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- // SPDX-License-Identifier: GPL-2.0
- #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
- #include <linux/mm.h>
- #include <linux/sched.h>
- #include <linux/sched/mm.h>
- #include <linux/sched/coredump.h>
- #include <linux/mmu_notifier.h>
- #include <linux/rmap.h>
- #include <linux/swap.h>
- #include <linux/mm_inline.h>
- #include <linux/kthread.h>
- #include <linux/khugepaged.h>
- #include <linux/freezer.h>
- #include <linux/mman.h>
- #include <linux/hashtable.h>
- #include <linux/userfaultfd_k.h>
- #include <linux/page_idle.h>
- #include <linux/page_table_check.h>
- #include <linux/swapops.h>
- #include <linux/shmem_fs.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,
- SCAN_SCAN_ABORT,
- SCAN_PAGE_COUNT,
- SCAN_PAGE_LRU,
- SCAN_PAGE_LOCK,
- SCAN_PAGE_ANON,
- SCAN_PAGE_COMPOUND,
- SCAN_ANY_PROCESS,
- SCAN_VMA_NULL,
- SCAN_VMA_CHECK,
- SCAN_ADDRESS_RANGE,
- SCAN_DEL_PAGE_LRU,
- SCAN_ALLOC_HUGE_PAGE_FAIL,
- SCAN_CGROUP_CHARGE_FAIL,
- SCAN_TRUNCATED,
- SCAN_PAGE_HAS_PRIVATE,
- };
- #define CREATE_TRACE_POINTS
- #include <trace/events/huge_memory.h>
- static struct task_struct *khugepaged_thread __read_mostly;
- static DEFINE_MUTEX(khugepaged_mutex);
- /* default scan 8*512 pte (or vmas) every 30 second */
- static unsigned int khugepaged_pages_to_scan __read_mostly;
- static unsigned int khugepaged_pages_collapsed;
- static unsigned int khugepaged_full_scans;
- static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
- /* during fragmentation poll the hugepage allocator once every minute */
- static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
- static unsigned long khugepaged_sleep_expire;
- static DEFINE_SPINLOCK(khugepaged_mm_lock);
- 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 struct kmem_cache *mm_slot_cache __read_mostly;
- #define MAX_PTE_MAPPED_THP 8
- struct collapse_control {
- bool is_khugepaged;
- /* Num pages scanned per node */
- u32 node_load[MAX_NUMNODES];
- /* nodemask for allocation fallback */
- nodemask_t alloc_nmask;
- };
- /**
- * struct khugepaged_mm_slot - khugepaged information per mm that is being scanned
- * @slot: hash lookup from mm to mm_slot
- * @nr_pte_mapped_thp: number of pte mapped THP
- * @pte_mapped_thp: address array corresponding pte mapped THP
- */
- struct khugepaged_mm_slot {
- struct mm_slot slot;
- /* pte-mapped THP in this mm */
- int nr_pte_mapped_thp;
- unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP];
- };
- /**
- * struct khugepaged_scan - cursor for scanning
- * @mm_head: the head of the mm list to scan
- * @mm_slot: the current mm_slot we are scanning
- * @address: the next address inside that to be scanned
- *
- * There is only the one khugepaged_scan instance of this cursor structure.
- */
- struct khugepaged_scan {
- struct list_head mm_head;
- struct khugepaged_mm_slot *mm_slot;
- unsigned long address;
- };
- static struct khugepaged_scan khugepaged_scan = {
- .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
- };
- #ifdef CONFIG_SYSFS
- static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
- struct kobj_attribute *attr,
- char *buf)
- {
- 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 int msecs;
- int err;
- err = kstrtouint(buf, 10, &msecs);
- if (err)
- return -EINVAL;
- khugepaged_scan_sleep_millisecs = msecs;
- khugepaged_sleep_expire = 0;
- wake_up_interruptible(&khugepaged_wait);
- return count;
- }
- static struct kobj_attribute scan_sleep_millisecs_attr =
- __ATTR_RW(scan_sleep_millisecs);
- static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
- struct kobj_attribute *attr,
- char *buf)
- {
- 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 int msecs;
- int err;
- err = kstrtouint(buf, 10, &msecs);
- if (err)
- return -EINVAL;
- khugepaged_alloc_sleep_millisecs = msecs;
- khugepaged_sleep_expire = 0;
- wake_up_interruptible(&khugepaged_wait);
- return count;
- }
- static struct kobj_attribute alloc_sleep_millisecs_attr =
- __ATTR_RW(alloc_sleep_millisecs);
- static ssize_t pages_to_scan_show(struct kobject *kobj,
- struct kobj_attribute *attr,
- char *buf)
- {
- 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;
- err = kstrtouint(buf, 10, &pages);
- if (err || !pages)
- return -EINVAL;
- khugepaged_pages_to_scan = pages;
- return count;
- }
- static struct kobj_attribute pages_to_scan_attr =
- __ATTR_RW(pages_to_scan);
- static ssize_t pages_collapsed_show(struct kobject *kobj,
- struct kobj_attribute *attr,
- char *buf)
- {
- return sysfs_emit(buf, "%u\n", khugepaged_pages_collapsed);
- }
- static struct kobj_attribute pages_collapsed_attr =
- __ATTR_RO(pages_collapsed);
- static ssize_t full_scans_show(struct kobject *kobj,
- struct kobj_attribute *attr,
- char *buf)
- {
- return sysfs_emit(buf, "%u\n", khugepaged_full_scans);
- }
- static struct kobj_attribute full_scans_attr =
- __ATTR_RO(full_scans);
- 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);
- }
- 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_RW(defrag);
- /*
- * max_ptes_none controls if khugepaged should collapse hugepages over
- * any unmapped ptes in turn potentially increasing the memory
- * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
- * reduce the available free memory in the system as it
- * runs. Increasing max_ptes_none will instead potentially reduce the
- * free memory in the system during the khugepaged scan.
- */
- static ssize_t max_ptes_none_show(struct kobject *kobj,
- struct kobj_attribute *attr,
- char *buf)
- {
- return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_none);
- }
- 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)
- return -EINVAL;
- khugepaged_max_ptes_none = max_ptes_none;
- return count;
- }
- static struct kobj_attribute khugepaged_max_ptes_none_attr =
- __ATTR_RW(max_ptes_none);
- static ssize_t max_ptes_swap_show(struct kobject *kobj,
- struct kobj_attribute *attr,
- char *buf)
- {
- return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_swap);
- }
- 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)
- return -EINVAL;
- khugepaged_max_ptes_swap = max_ptes_swap;
- return count;
- }
- static struct kobj_attribute khugepaged_max_ptes_swap_attr =
- __ATTR_RW(max_ptes_swap);
- static ssize_t max_ptes_shared_show(struct kobject *kobj,
- struct kobj_attribute *attr,
- char *buf)
- {
- return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_shared);
- }
- 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)
- return -EINVAL;
- khugepaged_max_ptes_shared = max_ptes_shared;
- return count;
- }
- static struct kobj_attribute khugepaged_max_ptes_shared_attr =
- __ATTR_RW(max_ptes_shared);
- static struct attribute *khugepaged_attr[] = {
- &khugepaged_defrag_attr.attr,
- &khugepaged_max_ptes_none_attr.attr,
- &khugepaged_max_ptes_swap_attr.attr,
- &khugepaged_max_ptes_shared_attr.attr,
- &pages_to_scan_attr.attr,
- &pages_collapsed_attr.attr,
- &full_scans_attr.attr,
- &scan_sleep_millisecs_attr.attr,
- &alloc_sleep_millisecs_attr.attr,
- NULL,
- };
- struct attribute_group khugepaged_attr_group = {
- .attrs = khugepaged_attr,
- .name = "khugepaged",
- };
- #endif /* CONFIG_SYSFS */
- int hugepage_madvise(struct vm_area_struct *vma,
- unsigned long *vm_flags, int advice)
- {
- switch (advice) {
- case MADV_HUGEPAGE:
- #ifdef CONFIG_S390
- /*
- * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
- * can't handle this properly after s390_enable_sie, so we simply
- * ignore the madvise to prevent qemu from causing a SIGSEGV.
- */
- if (mm_has_pgste(vma->vm_mm))
- return 0;
- #endif
- *vm_flags &= ~VM_NOHUGEPAGE;
- *vm_flags |= VM_HUGEPAGE;
- /*
- * If the vma become good for khugepaged to scan,
- * register it here without waiting a page fault that
- * may not happen any time soon.
- */
- khugepaged_enter_vma(vma, *vm_flags);
- break;
- case MADV_NOHUGEPAGE:
- *vm_flags &= ~VM_HUGEPAGE;
- *vm_flags |= VM_NOHUGEPAGE;
- /*
- * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
- * this vma even if we leave the mm registered in khugepaged if
- * it got registered before VM_NOHUGEPAGE was set.
- */
- break;
- }
- return 0;
- }
- int __init khugepaged_init(void)
- {
- mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
- sizeof(struct khugepaged_mm_slot),
- __alignof__(struct khugepaged_mm_slot),
- 0, NULL);
- if (!mm_slot_cache)
- return -ENOMEM;
- khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
- khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
- khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
- khugepaged_max_ptes_shared = HPAGE_PMD_NR / 2;
- return 0;
- }
- void __init khugepaged_destroy(void)
- {
- kmem_cache_destroy(mm_slot_cache);
- }
- static inline int hpage_collapse_test_exit(struct mm_struct *mm)
- {
- return atomic_read(&mm->mm_users) == 0;
- }
- void __khugepaged_enter(struct mm_struct *mm)
- {
- struct khugepaged_mm_slot *mm_slot;
- struct mm_slot *slot;
- int wakeup;
- mm_slot = mm_slot_alloc(mm_slot_cache);
- if (!mm_slot)
- return;
- slot = &mm_slot->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))) {
- mm_slot_free(mm_slot_cache, mm_slot);
- return;
- }
- spin_lock(&khugepaged_mm_lock);
- 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(&slot->mm_node, &khugepaged_scan.mm_head);
- spin_unlock(&khugepaged_mm_lock);
- mmgrab(mm);
- if (wakeup)
- wake_up_interruptible(&khugepaged_wait);
- }
- void khugepaged_enter_vma(struct vm_area_struct *vma,
- unsigned long vm_flags)
- {
- if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
- hugepage_flags_enabled()) {
- if (hugepage_vma_check(vma, vm_flags, false, false, true))
- __khugepaged_enter(vma->vm_mm);
- }
- }
- void __khugepaged_exit(struct mm_struct *mm)
- {
- struct khugepaged_mm_slot *mm_slot;
- struct mm_slot *slot;
- int free = 0;
- spin_lock(&khugepaged_mm_lock);
- 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(&slot->hash);
- list_del(&slot->mm_node);
- free = 1;
- }
- spin_unlock(&khugepaged_mm_lock);
- if (free) {
- clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
- mm_slot_free(mm_slot_cache, mm_slot);
- mmdrop(mm);
- } else if (mm_slot) {
- /*
- * This is required to serialize against
- * 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)
- {
- 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);
- }
- static void release_pte_pages(pte_t *pte, pte_t *_pte,
- struct list_head *compound_pagelist)
- {
- struct page *page, *tmp;
- while (--_pte >= pte) {
- pte_t pteval = *_pte;
- page = pte_page(pteval);
- if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)) &&
- !PageCompound(page))
- release_pte_page(page);
- }
- list_for_each_entry_safe(page, tmp, compound_pagelist, lru) {
- list_del(&page->lru);
- release_pte_page(page);
- }
- }
- static bool is_refcount_suitable(struct page *page)
- {
- int expected_refcount;
- expected_refcount = total_mapcount(page);
- if (PageSwapCache(page))
- expected_refcount += compound_nr(page);
- return page_count(page) == 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;
- pte_t *_pte;
- int none_or_zero = 0, shared = 0, result = SCAN_FAIL, referenced = 0;
- bool writable = false;
- for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
- _pte++, address += PAGE_SIZE) {
- pte_t pteval = *_pte;
- if (pte_none(pteval) || (pte_present(pteval) &&
- is_zero_pfn(pte_pfn(pteval)))) {
- ++none_or_zero;
- if (!userfaultfd_armed(vma) &&
- (!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;
- }
- }
- if (!pte_present(pteval)) {
- 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) || unlikely(is_zone_device_page(page))) {
- result = SCAN_PAGE_NULL;
- goto out;
- }
- VM_BUG_ON_PAGE(!PageAnon(page), page);
- 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);
- /*
- * Check if we have dealt with the compound page
- * already
- */
- list_for_each_entry(p, compound_pagelist, lru) {
- if (page == p)
- goto next;
- }
- }
- /*
- * We can do it before isolate_lru_page because the
- * page can't be freed from under us. NOTE: PG_lock
- * is needed to serialize against split_huge_page
- * when invoked from the VM.
- */
- if (!trylock_page(page)) {
- result = SCAN_PAGE_LOCK;
- goto out;
- }
- /*
- * Check if the page has any GUP (or other external) pins.
- *
- * The page table that maps the page has been already unlinked
- * from the page table tree and this process cannot get
- * 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);
- result = SCAN_PAGE_COUNT;
- goto out;
- }
- /*
- * Isolate the page to avoid collapsing an hugepage
- * currently in use by the VM.
- */
- if (isolate_lru_page(page)) {
- unlock_page(page);
- 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);
- next:
- /*
- * 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) || page_is_young(page) ||
- PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm,
- address)))
- referenced++;
- if (pte_write(pteval))
- writable = true;
- }
- 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(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,
- referenced, writable, result);
- 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)
- {
- struct page *src_page, *tmp;
- pte_t *_pte;
- for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
- _pte++, page++, address += PAGE_SIZE) {
- pte_t pteval = *_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);
- ptep_clear(vma->vm_mm, address, _pte);
- spin_unlock(ptl);
- }
- } else {
- src_page = pte_page(pteval);
- copy_user_highpage(page, src_page, address, vma);
- if (!PageCompound(src_page))
- release_pte_page(src_page);
- /*
- * ptl mostly unnecessary, but preempt has to
- * be disabled to update the per-cpu stats
- * inside page_remove_rmap().
- */
- spin_lock(ptl);
- ptep_clear(vma->vm_mm, address, _pte);
- page_remove_rmap(src_page, vma, false);
- spin_unlock(ptl);
- free_page_and_swap_cache(src_page);
- }
- }
- list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
- list_del(&src_page->lru);
- 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 khugepaged_alloc_sleep(void)
- {
- DEFINE_WAIT(wait);
- add_wait_queue(&khugepaged_wait, &wait);
- __set_current_state(TASK_INTERRUPTIBLE|TASK_FREEZABLE);
- schedule_timeout(msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
- remove_wait_queue(&khugepaged_wait, &wait);
- }
- struct collapse_control khugepaged_collapse_control = {
- .is_khugepaged = true,
- };
- static bool hpage_collapse_scan_abort(int nid, struct collapse_control *cc)
- {
- int i;
- /*
- * If node_reclaim_mode is disabled, then no extra effort is made to
- * allocate memory locally.
- */
- if (!node_reclaim_enabled())
- return false;
- /* If there is a count for this node already, it must be acceptable */
- if (cc->node_load[nid])
- return false;
- for (i = 0; i < MAX_NUMNODES; i++) {
- if (!cc->node_load[i])
- continue;
- if (node_distance(nid, i) > node_reclaim_distance)
- return true;
- }
- 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)
- {
- return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT;
- }
- #ifdef CONFIG_NUMA
- static int hpage_collapse_find_target_node(struct collapse_control *cc)
- {
- int nid, target_node = 0, max_value = 0;
- /* find first node with max normal pages hit */
- for (nid = 0; nid < MAX_NUMNODES; nid++)
- if (cc->node_load[nid] > max_value) {
- max_value = cc->node_load[nid];
- target_node = nid;
- }
- for_each_online_node(nid) {
- if (max_value == cc->node_load[nid])
- node_set(nid, cc->alloc_nmask);
- }
- return target_node;
- }
- #else
- static int hpage_collapse_find_target_node(struct collapse_control *cc)
- {
- return 0;
- }
- #endif
- static bool hpage_collapse_alloc_page(struct page **hpage, gfp_t gfp, int node,
- nodemask_t *nmask)
- {
- *hpage = __alloc_pages(gfp, HPAGE_PMD_ORDER, node, nmask);
- if (unlikely(!*hpage)) {
- count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
- return false;
- }
- prep_transhuge_page(*hpage);
- count_vm_event(THP_COLLAPSE_ALLOC);
- return true;
- }
- /*
- * If mmap_lock temporarily dropped, revalidate vma
- * before taking mmap_lock.
- * Returns enum scan_result value.
- */
- static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
- bool expect_anon,
- struct vm_area_struct **vmap,
- struct collapse_control *cc)
- {
- struct vm_area_struct *vma;
- if (unlikely(hpage_collapse_test_exit(mm)))
- return SCAN_ANY_PROCESS;
- *vmap = vma = find_vma(mm, address);
- if (!vma)
- return SCAN_VMA_NULL;
- if (!transhuge_vma_suitable(vma, address))
- return SCAN_ADDRESS_RANGE;
- if (!hugepage_vma_check(vma, vma->vm_flags, false, false,
- cc->is_khugepaged))
- return SCAN_VMA_CHECK;
- /*
- * Anon VMA expected, the address may be unmapped then
- * remapped to file after khugepaged reaquired the mmap_lock.
- *
- * hugepage_vma_check may return true for qualified file
- * vmas.
- */
- if (expect_anon && (!(*vmap)->anon_vma || !vma_is_anonymous(*vmap)))
- return SCAN_PAGE_ANON;
- return SCAN_SUCCEED;
- }
- /*
- * See pmd_trans_unstable() for how the result may change out from
- * underneath us, even if we hold mmap_lock in read.
- */
- 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 = pmd_read_atomic(*pmd);
- #ifdef CONFIG_TRANSPARENT_HUGEPAGE
- /* See comments in pmd_none_or_trans_huge_or_clear_bad() */
- barrier();
- #endif
- 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 hpage_collapse_scan_pmd believes it is worthwhile.
- *
- * Called and returns without pte mapped or spinlocks held.
- * Note that if false is returned, mmap_lock will be released.
- */
- 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;
- unsigned long address, end = haddr + (HPAGE_PMD_NR * PAGE_SIZE);
- for (address = haddr; address < end; address += PAGE_SIZE) {
- struct vm_fault vmf = {
- .vma = vma,
- .address = address,
- .pgoff = linear_page_index(vma, haddr),
- .flags = FAULT_FLAG_ALLOW_RETRY,
- .pmd = pmd,
- };
- vmf.pte = pte_offset_map(pmd, address);
- vmf.orig_pte = *vmf.pte;
- if (!is_swap_pte(vmf.orig_pte)) {
- pte_unmap(vmf.pte);
- continue;
- }
- ret = do_swap_page(&vmf);
- /*
- * 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) {
- trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
- /* Likely, but not guaranteed, that page lock failed */
- return SCAN_PAGE_LOCK;
- }
- if (ret & VM_FAULT_ERROR) {
- mmap_read_unlock(mm);
- trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
- return SCAN_FAIL;
- }
- swapped_in++;
- }
- /* Drain LRU add pagevec 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 SCAN_SUCCEED;
- }
- 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);
- if (!hpage_collapse_alloc_page(hpage, gfp, node, &cc->alloc_nmask))
- return SCAN_ALLOC_HUGE_PAGE_FAIL;
- if (unlikely(mem_cgroup_charge(page_folio(*hpage), mm, gfp)))
- return SCAN_CGROUP_CHARGE_FAIL;
- count_memcg_page_event(*hpage, THP_COLLAPSE_ALLOC);
- 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 *hpage;
- spinlock_t *pmd_ptl, *pte_ptl;
- int result = SCAN_FAIL;
- struct vm_area_struct *vma;
- struct mmu_notifier_range range;
- VM_BUG_ON(address & ~HPAGE_PMD_MASK);
- /*
- * Before allocating the hugepage, release the mmap_lock read lock.
- * The allocation can take potentially a long time if it involves
- * sync compaction, and we do not need to hold the mmap_lock during
- * that. We will recheck the vma after taking it again in write mode.
- */
- mmap_read_unlock(mm);
- result = alloc_charge_hpage(&hpage, mm, cc);
- if (result != SCAN_SUCCEED)
- goto out_nolock;
- mmap_read_lock(mm);
- result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
- if (result != SCAN_SUCCEED) {
- mmap_read_unlock(mm);
- goto out_nolock;
- }
- result = find_pmd_or_thp_or_none(mm, address, &pmd);
- if (result != SCAN_SUCCEED) {
- 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);
- /*
- * 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.
- */
- mmap_write_lock(mm);
- result = hugepage_vma_revalidate(mm, address, true, &vma, cc);
- if (result != SCAN_SUCCEED)
- goto out_up_write;
- /* check if the pmd is still valid */
- 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_invalidate_range_start(&range);
- pte = pte_offset_map(pmd, address);
- pte_ptl = pte_lockptr(mm, pmd);
- pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
- /*
- * 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);
- result = __collapse_huge_page_isolate(vma, address, pte, cc,
- &compound_pagelist);
- spin_unlock(pte_ptl);
- if (unlikely(result != SCAN_SUCCEED)) {
- pte_unmap(pte);
- spin_lock(pmd_ptl);
- BUG_ON(!pmd_none(*pmd));
- /*
- * We can only use set_pmd_at when establishing
- * hugepmds and never for establishing regular pmds that
- * points to regular pagetables. Use pmd_populate for that
- */
- pmd_populate(mm, pmd, pmd_pgtable(_pmd));
- spin_unlock(pmd_ptl);
- anon_vma_unlock_write(vma->anon_vma);
- goto out_up_write;
- }
- /*
- * All pages are isolated and locked so anon_vma rmap
- * can't run anymore.
- */
- anon_vma_unlock_write(vma->anon_vma);
- __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl,
- &compound_pagelist);
- pte_unmap(pte);
- /*
- * spin_lock() below is not the equivalent of smp_wmb(), but
- * the smp_wmb() inside __SetPageUptodate() can be reused to
- * avoid the copy_huge_page writes to become visible after
- * the set_pmd_at() write.
- */
- __SetPageUptodate(hpage);
- 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(hpage, vma, address);
- lru_cache_add_inactive_or_unevictable(hpage, 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;
- result = SCAN_SUCCEED;
- out_up_write:
- mmap_write_unlock(mm);
- out_nolock:
- if (hpage) {
- mem_cgroup_uncharge(page_folio(hpage));
- put_page(hpage);
- }
- trace_mm_collapse_huge_page(mm, result == SCAN_SUCCEED, result);
- return result;
- }
- 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 result = SCAN_FAIL, referenced = 0;
- int none_or_zero = 0, shared = 0;
- struct page *page = NULL;
- unsigned long _address;
- spinlock_t *ptl;
- int node = NUMA_NO_NODE, unmapped = 0;
- bool writable = false;
- VM_BUG_ON(address & ~HPAGE_PMD_MASK);
- 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);
- for (_address = address, _pte = pte; _pte < pte + HPAGE_PMD_NR;
- _pte++, _address += PAGE_SIZE) {
- pte_t pteval = *_pte;
- if (is_swap_pte(pteval)) {
- ++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)) {
- 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) &&
- (!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_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 unknown
- * userfault messages that falls outside of
- * the registered range. So, just be simple.
- */
- result = SCAN_PTE_UFFD_WP;
- goto out_unmap;
- }
- if (pte_write(pteval))
- writable = true;
- page = vm_normal_page(vma, _address, pteval);
- if (unlikely(!page) || unlikely(is_zone_device_page(page))) {
- result = SCAN_PAGE_NULL;
- 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);
- /*
- * Record which node the original page is from and save this
- * information to cc->node_load[].
- * Khugepaged will allocate hugepage from the node has the max
- * hit record.
- */
- node = page_to_nid(page);
- if (hpage_collapse_scan_abort(node, cc)) {
- result = SCAN_SCAN_ABORT;
- goto out_unmap;
- }
- cc->node_load[node]++;
- if (!PageLRU(page)) {
- result = SCAN_PAGE_LRU;
- goto out_unmap;
- }
- if (PageLocked(page)) {
- result = SCAN_PAGE_LOCK;
- goto out_unmap;
- }
- if (!PageAnon(page)) {
- result = SCAN_PAGE_ANON;
- goto out_unmap;
- }
- /*
- * Check if the page has any GUP (or other external) pins.
- *
- * Here the check is racy it may see total_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.
- *
- * 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)) {
- result = SCAN_PAGE_COUNT;
- goto out_unmap;
- }
- /*
- * 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) || page_is_young(page) ||
- PageReferenced(page) || mmu_notifier_test_young(vma->vm_mm,
- address)))
- referenced++;
- }
- if (!writable) {
- result = SCAN_PAGE_RO;
- } else if (cc->is_khugepaged &&
- (!referenced ||
- (unmapped && referenced < HPAGE_PMD_NR / 2))) {
- result = SCAN_LACK_REFERENCED_PAGE;
- } else {
- result = SCAN_SUCCEED;
- }
- out_unmap:
- pte_unmap_unlock(pte, ptl);
- if (result == SCAN_SUCCEED) {
- result = collapse_huge_page(mm, address, referenced,
- unmapped, cc);
- /* collapse_huge_page will return with the mmap_lock released */
- *mmap_locked = false;
- }
- out:
- trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
- none_or_zero, result, unmapped);
- return result;
- }
- static void collect_mm_slot(struct khugepaged_mm_slot *mm_slot)
- {
- struct mm_slot *slot = &mm_slot->slot;
- struct mm_struct *mm = slot->mm;
- lockdep_assert_held(&khugepaged_mm_lock);
- if (hpage_collapse_test_exit(mm)) {
- /* free mm_slot */
- hash_del(&slot->hash);
- list_del(&slot->mm_node);
- /*
- * Not strictly needed because the mm exited already.
- *
- * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
- */
- /* khugepaged_mm_lock actually not necessary for the below */
- 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.
- *
- * Note that following race exists:
- * (1) khugepaged calls khugepaged_collapse_pte_mapped_thps() for mm_struct A,
- * emptying the A's ->pte_mapped_thp[] array.
- * (2) MADV_COLLAPSE collapses some file extent with target mm_struct B, and
- * retract_page_tables() finds a VMA in mm_struct A mapping the same extent
- * (at virtual address X) and adds an entry (for X) into mm_struct A's
- * ->pte-mapped_thp[] array.
- * (3) khugepaged calls khugepaged_collapse_scan_file() for mm_struct A at X,
- * sees a pte-mapped THP (SCAN_PTE_MAPPED_HUGEPAGE) and adds an entry
- * (for X) into mm_struct A's ->pte-mapped_thp[] array.
- * Thus, it's possible the same address is added multiple times for the same
- * mm_struct. Should this happen, we'll simply attempt
- * collapse_pte_mapped_thp() multiple times for the same address, under the same
- * exclusive mmap_lock, and assuming the first call is successful, subsequent
- * attempts will return quickly (without grabbing any additional locks) when
- * a huge pmd is found in find_pmd_or_thp_or_none(). Since this is a cheap
- * check, and since this is a rare occurrence, the cost of preventing this
- * "multiple-add" is thought to be more expensive than just handling it, should
- * it occur.
- */
- static bool khugepaged_add_pte_mapped_thp(struct mm_struct *mm,
- unsigned long addr)
- {
- struct khugepaged_mm_slot *mm_slot;
- struct mm_slot *slot;
- bool ret = false;
- VM_BUG_ON(addr & ~HPAGE_PMD_MASK);
- spin_lock(&khugepaged_mm_lock);
- slot = mm_slot_lookup(mm_slots_hash, mm);
- mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot);
- 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;
- ret = true;
- }
- spin_unlock(&khugepaged_mm_lock);
- return ret;
- }
- /* hpage must be locked, and mmap_lock must be held in write */
- static int set_huge_pmd(struct vm_area_struct *vma, unsigned long addr,
- pmd_t *pmdp, struct page *hpage)
- {
- struct vm_fault vmf = {
- .vma = vma,
- .address = addr,
- .flags = 0,
- .pmd = pmdp,
- };
- VM_BUG_ON(!PageTransHuge(hpage));
- mmap_assert_write_locked(vma->vm_mm);
- if (do_set_pmd(&vmf, hpage))
- return SCAN_FAIL;
- get_page(hpage);
- return SCAN_SUCCEED;
- }
- /*
- * A note about locking:
- * Trying to take the page table spinlocks would be useless here because those
- * are only used to synchronize:
- *
- * - modifying terminal entries (ones that point to a data page, not to another
- * page table)
- * - installing *new* non-terminal entries
- *
- * Instead, we need roughly the same kind of protection as free_pgtables() or
- * mm_take_all_locks() (but only for a single VMA):
- * The mmap lock together with this VMA's rmap locks covers all paths towards
- * the page table entries we're messing with here, except for hardware page
- * table walks and lockless_pages_from_mm().
- */
- static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long addr, pmd_t *pmdp)
- {
- pmd_t pmd;
- struct mmu_notifier_range range;
- mmap_assert_write_locked(mm);
- if (vma->vm_file)
- lockdep_assert_held_write(&vma->vm_file->f_mapping->i_mmap_rwsem);
- /*
- * All anon_vmas attached to the VMA have the same root and are
- * therefore locked by the same lock.
- */
- if (vma->anon_vma)
- lockdep_assert_held_write(&vma->anon_vma->root->rwsem);
- mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, addr,
- addr + HPAGE_PMD_SIZE);
- mmu_notifier_invalidate_range_start(&range);
- pmd = pmdp_collapse_flush(vma, addr, pmdp);
- tlb_remove_table_sync_one();
- mmu_notifier_invalidate_range_end(&range);
- mm_dec_nr_ptes(mm);
- page_table_check_pte_clear_range(mm, addr, pmd);
- pte_free(mm, pmd_pgtable(pmd));
- }
- /**
- * 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. Possibly install a huge PMD mapping the THP.
- */
- int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
- bool install_pmd)
- {
- unsigned long haddr = addr & HPAGE_PMD_MASK;
- struct vm_area_struct *vma = vma_lookup(mm, haddr);
- struct page *hpage;
- pte_t *start_pte, *pte;
- pmd_t *pmd;
- spinlock_t *ptl;
- int count = 0, result = SCAN_FAIL;
- int i;
- mmap_assert_write_locked(mm);
- /* 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;
- if (!vma || !vma->vm_file ||
- !range_in_vma(vma, haddr, haddr + HPAGE_PMD_SIZE))
- return SCAN_VMA_CHECK;
- /*
- * 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, false, false, false))
- return SCAN_VMA_CHECK;
- /* Keep pmd pgtable for uffd-wp; see comment in retract_page_tables() */
- if (userfaultfd_wp(vma))
- return SCAN_PTE_UFFD_WP;
- hpage = find_lock_page(vma->vm_file->f_mapping,
- linear_page_index(vma, haddr));
- if (!hpage)
- return SCAN_PAGE_NULL;
- if (!PageHead(hpage)) {
- result = SCAN_FAIL;
- goto drop_hpage;
- }
- if (compound_order(hpage) != HPAGE_PMD_ORDER) {
- result = SCAN_PAGE_COMPOUND;
- goto drop_hpage;
- }
- switch (result) {
- case SCAN_SUCCEED:
- break;
- case SCAN_PMD_NONE:
- /*
- * In MADV_COLLAPSE path, possible race with khugepaged where
- * all pte entries have been removed and pmd cleared. If so,
- * skip all the pte checks and just update the pmd mapping.
- */
- goto maybe_install_pmd;
- default:
- goto drop_hpage;
- }
- /* Lock the vma before taking i_mmap and page table locks */
- vma_start_write(vma);
- /*
- * We need to lock the mapping so that from here on, only GUP-fast and
- * hardware page walks can access the parts of the page tables that
- * we're operating on.
- * See collapse_and_free_pmd().
- */
- i_mmap_lock_write(vma->vm_file->f_mapping);
- /*
- * This spinlock should be unnecessary: Nobody else should be accessing
- * the page tables under spinlock protection here, only
- * lockless_pages_from_mm() and the hardware page walker can access page
- * tables while all the high-level locks are held in write mode.
- */
- start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl);
- result = SCAN_FAIL;
- /* 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;
- /* empty pte, skip */
- if (pte_none(*pte))
- continue;
- /* page swapped out, abort */
- if (!pte_present(*pte)) {
- result = SCAN_PTE_NON_PRESENT;
- goto abort;
- }
- page = vm_normal_page(vma, addr, *pte);
- 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)
- goto abort;
- count++;
- }
- /* step 2: adjust rmap */
- for (i = 0, addr = haddr, pte = start_pte;
- i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) {
- struct page *page;
- if (pte_none(*pte))
- continue;
- page = vm_normal_page(vma, addr, *pte);
- if (WARN_ON_ONCE(page && is_zone_device_page(page)))
- goto abort;
- page_remove_rmap(page, vma, false);
- }
- pte_unmap_unlock(start_pte, 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);
- }
- /* step 4: remove pte entries */
- /* we make no change to anon, but protect concurrent anon page lookup */
- if (vma->anon_vma)
- anon_vma_lock_write(vma->anon_vma);
- collapse_and_free_pmd(mm, vma, haddr, pmd);
- if (vma->anon_vma)
- anon_vma_unlock_write(vma->anon_vma);
- i_mmap_unlock_write(vma->vm_file->f_mapping);
- maybe_install_pmd:
- /* step 5: install pmd entry */
- result = install_pmd
- ? set_huge_pmd(vma, haddr, pmd, hpage)
- : SCAN_SUCCEED;
- drop_hpage:
- unlock_page(hpage);
- put_page(hpage);
- return result;
- abort:
- pte_unmap_unlock(start_pte, ptl);
- i_mmap_unlock_write(vma->vm_file->f_mapping);
- goto drop_hpage;
- }
- static void khugepaged_collapse_pte_mapped_thps(struct khugepaged_mm_slot *mm_slot)
- {
- struct mm_slot *slot = &mm_slot->slot;
- struct mm_struct *mm = slot->mm;
- int i;
- if (likely(mm_slot->nr_pte_mapped_thp == 0))
- return;
- if (!mmap_write_trylock(mm))
- return;
- if (unlikely(hpage_collapse_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], false);
- out:
- mm_slot->nr_pte_mapped_thp = 0;
- mmap_write_unlock(mm);
- }
- static int retract_page_tables(struct address_space *mapping, pgoff_t pgoff,
- struct mm_struct *target_mm,
- unsigned long target_addr, struct page *hpage,
- struct collapse_control *cc)
- {
- struct vm_area_struct *vma;
- int target_result = SCAN_FAIL;
- i_mmap_lock_write(mapping);
- vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
- int result = SCAN_FAIL;
- struct mm_struct *mm = NULL;
- unsigned long addr = 0;
- pmd_t *pmd;
- bool is_target = 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.
- *
- * Note 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. It would also probably require locking
- * the anon_vma.
- */
- if (READ_ONCE(vma->anon_vma)) {
- result = SCAN_PAGE_ANON;
- goto next;
- }
- addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
- if (addr & ~HPAGE_PMD_MASK ||
- vma->vm_end < addr + HPAGE_PMD_SIZE) {
- result = SCAN_VMA_CHECK;
- goto next;
- }
- mm = vma->vm_mm;
- is_target = mm == target_mm && addr == target_addr;
- result = find_pmd_or_thp_or_none(mm, addr, &pmd);
- if (result != SCAN_SUCCEED)
- goto next;
- /*
- * 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.
- *
- * Also, it's not MADV_COLLAPSE's job to collapse other
- * mappings - let khugepaged take care of them later.
- */
- result = SCAN_PTE_MAPPED_HUGEPAGE;
- if ((cc->is_khugepaged || is_target) &&
- mmap_write_trylock(mm)) {
- /* trylock for the same lock inversion as above */
- if (!vma_try_start_write(vma))
- goto unlock_next;
- /*
- * Re-check whether we have an ->anon_vma, because
- * collapse_and_free_pmd() requires that either no
- * ->anon_vma exists or the anon_vma is locked.
- * We already checked ->anon_vma above, but that check
- * is racy because ->anon_vma can be populated under the
- * mmap lock in read mode.
- */
- if (vma->anon_vma) {
- result = SCAN_PAGE_ANON;
- goto unlock_next;
- }
- /*
- * When a vma is registered with uffd-wp, we can't
- * recycle the pmd pgtable because there can be pte
- * markers installed. Skip it only, so the rest mm/vma
- * can still have the same file mapped hugely, however
- * it'll always mapped in small page size for uffd-wp
- * registered ranges.
- */
- if (hpage_collapse_test_exit(mm)) {
- result = SCAN_ANY_PROCESS;
- goto unlock_next;
- }
- if (userfaultfd_wp(vma)) {
- result = SCAN_PTE_UFFD_WP;
- goto unlock_next;
- }
- collapse_and_free_pmd(mm, vma, addr, pmd);
- if (!cc->is_khugepaged && is_target)
- result = set_huge_pmd(vma, addr, pmd, hpage);
- else
- result = SCAN_SUCCEED;
- unlock_next:
- mmap_write_unlock(mm);
- goto next;
- }
- /*
- * Calling context will handle target mm/addr. Otherwise, let
- * khugepaged try again later.
- */
- if (!is_target) {
- khugepaged_add_pte_mapped_thp(mm, addr);
- continue;
- }
- next:
- if (is_target)
- target_result = result;
- }
- i_mmap_unlock_write(mapping);
- return target_result;
- }
- /**
- * 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
- * + swap/gup in pages if necessary;
- * + fill in gaps;
- * + keep old pages around in case rollback is required;
- * - if replacing succeeds:
- * + copy data over;
- * + free old pages;
- * + unlock huge page;
- * - if replacing failed;
- * + put all pages back and unfreeze them;
- * + restore gaps in the page cache;
- * + unlock and free huge page;
- */
- 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;
- struct page *hpage;
- pgoff_t index, 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;
- VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
- VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
- result = alloc_charge_hpage(&hpage, mm, cc);
- if (result != SCAN_SUCCEED)
- goto out;
- /*
- * 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);
- if (!xas_error(&xas))
- break;
- xas_unlock_irq(&xas);
- if (!xas_nomem(&xas, GFP_KERNEL)) {
- result = SCAN_FAIL;
- goto out;
- }
- } while (1);
- __SetPageLocked(hpage);
- if (is_shmem)
- __SetPageSwapBacked(hpage);
- hpage->index = start;
- hpage->mapping = mapping;
- /*
- * At this point the hpage 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);
- VM_BUG_ON(index != xas.xa_index);
- if (is_shmem) {
- if (!page) {
- /*
- * Stop if extent has been truncated or
- * hole-punched, and is now completely
- * empty.
- */
- if (index == start) {
- if (!xas_next_entry(&xas, end - 1)) {
- 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, hpage);
- nr_none++;
- continue;
- }
- if (xa_is_value(page) || !PageUptodate(page)) {
- struct folio *folio;
- xas_unlock_irq(&xas);
- /* swap in or instantiate fallocated page */
- if (shmem_get_folio(mapping->host, index,
- &folio, SGP_NOALLOC)) {
- result = SCAN_FAIL;
- goto xa_unlocked;
- }
- page = folio_file_page(folio, index);
- } else if (trylock_page(page)) {
- get_page(page);
- xas_unlock_irq(&xas);
- } else {
- result = SCAN_PAGE_LOCK;
- goto xa_locked;
- }
- } else { /* !is_shmem */
- if (!page || xa_is_value(page)) {
- xas_unlock_irq(&xas);
- page_cache_sync_readahead(mapping, &file->f_ra,
- file, index,
- end - index);
- /* drain pagevecs to help isolate_lru_page() */
- lru_add_drain();
- page = find_lock_page(mapping, index);
- if (unlikely(page == NULL)) {
- result = SCAN_FAIL;
- goto xa_unlocked;
- }
- } else if (PageDirty(page)) {
- /*
- * khugepaged only works on read-only fd,
- * so this page is dirty because it hasn't
- * been flushed since first write. There
- * won't be new dirty pages.
- *
- * Trigger async flush here and hope the
- * writeback is done when khugepaged
- * revisits this page.
- *
- * This is a one-off situation. We are not
- * forcing writeback in loop.
- */
- xas_unlock_irq(&xas);
- 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);
- } else {
- result = SCAN_PAGE_LOCK;
- goto xa_locked;
- }
- }
- /*
- * The page must be locked, so we can drop the i_pages lock
- * without racing with truncate.
- */
- VM_BUG_ON_PAGE(!PageLocked(page), page);
- /* make sure the page is up to date */
- if (unlikely(!PageUptodate(page))) {
- result = SCAN_FAIL;
- goto out_unlock;
- }
- /*
- * 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)) {
- 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) {
- result = SCAN_TRUNCATED;
- goto out_unlock;
- }
- if (!is_shmem && (PageDirty(page) ||
- PageWriteback(page))) {
- /*
- * khugepaged only works on read-only fd, so this
- * page is dirty because it hasn't been flushed
- * since first write.
- */
- result = SCAN_FAIL;
- goto out_unlock;
- }
- if (isolate_lru_page(page)) {
- result = SCAN_DEL_PAGE_LRU;
- goto out_unlock;
- }
- if (page_has_private(page) &&
- !try_to_release_page(page, GFP_KERNEL)) {
- result = SCAN_PAGE_HAS_PRIVATE;
- putback_lru_page(page);
- goto out_unlock;
- }
- if (page_mapped(page))
- try_to_unmap(page_folio(page),
- TTU_IGNORE_MLOCK | TTU_BATCH_FLUSH);
- xas_lock_irq(&xas);
- xas_set(&xas, index);
- VM_BUG_ON_PAGE(page != xas_load(&xas), page);
- /*
- * The page is expected to have page_count() == 3:
- * - we hold a pin on it;
- * - one reference from page cache;
- * - one from isolate_lru_page;
- */
- if (!page_ref_freeze(page, 3)) {
- result = SCAN_PAGE_COUNT;
- xas_unlock_irq(&xas);
- putback_lru_page(page);
- goto out_unlock;
- }
- /*
- * Add the page to the list to be able to undo the collapse if
- * something go wrong.
- */
- list_add_tail(&page->lru, &pagelist);
- /* Finally, replace with the new page. */
- xas_store(&xas, hpage);
- continue;
- out_unlock:
- unlock_page(page);
- put_page(page);
- goto xa_unlocked;
- }
- nr = thp_nr_pages(hpage);
- if (is_shmem)
- __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
- else {
- __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
- filemap_nr_thps_inc(mapping);
- /*
- * 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;
- __mod_lruvec_page_state(hpage, NR_FILE_THPS, -nr);
- filemap_nr_thps_dec(mapping);
- goto xa_locked;
- }
- }
- if (nr_none) {
- __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none);
- /* nr_none is always 0 for non-shmem. */
- __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none);
- }
- /* Join all the small entries into a single multi-index entry */
- xas_set_order(&xas, start, HPAGE_PMD_ORDER);
- xas_store(&xas, hpage);
- xa_locked:
- xas_unlock_irq(&xas);
- xa_unlocked:
- /*
- * 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();
- if (result == SCAN_SUCCEED) {
- struct page *page, *tmp;
- /*
- * 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(hpage + (index % HPAGE_PMD_NR));
- index++;
- }
- copy_highpage(hpage + (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);
- index++;
- }
- while (index < end) {
- clear_highpage(hpage + (index % HPAGE_PMD_NR));
- index++;
- }
- SetPageUptodate(hpage);
- page_ref_add(hpage, HPAGE_PMD_NR - 1);
- if (is_shmem)
- set_page_dirty(hpage);
- lru_cache_add(hpage);
- /*
- * Remove pte page tables, so we can re-fault the page as huge.
- */
- result = retract_page_tables(mapping, start, mm, addr, hpage,
- cc);
- unlock_page(hpage);
- hpage = NULL;
- } else {
- struct page *page;
- /* Something went wrong: roll back page cache changes */
- xas_lock_irq(&xas);
- if (nr_none) {
- mapping->nrpages -= nr_none;
- shmem_uncharge(mapping->host, nr_none);
- }
- 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;
- }
- VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
- /* 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);
- xas_unlock_irq(&xas);
- hpage->mapping = NULL;
- }
- if (hpage)
- unlock_page(hpage);
- out:
- VM_BUG_ON(!list_empty(&pagelist));
- if (hpage) {
- mem_cgroup_uncharge(page_folio(hpage));
- put_page(hpage);
- }
- /* TODO: tracepoints */
- return result;
- }
- 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;
- XA_STATE(xas, &mapping->i_pages, start);
- int present, swap;
- int node = NUMA_NO_NODE;
- int result = SCAN_SUCCEED;
- present = 0;
- swap = 0;
- 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)) {
- ++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)) {
- 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 (hpage_collapse_scan_abort(node, cc)) {
- result = SCAN_SCAN_ABORT;
- break;
- }
- cc->node_load[node]++;
- if (!PageLRU(page)) {
- result = SCAN_PAGE_LRU;
- break;
- }
- if (page_count(page) !=
- 1 + page_mapcount(page) + page_has_private(page)) {
- result = SCAN_PAGE_COUNT;
- break;
- }
- /*
- * We probably should check if the page is referenced here, but
- * nobody would transfer pte_young() to PageReferenced() for us.
- * And rmap walk here is just too costly...
- */
- present++;
- if (need_resched()) {
- xas_pause(&xas);
- cond_resched_rcu();
- }
- }
- rcu_read_unlock();
- if (result == SCAN_SUCCEED) {
- 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 {
- result = collapse_file(mm, addr, file, start, cc);
- }
- }
- trace_mm_khugepaged_scan_file(mm, page, file, present, swap, result);
- return result;
- }
- #else
- 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 void khugepaged_collapse_pte_mapped_thps(struct khugepaged_mm_slot *mm_slot)
- {
- }
- static bool khugepaged_add_pte_mapped_thp(struct mm_struct *mm,
- unsigned long addr)
- {
- return false;
- }
- #endif
- 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 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) {
- mm_slot = khugepaged_scan.mm_slot;
- 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 = slot->mm;
- /*
- * Don't wait for semaphore (to avoid long wait times). Just move to
- * the next mm on the list.
- */
- vma = NULL;
- if (unlikely(!mmap_read_trylock(mm)))
- goto breakouterloop_mmap_lock;
- progress++;
- 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(hpage_collapse_test_exit(mm))) {
- progress++;
- break;
- }
- if (!hugepage_vma_check(vma, vma->vm_flags, false, false, true)) {
- skip:
- progress++;
- continue;
- }
- 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);
- while (khugepaged_scan.address < hend) {
- bool mmap_locked = true;
- cond_resched();
- if (unlikely(hpage_collapse_test_exit(mm)))
- goto breakouterloop;
- VM_BUG_ON(khugepaged_scan.address < hstart ||
- khugepaged_scan.address + HPAGE_PMD_SIZE >
- hend);
- if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) {
- struct file *file = get_file(vma->vm_file);
- pgoff_t pgoff = linear_page_index(vma,
- khugepaged_scan.address);
- mmap_read_unlock(mm);
- *result = hpage_collapse_scan_file(mm,
- khugepaged_scan.address,
- file, pgoff, cc);
- mmap_locked = false;
- fput(file);
- } else {
- *result = hpage_collapse_scan_pmd(mm, vma,
- khugepaged_scan.address,
- &mmap_locked,
- cc);
- }
- switch (*result) {
- case SCAN_PTE_MAPPED_HUGEPAGE: {
- pmd_t *pmd;
- *result = find_pmd_or_thp_or_none(mm,
- khugepaged_scan.address,
- &pmd);
- if (*result != SCAN_SUCCEED)
- break;
- if (!khugepaged_add_pte_mapped_thp(mm,
- khugepaged_scan.address))
- break;
- } fallthrough;
- case SCAN_SUCCEED:
- ++khugepaged_pages_collapsed;
- break;
- default:
- break;
- }
- /* move to next address */
- khugepaged_scan.address += HPAGE_PMD_SIZE;
- progress += HPAGE_PMD_NR;
- 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;
- }
- }
- breakouterloop:
- mmap_read_unlock(mm); /* exit_mmap will destroy ptes after this */
- breakouterloop_mmap_lock:
- spin_lock(&khugepaged_mm_lock);
- VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
- /*
- * Release the current mm_slot if this mm is about to die, or
- * if we scanned all vmas of this mm.
- */
- 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 (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;
- khugepaged_full_scans++;
- }
- collect_mm_slot(mm_slot);
- }
- return progress;
- }
- static int khugepaged_has_work(void)
- {
- return !list_empty(&khugepaged_scan.mm_head) &&
- hugepage_flags_enabled();
- }
- static int khugepaged_wait_event(void)
- {
- return !list_empty(&khugepaged_scan.mm_head) ||
- kthread_should_stop();
- }
- static void khugepaged_do_scan(struct collapse_control *cc)
- {
- unsigned int progress = 0, pass_through_head = 0;
- unsigned int pages = READ_ONCE(khugepaged_pages_to_scan);
- bool wait = true;
- int result = SCAN_SUCCEED;
- lru_add_drain_all();
- while (true) {
- cond_resched();
- if (unlikely(kthread_should_stop() || try_to_freeze()))
- break;
- spin_lock(&khugepaged_mm_lock);
- if (!khugepaged_scan.mm_slot)
- pass_through_head++;
- if (khugepaged_has_work() &&
- pass_through_head < 2)
- progress += khugepaged_scan_mm_slot(pages - progress,
- &result, cc);
- else
- progress = pages;
- spin_unlock(&khugepaged_mm_lock);
- 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)
- {
- return kthread_should_stop() ||
- time_after_eq(jiffies, khugepaged_sleep_expire);
- }
- static void khugepaged_wait_work(void)
- {
- if (khugepaged_has_work()) {
- const unsigned long scan_sleep_jiffies =
- msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
- if (!scan_sleep_jiffies)
- return;
- khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
- wait_event_freezable_timeout(khugepaged_wait,
- khugepaged_should_wakeup(),
- scan_sleep_jiffies);
- return;
- }
- if (hugepage_flags_enabled())
- wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
- }
- static int khugepaged(void *none)
- {
- struct khugepaged_mm_slot *mm_slot;
- set_freezable();
- set_user_nice(current, MAX_NICE);
- while (!kthread_should_stop()) {
- khugepaged_do_scan(&khugepaged_collapse_control);
- khugepaged_wait_work();
- }
- spin_lock(&khugepaged_mm_lock);
- mm_slot = khugepaged_scan.mm_slot;
- khugepaged_scan.mm_slot = NULL;
- if (mm_slot)
- collect_mm_slot(mm_slot);
- spin_unlock(&khugepaged_mm_lock);
- return 0;
- }
- static void set_recommended_min_free_kbytes(void)
- {
- struct zone *zone;
- 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
- * ZONE_MOVABLE since it only has movable pages.
- */
- if (zone_idx(zone) > gfp_zone(GFP_USER))
- continue;
- nr_zones++;
- }
- /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
- recommended_min = pageblock_nr_pages * nr_zones * 2;
- /*
- * Make sure that on average at least two pageblocks are almost free
- * of another type, one for a migratetype to fall back to and a
- * second to avoid subsequent fallbacks of other types There are 3
- * MIGRATE_TYPES we care about.
- */
- recommended_min += pageblock_nr_pages * nr_zones *
- MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
- /* don't ever allow to reserve more than 5% of the lowmem */
- recommended_min = min(recommended_min,
- (unsigned long) nr_free_buffer_pages() / 20);
- recommended_min <<= (PAGE_SHIFT-10);
- if (recommended_min > min_free_kbytes) {
- if (user_min_free_kbytes >= 0)
- pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
- min_free_kbytes, recommended_min);
- min_free_kbytes = recommended_min;
- }
- update_wmarks:
- setup_per_zone_wmarks();
- }
- int start_stop_khugepaged(void)
- {
- int err = 0;
- mutex_lock(&khugepaged_mutex);
- if (hugepage_flags_enabled()) {
- if (!khugepaged_thread)
- khugepaged_thread = kthread_run(khugepaged, NULL,
- "khugepaged");
- if (IS_ERR(khugepaged_thread)) {
- pr_err("khugepaged: kthread_run(khugepaged) failed\n");
- err = PTR_ERR(khugepaged_thread);
- khugepaged_thread = NULL;
- goto fail;
- }
- if (!list_empty(&khugepaged_scan.mm_head))
- wake_up_interruptible(&khugepaged_wait);
- } else if (khugepaged_thread) {
- kthread_stop(khugepaged_thread);
- khugepaged_thread = NULL;
- }
- set_recommended_min_free_kbytes();
- fail:
- mutex_unlock(&khugepaged_mutex);
- return err;
- }
- void khugepaged_min_free_kbytes_update(void)
- {
- mutex_lock(&khugepaged_mutex);
- if (hugepage_flags_enabled() && khugepaged_thread)
- set_recommended_min_free_kbytes();
- mutex_unlock(&khugepaged_mutex);
- }
- 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:
- 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:
- 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 (!hugepage_vma_check(vma, vma->vm_flags, false, false, false))
- 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_write_lock(mm);
- result = collapse_pte_mapped_thp(mm, addr, true);
- mmap_write_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);
- }
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