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Thu, 26 Feb 2026 01:30:39 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.64.173]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1CD923003D8C; Thu, 26 Feb 2026 01:30:18 +0000 (UTC) From: Nico Pache To: 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, 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, npache@redhat.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 Subject: [PATCH mm-unstable v2 1/5] mm: consolidate anonymous folio PTE mapping into helpers Date: Wed, 25 Feb 2026 18:29:25 -0700 Message-ID: <20260226012929.169479-2-npache@redhat.com> In-Reply-To: <20260226012929.169479-1-npache@redhat.com> References: <20260226012929.169479-1-npache@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 9YbwYi_45OlN3yy6aRIIU4v1sHYWYGI64Rpg-_8imZQ_1772069441 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspamd-Queue-Id: AB3A9A0005 X-Stat-Signature: y5rwpji5qi5iorhoqoypzmiscndysbf3 X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1772069451-944929 X-HE-Meta: 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 6kRKQICz ahyXmcDuMeCov2yylXJ5+cqQRMdMONhZTCLkn8iu0Lm31wk/1EMevnq+Vp7LfbByVeErXMn2Y8ZcQdL7KHydXtUKlS7UpEltUBzkYJJKxkAeN2NIgr7TweGQ1pNdiCsxiIJDlHOAvGH8g6Cb27lRuiaYtSokxr1ShE4py9IW2lrFr1kBIjcVbDRZx7xiRM6DMjFolHqhvnw8vy7ZgTvBwFzn6iRHwTs0ORBehse+YqHzVFw1uUcnLXfUqhgg5o3oIAU3l4KHn71XlsDCvzcJfDIOqBSF/vyGH2sa1EuLesjRcblcamIgAcplXzGWWOkkKJFPIwxX8D1EF5uKpdydrHy0+aFJ/5cpmZfgCpayo/ujQhc1fVygVUeyvzB3Qn0jc4UNbIUk5WoXzHyeKHe83CXNjdcBQ9ys00u7W Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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); +} + /* * 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); -- 2.53.0