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- // SPDX-License-Identifier: GPL-2.0
- #include <linux/init.h>
- #include <linux/memblock.h>
- #include <linux/fs.h>
- #include <linux/sysfs.h>
- #include <linux/kobject.h>
- #include <linux/memory_hotplug.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>
- #include "internal.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 = pfn_to_online_page(pfn);
- if (!page || !PageLRU(page) ||
- !get_page_unless_zero(page))
- return NULL;
- if (unlikely(!PageLRU(page))) {
- put_page(page);
- page = NULL;
- }
- return page;
- }
- static bool page_idle_clear_pte_refs_one(struct folio *folio,
- struct vm_area_struct *vma,
- unsigned long addr, void *arg)
- {
- DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, addr, 0);
- 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) {
- folio_clear_idle(folio);
- /*
- * We cleared the referenced bit in a mapping to this page. To
- * avoid interference with page reclaim, mark it young so that
- * folio_referenced() will return > 0.
- */
- folio_set_young(folio);
- }
- return true;
- }
- static void page_idle_clear_pte_refs(struct page *page)
- {
- struct folio *folio = page_folio(page);
- /*
- * Since rwc.try_lock is unused, rwc is effectively immutable, so we
- * can make it static to save some cycles and stack.
- */
- static struct rmap_walk_control rwc = {
- .rmap_one = page_idle_clear_pte_refs_one,
- .anon_lock = folio_lock_anon_vma_read,
- };
- bool need_lock;
- if (!folio_mapped(folio) || !folio_raw_mapping(folio))
- return;
- need_lock = !folio_test_anon(folio) || folio_test_ksm(folio);
- if (need_lock && !folio_trylock(folio))
- return;
- rmap_walk(folio, &rwc);
- if (need_lock)
- folio_unlock(folio);
- }
- 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 = max_pfn;
- 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 = max_pfn;
- 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, 0600,
- 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",
- };
- 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);
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