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![Song Liu](/assets/img/avatar_default.png)
For non-shmem file THPs, khugepaged only collapses read only .text mapping (VM_DENYWRITE). These pages should not be dirty except the case where the file hasn't been flushed since first write. Call filemap_flush() in collapse_file() to accelerate the write back in such cases. Link: http://lkml.kernel.org/r/20191106060930.2571389-3-songliubraving@fb.com Signed-off-by: Song Liu <songliubraving@fb.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: William Kucharski <william.kucharski@oracle.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2214 lines
55 KiB
C
2214 lines
55 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/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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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_EXCEED_NONE_PTE,
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SCAN_PTE_NON_PRESENT,
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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_SWAP_CACHE_PAGE,
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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_EXCEED_SWAP_PTE,
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SCAN_TRUNCATED,
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SCAN_PAGE_HAS_PRIVATE,
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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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/* 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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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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#define MM_SLOTS_HASH_BITS 10
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static __read_mostly DEFINE_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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/**
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* struct mm_slot - hash lookup from mm to mm_slot
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* @hash: hash collision list
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* @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
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* @mm: the mm that this information is valid for
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*/
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struct mm_slot {
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struct hlist_node hash;
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struct list_head mm_node;
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struct mm_struct *mm;
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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 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 sprintf(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 long msecs;
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int err;
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err = kstrtoul(buf, 10, &msecs);
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if (err || msecs > UINT_MAX)
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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(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
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scan_sleep_millisecs_store);
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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 sprintf(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 long msecs;
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int err;
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err = kstrtoul(buf, 10, &msecs);
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if (err || msecs > UINT_MAX)
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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(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
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alloc_sleep_millisecs_store);
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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 sprintf(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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int err;
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unsigned long pages;
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err = kstrtoul(buf, 10, &pages);
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if (err || !pages || pages > UINT_MAX)
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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(pages_to_scan, 0644, pages_to_scan_show,
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pages_to_scan_store);
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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 sprintf(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 sprintf(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 khugepaged_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 khugepaged_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(defrag, 0644, khugepaged_defrag_show,
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khugepaged_defrag_store);
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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 khugepaged_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 sprintf(buf, "%u\n", khugepaged_max_ptes_none);
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}
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static ssize_t khugepaged_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(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
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khugepaged_max_ptes_none_store);
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static ssize_t khugepaged_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 sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
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}
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static ssize_t khugepaged_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(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
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khugepaged_max_ptes_swap_store);
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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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&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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&khugepaged_max_ptes_swap_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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#define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB)
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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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if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
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khugepaged_enter_vma_merge(vma, *vm_flags))
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return -ENOMEM;
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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 mm_slot),
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__alignof__(struct mm_slot), 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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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 struct mm_slot *alloc_mm_slot(void)
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{
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if (!mm_slot_cache) /* initialization failed */
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return NULL;
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return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
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}
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static inline void free_mm_slot(struct mm_slot *mm_slot)
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{
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kmem_cache_free(mm_slot_cache, mm_slot);
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}
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static struct mm_slot *get_mm_slot(struct mm_struct *mm)
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{
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struct mm_slot *mm_slot;
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hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
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if (mm == mm_slot->mm)
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return mm_slot;
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return NULL;
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}
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static void insert_to_mm_slots_hash(struct mm_struct *mm,
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struct mm_slot *mm_slot)
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{
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mm_slot->mm = mm;
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hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
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}
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static inline int khugepaged_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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static bool hugepage_vma_check(struct vm_area_struct *vma,
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unsigned long vm_flags)
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{
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if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
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(vm_flags & VM_NOHUGEPAGE) ||
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test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
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return false;
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if (shmem_file(vma->vm_file) ||
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(IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) &&
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vma->vm_file &&
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(vm_flags & VM_DENYWRITE))) {
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if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
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return false;
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return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
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HPAGE_PMD_NR);
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}
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if (!vma->anon_vma || vma->vm_ops)
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return false;
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if (is_vma_temporary_stack(vma))
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return false;
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return !(vm_flags & VM_NO_KHUGEPAGED);
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}
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int __khugepaged_enter(struct mm_struct *mm)
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{
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struct mm_slot *mm_slot;
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int wakeup;
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mm_slot = alloc_mm_slot();
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if (!mm_slot)
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return -ENOMEM;
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/* __khugepaged_exit() must not run from under us */
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VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
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if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
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free_mm_slot(mm_slot);
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return 0;
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}
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spin_lock(&khugepaged_mm_lock);
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insert_to_mm_slots_hash(mm, 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(&mm_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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return 0;
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}
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int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
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unsigned long vm_flags)
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{
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unsigned long hstart, hend;
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|
/*
|
|
* khugepaged only supports read-only files for non-shmem files.
|
|
* khugepaged does not yet work on special mappings. And
|
|
* file-private shmem THP is not supported.
|
|
*/
|
|
if (!hugepage_vma_check(vma, vm_flags))
|
|
return 0;
|
|
|
|
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
|
|
hend = vma->vm_end & HPAGE_PMD_MASK;
|
|
if (hstart < hend)
|
|
return khugepaged_enter(vma, vm_flags);
|
|
return 0;
|
|
}
|
|
|
|
void __khugepaged_exit(struct mm_struct *mm)
|
|
{
|
|
struct mm_slot *mm_slot;
|
|
int free = 0;
|
|
|
|
spin_lock(&khugepaged_mm_lock);
|
|
mm_slot = get_mm_slot(mm);
|
|
if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
|
|
hash_del(&mm_slot->hash);
|
|
list_del(&mm_slot->mm_node);
|
|
free = 1;
|
|
}
|
|
spin_unlock(&khugepaged_mm_lock);
|
|
|
|
if (free) {
|
|
clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
|
|
free_mm_slot(mm_slot);
|
|
mmdrop(mm);
|
|
} else if (mm_slot) {
|
|
/*
|
|
* This is required to serialize against
|
|
* khugepaged_test_exit() (which is guaranteed to run
|
|
* under mmap sem read mode). Stop here (after we
|
|
* return all pagetables will be destroyed) until
|
|
* khugepaged has finished working on the pagetables
|
|
* under the mmap_sem.
|
|
*/
|
|
down_write(&mm->mmap_sem);
|
|
up_write(&mm->mmap_sem);
|
|
}
|
|
}
|
|
|
|
static void release_pte_page(struct page *page)
|
|
{
|
|
dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page));
|
|
unlock_page(page);
|
|
putback_lru_page(page);
|
|
}
|
|
|
|
static void release_pte_pages(pte_t *pte, pte_t *_pte)
|
|
{
|
|
while (--_pte >= pte) {
|
|
pte_t pteval = *_pte;
|
|
if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
|
|
release_pte_page(pte_page(pteval));
|
|
}
|
|
}
|
|
|
|
static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
|
|
unsigned long address,
|
|
pte_t *pte)
|
|
{
|
|
struct page *page = NULL;
|
|
pte_t *_pte;
|
|
int none_or_zero = 0, result = 0, referenced = 0;
|
|
bool writable = false;
|
|
|
|
for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
|
|
_pte++, address += PAGE_SIZE) {
|
|
pte_t pteval = *_pte;
|
|
if (pte_none(pteval) || (pte_present(pteval) &&
|
|
is_zero_pfn(pte_pfn(pteval)))) {
|
|
if (!userfaultfd_armed(vma) &&
|
|
++none_or_zero <= khugepaged_max_ptes_none) {
|
|
continue;
|
|
} else {
|
|
result = SCAN_EXCEED_NONE_PTE;
|
|
goto out;
|
|
}
|
|
}
|
|
if (!pte_present(pteval)) {
|
|
result = SCAN_PTE_NON_PRESENT;
|
|
goto out;
|
|
}
|
|
page = vm_normal_page(vma, address, pteval);
|
|
if (unlikely(!page)) {
|
|
result = SCAN_PAGE_NULL;
|
|
goto out;
|
|
}
|
|
|
|
/* TODO: teach khugepaged to collapse THP mapped with pte */
|
|
if (PageCompound(page)) {
|
|
result = SCAN_PAGE_COMPOUND;
|
|
goto out;
|
|
}
|
|
|
|
VM_BUG_ON_PAGE(!PageAnon(page), page);
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/*
|
|
* cannot use mapcount: can't collapse if there's a gup pin.
|
|
* The page must only be referenced by the scanned process
|
|
* and page swap cache.
|
|
*/
|
|
if (page_count(page) != 1 + PageSwapCache(page)) {
|
|
unlock_page(page);
|
|
result = SCAN_PAGE_COUNT;
|
|
goto out;
|
|
}
|
|
if (pte_write(pteval)) {
|
|
writable = true;
|
|
} else {
|
|
if (PageSwapCache(page) &&
|
|
!reuse_swap_page(page, NULL)) {
|
|
unlock_page(page);
|
|
result = SCAN_SWAP_CACHE_PAGE;
|
|
goto out;
|
|
}
|
|
/*
|
|
* Page is not in the swap cache. It can be collapsed
|
|
* into a THP.
|
|
*/
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
inc_node_page_state(page,
|
|
NR_ISOLATED_ANON + page_is_file_cache(page));
|
|
VM_BUG_ON_PAGE(!PageLocked(page), page);
|
|
VM_BUG_ON_PAGE(PageLRU(page), page);
|
|
|
|
/* There should be enough young pte to collapse the page */
|
|
if (pte_young(pteval) ||
|
|
page_is_young(page) || PageReferenced(page) ||
|
|
mmu_notifier_test_young(vma->vm_mm, address))
|
|
referenced++;
|
|
}
|
|
if (likely(writable)) {
|
|
if (likely(referenced)) {
|
|
result = SCAN_SUCCEED;
|
|
trace_mm_collapse_huge_page_isolate(page, none_or_zero,
|
|
referenced, writable, result);
|
|
return 1;
|
|
}
|
|
} else {
|
|
result = SCAN_PAGE_RO;
|
|
}
|
|
|
|
out:
|
|
release_pte_pages(pte, _pte);
|
|
trace_mm_collapse_huge_page_isolate(page, none_or_zero,
|
|
referenced, writable, result);
|
|
return 0;
|
|
}
|
|
|
|
static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
|
|
struct vm_area_struct *vma,
|
|
unsigned long address,
|
|
spinlock_t *ptl)
|
|
{
|
|
pte_t *_pte;
|
|
for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
|
|
_pte++, page++, address += PAGE_SIZE) {
|
|
pte_t pteval = *_pte;
|
|
struct page *src_page;
|
|
|
|
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
|
|
clear_user_highpage(page, address);
|
|
add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
|
|
if (is_zero_pfn(pte_pfn(pteval))) {
|
|
/*
|
|
* ptl mostly unnecessary.
|
|
*/
|
|
spin_lock(ptl);
|
|
/*
|
|
* paravirt calls inside pte_clear here are
|
|
* superfluous.
|
|
*/
|
|
pte_clear(vma->vm_mm, address, _pte);
|
|
spin_unlock(ptl);
|
|
}
|
|
} else {
|
|
src_page = pte_page(pteval);
|
|
copy_user_highpage(page, src_page, address, vma);
|
|
VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, 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);
|
|
/*
|
|
* paravirt calls inside pte_clear here are
|
|
* superfluous.
|
|
*/
|
|
pte_clear(vma->vm_mm, address, _pte);
|
|
page_remove_rmap(src_page, false);
|
|
spin_unlock(ptl);
|
|
free_page_and_swap_cache(src_page);
|
|
}
|
|
}
|
|
}
|
|
|
|
static void khugepaged_alloc_sleep(void)
|
|
{
|
|
DEFINE_WAIT(wait);
|
|
|
|
add_wait_queue(&khugepaged_wait, &wait);
|
|
freezable_schedule_timeout_interruptible(
|
|
msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
|
|
remove_wait_queue(&khugepaged_wait, &wait);
|
|
}
|
|
|
|
static int khugepaged_node_load[MAX_NUMNODES];
|
|
|
|
static bool khugepaged_scan_abort(int nid)
|
|
{
|
|
int i;
|
|
|
|
/*
|
|
* If node_reclaim_mode is disabled, then no extra effort is made to
|
|
* allocate memory locally.
|
|
*/
|
|
if (!node_reclaim_mode)
|
|
return false;
|
|
|
|
/* If there is a count for this node already, it must be acceptable */
|
|
if (khugepaged_node_load[nid])
|
|
return false;
|
|
|
|
for (i = 0; i < MAX_NUMNODES; i++) {
|
|
if (!khugepaged_node_load[i])
|
|
continue;
|
|
if (node_distance(nid, i) > node_reclaim_distance)
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/* 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 khugepaged_find_target_node(void)
|
|
{
|
|
static int last_khugepaged_target_node = NUMA_NO_NODE;
|
|
int nid, target_node = 0, max_value = 0;
|
|
|
|
/* find first node with max normal pages hit */
|
|
for (nid = 0; nid < MAX_NUMNODES; nid++)
|
|
if (khugepaged_node_load[nid] > max_value) {
|
|
max_value = khugepaged_node_load[nid];
|
|
target_node = nid;
|
|
}
|
|
|
|
/* do some balance if several nodes have the same hit record */
|
|
if (target_node <= last_khugepaged_target_node)
|
|
for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
|
|
nid++)
|
|
if (max_value == khugepaged_node_load[nid]) {
|
|
target_node = nid;
|
|
break;
|
|
}
|
|
|
|
last_khugepaged_target_node = target_node;
|
|
return target_node;
|
|
}
|
|
|
|
static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
|
|
{
|
|
if (IS_ERR(*hpage)) {
|
|
if (!*wait)
|
|
return false;
|
|
|
|
*wait = false;
|
|
*hpage = NULL;
|
|
khugepaged_alloc_sleep();
|
|
} else if (*hpage) {
|
|
put_page(*hpage);
|
|
*hpage = NULL;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
static struct page *
|
|
khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
|
|
{
|
|
VM_BUG_ON_PAGE(*hpage, *hpage);
|
|
|
|
*hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
|
|
if (unlikely(!*hpage)) {
|
|
count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
|
|
*hpage = ERR_PTR(-ENOMEM);
|
|
return NULL;
|
|
}
|
|
|
|
prep_transhuge_page(*hpage);
|
|
count_vm_event(THP_COLLAPSE_ALLOC);
|
|
return *hpage;
|
|
}
|
|
#else
|
|
static int khugepaged_find_target_node(void)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline struct page *alloc_khugepaged_hugepage(void)
|
|
{
|
|
struct page *page;
|
|
|
|
page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
|
|
HPAGE_PMD_ORDER);
|
|
if (page)
|
|
prep_transhuge_page(page);
|
|
return page;
|
|
}
|
|
|
|
static struct page *khugepaged_alloc_hugepage(bool *wait)
|
|
{
|
|
struct page *hpage;
|
|
|
|
do {
|
|
hpage = alloc_khugepaged_hugepage();
|
|
if (!hpage) {
|
|
count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
|
|
if (!*wait)
|
|
return NULL;
|
|
|
|
*wait = false;
|
|
khugepaged_alloc_sleep();
|
|
} else
|
|
count_vm_event(THP_COLLAPSE_ALLOC);
|
|
} while (unlikely(!hpage) && likely(khugepaged_enabled()));
|
|
|
|
return hpage;
|
|
}
|
|
|
|
static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
|
|
{
|
|
if (!*hpage)
|
|
*hpage = khugepaged_alloc_hugepage(wait);
|
|
|
|
if (unlikely(!*hpage))
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
static struct page *
|
|
khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
|
|
{
|
|
VM_BUG_ON(!*hpage);
|
|
|
|
return *hpage;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* If mmap_sem temporarily dropped, revalidate vma
|
|
* before taking mmap_sem.
|
|
* Return 0 if succeeds, otherwise return none-zero
|
|
* value (scan code).
|
|
*/
|
|
|
|
static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
|
|
struct vm_area_struct **vmap)
|
|
{
|
|
struct vm_area_struct *vma;
|
|
unsigned long hstart, hend;
|
|
|
|
if (unlikely(khugepaged_test_exit(mm)))
|
|
return SCAN_ANY_PROCESS;
|
|
|
|
*vmap = vma = find_vma(mm, address);
|
|
if (!vma)
|
|
return SCAN_VMA_NULL;
|
|
|
|
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
|
|
hend = vma->vm_end & HPAGE_PMD_MASK;
|
|
if (address < hstart || address + HPAGE_PMD_SIZE > hend)
|
|
return SCAN_ADDRESS_RANGE;
|
|
if (!hugepage_vma_check(vma, vma->vm_flags))
|
|
return SCAN_VMA_CHECK;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Bring missing pages in from swap, to complete THP collapse.
|
|
* Only done if khugepaged_scan_pmd believes it is worthwhile.
|
|
*
|
|
* Called and returns without pte mapped or spinlocks held,
|
|
* but with mmap_sem held to protect against vma changes.
|
|
*/
|
|
|
|
static bool __collapse_huge_page_swapin(struct mm_struct *mm,
|
|
struct vm_area_struct *vma,
|
|
unsigned long address, pmd_t *pmd,
|
|
int referenced)
|
|
{
|
|
int swapped_in = 0;
|
|
vm_fault_t ret = 0;
|
|
struct vm_fault vmf = {
|
|
.vma = vma,
|
|
.address = address,
|
|
.flags = FAULT_FLAG_ALLOW_RETRY,
|
|
.pmd = pmd,
|
|
.pgoff = linear_page_index(vma, address),
|
|
};
|
|
|
|
/* we only decide to swapin, if there is enough young ptes */
|
|
if (referenced < HPAGE_PMD_NR/2) {
|
|
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
|
|
return false;
|
|
}
|
|
vmf.pte = pte_offset_map(pmd, address);
|
|
for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE;
|
|
vmf.pte++, vmf.address += PAGE_SIZE) {
|
|
vmf.orig_pte = *vmf.pte;
|
|
if (!is_swap_pte(vmf.orig_pte))
|
|
continue;
|
|
swapped_in++;
|
|
ret = do_swap_page(&vmf);
|
|
|
|
/* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
|
|
if (ret & VM_FAULT_RETRY) {
|
|
down_read(&mm->mmap_sem);
|
|
if (hugepage_vma_revalidate(mm, address, &vmf.vma)) {
|
|
/* vma is no longer available, don't continue to swapin */
|
|
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
|
|
return false;
|
|
}
|
|
/* check if the pmd is still valid */
|
|
if (mm_find_pmd(mm, address) != pmd) {
|
|
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
|
|
return false;
|
|
}
|
|
}
|
|
if (ret & VM_FAULT_ERROR) {
|
|
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
|
|
return false;
|
|
}
|
|
/* pte is unmapped now, we need to map it */
|
|
vmf.pte = pte_offset_map(pmd, vmf.address);
|
|
}
|
|
vmf.pte--;
|
|
pte_unmap(vmf.pte);
|
|
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
|
|
return true;
|
|
}
|
|
|
|
static void collapse_huge_page(struct mm_struct *mm,
|
|
unsigned long address,
|
|
struct page **hpage,
|
|
int node, int referenced)
|
|
{
|
|
pmd_t *pmd, _pmd;
|
|
pte_t *pte;
|
|
pgtable_t pgtable;
|
|
struct page *new_page;
|
|
spinlock_t *pmd_ptl, *pte_ptl;
|
|
int isolated = 0, result = 0;
|
|
struct mem_cgroup *memcg;
|
|
struct vm_area_struct *vma;
|
|
struct mmu_notifier_range range;
|
|
gfp_t gfp;
|
|
|
|
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
|
|
|
|
/* Only allocate from the target node */
|
|
gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
|
|
|
|
/*
|
|
* Before allocating the hugepage, release the mmap_sem read lock.
|
|
* The allocation can take potentially a long time if it involves
|
|
* sync compaction, and we do not need to hold the mmap_sem during
|
|
* that. We will recheck the vma after taking it again in write mode.
|
|
*/
|
|
up_read(&mm->mmap_sem);
|
|
new_page = khugepaged_alloc_page(hpage, gfp, node);
|
|
if (!new_page) {
|
|
result = SCAN_ALLOC_HUGE_PAGE_FAIL;
|
|
goto out_nolock;
|
|
}
|
|
|
|
if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
|
|
result = SCAN_CGROUP_CHARGE_FAIL;
|
|
goto out_nolock;
|
|
}
|
|
|
|
down_read(&mm->mmap_sem);
|
|
result = hugepage_vma_revalidate(mm, address, &vma);
|
|
if (result) {
|
|
mem_cgroup_cancel_charge(new_page, memcg, true);
|
|
up_read(&mm->mmap_sem);
|
|
goto out_nolock;
|
|
}
|
|
|
|
pmd = mm_find_pmd(mm, address);
|
|
if (!pmd) {
|
|
result = SCAN_PMD_NULL;
|
|
mem_cgroup_cancel_charge(new_page, memcg, true);
|
|
up_read(&mm->mmap_sem);
|
|
goto out_nolock;
|
|
}
|
|
|
|
/*
|
|
* __collapse_huge_page_swapin always returns with mmap_sem locked.
|
|
* If it fails, we release mmap_sem and jump out_nolock.
|
|
* Continuing to collapse causes inconsistency.
|
|
*/
|
|
if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) {
|
|
mem_cgroup_cancel_charge(new_page, memcg, true);
|
|
up_read(&mm->mmap_sem);
|
|
goto out_nolock;
|
|
}
|
|
|
|
up_read(&mm->mmap_sem);
|
|
/*
|
|
* 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.
|
|
*/
|
|
down_write(&mm->mmap_sem);
|
|
result = SCAN_ANY_PROCESS;
|
|
if (!mmget_still_valid(mm))
|
|
goto out;
|
|
result = hugepage_vma_revalidate(mm, address, &vma);
|
|
if (result)
|
|
goto out;
|
|
/* check if the pmd is still valid */
|
|
if (mm_find_pmd(mm, address) != pmd)
|
|
goto out;
|
|
|
|
anon_vma_lock_write(vma->anon_vma);
|
|
|
|
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm,
|
|
address, address + HPAGE_PMD_SIZE);
|
|
mmu_notifier_invalidate_range_start(&range);
|
|
|
|
pte = pte_offset_map(pmd, address);
|
|
pte_ptl = pte_lockptr(mm, pmd);
|
|
|
|
pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
|
|
/*
|
|
* After this gup_fast can't run anymore. This also removes
|
|
* any huge TLB entry from the CPU so we won't allow
|
|
* huge and small TLB entries for the same virtual address
|
|
* to avoid the risk of CPU bugs in that area.
|
|
*/
|
|
_pmd = pmdp_collapse_flush(vma, address, pmd);
|
|
spin_unlock(pmd_ptl);
|
|
mmu_notifier_invalidate_range_end(&range);
|
|
|
|
spin_lock(pte_ptl);
|
|
isolated = __collapse_huge_page_isolate(vma, address, pte);
|
|
spin_unlock(pte_ptl);
|
|
|
|
if (unlikely(!isolated)) {
|
|
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);
|
|
result = SCAN_FAIL;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* All pages are isolated and locked so anon_vma rmap
|
|
* can't run anymore.
|
|
*/
|
|
anon_vma_unlock_write(vma->anon_vma);
|
|
|
|
__collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
|
|
pte_unmap(pte);
|
|
__SetPageUptodate(new_page);
|
|
pgtable = pmd_pgtable(_pmd);
|
|
|
|
_pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
|
|
_pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
|
|
|
|
/*
|
|
* spin_lock() below is not the equivalent of smp_wmb(), so
|
|
* this is needed to avoid the copy_huge_page writes to become
|
|
* visible after the set_pmd_at() write.
|
|
*/
|
|
smp_wmb();
|
|
|
|
spin_lock(pmd_ptl);
|
|
BUG_ON(!pmd_none(*pmd));
|
|
page_add_new_anon_rmap(new_page, vma, address, true);
|
|
mem_cgroup_commit_charge(new_page, memcg, false, true);
|
|
count_memcg_events(memcg, THP_COLLAPSE_ALLOC, 1);
|
|
lru_cache_add_active_or_unevictable(new_page, 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;
|
|
|
|
khugepaged_pages_collapsed++;
|
|
result = SCAN_SUCCEED;
|
|
out_up_write:
|
|
up_write(&mm->mmap_sem);
|
|
out_nolock:
|
|
trace_mm_collapse_huge_page(mm, isolated, result);
|
|
return;
|
|
out:
|
|
mem_cgroup_cancel_charge(new_page, memcg, true);
|
|
goto out_up_write;
|
|
}
|
|
|
|
static int khugepaged_scan_pmd(struct mm_struct *mm,
|
|
struct vm_area_struct *vma,
|
|
unsigned long address,
|
|
struct page **hpage)
|
|
{
|
|
pmd_t *pmd;
|
|
pte_t *pte, *_pte;
|
|
int ret = 0, none_or_zero = 0, result = 0, referenced = 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);
|
|
|
|
pmd = mm_find_pmd(mm, address);
|
|
if (!pmd) {
|
|
result = SCAN_PMD_NULL;
|
|
goto out;
|
|
}
|
|
|
|
memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
|
|
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
|
|
for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
|
|
_pte++, _address += PAGE_SIZE) {
|
|
pte_t pteval = *_pte;
|
|
if (is_swap_pte(pteval)) {
|
|
if (++unmapped <= khugepaged_max_ptes_swap) {
|
|
continue;
|
|
} else {
|
|
result = SCAN_EXCEED_SWAP_PTE;
|
|
goto out_unmap;
|
|
}
|
|
}
|
|
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
|
|
if (!userfaultfd_armed(vma) &&
|
|
++none_or_zero <= khugepaged_max_ptes_none) {
|
|
continue;
|
|
} else {
|
|
result = SCAN_EXCEED_NONE_PTE;
|
|
goto out_unmap;
|
|
}
|
|
}
|
|
if (!pte_present(pteval)) {
|
|
result = SCAN_PTE_NON_PRESENT;
|
|
goto out_unmap;
|
|
}
|
|
if (pte_write(pteval))
|
|
writable = true;
|
|
|
|
page = vm_normal_page(vma, _address, pteval);
|
|
if (unlikely(!page)) {
|
|
result = SCAN_PAGE_NULL;
|
|
goto out_unmap;
|
|
}
|
|
|
|
/* TODO: teach khugepaged to collapse THP mapped with pte */
|
|
if (PageCompound(page)) {
|
|
result = SCAN_PAGE_COMPOUND;
|
|
goto out_unmap;
|
|
}
|
|
|
|
/*
|
|
* Record which node the original page is from and save this
|
|
* information to khugepaged_node_load[].
|
|
* Khupaged will allocate hugepage from the node has the max
|
|
* hit record.
|
|
*/
|
|
node = page_to_nid(page);
|
|
if (khugepaged_scan_abort(node)) {
|
|
result = SCAN_SCAN_ABORT;
|
|
goto out_unmap;
|
|
}
|
|
khugepaged_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;
|
|
}
|
|
|
|
/*
|
|
* cannot use mapcount: can't collapse if there's a gup pin.
|
|
* The page must only be referenced by the scanned process
|
|
* and page swap cache.
|
|
*/
|
|
if (page_count(page) != 1 + PageSwapCache(page)) {
|
|
result = SCAN_PAGE_COUNT;
|
|
goto out_unmap;
|
|
}
|
|
if (pte_young(pteval) ||
|
|
page_is_young(page) || PageReferenced(page) ||
|
|
mmu_notifier_test_young(vma->vm_mm, address))
|
|
referenced++;
|
|
}
|
|
if (writable) {
|
|
if (referenced) {
|
|
result = SCAN_SUCCEED;
|
|
ret = 1;
|
|
} else {
|
|
result = SCAN_LACK_REFERENCED_PAGE;
|
|
}
|
|
} else {
|
|
result = SCAN_PAGE_RO;
|
|
}
|
|
out_unmap:
|
|
pte_unmap_unlock(pte, ptl);
|
|
if (ret) {
|
|
node = khugepaged_find_target_node();
|
|
/* collapse_huge_page will return with the mmap_sem released */
|
|
collapse_huge_page(mm, address, hpage, node, referenced);
|
|
}
|
|
out:
|
|
trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
|
|
none_or_zero, result, unmapped);
|
|
return ret;
|
|
}
|
|
|
|
static void collect_mm_slot(struct mm_slot *mm_slot)
|
|
{
|
|
struct mm_struct *mm = mm_slot->mm;
|
|
|
|
lockdep_assert_held(&khugepaged_mm_lock);
|
|
|
|
if (khugepaged_test_exit(mm)) {
|
|
/* free mm_slot */
|
|
hash_del(&mm_slot->hash);
|
|
list_del(&mm_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 */
|
|
free_mm_slot(mm_slot);
|
|
mmdrop(mm);
|
|
}
|
|
}
|
|
|
|
#if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
|
|
/*
|
|
* Notify khugepaged that given addr of the mm is pte-mapped THP. Then
|
|
* khugepaged should try to collapse the page table.
|
|
*/
|
|
static int khugepaged_add_pte_mapped_thp(struct mm_struct *mm,
|
|
unsigned long addr)
|
|
{
|
|
struct mm_slot *mm_slot;
|
|
|
|
VM_BUG_ON(addr & ~HPAGE_PMD_MASK);
|
|
|
|
spin_lock(&khugepaged_mm_lock);
|
|
mm_slot = get_mm_slot(mm);
|
|
if (likely(mm_slot && mm_slot->nr_pte_mapped_thp < MAX_PTE_MAPPED_THP))
|
|
mm_slot->pte_mapped_thp[mm_slot->nr_pte_mapped_thp++] = addr;
|
|
spin_unlock(&khugepaged_mm_lock);
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* Try to collapse a pte-mapped THP for mm at address haddr.
|
|
*
|
|
* 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.
|
|
*/
|
|
void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr)
|
|
{
|
|
unsigned long haddr = addr & HPAGE_PMD_MASK;
|
|
struct vm_area_struct *vma = find_vma(mm, haddr);
|
|
struct page *hpage = NULL;
|
|
pte_t *start_pte, *pte;
|
|
pmd_t *pmd, _pmd;
|
|
spinlock_t *ptl;
|
|
int count = 0;
|
|
int i;
|
|
|
|
if (!vma || !vma->vm_file ||
|
|
vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE)
|
|
return;
|
|
|
|
/*
|
|
* This vm_flags may not have VM_HUGEPAGE if the page was not
|
|
* collapsed by this mm. But we can still collapse if the page is
|
|
* the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check()
|
|
* will not fail the vma for missing VM_HUGEPAGE
|
|
*/
|
|
if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE))
|
|
return;
|
|
|
|
pmd = mm_find_pmd(mm, haddr);
|
|
if (!pmd)
|
|
return;
|
|
|
|
start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl);
|
|
|
|
/* step 1: check all mapped PTEs are to the right huge page */
|
|
for (i = 0, addr = haddr, pte = start_pte;
|
|
i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) {
|
|
struct page *page;
|
|
|
|
/* empty pte, skip */
|
|
if (pte_none(*pte))
|
|
continue;
|
|
|
|
/* page swapped out, abort */
|
|
if (!pte_present(*pte))
|
|
goto abort;
|
|
|
|
page = vm_normal_page(vma, addr, *pte);
|
|
|
|
if (!page || !PageCompound(page))
|
|
goto abort;
|
|
|
|
if (!hpage) {
|
|
hpage = compound_head(page);
|
|
/*
|
|
* The mapping of the THP should not change.
|
|
*
|
|
* Note that uprobe, debugger, or MAP_PRIVATE may
|
|
* change the page table, but the new page will
|
|
* not pass PageCompound() check.
|
|
*/
|
|
if (WARN_ON(hpage->mapping != vma->vm_file->f_mapping))
|
|
goto abort;
|
|
}
|
|
|
|
/*
|
|
* Confirm the page maps to the correct subpage.
|
|
*
|
|
* Note that uprobe, debugger, or MAP_PRIVATE may change
|
|
* the page table, but the new page will not pass
|
|
* PageCompound() check.
|
|
*/
|
|
if (WARN_ON(hpage + i != page))
|
|
goto abort;
|
|
count++;
|
|
}
|
|
|
|
/* step 2: adjust rmap */
|
|
for (i = 0, addr = haddr, pte = start_pte;
|
|
i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) {
|
|
struct page *page;
|
|
|
|
if (pte_none(*pte))
|
|
continue;
|
|
page = vm_normal_page(vma, addr, *pte);
|
|
page_remove_rmap(page, false);
|
|
}
|
|
|
|
pte_unmap_unlock(start_pte, ptl);
|
|
|
|
/* step 3: set proper refcount and mm_counters. */
|
|
if (hpage) {
|
|
page_ref_sub(hpage, count);
|
|
add_mm_counter(vma->vm_mm, mm_counter_file(hpage), -count);
|
|
}
|
|
|
|
/* step 4: collapse pmd */
|
|
ptl = pmd_lock(vma->vm_mm, pmd);
|
|
_pmd = pmdp_collapse_flush(vma, addr, pmd);
|
|
spin_unlock(ptl);
|
|
mm_dec_nr_ptes(mm);
|
|
pte_free(mm, pmd_pgtable(_pmd));
|
|
return;
|
|
|
|
abort:
|
|
pte_unmap_unlock(start_pte, ptl);
|
|
}
|
|
|
|
static int khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot)
|
|
{
|
|
struct mm_struct *mm = mm_slot->mm;
|
|
int i;
|
|
|
|
if (likely(mm_slot->nr_pte_mapped_thp == 0))
|
|
return 0;
|
|
|
|
if (!down_write_trylock(&mm->mmap_sem))
|
|
return -EBUSY;
|
|
|
|
if (unlikely(khugepaged_test_exit(mm)))
|
|
goto out;
|
|
|
|
for (i = 0; i < mm_slot->nr_pte_mapped_thp; i++)
|
|
collapse_pte_mapped_thp(mm, mm_slot->pte_mapped_thp[i]);
|
|
|
|
out:
|
|
mm_slot->nr_pte_mapped_thp = 0;
|
|
up_write(&mm->mmap_sem);
|
|
return 0;
|
|
}
|
|
|
|
static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
|
|
{
|
|
struct vm_area_struct *vma;
|
|
unsigned long addr;
|
|
pmd_t *pmd, _pmd;
|
|
|
|
i_mmap_lock_write(mapping);
|
|
vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
|
|
/*
|
|
* Check vma->anon_vma to exclude MAP_PRIVATE mappings that
|
|
* got written to. These VMAs are likely not worth investing
|
|
* down_write(mmap_sem) as PMD-mapping is likely to be split
|
|
* later.
|
|
*
|
|
* Not that vma->anon_vma check is racy: it can be set up after
|
|
* the check but before we took mmap_sem 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.
|
|
*/
|
|
if (vma->anon_vma)
|
|
continue;
|
|
addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
|
|
if (addr & ~HPAGE_PMD_MASK)
|
|
continue;
|
|
if (vma->vm_end < addr + HPAGE_PMD_SIZE)
|
|
continue;
|
|
pmd = mm_find_pmd(vma->vm_mm, addr);
|
|
if (!pmd)
|
|
continue;
|
|
/*
|
|
* We need exclusive mmap_sem to retract page table.
|
|
*
|
|
* We use trylock due to lock inversion: we need to acquire
|
|
* mmap_sem while holding page lock. Fault path does it in
|
|
* reverse order. Trylock is a way to avoid deadlock.
|
|
*/
|
|
if (down_write_trylock(&vma->vm_mm->mmap_sem)) {
|
|
spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd);
|
|
/* assume page table is clear */
|
|
_pmd = pmdp_collapse_flush(vma, addr, pmd);
|
|
spin_unlock(ptl);
|
|
up_write(&vma->vm_mm->mmap_sem);
|
|
mm_dec_nr_ptes(vma->vm_mm);
|
|
pte_free(vma->vm_mm, pmd_pgtable(_pmd));
|
|
} else {
|
|
/* Try again later */
|
|
khugepaged_add_pte_mapped_thp(vma->vm_mm, addr);
|
|
}
|
|
}
|
|
i_mmap_unlock_write(mapping);
|
|
}
|
|
|
|
/**
|
|
* collapse_file - collapse filemap/tmpfs/shmem pages into huge one.
|
|
*
|
|
* Basic scheme is simple, details are more complex:
|
|
* - allocate and lock a new huge page;
|
|
* - scan page cache replacing old pages with the new one
|
|
* + swap/gup in pages if necessary;
|
|
* + fill in gaps;
|
|
* + keep old pages around in case rollback is required;
|
|
* - if replacing succeeds:
|
|
* + copy data over;
|
|
* + free old pages;
|
|
* + unlock huge page;
|
|
* - if replacing failed;
|
|
* + put all pages back and unfreeze them;
|
|
* + restore gaps in the page cache;
|
|
* + unlock and free huge page;
|
|
*/
|
|
static void collapse_file(struct mm_struct *mm,
|
|
struct file *file, pgoff_t start,
|
|
struct page **hpage, int node)
|
|
{
|
|
struct address_space *mapping = file->f_mapping;
|
|
gfp_t gfp;
|
|
struct page *new_page;
|
|
struct mem_cgroup *memcg;
|
|
pgoff_t index, end = start + HPAGE_PMD_NR;
|
|
LIST_HEAD(pagelist);
|
|
XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
|
|
int nr_none = 0, result = SCAN_SUCCEED;
|
|
bool is_shmem = shmem_file(file);
|
|
|
|
VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
|
|
VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
|
|
|
|
/* Only allocate from the target node */
|
|
gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
|
|
|
|
new_page = khugepaged_alloc_page(hpage, gfp, node);
|
|
if (!new_page) {
|
|
result = SCAN_ALLOC_HUGE_PAGE_FAIL;
|
|
goto out;
|
|
}
|
|
|
|
if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
|
|
result = SCAN_CGROUP_CHARGE_FAIL;
|
|
goto out;
|
|
}
|
|
|
|
/* This will be less messy when we use multi-index entries */
|
|
do {
|
|
xas_lock_irq(&xas);
|
|
xas_create_range(&xas);
|
|
if (!xas_error(&xas))
|
|
break;
|
|
xas_unlock_irq(&xas);
|
|
if (!xas_nomem(&xas, GFP_KERNEL)) {
|
|
mem_cgroup_cancel_charge(new_page, memcg, true);
|
|
result = SCAN_FAIL;
|
|
goto out;
|
|
}
|
|
} while (1);
|
|
|
|
__SetPageLocked(new_page);
|
|
if (is_shmem)
|
|
__SetPageSwapBacked(new_page);
|
|
new_page->index = start;
|
|
new_page->mapping = mapping;
|
|
|
|
/*
|
|
* At this point the new_page is locked and not up-to-date.
|
|
* It's safe to insert it into the page cache, because nobody would
|
|
* be able to map it or use it in another way until we unlock it.
|
|
*/
|
|
|
|
xas_set(&xas, start);
|
|
for (index = start; index < end; index++) {
|
|
struct page *page = xas_next(&xas);
|
|
|
|
VM_BUG_ON(index != xas.xa_index);
|
|
if (is_shmem) {
|
|
if (!page) {
|
|
/*
|
|
* Stop if extent has been truncated or
|
|
* hole-punched, and is now completely
|
|
* empty.
|
|
*/
|
|
if (index == start) {
|
|
if (!xas_next_entry(&xas, end - 1)) {
|
|
result = SCAN_TRUNCATED;
|
|
goto xa_locked;
|
|
}
|
|
xas_set(&xas, index);
|
|
}
|
|
if (!shmem_charge(mapping->host, 1)) {
|
|
result = SCAN_FAIL;
|
|
goto xa_locked;
|
|
}
|
|
xas_store(&xas, new_page);
|
|
nr_none++;
|
|
continue;
|
|
}
|
|
|
|
if (xa_is_value(page) || !PageUptodate(page)) {
|
|
xas_unlock_irq(&xas);
|
|
/* swap in or instantiate fallocated page */
|
|
if (shmem_getpage(mapping->host, index, &page,
|
|
SGP_NOHUGE)) {
|
|
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;
|
|
}
|
|
} else { /* !is_shmem */
|
|
if (!page || xa_is_value(page)) {
|
|
xas_unlock_irq(&xas);
|
|
page_cache_sync_readahead(mapping, &file->f_ra,
|
|
file, index,
|
|
PAGE_SIZE);
|
|
/* drain pagevecs to help isolate_lru_page() */
|
|
lru_add_drain();
|
|
page = find_lock_page(mapping, index);
|
|
if (unlikely(page == NULL)) {
|
|
result = SCAN_FAIL;
|
|
goto xa_unlocked;
|
|
}
|
|
} else if (PageDirty(page)) {
|
|
/*
|
|
* khugepaged only works on read-only fd,
|
|
* so this page is dirty because it hasn't
|
|
* been flushed since first write. There
|
|
* won't be new dirty pages.
|
|
*
|
|
* Trigger async flush here and hope the
|
|
* writeback is done when khugepaged
|
|
* revisits this page.
|
|
*
|
|
* This is a one-off situation. We are not
|
|
* forcing writeback in loop.
|
|
*/
|
|
xas_unlock_irq(&xas);
|
|
filemap_flush(mapping);
|
|
result = SCAN_FAIL;
|
|
goto xa_unlocked;
|
|
} else if (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.
|
|
*/
|
|
if (PageTransCompound(page)) {
|
|
result = SCAN_PAGE_COMPOUND;
|
|
goto out_unlock;
|
|
}
|
|
|
|
if (page_mapping(page) != mapping) {
|
|
result = SCAN_TRUNCATED;
|
|
goto out_unlock;
|
|
}
|
|
|
|
if (!is_shmem && PageDirty(page)) {
|
|
/*
|
|
* khugepaged only works on read-only fd, so this
|
|
* page is dirty because it hasn't been flushed
|
|
* since first write.
|
|
*/
|
|
result = SCAN_FAIL;
|
|
goto out_unlock;
|
|
}
|
|
|
|
if (isolate_lru_page(page)) {
|
|
result = SCAN_DEL_PAGE_LRU;
|
|
goto out_unlock;
|
|
}
|
|
|
|
if (page_has_private(page) &&
|
|
!try_to_release_page(page, GFP_KERNEL)) {
|
|
result = SCAN_PAGE_HAS_PRIVATE;
|
|
goto out_unlock;
|
|
}
|
|
|
|
if (page_mapped(page))
|
|
unmap_mapping_pages(mapping, index, 1, false);
|
|
|
|
xas_lock_irq(&xas);
|
|
xas_set(&xas, index);
|
|
|
|
VM_BUG_ON_PAGE(page != xas_load(&xas), page);
|
|
VM_BUG_ON_PAGE(page_mapped(page), page);
|
|
|
|
/*
|
|
* The page is expected to have page_count() == 3:
|
|
* - we hold a pin on it;
|
|
* - one reference from page cache;
|
|
* - one from isolate_lru_page;
|
|
*/
|
|
if (!page_ref_freeze(page, 3)) {
|
|
result = SCAN_PAGE_COUNT;
|
|
xas_unlock_irq(&xas);
|
|
putback_lru_page(page);
|
|
goto out_unlock;
|
|
}
|
|
|
|
/*
|
|
* Add the page to the list to be able to undo the collapse if
|
|
* something go wrong.
|
|
*/
|
|
list_add_tail(&page->lru, &pagelist);
|
|
|
|
/* Finally, replace with the new page. */
|
|
xas_store(&xas, new_page);
|
|
continue;
|
|
out_unlock:
|
|
unlock_page(page);
|
|
put_page(page);
|
|
goto xa_unlocked;
|
|
}
|
|
|
|
if (is_shmem)
|
|
__inc_node_page_state(new_page, NR_SHMEM_THPS);
|
|
else {
|
|
__inc_node_page_state(new_page, NR_FILE_THPS);
|
|
filemap_nr_thps_inc(mapping);
|
|
}
|
|
|
|
if (nr_none) {
|
|
struct zone *zone = page_zone(new_page);
|
|
|
|
__mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
|
|
if (is_shmem)
|
|
__mod_node_page_state(zone->zone_pgdat,
|
|
NR_SHMEM, nr_none);
|
|
}
|
|
|
|
xa_locked:
|
|
xas_unlock_irq(&xas);
|
|
xa_unlocked:
|
|
|
|
if (result == SCAN_SUCCEED) {
|
|
struct page *page, *tmp;
|
|
|
|
/*
|
|
* Replacing old pages with new one has succeeded, now we
|
|
* need to copy the content and free the old pages.
|
|
*/
|
|
index = start;
|
|
list_for_each_entry_safe(page, tmp, &pagelist, lru) {
|
|
while (index < page->index) {
|
|
clear_highpage(new_page + (index % HPAGE_PMD_NR));
|
|
index++;
|
|
}
|
|
copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
|
|
page);
|
|
list_del(&page->lru);
|
|
page->mapping = NULL;
|
|
page_ref_unfreeze(page, 1);
|
|
ClearPageActive(page);
|
|
ClearPageUnevictable(page);
|
|
unlock_page(page);
|
|
put_page(page);
|
|
index++;
|
|
}
|
|
while (index < end) {
|
|
clear_highpage(new_page + (index % HPAGE_PMD_NR));
|
|
index++;
|
|
}
|
|
|
|
SetPageUptodate(new_page);
|
|
page_ref_add(new_page, HPAGE_PMD_NR - 1);
|
|
mem_cgroup_commit_charge(new_page, memcg, false, true);
|
|
|
|
if (is_shmem) {
|
|
set_page_dirty(new_page);
|
|
lru_cache_add_anon(new_page);
|
|
} else {
|
|
lru_cache_add_file(new_page);
|
|
}
|
|
count_memcg_events(memcg, THP_COLLAPSE_ALLOC, 1);
|
|
|
|
/*
|
|
* Remove pte page tables, so we can re-fault the page as huge.
|
|
*/
|
|
retract_page_tables(mapping, start);
|
|
*hpage = NULL;
|
|
|
|
khugepaged_pages_collapsed++;
|
|
} else {
|
|
struct page *page;
|
|
|
|
/* Something went wrong: roll back page cache changes */
|
|
xas_lock_irq(&xas);
|
|
mapping->nrpages -= nr_none;
|
|
|
|
if (is_shmem)
|
|
shmem_uncharge(mapping->host, nr_none);
|
|
|
|
xas_set(&xas, start);
|
|
xas_for_each(&xas, page, end - 1) {
|
|
page = list_first_entry_or_null(&pagelist,
|
|
struct page, lru);
|
|
if (!page || xas.xa_index < page->index) {
|
|
if (!nr_none)
|
|
break;
|
|
nr_none--;
|
|
/* Put holes back where they were */
|
|
xas_store(&xas, NULL);
|
|
continue;
|
|
}
|
|
|
|
VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
|
|
|
|
/* Unfreeze the page. */
|
|
list_del(&page->lru);
|
|
page_ref_unfreeze(page, 2);
|
|
xas_store(&xas, page);
|
|
xas_pause(&xas);
|
|
xas_unlock_irq(&xas);
|
|
unlock_page(page);
|
|
putback_lru_page(page);
|
|
xas_lock_irq(&xas);
|
|
}
|
|
VM_BUG_ON(nr_none);
|
|
xas_unlock_irq(&xas);
|
|
|
|
mem_cgroup_cancel_charge(new_page, memcg, true);
|
|
new_page->mapping = NULL;
|
|
}
|
|
|
|
unlock_page(new_page);
|
|
out:
|
|
VM_BUG_ON(!list_empty(&pagelist));
|
|
/* TODO: tracepoints */
|
|
}
|
|
|
|
static void khugepaged_scan_file(struct mm_struct *mm,
|
|
struct file *file, pgoff_t start, struct page **hpage)
|
|
{
|
|
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(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
|
|
rcu_read_lock();
|
|
xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) {
|
|
if (xas_retry(&xas, page))
|
|
continue;
|
|
|
|
if (xa_is_value(page)) {
|
|
if (++swap > khugepaged_max_ptes_swap) {
|
|
result = SCAN_EXCEED_SWAP_PTE;
|
|
break;
|
|
}
|
|
continue;
|
|
}
|
|
|
|
if (PageTransCompound(page)) {
|
|
result = SCAN_PAGE_COMPOUND;
|
|
break;
|
|
}
|
|
|
|
node = page_to_nid(page);
|
|
if (khugepaged_scan_abort(node)) {
|
|
result = SCAN_SCAN_ABORT;
|
|
break;
|
|
}
|
|
khugepaged_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 (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
|
|
result = SCAN_EXCEED_NONE_PTE;
|
|
} else {
|
|
node = khugepaged_find_target_node();
|
|
collapse_file(mm, file, start, hpage, node);
|
|
}
|
|
}
|
|
|
|
/* TODO: tracepoints */
|
|
}
|
|
#else
|
|
static void khugepaged_scan_file(struct mm_struct *mm,
|
|
struct file *file, pgoff_t start, struct page **hpage)
|
|
{
|
|
BUILD_BUG();
|
|
}
|
|
|
|
static int khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
|
|
struct page **hpage)
|
|
__releases(&khugepaged_mm_lock)
|
|
__acquires(&khugepaged_mm_lock)
|
|
{
|
|
struct mm_slot *mm_slot;
|
|
struct mm_struct *mm;
|
|
struct vm_area_struct *vma;
|
|
int progress = 0;
|
|
|
|
VM_BUG_ON(!pages);
|
|
lockdep_assert_held(&khugepaged_mm_lock);
|
|
|
|
if (khugepaged_scan.mm_slot)
|
|
mm_slot = khugepaged_scan.mm_slot;
|
|
else {
|
|
mm_slot = list_entry(khugepaged_scan.mm_head.next,
|
|
struct mm_slot, mm_node);
|
|
khugepaged_scan.address = 0;
|
|
khugepaged_scan.mm_slot = mm_slot;
|
|
}
|
|
spin_unlock(&khugepaged_mm_lock);
|
|
khugepaged_collapse_pte_mapped_thps(mm_slot);
|
|
|
|
mm = mm_slot->mm;
|
|
/*
|
|
* Don't wait for semaphore (to avoid long wait times). Just move to
|
|
* the next mm on the list.
|
|
*/
|
|
vma = NULL;
|
|
if (unlikely(!down_read_trylock(&mm->mmap_sem)))
|
|
goto breakouterloop_mmap_sem;
|
|
if (likely(!khugepaged_test_exit(mm)))
|
|
vma = find_vma(mm, khugepaged_scan.address);
|
|
|
|
progress++;
|
|
for (; vma; vma = vma->vm_next) {
|
|
unsigned long hstart, hend;
|
|
|
|
cond_resched();
|
|
if (unlikely(khugepaged_test_exit(mm))) {
|
|
progress++;
|
|
break;
|
|
}
|
|
if (!hugepage_vma_check(vma, vma->vm_flags)) {
|
|
skip:
|
|
progress++;
|
|
continue;
|
|
}
|
|
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
|
|
hend = vma->vm_end & HPAGE_PMD_MASK;
|
|
if (hstart >= hend)
|
|
goto skip;
|
|
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) {
|
|
int ret;
|
|
cond_resched();
|
|
if (unlikely(khugepaged_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;
|
|
pgoff_t pgoff = linear_page_index(vma,
|
|
khugepaged_scan.address);
|
|
|
|
if (shmem_file(vma->vm_file)
|
|
&& !shmem_huge_enabled(vma))
|
|
goto skip;
|
|
file = get_file(vma->vm_file);
|
|
up_read(&mm->mmap_sem);
|
|
ret = 1;
|
|
khugepaged_scan_file(mm, file, pgoff, hpage);
|
|
fput(file);
|
|
} else {
|
|
ret = khugepaged_scan_pmd(mm, vma,
|
|
khugepaged_scan.address,
|
|
hpage);
|
|
}
|
|
/* move to next address */
|
|
khugepaged_scan.address += HPAGE_PMD_SIZE;
|
|
progress += HPAGE_PMD_NR;
|
|
if (ret)
|
|
/* we released mmap_sem so break loop */
|
|
goto breakouterloop_mmap_sem;
|
|
if (progress >= pages)
|
|
goto breakouterloop;
|
|
}
|
|
}
|
|
breakouterloop:
|
|
up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
|
|
breakouterloop_mmap_sem:
|
|
|
|
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 (khugepaged_test_exit(mm) || !vma) {
|
|
/*
|
|
* Make sure that if mm_users is reaching zero while
|
|
* khugepaged runs here, khugepaged_exit will find
|
|
* mm_slot not pointing to the exiting mm.
|
|
*/
|
|
if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
|
|
khugepaged_scan.mm_slot = list_entry(
|
|
mm_slot->mm_node.next,
|
|
struct mm_slot, mm_node);
|
|
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) &&
|
|
khugepaged_enabled();
|
|
}
|
|
|
|
static int khugepaged_wait_event(void)
|
|
{
|
|
return !list_empty(&khugepaged_scan.mm_head) ||
|
|
kthread_should_stop();
|
|
}
|
|
|
|
static void khugepaged_do_scan(void)
|
|
{
|
|
struct page *hpage = NULL;
|
|
unsigned int progress = 0, pass_through_head = 0;
|
|
unsigned int pages = khugepaged_pages_to_scan;
|
|
bool wait = true;
|
|
|
|
barrier(); /* write khugepaged_pages_to_scan to local stack */
|
|
|
|
while (progress < pages) {
|
|
if (!khugepaged_prealloc_page(&hpage, &wait))
|
|
break;
|
|
|
|
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,
|
|
&hpage);
|
|
else
|
|
progress = pages;
|
|
spin_unlock(&khugepaged_mm_lock);
|
|
}
|
|
|
|
if (!IS_ERR_OR_NULL(hpage))
|
|
put_page(hpage);
|
|
}
|
|
|
|
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 (khugepaged_enabled())
|
|
wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
|
|
}
|
|
|
|
static int khugepaged(void *none)
|
|
{
|
|
struct mm_slot *mm_slot;
|
|
|
|
set_freezable();
|
|
set_user_nice(current, MAX_NICE);
|
|
|
|
while (!kthread_should_stop()) {
|
|
khugepaged_do_scan();
|
|
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;
|
|
|
|
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;
|
|
}
|
|
setup_per_zone_wmarks();
|
|
}
|
|
|
|
int start_stop_khugepaged(void)
|
|
{
|
|
static struct task_struct *khugepaged_thread __read_mostly;
|
|
static DEFINE_MUTEX(khugepaged_mutex);
|
|
int err = 0;
|
|
|
|
mutex_lock(&khugepaged_mutex);
|
|
if (khugepaged_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);
|
|
|
|
set_recommended_min_free_kbytes();
|
|
} else if (khugepaged_thread) {
|
|
kthread_stop(khugepaged_thread);
|
|
khugepaged_thread = NULL;
|
|
}
|
|
fail:
|
|
mutex_unlock(&khugepaged_mutex);
|
|
return err;
|
|
}
|