From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 5C7DA5EE6F; Tue, 23 Jan 2024 12:35:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706013318; cv=none; b=ZQ2GD+o5e+nZZcmsS62BcVaLNO57oGynKgst5SaKi+pfhZs4kQ82KnVIFsDCSqbWMw8MkvVMhwiAYgGT86KIobvGS+rE97kvuB+J/bGlHzCUlBuB1wnuJsZc8G6/8v7c8on4tNu98IcOVF0yWlYX9EdULDPNdHIw9+tSlI6K6H4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706013318; c=relaxed/simple; bh=lh1scRV+11oHRBnaYK5zPIZK1TcAM5fnn42pUqvwwOM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=TxFXMaHMITmM7kR+wX1vGk+0IQap8UDM9fBG+bY338lZ3x2DG8sZV9NfWOpMlTXLKV/25HvJiDiDFflQZloMD0MOeFcvU96WR4jdVavRJ9i1nXVfME3PpQ3UAw2MxWm3dL+QIAIUGFd1I5Q3WJL0uG0bvYLAhPrLFPfFC0hA6pE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=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 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 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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;