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 */
page_idle_get_page(unsigned long pfn)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
page_idle_clear_pte_refs_one(struct folio * folio,struct vm_area_struct * vma,unsigned long addr,void * arg)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
page_idle_clear_pte_refs(struct page * page)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
page_idle_bitmap_read(struct file * file,struct kobject * kobj,struct bin_attribute * attr,char * buf,loff_t pos,size_t count)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
page_idle_bitmap_write(struct file * file,struct kobject * kobj,struct bin_attribute * attr,char * buf,loff_t pos,size_t count)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
page_idle_init(void)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
