1 // SPDX-License-Identifier: GPL-2.0-only
3 * Copyright (C) 2009 Red Hat, Inc.
6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9 #include <linux/sched.h>
10 #include <linux/sched/mm.h>
11 #include <linux/sched/coredump.h>
12 #include <linux/sched/numa_balancing.h>
13 #include <linux/highmem.h>
14 #include <linux/hugetlb.h>
15 #include <linux/mmu_notifier.h>
16 #include <linux/rmap.h>
17 #include <linux/swap.h>
18 #include <linux/shrinker.h>
19 #include <linux/mm_inline.h>
20 #include <linux/swapops.h>
21 #include <linux/backing-dev.h>
22 #include <linux/dax.h>
23 #include <linux/khugepaged.h>
24 #include <linux/freezer.h>
25 #include <linux/pfn_t.h>
26 #include <linux/mman.h>
27 #include <linux/memremap.h>
28 #include <linux/pagemap.h>
29 #include <linux/debugfs.h>
30 #include <linux/migrate.h>
31 #include <linux/hashtable.h>
32 #include <linux/userfaultfd_k.h>
33 #include <linux/page_idle.h>
34 #include <linux/shmem_fs.h>
35 #include <linux/oom.h>
36 #include <linux/numa.h>
37 #include <linux/page_owner.h>
38 #include <linux/sched/sysctl.h>
39 #include <linux/memory-tiers.h>
42 #include <asm/pgalloc.h>
46 #define CREATE_TRACE_POINTS
47 #include <trace/events/thp.h>
50 * By default, transparent hugepage support is disabled in order to avoid
51 * risking an increased memory footprint for applications that are not
52 * guaranteed to benefit from it. When transparent hugepage support is
53 * enabled, it is for all mappings, and khugepaged scans all mappings.
54 * Defrag is invoked by khugepaged hugepage allocations and by page faults
55 * for all hugepage allocations.
57 unsigned long transparent_hugepage_flags __read_mostly =
58 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
59 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
61 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
62 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
64 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
65 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
66 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
68 static struct shrinker deferred_split_shrinker;
70 static atomic_t huge_zero_refcount;
71 struct page *huge_zero_page __read_mostly;
72 unsigned long huge_zero_pfn __read_mostly = ~0UL;
74 bool hugepage_vma_check(struct vm_area_struct *vma, unsigned long vm_flags,
75 bool smaps, bool in_pf, bool enforce_sysfs)
77 if (!vma->vm_mm) /* vdso */
81 * Explicitly disabled through madvise or prctl, or some
82 * architectures may disable THP for some mappings, for
85 if ((vm_flags & VM_NOHUGEPAGE) ||
86 test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
89 * If the hardware/firmware marked hugepage support disabled.
91 if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED))
94 /* khugepaged doesn't collapse DAX vma, but page fault is fine. */
99 * Special VMA and hugetlb VMA.
100 * Must be checked after dax since some dax mappings may have
103 if (vm_flags & VM_NO_KHUGEPAGED)
107 * Check alignment for file vma and size for both file and anon vma.
109 * Skip the check for page fault. Huge fault does the check in fault
110 * handlers. And this check is not suitable for huge PUD fault.
113 !transhuge_vma_suitable(vma, (vma->vm_end - HPAGE_PMD_SIZE)))
117 * Enabled via shmem mount options or sysfs settings.
118 * Must be done before hugepage flags check since shmem has its
121 if (!in_pf && shmem_file(vma->vm_file))
122 return shmem_is_huge(file_inode(vma->vm_file), vma->vm_pgoff,
123 !enforce_sysfs, vma->vm_mm, vm_flags);
125 /* Enforce sysfs THP requirements as necessary */
127 (!hugepage_flags_enabled() || (!(vm_flags & VM_HUGEPAGE) &&
128 !hugepage_flags_always())))
131 /* Only regular file is valid */
132 if (!in_pf && file_thp_enabled(vma))
135 if (!vma_is_anonymous(vma))
138 if (vma_is_temporary_stack(vma))
142 * THPeligible bit of smaps should show 1 for proper VMAs even
143 * though anon_vma is not initialized yet.
145 * Allow page fault since anon_vma may be not initialized until
146 * the first page fault.
149 return (smaps || in_pf);
154 static bool get_huge_zero_page(void)
156 struct page *zero_page;
158 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
161 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
164 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
168 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
170 __free_pages(zero_page, compound_order(zero_page));
173 WRITE_ONCE(huge_zero_pfn, page_to_pfn(zero_page));
175 /* We take additional reference here. It will be put back by shrinker */
176 atomic_set(&huge_zero_refcount, 2);
178 count_vm_event(THP_ZERO_PAGE_ALLOC);
182 static void put_huge_zero_page(void)
185 * Counter should never go to zero here. Only shrinker can put
188 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
191 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
193 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
194 return READ_ONCE(huge_zero_page);
196 if (!get_huge_zero_page())
199 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
200 put_huge_zero_page();
202 return READ_ONCE(huge_zero_page);
205 void mm_put_huge_zero_page(struct mm_struct *mm)
207 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
208 put_huge_zero_page();
211 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
212 struct shrink_control *sc)
214 /* we can free zero page only if last reference remains */
215 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
218 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
219 struct shrink_control *sc)
221 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
222 struct page *zero_page = xchg(&huge_zero_page, NULL);
223 BUG_ON(zero_page == NULL);
224 WRITE_ONCE(huge_zero_pfn, ~0UL);
225 __free_pages(zero_page, compound_order(zero_page));
232 static struct shrinker huge_zero_page_shrinker = {
233 .count_objects = shrink_huge_zero_page_count,
234 .scan_objects = shrink_huge_zero_page_scan,
235 .seeks = DEFAULT_SEEKS,
239 static ssize_t enabled_show(struct kobject *kobj,
240 struct kobj_attribute *attr, char *buf)
244 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
245 output = "[always] madvise never";
246 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
247 &transparent_hugepage_flags))
248 output = "always [madvise] never";
250 output = "always madvise [never]";
252 return sysfs_emit(buf, "%s\n", output);
255 static ssize_t enabled_store(struct kobject *kobj,
256 struct kobj_attribute *attr,
257 const char *buf, size_t count)
261 if (sysfs_streq(buf, "always")) {
262 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
263 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
264 } else if (sysfs_streq(buf, "madvise")) {
265 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
266 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
267 } else if (sysfs_streq(buf, "never")) {
268 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
269 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
274 int err = start_stop_khugepaged();
281 static struct kobj_attribute enabled_attr = __ATTR_RW(enabled);
283 ssize_t single_hugepage_flag_show(struct kobject *kobj,
284 struct kobj_attribute *attr, char *buf,
285 enum transparent_hugepage_flag flag)
287 return sysfs_emit(buf, "%d\n",
288 !!test_bit(flag, &transparent_hugepage_flags));
291 ssize_t single_hugepage_flag_store(struct kobject *kobj,
292 struct kobj_attribute *attr,
293 const char *buf, size_t count,
294 enum transparent_hugepage_flag flag)
299 ret = kstrtoul(buf, 10, &value);
306 set_bit(flag, &transparent_hugepage_flags);
308 clear_bit(flag, &transparent_hugepage_flags);
313 static ssize_t defrag_show(struct kobject *kobj,
314 struct kobj_attribute *attr, char *buf)
318 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
319 &transparent_hugepage_flags))
320 output = "[always] defer defer+madvise madvise never";
321 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
322 &transparent_hugepage_flags))
323 output = "always [defer] defer+madvise madvise never";
324 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG,
325 &transparent_hugepage_flags))
326 output = "always defer [defer+madvise] madvise never";
327 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
328 &transparent_hugepage_flags))
329 output = "always defer defer+madvise [madvise] never";
331 output = "always defer defer+madvise madvise [never]";
333 return sysfs_emit(buf, "%s\n", output);
336 static ssize_t defrag_store(struct kobject *kobj,
337 struct kobj_attribute *attr,
338 const char *buf, size_t count)
340 if (sysfs_streq(buf, "always")) {
341 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
342 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
343 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
344 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
345 } else if (sysfs_streq(buf, "defer+madvise")) {
346 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
347 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
348 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
349 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
350 } else if (sysfs_streq(buf, "defer")) {
351 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
352 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
353 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
354 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
355 } else if (sysfs_streq(buf, "madvise")) {
356 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
357 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
358 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
359 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
360 } else if (sysfs_streq(buf, "never")) {
361 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
362 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
363 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
364 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
370 static struct kobj_attribute defrag_attr = __ATTR_RW(defrag);
372 static ssize_t use_zero_page_show(struct kobject *kobj,
373 struct kobj_attribute *attr, char *buf)
375 return single_hugepage_flag_show(kobj, attr, buf,
376 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
378 static ssize_t use_zero_page_store(struct kobject *kobj,
379 struct kobj_attribute *attr, const char *buf, size_t count)
381 return single_hugepage_flag_store(kobj, attr, buf, count,
382 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
384 static struct kobj_attribute use_zero_page_attr = __ATTR_RW(use_zero_page);
386 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
387 struct kobj_attribute *attr, char *buf)
389 return sysfs_emit(buf, "%lu\n", HPAGE_PMD_SIZE);
391 static struct kobj_attribute hpage_pmd_size_attr =
392 __ATTR_RO(hpage_pmd_size);
394 static struct attribute *hugepage_attr[] = {
397 &use_zero_page_attr.attr,
398 &hpage_pmd_size_attr.attr,
400 &shmem_enabled_attr.attr,
405 static const struct attribute_group hugepage_attr_group = {
406 .attrs = hugepage_attr,
409 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
413 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
414 if (unlikely(!*hugepage_kobj)) {
415 pr_err("failed to create transparent hugepage kobject\n");
419 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
421 pr_err("failed to register transparent hugepage group\n");
425 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
427 pr_err("failed to register transparent hugepage group\n");
428 goto remove_hp_group;
434 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
436 kobject_put(*hugepage_kobj);
440 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
442 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
443 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
444 kobject_put(hugepage_kobj);
447 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
452 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
455 #endif /* CONFIG_SYSFS */
457 static int __init hugepage_init(void)
460 struct kobject *hugepage_kobj;
462 if (!has_transparent_hugepage()) {
463 transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED;
468 * hugepages can't be allocated by the buddy allocator
470 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER > MAX_ORDER);
472 * we use page->mapping and page->index in second tail page
473 * as list_head: assuming THP order >= 2
475 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
477 err = hugepage_init_sysfs(&hugepage_kobj);
481 err = khugepaged_init();
485 err = register_shrinker(&huge_zero_page_shrinker, "thp-zero");
487 goto err_hzp_shrinker;
488 err = register_shrinker(&deferred_split_shrinker, "thp-deferred_split");
490 goto err_split_shrinker;
493 * By default disable transparent hugepages on smaller systems,
494 * where the extra memory used could hurt more than TLB overhead
495 * is likely to save. The admin can still enable it through /sys.
497 if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
498 transparent_hugepage_flags = 0;
502 err = start_stop_khugepaged();
508 unregister_shrinker(&deferred_split_shrinker);
510 unregister_shrinker(&huge_zero_page_shrinker);
512 khugepaged_destroy();
514 hugepage_exit_sysfs(hugepage_kobj);
518 subsys_initcall(hugepage_init);
520 static int __init setup_transparent_hugepage(char *str)
525 if (!strcmp(str, "always")) {
526 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
527 &transparent_hugepage_flags);
528 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
529 &transparent_hugepage_flags);
531 } else if (!strcmp(str, "madvise")) {
532 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
533 &transparent_hugepage_flags);
534 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
535 &transparent_hugepage_flags);
537 } else if (!strcmp(str, "never")) {
538 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
539 &transparent_hugepage_flags);
540 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
541 &transparent_hugepage_flags);
546 pr_warn("transparent_hugepage= cannot parse, ignored\n");
549 __setup("transparent_hugepage=", setup_transparent_hugepage);
551 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
553 if (likely(vma->vm_flags & VM_WRITE))
554 pmd = pmd_mkwrite(pmd);
560 struct deferred_split *get_deferred_split_queue(struct folio *folio)
562 struct mem_cgroup *memcg = folio_memcg(folio);
563 struct pglist_data *pgdat = NODE_DATA(folio_nid(folio));
566 return &memcg->deferred_split_queue;
568 return &pgdat->deferred_split_queue;
572 struct deferred_split *get_deferred_split_queue(struct folio *folio)
574 struct pglist_data *pgdat = NODE_DATA(folio_nid(folio));
576 return &pgdat->deferred_split_queue;
580 void prep_transhuge_page(struct page *page)
582 struct folio *folio = (struct folio *)page;
584 VM_BUG_ON_FOLIO(folio_order(folio) < 2, folio);
585 INIT_LIST_HEAD(&folio->_deferred_list);
586 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
589 static inline bool is_transparent_hugepage(struct page *page)
593 if (!PageCompound(page))
596 folio = page_folio(page);
597 return is_huge_zero_page(&folio->page) ||
598 folio->_folio_dtor == TRANSHUGE_PAGE_DTOR;
601 static unsigned long __thp_get_unmapped_area(struct file *filp,
602 unsigned long addr, unsigned long len,
603 loff_t off, unsigned long flags, unsigned long size)
605 loff_t off_end = off + len;
606 loff_t off_align = round_up(off, size);
607 unsigned long len_pad, ret;
609 if (off_end <= off_align || (off_end - off_align) < size)
612 len_pad = len + size;
613 if (len_pad < len || (off + len_pad) < off)
616 ret = current->mm->get_unmapped_area(filp, addr, len_pad,
617 off >> PAGE_SHIFT, flags);
620 * The failure might be due to length padding. The caller will retry
621 * without the padding.
623 if (IS_ERR_VALUE(ret))
627 * Do not try to align to THP boundary if allocation at the address
633 ret += (off - ret) & (size - 1);
637 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
638 unsigned long len, unsigned long pgoff, unsigned long flags)
641 loff_t off = (loff_t)pgoff << PAGE_SHIFT;
643 ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE);
647 return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
649 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
651 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
652 struct page *page, gfp_t gfp)
654 struct vm_area_struct *vma = vmf->vma;
655 struct folio *folio = page_folio(page);
657 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
660 VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
662 if (mem_cgroup_charge(folio, vma->vm_mm, gfp)) {
664 count_vm_event(THP_FAULT_FALLBACK);
665 count_vm_event(THP_FAULT_FALLBACK_CHARGE);
666 return VM_FAULT_FALLBACK;
668 folio_throttle_swaprate(folio, gfp);
670 pgtable = pte_alloc_one(vma->vm_mm);
671 if (unlikely(!pgtable)) {
676 clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
678 * The memory barrier inside __folio_mark_uptodate makes sure that
679 * clear_huge_page writes become visible before the set_pmd_at()
682 __folio_mark_uptodate(folio);
684 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
685 if (unlikely(!pmd_none(*vmf->pmd))) {
690 ret = check_stable_address_space(vma->vm_mm);
694 /* Deliver the page fault to userland */
695 if (userfaultfd_missing(vma)) {
696 spin_unlock(vmf->ptl);
698 pte_free(vma->vm_mm, pgtable);
699 ret = handle_userfault(vmf, VM_UFFD_MISSING);
700 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
704 entry = mk_huge_pmd(page, vma->vm_page_prot);
705 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
706 folio_add_new_anon_rmap(folio, vma, haddr);
707 folio_add_lru_vma(folio, vma);
708 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
709 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
710 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
711 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
712 mm_inc_nr_ptes(vma->vm_mm);
713 spin_unlock(vmf->ptl);
714 count_vm_event(THP_FAULT_ALLOC);
715 count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
720 spin_unlock(vmf->ptl);
723 pte_free(vma->vm_mm, pgtable);
730 * always: directly stall for all thp allocations
731 * defer: wake kswapd and fail if not immediately available
732 * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
733 * fail if not immediately available
734 * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
736 * never: never stall for any thp allocation
738 gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma)
740 const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE);
742 /* Always do synchronous compaction */
743 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
744 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
746 /* Kick kcompactd and fail quickly */
747 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
748 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
750 /* Synchronous compaction if madvised, otherwise kick kcompactd */
751 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
752 return GFP_TRANSHUGE_LIGHT |
753 (vma_madvised ? __GFP_DIRECT_RECLAIM :
754 __GFP_KSWAPD_RECLAIM);
756 /* Only do synchronous compaction if madvised */
757 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
758 return GFP_TRANSHUGE_LIGHT |
759 (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
761 return GFP_TRANSHUGE_LIGHT;
764 /* Caller must hold page table lock. */
765 static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
766 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
767 struct page *zero_page)
772 entry = mk_pmd(zero_page, vma->vm_page_prot);
773 entry = pmd_mkhuge(entry);
774 pgtable_trans_huge_deposit(mm, pmd, pgtable);
775 set_pmd_at(mm, haddr, pmd, entry);
779 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
781 struct vm_area_struct *vma = vmf->vma;
784 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
786 if (!transhuge_vma_suitable(vma, haddr))
787 return VM_FAULT_FALLBACK;
788 if (unlikely(anon_vma_prepare(vma)))
790 khugepaged_enter_vma(vma, vma->vm_flags);
792 if (!(vmf->flags & FAULT_FLAG_WRITE) &&
793 !mm_forbids_zeropage(vma->vm_mm) &&
794 transparent_hugepage_use_zero_page()) {
796 struct page *zero_page;
798 pgtable = pte_alloc_one(vma->vm_mm);
799 if (unlikely(!pgtable))
801 zero_page = mm_get_huge_zero_page(vma->vm_mm);
802 if (unlikely(!zero_page)) {
803 pte_free(vma->vm_mm, pgtable);
804 count_vm_event(THP_FAULT_FALLBACK);
805 return VM_FAULT_FALLBACK;
807 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
809 if (pmd_none(*vmf->pmd)) {
810 ret = check_stable_address_space(vma->vm_mm);
812 spin_unlock(vmf->ptl);
813 pte_free(vma->vm_mm, pgtable);
814 } else if (userfaultfd_missing(vma)) {
815 spin_unlock(vmf->ptl);
816 pte_free(vma->vm_mm, pgtable);
817 ret = handle_userfault(vmf, VM_UFFD_MISSING);
818 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
820 set_huge_zero_page(pgtable, vma->vm_mm, vma,
821 haddr, vmf->pmd, zero_page);
822 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
823 spin_unlock(vmf->ptl);
826 spin_unlock(vmf->ptl);
827 pte_free(vma->vm_mm, pgtable);
831 gfp = vma_thp_gfp_mask(vma);
832 folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, vma, haddr, true);
833 if (unlikely(!folio)) {
834 count_vm_event(THP_FAULT_FALLBACK);
835 return VM_FAULT_FALLBACK;
837 return __do_huge_pmd_anonymous_page(vmf, &folio->page, gfp);
840 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
841 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
844 struct mm_struct *mm = vma->vm_mm;
848 ptl = pmd_lock(mm, pmd);
849 if (!pmd_none(*pmd)) {
851 if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
852 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
855 entry = pmd_mkyoung(*pmd);
856 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
857 if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
858 update_mmu_cache_pmd(vma, addr, pmd);
864 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
865 if (pfn_t_devmap(pfn))
866 entry = pmd_mkdevmap(entry);
868 entry = pmd_mkyoung(pmd_mkdirty(entry));
869 entry = maybe_pmd_mkwrite(entry, vma);
873 pgtable_trans_huge_deposit(mm, pmd, pgtable);
878 set_pmd_at(mm, addr, pmd, entry);
879 update_mmu_cache_pmd(vma, addr, pmd);
884 pte_free(mm, pgtable);
888 * vmf_insert_pfn_pmd - insert a pmd size pfn
889 * @vmf: Structure describing the fault
890 * @pfn: pfn to insert
891 * @write: whether it's a write fault
893 * Insert a pmd size pfn. See vmf_insert_pfn() for additional info.
895 * Return: vm_fault_t value.
897 vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write)
899 unsigned long addr = vmf->address & PMD_MASK;
900 struct vm_area_struct *vma = vmf->vma;
901 pgprot_t pgprot = vma->vm_page_prot;
902 pgtable_t pgtable = NULL;
905 * If we had pmd_special, we could avoid all these restrictions,
906 * but we need to be consistent with PTEs and architectures that
907 * can't support a 'special' bit.
909 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
911 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
912 (VM_PFNMAP|VM_MIXEDMAP));
913 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
915 if (addr < vma->vm_start || addr >= vma->vm_end)
916 return VM_FAULT_SIGBUS;
918 if (arch_needs_pgtable_deposit()) {
919 pgtable = pte_alloc_one(vma->vm_mm);
924 track_pfn_insert(vma, &pgprot, pfn);
926 insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
927 return VM_FAULT_NOPAGE;
929 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
931 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
932 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
934 if (likely(vma->vm_flags & VM_WRITE))
935 pud = pud_mkwrite(pud);
939 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
940 pud_t *pud, pfn_t pfn, bool write)
942 struct mm_struct *mm = vma->vm_mm;
943 pgprot_t prot = vma->vm_page_prot;
947 ptl = pud_lock(mm, pud);
948 if (!pud_none(*pud)) {
950 if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
951 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
954 entry = pud_mkyoung(*pud);
955 entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
956 if (pudp_set_access_flags(vma, addr, pud, entry, 1))
957 update_mmu_cache_pud(vma, addr, pud);
962 entry = pud_mkhuge(pfn_t_pud(pfn, prot));
963 if (pfn_t_devmap(pfn))
964 entry = pud_mkdevmap(entry);
966 entry = pud_mkyoung(pud_mkdirty(entry));
967 entry = maybe_pud_mkwrite(entry, vma);
969 set_pud_at(mm, addr, pud, entry);
970 update_mmu_cache_pud(vma, addr, pud);
977 * vmf_insert_pfn_pud - insert a pud size pfn
978 * @vmf: Structure describing the fault
979 * @pfn: pfn to insert
980 * @write: whether it's a write fault
982 * Insert a pud size pfn. See vmf_insert_pfn() for additional info.
984 * Return: vm_fault_t value.
986 vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
988 unsigned long addr = vmf->address & PUD_MASK;
989 struct vm_area_struct *vma = vmf->vma;
990 pgprot_t pgprot = vma->vm_page_prot;
993 * If we had pud_special, we could avoid all these restrictions,
994 * but we need to be consistent with PTEs and architectures that
995 * can't support a 'special' bit.
997 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
999 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1000 (VM_PFNMAP|VM_MIXEDMAP));
1001 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1003 if (addr < vma->vm_start || addr >= vma->vm_end)
1004 return VM_FAULT_SIGBUS;
1006 track_pfn_insert(vma, &pgprot, pfn);
1008 insert_pfn_pud(vma, addr, vmf->pud, pfn, write);
1009 return VM_FAULT_NOPAGE;
1011 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
1012 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1014 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
1015 pmd_t *pmd, bool write)
1019 _pmd = pmd_mkyoung(*pmd);
1021 _pmd = pmd_mkdirty(_pmd);
1022 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1024 update_mmu_cache_pmd(vma, addr, pmd);
1027 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
1028 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
1030 unsigned long pfn = pmd_pfn(*pmd);
1031 struct mm_struct *mm = vma->vm_mm;
1035 assert_spin_locked(pmd_lockptr(mm, pmd));
1037 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1040 if (pmd_present(*pmd) && pmd_devmap(*pmd))
1045 if (flags & FOLL_TOUCH)
1046 touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);
1049 * device mapped pages can only be returned if the
1050 * caller will manage the page reference count.
1052 if (!(flags & (FOLL_GET | FOLL_PIN)))
1053 return ERR_PTR(-EEXIST);
1055 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1056 *pgmap = get_dev_pagemap(pfn, *pgmap);
1058 return ERR_PTR(-EFAULT);
1059 page = pfn_to_page(pfn);
1060 ret = try_grab_page(page, flags);
1062 page = ERR_PTR(ret);
1067 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1068 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1069 struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
1071 spinlock_t *dst_ptl, *src_ptl;
1072 struct page *src_page;
1074 pgtable_t pgtable = NULL;
1077 /* Skip if can be re-fill on fault */
1078 if (!vma_is_anonymous(dst_vma))
1081 pgtable = pte_alloc_one(dst_mm);
1082 if (unlikely(!pgtable))
1085 dst_ptl = pmd_lock(dst_mm, dst_pmd);
1086 src_ptl = pmd_lockptr(src_mm, src_pmd);
1087 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1092 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1093 if (unlikely(is_swap_pmd(pmd))) {
1094 swp_entry_t entry = pmd_to_swp_entry(pmd);
1096 VM_BUG_ON(!is_pmd_migration_entry(pmd));
1097 if (!is_readable_migration_entry(entry)) {
1098 entry = make_readable_migration_entry(
1100 pmd = swp_entry_to_pmd(entry);
1101 if (pmd_swp_soft_dirty(*src_pmd))
1102 pmd = pmd_swp_mksoft_dirty(pmd);
1103 if (pmd_swp_uffd_wp(*src_pmd))
1104 pmd = pmd_swp_mkuffd_wp(pmd);
1105 set_pmd_at(src_mm, addr, src_pmd, pmd);
1107 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1108 mm_inc_nr_ptes(dst_mm);
1109 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1110 if (!userfaultfd_wp(dst_vma))
1111 pmd = pmd_swp_clear_uffd_wp(pmd);
1112 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1118 if (unlikely(!pmd_trans_huge(pmd))) {
1119 pte_free(dst_mm, pgtable);
1123 * When page table lock is held, the huge zero pmd should not be
1124 * under splitting since we don't split the page itself, only pmd to
1127 if (is_huge_zero_pmd(pmd)) {
1129 * get_huge_zero_page() will never allocate a new page here,
1130 * since we already have a zero page to copy. It just takes a
1133 mm_get_huge_zero_page(dst_mm);
1137 src_page = pmd_page(pmd);
1138 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1141 if (unlikely(page_try_dup_anon_rmap(src_page, true, src_vma))) {
1142 /* Page maybe pinned: split and retry the fault on PTEs. */
1144 pte_free(dst_mm, pgtable);
1145 spin_unlock(src_ptl);
1146 spin_unlock(dst_ptl);
1147 __split_huge_pmd(src_vma, src_pmd, addr, false, NULL);
1150 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1152 mm_inc_nr_ptes(dst_mm);
1153 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1154 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1155 if (!userfaultfd_wp(dst_vma))
1156 pmd = pmd_clear_uffd_wp(pmd);
1157 pmd = pmd_mkold(pmd_wrprotect(pmd));
1158 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1162 spin_unlock(src_ptl);
1163 spin_unlock(dst_ptl);
1168 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1169 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1170 pud_t *pud, bool write)
1174 _pud = pud_mkyoung(*pud);
1176 _pud = pud_mkdirty(_pud);
1177 if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1179 update_mmu_cache_pud(vma, addr, pud);
1182 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1183 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1185 unsigned long pfn = pud_pfn(*pud);
1186 struct mm_struct *mm = vma->vm_mm;
1190 assert_spin_locked(pud_lockptr(mm, pud));
1192 if (flags & FOLL_WRITE && !pud_write(*pud))
1195 if (pud_present(*pud) && pud_devmap(*pud))
1200 if (flags & FOLL_TOUCH)
1201 touch_pud(vma, addr, pud, flags & FOLL_WRITE);
1204 * device mapped pages can only be returned if the
1205 * caller will manage the page reference count.
1207 * At least one of FOLL_GET | FOLL_PIN must be set, so assert that here:
1209 if (!(flags & (FOLL_GET | FOLL_PIN)))
1210 return ERR_PTR(-EEXIST);
1212 pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1213 *pgmap = get_dev_pagemap(pfn, *pgmap);
1215 return ERR_PTR(-EFAULT);
1216 page = pfn_to_page(pfn);
1218 ret = try_grab_page(page, flags);
1220 page = ERR_PTR(ret);
1225 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1226 pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1227 struct vm_area_struct *vma)
1229 spinlock_t *dst_ptl, *src_ptl;
1233 dst_ptl = pud_lock(dst_mm, dst_pud);
1234 src_ptl = pud_lockptr(src_mm, src_pud);
1235 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1239 if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1243 * When page table lock is held, the huge zero pud should not be
1244 * under splitting since we don't split the page itself, only pud to
1247 if (is_huge_zero_pud(pud)) {
1248 /* No huge zero pud yet */
1252 * TODO: once we support anonymous pages, use page_try_dup_anon_rmap()
1253 * and split if duplicating fails.
1255 pudp_set_wrprotect(src_mm, addr, src_pud);
1256 pud = pud_mkold(pud_wrprotect(pud));
1257 set_pud_at(dst_mm, addr, dst_pud, pud);
1261 spin_unlock(src_ptl);
1262 spin_unlock(dst_ptl);
1266 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1268 bool write = vmf->flags & FAULT_FLAG_WRITE;
1270 vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1271 if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1274 touch_pud(vmf->vma, vmf->address, vmf->pud, write);
1276 spin_unlock(vmf->ptl);
1278 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1280 void huge_pmd_set_accessed(struct vm_fault *vmf)
1282 bool write = vmf->flags & FAULT_FLAG_WRITE;
1284 vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1285 if (unlikely(!pmd_same(*vmf->pmd, vmf->orig_pmd)))
1288 touch_pmd(vmf->vma, vmf->address, vmf->pmd, write);
1291 spin_unlock(vmf->ptl);
1294 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
1296 const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
1297 struct vm_area_struct *vma = vmf->vma;
1298 struct folio *folio;
1300 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1301 pmd_t orig_pmd = vmf->orig_pmd;
1303 vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1304 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1306 if (is_huge_zero_pmd(orig_pmd))
1309 spin_lock(vmf->ptl);
1311 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1312 spin_unlock(vmf->ptl);
1316 page = pmd_page(orig_pmd);
1317 folio = page_folio(page);
1318 VM_BUG_ON_PAGE(!PageHead(page), page);
1320 /* Early check when only holding the PT lock. */
1321 if (PageAnonExclusive(page))
1324 if (!folio_trylock(folio)) {
1326 spin_unlock(vmf->ptl);
1328 spin_lock(vmf->ptl);
1329 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1330 spin_unlock(vmf->ptl);
1331 folio_unlock(folio);
1338 /* Recheck after temporarily dropping the PT lock. */
1339 if (PageAnonExclusive(page)) {
1340 folio_unlock(folio);
1345 * See do_wp_page(): we can only reuse the folio exclusively if
1346 * there are no additional references. Note that we always drain
1347 * the LRU pagevecs immediately after adding a THP.
1349 if (folio_ref_count(folio) >
1350 1 + folio_test_swapcache(folio) * folio_nr_pages(folio))
1351 goto unlock_fallback;
1352 if (folio_test_swapcache(folio))
1353 folio_free_swap(folio);
1354 if (folio_ref_count(folio) == 1) {
1357 page_move_anon_rmap(page, vma);
1358 folio_unlock(folio);
1360 if (unlikely(unshare)) {
1361 spin_unlock(vmf->ptl);
1364 entry = pmd_mkyoung(orig_pmd);
1365 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1366 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
1367 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1368 spin_unlock(vmf->ptl);
1373 folio_unlock(folio);
1374 spin_unlock(vmf->ptl);
1376 __split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL);
1377 return VM_FAULT_FALLBACK;
1380 static inline bool can_change_pmd_writable(struct vm_area_struct *vma,
1381 unsigned long addr, pmd_t pmd)
1385 if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
1388 /* Don't touch entries that are not even readable (NUMA hinting). */
1389 if (pmd_protnone(pmd))
1392 /* Do we need write faults for softdirty tracking? */
1393 if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
1396 /* Do we need write faults for uffd-wp tracking? */
1397 if (userfaultfd_huge_pmd_wp(vma, pmd))
1400 if (!(vma->vm_flags & VM_SHARED)) {
1401 /* See can_change_pte_writable(). */
1402 page = vm_normal_page_pmd(vma, addr, pmd);
1403 return page && PageAnon(page) && PageAnonExclusive(page);
1406 /* See can_change_pte_writable(). */
1407 return pmd_dirty(pmd);
1410 /* FOLL_FORCE can write to even unwritable PMDs in COW mappings. */
1411 static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page,
1412 struct vm_area_struct *vma,
1415 /* If the pmd is writable, we can write to the page. */
1419 /* Maybe FOLL_FORCE is set to override it? */
1420 if (!(flags & FOLL_FORCE))
1423 /* But FOLL_FORCE has no effect on shared mappings */
1424 if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED))
1427 /* ... or read-only private ones */
1428 if (!(vma->vm_flags & VM_MAYWRITE))
1431 /* ... or already writable ones that just need to take a write fault */
1432 if (vma->vm_flags & VM_WRITE)
1436 * See can_change_pte_writable(): we broke COW and could map the page
1437 * writable if we have an exclusive anonymous page ...
1439 if (!page || !PageAnon(page) || !PageAnonExclusive(page))
1442 /* ... and a write-fault isn't required for other reasons. */
1443 if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
1445 return !userfaultfd_huge_pmd_wp(vma, pmd);
1448 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1453 struct mm_struct *mm = vma->vm_mm;
1457 assert_spin_locked(pmd_lockptr(mm, pmd));
1459 page = pmd_page(*pmd);
1460 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1462 if ((flags & FOLL_WRITE) &&
1463 !can_follow_write_pmd(*pmd, page, vma, flags))
1466 /* Avoid dumping huge zero page */
1467 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1468 return ERR_PTR(-EFAULT);
1470 if (pmd_protnone(*pmd) && !gup_can_follow_protnone(vma, flags))
1473 if (!pmd_write(*pmd) && gup_must_unshare(vma, flags, page))
1474 return ERR_PTR(-EMLINK);
1476 VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
1477 !PageAnonExclusive(page), page);
1479 ret = try_grab_page(page, flags);
1481 return ERR_PTR(ret);
1483 if (flags & FOLL_TOUCH)
1484 touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);
1486 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1487 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1492 /* NUMA hinting page fault entry point for trans huge pmds */
1493 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
1495 struct vm_area_struct *vma = vmf->vma;
1496 pmd_t oldpmd = vmf->orig_pmd;
1499 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1500 int page_nid = NUMA_NO_NODE;
1501 int target_nid, last_cpupid = (-1 & LAST_CPUPID_MASK);
1502 bool migrated = false, writable = false;
1505 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1506 if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
1507 spin_unlock(vmf->ptl);
1511 pmd = pmd_modify(oldpmd, vma->vm_page_prot);
1514 * Detect now whether the PMD could be writable; this information
1515 * is only valid while holding the PT lock.
1517 writable = pmd_write(pmd);
1518 if (!writable && vma_wants_manual_pte_write_upgrade(vma) &&
1519 can_change_pmd_writable(vma, vmf->address, pmd))
1522 page = vm_normal_page_pmd(vma, haddr, pmd);
1526 /* See similar comment in do_numa_page for explanation */
1528 flags |= TNF_NO_GROUP;
1530 page_nid = page_to_nid(page);
1532 * For memory tiering mode, cpupid of slow memory page is used
1533 * to record page access time. So use default value.
1535 if (node_is_toptier(page_nid))
1536 last_cpupid = page_cpupid_last(page);
1537 target_nid = numa_migrate_prep(page, vma, haddr, page_nid,
1540 if (target_nid == NUMA_NO_NODE) {
1545 spin_unlock(vmf->ptl);
1548 migrated = migrate_misplaced_page(page, vma, target_nid);
1550 flags |= TNF_MIGRATED;
1551 page_nid = target_nid;
1553 flags |= TNF_MIGRATE_FAIL;
1554 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1555 if (unlikely(!pmd_same(oldpmd, *vmf->pmd))) {
1556 spin_unlock(vmf->ptl);
1563 if (page_nid != NUMA_NO_NODE)
1564 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1570 /* Restore the PMD */
1571 pmd = pmd_modify(oldpmd, vma->vm_page_prot);
1572 pmd = pmd_mkyoung(pmd);
1574 pmd = pmd_mkwrite(pmd);
1575 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1576 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1577 spin_unlock(vmf->ptl);
1582 * Return true if we do MADV_FREE successfully on entire pmd page.
1583 * Otherwise, return false.
1585 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1586 pmd_t *pmd, unsigned long addr, unsigned long next)
1590 struct folio *folio;
1591 struct mm_struct *mm = tlb->mm;
1594 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1596 ptl = pmd_trans_huge_lock(pmd, vma);
1601 if (is_huge_zero_pmd(orig_pmd))
1604 if (unlikely(!pmd_present(orig_pmd))) {
1605 VM_BUG_ON(thp_migration_supported() &&
1606 !is_pmd_migration_entry(orig_pmd));
1610 folio = pfn_folio(pmd_pfn(orig_pmd));
1612 * If other processes are mapping this folio, we couldn't discard
1613 * the folio unless they all do MADV_FREE so let's skip the folio.
1615 if (folio_mapcount(folio) != 1)
1618 if (!folio_trylock(folio))
1622 * If user want to discard part-pages of THP, split it so MADV_FREE
1623 * will deactivate only them.
1625 if (next - addr != HPAGE_PMD_SIZE) {
1629 folio_unlock(folio);
1634 if (folio_test_dirty(folio))
1635 folio_clear_dirty(folio);
1636 folio_unlock(folio);
1638 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1639 pmdp_invalidate(vma, addr, pmd);
1640 orig_pmd = pmd_mkold(orig_pmd);
1641 orig_pmd = pmd_mkclean(orig_pmd);
1643 set_pmd_at(mm, addr, pmd, orig_pmd);
1644 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1647 folio_mark_lazyfree(folio);
1655 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1659 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1660 pte_free(mm, pgtable);
1664 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1665 pmd_t *pmd, unsigned long addr)
1670 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1672 ptl = __pmd_trans_huge_lock(pmd, vma);
1676 * For architectures like ppc64 we look at deposited pgtable
1677 * when calling pmdp_huge_get_and_clear. So do the
1678 * pgtable_trans_huge_withdraw after finishing pmdp related
1681 orig_pmd = pmdp_huge_get_and_clear_full(vma, addr, pmd,
1683 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1684 if (vma_is_special_huge(vma)) {
1685 if (arch_needs_pgtable_deposit())
1686 zap_deposited_table(tlb->mm, pmd);
1688 } else if (is_huge_zero_pmd(orig_pmd)) {
1689 zap_deposited_table(tlb->mm, pmd);
1692 struct page *page = NULL;
1693 int flush_needed = 1;
1695 if (pmd_present(orig_pmd)) {
1696 page = pmd_page(orig_pmd);
1697 page_remove_rmap(page, vma, true);
1698 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1699 VM_BUG_ON_PAGE(!PageHead(page), page);
1700 } else if (thp_migration_supported()) {
1703 VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1704 entry = pmd_to_swp_entry(orig_pmd);
1705 page = pfn_swap_entry_to_page(entry);
1708 WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1710 if (PageAnon(page)) {
1711 zap_deposited_table(tlb->mm, pmd);
1712 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1714 if (arch_needs_pgtable_deposit())
1715 zap_deposited_table(tlb->mm, pmd);
1716 add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1721 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1726 #ifndef pmd_move_must_withdraw
1727 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1728 spinlock_t *old_pmd_ptl,
1729 struct vm_area_struct *vma)
1732 * With split pmd lock we also need to move preallocated
1733 * PTE page table if new_pmd is on different PMD page table.
1735 * We also don't deposit and withdraw tables for file pages.
1737 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1741 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1743 #ifdef CONFIG_MEM_SOFT_DIRTY
1744 if (unlikely(is_pmd_migration_entry(pmd)))
1745 pmd = pmd_swp_mksoft_dirty(pmd);
1746 else if (pmd_present(pmd))
1747 pmd = pmd_mksoft_dirty(pmd);
1752 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1753 unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
1755 spinlock_t *old_ptl, *new_ptl;
1757 struct mm_struct *mm = vma->vm_mm;
1758 bool force_flush = false;
1761 * The destination pmd shouldn't be established, free_pgtables()
1762 * should have release it.
1764 if (WARN_ON(!pmd_none(*new_pmd))) {
1765 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1770 * We don't have to worry about the ordering of src and dst
1771 * ptlocks because exclusive mmap_lock prevents deadlock.
1773 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1775 new_ptl = pmd_lockptr(mm, new_pmd);
1776 if (new_ptl != old_ptl)
1777 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1778 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1779 if (pmd_present(pmd))
1781 VM_BUG_ON(!pmd_none(*new_pmd));
1783 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1785 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1786 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1788 pmd = move_soft_dirty_pmd(pmd);
1789 set_pmd_at(mm, new_addr, new_pmd, pmd);
1791 flush_pmd_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1792 if (new_ptl != old_ptl)
1793 spin_unlock(new_ptl);
1794 spin_unlock(old_ptl);
1802 * - 0 if PMD could not be locked
1803 * - 1 if PMD was locked but protections unchanged and TLB flush unnecessary
1804 * or if prot_numa but THP migration is not supported
1805 * - HPAGE_PMD_NR if protections changed and TLB flush necessary
1807 int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1808 pmd_t *pmd, unsigned long addr, pgprot_t newprot,
1809 unsigned long cp_flags)
1811 struct mm_struct *mm = vma->vm_mm;
1813 pmd_t oldpmd, entry;
1814 bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
1815 bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
1816 bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
1819 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1821 if (prot_numa && !thp_migration_supported())
1824 ptl = __pmd_trans_huge_lock(pmd, vma);
1828 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1829 if (is_swap_pmd(*pmd)) {
1830 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1831 struct page *page = pfn_swap_entry_to_page(entry);
1834 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1835 if (is_writable_migration_entry(entry)) {
1837 * A protection check is difficult so
1838 * just be safe and disable write
1841 entry = make_readable_exclusive_migration_entry(swp_offset(entry));
1843 entry = make_readable_migration_entry(swp_offset(entry));
1844 newpmd = swp_entry_to_pmd(entry);
1845 if (pmd_swp_soft_dirty(*pmd))
1846 newpmd = pmd_swp_mksoft_dirty(newpmd);
1852 newpmd = pmd_swp_mkuffd_wp(newpmd);
1853 else if (uffd_wp_resolve)
1854 newpmd = pmd_swp_clear_uffd_wp(newpmd);
1855 if (!pmd_same(*pmd, newpmd))
1856 set_pmd_at(mm, addr, pmd, newpmd);
1865 * Avoid trapping faults against the zero page. The read-only
1866 * data is likely to be read-cached on the local CPU and
1867 * local/remote hits to the zero page are not interesting.
1869 if (is_huge_zero_pmd(*pmd))
1872 if (pmd_protnone(*pmd))
1875 page = pmd_page(*pmd);
1876 toptier = node_is_toptier(page_to_nid(page));
1878 * Skip scanning top tier node if normal numa
1879 * balancing is disabled
1881 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
1885 if (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING &&
1887 xchg_page_access_time(page, jiffies_to_msecs(jiffies));
1890 * In case prot_numa, we are under mmap_read_lock(mm). It's critical
1891 * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1892 * which is also under mmap_read_lock(mm):
1895 * change_huge_pmd(prot_numa=1)
1896 * pmdp_huge_get_and_clear_notify()
1897 * madvise_dontneed()
1899 * pmd_trans_huge(*pmd) == 0 (without ptl)
1902 * // pmd is re-established
1904 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1905 * which may break userspace.
1907 * pmdp_invalidate_ad() is required to make sure we don't miss
1908 * dirty/young flags set by hardware.
1910 oldpmd = pmdp_invalidate_ad(vma, addr, pmd);
1912 entry = pmd_modify(oldpmd, newprot);
1914 entry = pmd_mkuffd_wp(entry);
1915 else if (uffd_wp_resolve)
1917 * Leave the write bit to be handled by PF interrupt
1918 * handler, then things like COW could be properly
1921 entry = pmd_clear_uffd_wp(entry);
1923 /* See change_pte_range(). */
1924 if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && !pmd_write(entry) &&
1925 can_change_pmd_writable(vma, addr, entry))
1926 entry = pmd_mkwrite(entry);
1929 set_pmd_at(mm, addr, pmd, entry);
1931 if (huge_pmd_needs_flush(oldpmd, entry))
1932 tlb_flush_pmd_range(tlb, addr, HPAGE_PMD_SIZE);
1939 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1941 * Note that if it returns page table lock pointer, this routine returns without
1942 * unlocking page table lock. So callers must unlock it.
1944 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1947 ptl = pmd_lock(vma->vm_mm, pmd);
1948 if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1956 * Returns page table lock pointer if a given pud maps a thp, NULL otherwise.
1958 * Note that if it returns page table lock pointer, this routine returns without
1959 * unlocking page table lock. So callers must unlock it.
1961 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1965 ptl = pud_lock(vma->vm_mm, pud);
1966 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1972 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1973 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1974 pud_t *pud, unsigned long addr)
1978 ptl = __pud_trans_huge_lock(pud, vma);
1982 pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
1983 tlb_remove_pud_tlb_entry(tlb, pud, addr);
1984 if (vma_is_special_huge(vma)) {
1986 /* No zero page support yet */
1988 /* No support for anonymous PUD pages yet */
1994 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
1995 unsigned long haddr)
1997 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
1998 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1999 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2000 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2002 count_vm_event(THP_SPLIT_PUD);
2004 pudp_huge_clear_flush_notify(vma, haddr, pud);
2007 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2008 unsigned long address)
2011 struct mmu_notifier_range range;
2013 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
2014 address & HPAGE_PUD_MASK,
2015 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2016 mmu_notifier_invalidate_range_start(&range);
2017 ptl = pud_lock(vma->vm_mm, pud);
2018 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2020 __split_huge_pud_locked(vma, pud, range.start);
2025 * No need to double call mmu_notifier->invalidate_range() callback as
2026 * the above pudp_huge_clear_flush_notify() did already call it.
2028 mmu_notifier_invalidate_range_only_end(&range);
2030 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2032 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2033 unsigned long haddr, pmd_t *pmd)
2035 struct mm_struct *mm = vma->vm_mm;
2037 pmd_t _pmd, old_pmd;
2041 * Leave pmd empty until pte is filled note that it is fine to delay
2042 * notification until mmu_notifier_invalidate_range_end() as we are
2043 * replacing a zero pmd write protected page with a zero pte write
2046 * See Documentation/mm/mmu_notifier.rst
2048 old_pmd = pmdp_huge_clear_flush(vma, haddr, pmd);
2050 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2051 pmd_populate(mm, &_pmd, pgtable);
2053 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2055 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2056 entry = pte_mkspecial(entry);
2057 if (pmd_uffd_wp(old_pmd))
2058 entry = pte_mkuffd_wp(entry);
2059 pte = pte_offset_map(&_pmd, haddr);
2060 VM_BUG_ON(!pte_none(*pte));
2061 set_pte_at(mm, haddr, pte, entry);
2064 smp_wmb(); /* make pte visible before pmd */
2065 pmd_populate(mm, pmd, pgtable);
2068 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2069 unsigned long haddr, bool freeze)
2071 struct mm_struct *mm = vma->vm_mm;
2074 pmd_t old_pmd, _pmd;
2075 bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false;
2076 bool anon_exclusive = false, dirty = false;
2080 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2081 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2082 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2083 VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2084 && !pmd_devmap(*pmd));
2086 count_vm_event(THP_SPLIT_PMD);
2088 if (!vma_is_anonymous(vma)) {
2089 old_pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2091 * We are going to unmap this huge page. So
2092 * just go ahead and zap it
2094 if (arch_needs_pgtable_deposit())
2095 zap_deposited_table(mm, pmd);
2096 if (vma_is_special_huge(vma))
2098 if (unlikely(is_pmd_migration_entry(old_pmd))) {
2101 entry = pmd_to_swp_entry(old_pmd);
2102 page = pfn_swap_entry_to_page(entry);
2104 page = pmd_page(old_pmd);
2105 if (!PageDirty(page) && pmd_dirty(old_pmd))
2106 set_page_dirty(page);
2107 if (!PageReferenced(page) && pmd_young(old_pmd))
2108 SetPageReferenced(page);
2109 page_remove_rmap(page, vma, true);
2112 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2116 if (is_huge_zero_pmd(*pmd)) {
2118 * FIXME: Do we want to invalidate secondary mmu by calling
2119 * mmu_notifier_invalidate_range() see comments below inside
2120 * __split_huge_pmd() ?
2122 * We are going from a zero huge page write protected to zero
2123 * small page also write protected so it does not seems useful
2124 * to invalidate secondary mmu at this time.
2126 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2130 * Up to this point the pmd is present and huge and userland has the
2131 * whole access to the hugepage during the split (which happens in
2132 * place). If we overwrite the pmd with the not-huge version pointing
2133 * to the pte here (which of course we could if all CPUs were bug
2134 * free), userland could trigger a small page size TLB miss on the
2135 * small sized TLB while the hugepage TLB entry is still established in
2136 * the huge TLB. Some CPU doesn't like that.
2137 * See http://support.amd.com/TechDocs/41322_10h_Rev_Gd.pdf, Erratum
2138 * 383 on page 105. Intel should be safe but is also warns that it's
2139 * only safe if the permission and cache attributes of the two entries
2140 * loaded in the two TLB is identical (which should be the case here).
2141 * But it is generally safer to never allow small and huge TLB entries
2142 * for the same virtual address to be loaded simultaneously. So instead
2143 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2144 * current pmd notpresent (atomically because here the pmd_trans_huge
2145 * must remain set at all times on the pmd until the split is complete
2146 * for this pmd), then we flush the SMP TLB and finally we write the
2147 * non-huge version of the pmd entry with pmd_populate.
2149 old_pmd = pmdp_invalidate(vma, haddr, pmd);
2151 pmd_migration = is_pmd_migration_entry(old_pmd);
2152 if (unlikely(pmd_migration)) {
2155 entry = pmd_to_swp_entry(old_pmd);
2156 page = pfn_swap_entry_to_page(entry);
2157 write = is_writable_migration_entry(entry);
2159 anon_exclusive = is_readable_exclusive_migration_entry(entry);
2160 young = is_migration_entry_young(entry);
2161 dirty = is_migration_entry_dirty(entry);
2162 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2163 uffd_wp = pmd_swp_uffd_wp(old_pmd);
2165 page = pmd_page(old_pmd);
2166 if (pmd_dirty(old_pmd)) {
2170 write = pmd_write(old_pmd);
2171 young = pmd_young(old_pmd);
2172 soft_dirty = pmd_soft_dirty(old_pmd);
2173 uffd_wp = pmd_uffd_wp(old_pmd);
2175 VM_BUG_ON_PAGE(!page_count(page), page);
2178 * Without "freeze", we'll simply split the PMD, propagating the
2179 * PageAnonExclusive() flag for each PTE by setting it for
2180 * each subpage -- no need to (temporarily) clear.
2182 * With "freeze" we want to replace mapped pages by
2183 * migration entries right away. This is only possible if we
2184 * managed to clear PageAnonExclusive() -- see
2185 * set_pmd_migration_entry().
2187 * In case we cannot clear PageAnonExclusive(), split the PMD
2188 * only and let try_to_migrate_one() fail later.
2190 * See page_try_share_anon_rmap(): invalidate PMD first.
2192 anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
2193 if (freeze && anon_exclusive && page_try_share_anon_rmap(page))
2196 page_ref_add(page, HPAGE_PMD_NR - 1);
2200 * Withdraw the table only after we mark the pmd entry invalid.
2201 * This's critical for some architectures (Power).
2203 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2204 pmd_populate(mm, &_pmd, pgtable);
2206 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2209 * Note that NUMA hinting access restrictions are not
2210 * transferred to avoid any possibility of altering
2211 * permissions across VMAs.
2213 if (freeze || pmd_migration) {
2214 swp_entry_t swp_entry;
2216 swp_entry = make_writable_migration_entry(
2217 page_to_pfn(page + i));
2218 else if (anon_exclusive)
2219 swp_entry = make_readable_exclusive_migration_entry(
2220 page_to_pfn(page + i));
2222 swp_entry = make_readable_migration_entry(
2223 page_to_pfn(page + i));
2225 swp_entry = make_migration_entry_young(swp_entry);
2227 swp_entry = make_migration_entry_dirty(swp_entry);
2228 entry = swp_entry_to_pte(swp_entry);
2230 entry = pte_swp_mksoft_dirty(entry);
2232 entry = pte_swp_mkuffd_wp(entry);
2234 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2236 entry = pte_mkwrite(entry);
2238 SetPageAnonExclusive(page + i);
2240 entry = pte_mkold(entry);
2241 /* NOTE: this may set soft-dirty too on some archs */
2243 entry = pte_mkdirty(entry);
2245 entry = pte_mksoft_dirty(entry);
2247 entry = pte_mkuffd_wp(entry);
2248 page_add_anon_rmap(page + i, vma, addr, false);
2250 pte = pte_offset_map(&_pmd, addr);
2251 BUG_ON(!pte_none(*pte));
2252 set_pte_at(mm, addr, pte, entry);
2257 page_remove_rmap(page, vma, true);
2261 smp_wmb(); /* make pte visible before pmd */
2262 pmd_populate(mm, pmd, pgtable);
2265 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2266 unsigned long address, bool freeze, struct folio *folio)
2269 struct mmu_notifier_range range;
2271 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
2272 address & HPAGE_PMD_MASK,
2273 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2274 mmu_notifier_invalidate_range_start(&range);
2275 ptl = pmd_lock(vma->vm_mm, pmd);
2278 * If caller asks to setup a migration entry, we need a folio to check
2279 * pmd against. Otherwise we can end up replacing wrong folio.
2281 VM_BUG_ON(freeze && !folio);
2282 VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
2284 if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
2285 is_pmd_migration_entry(*pmd)) {
2287 * It's safe to call pmd_page when folio is set because it's
2288 * guaranteed that pmd is present.
2290 if (folio && folio != page_folio(pmd_page(*pmd)))
2292 __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2298 * No need to double call mmu_notifier->invalidate_range() callback.
2299 * They are 3 cases to consider inside __split_huge_pmd_locked():
2300 * 1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2301 * 2) __split_huge_zero_page_pmd() read only zero page and any write
2302 * fault will trigger a flush_notify before pointing to a new page
2303 * (it is fine if the secondary mmu keeps pointing to the old zero
2304 * page in the meantime)
2305 * 3) Split a huge pmd into pte pointing to the same page. No need
2306 * to invalidate secondary tlb entry they are all still valid.
2307 * any further changes to individual pte will notify. So no need
2308 * to call mmu_notifier->invalidate_range()
2310 mmu_notifier_invalidate_range_only_end(&range);
2313 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2314 bool freeze, struct folio *folio)
2316 pmd_t *pmd = mm_find_pmd(vma->vm_mm, address);
2321 __split_huge_pmd(vma, pmd, address, freeze, folio);
2324 static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address)
2327 * If the new address isn't hpage aligned and it could previously
2328 * contain an hugepage: check if we need to split an huge pmd.
2330 if (!IS_ALIGNED(address, HPAGE_PMD_SIZE) &&
2331 range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE),
2332 ALIGN(address, HPAGE_PMD_SIZE)))
2333 split_huge_pmd_address(vma, address, false, NULL);
2336 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2337 unsigned long start,
2341 /* Check if we need to split start first. */
2342 split_huge_pmd_if_needed(vma, start);
2344 /* Check if we need to split end next. */
2345 split_huge_pmd_if_needed(vma, end);
2348 * If we're also updating the next vma vm_start,
2349 * check if we need to split it.
2351 if (adjust_next > 0) {
2352 struct vm_area_struct *next = find_vma(vma->vm_mm, vma->vm_end);
2353 unsigned long nstart = next->vm_start;
2354 nstart += adjust_next;
2355 split_huge_pmd_if_needed(next, nstart);
2359 static void unmap_folio(struct folio *folio)
2361 enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
2364 VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
2367 * Anon pages need migration entries to preserve them, but file
2368 * pages can simply be left unmapped, then faulted back on demand.
2369 * If that is ever changed (perhaps for mlock), update remap_page().
2371 if (folio_test_anon(folio))
2372 try_to_migrate(folio, ttu_flags);
2374 try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK);
2377 static void remap_page(struct folio *folio, unsigned long nr)
2381 /* If unmap_folio() uses try_to_migrate() on file, remove this check */
2382 if (!folio_test_anon(folio))
2385 remove_migration_ptes(folio, folio, true);
2386 i += folio_nr_pages(folio);
2389 folio = folio_next(folio);
2393 static void lru_add_page_tail(struct page *head, struct page *tail,
2394 struct lruvec *lruvec, struct list_head *list)
2396 VM_BUG_ON_PAGE(!PageHead(head), head);
2397 VM_BUG_ON_PAGE(PageCompound(tail), head);
2398 VM_BUG_ON_PAGE(PageLRU(tail), head);
2399 lockdep_assert_held(&lruvec->lru_lock);
2402 /* page reclaim is reclaiming a huge page */
2403 VM_WARN_ON(PageLRU(head));
2405 list_add_tail(&tail->lru, list);
2407 /* head is still on lru (and we have it frozen) */
2408 VM_WARN_ON(!PageLRU(head));
2409 if (PageUnevictable(tail))
2410 tail->mlock_count = 0;
2412 list_add_tail(&tail->lru, &head->lru);
2417 static void __split_huge_page_tail(struct page *head, int tail,
2418 struct lruvec *lruvec, struct list_head *list)
2420 struct page *page_tail = head + tail;
2422 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2425 * Clone page flags before unfreezing refcount.
2427 * After successful get_page_unless_zero() might follow flags change,
2428 * for example lock_page() which set PG_waiters.
2430 * Note that for mapped sub-pages of an anonymous THP,
2431 * PG_anon_exclusive has been cleared in unmap_folio() and is stored in
2432 * the migration entry instead from where remap_page() will restore it.
2433 * We can still have PG_anon_exclusive set on effectively unmapped and
2434 * unreferenced sub-pages of an anonymous THP: we can simply drop
2435 * PG_anon_exclusive (-> PG_mappedtodisk) for these here.
2437 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2438 page_tail->flags |= (head->flags &
2439 ((1L << PG_referenced) |
2440 (1L << PG_swapbacked) |
2441 (1L << PG_swapcache) |
2442 (1L << PG_mlocked) |
2443 (1L << PG_uptodate) |
2445 (1L << PG_workingset) |
2447 (1L << PG_unevictable) |
2448 #ifdef CONFIG_ARCH_USES_PG_ARCH_X
2453 LRU_GEN_MASK | LRU_REFS_MASK));
2455 /* ->mapping in first and second tail page is replaced by other uses */
2456 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2458 page_tail->mapping = head->mapping;
2459 page_tail->index = head->index + tail;
2462 * page->private should not be set in tail pages with the exception
2463 * of swap cache pages that store the swp_entry_t in tail pages.
2464 * Fix up and warn once if private is unexpectedly set.
2466 * What of 32-bit systems, on which folio->_pincount overlays
2467 * head[1].private? No problem: THP_SWAP is not enabled on 32-bit, and
2468 * pincount must be 0 for folio_ref_freeze() to have succeeded.
2470 if (!folio_test_swapcache(page_folio(head))) {
2471 VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, page_tail);
2472 page_tail->private = 0;
2475 /* Page flags must be visible before we make the page non-compound. */
2479 * Clear PageTail before unfreezing page refcount.
2481 * After successful get_page_unless_zero() might follow put_page()
2482 * which needs correct compound_head().
2484 clear_compound_head(page_tail);
2486 /* Finally unfreeze refcount. Additional reference from page cache. */
2487 page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2488 PageSwapCache(head)));
2490 if (page_is_young(head))
2491 set_page_young(page_tail);
2492 if (page_is_idle(head))
2493 set_page_idle(page_tail);
2495 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2498 * always add to the tail because some iterators expect new
2499 * pages to show after the currently processed elements - e.g.
2502 lru_add_page_tail(head, page_tail, lruvec, list);
2505 static void __split_huge_page(struct page *page, struct list_head *list,
2508 struct folio *folio = page_folio(page);
2509 struct page *head = &folio->page;
2510 struct lruvec *lruvec;
2511 struct address_space *swap_cache = NULL;
2512 unsigned long offset = 0;
2513 unsigned int nr = thp_nr_pages(head);
2516 /* complete memcg works before add pages to LRU */
2517 split_page_memcg(head, nr);
2519 if (PageAnon(head) && PageSwapCache(head)) {
2520 swp_entry_t entry = { .val = page_private(head) };
2522 offset = swp_offset(entry);
2523 swap_cache = swap_address_space(entry);
2524 xa_lock(&swap_cache->i_pages);
2527 /* lock lru list/PageCompound, ref frozen by page_ref_freeze */
2528 lruvec = folio_lruvec_lock(folio);
2530 ClearPageHasHWPoisoned(head);
2532 for (i = nr - 1; i >= 1; i--) {
2533 __split_huge_page_tail(head, i, lruvec, list);
2534 /* Some pages can be beyond EOF: drop them from page cache */
2535 if (head[i].index >= end) {
2536 struct folio *tail = page_folio(head + i);
2538 if (shmem_mapping(head->mapping))
2539 shmem_uncharge(head->mapping->host, 1);
2540 else if (folio_test_clear_dirty(tail))
2541 folio_account_cleaned(tail,
2542 inode_to_wb(folio->mapping->host));
2543 __filemap_remove_folio(tail, NULL);
2545 } else if (!PageAnon(page)) {
2546 __xa_store(&head->mapping->i_pages, head[i].index,
2548 } else if (swap_cache) {
2549 __xa_store(&swap_cache->i_pages, offset + i,
2554 ClearPageCompound(head);
2555 unlock_page_lruvec(lruvec);
2556 /* Caller disabled irqs, so they are still disabled here */
2558 split_page_owner(head, nr);
2560 /* See comment in __split_huge_page_tail() */
2561 if (PageAnon(head)) {
2562 /* Additional pin to swap cache */
2563 if (PageSwapCache(head)) {
2564 page_ref_add(head, 2);
2565 xa_unlock(&swap_cache->i_pages);
2570 /* Additional pin to page cache */
2571 page_ref_add(head, 2);
2572 xa_unlock(&head->mapping->i_pages);
2576 remap_page(folio, nr);
2578 if (PageSwapCache(head)) {
2579 swp_entry_t entry = { .val = page_private(head) };
2581 split_swap_cluster(entry);
2584 for (i = 0; i < nr; i++) {
2585 struct page *subpage = head + i;
2586 if (subpage == page)
2588 unlock_page(subpage);
2591 * Subpages may be freed if there wasn't any mapping
2592 * like if add_to_swap() is running on a lru page that
2593 * had its mapping zapped. And freeing these pages
2594 * requires taking the lru_lock so we do the put_page
2595 * of the tail pages after the split is complete.
2597 free_page_and_swap_cache(subpage);
2601 /* Racy check whether the huge page can be split */
2602 bool can_split_folio(struct folio *folio, int *pextra_pins)
2606 /* Additional pins from page cache */
2607 if (folio_test_anon(folio))
2608 extra_pins = folio_test_swapcache(folio) ?
2609 folio_nr_pages(folio) : 0;
2611 extra_pins = folio_nr_pages(folio);
2613 *pextra_pins = extra_pins;
2614 return folio_mapcount(folio) == folio_ref_count(folio) - extra_pins - 1;
2618 * This function splits huge page into normal pages. @page can point to any
2619 * subpage of huge page to split. Split doesn't change the position of @page.
2621 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2622 * The huge page must be locked.
2624 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2626 * Both head page and tail pages will inherit mapping, flags, and so on from
2629 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2630 * they are not mapped.
2632 * Returns 0 if the hugepage is split successfully.
2633 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2636 int split_huge_page_to_list(struct page *page, struct list_head *list)
2638 struct folio *folio = page_folio(page);
2639 struct deferred_split *ds_queue = get_deferred_split_queue(folio);
2640 XA_STATE(xas, &folio->mapping->i_pages, folio->index);
2641 struct anon_vma *anon_vma = NULL;
2642 struct address_space *mapping = NULL;
2643 int extra_pins, ret;
2647 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
2648 VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
2650 is_hzp = is_huge_zero_page(&folio->page);
2652 pr_warn_ratelimited("Called split_huge_page for huge zero page\n");
2656 if (folio_test_writeback(folio))
2659 if (folio_test_anon(folio)) {
2661 * The caller does not necessarily hold an mmap_lock that would
2662 * prevent the anon_vma disappearing so we first we take a
2663 * reference to it and then lock the anon_vma for write. This
2664 * is similar to folio_lock_anon_vma_read except the write lock
2665 * is taken to serialise against parallel split or collapse
2668 anon_vma = folio_get_anon_vma(folio);
2675 anon_vma_lock_write(anon_vma);
2679 mapping = folio->mapping;
2687 gfp = current_gfp_context(mapping_gfp_mask(mapping) &
2690 if (folio_test_private(folio) &&
2691 !filemap_release_folio(folio, gfp)) {
2696 xas_split_alloc(&xas, folio, folio_order(folio), gfp);
2697 if (xas_error(&xas)) {
2698 ret = xas_error(&xas);
2703 i_mmap_lock_read(mapping);
2706 *__split_huge_page() may need to trim off pages beyond EOF:
2707 * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2708 * which cannot be nested inside the page tree lock. So note
2709 * end now: i_size itself may be changed at any moment, but
2710 * folio lock is good enough to serialize the trimming.
2712 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2713 if (shmem_mapping(mapping))
2714 end = shmem_fallocend(mapping->host, end);
2718 * Racy check if we can split the page, before unmap_folio() will
2721 if (!can_split_folio(folio, &extra_pins)) {
2728 /* block interrupt reentry in xa_lock and spinlock */
2729 local_irq_disable();
2732 * Check if the folio is present in page cache.
2733 * We assume all tail are present too, if folio is there.
2737 if (xas_load(&xas) != folio)
2741 /* Prevent deferred_split_scan() touching ->_refcount */
2742 spin_lock(&ds_queue->split_queue_lock);
2743 if (folio_ref_freeze(folio, 1 + extra_pins)) {
2744 if (!list_empty(&folio->_deferred_list)) {
2745 ds_queue->split_queue_len--;
2746 list_del(&folio->_deferred_list);
2748 spin_unlock(&ds_queue->split_queue_lock);
2750 int nr = folio_nr_pages(folio);
2752 xas_split(&xas, folio, folio_order(folio));
2753 if (folio_test_swapbacked(folio)) {
2754 __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS,
2757 __lruvec_stat_mod_folio(folio, NR_FILE_THPS,
2759 filemap_nr_thps_dec(mapping);
2763 __split_huge_page(page, list, end);
2766 spin_unlock(&ds_queue->split_queue_lock);
2771 remap_page(folio, folio_nr_pages(folio));
2777 anon_vma_unlock_write(anon_vma);
2778 put_anon_vma(anon_vma);
2781 i_mmap_unlock_read(mapping);
2784 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2788 void free_transhuge_page(struct page *page)
2790 struct folio *folio = (struct folio *)page;
2791 struct deferred_split *ds_queue = get_deferred_split_queue(folio);
2792 unsigned long flags;
2794 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2795 if (!list_empty(&folio->_deferred_list)) {
2796 ds_queue->split_queue_len--;
2797 list_del(&folio->_deferred_list);
2799 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2800 free_compound_page(page);
2803 void deferred_split_folio(struct folio *folio)
2805 struct deferred_split *ds_queue = get_deferred_split_queue(folio);
2807 struct mem_cgroup *memcg = folio_memcg(folio);
2809 unsigned long flags;
2811 VM_BUG_ON_FOLIO(folio_order(folio) < 2, folio);
2814 * The try_to_unmap() in page reclaim path might reach here too,
2815 * this may cause a race condition to corrupt deferred split queue.
2816 * And, if page reclaim is already handling the same folio, it is
2817 * unnecessary to handle it again in shrinker.
2819 * Check the swapcache flag to determine if the folio is being
2820 * handled by page reclaim since THP swap would add the folio into
2821 * swap cache before calling try_to_unmap().
2823 if (folio_test_swapcache(folio))
2826 if (!list_empty(&folio->_deferred_list))
2829 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2830 if (list_empty(&folio->_deferred_list)) {
2831 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2832 list_add_tail(&folio->_deferred_list, &ds_queue->split_queue);
2833 ds_queue->split_queue_len++;
2836 set_shrinker_bit(memcg, folio_nid(folio),
2837 deferred_split_shrinker.id);
2840 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2843 static unsigned long deferred_split_count(struct shrinker *shrink,
2844 struct shrink_control *sc)
2846 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2847 struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2851 ds_queue = &sc->memcg->deferred_split_queue;
2853 return READ_ONCE(ds_queue->split_queue_len);
2856 static unsigned long deferred_split_scan(struct shrinker *shrink,
2857 struct shrink_control *sc)
2859 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2860 struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2861 unsigned long flags;
2863 struct folio *folio, *next;
2868 ds_queue = &sc->memcg->deferred_split_queue;
2871 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2872 /* Take pin on all head pages to avoid freeing them under us */
2873 list_for_each_entry_safe(folio, next, &ds_queue->split_queue,
2875 if (folio_try_get(folio)) {
2876 list_move(&folio->_deferred_list, &list);
2878 /* We lost race with folio_put() */
2879 list_del_init(&folio->_deferred_list);
2880 ds_queue->split_queue_len--;
2882 if (!--sc->nr_to_scan)
2885 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2887 list_for_each_entry_safe(folio, next, &list, _deferred_list) {
2888 if (!folio_trylock(folio))
2890 /* split_huge_page() removes page from list on success */
2891 if (!split_folio(folio))
2893 folio_unlock(folio);
2898 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2899 list_splice_tail(&list, &ds_queue->split_queue);
2900 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2903 * Stop shrinker if we didn't split any page, but the queue is empty.
2904 * This can happen if pages were freed under us.
2906 if (!split && list_empty(&ds_queue->split_queue))
2911 static struct shrinker deferred_split_shrinker = {
2912 .count_objects = deferred_split_count,
2913 .scan_objects = deferred_split_scan,
2914 .seeks = DEFAULT_SEEKS,
2915 .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
2919 #ifdef CONFIG_DEBUG_FS
2920 static void split_huge_pages_all(void)
2924 struct folio *folio;
2925 unsigned long pfn, max_zone_pfn;
2926 unsigned long total = 0, split = 0;
2928 pr_debug("Split all THPs\n");
2929 for_each_zone(zone) {
2930 if (!managed_zone(zone))
2932 max_zone_pfn = zone_end_pfn(zone);
2933 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2936 page = pfn_to_online_page(pfn);
2937 if (!page || PageTail(page))
2939 folio = page_folio(page);
2940 if (!folio_try_get(folio))
2943 if (unlikely(page_folio(page) != folio))
2946 if (zone != folio_zone(folio))
2949 if (!folio_test_large(folio)
2950 || folio_test_hugetlb(folio)
2951 || !folio_test_lru(folio))
2956 nr_pages = folio_nr_pages(folio);
2957 if (!split_folio(folio))
2959 pfn += nr_pages - 1;
2960 folio_unlock(folio);
2967 pr_debug("%lu of %lu THP split\n", split, total);
2970 static inline bool vma_not_suitable_for_thp_split(struct vm_area_struct *vma)
2972 return vma_is_special_huge(vma) || (vma->vm_flags & VM_IO) ||
2973 is_vm_hugetlb_page(vma);
2976 static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
2977 unsigned long vaddr_end)
2980 struct task_struct *task;
2981 struct mm_struct *mm;
2982 unsigned long total = 0, split = 0;
2985 vaddr_start &= PAGE_MASK;
2986 vaddr_end &= PAGE_MASK;
2988 /* Find the task_struct from pid */
2990 task = find_task_by_vpid(pid);
2996 get_task_struct(task);
2999 /* Find the mm_struct */
3000 mm = get_task_mm(task);
3001 put_task_struct(task);
3008 pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx]\n",
3009 pid, vaddr_start, vaddr_end);
3013 * always increase addr by PAGE_SIZE, since we could have a PTE page
3014 * table filled with PTE-mapped THPs, each of which is distinct.
3016 for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) {
3017 struct vm_area_struct *vma = vma_lookup(mm, addr);
3023 /* skip special VMA and hugetlb VMA */
3024 if (vma_not_suitable_for_thp_split(vma)) {
3029 /* FOLL_DUMP to ignore special (like zero) pages */
3030 page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
3032 if (IS_ERR_OR_NULL(page))
3035 if (!is_transparent_hugepage(page))
3039 if (!can_split_folio(page_folio(page), NULL))
3042 if (!trylock_page(page))
3045 if (!split_huge_page(page))
3053 mmap_read_unlock(mm);
3056 pr_debug("%lu of %lu THP split\n", split, total);
3062 static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
3065 struct filename *file;
3066 struct file *candidate;
3067 struct address_space *mapping;
3071 unsigned long total = 0, split = 0;
3073 file = getname_kernel(file_path);
3077 candidate = file_open_name(file, O_RDONLY, 0);
3078 if (IS_ERR(candidate))
3081 pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n",
3082 file_path, off_start, off_end);
3084 mapping = candidate->f_mapping;
3086 for (index = off_start; index < off_end; index += nr_pages) {
3087 struct folio *folio = filemap_get_folio(mapping, index);
3093 if (!folio_test_large(folio))
3097 nr_pages = folio_nr_pages(folio);
3099 if (!folio_trylock(folio))
3102 if (!split_folio(folio))
3105 folio_unlock(folio);
3111 filp_close(candidate, NULL);
3114 pr_debug("%lu of %lu file-backed THP split\n", split, total);
3120 #define MAX_INPUT_BUF_SZ 255
3122 static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
3123 size_t count, loff_t *ppops)
3125 static DEFINE_MUTEX(split_debug_mutex);
3127 /* hold pid, start_vaddr, end_vaddr or file_path, off_start, off_end */
3128 char input_buf[MAX_INPUT_BUF_SZ];
3130 unsigned long vaddr_start, vaddr_end;
3132 ret = mutex_lock_interruptible(&split_debug_mutex);
3138 memset(input_buf, 0, MAX_INPUT_BUF_SZ);
3139 if (copy_from_user(input_buf, buf, min_t(size_t, count, MAX_INPUT_BUF_SZ)))
3142 input_buf[MAX_INPUT_BUF_SZ - 1] = '\0';
3144 if (input_buf[0] == '/') {
3146 char *buf = input_buf;
3147 char file_path[MAX_INPUT_BUF_SZ];
3148 pgoff_t off_start = 0, off_end = 0;
3149 size_t input_len = strlen(input_buf);
3151 tok = strsep(&buf, ",");
3153 strcpy(file_path, tok);
3159 ret = sscanf(buf, "0x%lx,0x%lx", &off_start, &off_end);
3164 ret = split_huge_pages_in_file(file_path, off_start, off_end);
3171 ret = sscanf(input_buf, "%d,0x%lx,0x%lx", &pid, &vaddr_start, &vaddr_end);
3172 if (ret == 1 && pid == 1) {
3173 split_huge_pages_all();
3174 ret = strlen(input_buf);
3176 } else if (ret != 3) {
3181 ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end);
3183 ret = strlen(input_buf);
3185 mutex_unlock(&split_debug_mutex);
3190 static const struct file_operations split_huge_pages_fops = {
3191 .owner = THIS_MODULE,
3192 .write = split_huge_pages_write,
3193 .llseek = no_llseek,
3196 static int __init split_huge_pages_debugfs(void)
3198 debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3199 &split_huge_pages_fops);
3202 late_initcall(split_huge_pages_debugfs);
3205 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
3206 int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
3209 struct vm_area_struct *vma = pvmw->vma;
3210 struct mm_struct *mm = vma->vm_mm;
3211 unsigned long address = pvmw->address;
3212 bool anon_exclusive;
3217 if (!(pvmw->pmd && !pvmw->pte))
3220 flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
3221 pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
3223 /* See page_try_share_anon_rmap(): invalidate PMD first. */
3224 anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
3225 if (anon_exclusive && page_try_share_anon_rmap(page)) {
3226 set_pmd_at(mm, address, pvmw->pmd, pmdval);
3230 if (pmd_dirty(pmdval))
3231 set_page_dirty(page);
3232 if (pmd_write(pmdval))
3233 entry = make_writable_migration_entry(page_to_pfn(page));
3234 else if (anon_exclusive)
3235 entry = make_readable_exclusive_migration_entry(page_to_pfn(page));
3237 entry = make_readable_migration_entry(page_to_pfn(page));
3238 if (pmd_young(pmdval))
3239 entry = make_migration_entry_young(entry);
3240 if (pmd_dirty(pmdval))
3241 entry = make_migration_entry_dirty(entry);
3242 pmdswp = swp_entry_to_pmd(entry);
3243 if (pmd_soft_dirty(pmdval))
3244 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
3245 if (pmd_uffd_wp(pmdval))
3246 pmdswp = pmd_swp_mkuffd_wp(pmdswp);
3247 set_pmd_at(mm, address, pvmw->pmd, pmdswp);
3248 page_remove_rmap(page, vma, true);
3250 trace_set_migration_pmd(address, pmd_val(pmdswp));
3255 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
3257 struct vm_area_struct *vma = pvmw->vma;
3258 struct mm_struct *mm = vma->vm_mm;
3259 unsigned long address = pvmw->address;
3260 unsigned long haddr = address & HPAGE_PMD_MASK;
3264 if (!(pvmw->pmd && !pvmw->pte))
3267 entry = pmd_to_swp_entry(*pvmw->pmd);
3269 pmde = mk_huge_pmd(new, READ_ONCE(vma->vm_page_prot));
3270 if (pmd_swp_soft_dirty(*pvmw->pmd))
3271 pmde = pmd_mksoft_dirty(pmde);
3272 if (is_writable_migration_entry(entry))
3273 pmde = pmd_mkwrite(pmde);
3274 if (pmd_swp_uffd_wp(*pvmw->pmd))
3275 pmde = pmd_mkuffd_wp(pmde);
3276 if (!is_migration_entry_young(entry))
3277 pmde = pmd_mkold(pmde);
3278 /* NOTE: this may contain setting soft-dirty on some archs */
3279 if (PageDirty(new) && is_migration_entry_dirty(entry))
3280 pmde = pmd_mkdirty(pmde);
3282 if (PageAnon(new)) {
3283 rmap_t rmap_flags = RMAP_COMPOUND;
3285 if (!is_readable_migration_entry(entry))
3286 rmap_flags |= RMAP_EXCLUSIVE;
3288 page_add_anon_rmap(new, vma, haddr, rmap_flags);
3290 page_add_file_rmap(new, vma, true);
3292 VM_BUG_ON(pmd_write(pmde) && PageAnon(new) && !PageAnonExclusive(new));
3293 set_pmd_at(mm, haddr, pvmw->pmd, pmde);
3295 /* No need to invalidate - it was non-present before */
3296 update_mmu_cache_pmd(vma, address, pvmw->pmd);
3297 trace_remove_migration_pmd(address, pmd_val(pmde));