From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0FEA639E6F6 for ; Thu, 26 Feb 2026 09:28:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772098089; cv=none; b=Yq01+f+5GSMulWH51uOsxRIuFsyAxN0PorJMQWq7P+BXDZntqthFUFzuws9K8KxI9L/GNUMAdZxCig6EO4bciTv1pswe0B88M6ba/yq4v6sNDe4h66B+AMrOoIv/1u68KMY4OwdZWSuoCDFSDKHvbYOFsZe2kPQTcmkQEkaUMmM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772098089; c=relaxed/simple; bh=rgQOASaEYaTnnA/hyNxk7Xs4bJb1VJjlN0QqngKbpqc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Gmou6hIXE9qxbexFK+Ld106a2qZQOYKXxyIzH58ZbRmGyRmddOHvx0rbczM2Xl3hbXgwm7EGEMwT6DFLVsgjnDF5IkIXwTKDWNNasJbFnNICnN6JBlEyNcysnkwv9/rwWwhaG25JuFNM0Yfw5sc8mhs0JPf1+Agxa4euDu0wmb8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bxMLcIyF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bxMLcIyF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74B4CC19425; Thu, 26 Feb 2026 09:27:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772098088; bh=rgQOASaEYaTnnA/hyNxk7Xs4bJb1VJjlN0QqngKbpqc=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=bxMLcIyFw+HsCDeyhLytU64ia68W3qqqTiRWYJZwH3Mw5P62fDVb+xqcp7JewiW/Z Uor+8JtA2/ngkAi57ddJwXAhNRwK4FnRiag2qcFeLFHohKGzNFOncPccbl3B4UwJzK 2I+Z/R8tCwdDRMeLr970Z5dyn0pBN2sjVG44pk7uATFzbMZ2CReu7KJsQ6Jjn17aNH 2c+tIrAOa7h+FuxfQy/lvM7FgaFebx94+9/DKQ4fuUNsN54v6YRz00a1PEOZKlSLwo GhsgBSGsCRZCFNM7CQbuXcy3fNKZ9R7pkSENQS+SprmUecuAx3GKiFh7oPrk338gT2 7YPPx/HVe0jqg== Message-ID: <7334b702-f6a0-4ccf-8ac6-8426a90d1846@kernel.org> Date: Thu, 26 Feb 2026 10:27:54 +0100 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, dev.jain@arm.com, 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> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/26/26 02:29, 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 > --- > 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); > +} One thing: You can also void passing in "nr_pages" here, especially when you query the order below, and simply do unsigned int order = folio_order(folio); map_anon_folio_pte_nopf(folio, pte, vma, addr, uffd_wp); add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1U << order); count_mthp_stat(order, MTHP_STAT_ANON_FAULT_ALLOC); Apart from that Acked-by: David Hildenbrand (Arm) -- Cheers, David