Merge tag 'mm-stable-2024-09-20-02-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:
 "Along with the usual shower of singleton patches, notable patch series
  in this pull request are:

   - "Align kvrealloc() with krealloc()" from Danilo Krummrich. Adds
     consistency to the APIs and behaviour of these two core allocation
     functions. This also simplifies/enables Rustification.

   - "Some cleanups for shmem" from Baolin Wang. No functional changes -
     mode code reuse, better function naming, logic simplifications.

   - "mm: some small page fault cleanups" from Josef Bacik. No
     functional changes - code cleanups only.

   - "Various memory tiering fixes" from Zi Yan. A small fix and a
     little cleanup.

   - "mm/swap: remove boilerplate" from Yu Zhao. Code cleanups and
     simplifications and .text shrinkage.

   - "Kernel stack usage histogram" from Pasha Tatashin and Shakeel
     Butt. This is a feature, it adds new feilds to /proc/vmstat such as

       $ grep kstack /proc/vmstat
       kstack_1k 3
       kstack_2k 188
       kstack_4k 11391
       kstack_8k 243
       kstack_16k 0

     which tells us that 11391 processes used 4k of stack while none at
     all used 16k. Useful for some system tuning things, but
     partivularly useful for "the dynamic kernel stack project".

   - "kmemleak: support for percpu memory leak detect" from Pavel
     Tikhomirov. Teaches kmemleak to detect leaksage of percpu memory.

   - "mm: memcg: page counters optimizations" from Roman Gushchin. "3
     independent small optimizations of page counters".

   - "mm: split PTE/PMD PT table Kconfig cleanups+clarifications" from
     David Hildenbrand. Improves PTE/PMD splitlock detection, makes
     powerpc/8xx work correctly by design rather than by accident.

   - "mm: remove arch_make_page_accessible()" from David Hildenbrand.
     Some folio conversions which make arch_make_page_accessible()
     unneeded.

   - "mm, memcg: cg2 memory{.swap,}.peak write handlers" fro David
     Finkel. Cleans up and fixes our handling of the resetting of the
     cgroup/process peak-memory-use detector.

   - "Make core VMA operations internal and testable" from Lorenzo
     Stoakes. Rationalizaion and encapsulation of the VMA manipulation
     APIs. With a view to better enable testing of the VMA functions,
     even from a userspace-only harness.

   - "mm: zswap: fixes for global shrinker" from Takero Funaki. Fix
     issues in the zswap global shrinker, resulting in improved
     performance.

   - "mm: print the promo watermark in zoneinfo" from Kaiyang Zhao. Fill
     in some missing info in /proc/zoneinfo.

   - "mm: replace follow_page() by folio_walk" from David Hildenbrand.
     Code cleanups and rationalizations (conversion to folio_walk())
     resulting in the removal of follow_page().

   - "improving dynamic zswap shrinker protection scheme" from Nhat
     Pham. Some tuning to improve zswap's dynamic shrinker. Significant
     reductions in swapin and improvements in performance are shown.

   - "mm: Fix several issues with unaccepted memory" from Kirill
     Shutemov. Improvements to the new unaccepted memory feature,

   - "mm/mprotect: Fix dax puds" from Peter Xu. Implements mprotect on
     DAX PUDs. This was missing, although nobody seems to have notied
     yet.

   - "Introduce a store type enum for the Maple tree" from Sidhartha
     Kumar. Cleanups and modest performance improvements for the maple
     tree library code.

   - "memcg: further decouple v1 code from v2" from Shakeel Butt. Move
     more cgroup v1 remnants away from the v2 memcg code.

   - "memcg: initiate deprecation of v1 features" from Shakeel Butt.
     Adds various warnings telling users that memcg v1 features are
     deprecated.

   - "mm: swap: mTHP swap allocator base on swap cluster order" from
     Chris Li. Greatly improves the success rate of the mTHP swap
     allocation.

   - "mm: introduce numa_memblks" from Mike Rapoport. Moves various
     disparate per-arch implementations of numa_memblk code into generic
     code.

   - "mm: batch free swaps for zap_pte_range()" from Barry Song. Greatly
     improves the performance of munmap() of swap-filled ptes.

   - "support large folio swap-out and swap-in for shmem" from Baolin
     Wang. With this series we no longer split shmem large folios into
     simgle-page folios when swapping out shmem.

   - "mm/hugetlb: alloc/free gigantic folios" from Yu Zhao. Nice
     performance improvements and code reductions for gigantic folios.

   - "support shmem mTHP collapse" from Baolin Wang. Adds support for
     khugepaged's collapsing of shmem mTHP folios.

   - "mm: Optimize mseal checks" from Pedro Falcato. Fixes an mprotect()
     performance regression due to the addition of mseal().

   - "Increase the number of bits available in page_type" from Matthew
     Wilcox. Increases the number of bits available in page_type!

   - "Simplify the page flags a little" from Matthew Wilcox. Many legacy
     page flags are now folio flags, so the page-based flags and their
     accessors/mutators can be removed.

   - "mm: store zero pages to be swapped out in a bitmap" from Usama
     Arif. An optimization which permits us to avoid writing/reading
     zero-filled zswap pages to backing store.

   - "Avoid MAP_FIXED gap exposure" from Liam Howlett. Fixes a race
     window which occurs when a MAP_FIXED operqtion is occurring during
     an unrelated vma tree walk.

   - "mm: remove vma_merge()" from Lorenzo Stoakes. Major rotorooting of
     the vma_merge() functionality, making ot cleaner, more testable and
     better tested.

   - "misc fixups for DAMON {self,kunit} tests" from SeongJae Park.
     Minor fixups of DAMON selftests and kunit tests.

   - "mm: memory_hotplug: improve do_migrate_range()" from Kefeng Wang.
     Code cleanups and folio conversions.

   - "Shmem mTHP controls and stats improvements" from Ryan Roberts.
     Cleanups for shmem controls and stats.

   - "mm: count the number of anonymous THPs per size" from Barry Song.
     Expose additional anon THP stats to userspace for improved tuning.

   - "mm: finish isolate/putback_lru_page()" from Kefeng Wang: more
     folio conversions and removal of now-unused page-based APIs.

   - "replace per-quota region priorities histogram buffer with
     per-context one" from SeongJae Park. DAMON histogram
     rationalization.

   - "Docs/damon: update GitHub repo URLs and maintainer-profile" from
     SeongJae Park. DAMON documentation updates.

   - "mm/vdpa: correct misuse of non-direct-reclaim __GFP_NOFAIL and
     improve related doc and warn" from Jason Wang: fixes usage of page
     allocator __GFP_NOFAIL and GFP_ATOMIC flags.

   - "mm: split underused THPs" from Yu Zhao. Improve THP=always policy.
     This was overprovisioning THPs in sparsely accessed memory areas.

   - "zram: introduce custom comp backends API" frm Sergey Senozhatsky.
     Add support for zram run-time compression algorithm tuning.

   - "mm: Care about shadow stack guard gap when getting an unmapped
     area" from Mark Brown. Fix up the various arch_get_unmapped_area()
     implementations to better respect guard areas.

   - "Improve mem_cgroup_iter()" from Kinsey Ho. Improve the reliability
     of mem_cgroup_iter() and various code cleanups.

   - "mm: Support huge pfnmaps" from Peter Xu. Extends the usage of huge
     pfnmap support.

   - "resource: Fix region_intersects() vs add_memory_driver_managed()"
     from Huang Ying. Fix a bug in region_intersects() for systems with
     CXL memory.

   - "mm: hwpoison: two more poison recovery" from Kefeng Wang. Teaches
     a couple more code paths to correctly recover from the encountering
     of poisoned memry.

   - "mm: enable large folios swap-in support" from Barry Song. Support
     the swapin of mTHP memory into appropriately-sized folios, rather
     than into single-page folios"

* tag 'mm-stable-2024-09-20-02-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (416 commits)
  zram: free secondary algorithms names
  uprobes: turn xol_area->pages[2] into xol_area->page
  uprobes: introduce the global struct vm_special_mapping xol_mapping
  Revert "uprobes: use vm_special_mapping close() functionality"
  mm: support large folios swap-in for sync io devices
  mm: add nr argument in mem_cgroup_swapin_uncharge_swap() helper to support large folios
  mm: fix swap_read_folio_zeromap() for large folios with partial zeromap
  mm/debug_vm_pgtable: Use pxdp_get() for accessing page table entries
  set_memory: add __must_check to generic stubs
  mm/vma: return the exact errno in vms_gather_munmap_vmas()
  memcg: cleanup with !CONFIG_MEMCG_V1
  mm/show_mem.c: report alloc tags in human readable units
  mm: support poison recovery from copy_present_page()
  mm: support poison recovery from do_cow_fault()
  resource, kunit: add test case for region_intersects()
  resource: make alloc_free_mem_region() works for iomem_resource
  mm: z3fold: deprecate CONFIG_Z3FOLD
  vfio/pci: implement huge_fault support
  mm/arm64: support large pfn mappings
  mm/x86: support large pfn mappings
  ...

1 files changed, 202 insertions, 0 deletions

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index ae2f08ce991b..461ea3bbd8d9 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -3,6 +3,8 @@
 #include <linux/highmem.h>
 #include <linux/sched.h>
 #include <linux/hugetlb.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
 
 /*
  * We want to know the real level where a entry is located ignoring any
@@ -654,3 +656,203 @@ int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
 
 	return err;
 }
+
+/**
+ * folio_walk_start - walk the page tables to a folio
+ * @fw: filled with information on success.
+ * @vma: the VMA.
+ * @addr: the virtual address to use for the page table walk.
+ * @flags: flags modifying which folios to walk to.
+ *
+ * Walk the page tables using @addr in a given @vma to a mapped folio and
+ * return the folio, making sure that the page table entry referenced by
+ * @addr cannot change until folio_walk_end() was called.
+ *
+ * As default, this function returns only folios that are not special (e.g., not
+ * the zeropage) and never returns folios that are supposed to be ignored by the
+ * VM as documented by vm_normal_page(). If requested, zeropages will be
+ * returned as well.
+ *
+ * As default, this function only considers present page table entries.
+ * If requested, it will also consider migration entries.
+ *
+ * If this function returns NULL it might either indicate "there is nothing" or
+ * "there is nothing suitable".
+ *
+ * On success, @fw is filled and the function returns the folio while the PTL
+ * is still held and folio_walk_end() must be called to clean up,
+ * releasing any held locks. The returned folio must *not* be used after the
+ * call to folio_walk_end(), unless a short-term folio reference is taken before
+ * that call.
+ *
+ * @fw->page will correspond to the page that is effectively referenced by
+ * @addr. However, for migration entries and shared zeropages @fw->page is
+ * set to NULL. Note that large folios might be mapped by multiple page table
+ * entries, and this function will always only lookup a single entry as
+ * specified by @addr, which might or might not cover more than a single page of
+ * the returned folio.
+ *
+ * This function must *not* be used as a naive replacement for
+ * get_user_pages() / pin_user_pages(), especially not to perform DMA or
+ * to carelessly modify page content. This function may *only* be used to grab
+ * short-term folio references, never to grab long-term folio references.
+ *
+ * Using the page table entry pointers in @fw for reading or modifying the
+ * entry should be avoided where possible: however, there might be valid
+ * use cases.
+ *
+ * WARNING: Modifying page table entries in hugetlb VMAs requires a lot of care.
+ * For example, PMD page table sharing might require prior unsharing. Also,
+ * logical hugetlb entries might span multiple physical page table entries,
+ * which *must* be modified in a single operation (set_huge_pte_at(),
+ * huge_ptep_set_*, ...). Note that the page table entry stored in @fw might
+ * not correspond to the first physical entry of a logical hugetlb entry.
+ *
+ * The mmap lock must be held in read mode.
+ *
+ * Return: folio pointer on success, otherwise NULL.
+ */
+struct folio *folio_walk_start(struct folio_walk *fw,
+		struct vm_area_struct *vma, unsigned long addr,
+		folio_walk_flags_t flags)
+{
+	unsigned long entry_size;
+	bool expose_page = true;
+	struct page *page;
+	pud_t *pudp, pud;
+	pmd_t *pmdp, pmd;
+	pte_t *ptep, pte;
+	spinlock_t *ptl;
+	pgd_t *pgdp;
+	p4d_t *p4dp;
+
+	mmap_assert_locked(vma->vm_mm);
+	vma_pgtable_walk_begin(vma);
+
+	if (WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end))
+		goto not_found;
+
+	pgdp = pgd_offset(vma->vm_mm, addr);
+	if (pgd_none_or_clear_bad(pgdp))
+		goto not_found;
+
+	p4dp = p4d_offset(pgdp, addr);
+	if (p4d_none_or_clear_bad(p4dp))
+		goto not_found;
+
+	pudp = pud_offset(p4dp, addr);
+	pud = pudp_get(pudp);
+	if (pud_none(pud))
+		goto not_found;
+	if (IS_ENABLED(CONFIG_PGTABLE_HAS_HUGE_LEAVES) && pud_leaf(pud)) {
+		ptl = pud_lock(vma->vm_mm, pudp);
+		pud = pudp_get(pudp);
+
+		entry_size = PUD_SIZE;
+		fw->level = FW_LEVEL_PUD;
+		fw->pudp = pudp;
+		fw->pud = pud;
+
+		if (!pud_present(pud) || pud_devmap(pud) || pud_special(pud)) {
+			spin_unlock(ptl);
+			goto not_found;
+		} else if (!pud_leaf(pud)) {
+			spin_unlock(ptl);
+			goto pmd_table;
+		}
+		/*
+		 * TODO: vm_normal_page_pud() will be handy once we want to
+		 * support PUD mappings in VM_PFNMAP|VM_MIXEDMAP VMAs.
+		 */
+		page = pud_page(pud);
+		goto found;
+	}
+
+pmd_table:
+	VM_WARN_ON_ONCE(pud_leaf(*pudp));
+	pmdp = pmd_offset(pudp, addr);
+	pmd = pmdp_get_lockless(pmdp);
+	if (pmd_none(pmd))
+		goto not_found;
+	if (IS_ENABLED(CONFIG_PGTABLE_HAS_HUGE_LEAVES) && pmd_leaf(pmd)) {
+		ptl = pmd_lock(vma->vm_mm, pmdp);
+		pmd = pmdp_get(pmdp);
+
+		entry_size = PMD_SIZE;
+		fw->level = FW_LEVEL_PMD;
+		fw->pmdp = pmdp;
+		fw->pmd = pmd;
+
+		if (pmd_none(pmd)) {
+			spin_unlock(ptl);
+			goto not_found;
+		} else if (!pmd_leaf(pmd)) {
+			spin_unlock(ptl);
+			goto pte_table;
+		} else if (pmd_present(pmd)) {
+			page = vm_normal_page_pmd(vma, addr, pmd);
+			if (page) {
+				goto found;
+			} else if ((flags & FW_ZEROPAGE) &&
+				    is_huge_zero_pmd(pmd)) {
+				page = pfn_to_page(pmd_pfn(pmd));
+				expose_page = false;
+				goto found;
+			}
+		} else if ((flags & FW_MIGRATION) &&
+			   is_pmd_migration_entry(pmd)) {
+			swp_entry_t entry = pmd_to_swp_entry(pmd);
+
+			page = pfn_swap_entry_to_page(entry);
+			expose_page = false;
+			goto found;
+		}
+		spin_unlock(ptl);
+		goto not_found;
+	}
+
+pte_table:
+	VM_WARN_ON_ONCE(pmd_leaf(pmdp_get_lockless(pmdp)));
+	ptep = pte_offset_map_lock(vma->vm_mm, pmdp, addr, &ptl);
+	if (!ptep)
+		goto not_found;
+	pte = ptep_get(ptep);
+
+	entry_size = PAGE_SIZE;
+	fw->level = FW_LEVEL_PTE;
+	fw->ptep = ptep;
+	fw->pte = pte;
+
+	if (pte_present(pte)) {
+		page = vm_normal_page(vma, addr, pte);
+		if (page)
+			goto found;
+		if ((flags & FW_ZEROPAGE) &&
+		    is_zero_pfn(pte_pfn(pte))) {
+			page = pfn_to_page(pte_pfn(pte));
+			expose_page = false;
+			goto found;
+		}
+	} else if (!pte_none(pte)) {
+		swp_entry_t entry = pte_to_swp_entry(pte);
+
+		if ((flags & FW_MIGRATION) &&
+		    is_migration_entry(entry)) {
+			page = pfn_swap_entry_to_page(entry);
+			expose_page = false;
+			goto found;
+		}
+	}
+	pte_unmap_unlock(ptep, ptl);
+not_found:
+	vma_pgtable_walk_end(vma);
+	return NULL;
+found:
+	if (expose_page)
+		/* Note: Offset from the mapped page, not the folio start. */
+		fw->page = nth_page(page, (addr & (entry_size - 1)) >> PAGE_SHIFT);
+	else
+		fw->page = NULL;
+	fw->ptl = ptl;
+	return page_folio(page);
+}