static inline bool can_follow_write_common(struct page *page, > return false; > > /* > - * See can_change_pte_writable(): we broke COW and could map the page > + * See can_change_ptes_writable(): we broke COW and could map the page > * writable if we have an exclusive anonymous page ... > */ > return page && PageAnon(page) && PageAnonExclusive(page); > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 28c87e0e036f..e5496c0d9e7e 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2032,12 +2032,12 @@ static inline bool can_change_pmd_writable(struct vm_area_struct *vma, > return false; > > if (!(vma->vm_flags & VM_SHARED)) { > - /* See can_change_pte_writable(). */ > + /* See can_change_ptes_writable(). */ > page = vm_normal_page_pmd(vma, addr, pmd); > return page && PageAnon(page) && PageAnonExclusive(page); > } > > - /* See can_change_pte_writable(). */ > + /* See can_change_ptes_writable(). */ > return pmd_dirty(pmd); > } > > diff --git a/mm/memory.c b/mm/memory.c > index b9e8443aaa86..b1fda3de8d27 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -750,7 +750,7 @@ static void restore_exclusive_pte(struct vm_area_struct *vma, > pte = pte_mkuffd_wp(pte); > > if ((vma->vm_flags & VM_WRITE) && > - can_change_pte_writable(vma, address, pte)) { > + can_change_ptes_writable(vma, address, pte, NULL, 1)) { > if (folio_test_dirty(folio)) > pte = pte_mkdirty(pte); > pte = pte_mkwrite(pte, vma); > @@ -5767,7 +5767,7 @@ static void numa_rebuild_large_mapping(struct vm_fault *vmf, struct vm_area_stru > ptent = pte_modify(ptent, vma->vm_page_prot); > writable = pte_write(ptent); > if (!writable && pte_write_upgrade && > - can_change_pte_writable(vma, addr, ptent)) > + can_change_ptes_writable(vma, addr, ptent, NULL, 1)) > writable = true; > } > > @@ -5808,7 +5808,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) > */ > writable = pte_write(pte); > if (!writable && pte_write_upgrade && > - can_change_pte_writable(vma, vmf->address, pte)) > + can_change_ptes_writable(vma, vmf->address, pte, NULL, 1)) > writable = true; > > folio = vm_normal_folio(vma, vmf->address, pte); > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 33eabc995584..362fd7e5457d 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -40,8 +40,8 @@ > > #include "internal.h" > > -bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, > - pte_t pte) > +bool can_change_ptes_writable(struct vm_area_struct *vma, unsigned long addr, > + pte_t pte, struct folio *folio, unsigned int nr) > { > struct page *page; > > @@ -67,6 +67,9 @@ bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr, > * write-fault handler similarly would map them writable without > * any additional checks while holding the PT lock. > */ > + if (unlikely(nr != 1)) > + return !folio_maybe_mapped_shared(folio); > + > page = vm_normal_page(vma, addr, pte); > return page && PageAnon(page) && PageAnonExclusive(page); > } IIUC, As mentioned in the comment above, we should do the same anonymous check to large folios. And folio_maybe_mapped_shared() already handles both order-0 and large folios nicely, so we could simplify the logic as follows: diff --git a/mm/mprotect.c b/mm/mprotect.c index 1605e89349d2..df56a30bb241 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -43,8 +43,6 @@ bool can_change_ptes_writable(struct vm_area_struct *vma, unsigned long addr, pte_t pte, struct folio *folio, unsigned int nr) { - struct page *page; - if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE))) return false; @@ -67,11 +65,7 @@ bool can_change_ptes_writable(struct vm_area_struct *vma, unsigned long addr, * write-fault handler similarly would map them writable without * any additional checks while holding the PT lock. */ - if (unlikely(nr != 1)) - return !folio_maybe_mapped_shared(folio); - - page = vm_normal_page(vma, addr, pte); - return page && PageAnon(page) && PageAnonExclusive(page); + return folio_test_anon(folio) && !folio_maybe_mapped_shared(folio); } VM_WARN_ON_ONCE(is_zero_pfn(pte_pfn(pte)) && pte_dirty(pte)); -- Thanks, Lance > @@ -222,7 +225,7 @@ static long change_pte_range(struct mmu_gather *tlb, > */ > if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && > !pte_write(ptent) && > - can_change_pte_writable(vma, addr, ptent)) > + can_change_ptes_writable(vma, addr, ptent, folio, 1)) > ptent = pte_mkwrite(ptent, vma); > > ptep_modify_prot_commit(vma, addr, pte, oldpte, ptent);