Merge tag 'mm-stable-2025-10-01-19-00' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:

 - "mm, swap: improve cluster scan strategy" from Kairui Song improves
   performance and reduces the failure rate of swap cluster allocation

 - "support large align and nid in Rust allocators" from Vitaly Wool
   permits Rust allocators to set NUMA node and large alignment when
   perforning slub and vmalloc reallocs

 - "mm/damon/vaddr: support stat-purpose DAMOS" from Yueyang Pan extend
   DAMOS_STAT's handling of the DAMON operations sets for virtual
   address spaces for ops-level DAMOS filters

 - "execute PROCMAP_QUERY ioctl under per-vma lock" from Suren
   Baghdasaryan reduces mmap_lock contention during reads of
   /proc/pid/maps

 - "mm/mincore: minor clean up for swap cache checking" from Kairui Song
   performs some cleanup in the swap code

 - "mm: vm_normal_page*() improvements" from David Hildenbrand provides
   code cleanup in the pagemap code

 - "add persistent huge zero folio support" from Pankaj Raghav provides
   a block layer speedup by optionalls making the
   huge_zero_pagepersistent, instead of releasing it when its refcount
   falls to zero

 - "kho: fixes and cleanups" from Mike Rapoport adds a few touchups to
   the recently added Kexec Handover feature

 - "mm: make mm->flags a bitmap and 64-bit on all arches" from Lorenzo
   Stoakes turns mm_struct.flags into a bitmap. To end the constant
   struggle with space shortage on 32-bit conflicting with 64-bit's
   needs

 - "mm/swapfile.c and swap.h cleanup" from Chris Li cleans up some swap
   code

 - "selftests/mm: Fix false positives and skip unsupported tests" from
   Donet Tom fixes a few things in our selftests code

 - "prctl: extend PR_SET_THP_DISABLE to only provide THPs when advised"
   from David Hildenbrand "allows individual processes to opt-out of
   THP=always into THP=madvise, without affecting other workloads on the
   system".

   It's a long story - the [1/N] changelog spells out the considerations

 - "Add and use memdesc_flags_t" from Matthew Wilcox gets us started on
   the memdesc project. Please see

      https://kernelnewbies.org/MatthewWilcox/Memdescs and
      https://blogs.oracle.com/linux/post/introducing-memdesc

 - "Tiny optimization for large read operations" from Chi Zhiling
   improves the efficiency of the pagecache read path

 - "Better split_huge_page_test result check" from Zi Yan improves our
   folio splitting selftest code

 - "test that rmap behaves as expected" from Wei Yang adds some rmap
   selftests

 - "remove write_cache_pages()" from Christoph Hellwig removes that
   function and converts its two remaining callers

 - "selftests/mm: uffd-stress fixes" from Dev Jain fixes some UFFD
   selftests issues

 - "introduce kernel file mapped folios" from Boris Burkov introduces
   the concept of "kernel file pages". Using these permits btrfs to
   account its metadata pages to the root cgroup, rather than to the
   cgroups of random inappropriate tasks

 - "mm/pageblock: improve readability of some pageblock handling" from
   Wei Yang provides some readability improvements to the page allocator
   code

 - "mm/damon: support ARM32 with LPAE" from SeongJae Park teaches DAMON
   to understand arm32 highmem

 - "tools: testing: Use existing atomic.h for vma/maple tests" from
   Brendan Jackman performs some code cleanups and deduplication under
   tools/testing/

 - "maple_tree: Fix testing for 32bit compiles" from Liam Howlett fixes
   a couple of 32-bit issues in tools/testing/radix-tree.c

 - "kasan: unify kasan_enabled() and remove arch-specific
   implementations" from Sabyrzhan Tasbolatov moves KASAN arch-specific
   initialization code into a common arch-neutral implementation

 - "mm: remove zpool" from Johannes Weiner removes zspool - an
   indirection layer which now only redirects to a single thing
   (zsmalloc)

 - "mm: task_stack: Stack handling cleanups" from Pasha Tatashin makes a
   couple of cleanups in the fork code

 - "mm: remove nth_page()" from David Hildenbrand makes rather a lot of
   adjustments at various nth_page() callsites, eventually permitting
   the removal of that undesirable helper function

 - "introduce kasan.write_only option in hw-tags" from Yeoreum Yun
   creates a KASAN read-only mode for ARM, using that architecture's
   memory tagging feature. It is felt that a read-only mode KASAN is
   suitable for use in production systems rather than debug-only

 - "mm: hugetlb: cleanup hugetlb folio allocation" from Kefeng Wang does
   some tidying in the hugetlb folio allocation code

 - "mm: establish const-correctness for pointer parameters" from Max
   Kellermann makes quite a number of the MM API functions more accurate
   about the constness of their arguments. This was getting in the way
   of subsystems (in this case CEPH) when they attempt to improving
   their own const/non-const accuracy

 - "Cleanup free_pages() misuse" from Vishal Moola fixes a number of
   code sites which were confused over when to use free_pages() vs
   __free_pages()

 - "Add Rust abstraction for Maple Trees" from Alice Ryhl makes the
   mapletree code accessible to Rust. Required by nouveau and by its
   forthcoming successor: the new Rust Nova driver

 - "selftests/mm: split_huge_page_test: split_pte_mapped_thp
   improvements" from David Hildenbrand adds a fix and some cleanups to
   the thp selftesting code

 - "mm, swap: introduce swap table as swap cache (phase I)" from Chris
   Li and Kairui Song is the first step along the path to implementing
   "swap tables" - a new approach to swap allocation and state tracking
   which is expected to yield speed and space improvements. This
   patchset itself yields a 5-20% performance benefit in some situations

 - "Some ptdesc cleanups" from Matthew Wilcox utilizes the new memdesc
   layer to clean up the ptdesc code a little

 - "Fix va_high_addr_switch.sh test failure" from Chunyu Hu fixes some
   issues in our 5-level pagetable selftesting code

 - "Minor fixes for memory allocation profiling" from Suren Baghdasaryan
   addresses a couple of minor issues in relatively new memory
   allocation profiling feature

 - "Small cleanups" from Matthew Wilcox has a few cleanups in
   preparation for more memdesc work

 - "mm/damon: add addr_unit for DAMON_LRU_SORT and DAMON_RECLAIM" from
   Quanmin Yan makes some changes to DAMON in furtherance of supporting
   arm highmem

 - "selftests/mm: Add -Wunreachable-code and fix warnings" from Muhammad
   Anjum adds that compiler check to selftests code and fixes the
   fallout, by removing dead code

 - "Improvements to Victim Process Thawing and OOM Reaper Traversal
   Order" from zhongjinji makes a number of improvements in the OOM
   killer: mainly thawing a more appropriate group of victim threads so
   they can release resources

 - "mm/damon: misc fixups and improvements for 6.18" from SeongJae Park
   is a bunch of small and unrelated fixups for DAMON

 - "mm/damon: define and use DAMON initialization check function" from
   SeongJae Park implement reliability and maintainability improvements
   to a recently-added bug fix

 - "mm/damon/stat: expose auto-tuned intervals and non-idle ages" from
   SeongJae Park provides additional transparency to userspace clients
   of the DAMON_STAT information

 - "Expand scope of khugepaged anonymous collapse" from Dev Jain removes
   some constraints on khubepaged's collapsing of anon VMAs. It also
   increases the success rate of MADV_COLLAPSE against an anon vma

 - "mm: do not assume file == vma->vm_file in compat_vma_mmap_prepare()"
   from Lorenzo Stoakes moves us further towards removal of
   file_operations.mmap(). This patchset concentrates upon clearing up
   the treatment of stacked filesystems

 - "mm: Improve mlock tracking for large folios" from Kiryl Shutsemau
   provides some fixes and improvements to mlock's tracking of large
   folios. /proc/meminfo's "Mlocked" field became more accurate

 - "mm/ksm: Fix incorrect accounting of KSM counters during fork" from
   Donet Tom fixes several user-visible KSM stats inaccuracies across
   forks and adds selftest code to verify these counters

 - "mm_slot: fix the usage of mm_slot_entry" from Wei Yang addresses
   some potential but presently benign issues in KSM's mm_slot handling

* tag 'mm-stable-2025-10-01-19-00' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (372 commits)
  mm: swap: check for stable address space before operating on the VMA
  mm: convert folio_page() back to a macro
  mm/khugepaged: use start_addr/addr for improved readability
  hugetlbfs: skip VMAs without shareable locks in hugetlb_vmdelete_list
  alloc_tag: fix boot failure due to NULL pointer dereference
  mm: silence data-race in update_hiwater_rss
  mm/memory-failure: don't select MEMORY_ISOLATION
  mm/khugepaged: remove definition of struct khugepaged_mm_slot
  mm/ksm: get mm_slot by mm_slot_entry() when slot is !NULL
  hugetlb: increase number of reserving hugepages via cmdline
  selftests/mm: add fork inheritance test for ksm_merging_pages counter
  mm/ksm: fix incorrect KSM counter handling in mm_struct during fork
  drivers/base/node: fix double free in register_one_node()
  mm: remove PMD alignment constraint in execmem_vmalloc()
  mm/memory_hotplug: fix typo 'esecially' -> 'especially'
  mm/rmap: improve mlock tracking for large folios
  mm/filemap: map entire large folio faultaround
  mm/fault: try to map the entire file folio in finish_fault()
  mm/rmap: mlock large folios in try_to_unmap_one()
  mm/rmap: fix a mlock race condition in folio_referenced_one()
  ...

1 files changed, 121 insertions, 125 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9c38a95e9f09..5acca24bbabb 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -99,12 +99,12 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma)
 
 unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
 					 vm_flags_t vm_flags,
-					 unsigned long tva_flags,
+					 enum tva_type type,
 					 unsigned long orders)
 {
-	bool smaps = tva_flags & TVA_SMAPS;
-	bool in_pf = tva_flags & TVA_IN_PF;
-	bool enforce_sysfs = tva_flags & TVA_ENFORCE_SYSFS;
+	const bool smaps = type == TVA_SMAPS;
+	const bool in_pf = type == TVA_PAGEFAULT;
+	const bool forced_collapse = type == TVA_FORCED_COLLAPSE;
 	unsigned long supported_orders;
 
 	/* Check the intersection of requested and supported orders. */
@@ -122,7 +122,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
 	if (!vma->vm_mm)		/* vdso */
 		return 0;
 
-	if (thp_disabled_by_hw() || vma_thp_disabled(vma, vm_flags))
+	if (thp_disabled_by_hw() || vma_thp_disabled(vma, vm_flags, forced_collapse))
 		return 0;
 
 	/* khugepaged doesn't collapse DAX vma, but page fault is fine. */
@@ -167,14 +167,14 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
 	if (!in_pf && shmem_file(vma->vm_file))
 		return orders & shmem_allowable_huge_orders(file_inode(vma->vm_file),
 						   vma, vma->vm_pgoff, 0,
-						   !enforce_sysfs);
+						   forced_collapse);
 
 	if (!vma_is_anonymous(vma)) {
 		/*
-		 * Enforce sysfs THP requirements as necessary. Anonymous vmas
+		 * Enforce THP collapse requirements as necessary. Anonymous vmas
 		 * were already handled in thp_vma_allowable_orders().
 		 */
-		if (enforce_sysfs &&
+		if (!forced_collapse &&
 		    (!hugepage_global_enabled() || (!(vm_flags & VM_HUGEPAGE) &&
 						    !hugepage_global_always())))
 			return 0;
@@ -207,7 +207,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
 	return orders;
 }
 
-static bool get_huge_zero_page(void)
+static bool get_huge_zero_folio(void)
 {
 	struct folio *zero_folio;
 retry:
@@ -237,7 +237,7 @@ retry:
 	return true;
 }
 
-static void put_huge_zero_page(void)
+static void put_huge_zero_folio(void)
 {
 	/*
 	 * Counter should never go to zero here. Only shrinker can put
@@ -248,33 +248,39 @@ static void put_huge_zero_page(void)
 
 struct folio *mm_get_huge_zero_folio(struct mm_struct *mm)
 {
-	if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
+	if (IS_ENABLED(CONFIG_PERSISTENT_HUGE_ZERO_FOLIO))
+		return huge_zero_folio;
+
+	if (mm_flags_test(MMF_HUGE_ZERO_FOLIO, mm))
 		return READ_ONCE(huge_zero_folio);
 
-	if (!get_huge_zero_page())
+	if (!get_huge_zero_folio())
 		return NULL;
 
-	if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
-		put_huge_zero_page();
+	if (mm_flags_test_and_set(MMF_HUGE_ZERO_FOLIO, mm))
+		put_huge_zero_folio();
 
 	return READ_ONCE(huge_zero_folio);
 }
 
 void mm_put_huge_zero_folio(struct mm_struct *mm)
 {
-	if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
-		put_huge_zero_page();
+	if (IS_ENABLED(CONFIG_PERSISTENT_HUGE_ZERO_FOLIO))
+		return;
+
+	if (mm_flags_test(MMF_HUGE_ZERO_FOLIO, mm))
+		put_huge_zero_folio();
 }
 
-static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
-					struct shrink_control *sc)
+static unsigned long shrink_huge_zero_folio_count(struct shrinker *shrink,
+						  struct shrink_control *sc)
 {
 	/* we can free zero page only if last reference remains */
 	return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
 }
 
-static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
-				       struct shrink_control *sc)
+static unsigned long shrink_huge_zero_folio_scan(struct shrinker *shrink,
+						 struct shrink_control *sc)
 {
 	if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 		struct folio *zero_folio = xchg(&huge_zero_folio, NULL);
@@ -287,7 +293,7 @@ static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 	return 0;
 }
 
-static struct shrinker *huge_zero_page_shrinker;
+static struct shrinker *huge_zero_folio_shrinker;
 
 #ifdef CONFIG_SYSFS
 static ssize_t enabled_show(struct kobject *kobj,
@@ -849,33 +855,47 @@ static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
 
 static int __init thp_shrinker_init(void)
 {
-	huge_zero_page_shrinker = shrinker_alloc(0, "thp-zero");
-	if (!huge_zero_page_shrinker)
-		return -ENOMEM;
-
 	deferred_split_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE |
 						 SHRINKER_MEMCG_AWARE |
 						 SHRINKER_NONSLAB,
 						 "thp-deferred_split");
-	if (!deferred_split_shrinker) {
-		shrinker_free(huge_zero_page_shrinker);
+	if (!deferred_split_shrinker)
 		return -ENOMEM;
-	}
-
-	huge_zero_page_shrinker->count_objects = shrink_huge_zero_page_count;
-	huge_zero_page_shrinker->scan_objects = shrink_huge_zero_page_scan;
-	shrinker_register(huge_zero_page_shrinker);
 
 	deferred_split_shrinker->count_objects = deferred_split_count;
 	deferred_split_shrinker->scan_objects = deferred_split_scan;
 	shrinker_register(deferred_split_shrinker);
 
+	if (IS_ENABLED(CONFIG_PERSISTENT_HUGE_ZERO_FOLIO)) {
+		/*
+		 * Bump the reference of the huge_zero_folio and do not
+		 * initialize the shrinker.
+		 *
+		 * huge_zero_folio will always be NULL on failure. We assume
+		 * that get_huge_zero_folio() will most likely not fail as
+		 * thp_shrinker_init() is invoked early on during boot.
+		 */
+		if (!get_huge_zero_folio())
+			pr_warn("Allocating persistent huge zero folio failed\n");
+		return 0;
+	}
+
+	huge_zero_folio_shrinker = shrinker_alloc(0, "thp-zero");
+	if (!huge_zero_folio_shrinker) {
+		shrinker_free(deferred_split_shrinker);
+		return -ENOMEM;
+	}
+
+	huge_zero_folio_shrinker->count_objects = shrink_huge_zero_folio_count;
+	huge_zero_folio_shrinker->scan_objects = shrink_huge_zero_folio_scan;
+	shrinker_register(huge_zero_folio_shrinker);
+
 	return 0;
 }
 
 static void __init thp_shrinker_exit(void)
 {
-	shrinker_free(huge_zero_page_shrinker);
+	shrinker_free(huge_zero_folio_shrinker);
 	shrinker_free(deferred_split_shrinker);
 }
 
@@ -911,7 +931,7 @@ static int __init hugepage_init(void)
 	 * where the extra memory used could hurt more than TLB overhead
 	 * is likely to save.  The admin can still enable it through /sys.
 	 */
-	if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
+	if (totalram_pages() < MB_TO_PAGES(512)) {
 		transparent_hugepage_flags = 0;
 		return 0;
 	}
@@ -1125,7 +1145,7 @@ static unsigned long __thp_get_unmapped_area(struct file *filp,
 
 	off_sub = (off - ret) & (size - 1);
 
-	if (test_bit(MMF_TOPDOWN, &current->mm->flags) && !off_sub)
+	if (mm_flags_test(MMF_TOPDOWN, current->mm) && !off_sub)
 		return ret + size;
 
 	ret += off_sub;
@@ -1309,6 +1329,7 @@ static void set_huge_zero_folio(pgtable_t pgtable, struct mm_struct *mm,
 {
 	pmd_t entry;
 	entry = folio_mk_pmd(zero_folio, vma->vm_page_prot);
+	entry = pmd_mkspecial(entry);
 	pgtable_trans_huge_deposit(mm, pmd, pgtable);
 	set_pmd_at(mm, haddr, pmd, entry);
 	mm_inc_nr_ptes(mm);
@@ -1379,15 +1400,25 @@ struct folio_or_pfn {
 	bool is_folio;
 };
 
-static int insert_pmd(struct vm_area_struct *vma, unsigned long addr,
+static vm_fault_t insert_pmd(struct vm_area_struct *vma, unsigned long addr,
 		pmd_t *pmd, struct folio_or_pfn fop, pgprot_t prot,
-		bool write, pgtable_t pgtable)
+		bool write)
 {
 	struct mm_struct *mm = vma->vm_mm;
+	pgtable_t pgtable = NULL;
+	spinlock_t *ptl;
 	pmd_t entry;
 
-	lockdep_assert_held(pmd_lockptr(mm, pmd));
+	if (addr < vma->vm_start || addr >= vma->vm_end)
+		return VM_FAULT_SIGBUS;
+
+	if (arch_needs_pgtable_deposit()) {
+		pgtable = pte_alloc_one(vma->vm_mm);
+		if (!pgtable)
+			return VM_FAULT_OOM;
+	}
 
+	ptl = pmd_lock(mm, pmd);
 	if (!pmd_none(*pmd)) {
 		const unsigned long pfn = fop.is_folio ? folio_pfn(fop.folio) :
 					  fop.pfn;
@@ -1395,23 +1426,26 @@ static int insert_pmd(struct vm_area_struct *vma, unsigned long addr,
 		if (write) {
 			if (pmd_pfn(*pmd) != pfn) {
 				WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
-				return -EEXIST;
+				goto out_unlock;
 			}
 			entry = pmd_mkyoung(*pmd);
 			entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
 			if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
 				update_mmu_cache_pmd(vma, addr, pmd);
 		}
-
-		return -EEXIST;
+		goto out_unlock;
 	}
 
 	if (fop.is_folio) {
 		entry = folio_mk_pmd(fop.folio, vma->vm_page_prot);
 
-		folio_get(fop.folio);
-		folio_add_file_rmap_pmd(fop.folio, &fop.folio->page, vma);
-		add_mm_counter(mm, mm_counter_file(fop.folio), HPAGE_PMD_NR);
+		if (is_huge_zero_folio(fop.folio)) {
+			entry = pmd_mkspecial(entry);
+		} else {
+			folio_get(fop.folio);
+			folio_add_file_rmap_pmd(fop.folio, &fop.folio->page, vma);
+			add_mm_counter(mm, mm_counter_file(fop.folio), HPAGE_PMD_NR);
+		}
 	} else {
 		entry = pmd_mkhuge(pfn_pmd(fop.pfn, prot));
 		entry = pmd_mkspecial(entry);
@@ -1424,11 +1458,17 @@ static int insert_pmd(struct vm_area_struct *vma, unsigned long addr,
 	if (pgtable) {
 		pgtable_trans_huge_deposit(mm, pmd, pgtable);
 		mm_inc_nr_ptes(mm);
+		pgtable = NULL;
 	}
 
 	set_pmd_at(mm, addr, pmd, entry);
 	update_mmu_cache_pmd(vma, addr, pmd);
-	return 0;
+
+out_unlock:
+	spin_unlock(ptl);
+	if (pgtable)
+		pte_free(mm, pgtable);
+	return VM_FAULT_NOPAGE;
 }
 
 /**
@@ -1450,9 +1490,6 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, unsigned long pfn,
 	struct folio_or_pfn fop = {
 		.pfn = pfn,
 	};
-	pgtable_t pgtable = NULL;
-	spinlock_t *ptl;
-	int error;
 
 	/*
 	 * If we had pmd_special, we could avoid all these restrictions,
@@ -1464,25 +1501,9 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, unsigned long pfn,
 						(VM_PFNMAP|VM_MIXEDMAP));
 	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 
-	if (addr < vma->vm_start || addr >= vma->vm_end)
-		return VM_FAULT_SIGBUS;
-
-	if (arch_needs_pgtable_deposit()) {
-		pgtable = pte_alloc_one(vma->vm_mm);
-		if (!pgtable)
-			return VM_FAULT_OOM;
-	}
-
 	pfnmap_setup_cachemode_pfn(pfn, &pgprot);
 
-	ptl = pmd_lock(vma->vm_mm, vmf->pmd);
-	error = insert_pmd(vma, addr, vmf->pmd, fop, pgprot, write,
-			   pgtable);
-	spin_unlock(ptl);
-	if (error && pgtable)
-		pte_free(vma->vm_mm, pgtable);
-
-	return VM_FAULT_NOPAGE;
+	return insert_pmd(vma, addr, vmf->pmd, fop, pgprot, write);
 }
 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
 
@@ -1491,35 +1512,15 @@ vm_fault_t vmf_insert_folio_pmd(struct vm_fault *vmf, struct folio *folio,
 {
 	struct vm_area_struct *vma = vmf->vma;
 	unsigned long addr = vmf->address & PMD_MASK;
-	struct mm_struct *mm = vma->vm_mm;
 	struct folio_or_pfn fop = {
 		.folio = folio,
 		.is_folio = true,
 	};
-	spinlock_t *ptl;
-	pgtable_t pgtable = NULL;
-	int error;
-
-	if (addr < vma->vm_start || addr >= vma->vm_end)
-		return VM_FAULT_SIGBUS;
 
 	if (WARN_ON_ONCE(folio_order(folio) != PMD_ORDER))
 		return VM_FAULT_SIGBUS;
 
-	if (arch_needs_pgtable_deposit()) {
-		pgtable = pte_alloc_one(vma->vm_mm);
-		if (!pgtable)
-			return VM_FAULT_OOM;
-	}
-
-	ptl = pmd_lock(mm, vmf->pmd);
-	error = insert_pmd(vma, addr, vmf->pmd, fop, vma->vm_page_prot,
-			   write, pgtable);
-	spin_unlock(ptl);
-	if (error && pgtable)
-		pte_free(mm, pgtable);
-
-	return VM_FAULT_NOPAGE;
+	return insert_pmd(vma, addr, vmf->pmd, fop, vma->vm_page_prot, write);
 }
 EXPORT_SYMBOL_GPL(vmf_insert_folio_pmd);
 
@@ -1531,25 +1532,30 @@ static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
 	return pud;
 }
 
-static void insert_pud(struct vm_area_struct *vma, unsigned long addr,
+static vm_fault_t insert_pud(struct vm_area_struct *vma, unsigned long addr,
 		pud_t *pud, struct folio_or_pfn fop, pgprot_t prot, bool write)
 {
 	struct mm_struct *mm = vma->vm_mm;
+	spinlock_t *ptl;
 	pud_t entry;
 
+	if (addr < vma->vm_start || addr >= vma->vm_end)
+		return VM_FAULT_SIGBUS;
+
+	ptl = pud_lock(mm, pud);
 	if (!pud_none(*pud)) {
 		const unsigned long pfn = fop.is_folio ? folio_pfn(fop.folio) :
 					  fop.pfn;
 
 		if (write) {
 			if (WARN_ON_ONCE(pud_pfn(*pud) != pfn))
-				return;
+				goto out_unlock;
 			entry = pud_mkyoung(*pud);
 			entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
 			if (pudp_set_access_flags(vma, addr, pud, entry, 1))
 				update_mmu_cache_pud(vma, addr, pud);
 		}
-		return;
+		goto out_unlock;
 	}
 
 	if (fop.is_folio) {
@@ -1568,6 +1574,9 @@ static void insert_pud(struct vm_area_struct *vma, unsigned long addr,
 	}
 	set_pud_at(mm, addr, pud, entry);
 	update_mmu_cache_pud(vma, addr, pud);
+out_unlock:
+	spin_unlock(ptl);
+	return VM_FAULT_NOPAGE;
 }
 
 /**
@@ -1589,7 +1598,6 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, unsigned long pfn,
 	struct folio_or_pfn fop = {
 		.pfn = pfn,
 	};
-	spinlock_t *ptl;
 
 	/*
 	 * If we had pud_special, we could avoid all these restrictions,
@@ -1601,16 +1609,9 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, unsigned long pfn,
 						(VM_PFNMAP|VM_MIXEDMAP));
 	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
 
-	if (addr < vma->vm_start || addr >= vma->vm_end)
-		return VM_FAULT_SIGBUS;
-
 	pfnmap_setup_cachemode_pfn(pfn, &pgprot);
 
-	ptl = pud_lock(vma->vm_mm, vmf->pud);
-	insert_pud(vma, addr, vmf->pud, fop, pgprot, write);
-	spin_unlock(ptl);
-
-	return VM_FAULT_NOPAGE;
+	return insert_pud(vma, addr, vmf->pud, fop, pgprot, write);
 }
 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
 
@@ -1627,25 +1628,15 @@ vm_fault_t vmf_insert_folio_pud(struct vm_fault *vmf, struct folio *folio,
 {
 	struct vm_area_struct *vma = vmf->vma;
 	unsigned long addr = vmf->address & PUD_MASK;
-	pud_t *pud = vmf->pud;
-	struct mm_struct *mm = vma->vm_mm;
 	struct folio_or_pfn fop = {
 		.folio = folio,
 		.is_folio = true,
 	};
-	spinlock_t *ptl;
-
-	if (addr < vma->vm_start || addr >= vma->vm_end)
-		return VM_FAULT_SIGBUS;
 
 	if (WARN_ON_ONCE(folio_order(folio) != PUD_ORDER))
 		return VM_FAULT_SIGBUS;
 
-	ptl = pud_lock(mm, pud);
-	insert_pud(vma, addr, vmf->pud, fop, vma->vm_page_prot, write);
-	spin_unlock(ptl);
-
-	return VM_FAULT_NOPAGE;
+	return insert_pud(vma, addr, vmf->pud, fop, vma->vm_page_prot, write);
 }
 EXPORT_SYMBOL_GPL(vmf_insert_folio_pud);
 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
@@ -1675,7 +1666,8 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 	int ret = -ENOMEM;
 
 	pmd = pmdp_get_lockless(src_pmd);
-	if (unlikely(pmd_present(pmd) && pmd_special(pmd))) {
+	if (unlikely(pmd_present(pmd) && pmd_special(pmd) &&
+		     !is_huge_zero_pmd(pmd))) {
 		dst_ptl = pmd_lock(dst_mm, dst_pmd);
 		src_ptl = pmd_lockptr(src_mm, src_pmd);
 		spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
@@ -3310,8 +3302,8 @@ static void __split_folio_to_order(struct folio *folio, int old_order,
 		 * unreferenced sub-pages of an anonymous THP: we can simply drop
 		 * PG_anon_exclusive (-> PG_mappedtodisk) for these here.
 		 */
-		new_folio->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
-		new_folio->flags |= (folio->flags &
+		new_folio->flags.f &= ~PAGE_FLAGS_CHECK_AT_PREP;
+		new_folio->flags.f |= (folio->flags.f &
 				((1L << PG_referenced) |
 				 (1L << PG_swapbacked) |
 				 (1L << PG_swapcache) |
@@ -3728,7 +3720,7 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
 	/* Prevent deferred_split_scan() touching ->_refcount */
 	spin_lock(&ds_queue->split_queue_lock);
 	if (folio_ref_freeze(folio, 1 + extra_pins)) {
-		struct address_space *swap_cache = NULL;
+		struct swap_cluster_info *ci = NULL;
 		struct lruvec *lruvec;
 		int expected_refs;
 
@@ -3772,8 +3764,7 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
 				goto fail;
 			}
 
-			swap_cache = swap_address_space(folio->swap);
-			xa_lock(&swap_cache->i_pages);
+			ci = swap_cluster_get_and_lock(folio);
 		}
 
 		/* lock lru list/PageCompound, ref frozen by page_ref_freeze */
@@ -3805,10 +3796,8 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
 			 * Anonymous folio with swap cache.
 			 * NOTE: shmem in swap cache is not supported yet.
 			 */
-			if (swap_cache) {
-				__xa_store(&swap_cache->i_pages,
-					   swap_cache_index(new_folio->swap),
-					   new_folio, 0);
+			if (ci) {
+				__swap_cache_replace_folio(ci, folio, new_folio);
 				continue;
 			}
 
@@ -3843,8 +3832,8 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
 
 		unlock_page_lruvec(lruvec);
 
-		if (swap_cache)
-			xa_unlock(&swap_cache->i_pages);
+		if (ci)
+			swap_cluster_unlock(ci);
 	} else {
 		spin_unlock(&ds_queue->split_queue_lock);
 		ret = -EAGAIN;
@@ -4186,6 +4175,13 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
 		bool underused = false;
 
 		if (!folio_test_partially_mapped(folio)) {
+			/*
+			 * See try_to_map_unused_to_zeropage(): we cannot
+			 * optimize zero-filled pages after splitting an
+			 * mlocked folio.
+			 */
+			if (folio_test_mlocked(folio))
+				goto next;
 			underused = thp_underused(folio);
 			if (!underused)
 				goto next;
@@ -4327,8 +4323,8 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
 		goto out;
 	}
 
-	pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx]\n",
-		 pid, vaddr_start, vaddr_end);
+	pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx], new_order: %u, in_folio_offset: %ld\n",
+		 pid, vaddr_start, vaddr_end, new_order, in_folio_offset);
 
 	mmap_read_lock(mm);
 	/*
@@ -4438,8 +4434,8 @@ static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
 	if (IS_ERR(candidate))
 		goto out;
 
-	pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n",
-		 file_path, off_start, off_end);
+	pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx], new_order: %u, in_folio_offset: %ld\n",
+		 file_path, off_start, off_end, new_order, in_folio_offset);
 
 	mapping = candidate->f_mapping;
 	min_order = mapping_min_folio_order(mapping);