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Sun, 26 Jun 2022 20:32:37 -0700 (PDT) Date: Mon, 27 Jun 2022 11:32:33 +0800 From: Muchun Song To: Qi Zheng Cc: mike.kravetz@oracle.com, akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm: hugetlb: kill set_huge_swap_pte_at() Message-ID: References: <20220626145717.53572-1-zhengqi.arch@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220626145717.53572-1-zhengqi.arch@bytedance.com> ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=d3N0wblG; spf=pass (imf11.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.214.174 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; 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spf=pass (imf11.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.214.174 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com X-Rspamd-Server: rspam02 X-HE-Tag: 1656300759-627020 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: On Sun, Jun 26, 2022 at 10:57:17PM +0800, Qi Zheng wrote: > The commit e5251fd43007 ("mm/hugetlb: introduce set_huge_swap_pte_at() > helper") add set_huge_swap_pte_at() to handle swap entries on > architectures that support hugepages consisting of contiguous ptes. > And currently the set_huge_swap_pte_at() is only overridden by arm64. > > The set_huge_swap_pte_at() provide a sz parameter to help determine > the number of entries to be updated. But in fact, all hugetlb swap > entries contain pfn information, so we can find the corresponding > folio through the pfn recorded in the swap entry, then the folio_size() > is the number of entries that need to be updated. > > And considering that users will easily cause bugs by ignoring the > difference between set_huge_swap_pte_at() and set_huge_pte_at(). > Let's handle swap entries in set_huge_pte_at() and remove the > set_huge_swap_pte_at(), then we can call set_huge_pte_at() > anywhere, which simplifies our coding. > > Signed-off-by: Qi Zheng I think it is a nice cleanup since it simplify the code enough. We do not need to struggle between set_huge_swap_pte_at() and set_huge_pte_at(), it is very easy to make mistakes (see commit 5d4af6195c87 and e5251fd43007). And arm64 is the only user which needs a special set_huge_swap_pte_at(), it would be nicer if arm64 could handle it transparently. So Acked-by: Muchun Song > --- > arch/arm64/include/asm/hugetlb.h | 3 --- > arch/arm64/mm/hugetlbpage.c | 34 ++++++++++++++++---------------- > include/linux/hugetlb.h | 13 ------------ > mm/hugetlb.c | 8 +++----- > mm/rmap.c | 11 +++-------- > 5 files changed, 23 insertions(+), 46 deletions(-) > > diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h > index 1fd2846dbefe..d20f5da2d76f 100644 > --- a/arch/arm64/include/asm/hugetlb.h > +++ b/arch/arm64/include/asm/hugetlb.h > @@ -46,9 +46,6 @@ extern void huge_pte_clear(struct mm_struct *mm, unsigned long addr, > pte_t *ptep, unsigned long sz); > #define __HAVE_ARCH_HUGE_PTEP_GET > extern pte_t huge_ptep_get(pte_t *ptep); > -extern void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr, > - pte_t *ptep, pte_t pte, unsigned long sz); > -#define set_huge_swap_pte_at set_huge_swap_pte_at > > void __init arm64_hugetlb_cma_reserve(void); > > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c > index c9e076683e5d..58b89b9d13e0 100644 > --- a/arch/arm64/mm/hugetlbpage.c > +++ b/arch/arm64/mm/hugetlbpage.c > @@ -238,6 +238,13 @@ static void clear_flush(struct mm_struct *mm, > flush_tlb_range(&vma, saddr, addr); > } > > +static inline struct folio *hugetlb_swap_entry_to_folio(swp_entry_t entry) > +{ > + VM_BUG_ON(!is_migration_entry(entry) && !is_hwpoison_entry(entry)); > + > + return page_folio(pfn_to_page(swp_offset(entry))); > +} > + > void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, > pte_t *ptep, pte_t pte) > { > @@ -247,11 +254,16 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, > unsigned long pfn, dpfn; > pgprot_t hugeprot; > > - /* > - * Code needs to be expanded to handle huge swap and migration > - * entries. Needed for HUGETLB and MEMORY_FAILURE. > - */ When I noticed the comments here, seems this cleanup was on the plan a few years ago? > - WARN_ON(!pte_present(pte)); > + if (!pte_present(pte)) { > + struct folio *folio; > + > + folio = hugetlb_swap_entry_to_folio(pte_to_swp_entry(pte)); > + ncontig = num_contig_ptes(folio_size(folio), &pgsize); > + > + for (i = 0; i < ncontig; i++, ptep++) > + set_pte_at(mm, addr, ptep, pte); > + return; > + } > > if (!pte_cont(pte)) { > set_pte_at(mm, addr, ptep, pte); > @@ -269,18 +281,6 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, > set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot)); > } > > -void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr, > - pte_t *ptep, pte_t pte, unsigned long sz) > -{ > - int i, ncontig; > - size_t pgsize; > - > - ncontig = num_contig_ptes(sz, &pgsize); > - > - for (i = 0; i < ncontig; i++, ptep++) > - set_pte(ptep, pte); > -} > - > pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma, > unsigned long addr, unsigned long sz) > { > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index ee9a28ef26ee..3bb98434550a 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -928,14 +928,6 @@ static inline void hugetlb_count_sub(long l, struct mm_struct *mm) > atomic_long_sub(l, &mm->hugetlb_usage); > } > > -#ifndef set_huge_swap_pte_at > -static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr, > - pte_t *ptep, pte_t pte, unsigned long sz) > -{ > - set_huge_pte_at(mm, addr, ptep, pte); > -} > -#endif > - > #ifndef huge_ptep_modify_prot_start > #define huge_ptep_modify_prot_start huge_ptep_modify_prot_start > static inline pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma, > @@ -1119,11 +1111,6 @@ static inline void hugetlb_count_sub(long l, struct mm_struct *mm) > { > } > > -static inline void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr, > - pte_t *ptep, pte_t pte, unsigned long sz) > -{ > -} > - > static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma, > unsigned long addr, pte_t *ptep) > { > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index f338640fbe4a..559084d96082 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -4813,12 +4813,11 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, > entry = swp_entry_to_pte(swp_entry); > if (userfaultfd_wp(src_vma) && uffd_wp) > entry = huge_pte_mkuffd_wp(entry); > - set_huge_swap_pte_at(src, addr, src_pte, > - entry, sz); > + set_huge_pte_at(src, addr, src_pte, entry); > } > if (!userfaultfd_wp(dst_vma) && uffd_wp) > entry = huge_pte_clear_uffd_wp(entry); > - set_huge_swap_pte_at(dst, addr, dst_pte, entry, sz); > + set_huge_pte_at(dst, addr, dst_pte, entry); > } else if (unlikely(is_pte_marker(entry))) { > /* > * We copy the pte marker only if the dst vma has > @@ -6375,8 +6374,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma, > newpte = pte_swp_mkuffd_wp(newpte); > else if (uffd_wp_resolve) > newpte = pte_swp_clear_uffd_wp(newpte); > - set_huge_swap_pte_at(mm, address, ptep, > - newpte, psize); > + set_huge_pte_at(mm, address, ptep, newpte); > pages++; > } > spin_unlock(ptl); > diff --git a/mm/rmap.c b/mm/rmap.c > index 062e8655f337..338fbb24c602 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1618,9 +1618,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, > pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); > if (folio_test_hugetlb(folio)) { > hugetlb_count_sub(folio_nr_pages(folio), mm); > - set_huge_swap_pte_at(mm, address, > - pvmw.pte, pteval, > - vma_mmu_pagesize(vma)); > + set_huge_pte_at(mm, address, pvmw.pte, pteval); > } else { > dec_mm_counter(mm, mm_counter(&folio->page)); > set_pte_at(mm, address, pvmw.pte, pteval); > @@ -2004,9 +2002,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, > pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); > if (folio_test_hugetlb(folio)) { > hugetlb_count_sub(folio_nr_pages(folio), mm); > - set_huge_swap_pte_at(mm, address, > - pvmw.pte, pteval, > - vma_mmu_pagesize(vma)); > + set_huge_pte_at(mm, address, pvmw.pte, pteval); > } else { > dec_mm_counter(mm, mm_counter(&folio->page)); > set_pte_at(mm, address, pvmw.pte, pteval); > @@ -2074,8 +2070,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, > if (pte_uffd_wp(pteval)) > swp_pte = pte_swp_mkuffd_wp(swp_pte); > if (folio_test_hugetlb(folio)) > - set_huge_swap_pte_at(mm, address, pvmw.pte, > - swp_pte, vma_mmu_pagesize(vma)); > + set_huge_pte_at(mm, address, pvmw.pte, swp_pte); > else > set_pte_at(mm, address, pvmw.pte, swp_pte); > trace_set_migration_pte(address, pte_val(swp_pte), > -- > 2.20.1 > >