diff options
Diffstat (limited to 'mm/khugepaged.c')
| -rw-r--r-- | mm/khugepaged.c | 2315 |
1 files changed, 1390 insertions, 925 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 58b0d9c502a1..2b219acb528e 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -16,22 +16,29 @@ #include <linux/hashtable.h> #include <linux/userfaultfd_k.h> #include <linux/page_idle.h> +#include <linux/page_table_check.h> +#include <linux/rcupdate_wait.h> #include <linux/swapops.h> #include <linux/shmem_fs.h> +#include <linux/ksm.h> #include <asm/tlb.h> #include <asm/pgalloc.h> #include "internal.h" +#include "mm_slot.h" enum scan_result { SCAN_FAIL, SCAN_SUCCEED, SCAN_PMD_NULL, + SCAN_PMD_NONE, + SCAN_PMD_MAPPED, SCAN_EXCEED_NONE_PTE, SCAN_EXCEED_SWAP_PTE, SCAN_EXCEED_SHARED_PTE, SCAN_PTE_NON_PRESENT, SCAN_PTE_UFFD_WP, + SCAN_PTE_MAPPED_HUGEPAGE, SCAN_PAGE_RO, SCAN_LACK_REFERENCED_PAGE, SCAN_PAGE_NULL, @@ -45,12 +52,14 @@ enum scan_result { SCAN_VMA_NULL, SCAN_VMA_CHECK, SCAN_ADDRESS_RANGE, - SCAN_SWAP_CACHE_PAGE, SCAN_DEL_PAGE_LRU, SCAN_ALLOC_HUGE_PAGE_FAIL, SCAN_CGROUP_CHARGE_FAIL, SCAN_TRUNCATED, SCAN_PAGE_HAS_PRIVATE, + SCAN_STORE_FAILED, + SCAN_COPY_MC, + SCAN_PAGE_FILLED, }; #define CREATE_TRACE_POINTS @@ -73,32 +82,34 @@ static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); * default collapse hugepages if there is at least one pte mapped like * it would have happened if the vma was large enough during page * fault. + * + * Note that these are only respected if collapse was initiated by khugepaged. */ static unsigned int khugepaged_max_ptes_none __read_mostly; static unsigned int khugepaged_max_ptes_swap __read_mostly; static unsigned int khugepaged_max_ptes_shared __read_mostly; #define MM_SLOTS_HASH_BITS 10 -static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); +static DEFINE_READ_MOSTLY_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); + +static struct kmem_cache *mm_slot_cache __ro_after_init; -static struct kmem_cache *mm_slot_cache __read_mostly; +struct collapse_control { + bool is_khugepaged; -#define MAX_PTE_MAPPED_THP 8 + /* Num pages scanned per node */ + u32 node_load[MAX_NUMNODES]; + + /* nodemask for allocation fallback */ + nodemask_t alloc_nmask; +}; /** - * struct mm_slot - hash lookup from mm to mm_slot - * @hash: hash collision list - * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head - * @mm: the mm that this information is valid for + * struct khugepaged_mm_slot - khugepaged information per mm that is being scanned + * @slot: hash lookup from mm to mm_slot */ -struct mm_slot { - struct hlist_node hash; - struct list_head mm_node; - struct mm_struct *mm; - - /* pte-mapped THP in this mm */ - int nr_pte_mapped_thp; - unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP]; +struct khugepaged_mm_slot { + struct mm_slot slot; }; /** @@ -111,7 +122,7 @@ struct mm_slot { */ struct khugepaged_scan { struct list_head mm_head; - struct mm_slot *mm_slot; + struct khugepaged_mm_slot *mm_slot; unsigned long address; }; @@ -124,18 +135,18 @@ static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); + return sysfs_emit(buf, "%u\n", khugepaged_scan_sleep_millisecs); } static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { - unsigned long msecs; + unsigned int msecs; int err; - err = kstrtoul(buf, 10, &msecs); - if (err || msecs > UINT_MAX) + err = kstrtouint(buf, 10, &msecs); + if (err) return -EINVAL; khugepaged_scan_sleep_millisecs = msecs; @@ -145,25 +156,24 @@ static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, return count; } static struct kobj_attribute scan_sleep_millisecs_attr = - __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, - scan_sleep_millisecs_store); + __ATTR_RW(scan_sleep_millisecs); static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); + return sysfs_emit(buf, "%u\n", khugepaged_alloc_sleep_millisecs); } static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { - unsigned long msecs; + unsigned int msecs; int err; - err = kstrtoul(buf, 10, &msecs); - if (err || msecs > UINT_MAX) + err = kstrtouint(buf, 10, &msecs); + if (err) return -EINVAL; khugepaged_alloc_sleep_millisecs = msecs; @@ -173,24 +183,23 @@ static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, return count; } static struct kobj_attribute alloc_sleep_millisecs_attr = - __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, - alloc_sleep_millisecs_store); + __ATTR_RW(alloc_sleep_millisecs); static ssize_t pages_to_scan_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%u\n", khugepaged_pages_to_scan); + return sysfs_emit(buf, "%u\n", khugepaged_pages_to_scan); } static ssize_t pages_to_scan_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { + unsigned int pages; int err; - unsigned long pages; - err = kstrtoul(buf, 10, &pages); - if (err || !pages || pages > UINT_MAX) + err = kstrtouint(buf, 10, &pages); + if (err || !pages) return -EINVAL; khugepaged_pages_to_scan = pages; @@ -198,14 +207,13 @@ static ssize_t pages_to_scan_store(struct kobject *kobj, return count; } static struct kobj_attribute pages_to_scan_attr = - __ATTR(pages_to_scan, 0644, pages_to_scan_show, - pages_to_scan_store); + __ATTR_RW(pages_to_scan); static ssize_t pages_collapsed_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%u\n", khugepaged_pages_collapsed); + return sysfs_emit(buf, "%u\n", khugepaged_pages_collapsed); } static struct kobj_attribute pages_collapsed_attr = __ATTR_RO(pages_collapsed); @@ -214,27 +222,26 @@ static ssize_t full_scans_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%u\n", khugepaged_full_scans); + return sysfs_emit(buf, "%u\n", khugepaged_full_scans); } static struct kobj_attribute full_scans_attr = __ATTR_RO(full_scans); -static ssize_t khugepaged_defrag_show(struct kobject *kobj, - struct kobj_attribute *attr, char *buf) +static ssize_t defrag_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) { return single_hugepage_flag_show(kobj, attr, buf, - TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); + TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); } -static ssize_t khugepaged_defrag_store(struct kobject *kobj, - struct kobj_attribute *attr, - const char *buf, size_t count) +static ssize_t defrag_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) { return single_hugepage_flag_store(kobj, attr, buf, count, TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); } static struct kobj_attribute khugepaged_defrag_attr = - __ATTR(defrag, 0644, khugepaged_defrag_show, - khugepaged_defrag_store); + __ATTR_RW(defrag); /* * max_ptes_none controls if khugepaged should collapse hugepages over @@ -244,21 +251,21 @@ static struct kobj_attribute khugepaged_defrag_attr = * runs. Increasing max_ptes_none will instead potentially reduce the * free memory in the system during the khugepaged scan. */ -static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, - struct kobj_attribute *attr, - char *buf) +static ssize_t max_ptes_none_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) { - return sprintf(buf, "%u\n", khugepaged_max_ptes_none); + return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_none); } -static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, - struct kobj_attribute *attr, - const char *buf, size_t count) +static ssize_t max_ptes_none_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) { int err; unsigned long max_ptes_none; err = kstrtoul(buf, 10, &max_ptes_none); - if (err || max_ptes_none > HPAGE_PMD_NR-1) + if (err || max_ptes_none > HPAGE_PMD_NR - 1) return -EINVAL; khugepaged_max_ptes_none = max_ptes_none; @@ -266,25 +273,24 @@ static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, return count; } static struct kobj_attribute khugepaged_max_ptes_none_attr = - __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, - khugepaged_max_ptes_none_store); + __ATTR_RW(max_ptes_none); -static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj, - struct kobj_attribute *attr, - char *buf) +static ssize_t max_ptes_swap_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) { - return sprintf(buf, "%u\n", khugepaged_max_ptes_swap); + return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_swap); } -static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj, - struct kobj_attribute *attr, - const char *buf, size_t count) +static ssize_t max_ptes_swap_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) { int err; unsigned long max_ptes_swap; err = kstrtoul(buf, 10, &max_ptes_swap); - if (err || max_ptes_swap > HPAGE_PMD_NR-1) + if (err || max_ptes_swap > HPAGE_PMD_NR - 1) return -EINVAL; khugepaged_max_ptes_swap = max_ptes_swap; @@ -293,25 +299,24 @@ static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj, } static struct kobj_attribute khugepaged_max_ptes_swap_attr = - __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show, - khugepaged_max_ptes_swap_store); + __ATTR_RW(max_ptes_swap); -static ssize_t khugepaged_max_ptes_shared_show(struct kobject *kobj, - struct kobj_attribute *attr, - char *buf) +static ssize_t max_ptes_shared_show(struct kobject *kobj, + struct kobj_attribute *attr, + char *buf) { - return sprintf(buf, "%u\n", khugepaged_max_ptes_shared); + return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_shared); } -static ssize_t khugepaged_max_ptes_shared_store(struct kobject *kobj, - struct kobj_attribute *attr, - const char *buf, size_t count) +static ssize_t max_ptes_shared_store(struct kobject *kobj, + struct kobj_attribute *attr, + const char *buf, size_t count) { int err; unsigned long max_ptes_shared; err = kstrtoul(buf, 10, &max_ptes_shared); - if (err || max_ptes_shared > HPAGE_PMD_NR-1) + if (err || max_ptes_shared > HPAGE_PMD_NR - 1) return -EINVAL; khugepaged_max_ptes_shared = max_ptes_shared; @@ -320,8 +325,7 @@ static ssize_t khugepaged_max_ptes_shared_store(struct kobject *kobj, } static struct kobj_attribute khugepaged_max_ptes_shared_attr = - __ATTR(max_ptes_shared, 0644, khugepaged_max_ptes_shared_show, - khugepaged_max_ptes_shared_store); + __ATTR_RW(max_ptes_shared); static struct attribute *khugepaged_attr[] = { &khugepaged_defrag_attr.attr, @@ -363,9 +367,7 @@ int hugepage_madvise(struct vm_area_struct *vma, * register it here without waiting a page fault that * may not happen any time soon. */ - if (!(*vm_flags & VM_NO_KHUGEPAGED) && - khugepaged_enter_vma_merge(vma, *vm_flags)) - return -ENOMEM; + khugepaged_enter_vma(vma, *vm_flags); break; case MADV_NOHUGEPAGE: *vm_flags &= ~VM_HUGEPAGE; @@ -384,8 +386,9 @@ int hugepage_madvise(struct vm_area_struct *vma, int __init khugepaged_init(void) { mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", - sizeof(struct mm_slot), - __alignof__(struct mm_slot), 0, NULL); + sizeof(struct khugepaged_mm_slot), + __alignof__(struct khugepaged_mm_slot), + 0, NULL); if (!mm_slot_cache) return -ENOMEM; @@ -402,208 +405,158 @@ void __init khugepaged_destroy(void) kmem_cache_destroy(mm_slot_cache); } -static inline struct mm_slot *alloc_mm_slot(void) +static inline int hpage_collapse_test_exit(struct mm_struct *mm) { - if (!mm_slot_cache) /* initialization failed */ - return NULL; - return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); -} - -static inline void free_mm_slot(struct mm_slot *mm_slot) -{ - kmem_cache_free(mm_slot_cache, mm_slot); -} - -static struct mm_slot *get_mm_slot(struct mm_struct *mm) -{ - struct mm_slot *mm_slot; - - hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) - if (mm == mm_slot->mm) - return mm_slot; - - return NULL; -} - -static void insert_to_mm_slots_hash(struct mm_struct *mm, - struct mm_slot *mm_slot) -{ - mm_slot->mm = mm; - hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); -} - -static inline int khugepaged_test_exit(struct mm_struct *mm) -{ - return atomic_read(&mm->mm_users) == 0 || !mmget_still_valid(mm); -} - -static bool hugepage_vma_check(struct vm_area_struct *vma, - unsigned long vm_flags) -{ - if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || - (vm_flags & VM_NOHUGEPAGE) || - test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) - return false; - - if (shmem_file(vma->vm_file) || - (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && - vma->vm_file && - (vm_flags & VM_DENYWRITE))) { - return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, - HPAGE_PMD_NR); - } - if (!vma->anon_vma || vma->vm_ops) - return false; - if (vma_is_temporary_stack(vma)) - return false; - return !(vm_flags & VM_NO_KHUGEPAGED); + return atomic_read(&mm->mm_users) == 0; } -int __khugepaged_enter(struct mm_struct *mm) +void __khugepaged_enter(struct mm_struct *mm) { - struct mm_slot *mm_slot; + struct khugepaged_mm_slot *mm_slot; + struct mm_slot *slot; int wakeup; - mm_slot = alloc_mm_slot(); + /* __khugepaged_exit() must not run from under us */ + VM_BUG_ON_MM(hpage_collapse_test_exit(mm), mm); + if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) + return; + + mm_slot = mm_slot_alloc(mm_slot_cache); if (!mm_slot) - return -ENOMEM; + return; - /* __khugepaged_exit() must not run from under us */ - VM_BUG_ON_MM(atomic_read(&mm->mm_users) == 0, mm); - if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { - free_mm_slot(mm_slot); - return 0; - } + slot = &mm_slot->slot; spin_lock(&khugepaged_mm_lock); - insert_to_mm_slots_hash(mm, mm_slot); + mm_slot_insert(mm_slots_hash, mm, slot); /* * Insert just behind the scanning cursor, to let the area settle * down a little. */ wakeup = list_empty(&khugepaged_scan.mm_head); - list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); + list_add_tail(&slot->mm_node, &khugepaged_scan.mm_head); spin_unlock(&khugepaged_mm_lock); mmgrab(mm); if (wakeup) wake_up_interruptible(&khugepaged_wait); - - return 0; } -int khugepaged_enter_vma_merge(struct vm_area_struct *vma, - unsigned long vm_flags) +void khugepaged_enter_vma(struct vm_area_struct *vma, + unsigned long vm_flags) { - unsigned long hstart, hend; - - /* - * khugepaged only supports read-only files for non-shmem files. - * khugepaged does not yet work on special mappings. And - * file-private shmem THP is not supported. - */ - if (!hugepage_vma_check(vma, vm_flags)) - return 0; - - hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; - hend = vma->vm_end & HPAGE_PMD_MASK; - if (hstart < hend) - return khugepaged_enter(vma, vm_flags); - return 0; + if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) && + hugepage_flags_enabled()) { + if (thp_vma_allowable_order(vma, vm_flags, false, false, true, + PMD_ORDER)) + __khugepaged_enter(vma->vm_mm); + } } void __khugepaged_exit(struct mm_struct *mm) { - struct mm_slot *mm_slot; + struct khugepaged_mm_slot *mm_slot; + struct mm_slot *slot; int free = 0; spin_lock(&khugepaged_mm_lock); - mm_slot = get_mm_slot(mm); + slot = mm_slot_lookup(mm_slots_hash, mm); + mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot); if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { - hash_del(&mm_slot->hash); - list_del(&mm_slot->mm_node); + hash_del(&slot->hash); + list_del(&slot->mm_node); free = 1; } spin_unlock(&khugepaged_mm_lock); if (free) { clear_bit(MMF_VM_HUGEPAGE, &mm->flags); - free_mm_slot(mm_slot); + mm_slot_free(mm_slot_cache, mm_slot); mmdrop(mm); } else if (mm_slot) { /* * This is required to serialize against - * khugepaged_test_exit() (which is guaranteed to run - * under mmap sem read mode). Stop here (after we - * return all pagetables will be destroyed) until - * khugepaged has finished working on the pagetables - * under the mmap_lock. + * hpage_collapse_test_exit() (which is guaranteed to run + * under mmap sem read mode). Stop here (after we return all + * pagetables will be destroyed) until khugepaged has finished + * working on the pagetables under the mmap_lock. */ mmap_write_lock(mm); mmap_write_unlock(mm); } } -static void release_pte_page(struct page *page) +static void release_pte_folio(struct folio *folio) { - mod_node_page_state(page_pgdat(page), - NR_ISOLATED_ANON + page_is_file_lru(page), - -compound_nr(page)); - unlock_page(page); - putback_lru_page(page); + node_stat_mod_folio(folio, + NR_ISOLATED_ANON + folio_is_file_lru(folio), + -folio_nr_pages(folio)); + folio_unlock(folio); + folio_putback_lru(folio); } static void release_pte_pages(pte_t *pte, pte_t *_pte, struct list_head *compound_pagelist) { - struct page *page, *tmp; + struct folio *folio, *tmp; while (--_pte >= pte) { - pte_t pteval = *_pte; + pte_t pteval = ptep_get(_pte); + unsigned long pfn; - page = pte_page(pteval); - if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)) && - !PageCompound(page)) - release_pte_page(page); + if (pte_none(pteval)) + continue; + pfn = pte_pfn(pteval); + if (is_zero_pfn(pfn)) + continue; + folio = pfn_folio(pfn); + if (folio_test_large(folio)) + continue; + release_pte_folio(folio); } - list_for_each_entry_safe(page, tmp, compound_pagelist, lru) { - list_del(&page->lru); - release_pte_page(page); + list_for_each_entry_safe(folio, tmp, compound_pagelist, lru) { + list_del(&folio->lru); + release_pte_folio(folio); } } -static bool is_refcount_suitable(struct page *page) +static bool is_refcount_suitable(struct folio *folio) { int expected_refcount; - expected_refcount = total_mapcount(page); - if (PageSwapCache(page)) - expected_refcount += compound_nr(page); + expected_refcount = folio_mapcount(folio); + if (folio_test_swapcache(folio)) + expected_refcount += folio_nr_pages(folio); - return page_count(page) == expected_refcount; + return folio_ref_count(folio) == expected_refcount; } static int __collapse_huge_page_isolate(struct vm_area_struct *vma, unsigned long address, pte_t *pte, + struct collapse_control *cc, struct list_head *compound_pagelist) { struct page *page = NULL; + struct folio *folio = NULL; pte_t *_pte; - int none_or_zero = 0, shared = 0, result = 0, referenced = 0; + int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0; bool writable = false; - for (_pte = pte; _pte < pte+HPAGE_PMD_NR; + for (_pte = pte; _pte < pte + HPAGE_PMD_NR; _pte++, address += PAGE_SIZE) { - pte_t pteval = *_pte; + pte_t pteval = ptep_get(_pte); if (pte_none(pteval) || (pte_present(pteval) && is_zero_pfn(pte_pfn(pteval)))) { + ++none_or_zero; if (!userfaultfd_armed(vma) && - ++none_or_zero <= khugepaged_max_ptes_none) { + (!cc->is_khugepaged || + none_or_zero <= khugepaged_max_ptes_none)) { continue; } else { result = SCAN_EXCEED_NONE_PTE; + count_vm_event(THP_SCAN_EXCEED_NONE_PTE); goto out; } } @@ -611,30 +564,38 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, result = SCAN_PTE_NON_PRESENT; goto out; } + if (pte_uffd_wp(pteval)) { + result = SCAN_PTE_UFFD_WP; + goto out; + } page = vm_normal_page(vma, address, pteval); - if (unlikely(!page)) { + if (unlikely(!page) || unlikely(is_zone_device_page(page))) { result = SCAN_PAGE_NULL; goto out; } - VM_BUG_ON_PAGE(!PageAnon(page), page); + folio = page_folio(page); + VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio); - if (page_mapcount(page) > 1 && - ++shared > khugepaged_max_ptes_shared) { - result = SCAN_EXCEED_SHARED_PTE; - goto out; + if (page_mapcount(page) > 1) { + ++shared; + if (cc->is_khugepaged && + shared > khugepaged_max_ptes_shared) { + result = SCAN_EXCEED_SHARED_PTE; + count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); + goto out; + } } - if (PageCompound(page)) { - struct page *p; - page = compound_head(page); + if (folio_test_large(folio)) { + struct folio *f; /* * Check if we have dealt with the compound page * already */ - list_for_each_entry(p, compound_pagelist, lru) { - if (page == p) + list_for_each_entry(f, compound_pagelist, lru) { + if (folio == f) goto next; } } @@ -645,7 +606,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, * is needed to serialize against split_huge_page * when invoked from the VM. */ - if (!trylock_page(page)) { + if (!folio_trylock(folio)) { result = SCAN_PAGE_LOCK; goto out; } @@ -655,117 +616,106 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, * * The page table that maps the page has been already unlinked * from the page table tree and this process cannot get - * an additinal pin on the page. + * an additional pin on the page. * * New pins can come later if the page is shared across fork, * but not from this process. The other process cannot write to * the page, only trigger CoW. */ - if (!is_refcount_suitable(page)) { - unlock_page(page); + if (!is_refcount_suitable(folio)) { + folio_unlock(folio); result = SCAN_PAGE_COUNT; goto out; } - if (!pte_write(pteval) && PageSwapCache(page) && - !reuse_swap_page(page, NULL)) { - /* - * Page is in the swap cache and cannot be re-used. - * It cannot be collapsed into a THP. - */ - unlock_page(page); - result = SCAN_SWAP_CACHE_PAGE; - goto out; - } /* * Isolate the page to avoid collapsing an hugepage * currently in use by the VM. */ - if (isolate_lru_page(page)) { - unlock_page(page); + if (!folio_isolate_lru(folio)) { + folio_unlock(folio); result = SCAN_DEL_PAGE_LRU; goto out; } - mod_node_page_state(page_pgdat(page), - NR_ISOLATED_ANON + page_is_file_lru(page), - compound_nr(page)); - VM_BUG_ON_PAGE(!PageLocked(page), page); - VM_BUG_ON_PAGE(PageLRU(page), page); - - if (PageCompound(page)) - list_add_tail(&page->lru, compound_pagelist); + node_stat_mod_folio(folio, + NR_ISOLATED_ANON + folio_is_file_lru(folio), + folio_nr_pages(folio)); + VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); + VM_BUG_ON_FOLIO(folio_test_lru(folio), folio); + + if (folio_test_large(folio)) + list_add_tail(&folio->lru, compound_pagelist); next: - /* There should be enough young pte to collapse the page */ - if (pte_young(pteval) || - page_is_young(page) || PageReferenced(page) || - mmu_notifier_test_young(vma->vm_mm, address)) + /* + * If collapse was initiated by khugepaged, check that there is + * enough young pte to justify collapsing the page + */ + if (cc->is_khugepaged && + (pte_young(pteval) || folio_test_young(folio) || + folio_test_referenced(folio) || mmu_notifier_test_young(vma->vm_mm, + address))) referenced++; if (pte_write(pteval)) writable = true; } - if (likely(writable)) { - if (likely(referenced)) { - result = SCAN_SUCCEED; - trace_mm_collapse_huge_page_isolate(page, none_or_zero, - referenced, writable, result); - return 1; - } - } else { + + if (unlikely(!writable)) { result = SCAN_PAGE_RO; + } else if (unlikely(cc->is_khugepaged && !referenced)) { + result = SCAN_LACK_REFERENCED_PAGE; + } else { + result = SCAN_SUCCEED; + trace_mm_collapse_huge_page_isolate(&folio->page, none_or_zero, + referenced, writable, result); + return result; } - out: release_pte_pages(pte, _pte, compound_pagelist); - trace_mm_collapse_huge_page_isolate(page, none_or_zero, + trace_mm_collapse_huge_page_isolate(&folio->page, none_or_zero, referenced, writable, result); - return 0; + return result; } -static void __collapse_huge_page_copy(pte_t *pte, struct page *page, - struct vm_area_struct *vma, - unsigned long address, - spinlock_t *ptl, - struct list_head *compound_pagelist) +static void __collapse_huge_page_copy_succeeded(pte_t *pte, + struct vm_area_struct *vma, + unsigned long address, + spinlock_t *ptl, + struct list_head *compound_pagelist) { - struct page *src_page, *tmp; + struct folio *src_folio; + struct page *src_page; + struct page *tmp; pte_t *_pte; - for (_pte = pte; _pte < pte + HPAGE_PMD_NR; - _pte++, page++, address += PAGE_SIZE) { - pte_t pteval = *_pte; + pte_t pteval; + for (_pte = pte; _pte < pte + HPAGE_PMD_NR; + _pte++, address += PAGE_SIZE) { + pteval = ptep_get(_pte); if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { - clear_user_highpage(page, address); add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); if (is_zero_pfn(pte_pfn(pteval))) { /* * ptl mostly unnecessary. */ spin_lock(ptl); - /* - * paravirt calls inside pte_clear here are - * superfluous. - */ - pte_clear(vma->vm_mm, address, _pte); + ptep_clear(vma->vm_mm, address, _pte); spin_unlock(ptl); + ksm_might_unmap_zero_page(vma->vm_mm, pteval); } } else { src_page = pte_page(pteval); - copy_user_highpage(page, src_page, address, vma); - if (!PageCompound(src_page)) - release_pte_page(src_page); + src_folio = page_folio(src_page); + if (!folio_test_large(src_folio)) + release_pte_folio(src_folio); /* * ptl mostly unnecessary, but preempt has to * be disabled to update the per-cpu stats - * inside page_remove_rmap(). + * inside folio_remove_rmap_pte(). */ spin_lock(ptl); - /* - * paravirt calls inside pte_clear here are - * superfluous. - */ - pte_clear(vma->vm_mm, address, _pte); - page_remove_rmap(src_page, false); + ptep_clear(vma->vm_mm, address, _pte); + folio_remove_rmap_pte(src_folio, src_page, vma); spin_unlock(ptl); free_page_and_swap_cache(src_page); } @@ -773,23 +723,111 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page, list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) { list_del(&src_page->lru); - release_pte_page(src_page); + mod_node_page_state(page_pgdat(src_page), + NR_ISOLATED_ANON + page_is_file_lru(src_page), + -compound_nr(src_page)); + unlock_page(src_page); + free_swap_cache(src_page); + putback_lru_page(src_page); } } +static void __collapse_huge_page_copy_failed(pte_t *pte, + pmd_t *pmd, + pmd_t orig_pmd, + struct vm_area_struct *vma, + struct list_head *compound_pagelist) +{ + spinlock_t *pmd_ptl; + + /* + * Re-establish the PMD to point to the original page table + * entry. Restoring PMD needs to be done prior to releasing + * pages. Since pages are still isolated and locked here, + * acquiring anon_vma_lock_write is unnecessary. + */ + pmd_ptl = pmd_lock(vma->vm_mm, pmd); + pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd)); + spin_unlock(pmd_ptl); + /* + * Release both raw and compound pages isolated + * in __collapse_huge_page_isolate. + */ + release_pte_pages(pte, pte + HPAGE_PMD_NR, compound_pagelist); +} + +/* + * __collapse_huge_page_copy - attempts to copy memory contents from raw + * pages to a hugepage. Cleans up the raw pages if copying succeeds; + * otherwise restores the original page table and releases isolated raw pages. + * Returns SCAN_SUCCEED if copying succeeds, otherwise returns SCAN_COPY_MC. + * + * @pte: starting of the PTEs to copy from + * @page: the new hugepage to copy contents to + * @pmd: pointer to the new hugepage's PMD + * @orig_pmd: the original raw pages' PMD + * @vma: the original raw pages' virtual memory area + * @address: starting address to copy + * @ptl: lock on raw pages' PTEs + * @compound_pagelist: list that stores compound pages + */ +static int __collapse_huge_page_copy(pte_t *pte, + struct page *page, + pmd_t *pmd, + pmd_t orig_pmd, + struct vm_area_struct *vma, + unsigned long address, + spinlock_t *ptl, + struct list_head *compound_pagelist) +{ + struct page *src_page; + pte_t *_pte; + pte_t pteval; + unsigned long _address; + int result = SCAN_SUCCEED; + + /* + * Copying pages' contents is subject to memory poison at any iteration. + */ + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR; + _pte++, page++, _address += PAGE_SIZE) { + pteval = ptep_get(_pte); + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { + clear_user_highpage(page, _address); + continue; + } + src_page = pte_page(pteval); + if (copy_mc_user_highpage(page, src_page, _address, vma) > 0) { + result = SCAN_COPY_MC; + break; + } + } + + if (likely(result == SCAN_SUCCEED)) + __collapse_huge_page_copy_succeeded(pte, vma, address, ptl, + compound_pagelist); + else + __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma, + compound_pagelist); + + return result; +} + static void khugepaged_alloc_sleep(void) { DEFINE_WAIT(wait); add_wait_queue(&khugepaged_wait, &wait); - freezable_schedule_timeout_interruptible( - msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); + __set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE); + schedule_timeout(msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); remove_wait_queue(&khugepaged_wait, &wait); } -static int khugepaged_node_load[MAX_NUMNODES]; +struct collapse_control khugepaged_collapse_control = { + .is_khugepaged = true, +}; -static bool khugepaged_scan_abort(int nid) +static bool hpage_collapse_scan_abort(int nid, struct collapse_control *cc) { int i; @@ -797,15 +835,15 @@ static bool khugepaged_scan_abort(int nid) * If node_reclaim_mode is disabled, then no extra effort is made to * allocate memory locally. */ - if (!node_reclaim_mode) + if (!node_reclaim_enabled()) return false; /* If there is a count for this node already, it must be acceptable */ - if (khugepaged_node_load[nid]) + if (cc->node_load[nid]) return false; for (i = 0; i < MAX_NUMNODES; i++) { - if (!khugepaged_node_load[i]) + if (!cc->node_load[i]) continue; if (node_distance(nid, i) > node_reclaim_distance) return true; @@ -813,6 +851,10 @@ static bool khugepaged_scan_abort(int nid) return false; } +#define khugepaged_defrag() \ + (transparent_hugepage_flags & \ + (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)) + /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) { @@ -820,250 +862,241 @@ static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) } #ifdef CONFIG_NUMA -static int khugepaged_find_target_node(void) +static int hpage_collapse_find_target_node(struct collapse_control *cc) { - static int last_khugepaged_target_node = NUMA_NO_NODE; int nid, target_node = 0, max_value = 0; /* find first node with max normal pages hit */ for (nid = 0; nid < MAX_NUMNODES; nid++) - if (khugepaged_node_load[nid] > max_value) { - max_value = khugepaged_node_load[nid]; + if (cc->node_load[nid] > max_value) { + max_value = cc->node_load[nid]; target_node = nid; } - /* do some balance if several nodes have the same hit record */ - if (target_node <= last_khugepaged_target_node) - for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; - nid++) - if (max_value == khugepaged_node_load[nid]) { - target_node = nid; - break; - } - - last_khugepaged_target_node = target_node; - return target_node; -} - -static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) -{ - if (IS_ERR(*hpage)) { - if (!*wait) - return false; - - *wait = false; - *hpage = NULL; - khugepaged_alloc_sleep(); - } else if (*hpage) { - put_page(*hpage); - *hpage = NULL; + for_each_online_node(nid) { + if (max_value == cc->node_load[nid]) + node_set(nid, cc->alloc_nmask); } - return true; -} - -static struct page * -khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) -{ - VM_BUG_ON_PAGE(*hpage, *hpage); - - *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); - if (unlikely(!*hpage)) { - count_vm_event(THP_COLLAPSE_ALLOC_FAILED); - *hpage = ERR_PTR(-ENOMEM); - return NULL; - } - - prep_transhuge_page(*hpage); - count_vm_event(THP_COLLAPSE_ALLOC); - return *hpage; + return target_node; } #else -static int khugepaged_find_target_node(void) +static int hpage_collapse_find_target_node(struct collapse_control *cc) { return 0; } +#endif -static inline struct page *alloc_khugepaged_hugepage(void) -{ - struct page *page; - - page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), - HPAGE_PMD_ORDER); - if (page) - prep_transhuge_page(page); - return page; -} - -static struct page *khugepaged_alloc_hugepage(bool *wait) -{ - struct page *hpage; - - do { - hpage = alloc_khugepaged_hugepage(); - if (!hpage) { - count_vm_event(THP_COLLAPSE_ALLOC_FAILED); - if (!*wait) - return NULL; - - *wait = false; - khugepaged_alloc_sleep(); - } else - count_vm_event(THP_COLLAPSE_ALLOC); - } while (unlikely(!hpage) && likely(khugepaged_enabled())); - - return hpage; -} - -static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) +static bool hpage_collapse_alloc_folio(struct folio **folio, gfp_t gfp, int node, + nodemask_t *nmask) { - /* - * If the hpage allocated earlier was briefly exposed in page cache - * before collapse_file() failed, it is possible that racing lookups - * have not yet completed, and would then be unpleasantly surprised by - * finding the hpage reused for the same mapping at a different offset. - * Just release the previous allocation if there is any danger of that. - */ - if (*hpage && page_count(*hpage) > 1) { - put_page(*hpage); - *hpage = NULL; - } + *folio = __folio_alloc(gfp, HPAGE_PMD_ORDER, node, nmask); - if (!*hpage) - *hpage = khugepaged_alloc_hugepage(wait); - - if (unlikely(!*hpage)) + if (unlikely(!*folio)) { + count_vm_event(THP_COLLAPSE_ALLOC_FAILED); return false; + } + count_vm_event(THP_COLLAPSE_ALLOC); return true; } -static struct page * -khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) -{ - VM_BUG_ON(!*hpage); - - return *hpage; -} -#endif - /* * If mmap_lock temporarily dropped, revalidate vma * before taking mmap_lock. - * Return 0 if succeeds, otherwise return none-zero - * value (scan code). + * Returns enum scan_result value. */ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, - struct vm_area_struct **vmap) + bool expect_anon, + struct vm_area_struct **vmap, + struct collapse_control *cc) { struct vm_area_struct *vma; - unsigned long hstart, hend; - if (unlikely(khugepaged_test_exit(mm))) + if (unlikely(hpage_collapse_test_exit(mm))) return SCAN_ANY_PROCESS; *vmap = vma = find_vma(mm, address); if (!vma) return SCAN_VMA_NULL; - hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; - hend = vma->vm_end & HPAGE_PMD_MASK; - if (address < hstart || address + HPAGE_PMD_SIZE > hend) + if (!thp_vma_suitable_order(vma, address, PMD_ORDER)) return SCAN_ADDRESS_RANGE; - if (!hugepage_vma_check(vma, vma->vm_flags)) + if (!thp_vma_allowable_order(vma, vma->vm_flags, false, false, + cc->is_khugepaged, PMD_ORDER)) return SCAN_VMA_CHECK; - /* Anon VMA expected */ - if (!vma->anon_vma || vma->vm_ops) - return SCAN_VMA_CHECK; - return 0; + /* + * Anon VMA expected, the address may be unmapped then + * remapped to file after khugepaged reaquired the mmap_lock. + * + * thp_vma_allowable_order may return true for qualified file + * vmas. + */ + if (expect_anon && (!(*vmap)->anon_vma || !vma_is_anonymous(*vmap))) + return SCAN_PAGE_ANON; + return SCAN_SUCCEED; +} + +static int find_pmd_or_thp_or_none(struct mm_struct *mm, + unsigned long address, + pmd_t **pmd) +{ + pmd_t pmde; + + *pmd = mm_find_pmd(mm, address); + if (!*pmd) + return SCAN_PMD_NULL; + + pmde = pmdp_get_lockless(*pmd); + if (pmd_none(pmde)) + return SCAN_PMD_NONE; + if (!pmd_present(pmde)) + return SCAN_PMD_NULL; + if (pmd_trans_huge(pmde)) + return SCAN_PMD_MAPPED; + if (pmd_devmap(pmde)) + return SCAN_PMD_NULL; + if (pmd_bad(pmde)) + return SCAN_PMD_NULL; + return SCAN_SUCCEED; +} + +static int check_pmd_still_valid(struct mm_struct *mm, + unsigned long address, + pmd_t *pmd) +{ + pmd_t *new_pmd; + int result = find_pmd_or_thp_or_none(mm, address, &new_pmd); + + if (result != SCAN_SUCCEED) + return result; + if (new_pmd != pmd) + return SCAN_FAIL; + return SCAN_SUCCEED; } /* * Bring missing pages in from swap, to complete THP collapse. - * Only done if khugepaged_scan_pmd believes it is worthwhile. + * Only done if hpage_collapse_scan_pmd believes it is worthwhile. * - * Called and returns without pte mapped or spinlocks held, - * but with mmap_lock held to protect against vma changes. + * Called and returns without pte mapped or spinlocks held. + * Returns result: if not SCAN_SUCCEED, mmap_lock has been released. */ - -static bool __collapse_huge_page_swapin(struct mm_struct *mm, - struct vm_area_struct *vma, - unsigned long address, pmd_t *pmd, - int referenced) +static int __collapse_huge_page_swapin(struct mm_struct *mm, + struct vm_area_struct *vma, + unsigned long haddr, pmd_t *pmd, + int referenced) { int swapped_in = 0; vm_fault_t ret = 0; - struct vm_fault vmf = { - .vma = vma, - .address = address, - .flags = FAULT_FLAG_ALLOW_RETRY, - .pmd = pmd, - .pgoff = linear_page_index(vma, address), - }; + unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE); + int result; + pte_t *pte = NULL; + spinlock_t *ptl; - vmf.pte = pte_offset_map(pmd, address); - for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; - vmf.pte++, vmf.address += PAGE_SIZE) { - vmf.orig_pte = *vmf.pte; + for (address = haddr; address < end; address += PAGE_SIZE) { + struct vm_fault vmf = { + .vma = vma, + .address = address, + .pgoff = linear_page_index(vma, address), + .flags = FAULT_FLAG_ALLOW_RETRY, + .pmd = pmd, + }; + + if (!pte++) { + pte = pte_offset_map_nolock(mm, pmd, address, &ptl); + if (!pte) { + mmap_read_unlock(mm); + result = SCAN_PMD_NULL; + goto out; + } + } + + vmf.orig_pte = ptep_get_lockless(pte); if (!is_swap_pte(vmf.orig_pte)) continue; - swapped_in++; + + vmf.pte = pte; + vmf.ptl = ptl; ret = do_swap_page(&vmf); + /* Which unmaps pte (after perhaps re-checking the entry) */ + pte = NULL; - /* do_swap_page returns VM_FAULT_RETRY with released mmap_lock */ + /* + * do_swap_page returns VM_FAULT_RETRY with released mmap_lock. + * Note we treat VM_FAULT_RETRY as VM_FAULT_ERROR here because + * we do not retry here and swap entry will remain in pagetable + * resulting in later failure. + */ if (ret & VM_FAULT_RETRY) { - mmap_read_lock(mm); - if (hugepage_vma_revalidate(mm, address, &vmf.vma)) { - /* vma is no longer available, don't continue to swapin */ - trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); - return false; - } - /* check if the pmd is still valid */ - if (mm_find_pmd(mm, address) != pmd) { - trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); - return false; - } + /* Likely, but not guaranteed, that page lock failed */ + result = SCAN_PAGE_LOCK; + goto out; } if (ret & VM_FAULT_ERROR) { - trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); - return false; + mmap_read_unlock(mm); + result = SCAN_FAIL; + goto out; } - /* pte is unmapped now, we need to map it */ - vmf.pte = pte_offset_map(pmd, vmf.address); + swapped_in++; } - vmf.pte--; - pte_unmap(vmf.pte); - /* Drain LRU add pagevec to remove extra pin on the swapped in pages */ + if (pte) + pte_unmap(pte); + + /* Drain LRU cache to remove extra pin on the swapped in pages */ if (swapped_in) lru_add_drain(); - trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); - return true; + result = SCAN_SUCCEED; +out: + trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, result); + return result; } -static void collapse_huge_page(struct mm_struct *mm, - unsigned long address, - struct page **hpage, - int node, int referenced, int unmapped) +static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm, + struct collapse_control *cc) +{ + gfp_t gfp = (cc->is_khugepaged ? alloc_hugepage_khugepaged_gfpmask() : + GFP_TRANSHUGE); + int node = hpage_collapse_find_target_node(cc); + struct folio *folio; + + if (!hpage_collapse_alloc_folio(&folio, gfp, node, &cc->alloc_nmask)) { + *hpage = NULL; + return SCAN_ALLOC_HUGE_PAGE_FAIL; + } + + if (unlikely(mem_cgroup_charge(folio, mm, gfp))) { + folio_put(folio); + *hpage = NULL; + return SCAN_CGROUP_CHARGE_FAIL; + } + + count_memcg_folio_events(folio, THP_COLLAPSE_ALLOC, 1); + + *hpage = folio_page(folio, 0); + return SCAN_SUCCEED; +} + +static int collapse_huge_page(struct mm_struct *mm, unsigned long address, + int referenced, int unmapped, + struct collapse_control *cc) { LIST_HEAD(compound_pagelist); pmd_t *pmd, _pmd; pte_t *pte; pgtable_t pgtable; - struct page *new_page; + struct folio *folio; + struct page *hpage; spinlock_t *pmd_ptl, *pte_ptl; - int isolated = 0, result = 0; + int result = SCAN_FAIL; struct vm_area_struct *vma; struct mmu_notifier_range range; - gfp_t gfp; VM_BUG_ON(address & ~HPAGE_PMD_MASK); - /* Only allocate from the target node */ - gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; - /* * Before allocating the hugepage, release the mmap_lock read lock. * The allocation can take potentially a long time if it involves @@ -1071,41 +1104,34 @@ static void collapse_huge_page(struct mm_struct *mm, * that. We will recheck the vma after taking it again in write mode. */ mmap_read_unlock(mm); - new_page = khugepaged_alloc_page(hpage, gfp, node); - if (!new_page) { - result = SCAN_ALLOC_HUGE_PAGE_FAIL; - goto out_nolock; - } - if (unlikely(mem_cgroup_charge(new_page, mm, gfp))) { - result = SCAN_CGROUP_CHARGE_FAIL; + result = alloc_charge_hpage(&hpage, mm, cc); + if (result != SCAN_SUCCEED) goto out_nolock; - } - count_memcg_page_event(new_page, THP_COLLAPSE_ALLOC); mmap_read_lock(mm); - result = hugepage_vma_revalidate(mm, address, &vma); - if (result) { + result = hugepage_vma_revalidate(mm, address, true, &vma, cc); + if (result != SCAN_SUCCEED) { mmap_read_unlock(mm); goto out_nolock; } - pmd = mm_find_pmd(mm, address); - if (!pmd) { - result = SCAN_PMD_NULL; + result = find_pmd_or_thp_or_none(mm, address, &pmd); + if (result != SCAN_SUCCEED) { mmap_read_unlock(mm); goto out_nolock; } - /* - * __collapse_huge_page_swapin always returns with mmap_lock locked. - * If it fails, we release mmap_lock and jump out_nolock. - * Continuing to collapse causes inconsistency. - */ - if (unmapped && !__collapse_huge_page_swapin(mm, vma, address, - pmd, referenced)) { - mmap_read_unlock(mm); - goto out_nolock; + if (unmapped) { + /* + * __collapse_huge_page_swapin will return with mmap_lock + * released when it fails. So we jump out_nolock directly in + * that case. Continuing to collapse causes inconsistency. + */ + result = __collapse_huge_page_swapin(mm, vma, address, pmd, + referenced); + if (result != SCAN_SUCCEED) + goto out_nolock; } mmap_read_unlock(mm); @@ -1113,42 +1139,52 @@ static void collapse_huge_page(struct mm_struct *mm, * Prevent all access to pagetables with the exception of * gup_fast later handled by the ptep_clear_flush and the VM * handled by the anon_vma lock + PG_lock. + * + * UFFDIO_MOVE is prevented to race as well thanks to the + * mmap_lock. */ mmap_write_lock(mm); - result = hugepage_vma_revalidate(mm, address, &vma); - if (result) - goto out; + result = hugepage_vma_revalidate(mm, address, true, &vma, cc); + if (result != SCAN_SUCCEED) + goto out_up_write; /* check if the pmd is still valid */ - if (mm_find_pmd(mm, address) != pmd) - goto out; + result = check_pmd_still_valid(mm, address, pmd); + if (result != SCAN_SUCCEED) + goto out_up_write; + vma_start_write(vma); anon_vma_lock_write(vma->anon_vma); - mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, - address, address + HPAGE_PMD_SIZE); + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, address, + address + HPAGE_PMD_SIZE); mmu_notifier_invalidate_range_start(&range); - pte = pte_offset_map(pmd, address); - pte_ptl = pte_lockptr(mm, pmd); - pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ /* - * After this gup_fast can't run anymore. This also removes - * any huge TLB entry from the CPU so we won't allow - * huge and small TLB entries for the same virtual address - * to avoid the risk of CPU bugs in that area. + * This removes any huge TLB entry from the CPU so we won't allow + * huge and small TLB entries for the same virtual address to + * avoid the risk of CPU bugs in that area. + * + * Parallel fast GUP is fine since fast GUP will back off when + * it detects PMD is changed. */ _pmd = pmdp_collapse_flush(vma, address, pmd); spin_unlock(pmd_ptl); mmu_notifier_invalidate_range_end(&range); + tlb_remove_table_sync_one(); - spin_lock(pte_ptl); - isolated = __collapse_huge_page_isolate(vma, address, pte, - &compound_pagelist); - spin_unlock(pte_ptl); + pte = pte_offset_map_lock(mm, &_pmd, address, &pte_ptl); + if (pte) { + result = __collapse_huge_page_isolate(vma, address, pte, cc, + &compound_pagelist); + spin_unlock(pte_ptl); + } else { + result = SCAN_PMD_NULL; + } - if (unlikely(!isolated)) { - pte_unmap(pte); + if (unlikely(result != SCAN_SUCCEED)) { + if (pte) + pte_unmap(pte); spin_lock(pmd_ptl); BUG_ON(!pmd_none(*pmd)); /* @@ -1159,8 +1195,7 @@ static void collapse_huge_page(struct mm_struct *mm, pmd_populate(mm, pmd, pmd_pgtable(_pmd)); spin_unlock(pmd_ptl); anon_vma_unlock_write(vma->anon_vma); - result = SCAN_FAIL; - goto out; + goto out_up_write; } /* @@ -1169,56 +1204,57 @@ static void collapse_huge_page(struct mm_struct *mm, */ anon_vma_unlock_write(vma->anon_vma); - __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl, - &compound_pagelist); + result = __collapse_huge_page_copy(pte, hpage, pmd, _pmd, + vma, address, pte_ptl, + &compound_pagelist); pte_unmap(pte); - __SetPageUptodate(new_page); - pgtable = pmd_pgtable(_pmd); - - _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); - _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); + if (unlikely(result != SCAN_SUCCEED)) + goto out_up_write; + folio = page_folio(hpage); /* - * spin_lock() below is not the equivalent of smp_wmb(), so - * this is needed to avoid the copy_huge_page writes to become - * visible after the set_pmd_at() write. + * The smp_wmb() inside __folio_mark_uptodate() ensures the + * copy_huge_page writes become visible before the set_pmd_at() + * write. */ - smp_wmb(); + __folio_mark_uptodate(folio); + pgtable = pmd_pgtable(_pmd); + + _pmd = mk_huge_pmd(hpage, vma->vm_page_prot); + _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); spin_lock(pmd_ptl); BUG_ON(!pmd_none(*pmd)); - page_add_new_anon_rmap(new_page, vma, address, true); - lru_cache_add_inactive_or_unevictable(new_page, vma); + folio_add_new_anon_rmap(folio, vma, address); + folio_add_lru_vma(folio, vma); pgtable_trans_huge_deposit(mm, pmd, pgtable); set_pmd_at(mm, address, pmd, _pmd); update_mmu_cache_pmd(vma, address, pmd); spin_unlock(pmd_ptl); - *hpage = NULL; + hpage = NULL; - khugepaged_pages_collapsed++; result = SCAN_SUCCEED; out_up_write: mmap_write_unlock(mm); out_nolock: - if (!IS_ERR_OR_NULL(*hpage)) - mem_cgroup_uncharge(*hpage); - trace_mm_collapse_huge_page(mm, isolated, result); - return; -out: - goto out_up_write; + if (hpage) + put_page(hpage); + trace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result); + return result; } -static int khugepaged_scan_pmd(struct mm_struct *mm, - struct vm_area_struct *vma, - unsigned long address, - struct page **hpage) +static int hpage_collapse_scan_pmd(struct mm_struct *mm, + struct vm_area_struct *vma, + unsigned long address, bool *mmap_locked, + struct collapse_control *cc) { pmd_t *pmd; pte_t *pte, *_pte; - int ret = 0, result = 0, referenced = 0; + int result = SCAN_FAIL, referenced = 0; int none_or_zero = 0, shared = 0; struct page *page = NULL; + struct folio *folio = NULL; unsigned long _address; spinlock_t *ptl; int node = NUMA_NO_NODE, unmapped = 0; @@ -1226,54 +1262,60 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, VM_BUG_ON(address & ~HPAGE_PMD_MASK); - pmd = mm_find_pmd(mm, address); - if (!pmd) { + result = find_pmd_or_thp_or_none(mm, address, &pmd); + if (result != SCAN_SUCCEED) + goto out; + + memset(cc->node_load, 0, sizeof(cc->node_load)); + nodes_clear(cc->alloc_nmask); + pte = pte_offset_map_lock(mm, pmd, address, &ptl); + if (!pte) { result = SCAN_PMD_NULL; goto out; } - memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); - pte = pte_offset_map_lock(mm, pmd, address, &ptl); - for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; + for (_address = address, _pte = pte; _pte < pte + HPAGE_PMD_NR; _pte++, _address += PAGE_SIZE) { - pte_t pteval = *_pte; + pte_t pteval = ptep_get(_pte); if (is_swap_pte(pteval)) { - if (++unmapped <= khugepaged_max_ptes_swap) { + ++unmapped; + if (!cc->is_khugepaged || + unmapped <= khugepaged_max_ptes_swap) { /* * Always be strict with uffd-wp * enabled swap entries. Please see * comment below for pte_uffd_wp(). */ - if (pte_swp_uffd_wp(pteval)) { + if (pte_swp_uffd_wp_any(pteval)) { result = SCAN_PTE_UFFD_WP; goto out_unmap; } continue; } else { result = SCAN_EXCEED_SWAP_PTE; + count_vm_event(THP_SCAN_EXCEED_SWAP_PTE); goto out_unmap; } } if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { + ++none_or_zero; if (!userfaultfd_armed(vma) && - ++none_or_zero <= khugepaged_max_ptes_none) { + (!cc->is_khugepaged || + none_or_zero <= khugepaged_max_ptes_none)) { continue; } else { result = SCAN_EXCEED_NONE_PTE; + count_vm_event(THP_SCAN_EXCEED_NONE_PTE); goto out_unmap; } } - if (!pte_present(pteval)) { - result = SCAN_PTE_NON_PRESENT; - goto out_unmap; - } if (pte_uffd_wp(pteval)) { /* * Don't collapse the page if any of the small * PTEs are armed with uffd write protection. * Here we can also mark the new huge pmd as * write protected if any of the small ones is - * marked but that could bring uknown + * marked but that could bring unknown * userfault messages that falls outside of * the registered range. So, just be simple. */ @@ -1284,40 +1326,43 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, writable = true; page = vm_normal_page(vma, _address, pteval); - if (unlikely(!page)) { + if (unlikely(!page) || unlikely(is_zone_device_page(page))) { result = SCAN_PAGE_NULL; goto out_unmap; } - if (page_mapcount(page) > 1 && - ++shared > khugepaged_max_ptes_shared) { - result = SCAN_EXCEED_SHARED_PTE; - goto out_unmap; + if (page_mapcount(page) > 1) { + ++shared; + if (cc->is_khugepaged && + shared > khugepaged_max_ptes_shared) { + result = SCAN_EXCEED_SHARED_PTE; + count_vm_event(THP_SCAN_EXCEED_SHARED_PTE); + goto out_unmap; + } } - page = compound_head(page); - + folio = page_folio(page); /* * Record which node the original page is from and save this - * information to khugepaged_node_load[]. - * Khupaged will allocate hugepage from the node has the max + * information to cc->node_load[]. + * Khugepaged will allocate hugepage from the node has the max * hit record. */ - node = page_to_nid(page); - if (khugepaged_scan_abort(node)) { + node = folio_nid(folio); + if (hpage_collapse_scan_abort(node, cc)) { result = SCAN_SCAN_ABORT; goto out_unmap; } - khugepaged_node_load[node]++; - if (!PageLRU(page)) { + cc->node_load[node]++; + if (!folio_test_lru(folio)) { result = SCAN_PAGE_LRU; goto out_unmap; } - if (PageLocked(page)) { + if (folio_test_locked(folio)) { result = SCAN_PAGE_LOCK; goto out_unmap; } - if (!PageAnon(page)) { + if (!folio_test_anon(folio)) { result = SCAN_PAGE_ANON; goto out_unmap; } @@ -1325,61 +1370,62 @@ static int khugepaged_scan_pmd(struct mm_struct *mm, /* * Check if the page has any GUP (or other external) pins. * - * Here the check is racy it may see totmal_mapcount > refcount - * in some cases. - * For example, one process with one forked child process. - * The parent has the PMD split due to MADV_DONTNEED, then - * the child is trying unmap the whole PMD, but khugepaged - * may be scanning the parent between the child has - * PageDoubleMap flag cleared and dec the mapcount. So - * khugepaged may see total_mapcount > refcount. - * + * Here the check may be racy: + * it may see total_mapcount > refcount in some cases? * But such case is ephemeral we could always retry collapse * later. However it may report false positive if the page * has excessive GUP pins (i.e. 512). Anyway the same check * will be done again later the risk seems low. */ - if (!is_refcount_suitable(page)) { + if (!is_refcount_suitable(folio)) { result = SCAN_PAGE_COUNT; goto out_unmap; } - if (pte_young(pteval) || - page_is_young(page) || PageReferenced(page) || - mmu_notifier_test_young(vma->vm_mm, address)) + + /* + * If collapse was initiated by khugepaged, check that there is + * enough young pte to justify collapsing the page + */ + if (cc->is_khugepaged && + (pte_young(pteval) || folio_test_young(folio) || + folio_test_referenced(folio) || mmu_notifier_test_young(vma->vm_mm, + address))) referenced++; } if (!writable) { result = SCAN_PAGE_RO; - } else if (!referenced || (unmapped && referenced < HPAGE_PMD_NR/2)) { + } else if (cc->is_khugepaged && + (!referenced || + (unmapped && referenced < HPAGE_PMD_NR / 2))) { result = SCAN_LACK_REFERENCED_PAGE; } else { result = SCAN_SUCCEED; - ret = 1; } out_unmap: pte_unmap_unlock(pte, ptl); - if (ret) { - node = khugepaged_find_target_node(); + if (result == SCAN_SUCCEED) { + result = collapse_huge_page(mm, address, referenced, + unmapped, cc); /* collapse_huge_page will return with the mmap_lock released */ - collapse_huge_page(mm, address, hpage, node, - referenced, unmapped); + *mmap_locked = false; } out: - trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, + trace_mm_khugepaged_scan_pmd(mm, &folio->page, writable, referenced, none_or_zero, result, unmapped); - return ret; + return result; } -static void collect_mm_slot(struct mm_slot *mm_slot) +static void collect_mm_slot(struct khugepaged_mm_slot *mm_slot) { - struct mm_struct *mm = mm_slot->mm; + struct mm_slot *slot = &mm_slot->slot; + struct mm_struct *mm = slot->mm; lockdep_assert_held(&khugepaged_mm_lock); - if (khugepaged_test_exit(mm)) { + if (hpage_collapse_test_exit(mm)) { /* free mm_slot */ - hash_del(&mm_slot->hash); - list_del(&mm_slot->mm_node); + hash_del(&slot->hash); + list_del(&slot->mm_node); /* * Not strictly needed because the mm exited already. @@ -1388,270 +1434,393 @@ static void collect_mm_slot(struct mm_slot *mm_slot) */ /* khugepaged_mm_lock actually not necessary for the below */ - free_mm_slot(mm_slot); + mm_slot_free(mm_slot_cache, mm_slot); mmdrop(mm); } } #ifdef CONFIG_SHMEM -/* - * Notify khugepaged that given addr of the mm is pte-mapped THP. Then - * khugepaged should try to collapse the page table. - */ -static int khugepaged_add_pte_mapped_thp(struct mm_struct *mm, - unsigned long addr) +/* hpage must be locked, and mmap_lock must be held */ +static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr, + pmd_t *pmdp, struct page *hpage) { - struct mm_slot *mm_slot; + struct vm_fault vmf = { + .vma = vma, + .address = addr, + .flags = 0, + .pmd = pmdp, + }; - VM_BUG_ON(addr & ~HPAGE_PMD_MASK); + VM_BUG_ON(!PageTransHuge(hpage)); + mmap_assert_locked(vma->vm_mm); - spin_lock(&khugepaged_mm_lock); - mm_slot = get_mm_slot(mm); - if (likely(mm_slot && mm_slot->nr_pte_mapped_thp < MAX_PTE_MAPPED_THP)) - mm_slot->pte_mapped_thp[mm_slot->nr_pte_mapped_thp++] = addr; - spin_unlock(&khugepaged_mm_lock); - return 0; + if (do_set_pmd(&vmf, hpage)) + return SCAN_FAIL; + + get_page(hpage); + return SCAN_SUCCEED; } /** - * Try to collapse a pte-mapped THP for mm at address haddr. + * collapse_pte_mapped_thp - Try to collapse a pte-mapped THP for mm at + * address haddr. + * + * @mm: process address space where collapse happens + * @addr: THP collapse address + * @install_pmd: If a huge PMD should be installed * * This function checks whether all the PTEs in the PMD are pointing to the * right THP. If so, retract the page table so the THP can refault in with - * as pmd-mapped. + * as pmd-mapped. Possibly install a huge PMD mapping the THP. */ -void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) +int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, + bool install_pmd) { + struct mmu_notifier_range range; + bool notified = false; unsigned long haddr = addr & HPAGE_PMD_MASK; - struct vm_area_struct *vma = find_vma(mm, haddr); - struct page *hpage; + struct vm_area_struct *vma = vma_lookup(mm, haddr); + struct folio *folio; pte_t *start_pte, *pte; - pmd_t *pmd, _pmd; - spinlock_t *ptl; - int count = 0; + pmd_t *pmd, pgt_pmd; + spinlock_t *pml = NULL, *ptl; + int nr_ptes = 0, result = SCAN_FAIL; int i; + mmap_assert_locked(mm); + + /* First check VMA found, in case page tables are being torn down */ if (!vma || !vma->vm_file || - vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE) - return; + !range_in_vma(vma, haddr, haddr + HPAGE_PMD_SIZE)) + return SCAN_VMA_CHECK; + + /* Fast check before locking page if already PMD-mapped */ + result = find_pmd_or_thp_or_none(mm, haddr, &pmd); + if (result == SCAN_PMD_MAPPED) + return result; /* - * This vm_flags may not have VM_HUGEPAGE if the page was not - * collapsed by this mm. But we can still collapse if the page is - * the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check() - * will not fail the vma for missing VM_HUGEPAGE + * If we are here, we've succeeded in replacing all the native pages + * in the page cache with a single hugepage. If a mm were to fault-in + * this memory (mapped by a suitably aligned VMA), we'd get the hugepage + * and map it by a PMD, regardless of sysfs THP settings. As such, let's + * analogously elide sysfs THP settings here. */ - if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE)) - return; + if (!thp_vma_allowable_order(vma, vma->vm_flags, false, false, false, + PMD_ORDER)) + return SCAN_VMA_CHECK; - hpage = find_lock_page(vma->vm_file->f_mapping, + /* Keep pmd pgtable for uffd-wp; see comment in retract_page_tables() */ + if (userfaultfd_wp(vma)) + return SCAN_PTE_UFFD_WP; + + folio = filemap_lock_folio(vma->vm_file->f_mapping, linear_page_index(vma, haddr)); - if (!hpage) - return; + if (IS_ERR(folio)) + return SCAN_PAGE_NULL; - if (!PageHead(hpage)) - goto drop_hpage; + if (folio_order(folio) != HPAGE_PMD_ORDER) { + result = SCAN_PAGE_COMPOUND; + goto drop_folio; + } - pmd = mm_find_pmd(mm, haddr); - if (!pmd) - goto drop_hpage; + result = find_pmd_or_thp_or_none(mm, haddr, &pmd); + switch (result) { + case SCAN_SUCCEED: + break; + case SCAN_PMD_NONE: + /* + * All pte entries have been removed and pmd cleared. + * Skip all the pte checks and just update the pmd mapping. + */ + goto maybe_install_pmd; + default: + goto drop_folio; + } + result = SCAN_FAIL; start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl); + if (!start_pte) /* mmap_lock + page lock should prevent this */ + goto drop_folio; /* step 1: check all mapped PTEs are to the right huge page */ for (i = 0, addr = haddr, pte = start_pte; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) { struct page *page; + pte_t ptent = ptep_get(pte); /* empty pte, skip */ - if (pte_none(*pte)) + if (pte_none(ptent)) continue; /* page swapped out, abort */ - if (!pte_present(*pte)) + if (!pte_present(ptent)) { + result = SCAN_PTE_NON_PRESENT; goto abort; + } - page = vm_normal_page(vma, addr, *pte); - + page = vm_normal_page(vma, addr, ptent); + if (WARN_ON_ONCE(page && is_zone_device_page(page))) + page = NULL; /* * Note that uprobe, debugger, or MAP_PRIVATE may change the * page table, but the new page will not be a subpage of hpage. */ - if (hpage + i != page) + if (folio_page(folio, i) != page) goto abort; - count++; } - /* step 2: adjust rmap */ + pte_unmap_unlock(start_pte, ptl); + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, + haddr, haddr + HPAGE_PMD_SIZE); + mmu_notifier_invalidate_range_start(&range); + notified = true; + + /* + * pmd_lock covers a wider range than ptl, and (if split from mm's + * page_table_lock) ptl nests inside pml. The less time we hold pml, + * the better; but userfaultfd's mfill_atomic_pte() on a private VMA + * inserts a valid as-if-COWed PTE without even looking up page cache. + * So page lock of folio does not protect from it, so we must not drop + * ptl before pgt_pmd is removed, so uffd private needs pml taken now. + */ + if (userfaultfd_armed(vma) && !(vma->vm_flags & VM_SHARED)) + pml = pmd_lock(mm, pmd); + + start_pte = pte_offset_map_nolock(mm, pmd, haddr, &ptl); + if (!start_pte) /* mmap_lock + page lock should prevent this */ + goto abort; + if (!pml) + spin_lock(ptl); + else if (ptl != pml) + spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); + + /* step 2: clear page table and adjust rmap */ for (i = 0, addr = haddr, pte = start_pte; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) { struct page *page; + pte_t ptent = ptep_get(pte); - if (pte_none(*pte)) + if (pte_none(ptent)) continue; - page = vm_normal_page(vma, addr, *pte); - page_remove_rmap(page, false); + /* + * We dropped ptl after the first scan, to do the mmu_notifier: + * page lock stops more PTEs of the folio being faulted in, but + * does not stop write faults COWing anon copies from existing + * PTEs; and does not stop those being swapped out or migrated. + */ + if (!pte_present(ptent)) { + result = SCAN_PTE_NON_PRESENT; + goto abort; + } + page = vm_normal_page(vma, addr, ptent); + if (folio_page(folio, i) != page) + goto abort; + + /* + * Must clear entry, or a racing truncate may re-remove it. + * TLB flush can be left until pmdp_collapse_flush() does it. + * PTE dirty? Shmem page is already dirty; file is read-only. + */ + ptep_clear(mm, addr, pte); + folio_remove_rmap_pte(folio, page, vma); + nr_ptes++; } - pte_unmap_unlock(start_pte, ptl); + pte_unmap(start_pte); + if (!pml) + spin_unlock(ptl); /* step 3: set proper refcount and mm_counters. */ - if (count) { - page_ref_sub(hpage, count); - add_mm_counter(vma->vm_mm, mm_counter_file(hpage), -count); + if (nr_ptes) { + folio_ref_sub(folio, nr_ptes); + add_mm_counter(mm, mm_counter_file(&folio->page), -nr_ptes); } - /* step 4: collapse pmd */ - ptl = pmd_lock(vma->vm_mm, pmd); - _pmd = pmdp_collapse_flush(vma, haddr, pmd); - spin_unlock(ptl); - mm_dec_nr_ptes(mm); - pte_free(mm, pmd_pgtable(_pmd)); + /* step 4: remove empty page table */ + if (!pml) { + pml = pmd_lock(mm, pmd); + if (ptl != pml) + spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); + } + pgt_pmd = pmdp_collapse_flush(vma, haddr, pmd); + pmdp_get_lockless_sync(); + if (ptl != pml) + spin_unlock(ptl); + spin_unlock(pml); -drop_hpage: - unlock_page(hpage); - put_page(hpage); - return; + mmu_notifier_invalidate_range_end(&range); + mm_dec_nr_ptes(mm); + page_table_check_pte_clear_range(mm, haddr, pgt_pmd); + pte_free_defer(mm, pmd_pgtable(pgt_pmd)); + +maybe_install_pmd: + /* step 5: install pmd entry */ + result = install_pmd + ? set_huge_pmd(vma, haddr, pmd, &folio->page) + : SCAN_SUCCEED; + goto drop_folio; abort: - pte_unmap_unlock(start_pte, ptl); - goto drop_hpage; -} - -static int khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot) -{ - struct mm_struct *mm = mm_slot->mm; - int i; - - if (likely(mm_slot->nr_pte_mapped_thp == 0)) - return 0; - - if (!mmap_write_trylock(mm)) - return -EBUSY; - - if (unlikely(khugepaged_test_exit(mm))) - goto out; - - for (i = 0; i < mm_slot->nr_pte_mapped_thp; i++) - collapse_pte_mapped_thp(mm, mm_slot->pte_mapped_thp[i]); - -out: - mm_slot->nr_pte_mapped_thp = 0; - mmap_write_unlock(mm); - return 0; + if (nr_ptes) { + flush_tlb_mm(mm); + folio_ref_sub(folio, nr_ptes); + add_mm_counter(mm, mm_counter_file(&folio->page), -nr_ptes); + } + if (start_pte) + pte_unmap_unlock(start_pte, ptl); + if (pml && pml != ptl) + spin_unlock(pml); + if (notified) + mmu_notifier_invalidate_range_end(&range); +drop_folio: + folio_unlock(folio); + folio_put(folio); + return result; } static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) { struct vm_area_struct *vma; - struct mm_struct *mm; - unsigned long addr; - pmd_t *pmd, _pmd; - i_mmap_lock_write(mapping); + i_mmap_lock_read(mapping); vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { + struct mmu_notifier_range range; + struct mm_struct *mm; + unsigned long addr; + pmd_t *pmd, pgt_pmd; + spinlock_t *pml; + spinlock_t *ptl; + bool skipped_uffd = false; + /* * Check vma->anon_vma to exclude MAP_PRIVATE mappings that - * got written to. These VMAs are likely not worth investing - * mmap_write_lock(mm) as PMD-mapping is likely to be split - * later. - * - * Not that vma->anon_vma check is racy: it can be set up after - * the check but before we took mmap_lock by the fault path. - * But page lock would prevent establishing any new ptes of the - * page, so we are safe. - * - * An alternative would be drop the check, but check that page - * table is clear before calling pmdp_collapse_flush() under - * ptl. It has higher chance to recover THP for the VMA, but - * has higher cost too. + * got written to. These VMAs are likely not worth removing + * page tables from, as PMD-mapping is likely to be split later. */ - if (vma->anon_vma) + if (READ_ONCE(vma->anon_vma)) continue; + addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); - if (addr & ~HPAGE_PMD_MASK) - continue; - if (vma->vm_end < addr + HPAGE_PMD_SIZE) + if (addr & ~HPAGE_PMD_MASK || + vma->vm_end < addr + HPAGE_PMD_SIZE) continue; + mm = vma->vm_mm; - pmd = mm_find_pmd(mm, addr); - if (!pmd) + if (find_pmd_or_thp_or_none(mm, addr, &pmd) != SCAN_SUCCEED) + continue; + + if (hpage_collapse_test_exit(mm)) continue; /* - * We need exclusive mmap_lock to retract page table. - * - * We use trylock due to lock inversion: we need to acquire - * mmap_lock while holding page lock. Fault path does it in - * reverse order. Trylock is a way to avoid deadlock. + * When a vma is registered with uffd-wp, we cannot recycle + * the page table because there may be pte markers installed. + * Other vmas can still have the same file mapped hugely, but + * skip this one: it will always be mapped in small page size + * for uffd-wp registered ranges. */ - if (mmap_write_trylock(mm)) { - if (!khugepaged_test_exit(mm)) { - spinlock_t *ptl = pmd_lock(mm, pmd); - /* assume page table is clear */ - _pmd = pmdp_collapse_flush(vma, addr, pmd); - spin_unlock(ptl); - mm_dec_nr_ptes(mm); - pte_free(mm, pmd_pgtable(_pmd)); - } - mmap_write_unlock(mm); + if (userfaultfd_wp(vma)) + continue; + + /* PTEs were notified when unmapped; but now for the PMD? */ + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, + addr, addr + HPAGE_PMD_SIZE); + mmu_notifier_invalidate_range_start(&range); + + pml = pmd_lock(mm, pmd); + ptl = pte_lockptr(mm, pmd); + if (ptl != pml) + spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); + + /* + * Huge page lock is still held, so normally the page table + * must remain empty; and we have already skipped anon_vma + * and userfaultfd_wp() vmas. But since the mmap_lock is not + * held, it is still possible for a racing userfaultfd_ioctl() + * to have inserted ptes or markers. Now that we hold ptlock, + * repeating the anon_vma check protects from one category, + * and repeating the userfaultfd_wp() check from another. + */ + if (unlikely(vma->anon_vma || userfaultfd_wp(vma))) { + skipped_uffd = true; } else { - /* Try again later */ - khugepaged_add_pte_mapped_thp(mm, addr); + pgt_pmd = pmdp_collapse_flush(vma, addr, pmd); + pmdp_get_lockless_sync(); + } + + if (ptl != pml) + spin_unlock(ptl); + spin_unlock(pml); + + mmu_notifier_invalidate_range_end(&range); + + if (!skipped_uffd) { + mm_dec_nr_ptes(mm); + page_table_check_pte_clear_range(mm, addr, pgt_pmd); + pte_free_defer(mm, pmd_pgtable(pgt_pmd)); } } - i_mmap_unlock_write(mapping); + i_mmap_unlock_read(mapping); } /** * collapse_file - collapse filemap/tmpfs/shmem pages into huge one. * + * @mm: process address space where collapse happens + * @addr: virtual collapse start address + * @file: file that collapse on + * @start: collapse start address + * @cc: collapse context and scratchpad + * * Basic scheme is simple, details are more complex: * - allocate and lock a new huge page; - * - scan page cache replacing old pages with the new one + * - scan page cache, locking old pages * + swap/gup in pages if necessary; - * + fill in gaps; - * + keep old pages around in case rollback is required; + * - copy data to new page + * - handle shmem holes + * + re-validate that holes weren't filled by someone else + * + check for userfaultfd + * - finalize updates to the page cache; * - if replacing succeeds: - * + copy data over; - * + free old pages; * + unlock huge page; + * + free old pages; * - if replacing failed; - * + put all pages back and unfreeze them; - * + restore gaps in the page cache; + * + unlock old pages * + unlock and free huge page; */ -static void collapse_file(struct mm_struct *mm, - struct file *file, pgoff_t start, - struct page **hpage, int node) +static int collapse_file(struct mm_struct *mm, unsigned long addr, + struct file *file, pgoff_t start, + struct collapse_control *cc) { struct address_space *mapping = file->f_mapping; - gfp_t gfp; - struct page *new_page; - pgoff_t index, end = start + HPAGE_PMD_NR; + struct page *hpage; + struct page *page; + struct page *tmp; + struct folio *folio; + pgoff_t index = 0, end = start + HPAGE_PMD_NR; LIST_HEAD(pagelist); XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); int nr_none = 0, result = SCAN_SUCCEED; bool is_shmem = shmem_file(file); + int nr = 0; VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); - /* Only allocate from the target node */ - gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; - - new_page = khugepaged_alloc_page(hpage, gfp, node); - if (!new_page) { - result = SCAN_ALLOC_HUGE_PAGE_FAIL; + result = alloc_charge_hpage(&hpage, mm, cc); + if (result != SCAN_SUCCEED) goto out; - } - if (unlikely(mem_cgroup_charge(new_page, mm, gfp))) { - result = SCAN_CGROUP_CHARGE_FAIL; - goto out; - } - count_memcg_page_event(new_page, THP_COLLAPSE_ALLOC); + __SetPageLocked(hpage); + if (is_shmem) + __SetPageSwapBacked(hpage); + hpage->index = start; + hpage->mapping = mapping; - /* This will be less messy when we use multi-index entries */ + /* + * Ensure we have slots for all the pages in the range. This is + * almost certainly a no-op because most of the pages must be present + */ do { xas_lock_irq(&xas); xas_create_range(&xas); @@ -1660,25 +1829,13 @@ static void collapse_file(struct mm_struct *mm, xas_unlock_irq(&xas); if (!xas_nomem(&xas, GFP_KERNEL)) { result = SCAN_FAIL; - goto out; + goto rollback; } } while (1); - __SetPageLocked(new_page); - if (is_shmem) - __SetPageSwapBacked(new_page); - new_page->index = start; - new_page->mapping = mapping; - - /* - * At this point the new_page is locked and not up-to-date. - * It's safe to insert it into the page cache, because nobody would - * be able to map it or use it in another way until we unlock it. - */ - - xas_set(&xas, start); for (index = start; index < end; index++) { - struct page *page = xas_next(&xas); + xas_set(&xas, index); + page = xas_load(&xas); VM_BUG_ON(index != xas.xa_index); if (is_shmem) { @@ -1693,13 +1850,7 @@ static void collapse_file(struct mm_struct *mm, result = SCAN_TRUNCATED; goto xa_locked; } - xas_set(&xas, index); - } - if (!shmem_charge(mapping->host, 1)) { - result = SCAN_FAIL; - goto xa_locked; } - xas_store(&xas, new_page); nr_none++; continue; } @@ -1707,11 +1858,14 @@ static void collapse_file(struct mm_struct *mm, if (xa_is_value(page) || !PageUptodate(page)) { xas_unlock_irq(&xas); /* swap in or instantiate fallocated page */ - if (shmem_getpage(mapping->host, index, &page, - SGP_NOHUGE)) { + if (shmem_get_folio(mapping->host, index, + &folio, SGP_NOALLOC)) { result = SCAN_FAIL; goto xa_unlocked; } + /* drain lru cache to help isolate_lru_page() */ + lru_add_drain(); + page = folio_file_page(folio, index); } else if (trylock_page(page)) { get_page(page); xas_unlock_irq(&xas); @@ -1725,7 +1879,7 @@ static void collapse_file(struct mm_struct *mm, page_cache_sync_readahead(mapping, &file->f_ra, file, index, end - index); - /* drain pagevecs to help isolate_lru_page() */ + /* drain lru cache to help isolate_lru_page() */ lru_add_drain(); page = find_lock_page(mapping, index); if (unlikely(page == NULL)) { @@ -1750,6 +1904,10 @@ static void collapse_file(struct mm_struct *mm, filemap_flush(mapping); result = SCAN_FAIL; goto xa_unlocked; + } else if (PageWriteback(page)) { + xas_unlock_irq(&xas); + result = SCAN_FAIL; + goto xa_unlocked; } else if (trylock_page(page)) { get_page(page); xas_unlock_irq(&xas); @@ -1774,18 +1932,28 @@ static void collapse_file(struct mm_struct *mm, /* * If file was truncated then extended, or hole-punched, before * we locked the first page, then a THP might be there already. + * This will be discovered on the first iteration. */ if (PageTransCompound(page)) { - result = SCAN_PAGE_COMPOUND; + struct page *head = compound_head(page); + + result = compound_order(head) == HPAGE_PMD_ORDER && + head->index == start + /* Maybe PMD-mapped */ + ? SCAN_PTE_MAPPED_HUGEPAGE + : SCAN_PAGE_COMPOUND; goto out_unlock; } - if (page_mapping(page) != mapping) { + folio = page_folio(page); + + if (folio_mapping(folio) != mapping) { result = SCAN_TRUNCATED; goto out_unlock; } - if (!is_shmem && PageDirty(page)) { + if (!is_shmem && (folio_test_dirty(folio) || + folio_test_writeback(folio))) { /* * khugepaged only works on read-only fd, so this * page is dirty because it hasn't been flushed @@ -1795,34 +1963,36 @@ static void collapse_file(struct mm_struct *mm, goto out_unlock; } - if (isolate_lru_page(page)) { + if (!folio_isolate_lru(folio)) { result = SCAN_DEL_PAGE_LRU; goto out_unlock; } - if (page_has_private(page) && - !try_to_release_page(page, GFP_KERNEL)) { + if (!filemap_release_folio(folio, GFP_KERNEL)) { result = SCAN_PAGE_HAS_PRIVATE; - putback_lru_page(page); + folio_putback_lru(folio); goto out_unlock; } - if (page_mapped(page)) - unmap_mapping_pages(mapping, index, 1, false); + if (folio_mapped(folio)) + try_to_unmap(folio, + TTU_IGNORE_MLOCK | TTU_BATCH_FLUSH); xas_lock_irq(&xas); - xas_set(&xas, index); - VM_BUG_ON_PAGE(page != xas_load(&xas), page); - VM_BUG_ON_PAGE(page_mapped(page), page); + VM_BUG_ON_PAGE(page != xa_load(xas.xa, index), page); /* - * The page is expected to have page_count() == 3: + * We control three references to the page: * - we hold a pin on it; * - one reference from page cache; * - one from isolate_lru_page; + * If those are the only references, then any new usage of the + * page will have to fetch it from the page cache. That requires + * locking the page to handle truncate, so any new usage will be + * blocked until we unlock page after collapse/during rollback. */ - if (!page_ref_freeze(page, 3)) { + if (page_count(page) != 3) { result = SCAN_PAGE_COUNT; xas_unlock_irq(&xas); putback_lru_page(page); @@ -1830,13 +2000,9 @@ static void collapse_file(struct mm_struct *mm, } /* - * Add the page to the list to be able to undo the collapse if - * something go wrong. + * Accumulate the pages that are being collapsed. */ list_add_tail(&page->lru, &pagelist); - - /* Finally, replace with the new page. */ - xas_store(&xas, new_page); continue; out_unlock: unlock_page(page); @@ -1844,116 +2010,214 @@ out_unlock: goto xa_unlocked; } - if (is_shmem) - __inc_node_page_state(new_page, NR_SHMEM_THPS); - else { - __inc_node_page_state(new_page, NR_FILE_THPS); + if (!is_shmem) { filemap_nr_thps_inc(mapping); - } - - if (nr_none) { - __mod_lruvec_page_state(new_page, NR_FILE_PAGES, nr_none); - if (is_shmem) - __mod_lruvec_page_state(new_page, NR_SHMEM, nr_none); + /* + * Paired with smp_mb() in do_dentry_open() to ensure + * i_writecount is up to date and the update to nr_thps is + * visible. Ensures the page cache will be truncated if the + * file is opened writable. + */ + smp_mb(); + if (inode_is_open_for_write(mapping->host)) { + result = SCAN_FAIL; + filemap_nr_thps_dec(mapping); + } } xa_locked: xas_unlock_irq(&xas); xa_unlocked: - if (result == SCAN_SUCCEED) { - struct page *page, *tmp; + /* + * If collapse is successful, flush must be done now before copying. + * If collapse is unsuccessful, does flush actually need to be done? + * Do it anyway, to clear the state. + */ + try_to_unmap_flush(); - /* - * Replacing old pages with new one has succeeded, now we - * need to copy the content and free the old pages. - */ - index = start; - list_for_each_entry_safe(page, tmp, &pagelist, lru) { - while (index < page->index) { - clear_highpage(new_page + (index % HPAGE_PMD_NR)); - index++; - } - copy_highpage(new_page + (page->index % HPAGE_PMD_NR), - page); - list_del(&page->lru); - page->mapping = NULL; - page_ref_unfreeze(page, 1); - ClearPageActive(page); - ClearPageUnevictable(page); - unlock_page(page); - put_page(page); + if (result == SCAN_SUCCEED && nr_none && + !shmem_charge(mapping->host, nr_none)) + result = SCAN_FAIL; + if (result != SCAN_SUCCEED) { + nr_none = 0; + goto rollback; + } + + /* + * The old pages are locked, so they won't change anymore. + */ + index = start; + list_for_each_entry(page, &pagelist, lru) { + while (index < page->index) { + clear_highpage(hpage + (index % HPAGE_PMD_NR)); index++; } - while (index < end) { - clear_highpage(new_page + (index % HPAGE_PMD_NR)); - index++; + if (copy_mc_highpage(hpage + (page->index % HPAGE_PMD_NR), page) > 0) { + result = SCAN_COPY_MC; + goto rollback; + } + index++; + } + while (index < end) { + clear_highpage(hpage + (index % HPAGE_PMD_NR)); + index++; + } + + if (nr_none) { + struct vm_area_struct *vma; + int nr_none_check = 0; + + i_mmap_lock_read(mapping); + xas_lock_irq(&xas); + + xas_set(&xas, start); + for (index = start; index < end; index++) { + if (!xas_next(&xas)) { + xas_store(&xas, XA_RETRY_ENTRY); + if (xas_error(&xas)) { + result = SCAN_STORE_FAILED; + goto immap_locked; + } + nr_none_check++; + } } - SetPageUptodate(new_page); - page_ref_add(new_page, HPAGE_PMD_NR - 1); - if (is_shmem) - set_page_dirty(new_page); - lru_cache_add(new_page); + if (nr_none != nr_none_check) { + result = SCAN_PAGE_FILLED; + goto immap_locked; + } /* - * Remove pte page tables, so we can re-fault the page as huge. + * If userspace observed a missing page in a VMA with a MODE_MISSING + * userfaultfd, then it might expect a UFFD_EVENT_PAGEFAULT for that + * page. If so, we need to roll back to avoid suppressing such an + * event. Since wp/minor userfaultfds don't give userspace any + * guarantees that the kernel doesn't fill a missing page with a zero + * page, so they don't matter here. + * + * Any userfaultfds registered after this point will not be able to + * observe any missing pages due to the previously inserted retry + * entries. */ - retract_page_tables(mapping, start); - *hpage = NULL; + vma_interval_tree_foreach(vma, &mapping->i_mmap, start, end) { + if (userfaultfd_missing(vma)) { + result = SCAN_EXCEED_NONE_PTE; + goto immap_locked; + } + } - khugepaged_pages_collapsed++; - } else { - struct page *page; +immap_locked: + i_mmap_unlock_read(mapping); + if (result != SCAN_SUCCEED) { + xas_set(&xas, start); + for (index = start; index < end; index++) { + if (xas_next(&xas) == XA_RETRY_ENTRY) + xas_store(&xas, NULL); + } - /* Something went wrong: roll back page cache changes */ + xas_unlock_irq(&xas); + goto rollback; + } + } else { xas_lock_irq(&xas); - mapping->nrpages -= nr_none; + } - if (is_shmem) - shmem_uncharge(mapping->host, nr_none); + folio = page_folio(hpage); + nr = folio_nr_pages(folio); + if (is_shmem) + __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, nr); + else + __lruvec_stat_mod_folio(folio, NR_FILE_THPS, nr); - xas_set(&xas, start); - xas_for_each(&xas, page, end - 1) { - page = list_first_entry_or_null(&pagelist, - struct page, lru); - if (!page || xas.xa_index < page->index) { - if (!nr_none) - break; - nr_none--; - /* Put holes back where they were */ - xas_store(&xas, NULL); - continue; - } + if (nr_none) { + __lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr_none); + /* nr_none is always 0 for non-shmem. */ + __lruvec_stat_mod_folio(folio, NR_SHMEM, nr_none); + } - VM_BUG_ON_PAGE(page->index != xas.xa_index, page); + /* + * Mark hpage as uptodate before inserting it into the page cache so + * that it isn't mistaken for an fallocated but unwritten page. + */ + folio_mark_uptodate(folio); + folio_ref_add(folio, HPAGE_PMD_NR - 1); - /* Unfreeze the page. */ - list_del(&page->lru); - page_ref_unfreeze(page, 2); - xas_store(&xas, page); - xas_pause(&xas); - xas_unlock_irq(&xas); - unlock_page(page); - putback_lru_page(page); - xas_lock_irq(&xas); - } - VM_BUG_ON(nr_none); + if (is_shmem) + folio_mark_dirty(folio); + folio_add_lru(folio); + + /* Join all the small entries into a single multi-index entry. */ + xas_set_order(&xas, start, HPAGE_PMD_ORDER); + xas_store(&xas, folio); + WARN_ON_ONCE(xas_error(&xas)); + xas_unlock_irq(&xas); + + /* + * Remove pte page tables, so we can re-fault the page as huge. + * If MADV_COLLAPSE, adjust result to call collapse_pte_mapped_thp(). + */ + retract_page_tables(mapping, start); + if (cc && !cc->is_khugepaged) + result = SCAN_PTE_MAPPED_HUGEPAGE; + folio_unlock(folio); + + /* + * The collapse has succeeded, so free the old pages. + */ + list_for_each_entry_safe(page, tmp, &pagelist, lru) { + list_del(&page->lru); + page->mapping = NULL; + ClearPageActive(page); + ClearPageUnevictable(page); + unlock_page(page); + folio_put_refs(page_folio(page), 3); + } + + goto out; + +rollback: + /* Something went wrong: roll back page cache changes */ + if (nr_none) { + xas_lock_irq(&xas); + mapping->nrpages -= nr_none; xas_unlock_irq(&xas); + shmem_uncharge(mapping->host, nr_none); + } - new_page->mapping = NULL; + list_for_each_entry_safe(page, tmp, &pagelist, lru) { + list_del(&page->lru); + unlock_page(page); + putback_lru_page(page); + put_page(page); } + /* + * Undo the updates of filemap_nr_thps_inc for non-SHMEM + * file only. This undo is not needed unless failure is + * due to SCAN_COPY_MC. + */ + if (!is_shmem && result == SCAN_COPY_MC) { + filemap_nr_thps_dec(mapping); + /* + * Paired with smp_mb() in do_dentry_open() to + * ensure the update to nr_thps is visible. + */ + smp_mb(); + } + + hpage->mapping = NULL; - unlock_page(new_page); + unlock_page(hpage); + put_page(hpage); out: VM_BUG_ON(!list_empty(&pagelist)); - if (!IS_ERR_OR_NULL(*hpage)) - mem_cgroup_uncharge(*hpage); - /* TODO: tracepoints */ + trace_mm_khugepaged_collapse_file(mm, hpage, index, is_shmem, addr, file, nr, result); + return result; } -static void khugepaged_scan_file(struct mm_struct *mm, - struct file *file, pgoff_t start, struct page **hpage) +static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr, + struct file *file, pgoff_t start, + struct collapse_control *cc) { struct page *page = NULL; struct address_space *mapping = file->f_mapping; @@ -1964,31 +2228,51 @@ static void khugepaged_scan_file(struct mm_struct *mm, present = 0; swap = 0; - memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); + memset(cc->node_load, 0, sizeof(cc->node_load)); + nodes_clear(cc->alloc_nmask); rcu_read_lock(); xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) { if (xas_retry(&xas, page)) continue; if (xa_is_value(page)) { - if (++swap > khugepaged_max_ptes_swap) { + ++swap; + if (cc->is_khugepaged && + swap > khugepaged_max_ptes_swap) { result = SCAN_EXCEED_SWAP_PTE; + count_vm_event(THP_SCAN_EXCEED_SWAP_PTE); break; } continue; } + /* + * TODO: khugepaged should compact smaller compound pages + * into a PMD sized page + */ if (PageTransCompound(page)) { - result = SCAN_PAGE_COMPOUND; + struct page *head = compound_head(page); + + result = compound_order(head) == HPAGE_PMD_ORDER && + head->index == start + /* Maybe PMD-mapped */ + ? SCAN_PTE_MAPPED_HUGEPAGE + : SCAN_PAGE_COMPOUND; + /* + * For SCAN_PTE_MAPPED_HUGEPAGE, further processing + * by the caller won't touch the page cache, and so + * it's safe to skip LRU and refcount checks before + * returning. + */ break; } node = page_to_nid(page); - if (khugepaged_scan_abort(node)) { + if (hpage_collapse_scan_abort(node, cc)) { result = SCAN_SCAN_ABORT; break; } - khugepaged_node_load[node]++; + cc->node_load[node]++; if (!PageLRU(page)) { result = SCAN_PAGE_LRU; @@ -2017,54 +2301,56 @@ static void khugepaged_scan_file(struct mm_struct *mm, rcu_read_unlock(); if (result == SCAN_SUCCEED) { - if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { + if (cc->is_khugepaged && + present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { result = SCAN_EXCEED_NONE_PTE; + count_vm_event(THP_SCAN_EXCEED_NONE_PTE); } else { - node = khugepaged_find_target_node(); - collapse_file(mm, file, start, hpage, node); + result = collapse_file(mm, addr, file, start, cc); } } - /* TODO: tracepoints */ + trace_mm_khugepaged_scan_file(mm, page, file, present, swap, result); + return result; } #else -static void khugepaged_scan_file(struct mm_struct *mm, - struct file *file, pgoff_t start, struct page **hpage) +static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr, + struct file *file, pgoff_t start, + struct collapse_control *cc) { BUILD_BUG(); } - -static int khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot) -{ - return 0; -} #endif -static unsigned int khugepaged_scan_mm_slot(unsigned int pages, - struct page **hpage) +static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result, + struct collapse_control *cc) __releases(&khugepaged_mm_lock) __acquires(&khugepaged_mm_lock) { - struct mm_slot *mm_slot; + struct vma_iterator vmi; + struct khugepaged_mm_slot *mm_slot; + struct mm_slot *slot; struct mm_struct *mm; struct vm_area_struct *vma; int progress = 0; VM_BUG_ON(!pages); lockdep_assert_held(&khugepaged_mm_lock); + *result = SCAN_FAIL; - if (khugepaged_scan.mm_slot) + if (khugepaged_scan.mm_slot) { mm_slot = khugepaged_scan.mm_slot; - else { - mm_slot = list_entry(khugepaged_scan.mm_head.next, + slot = &mm_slot->slot; + } else { + slot = list_entry(khugepaged_scan.mm_head.next, struct mm_slot, mm_node); + mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot); khugepaged_scan.address = 0; khugepaged_scan.mm_slot = mm_slot; } spin_unlock(&khugepaged_mm_lock); - khugepaged_collapse_pte_mapped_thps(mm_slot); - mm = mm_slot->mm; + mm = slot->mm; /* * Don't wait for semaphore (to avoid long wait times). Just move to * the next mm on the list. @@ -2072,39 +2358,39 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, vma = NULL; if (unlikely(!mmap_read_trylock(mm))) goto breakouterloop_mmap_lock; - if (likely(!khugepaged_test_exit(mm))) - vma = find_vma(mm, khugepaged_scan.address); progress++; - for (; vma; vma = vma->vm_next) { + if (unlikely(hpage_collapse_test_exit(mm))) + goto breakouterloop; + + vma_iter_init(&vmi, mm, khugepaged_scan.address); + for_each_vma(vmi, vma) { unsigned long hstart, hend; cond_resched(); - if (unlikely(khugepaged_test_exit(mm))) { + if (unlikely(hpage_collapse_test_exit(mm))) { progress++; break; } - if (!hugepage_vma_check(vma, vma->vm_flags)) { + if (!thp_vma_allowable_order(vma, vma->vm_flags, false, false, + true, PMD_ORDER)) { skip: progress++; continue; } - hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; - hend = vma->vm_end & HPAGE_PMD_MASK; - if (hstart >= hend) - goto skip; + hstart = round_up(vma->vm_start, HPAGE_PMD_SIZE); + hend = round_down(vma->vm_end, HPAGE_PMD_SIZE); if (khugepaged_scan.address > hend) goto skip; if (khugepaged_scan.address < hstart) khugepaged_scan.address = hstart; VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); - if (shmem_file(vma->vm_file) && !shmem_huge_enabled(vma)) - goto skip; while (khugepaged_scan.address < hend) { - int ret; + bool mmap_locked = true; + cond_resched(); - if (unlikely(khugepaged_test_exit(mm))) + if (unlikely(hpage_collapse_test_exit(mm))) goto breakouterloop; VM_BUG_ON(khugepaged_scan.address < hstart || @@ -2116,19 +2402,39 @@ skip: khugepaged_scan.address); mmap_read_unlock(mm); - ret = 1; - khugepaged_scan_file(mm, file, pgoff, hpage); + mmap_locked = false; + *result = hpage_collapse_scan_file(mm, + khugepaged_scan.address, file, pgoff, cc); fput(file); + if (*result == SCAN_PTE_MAPPED_HUGEPAGE) { + mmap_read_lock(mm); + if (hpage_collapse_test_exit(mm)) + goto breakouterloop; + *result = collapse_pte_mapped_thp(mm, + khugepaged_scan.address, false); + if (*result == SCAN_PMD_MAPPED) + *result = SCAN_SUCCEED; + mmap_read_unlock(mm); + } } else { - ret = khugepaged_scan_pmd(mm, vma, - khugepaged_scan.address, - hpage); + *result = hpage_collapse_scan_pmd(mm, vma, + khugepaged_scan.address, &mmap_locked, cc); } + + if (*result == SCAN_SUCCEED) + ++khugepaged_pages_collapsed; + /* move to next address */ khugepaged_scan.address += HPAGE_PMD_SIZE; progress += HPAGE_PMD_NR; - if (ret) - /* we released mmap_lock so break loop */ + if (!mmap_locked) + /* + * We released mmap_lock so break loop. Note + * that we drop mmap_lock before all hugepage + * allocations, so if allocation fails, we are + * guaranteed to break here and report the + * correct result back to caller. + */ goto breakouterloop_mmap_lock; if (progress >= pages) goto breakouterloop; @@ -2144,16 +2450,17 @@ breakouterloop_mmap_lock: * Release the current mm_slot if this mm is about to die, or * if we scanned all vmas of this mm. */ - if (khugepaged_test_exit(mm) || !vma) { + if (hpage_collapse_test_exit(mm) || !vma) { /* * Make sure that if mm_users is reaching zero while * khugepaged runs here, khugepaged_exit will find * mm_slot not pointing to the exiting mm. */ - if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { - khugepaged_scan.mm_slot = list_entry( - mm_slot->mm_node.next, - struct mm_slot, mm_node); + if (slot->mm_node.next != &khugepaged_scan.mm_head) { + slot = list_entry(slot->mm_node.next, + struct mm_slot, mm_node); + khugepaged_scan.mm_slot = + mm_slot_entry(slot, struct khugepaged_mm_slot, slot); khugepaged_scan.address = 0; } else { khugepaged_scan.mm_slot = NULL; @@ -2169,7 +2476,7 @@ breakouterloop_mmap_lock: static int khugepaged_has_work(void) { return !list_empty(&khugepaged_scan.mm_head) && - khugepaged_enabled(); + hugepage_flags_enabled(); } static int khugepaged_wait_event(void) @@ -2178,24 +2485,19 @@ static int khugepaged_wait_event(void) kthread_should_stop(); } -static void khugepaged_do_scan(void) +static void khugepaged_do_scan(struct collapse_control *cc) { - struct page *hpage = NULL; unsigned int progress = 0, pass_through_head = 0; - unsigned int pages = khugepaged_pages_to_scan; + unsigned int pages = READ_ONCE(khugepaged_pages_to_scan); bool wait = true; - - barrier(); /* write khugepaged_pages_to_scan to local stack */ + int result = SCAN_SUCCEED; lru_add_drain_all(); - while (progress < pages) { - if (!khugepaged_prealloc_page(&hpage, &wait)) - break; - + while (true) { cond_resched(); - if (unlikely(kthread_should_stop() || try_to_freeze())) + if (unlikely(kthread_should_stop())) break; spin_lock(&khugepaged_mm_lock); @@ -2204,14 +2506,25 @@ static void khugepaged_do_scan(void) if (khugepaged_has_work() && pass_through_head < 2) progress += khugepaged_scan_mm_slot(pages - progress, - &hpage); + &result, cc); else progress = pages; spin_unlock(&khugepaged_mm_lock); - } - if (!IS_ERR_OR_NULL(hpage)) - put_page(hpage); + if (progress >= pages) + break; + + if (result == SCAN_ALLOC_HUGE_PAGE_FAIL) { + /* + * If fail to allocate the first time, try to sleep for + * a while. When hit again, cancel the scan. + */ + if (!wait) + break; + wait = false; + khugepaged_alloc_sleep(); + } + } } static bool khugepaged_should_wakeup(void) @@ -2236,19 +2549,19 @@ static void khugepaged_wait_work(void) return; } - if (khugepaged_enabled()) + if (hugepage_flags_enabled()) wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); } static int khugepaged(void *none) { - struct mm_slot *mm_slot; + struct khugepaged_mm_slot *mm_slot; set_freezable(); set_user_nice(current, MAX_NICE); while (!kthread_should_stop()) { - khugepaged_do_scan(); + khugepaged_do_scan(&khugepaged_collapse_control); khugepaged_wait_work(); } @@ -2267,6 +2580,11 @@ static void set_recommended_min_free_kbytes(void) int nr_zones = 0; unsigned long recommended_min; + if (!hugepage_flags_enabled()) { + calculate_min_free_kbytes(); + goto update_wmarks; + } + for_each_populated_zone(zone) { /* * We don't need to worry about fragmentation of @@ -2302,6 +2620,8 @@ static void set_recommended_min_free_kbytes(void) min_free_kbytes = recommended_min; } + +update_wmarks: setup_per_zone_wmarks(); } @@ -2310,7 +2630,7 @@ int start_stop_khugepaged(void) int err = 0; mutex_lock(&khugepaged_mutex); - if (khugepaged_enabled()) { + if (hugepage_flags_enabled()) { if (!khugepaged_thread) khugepaged_thread = kthread_run(khugepaged, NULL, "khugepaged"); @@ -2323,12 +2643,11 @@ int start_stop_khugepaged(void) if (!list_empty(&khugepaged_scan.mm_head)) wake_up_interruptible(&khugepaged_wait); - - set_recommended_min_free_kbytes(); } else if (khugepaged_thread) { kthread_stop(khugepaged_thread); khugepaged_thread = NULL; } + set_recommended_min_free_kbytes(); fail: mutex_unlock(&khugepaged_mutex); return err; @@ -2337,7 +2656,153 @@ fail: void khugepaged_min_free_kbytes_update(void) { mutex_lock(&khugepaged_mutex); - if (khugepaged_enabled() && khugepaged_thread) + if (hugepage_flags_enabled() && khugepaged_thread) set_recommended_min_free_kbytes(); mutex_unlock(&khugepaged_mutex); } + +bool current_is_khugepaged(void) +{ + return kthread_func(current) == khugepaged; +} + +static int madvise_collapse_errno(enum scan_result r) +{ + /* + * MADV_COLLAPSE breaks from existing madvise(2) conventions to provide + * actionable feedback to caller, so they may take an appropriate + * fallback measure depending on the nature of the failure. + */ + switch (r) { + case SCAN_ALLOC_HUGE_PAGE_FAIL: + return -ENOMEM; + case SCAN_CGROUP_CHARGE_FAIL: + case SCAN_EXCEED_NONE_PTE: + return -EBUSY; + /* Resource temporary unavailable - trying again might succeed */ + case SCAN_PAGE_COUNT: + case SCAN_PAGE_LOCK: + case SCAN_PAGE_LRU: + case SCAN_DEL_PAGE_LRU: + case SCAN_PAGE_FILLED: + return -EAGAIN; + /* + * Other: Trying again likely not to succeed / error intrinsic to + * specified memory range. khugepaged likely won't be able to collapse + * either. + */ + default: + return -EINVAL; + } +} + +int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev, + unsigned long start, unsigned long end) +{ + struct collapse_control *cc; + struct mm_struct *mm = vma->vm_mm; + unsigned long hstart, hend, addr; + int thps = 0, last_fail = SCAN_FAIL; + bool mmap_locked = true; + + BUG_ON(vma->vm_start > start); + BUG_ON(vma->vm_end < end); + + *prev = vma; + + if (!thp_vma_allowable_order(vma, vma->vm_flags, false, false, false, + PMD_ORDER)) + return -EINVAL; + + cc = kmalloc(sizeof(*cc), GFP_KERNEL); + if (!cc) + return -ENOMEM; + cc->is_khugepaged = false; + + mmgrab(mm); + lru_add_drain_all(); + + hstart = (start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; + hend = end & HPAGE_PMD_MASK; + + for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) { + int result = SCAN_FAIL; + + if (!mmap_locked) { + cond_resched(); + mmap_read_lock(mm); + mmap_locked = true; + result = hugepage_vma_revalidate(mm, addr, false, &vma, + cc); + if (result != SCAN_SUCCEED) { + last_fail = result; + goto out_nolock; + } + + hend = min(hend, vma->vm_end & HPAGE_PMD_MASK); + } + mmap_assert_locked(mm); + memset(cc->node_load, 0, sizeof(cc->node_load)); + nodes_clear(cc->alloc_nmask); + if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) { + struct file *file = get_file(vma->vm_file); + pgoff_t pgoff = linear_page_index(vma, addr); + + mmap_read_unlock(mm); + mmap_locked = false; + result = hpage_collapse_scan_file(mm, addr, file, pgoff, + cc); + fput(file); + } else { + result = hpage_collapse_scan_pmd(mm, vma, addr, + &mmap_locked, cc); + } + if (!mmap_locked) + *prev = NULL; /* Tell caller we dropped mmap_lock */ + +handle_result: + switch (result) { + case SCAN_SUCCEED: + case SCAN_PMD_MAPPED: + ++thps; + break; + case SCAN_PTE_MAPPED_HUGEPAGE: + BUG_ON(mmap_locked); + BUG_ON(*prev); + mmap_read_lock(mm); + result = collapse_pte_mapped_thp(mm, addr, true); + mmap_read_unlock(mm); + goto handle_result; + /* Whitelisted set of results where continuing OK */ + case SCAN_PMD_NULL: + case SCAN_PTE_NON_PRESENT: + case SCAN_PTE_UFFD_WP: + case SCAN_PAGE_RO: + case SCAN_LACK_REFERENCED_PAGE: + case SCAN_PAGE_NULL: + case SCAN_PAGE_COUNT: + case SCAN_PAGE_LOCK: + case SCAN_PAGE_COMPOUND: + case SCAN_PAGE_LRU: + case SCAN_DEL_PAGE_LRU: + last_fail = result; + break; + default: + last_fail = result; + /* Other error, exit */ + goto out_maybelock; + } + } + +out_maybelock: + /* Caller expects us to hold mmap_lock on return */ + if (!mmap_locked) + mmap_read_lock(mm); +out_nolock: + mmap_assert_locked(mm); + mmdrop(mm); + kfree(cc); + + return thps == ((hend - hstart) >> HPAGE_PMD_SHIFT) ? 0 + : madvise_collapse_errno(last_fail); +} |