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1 | /* | |
2 | * Copyright (C) 2009 Red Hat, Inc. | |
3 | * | |
4 | * This work is licensed under the terms of the GNU GPL, version 2. See | |
5 | * the COPYING file in the top-level directory. | |
6 | */ | |
7 | ||
8 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt | |
9 | ||
10 | #include <linux/mm.h> | |
11 | #include <linux/sched.h> | |
12 | #include <linux/highmem.h> | |
13 | #include <linux/hugetlb.h> | |
14 | #include <linux/mmu_notifier.h> | |
15 | #include <linux/rmap.h> | |
16 | #include <linux/swap.h> | |
17 | #include <linux/shrinker.h> | |
18 | #include <linux/mm_inline.h> | |
19 | #include <linux/kthread.h> | |
20 | #include <linux/khugepaged.h> | |
21 | #include <linux/freezer.h> | |
22 | #include <linux/mman.h> | |
23 | #include <linux/pagemap.h> | |
24 | #include <linux/migrate.h> | |
25 | #include <linux/hashtable.h> | |
26 | ||
27 | #include <asm/tlb.h> | |
28 | #include <asm/pgalloc.h> | |
29 | #include "internal.h" | |
30 | ||
31 | /* | |
32 | * By default transparent hugepage support is disabled in order that avoid | |
33 | * to risk increase the memory footprint of applications without a guaranteed | |
34 | * benefit. When transparent hugepage support is enabled, is for all mappings, | |
35 | * and khugepaged scans all mappings. | |
36 | * Defrag is invoked by khugepaged hugepage allocations and by page faults | |
37 | * for all hugepage allocations. | |
38 | */ | |
39 | unsigned long transparent_hugepage_flags __read_mostly = | |
40 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS | |
41 | (1<<TRANSPARENT_HUGEPAGE_FLAG)| | |
42 | #endif | |
43 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE | |
44 | (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| | |
45 | #endif | |
46 | (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)| | |
47 | (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| | |
48 | (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); | |
49 | ||
50 | /* default scan 8*512 pte (or vmas) every 30 second */ | |
51 | static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; | |
52 | static unsigned int khugepaged_pages_collapsed; | |
53 | static unsigned int khugepaged_full_scans; | |
54 | static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; | |
55 | /* during fragmentation poll the hugepage allocator once every minute */ | |
56 | static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; | |
57 | static struct task_struct *khugepaged_thread __read_mostly; | |
58 | static DEFINE_MUTEX(khugepaged_mutex); | |
59 | static DEFINE_SPINLOCK(khugepaged_mm_lock); | |
60 | static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); | |
61 | /* | |
62 | * default collapse hugepages if there is at least one pte mapped like | |
63 | * it would have happened if the vma was large enough during page | |
64 | * fault. | |
65 | */ | |
66 | static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1; | |
67 | ||
68 | static int khugepaged(void *none); | |
69 | static int khugepaged_slab_init(void); | |
70 | static void khugepaged_slab_exit(void); | |
71 | ||
72 | #define MM_SLOTS_HASH_BITS 10 | |
73 | static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); | |
74 | ||
75 | static struct kmem_cache *mm_slot_cache __read_mostly; | |
76 | ||
77 | /** | |
78 | * struct mm_slot - hash lookup from mm to mm_slot | |
79 | * @hash: hash collision list | |
80 | * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head | |
81 | * @mm: the mm that this information is valid for | |
82 | */ | |
83 | struct mm_slot { | |
84 | struct hlist_node hash; | |
85 | struct list_head mm_node; | |
86 | struct mm_struct *mm; | |
87 | }; | |
88 | ||
89 | /** | |
90 | * struct khugepaged_scan - cursor for scanning | |
91 | * @mm_head: the head of the mm list to scan | |
92 | * @mm_slot: the current mm_slot we are scanning | |
93 | * @address: the next address inside that to be scanned | |
94 | * | |
95 | * There is only the one khugepaged_scan instance of this cursor structure. | |
96 | */ | |
97 | struct khugepaged_scan { | |
98 | struct list_head mm_head; | |
99 | struct mm_slot *mm_slot; | |
100 | unsigned long address; | |
101 | }; | |
102 | static struct khugepaged_scan khugepaged_scan = { | |
103 | .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), | |
104 | }; | |
105 | ||
106 | ||
107 | static int set_recommended_min_free_kbytes(void) | |
108 | { | |
109 | struct zone *zone; | |
110 | int nr_zones = 0; | |
111 | unsigned long recommended_min; | |
112 | ||
113 | /* khugepaged thread has stopped to failed to start */ | |
114 | if (!khugepaged_thread) | |
115 | return 0; | |
116 | ||
117 | for_each_populated_zone(zone) | |
118 | nr_zones++; | |
119 | ||
120 | /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */ | |
121 | recommended_min = pageblock_nr_pages * nr_zones * 2; | |
122 | ||
123 | /* | |
124 | * Make sure that on average at least two pageblocks are almost free | |
125 | * of another type, one for a migratetype to fall back to and a | |
126 | * second to avoid subsequent fallbacks of other types There are 3 | |
127 | * MIGRATE_TYPES we care about. | |
128 | */ | |
129 | recommended_min += pageblock_nr_pages * nr_zones * | |
130 | MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; | |
131 | ||
132 | /* don't ever allow to reserve more than 5% of the lowmem */ | |
133 | recommended_min = min(recommended_min, | |
134 | (unsigned long) nr_free_buffer_pages() / 20); | |
135 | recommended_min <<= (PAGE_SHIFT-10); | |
136 | ||
137 | if (recommended_min > min_free_kbytes) { | |
138 | if (user_min_free_kbytes >= 0) | |
139 | pr_info("raising min_free_kbytes from %d to %lu " | |
140 | "to help transparent hugepage allocations\n", | |
141 | min_free_kbytes, recommended_min); | |
142 | ||
143 | min_free_kbytes = recommended_min; | |
144 | } | |
145 | setup_per_zone_wmarks(); | |
146 | return 0; | |
147 | } | |
148 | late_initcall(set_recommended_min_free_kbytes); | |
149 | ||
150 | static int start_khugepaged(void) | |
151 | { | |
152 | int err = 0; | |
153 | if (khugepaged_enabled()) { | |
154 | if (!khugepaged_thread) | |
155 | khugepaged_thread = kthread_run(khugepaged, NULL, | |
156 | "khugepaged"); | |
157 | if (unlikely(IS_ERR(khugepaged_thread))) { | |
158 | pr_err("khugepaged: kthread_run(khugepaged) failed\n"); | |
159 | err = PTR_ERR(khugepaged_thread); | |
160 | khugepaged_thread = NULL; | |
161 | } | |
162 | ||
163 | if (!list_empty(&khugepaged_scan.mm_head)) | |
164 | wake_up_interruptible(&khugepaged_wait); | |
165 | ||
166 | set_recommended_min_free_kbytes(); | |
167 | } else if (khugepaged_thread) { | |
168 | kthread_stop(khugepaged_thread); | |
169 | khugepaged_thread = NULL; | |
170 | } | |
171 | ||
172 | return err; | |
173 | } | |
174 | ||
175 | static atomic_t huge_zero_refcount; | |
176 | struct page *huge_zero_page __read_mostly; | |
177 | ||
178 | static inline bool is_huge_zero_pmd(pmd_t pmd) | |
179 | { | |
180 | return is_huge_zero_page(pmd_page(pmd)); | |
181 | } | |
182 | ||
183 | static struct page *get_huge_zero_page(void) | |
184 | { | |
185 | struct page *zero_page; | |
186 | retry: | |
187 | if (likely(atomic_inc_not_zero(&huge_zero_refcount))) | |
188 | return READ_ONCE(huge_zero_page); | |
189 | ||
190 | zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, | |
191 | HPAGE_PMD_ORDER); | |
192 | if (!zero_page) { | |
193 | count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); | |
194 | return NULL; | |
195 | } | |
196 | count_vm_event(THP_ZERO_PAGE_ALLOC); | |
197 | preempt_disable(); | |
198 | if (cmpxchg(&huge_zero_page, NULL, zero_page)) { | |
199 | preempt_enable(); | |
200 | __free_pages(zero_page, compound_order(zero_page)); | |
201 | goto retry; | |
202 | } | |
203 | ||
204 | /* We take additional reference here. It will be put back by shrinker */ | |
205 | atomic_set(&huge_zero_refcount, 2); | |
206 | preempt_enable(); | |
207 | return READ_ONCE(huge_zero_page); | |
208 | } | |
209 | ||
210 | static void put_huge_zero_page(void) | |
211 | { | |
212 | /* | |
213 | * Counter should never go to zero here. Only shrinker can put | |
214 | * last reference. | |
215 | */ | |
216 | BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); | |
217 | } | |
218 | ||
219 | static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, | |
220 | struct shrink_control *sc) | |
221 | { | |
222 | /* we can free zero page only if last reference remains */ | |
223 | return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; | |
224 | } | |
225 | ||
226 | static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, | |
227 | struct shrink_control *sc) | |
228 | { | |
229 | if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { | |
230 | struct page *zero_page = xchg(&huge_zero_page, NULL); | |
231 | BUG_ON(zero_page == NULL); | |
232 | __free_pages(zero_page, compound_order(zero_page)); | |
233 | return HPAGE_PMD_NR; | |
234 | } | |
235 | ||
236 | return 0; | |
237 | } | |
238 | ||
239 | static struct shrinker huge_zero_page_shrinker = { | |
240 | .count_objects = shrink_huge_zero_page_count, | |
241 | .scan_objects = shrink_huge_zero_page_scan, | |
242 | .seeks = DEFAULT_SEEKS, | |
243 | }; | |
244 | ||
245 | #ifdef CONFIG_SYSFS | |
246 | ||
247 | static ssize_t double_flag_show(struct kobject *kobj, | |
248 | struct kobj_attribute *attr, char *buf, | |
249 | enum transparent_hugepage_flag enabled, | |
250 | enum transparent_hugepage_flag req_madv) | |
251 | { | |
252 | if (test_bit(enabled, &transparent_hugepage_flags)) { | |
253 | VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); | |
254 | return sprintf(buf, "[always] madvise never\n"); | |
255 | } else if (test_bit(req_madv, &transparent_hugepage_flags)) | |
256 | return sprintf(buf, "always [madvise] never\n"); | |
257 | else | |
258 | return sprintf(buf, "always madvise [never]\n"); | |
259 | } | |
260 | static ssize_t double_flag_store(struct kobject *kobj, | |
261 | struct kobj_attribute *attr, | |
262 | const char *buf, size_t count, | |
263 | enum transparent_hugepage_flag enabled, | |
264 | enum transparent_hugepage_flag req_madv) | |
265 | { | |
266 | if (!memcmp("always", buf, | |
267 | min(sizeof("always")-1, count))) { | |
268 | set_bit(enabled, &transparent_hugepage_flags); | |
269 | clear_bit(req_madv, &transparent_hugepage_flags); | |
270 | } else if (!memcmp("madvise", buf, | |
271 | min(sizeof("madvise")-1, count))) { | |
272 | clear_bit(enabled, &transparent_hugepage_flags); | |
273 | set_bit(req_madv, &transparent_hugepage_flags); | |
274 | } else if (!memcmp("never", buf, | |
275 | min(sizeof("never")-1, count))) { | |
276 | clear_bit(enabled, &transparent_hugepage_flags); | |
277 | clear_bit(req_madv, &transparent_hugepage_flags); | |
278 | } else | |
279 | return -EINVAL; | |
280 | ||
281 | return count; | |
282 | } | |
283 | ||
284 | static ssize_t enabled_show(struct kobject *kobj, | |
285 | struct kobj_attribute *attr, char *buf) | |
286 | { | |
287 | return double_flag_show(kobj, attr, buf, | |
288 | TRANSPARENT_HUGEPAGE_FLAG, | |
289 | TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); | |
290 | } | |
291 | static ssize_t enabled_store(struct kobject *kobj, | |
292 | struct kobj_attribute *attr, | |
293 | const char *buf, size_t count) | |
294 | { | |
295 | ssize_t ret; | |
296 | ||
297 | ret = double_flag_store(kobj, attr, buf, count, | |
298 | TRANSPARENT_HUGEPAGE_FLAG, | |
299 | TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); | |
300 | ||
301 | if (ret > 0) { | |
302 | int err; | |
303 | ||
304 | mutex_lock(&khugepaged_mutex); | |
305 | err = start_khugepaged(); | |
306 | mutex_unlock(&khugepaged_mutex); | |
307 | ||
308 | if (err) | |
309 | ret = err; | |
310 | } | |
311 | ||
312 | return ret; | |
313 | } | |
314 | static struct kobj_attribute enabled_attr = | |
315 | __ATTR(enabled, 0644, enabled_show, enabled_store); | |
316 | ||
317 | static ssize_t single_flag_show(struct kobject *kobj, | |
318 | struct kobj_attribute *attr, char *buf, | |
319 | enum transparent_hugepage_flag flag) | |
320 | { | |
321 | return sprintf(buf, "%d\n", | |
322 | !!test_bit(flag, &transparent_hugepage_flags)); | |
323 | } | |
324 | ||
325 | static ssize_t single_flag_store(struct kobject *kobj, | |
326 | struct kobj_attribute *attr, | |
327 | const char *buf, size_t count, | |
328 | enum transparent_hugepage_flag flag) | |
329 | { | |
330 | unsigned long value; | |
331 | int ret; | |
332 | ||
333 | ret = kstrtoul(buf, 10, &value); | |
334 | if (ret < 0) | |
335 | return ret; | |
336 | if (value > 1) | |
337 | return -EINVAL; | |
338 | ||
339 | if (value) | |
340 | set_bit(flag, &transparent_hugepage_flags); | |
341 | else | |
342 | clear_bit(flag, &transparent_hugepage_flags); | |
343 | ||
344 | return count; | |
345 | } | |
346 | ||
347 | /* | |
348 | * Currently defrag only disables __GFP_NOWAIT for allocation. A blind | |
349 | * __GFP_REPEAT is too aggressive, it's never worth swapping tons of | |
350 | * memory just to allocate one more hugepage. | |
351 | */ | |
352 | static ssize_t defrag_show(struct kobject *kobj, | |
353 | struct kobj_attribute *attr, char *buf) | |
354 | { | |
355 | return double_flag_show(kobj, attr, buf, | |
356 | TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, | |
357 | TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); | |
358 | } | |
359 | static ssize_t defrag_store(struct kobject *kobj, | |
360 | struct kobj_attribute *attr, | |
361 | const char *buf, size_t count) | |
362 | { | |
363 | return double_flag_store(kobj, attr, buf, count, | |
364 | TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, | |
365 | TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); | |
366 | } | |
367 | static struct kobj_attribute defrag_attr = | |
368 | __ATTR(defrag, 0644, defrag_show, defrag_store); | |
369 | ||
370 | static ssize_t use_zero_page_show(struct kobject *kobj, | |
371 | struct kobj_attribute *attr, char *buf) | |
372 | { | |
373 | return single_flag_show(kobj, attr, buf, | |
374 | TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); | |
375 | } | |
376 | static ssize_t use_zero_page_store(struct kobject *kobj, | |
377 | struct kobj_attribute *attr, const char *buf, size_t count) | |
378 | { | |
379 | return single_flag_store(kobj, attr, buf, count, | |
380 | TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); | |
381 | } | |
382 | static struct kobj_attribute use_zero_page_attr = | |
383 | __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); | |
384 | #ifdef CONFIG_DEBUG_VM | |
385 | static ssize_t debug_cow_show(struct kobject *kobj, | |
386 | struct kobj_attribute *attr, char *buf) | |
387 | { | |
388 | return single_flag_show(kobj, attr, buf, | |
389 | TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); | |
390 | } | |
391 | static ssize_t debug_cow_store(struct kobject *kobj, | |
392 | struct kobj_attribute *attr, | |
393 | const char *buf, size_t count) | |
394 | { | |
395 | return single_flag_store(kobj, attr, buf, count, | |
396 | TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); | |
397 | } | |
398 | static struct kobj_attribute debug_cow_attr = | |
399 | __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); | |
400 | #endif /* CONFIG_DEBUG_VM */ | |
401 | ||
402 | static struct attribute *hugepage_attr[] = { | |
403 | &enabled_attr.attr, | |
404 | &defrag_attr.attr, | |
405 | &use_zero_page_attr.attr, | |
406 | #ifdef CONFIG_DEBUG_VM | |
407 | &debug_cow_attr.attr, | |
408 | #endif | |
409 | NULL, | |
410 | }; | |
411 | ||
412 | static struct attribute_group hugepage_attr_group = { | |
413 | .attrs = hugepage_attr, | |
414 | }; | |
415 | ||
416 | static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, | |
417 | struct kobj_attribute *attr, | |
418 | char *buf) | |
419 | { | |
420 | return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); | |
421 | } | |
422 | ||
423 | static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, | |
424 | struct kobj_attribute *attr, | |
425 | const char *buf, size_t count) | |
426 | { | |
427 | unsigned long msecs; | |
428 | int err; | |
429 | ||
430 | err = kstrtoul(buf, 10, &msecs); | |
431 | if (err || msecs > UINT_MAX) | |
432 | return -EINVAL; | |
433 | ||
434 | khugepaged_scan_sleep_millisecs = msecs; | |
435 | wake_up_interruptible(&khugepaged_wait); | |
436 | ||
437 | return count; | |
438 | } | |
439 | static struct kobj_attribute scan_sleep_millisecs_attr = | |
440 | __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, | |
441 | scan_sleep_millisecs_store); | |
442 | ||
443 | static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, | |
444 | struct kobj_attribute *attr, | |
445 | char *buf) | |
446 | { | |
447 | return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); | |
448 | } | |
449 | ||
450 | static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, | |
451 | struct kobj_attribute *attr, | |
452 | const char *buf, size_t count) | |
453 | { | |
454 | unsigned long msecs; | |
455 | int err; | |
456 | ||
457 | err = kstrtoul(buf, 10, &msecs); | |
458 | if (err || msecs > UINT_MAX) | |
459 | return -EINVAL; | |
460 | ||
461 | khugepaged_alloc_sleep_millisecs = msecs; | |
462 | wake_up_interruptible(&khugepaged_wait); | |
463 | ||
464 | return count; | |
465 | } | |
466 | static struct kobj_attribute alloc_sleep_millisecs_attr = | |
467 | __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, | |
468 | alloc_sleep_millisecs_store); | |
469 | ||
470 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
471 | struct kobj_attribute *attr, | |
472 | char *buf) | |
473 | { | |
474 | return sprintf(buf, "%u\n", khugepaged_pages_to_scan); | |
475 | } | |
476 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
477 | struct kobj_attribute *attr, | |
478 | const char *buf, size_t count) | |
479 | { | |
480 | int err; | |
481 | unsigned long pages; | |
482 | ||
483 | err = kstrtoul(buf, 10, &pages); | |
484 | if (err || !pages || pages > UINT_MAX) | |
485 | return -EINVAL; | |
486 | ||
487 | khugepaged_pages_to_scan = pages; | |
488 | ||
489 | return count; | |
490 | } | |
491 | static struct kobj_attribute pages_to_scan_attr = | |
492 | __ATTR(pages_to_scan, 0644, pages_to_scan_show, | |
493 | pages_to_scan_store); | |
494 | ||
495 | static ssize_t pages_collapsed_show(struct kobject *kobj, | |
496 | struct kobj_attribute *attr, | |
497 | char *buf) | |
498 | { | |
499 | return sprintf(buf, "%u\n", khugepaged_pages_collapsed); | |
500 | } | |
501 | static struct kobj_attribute pages_collapsed_attr = | |
502 | __ATTR_RO(pages_collapsed); | |
503 | ||
504 | static ssize_t full_scans_show(struct kobject *kobj, | |
505 | struct kobj_attribute *attr, | |
506 | char *buf) | |
507 | { | |
508 | return sprintf(buf, "%u\n", khugepaged_full_scans); | |
509 | } | |
510 | static struct kobj_attribute full_scans_attr = | |
511 | __ATTR_RO(full_scans); | |
512 | ||
513 | static ssize_t khugepaged_defrag_show(struct kobject *kobj, | |
514 | struct kobj_attribute *attr, char *buf) | |
515 | { | |
516 | return single_flag_show(kobj, attr, buf, | |
517 | TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); | |
518 | } | |
519 | static ssize_t khugepaged_defrag_store(struct kobject *kobj, | |
520 | struct kobj_attribute *attr, | |
521 | const char *buf, size_t count) | |
522 | { | |
523 | return single_flag_store(kobj, attr, buf, count, | |
524 | TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); | |
525 | } | |
526 | static struct kobj_attribute khugepaged_defrag_attr = | |
527 | __ATTR(defrag, 0644, khugepaged_defrag_show, | |
528 | khugepaged_defrag_store); | |
529 | ||
530 | /* | |
531 | * max_ptes_none controls if khugepaged should collapse hugepages over | |
532 | * any unmapped ptes in turn potentially increasing the memory | |
533 | * footprint of the vmas. When max_ptes_none is 0 khugepaged will not | |
534 | * reduce the available free memory in the system as it | |
535 | * runs. Increasing max_ptes_none will instead potentially reduce the | |
536 | * free memory in the system during the khugepaged scan. | |
537 | */ | |
538 | static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, | |
539 | struct kobj_attribute *attr, | |
540 | char *buf) | |
541 | { | |
542 | return sprintf(buf, "%u\n", khugepaged_max_ptes_none); | |
543 | } | |
544 | static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, | |
545 | struct kobj_attribute *attr, | |
546 | const char *buf, size_t count) | |
547 | { | |
548 | int err; | |
549 | unsigned long max_ptes_none; | |
550 | ||
551 | err = kstrtoul(buf, 10, &max_ptes_none); | |
552 | if (err || max_ptes_none > HPAGE_PMD_NR-1) | |
553 | return -EINVAL; | |
554 | ||
555 | khugepaged_max_ptes_none = max_ptes_none; | |
556 | ||
557 | return count; | |
558 | } | |
559 | static struct kobj_attribute khugepaged_max_ptes_none_attr = | |
560 | __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, | |
561 | khugepaged_max_ptes_none_store); | |
562 | ||
563 | static struct attribute *khugepaged_attr[] = { | |
564 | &khugepaged_defrag_attr.attr, | |
565 | &khugepaged_max_ptes_none_attr.attr, | |
566 | &pages_to_scan_attr.attr, | |
567 | &pages_collapsed_attr.attr, | |
568 | &full_scans_attr.attr, | |
569 | &scan_sleep_millisecs_attr.attr, | |
570 | &alloc_sleep_millisecs_attr.attr, | |
571 | NULL, | |
572 | }; | |
573 | ||
574 | static struct attribute_group khugepaged_attr_group = { | |
575 | .attrs = khugepaged_attr, | |
576 | .name = "khugepaged", | |
577 | }; | |
578 | ||
579 | static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) | |
580 | { | |
581 | int err; | |
582 | ||
583 | *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); | |
584 | if (unlikely(!*hugepage_kobj)) { | |
585 | pr_err("failed to create transparent hugepage kobject\n"); | |
586 | return -ENOMEM; | |
587 | } | |
588 | ||
589 | err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); | |
590 | if (err) { | |
591 | pr_err("failed to register transparent hugepage group\n"); | |
592 | goto delete_obj; | |
593 | } | |
594 | ||
595 | err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); | |
596 | if (err) { | |
597 | pr_err("failed to register transparent hugepage group\n"); | |
598 | goto remove_hp_group; | |
599 | } | |
600 | ||
601 | return 0; | |
602 | ||
603 | remove_hp_group: | |
604 | sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); | |
605 | delete_obj: | |
606 | kobject_put(*hugepage_kobj); | |
607 | return err; | |
608 | } | |
609 | ||
610 | static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) | |
611 | { | |
612 | sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); | |
613 | sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); | |
614 | kobject_put(hugepage_kobj); | |
615 | } | |
616 | #else | |
617 | static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) | |
618 | { | |
619 | return 0; | |
620 | } | |
621 | ||
622 | static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) | |
623 | { | |
624 | } | |
625 | #endif /* CONFIG_SYSFS */ | |
626 | ||
627 | static int __init hugepage_init(void) | |
628 | { | |
629 | int err; | |
630 | struct kobject *hugepage_kobj; | |
631 | ||
632 | if (!has_transparent_hugepage()) { | |
633 | transparent_hugepage_flags = 0; | |
634 | return -EINVAL; | |
635 | } | |
636 | ||
637 | err = hugepage_init_sysfs(&hugepage_kobj); | |
638 | if (err) | |
639 | goto err_sysfs; | |
640 | ||
641 | err = khugepaged_slab_init(); | |
642 | if (err) | |
643 | goto err_slab; | |
644 | ||
645 | err = register_shrinker(&huge_zero_page_shrinker); | |
646 | if (err) | |
647 | goto err_hzp_shrinker; | |
648 | ||
649 | /* | |
650 | * By default disable transparent hugepages on smaller systems, | |
651 | * where the extra memory used could hurt more than TLB overhead | |
652 | * is likely to save. The admin can still enable it through /sys. | |
653 | */ | |
654 | if (totalram_pages < (512 << (20 - PAGE_SHIFT))) | |
655 | transparent_hugepage_flags = 0; | |
656 | ||
657 | err = start_khugepaged(); | |
658 | if (err) | |
659 | goto err_khugepaged; | |
660 | ||
661 | return 0; | |
662 | err_khugepaged: | |
663 | unregister_shrinker(&huge_zero_page_shrinker); | |
664 | err_hzp_shrinker: | |
665 | khugepaged_slab_exit(); | |
666 | err_slab: | |
667 | hugepage_exit_sysfs(hugepage_kobj); | |
668 | err_sysfs: | |
669 | return err; | |
670 | } | |
671 | subsys_initcall(hugepage_init); | |
672 | ||
673 | static int __init setup_transparent_hugepage(char *str) | |
674 | { | |
675 | int ret = 0; | |
676 | if (!str) | |
677 | goto out; | |
678 | if (!strcmp(str, "always")) { | |
679 | set_bit(TRANSPARENT_HUGEPAGE_FLAG, | |
680 | &transparent_hugepage_flags); | |
681 | clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, | |
682 | &transparent_hugepage_flags); | |
683 | ret = 1; | |
684 | } else if (!strcmp(str, "madvise")) { | |
685 | clear_bit(TRANSPARENT_HUGEPAGE_FLAG, | |
686 | &transparent_hugepage_flags); | |
687 | set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, | |
688 | &transparent_hugepage_flags); | |
689 | ret = 1; | |
690 | } else if (!strcmp(str, "never")) { | |
691 | clear_bit(TRANSPARENT_HUGEPAGE_FLAG, | |
692 | &transparent_hugepage_flags); | |
693 | clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, | |
694 | &transparent_hugepage_flags); | |
695 | ret = 1; | |
696 | } | |
697 | out: | |
698 | if (!ret) | |
699 | pr_warn("transparent_hugepage= cannot parse, ignored\n"); | |
700 | return ret; | |
701 | } | |
702 | __setup("transparent_hugepage=", setup_transparent_hugepage); | |
703 | ||
704 | pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) | |
705 | { | |
706 | if (likely(vma->vm_flags & VM_WRITE)) | |
707 | pmd = pmd_mkwrite(pmd); | |
708 | return pmd; | |
709 | } | |
710 | ||
711 | static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot) | |
712 | { | |
713 | pmd_t entry; | |
714 | entry = mk_pmd(page, prot); | |
715 | entry = pmd_mkhuge(entry); | |
716 | return entry; | |
717 | } | |
718 | ||
719 | static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, | |
720 | struct vm_area_struct *vma, | |
721 | unsigned long haddr, pmd_t *pmd, | |
722 | struct page *page, gfp_t gfp) | |
723 | { | |
724 | struct mem_cgroup *memcg; | |
725 | pgtable_t pgtable; | |
726 | spinlock_t *ptl; | |
727 | ||
728 | VM_BUG_ON_PAGE(!PageCompound(page), page); | |
729 | ||
730 | if (mem_cgroup_try_charge(page, mm, gfp, &memcg)) | |
731 | return VM_FAULT_OOM; | |
732 | ||
733 | pgtable = pte_alloc_one(mm, haddr); | |
734 | if (unlikely(!pgtable)) { | |
735 | mem_cgroup_cancel_charge(page, memcg); | |
736 | return VM_FAULT_OOM; | |
737 | } | |
738 | ||
739 | clear_huge_page(page, haddr, HPAGE_PMD_NR); | |
740 | /* | |
741 | * The memory barrier inside __SetPageUptodate makes sure that | |
742 | * clear_huge_page writes become visible before the set_pmd_at() | |
743 | * write. | |
744 | */ | |
745 | __SetPageUptodate(page); | |
746 | ||
747 | ptl = pmd_lock(mm, pmd); | |
748 | if (unlikely(!pmd_none(*pmd))) { | |
749 | spin_unlock(ptl); | |
750 | mem_cgroup_cancel_charge(page, memcg); | |
751 | put_page(page); | |
752 | pte_free(mm, pgtable); | |
753 | } else { | |
754 | pmd_t entry; | |
755 | entry = mk_huge_pmd(page, vma->vm_page_prot); | |
756 | entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); | |
757 | page_add_new_anon_rmap(page, vma, haddr); | |
758 | mem_cgroup_commit_charge(page, memcg, false); | |
759 | lru_cache_add_active_or_unevictable(page, vma); | |
760 | pgtable_trans_huge_deposit(mm, pmd, pgtable); | |
761 | set_pmd_at(mm, haddr, pmd, entry); | |
762 | add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); | |
763 | atomic_long_inc(&mm->nr_ptes); | |
764 | spin_unlock(ptl); | |
765 | } | |
766 | ||
767 | return 0; | |
768 | } | |
769 | ||
770 | static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) | |
771 | { | |
772 | return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; | |
773 | } | |
774 | ||
775 | /* Caller must hold page table lock. */ | |
776 | static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, | |
777 | struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, | |
778 | struct page *zero_page) | |
779 | { | |
780 | pmd_t entry; | |
781 | if (!pmd_none(*pmd)) | |
782 | return false; | |
783 | entry = mk_pmd(zero_page, vma->vm_page_prot); | |
784 | entry = pmd_mkhuge(entry); | |
785 | pgtable_trans_huge_deposit(mm, pmd, pgtable); | |
786 | set_pmd_at(mm, haddr, pmd, entry); | |
787 | atomic_long_inc(&mm->nr_ptes); | |
788 | return true; | |
789 | } | |
790 | ||
791 | int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, | |
792 | unsigned long address, pmd_t *pmd, | |
793 | unsigned int flags) | |
794 | { | |
795 | gfp_t gfp; | |
796 | struct page *page; | |
797 | unsigned long haddr = address & HPAGE_PMD_MASK; | |
798 | ||
799 | if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end) | |
800 | return VM_FAULT_FALLBACK; | |
801 | if (unlikely(anon_vma_prepare(vma))) | |
802 | return VM_FAULT_OOM; | |
803 | if (unlikely(khugepaged_enter(vma, vma->vm_flags))) | |
804 | return VM_FAULT_OOM; | |
805 | if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) && | |
806 | transparent_hugepage_use_zero_page()) { | |
807 | spinlock_t *ptl; | |
808 | pgtable_t pgtable; | |
809 | struct page *zero_page; | |
810 | bool set; | |
811 | pgtable = pte_alloc_one(mm, haddr); | |
812 | if (unlikely(!pgtable)) | |
813 | return VM_FAULT_OOM; | |
814 | zero_page = get_huge_zero_page(); | |
815 | if (unlikely(!zero_page)) { | |
816 | pte_free(mm, pgtable); | |
817 | count_vm_event(THP_FAULT_FALLBACK); | |
818 | return VM_FAULT_FALLBACK; | |
819 | } | |
820 | ptl = pmd_lock(mm, pmd); | |
821 | set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, | |
822 | zero_page); | |
823 | spin_unlock(ptl); | |
824 | if (!set) { | |
825 | pte_free(mm, pgtable); | |
826 | put_huge_zero_page(); | |
827 | } | |
828 | return 0; | |
829 | } | |
830 | gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0); | |
831 | page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); | |
832 | if (unlikely(!page)) { | |
833 | count_vm_event(THP_FAULT_FALLBACK); | |
834 | return VM_FAULT_FALLBACK; | |
835 | } | |
836 | if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page, gfp))) { | |
837 | put_page(page); | |
838 | count_vm_event(THP_FAULT_FALLBACK); | |
839 | return VM_FAULT_FALLBACK; | |
840 | } | |
841 | ||
842 | count_vm_event(THP_FAULT_ALLOC); | |
843 | return 0; | |
844 | } | |
845 | ||
846 | int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, | |
847 | pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, | |
848 | struct vm_area_struct *vma) | |
849 | { | |
850 | spinlock_t *dst_ptl, *src_ptl; | |
851 | struct page *src_page; | |
852 | pmd_t pmd; | |
853 | pgtable_t pgtable; | |
854 | int ret; | |
855 | ||
856 | ret = -ENOMEM; | |
857 | pgtable = pte_alloc_one(dst_mm, addr); | |
858 | if (unlikely(!pgtable)) | |
859 | goto out; | |
860 | ||
861 | dst_ptl = pmd_lock(dst_mm, dst_pmd); | |
862 | src_ptl = pmd_lockptr(src_mm, src_pmd); | |
863 | spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); | |
864 | ||
865 | ret = -EAGAIN; | |
866 | pmd = *src_pmd; | |
867 | if (unlikely(!pmd_trans_huge(pmd))) { | |
868 | pte_free(dst_mm, pgtable); | |
869 | goto out_unlock; | |
870 | } | |
871 | /* | |
872 | * When page table lock is held, the huge zero pmd should not be | |
873 | * under splitting since we don't split the page itself, only pmd to | |
874 | * a page table. | |
875 | */ | |
876 | if (is_huge_zero_pmd(pmd)) { | |
877 | struct page *zero_page; | |
878 | bool set; | |
879 | /* | |
880 | * get_huge_zero_page() will never allocate a new page here, | |
881 | * since we already have a zero page to copy. It just takes a | |
882 | * reference. | |
883 | */ | |
884 | zero_page = get_huge_zero_page(); | |
885 | set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, | |
886 | zero_page); | |
887 | BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ | |
888 | ret = 0; | |
889 | goto out_unlock; | |
890 | } | |
891 | ||
892 | if (unlikely(pmd_trans_splitting(pmd))) { | |
893 | /* split huge page running from under us */ | |
894 | spin_unlock(src_ptl); | |
895 | spin_unlock(dst_ptl); | |
896 | pte_free(dst_mm, pgtable); | |
897 | ||
898 | wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */ | |
899 | goto out; | |
900 | } | |
901 | src_page = pmd_page(pmd); | |
902 | VM_BUG_ON_PAGE(!PageHead(src_page), src_page); | |
903 | get_page(src_page); | |
904 | page_dup_rmap(src_page); | |
905 | add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); | |
906 | ||
907 | pmdp_set_wrprotect(src_mm, addr, src_pmd); | |
908 | pmd = pmd_mkold(pmd_wrprotect(pmd)); | |
909 | pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); | |
910 | set_pmd_at(dst_mm, addr, dst_pmd, pmd); | |
911 | atomic_long_inc(&dst_mm->nr_ptes); | |
912 | ||
913 | ret = 0; | |
914 | out_unlock: | |
915 | spin_unlock(src_ptl); | |
916 | spin_unlock(dst_ptl); | |
917 | out: | |
918 | return ret; | |
919 | } | |
920 | ||
921 | void huge_pmd_set_accessed(struct mm_struct *mm, | |
922 | struct vm_area_struct *vma, | |
923 | unsigned long address, | |
924 | pmd_t *pmd, pmd_t orig_pmd, | |
925 | int dirty) | |
926 | { | |
927 | spinlock_t *ptl; | |
928 | pmd_t entry; | |
929 | unsigned long haddr; | |
930 | ||
931 | ptl = pmd_lock(mm, pmd); | |
932 | if (unlikely(!pmd_same(*pmd, orig_pmd))) | |
933 | goto unlock; | |
934 | ||
935 | entry = pmd_mkyoung(orig_pmd); | |
936 | haddr = address & HPAGE_PMD_MASK; | |
937 | if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty)) | |
938 | update_mmu_cache_pmd(vma, address, pmd); | |
939 | ||
940 | unlock: | |
941 | spin_unlock(ptl); | |
942 | } | |
943 | ||
944 | /* | |
945 | * Save CONFIG_DEBUG_PAGEALLOC from faulting falsely on tail pages | |
946 | * during copy_user_huge_page()'s copy_page_rep(): in the case when | |
947 | * the source page gets split and a tail freed before copy completes. | |
948 | * Called under pmd_lock of checked pmd, so safe from splitting itself. | |
949 | */ | |
950 | static void get_user_huge_page(struct page *page) | |
951 | { | |
952 | if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { | |
953 | struct page *endpage = page + HPAGE_PMD_NR; | |
954 | ||
955 | atomic_add(HPAGE_PMD_NR, &page->_count); | |
956 | while (++page < endpage) | |
957 | get_huge_page_tail(page); | |
958 | } else { | |
959 | get_page(page); | |
960 | } | |
961 | } | |
962 | ||
963 | static void put_user_huge_page(struct page *page) | |
964 | { | |
965 | if (IS_ENABLED(CONFIG_DEBUG_PAGEALLOC)) { | |
966 | struct page *endpage = page + HPAGE_PMD_NR; | |
967 | ||
968 | while (page < endpage) | |
969 | put_page(page++); | |
970 | } else { | |
971 | put_page(page); | |
972 | } | |
973 | } | |
974 | ||
975 | static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, | |
976 | struct vm_area_struct *vma, | |
977 | unsigned long address, | |
978 | pmd_t *pmd, pmd_t orig_pmd, | |
979 | struct page *page, | |
980 | unsigned long haddr) | |
981 | { | |
982 | struct mem_cgroup *memcg; | |
983 | spinlock_t *ptl; | |
984 | pgtable_t pgtable; | |
985 | pmd_t _pmd; | |
986 | int ret = 0, i; | |
987 | struct page **pages; | |
988 | unsigned long mmun_start; /* For mmu_notifiers */ | |
989 | unsigned long mmun_end; /* For mmu_notifiers */ | |
990 | ||
991 | pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, | |
992 | GFP_KERNEL); | |
993 | if (unlikely(!pages)) { | |
994 | ret |= VM_FAULT_OOM; | |
995 | goto out; | |
996 | } | |
997 | ||
998 | for (i = 0; i < HPAGE_PMD_NR; i++) { | |
999 | pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE | | |
1000 | __GFP_OTHER_NODE, | |
1001 | vma, address, page_to_nid(page)); | |
1002 | if (unlikely(!pages[i] || | |
1003 | mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL, | |
1004 | &memcg))) { | |
1005 | if (pages[i]) | |
1006 | put_page(pages[i]); | |
1007 | while (--i >= 0) { | |
1008 | memcg = (void *)page_private(pages[i]); | |
1009 | set_page_private(pages[i], 0); | |
1010 | mem_cgroup_cancel_charge(pages[i], memcg); | |
1011 | put_page(pages[i]); | |
1012 | } | |
1013 | kfree(pages); | |
1014 | ret |= VM_FAULT_OOM; | |
1015 | goto out; | |
1016 | } | |
1017 | set_page_private(pages[i], (unsigned long)memcg); | |
1018 | } | |
1019 | ||
1020 | for (i = 0; i < HPAGE_PMD_NR; i++) { | |
1021 | copy_user_highpage(pages[i], page + i, | |
1022 | haddr + PAGE_SIZE * i, vma); | |
1023 | __SetPageUptodate(pages[i]); | |
1024 | cond_resched(); | |
1025 | } | |
1026 | ||
1027 | mmun_start = haddr; | |
1028 | mmun_end = haddr + HPAGE_PMD_SIZE; | |
1029 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); | |
1030 | ||
1031 | ptl = pmd_lock(mm, pmd); | |
1032 | if (unlikely(!pmd_same(*pmd, orig_pmd))) | |
1033 | goto out_free_pages; | |
1034 | VM_BUG_ON_PAGE(!PageHead(page), page); | |
1035 | ||
1036 | pmdp_clear_flush_notify(vma, haddr, pmd); | |
1037 | /* leave pmd empty until pte is filled */ | |
1038 | ||
1039 | pgtable = pgtable_trans_huge_withdraw(mm, pmd); | |
1040 | pmd_populate(mm, &_pmd, pgtable); | |
1041 | ||
1042 | for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { | |
1043 | pte_t *pte, entry; | |
1044 | entry = mk_pte(pages[i], vma->vm_page_prot); | |
1045 | entry = maybe_mkwrite(pte_mkdirty(entry), vma); | |
1046 | memcg = (void *)page_private(pages[i]); | |
1047 | set_page_private(pages[i], 0); | |
1048 | page_add_new_anon_rmap(pages[i], vma, haddr); | |
1049 | mem_cgroup_commit_charge(pages[i], memcg, false); | |
1050 | lru_cache_add_active_or_unevictable(pages[i], vma); | |
1051 | pte = pte_offset_map(&_pmd, haddr); | |
1052 | VM_BUG_ON(!pte_none(*pte)); | |
1053 | set_pte_at(mm, haddr, pte, entry); | |
1054 | pte_unmap(pte); | |
1055 | } | |
1056 | kfree(pages); | |
1057 | ||
1058 | smp_wmb(); /* make pte visible before pmd */ | |
1059 | pmd_populate(mm, pmd, pgtable); | |
1060 | page_remove_rmap(page); | |
1061 | spin_unlock(ptl); | |
1062 | ||
1063 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
1064 | ||
1065 | ret |= VM_FAULT_WRITE; | |
1066 | put_page(page); | |
1067 | ||
1068 | out: | |
1069 | return ret; | |
1070 | ||
1071 | out_free_pages: | |
1072 | spin_unlock(ptl); | |
1073 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
1074 | for (i = 0; i < HPAGE_PMD_NR; i++) { | |
1075 | memcg = (void *)page_private(pages[i]); | |
1076 | set_page_private(pages[i], 0); | |
1077 | mem_cgroup_cancel_charge(pages[i], memcg); | |
1078 | put_page(pages[i]); | |
1079 | } | |
1080 | kfree(pages); | |
1081 | goto out; | |
1082 | } | |
1083 | ||
1084 | int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, | |
1085 | unsigned long address, pmd_t *pmd, pmd_t orig_pmd) | |
1086 | { | |
1087 | spinlock_t *ptl; | |
1088 | int ret = 0; | |
1089 | struct page *page = NULL, *new_page; | |
1090 | struct mem_cgroup *memcg; | |
1091 | unsigned long haddr; | |
1092 | unsigned long mmun_start; /* For mmu_notifiers */ | |
1093 | unsigned long mmun_end; /* For mmu_notifiers */ | |
1094 | gfp_t huge_gfp; /* for allocation and charge */ | |
1095 | ||
1096 | ptl = pmd_lockptr(mm, pmd); | |
1097 | VM_BUG_ON_VMA(!vma->anon_vma, vma); | |
1098 | haddr = address & HPAGE_PMD_MASK; | |
1099 | if (is_huge_zero_pmd(orig_pmd)) | |
1100 | goto alloc; | |
1101 | spin_lock(ptl); | |
1102 | if (unlikely(!pmd_same(*pmd, orig_pmd))) | |
1103 | goto out_unlock; | |
1104 | ||
1105 | page = pmd_page(orig_pmd); | |
1106 | VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); | |
1107 | if (page_mapcount(page) == 1) { | |
1108 | pmd_t entry; | |
1109 | entry = pmd_mkyoung(orig_pmd); | |
1110 | entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); | |
1111 | if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1)) | |
1112 | update_mmu_cache_pmd(vma, address, pmd); | |
1113 | ret |= VM_FAULT_WRITE; | |
1114 | goto out_unlock; | |
1115 | } | |
1116 | get_user_huge_page(page); | |
1117 | spin_unlock(ptl); | |
1118 | alloc: | |
1119 | if (transparent_hugepage_enabled(vma) && | |
1120 | !transparent_hugepage_debug_cow()) { | |
1121 | huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0); | |
1122 | new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER); | |
1123 | } else | |
1124 | new_page = NULL; | |
1125 | ||
1126 | if (unlikely(!new_page)) { | |
1127 | if (!page) { | |
1128 | split_huge_page_pmd(vma, address, pmd); | |
1129 | ret |= VM_FAULT_FALLBACK; | |
1130 | } else { | |
1131 | ret = do_huge_pmd_wp_page_fallback(mm, vma, address, | |
1132 | pmd, orig_pmd, page, haddr); | |
1133 | if (ret & VM_FAULT_OOM) { | |
1134 | split_huge_page(page); | |
1135 | ret |= VM_FAULT_FALLBACK; | |
1136 | } | |
1137 | put_user_huge_page(page); | |
1138 | } | |
1139 | count_vm_event(THP_FAULT_FALLBACK); | |
1140 | goto out; | |
1141 | } | |
1142 | ||
1143 | if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg))) { | |
1144 | put_page(new_page); | |
1145 | if (page) { | |
1146 | split_huge_page(page); | |
1147 | put_user_huge_page(page); | |
1148 | } else | |
1149 | split_huge_page_pmd(vma, address, pmd); | |
1150 | ret |= VM_FAULT_FALLBACK; | |
1151 | count_vm_event(THP_FAULT_FALLBACK); | |
1152 | goto out; | |
1153 | } | |
1154 | ||
1155 | count_vm_event(THP_FAULT_ALLOC); | |
1156 | ||
1157 | if (!page) | |
1158 | clear_huge_page(new_page, haddr, HPAGE_PMD_NR); | |
1159 | else | |
1160 | copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); | |
1161 | __SetPageUptodate(new_page); | |
1162 | ||
1163 | mmun_start = haddr; | |
1164 | mmun_end = haddr + HPAGE_PMD_SIZE; | |
1165 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); | |
1166 | ||
1167 | spin_lock(ptl); | |
1168 | if (page) | |
1169 | put_user_huge_page(page); | |
1170 | if (unlikely(!pmd_same(*pmd, orig_pmd))) { | |
1171 | spin_unlock(ptl); | |
1172 | mem_cgroup_cancel_charge(new_page, memcg); | |
1173 | put_page(new_page); | |
1174 | goto out_mn; | |
1175 | } else { | |
1176 | pmd_t entry; | |
1177 | entry = mk_huge_pmd(new_page, vma->vm_page_prot); | |
1178 | entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); | |
1179 | pmdp_clear_flush_notify(vma, haddr, pmd); | |
1180 | page_add_new_anon_rmap(new_page, vma, haddr); | |
1181 | mem_cgroup_commit_charge(new_page, memcg, false); | |
1182 | lru_cache_add_active_or_unevictable(new_page, vma); | |
1183 | set_pmd_at(mm, haddr, pmd, entry); | |
1184 | update_mmu_cache_pmd(vma, address, pmd); | |
1185 | if (!page) { | |
1186 | add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); | |
1187 | put_huge_zero_page(); | |
1188 | } else { | |
1189 | VM_BUG_ON_PAGE(!PageHead(page), page); | |
1190 | page_remove_rmap(page); | |
1191 | put_page(page); | |
1192 | } | |
1193 | ret |= VM_FAULT_WRITE; | |
1194 | } | |
1195 | spin_unlock(ptl); | |
1196 | out_mn: | |
1197 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
1198 | out: | |
1199 | return ret; | |
1200 | out_unlock: | |
1201 | spin_unlock(ptl); | |
1202 | return ret; | |
1203 | } | |
1204 | ||
1205 | struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, | |
1206 | unsigned long addr, | |
1207 | pmd_t *pmd, | |
1208 | unsigned int flags) | |
1209 | { | |
1210 | struct mm_struct *mm = vma->vm_mm; | |
1211 | struct page *page = NULL; | |
1212 | ||
1213 | assert_spin_locked(pmd_lockptr(mm, pmd)); | |
1214 | ||
1215 | if (flags & FOLL_WRITE && !pmd_write(*pmd)) | |
1216 | goto out; | |
1217 | ||
1218 | /* Avoid dumping huge zero page */ | |
1219 | if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) | |
1220 | return ERR_PTR(-EFAULT); | |
1221 | ||
1222 | /* Full NUMA hinting faults to serialise migration in fault paths */ | |
1223 | if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) | |
1224 | goto out; | |
1225 | ||
1226 | page = pmd_page(*pmd); | |
1227 | VM_BUG_ON_PAGE(!PageHead(page), page); | |
1228 | if (flags & FOLL_TOUCH) { | |
1229 | pmd_t _pmd; | |
1230 | /* | |
1231 | * We should set the dirty bit only for FOLL_WRITE but | |
1232 | * for now the dirty bit in the pmd is meaningless. | |
1233 | * And if the dirty bit will become meaningful and | |
1234 | * we'll only set it with FOLL_WRITE, an atomic | |
1235 | * set_bit will be required on the pmd to set the | |
1236 | * young bit, instead of the current set_pmd_at. | |
1237 | */ | |
1238 | _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); | |
1239 | if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, | |
1240 | pmd, _pmd, 1)) | |
1241 | update_mmu_cache_pmd(vma, addr, pmd); | |
1242 | } | |
1243 | if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) { | |
1244 | if (page->mapping && trylock_page(page)) { | |
1245 | lru_add_drain(); | |
1246 | if (page->mapping) | |
1247 | mlock_vma_page(page); | |
1248 | unlock_page(page); | |
1249 | } | |
1250 | } | |
1251 | page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; | |
1252 | VM_BUG_ON_PAGE(!PageCompound(page), page); | |
1253 | if (flags & FOLL_GET) | |
1254 | get_page_foll(page); | |
1255 | ||
1256 | out: | |
1257 | return page; | |
1258 | } | |
1259 | ||
1260 | /* NUMA hinting page fault entry point for trans huge pmds */ | |
1261 | int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma, | |
1262 | unsigned long addr, pmd_t pmd, pmd_t *pmdp) | |
1263 | { | |
1264 | spinlock_t *ptl; | |
1265 | struct anon_vma *anon_vma = NULL; | |
1266 | struct page *page; | |
1267 | unsigned long haddr = addr & HPAGE_PMD_MASK; | |
1268 | int page_nid = -1, this_nid = numa_node_id(); | |
1269 | int target_nid, last_cpupid = -1; | |
1270 | bool page_locked; | |
1271 | bool migrated = false; | |
1272 | bool was_writable; | |
1273 | int flags = 0; | |
1274 | ||
1275 | /* A PROT_NONE fault should not end up here */ | |
1276 | BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))); | |
1277 | ||
1278 | ptl = pmd_lock(mm, pmdp); | |
1279 | if (unlikely(!pmd_same(pmd, *pmdp))) | |
1280 | goto out_unlock; | |
1281 | ||
1282 | /* | |
1283 | * If there are potential migrations, wait for completion and retry | |
1284 | * without disrupting NUMA hinting information. Do not relock and | |
1285 | * check_same as the page may no longer be mapped. | |
1286 | */ | |
1287 | if (unlikely(pmd_trans_migrating(*pmdp))) { | |
1288 | page = pmd_page(*pmdp); | |
1289 | spin_unlock(ptl); | |
1290 | wait_on_page_locked(page); | |
1291 | goto out; | |
1292 | } | |
1293 | ||
1294 | page = pmd_page(pmd); | |
1295 | BUG_ON(is_huge_zero_page(page)); | |
1296 | page_nid = page_to_nid(page); | |
1297 | last_cpupid = page_cpupid_last(page); | |
1298 | count_vm_numa_event(NUMA_HINT_FAULTS); | |
1299 | if (page_nid == this_nid) { | |
1300 | count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); | |
1301 | flags |= TNF_FAULT_LOCAL; | |
1302 | } | |
1303 | ||
1304 | /* See similar comment in do_numa_page for explanation */ | |
1305 | if (!(vma->vm_flags & VM_WRITE)) | |
1306 | flags |= TNF_NO_GROUP; | |
1307 | ||
1308 | /* | |
1309 | * Acquire the page lock to serialise THP migrations but avoid dropping | |
1310 | * page_table_lock if at all possible | |
1311 | */ | |
1312 | page_locked = trylock_page(page); | |
1313 | target_nid = mpol_misplaced(page, vma, haddr); | |
1314 | if (target_nid == -1) { | |
1315 | /* If the page was locked, there are no parallel migrations */ | |
1316 | if (page_locked) | |
1317 | goto clear_pmdnuma; | |
1318 | } | |
1319 | ||
1320 | /* Migration could have started since the pmd_trans_migrating check */ | |
1321 | if (!page_locked) { | |
1322 | spin_unlock(ptl); | |
1323 | wait_on_page_locked(page); | |
1324 | page_nid = -1; | |
1325 | goto out; | |
1326 | } | |
1327 | ||
1328 | /* | |
1329 | * Page is misplaced. Page lock serialises migrations. Acquire anon_vma | |
1330 | * to serialises splits | |
1331 | */ | |
1332 | get_page(page); | |
1333 | spin_unlock(ptl); | |
1334 | anon_vma = page_lock_anon_vma_read(page); | |
1335 | ||
1336 | /* Confirm the PMD did not change while page_table_lock was released */ | |
1337 | spin_lock(ptl); | |
1338 | if (unlikely(!pmd_same(pmd, *pmdp))) { | |
1339 | unlock_page(page); | |
1340 | put_page(page); | |
1341 | page_nid = -1; | |
1342 | goto out_unlock; | |
1343 | } | |
1344 | ||
1345 | /* Bail if we fail to protect against THP splits for any reason */ | |
1346 | if (unlikely(!anon_vma)) { | |
1347 | put_page(page); | |
1348 | page_nid = -1; | |
1349 | goto clear_pmdnuma; | |
1350 | } | |
1351 | ||
1352 | /* | |
1353 | * Migrate the THP to the requested node, returns with page unlocked | |
1354 | * and access rights restored. | |
1355 | */ | |
1356 | spin_unlock(ptl); | |
1357 | migrated = migrate_misplaced_transhuge_page(mm, vma, | |
1358 | pmdp, pmd, addr, page, target_nid); | |
1359 | if (migrated) { | |
1360 | flags |= TNF_MIGRATED; | |
1361 | page_nid = target_nid; | |
1362 | } else | |
1363 | flags |= TNF_MIGRATE_FAIL; | |
1364 | ||
1365 | goto out; | |
1366 | clear_pmdnuma: | |
1367 | BUG_ON(!PageLocked(page)); | |
1368 | was_writable = pmd_write(pmd); | |
1369 | pmd = pmd_modify(pmd, vma->vm_page_prot); | |
1370 | pmd = pmd_mkyoung(pmd); | |
1371 | if (was_writable) | |
1372 | pmd = pmd_mkwrite(pmd); | |
1373 | set_pmd_at(mm, haddr, pmdp, pmd); | |
1374 | update_mmu_cache_pmd(vma, addr, pmdp); | |
1375 | unlock_page(page); | |
1376 | out_unlock: | |
1377 | spin_unlock(ptl); | |
1378 | ||
1379 | out: | |
1380 | if (anon_vma) | |
1381 | page_unlock_anon_vma_read(anon_vma); | |
1382 | ||
1383 | if (page_nid != -1) | |
1384 | task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags); | |
1385 | ||
1386 | return 0; | |
1387 | } | |
1388 | ||
1389 | int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, | |
1390 | pmd_t *pmd, unsigned long addr) | |
1391 | { | |
1392 | spinlock_t *ptl; | |
1393 | int ret = 0; | |
1394 | ||
1395 | if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { | |
1396 | struct page *page; | |
1397 | pgtable_t pgtable; | |
1398 | pmd_t orig_pmd; | |
1399 | /* | |
1400 | * For architectures like ppc64 we look at deposited pgtable | |
1401 | * when calling pmdp_get_and_clear. So do the | |
1402 | * pgtable_trans_huge_withdraw after finishing pmdp related | |
1403 | * operations. | |
1404 | */ | |
1405 | orig_pmd = pmdp_get_and_clear_full(tlb->mm, addr, pmd, | |
1406 | tlb->fullmm); | |
1407 | tlb_remove_pmd_tlb_entry(tlb, pmd, addr); | |
1408 | pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd); | |
1409 | if (is_huge_zero_pmd(orig_pmd)) { | |
1410 | atomic_long_dec(&tlb->mm->nr_ptes); | |
1411 | spin_unlock(ptl); | |
1412 | put_huge_zero_page(); | |
1413 | } else { | |
1414 | page = pmd_page(orig_pmd); | |
1415 | page_remove_rmap(page); | |
1416 | VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); | |
1417 | add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); | |
1418 | VM_BUG_ON_PAGE(!PageHead(page), page); | |
1419 | atomic_long_dec(&tlb->mm->nr_ptes); | |
1420 | spin_unlock(ptl); | |
1421 | tlb_remove_page(tlb, page); | |
1422 | } | |
1423 | pte_free(tlb->mm, pgtable); | |
1424 | ret = 1; | |
1425 | } | |
1426 | return ret; | |
1427 | } | |
1428 | ||
1429 | int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma, | |
1430 | unsigned long old_addr, | |
1431 | unsigned long new_addr, unsigned long old_end, | |
1432 | pmd_t *old_pmd, pmd_t *new_pmd) | |
1433 | { | |
1434 | spinlock_t *old_ptl, *new_ptl; | |
1435 | int ret = 0; | |
1436 | pmd_t pmd; | |
1437 | ||
1438 | struct mm_struct *mm = vma->vm_mm; | |
1439 | ||
1440 | if ((old_addr & ~HPAGE_PMD_MASK) || | |
1441 | (new_addr & ~HPAGE_PMD_MASK) || | |
1442 | old_end - old_addr < HPAGE_PMD_SIZE || | |
1443 | (new_vma->vm_flags & VM_NOHUGEPAGE)) | |
1444 | goto out; | |
1445 | ||
1446 | /* | |
1447 | * The destination pmd shouldn't be established, free_pgtables() | |
1448 | * should have release it. | |
1449 | */ | |
1450 | if (WARN_ON(!pmd_none(*new_pmd))) { | |
1451 | VM_BUG_ON(pmd_trans_huge(*new_pmd)); | |
1452 | goto out; | |
1453 | } | |
1454 | ||
1455 | /* | |
1456 | * We don't have to worry about the ordering of src and dst | |
1457 | * ptlocks because exclusive mmap_sem prevents deadlock. | |
1458 | */ | |
1459 | ret = __pmd_trans_huge_lock(old_pmd, vma, &old_ptl); | |
1460 | if (ret == 1) { | |
1461 | new_ptl = pmd_lockptr(mm, new_pmd); | |
1462 | if (new_ptl != old_ptl) | |
1463 | spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); | |
1464 | pmd = pmdp_get_and_clear(mm, old_addr, old_pmd); | |
1465 | VM_BUG_ON(!pmd_none(*new_pmd)); | |
1466 | ||
1467 | if (pmd_move_must_withdraw(new_ptl, old_ptl)) { | |
1468 | pgtable_t pgtable; | |
1469 | pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); | |
1470 | pgtable_trans_huge_deposit(mm, new_pmd, pgtable); | |
1471 | } | |
1472 | set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); | |
1473 | if (new_ptl != old_ptl) | |
1474 | spin_unlock(new_ptl); | |
1475 | spin_unlock(old_ptl); | |
1476 | } | |
1477 | out: | |
1478 | return ret; | |
1479 | } | |
1480 | ||
1481 | /* | |
1482 | * Returns | |
1483 | * - 0 if PMD could not be locked | |
1484 | * - 1 if PMD was locked but protections unchange and TLB flush unnecessary | |
1485 | * - HPAGE_PMD_NR is protections changed and TLB flush necessary | |
1486 | */ | |
1487 | int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, | |
1488 | unsigned long addr, pgprot_t newprot, int prot_numa) | |
1489 | { | |
1490 | struct mm_struct *mm = vma->vm_mm; | |
1491 | spinlock_t *ptl; | |
1492 | int ret = 0; | |
1493 | ||
1494 | if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) { | |
1495 | pmd_t entry; | |
1496 | bool preserve_write = prot_numa && pmd_write(*pmd); | |
1497 | ret = 1; | |
1498 | ||
1499 | /* | |
1500 | * Avoid trapping faults against the zero page. The read-only | |
1501 | * data is likely to be read-cached on the local CPU and | |
1502 | * local/remote hits to the zero page are not interesting. | |
1503 | */ | |
1504 | if (prot_numa && is_huge_zero_pmd(*pmd)) { | |
1505 | spin_unlock(ptl); | |
1506 | return ret; | |
1507 | } | |
1508 | ||
1509 | if (!prot_numa || !pmd_protnone(*pmd)) { | |
1510 | entry = pmdp_get_and_clear_notify(mm, addr, pmd); | |
1511 | entry = pmd_modify(entry, newprot); | |
1512 | if (preserve_write) | |
1513 | entry = pmd_mkwrite(entry); | |
1514 | ret = HPAGE_PMD_NR; | |
1515 | set_pmd_at(mm, addr, pmd, entry); | |
1516 | BUG_ON(!preserve_write && pmd_write(entry)); | |
1517 | } | |
1518 | spin_unlock(ptl); | |
1519 | } | |
1520 | ||
1521 | return ret; | |
1522 | } | |
1523 | ||
1524 | /* | |
1525 | * Returns 1 if a given pmd maps a stable (not under splitting) thp. | |
1526 | * Returns -1 if it maps a thp under splitting. Returns 0 otherwise. | |
1527 | * | |
1528 | * Note that if it returns 1, this routine returns without unlocking page | |
1529 | * table locks. So callers must unlock them. | |
1530 | */ | |
1531 | int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma, | |
1532 | spinlock_t **ptl) | |
1533 | { | |
1534 | *ptl = pmd_lock(vma->vm_mm, pmd); | |
1535 | if (likely(pmd_trans_huge(*pmd))) { | |
1536 | if (unlikely(pmd_trans_splitting(*pmd))) { | |
1537 | spin_unlock(*ptl); | |
1538 | wait_split_huge_page(vma->anon_vma, pmd); | |
1539 | return -1; | |
1540 | } else { | |
1541 | /* Thp mapped by 'pmd' is stable, so we can | |
1542 | * handle it as it is. */ | |
1543 | return 1; | |
1544 | } | |
1545 | } | |
1546 | spin_unlock(*ptl); | |
1547 | return 0; | |
1548 | } | |
1549 | ||
1550 | /* | |
1551 | * This function returns whether a given @page is mapped onto the @address | |
1552 | * in the virtual space of @mm. | |
1553 | * | |
1554 | * When it's true, this function returns *pmd with holding the page table lock | |
1555 | * and passing it back to the caller via @ptl. | |
1556 | * If it's false, returns NULL without holding the page table lock. | |
1557 | */ | |
1558 | pmd_t *page_check_address_pmd(struct page *page, | |
1559 | struct mm_struct *mm, | |
1560 | unsigned long address, | |
1561 | enum page_check_address_pmd_flag flag, | |
1562 | spinlock_t **ptl) | |
1563 | { | |
1564 | pgd_t *pgd; | |
1565 | pud_t *pud; | |
1566 | pmd_t *pmd; | |
1567 | ||
1568 | if (address & ~HPAGE_PMD_MASK) | |
1569 | return NULL; | |
1570 | ||
1571 | pgd = pgd_offset(mm, address); | |
1572 | if (!pgd_present(*pgd)) | |
1573 | return NULL; | |
1574 | pud = pud_offset(pgd, address); | |
1575 | if (!pud_present(*pud)) | |
1576 | return NULL; | |
1577 | pmd = pmd_offset(pud, address); | |
1578 | ||
1579 | *ptl = pmd_lock(mm, pmd); | |
1580 | if (!pmd_present(*pmd)) | |
1581 | goto unlock; | |
1582 | if (pmd_page(*pmd) != page) | |
1583 | goto unlock; | |
1584 | /* | |
1585 | * split_vma() may create temporary aliased mappings. There is | |
1586 | * no risk as long as all huge pmd are found and have their | |
1587 | * splitting bit set before __split_huge_page_refcount | |
1588 | * runs. Finding the same huge pmd more than once during the | |
1589 | * same rmap walk is not a problem. | |
1590 | */ | |
1591 | if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG && | |
1592 | pmd_trans_splitting(*pmd)) | |
1593 | goto unlock; | |
1594 | if (pmd_trans_huge(*pmd)) { | |
1595 | VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG && | |
1596 | !pmd_trans_splitting(*pmd)); | |
1597 | return pmd; | |
1598 | } | |
1599 | unlock: | |
1600 | spin_unlock(*ptl); | |
1601 | return NULL; | |
1602 | } | |
1603 | ||
1604 | static int __split_huge_page_splitting(struct page *page, | |
1605 | struct vm_area_struct *vma, | |
1606 | unsigned long address) | |
1607 | { | |
1608 | struct mm_struct *mm = vma->vm_mm; | |
1609 | spinlock_t *ptl; | |
1610 | pmd_t *pmd; | |
1611 | int ret = 0; | |
1612 | /* For mmu_notifiers */ | |
1613 | const unsigned long mmun_start = address; | |
1614 | const unsigned long mmun_end = address + HPAGE_PMD_SIZE; | |
1615 | ||
1616 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); | |
1617 | pmd = page_check_address_pmd(page, mm, address, | |
1618 | PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG, &ptl); | |
1619 | if (pmd) { | |
1620 | /* | |
1621 | * We can't temporarily set the pmd to null in order | |
1622 | * to split it, the pmd must remain marked huge at all | |
1623 | * times or the VM won't take the pmd_trans_huge paths | |
1624 | * and it won't wait on the anon_vma->root->rwsem to | |
1625 | * serialize against split_huge_page*. | |
1626 | */ | |
1627 | pmdp_splitting_flush(vma, address, pmd); | |
1628 | ||
1629 | ret = 1; | |
1630 | spin_unlock(ptl); | |
1631 | } | |
1632 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
1633 | ||
1634 | return ret; | |
1635 | } | |
1636 | ||
1637 | static void __split_huge_page_refcount(struct page *page, | |
1638 | struct list_head *list) | |
1639 | { | |
1640 | int i; | |
1641 | struct zone *zone = page_zone(page); | |
1642 | struct lruvec *lruvec; | |
1643 | int tail_count = 0; | |
1644 | ||
1645 | /* prevent PageLRU to go away from under us, and freeze lru stats */ | |
1646 | spin_lock_irq(&zone->lru_lock); | |
1647 | lruvec = mem_cgroup_page_lruvec(page, zone); | |
1648 | ||
1649 | compound_lock(page); | |
1650 | /* complete memcg works before add pages to LRU */ | |
1651 | mem_cgroup_split_huge_fixup(page); | |
1652 | ||
1653 | for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { | |
1654 | struct page *page_tail = page + i; | |
1655 | ||
1656 | /* tail_page->_mapcount cannot change */ | |
1657 | BUG_ON(page_mapcount(page_tail) < 0); | |
1658 | tail_count += page_mapcount(page_tail); | |
1659 | /* check for overflow */ | |
1660 | BUG_ON(tail_count < 0); | |
1661 | BUG_ON(atomic_read(&page_tail->_count) != 0); | |
1662 | /* | |
1663 | * tail_page->_count is zero and not changing from | |
1664 | * under us. But get_page_unless_zero() may be running | |
1665 | * from under us on the tail_page. If we used | |
1666 | * atomic_set() below instead of atomic_add(), we | |
1667 | * would then run atomic_set() concurrently with | |
1668 | * get_page_unless_zero(), and atomic_set() is | |
1669 | * implemented in C not using locked ops. spin_unlock | |
1670 | * on x86 sometime uses locked ops because of PPro | |
1671 | * errata 66, 92, so unless somebody can guarantee | |
1672 | * atomic_set() here would be safe on all archs (and | |
1673 | * not only on x86), it's safer to use atomic_add(). | |
1674 | */ | |
1675 | atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1, | |
1676 | &page_tail->_count); | |
1677 | ||
1678 | /* after clearing PageTail the gup refcount can be released */ | |
1679 | smp_mb__after_atomic(); | |
1680 | ||
1681 | /* | |
1682 | * retain hwpoison flag of the poisoned tail page: | |
1683 | * fix for the unsuitable process killed on Guest Machine(KVM) | |
1684 | * by the memory-failure. | |
1685 | */ | |
1686 | page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON; | |
1687 | page_tail->flags |= (page->flags & | |
1688 | ((1L << PG_referenced) | | |
1689 | (1L << PG_swapbacked) | | |
1690 | (1L << PG_mlocked) | | |
1691 | (1L << PG_uptodate) | | |
1692 | (1L << PG_active) | | |
1693 | (1L << PG_unevictable))); | |
1694 | page_tail->flags |= (1L << PG_dirty); | |
1695 | ||
1696 | /* clear PageTail before overwriting first_page */ | |
1697 | smp_wmb(); | |
1698 | ||
1699 | /* | |
1700 | * __split_huge_page_splitting() already set the | |
1701 | * splitting bit in all pmd that could map this | |
1702 | * hugepage, that will ensure no CPU can alter the | |
1703 | * mapcount on the head page. The mapcount is only | |
1704 | * accounted in the head page and it has to be | |
1705 | * transferred to all tail pages in the below code. So | |
1706 | * for this code to be safe, the split the mapcount | |
1707 | * can't change. But that doesn't mean userland can't | |
1708 | * keep changing and reading the page contents while | |
1709 | * we transfer the mapcount, so the pmd splitting | |
1710 | * status is achieved setting a reserved bit in the | |
1711 | * pmd, not by clearing the present bit. | |
1712 | */ | |
1713 | page_tail->_mapcount = page->_mapcount; | |
1714 | ||
1715 | BUG_ON(page_tail->mapping); | |
1716 | page_tail->mapping = page->mapping; | |
1717 | ||
1718 | page_tail->index = page->index + i; | |
1719 | page_cpupid_xchg_last(page_tail, page_cpupid_last(page)); | |
1720 | ||
1721 | BUG_ON(!PageAnon(page_tail)); | |
1722 | BUG_ON(!PageUptodate(page_tail)); | |
1723 | BUG_ON(!PageDirty(page_tail)); | |
1724 | BUG_ON(!PageSwapBacked(page_tail)); | |
1725 | ||
1726 | lru_add_page_tail(page, page_tail, lruvec, list); | |
1727 | } | |
1728 | atomic_sub(tail_count, &page->_count); | |
1729 | BUG_ON(atomic_read(&page->_count) <= 0); | |
1730 | ||
1731 | __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1); | |
1732 | ||
1733 | ClearPageCompound(page); | |
1734 | compound_unlock(page); | |
1735 | spin_unlock_irq(&zone->lru_lock); | |
1736 | ||
1737 | for (i = 1; i < HPAGE_PMD_NR; i++) { | |
1738 | struct page *page_tail = page + i; | |
1739 | BUG_ON(page_count(page_tail) <= 0); | |
1740 | /* | |
1741 | * Tail pages may be freed if there wasn't any mapping | |
1742 | * like if add_to_swap() is running on a lru page that | |
1743 | * had its mapping zapped. And freeing these pages | |
1744 | * requires taking the lru_lock so we do the put_page | |
1745 | * of the tail pages after the split is complete. | |
1746 | */ | |
1747 | put_page(page_tail); | |
1748 | } | |
1749 | ||
1750 | /* | |
1751 | * Only the head page (now become a regular page) is required | |
1752 | * to be pinned by the caller. | |
1753 | */ | |
1754 | BUG_ON(page_count(page) <= 0); | |
1755 | } | |
1756 | ||
1757 | static int __split_huge_page_map(struct page *page, | |
1758 | struct vm_area_struct *vma, | |
1759 | unsigned long address) | |
1760 | { | |
1761 | struct mm_struct *mm = vma->vm_mm; | |
1762 | spinlock_t *ptl; | |
1763 | pmd_t *pmd, _pmd; | |
1764 | int ret = 0, i; | |
1765 | pgtable_t pgtable; | |
1766 | unsigned long haddr; | |
1767 | ||
1768 | pmd = page_check_address_pmd(page, mm, address, | |
1769 | PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG, &ptl); | |
1770 | if (pmd) { | |
1771 | pgtable = pgtable_trans_huge_withdraw(mm, pmd); | |
1772 | pmd_populate(mm, &_pmd, pgtable); | |
1773 | if (pmd_write(*pmd)) | |
1774 | BUG_ON(page_mapcount(page) != 1); | |
1775 | ||
1776 | haddr = address; | |
1777 | for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { | |
1778 | pte_t *pte, entry; | |
1779 | BUG_ON(PageCompound(page+i)); | |
1780 | /* | |
1781 | * Note that NUMA hinting access restrictions are not | |
1782 | * transferred to avoid any possibility of altering | |
1783 | * permissions across VMAs. | |
1784 | */ | |
1785 | entry = mk_pte(page + i, vma->vm_page_prot); | |
1786 | entry = maybe_mkwrite(pte_mkdirty(entry), vma); | |
1787 | if (!pmd_write(*pmd)) | |
1788 | entry = pte_wrprotect(entry); | |
1789 | if (!pmd_young(*pmd)) | |
1790 | entry = pte_mkold(entry); | |
1791 | pte = pte_offset_map(&_pmd, haddr); | |
1792 | BUG_ON(!pte_none(*pte)); | |
1793 | set_pte_at(mm, haddr, pte, entry); | |
1794 | pte_unmap(pte); | |
1795 | } | |
1796 | ||
1797 | smp_wmb(); /* make pte visible before pmd */ | |
1798 | /* | |
1799 | * Up to this point the pmd is present and huge and | |
1800 | * userland has the whole access to the hugepage | |
1801 | * during the split (which happens in place). If we | |
1802 | * overwrite the pmd with the not-huge version | |
1803 | * pointing to the pte here (which of course we could | |
1804 | * if all CPUs were bug free), userland could trigger | |
1805 | * a small page size TLB miss on the small sized TLB | |
1806 | * while the hugepage TLB entry is still established | |
1807 | * in the huge TLB. Some CPU doesn't like that. See | |
1808 | * http://support.amd.com/us/Processor_TechDocs/41322.pdf, | |
1809 | * Erratum 383 on page 93. Intel should be safe but is | |
1810 | * also warns that it's only safe if the permission | |
1811 | * and cache attributes of the two entries loaded in | |
1812 | * the two TLB is identical (which should be the case | |
1813 | * here). But it is generally safer to never allow | |
1814 | * small and huge TLB entries for the same virtual | |
1815 | * address to be loaded simultaneously. So instead of | |
1816 | * doing "pmd_populate(); flush_tlb_range();" we first | |
1817 | * mark the current pmd notpresent (atomically because | |
1818 | * here the pmd_trans_huge and pmd_trans_splitting | |
1819 | * must remain set at all times on the pmd until the | |
1820 | * split is complete for this pmd), then we flush the | |
1821 | * SMP TLB and finally we write the non-huge version | |
1822 | * of the pmd entry with pmd_populate. | |
1823 | */ | |
1824 | pmdp_invalidate(vma, address, pmd); | |
1825 | pmd_populate(mm, pmd, pgtable); | |
1826 | ret = 1; | |
1827 | spin_unlock(ptl); | |
1828 | } | |
1829 | ||
1830 | return ret; | |
1831 | } | |
1832 | ||
1833 | /* must be called with anon_vma->root->rwsem held */ | |
1834 | static void __split_huge_page(struct page *page, | |
1835 | struct anon_vma *anon_vma, | |
1836 | struct list_head *list) | |
1837 | { | |
1838 | int mapcount, mapcount2; | |
1839 | pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); | |
1840 | struct anon_vma_chain *avc; | |
1841 | ||
1842 | BUG_ON(!PageHead(page)); | |
1843 | BUG_ON(PageTail(page)); | |
1844 | ||
1845 | mapcount = 0; | |
1846 | anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { | |
1847 | struct vm_area_struct *vma = avc->vma; | |
1848 | unsigned long addr = vma_address(page, vma); | |
1849 | BUG_ON(is_vma_temporary_stack(vma)); | |
1850 | mapcount += __split_huge_page_splitting(page, vma, addr); | |
1851 | } | |
1852 | /* | |
1853 | * It is critical that new vmas are added to the tail of the | |
1854 | * anon_vma list. This guarantes that if copy_huge_pmd() runs | |
1855 | * and establishes a child pmd before | |
1856 | * __split_huge_page_splitting() freezes the parent pmd (so if | |
1857 | * we fail to prevent copy_huge_pmd() from running until the | |
1858 | * whole __split_huge_page() is complete), we will still see | |
1859 | * the newly established pmd of the child later during the | |
1860 | * walk, to be able to set it as pmd_trans_splitting too. | |
1861 | */ | |
1862 | if (mapcount != page_mapcount(page)) { | |
1863 | pr_err("mapcount %d page_mapcount %d\n", | |
1864 | mapcount, page_mapcount(page)); | |
1865 | BUG(); | |
1866 | } | |
1867 | ||
1868 | __split_huge_page_refcount(page, list); | |
1869 | ||
1870 | mapcount2 = 0; | |
1871 | anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { | |
1872 | struct vm_area_struct *vma = avc->vma; | |
1873 | unsigned long addr = vma_address(page, vma); | |
1874 | BUG_ON(is_vma_temporary_stack(vma)); | |
1875 | mapcount2 += __split_huge_page_map(page, vma, addr); | |
1876 | } | |
1877 | if (mapcount != mapcount2) { | |
1878 | pr_err("mapcount %d mapcount2 %d page_mapcount %d\n", | |
1879 | mapcount, mapcount2, page_mapcount(page)); | |
1880 | BUG(); | |
1881 | } | |
1882 | } | |
1883 | ||
1884 | /* | |
1885 | * Split a hugepage into normal pages. This doesn't change the position of head | |
1886 | * page. If @list is null, tail pages will be added to LRU list, otherwise, to | |
1887 | * @list. Both head page and tail pages will inherit mapping, flags, and so on | |
1888 | * from the hugepage. | |
1889 | * Return 0 if the hugepage is split successfully otherwise return 1. | |
1890 | */ | |
1891 | int split_huge_page_to_list(struct page *page, struct list_head *list) | |
1892 | { | |
1893 | struct anon_vma *anon_vma; | |
1894 | int ret = 1; | |
1895 | ||
1896 | BUG_ON(is_huge_zero_page(page)); | |
1897 | BUG_ON(!PageAnon(page)); | |
1898 | ||
1899 | /* | |
1900 | * The caller does not necessarily hold an mmap_sem that would prevent | |
1901 | * the anon_vma disappearing so we first we take a reference to it | |
1902 | * and then lock the anon_vma for write. This is similar to | |
1903 | * page_lock_anon_vma_read except the write lock is taken to serialise | |
1904 | * against parallel split or collapse operations. | |
1905 | */ | |
1906 | anon_vma = page_get_anon_vma(page); | |
1907 | if (!anon_vma) | |
1908 | goto out; | |
1909 | anon_vma_lock_write(anon_vma); | |
1910 | ||
1911 | ret = 0; | |
1912 | if (!PageCompound(page)) | |
1913 | goto out_unlock; | |
1914 | ||
1915 | BUG_ON(!PageSwapBacked(page)); | |
1916 | __split_huge_page(page, anon_vma, list); | |
1917 | count_vm_event(THP_SPLIT); | |
1918 | ||
1919 | BUG_ON(PageCompound(page)); | |
1920 | out_unlock: | |
1921 | anon_vma_unlock_write(anon_vma); | |
1922 | put_anon_vma(anon_vma); | |
1923 | out: | |
1924 | return ret; | |
1925 | } | |
1926 | ||
1927 | #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE) | |
1928 | ||
1929 | int hugepage_madvise(struct vm_area_struct *vma, | |
1930 | unsigned long *vm_flags, int advice) | |
1931 | { | |
1932 | switch (advice) { | |
1933 | case MADV_HUGEPAGE: | |
1934 | #ifdef CONFIG_S390 | |
1935 | /* | |
1936 | * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 | |
1937 | * can't handle this properly after s390_enable_sie, so we simply | |
1938 | * ignore the madvise to prevent qemu from causing a SIGSEGV. | |
1939 | */ | |
1940 | if (mm_has_pgste(vma->vm_mm)) | |
1941 | return 0; | |
1942 | #endif | |
1943 | /* | |
1944 | * Be somewhat over-protective like KSM for now! | |
1945 | */ | |
1946 | if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) | |
1947 | return -EINVAL; | |
1948 | *vm_flags &= ~VM_NOHUGEPAGE; | |
1949 | *vm_flags |= VM_HUGEPAGE; | |
1950 | /* | |
1951 | * If the vma become good for khugepaged to scan, | |
1952 | * register it here without waiting a page fault that | |
1953 | * may not happen any time soon. | |
1954 | */ | |
1955 | if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags))) | |
1956 | return -ENOMEM; | |
1957 | break; | |
1958 | case MADV_NOHUGEPAGE: | |
1959 | /* | |
1960 | * Be somewhat over-protective like KSM for now! | |
1961 | */ | |
1962 | if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) | |
1963 | return -EINVAL; | |
1964 | *vm_flags &= ~VM_HUGEPAGE; | |
1965 | *vm_flags |= VM_NOHUGEPAGE; | |
1966 | /* | |
1967 | * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning | |
1968 | * this vma even if we leave the mm registered in khugepaged if | |
1969 | * it got registered before VM_NOHUGEPAGE was set. | |
1970 | */ | |
1971 | break; | |
1972 | } | |
1973 | ||
1974 | return 0; | |
1975 | } | |
1976 | ||
1977 | static int __init khugepaged_slab_init(void) | |
1978 | { | |
1979 | mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", | |
1980 | sizeof(struct mm_slot), | |
1981 | __alignof__(struct mm_slot), 0, NULL); | |
1982 | if (!mm_slot_cache) | |
1983 | return -ENOMEM; | |
1984 | ||
1985 | return 0; | |
1986 | } | |
1987 | ||
1988 | static void __init khugepaged_slab_exit(void) | |
1989 | { | |
1990 | kmem_cache_destroy(mm_slot_cache); | |
1991 | } | |
1992 | ||
1993 | static inline struct mm_slot *alloc_mm_slot(void) | |
1994 | { | |
1995 | if (!mm_slot_cache) /* initialization failed */ | |
1996 | return NULL; | |
1997 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
1998 | } | |
1999 | ||
2000 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
2001 | { | |
2002 | kmem_cache_free(mm_slot_cache, mm_slot); | |
2003 | } | |
2004 | ||
2005 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) | |
2006 | { | |
2007 | struct mm_slot *mm_slot; | |
2008 | ||
2009 | hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) | |
2010 | if (mm == mm_slot->mm) | |
2011 | return mm_slot; | |
2012 | ||
2013 | return NULL; | |
2014 | } | |
2015 | ||
2016 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
2017 | struct mm_slot *mm_slot) | |
2018 | { | |
2019 | mm_slot->mm = mm; | |
2020 | hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); | |
2021 | } | |
2022 | ||
2023 | static inline int khugepaged_test_exit(struct mm_struct *mm) | |
2024 | { | |
2025 | return atomic_read(&mm->mm_users) == 0; | |
2026 | } | |
2027 | ||
2028 | int __khugepaged_enter(struct mm_struct *mm) | |
2029 | { | |
2030 | struct mm_slot *mm_slot; | |
2031 | int wakeup; | |
2032 | ||
2033 | mm_slot = alloc_mm_slot(); | |
2034 | if (!mm_slot) | |
2035 | return -ENOMEM; | |
2036 | ||
2037 | /* __khugepaged_exit() must not run from under us */ | |
2038 | VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); | |
2039 | if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { | |
2040 | free_mm_slot(mm_slot); | |
2041 | return 0; | |
2042 | } | |
2043 | ||
2044 | spin_lock(&khugepaged_mm_lock); | |
2045 | insert_to_mm_slots_hash(mm, mm_slot); | |
2046 | /* | |
2047 | * Insert just behind the scanning cursor, to let the area settle | |
2048 | * down a little. | |
2049 | */ | |
2050 | wakeup = list_empty(&khugepaged_scan.mm_head); | |
2051 | list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); | |
2052 | spin_unlock(&khugepaged_mm_lock); | |
2053 | ||
2054 | atomic_inc(&mm->mm_count); | |
2055 | if (wakeup) | |
2056 | wake_up_interruptible(&khugepaged_wait); | |
2057 | ||
2058 | return 0; | |
2059 | } | |
2060 | ||
2061 | int khugepaged_enter_vma_merge(struct vm_area_struct *vma, | |
2062 | unsigned long vm_flags) | |
2063 | { | |
2064 | unsigned long hstart, hend; | |
2065 | if (!vma->anon_vma) | |
2066 | /* | |
2067 | * Not yet faulted in so we will register later in the | |
2068 | * page fault if needed. | |
2069 | */ | |
2070 | return 0; | |
2071 | if (vma->vm_ops) | |
2072 | /* khugepaged not yet working on file or special mappings */ | |
2073 | return 0; | |
2074 | VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma); | |
2075 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; | |
2076 | hend = vma->vm_end & HPAGE_PMD_MASK; | |
2077 | if (hstart < hend) | |
2078 | return khugepaged_enter(vma, vm_flags); | |
2079 | return 0; | |
2080 | } | |
2081 | ||
2082 | void __khugepaged_exit(struct mm_struct *mm) | |
2083 | { | |
2084 | struct mm_slot *mm_slot; | |
2085 | int free = 0; | |
2086 | ||
2087 | spin_lock(&khugepaged_mm_lock); | |
2088 | mm_slot = get_mm_slot(mm); | |
2089 | if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { | |
2090 | hash_del(&mm_slot->hash); | |
2091 | list_del(&mm_slot->mm_node); | |
2092 | free = 1; | |
2093 | } | |
2094 | spin_unlock(&khugepaged_mm_lock); | |
2095 | ||
2096 | if (free) { | |
2097 | clear_bit(MMF_VM_HUGEPAGE, &mm->flags); | |
2098 | free_mm_slot(mm_slot); | |
2099 | mmdrop(mm); | |
2100 | } else if (mm_slot) { | |
2101 | /* | |
2102 | * This is required to serialize against | |
2103 | * khugepaged_test_exit() (which is guaranteed to run | |
2104 | * under mmap sem read mode). Stop here (after we | |
2105 | * return all pagetables will be destroyed) until | |
2106 | * khugepaged has finished working on the pagetables | |
2107 | * under the mmap_sem. | |
2108 | */ | |
2109 | down_write(&mm->mmap_sem); | |
2110 | up_write(&mm->mmap_sem); | |
2111 | } | |
2112 | } | |
2113 | ||
2114 | static void release_pte_page(struct page *page) | |
2115 | { | |
2116 | /* 0 stands for page_is_file_cache(page) == false */ | |
2117 | dec_zone_page_state(page, NR_ISOLATED_ANON + 0); | |
2118 | unlock_page(page); | |
2119 | putback_lru_page(page); | |
2120 | } | |
2121 | ||
2122 | static void release_pte_pages(pte_t *pte, pte_t *_pte) | |
2123 | { | |
2124 | while (--_pte >= pte) { | |
2125 | pte_t pteval = *_pte; | |
2126 | if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) | |
2127 | release_pte_page(pte_page(pteval)); | |
2128 | } | |
2129 | } | |
2130 | ||
2131 | static int __collapse_huge_page_isolate(struct vm_area_struct *vma, | |
2132 | unsigned long address, | |
2133 | pte_t *pte) | |
2134 | { | |
2135 | struct page *page; | |
2136 | pte_t *_pte; | |
2137 | int none_or_zero = 0; | |
2138 | bool referenced = false, writable = false; | |
2139 | for (_pte = pte; _pte < pte+HPAGE_PMD_NR; | |
2140 | _pte++, address += PAGE_SIZE) { | |
2141 | pte_t pteval = *_pte; | |
2142 | if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { | |
2143 | if (++none_or_zero <= khugepaged_max_ptes_none) | |
2144 | continue; | |
2145 | else | |
2146 | goto out; | |
2147 | } | |
2148 | if (!pte_present(pteval)) | |
2149 | goto out; | |
2150 | page = vm_normal_page(vma, address, pteval); | |
2151 | if (unlikely(!page)) | |
2152 | goto out; | |
2153 | ||
2154 | VM_BUG_ON_PAGE(PageCompound(page), page); | |
2155 | VM_BUG_ON_PAGE(!PageAnon(page), page); | |
2156 | VM_BUG_ON_PAGE(!PageSwapBacked(page), page); | |
2157 | ||
2158 | /* | |
2159 | * We can do it before isolate_lru_page because the | |
2160 | * page can't be freed from under us. NOTE: PG_lock | |
2161 | * is needed to serialize against split_huge_page | |
2162 | * when invoked from the VM. | |
2163 | */ | |
2164 | if (!trylock_page(page)) | |
2165 | goto out; | |
2166 | ||
2167 | /* | |
2168 | * cannot use mapcount: can't collapse if there's a gup pin. | |
2169 | * The page must only be referenced by the scanned process | |
2170 | * and page swap cache. | |
2171 | */ | |
2172 | if (page_count(page) != 1 + !!PageSwapCache(page)) { | |
2173 | unlock_page(page); | |
2174 | goto out; | |
2175 | } | |
2176 | if (pte_write(pteval)) { | |
2177 | writable = true; | |
2178 | } else { | |
2179 | if (PageSwapCache(page) && !reuse_swap_page(page)) { | |
2180 | unlock_page(page); | |
2181 | goto out; | |
2182 | } | |
2183 | /* | |
2184 | * Page is not in the swap cache. It can be collapsed | |
2185 | * into a THP. | |
2186 | */ | |
2187 | } | |
2188 | ||
2189 | /* | |
2190 | * Isolate the page to avoid collapsing an hugepage | |
2191 | * currently in use by the VM. | |
2192 | */ | |
2193 | if (isolate_lru_page(page)) { | |
2194 | unlock_page(page); | |
2195 | goto out; | |
2196 | } | |
2197 | /* 0 stands for page_is_file_cache(page) == false */ | |
2198 | inc_zone_page_state(page, NR_ISOLATED_ANON + 0); | |
2199 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
2200 | VM_BUG_ON_PAGE(PageLRU(page), page); | |
2201 | ||
2202 | /* If there is no mapped pte young don't collapse the page */ | |
2203 | if (pte_young(pteval) || PageReferenced(page) || | |
2204 | mmu_notifier_test_young(vma->vm_mm, address)) | |
2205 | referenced = true; | |
2206 | } | |
2207 | if (likely(referenced && writable)) | |
2208 | return 1; | |
2209 | out: | |
2210 | release_pte_pages(pte, _pte); | |
2211 | return 0; | |
2212 | } | |
2213 | ||
2214 | static void __collapse_huge_page_copy(pte_t *pte, struct page *page, | |
2215 | struct vm_area_struct *vma, | |
2216 | unsigned long address, | |
2217 | spinlock_t *ptl) | |
2218 | { | |
2219 | pte_t *_pte; | |
2220 | for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) { | |
2221 | pte_t pteval = *_pte; | |
2222 | struct page *src_page; | |
2223 | ||
2224 | if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { | |
2225 | clear_user_highpage(page, address); | |
2226 | add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); | |
2227 | if (is_zero_pfn(pte_pfn(pteval))) { | |
2228 | /* | |
2229 | * ptl mostly unnecessary. | |
2230 | */ | |
2231 | spin_lock(ptl); | |
2232 | /* | |
2233 | * paravirt calls inside pte_clear here are | |
2234 | * superfluous. | |
2235 | */ | |
2236 | pte_clear(vma->vm_mm, address, _pte); | |
2237 | spin_unlock(ptl); | |
2238 | } | |
2239 | } else { | |
2240 | src_page = pte_page(pteval); | |
2241 | copy_user_highpage(page, src_page, address, vma); | |
2242 | VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); | |
2243 | release_pte_page(src_page); | |
2244 | /* | |
2245 | * ptl mostly unnecessary, but preempt has to | |
2246 | * be disabled to update the per-cpu stats | |
2247 | * inside page_remove_rmap(). | |
2248 | */ | |
2249 | spin_lock(ptl); | |
2250 | /* | |
2251 | * paravirt calls inside pte_clear here are | |
2252 | * superfluous. | |
2253 | */ | |
2254 | pte_clear(vma->vm_mm, address, _pte); | |
2255 | page_remove_rmap(src_page); | |
2256 | spin_unlock(ptl); | |
2257 | free_page_and_swap_cache(src_page); | |
2258 | } | |
2259 | ||
2260 | address += PAGE_SIZE; | |
2261 | page++; | |
2262 | } | |
2263 | } | |
2264 | ||
2265 | static void khugepaged_alloc_sleep(void) | |
2266 | { | |
2267 | wait_event_freezable_timeout(khugepaged_wait, false, | |
2268 | msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); | |
2269 | } | |
2270 | ||
2271 | static int khugepaged_node_load[MAX_NUMNODES]; | |
2272 | ||
2273 | static bool khugepaged_scan_abort(int nid) | |
2274 | { | |
2275 | int i; | |
2276 | ||
2277 | /* | |
2278 | * If zone_reclaim_mode is disabled, then no extra effort is made to | |
2279 | * allocate memory locally. | |
2280 | */ | |
2281 | if (!zone_reclaim_mode) | |
2282 | return false; | |
2283 | ||
2284 | /* If there is a count for this node already, it must be acceptable */ | |
2285 | if (khugepaged_node_load[nid]) | |
2286 | return false; | |
2287 | ||
2288 | for (i = 0; i < MAX_NUMNODES; i++) { | |
2289 | if (!khugepaged_node_load[i]) | |
2290 | continue; | |
2291 | if (node_distance(nid, i) > RECLAIM_DISTANCE) | |
2292 | return true; | |
2293 | } | |
2294 | return false; | |
2295 | } | |
2296 | ||
2297 | #ifdef CONFIG_NUMA | |
2298 | static int khugepaged_find_target_node(void) | |
2299 | { | |
2300 | static int last_khugepaged_target_node = NUMA_NO_NODE; | |
2301 | int nid, target_node = 0, max_value = 0; | |
2302 | ||
2303 | /* find first node with max normal pages hit */ | |
2304 | for (nid = 0; nid < MAX_NUMNODES; nid++) | |
2305 | if (khugepaged_node_load[nid] > max_value) { | |
2306 | max_value = khugepaged_node_load[nid]; | |
2307 | target_node = nid; | |
2308 | } | |
2309 | ||
2310 | /* do some balance if several nodes have the same hit record */ | |
2311 | if (target_node <= last_khugepaged_target_node) | |
2312 | for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; | |
2313 | nid++) | |
2314 | if (max_value == khugepaged_node_load[nid]) { | |
2315 | target_node = nid; | |
2316 | break; | |
2317 | } | |
2318 | ||
2319 | last_khugepaged_target_node = target_node; | |
2320 | return target_node; | |
2321 | } | |
2322 | ||
2323 | static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) | |
2324 | { | |
2325 | if (IS_ERR(*hpage)) { | |
2326 | if (!*wait) | |
2327 | return false; | |
2328 | ||
2329 | *wait = false; | |
2330 | *hpage = NULL; | |
2331 | khugepaged_alloc_sleep(); | |
2332 | } else if (*hpage) { | |
2333 | put_page(*hpage); | |
2334 | *hpage = NULL; | |
2335 | } | |
2336 | ||
2337 | return true; | |
2338 | } | |
2339 | ||
2340 | static struct page * | |
2341 | khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, | |
2342 | struct vm_area_struct *vma, unsigned long address, | |
2343 | int node) | |
2344 | { | |
2345 | VM_BUG_ON_PAGE(*hpage, *hpage); | |
2346 | ||
2347 | /* | |
2348 | * Before allocating the hugepage, release the mmap_sem read lock. | |
2349 | * The allocation can take potentially a long time if it involves | |
2350 | * sync compaction, and we do not need to hold the mmap_sem during | |
2351 | * that. We will recheck the vma after taking it again in write mode. | |
2352 | */ | |
2353 | up_read(&mm->mmap_sem); | |
2354 | ||
2355 | *hpage = alloc_pages_exact_node(node, gfp, HPAGE_PMD_ORDER); | |
2356 | if (unlikely(!*hpage)) { | |
2357 | count_vm_event(THP_COLLAPSE_ALLOC_FAILED); | |
2358 | *hpage = ERR_PTR(-ENOMEM); | |
2359 | return NULL; | |
2360 | } | |
2361 | ||
2362 | count_vm_event(THP_COLLAPSE_ALLOC); | |
2363 | return *hpage; | |
2364 | } | |
2365 | #else | |
2366 | static int khugepaged_find_target_node(void) | |
2367 | { | |
2368 | return 0; | |
2369 | } | |
2370 | ||
2371 | static inline struct page *alloc_hugepage(int defrag) | |
2372 | { | |
2373 | return alloc_pages(alloc_hugepage_gfpmask(defrag, 0), | |
2374 | HPAGE_PMD_ORDER); | |
2375 | } | |
2376 | ||
2377 | static struct page *khugepaged_alloc_hugepage(bool *wait) | |
2378 | { | |
2379 | struct page *hpage; | |
2380 | ||
2381 | do { | |
2382 | hpage = alloc_hugepage(khugepaged_defrag()); | |
2383 | if (!hpage) { | |
2384 | count_vm_event(THP_COLLAPSE_ALLOC_FAILED); | |
2385 | if (!*wait) | |
2386 | return NULL; | |
2387 | ||
2388 | *wait = false; | |
2389 | khugepaged_alloc_sleep(); | |
2390 | } else | |
2391 | count_vm_event(THP_COLLAPSE_ALLOC); | |
2392 | } while (unlikely(!hpage) && likely(khugepaged_enabled())); | |
2393 | ||
2394 | return hpage; | |
2395 | } | |
2396 | ||
2397 | static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) | |
2398 | { | |
2399 | if (!*hpage) | |
2400 | *hpage = khugepaged_alloc_hugepage(wait); | |
2401 | ||
2402 | if (unlikely(!*hpage)) | |
2403 | return false; | |
2404 | ||
2405 | return true; | |
2406 | } | |
2407 | ||
2408 | static struct page * | |
2409 | khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm, | |
2410 | struct vm_area_struct *vma, unsigned long address, | |
2411 | int node) | |
2412 | { | |
2413 | up_read(&mm->mmap_sem); | |
2414 | VM_BUG_ON(!*hpage); | |
2415 | ||
2416 | return *hpage; | |
2417 | } | |
2418 | #endif | |
2419 | ||
2420 | static bool hugepage_vma_check(struct vm_area_struct *vma) | |
2421 | { | |
2422 | if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || | |
2423 | (vma->vm_flags & VM_NOHUGEPAGE)) | |
2424 | return false; | |
2425 | ||
2426 | if (!vma->anon_vma || vma->vm_ops) | |
2427 | return false; | |
2428 | if (is_vma_temporary_stack(vma)) | |
2429 | return false; | |
2430 | VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma); | |
2431 | return true; | |
2432 | } | |
2433 | ||
2434 | static void collapse_huge_page(struct mm_struct *mm, | |
2435 | unsigned long address, | |
2436 | struct page **hpage, | |
2437 | struct vm_area_struct *vma, | |
2438 | int node) | |
2439 | { | |
2440 | pmd_t *pmd, _pmd; | |
2441 | pte_t *pte; | |
2442 | pgtable_t pgtable; | |
2443 | struct page *new_page; | |
2444 | spinlock_t *pmd_ptl, *pte_ptl; | |
2445 | int isolated; | |
2446 | unsigned long hstart, hend; | |
2447 | struct mem_cgroup *memcg; | |
2448 | unsigned long mmun_start; /* For mmu_notifiers */ | |
2449 | unsigned long mmun_end; /* For mmu_notifiers */ | |
2450 | gfp_t gfp; | |
2451 | ||
2452 | VM_BUG_ON(address & ~HPAGE_PMD_MASK); | |
2453 | ||
2454 | /* Only allocate from the target node */ | |
2455 | gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) | | |
2456 | __GFP_THISNODE; | |
2457 | ||
2458 | /* release the mmap_sem read lock. */ | |
2459 | new_page = khugepaged_alloc_page(hpage, gfp, mm, vma, address, node); | |
2460 | if (!new_page) | |
2461 | return; | |
2462 | ||
2463 | if (unlikely(mem_cgroup_try_charge(new_page, mm, | |
2464 | gfp, &memcg))) | |
2465 | return; | |
2466 | ||
2467 | /* | |
2468 | * Prevent all access to pagetables with the exception of | |
2469 | * gup_fast later hanlded by the ptep_clear_flush and the VM | |
2470 | * handled by the anon_vma lock + PG_lock. | |
2471 | */ | |
2472 | down_write(&mm->mmap_sem); | |
2473 | if (unlikely(khugepaged_test_exit(mm))) | |
2474 | goto out; | |
2475 | ||
2476 | vma = find_vma(mm, address); | |
2477 | if (!vma) | |
2478 | goto out; | |
2479 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; | |
2480 | hend = vma->vm_end & HPAGE_PMD_MASK; | |
2481 | if (address < hstart || address + HPAGE_PMD_SIZE > hend) | |
2482 | goto out; | |
2483 | if (!hugepage_vma_check(vma)) | |
2484 | goto out; | |
2485 | pmd = mm_find_pmd(mm, address); | |
2486 | if (!pmd) | |
2487 | goto out; | |
2488 | ||
2489 | anon_vma_lock_write(vma->anon_vma); | |
2490 | ||
2491 | pte = pte_offset_map(pmd, address); | |
2492 | pte_ptl = pte_lockptr(mm, pmd); | |
2493 | ||
2494 | mmun_start = address; | |
2495 | mmun_end = address + HPAGE_PMD_SIZE; | |
2496 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); | |
2497 | pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ | |
2498 | /* | |
2499 | * After this gup_fast can't run anymore. This also removes | |
2500 | * any huge TLB entry from the CPU so we won't allow | |
2501 | * huge and small TLB entries for the same virtual address | |
2502 | * to avoid the risk of CPU bugs in that area. | |
2503 | */ | |
2504 | _pmd = pmdp_clear_flush(vma, address, pmd); | |
2505 | spin_unlock(pmd_ptl); | |
2506 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
2507 | ||
2508 | spin_lock(pte_ptl); | |
2509 | isolated = __collapse_huge_page_isolate(vma, address, pte); | |
2510 | spin_unlock(pte_ptl); | |
2511 | ||
2512 | if (unlikely(!isolated)) { | |
2513 | pte_unmap(pte); | |
2514 | spin_lock(pmd_ptl); | |
2515 | BUG_ON(!pmd_none(*pmd)); | |
2516 | /* | |
2517 | * We can only use set_pmd_at when establishing | |
2518 | * hugepmds and never for establishing regular pmds that | |
2519 | * points to regular pagetables. Use pmd_populate for that | |
2520 | */ | |
2521 | pmd_populate(mm, pmd, pmd_pgtable(_pmd)); | |
2522 | spin_unlock(pmd_ptl); | |
2523 | anon_vma_unlock_write(vma->anon_vma); | |
2524 | goto out; | |
2525 | } | |
2526 | ||
2527 | /* | |
2528 | * All pages are isolated and locked so anon_vma rmap | |
2529 | * can't run anymore. | |
2530 | */ | |
2531 | anon_vma_unlock_write(vma->anon_vma); | |
2532 | ||
2533 | __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); | |
2534 | pte_unmap(pte); | |
2535 | __SetPageUptodate(new_page); | |
2536 | pgtable = pmd_pgtable(_pmd); | |
2537 | ||
2538 | _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); | |
2539 | _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); | |
2540 | ||
2541 | /* | |
2542 | * spin_lock() below is not the equivalent of smp_wmb(), so | |
2543 | * this is needed to avoid the copy_huge_page writes to become | |
2544 | * visible after the set_pmd_at() write. | |
2545 | */ | |
2546 | smp_wmb(); | |
2547 | ||
2548 | spin_lock(pmd_ptl); | |
2549 | BUG_ON(!pmd_none(*pmd)); | |
2550 | page_add_new_anon_rmap(new_page, vma, address); | |
2551 | mem_cgroup_commit_charge(new_page, memcg, false); | |
2552 | lru_cache_add_active_or_unevictable(new_page, vma); | |
2553 | pgtable_trans_huge_deposit(mm, pmd, pgtable); | |
2554 | set_pmd_at(mm, address, pmd, _pmd); | |
2555 | update_mmu_cache_pmd(vma, address, pmd); | |
2556 | spin_unlock(pmd_ptl); | |
2557 | ||
2558 | *hpage = NULL; | |
2559 | ||
2560 | khugepaged_pages_collapsed++; | |
2561 | out_up_write: | |
2562 | up_write(&mm->mmap_sem); | |
2563 | return; | |
2564 | ||
2565 | out: | |
2566 | mem_cgroup_cancel_charge(new_page, memcg); | |
2567 | goto out_up_write; | |
2568 | } | |
2569 | ||
2570 | static int khugepaged_scan_pmd(struct mm_struct *mm, | |
2571 | struct vm_area_struct *vma, | |
2572 | unsigned long address, | |
2573 | struct page **hpage) | |
2574 | { | |
2575 | pmd_t *pmd; | |
2576 | pte_t *pte, *_pte; | |
2577 | int ret = 0, none_or_zero = 0; | |
2578 | struct page *page; | |
2579 | unsigned long _address; | |
2580 | spinlock_t *ptl; | |
2581 | int node = NUMA_NO_NODE; | |
2582 | bool writable = false, referenced = false; | |
2583 | ||
2584 | VM_BUG_ON(address & ~HPAGE_PMD_MASK); | |
2585 | ||
2586 | pmd = mm_find_pmd(mm, address); | |
2587 | if (!pmd) | |
2588 | goto out; | |
2589 | ||
2590 | memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); | |
2591 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); | |
2592 | for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; | |
2593 | _pte++, _address += PAGE_SIZE) { | |
2594 | pte_t pteval = *_pte; | |
2595 | if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { | |
2596 | if (++none_or_zero <= khugepaged_max_ptes_none) | |
2597 | continue; | |
2598 | else | |
2599 | goto out_unmap; | |
2600 | } | |
2601 | if (!pte_present(pteval)) | |
2602 | goto out_unmap; | |
2603 | if (pte_write(pteval)) | |
2604 | writable = true; | |
2605 | ||
2606 | page = vm_normal_page(vma, _address, pteval); | |
2607 | if (unlikely(!page)) | |
2608 | goto out_unmap; | |
2609 | /* | |
2610 | * Record which node the original page is from and save this | |
2611 | * information to khugepaged_node_load[]. | |
2612 | * Khupaged will allocate hugepage from the node has the max | |
2613 | * hit record. | |
2614 | */ | |
2615 | node = page_to_nid(page); | |
2616 | if (khugepaged_scan_abort(node)) | |
2617 | goto out_unmap; | |
2618 | khugepaged_node_load[node]++; | |
2619 | VM_BUG_ON_PAGE(PageCompound(page), page); | |
2620 | if (!PageLRU(page) || PageLocked(page) || !PageAnon(page)) | |
2621 | goto out_unmap; | |
2622 | /* | |
2623 | * cannot use mapcount: can't collapse if there's a gup pin. | |
2624 | * The page must only be referenced by the scanned process | |
2625 | * and page swap cache. | |
2626 | */ | |
2627 | if (page_count(page) != 1 + !!PageSwapCache(page)) | |
2628 | goto out_unmap; | |
2629 | if (pte_young(pteval) || PageReferenced(page) || | |
2630 | mmu_notifier_test_young(vma->vm_mm, address)) | |
2631 | referenced = true; | |
2632 | } | |
2633 | if (referenced && writable) | |
2634 | ret = 1; | |
2635 | out_unmap: | |
2636 | pte_unmap_unlock(pte, ptl); | |
2637 | if (ret) { | |
2638 | node = khugepaged_find_target_node(); | |
2639 | /* collapse_huge_page will return with the mmap_sem released */ | |
2640 | collapse_huge_page(mm, address, hpage, vma, node); | |
2641 | } | |
2642 | out: | |
2643 | return ret; | |
2644 | } | |
2645 | ||
2646 | static void collect_mm_slot(struct mm_slot *mm_slot) | |
2647 | { | |
2648 | struct mm_struct *mm = mm_slot->mm; | |
2649 | ||
2650 | VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); | |
2651 | ||
2652 | if (khugepaged_test_exit(mm)) { | |
2653 | /* free mm_slot */ | |
2654 | hash_del(&mm_slot->hash); | |
2655 | list_del(&mm_slot->mm_node); | |
2656 | ||
2657 | /* | |
2658 | * Not strictly needed because the mm exited already. | |
2659 | * | |
2660 | * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); | |
2661 | */ | |
2662 | ||
2663 | /* khugepaged_mm_lock actually not necessary for the below */ | |
2664 | free_mm_slot(mm_slot); | |
2665 | mmdrop(mm); | |
2666 | } | |
2667 | } | |
2668 | ||
2669 | static unsigned int khugepaged_scan_mm_slot(unsigned int pages, | |
2670 | struct page **hpage) | |
2671 | __releases(&khugepaged_mm_lock) | |
2672 | __acquires(&khugepaged_mm_lock) | |
2673 | { | |
2674 | struct mm_slot *mm_slot; | |
2675 | struct mm_struct *mm; | |
2676 | struct vm_area_struct *vma; | |
2677 | int progress = 0; | |
2678 | ||
2679 | VM_BUG_ON(!pages); | |
2680 | VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); | |
2681 | ||
2682 | if (khugepaged_scan.mm_slot) | |
2683 | mm_slot = khugepaged_scan.mm_slot; | |
2684 | else { | |
2685 | mm_slot = list_entry(khugepaged_scan.mm_head.next, | |
2686 | struct mm_slot, mm_node); | |
2687 | khugepaged_scan.address = 0; | |
2688 | khugepaged_scan.mm_slot = mm_slot; | |
2689 | } | |
2690 | spin_unlock(&khugepaged_mm_lock); | |
2691 | ||
2692 | mm = mm_slot->mm; | |
2693 | down_read(&mm->mmap_sem); | |
2694 | if (unlikely(khugepaged_test_exit(mm))) | |
2695 | vma = NULL; | |
2696 | else | |
2697 | vma = find_vma(mm, khugepaged_scan.address); | |
2698 | ||
2699 | progress++; | |
2700 | for (; vma; vma = vma->vm_next) { | |
2701 | unsigned long hstart, hend; | |
2702 | ||
2703 | cond_resched(); | |
2704 | if (unlikely(khugepaged_test_exit(mm))) { | |
2705 | progress++; | |
2706 | break; | |
2707 | } | |
2708 | if (!hugepage_vma_check(vma)) { | |
2709 | skip: | |
2710 | progress++; | |
2711 | continue; | |
2712 | } | |
2713 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; | |
2714 | hend = vma->vm_end & HPAGE_PMD_MASK; | |
2715 | if (hstart >= hend) | |
2716 | goto skip; | |
2717 | if (khugepaged_scan.address > hend) | |
2718 | goto skip; | |
2719 | if (khugepaged_scan.address < hstart) | |
2720 | khugepaged_scan.address = hstart; | |
2721 | VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); | |
2722 | ||
2723 | while (khugepaged_scan.address < hend) { | |
2724 | int ret; | |
2725 | cond_resched(); | |
2726 | if (unlikely(khugepaged_test_exit(mm))) | |
2727 | goto breakouterloop; | |
2728 | ||
2729 | VM_BUG_ON(khugepaged_scan.address < hstart || | |
2730 | khugepaged_scan.address + HPAGE_PMD_SIZE > | |
2731 | hend); | |
2732 | ret = khugepaged_scan_pmd(mm, vma, | |
2733 | khugepaged_scan.address, | |
2734 | hpage); | |
2735 | /* move to next address */ | |
2736 | khugepaged_scan.address += HPAGE_PMD_SIZE; | |
2737 | progress += HPAGE_PMD_NR; | |
2738 | if (ret) | |
2739 | /* we released mmap_sem so break loop */ | |
2740 | goto breakouterloop_mmap_sem; | |
2741 | if (progress >= pages) | |
2742 | goto breakouterloop; | |
2743 | } | |
2744 | } | |
2745 | breakouterloop: | |
2746 | up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ | |
2747 | breakouterloop_mmap_sem: | |
2748 | ||
2749 | spin_lock(&khugepaged_mm_lock); | |
2750 | VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); | |
2751 | /* | |
2752 | * Release the current mm_slot if this mm is about to die, or | |
2753 | * if we scanned all vmas of this mm. | |
2754 | */ | |
2755 | if (khugepaged_test_exit(mm) || !vma) { | |
2756 | /* | |
2757 | * Make sure that if mm_users is reaching zero while | |
2758 | * khugepaged runs here, khugepaged_exit will find | |
2759 | * mm_slot not pointing to the exiting mm. | |
2760 | */ | |
2761 | if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { | |
2762 | khugepaged_scan.mm_slot = list_entry( | |
2763 | mm_slot->mm_node.next, | |
2764 | struct mm_slot, mm_node); | |
2765 | khugepaged_scan.address = 0; | |
2766 | } else { | |
2767 | khugepaged_scan.mm_slot = NULL; | |
2768 | khugepaged_full_scans++; | |
2769 | } | |
2770 | ||
2771 | collect_mm_slot(mm_slot); | |
2772 | } | |
2773 | ||
2774 | return progress; | |
2775 | } | |
2776 | ||
2777 | static int khugepaged_has_work(void) | |
2778 | { | |
2779 | return !list_empty(&khugepaged_scan.mm_head) && | |
2780 | khugepaged_enabled(); | |
2781 | } | |
2782 | ||
2783 | static int khugepaged_wait_event(void) | |
2784 | { | |
2785 | return !list_empty(&khugepaged_scan.mm_head) || | |
2786 | kthread_should_stop(); | |
2787 | } | |
2788 | ||
2789 | static void khugepaged_do_scan(void) | |
2790 | { | |
2791 | struct page *hpage = NULL; | |
2792 | unsigned int progress = 0, pass_through_head = 0; | |
2793 | unsigned int pages = khugepaged_pages_to_scan; | |
2794 | bool wait = true; | |
2795 | ||
2796 | barrier(); /* write khugepaged_pages_to_scan to local stack */ | |
2797 | ||
2798 | while (progress < pages) { | |
2799 | if (!khugepaged_prealloc_page(&hpage, &wait)) | |
2800 | break; | |
2801 | ||
2802 | cond_resched(); | |
2803 | ||
2804 | if (unlikely(kthread_should_stop() || freezing(current))) | |
2805 | break; | |
2806 | ||
2807 | spin_lock(&khugepaged_mm_lock); | |
2808 | if (!khugepaged_scan.mm_slot) | |
2809 | pass_through_head++; | |
2810 | if (khugepaged_has_work() && | |
2811 | pass_through_head < 2) | |
2812 | progress += khugepaged_scan_mm_slot(pages - progress, | |
2813 | &hpage); | |
2814 | else | |
2815 | progress = pages; | |
2816 | spin_unlock(&khugepaged_mm_lock); | |
2817 | } | |
2818 | ||
2819 | if (!IS_ERR_OR_NULL(hpage)) | |
2820 | put_page(hpage); | |
2821 | } | |
2822 | ||
2823 | static void khugepaged_wait_work(void) | |
2824 | { | |
2825 | try_to_freeze(); | |
2826 | ||
2827 | if (khugepaged_has_work()) { | |
2828 | if (!khugepaged_scan_sleep_millisecs) | |
2829 | return; | |
2830 | ||
2831 | wait_event_freezable_timeout(khugepaged_wait, | |
2832 | kthread_should_stop(), | |
2833 | msecs_to_jiffies(khugepaged_scan_sleep_millisecs)); | |
2834 | return; | |
2835 | } | |
2836 | ||
2837 | if (khugepaged_enabled()) | |
2838 | wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); | |
2839 | } | |
2840 | ||
2841 | static int khugepaged(void *none) | |
2842 | { | |
2843 | struct mm_slot *mm_slot; | |
2844 | ||
2845 | set_freezable(); | |
2846 | set_user_nice(current, MAX_NICE); | |
2847 | ||
2848 | while (!kthread_should_stop()) { | |
2849 | khugepaged_do_scan(); | |
2850 | khugepaged_wait_work(); | |
2851 | } | |
2852 | ||
2853 | spin_lock(&khugepaged_mm_lock); | |
2854 | mm_slot = khugepaged_scan.mm_slot; | |
2855 | khugepaged_scan.mm_slot = NULL; | |
2856 | if (mm_slot) | |
2857 | collect_mm_slot(mm_slot); | |
2858 | spin_unlock(&khugepaged_mm_lock); | |
2859 | return 0; | |
2860 | } | |
2861 | ||
2862 | static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, | |
2863 | unsigned long haddr, pmd_t *pmd) | |
2864 | { | |
2865 | struct mm_struct *mm = vma->vm_mm; | |
2866 | pgtable_t pgtable; | |
2867 | pmd_t _pmd; | |
2868 | int i; | |
2869 | ||
2870 | pmdp_clear_flush_notify(vma, haddr, pmd); | |
2871 | /* leave pmd empty until pte is filled */ | |
2872 | ||
2873 | pgtable = pgtable_trans_huge_withdraw(mm, pmd); | |
2874 | pmd_populate(mm, &_pmd, pgtable); | |
2875 | ||
2876 | for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { | |
2877 | pte_t *pte, entry; | |
2878 | entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); | |
2879 | entry = pte_mkspecial(entry); | |
2880 | pte = pte_offset_map(&_pmd, haddr); | |
2881 | VM_BUG_ON(!pte_none(*pte)); | |
2882 | set_pte_at(mm, haddr, pte, entry); | |
2883 | pte_unmap(pte); | |
2884 | } | |
2885 | smp_wmb(); /* make pte visible before pmd */ | |
2886 | pmd_populate(mm, pmd, pgtable); | |
2887 | put_huge_zero_page(); | |
2888 | } | |
2889 | ||
2890 | void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, | |
2891 | pmd_t *pmd) | |
2892 | { | |
2893 | spinlock_t *ptl; | |
2894 | struct page *page; | |
2895 | struct mm_struct *mm = vma->vm_mm; | |
2896 | unsigned long haddr = address & HPAGE_PMD_MASK; | |
2897 | unsigned long mmun_start; /* For mmu_notifiers */ | |
2898 | unsigned long mmun_end; /* For mmu_notifiers */ | |
2899 | ||
2900 | BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE); | |
2901 | ||
2902 | mmun_start = haddr; | |
2903 | mmun_end = haddr + HPAGE_PMD_SIZE; | |
2904 | again: | |
2905 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); | |
2906 | ptl = pmd_lock(mm, pmd); | |
2907 | if (unlikely(!pmd_trans_huge(*pmd))) { | |
2908 | spin_unlock(ptl); | |
2909 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
2910 | return; | |
2911 | } | |
2912 | if (is_huge_zero_pmd(*pmd)) { | |
2913 | __split_huge_zero_page_pmd(vma, haddr, pmd); | |
2914 | spin_unlock(ptl); | |
2915 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
2916 | return; | |
2917 | } | |
2918 | page = pmd_page(*pmd); | |
2919 | VM_BUG_ON_PAGE(!page_count(page), page); | |
2920 | get_page(page); | |
2921 | spin_unlock(ptl); | |
2922 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
2923 | ||
2924 | split_huge_page(page); | |
2925 | ||
2926 | put_page(page); | |
2927 | ||
2928 | /* | |
2929 | * We don't always have down_write of mmap_sem here: a racing | |
2930 | * do_huge_pmd_wp_page() might have copied-on-write to another | |
2931 | * huge page before our split_huge_page() got the anon_vma lock. | |
2932 | */ | |
2933 | if (unlikely(pmd_trans_huge(*pmd))) | |
2934 | goto again; | |
2935 | } | |
2936 | ||
2937 | void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address, | |
2938 | pmd_t *pmd) | |
2939 | { | |
2940 | struct vm_area_struct *vma; | |
2941 | ||
2942 | vma = find_vma(mm, address); | |
2943 | BUG_ON(vma == NULL); | |
2944 | split_huge_page_pmd(vma, address, pmd); | |
2945 | } | |
2946 | ||
2947 | static void split_huge_page_address(struct mm_struct *mm, | |
2948 | unsigned long address) | |
2949 | { | |
2950 | pgd_t *pgd; | |
2951 | pud_t *pud; | |
2952 | pmd_t *pmd; | |
2953 | ||
2954 | VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); | |
2955 | ||
2956 | pgd = pgd_offset(mm, address); | |
2957 | if (!pgd_present(*pgd)) | |
2958 | return; | |
2959 | ||
2960 | pud = pud_offset(pgd, address); | |
2961 | if (!pud_present(*pud)) | |
2962 | return; | |
2963 | ||
2964 | pmd = pmd_offset(pud, address); | |
2965 | if (!pmd_present(*pmd)) | |
2966 | return; | |
2967 | /* | |
2968 | * Caller holds the mmap_sem write mode, so a huge pmd cannot | |
2969 | * materialize from under us. | |
2970 | */ | |
2971 | split_huge_page_pmd_mm(mm, address, pmd); | |
2972 | } | |
2973 | ||
2974 | void __vma_adjust_trans_huge(struct vm_area_struct *vma, | |
2975 | unsigned long start, | |
2976 | unsigned long end, | |
2977 | long adjust_next) | |
2978 | { | |
2979 | /* | |
2980 | * If the new start address isn't hpage aligned and it could | |
2981 | * previously contain an hugepage: check if we need to split | |
2982 | * an huge pmd. | |
2983 | */ | |
2984 | if (start & ~HPAGE_PMD_MASK && | |
2985 | (start & HPAGE_PMD_MASK) >= vma->vm_start && | |
2986 | (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) | |
2987 | split_huge_page_address(vma->vm_mm, start); | |
2988 | ||
2989 | /* | |
2990 | * If the new end address isn't hpage aligned and it could | |
2991 | * previously contain an hugepage: check if we need to split | |
2992 | * an huge pmd. | |
2993 | */ | |
2994 | if (end & ~HPAGE_PMD_MASK && | |
2995 | (end & HPAGE_PMD_MASK) >= vma->vm_start && | |
2996 | (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) | |
2997 | split_huge_page_address(vma->vm_mm, end); | |
2998 | ||
2999 | /* | |
3000 | * If we're also updating the vma->vm_next->vm_start, if the new | |
3001 | * vm_next->vm_start isn't page aligned and it could previously | |
3002 | * contain an hugepage: check if we need to split an huge pmd. | |
3003 | */ | |
3004 | if (adjust_next > 0) { | |
3005 | struct vm_area_struct *next = vma->vm_next; | |
3006 | unsigned long nstart = next->vm_start; | |
3007 | nstart += adjust_next << PAGE_SHIFT; | |
3008 | if (nstart & ~HPAGE_PMD_MASK && | |
3009 | (nstart & HPAGE_PMD_MASK) >= next->vm_start && | |
3010 | (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) | |
3011 | split_huge_page_address(next->vm_mm, nstart); | |
3012 | } | |
3013 | } |