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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
33c3fc71 | 2 | #include <linux/init.h> |
57c8a661 | 3 | #include <linux/memblock.h> |
33c3fc71 VD |
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); | |
a52633d8 | 45 | spin_lock_irq(zone_lru_lock(zone)); |
33c3fc71 VD |
46 | if (unlikely(!PageLRU(page))) { |
47 | put_page(page); | |
48 | page = NULL; | |
49 | } | |
a52633d8 | 50 | spin_unlock_irq(zone_lru_lock(zone)); |
33c3fc71 VD |
51 | return page; |
52 | } | |
53 | ||
e4b82222 | 54 | static bool page_idle_clear_pte_refs_one(struct page *page, |
33c3fc71 VD |
55 | struct vm_area_struct *vma, |
56 | unsigned long addr, void *arg) | |
57 | { | |
699fa216 KS |
58 | struct page_vma_mapped_walk pvmw = { |
59 | .page = page, | |
60 | .vma = vma, | |
61 | .address = addr, | |
62 | }; | |
33c3fc71 VD |
63 | bool referenced = false; |
64 | ||
699fa216 KS |
65 | while (page_vma_mapped_walk(&pvmw)) { |
66 | addr = pvmw.address; | |
67 | if (pvmw.pte) { | |
f0849ac0 YS |
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; | |
699fa216 | 74 | } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { |
f0849ac0 YS |
75 | if (pmdp_clear_young_notify(vma, addr, pvmw.pmd)) |
76 | referenced = true; | |
699fa216 KS |
77 | } else { |
78 | /* unexpected pmd-mapped page? */ | |
79 | WARN_ON_ONCE(1); | |
80 | } | |
33c3fc71 | 81 | } |
b20ce5e0 | 82 | |
33c3fc71 VD |
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 | } | |
e4b82222 | 92 | return true; |
33c3fc71 VD |
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 = | |
0825a6f9 | 204 | __BIN_ATTR(bitmap, 0600, |
33c3fc71 VD |
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 | ||
fd147cbb | 212 | static const struct attribute_group page_idle_attr_group = { |
33c3fc71 VD |
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); |