Merge tag 'mm-stable-2025-05-31-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:

 - "Add folio_mk_pte()" from Matthew Wilcox simplifies the act of
   creating a pte which addresses the first page in a folio and reduces
   the amount of plumbing which architecture must implement to provide
   this.

 - "Misc folio patches for 6.16" from Matthew Wilcox is a shower of
   largely unrelated folio infrastructure changes which clean things up
   and better prepare us for future work.

 - "memory,x86,acpi: hotplug memory alignment advisement" from Gregory
   Price adds early-init code to prevent x86 from leaving physical
   memory unused when physical address regions are not aligned to memory
   block size.

 - "mm/compaction: allow more aggressive proactive compaction" from
   Michal Clapinski provides some tuning of the (sadly, hard-coded (more
   sadly, not auto-tuned)) thresholds for our invokation of proactive
   compaction. In a simple test case, the reduction of a guest VM's
   memory consumption was dramatic.

 - "Minor cleanups and improvements to swap freeing code" from Kemeng
   Shi provides some code cleaups and a small efficiency improvement to
   this part of our swap handling code.

 - "ptrace: introduce PTRACE_SET_SYSCALL_INFO API" from Dmitry Levin
   adds the ability for a ptracer to modify syscalls arguments. At this
   time we can alter only "system call information that are used by
   strace system call tampering, namely, syscall number, syscall
   arguments, and syscall return value.

   This series should have been incorporated into mm.git's "non-MM"
   branch, but I goofed.

 - "fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions" from
   Andrei Vagin extends the info returned by the PAGEMAP_SCAN ioctl
   against /proc/pid/pagemap. This permits CRIU to more efficiently get
   at the info about guard regions.

 - "Fix parameter passed to page_mapcount_is_type()" from Gavin Shan
   implements that fix. No runtime effect is expected because
   validate_page_before_insert() happens to fix up this error.

 - "kernel/events/uprobes: uprobe_write_opcode() rewrite" from David
   Hildenbrand basically brings uprobe text poking into the current
   decade. Remove a bunch of hand-rolled implementation in favor of
   using more current facilities.

 - "mm/ptdump: Drop assumption that pxd_val() is u64" from Anshuman
   Khandual provides enhancements and generalizations to the pte dumping
   code. This might be needed when 128-bit Page Table Descriptors are
   enabled for ARM.

 - "Always call constructor for kernel page tables" from Kevin Brodsky
   ensures that the ctor/dtor is always called for kernel pgtables, as
   it already is for user pgtables.

   This permits the addition of more functionality such as "insert hooks
   to protect page tables". This change does result in various
   architectures performing unnecesary work, but this is fixed up where
   it is anticipated to occur.

 - "Rust support for mm_struct, vm_area_struct, and mmap" from Alice
   Ryhl adds plumbing to permit Rust access to core MM structures.

 - "fix incorrectly disallowed anonymous VMA merges" from Lorenzo
   Stoakes takes advantage of some VMA merging opportunities which we've
   been missing for 15 years.

 - "mm/madvise: batch tlb flushes for MADV_DONTNEED and MADV_FREE" from
   SeongJae Park optimizes process_madvise()'s TLB flushing.

   Instead of flushing each address range in the provided iovec, we
   batch the flushing across all the iovec entries. The syscall's cost
   was approximately halved with a microbenchmark which was designed to
   load this particular operation.

 - "Track node vacancy to reduce worst case allocation counts" from
   Sidhartha Kumar makes the maple tree smarter about its node
   preallocation.

   stress-ng mmap performance increased by single-digit percentages and
   the amount of unnecessarily preallocated memory was dramaticelly
   reduced.

 - "mm/gup: Minor fix, cleanup and improvements" from Baoquan He removes
   a few unnecessary things which Baoquan noted when reading the code.

 - ""Enhance sysfs handling for memory hotplug in weighted interleave"
   from Rakie Kim "enhances the weighted interleave policy in the memory
   management subsystem by improving sysfs handling, fixing memory
   leaks, and introducing dynamic sysfs updates for memory hotplug
   support". Fixes things on error paths which we are unlikely to hit.

 - "mm/damon: auto-tune DAMOS for NUMA setups including tiered memory"
   from SeongJae Park introduces new DAMOS quota goal metrics which
   eliminate the manual tuning which is required when utilizing DAMON
   for memory tiering.

 - "mm/vmalloc.c: code cleanup and improvements" from Baoquan He
   provides cleanups and small efficiency improvements which Baoquan
   found via code inspection.

 - "vmscan: enforce mems_effective during demotion" from Gregory Price
   changes reclaim to respect cpuset.mems_effective during demotion when
   possible. because presently, reclaim explicitly ignores
   cpuset.mems_effective when demoting, which may cause the cpuset
   settings to violated.

   This is useful for isolating workloads on a multi-tenant system from
   certain classes of memory more consistently.

 - "Clean up split_huge_pmd_locked() and remove unnecessary folio
   pointers" from Gavin Guo provides minor cleanups and efficiency gains
   in in the huge page splitting and migrating code.

 - "Use kmem_cache for memcg alloc" from Huan Yang creates a slab cache
   for `struct mem_cgroup', yielding improved memory utilization.

 - "add max arg to swappiness in memory.reclaim and lru_gen" from
   Zhongkun He adds a new "max" argument to the "swappiness=" argument
   for memory.reclaim MGLRU's lru_gen.

   This directs proactive reclaim to reclaim from only anon folios
   rather than file-backed folios.

 - "kexec: introduce Kexec HandOver (KHO)" from Mike Rapoport is the
   first step on the path to permitting the kernel to maintain existing
   VMs while replacing the host kernel via file-based kexec. At this
   time only memblock's reserve_mem is preserved.

 - "mm: Introduce for_each_valid_pfn()" from David Woodhouse provides
   and uses a smarter way of looping over a pfn range. By skipping
   ranges of invalid pfns.

 - "sched/numa: Skip VMA scanning on memory pinned to one NUMA node via
   cpuset.mems" from Libo Chen removes a lot of pointless VMA scanning
   when a task is pinned a single NUMA mode.

   Dramatic performance benefits were seen in some real world cases.

 - "JFS: Implement migrate_folio for jfs_metapage_aops" from Shivank
   Garg addresses a warning which occurs during memory compaction when
   using JFS.

 - "move all VMA allocation, freeing and duplication logic to mm" from
   Lorenzo Stoakes moves some VMA code from kernel/fork.c into the more
   appropriate mm/vma.c.

 - "mm, swap: clean up swap cache mapping helper" from Kairui Song
   provides code consolidation and cleanups related to the folio_index()
   function.

 - "mm/gup: Cleanup memfd_pin_folios()" from Vishal Moola does that.

 - "memcg: Fix test_memcg_min/low test failures" from Waiman Long
   addresses some bogus failures which are being reported by the
   test_memcontrol selftest.

 - "eliminate mmap() retry merge, add .mmap_prepare hook" from Lorenzo
   Stoakes commences the deprecation of file_operations.mmap() in favor
   of the new file_operations.mmap_prepare().

   The latter is more restrictive and prevents drivers from messing with
   things in ways which, amongst other problems, may defeat VMA merging.

 - "memcg: decouple memcg and objcg stocks"" from Shakeel Butt decouples
   the per-cpu memcg charge cache from the objcg's one.

   This is a step along the way to making memcg and objcg charging
   NMI-safe, which is a BPF requirement.

 - "mm/damon: minor fixups and improvements for code, tests, and
   documents" from SeongJae Park is yet another batch of miscellaneous
   DAMON changes. Fix and improve minor problems in code, tests and
   documents.

 - "memcg: make memcg stats irq safe" from Shakeel Butt converts memcg
   stats to be irq safe. Another step along the way to making memcg
   charging and stats updates NMI-safe, a BPF requirement.

 - "Let unmap_hugepage_range() and several related functions take folio
   instead of page" from Fan Ni provides folio conversions in the
   hugetlb code.

* tag 'mm-stable-2025-05-31-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (285 commits)
  mm: pcp: increase pcp->free_count threshold to trigger free_high
  mm/hugetlb: convert use of struct page to folio in __unmap_hugepage_range()
  mm/hugetlb: refactor __unmap_hugepage_range() to take folio instead of page
  mm/hugetlb: refactor unmap_hugepage_range() to take folio instead of page
  mm/hugetlb: pass folio instead of page to unmap_ref_private()
  memcg: objcg stock trylock without irq disabling
  memcg: no stock lock for cpu hot-unplug
  memcg: make __mod_memcg_lruvec_state re-entrant safe against irqs
  memcg: make count_memcg_events re-entrant safe against irqs
  memcg: make mod_memcg_state re-entrant safe against irqs
  memcg: move preempt disable to callers of memcg_rstat_updated
  memcg: memcg_rstat_updated re-entrant safe against irqs
  mm: khugepaged: decouple SHMEM and file folios' collapse
  selftests/eventfd: correct test name and improve messages
  alloc_tag: check mem_profiling_support in alloc_tag_init
  Docs/damon: update titles and brief introductions to explain DAMOS
  selftests/damon/_damon_sysfs: read tried regions directories in order
  mm/damon/tests/core-kunit: add a test for damos_set_filters_default_reject()
  mm/damon/paddr: remove unused variable, folio_list, in damon_pa_stat()
  mm/damon/sysfs-schemes: fix wrong comment on damons_sysfs_quota_goal_metric_strs
  ...

1 files changed, 167 insertions, 37 deletions

diff --git a/mm/vma.c b/mm/vma.c
index a468d4c29c0c..1c6595f282e5 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -17,9 +17,13 @@ struct mmap_state {
 	unsigned long pglen;
 	unsigned long flags;
 	struct file *file;
+	pgprot_t page_prot;
+
+	/* User-defined fields, perhaps updated by .mmap_prepare(). */
+	const struct vm_operations_struct *vm_ops;
+	void *vm_private_data;
 
 	unsigned long charged;
-	bool retry_merge;
 
 	struct vm_area_struct *prev;
 	struct vm_area_struct *next;
@@ -40,6 +44,7 @@ struct mmap_state {
 		.pglen = PHYS_PFN(len_),				\
 		.flags = flags_,					\
 		.file = file_,						\
+		.page_prot = vm_get_page_prot(flags_),			\
 	}
 
 #define VMG_MMAP_STATE(name, map_, vma_)				\
@@ -57,6 +62,22 @@ struct mmap_state {
 		.state = VMA_MERGE_START,				\
 	}
 
+/*
+ * If, at any point, the VMA had unCoW'd mappings from parents, it will maintain
+ * more than one anon_vma_chain connecting it to more than one anon_vma. A merge
+ * would mean a wider range of folios sharing the root anon_vma lock, and thus
+ * potential lock contention, we do not wish to encourage merging such that this
+ * scales to a problem.
+ */
+static bool vma_had_uncowed_parents(struct vm_area_struct *vma)
+{
+	/*
+	 * The list_is_singular() test is to avoid merging VMA cloned from
+	 * parents. This can improve scalability caused by anon_vma lock.
+	 */
+	return vma && vma->anon_vma && !list_is_singular(&vma->anon_vma_chain);
+}
+
 static inline bool is_mergeable_vma(struct vma_merge_struct *vmg, bool merge_next)
 {
 	struct vm_area_struct *vma = merge_next ? vmg->next : vmg->prev;
@@ -82,24 +103,28 @@ static inline bool is_mergeable_vma(struct vma_merge_struct *vmg, bool merge_nex
 	return true;
 }
 
-static inline bool is_mergeable_anon_vma(struct anon_vma *anon_vma1,
-		 struct anon_vma *anon_vma2, struct vm_area_struct *vma)
+static bool is_mergeable_anon_vma(struct vma_merge_struct *vmg, bool merge_next)
 {
+	struct vm_area_struct *tgt = merge_next ? vmg->next : vmg->prev;
+	struct vm_area_struct *src = vmg->middle; /* exisitng merge case. */
+	struct anon_vma *tgt_anon = tgt->anon_vma;
+	struct anon_vma *src_anon = vmg->anon_vma;
+
 	/*
-	 * The list_is_singular() test is to avoid merging VMA cloned from
-	 * parents. This can improve scalability caused by anon_vma lock.
+	 * We _can_ have !src, vmg->anon_vma via copy_vma(). In this instance we
+	 * will remove the existing VMA's anon_vma's so there's no scalability
+	 * concerns.
 	 */
-	if ((!anon_vma1 || !anon_vma2) && (!vma ||
-		list_is_singular(&vma->anon_vma_chain)))
-		return true;
-	return anon_vma1 == anon_vma2;
-}
+	VM_WARN_ON(src && src_anon != src->anon_vma);
 
-/* Are the anon_vma's belonging to each VMA compatible with one another? */
-static inline bool are_anon_vmas_compatible(struct vm_area_struct *vma1,
-					    struct vm_area_struct *vma2)
-{
-	return is_mergeable_anon_vma(vma1->anon_vma, vma2->anon_vma, NULL);
+	/* Case 1 - we will dup_anon_vma() from src into tgt. */
+	if (!tgt_anon && src_anon)
+		return !vma_had_uncowed_parents(src);
+	/* Case 2 - we will simply use tgt's anon_vma. */
+	if (tgt_anon && !src_anon)
+		return !vma_had_uncowed_parents(tgt);
+	/* Case 3 - the anon_vma's are already shared. */
+	return src_anon == tgt_anon;
 }
 
 /*
@@ -164,7 +189,7 @@ static bool can_vma_merge_before(struct vma_merge_struct *vmg)
 	pgoff_t pglen = PHYS_PFN(vmg->end - vmg->start);
 
 	if (is_mergeable_vma(vmg, /* merge_next = */ true) &&
-	    is_mergeable_anon_vma(vmg->anon_vma, vmg->next->anon_vma, vmg->next)) {
+	    is_mergeable_anon_vma(vmg, /* merge_next = */ true)) {
 		if (vmg->next->vm_pgoff == vmg->pgoff + pglen)
 			return true;
 	}
@@ -184,7 +209,7 @@ static bool can_vma_merge_before(struct vma_merge_struct *vmg)
 static bool can_vma_merge_after(struct vma_merge_struct *vmg)
 {
 	if (is_mergeable_vma(vmg, /* merge_next = */ false) &&
-	    is_mergeable_anon_vma(vmg->anon_vma, vmg->prev->anon_vma, vmg->prev)) {
+	    is_mergeable_anon_vma(vmg, /* merge_next = */ false)) {
 		if (vmg->prev->vm_pgoff + vma_pages(vmg->prev) == vmg->pgoff)
 			return true;
 	}
@@ -400,8 +425,10 @@ static bool can_vma_merge_left(struct vma_merge_struct *vmg)
 static bool can_vma_merge_right(struct vma_merge_struct *vmg,
 				bool can_merge_left)
 {
-	if (!vmg->next || vmg->end != vmg->next->vm_start ||
-	    !can_vma_merge_before(vmg))
+	struct vm_area_struct *next = vmg->next;
+	struct vm_area_struct *prev;
+
+	if (!next || vmg->end != next->vm_start || !can_vma_merge_before(vmg))
 		return false;
 
 	if (!can_merge_left)
@@ -414,7 +441,9 @@ static bool can_vma_merge_right(struct vma_merge_struct *vmg,
 	 *
 	 * We therefore check this in addition to mergeability to either side.
 	 */
-	return are_anon_vmas_compatible(vmg->prev, vmg->next);
+	prev = vmg->prev;
+	return !prev->anon_vma || !next->anon_vma ||
+		prev->anon_vma == next->anon_vma;
 }
 
 /*
@@ -554,7 +583,9 @@ static int split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
 }
 
 /*
- * dup_anon_vma() - Helper function to duplicate anon_vma
+ * dup_anon_vma() - Helper function to duplicate anon_vma on VMA merge in the
+ * instance that the destination VMA has no anon_vma but the source does.
+ *
  * @dst: The destination VMA
  * @src: The source VMA
  * @dup: Pointer to the destination VMA when successful.
@@ -565,9 +596,18 @@ static int dup_anon_vma(struct vm_area_struct *dst,
 			struct vm_area_struct *src, struct vm_area_struct **dup)
 {
 	/*
-	 * Easily overlooked: when mprotect shifts the boundary, make sure the
-	 * expanding vma has anon_vma set if the shrinking vma had, to cover any
-	 * anon pages imported.
+	 * There are three cases to consider for correctly propagating
+	 * anon_vma's on merge.
+	 *
+	 * The first is trivial - neither VMA has anon_vma, we need not do
+	 * anything.
+	 *
+	 * The second where both have anon_vma is also a no-op, as they must
+	 * then be the same, so there is simply nothing to copy.
+	 *
+	 * Here we cover the third - if the destination VMA has no anon_vma,
+	 * that is it is unfaulted, we need to ensure that the newly merged
+	 * range is referenced by the anon_vma's of the source.
 	 */
 	if (src->anon_vma && !dst->anon_vma) {
 		int ret;
@@ -2351,6 +2391,10 @@ static int __mmap_new_file_vma(struct mmap_state *map,
 	int error;
 
 	vma->vm_file = get_file(map->file);
+
+	if (!map->file->f_op->mmap)
+		return 0;
+
 	error = mmap_file(vma->vm_file, vma);
 	if (error) {
 		fput(vma->vm_file);
@@ -2373,8 +2417,6 @@ static int __mmap_new_file_vma(struct mmap_state *map,
 			!(map->flags & VM_MAYWRITE) &&
 			(vma->vm_flags & VM_MAYWRITE));
 
-	/* If the flags change (and are mergeable), let's retry later. */
-	map->retry_merge = vma->vm_flags != map->flags && !(vma->vm_flags & VM_SPECIAL);
 	map->flags = vma->vm_flags;
 
 	return 0;
@@ -2407,7 +2449,7 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap)
 	vma_iter_config(vmi, map->addr, map->end);
 	vma_set_range(vma, map->addr, map->end, map->pgoff);
 	vm_flags_init(vma, map->flags);
-	vma->vm_page_prot = vm_get_page_prot(map->flags);
+	vma->vm_page_prot = map->page_prot;
 
 	if (vma_iter_prealloc(vmi, vma)) {
 		error = -ENOMEM;
@@ -2494,6 +2536,56 @@ static void __mmap_complete(struct mmap_state *map, struct vm_area_struct *vma)
 	vma_set_page_prot(vma);
 }
 
+/*
+ * Invoke the f_op->mmap_prepare() callback for a file-backed mapping that
+ * specifies it.
+ *
+ * This is called prior to any merge attempt, and updates whitelisted fields
+ * that are permitted to be updated by the caller.
+ *
+ * All but user-defined fields will be pre-populated with original values.
+ *
+ * Returns 0 on success, or an error code otherwise.
+ */
+static int call_mmap_prepare(struct mmap_state *map)
+{
+	int err;
+	struct vm_area_desc desc = {
+		.mm = map->mm,
+		.start = map->addr,
+		.end = map->end,
+
+		.pgoff = map->pgoff,
+		.file = map->file,
+		.vm_flags = map->flags,
+		.page_prot = map->page_prot,
+	};
+
+	/* Invoke the hook. */
+	err = __call_mmap_prepare(map->file, &desc);
+	if (err)
+		return err;
+
+	/* Update fields permitted to be changed. */
+	map->pgoff = desc.pgoff;
+	map->file = desc.file;
+	map->flags = desc.vm_flags;
+	map->page_prot = desc.page_prot;
+	/* User-defined fields. */
+	map->vm_ops = desc.vm_ops;
+	map->vm_private_data = desc.private_data;
+
+	return 0;
+}
+
+static void set_vma_user_defined_fields(struct vm_area_struct *vma,
+		struct mmap_state *map)
+{
+	if (map->vm_ops)
+		vma->vm_ops = map->vm_ops;
+	vma->vm_private_data = map->vm_private_data;
+}
+
 static unsigned long __mmap_region(struct file *file, unsigned long addr,
 		unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
 		struct list_head *uf)
@@ -2501,10 +2593,13 @@ static unsigned long __mmap_region(struct file *file, unsigned long addr,
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma = NULL;
 	int error;
+	bool have_mmap_prepare = file && file->f_op->mmap_prepare;
 	VMA_ITERATOR(vmi, mm, addr);
 	MMAP_STATE(map, mm, &vmi, addr, len, pgoff, vm_flags, file);
 
 	error = __mmap_prepare(&map, uf);
+	if (!error && have_mmap_prepare)
+		error = call_mmap_prepare(&map);
 	if (error)
 		goto abort_munmap;
 
@@ -2522,16 +2617,8 @@ static unsigned long __mmap_region(struct file *file, unsigned long addr,
 			goto unacct_error;
 	}
 
-	/* If flags changed, we might be able to merge, so try again. */
-	if (map.retry_merge) {
-		struct vm_area_struct *merged;
-		VMG_MMAP_STATE(vmg, &map, vma);
-
-		vma_iter_config(map.vmi, map.addr, map.end);
-		merged = vma_merge_existing_range(&vmg);
-		if (merged)
-			vma = merged;
-	}
+	if (have_mmap_prepare)
+		set_vma_user_defined_fields(vma, &map);
 
 	__mmap_complete(&map, vma);
 
@@ -3018,3 +3105,46 @@ int __vm_munmap(unsigned long start, size_t len, bool unlock)
 	userfaultfd_unmap_complete(mm, &uf);
 	return ret;
 }
+
+
+/* Insert vm structure into process list sorted by address
+ * and into the inode's i_mmap tree.  If vm_file is non-NULL
+ * then i_mmap_rwsem is taken here.
+ */
+int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
+{
+	unsigned long charged = vma_pages(vma);
+
+
+	if (find_vma_intersection(mm, vma->vm_start, vma->vm_end))
+		return -ENOMEM;
+
+	if ((vma->vm_flags & VM_ACCOUNT) &&
+	     security_vm_enough_memory_mm(mm, charged))
+		return -ENOMEM;
+
+	/*
+	 * The vm_pgoff of a purely anonymous vma should be irrelevant
+	 * until its first write fault, when page's anon_vma and index
+	 * are set.  But now set the vm_pgoff it will almost certainly
+	 * end up with (unless mremap moves it elsewhere before that
+	 * first wfault), so /proc/pid/maps tells a consistent story.
+	 *
+	 * By setting it to reflect the virtual start address of the
+	 * vma, merges and splits can happen in a seamless way, just
+	 * using the existing file pgoff checks and manipulations.
+	 * Similarly in do_mmap and in do_brk_flags.
+	 */
+	if (vma_is_anonymous(vma)) {
+		BUG_ON(vma->anon_vma);
+		vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
+	}
+
+	if (vma_link(mm, vma)) {
+		if (vma->vm_flags & VM_ACCOUNT)
+			vm_unacct_memory(charged);
+		return -ENOMEM;
+	}
+
+	return 0;
+}