linux/mm/page_idle.c
Yang Shi f0849ac0b8 mm: thp: fix potential clearing to referenced flag in page_idle_clear_pte_refs_one()
For PTE-mapped THP, the compound THP has not been split to normal 4K
pages yet, the whole THP is considered referenced if any one of sub page
is referenced.

When walking PTE-mapped THP by pvmw, all relevant PTEs will be checked
to retrieve referenced bit.  But, the current code just returns the
result of the last PTE.  If the last PTE has not referenced, the
referenced flag will be cleared.

Just set referenced when ptep{pmdp}_clear_young_notify() returns true.

Link: http://lkml.kernel.org/r/1518212451-87134-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Reported-by: Gang Deng <gavin.dg@linux.alibaba.com>
Suggested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-05 21:36:25 -07:00

239 lines
5.5 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/fs.h>
#include <linux/sysfs.h>
#include <linux/kobject.h>
#include <linux/mm.h>
#include <linux/mmzone.h>
#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/mmu_notifier.h>
#include <linux/page_ext.h>
#include <linux/page_idle.h>
#define BITMAP_CHUNK_SIZE sizeof(u64)
#define BITMAP_CHUNK_BITS (BITMAP_CHUNK_SIZE * BITS_PER_BYTE)
/*
* Idle page tracking only considers user memory pages, for other types of
* pages the idle flag is always unset and an attempt to set it is silently
* ignored.
*
* We treat a page as a user memory page if it is on an LRU list, because it is
* always safe to pass such a page to rmap_walk(), which is essential for idle
* page tracking. With such an indicator of user pages we can skip isolated
* pages, but since there are not usually many of them, it will hardly affect
* the overall result.
*
* This function tries to get a user memory page by pfn as described above.
*/
static struct page *page_idle_get_page(unsigned long pfn)
{
struct page *page;
struct zone *zone;
if (!pfn_valid(pfn))
return NULL;
page = pfn_to_page(pfn);
if (!page || !PageLRU(page) ||
!get_page_unless_zero(page))
return NULL;
zone = page_zone(page);
spin_lock_irq(zone_lru_lock(zone));
if (unlikely(!PageLRU(page))) {
put_page(page);
page = NULL;
}
spin_unlock_irq(zone_lru_lock(zone));
return page;
}
static bool page_idle_clear_pte_refs_one(struct page *page,
struct vm_area_struct *vma,
unsigned long addr, void *arg)
{
struct page_vma_mapped_walk pvmw = {
.page = page,
.vma = vma,
.address = addr,
};
bool referenced = false;
while (page_vma_mapped_walk(&pvmw)) {
addr = pvmw.address;
if (pvmw.pte) {
/*
* For PTE-mapped THP, one sub page is referenced,
* the whole THP is referenced.
*/
if (ptep_clear_young_notify(vma, addr, pvmw.pte))
referenced = true;
} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
if (pmdp_clear_young_notify(vma, addr, pvmw.pmd))
referenced = true;
} else {
/* unexpected pmd-mapped page? */
WARN_ON_ONCE(1);
}
}
if (referenced) {
clear_page_idle(page);
/*
* We cleared the referenced bit in a mapping to this page. To
* avoid interference with page reclaim, mark it young so that
* page_referenced() will return > 0.
*/
set_page_young(page);
}
return true;
}
static void page_idle_clear_pte_refs(struct page *page)
{
/*
* Since rwc.arg is unused, rwc is effectively immutable, so we
* can make it static const to save some cycles and stack.
*/
static const struct rmap_walk_control rwc = {
.rmap_one = page_idle_clear_pte_refs_one,
.anon_lock = page_lock_anon_vma_read,
};
bool need_lock;
if (!page_mapped(page) ||
!page_rmapping(page))
return;
need_lock = !PageAnon(page) || PageKsm(page);
if (need_lock && !trylock_page(page))
return;
rmap_walk(page, (struct rmap_walk_control *)&rwc);
if (need_lock)
unlock_page(page);
}
static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
struct bin_attribute *attr, char *buf,
loff_t pos, size_t count)
{
u64 *out = (u64 *)buf;
struct page *page;
unsigned long pfn, end_pfn;
int bit;
if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
return -EINVAL;
pfn = pos * BITS_PER_BYTE;
if (pfn >= max_pfn)
return 0;
end_pfn = pfn + count * BITS_PER_BYTE;
if (end_pfn > max_pfn)
end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
for (; pfn < end_pfn; pfn++) {
bit = pfn % BITMAP_CHUNK_BITS;
if (!bit)
*out = 0ULL;
page = page_idle_get_page(pfn);
if (page) {
if (page_is_idle(page)) {
/*
* The page might have been referenced via a
* pte, in which case it is not idle. Clear
* refs and recheck.
*/
page_idle_clear_pte_refs(page);
if (page_is_idle(page))
*out |= 1ULL << bit;
}
put_page(page);
}
if (bit == BITMAP_CHUNK_BITS - 1)
out++;
cond_resched();
}
return (char *)out - buf;
}
static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
struct bin_attribute *attr, char *buf,
loff_t pos, size_t count)
{
const u64 *in = (u64 *)buf;
struct page *page;
unsigned long pfn, end_pfn;
int bit;
if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
return -EINVAL;
pfn = pos * BITS_PER_BYTE;
if (pfn >= max_pfn)
return -ENXIO;
end_pfn = pfn + count * BITS_PER_BYTE;
if (end_pfn > max_pfn)
end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
for (; pfn < end_pfn; pfn++) {
bit = pfn % BITMAP_CHUNK_BITS;
if ((*in >> bit) & 1) {
page = page_idle_get_page(pfn);
if (page) {
page_idle_clear_pte_refs(page);
set_page_idle(page);
put_page(page);
}
}
if (bit == BITMAP_CHUNK_BITS - 1)
in++;
cond_resched();
}
return (char *)in - buf;
}
static struct bin_attribute page_idle_bitmap_attr =
__BIN_ATTR(bitmap, S_IRUSR | S_IWUSR,
page_idle_bitmap_read, page_idle_bitmap_write, 0);
static struct bin_attribute *page_idle_bin_attrs[] = {
&page_idle_bitmap_attr,
NULL,
};
static const struct attribute_group page_idle_attr_group = {
.bin_attrs = page_idle_bin_attrs,
.name = "page_idle",
};
#ifndef CONFIG_64BIT
static bool need_page_idle(void)
{
return true;
}
struct page_ext_operations page_idle_ops = {
.need = need_page_idle,
};
#endif
static int __init page_idle_init(void)
{
int err;
err = sysfs_create_group(mm_kobj, &page_idle_attr_group);
if (err) {
pr_err("page_idle: register sysfs failed\n");
return err;
}
return 0;
}
subsys_initcall(page_idle_init);