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![SeongJae Park](/assets/img/avatar_default.png)
'Idle page tracking' users can pass random pfn that might be mapped to an offline page. To avoid accessing such pages, this commit modifies the 'page_idle_get_page()' to use 'pfn_to_online_page()' instead of 'pfn_valid()' and 'pfn_to_page()' combination, so that the pfn mapped to an offline page can be skipped. Reported-by: David Hildenbrand <david@redhat.com> Signed-off-by: SeongJae Park <sjpark@amazon.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Link: http://lkml.kernel.org/r/20200605092502.18018-2-sjpark@amazon.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
235 lines
5.5 KiB
C
235 lines
5.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/init.h>
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#include <linux/memblock.h>
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#include <linux/fs.h>
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#include <linux/sysfs.h>
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#include <linux/kobject.h>
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#include <linux/memory_hotplug.h>
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#include <linux/mm.h>
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#include <linux/mmzone.h>
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#include <linux/pagemap.h>
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#include <linux/rmap.h>
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#include <linux/mmu_notifier.h>
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#include <linux/page_ext.h>
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#include <linux/page_idle.h>
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#define BITMAP_CHUNK_SIZE sizeof(u64)
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#define BITMAP_CHUNK_BITS (BITMAP_CHUNK_SIZE * BITS_PER_BYTE)
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/*
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* Idle page tracking only considers user memory pages, for other types of
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* pages the idle flag is always unset and an attempt to set it is silently
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* ignored.
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*
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* We treat a page as a user memory page if it is on an LRU list, because it is
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* always safe to pass such a page to rmap_walk(), which is essential for idle
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* page tracking. With such an indicator of user pages we can skip isolated
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* pages, but since there are not usually many of them, it will hardly affect
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* the overall result.
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*
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* This function tries to get a user memory page by pfn as described above.
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*/
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static struct page *page_idle_get_page(unsigned long pfn)
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{
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struct page *page = pfn_to_online_page(pfn);
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pg_data_t *pgdat;
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if (!page || !PageLRU(page) ||
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!get_page_unless_zero(page))
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return NULL;
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pgdat = page_pgdat(page);
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spin_lock_irq(&pgdat->lru_lock);
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if (unlikely(!PageLRU(page))) {
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put_page(page);
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page = NULL;
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}
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spin_unlock_irq(&pgdat->lru_lock);
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return page;
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}
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static bool page_idle_clear_pte_refs_one(struct page *page,
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struct vm_area_struct *vma,
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unsigned long addr, void *arg)
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{
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struct page_vma_mapped_walk pvmw = {
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.page = page,
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.vma = vma,
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.address = addr,
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};
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bool referenced = false;
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while (page_vma_mapped_walk(&pvmw)) {
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addr = pvmw.address;
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if (pvmw.pte) {
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/*
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* For PTE-mapped THP, one sub page is referenced,
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* the whole THP is referenced.
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*/
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if (ptep_clear_young_notify(vma, addr, pvmw.pte))
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referenced = true;
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} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
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if (pmdp_clear_young_notify(vma, addr, pvmw.pmd))
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referenced = true;
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} else {
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/* unexpected pmd-mapped page? */
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WARN_ON_ONCE(1);
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}
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}
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if (referenced) {
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clear_page_idle(page);
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/*
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* We cleared the referenced bit in a mapping to this page. To
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* avoid interference with page reclaim, mark it young so that
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* page_referenced() will return > 0.
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*/
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set_page_young(page);
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}
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return true;
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}
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static void page_idle_clear_pte_refs(struct page *page)
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{
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/*
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* Since rwc.arg is unused, rwc is effectively immutable, so we
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* can make it static const to save some cycles and stack.
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*/
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static const struct rmap_walk_control rwc = {
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.rmap_one = page_idle_clear_pte_refs_one,
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.anon_lock = page_lock_anon_vma_read,
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};
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bool need_lock;
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if (!page_mapped(page) ||
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!page_rmapping(page))
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return;
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need_lock = !PageAnon(page) || PageKsm(page);
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if (need_lock && !trylock_page(page))
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return;
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rmap_walk(page, (struct rmap_walk_control *)&rwc);
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if (need_lock)
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unlock_page(page);
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}
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static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
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struct bin_attribute *attr, char *buf,
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loff_t pos, size_t count)
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{
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u64 *out = (u64 *)buf;
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struct page *page;
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unsigned long pfn, end_pfn;
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int bit;
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if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
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return -EINVAL;
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pfn = pos * BITS_PER_BYTE;
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if (pfn >= max_pfn)
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return 0;
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end_pfn = pfn + count * BITS_PER_BYTE;
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if (end_pfn > max_pfn)
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end_pfn = max_pfn;
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for (; pfn < end_pfn; pfn++) {
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bit = pfn % BITMAP_CHUNK_BITS;
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if (!bit)
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*out = 0ULL;
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page = page_idle_get_page(pfn);
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if (page) {
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if (page_is_idle(page)) {
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/*
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* The page might have been referenced via a
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* pte, in which case it is not idle. Clear
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* refs and recheck.
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*/
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page_idle_clear_pte_refs(page);
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if (page_is_idle(page))
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*out |= 1ULL << bit;
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}
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put_page(page);
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}
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if (bit == BITMAP_CHUNK_BITS - 1)
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out++;
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cond_resched();
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}
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return (char *)out - buf;
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}
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static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
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struct bin_attribute *attr, char *buf,
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loff_t pos, size_t count)
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{
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const u64 *in = (u64 *)buf;
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struct page *page;
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unsigned long pfn, end_pfn;
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int bit;
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if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE)
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return -EINVAL;
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pfn = pos * BITS_PER_BYTE;
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if (pfn >= max_pfn)
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return -ENXIO;
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end_pfn = pfn + count * BITS_PER_BYTE;
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if (end_pfn > max_pfn)
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end_pfn = max_pfn;
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for (; pfn < end_pfn; pfn++) {
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bit = pfn % BITMAP_CHUNK_BITS;
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if ((*in >> bit) & 1) {
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page = page_idle_get_page(pfn);
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if (page) {
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page_idle_clear_pte_refs(page);
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set_page_idle(page);
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put_page(page);
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}
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}
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if (bit == BITMAP_CHUNK_BITS - 1)
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in++;
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cond_resched();
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}
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return (char *)in - buf;
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}
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static struct bin_attribute page_idle_bitmap_attr =
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__BIN_ATTR(bitmap, 0600,
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page_idle_bitmap_read, page_idle_bitmap_write, 0);
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static struct bin_attribute *page_idle_bin_attrs[] = {
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&page_idle_bitmap_attr,
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NULL,
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};
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static const struct attribute_group page_idle_attr_group = {
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.bin_attrs = page_idle_bin_attrs,
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.name = "page_idle",
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};
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#ifndef CONFIG_64BIT
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static bool need_page_idle(void)
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{
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return true;
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}
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struct page_ext_operations page_idle_ops = {
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.need = need_page_idle,
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};
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#endif
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static int __init page_idle_init(void)
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{
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int err;
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err = sysfs_create_group(mm_kobj, &page_idle_attr_group);
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if (err) {
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pr_err("page_idle: register sysfs failed\n");
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return err;
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}
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return 0;
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}
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subsys_initcall(page_idle_init);
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