1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/init.h> 3 #include <linux/bootmem.h> 4 #include <linux/fs.h> 5 #include <linux/sysfs.h> 6 #include <linux/kobject.h> 7 #include <linux/mm.h> 8 #include <linux/mmzone.h> 9 #include <linux/pagemap.h> 10 #include <linux/rmap.h> 11 #include <linux/mmu_notifier.h> 12 #include <linux/page_ext.h> 13 #include <linux/page_idle.h> 14 15 #define BITMAP_CHUNK_SIZE sizeof(u64) 16 #define BITMAP_CHUNK_BITS (BITMAP_CHUNK_SIZE * BITS_PER_BYTE) 17 18 /* 19 * Idle page tracking only considers user memory pages, for other types of 20 * pages the idle flag is always unset and an attempt to set it is silently 21 * ignored. 22 * 23 * We treat a page as a user memory page if it is on an LRU list, because it is 24 * always safe to pass such a page to rmap_walk(), which is essential for idle 25 * page tracking. With such an indicator of user pages we can skip isolated 26 * pages, but since there are not usually many of them, it will hardly affect 27 * the overall result. 28 * 29 * This function tries to get a user memory page by pfn as described above. 30 */ 31 static struct page *page_idle_get_page(unsigned long pfn) 32 { 33 struct page *page; 34 struct zone *zone; 35 36 if (!pfn_valid(pfn)) 37 return NULL; 38 39 page = pfn_to_page(pfn); 40 if (!page || !PageLRU(page) || 41 !get_page_unless_zero(page)) 42 return NULL; 43 44 zone = page_zone(page); 45 spin_lock_irq(zone_lru_lock(zone)); 46 if (unlikely(!PageLRU(page))) { 47 put_page(page); 48 page = NULL; 49 } 50 spin_unlock_irq(zone_lru_lock(zone)); 51 return page; 52 } 53 54 static bool page_idle_clear_pte_refs_one(struct page *page, 55 struct vm_area_struct *vma, 56 unsigned long addr, void *arg) 57 { 58 struct page_vma_mapped_walk pvmw = { 59 .page = page, 60 .vma = vma, 61 .address = addr, 62 }; 63 bool referenced = false; 64 65 while (page_vma_mapped_walk(&pvmw)) { 66 addr = pvmw.address; 67 if (pvmw.pte) { 68 /* 69 * For PTE-mapped THP, one sub page is referenced, 70 * the whole THP is referenced. 71 */ 72 if (ptep_clear_young_notify(vma, addr, pvmw.pte)) 73 referenced = true; 74 } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { 75 if (pmdp_clear_young_notify(vma, addr, pvmw.pmd)) 76 referenced = true; 77 } else { 78 /* unexpected pmd-mapped page? */ 79 WARN_ON_ONCE(1); 80 } 81 } 82 83 if (referenced) { 84 clear_page_idle(page); 85 /* 86 * We cleared the referenced bit in a mapping to this page. To 87 * avoid interference with page reclaim, mark it young so that 88 * page_referenced() will return > 0. 89 */ 90 set_page_young(page); 91 } 92 return true; 93 } 94 95 static void page_idle_clear_pte_refs(struct page *page) 96 { 97 /* 98 * Since rwc.arg is unused, rwc is effectively immutable, so we 99 * can make it static const to save some cycles and stack. 100 */ 101 static const struct rmap_walk_control rwc = { 102 .rmap_one = page_idle_clear_pte_refs_one, 103 .anon_lock = page_lock_anon_vma_read, 104 }; 105 bool need_lock; 106 107 if (!page_mapped(page) || 108 !page_rmapping(page)) 109 return; 110 111 need_lock = !PageAnon(page) || PageKsm(page); 112 if (need_lock && !trylock_page(page)) 113 return; 114 115 rmap_walk(page, (struct rmap_walk_control *)&rwc); 116 117 if (need_lock) 118 unlock_page(page); 119 } 120 121 static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj, 122 struct bin_attribute *attr, char *buf, 123 loff_t pos, size_t count) 124 { 125 u64 *out = (u64 *)buf; 126 struct page *page; 127 unsigned long pfn, end_pfn; 128 int bit; 129 130 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) 131 return -EINVAL; 132 133 pfn = pos * BITS_PER_BYTE; 134 if (pfn >= max_pfn) 135 return 0; 136 137 end_pfn = pfn + count * BITS_PER_BYTE; 138 if (end_pfn > max_pfn) 139 end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS); 140 141 for (; pfn < end_pfn; pfn++) { 142 bit = pfn % BITMAP_CHUNK_BITS; 143 if (!bit) 144 *out = 0ULL; 145 page = page_idle_get_page(pfn); 146 if (page) { 147 if (page_is_idle(page)) { 148 /* 149 * The page might have been referenced via a 150 * pte, in which case it is not idle. Clear 151 * refs and recheck. 152 */ 153 page_idle_clear_pte_refs(page); 154 if (page_is_idle(page)) 155 *out |= 1ULL << bit; 156 } 157 put_page(page); 158 } 159 if (bit == BITMAP_CHUNK_BITS - 1) 160 out++; 161 cond_resched(); 162 } 163 return (char *)out - buf; 164 } 165 166 static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj, 167 struct bin_attribute *attr, char *buf, 168 loff_t pos, size_t count) 169 { 170 const u64 *in = (u64 *)buf; 171 struct page *page; 172 unsigned long pfn, end_pfn; 173 int bit; 174 175 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) 176 return -EINVAL; 177 178 pfn = pos * BITS_PER_BYTE; 179 if (pfn >= max_pfn) 180 return -ENXIO; 181 182 end_pfn = pfn + count * BITS_PER_BYTE; 183 if (end_pfn > max_pfn) 184 end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS); 185 186 for (; pfn < end_pfn; pfn++) { 187 bit = pfn % BITMAP_CHUNK_BITS; 188 if ((*in >> bit) & 1) { 189 page = page_idle_get_page(pfn); 190 if (page) { 191 page_idle_clear_pte_refs(page); 192 set_page_idle(page); 193 put_page(page); 194 } 195 } 196 if (bit == BITMAP_CHUNK_BITS - 1) 197 in++; 198 cond_resched(); 199 } 200 return (char *)in - buf; 201 } 202 203 static struct bin_attribute page_idle_bitmap_attr = 204 __BIN_ATTR(bitmap, S_IRUSR | S_IWUSR, 205 page_idle_bitmap_read, page_idle_bitmap_write, 0); 206 207 static struct bin_attribute *page_idle_bin_attrs[] = { 208 &page_idle_bitmap_attr, 209 NULL, 210 }; 211 212 static const struct attribute_group page_idle_attr_group = { 213 .bin_attrs = page_idle_bin_attrs, 214 .name = "page_idle", 215 }; 216 217 #ifndef CONFIG_64BIT 218 static bool need_page_idle(void) 219 { 220 return true; 221 } 222 struct page_ext_operations page_idle_ops = { 223 .need = need_page_idle, 224 }; 225 #endif 226 227 static int __init page_idle_init(void) 228 { 229 int err; 230 231 err = sysfs_create_group(mm_kobj, &page_idle_attr_group); 232 if (err) { 233 pr_err("page_idle: register sysfs failed\n"); 234 return err; 235 } 236 return 0; 237 } 238 subsys_initcall(page_idle_init); 239