From 381a0a524e967a8bb887372af64433e442e846ad Mon Sep 17 00:00:00 2001 From: Lorenzo Stoakes Date: Thu, 3 Sep 2026 19:56:30 -0400 Subject: mm: avoid unnecessary use of is_swap_pmd() [ Upstream commit aa62204cb680d8ff32497181fc9e0dac4956f7e5 ] PMD 'non-swap' swap entries are currently used for PMD-level migration entries and device private entries. To add to the confusion in this terminology we use is_swap_pmd() in an inconsistent way similar to how is_swap_pte() was being used - sometimes adopting the convention that !pmd_none(), !pmd_present() implies PMD 'swap' entry, sometimes not. This patch handles the low-hanging fruit of cases where we can simply substitute other predicates for is_swap_pmd(). No functional change intended. Link: https://lkml.kernel.org/r/8a1704b36a009c18032d5bea4cb68e71448fbbe5.1762812360.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka Cc: Alexander Gordeev Cc: Alistair Popple Cc: Al Viro Cc: Arnd Bergmann Cc: Axel Rasmussen Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Byungchul Park Cc: Chengming Zhou Cc: Chris Li Cc: Christian Borntraeger Cc: Christian Brauner Cc: Claudio Imbrenda Cc: David Hildenbrand Cc: Dev Jain Cc: Gerald Schaefer Cc: Gregory Price Cc: Heiko Carstens Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Jan Kara Cc: Jann Horn Cc: Janosch Frank Cc: Jason Gunthorpe Cc: Joshua Hahn Cc: Kairui Song Cc: Kemeng Shi Cc: Lance Yang Cc: Leon Romanovsky Cc: Liam Howlett Cc: Mathew Brost Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Naoya Horiguchi Cc: Nhat Pham Cc: Nico Pache Cc: Oscar Salvador Cc: Pasha Tatashin Cc: Peter Xu Cc: Rakie Kim Cc: Rik van Riel Cc: Ryan Roberts Cc: SeongJae Park Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Vasily Gorbik Cc: Vlastimil Babka Cc: Wei Xu Cc: xu xin Cc: Yuanchu Xie Cc: Zi Yan Signed-off-by: Andrew Morton Stable-dep-of: f5407e9b697c ("mm/rmap: use huge_ptep_get() in try_to_unmap_one()") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/proc/task_mmu.c | 15 ++++++++++++--- include/linux/mm_types.h | 2 ++ include/linux/swapops.h | 12 +++++++++++- mm/huge_memory.c | 4 +++- mm/memory.c | 49 ++++++++++++++++++++++++++---------------------- mm/page_table_check.c | 12 ++++++++---- mm/rmap.c | 4 +++- 7 files changed, 66 insertions(+), 32 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 6dc16295e307..5c3d966b70f2 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1073,10 +1073,12 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr, bool present = false; struct folio *folio; + if (pmd_none(*pmd)) + return; if (pmd_present(*pmd)) { page = vm_normal_page_pmd(vma, addr, *pmd); present = true; - } else if (unlikely(thp_migration_supported() && is_swap_pmd(*pmd))) { + } else if (unlikely(thp_migration_supported())) { swp_entry_t entry = pmd_to_swp_entry(*pmd); if (is_pfn_swap_entry(entry)) @@ -2004,6 +2006,9 @@ static int pagemap_pmd_range_thp(pmd_t *pmdp, unsigned long addr, if (vma->vm_flags & VM_SOFTDIRTY) flags |= PM_SOFT_DIRTY; + if (pmd_none(pmd)) + goto populate_pagemap; + if (pmd_present(pmd)) { page = pmd_page(pmd); @@ -2014,7 +2019,7 @@ static int pagemap_pmd_range_thp(pmd_t *pmdp, unsigned long addr, flags |= PM_UFFD_WP; if (pm->show_pfn) frame = pmd_pfn(pmd) + idx; - } else if (thp_migration_supported() && is_swap_pmd(pmd)) { + } else if (thp_migration_supported()) { swp_entry_t entry = pmd_to_swp_entry(pmd); unsigned long offset; @@ -2041,6 +2046,7 @@ static int pagemap_pmd_range_thp(pmd_t *pmdp, unsigned long addr, flags |= PM_FILE; } +populate_pagemap: for (; addr != end; addr += PAGE_SIZE, idx++) { u64 cur_flags = flags; pagemap_entry_t pme; @@ -2411,6 +2417,9 @@ static unsigned long pagemap_thp_category(struct pagemap_scan_private *p, { unsigned long categories = PAGE_IS_HUGE; + if (pmd_none(pmd)) + return categories; + if (pmd_present(pmd)) { struct page *page; @@ -2428,7 +2437,7 @@ static unsigned long pagemap_thp_category(struct pagemap_scan_private *p, categories |= PAGE_IS_PFNZERO; if (pmd_soft_dirty(pmd)) categories |= PAGE_IS_SOFT_DIRTY; - } else if (is_swap_pmd(pmd)) { + } else { swp_entry_t swp; categories |= PAGE_IS_SWAPPED; diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 8b1045c51e0a..f9c552744b71 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -285,6 +285,8 @@ typedef struct { unsigned long val; } swp_entry_t; +typedef swp_entry_t softleaf_t; + #if defined(CONFIG_MEMCG) || defined(CONFIG_SLAB_OBJ_EXT) /* We have some extra room after the refcount in tail pages. */ #define NR_PAGES_IN_LARGE_FOLIO diff --git a/include/linux/swapops.h b/include/linux/swapops.h index 57aad87e46a6..1966b4890d46 100644 --- a/include/linux/swapops.h +++ b/include/linux/swapops.h @@ -120,6 +120,8 @@ static inline unsigned long swp_offset_pfn(swp_entry_t entry) return swp_offset(entry) & SWP_PFN_MASK; } +#define softleaf_to_pfn swp_offset_pfn + /* check whether a pte points to a swap entry */ static inline int is_swap_pte(pte_t pte) { @@ -139,6 +141,8 @@ static inline swp_entry_t pte_to_swp_entry(pte_t pte) return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry)); } +#define softleaf_from_pte pte_to_swp_entry + /* * Convert the arch-independent representation of a swp_entry_t into the * arch-dependent pte representation. @@ -572,7 +576,13 @@ static inline pmd_t swp_entry_to_pmd(swp_entry_t entry) static inline int pmd_is_migration_entry(pmd_t pmd) { - return is_swap_pmd(pmd) && is_migration_entry(pmd_to_swp_entry(pmd)); + swp_entry_t entry; + + if (pmd_present(pmd)) + return 0; + + entry = pmd_to_swp_entry(pmd); + return is_migration_entry(entry); } #else /* CONFIG_ARCH_ENABLE_THP_MIGRATION */ static inline int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw, diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 227aeffae8ee..8564a92d83f0 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2293,9 +2293,11 @@ static pmd_t move_soft_dirty_pmd(pmd_t pmd) static pmd_t clear_uffd_wp_pmd(pmd_t pmd) { + if (pmd_none(pmd)) + return pmd; if (pmd_present(pmd)) pmd = pmd_clear_uffd_wp(pmd); - else if (is_swap_pmd(pmd)) + else pmd = pmd_swp_clear_uffd_wp(pmd); return pmd; diff --git a/mm/memory.c b/mm/memory.c index 6b4cdb8bd8db..72793ec63107 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6320,34 +6320,39 @@ retry_pud: if (pmd_none(*vmf.pmd) && thp_vma_allowable_order(vma, vm_flags, TVA_PAGEFAULT, PMD_ORDER)) { ret = create_huge_pmd(&vmf); - if (!(ret & VM_FAULT_FALLBACK)) + if (ret & VM_FAULT_FALLBACK) + goto fallback; + else return ret; - } else { - vmf.orig_pmd = pmdp_get_lockless(vmf.pmd); + } - if (unlikely(is_swap_pmd(vmf.orig_pmd))) { - VM_BUG_ON(thp_migration_supported() && - !pmd_is_migration_entry(vmf.orig_pmd)); - if (pmd_is_migration_entry(vmf.orig_pmd)) - pmd_migration_entry_wait(mm, vmf.pmd); - return 0; - } - if (pmd_trans_huge(vmf.orig_pmd)) { - if (pmd_protnone(vmf.orig_pmd) && vma_is_accessible(vma)) - return do_huge_pmd_numa_page(&vmf); + vmf.orig_pmd = pmdp_get_lockless(vmf.pmd); + if (pmd_none(vmf.orig_pmd)) + goto fallback; - if ((flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) && - !pmd_write(vmf.orig_pmd)) { - ret = wp_huge_pmd(&vmf); - if (!(ret & VM_FAULT_FALLBACK)) - return ret; - } else { - huge_pmd_set_accessed(&vmf); - return 0; - } + if (unlikely(!pmd_present(vmf.orig_pmd))) { + VM_BUG_ON(thp_migration_supported() && + !pmd_is_migration_entry(vmf.orig_pmd)); + if (pmd_is_migration_entry(vmf.orig_pmd)) + pmd_migration_entry_wait(mm, vmf.pmd); + return 0; + } + if (pmd_trans_huge(vmf.orig_pmd)) { + if (pmd_protnone(vmf.orig_pmd) && vma_is_accessible(vma)) + return do_huge_pmd_numa_page(&vmf); + + if ((flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) && + !pmd_write(vmf.orig_pmd)) { + ret = wp_huge_pmd(&vmf); + if (!(ret & VM_FAULT_FALLBACK)) + return ret; + } else { + huge_pmd_set_accessed(&vmf); + return 0; } } +fallback: return handle_pte_fault(&vmf); } diff --git a/mm/page_table_check.c b/mm/page_table_check.c index 0a5ab62c9c59..91c4dacc41fb 100644 --- a/mm/page_table_check.c +++ b/mm/page_table_check.c @@ -223,10 +223,14 @@ EXPORT_SYMBOL(__page_table_check_ptes_set); static inline void page_table_check_pmd_flags(pmd_t pmd) { - if (pmd_present(pmd) && pmd_uffd_wp(pmd)) - WARN_ON_ONCE(pmd_write(pmd)); - else if (is_swap_pmd(pmd) && pmd_swp_uffd_wp(pmd)) - WARN_ON_ONCE(swap_cached_writable(pmd_to_swp_entry(pmd))); + if (pmd_present(pmd)) { + if (pmd_uffd_wp(pmd)) + WARN_ON_ONCE(pmd_write(pmd)); + } else if (pmd_swp_uffd_wp(pmd)) { + swp_entry_t entry = pmd_to_swp_entry(pmd); + + WARN_ON_ONCE(swap_cached_writable(entry)); + } } void __page_table_check_pmds_set(struct mm_struct *mm, pmd_t *pmdp, pmd_t pmd, diff --git a/mm/rmap.c b/mm/rmap.c index 4c78c7109909..6053eb822a26 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1991,7 +1991,9 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, if (likely(pte_present(pteval))) { pfn = pte_pfn(pteval); } else { - pfn = swp_offset_pfn(pte_to_swp_entry(pteval)); + const softleaf_t entry = softleaf_from_pte(pteval); + + pfn = softleaf_to_pfn(entry); VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio); } -- cgit v1.2.3