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serial: 8250_dw: Do not use readl/writel before checking port iotype
[linux/fpc-iii.git] / mm / huge_memory.c
blobfd3a07b3e6f4e086b2111c312a78512bed927f9b
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/swapops.h>
20 #include <linux/dax.h>
21 #include <linux/kthread.h>
22 #include <linux/khugepaged.h>
23 #include <linux/freezer.h>
24 #include <linux/pfn_t.h>
25 #include <linux/mman.h>
26 #include <linux/memremap.h>
27 #include <linux/pagemap.h>
28 #include <linux/debugfs.h>
29 #include <linux/migrate.h>
30 #include <linux/hashtable.h>
31 #include <linux/userfaultfd_k.h>
32 #include <linux/page_idle.h>
33
34 #include <asm/tlb.h>
35 #include <asm/pgalloc.h>
36 #include "internal.h"
37
38 enum scan_result {
39 SCAN_FAIL,
40 SCAN_SUCCEED,
41 SCAN_PMD_NULL,
42 SCAN_EXCEED_NONE_PTE,
43 SCAN_PTE_NON_PRESENT,
44 SCAN_PAGE_RO,
45 SCAN_NO_REFERENCED_PAGE,
46 SCAN_PAGE_NULL,
47 SCAN_SCAN_ABORT,
48 SCAN_PAGE_COUNT,
49 SCAN_PAGE_LRU,
50 SCAN_PAGE_LOCK,
51 SCAN_PAGE_ANON,
52 SCAN_PAGE_COMPOUND,
53 SCAN_ANY_PROCESS,
54 SCAN_VMA_NULL,
55 SCAN_VMA_CHECK,
56 SCAN_ADDRESS_RANGE,
57 SCAN_SWAP_CACHE_PAGE,
58 SCAN_DEL_PAGE_LRU,
59 SCAN_ALLOC_HUGE_PAGE_FAIL,
60 SCAN_CGROUP_CHARGE_FAIL
61 };
62
63 #define CREATE_TRACE_POINTS
64 #include <trace/events/huge_memory.h>
65
66 /*
67 * By default transparent hugepage support is disabled in order that avoid
68 * to risk increase the memory footprint of applications without a guaranteed
69 * benefit. When transparent hugepage support is enabled, is for all mappings,
70 * and khugepaged scans all mappings.
71 * Defrag is invoked by khugepaged hugepage allocations and by page faults
72 * for all hugepage allocations.
73 */
74 unsigned long transparent_hugepage_flags __read_mostly =
75 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
76 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
77 #endif
78 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
79 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
80 #endif
81 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
82 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
83 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
84
85 /* default scan 8*512 pte (or vmas) every 30 second */
86 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
87 static unsigned int khugepaged_pages_collapsed;
88 static unsigned int khugepaged_full_scans;
89 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
90 /* during fragmentation poll the hugepage allocator once every minute */
91 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
92 static struct task_struct *khugepaged_thread __read_mostly;
93 static DEFINE_MUTEX(khugepaged_mutex);
94 static DEFINE_SPINLOCK(khugepaged_mm_lock);
95 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
96 /*
97 * default collapse hugepages if there is at least one pte mapped like
98 * it would have happened if the vma was large enough during page
99 * fault.
100 */
101 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
102
103 static int khugepaged(void *none);
104 static int khugepaged_slab_init(void);
105 static void khugepaged_slab_exit(void);
106
107 #define MM_SLOTS_HASH_BITS 10
108 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
109
110 static struct kmem_cache *mm_slot_cache __read_mostly;
111
112 /**
113 * struct mm_slot - hash lookup from mm to mm_slot
114 * @hash: hash collision list
115 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
116 * @mm: the mm that this information is valid for
117 */
118 struct mm_slot {
119 struct hlist_node hash;
120 struct list_head mm_node;
121 struct mm_struct *mm;
122 };
123
124 /**
125 * struct khugepaged_scan - cursor for scanning
126 * @mm_head: the head of the mm list to scan
127 * @mm_slot: the current mm_slot we are scanning
128 * @address: the next address inside that to be scanned
129 *
130 * There is only the one khugepaged_scan instance of this cursor structure.
131 */
132 struct khugepaged_scan {
133 struct list_head mm_head;
134 struct mm_slot *mm_slot;
135 unsigned long address;
136 };
137 static struct khugepaged_scan khugepaged_scan = {
138 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
139 };
140
141 static DEFINE_SPINLOCK(split_queue_lock);
142 static LIST_HEAD(split_queue);
143 static unsigned long split_queue_len;
144 static struct shrinker deferred_split_shrinker;
145
146 static void set_recommended_min_free_kbytes(void)
147 {
148 struct zone *zone;
149 int nr_zones = 0;
150 unsigned long recommended_min;
151
152 for_each_populated_zone(zone)
153 nr_zones++;
154
155 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
156 recommended_min = pageblock_nr_pages * nr_zones * 2;
157
158 /*
159 * Make sure that on average at least two pageblocks are almost free
160 * of another type, one for a migratetype to fall back to and a
161 * second to avoid subsequent fallbacks of other types There are 3
162 * MIGRATE_TYPES we care about.
163 */
164 recommended_min += pageblock_nr_pages * nr_zones *
165 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
166
167 /* don't ever allow to reserve more than 5% of the lowmem */
168 recommended_min = min(recommended_min,
169 (unsigned long) nr_free_buffer_pages() / 20);
170 recommended_min <<= (PAGE_SHIFT-10);
171
172 if (recommended_min > min_free_kbytes) {
173 if (user_min_free_kbytes >= 0)
174 pr_info("raising min_free_kbytes from %d to %lu "
175 "to help transparent hugepage allocations\n",
176 min_free_kbytes, recommended_min);
177
178 min_free_kbytes = recommended_min;
179 }
180 setup_per_zone_wmarks();
181 }
182
183 static int start_stop_khugepaged(void)
184 {
185 int err = 0;
186 if (khugepaged_enabled()) {
187 if (!khugepaged_thread)
188 khugepaged_thread = kthread_run(khugepaged, NULL,
189 "khugepaged");
190 if (IS_ERR(khugepaged_thread)) {
191 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
192 err = PTR_ERR(khugepaged_thread);
193 khugepaged_thread = NULL;
194 goto fail;
195 }
196
197 if (!list_empty(&khugepaged_scan.mm_head))
198 wake_up_interruptible(&khugepaged_wait);
199
200 set_recommended_min_free_kbytes();
201 } else if (khugepaged_thread) {
202 kthread_stop(khugepaged_thread);
203 khugepaged_thread = NULL;
204 }
205 fail:
206 return err;
207 }
208
209 static atomic_t huge_zero_refcount;
210 struct page *huge_zero_page __read_mostly;
211
212 struct page *get_huge_zero_page(void)
213 {
214 struct page *zero_page;
215 retry:
216 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
217 return READ_ONCE(huge_zero_page);
218
219 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
220 HPAGE_PMD_ORDER);
221 if (!zero_page) {
222 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
223 return NULL;
224 }
225 count_vm_event(THP_ZERO_PAGE_ALLOC);
226 preempt_disable();
227 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
228 preempt_enable();
229 __free_pages(zero_page, compound_order(zero_page));
230 goto retry;
231 }
232
233 /* We take additional reference here. It will be put back by shrinker */
234 atomic_set(&huge_zero_refcount, 2);
235 preempt_enable();
236 return READ_ONCE(huge_zero_page);
237 }
238
239 static void put_huge_zero_page(void)
240 {
241 /*
242 * Counter should never go to zero here. Only shrinker can put
243 * last reference.
244 */
245 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
246 }
247
248 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
249 struct shrink_control *sc)
250 {
251 /* we can free zero page only if last reference remains */
252 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
253 }
254
255 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
256 struct shrink_control *sc)
257 {
258 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
259 struct page *zero_page = xchg(&huge_zero_page, NULL);
260 BUG_ON(zero_page == NULL);
261 __free_pages(zero_page, compound_order(zero_page));
262 return HPAGE_PMD_NR;
263 }
264
265 return 0;
266 }
267
268 static struct shrinker huge_zero_page_shrinker = {
269 .count_objects = shrink_huge_zero_page_count,
270 .scan_objects = shrink_huge_zero_page_scan,
271 .seeks = DEFAULT_SEEKS,
272 };
273
274 #ifdef CONFIG_SYSFS
275
276 static ssize_t double_flag_show(struct kobject *kobj,
277 struct kobj_attribute *attr, char *buf,
278 enum transparent_hugepage_flag enabled,
279 enum transparent_hugepage_flag req_madv)
280 {
281 if (test_bit(enabled, &transparent_hugepage_flags)) {
282 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
283 return sprintf(buf, "[always] madvise never\n");
284 } else if (test_bit(req_madv, &transparent_hugepage_flags))
285 return sprintf(buf, "always [madvise] never\n");
286 else
287 return sprintf(buf, "always madvise [never]\n");
288 }
289 static ssize_t double_flag_store(struct kobject *kobj,
290 struct kobj_attribute *attr,
291 const char *buf, size_t count,
292 enum transparent_hugepage_flag enabled,
293 enum transparent_hugepage_flag req_madv)
294 {
295 if (!memcmp("always", buf,
296 min(sizeof("always")-1, count))) {
297 set_bit(enabled, &transparent_hugepage_flags);
298 clear_bit(req_madv, &transparent_hugepage_flags);
299 } else if (!memcmp("madvise", buf,
300 min(sizeof("madvise")-1, count))) {
301 clear_bit(enabled, &transparent_hugepage_flags);
302 set_bit(req_madv, &transparent_hugepage_flags);
303 } else if (!memcmp("never", buf,
304 min(sizeof("never")-1, count))) {
305 clear_bit(enabled, &transparent_hugepage_flags);
306 clear_bit(req_madv, &transparent_hugepage_flags);
307 } else
308 return -EINVAL;
309
310 return count;
311 }
312
313 static ssize_t enabled_show(struct kobject *kobj,
314 struct kobj_attribute *attr, char *buf)
315 {
316 return double_flag_show(kobj, attr, buf,
317 TRANSPARENT_HUGEPAGE_FLAG,
318 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
319 }
320 static ssize_t enabled_store(struct kobject *kobj,
321 struct kobj_attribute *attr,
322 const char *buf, size_t count)
323 {
324 ssize_t ret;
325
326 ret = double_flag_store(kobj, attr, buf, count,
327 TRANSPARENT_HUGEPAGE_FLAG,
328 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
329
330 if (ret > 0) {
331 int err;
332
333 mutex_lock(&khugepaged_mutex);
334 err = start_stop_khugepaged();
335 mutex_unlock(&khugepaged_mutex);
336
337 if (err)
338 ret = err;
339 }
340
341 return ret;
342 }
343 static struct kobj_attribute enabled_attr =
344 __ATTR(enabled, 0644, enabled_show, enabled_store);
345
346 static ssize_t single_flag_show(struct kobject *kobj,
347 struct kobj_attribute *attr, char *buf,
348 enum transparent_hugepage_flag flag)
349 {
350 return sprintf(buf, "%d\n",
351 !!test_bit(flag, &transparent_hugepage_flags));
352 }
353
354 static ssize_t single_flag_store(struct kobject *kobj,
355 struct kobj_attribute *attr,
356 const char *buf, size_t count,
357 enum transparent_hugepage_flag flag)
358 {
359 unsigned long value;
360 int ret;
361
362 ret = kstrtoul(buf, 10, &value);
363 if (ret < 0)
364 return ret;
365 if (value > 1)
366 return -EINVAL;
367
368 if (value)
369 set_bit(flag, &transparent_hugepage_flags);
370 else
371 clear_bit(flag, &transparent_hugepage_flags);
372
373 return count;
374 }
375
376 /*
377 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
378 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
379 * memory just to allocate one more hugepage.
380 */
381 static ssize_t defrag_show(struct kobject *kobj,
382 struct kobj_attribute *attr, char *buf)
383 {
384 return double_flag_show(kobj, attr, buf,
385 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
386 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
387 }
388 static ssize_t defrag_store(struct kobject *kobj,
389 struct kobj_attribute *attr,
390 const char *buf, size_t count)
391 {
392 return double_flag_store(kobj, attr, buf, count,
393 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
394 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
395 }
396 static struct kobj_attribute defrag_attr =
397 __ATTR(defrag, 0644, defrag_show, defrag_store);
398
399 static ssize_t use_zero_page_show(struct kobject *kobj,
400 struct kobj_attribute *attr, char *buf)
401 {
402 return single_flag_show(kobj, attr, buf,
403 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
404 }
405 static ssize_t use_zero_page_store(struct kobject *kobj,
406 struct kobj_attribute *attr, const char *buf, size_t count)
407 {
408 return single_flag_store(kobj, attr, buf, count,
409 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
410 }
411 static struct kobj_attribute use_zero_page_attr =
412 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
413 #ifdef CONFIG_DEBUG_VM
414 static ssize_t debug_cow_show(struct kobject *kobj,
415 struct kobj_attribute *attr, char *buf)
416 {
417 return single_flag_show(kobj, attr, buf,
418 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
419 }
420 static ssize_t debug_cow_store(struct kobject *kobj,
421 struct kobj_attribute *attr,
422 const char *buf, size_t count)
423 {
424 return single_flag_store(kobj, attr, buf, count,
425 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
426 }
427 static struct kobj_attribute debug_cow_attr =
428 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
429 #endif /* CONFIG_DEBUG_VM */
430
431 static struct attribute *hugepage_attr[] = {
432 &enabled_attr.attr,
433 &defrag_attr.attr,
434 &use_zero_page_attr.attr,
435 #ifdef CONFIG_DEBUG_VM
436 &debug_cow_attr.attr,
437 #endif
438 NULL,
439 };
440
441 static struct attribute_group hugepage_attr_group = {
442 .attrs = hugepage_attr,
443 };
444
445 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
446 struct kobj_attribute *attr,
447 char *buf)
448 {
449 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
450 }
451
452 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
453 struct kobj_attribute *attr,
454 const char *buf, size_t count)
455 {
456 unsigned long msecs;
457 int err;
458
459 err = kstrtoul(buf, 10, &msecs);
460 if (err || msecs > UINT_MAX)
461 return -EINVAL;
462
463 khugepaged_scan_sleep_millisecs = msecs;
464 wake_up_interruptible(&khugepaged_wait);
465
466 return count;
467 }
468 static struct kobj_attribute scan_sleep_millisecs_attr =
469 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
470 scan_sleep_millisecs_store);
471
472 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
473 struct kobj_attribute *attr,
474 char *buf)
475 {
476 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
477 }
478
479 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
480 struct kobj_attribute *attr,
481 const char *buf, size_t count)
482 {
483 unsigned long msecs;
484 int err;
485
486 err = kstrtoul(buf, 10, &msecs);
487 if (err || msecs > UINT_MAX)
488 return -EINVAL;
489
490 khugepaged_alloc_sleep_millisecs = msecs;
491 wake_up_interruptible(&khugepaged_wait);
492
493 return count;
494 }
495 static struct kobj_attribute alloc_sleep_millisecs_attr =
496 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
497 alloc_sleep_millisecs_store);
498
499 static ssize_t pages_to_scan_show(struct kobject *kobj,
500 struct kobj_attribute *attr,
501 char *buf)
502 {
503 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
504 }
505 static ssize_t pages_to_scan_store(struct kobject *kobj,
506 struct kobj_attribute *attr,
507 const char *buf, size_t count)
508 {
509 int err;
510 unsigned long pages;
511
512 err = kstrtoul(buf, 10, &pages);
513 if (err || !pages || pages > UINT_MAX)
514 return -EINVAL;
515
516 khugepaged_pages_to_scan = pages;
517
518 return count;
519 }
520 static struct kobj_attribute pages_to_scan_attr =
521 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
522 pages_to_scan_store);
523
524 static ssize_t pages_collapsed_show(struct kobject *kobj,
525 struct kobj_attribute *attr,
526 char *buf)
527 {
528 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
529 }
530 static struct kobj_attribute pages_collapsed_attr =
531 __ATTR_RO(pages_collapsed);
532
533 static ssize_t full_scans_show(struct kobject *kobj,
534 struct kobj_attribute *attr,
535 char *buf)
536 {
537 return sprintf(buf, "%u\n", khugepaged_full_scans);
538 }
539 static struct kobj_attribute full_scans_attr =
540 __ATTR_RO(full_scans);
541
542 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
543 struct kobj_attribute *attr, char *buf)
544 {
545 return single_flag_show(kobj, attr, buf,
546 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
547 }
548 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
549 struct kobj_attribute *attr,
550 const char *buf, size_t count)
551 {
552 return single_flag_store(kobj, attr, buf, count,
553 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
554 }
555 static struct kobj_attribute khugepaged_defrag_attr =
556 __ATTR(defrag, 0644, khugepaged_defrag_show,
557 khugepaged_defrag_store);
558
559 /*
560 * max_ptes_none controls if khugepaged should collapse hugepages over
561 * any unmapped ptes in turn potentially increasing the memory
562 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
563 * reduce the available free memory in the system as it
564 * runs. Increasing max_ptes_none will instead potentially reduce the
565 * free memory in the system during the khugepaged scan.
566 */
567 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
568 struct kobj_attribute *attr,
569 char *buf)
570 {
571 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
572 }
573 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
574 struct kobj_attribute *attr,
575 const char *buf, size_t count)
576 {
577 int err;
578 unsigned long max_ptes_none;
579
580 err = kstrtoul(buf, 10, &max_ptes_none);
581 if (err || max_ptes_none > HPAGE_PMD_NR-1)
582 return -EINVAL;
583
584 khugepaged_max_ptes_none = max_ptes_none;
585
586 return count;
587 }
588 static struct kobj_attribute khugepaged_max_ptes_none_attr =
589 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
590 khugepaged_max_ptes_none_store);
591
592 static struct attribute *khugepaged_attr[] = {
593 &khugepaged_defrag_attr.attr,
594 &khugepaged_max_ptes_none_attr.attr,
595 &pages_to_scan_attr.attr,
596 &pages_collapsed_attr.attr,
597 &full_scans_attr.attr,
598 &scan_sleep_millisecs_attr.attr,
599 &alloc_sleep_millisecs_attr.attr,
600 NULL,
601 };
602
603 static struct attribute_group khugepaged_attr_group = {
604 .attrs = khugepaged_attr,
605 .name = "khugepaged",
606 };
607
608 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
609 {
610 int err;
611
612 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
613 if (unlikely(!*hugepage_kobj)) {
614 pr_err("failed to create transparent hugepage kobject\n");
615 return -ENOMEM;
616 }
617
618 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
619 if (err) {
620 pr_err("failed to register transparent hugepage group\n");
621 goto delete_obj;
622 }
623
624 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
625 if (err) {
626 pr_err("failed to register transparent hugepage group\n");
627 goto remove_hp_group;
628 }
629
630 return 0;
631
632 remove_hp_group:
633 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
634 delete_obj:
635 kobject_put(*hugepage_kobj);
636 return err;
637 }
638
639 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
640 {
641 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
642 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
643 kobject_put(hugepage_kobj);
644 }
645 #else
646 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
647 {
648 return 0;
649 }
650
651 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
652 {
653 }
654 #endif /* CONFIG_SYSFS */
655
656 static int __init hugepage_init(void)
657 {
658 int err;
659 struct kobject *hugepage_kobj;
660
661 if (!has_transparent_hugepage()) {
662 transparent_hugepage_flags = 0;
663 return -EINVAL;
664 }
665
666 err = hugepage_init_sysfs(&hugepage_kobj);
667 if (err)
668 goto err_sysfs;
669
670 err = khugepaged_slab_init();
671 if (err)
672 goto err_slab;
673
674 err = register_shrinker(&huge_zero_page_shrinker);
675 if (err)
676 goto err_hzp_shrinker;
677 err = register_shrinker(&deferred_split_shrinker);
678 if (err)
679 goto err_split_shrinker;
680
681 /*
682 * By default disable transparent hugepages on smaller systems,
683 * where the extra memory used could hurt more than TLB overhead
684 * is likely to save. The admin can still enable it through /sys.
685 */
686 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
687 transparent_hugepage_flags = 0;
688 return 0;
689 }
690
691 err = start_stop_khugepaged();
692 if (err)
693 goto err_khugepaged;
694
695 return 0;
696 err_khugepaged:
697 unregister_shrinker(&deferred_split_shrinker);
698 err_split_shrinker:
699 unregister_shrinker(&huge_zero_page_shrinker);
700 err_hzp_shrinker:
701 khugepaged_slab_exit();
702 err_slab:
703 hugepage_exit_sysfs(hugepage_kobj);
704 err_sysfs:
705 return err;
706 }
707 subsys_initcall(hugepage_init);
708
709 static int __init setup_transparent_hugepage(char *str)
710 {
711 int ret = 0;
712 if (!str)
713 goto out;
714 if (!strcmp(str, "always")) {
715 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
716 &transparent_hugepage_flags);
717 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
718 &transparent_hugepage_flags);
719 ret = 1;
720 } else if (!strcmp(str, "madvise")) {
721 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
722 &transparent_hugepage_flags);
723 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
724 &transparent_hugepage_flags);
725 ret = 1;
726 } else if (!strcmp(str, "never")) {
727 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
728 &transparent_hugepage_flags);
729 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
730 &transparent_hugepage_flags);
731 ret = 1;
732 }
733 out:
734 if (!ret)
735 pr_warn("transparent_hugepage= cannot parse, ignored\n");
736 return ret;
737 }
738 __setup("transparent_hugepage=", setup_transparent_hugepage);
739
740 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
741 {
742 if (likely(vma->vm_flags & VM_WRITE))
743 pmd = pmd_mkwrite(pmd);
744 return pmd;
745 }
746
747 static inline pmd_t mk_huge_pmd(struct page *page, pgprot_t prot)
748 {
749 pmd_t entry;
750 entry = mk_pmd(page, prot);
751 entry = pmd_mkhuge(entry);
752 return entry;
753 }
754
755 static inline struct list_head *page_deferred_list(struct page *page)
756 {
757 /*
758 * ->lru in the tail pages is occupied by compound_head.
759 * Let's use ->mapping + ->index in the second tail page as list_head.
760 */
761 return (struct list_head *)&page[2].mapping;
762 }
763
764 void prep_transhuge_page(struct page *page)
765 {
766 /*
767 * we use page->mapping and page->indexlru in second tail page
768 * as list_head: assuming THP order >= 2
769 */
770 BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
771
772 INIT_LIST_HEAD(page_deferred_list(page));
773 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
774 }
775
776 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
777 struct vm_area_struct *vma,
778 unsigned long address, pmd_t *pmd,
779 struct page *page, gfp_t gfp,
780 unsigned int flags)
781 {
782 struct mem_cgroup *memcg;
783 pgtable_t pgtable;
784 spinlock_t *ptl;
785 unsigned long haddr = address & HPAGE_PMD_MASK;
786
787 VM_BUG_ON_PAGE(!PageCompound(page), page);
788
789 if (mem_cgroup_try_charge(page, mm, gfp, &memcg, true)) {
790 put_page(page);
791 count_vm_event(THP_FAULT_FALLBACK);
792 return VM_FAULT_FALLBACK;
793 }
794
795 pgtable = pte_alloc_one(mm, haddr);
796 if (unlikely(!pgtable)) {
797 mem_cgroup_cancel_charge(page, memcg, true);
798 put_page(page);
799 return VM_FAULT_OOM;
800 }
801
802 clear_huge_page(page, haddr, HPAGE_PMD_NR);
803 /*
804 * The memory barrier inside __SetPageUptodate makes sure that
805 * clear_huge_page writes become visible before the set_pmd_at()
806 * write.
807 */
808 __SetPageUptodate(page);
809
810 ptl = pmd_lock(mm, pmd);
811 if (unlikely(!pmd_none(*pmd))) {
812 spin_unlock(ptl);
813 mem_cgroup_cancel_charge(page, memcg, true);
814 put_page(page);
815 pte_free(mm, pgtable);
816 } else {
817 pmd_t entry;
818
819 /* Deliver the page fault to userland */
820 if (userfaultfd_missing(vma)) {
821 int ret;
822
823 spin_unlock(ptl);
824 mem_cgroup_cancel_charge(page, memcg, true);
825 put_page(page);
826 pte_free(mm, pgtable);
827 ret = handle_userfault(vma, address, flags,
828 VM_UFFD_MISSING);
829 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
830 return ret;
831 }
832
833 entry = mk_huge_pmd(page, vma->vm_page_prot);
834 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
835 page_add_new_anon_rmap(page, vma, haddr, true);
836 mem_cgroup_commit_charge(page, memcg, false, true);
837 lru_cache_add_active_or_unevictable(page, vma);
838 pgtable_trans_huge_deposit(mm, pmd, pgtable);
839 set_pmd_at(mm, haddr, pmd, entry);
840 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
841 atomic_long_inc(&mm->nr_ptes);
842 spin_unlock(ptl);
843 count_vm_event(THP_FAULT_ALLOC);
844 }
845
846 return 0;
847 }
848
849 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
850 {
851 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_RECLAIM)) | extra_gfp;
852 }
853
854 /* Caller must hold page table lock. */
855 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
856 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
857 struct page *zero_page)
858 {
859 pmd_t entry;
860 if (!pmd_none(*pmd))
861 return false;
862 entry = mk_pmd(zero_page, vma->vm_page_prot);
863 entry = pmd_mkhuge(entry);
864 pgtable_trans_huge_deposit(mm, pmd, pgtable);
865 set_pmd_at(mm, haddr, pmd, entry);
866 atomic_long_inc(&mm->nr_ptes);
867 return true;
868 }
869
870 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
871 unsigned long address, pmd_t *pmd,
872 unsigned int flags)
873 {
874 gfp_t gfp;
875 struct page *page;
876 unsigned long haddr = address & HPAGE_PMD_MASK;
877
878 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
879 return VM_FAULT_FALLBACK;
880 if (unlikely(anon_vma_prepare(vma)))
881 return VM_FAULT_OOM;
882 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
883 return VM_FAULT_OOM;
884 if (!(flags & FAULT_FLAG_WRITE) && !mm_forbids_zeropage(mm) &&
885 transparent_hugepage_use_zero_page()) {
886 spinlock_t *ptl;
887 pgtable_t pgtable;
888 struct page *zero_page;
889 bool set;
890 int ret;
891 pgtable = pte_alloc_one(mm, haddr);
892 if (unlikely(!pgtable))
893 return VM_FAULT_OOM;
894 zero_page = get_huge_zero_page();
895 if (unlikely(!zero_page)) {
896 pte_free(mm, pgtable);
897 count_vm_event(THP_FAULT_FALLBACK);
898 return VM_FAULT_FALLBACK;
899 }
900 ptl = pmd_lock(mm, pmd);
901 ret = 0;
902 set = false;
903 if (pmd_none(*pmd)) {
904 if (userfaultfd_missing(vma)) {
905 spin_unlock(ptl);
906 ret = handle_userfault(vma, address, flags,
907 VM_UFFD_MISSING);
908 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
909 } else {
910 set_huge_zero_page(pgtable, mm, vma,
911 haddr, pmd,
912 zero_page);
913 spin_unlock(ptl);
914 set = true;
915 }
916 } else
917 spin_unlock(ptl);
918 if (!set) {
919 pte_free(mm, pgtable);
920 put_huge_zero_page();
921 }
922 return ret;
923 }
924 gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
925 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
926 if (unlikely(!page)) {
927 count_vm_event(THP_FAULT_FALLBACK);
928 return VM_FAULT_FALLBACK;
929 }
930 prep_transhuge_page(page);
931 return __do_huge_pmd_anonymous_page(mm, vma, address, pmd, page, gfp,
932 flags);
933 }
934
935 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
936 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write)
937 {
938 struct mm_struct *mm = vma->vm_mm;
939 pmd_t entry;
940 spinlock_t *ptl;
941
942 ptl = pmd_lock(mm, pmd);
943 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
944 if (pfn_t_devmap(pfn))
945 entry = pmd_mkdevmap(entry);
946 if (write) {
947 entry = pmd_mkyoung(pmd_mkdirty(entry));
948 entry = maybe_pmd_mkwrite(entry, vma);
949 }
950 set_pmd_at(mm, addr, pmd, entry);
951 update_mmu_cache_pmd(vma, addr, pmd);
952 spin_unlock(ptl);
953 }
954
955 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
956 pmd_t *pmd, pfn_t pfn, bool write)
957 {
958 pgprot_t pgprot = vma->vm_page_prot;
959 /*
960 * If we had pmd_special, we could avoid all these restrictions,
961 * but we need to be consistent with PTEs and architectures that
962 * can't support a 'special' bit.
963 */
964 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
965 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
966 (VM_PFNMAP|VM_MIXEDMAP));
967 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
968 BUG_ON(!pfn_t_devmap(pfn));
969
970 if (addr < vma->vm_start || addr >= vma->vm_end)
971 return VM_FAULT_SIGBUS;
972 if (track_pfn_insert(vma, &pgprot, pfn))
973 return VM_FAULT_SIGBUS;
974 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
975 return VM_FAULT_NOPAGE;
976 }
977
978 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
979 pmd_t *pmd)
980 {
981 pmd_t _pmd;
982
983 /*
984 * We should set the dirty bit only for FOLL_WRITE but for now
985 * the dirty bit in the pmd is meaningless. And if the dirty
986 * bit will become meaningful and we'll only set it with
987 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
988 * set the young bit, instead of the current set_pmd_at.
989 */
990 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
991 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
992 pmd, _pmd, 1))
993 update_mmu_cache_pmd(vma, addr, pmd);
994 }
995
996 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
997 pmd_t *pmd, int flags)
998 {
999 unsigned long pfn = pmd_pfn(*pmd);
1000 struct mm_struct *mm = vma->vm_mm;
1001 struct dev_pagemap *pgmap;
1002 struct page *page;
1003
1004 assert_spin_locked(pmd_lockptr(mm, pmd));
1005
1006 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1007 return NULL;
1008
1009 if (pmd_present(*pmd) && pmd_devmap(*pmd))
1010 /* pass */;
1011 else
1012 return NULL;
1013
1014 if (flags & FOLL_TOUCH)
1015 touch_pmd(vma, addr, pmd);
1016
1017 /*
1018 * device mapped pages can only be returned if the
1019 * caller will manage the page reference count.
1020 */
1021 if (!(flags & FOLL_GET))
1022 return ERR_PTR(-EEXIST);
1023
1024 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1025 pgmap = get_dev_pagemap(pfn, NULL);
1026 if (!pgmap)
1027 return ERR_PTR(-EFAULT);
1028 page = pfn_to_page(pfn);
1029 get_page(page);
1030 put_dev_pagemap(pgmap);
1031
1032 return page;
1033 }
1034
1035 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1036 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1037 struct vm_area_struct *vma)
1038 {
1039 spinlock_t *dst_ptl, *src_ptl;
1040 struct page *src_page;
1041 pmd_t pmd;
1042 pgtable_t pgtable;
1043 int ret;
1044
1045 ret = -ENOMEM;
1046 pgtable = pte_alloc_one(dst_mm, addr);
1047 if (unlikely(!pgtable))
1048 goto out;
1049
1050 dst_ptl = pmd_lock(dst_mm, dst_pmd);
1051 src_ptl = pmd_lockptr(src_mm, src_pmd);
1052 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1053
1054 ret = -EAGAIN;
1055 pmd = *src_pmd;
1056 if (unlikely(!pmd_trans_huge(pmd) && !pmd_devmap(pmd))) {
1057 pte_free(dst_mm, pgtable);
1058 goto out_unlock;
1059 }
1060 /*
1061 * When page table lock is held, the huge zero pmd should not be
1062 * under splitting since we don't split the page itself, only pmd to
1063 * a page table.
1064 */
1065 if (is_huge_zero_pmd(pmd)) {
1066 struct page *zero_page;
1067 /*
1068 * get_huge_zero_page() will never allocate a new page here,
1069 * since we already have a zero page to copy. It just takes a
1070 * reference.
1071 */
1072 zero_page = get_huge_zero_page();
1073 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1074 zero_page);
1075 ret = 0;
1076 goto out_unlock;
1077 }
1078
1079 if (pmd_trans_huge(pmd)) {
1080 /* thp accounting separate from pmd_devmap accounting */
1081 src_page = pmd_page(pmd);
1082 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1083 get_page(src_page);
1084 page_dup_rmap(src_page, true);
1085 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1086 atomic_long_inc(&dst_mm->nr_ptes);
1087 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1088 }
1089
1090 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1091 pmd = pmd_mkold(pmd_wrprotect(pmd));
1092 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1093
1094 ret = 0;
1095 out_unlock:
1096 spin_unlock(src_ptl);
1097 spin_unlock(dst_ptl);
1098 out:
1099 return ret;
1100 }
1101
1102 void huge_pmd_set_accessed(struct mm_struct *mm,
1103 struct vm_area_struct *vma,
1104 unsigned long address,
1105 pmd_t *pmd, pmd_t orig_pmd,
1106 int dirty)
1107 {
1108 spinlock_t *ptl;
1109 pmd_t entry;
1110 unsigned long haddr;
1111
1112 ptl = pmd_lock(mm, pmd);
1113 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1114 goto unlock;
1115
1116 entry = pmd_mkyoung(orig_pmd);
1117 haddr = address & HPAGE_PMD_MASK;
1118 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
1119 update_mmu_cache_pmd(vma, address, pmd);
1120
1121 unlock:
1122 spin_unlock(ptl);
1123 }
1124
1125 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1126 struct vm_area_struct *vma,
1127 unsigned long address,
1128 pmd_t *pmd, pmd_t orig_pmd,
1129 struct page *page,
1130 unsigned long haddr)
1131 {
1132 struct mem_cgroup *memcg;
1133 spinlock_t *ptl;
1134 pgtable_t pgtable;
1135 pmd_t _pmd;
1136 int ret = 0, i;
1137 struct page **pages;
1138 unsigned long mmun_start; /* For mmu_notifiers */
1139 unsigned long mmun_end; /* For mmu_notifiers */
1140
1141 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1142 GFP_KERNEL);
1143 if (unlikely(!pages)) {
1144 ret |= VM_FAULT_OOM;
1145 goto out;
1146 }
1147
1148 for (i = 0; i < HPAGE_PMD_NR; i++) {
1149 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1150 __GFP_OTHER_NODE,
1151 vma, address, page_to_nid(page));
1152 if (unlikely(!pages[i] ||
1153 mem_cgroup_try_charge(pages[i], mm, GFP_KERNEL,
1154 &memcg, false))) {
1155 if (pages[i])
1156 put_page(pages[i]);
1157 while (--i >= 0) {
1158 memcg = (void *)page_private(pages[i]);
1159 set_page_private(pages[i], 0);
1160 mem_cgroup_cancel_charge(pages[i], memcg,
1161 false);
1162 put_page(pages[i]);
1163 }
1164 kfree(pages);
1165 ret |= VM_FAULT_OOM;
1166 goto out;
1167 }
1168 set_page_private(pages[i], (unsigned long)memcg);
1169 }
1170
1171 for (i = 0; i < HPAGE_PMD_NR; i++) {
1172 copy_user_highpage(pages[i], page + i,
1173 haddr + PAGE_SIZE * i, vma);
1174 __SetPageUptodate(pages[i]);
1175 cond_resched();
1176 }
1177
1178 mmun_start = haddr;
1179 mmun_end = haddr + HPAGE_PMD_SIZE;
1180 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1181
1182 ptl = pmd_lock(mm, pmd);
1183 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1184 goto out_free_pages;
1185 VM_BUG_ON_PAGE(!PageHead(page), page);
1186
1187 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1188 /* leave pmd empty until pte is filled */
1189
1190 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1191 pmd_populate(mm, &_pmd, pgtable);
1192
1193 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1194 pte_t *pte, entry;
1195 entry = mk_pte(pages[i], vma->vm_page_prot);
1196 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1197 memcg = (void *)page_private(pages[i]);
1198 set_page_private(pages[i], 0);
1199 page_add_new_anon_rmap(pages[i], vma, haddr, false);
1200 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1201 lru_cache_add_active_or_unevictable(pages[i], vma);
1202 pte = pte_offset_map(&_pmd, haddr);
1203 VM_BUG_ON(!pte_none(*pte));
1204 set_pte_at(mm, haddr, pte, entry);
1205 pte_unmap(pte);
1206 }
1207 kfree(pages);
1208
1209 smp_wmb(); /* make pte visible before pmd */
1210 pmd_populate(mm, pmd, pgtable);
1211 page_remove_rmap(page, true);
1212 spin_unlock(ptl);
1213
1214 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1215
1216 ret |= VM_FAULT_WRITE;
1217 put_page(page);
1218
1219 out:
1220 return ret;
1221
1222 out_free_pages:
1223 spin_unlock(ptl);
1224 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1225 for (i = 0; i < HPAGE_PMD_NR; i++) {
1226 memcg = (void *)page_private(pages[i]);
1227 set_page_private(pages[i], 0);
1228 mem_cgroup_cancel_charge(pages[i], memcg, false);
1229 put_page(pages[i]);
1230 }
1231 kfree(pages);
1232 goto out;
1233 }
1234
1235 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1236 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1237 {
1238 spinlock_t *ptl;
1239 int ret = 0;
1240 struct page *page = NULL, *new_page;
1241 struct mem_cgroup *memcg;
1242 unsigned long haddr;
1243 unsigned long mmun_start; /* For mmu_notifiers */
1244 unsigned long mmun_end; /* For mmu_notifiers */
1245 gfp_t huge_gfp; /* for allocation and charge */
1246
1247 ptl = pmd_lockptr(mm, pmd);
1248 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1249 haddr = address & HPAGE_PMD_MASK;
1250 if (is_huge_zero_pmd(orig_pmd))
1251 goto alloc;
1252 spin_lock(ptl);
1253 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1254 goto out_unlock;
1255
1256 page = pmd_page(orig_pmd);
1257 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1258 /*
1259 * We can only reuse the page if nobody else maps the huge page or it's
1260 * part. We can do it by checking page_mapcount() on each sub-page, but
1261 * it's expensive.
1262 * The cheaper way is to check page_count() to be equal 1: every
1263 * mapcount takes page reference reference, so this way we can
1264 * guarantee, that the PMD is the only mapping.
1265 * This can give false negative if somebody pinned the page, but that's
1266 * fine.
1267 */
1268 if (page_mapcount(page) == 1 && page_count(page) == 1) {
1269 pmd_t entry;
1270 entry = pmd_mkyoung(orig_pmd);
1271 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1272 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1273 update_mmu_cache_pmd(vma, address, pmd);
1274 ret |= VM_FAULT_WRITE;
1275 goto out_unlock;
1276 }
1277 get_page(page);
1278 spin_unlock(ptl);
1279 alloc:
1280 if (transparent_hugepage_enabled(vma) &&
1281 !transparent_hugepage_debug_cow()) {
1282 huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0);
1283 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1284 } else
1285 new_page = NULL;
1286
1287 if (likely(new_page)) {
1288 prep_transhuge_page(new_page);
1289 } else {
1290 if (!page) {
1291 split_huge_pmd(vma, pmd, address);
1292 ret |= VM_FAULT_FALLBACK;
1293 } else {
1294 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1295 pmd, orig_pmd, page, haddr);
1296 if (ret & VM_FAULT_OOM) {
1297 split_huge_pmd(vma, pmd, address);
1298 ret |= VM_FAULT_FALLBACK;
1299 }
1300 put_page(page);
1301 }
1302 count_vm_event(THP_FAULT_FALLBACK);
1303 goto out;
1304 }
1305
1306 if (unlikely(mem_cgroup_try_charge(new_page, mm, huge_gfp, &memcg,
1307 true))) {
1308 put_page(new_page);
1309 if (page) {
1310 split_huge_pmd(vma, pmd, address);
1311 put_page(page);
1312 } else
1313 split_huge_pmd(vma, pmd, address);
1314 ret |= VM_FAULT_FALLBACK;
1315 count_vm_event(THP_FAULT_FALLBACK);
1316 goto out;
1317 }
1318
1319 count_vm_event(THP_FAULT_ALLOC);
1320
1321 if (!page)
1322 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1323 else
1324 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1325 __SetPageUptodate(new_page);
1326
1327 mmun_start = haddr;
1328 mmun_end = haddr + HPAGE_PMD_SIZE;
1329 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1330
1331 spin_lock(ptl);
1332 if (page)
1333 put_page(page);
1334 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1335 spin_unlock(ptl);
1336 mem_cgroup_cancel_charge(new_page, memcg, true);
1337 put_page(new_page);
1338 goto out_mn;
1339 } else {
1340 pmd_t entry;
1341 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1342 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1343 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1344 page_add_new_anon_rmap(new_page, vma, haddr, true);
1345 mem_cgroup_commit_charge(new_page, memcg, false, true);
1346 lru_cache_add_active_or_unevictable(new_page, vma);
1347 set_pmd_at(mm, haddr, pmd, entry);
1348 update_mmu_cache_pmd(vma, address, pmd);
1349 if (!page) {
1350 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1351 put_huge_zero_page();
1352 } else {
1353 VM_BUG_ON_PAGE(!PageHead(page), page);
1354 page_remove_rmap(page, true);
1355 put_page(page);
1356 }
1357 ret |= VM_FAULT_WRITE;
1358 }
1359 spin_unlock(ptl);
1360 out_mn:
1361 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1362 out:
1363 return ret;
1364 out_unlock:
1365 spin_unlock(ptl);
1366 return ret;
1367 }
1368
1369 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1370 unsigned long addr,
1371 pmd_t *pmd,
1372 unsigned int flags)
1373 {
1374 struct mm_struct *mm = vma->vm_mm;
1375 struct page *page = NULL;
1376
1377 assert_spin_locked(pmd_lockptr(mm, pmd));
1378
1379 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1380 goto out;
1381
1382 /* Avoid dumping huge zero page */
1383 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1384 return ERR_PTR(-EFAULT);
1385
1386 /* Full NUMA hinting faults to serialise migration in fault paths */
1387 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1388 goto out;
1389
1390 page = pmd_page(*pmd);
1391 VM_BUG_ON_PAGE(!PageHead(page), page);
1392 if (flags & FOLL_TOUCH)
1393 touch_pmd(vma, addr, pmd);
1394 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1395 /*
1396 * We don't mlock() pte-mapped THPs. This way we can avoid
1397 * leaking mlocked pages into non-VM_LOCKED VMAs.
1398 *
1399 * In most cases the pmd is the only mapping of the page as we
1400 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1401 * writable private mappings in populate_vma_page_range().
1402 *
1403 * The only scenario when we have the page shared here is if we
1404 * mlocking read-only mapping shared over fork(). We skip
1405 * mlocking such pages.
1406 */
1407 if (compound_mapcount(page) == 1 && !PageDoubleMap(page) &&
1408 page->mapping && trylock_page(page)) {
1409 lru_add_drain();
1410 if (page->mapping)
1411 mlock_vma_page(page);
1412 unlock_page(page);
1413 }
1414 }
1415 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1416 VM_BUG_ON_PAGE(!PageCompound(page), page);
1417 if (flags & FOLL_GET)
1418 get_page(page);
1419
1420 out:
1421 return page;
1422 }
1423
1424 /* NUMA hinting page fault entry point for trans huge pmds */
1425 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1426 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1427 {
1428 spinlock_t *ptl;
1429 struct anon_vma *anon_vma = NULL;
1430 struct page *page;
1431 unsigned long haddr = addr & HPAGE_PMD_MASK;
1432 int page_nid = -1, this_nid = numa_node_id();
1433 int target_nid, last_cpupid = -1;
1434 bool page_locked;
1435 bool migrated = false;
1436 bool was_writable;
1437 int flags = 0;
1438
1439 /* A PROT_NONE fault should not end up here */
1440 BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
1441
1442 ptl = pmd_lock(mm, pmdp);
1443 if (unlikely(!pmd_same(pmd, *pmdp)))
1444 goto out_unlock;
1445
1446 /*
1447 * If there are potential migrations, wait for completion and retry
1448 * without disrupting NUMA hinting information. Do not relock and
1449 * check_same as the page may no longer be mapped.
1450 */
1451 if (unlikely(pmd_trans_migrating(*pmdp))) {
1452 page = pmd_page(*pmdp);
1453 spin_unlock(ptl);
1454 wait_on_page_locked(page);
1455 goto out;
1456 }
1457
1458 page = pmd_page(pmd);
1459 BUG_ON(is_huge_zero_page(page));
1460 page_nid = page_to_nid(page);
1461 last_cpupid = page_cpupid_last(page);
1462 count_vm_numa_event(NUMA_HINT_FAULTS);
1463 if (page_nid == this_nid) {
1464 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1465 flags |= TNF_FAULT_LOCAL;
1466 }
1467
1468 /* See similar comment in do_numa_page for explanation */
1469 if (!(vma->vm_flags & VM_WRITE))
1470 flags |= TNF_NO_GROUP;
1471
1472 /*
1473 * Acquire the page lock to serialise THP migrations but avoid dropping
1474 * page_table_lock if at all possible
1475 */
1476 page_locked = trylock_page(page);
1477 target_nid = mpol_misplaced(page, vma, haddr);
1478 if (target_nid == -1) {
1479 /* If the page was locked, there are no parallel migrations */
1480 if (page_locked)
1481 goto clear_pmdnuma;
1482 }
1483
1484 /* Migration could have started since the pmd_trans_migrating check */
1485 if (!page_locked) {
1486 spin_unlock(ptl);
1487 wait_on_page_locked(page);
1488 page_nid = -1;
1489 goto out;
1490 }
1491
1492 /*
1493 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1494 * to serialises splits
1495 */
1496 get_page(page);
1497 spin_unlock(ptl);
1498 anon_vma = page_lock_anon_vma_read(page);
1499
1500 /* Confirm the PMD did not change while page_table_lock was released */
1501 spin_lock(ptl);
1502 if (unlikely(!pmd_same(pmd, *pmdp))) {
1503 unlock_page(page);
1504 put_page(page);
1505 page_nid = -1;
1506 goto out_unlock;
1507 }
1508
1509 /* Bail if we fail to protect against THP splits for any reason */
1510 if (unlikely(!anon_vma)) {
1511 put_page(page);
1512 page_nid = -1;
1513 goto clear_pmdnuma;
1514 }
1515
1516 /*
1517 * Migrate the THP to the requested node, returns with page unlocked
1518 * and access rights restored.
1519 */
1520 spin_unlock(ptl);
1521 migrated = migrate_misplaced_transhuge_page(mm, vma,
1522 pmdp, pmd, addr, page, target_nid);
1523 if (migrated) {
1524 flags |= TNF_MIGRATED;
1525 page_nid = target_nid;
1526 } else
1527 flags |= TNF_MIGRATE_FAIL;
1528
1529 goto out;
1530 clear_pmdnuma:
1531 BUG_ON(!PageLocked(page));
1532 was_writable = pmd_write(pmd);
1533 pmd = pmd_modify(pmd, vma->vm_page_prot);
1534 pmd = pmd_mkyoung(pmd);
1535 if (was_writable)
1536 pmd = pmd_mkwrite(pmd);
1537 set_pmd_at(mm, haddr, pmdp, pmd);
1538 update_mmu_cache_pmd(vma, addr, pmdp);
1539 unlock_page(page);
1540 out_unlock:
1541 spin_unlock(ptl);
1542
1543 out:
1544 if (anon_vma)
1545 page_unlock_anon_vma_read(anon_vma);
1546
1547 if (page_nid != -1)
1548 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, flags);
1549
1550 return 0;
1551 }
1552
1553 int madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1554 pmd_t *pmd, unsigned long addr, unsigned long next)
1555
1556 {
1557 spinlock_t *ptl;
1558 pmd_t orig_pmd;
1559 struct page *page;
1560 struct mm_struct *mm = tlb->mm;
1561 int ret = 0;
1562
1563 ptl = pmd_trans_huge_lock(pmd, vma);
1564 if (!ptl)
1565 goto out_unlocked;
1566
1567 orig_pmd = *pmd;
1568 if (is_huge_zero_pmd(orig_pmd)) {
1569 ret = 1;
1570 goto out;
1571 }
1572
1573 page = pmd_page(orig_pmd);
1574 /*
1575 * If other processes are mapping this page, we couldn't discard
1576 * the page unless they all do MADV_FREE so let's skip the page.
1577 */
1578 if (page_mapcount(page) != 1)
1579 goto out;
1580
1581 if (!trylock_page(page))
1582 goto out;
1583
1584 /*
1585 * If user want to discard part-pages of THP, split it so MADV_FREE
1586 * will deactivate only them.
1587 */
1588 if (next - addr != HPAGE_PMD_SIZE) {
1589 get_page(page);
1590 spin_unlock(ptl);
1591 if (split_huge_page(page)) {
1592 put_page(page);
1593 unlock_page(page);
1594 goto out_unlocked;
1595 }
1596 put_page(page);
1597 unlock_page(page);
1598 ret = 1;
1599 goto out_unlocked;
1600 }
1601
1602 if (PageDirty(page))
1603 ClearPageDirty(page);
1604 unlock_page(page);
1605
1606 if (PageActive(page))
1607 deactivate_page(page);
1608
1609 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1610 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1611 tlb->fullmm);
1612 orig_pmd = pmd_mkold(orig_pmd);
1613 orig_pmd = pmd_mkclean(orig_pmd);
1614
1615 set_pmd_at(mm, addr, pmd, orig_pmd);
1616 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1617 }
1618 ret = 1;
1619 out:
1620 spin_unlock(ptl);
1621 out_unlocked:
1622 return ret;
1623 }
1624
1625 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1626 pmd_t *pmd, unsigned long addr)
1627 {
1628 pmd_t orig_pmd;
1629 spinlock_t *ptl;
1630
1631 ptl = __pmd_trans_huge_lock(pmd, vma);
1632 if (!ptl)
1633 return 0;
1634 /*
1635 * For architectures like ppc64 we look at deposited pgtable
1636 * when calling pmdp_huge_get_and_clear. So do the
1637 * pgtable_trans_huge_withdraw after finishing pmdp related
1638 * operations.
1639 */
1640 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1641 tlb->fullmm);
1642 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1643 if (vma_is_dax(vma)) {
1644 spin_unlock(ptl);
1645 if (is_huge_zero_pmd(orig_pmd))
1646 put_huge_zero_page();
1647 } else if (is_huge_zero_pmd(orig_pmd)) {
1648 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1649 atomic_long_dec(&tlb->mm->nr_ptes);
1650 spin_unlock(ptl);
1651 put_huge_zero_page();
1652 } else {
1653 struct page *page = pmd_page(orig_pmd);
1654 page_remove_rmap(page, true);
1655 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1656 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1657 VM_BUG_ON_PAGE(!PageHead(page), page);
1658 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1659 atomic_long_dec(&tlb->mm->nr_ptes);
1660 spin_unlock(ptl);
1661 tlb_remove_page(tlb, page);
1662 }
1663 return 1;
1664 }
1665
1666 bool move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1667 unsigned long old_addr,
1668 unsigned long new_addr, unsigned long old_end,
1669 pmd_t *old_pmd, pmd_t *new_pmd)
1670 {
1671 spinlock_t *old_ptl, *new_ptl;
1672 pmd_t pmd;
1673
1674 struct mm_struct *mm = vma->vm_mm;
1675
1676 if ((old_addr & ~HPAGE_PMD_MASK) ||
1677 (new_addr & ~HPAGE_PMD_MASK) ||
1678 old_end - old_addr < HPAGE_PMD_SIZE ||
1679 (new_vma->vm_flags & VM_NOHUGEPAGE))
1680 return false;
1681
1682 /*
1683 * The destination pmd shouldn't be established, free_pgtables()
1684 * should have release it.
1685 */
1686 if (WARN_ON(!pmd_none(*new_pmd))) {
1687 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1688 return false;
1689 }
1690
1691 /*
1692 * We don't have to worry about the ordering of src and dst
1693 * ptlocks because exclusive mmap_sem prevents deadlock.
1694 */
1695 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1696 if (old_ptl) {
1697 new_ptl = pmd_lockptr(mm, new_pmd);
1698 if (new_ptl != old_ptl)
1699 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1700 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1701 VM_BUG_ON(!pmd_none(*new_pmd));
1702
1703 if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
1704 pgtable_t pgtable;
1705 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1706 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1707 }
1708 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1709 if (new_ptl != old_ptl)
1710 spin_unlock(new_ptl);
1711 spin_unlock(old_ptl);
1712 return true;
1713 }
1714 return false;
1715 }
1716
1717 /*
1718 * Returns
1719 * - 0 if PMD could not be locked
1720 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1721 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1722 */
1723 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1724 unsigned long addr, pgprot_t newprot, int prot_numa)
1725 {
1726 struct mm_struct *mm = vma->vm_mm;
1727 spinlock_t *ptl;
1728 int ret = 0;
1729
1730 ptl = __pmd_trans_huge_lock(pmd, vma);
1731 if (ptl) {
1732 pmd_t entry;
1733 bool preserve_write = prot_numa && pmd_write(*pmd);
1734 ret = 1;
1735
1736 /*
1737 * Avoid trapping faults against the zero page. The read-only
1738 * data is likely to be read-cached on the local CPU and
1739 * local/remote hits to the zero page are not interesting.
1740 */
1741 if (prot_numa && is_huge_zero_pmd(*pmd)) {
1742 spin_unlock(ptl);
1743 return ret;
1744 }
1745
1746 if (!prot_numa || !pmd_protnone(*pmd)) {
1747 entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd);
1748 entry = pmd_modify(entry, newprot);
1749 if (preserve_write)
1750 entry = pmd_mkwrite(entry);
1751 ret = HPAGE_PMD_NR;
1752 set_pmd_at(mm, addr, pmd, entry);
1753 BUG_ON(!preserve_write && pmd_write(entry));
1754 }
1755 spin_unlock(ptl);
1756 }
1757
1758 return ret;
1759 }
1760
1761 /*
1762 * Returns true if a given pmd maps a thp, false otherwise.
1763 *
1764 * Note that if it returns true, this routine returns without unlocking page
1765 * table lock. So callers must unlock it.
1766 */
1767 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1768 {
1769 spinlock_t *ptl;
1770 ptl = pmd_lock(vma->vm_mm, pmd);
1771 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1772 return ptl;
1773 spin_unlock(ptl);
1774 return NULL;
1775 }
1776
1777 #define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
1778
1779 int hugepage_madvise(struct vm_area_struct *vma,
1780 unsigned long *vm_flags, int advice)
1781 {
1782 switch (advice) {
1783 case MADV_HUGEPAGE:
1784 #ifdef CONFIG_S390
1785 /*
1786 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
1787 * can't handle this properly after s390_enable_sie, so we simply
1788 * ignore the madvise to prevent qemu from causing a SIGSEGV.
1789 */
1790 if (mm_has_pgste(vma->vm_mm))
1791 return 0;
1792 #endif
1793 /*
1794 * Be somewhat over-protective like KSM for now!
1795 */
1796 if (*vm_flags & VM_NO_THP)
1797 return -EINVAL;
1798 *vm_flags &= ~VM_NOHUGEPAGE;
1799 *vm_flags |= VM_HUGEPAGE;
1800 /*
1801 * If the vma become good for khugepaged to scan,
1802 * register it here without waiting a page fault that
1803 * may not happen any time soon.
1804 */
1805 if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
1806 return -ENOMEM;
1807 break;
1808 case MADV_NOHUGEPAGE:
1809 /*
1810 * Be somewhat over-protective like KSM for now!
1811 */
1812 if (*vm_flags & VM_NO_THP)
1813 return -EINVAL;
1814 *vm_flags &= ~VM_HUGEPAGE;
1815 *vm_flags |= VM_NOHUGEPAGE;
1816 /*
1817 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1818 * this vma even if we leave the mm registered in khugepaged if
1819 * it got registered before VM_NOHUGEPAGE was set.
1820 */
1821 break;
1822 }
1823
1824 return 0;
1825 }
1826
1827 static int __init khugepaged_slab_init(void)
1828 {
1829 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1830 sizeof(struct mm_slot),
1831 __alignof__(struct mm_slot), 0, NULL);
1832 if (!mm_slot_cache)
1833 return -ENOMEM;
1834
1835 return 0;
1836 }
1837
1838 static void __init khugepaged_slab_exit(void)
1839 {
1840 kmem_cache_destroy(mm_slot_cache);
1841 }
1842
1843 static inline struct mm_slot *alloc_mm_slot(void)
1844 {
1845 if (!mm_slot_cache) /* initialization failed */
1846 return NULL;
1847 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1848 }
1849
1850 static inline void free_mm_slot(struct mm_slot *mm_slot)
1851 {
1852 kmem_cache_free(mm_slot_cache, mm_slot);
1853 }
1854
1855 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1856 {
1857 struct mm_slot *mm_slot;
1858
1859 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
1860 if (mm == mm_slot->mm)
1861 return mm_slot;
1862
1863 return NULL;
1864 }
1865
1866 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1867 struct mm_slot *mm_slot)
1868 {
1869 mm_slot->mm = mm;
1870 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
1871 }
1872
1873 static inline int khugepaged_test_exit(struct mm_struct *mm)
1874 {
1875 return atomic_read(&mm->mm_users) == 0;
1876 }
1877
1878 int __khugepaged_enter(struct mm_struct *mm)
1879 {
1880 struct mm_slot *mm_slot;
1881 int wakeup;
1882
1883 mm_slot = alloc_mm_slot();
1884 if (!mm_slot)
1885 return -ENOMEM;
1886
1887 /* __khugepaged_exit() must not run from under us */
1888 VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
1889 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1890 free_mm_slot(mm_slot);
1891 return 0;
1892 }
1893
1894 spin_lock(&khugepaged_mm_lock);
1895 insert_to_mm_slots_hash(mm, mm_slot);
1896 /*
1897 * Insert just behind the scanning cursor, to let the area settle
1898 * down a little.
1899 */
1900 wakeup = list_empty(&khugepaged_scan.mm_head);
1901 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1902 spin_unlock(&khugepaged_mm_lock);
1903
1904 atomic_inc(&mm->mm_count);
1905 if (wakeup)
1906 wake_up_interruptible(&khugepaged_wait);
1907
1908 return 0;
1909 }
1910
1911 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
1912 unsigned long vm_flags)
1913 {
1914 unsigned long hstart, hend;
1915 if (!vma->anon_vma)
1916 /*
1917 * Not yet faulted in so we will register later in the
1918 * page fault if needed.
1919 */
1920 return 0;
1921 if (vma->vm_ops)
1922 /* khugepaged not yet working on file or special mappings */
1923 return 0;
1924 VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
1925 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1926 hend = vma->vm_end & HPAGE_PMD_MASK;
1927 if (hstart < hend)
1928 return khugepaged_enter(vma, vm_flags);
1929 return 0;
1930 }
1931
1932 void __khugepaged_exit(struct mm_struct *mm)
1933 {
1934 struct mm_slot *mm_slot;
1935 int free = 0;
1936
1937 spin_lock(&khugepaged_mm_lock);
1938 mm_slot = get_mm_slot(mm);
1939 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1940 hash_del(&mm_slot->hash);
1941 list_del(&mm_slot->mm_node);
1942 free = 1;
1943 }
1944 spin_unlock(&khugepaged_mm_lock);
1945
1946 if (free) {
1947 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1948 free_mm_slot(mm_slot);
1949 mmdrop(mm);
1950 } else if (mm_slot) {
1951 /*
1952 * This is required to serialize against
1953 * khugepaged_test_exit() (which is guaranteed to run
1954 * under mmap sem read mode). Stop here (after we
1955 * return all pagetables will be destroyed) until
1956 * khugepaged has finished working on the pagetables
1957 * under the mmap_sem.
1958 */
1959 down_write(&mm->mmap_sem);
1960 up_write(&mm->mmap_sem);
1961 }
1962 }
1963
1964 static void release_pte_page(struct page *page)
1965 {
1966 /* 0 stands for page_is_file_cache(page) == false */
1967 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1968 unlock_page(page);
1969 putback_lru_page(page);
1970 }
1971
1972 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1973 {
1974 while (--_pte >= pte) {
1975 pte_t pteval = *_pte;
1976 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
1977 release_pte_page(pte_page(pteval));
1978 }
1979 }
1980
1981 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1982 unsigned long address,
1983 pte_t *pte)
1984 {
1985 struct page *page = NULL;
1986 pte_t *_pte;
1987 int none_or_zero = 0, result = 0;
1988 bool referenced = false, writable = false;
1989
1990 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1991 _pte++, address += PAGE_SIZE) {
1992 pte_t pteval = *_pte;
1993 if (pte_none(pteval) || (pte_present(pteval) &&
1994 is_zero_pfn(pte_pfn(pteval)))) {
1995 if (!userfaultfd_armed(vma) &&
1996 ++none_or_zero <= khugepaged_max_ptes_none) {
1997 continue;
1998 } else {
1999 result = SCAN_EXCEED_NONE_PTE;
2000 goto out;
2001 }
2002 }
2003 if (!pte_present(pteval)) {
2004 result = SCAN_PTE_NON_PRESENT;
2005 goto out;
2006 }
2007 page = vm_normal_page(vma, address, pteval);
2008 if (unlikely(!page)) {
2009 result = SCAN_PAGE_NULL;
2010 goto out;
2011 }
2012
2013 VM_BUG_ON_PAGE(PageCompound(page), page);
2014 VM_BUG_ON_PAGE(!PageAnon(page), page);
2015 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2016
2017 /*
2018 * We can do it before isolate_lru_page because the
2019 * page can't be freed from under us. NOTE: PG_lock
2020 * is needed to serialize against split_huge_page
2021 * when invoked from the VM.
2022 */
2023 if (!trylock_page(page)) {
2024 result = SCAN_PAGE_LOCK;
2025 goto out;
2026 }
2027
2028 /*
2029 * cannot use mapcount: can't collapse if there's a gup pin.
2030 * The page must only be referenced by the scanned process
2031 * and page swap cache.
2032 */
2033 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2034 unlock_page(page);
2035 result = SCAN_PAGE_COUNT;
2036 goto out;
2037 }
2038 if (pte_write(pteval)) {
2039 writable = true;
2040 } else {
2041 if (PageSwapCache(page) && !reuse_swap_page(page)) {
2042 unlock_page(page);
2043 result = SCAN_SWAP_CACHE_PAGE;
2044 goto out;
2045 }
2046 /*
2047 * Page is not in the swap cache. It can be collapsed
2048 * into a THP.
2049 */
2050 }
2051
2052 /*
2053 * Isolate the page to avoid collapsing an hugepage
2054 * currently in use by the VM.
2055 */
2056 if (isolate_lru_page(page)) {
2057 unlock_page(page);
2058 result = SCAN_DEL_PAGE_LRU;
2059 goto out;
2060 }
2061 /* 0 stands for page_is_file_cache(page) == false */
2062 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2063 VM_BUG_ON_PAGE(!PageLocked(page), page);
2064 VM_BUG_ON_PAGE(PageLRU(page), page);
2065
2066 /* If there is no mapped pte young don't collapse the page */
2067 if (pte_young(pteval) ||
2068 page_is_young(page) || PageReferenced(page) ||
2069 mmu_notifier_test_young(vma->vm_mm, address))
2070 referenced = true;
2071 }
2072 if (likely(writable)) {
2073 if (likely(referenced)) {
2074 result = SCAN_SUCCEED;
2075 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2076 referenced, writable, result);
2077 return 1;
2078 }
2079 } else {
2080 result = SCAN_PAGE_RO;
2081 }
2082
2083 out:
2084 release_pte_pages(pte, _pte);
2085 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
2086 referenced, writable, result);
2087 return 0;
2088 }
2089
2090 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2091 struct vm_area_struct *vma,
2092 unsigned long address,
2093 spinlock_t *ptl)
2094 {
2095 pte_t *_pte;
2096 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2097 pte_t pteval = *_pte;
2098 struct page *src_page;
2099
2100 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2101 clear_user_highpage(page, address);
2102 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2103 if (is_zero_pfn(pte_pfn(pteval))) {
2104 /*
2105 * ptl mostly unnecessary.
2106 */
2107 spin_lock(ptl);
2108 /*
2109 * paravirt calls inside pte_clear here are
2110 * superfluous.
2111 */
2112 pte_clear(vma->vm_mm, address, _pte);
2113 spin_unlock(ptl);
2114 }
2115 } else {
2116 src_page = pte_page(pteval);
2117 copy_user_highpage(page, src_page, address, vma);
2118 VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
2119 release_pte_page(src_page);
2120 /*
2121 * ptl mostly unnecessary, but preempt has to
2122 * be disabled to update the per-cpu stats
2123 * inside page_remove_rmap().
2124 */
2125 spin_lock(ptl);
2126 /*
2127 * paravirt calls inside pte_clear here are
2128 * superfluous.
2129 */
2130 pte_clear(vma->vm_mm, address, _pte);
2131 page_remove_rmap(src_page, false);
2132 spin_unlock(ptl);
2133 free_page_and_swap_cache(src_page);
2134 }
2135
2136 address += PAGE_SIZE;
2137 page++;
2138 }
2139 }
2140
2141 static void khugepaged_alloc_sleep(void)
2142 {
2143 DEFINE_WAIT(wait);
2144
2145 add_wait_queue(&khugepaged_wait, &wait);
2146 freezable_schedule_timeout_interruptible(
2147 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2148 remove_wait_queue(&khugepaged_wait, &wait);
2149 }
2150
2151 static int khugepaged_node_load[MAX_NUMNODES];
2152
2153 static bool khugepaged_scan_abort(int nid)
2154 {
2155 int i;
2156
2157 /*
2158 * If zone_reclaim_mode is disabled, then no extra effort is made to
2159 * allocate memory locally.
2160 */
2161 if (!zone_reclaim_mode)
2162 return false;
2163
2164 /* If there is a count for this node already, it must be acceptable */
2165 if (khugepaged_node_load[nid])
2166 return false;
2167
2168 for (i = 0; i < MAX_NUMNODES; i++) {
2169 if (!khugepaged_node_load[i])
2170 continue;
2171 if (node_distance(nid, i) > RECLAIM_DISTANCE)
2172 return true;
2173 }
2174 return false;
2175 }
2176
2177 #ifdef CONFIG_NUMA
2178 static int khugepaged_find_target_node(void)
2179 {
2180 static int last_khugepaged_target_node = NUMA_NO_NODE;
2181 int nid, target_node = 0, max_value = 0;
2182
2183 /* find first node with max normal pages hit */
2184 for (nid = 0; nid < MAX_NUMNODES; nid++)
2185 if (khugepaged_node_load[nid] > max_value) {
2186 max_value = khugepaged_node_load[nid];
2187 target_node = nid;
2188 }
2189
2190 /* do some balance if several nodes have the same hit record */
2191 if (target_node <= last_khugepaged_target_node)
2192 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
2193 nid++)
2194 if (max_value == khugepaged_node_load[nid]) {
2195 target_node = nid;
2196 break;
2197 }
2198
2199 last_khugepaged_target_node = target_node;
2200 return target_node;
2201 }
2202
2203 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2204 {
2205 if (IS_ERR(*hpage)) {
2206 if (!*wait)
2207 return false;
2208
2209 *wait = false;
2210 *hpage = NULL;
2211 khugepaged_alloc_sleep();
2212 } else if (*hpage) {
2213 put_page(*hpage);
2214 *hpage = NULL;
2215 }
2216
2217 return true;
2218 }
2219
2220 static struct page *
2221 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2222 unsigned long address, int node)
2223 {
2224 VM_BUG_ON_PAGE(*hpage, *hpage);
2225
2226 /*
2227 * Before allocating the hugepage, release the mmap_sem read lock.
2228 * The allocation can take potentially a long time if it involves
2229 * sync compaction, and we do not need to hold the mmap_sem during
2230 * that. We will recheck the vma after taking it again in write mode.
2231 */
2232 up_read(&mm->mmap_sem);
2233
2234 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
2235 if (unlikely(!*hpage)) {
2236 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2237 *hpage = ERR_PTR(-ENOMEM);
2238 return NULL;
2239 }
2240
2241 prep_transhuge_page(*hpage);
2242 count_vm_event(THP_COLLAPSE_ALLOC);
2243 return *hpage;
2244 }
2245 #else
2246 static int khugepaged_find_target_node(void)
2247 {
2248 return 0;
2249 }
2250
2251 static inline struct page *alloc_hugepage(int defrag)
2252 {
2253 struct page *page;
2254
2255 page = alloc_pages(alloc_hugepage_gfpmask(defrag, 0), HPAGE_PMD_ORDER);
2256 if (page)
2257 prep_transhuge_page(page);
2258 return page;
2259 }
2260
2261 static struct page *khugepaged_alloc_hugepage(bool *wait)
2262 {
2263 struct page *hpage;
2264
2265 do {
2266 hpage = alloc_hugepage(khugepaged_defrag());
2267 if (!hpage) {
2268 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2269 if (!*wait)
2270 return NULL;
2271
2272 *wait = false;
2273 khugepaged_alloc_sleep();
2274 } else
2275 count_vm_event(THP_COLLAPSE_ALLOC);
2276 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2277
2278 return hpage;
2279 }
2280
2281 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2282 {
2283 if (!*hpage)
2284 *hpage = khugepaged_alloc_hugepage(wait);
2285
2286 if (unlikely(!*hpage))
2287 return false;
2288
2289 return true;
2290 }
2291
2292 static struct page *
2293 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, struct mm_struct *mm,
2294 unsigned long address, int node)
2295 {
2296 up_read(&mm->mmap_sem);
2297 VM_BUG_ON(!*hpage);
2298
2299 return *hpage;
2300 }
2301 #endif
2302
2303 static bool hugepage_vma_check(struct vm_area_struct *vma)
2304 {
2305 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2306 (vma->vm_flags & VM_NOHUGEPAGE))
2307 return false;
2308 if (!vma->anon_vma || vma->vm_ops)
2309 return false;
2310 if (is_vma_temporary_stack(vma))
2311 return false;
2312 VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
2313 return true;
2314 }
2315
2316 static void collapse_huge_page(struct mm_struct *mm,
2317 unsigned long address,
2318 struct page **hpage,
2319 struct vm_area_struct *vma,
2320 int node)
2321 {
2322 pmd_t *pmd, _pmd;
2323 pte_t *pte;
2324 pgtable_t pgtable;
2325 struct page *new_page;
2326 spinlock_t *pmd_ptl, *pte_ptl;
2327 int isolated = 0, result = 0;
2328 unsigned long hstart, hend;
2329 struct mem_cgroup *memcg;
2330 unsigned long mmun_start; /* For mmu_notifiers */
2331 unsigned long mmun_end; /* For mmu_notifiers */
2332 gfp_t gfp;
2333
2334 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2335
2336 /* Only allocate from the target node */
2337 gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) |
2338 __GFP_THISNODE;
2339
2340 /* release the mmap_sem read lock. */
2341 new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node);
2342 if (!new_page) {
2343 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
2344 goto out_nolock;
2345 }
2346
2347 if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
2348 result = SCAN_CGROUP_CHARGE_FAIL;
2349 goto out_nolock;
2350 }
2351
2352 /*
2353 * Prevent all access to pagetables with the exception of
2354 * gup_fast later hanlded by the ptep_clear_flush and the VM
2355 * handled by the anon_vma lock + PG_lock.
2356 */
2357 down_write(&mm->mmap_sem);
2358 if (unlikely(khugepaged_test_exit(mm))) {
2359 result = SCAN_ANY_PROCESS;
2360 goto out;
2361 }
2362
2363 vma = find_vma(mm, address);
2364 if (!vma) {
2365 result = SCAN_VMA_NULL;
2366 goto out;
2367 }
2368 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2369 hend = vma->vm_end & HPAGE_PMD_MASK;
2370 if (address < hstart || address + HPAGE_PMD_SIZE > hend) {
2371 result = SCAN_ADDRESS_RANGE;
2372 goto out;
2373 }
2374 if (!hugepage_vma_check(vma)) {
2375 result = SCAN_VMA_CHECK;
2376 goto out;
2377 }
2378 pmd = mm_find_pmd(mm, address);
2379 if (!pmd) {
2380 result = SCAN_PMD_NULL;
2381 goto out;
2382 }
2383
2384 anon_vma_lock_write(vma->anon_vma);
2385
2386 pte = pte_offset_map(pmd, address);
2387 pte_ptl = pte_lockptr(mm, pmd);
2388
2389 mmun_start = address;
2390 mmun_end = address + HPAGE_PMD_SIZE;
2391 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2392 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
2393 /*
2394 * After this gup_fast can't run anymore. This also removes
2395 * any huge TLB entry from the CPU so we won't allow
2396 * huge and small TLB entries for the same virtual address
2397 * to avoid the risk of CPU bugs in that area.
2398 */
2399 _pmd = pmdp_collapse_flush(vma, address, pmd);
2400 spin_unlock(pmd_ptl);
2401 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2402
2403 spin_lock(pte_ptl);
2404 isolated = __collapse_huge_page_isolate(vma, address, pte);
2405 spin_unlock(pte_ptl);
2406
2407 if (unlikely(!isolated)) {
2408 pte_unmap(pte);
2409 spin_lock(pmd_ptl);
2410 BUG_ON(!pmd_none(*pmd));
2411 /*
2412 * We can only use set_pmd_at when establishing
2413 * hugepmds and never for establishing regular pmds that
2414 * points to regular pagetables. Use pmd_populate for that
2415 */
2416 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
2417 spin_unlock(pmd_ptl);
2418 anon_vma_unlock_write(vma->anon_vma);
2419 result = SCAN_FAIL;
2420 goto out;
2421 }
2422
2423 /*
2424 * All pages are isolated and locked so anon_vma rmap
2425 * can't run anymore.
2426 */
2427 anon_vma_unlock_write(vma->anon_vma);
2428
2429 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
2430 pte_unmap(pte);
2431 __SetPageUptodate(new_page);
2432 pgtable = pmd_pgtable(_pmd);
2433
2434 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
2435 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2436
2437 /*
2438 * spin_lock() below is not the equivalent of smp_wmb(), so
2439 * this is needed to avoid the copy_huge_page writes to become
2440 * visible after the set_pmd_at() write.
2441 */
2442 smp_wmb();
2443
2444 spin_lock(pmd_ptl);
2445 BUG_ON(!pmd_none(*pmd));
2446 page_add_new_anon_rmap(new_page, vma, address, true);
2447 mem_cgroup_commit_charge(new_page, memcg, false, true);
2448 lru_cache_add_active_or_unevictable(new_page, vma);
2449 pgtable_trans_huge_deposit(mm, pmd, pgtable);
2450 set_pmd_at(mm, address, pmd, _pmd);
2451 update_mmu_cache_pmd(vma, address, pmd);
2452 spin_unlock(pmd_ptl);
2453
2454 *hpage = NULL;
2455
2456 khugepaged_pages_collapsed++;
2457 result = SCAN_SUCCEED;
2458 out_up_write:
2459 up_write(&mm->mmap_sem);
2460 trace_mm_collapse_huge_page(mm, isolated, result);
2461 return;
2462
2463 out_nolock:
2464 trace_mm_collapse_huge_page(mm, isolated, result);
2465 return;
2466 out:
2467 mem_cgroup_cancel_charge(new_page, memcg, true);
2468 goto out_up_write;
2469 }
2470
2471 static int khugepaged_scan_pmd(struct mm_struct *mm,
2472 struct vm_area_struct *vma,
2473 unsigned long address,
2474 struct page **hpage)
2475 {
2476 pmd_t *pmd;
2477 pte_t *pte, *_pte;
2478 int ret = 0, none_or_zero = 0, result = 0;
2479 struct page *page = NULL;
2480 unsigned long _address;
2481 spinlock_t *ptl;
2482 int node = NUMA_NO_NODE;
2483 bool writable = false, referenced = false;
2484
2485 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2486
2487 pmd = mm_find_pmd(mm, address);
2488 if (!pmd) {
2489 result = SCAN_PMD_NULL;
2490 goto out;
2491 }
2492
2493 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
2494 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2495 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2496 _pte++, _address += PAGE_SIZE) {
2497 pte_t pteval = *_pte;
2498 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
2499 if (!userfaultfd_armed(vma) &&
2500 ++none_or_zero <= khugepaged_max_ptes_none) {
2501 continue;
2502 } else {
2503 result = SCAN_EXCEED_NONE_PTE;
2504 goto out_unmap;
2505 }
2506 }
2507 if (!pte_present(pteval)) {
2508 result = SCAN_PTE_NON_PRESENT;
2509 goto out_unmap;
2510 }
2511 if (pte_write(pteval))
2512 writable = true;
2513
2514 page = vm_normal_page(vma, _address, pteval);
2515 if (unlikely(!page)) {
2516 result = SCAN_PAGE_NULL;
2517 goto out_unmap;
2518 }
2519
2520 /* TODO: teach khugepaged to collapse THP mapped with pte */
2521 if (PageCompound(page)) {
2522 result = SCAN_PAGE_COMPOUND;
2523 goto out_unmap;
2524 }
2525
2526 /*
2527 * Record which node the original page is from and save this
2528 * information to khugepaged_node_load[].
2529 * Khupaged will allocate hugepage from the node has the max
2530 * hit record.
2531 */
2532 node = page_to_nid(page);
2533 if (khugepaged_scan_abort(node)) {
2534 result = SCAN_SCAN_ABORT;
2535 goto out_unmap;
2536 }
2537 khugepaged_node_load[node]++;
2538 if (!PageLRU(page)) {
2539 result = SCAN_SCAN_ABORT;
2540 goto out_unmap;
2541 }
2542 if (PageLocked(page)) {
2543 result = SCAN_PAGE_LOCK;
2544 goto out_unmap;
2545 }
2546 if (!PageAnon(page)) {
2547 result = SCAN_PAGE_ANON;
2548 goto out_unmap;
2549 }
2550
2551 /*
2552 * cannot use mapcount: can't collapse if there's a gup pin.
2553 * The page must only be referenced by the scanned process
2554 * and page swap cache.
2555 */
2556 if (page_count(page) != 1 + !!PageSwapCache(page)) {
2557 result = SCAN_PAGE_COUNT;
2558 goto out_unmap;
2559 }
2560 if (pte_young(pteval) ||
2561 page_is_young(page) || PageReferenced(page) ||
2562 mmu_notifier_test_young(vma->vm_mm, address))
2563 referenced = true;
2564 }
2565 if (writable) {
2566 if (referenced) {
2567 result = SCAN_SUCCEED;
2568 ret = 1;
2569 } else {
2570 result = SCAN_NO_REFERENCED_PAGE;
2571 }
2572 } else {
2573 result = SCAN_PAGE_RO;
2574 }
2575 out_unmap:
2576 pte_unmap_unlock(pte, ptl);
2577 if (ret) {
2578 node = khugepaged_find_target_node();
2579 /* collapse_huge_page will return with the mmap_sem released */
2580 collapse_huge_page(mm, address, hpage, vma, node);
2581 }
2582 out:
2583 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
2584 none_or_zero, result);
2585 return ret;
2586 }
2587
2588 static void collect_mm_slot(struct mm_slot *mm_slot)
2589 {
2590 struct mm_struct *mm = mm_slot->mm;
2591
2592 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2593
2594 if (khugepaged_test_exit(mm)) {
2595 /* free mm_slot */
2596 hash_del(&mm_slot->hash);
2597 list_del(&mm_slot->mm_node);
2598
2599 /*
2600 * Not strictly needed because the mm exited already.
2601 *
2602 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2603 */
2604
2605 /* khugepaged_mm_lock actually not necessary for the below */
2606 free_mm_slot(mm_slot);
2607 mmdrop(mm);
2608 }
2609 }
2610
2611 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2612 struct page **hpage)
2613 __releases(&khugepaged_mm_lock)
2614 __acquires(&khugepaged_mm_lock)
2615 {
2616 struct mm_slot *mm_slot;
2617 struct mm_struct *mm;
2618 struct vm_area_struct *vma;
2619 int progress = 0;
2620
2621 VM_BUG_ON(!pages);
2622 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2623
2624 if (khugepaged_scan.mm_slot)
2625 mm_slot = khugepaged_scan.mm_slot;
2626 else {
2627 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2628 struct mm_slot, mm_node);
2629 khugepaged_scan.address = 0;
2630 khugepaged_scan.mm_slot = mm_slot;
2631 }
2632 spin_unlock(&khugepaged_mm_lock);
2633
2634 mm = mm_slot->mm;
2635 down_read(&mm->mmap_sem);
2636 if (unlikely(khugepaged_test_exit(mm)))
2637 vma = NULL;
2638 else
2639 vma = find_vma(mm, khugepaged_scan.address);
2640
2641 progress++;
2642 for (; vma; vma = vma->vm_next) {
2643 unsigned long hstart, hend;
2644
2645 cond_resched();
2646 if (unlikely(khugepaged_test_exit(mm))) {
2647 progress++;
2648 break;
2649 }
2650 if (!hugepage_vma_check(vma)) {
2651 skip:
2652 progress++;
2653 continue;
2654 }
2655 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2656 hend = vma->vm_end & HPAGE_PMD_MASK;
2657 if (hstart >= hend)
2658 goto skip;
2659 if (khugepaged_scan.address > hend)
2660 goto skip;
2661 if (khugepaged_scan.address < hstart)
2662 khugepaged_scan.address = hstart;
2663 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2664
2665 while (khugepaged_scan.address < hend) {
2666 int ret;
2667 cond_resched();
2668 if (unlikely(khugepaged_test_exit(mm)))
2669 goto breakouterloop;
2670
2671 VM_BUG_ON(khugepaged_scan.address < hstart ||
2672 khugepaged_scan.address + HPAGE_PMD_SIZE >
2673 hend);
2674 ret = khugepaged_scan_pmd(mm, vma,
2675 khugepaged_scan.address,
2676 hpage);
2677 /* move to next address */
2678 khugepaged_scan.address += HPAGE_PMD_SIZE;
2679 progress += HPAGE_PMD_NR;
2680 if (ret)
2681 /* we released mmap_sem so break loop */
2682 goto breakouterloop_mmap_sem;
2683 if (progress >= pages)
2684 goto breakouterloop;
2685 }
2686 }
2687 breakouterloop:
2688 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2689 breakouterloop_mmap_sem:
2690
2691 spin_lock(&khugepaged_mm_lock);
2692 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2693 /*
2694 * Release the current mm_slot if this mm is about to die, or
2695 * if we scanned all vmas of this mm.
2696 */
2697 if (khugepaged_test_exit(mm) || !vma) {
2698 /*
2699 * Make sure that if mm_users is reaching zero while
2700 * khugepaged runs here, khugepaged_exit will find
2701 * mm_slot not pointing to the exiting mm.
2702 */
2703 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2704 khugepaged_scan.mm_slot = list_entry(
2705 mm_slot->mm_node.next,
2706 struct mm_slot, mm_node);
2707 khugepaged_scan.address = 0;
2708 } else {
2709 khugepaged_scan.mm_slot = NULL;
2710 khugepaged_full_scans++;
2711 }
2712
2713 collect_mm_slot(mm_slot);
2714 }
2715
2716 return progress;
2717 }
2718
2719 static int khugepaged_has_work(void)
2720 {
2721 return !list_empty(&khugepaged_scan.mm_head) &&
2722 khugepaged_enabled();
2723 }
2724
2725 static int khugepaged_wait_event(void)
2726 {
2727 return !list_empty(&khugepaged_scan.mm_head) ||
2728 kthread_should_stop();
2729 }
2730
2731 static void khugepaged_do_scan(void)
2732 {
2733 struct page *hpage = NULL;
2734 unsigned int progress = 0, pass_through_head = 0;
2735 unsigned int pages = khugepaged_pages_to_scan;
2736 bool wait = true;
2737
2738 barrier(); /* write khugepaged_pages_to_scan to local stack */
2739
2740 while (progress < pages) {
2741 if (!khugepaged_prealloc_page(&hpage, &wait))
2742 break;
2743
2744 cond_resched();
2745
2746 if (unlikely(kthread_should_stop() || try_to_freeze()))
2747 break;
2748
2749 spin_lock(&khugepaged_mm_lock);
2750 if (!khugepaged_scan.mm_slot)
2751 pass_through_head++;
2752 if (khugepaged_has_work() &&
2753 pass_through_head < 2)
2754 progress += khugepaged_scan_mm_slot(pages - progress,
2755 &hpage);
2756 else
2757 progress = pages;
2758 spin_unlock(&khugepaged_mm_lock);
2759 }
2760
2761 if (!IS_ERR_OR_NULL(hpage))
2762 put_page(hpage);
2763 }
2764
2765 static void khugepaged_wait_work(void)
2766 {
2767 if (khugepaged_has_work()) {
2768 if (!khugepaged_scan_sleep_millisecs)
2769 return;
2770
2771 wait_event_freezable_timeout(khugepaged_wait,
2772 kthread_should_stop(),
2773 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2774 return;
2775 }
2776
2777 if (khugepaged_enabled())
2778 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2779 }
2780
2781 static int khugepaged(void *none)
2782 {
2783 struct mm_slot *mm_slot;
2784
2785 set_freezable();
2786 set_user_nice(current, MAX_NICE);
2787
2788 while (!kthread_should_stop()) {
2789 khugepaged_do_scan();
2790 khugepaged_wait_work();
2791 }
2792
2793 spin_lock(&khugepaged_mm_lock);
2794 mm_slot = khugepaged_scan.mm_slot;
2795 khugepaged_scan.mm_slot = NULL;
2796 if (mm_slot)
2797 collect_mm_slot(mm_slot);
2798 spin_unlock(&khugepaged_mm_lock);
2799 return 0;
2800 }
2801
2802 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2803 unsigned long haddr, pmd_t *pmd)
2804 {
2805 struct mm_struct *mm = vma->vm_mm;
2806 pgtable_t pgtable;
2807 pmd_t _pmd;
2808 int i;
2809
2810 /* leave pmd empty until pte is filled */
2811 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2812
2813 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2814 pmd_populate(mm, &_pmd, pgtable);
2815
2816 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2817 pte_t *pte, entry;
2818 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2819 entry = pte_mkspecial(entry);
2820 pte = pte_offset_map(&_pmd, haddr);
2821 VM_BUG_ON(!pte_none(*pte));
2822 set_pte_at(mm, haddr, pte, entry);
2823 pte_unmap(pte);
2824 }
2825 smp_wmb(); /* make pte visible before pmd */
2826 pmd_populate(mm, pmd, pgtable);
2827 put_huge_zero_page();
2828 }
2829
2830 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2831 unsigned long haddr, bool freeze)
2832 {
2833 struct mm_struct *mm = vma->vm_mm;
2834 struct page *page;
2835 pgtable_t pgtable;
2836 pmd_t _pmd;
2837 bool young, write, dirty;
2838 int i;
2839
2840 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2841 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2842 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2843 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
2844
2845 count_vm_event(THP_SPLIT_PMD);
2846
2847 if (vma_is_dax(vma)) {
2848 pmd_t _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2849 if (is_huge_zero_pmd(_pmd))
2850 put_huge_zero_page();
2851 return;
2852 } else if (is_huge_zero_pmd(*pmd)) {
2853 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2854 }
2855
2856 page = pmd_page(*pmd);
2857 VM_BUG_ON_PAGE(!page_count(page), page);
2858 atomic_add(HPAGE_PMD_NR - 1, &page->_count);
2859 write = pmd_write(*pmd);
2860 young = pmd_young(*pmd);
2861 dirty = pmd_dirty(*pmd);
2862
2863 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2864 pmd_populate(mm, &_pmd, pgtable);
2865
2866 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2867 pte_t entry, *pte;
2868 /*
2869 * Note that NUMA hinting access restrictions are not
2870 * transferred to avoid any possibility of altering
2871 * permissions across VMAs.
2872 */
2873 if (freeze) {
2874 swp_entry_t swp_entry;
2875 swp_entry = make_migration_entry(page + i, write);
2876 entry = swp_entry_to_pte(swp_entry);
2877 } else {
2878 entry = mk_pte(page + i, vma->vm_page_prot);
2879 entry = maybe_mkwrite(entry, vma);
2880 if (!write)
2881 entry = pte_wrprotect(entry);
2882 if (!young)
2883 entry = pte_mkold(entry);
2884 }
2885 if (dirty)
2886 SetPageDirty(page + i);
2887 pte = pte_offset_map(&_pmd, haddr);
2888 BUG_ON(!pte_none(*pte));
2889 set_pte_at(mm, haddr, pte, entry);
2890 atomic_inc(&page[i]._mapcount);
2891 pte_unmap(pte);
2892 }
2893
2894 /*
2895 * Set PG_double_map before dropping compound_mapcount to avoid
2896 * false-negative page_mapped().
2897 */
2898 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2899 for (i = 0; i < HPAGE_PMD_NR; i++)
2900 atomic_inc(&page[i]._mapcount);
2901 }
2902
2903 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2904 /* Last compound_mapcount is gone. */
2905 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
2906 if (TestClearPageDoubleMap(page)) {
2907 /* No need in mapcount reference anymore */
2908 for (i = 0; i < HPAGE_PMD_NR; i++)
2909 atomic_dec(&page[i]._mapcount);
2910 }
2911 }
2912
2913 smp_wmb(); /* make pte visible before pmd */
2914 /*
2915 * Up to this point the pmd is present and huge and userland has the
2916 * whole access to the hugepage during the split (which happens in
2917 * place). If we overwrite the pmd with the not-huge version pointing
2918 * to the pte here (which of course we could if all CPUs were bug
2919 * free), userland could trigger a small page size TLB miss on the
2920 * small sized TLB while the hugepage TLB entry is still established in
2921 * the huge TLB. Some CPU doesn't like that.
2922 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2923 * 383 on page 93. Intel should be safe but is also warns that it's
2924 * only safe if the permission and cache attributes of the two entries
2925 * loaded in the two TLB is identical (which should be the case here).
2926 * But it is generally safer to never allow small and huge TLB entries
2927 * for the same virtual address to be loaded simultaneously. So instead
2928 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2929 * current pmd notpresent (atomically because here the pmd_trans_huge
2930 * and pmd_trans_splitting must remain set at all times on the pmd
2931 * until the split is complete for this pmd), then we flush the SMP TLB
2932 * and finally we write the non-huge version of the pmd entry with
2933 * pmd_populate.
2934 */
2935 pmdp_invalidate(vma, haddr, pmd);
2936 pmd_populate(mm, pmd, pgtable);
2937
2938 if (freeze) {
2939 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2940 page_remove_rmap(page + i, false);
2941 put_page(page + i);
2942 }
2943 }
2944 }
2945
2946 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2947 unsigned long address)
2948 {
2949 spinlock_t *ptl;
2950 struct mm_struct *mm = vma->vm_mm;
2951 struct page *page = NULL;
2952 unsigned long haddr = address & HPAGE_PMD_MASK;
2953
2954 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2955 ptl = pmd_lock(mm, pmd);
2956 if (pmd_trans_huge(*pmd)) {
2957 page = pmd_page(*pmd);
2958 if (PageMlocked(page))
2959 get_page(page);
2960 else
2961 page = NULL;
2962 } else if (!pmd_devmap(*pmd))
2963 goto out;
2964 __split_huge_pmd_locked(vma, pmd, haddr, false);
2965 out:
2966 spin_unlock(ptl);
2967 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
2968 if (page) {
2969 lock_page(page);
2970 munlock_vma_page(page);
2971 unlock_page(page);
2972 put_page(page);
2973 }
2974 }
2975
2976 static void split_huge_pmd_address(struct vm_area_struct *vma,
2977 unsigned long address)
2978 {
2979 pgd_t *pgd;
2980 pud_t *pud;
2981 pmd_t *pmd;
2982
2983 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2984
2985 pgd = pgd_offset(vma->vm_mm, address);
2986 if (!pgd_present(*pgd))
2987 return;
2988
2989 pud = pud_offset(pgd, address);
2990 if (!pud_present(*pud))
2991 return;
2992
2993 pmd = pmd_offset(pud, address);
2994 if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)))
2995 return;
2996 /*
2997 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2998 * materialize from under us.
2999 */
3000 split_huge_pmd(vma, pmd, address);
3001 }
3002
3003 void vma_adjust_trans_huge(struct vm_area_struct *vma,
3004 unsigned long start,
3005 unsigned long end,
3006 long adjust_next)
3007 {
3008 /*
3009 * If the new start address isn't hpage aligned and it could
3010 * previously contain an hugepage: check if we need to split
3011 * an huge pmd.
3012 */
3013 if (start & ~HPAGE_PMD_MASK &&
3014 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
3015 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3016 split_huge_pmd_address(vma, start);
3017
3018 /*
3019 * If the new end address isn't hpage aligned and it could
3020 * previously contain an hugepage: check if we need to split
3021 * an huge pmd.
3022 */
3023 if (end & ~HPAGE_PMD_MASK &&
3024 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
3025 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
3026 split_huge_pmd_address(vma, end);
3027
3028 /*
3029 * If we're also updating the vma->vm_next->vm_start, if the new
3030 * vm_next->vm_start isn't page aligned and it could previously
3031 * contain an hugepage: check if we need to split an huge pmd.
3032 */
3033 if (adjust_next > 0) {
3034 struct vm_area_struct *next = vma->vm_next;
3035 unsigned long nstart = next->vm_start;
3036 nstart += adjust_next << PAGE_SHIFT;
3037 if (nstart & ~HPAGE_PMD_MASK &&
3038 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
3039 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
3040 split_huge_pmd_address(next, nstart);
3041 }
3042 }
3043
3044 static void freeze_page_vma(struct vm_area_struct *vma, struct page *page,
3045 unsigned long address)
3046 {
3047 unsigned long haddr = address & HPAGE_PMD_MASK;
3048 spinlock_t *ptl;
3049 pgd_t *pgd;
3050 pud_t *pud;
3051 pmd_t *pmd;
3052 pte_t *pte;
3053 int i, nr = HPAGE_PMD_NR;
3054
3055 /* Skip pages which doesn't belong to the VMA */
3056 if (address < vma->vm_start) {
3057 int off = (vma->vm_start - address) >> PAGE_SHIFT;
3058 page += off;
3059 nr -= off;
3060 address = vma->vm_start;
3061 }
3062
3063 pgd = pgd_offset(vma->vm_mm, address);
3064 if (!pgd_present(*pgd))
3065 return;
3066 pud = pud_offset(pgd, address);
3067 if (!pud_present(*pud))
3068 return;
3069 pmd = pmd_offset(pud, address);
3070 ptl = pmd_lock(vma->vm_mm, pmd);
3071 if (!pmd_present(*pmd)) {
3072 spin_unlock(ptl);
3073 return;
3074 }
3075 if (pmd_trans_huge(*pmd)) {
3076 if (page == pmd_page(*pmd))
3077 __split_huge_pmd_locked(vma, pmd, haddr, true);
3078 spin_unlock(ptl);
3079 return;
3080 }
3081 spin_unlock(ptl);
3082
3083 pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl);
3084 for (i = 0; i < nr; i++, address += PAGE_SIZE, page++, pte++) {
3085 pte_t entry, swp_pte;
3086 swp_entry_t swp_entry;
3087
3088 /*
3089 * We've just crossed page table boundary: need to map next one.
3090 * It can happen if THP was mremaped to non PMD-aligned address.
3091 */
3092 if (unlikely(address == haddr + HPAGE_PMD_SIZE)) {
3093 pte_unmap_unlock(pte - 1, ptl);
3094 pmd = mm_find_pmd(vma->vm_mm, address);
3095 if (!pmd)
3096 return;
3097 pte = pte_offset_map_lock(vma->vm_mm, pmd,
3098 address, &ptl);
3099 }
3100
3101 if (!pte_present(*pte))
3102 continue;
3103 if (page_to_pfn(page) != pte_pfn(*pte))
3104 continue;
3105 flush_cache_page(vma, address, page_to_pfn(page));
3106 entry = ptep_clear_flush(vma, address, pte);
3107 if (pte_dirty(entry))
3108 SetPageDirty(page);
3109 swp_entry = make_migration_entry(page, pte_write(entry));
3110 swp_pte = swp_entry_to_pte(swp_entry);
3111 if (pte_soft_dirty(entry))
3112 swp_pte = pte_swp_mksoft_dirty(swp_pte);
3113 set_pte_at(vma->vm_mm, address, pte, swp_pte);
3114 page_remove_rmap(page, false);
3115 put_page(page);
3116 }
3117 pte_unmap_unlock(pte - 1, ptl);
3118 }
3119
3120 static void freeze_page(struct anon_vma *anon_vma, struct page *page)
3121 {
3122 struct anon_vma_chain *avc;
3123 pgoff_t pgoff = page_to_pgoff(page);
3124
3125 VM_BUG_ON_PAGE(!PageHead(page), page);
3126
3127 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff,
3128 pgoff + HPAGE_PMD_NR - 1) {
3129 unsigned long address = __vma_address(page, avc->vma);
3130
3131 mmu_notifier_invalidate_range_start(avc->vma->vm_mm,
3132 address, address + HPAGE_PMD_SIZE);
3133 freeze_page_vma(avc->vma, page, address);
3134 mmu_notifier_invalidate_range_end(avc->vma->vm_mm,
3135 address, address + HPAGE_PMD_SIZE);
3136 }
3137 }
3138
3139 static void unfreeze_page_vma(struct vm_area_struct *vma, struct page *page,
3140 unsigned long address)
3141 {
3142 spinlock_t *ptl;
3143 pmd_t *pmd;
3144 pte_t *pte, entry;
3145 swp_entry_t swp_entry;
3146 unsigned long haddr = address & HPAGE_PMD_MASK;
3147 int i, nr = HPAGE_PMD_NR;
3148
3149 /* Skip pages which doesn't belong to the VMA */
3150 if (address < vma->vm_start) {
3151 int off = (vma->vm_start - address) >> PAGE_SHIFT;
3152 page += off;
3153 nr -= off;
3154 address = vma->vm_start;
3155 }
3156
3157 pmd = mm_find_pmd(vma->vm_mm, address);
3158 if (!pmd)
3159 return;
3160
3161 pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl);
3162 for (i = 0; i < nr; i++, address += PAGE_SIZE, page++, pte++) {
3163 /*
3164 * We've just crossed page table boundary: need to map next one.
3165 * It can happen if THP was mremaped to non-PMD aligned address.
3166 */
3167 if (unlikely(address == haddr + HPAGE_PMD_SIZE)) {
3168 pte_unmap_unlock(pte - 1, ptl);
3169 pmd = mm_find_pmd(vma->vm_mm, address);
3170 if (!pmd)
3171 return;
3172 pte = pte_offset_map_lock(vma->vm_mm, pmd,
3173 address, &ptl);
3174 }
3175
3176 if (!is_swap_pte(*pte))
3177 continue;
3178
3179 swp_entry = pte_to_swp_entry(*pte);
3180 if (!is_migration_entry(swp_entry))
3181 continue;
3182 if (migration_entry_to_page(swp_entry) != page)
3183 continue;
3184
3185 get_page(page);
3186 page_add_anon_rmap(page, vma, address, false);
3187
3188 entry = pte_mkold(mk_pte(page, vma->vm_page_prot));
3189 if (PageDirty(page))
3190 entry = pte_mkdirty(entry);
3191 if (is_write_migration_entry(swp_entry))
3192 entry = maybe_mkwrite(entry, vma);
3193
3194 flush_dcache_page(page);
3195 set_pte_at(vma->vm_mm, address, pte, entry);
3196
3197 /* No need to invalidate - it was non-present before */
3198 update_mmu_cache(vma, address, pte);
3199 }
3200 pte_unmap_unlock(pte - 1, ptl);
3201 }
3202
3203 static void unfreeze_page(struct anon_vma *anon_vma, struct page *page)
3204 {
3205 struct anon_vma_chain *avc;
3206 pgoff_t pgoff = page_to_pgoff(page);
3207
3208 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
3209 pgoff, pgoff + HPAGE_PMD_NR - 1) {
3210 unsigned long address = __vma_address(page, avc->vma);
3211
3212 mmu_notifier_invalidate_range_start(avc->vma->vm_mm,
3213 address, address + HPAGE_PMD_SIZE);
3214 unfreeze_page_vma(avc->vma, page, address);
3215 mmu_notifier_invalidate_range_end(avc->vma->vm_mm,
3216 address, address + HPAGE_PMD_SIZE);
3217 }
3218 }
3219
3220 static int __split_huge_page_tail(struct page *head, int tail,
3221 struct lruvec *lruvec, struct list_head *list)
3222 {
3223 int mapcount;
3224 struct page *page_tail = head + tail;
3225
3226 mapcount = atomic_read(&page_tail->_mapcount) + 1;
3227 VM_BUG_ON_PAGE(atomic_read(&page_tail->_count) != 0, page_tail);
3228
3229 /*
3230 * tail_page->_count is zero and not changing from under us. But
3231 * get_page_unless_zero() may be running from under us on the
3232 * tail_page. If we used atomic_set() below instead of atomic_add(), we
3233 * would then run atomic_set() concurrently with
3234 * get_page_unless_zero(), and atomic_set() is implemented in C not
3235 * using locked ops. spin_unlock on x86 sometime uses locked ops
3236 * because of PPro errata 66, 92, so unless somebody can guarantee
3237 * atomic_set() here would be safe on all archs (and not only on x86),
3238 * it's safer to use atomic_add().
3239 */
3240 atomic_add(mapcount + 1, &page_tail->_count);
3241
3242
3243 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
3244 page_tail->flags |= (head->flags &
3245 ((1L << PG_referenced) |
3246 (1L << PG_swapbacked) |
3247 (1L << PG_mlocked) |
3248 (1L << PG_uptodate) |
3249 (1L << PG_active) |
3250 (1L << PG_locked) |
3251 (1L << PG_unevictable) |
3252 (1L << PG_dirty)));
3253
3254 /*
3255 * After clearing PageTail the gup refcount can be released.
3256 * Page flags also must be visible before we make the page non-compound.
3257 */
3258 smp_wmb();
3259
3260 clear_compound_head(page_tail);
3261
3262 if (page_is_young(head))
3263 set_page_young(page_tail);
3264 if (page_is_idle(head))
3265 set_page_idle(page_tail);
3266
3267 /* ->mapping in first tail page is compound_mapcount */
3268 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
3269 page_tail);
3270 page_tail->mapping = head->mapping;
3271
3272 page_tail->index = head->index + tail;
3273 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
3274 lru_add_page_tail(head, page_tail, lruvec, list);
3275
3276 return mapcount;
3277 }
3278
3279 static void __split_huge_page(struct page *page, struct list_head *list)
3280 {
3281 struct page *head = compound_head(page);
3282 struct zone *zone = page_zone(head);
3283 struct lruvec *lruvec;
3284 int i, tail_mapcount;
3285
3286 /* prevent PageLRU to go away from under us, and freeze lru stats */
3287 spin_lock_irq(&zone->lru_lock);
3288 lruvec = mem_cgroup_page_lruvec(head, zone);
3289
3290 /* complete memcg works before add pages to LRU */
3291 mem_cgroup_split_huge_fixup(head);
3292
3293 tail_mapcount = 0;
3294 for (i = HPAGE_PMD_NR - 1; i >= 1; i--)
3295 tail_mapcount += __split_huge_page_tail(head, i, lruvec, list);
3296 atomic_sub(tail_mapcount, &head->_count);
3297
3298 ClearPageCompound(head);
3299 spin_unlock_irq(&zone->lru_lock);
3300
3301 unfreeze_page(page_anon_vma(head), head);
3302
3303 for (i = 0; i < HPAGE_PMD_NR; i++) {
3304 struct page *subpage = head + i;
3305 if (subpage == page)
3306 continue;
3307 unlock_page(subpage);
3308
3309 /*
3310 * Subpages may be freed if there wasn't any mapping
3311 * like if add_to_swap() is running on a lru page that
3312 * had its mapping zapped. And freeing these pages
3313 * requires taking the lru_lock so we do the put_page
3314 * of the tail pages after the split is complete.
3315 */
3316 put_page(subpage);
3317 }
3318 }
3319
3320 int total_mapcount(struct page *page)
3321 {
3322 int i, ret;
3323
3324 VM_BUG_ON_PAGE(PageTail(page), page);
3325
3326 if (likely(!PageCompound(page)))
3327 return atomic_read(&page->_mapcount) + 1;
3328
3329 ret = compound_mapcount(page);
3330 if (PageHuge(page))
3331 return ret;
3332 for (i = 0; i < HPAGE_PMD_NR; i++)
3333 ret += atomic_read(&page[i]._mapcount) + 1;
3334 if (PageDoubleMap(page))
3335 ret -= HPAGE_PMD_NR;
3336 return ret;
3337 }
3338
3339 /*
3340 * This function splits huge page into normal pages. @page can point to any
3341 * subpage of huge page to split. Split doesn't change the position of @page.
3342 *
3343 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
3344 * The huge page must be locked.
3345 *
3346 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3347 *
3348 * Both head page and tail pages will inherit mapping, flags, and so on from
3349 * the hugepage.
3350 *
3351 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
3352 * they are not mapped.
3353 *
3354 * Returns 0 if the hugepage is split successfully.
3355 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
3356 * us.
3357 */
3358 int split_huge_page_to_list(struct page *page, struct list_head *list)
3359 {
3360 struct page *head = compound_head(page);
3361 struct anon_vma *anon_vma;
3362 int count, mapcount, ret;
3363 bool mlocked;
3364 unsigned long flags;
3365
3366 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
3367 VM_BUG_ON_PAGE(!PageAnon(page), page);
3368 VM_BUG_ON_PAGE(!PageLocked(page), page);
3369 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
3370 VM_BUG_ON_PAGE(!PageCompound(page), page);
3371
3372 /*
3373 * The caller does not necessarily hold an mmap_sem that would prevent
3374 * the anon_vma disappearing so we first we take a reference to it
3375 * and then lock the anon_vma for write. This is similar to
3376 * page_lock_anon_vma_read except the write lock is taken to serialise
3377 * against parallel split or collapse operations.
3378 */
3379 anon_vma = page_get_anon_vma(head);
3380 if (!anon_vma) {
3381 ret = -EBUSY;
3382 goto out;
3383 }
3384 anon_vma_lock_write(anon_vma);
3385
3386 /*
3387 * Racy check if we can split the page, before freeze_page() will
3388 * split PMDs
3389 */
3390 if (total_mapcount(head) != page_count(head) - 1) {
3391 ret = -EBUSY;
3392 goto out_unlock;
3393 }
3394
3395 mlocked = PageMlocked(page);
3396 freeze_page(anon_vma, head);
3397 VM_BUG_ON_PAGE(compound_mapcount(head), head);
3398
3399 /* Make sure the page is not on per-CPU pagevec as it takes pin */
3400 if (mlocked)
3401 lru_add_drain();
3402
3403 /* Prevent deferred_split_scan() touching ->_count */
3404 spin_lock_irqsave(&split_queue_lock, flags);
3405 count = page_count(head);
3406 mapcount = total_mapcount(head);
3407 if (!mapcount && count == 1) {
3408 if (!list_empty(page_deferred_list(head))) {
3409 split_queue_len--;
3410 list_del(page_deferred_list(head));
3411 }
3412 spin_unlock_irqrestore(&split_queue_lock, flags);
3413 __split_huge_page(page, list);
3414 ret = 0;
3415 } else if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
3416 spin_unlock_irqrestore(&split_queue_lock, flags);
3417 pr_alert("total_mapcount: %u, page_count(): %u\n",
3418 mapcount, count);
3419 if (PageTail(page))
3420 dump_page(head, NULL);
3421 dump_page(page, "total_mapcount(head) > 0");
3422 BUG();
3423 } else {
3424 spin_unlock_irqrestore(&split_queue_lock, flags);
3425 unfreeze_page(anon_vma, head);
3426 ret = -EBUSY;
3427 }
3428
3429 out_unlock:
3430 anon_vma_unlock_write(anon_vma);
3431 put_anon_vma(anon_vma);
3432 out:
3433 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
3434 return ret;
3435 }
3436
3437 void free_transhuge_page(struct page *page)
3438 {
3439 unsigned long flags;
3440
3441 spin_lock_irqsave(&split_queue_lock, flags);
3442 if (!list_empty(page_deferred_list(page))) {
3443 split_queue_len--;
3444 list_del(page_deferred_list(page));
3445 }
3446 spin_unlock_irqrestore(&split_queue_lock, flags);
3447 free_compound_page(page);
3448 }
3449
3450 void deferred_split_huge_page(struct page *page)
3451 {
3452 unsigned long flags;
3453
3454 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
3455
3456 spin_lock_irqsave(&split_queue_lock, flags);
3457 if (list_empty(page_deferred_list(page))) {
3458 list_add_tail(page_deferred_list(page), &split_queue);
3459 split_queue_len++;
3460 }
3461 spin_unlock_irqrestore(&split_queue_lock, flags);
3462 }
3463
3464 static unsigned long deferred_split_count(struct shrinker *shrink,
3465 struct shrink_control *sc)
3466 {
3467 /*
3468 * Split a page from split_queue will free up at least one page,
3469 * at most HPAGE_PMD_NR - 1. We don't track exact number.
3470 * Let's use HPAGE_PMD_NR / 2 as ballpark.
3471 */
3472 return ACCESS_ONCE(split_queue_len) * HPAGE_PMD_NR / 2;
3473 }
3474
3475 static unsigned long deferred_split_scan(struct shrinker *shrink,
3476 struct shrink_control *sc)
3477 {
3478 unsigned long flags;
3479 LIST_HEAD(list), *pos, *next;
3480 struct page *page;
3481 int split = 0;
3482
3483 spin_lock_irqsave(&split_queue_lock, flags);
3484 list_splice_init(&split_queue, &list);
3485
3486 /* Take pin on all head pages to avoid freeing them under us */
3487 list_for_each_safe(pos, next, &list) {
3488 page = list_entry((void *)pos, struct page, mapping);
3489 page = compound_head(page);
3490 /* race with put_compound_page() */
3491 if (!get_page_unless_zero(page)) {
3492 list_del_init(page_deferred_list(page));
3493 split_queue_len--;
3494 }
3495 }
3496 spin_unlock_irqrestore(&split_queue_lock, flags);
3497
3498 list_for_each_safe(pos, next, &list) {
3499 page = list_entry((void *)pos, struct page, mapping);
3500 lock_page(page);
3501 /* split_huge_page() removes page from list on success */
3502 if (!split_huge_page(page))
3503 split++;
3504 unlock_page(page);
3505 put_page(page);
3506 }
3507
3508 spin_lock_irqsave(&split_queue_lock, flags);
3509 list_splice_tail(&list, &split_queue);
3510 spin_unlock_irqrestore(&split_queue_lock, flags);
3511
3512 return split * HPAGE_PMD_NR / 2;
3513 }
3514
3515 static struct shrinker deferred_split_shrinker = {
3516 .count_objects = deferred_split_count,
3517 .scan_objects = deferred_split_scan,
3518 .seeks = DEFAULT_SEEKS,
3519 };
3520
3521 #ifdef CONFIG_DEBUG_FS
3522 static int split_huge_pages_set(void *data, u64 val)
3523 {
3524 struct zone *zone;
3525 struct page *page;
3526 unsigned long pfn, max_zone_pfn;
3527 unsigned long total = 0, split = 0;
3528
3529 if (val != 1)
3530 return -EINVAL;
3531
3532 for_each_populated_zone(zone) {
3533 max_zone_pfn = zone_end_pfn(zone);
3534 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
3535 if (!pfn_valid(pfn))
3536 continue;
3537
3538 page = pfn_to_page(pfn);
3539 if (!get_page_unless_zero(page))
3540 continue;
3541
3542 if (zone != page_zone(page))
3543 goto next;
3544
3545 if (!PageHead(page) || !PageAnon(page) ||
3546 PageHuge(page))
3547 goto next;
3548
3549 total++;
3550 lock_page(page);
3551 if (!split_huge_page(page))
3552 split++;
3553 unlock_page(page);
3554 next:
3555 put_page(page);
3556 }
3557 }
3558
3559 pr_info("%lu of %lu THP split", split, total);
3560
3561 return 0;
3562 }
3563 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3564 "%llu\n");
3565
3566 static int __init split_huge_pages_debugfs(void)
3567 {
3568 void *ret;
3569
3570 ret = debugfs_create_file("split_huge_pages", 0644, NULL, NULL,
3571 &split_huge_pages_fops);
3572 if (!ret)
3573 pr_warn("Failed to create split_huge_pages in debugfs");
3574 return 0;
3575 }
3576 late_initcall(split_huge_pages_debugfs);
3577 #endif
Linux with added FPC-III support