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 CA38FC47258 for ; Tue, 23 Jan 2024 12:35:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 674B48D0003; Tue, 23 Jan 2024 07:35:15 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 624158D0002; Tue, 23 Jan 2024 07:35:15 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4EBBB8D0003; Tue, 23 Jan 2024 07:35:15 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 3E85B8D0002 for ; Tue, 23 Jan 2024 07:35:15 -0500 (EST) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 0ED34A03F5 for ; Tue, 23 Jan 2024 12:35:15 +0000 (UTC) X-FDA: 81710520990.03.28E27A7 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf10.hostedemail.com (Postfix) with ESMTP id 4042BC0026 for ; Tue, 23 Jan 2024 12:35:13 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf10.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1706013313; 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; bh=lF0UizJr+nfAntFb4iYgyC2Y/urHUe9COXlJM4uIGDY=; b=4j10Tgp2qaaOwKIaboKiSuYNBsbCTF3gUL3RoTsj6oGknBVENOYwJdyUDMntYWBC7nNta+ baf6LUjsEkj3VwRbmn3XhGw3oG81jUgck354RO88IBMiV+7Ih66aVtNfFvO4JeaMBl144P r5mDuMFxxbOrKFons89HTxoN5nsXifg= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf10.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1706013313; a=rsa-sha256; cv=none; b=tiNyVcU4azPws1lHC+TDcamTKSz/Z9FM5mp4nujMC0qMPoh26SLTCTb6Hj8Z+v730VeHBL Wh/ckNpABA8RPgE0gzChdSsjva283xlPyWgHo7512jiIawpxgs/MSnzdqmejHaamjvxqMN xzG4y7fD3qeSNMttIOXs6B/+EeSKGhA= 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 B2C011FB; Tue, 23 Jan 2024 04:35:57 -0800 (PST) Received: from [10.57.77.165] (unknown [10.57.77.165]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9D4703F762; Tue, 23 Jan 2024 04:35:08 -0800 (PST) Message-ID: <2ed34573-2f11-485d-9d8d-224e98aa59b2@arm.com> Date: Tue, 23 Jan 2024 12:35:07 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 11/11] mm/memory: ignore writable bit in folio_pte_batch() Content-Language: en-GB To: David Hildenbrand , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Russell King , Catalin Marinas , Will Deacon , Dinh Nguyen , Michael Ellerman , Nicholas Piggin , Christophe Leroy , "Aneesh Kumar K.V" , "Naveen N. Rao" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , "David S. Miller" , linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org References: <20240122194200.381241-1-david@redhat.com> <20240122194200.381241-12-david@redhat.com> From: Ryan Roberts In-Reply-To: <20240122194200.381241-12-david@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 4042BC0026 X-Stat-Signature: rbcw5cu5weqquisy1o4tk7f59k9k4c5e X-Rspam-User: X-HE-Tag: 1706013313-823861 X-HE-Meta: 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 awXqIyVd xMdhpQ1L+sIkHQKscjaBHCvF/VdNSFEa40pVGIBsQW1f7LKgWpz3IoxyCuSucM7+Kn0RIbdmQvSqi0+VjRPuUckjG5d1Z09nHPsu02EawJRcHge8aagS3Q1hcza0j2ZWkyjOZiC0MXpdC3xoZSC9H8Za+RL/bQlj2OtjwBrzeCh6bW5fkyUGhLBkBKVTXuNhNIYPtf+o884zOPvz9tpUxLTwfxbC6ofPH0zOqc6Gxrmn7ZymHtX2/mFGERTmZ7c4hbcA4/3LnEBTTcnUztOVcjbIUMw== 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 22/01/2024 19:42, David Hildenbrand wrote: > ... and conditionally return to the caller if any pte except the first one > is writable. fork() has to make sure to properly write-protect in case any > PTE is writable. Other users (e.g., page unmaping) won't care. > > Signed-off-by: David Hildenbrand Reviewed-by: Ryan Roberts > --- > mm/memory.c | 26 +++++++++++++++++++++----- > 1 file changed, 21 insertions(+), 5 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 341b2be845b6e..a26fd0669016b 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -955,7 +955,7 @@ static __always_inline void __copy_present_ptes(struct vm_area_struct *dst_vma, > > static inline pte_t __pte_batch_clear_ignored(pte_t pte) > { > - return pte_clear_soft_dirty(pte_mkclean(pte_mkold(pte))); > + return pte_wrprotect(pte_clear_soft_dirty(pte_mkclean(pte_mkold(pte)))); > } > > /* > @@ -963,20 +963,29 @@ static inline pte_t __pte_batch_clear_ignored(pte_t pte) > * pages of the same folio. > * > * All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN. > - * the accessed bit, dirty bit and soft-dirty bit. > + * the accessed bit, dirty bit, soft-dirty bit and writable bit. > + . If "any_writable" is set, it will indicate if any other PTE besides the > + * first (given) PTE is writable. > */ > static inline int folio_pte_batch(struct folio *folio, unsigned long addr, > - pte_t *start_ptep, pte_t pte, int max_nr) > + pte_t *start_ptep, pte_t pte, int max_nr, bool *any_writable) > { > unsigned long folio_end_pfn = folio_pfn(folio) + folio_nr_pages(folio); > const pte_t *end_ptep = start_ptep + max_nr; > pte_t expected_pte = __pte_batch_clear_ignored(pte_next_pfn(pte)); > pte_t *ptep = start_ptep + 1; > + bool writable; > + > + if (any_writable) > + *any_writable = false; > > VM_WARN_ON_FOLIO(!pte_present(pte), folio); > > while (ptep != end_ptep) { > - pte = __pte_batch_clear_ignored(ptep_get(ptep)); > + pte = ptep_get(ptep); > + if (any_writable) > + writable = !!pte_write(pte); > + pte = __pte_batch_clear_ignored(pte); > > if (!pte_same(pte, expected_pte)) > break; > @@ -989,6 +998,9 @@ static inline int folio_pte_batch(struct folio *folio, unsigned long addr, > if (pte_pfn(pte) == folio_end_pfn) > break; > > + if (any_writable) > + *any_writable |= writable; > + > expected_pte = pte_next_pfn(expected_pte); > ptep++; > } > @@ -1010,6 +1022,7 @@ copy_present_ptes(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma > { > struct page *page; > struct folio *folio; > + bool any_writable; > int err, nr; > > page = vm_normal_page(src_vma, addr, pte); > @@ -1024,7 +1037,8 @@ copy_present_ptes(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma > * by keeping the batching logic separate. > */ > if (unlikely(!*prealloc && folio_test_large(folio) && max_nr != 1)) { > - nr = folio_pte_batch(folio, addr, src_pte, pte, max_nr); > + nr = folio_pte_batch(folio, addr, src_pte, pte, max_nr, > + &any_writable); > if (folio_test_anon(folio)) { > folio_ref_add(folio, nr); > if (unlikely(folio_try_dup_anon_rmap_ptes(folio, page, > @@ -1039,6 +1053,8 @@ copy_present_ptes(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma > folio_dup_file_rmap_ptes(folio, page, nr); > rss[mm_counter_file(page)] += nr; > } > + if (any_writable) > + pte = pte_mkwrite(pte, src_vma); > __copy_present_ptes(dst_vma, src_vma, dst_pte, src_pte, pte, > addr, nr); > return nr;