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