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 9FF09368978 for ; Sat, 28 Feb 2026 09:30:24 +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=1772271026; cv=none; b=uedNC2oJWoyTJf3QNQ00oWG3qhAEYSf53KuLVvyxLeFAC9D26exoHktiUe+bb88MfW26NnMVOY10wHoufHTIlr0qFzr2GNywjc/XLlEEZ/ZzdvQb83zYsAAX4b4mKXv/gxSl3v5fTbx7IPpsSjzl7uxrWvoNFdV3jxS9YQN/Nks= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772271026; c=relaxed/simple; bh=QUhQPrwm0SMPLp75SsgLfI467uzKpai1C+x1uVUSmkM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Dt3/9vtS2vlc3goF3juk5ZazNegz5dkn2Ubsp+NZZ/F+5HKqYIsDaSIBpAw/Y9aco6Un/iQ/CWA7ODdsFPdd1SNhIElcxi/xCxVYU2uoaJkxBUBB0G0srwcfPQV9dwXVka4ARa5f/fmEvw4Y8Row/bIe2qo4vkT/pnlwZx5U2G4= 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 A0F8B19F6; Sat, 28 Feb 2026 01:30:17 -0800 (PST) Received: from [10.163.135.253] (unknown [10.163.135.253]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 29DAA3F73B; Sat, 28 Feb 2026 01:30:06 -0800 (PST) Message-ID: <94fcaf80-c812-43d9-8010-46eb9f913746@arm.com> Date: Sat, 28 Feb 2026 15:00:03 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v2 1/5] mm: consolidate anonymous folio PTE mapping into helpers To: Nico Pache , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@kernel.org, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jackmanb@google.com, jack@suse.cz, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com References: <20260226012929.169479-1-npache@redhat.com> <20260226012929.169479-2-npache@redhat.com> Content-Language: en-US From: Dev Jain In-Reply-To: <20260226012929.169479-2-npache@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 26/02/26 6:59 am, Nico Pache wrote: > The anonymous page fault handler in do_anonymous_page() open-codes the > sequence to map a newly allocated anonymous folio at the PTE level: > - construct the PTE entry > - add rmap > - add to LRU > - set the PTEs > - update the MMU cache. > > Introduce a two helpers to consolidate this duplicated logic, mirroring the > existing map_anon_folio_pmd_nopf() pattern for PMD-level mappings: > > map_anon_folio_pte_nopf(): constructs the PTE entry, takes folio > references, adds anon rmap and LRU. This function also handles the > uffd_wp that can occur in the pf variant. > > map_anon_folio_pte_pf(): extends the nopf variant to handle MM_ANONPAGES > counter updates, and mTHP fault allocation statistics for the page fault > path. > > The zero-page read path in do_anonymous_page() is also untangled from the > shared setpte label, since it does not allocate a folio and should not > share the same mapping sequence as the write path. Make nr_pages = 1 > rather than relying on the variable. This makes it more clear that we > are operating on the zero page only. > > This refactoring will also help reduce code duplication between mm/memory.c > and mm/khugepaged.c, and provides a clean API for PTE-level anonymous folio > mapping that can be reused by future callers. > > Signed-off-by: Nico Pache > --- Reviewed-by: Dev Jain Should we make map_anon_folio_pte_pf() inline, since it has only one caller. > include/linux/mm.h | 4 ++++ > mm/memory.c | 59 +++++++++++++++++++++++++++++++--------------- > 2 files changed, 44 insertions(+), 19 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 13336340612e..3ebf143c7502 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -4901,4 +4901,8 @@ static inline bool snapshot_page_is_faithful(const struct page_snapshot *ps) > > void snapshot_page(struct page_snapshot *ps, const struct page *page); > > +void map_anon_folio_pte_nopf(struct folio *folio, pte_t *pte, > + struct vm_area_struct *vma, unsigned long addr, > + bool uffd_wp); > + > #endif /* _LINUX_MM_H */ > diff --git a/mm/memory.c b/mm/memory.c > index 9385842c3503..a1a364e1fdcd 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -5189,6 +5189,36 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf) > return folio_prealloc(vma->vm_mm, vma, vmf->address, true); > } > > +void map_anon_folio_pte_nopf(struct folio *folio, pte_t *pte, > + struct vm_area_struct *vma, unsigned long addr, > + bool uffd_wp) > +{ > + unsigned int nr_pages = folio_nr_pages(folio); > + pte_t entry = folio_mk_pte(folio, vma->vm_page_prot); > + > + entry = pte_sw_mkyoung(entry); > + > + if (vma->vm_flags & VM_WRITE) > + entry = pte_mkwrite(pte_mkdirty(entry), vma); > + if (uffd_wp) > + entry = pte_mkuffd_wp(entry); > + > + folio_ref_add(folio, nr_pages - 1); > + folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE); > + folio_add_lru_vma(folio, vma); > + set_ptes(vma->vm_mm, addr, pte, entry, nr_pages); > + update_mmu_cache_range(NULL, vma, addr, pte, nr_pages); > +} > + > +static void map_anon_folio_pte_pf(struct folio *folio, pte_t *pte, > + struct vm_area_struct *vma, unsigned long addr, > + unsigned int nr_pages, bool uffd_wp) > +{ > + map_anon_folio_pte_nopf(folio, pte, vma, addr, uffd_wp); > + add_mm_counter(vma->vm_mm, MM_ANONPAGES, nr_pages); > + count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_FAULT_ALLOC); > +} > + > /* > * We enter with non-exclusive mmap_lock (to exclude vma changes, > * but allow concurrent faults), and pte mapped but not yet locked. > @@ -5235,7 +5265,14 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) > pte_unmap_unlock(vmf->pte, vmf->ptl); > return handle_userfault(vmf, VM_UFFD_MISSING); > } > - goto setpte; > + if (vmf_orig_pte_uffd_wp(vmf)) > + entry = pte_mkuffd_wp(entry); > + set_pte_at(vma->vm_mm, addr, vmf->pte, entry); > + > + /* No need to invalidate - it was non-present before */ > + update_mmu_cache_range(vmf, vma, addr, vmf->pte, > + /*nr_pages=*/ 1); > + goto unlock; > } > > /* Allocate our own private page. */ > @@ -5259,11 +5296,6 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) > */ > __folio_mark_uptodate(folio); > > - entry = folio_mk_pte(folio, vma->vm_page_prot); > - entry = pte_sw_mkyoung(entry); > - if (vma->vm_flags & VM_WRITE) > - entry = pte_mkwrite(pte_mkdirty(entry), vma); > - > vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl); > if (!vmf->pte) > goto release; > @@ -5285,19 +5317,8 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) > folio_put(folio); > return handle_userfault(vmf, VM_UFFD_MISSING); > } > - > - folio_ref_add(folio, nr_pages - 1); > - add_mm_counter(vma->vm_mm, MM_ANONPAGES, nr_pages); > - count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_FAULT_ALLOC); > - folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE); > - folio_add_lru_vma(folio, vma); > -setpte: > - if (vmf_orig_pte_uffd_wp(vmf)) > - entry = pte_mkuffd_wp(entry); > - set_ptes(vma->vm_mm, addr, vmf->pte, entry, nr_pages); > - > - /* No need to invalidate - it was non-present before */ > - update_mmu_cache_range(vmf, vma, addr, vmf->pte, nr_pages); > + map_anon_folio_pte_pf(folio, vmf->pte, vma, addr, nr_pages, > + vmf_orig_pte_uffd_wp(vmf)); > unlock: > if (vmf->pte) > pte_unmap_unlock(vmf->pte, vmf->ptl);