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 folio *page_idle_get_folio(unsigned long pfn) |
35 | { |
36 | struct page *page = pfn_to_online_page(pfn); |
37 | struct folio *folio; |
38 | |
39 | if (!page || PageTail(page)) |
40 | return NULL; |
41 | |
42 | folio = page_folio(page); |
43 | if (!folio_test_lru(folio) || !folio_try_get(folio)) |
44 | return NULL; |
45 | if (unlikely(page_folio(page) != folio || !folio_test_lru(folio))) { |
46 | folio_put(folio); |
47 | folio = NULL; |
48 | } |
49 | return folio; |
50 | } |
51 | |
52 | static bool page_idle_clear_pte_refs_one(struct folio *folio, |
53 | struct vm_area_struct *vma, |
54 | unsigned long addr, void *arg) |
55 | { |
56 | DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, addr, 0); |
57 | bool referenced = false; |
58 | |
59 | while (page_vma_mapped_walk(pvmw: &pvmw)) { |
60 | addr = pvmw.address; |
61 | if (pvmw.pte) { |
62 | /* |
63 | * For PTE-mapped THP, one sub page is referenced, |
64 | * the whole THP is referenced. |
65 | */ |
66 | if (ptep_clear_young_notify(vma, addr, pvmw.pte)) |
67 | referenced = true; |
68 | } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { |
69 | if (pmdp_clear_young_notify(vma, addr, pvmw.pmd)) |
70 | referenced = true; |
71 | } else { |
72 | /* unexpected pmd-mapped page? */ |
73 | WARN_ON_ONCE(1); |
74 | } |
75 | } |
76 | |
77 | if (referenced) { |
78 | folio_clear_idle(folio); |
79 | /* |
80 | * We cleared the referenced bit in a mapping to this page. To |
81 | * avoid interference with page reclaim, mark it young so that |
82 | * folio_referenced() will return > 0. |
83 | */ |
84 | folio_set_young(folio); |
85 | } |
86 | return true; |
87 | } |
88 | |
89 | static void page_idle_clear_pte_refs(struct folio *folio) |
90 | { |
91 | /* |
92 | * Since rwc.try_lock is unused, rwc is effectively immutable, so we |
93 | * can make it static to save some cycles and stack. |
94 | */ |
95 | static struct rmap_walk_control rwc = { |
96 | .rmap_one = page_idle_clear_pte_refs_one, |
97 | .anon_lock = folio_lock_anon_vma_read, |
98 | }; |
99 | bool need_lock; |
100 | |
101 | if (!folio_mapped(folio) || !folio_raw_mapping(folio)) |
102 | return; |
103 | |
104 | need_lock = !folio_test_anon(folio) || folio_test_ksm(folio); |
105 | if (need_lock && !folio_trylock(folio)) |
106 | return; |
107 | |
108 | rmap_walk(folio, rwc: &rwc); |
109 | |
110 | if (need_lock) |
111 | folio_unlock(folio); |
112 | } |
113 | |
114 | static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj, |
115 | struct bin_attribute *attr, char *buf, |
116 | loff_t pos, size_t count) |
117 | { |
118 | u64 *out = (u64 *)buf; |
119 | struct folio *folio; |
120 | unsigned long pfn, end_pfn; |
121 | int bit; |
122 | |
123 | if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) |
124 | return -EINVAL; |
125 | |
126 | pfn = pos * BITS_PER_BYTE; |
127 | if (pfn >= max_pfn) |
128 | return 0; |
129 | |
130 | end_pfn = pfn + count * BITS_PER_BYTE; |
131 | if (end_pfn > max_pfn) |
132 | end_pfn = max_pfn; |
133 | |
134 | for (; pfn < end_pfn; pfn++) { |
135 | bit = pfn % BITMAP_CHUNK_BITS; |
136 | if (!bit) |
137 | *out = 0ULL; |
138 | folio = page_idle_get_folio(pfn); |
139 | if (folio) { |
140 | if (folio_test_idle(folio)) { |
141 | /* |
142 | * The page might have been referenced via a |
143 | * pte, in which case it is not idle. Clear |
144 | * refs and recheck. |
145 | */ |
146 | page_idle_clear_pte_refs(folio); |
147 | if (folio_test_idle(folio)) |
148 | *out |= 1ULL << bit; |
149 | } |
150 | folio_put(folio); |
151 | } |
152 | if (bit == BITMAP_CHUNK_BITS - 1) |
153 | out++; |
154 | cond_resched(); |
155 | } |
156 | return (char *)out - buf; |
157 | } |
158 | |
159 | static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj, |
160 | struct bin_attribute *attr, char *buf, |
161 | loff_t pos, size_t count) |
162 | { |
163 | const u64 *in = (u64 *)buf; |
164 | struct folio *folio; |
165 | unsigned long pfn, end_pfn; |
166 | int bit; |
167 | |
168 | if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) |
169 | return -EINVAL; |
170 | |
171 | pfn = pos * BITS_PER_BYTE; |
172 | if (pfn >= max_pfn) |
173 | return -ENXIO; |
174 | |
175 | end_pfn = pfn + count * BITS_PER_BYTE; |
176 | if (end_pfn > max_pfn) |
177 | end_pfn = max_pfn; |
178 | |
179 | for (; pfn < end_pfn; pfn++) { |
180 | bit = pfn % BITMAP_CHUNK_BITS; |
181 | if ((*in >> bit) & 1) { |
182 | folio = page_idle_get_folio(pfn); |
183 | if (folio) { |
184 | page_idle_clear_pte_refs(folio); |
185 | folio_set_idle(folio); |
186 | folio_put(folio); |
187 | } |
188 | } |
189 | if (bit == BITMAP_CHUNK_BITS - 1) |
190 | in++; |
191 | cond_resched(); |
192 | } |
193 | return (char *)in - buf; |
194 | } |
195 | |
196 | static struct bin_attribute page_idle_bitmap_attr = |
197 | __BIN_ATTR(bitmap, 0600, |
198 | page_idle_bitmap_read, page_idle_bitmap_write, 0); |
199 | |
200 | static struct bin_attribute *page_idle_bin_attrs[] = { |
201 | &page_idle_bitmap_attr, |
202 | NULL, |
203 | }; |
204 | |
205 | static const struct attribute_group page_idle_attr_group = { |
206 | .bin_attrs = page_idle_bin_attrs, |
207 | .name = "page_idle" , |
208 | }; |
209 | |
210 | static int __init page_idle_init(void) |
211 | { |
212 | int err; |
213 | |
214 | err = sysfs_create_group(kobj: mm_kobj, grp: &page_idle_attr_group); |
215 | if (err) { |
216 | pr_err("page_idle: register sysfs failed\n" ); |
217 | return err; |
218 | } |
219 | return 0; |
220 | } |
221 | subsys_initcall(page_idle_init); |
222 | |