1// SPDX-License-Identifier: GPL-2.0 2#include <linux/init.h> 3#include <linux/memblock.h> 4#include <linux/fs.h> 5#include <linux/sysfs.h> 6#include <linux/kobject.h> 7#include <linux/memory_hotplug.h> 8#include <linux/mm.h> 9#include <linux/mmzone.h> 10#include <linux/pagemap.h> 11#include <linux/rmap.h> 12#include <linux/mmu_notifier.h> 13#include <linux/page_ext.h> 14#include <linux/page_idle.h> 15 16#define BITMAP_CHUNK_SIZE sizeof(u64) 17#define BITMAP_CHUNK_BITS (BITMAP_CHUNK_SIZE * BITS_PER_BYTE) 18 19/* 20 * Idle page tracking only considers user memory pages, for other types of 21 * pages the idle flag is always unset and an attempt to set it is silently 22 * ignored. 23 * 24 * We treat a page as a user memory page if it is on an LRU list, because it is 25 * always safe to pass such a page to rmap_walk(), which is essential for idle 26 * page tracking. With such an indicator of user pages we can skip isolated 27 * pages, but since there are not usually many of them, it will hardly affect 28 * the overall result. 29 * 30 * This function tries to get a user memory page by pfn as described above. 31 */ 32static struct page *page_idle_get_page(unsigned long pfn) 33{ 34 struct page *page = pfn_to_online_page(pfn); 35 pg_data_t *pgdat; 36 37 if (!page || !PageLRU(page) || 38 !get_page_unless_zero(page)) 39 return NULL; 40 41 pgdat = page_pgdat(page); 42 spin_lock_irq(&pgdat->lru_lock); 43 if (unlikely(!PageLRU(page))) { 44 put_page(page); 45 page = NULL; 46 } 47 spin_unlock_irq(&pgdat->lru_lock); 48 return page; 49} 50 51static bool page_idle_clear_pte_refs_one(struct page *page, 52 struct vm_area_struct *vma, 53 unsigned long addr, void *arg) 54{ 55 struct page_vma_mapped_walk pvmw = { 56 .page = page, 57 .vma = vma, 58 .address = addr, 59 }; 60 bool referenced = false; 61 62 while (page_vma_mapped_walk(&pvmw)) { 63 addr = pvmw.address; 64 if (pvmw.pte) { 65 /* 66 * For PTE-mapped THP, one sub page is referenced, 67 * the whole THP is referenced. 68 */ 69 if (ptep_clear_young_notify(vma, addr, pvmw.pte)) 70 referenced = true; 71 } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { 72 if (pmdp_clear_young_notify(vma, addr, pvmw.pmd)) 73 referenced = true; 74 } else { 75 /* unexpected pmd-mapped page? */ 76 WARN_ON_ONCE(1); 77 } 78 } 79 80 if (referenced) { 81 clear_page_idle(page); 82 /* 83 * We cleared the referenced bit in a mapping to this page. To 84 * avoid interference with page reclaim, mark it young so that 85 * page_referenced() will return > 0. 86 */ 87 set_page_young(page); 88 } 89 return true; 90} 91 92static void page_idle_clear_pte_refs(struct page *page) 93{ 94 /* 95 * Since rwc.arg is unused, rwc is effectively immutable, so we 96 * can make it static const to save some cycles and stack. 97 */ 98 static const struct rmap_walk_control rwc = { 99 .rmap_one = page_idle_clear_pte_refs_one, 100 .anon_lock = page_lock_anon_vma_read, 101 }; 102 bool need_lock; 103 104 if (!page_mapped(page) || 105 !page_rmapping(page)) 106 return; 107 108 need_lock = !PageAnon(page) || PageKsm(page); 109 if (need_lock && !trylock_page(page)) 110 return; 111 112 rmap_walk(page, (struct rmap_walk_control *)&rwc); 113 114 if (need_lock) 115 unlock_page(page); 116} 117 118static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj, 119 struct bin_attribute *attr, char *buf, 120 loff_t pos, size_t count) 121{ 122 u64 *out = (u64 *)buf; 123 struct page *page; 124 unsigned long pfn, end_pfn; 125 int bit; 126 127 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) 128 return -EINVAL; 129 130 pfn = pos * BITS_PER_BYTE; 131 if (pfn >= max_pfn) 132 return 0; 133 134 end_pfn = pfn + count * BITS_PER_BYTE; 135 if (end_pfn > max_pfn) 136 end_pfn = max_pfn; 137 138 for (; pfn < end_pfn; pfn++) { 139 bit = pfn % BITMAP_CHUNK_BITS; 140 if (!bit) 141 *out = 0ULL; 142 page = page_idle_get_page(pfn); 143 if (page) { 144 if (page_is_idle(page)) { 145 /* 146 * The page might have been referenced via a 147 * pte, in which case it is not idle. Clear 148 * refs and recheck. 149 */ 150 page_idle_clear_pte_refs(page); 151 if (page_is_idle(page)) 152 *out |= 1ULL << bit; 153 } 154 put_page(page); 155 } 156 if (bit == BITMAP_CHUNK_BITS - 1) 157 out++; 158 cond_resched(); 159 } 160 return (char *)out - buf; 161} 162 163static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj, 164 struct bin_attribute *attr, char *buf, 165 loff_t pos, size_t count) 166{ 167 const u64 *in = (u64 *)buf; 168 struct page *page; 169 unsigned long pfn, end_pfn; 170 int bit; 171 172 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) 173 return -EINVAL; 174 175 pfn = pos * BITS_PER_BYTE; 176 if (pfn >= max_pfn) 177 return -ENXIO; 178 179 end_pfn = pfn + count * BITS_PER_BYTE; 180 if (end_pfn > max_pfn) 181 end_pfn = max_pfn; 182 183 for (; pfn < end_pfn; pfn++) { 184 bit = pfn % BITMAP_CHUNK_BITS; 185 if ((*in >> bit) & 1) { 186 page = page_idle_get_page(pfn); 187 if (page) { 188 page_idle_clear_pte_refs(page); 189 set_page_idle(page); 190 put_page(page); 191 } 192 } 193 if (bit == BITMAP_CHUNK_BITS - 1) 194 in++; 195 cond_resched(); 196 } 197 return (char *)in - buf; 198} 199 200static struct bin_attribute page_idle_bitmap_attr = 201 __BIN_ATTR(bitmap, 0600, 202 page_idle_bitmap_read, page_idle_bitmap_write, 0); 203 204static struct bin_attribute *page_idle_bin_attrs[] = { 205 &page_idle_bitmap_attr, 206 NULL, 207}; 208 209static const struct attribute_group page_idle_attr_group = { 210 .bin_attrs = page_idle_bin_attrs, 211 .name = "page_idle", 212}; 213 214#ifndef CONFIG_64BIT 215static bool need_page_idle(void) 216{ 217 return true; 218} 219struct page_ext_operations page_idle_ops = { 220 .need = need_page_idle, 221}; 222#endif 223 224static int __init page_idle_init(void) 225{ 226 int err; 227 228 err = sysfs_create_group(mm_kobj, &page_idle_attr_group); 229 if (err) { 230 pr_err("page_idle: register sysfs failed\n"); 231 return err; 232 } 233 return 0; 234} 235subsys_initcall(page_idle_init); 236