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Wed, 25 Mar 2026 11:41:14 +0000 (UTC) Received: from p1.redhat.com (unknown [10.2.14.4]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id AD69118002A6; Wed, 25 Mar 2026 11:40:53 +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, "Lorenzo Stoakes (Oracle)" Subject: [PATCH mm-unstable v4 1/5] mm: consolidate anonymous folio PTE mapping into helpers Date: Wed, 25 Mar 2026 05:40:18 -0600 Message-ID: <20260325114022.444081-2-npache@redhat.com> In-Reply-To: <20260325114022.444081-1-npache@redhat.com> References: <20260325114022.444081-1-npache@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: BGDZaPCtsZqwYshk7imZDWtZ8rGD4qCPravyYTmBgbg_1774438875 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Rspam-User: X-Stat-Signature: w7ogmkw5p15i5d4gg1f8sbytpxpkzaj6 X-Rspamd-Queue-Id: 9974B40011 X-Rspamd-Server: rspam09 X-HE-Tag: 1774438886-645564 X-HE-Meta: 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 vBT1nErv 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 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 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. The future khugepaged mTHP code calls this to handle mapping the new collapsed mTHP to its folio. 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. We can now leave nr_pages undeclared at the function intialization, and use the single page update_mmu_cache function to handle the zero page update. 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 (like khugpeaged mTHP support) Suggested-by: Lorenzo Stoakes (Oracle) Reviewed-by: Lorenzo Stoakes (Oracle) Reviewed-by: Dev Jain Reviewed-by: Lance Yang Acked-by: David Hildenbrand (Arm) Signed-off-by: Nico Pache --- include/linux/mm.h | 4 +++ mm/memory.c | 61 +++++++++++++++++++++++++++++++--------------- 2 files changed, 45 insertions(+), 20 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index eebf940058da..7edebadb2cb2 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -5226,4 +5226,8 @@ 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 bd93f34b6120..6396d32c348a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5292,6 +5292,37 @@ 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) +{ + const 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, bool uffd_wp) +{ + const 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, 1L << order); + count_mthp_stat(order, 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. @@ -5303,7 +5334,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf) unsigned long addr = vmf->address; struct folio *folio; vm_fault_t ret = 0; - int nr_pages = 1; + int nr_pages; pte_t entry; /* File mapping without ->vm_ops ? */ @@ -5338,7 +5369,13 @@ 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(vma, addr, vmf->pte); + goto unlock; } /* Allocate our own private page. */ @@ -5362,11 +5399,6 @@ 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; @@ -5388,19 +5420,8 @@ 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, + vmf_orig_pte_uffd_wp(vmf)); unlock: if (vmf->pte) pte_unmap_unlock(vmf->pte, vmf->ptl); -- 2.53.0