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 34AB6C04A6A for ; Wed, 2 Aug 2023 15:28:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229460AbjHBP21 (ORCPT ); Wed, 2 Aug 2023 11:28:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49112 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235267AbjHBP2D (ORCPT ); Wed, 2 Aug 2023 11:28:03 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 5334A5BA1 for ; Wed, 2 Aug 2023 08:25:47 -0700 (PDT) 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 627C8113E; Wed, 2 Aug 2023 08:16:20 -0700 (PDT) Received: from [10.57.77.90] (unknown [10.57.77.90]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B73053F5A1; Wed, 2 Aug 2023 08:15:35 -0700 (PDT) Message-ID: Date: Wed, 2 Aug 2023 16:15:34 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH 1/3] mm: add functions folio_in_range() and folio_within_vma() To: Yin Fengwei , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, yuzhao@google.com, willy@infradead.org, david@redhat.com, shy828301@gmail.com, hughd@google.com References: <20230728070929.2487065-1-fengwei.yin@intel.com> <20230728070929.2487065-2-fengwei.yin@intel.com> From: Ryan Roberts In-Reply-To: <20230728070929.2487065-2-fengwei.yin@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/07/2023 08:09, Yin Fengwei wrote: > It will be used to check whether the folio is mapped to specific > VMA and whether the mapping address of folio is in the range. > > Also a helper function folio_within_vma() to check whether folio > is in the range of vma based on folio_in_range(). > > Signed-off-by: Yin Fengwei > --- > mm/internal.h | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 69 insertions(+) > > diff --git a/mm/internal.h b/mm/internal.h > index 5a03bc4782a2..63de32154a48 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -585,6 +585,75 @@ extern long faultin_vma_page_range(struct vm_area_struct *vma, > bool write, int *locked); > extern bool mlock_future_ok(struct mm_struct *mm, unsigned long flags, > unsigned long bytes); > + > +/* > + * Check whether the folio is in specific range > + * > + * First, check whether the folio is in the range of vma. > + * Then, check whether the folio is mapped to the range of [start, end]. > + * In the end, check whether the folio is fully mapped to the range. > + * > + * @pte page table pointer will be checked whether the large folio > + * is fully mapped to. Currently, if mremap in the middle of > + * large folio, the large folio could be mapped to to different > + * VMA and address check can't identify this situation. > + */ > +static inline bool > +folio_in_range(struct folio *folio, struct vm_area_struct *vma, > + unsigned long start, unsigned long end, pte_t *pte) > +{ > + pte_t ptent; > + unsigned long i, nr = folio_nr_pages(folio); > + pgoff_t pgoff, addr; > + unsigned long vma_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; > + > + VM_WARN_ON_FOLIO(folio_test_ksm(folio), folio); > + > + if (start < vma->vm_start) > + start = vma->vm_start; > + if (end > vma->vm_end) > + end = vma->vm_end; > + > + pgoff = folio_pgoff(folio); > + /* if folio start address is not in vma range */ > + if (pgoff < vma->vm_pgoff || pgoff > vma->vm_pgoff + vma_pglen) > + return false; I'm struggling with this logic. What happens for an anonymous folio in a (private) file mapping? Wouldn't the folio's pgoff be 0? In this case you could return false incorrectly? > + > + addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); > + if (addr < start || end - addr < folio_size(folio)) > + return false; > + > + /* not necessary to check pte for none large folio */ > + if (!folio_test_large(folio)) > + return true; > + > + if (!pte) > + return false; > + > + /* check whether parameter pte is associated with folio */ > + ptent = ptep_get(pte); > + if (pte_none(ptent) || !pte_present(ptent) || > + pte_pfn(ptent) - folio_pfn(folio) >= nr) > + return false; > + > + pte -= pte_pfn(ptent) - folio_pfn(folio); > + for (i = 0; i < nr; i++, pte++) { > + ptent = ptep_get(pte); > + > + if (pte_none(ptent) || !pte_present(ptent) || > + pte_pfn(ptent) - folio_pfn(folio) >= nr) > + return false; > + } > + > + return true; > +} > + > +static inline bool > +folio_within_vma(struct folio *folio, struct vm_area_struct *vma, pte_t *pte) > +{ > + return folio_in_range(folio, vma, vma->vm_start, vma->vm_end, pte); > +} > + > /* > * mlock_vma_folio() and munlock_vma_folio(): > * should be called with vma's mmap_lock held for read or write,