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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> | |
92fb1db2 | 7 | #include <linux/memory_hotplug.h> |
33c3fc71 VD |
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 | #define BITMAP_CHUNK_SIZE sizeof(u64) | |
17 | #define BITMAP_CHUNK_BITS (BITMAP_CHUNK_SIZE * BITS_PER_BYTE) | |
18 | ||
19 | /* | |
20 | * Idle page tracking only considers user memory pages, for other types of | |
21 | * pages the idle flag is always unset and an attempt to set it is silently | |
22 | * ignored. | |
23 | * | |
24 | * We treat a page as a user memory page if it is on an LRU list, because it is | |
25 | * always safe to pass such a page to rmap_walk(), which is essential for idle | |
26 | * page tracking. With such an indicator of user pages we can skip isolated | |
27 | * pages, but since there are not usually many of them, it will hardly affect | |
28 | * the overall result. | |
29 | * | |
30 | * This function tries to get a user memory page by pfn as described above. | |
31 | */ | |
32 | static struct page *page_idle_get_page(unsigned long pfn) | |
33 | { | |
92fb1db2 | 34 | struct page *page = pfn_to_online_page(pfn); |
f4b7e272 | 35 | pg_data_t *pgdat; |
33c3fc71 | 36 | |
33c3fc71 VD |
37 | if (!page || !PageLRU(page) || |
38 | !get_page_unless_zero(page)) | |
39 | return NULL; | |
40 | ||
f4b7e272 AR |
41 | pgdat = page_pgdat(page); |
42 | spin_lock_irq(&pgdat->lru_lock); | |
33c3fc71 VD |
43 | if (unlikely(!PageLRU(page))) { |
44 | put_page(page); | |
45 | page = NULL; | |
46 | } | |
f4b7e272 | 47 | spin_unlock_irq(&pgdat->lru_lock); |
33c3fc71 VD |
48 | return page; |
49 | } | |
50 | ||
e4b82222 | 51 | static bool page_idle_clear_pte_refs_one(struct page *page, |
33c3fc71 VD |
52 | struct vm_area_struct *vma, |
53 | unsigned long addr, void *arg) | |
54 | { | |
699fa216 KS |
55 | struct page_vma_mapped_walk pvmw = { |
56 | .page = page, | |
57 | .vma = vma, | |
58 | .address = addr, | |
59 | }; | |
33c3fc71 VD |
60 | bool referenced = false; |
61 | ||
699fa216 KS |
62 | while (page_vma_mapped_walk(&pvmw)) { |
63 | addr = pvmw.address; | |
64 | if (pvmw.pte) { | |
f0849ac0 YS |
65 | /* |
66 | * For PTE-mapped THP, one sub page is referenced, | |
67 | * the whole THP is referenced. | |
68 | */ | |
69 | if (ptep_clear_young_notify(vma, addr, pvmw.pte)) | |
70 | referenced = true; | |
699fa216 | 71 | } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { |
f0849ac0 YS |
72 | if (pmdp_clear_young_notify(vma, addr, pvmw.pmd)) |
73 | referenced = true; | |
699fa216 KS |
74 | } else { |
75 | /* unexpected pmd-mapped page? */ | |
76 | WARN_ON_ONCE(1); | |
77 | } | |
33c3fc71 | 78 | } |
b20ce5e0 | 79 | |
33c3fc71 VD |
80 | if (referenced) { |
81 | clear_page_idle(page); | |
82 | /* | |
83 | * We cleared the referenced bit in a mapping to this page. To | |
84 | * avoid interference with page reclaim, mark it young so that | |
85 | * page_referenced() will return > 0. | |
86 | */ | |
87 | set_page_young(page); | |
88 | } | |
e4b82222 | 89 | return true; |
33c3fc71 VD |
90 | } |
91 | ||
92 | static void page_idle_clear_pte_refs(struct page *page) | |
93 | { | |
94 | /* | |
95 | * Since rwc.arg is unused, rwc is effectively immutable, so we | |
96 | * can make it static const to save some cycles and stack. | |
97 | */ | |
98 | static const struct rmap_walk_control rwc = { | |
99 | .rmap_one = page_idle_clear_pte_refs_one, | |
100 | .anon_lock = page_lock_anon_vma_read, | |
101 | }; | |
102 | bool need_lock; | |
103 | ||
104 | if (!page_mapped(page) || | |
105 | !page_rmapping(page)) | |
106 | return; | |
107 | ||
108 | need_lock = !PageAnon(page) || PageKsm(page); | |
109 | if (need_lock && !trylock_page(page)) | |
110 | return; | |
111 | ||
112 | rmap_walk(page, (struct rmap_walk_control *)&rwc); | |
113 | ||
114 | if (need_lock) | |
115 | unlock_page(page); | |
116 | } | |
117 | ||
118 | static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj, | |
119 | struct bin_attribute *attr, char *buf, | |
120 | loff_t pos, size_t count) | |
121 | { | |
122 | u64 *out = (u64 *)buf; | |
123 | struct page *page; | |
124 | unsigned long pfn, end_pfn; | |
125 | int bit; | |
126 | ||
127 | if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) | |
128 | return -EINVAL; | |
129 | ||
130 | pfn = pos * BITS_PER_BYTE; | |
131 | if (pfn >= max_pfn) | |
132 | return 0; | |
133 | ||
134 | end_pfn = pfn + count * BITS_PER_BYTE; | |
135 | if (end_pfn > max_pfn) | |
7298e3b0 | 136 | end_pfn = max_pfn; |
33c3fc71 VD |
137 | |
138 | for (; pfn < end_pfn; pfn++) { | |
139 | bit = pfn % BITMAP_CHUNK_BITS; | |
140 | if (!bit) | |
141 | *out = 0ULL; | |
142 | page = page_idle_get_page(pfn); | |
143 | if (page) { | |
144 | if (page_is_idle(page)) { | |
145 | /* | |
146 | * The page might have been referenced via a | |
147 | * pte, in which case it is not idle. Clear | |
148 | * refs and recheck. | |
149 | */ | |
150 | page_idle_clear_pte_refs(page); | |
151 | if (page_is_idle(page)) | |
152 | *out |= 1ULL << bit; | |
153 | } | |
154 | put_page(page); | |
155 | } | |
156 | if (bit == BITMAP_CHUNK_BITS - 1) | |
157 | out++; | |
158 | cond_resched(); | |
159 | } | |
160 | return (char *)out - buf; | |
161 | } | |
162 | ||
163 | static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj, | |
164 | struct bin_attribute *attr, char *buf, | |
165 | loff_t pos, size_t count) | |
166 | { | |
167 | const u64 *in = (u64 *)buf; | |
168 | struct page *page; | |
169 | unsigned long pfn, end_pfn; | |
170 | int bit; | |
171 | ||
172 | if (pos % BITMAP_CHUNK_SIZE || count % BITMAP_CHUNK_SIZE) | |
173 | return -EINVAL; | |
174 | ||
175 | pfn = pos * BITS_PER_BYTE; | |
176 | if (pfn >= max_pfn) | |
177 | return -ENXIO; | |
178 | ||
179 | end_pfn = pfn + count * BITS_PER_BYTE; | |
180 | if (end_pfn > max_pfn) | |
7298e3b0 | 181 | end_pfn = max_pfn; |
33c3fc71 VD |
182 | |
183 | for (; pfn < end_pfn; pfn++) { | |
184 | bit = pfn % BITMAP_CHUNK_BITS; | |
185 | if ((*in >> bit) & 1) { | |
186 | page = page_idle_get_page(pfn); | |
187 | if (page) { | |
188 | page_idle_clear_pte_refs(page); | |
189 | set_page_idle(page); | |
190 | put_page(page); | |
191 | } | |
192 | } | |
193 | if (bit == BITMAP_CHUNK_BITS - 1) | |
194 | in++; | |
195 | cond_resched(); | |
196 | } | |
197 | return (char *)in - buf; | |
198 | } | |
199 | ||
200 | static struct bin_attribute page_idle_bitmap_attr = | |
0825a6f9 | 201 | __BIN_ATTR(bitmap, 0600, |
33c3fc71 VD |
202 | page_idle_bitmap_read, page_idle_bitmap_write, 0); |
203 | ||
204 | static struct bin_attribute *page_idle_bin_attrs[] = { | |
205 | &page_idle_bitmap_attr, | |
206 | NULL, | |
207 | }; | |
208 | ||
fd147cbb | 209 | static const struct attribute_group page_idle_attr_group = { |
33c3fc71 VD |
210 | .bin_attrs = page_idle_bin_attrs, |
211 | .name = "page_idle", | |
212 | }; | |
213 | ||
214 | #ifndef CONFIG_64BIT | |
215 | static bool need_page_idle(void) | |
216 | { | |
217 | return true; | |
218 | } | |
219 | struct page_ext_operations page_idle_ops = { | |
220 | .need = need_page_idle, | |
221 | }; | |
222 | #endif | |
223 | ||
224 | static int __init page_idle_init(void) | |
225 | { | |
226 | int err; | |
227 | ||
228 | err = sysfs_create_group(mm_kobj, &page_idle_attr_group); | |
229 | if (err) { | |
230 | pr_err("page_idle: register sysfs failed\n"); | |
231 | return err; | |
232 | } | |
233 | return 0; | |
234 | } | |
235 | subsys_initcall(page_idle_init); |