// 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, 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", }; #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);