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 referenced = ptep_clear_young_notify(vma, addr, 69 pvmw.pte); 70 } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { 71 referenced = pmdp_clear_young_notify(vma, addr, 72 pvmw.pmd); 73 } else { 74 /* unexpected pmd-mapped page? */ 75 WARN_ON_ONCE(1); 76 } 77 } 78 79 if (referenced) { 80 clear_page_idle(page); 81 /* 82 * We cleared the referenced bit in a mapping to this page. To 83 * avoid interference with page reclaim, mark it young so that 84 * page_referenced() will return > 0. 85 */ 86 set_page_young(page); 87 } 88 return true; 89 } 90 91 static void page_idle_clear_pte_refs(struct page *page) 92 { 93 /* 94 * Since rwc.arg is unused, rwc is effectively immutable, so we 95 * can make it static const to save some cycles and stack. 96 */ 97 static const struct rmap_walk_control rwc = { 98 .rmap_one = page_idle_clear_pte_refs_one, 99 .anon_lock = page_lock_anon_vma_read, 100 }; 101 bool need_lock; 102 103 if (!page_mapped(page) || 104 !page_rmapping(page)) 105 return; 106 107 need_lock = !PageAnon(page) || PageKsm(page); 108 if (need_lock && !trylock_page(page)) 109 return; 110 111 rmap_walk(page, (struct rmap_walk_control *)&rwc); 112 113 if (need_lock) 114 unlock_page(page); 115 } 116 117 static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj, 118 struct bin_attribute *attr, char *buf, 119 loff_t pos, size_t count) 120 { 121 u64 *out = (u64 *)buf; 122 struct page *page; 123 unsigned long pfn, end_pfn; 124 int bit; 125 126 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) 127 return -EINVAL; 128 129 pfn = pos * BITS_PER_BYTE; 130 if (pfn >= max_pfn) 131 return 0; 132 133 end_pfn = pfn + count * BITS_PER_BYTE; 134 if (end_pfn > max_pfn) 135 end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS); 136 137 for (; pfn < end_pfn; pfn++) { 138 bit = pfn % BITMAP_CHUNK_BITS; 139 if (!bit) 140 *out = 0ULL; 141 page = page_idle_get_page(pfn); 142 if (page) { 143 if (page_is_idle(page)) { 144 /* 145 * The page might have been referenced via a 146 * pte, in which case it is not idle. Clear 147 * refs and recheck. 148 */ 149 page_idle_clear_pte_refs(page); 150 if (page_is_idle(page)) 151 *out |= 1ULL << bit; 152 } 153 put_page(page); 154 } 155 if (bit == BITMAP_CHUNK_BITS - 1) 156 out++; 157 cond_resched(); 158 } 159 return (char *)out - buf; 160 } 161 162 static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj, 163 struct bin_attribute *attr, char *buf, 164 loff_t pos, size_t count) 165 { 166 const u64 *in = (u64 *)buf; 167 struct page *page; 168 unsigned long pfn, end_pfn; 169 int bit; 170 171 if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) 172 return -EINVAL; 173 174 pfn = pos * BITS_PER_BYTE; 175 if (pfn >= max_pfn) 176 return -ENXIO; 177 178 end_pfn = pfn + count * BITS_PER_BYTE; 179 if (end_pfn > max_pfn) 180 end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS); 181 182 for (; pfn < end_pfn; pfn++) { 183 bit = pfn % BITMAP_CHUNK_BITS; 184 if ((*in >> bit) & 1) { 185 page = page_idle_get_page(pfn); 186 if (page) { 187 page_idle_clear_pte_refs(page); 188 set_page_idle(page); 189 put_page(page); 190 } 191 } 192 if (bit == BITMAP_CHUNK_BITS - 1) 193 in++; 194 cond_resched(); 195 } 196 return (char *)in - buf; 197 } 198 199 static struct bin_attribute page_idle_bitmap_attr = 200 __BIN_ATTR(bitmap, S_IRUSR | S_IWUSR, 201 page_idle_bitmap_read, page_idle_bitmap_write, 0); 202 203 static struct bin_attribute *page_idle_bin_attrs[] = { 204 &page_idle_bitmap_attr, 205 NULL, 206 }; 207 208 static const struct attribute_group page_idle_attr_group = { 209 .bin_attrs = page_idle_bin_attrs, 210 .name = "page_idle", 211 }; 212 213 #ifndef CONFIG_64BIT 214 static bool need_page_idle(void) 215 { 216 return true; 217 } 218 struct page_ext_operations page_idle_ops = { 219 .need = need_page_idle, 220 }; 221 #endif 222 223 static int __init page_idle_init(void) 224 { 225 int err; 226 227 err = sysfs_create_group(mm_kobj, &page_idle_attr_group); 228 if (err) { 229 pr_err("page_idle: register sysfs failed\n"); 230 return err; 231 } 232 return 0; 233 } 234 subsys_initcall(page_idle_init); 235