2929 lines
75 KiB
C
2929 lines
75 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/sched/mm.h>
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#include <linux/sched/coredump.h>
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#include <linux/mmu_notifier.h>
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#include <linux/rmap.h>
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#include <linux/swap.h>
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#include <linux/mm_inline.h>
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#include <linux/kthread.h>
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#include <linux/khugepaged.h>
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#include <linux/freezer.h>
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#include <linux/mman.h>
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#include <linux/hashtable.h>
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#include <linux/userfaultfd_k.h>
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#include <linux/page_idle.h>
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#include <linux/page_table_check.h>
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#include <linux/swapops.h>
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#include <linux/shmem_fs.h>
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#include <asm/tlb.h>
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#include <asm/pgalloc.h>
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#include "internal.h"
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#include "mm_slot.h"
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enum scan_result {
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SCAN_FAIL,
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SCAN_SUCCEED,
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SCAN_PMD_NULL,
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SCAN_PMD_NONE,
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SCAN_PMD_MAPPED,
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SCAN_EXCEED_NONE_PTE,
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SCAN_EXCEED_SWAP_PTE,
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SCAN_EXCEED_SHARED_PTE,
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SCAN_PTE_NON_PRESENT,
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SCAN_PTE_UFFD_WP,
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SCAN_PTE_MAPPED_HUGEPAGE,
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SCAN_PAGE_RO,
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SCAN_LACK_REFERENCED_PAGE,
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SCAN_PAGE_NULL,
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SCAN_SCAN_ABORT,
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SCAN_PAGE_COUNT,
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SCAN_PAGE_LRU,
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SCAN_PAGE_LOCK,
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SCAN_PAGE_ANON,
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SCAN_PAGE_COMPOUND,
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SCAN_ANY_PROCESS,
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SCAN_VMA_NULL,
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SCAN_VMA_CHECK,
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SCAN_ADDRESS_RANGE,
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SCAN_DEL_PAGE_LRU,
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SCAN_ALLOC_HUGE_PAGE_FAIL,
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SCAN_CGROUP_CHARGE_FAIL,
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SCAN_TRUNCATED,
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SCAN_PAGE_HAS_PRIVATE,
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SCAN_STORE_FAILED,
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SCAN_COPY_MC,
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SCAN_PAGE_FILLED,
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};
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#define CREATE_TRACE_POINTS
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#include <trace/events/huge_memory.h>
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static struct task_struct *khugepaged_thread __read_mostly;
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static DEFINE_MUTEX(khugepaged_mutex);
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/* default scan 8*512 pte (or vmas) every 30 second */
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static unsigned int khugepaged_pages_to_scan __read_mostly;
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static unsigned int khugepaged_pages_collapsed;
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static unsigned int khugepaged_full_scans;
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static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
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/* during fragmentation poll the hugepage allocator once every minute */
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static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
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static unsigned long khugepaged_sleep_expire;
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static DEFINE_SPINLOCK(khugepaged_mm_lock);
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static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
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/*
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* default collapse hugepages if there is at least one pte mapped like
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* it would have happened if the vma was large enough during page
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* fault.
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*
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* Note that these are only respected if collapse was initiated by khugepaged.
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*/
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static unsigned int khugepaged_max_ptes_none __read_mostly;
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static unsigned int khugepaged_max_ptes_swap __read_mostly;
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static unsigned int khugepaged_max_ptes_shared __read_mostly;
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#define MM_SLOTS_HASH_BITS 10
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static DEFINE_READ_MOSTLY_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
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static struct kmem_cache *mm_slot_cache __read_mostly;
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#define MAX_PTE_MAPPED_THP 8
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struct collapse_control {
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bool is_khugepaged;
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/* Num pages scanned per node */
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u32 node_load[MAX_NUMNODES];
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/* nodemask for allocation fallback */
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nodemask_t alloc_nmask;
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};
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/**
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* struct khugepaged_mm_slot - khugepaged information per mm that is being scanned
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* @slot: hash lookup from mm to mm_slot
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* @nr_pte_mapped_thp: number of pte mapped THP
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* @pte_mapped_thp: address array corresponding pte mapped THP
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*/
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struct khugepaged_mm_slot {
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struct mm_slot slot;
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/* pte-mapped THP in this mm */
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int nr_pte_mapped_thp;
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unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP];
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};
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/**
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* struct khugepaged_scan - cursor for scanning
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* @mm_head: the head of the mm list to scan
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* @mm_slot: the current mm_slot we are scanning
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* @address: the next address inside that to be scanned
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*
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* There is only the one khugepaged_scan instance of this cursor structure.
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*/
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struct khugepaged_scan {
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struct list_head mm_head;
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struct khugepaged_mm_slot *mm_slot;
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unsigned long address;
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};
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static struct khugepaged_scan khugepaged_scan = {
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.mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
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};
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#ifdef CONFIG_SYSFS
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static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
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struct kobj_attribute *attr,
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char *buf)
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{
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return sysfs_emit(buf, "%u\n", khugepaged_scan_sleep_millisecs);
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}
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static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
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struct kobj_attribute *attr,
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const char *buf, size_t count)
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{
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unsigned int msecs;
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int err;
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err = kstrtouint(buf, 10, &msecs);
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if (err)
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return -EINVAL;
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khugepaged_scan_sleep_millisecs = msecs;
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khugepaged_sleep_expire = 0;
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wake_up_interruptible(&khugepaged_wait);
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return count;
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}
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static struct kobj_attribute scan_sleep_millisecs_attr =
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__ATTR_RW(scan_sleep_millisecs);
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static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
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struct kobj_attribute *attr,
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char *buf)
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{
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return sysfs_emit(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
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}
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static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
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struct kobj_attribute *attr,
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const char *buf, size_t count)
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{
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unsigned int msecs;
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int err;
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err = kstrtouint(buf, 10, &msecs);
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if (err)
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return -EINVAL;
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khugepaged_alloc_sleep_millisecs = msecs;
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khugepaged_sleep_expire = 0;
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wake_up_interruptible(&khugepaged_wait);
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return count;
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}
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static struct kobj_attribute alloc_sleep_millisecs_attr =
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__ATTR_RW(alloc_sleep_millisecs);
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static ssize_t pages_to_scan_show(struct kobject *kobj,
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struct kobj_attribute *attr,
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char *buf)
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{
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return sysfs_emit(buf, "%u\n", khugepaged_pages_to_scan);
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}
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static ssize_t pages_to_scan_store(struct kobject *kobj,
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struct kobj_attribute *attr,
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const char *buf, size_t count)
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{
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unsigned int pages;
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int err;
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err = kstrtouint(buf, 10, &pages);
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if (err || !pages)
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return -EINVAL;
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khugepaged_pages_to_scan = pages;
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return count;
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}
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static struct kobj_attribute pages_to_scan_attr =
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__ATTR_RW(pages_to_scan);
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static ssize_t pages_collapsed_show(struct kobject *kobj,
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struct kobj_attribute *attr,
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char *buf)
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{
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return sysfs_emit(buf, "%u\n", khugepaged_pages_collapsed);
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}
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static struct kobj_attribute pages_collapsed_attr =
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__ATTR_RO(pages_collapsed);
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static ssize_t full_scans_show(struct kobject *kobj,
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struct kobj_attribute *attr,
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char *buf)
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{
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return sysfs_emit(buf, "%u\n", khugepaged_full_scans);
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}
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static struct kobj_attribute full_scans_attr =
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__ATTR_RO(full_scans);
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static ssize_t defrag_show(struct kobject *kobj,
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struct kobj_attribute *attr, char *buf)
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{
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return single_hugepage_flag_show(kobj, attr, buf,
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TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
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}
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static ssize_t defrag_store(struct kobject *kobj,
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struct kobj_attribute *attr,
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const char *buf, size_t count)
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{
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return single_hugepage_flag_store(kobj, attr, buf, count,
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TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
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}
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static struct kobj_attribute khugepaged_defrag_attr =
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__ATTR_RW(defrag);
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/*
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* max_ptes_none controls if khugepaged should collapse hugepages over
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* any unmapped ptes in turn potentially increasing the memory
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* footprint of the vmas. When max_ptes_none is 0 khugepaged will not
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* reduce the available free memory in the system as it
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* runs. Increasing max_ptes_none will instead potentially reduce the
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* free memory in the system during the khugepaged scan.
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*/
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static ssize_t max_ptes_none_show(struct kobject *kobj,
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struct kobj_attribute *attr,
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char *buf)
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{
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return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_none);
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}
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static ssize_t max_ptes_none_store(struct kobject *kobj,
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struct kobj_attribute *attr,
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const char *buf, size_t count)
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{
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int err;
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unsigned long max_ptes_none;
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err = kstrtoul(buf, 10, &max_ptes_none);
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if (err || max_ptes_none > HPAGE_PMD_NR - 1)
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return -EINVAL;
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khugepaged_max_ptes_none = max_ptes_none;
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return count;
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}
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static struct kobj_attribute khugepaged_max_ptes_none_attr =
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__ATTR_RW(max_ptes_none);
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static ssize_t max_ptes_swap_show(struct kobject *kobj,
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struct kobj_attribute *attr,
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char *buf)
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{
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return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_swap);
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}
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static ssize_t max_ptes_swap_store(struct kobject *kobj,
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struct kobj_attribute *attr,
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const char *buf, size_t count)
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{
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int err;
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unsigned long max_ptes_swap;
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err = kstrtoul(buf, 10, &max_ptes_swap);
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if (err || max_ptes_swap > HPAGE_PMD_NR - 1)
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return -EINVAL;
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khugepaged_max_ptes_swap = max_ptes_swap;
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return count;
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}
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static struct kobj_attribute khugepaged_max_ptes_swap_attr =
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__ATTR_RW(max_ptes_swap);
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static ssize_t max_ptes_shared_show(struct kobject *kobj,
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struct kobj_attribute *attr,
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char *buf)
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{
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return sysfs_emit(buf, "%u\n", khugepaged_max_ptes_shared);
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}
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static ssize_t max_ptes_shared_store(struct kobject *kobj,
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struct kobj_attribute *attr,
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const char *buf, size_t count)
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{
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int err;
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unsigned long max_ptes_shared;
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err = kstrtoul(buf, 10, &max_ptes_shared);
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if (err || max_ptes_shared > HPAGE_PMD_NR - 1)
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return -EINVAL;
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khugepaged_max_ptes_shared = max_ptes_shared;
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return count;
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}
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static struct kobj_attribute khugepaged_max_ptes_shared_attr =
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__ATTR_RW(max_ptes_shared);
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static struct attribute *khugepaged_attr[] = {
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&khugepaged_defrag_attr.attr,
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&khugepaged_max_ptes_none_attr.attr,
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&khugepaged_max_ptes_swap_attr.attr,
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&khugepaged_max_ptes_shared_attr.attr,
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&pages_to_scan_attr.attr,
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&pages_collapsed_attr.attr,
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&full_scans_attr.attr,
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&scan_sleep_millisecs_attr.attr,
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&alloc_sleep_millisecs_attr.attr,
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NULL,
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};
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struct attribute_group khugepaged_attr_group = {
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.attrs = khugepaged_attr,
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.name = "khugepaged",
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};
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#endif /* CONFIG_SYSFS */
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int hugepage_madvise(struct vm_area_struct *vma,
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unsigned long *vm_flags, int advice)
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{
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switch (advice) {
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case MADV_HUGEPAGE:
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#ifdef CONFIG_S390
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/*
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* qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
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* can't handle this properly after s390_enable_sie, so we simply
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* ignore the madvise to prevent qemu from causing a SIGSEGV.
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*/
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if (mm_has_pgste(vma->vm_mm))
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return 0;
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#endif
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*vm_flags &= ~VM_NOHUGEPAGE;
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*vm_flags |= VM_HUGEPAGE;
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/*
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* If the vma become good for khugepaged to scan,
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* register it here without waiting a page fault that
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* may not happen any time soon.
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*/
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khugepaged_enter_vma(vma, *vm_flags);
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break;
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case MADV_NOHUGEPAGE:
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*vm_flags &= ~VM_HUGEPAGE;
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*vm_flags |= VM_NOHUGEPAGE;
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/*
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* Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
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* this vma even if we leave the mm registered in khugepaged if
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* it got registered before VM_NOHUGEPAGE was set.
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*/
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break;
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}
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return 0;
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}
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int __init khugepaged_init(void)
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{
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mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
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sizeof(struct khugepaged_mm_slot),
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__alignof__(struct khugepaged_mm_slot),
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0, NULL);
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if (!mm_slot_cache)
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return -ENOMEM;
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khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
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khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
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khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
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khugepaged_max_ptes_shared = HPAGE_PMD_NR / 2;
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return 0;
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}
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void __init khugepaged_destroy(void)
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{
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kmem_cache_destroy(mm_slot_cache);
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}
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static inline int hpage_collapse_test_exit(struct mm_struct *mm)
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{
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return atomic_read(&mm->mm_users) == 0;
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}
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void __khugepaged_enter(struct mm_struct *mm)
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{
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struct khugepaged_mm_slot *mm_slot;
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struct mm_slot *slot;
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int wakeup;
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/* __khugepaged_exit() must not run from under us */
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VM_BUG_ON_MM(hpage_collapse_test_exit(mm), mm);
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if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags)))
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return;
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mm_slot = mm_slot_alloc(mm_slot_cache);
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if (!mm_slot)
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return;
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slot = &mm_slot->slot;
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spin_lock(&khugepaged_mm_lock);
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mm_slot_insert(mm_slots_hash, mm, slot);
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/*
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* Insert just behind the scanning cursor, to let the area settle
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* down a little.
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*/
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wakeup = list_empty(&khugepaged_scan.mm_head);
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list_add_tail(&slot->mm_node, &khugepaged_scan.mm_head);
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spin_unlock(&khugepaged_mm_lock);
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mmgrab(mm);
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if (wakeup)
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wake_up_interruptible(&khugepaged_wait);
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}
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void khugepaged_enter_vma(struct vm_area_struct *vma,
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unsigned long vm_flags)
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{
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if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
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hugepage_flags_enabled()) {
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if (hugepage_vma_check(vma, vm_flags, false, false, true))
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__khugepaged_enter(vma->vm_mm);
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}
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}
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void __khugepaged_exit(struct mm_struct *mm)
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{
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struct khugepaged_mm_slot *mm_slot;
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struct mm_slot *slot;
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int free = 0;
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spin_lock(&khugepaged_mm_lock);
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slot = mm_slot_lookup(mm_slots_hash, mm);
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mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot);
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if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
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hash_del(&slot->hash);
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list_del(&slot->mm_node);
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free = 1;
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}
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spin_unlock(&khugepaged_mm_lock);
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if (free) {
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clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
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mm_slot_free(mm_slot_cache, mm_slot);
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mmdrop(mm);
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} else if (mm_slot) {
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/*
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* This is required to serialize against
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* hpage_collapse_test_exit() (which is guaranteed to run
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* under mmap sem read mode). Stop here (after we return all
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* pagetables will be destroyed) until khugepaged has finished
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* working on the pagetables under the mmap_lock.
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*/
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mmap_write_lock(mm);
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mmap_write_unlock(mm);
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}
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}
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|
|
static void release_pte_folio(struct folio *folio)
|
|
{
|
|
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_page(struct page *page)
|
|
{
|
|
release_pte_folio(page_folio(page));
|
|
}
|
|
|
|
static void release_pte_pages(pte_t *pte, pte_t *_pte,
|
|
struct list_head *compound_pagelist)
|
|
{
|
|
struct folio *folio, *tmp;
|
|
|
|
while (--_pte >= pte) {
|
|
pte_t pteval = ptep_get(_pte);
|
|
unsigned long pfn;
|
|
|
|
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(folio, tmp, compound_pagelist, lru) {
|
|
list_del(&folio->lru);
|
|
release_pte_folio(folio);
|
|
}
|
|
}
|
|
|
|
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 = ptep_get(_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_succeeded(pte_t *pte,
|
|
struct vm_area_struct *vma,
|
|
unsigned long address,
|
|
spinlock_t *ptl,
|
|
struct list_head *compound_pagelist)
|
|
{
|
|
struct page *src_page;
|
|
struct page *tmp;
|
|
pte_t *_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))) {
|
|
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);
|
|
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 __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);
|
|
__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;
|
|
}
|
|
|
|
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 hpage_collapse_scan_pmd believes it is worthwhile.
|
|
*
|
|
* Called and returns without pte mapped or spinlocks held.
|
|
* Returns result: if not SCAN_SUCCEED, mmap_lock has been 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);
|
|
int result;
|
|
pte_t *pte = NULL;
|
|
spinlock_t *ptl;
|
|
|
|
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;
|
|
|
|
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.
|
|
* 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) {
|
|
/* Likely, but not guaranteed, that page lock failed */
|
|
result = SCAN_PAGE_LOCK;
|
|
goto out;
|
|
}
|
|
if (ret & VM_FAULT_ERROR) {
|
|
mmap_read_unlock(mm);
|
|
result = SCAN_FAIL;
|
|
goto out;
|
|
}
|
|
swapped_in++;
|
|
}
|
|
|
|
if (pte)
|
|
pte_unmap(pte);
|
|
|
|
/* Drain LRU cache to remove extra pin on the swapped in pages */
|
|
if (swapped_in)
|
|
lru_add_drain();
|
|
|
|
result = SCAN_SUCCEED;
|
|
out:
|
|
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, result);
|
|
return result;
|
|
}
|
|
|
|
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_page(hpage, gfp, node, &cc->alloc_nmask))
|
|
return SCAN_ALLOC_HUGE_PAGE_FAIL;
|
|
|
|
folio = page_folio(*hpage);
|
|
if (unlikely(mem_cgroup_charge(folio, mm, gfp))) {
|
|
folio_put(folio);
|
|
*hpage = NULL;
|
|
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, mm, address,
|
|
address + HPAGE_PMD_SIZE);
|
|
mmu_notifier_invalidate_range_start(&range);
|
|
|
|
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();
|
|
|
|
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(result != SCAN_SUCCEED)) {
|
|
if (pte)
|
|
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);
|
|
|
|
result = __collapse_huge_page_copy(pte, hpage, pmd, _pmd,
|
|
vma, address, pte_ptl,
|
|
&compound_pagelist);
|
|
pte_unmap(pte);
|
|
if (unlikely(result != SCAN_SUCCEED))
|
|
goto out_up_write;
|
|
|
|
/*
|
|
* 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)
|
|
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);
|
|
if (!pte) {
|
|
result = SCAN_PMD_NULL;
|
|
goto out;
|
|
}
|
|
|
|
for (_address = address, _pte = pte; _pte < pte + HPAGE_PMD_NR;
|
|
_pte++, _address += PAGE_SIZE) {
|
|
pte_t pteval = ptep_get(_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_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) &&
|
|
(!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 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)) {
|
|
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, 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.
|
|
*/
|
|
result = SCAN_FAIL;
|
|
start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl);
|
|
if (!start_pte)
|
|
goto drop_immap;
|
|
|
|
/* 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(ptent))
|
|
continue;
|
|
|
|
/* page swapped out, abort */
|
|
if (!pte_present(ptent)) {
|
|
result = SCAN_PTE_NON_PRESENT;
|
|
goto abort;
|
|
}
|
|
|
|
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)
|
|
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;
|
|
pte_t ptent = ptep_get(pte);
|
|
|
|
if (pte_none(ptent))
|
|
continue;
|
|
page = vm_normal_page(vma, addr, ptent);
|
|
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);
|
|
drop_immap:
|
|
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, locking old pages
|
|
* + swap/gup in pages if necessary;
|
|
* - 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:
|
|
* + unlock huge page;
|
|
* + free old pages;
|
|
* - if replacing failed;
|
|
* + unlock old pages
|
|
* + 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;
|
|
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));
|
|
|
|
result = alloc_charge_hpage(&hpage, mm, cc);
|
|
if (result != SCAN_SUCCEED)
|
|
goto out;
|
|
|
|
__SetPageLocked(hpage);
|
|
if (is_shmem)
|
|
__SetPageSwapBacked(hpage);
|
|
hpage->index = start;
|
|
hpage->mapping = mapping;
|
|
|
|
/*
|
|
* 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 rollback;
|
|
}
|
|
} while (1);
|
|
|
|
for (index = start; index < end; index++) {
|
|
xas_set(&xas, index);
|
|
page = xas_load(&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;
|
|
}
|
|
}
|
|
if (!shmem_charge(mapping->host, 1)) {
|
|
result = SCAN_FAIL;
|
|
goto xa_locked;
|
|
}
|
|
nr_none++;
|
|
continue;
|
|
}
|
|
|
|
if (xa_is_value(page) || !PageUptodate(page)) {
|
|
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;
|
|
}
|
|
/* 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);
|
|
} 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 lru cache 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;
|
|
}
|
|
|
|
folio = page_folio(page);
|
|
|
|
if (folio_mapping(folio) != mapping) {
|
|
result = SCAN_TRUNCATED;
|
|
goto out_unlock;
|
|
}
|
|
|
|
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
|
|
* since first write.
|
|
*/
|
|
result = SCAN_FAIL;
|
|
goto out_unlock;
|
|
}
|
|
|
|
if (!folio_isolate_lru(folio)) {
|
|
result = SCAN_DEL_PAGE_LRU;
|
|
goto out_unlock;
|
|
}
|
|
|
|
if (folio_has_private(folio) &&
|
|
!filemap_release_folio(folio, GFP_KERNEL)) {
|
|
result = SCAN_PAGE_HAS_PRIVATE;
|
|
folio_putback_lru(folio);
|
|
goto out_unlock;
|
|
}
|
|
|
|
if (folio_mapped(folio))
|
|
try_to_unmap(folio,
|
|
TTU_IGNORE_MLOCK | TTU_BATCH_FLUSH);
|
|
|
|
xas_lock_irq(&xas);
|
|
|
|
VM_BUG_ON_PAGE(page != xa_load(xas.xa, index), page);
|
|
|
|
/*
|
|
* 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_count(page) != 3) {
|
|
result = SCAN_PAGE_COUNT;
|
|
xas_unlock_irq(&xas);
|
|
putback_lru_page(page);
|
|
goto out_unlock;
|
|
}
|
|
|
|
/*
|
|
* Accumulate the pages that are being collapsed.
|
|
*/
|
|
list_add_tail(&page->lru, &pagelist);
|
|
continue;
|
|
out_unlock:
|
|
unlock_page(page);
|
|
put_page(page);
|
|
goto xa_unlocked;
|
|
}
|
|
|
|
if (!is_shmem) {
|
|
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;
|
|
filemap_nr_thps_dec(mapping);
|
|
}
|
|
}
|
|
|
|
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)
|
|
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++;
|
|
}
|
|
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++;
|
|
}
|
|
}
|
|
|
|
if (nr_none != nr_none_check) {
|
|
result = SCAN_PAGE_FILLED;
|
|
goto immap_locked;
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
vma_interval_tree_foreach(vma, &mapping->i_mmap, start, end) {
|
|
if (userfaultfd_missing(vma)) {
|
|
result = SCAN_EXCEED_NONE_PTE;
|
|
goto immap_locked;
|
|
}
|
|
}
|
|
|
|
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);
|
|
}
|
|
|
|
xas_unlock_irq(&xas);
|
|
goto rollback;
|
|
}
|
|
} else {
|
|
xas_lock_irq(&xas);
|
|
}
|
|
|
|
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);
|
|
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* Mark hpage as uptodate before inserting it into the page cache so
|
|
* that it isn't mistaken for an fallocated but unwritten page.
|
|
*/
|
|
folio = page_folio(hpage);
|
|
folio_mark_uptodate(folio);
|
|
folio_ref_add(folio, HPAGE_PMD_NR - 1);
|
|
|
|
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, hpage);
|
|
WARN_ON_ONCE(xas_error(&xas));
|
|
xas_unlock_irq(&xas);
|
|
|
|
/*
|
|
* 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);
|
|
|
|
/*
|
|
* 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;
|
|
shmem_uncharge(mapping->host, nr_none);
|
|
xas_unlock_irq(&xas);
|
|
}
|
|
|
|
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(hpage);
|
|
put_page(hpage);
|
|
out:
|
|
VM_BUG_ON(!list_empty(&pagelist));
|
|
trace_mm_khugepaged_collapse_file(mm, hpage, index, is_shmem, addr, file, nr, result);
|
|
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);
|
|
}
|
|
|
|
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 (!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);
|
|
}
|