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net: introduce skb_transport_header_was_set()
[linux-2.6/cjktty.git] / mm / huge_memory.c
blob9e894edc7811ca66bda078e9606011ca25035238
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 #include <linux/mm.h>
9 #include <linux/sched.h>
10 #include <linux/highmem.h>
11 #include <linux/hugetlb.h>
12 #include <linux/mmu_notifier.h>
13 #include <linux/rmap.h>
14 #include <linux/swap.h>
15 #include <linux/shrinker.h>
16 #include <linux/mm_inline.h>
17 #include <linux/kthread.h>
18 #include <linux/khugepaged.h>
19 #include <linux/freezer.h>
20 #include <linux/mman.h>
21 #include <linux/pagemap.h>
22 #include <linux/migrate.h>
23
24 #include <asm/tlb.h>
25 #include <asm/pgalloc.h>
26 #include "internal.h"
27
28 /*
29 * By default transparent hugepage support is enabled for all mappings
30 * and khugepaged scans all mappings. Defrag is only invoked by
31 * khugepaged hugepage allocations and by page faults inside
32 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
33 * allocations.
34 */
35 unsigned long transparent_hugepage_flags __read_mostly =
36 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
37 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
38 #endif
39 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
40 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
41 #endif
42 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
43 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
44 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
45
46 /* default scan 8*512 pte (or vmas) every 30 second */
47 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
48 static unsigned int khugepaged_pages_collapsed;
49 static unsigned int khugepaged_full_scans;
50 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
51 /* during fragmentation poll the hugepage allocator once every minute */
52 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
53 static struct task_struct *khugepaged_thread __read_mostly;
54 static DEFINE_MUTEX(khugepaged_mutex);
55 static DEFINE_SPINLOCK(khugepaged_mm_lock);
56 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
57 /*
58 * default collapse hugepages if there is at least one pte mapped like
59 * it would have happened if the vma was large enough during page
60 * fault.
61 */
62 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
63
64 static int khugepaged(void *none);
65 static int mm_slots_hash_init(void);
66 static int khugepaged_slab_init(void);
67 static void khugepaged_slab_free(void);
68
69 #define MM_SLOTS_HASH_HEADS 1024
70 static struct hlist_head *mm_slots_hash __read_mostly;
71 static struct kmem_cache *mm_slot_cache __read_mostly;
72
73 /**
74 * struct mm_slot - hash lookup from mm to mm_slot
75 * @hash: hash collision list
76 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
77 * @mm: the mm that this information is valid for
78 */
79 struct mm_slot {
80 struct hlist_node hash;
81 struct list_head mm_node;
82 struct mm_struct *mm;
83 };
84
85 /**
86 * struct khugepaged_scan - cursor for scanning
87 * @mm_head: the head of the mm list to scan
88 * @mm_slot: the current mm_slot we are scanning
89 * @address: the next address inside that to be scanned
90 *
91 * There is only the one khugepaged_scan instance of this cursor structure.
92 */
93 struct khugepaged_scan {
94 struct list_head mm_head;
95 struct mm_slot *mm_slot;
96 unsigned long address;
97 };
98 static struct khugepaged_scan khugepaged_scan = {
99 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
100 };
101
102
103 static int set_recommended_min_free_kbytes(void)
104 {
105 struct zone *zone;
106 int nr_zones = 0;
107 unsigned long recommended_min;
108 extern int min_free_kbytes;
109
110 if (!khugepaged_enabled())
111 return 0;
112
113 for_each_populated_zone(zone)
114 nr_zones++;
115
116 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
117 recommended_min = pageblock_nr_pages * nr_zones * 2;
118
119 /*
120 * Make sure that on average at least two pageblocks are almost free
121 * of another type, one for a migratetype to fall back to and a
122 * second to avoid subsequent fallbacks of other types There are 3
123 * MIGRATE_TYPES we care about.
124 */
125 recommended_min += pageblock_nr_pages * nr_zones *
126 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
127
128 /* don't ever allow to reserve more than 5% of the lowmem */
129 recommended_min = min(recommended_min,
130 (unsigned long) nr_free_buffer_pages() / 20);
131 recommended_min <<= (PAGE_SHIFT-10);
132
133 if (recommended_min > min_free_kbytes)
134 min_free_kbytes = recommended_min;
135 setup_per_zone_wmarks();
136 return 0;
137 }
138 late_initcall(set_recommended_min_free_kbytes);
139
140 static int start_khugepaged(void)
141 {
142 int err = 0;
143 if (khugepaged_enabled()) {
144 if (!khugepaged_thread)
145 khugepaged_thread = kthread_run(khugepaged, NULL,
146 "khugepaged");
147 if (unlikely(IS_ERR(khugepaged_thread))) {
148 printk(KERN_ERR
149 "khugepaged: kthread_run(khugepaged) failed\n");
150 err = PTR_ERR(khugepaged_thread);
151 khugepaged_thread = NULL;
152 }
153
154 if (!list_empty(&khugepaged_scan.mm_head))
155 wake_up_interruptible(&khugepaged_wait);
156
157 set_recommended_min_free_kbytes();
158 } else if (khugepaged_thread) {
159 kthread_stop(khugepaged_thread);
160 khugepaged_thread = NULL;
161 }
162
163 return err;
164 }
165
166 static atomic_t huge_zero_refcount;
167 static unsigned long huge_zero_pfn __read_mostly;
168
169 static inline bool is_huge_zero_pfn(unsigned long pfn)
170 {
171 unsigned long zero_pfn = ACCESS_ONCE(huge_zero_pfn);
172 return zero_pfn && pfn == zero_pfn;
173 }
174
175 static inline bool is_huge_zero_pmd(pmd_t pmd)
176 {
177 return is_huge_zero_pfn(pmd_pfn(pmd));
178 }
179
180 static unsigned long get_huge_zero_page(void)
181 {
182 struct page *zero_page;
183 retry:
184 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
185 return ACCESS_ONCE(huge_zero_pfn);
186
187 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
188 HPAGE_PMD_ORDER);
189 if (!zero_page) {
190 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
191 return 0;
192 }
193 count_vm_event(THP_ZERO_PAGE_ALLOC);
194 preempt_disable();
195 if (cmpxchg(&huge_zero_pfn, 0, page_to_pfn(zero_page))) {
196 preempt_enable();
197 __free_page(zero_page);
198 goto retry;
199 }
200
201 /* We take additional reference here. It will be put back by shrinker */
202 atomic_set(&huge_zero_refcount, 2);
203 preempt_enable();
204 return ACCESS_ONCE(huge_zero_pfn);
205 }
206
207 static void put_huge_zero_page(void)
208 {
209 /*
210 * Counter should never go to zero here. Only shrinker can put
211 * last reference.
212 */
213 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
214 }
215
216 static int shrink_huge_zero_page(struct shrinker *shrink,
217 struct shrink_control *sc)
218 {
219 if (!sc->nr_to_scan)
220 /* we can free zero page only if last reference remains */
221 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
222
223 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
224 unsigned long zero_pfn = xchg(&huge_zero_pfn, 0);
225 BUG_ON(zero_pfn == 0);
226 __free_page(__pfn_to_page(zero_pfn));
227 }
228
229 return 0;
230 }
231
232 static struct shrinker huge_zero_page_shrinker = {
233 .shrink = shrink_huge_zero_page,
234 .seeks = DEFAULT_SEEKS,
235 };
236
237 #ifdef CONFIG_SYSFS
238
239 static ssize_t double_flag_show(struct kobject *kobj,
240 struct kobj_attribute *attr, char *buf,
241 enum transparent_hugepage_flag enabled,
242 enum transparent_hugepage_flag req_madv)
243 {
244 if (test_bit(enabled, &transparent_hugepage_flags)) {
245 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
246 return sprintf(buf, "[always] madvise never\n");
247 } else if (test_bit(req_madv, &transparent_hugepage_flags))
248 return sprintf(buf, "always [madvise] never\n");
249 else
250 return sprintf(buf, "always madvise [never]\n");
251 }
252 static ssize_t double_flag_store(struct kobject *kobj,
253 struct kobj_attribute *attr,
254 const char *buf, size_t count,
255 enum transparent_hugepage_flag enabled,
256 enum transparent_hugepage_flag req_madv)
257 {
258 if (!memcmp("always", buf,
259 min(sizeof("always")-1, count))) {
260 set_bit(enabled, &transparent_hugepage_flags);
261 clear_bit(req_madv, &transparent_hugepage_flags);
262 } else if (!memcmp("madvise", buf,
263 min(sizeof("madvise")-1, count))) {
264 clear_bit(enabled, &transparent_hugepage_flags);
265 set_bit(req_madv, &transparent_hugepage_flags);
266 } else if (!memcmp("never", buf,
267 min(sizeof("never")-1, count))) {
268 clear_bit(enabled, &transparent_hugepage_flags);
269 clear_bit(req_madv, &transparent_hugepage_flags);
270 } else
271 return -EINVAL;
272
273 return count;
274 }
275
276 static ssize_t enabled_show(struct kobject *kobj,
277 struct kobj_attribute *attr, char *buf)
278 {
279 return double_flag_show(kobj, attr, buf,
280 TRANSPARENT_HUGEPAGE_FLAG,
281 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
282 }
283 static ssize_t enabled_store(struct kobject *kobj,
284 struct kobj_attribute *attr,
285 const char *buf, size_t count)
286 {
287 ssize_t ret;
288
289 ret = double_flag_store(kobj, attr, buf, count,
290 TRANSPARENT_HUGEPAGE_FLAG,
291 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
292
293 if (ret > 0) {
294 int err;
295
296 mutex_lock(&khugepaged_mutex);
297 err = start_khugepaged();
298 mutex_unlock(&khugepaged_mutex);
299
300 if (err)
301 ret = err;
302 }
303
304 return ret;
305 }
306 static struct kobj_attribute enabled_attr =
307 __ATTR(enabled, 0644, enabled_show, enabled_store);
308
309 static ssize_t single_flag_show(struct kobject *kobj,
310 struct kobj_attribute *attr, char *buf,
311 enum transparent_hugepage_flag flag)
312 {
313 return sprintf(buf, "%d\n",
314 !!test_bit(flag, &transparent_hugepage_flags));
315 }
316
317 static ssize_t single_flag_store(struct kobject *kobj,
318 struct kobj_attribute *attr,
319 const char *buf, size_t count,
320 enum transparent_hugepage_flag flag)
321 {
322 unsigned long value;
323 int ret;
324
325 ret = kstrtoul(buf, 10, &value);
326 if (ret < 0)
327 return ret;
328 if (value > 1)
329 return -EINVAL;
330
331 if (value)
332 set_bit(flag, &transparent_hugepage_flags);
333 else
334 clear_bit(flag, &transparent_hugepage_flags);
335
336 return count;
337 }
338
339 /*
340 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
341 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
342 * memory just to allocate one more hugepage.
343 */
344 static ssize_t defrag_show(struct kobject *kobj,
345 struct kobj_attribute *attr, char *buf)
346 {
347 return double_flag_show(kobj, attr, buf,
348 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
349 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
350 }
351 static ssize_t defrag_store(struct kobject *kobj,
352 struct kobj_attribute *attr,
353 const char *buf, size_t count)
354 {
355 return double_flag_store(kobj, attr, buf, count,
356 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
357 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
358 }
359 static struct kobj_attribute defrag_attr =
360 __ATTR(defrag, 0644, defrag_show, defrag_store);
361
362 static ssize_t use_zero_page_show(struct kobject *kobj,
363 struct kobj_attribute *attr, char *buf)
364 {
365 return single_flag_show(kobj, attr, buf,
366 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
367 }
368 static ssize_t use_zero_page_store(struct kobject *kobj,
369 struct kobj_attribute *attr, const char *buf, size_t count)
370 {
371 return single_flag_store(kobj, attr, buf, count,
372 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
373 }
374 static struct kobj_attribute use_zero_page_attr =
375 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
376 #ifdef CONFIG_DEBUG_VM
377 static ssize_t debug_cow_show(struct kobject *kobj,
378 struct kobj_attribute *attr, char *buf)
379 {
380 return single_flag_show(kobj, attr, buf,
381 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
382 }
383 static ssize_t debug_cow_store(struct kobject *kobj,
384 struct kobj_attribute *attr,
385 const char *buf, size_t count)
386 {
387 return single_flag_store(kobj, attr, buf, count,
388 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
389 }
390 static struct kobj_attribute debug_cow_attr =
391 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
392 #endif /* CONFIG_DEBUG_VM */
393
394 static struct attribute *hugepage_attr[] = {
395 &enabled_attr.attr,
396 &defrag_attr.attr,
397 &use_zero_page_attr.attr,
398 #ifdef CONFIG_DEBUG_VM
399 &debug_cow_attr.attr,
400 #endif
401 NULL,
402 };
403
404 static struct attribute_group hugepage_attr_group = {
405 .attrs = hugepage_attr,
406 };
407
408 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
409 struct kobj_attribute *attr,
410 char *buf)
411 {
412 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
413 }
414
415 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
416 struct kobj_attribute *attr,
417 const char *buf, size_t count)
418 {
419 unsigned long msecs;
420 int err;
421
422 err = strict_strtoul(buf, 10, &msecs);
423 if (err || msecs > UINT_MAX)
424 return -EINVAL;
425
426 khugepaged_scan_sleep_millisecs = msecs;
427 wake_up_interruptible(&khugepaged_wait);
428
429 return count;
430 }
431 static struct kobj_attribute scan_sleep_millisecs_attr =
432 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
433 scan_sleep_millisecs_store);
434
435 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
436 struct kobj_attribute *attr,
437 char *buf)
438 {
439 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
440 }
441
442 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
443 struct kobj_attribute *attr,
444 const char *buf, size_t count)
445 {
446 unsigned long msecs;
447 int err;
448
449 err = strict_strtoul(buf, 10, &msecs);
450 if (err || msecs > UINT_MAX)
451 return -EINVAL;
452
453 khugepaged_alloc_sleep_millisecs = msecs;
454 wake_up_interruptible(&khugepaged_wait);
455
456 return count;
457 }
458 static struct kobj_attribute alloc_sleep_millisecs_attr =
459 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
460 alloc_sleep_millisecs_store);
461
462 static ssize_t pages_to_scan_show(struct kobject *kobj,
463 struct kobj_attribute *attr,
464 char *buf)
465 {
466 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
467 }
468 static ssize_t pages_to_scan_store(struct kobject *kobj,
469 struct kobj_attribute *attr,
470 const char *buf, size_t count)
471 {
472 int err;
473 unsigned long pages;
474
475 err = strict_strtoul(buf, 10, &pages);
476 if (err || !pages || pages > UINT_MAX)
477 return -EINVAL;
478
479 khugepaged_pages_to_scan = pages;
480
481 return count;
482 }
483 static struct kobj_attribute pages_to_scan_attr =
484 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
485 pages_to_scan_store);
486
487 static ssize_t pages_collapsed_show(struct kobject *kobj,
488 struct kobj_attribute *attr,
489 char *buf)
490 {
491 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
492 }
493 static struct kobj_attribute pages_collapsed_attr =
494 __ATTR_RO(pages_collapsed);
495
496 static ssize_t full_scans_show(struct kobject *kobj,
497 struct kobj_attribute *attr,
498 char *buf)
499 {
500 return sprintf(buf, "%u\n", khugepaged_full_scans);
501 }
502 static struct kobj_attribute full_scans_attr =
503 __ATTR_RO(full_scans);
504
505 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
506 struct kobj_attribute *attr, char *buf)
507 {
508 return single_flag_show(kobj, attr, buf,
509 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
510 }
511 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
512 struct kobj_attribute *attr,
513 const char *buf, size_t count)
514 {
515 return single_flag_store(kobj, attr, buf, count,
516 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
517 }
518 static struct kobj_attribute khugepaged_defrag_attr =
519 __ATTR(defrag, 0644, khugepaged_defrag_show,
520 khugepaged_defrag_store);
521
522 /*
523 * max_ptes_none controls if khugepaged should collapse hugepages over
524 * any unmapped ptes in turn potentially increasing the memory
525 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
526 * reduce the available free memory in the system as it
527 * runs. Increasing max_ptes_none will instead potentially reduce the
528 * free memory in the system during the khugepaged scan.
529 */
530 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
531 struct kobj_attribute *attr,
532 char *buf)
533 {
534 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
535 }
536 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
537 struct kobj_attribute *attr,
538 const char *buf, size_t count)
539 {
540 int err;
541 unsigned long max_ptes_none;
542
543 err = strict_strtoul(buf, 10, &max_ptes_none);
544 if (err || max_ptes_none > HPAGE_PMD_NR-1)
545 return -EINVAL;
546
547 khugepaged_max_ptes_none = max_ptes_none;
548
549 return count;
550 }
551 static struct kobj_attribute khugepaged_max_ptes_none_attr =
552 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
553 khugepaged_max_ptes_none_store);
554
555 static struct attribute *khugepaged_attr[] = {
556 &khugepaged_defrag_attr.attr,
557 &khugepaged_max_ptes_none_attr.attr,
558 &pages_to_scan_attr.attr,
559 &pages_collapsed_attr.attr,
560 &full_scans_attr.attr,
561 &scan_sleep_millisecs_attr.attr,
562 &alloc_sleep_millisecs_attr.attr,
563 NULL,
564 };
565
566 static struct attribute_group khugepaged_attr_group = {
567 .attrs = khugepaged_attr,
568 .name = "khugepaged",
569 };
570
571 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
572 {
573 int err;
574
575 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
576 if (unlikely(!*hugepage_kobj)) {
577 printk(KERN_ERR "hugepage: failed to create transparent hugepage kobject\n");
578 return -ENOMEM;
579 }
580
581 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
582 if (err) {
583 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
584 goto delete_obj;
585 }
586
587 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
588 if (err) {
589 printk(KERN_ERR "hugepage: failed to register transparent hugepage group\n");
590 goto remove_hp_group;
591 }
592
593 return 0;
594
595 remove_hp_group:
596 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
597 delete_obj:
598 kobject_put(*hugepage_kobj);
599 return err;
600 }
601
602 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
603 {
604 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
605 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
606 kobject_put(hugepage_kobj);
607 }
608 #else
609 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
610 {
611 return 0;
612 }
613
614 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
615 {
616 }
617 #endif /* CONFIG_SYSFS */
618
619 static int __init hugepage_init(void)
620 {
621 int err;
622 struct kobject *hugepage_kobj;
623
624 if (!has_transparent_hugepage()) {
625 transparent_hugepage_flags = 0;
626 return -EINVAL;
627 }
628
629 err = hugepage_init_sysfs(&hugepage_kobj);
630 if (err)
631 return err;
632
633 err = khugepaged_slab_init();
634 if (err)
635 goto out;
636
637 err = mm_slots_hash_init();
638 if (err) {
639 khugepaged_slab_free();
640 goto out;
641 }
642
643 register_shrinker(&huge_zero_page_shrinker);
644
645 /*
646 * By default disable transparent hugepages on smaller systems,
647 * where the extra memory used could hurt more than TLB overhead
648 * is likely to save. The admin can still enable it through /sys.
649 */
650 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
651 transparent_hugepage_flags = 0;
652
653 start_khugepaged();
654
655 return 0;
656 out:
657 hugepage_exit_sysfs(hugepage_kobj);
658 return err;
659 }
660 module_init(hugepage_init)
661
662 static int __init setup_transparent_hugepage(char *str)
663 {
664 int ret = 0;
665 if (!str)
666 goto out;
667 if (!strcmp(str, "always")) {
668 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
669 &transparent_hugepage_flags);
670 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
671 &transparent_hugepage_flags);
672 ret = 1;
673 } else if (!strcmp(str, "madvise")) {
674 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
675 &transparent_hugepage_flags);
676 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
677 &transparent_hugepage_flags);
678 ret = 1;
679 } else if (!strcmp(str, "never")) {
680 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
681 &transparent_hugepage_flags);
682 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
683 &transparent_hugepage_flags);
684 ret = 1;
685 }
686 out:
687 if (!ret)
688 printk(KERN_WARNING
689 "transparent_hugepage= cannot parse, ignored\n");
690 return ret;
691 }
692 __setup("transparent_hugepage=", setup_transparent_hugepage);
693
694 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
695 {
696 if (likely(vma->vm_flags & VM_WRITE))
697 pmd = pmd_mkwrite(pmd);
698 return pmd;
699 }
700
701 static inline pmd_t mk_huge_pmd(struct page *page, struct vm_area_struct *vma)
702 {
703 pmd_t entry;
704 entry = mk_pmd(page, vma->vm_page_prot);
705 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
706 entry = pmd_mkhuge(entry);
707 return entry;
708 }
709
710 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
711 struct vm_area_struct *vma,
712 unsigned long haddr, pmd_t *pmd,
713 struct page *page)
714 {
715 pgtable_t pgtable;
716
717 VM_BUG_ON(!PageCompound(page));
718 pgtable = pte_alloc_one(mm, haddr);
719 if (unlikely(!pgtable))
720 return VM_FAULT_OOM;
721
722 clear_huge_page(page, haddr, HPAGE_PMD_NR);
723 __SetPageUptodate(page);
724
725 spin_lock(&mm->page_table_lock);
726 if (unlikely(!pmd_none(*pmd))) {
727 spin_unlock(&mm->page_table_lock);
728 mem_cgroup_uncharge_page(page);
729 put_page(page);
730 pte_free(mm, pgtable);
731 } else {
732 pmd_t entry;
733 entry = mk_huge_pmd(page, vma);
734 /*
735 * The spinlocking to take the lru_lock inside
736 * page_add_new_anon_rmap() acts as a full memory
737 * barrier to be sure clear_huge_page writes become
738 * visible after the set_pmd_at() write.
739 */
740 page_add_new_anon_rmap(page, vma, haddr);
741 set_pmd_at(mm, haddr, pmd, entry);
742 pgtable_trans_huge_deposit(mm, pgtable);
743 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
744 mm->nr_ptes++;
745 spin_unlock(&mm->page_table_lock);
746 }
747
748 return 0;
749 }
750
751 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
752 {
753 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
754 }
755
756 static inline struct page *alloc_hugepage_vma(int defrag,
757 struct vm_area_struct *vma,
758 unsigned long haddr, int nd,
759 gfp_t extra_gfp)
760 {
761 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
762 HPAGE_PMD_ORDER, vma, haddr, nd);
763 }
764
765 #ifndef CONFIG_NUMA
766 static inline struct page *alloc_hugepage(int defrag)
767 {
768 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
769 HPAGE_PMD_ORDER);
770 }
771 #endif
772
773 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
774 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
775 unsigned long zero_pfn)
776 {
777 pmd_t entry;
778 if (!pmd_none(*pmd))
779 return false;
780 entry = pfn_pmd(zero_pfn, vma->vm_page_prot);
781 entry = pmd_wrprotect(entry);
782 entry = pmd_mkhuge(entry);
783 set_pmd_at(mm, haddr, pmd, entry);
784 pgtable_trans_huge_deposit(mm, pgtable);
785 mm->nr_ptes++;
786 return true;
787 }
788
789 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
790 unsigned long address, pmd_t *pmd,
791 unsigned int flags)
792 {
793 struct page *page;
794 unsigned long haddr = address & HPAGE_PMD_MASK;
795 pte_t *pte;
796
797 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
798 if (unlikely(anon_vma_prepare(vma)))
799 return VM_FAULT_OOM;
800 if (unlikely(khugepaged_enter(vma)))
801 return VM_FAULT_OOM;
802 if (!(flags & FAULT_FLAG_WRITE) &&
803 transparent_hugepage_use_zero_page()) {
804 pgtable_t pgtable;
805 unsigned long zero_pfn;
806 bool set;
807 pgtable = pte_alloc_one(mm, haddr);
808 if (unlikely(!pgtable))
809 return VM_FAULT_OOM;
810 zero_pfn = get_huge_zero_page();
811 if (unlikely(!zero_pfn)) {
812 pte_free(mm, pgtable);
813 count_vm_event(THP_FAULT_FALLBACK);
814 goto out;
815 }
816 spin_lock(&mm->page_table_lock);
817 set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd,
818 zero_pfn);
819 spin_unlock(&mm->page_table_lock);
820 if (!set) {
821 pte_free(mm, pgtable);
822 put_huge_zero_page();
823 }
824 return 0;
825 }
826 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
827 vma, haddr, numa_node_id(), 0);
828 if (unlikely(!page)) {
829 count_vm_event(THP_FAULT_FALLBACK);
830 goto out;
831 }
832 count_vm_event(THP_FAULT_ALLOC);
833 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
834 put_page(page);
835 goto out;
836 }
837 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
838 page))) {
839 mem_cgroup_uncharge_page(page);
840 put_page(page);
841 goto out;
842 }
843
844 return 0;
845 }
846 out:
847 /*
848 * Use __pte_alloc instead of pte_alloc_map, because we can't
849 * run pte_offset_map on the pmd, if an huge pmd could
850 * materialize from under us from a different thread.
851 */
852 if (unlikely(pmd_none(*pmd)) &&
853 unlikely(__pte_alloc(mm, vma, pmd, address)))
854 return VM_FAULT_OOM;
855 /* if an huge pmd materialized from under us just retry later */
856 if (unlikely(pmd_trans_huge(*pmd)))
857 return 0;
858 /*
859 * A regular pmd is established and it can't morph into a huge pmd
860 * from under us anymore at this point because we hold the mmap_sem
861 * read mode and khugepaged takes it in write mode. So now it's
862 * safe to run pte_offset_map().
863 */
864 pte = pte_offset_map(pmd, address);
865 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
866 }
867
868 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
869 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
870 struct vm_area_struct *vma)
871 {
872 struct page *src_page;
873 pmd_t pmd;
874 pgtable_t pgtable;
875 int ret;
876
877 ret = -ENOMEM;
878 pgtable = pte_alloc_one(dst_mm, addr);
879 if (unlikely(!pgtable))
880 goto out;
881
882 spin_lock(&dst_mm->page_table_lock);
883 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
884
885 ret = -EAGAIN;
886 pmd = *src_pmd;
887 if (unlikely(!pmd_trans_huge(pmd))) {
888 pte_free(dst_mm, pgtable);
889 goto out_unlock;
890 }
891 /*
892 * mm->page_table_lock is enough to be sure that huge zero pmd is not
893 * under splitting since we don't split the page itself, only pmd to
894 * a page table.
895 */
896 if (is_huge_zero_pmd(pmd)) {
897 unsigned long zero_pfn;
898 bool set;
899 /*
900 * get_huge_zero_page() will never allocate a new page here,
901 * since we already have a zero page to copy. It just takes a
902 * reference.
903 */
904 zero_pfn = get_huge_zero_page();
905 set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
906 zero_pfn);
907 BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */
908 ret = 0;
909 goto out_unlock;
910 }
911 if (unlikely(pmd_trans_splitting(pmd))) {
912 /* split huge page running from under us */
913 spin_unlock(&src_mm->page_table_lock);
914 spin_unlock(&dst_mm->page_table_lock);
915 pte_free(dst_mm, pgtable);
916
917 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
918 goto out;
919 }
920 src_page = pmd_page(pmd);
921 VM_BUG_ON(!PageHead(src_page));
922 get_page(src_page);
923 page_dup_rmap(src_page);
924 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
925
926 pmdp_set_wrprotect(src_mm, addr, src_pmd);
927 pmd = pmd_mkold(pmd_wrprotect(pmd));
928 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
929 pgtable_trans_huge_deposit(dst_mm, pgtable);
930 dst_mm->nr_ptes++;
931
932 ret = 0;
933 out_unlock:
934 spin_unlock(&src_mm->page_table_lock);
935 spin_unlock(&dst_mm->page_table_lock);
936 out:
937 return ret;
938 }
939
940 void huge_pmd_set_accessed(struct mm_struct *mm,
941 struct vm_area_struct *vma,
942 unsigned long address,
943 pmd_t *pmd, pmd_t orig_pmd,
944 int dirty)
945 {
946 pmd_t entry;
947 unsigned long haddr;
948
949 spin_lock(&mm->page_table_lock);
950 if (unlikely(!pmd_same(*pmd, orig_pmd)))
951 goto unlock;
952
953 entry = pmd_mkyoung(orig_pmd);
954 haddr = address & HPAGE_PMD_MASK;
955 if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
956 update_mmu_cache_pmd(vma, address, pmd);
957
958 unlock:
959 spin_unlock(&mm->page_table_lock);
960 }
961
962 static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm,
963 struct vm_area_struct *vma, unsigned long address,
964 pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr)
965 {
966 pgtable_t pgtable;
967 pmd_t _pmd;
968 struct page *page;
969 int i, ret = 0;
970 unsigned long mmun_start; /* For mmu_notifiers */
971 unsigned long mmun_end; /* For mmu_notifiers */
972
973 page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
974 if (!page) {
975 ret |= VM_FAULT_OOM;
976 goto out;
977 }
978
979 if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) {
980 put_page(page);
981 ret |= VM_FAULT_OOM;
982 goto out;
983 }
984
985 clear_user_highpage(page, address);
986 __SetPageUptodate(page);
987
988 mmun_start = haddr;
989 mmun_end = haddr + HPAGE_PMD_SIZE;
990 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
991
992 spin_lock(&mm->page_table_lock);
993 if (unlikely(!pmd_same(*pmd, orig_pmd)))
994 goto out_free_page;
995
996 pmdp_clear_flush(vma, haddr, pmd);
997 /* leave pmd empty until pte is filled */
998
999 pgtable = pgtable_trans_huge_withdraw(mm);
1000 pmd_populate(mm, &_pmd, pgtable);
1001
1002 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1003 pte_t *pte, entry;
1004 if (haddr == (address & PAGE_MASK)) {
1005 entry = mk_pte(page, vma->vm_page_prot);
1006 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1007 page_add_new_anon_rmap(page, vma, haddr);
1008 } else {
1009 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1010 entry = pte_mkspecial(entry);
1011 }
1012 pte = pte_offset_map(&_pmd, haddr);
1013 VM_BUG_ON(!pte_none(*pte));
1014 set_pte_at(mm, haddr, pte, entry);
1015 pte_unmap(pte);
1016 }
1017 smp_wmb(); /* make pte visible before pmd */
1018 pmd_populate(mm, pmd, pgtable);
1019 spin_unlock(&mm->page_table_lock);
1020 put_huge_zero_page();
1021 inc_mm_counter(mm, MM_ANONPAGES);
1022
1023 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1024
1025 ret |= VM_FAULT_WRITE;
1026 out:
1027 return ret;
1028 out_free_page:
1029 spin_unlock(&mm->page_table_lock);
1030 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1031 mem_cgroup_uncharge_page(page);
1032 put_page(page);
1033 goto out;
1034 }
1035
1036 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
1037 struct vm_area_struct *vma,
1038 unsigned long address,
1039 pmd_t *pmd, pmd_t orig_pmd,
1040 struct page *page,
1041 unsigned long haddr)
1042 {
1043 pgtable_t pgtable;
1044 pmd_t _pmd;
1045 int ret = 0, i;
1046 struct page **pages;
1047 unsigned long mmun_start; /* For mmu_notifiers */
1048 unsigned long mmun_end; /* For mmu_notifiers */
1049
1050 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1051 GFP_KERNEL);
1052 if (unlikely(!pages)) {
1053 ret |= VM_FAULT_OOM;
1054 goto out;
1055 }
1056
1057 for (i = 0; i < HPAGE_PMD_NR; i++) {
1058 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
1059 __GFP_OTHER_NODE,
1060 vma, address, page_to_nid(page));
1061 if (unlikely(!pages[i] ||
1062 mem_cgroup_newpage_charge(pages[i], mm,
1063 GFP_KERNEL))) {
1064 if (pages[i])
1065 put_page(pages[i]);
1066 mem_cgroup_uncharge_start();
1067 while (--i >= 0) {
1068 mem_cgroup_uncharge_page(pages[i]);
1069 put_page(pages[i]);
1070 }
1071 mem_cgroup_uncharge_end();
1072 kfree(pages);
1073 ret |= VM_FAULT_OOM;
1074 goto out;
1075 }
1076 }
1077
1078 for (i = 0; i < HPAGE_PMD_NR; i++) {
1079 copy_user_highpage(pages[i], page + i,
1080 haddr + PAGE_SIZE * i, vma);
1081 __SetPageUptodate(pages[i]);
1082 cond_resched();
1083 }
1084
1085 mmun_start = haddr;
1086 mmun_end = haddr + HPAGE_PMD_SIZE;
1087 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1088
1089 spin_lock(&mm->page_table_lock);
1090 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1091 goto out_free_pages;
1092 VM_BUG_ON(!PageHead(page));
1093
1094 pmdp_clear_flush(vma, haddr, pmd);
1095 /* leave pmd empty until pte is filled */
1096
1097 pgtable = pgtable_trans_huge_withdraw(mm);
1098 pmd_populate(mm, &_pmd, pgtable);
1099
1100 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1101 pte_t *pte, entry;
1102 entry = mk_pte(pages[i], vma->vm_page_prot);
1103 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1104 page_add_new_anon_rmap(pages[i], vma, haddr);
1105 pte = pte_offset_map(&_pmd, haddr);
1106 VM_BUG_ON(!pte_none(*pte));
1107 set_pte_at(mm, haddr, pte, entry);
1108 pte_unmap(pte);
1109 }
1110 kfree(pages);
1111
1112 smp_wmb(); /* make pte visible before pmd */
1113 pmd_populate(mm, pmd, pgtable);
1114 page_remove_rmap(page);
1115 spin_unlock(&mm->page_table_lock);
1116
1117 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1118
1119 ret |= VM_FAULT_WRITE;
1120 put_page(page);
1121
1122 out:
1123 return ret;
1124
1125 out_free_pages:
1126 spin_unlock(&mm->page_table_lock);
1127 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1128 mem_cgroup_uncharge_start();
1129 for (i = 0; i < HPAGE_PMD_NR; i++) {
1130 mem_cgroup_uncharge_page(pages[i]);
1131 put_page(pages[i]);
1132 }
1133 mem_cgroup_uncharge_end();
1134 kfree(pages);
1135 goto out;
1136 }
1137
1138 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
1139 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
1140 {
1141 int ret = 0;
1142 struct page *page = NULL, *new_page;
1143 unsigned long haddr;
1144 unsigned long mmun_start; /* For mmu_notifiers */
1145 unsigned long mmun_end; /* For mmu_notifiers */
1146
1147 VM_BUG_ON(!vma->anon_vma);
1148 haddr = address & HPAGE_PMD_MASK;
1149 if (is_huge_zero_pmd(orig_pmd))
1150 goto alloc;
1151 spin_lock(&mm->page_table_lock);
1152 if (unlikely(!pmd_same(*pmd, orig_pmd)))
1153 goto out_unlock;
1154
1155 page = pmd_page(orig_pmd);
1156 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
1157 if (page_mapcount(page) == 1) {
1158 pmd_t entry;
1159 entry = pmd_mkyoung(orig_pmd);
1160 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1161 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
1162 update_mmu_cache_pmd(vma, address, pmd);
1163 ret |= VM_FAULT_WRITE;
1164 goto out_unlock;
1165 }
1166 get_page(page);
1167 spin_unlock(&mm->page_table_lock);
1168 alloc:
1169 if (transparent_hugepage_enabled(vma) &&
1170 !transparent_hugepage_debug_cow())
1171 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
1172 vma, haddr, numa_node_id(), 0);
1173 else
1174 new_page = NULL;
1175
1176 if (unlikely(!new_page)) {
1177 count_vm_event(THP_FAULT_FALLBACK);
1178 if (is_huge_zero_pmd(orig_pmd)) {
1179 ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
1180 address, pmd, orig_pmd, haddr);
1181 } else {
1182 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
1183 pmd, orig_pmd, page, haddr);
1184 if (ret & VM_FAULT_OOM)
1185 split_huge_page(page);
1186 put_page(page);
1187 }
1188 goto out;
1189 }
1190 count_vm_event(THP_FAULT_ALLOC);
1191
1192 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1193 put_page(new_page);
1194 if (page) {
1195 split_huge_page(page);
1196 put_page(page);
1197 }
1198 ret |= VM_FAULT_OOM;
1199 goto out;
1200 }
1201
1202 if (is_huge_zero_pmd(orig_pmd))
1203 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1204 else
1205 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1206 __SetPageUptodate(new_page);
1207
1208 mmun_start = haddr;
1209 mmun_end = haddr + HPAGE_PMD_SIZE;
1210 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1211
1212 spin_lock(&mm->page_table_lock);
1213 if (page)
1214 put_page(page);
1215 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
1216 spin_unlock(&mm->page_table_lock);
1217 mem_cgroup_uncharge_page(new_page);
1218 put_page(new_page);
1219 goto out_mn;
1220 } else {
1221 pmd_t entry;
1222 entry = mk_huge_pmd(new_page, vma);
1223 pmdp_clear_flush(vma, haddr, pmd);
1224 page_add_new_anon_rmap(new_page, vma, haddr);
1225 set_pmd_at(mm, haddr, pmd, entry);
1226 update_mmu_cache_pmd(vma, address, pmd);
1227 if (is_huge_zero_pmd(orig_pmd)) {
1228 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
1229 put_huge_zero_page();
1230 } else {
1231 VM_BUG_ON(!PageHead(page));
1232 page_remove_rmap(page);
1233 put_page(page);
1234 }
1235 ret |= VM_FAULT_WRITE;
1236 }
1237 spin_unlock(&mm->page_table_lock);
1238 out_mn:
1239 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1240 out:
1241 return ret;
1242 out_unlock:
1243 spin_unlock(&mm->page_table_lock);
1244 return ret;
1245 }
1246
1247 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1248 unsigned long addr,
1249 pmd_t *pmd,
1250 unsigned int flags)
1251 {
1252 struct mm_struct *mm = vma->vm_mm;
1253 struct page *page = NULL;
1254
1255 assert_spin_locked(&mm->page_table_lock);
1256
1257 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1258 goto out;
1259
1260 page = pmd_page(*pmd);
1261 VM_BUG_ON(!PageHead(page));
1262 if (flags & FOLL_TOUCH) {
1263 pmd_t _pmd;
1264 /*
1265 * We should set the dirty bit only for FOLL_WRITE but
1266 * for now the dirty bit in the pmd is meaningless.
1267 * And if the dirty bit will become meaningful and
1268 * we'll only set it with FOLL_WRITE, an atomic
1269 * set_bit will be required on the pmd to set the
1270 * young bit, instead of the current set_pmd_at.
1271 */
1272 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1273 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
1274 }
1275 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1276 if (page->mapping && trylock_page(page)) {
1277 lru_add_drain();
1278 if (page->mapping)
1279 mlock_vma_page(page);
1280 unlock_page(page);
1281 }
1282 }
1283 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1284 VM_BUG_ON(!PageCompound(page));
1285 if (flags & FOLL_GET)
1286 get_page_foll(page);
1287
1288 out:
1289 return page;
1290 }
1291
1292 /* NUMA hinting page fault entry point for trans huge pmds */
1293 int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
1294 unsigned long addr, pmd_t pmd, pmd_t *pmdp)
1295 {
1296 struct page *page;
1297 unsigned long haddr = addr & HPAGE_PMD_MASK;
1298 int target_nid;
1299 int current_nid = -1;
1300 bool migrated;
1301 bool page_locked = false;
1302
1303 spin_lock(&mm->page_table_lock);
1304 if (unlikely(!pmd_same(pmd, *pmdp)))
1305 goto out_unlock;
1306
1307 page = pmd_page(pmd);
1308 get_page(page);
1309 current_nid = page_to_nid(page);
1310 count_vm_numa_event(NUMA_HINT_FAULTS);
1311 if (current_nid == numa_node_id())
1312 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1313
1314 target_nid = mpol_misplaced(page, vma, haddr);
1315 if (target_nid == -1) {
1316 put_page(page);
1317 goto clear_pmdnuma;
1318 }
1319
1320 /* Acquire the page lock to serialise THP migrations */
1321 spin_unlock(&mm->page_table_lock);
1322 lock_page(page);
1323 page_locked = true;
1324
1325 /* Confirm the PTE did not while locked */
1326 spin_lock(&mm->page_table_lock);
1327 if (unlikely(!pmd_same(pmd, *pmdp))) {
1328 unlock_page(page);
1329 put_page(page);
1330 goto out_unlock;
1331 }
1332 spin_unlock(&mm->page_table_lock);
1333
1334 /* Migrate the THP to the requested node */
1335 migrated = migrate_misplaced_transhuge_page(mm, vma,
1336 pmdp, pmd, addr,
1337 page, target_nid);
1338 if (migrated)
1339 current_nid = target_nid;
1340 else {
1341 spin_lock(&mm->page_table_lock);
1342 if (unlikely(!pmd_same(pmd, *pmdp))) {
1343 unlock_page(page);
1344 goto out_unlock;
1345 }
1346 goto clear_pmdnuma;
1347 }
1348
1349 task_numa_fault(current_nid, HPAGE_PMD_NR, migrated);
1350 return 0;
1351
1352 clear_pmdnuma:
1353 pmd = pmd_mknonnuma(pmd);
1354 set_pmd_at(mm, haddr, pmdp, pmd);
1355 VM_BUG_ON(pmd_numa(*pmdp));
1356 update_mmu_cache_pmd(vma, addr, pmdp);
1357 if (page_locked)
1358 unlock_page(page);
1359
1360 out_unlock:
1361 spin_unlock(&mm->page_table_lock);
1362 if (current_nid != -1)
1363 task_numa_fault(current_nid, HPAGE_PMD_NR, migrated);
1364 return 0;
1365 }
1366
1367 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1368 pmd_t *pmd, unsigned long addr)
1369 {
1370 int ret = 0;
1371
1372 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1373 struct page *page;
1374 pgtable_t pgtable;
1375 pmd_t orig_pmd;
1376 pgtable = pgtable_trans_huge_withdraw(tlb->mm);
1377 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
1378 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1379 if (is_huge_zero_pmd(orig_pmd)) {
1380 tlb->mm->nr_ptes--;
1381 spin_unlock(&tlb->mm->page_table_lock);
1382 put_huge_zero_page();
1383 } else {
1384 page = pmd_page(orig_pmd);
1385 page_remove_rmap(page);
1386 VM_BUG_ON(page_mapcount(page) < 0);
1387 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1388 VM_BUG_ON(!PageHead(page));
1389 tlb->mm->nr_ptes--;
1390 spin_unlock(&tlb->mm->page_table_lock);
1391 tlb_remove_page(tlb, page);
1392 }
1393 pte_free(tlb->mm, pgtable);
1394 ret = 1;
1395 }
1396 return ret;
1397 }
1398
1399 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1400 unsigned long addr, unsigned long end,
1401 unsigned char *vec)
1402 {
1403 int ret = 0;
1404
1405 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1406 /*
1407 * All logical pages in the range are present
1408 * if backed by a huge page.
1409 */
1410 spin_unlock(&vma->vm_mm->page_table_lock);
1411 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1412 ret = 1;
1413 }
1414
1415 return ret;
1416 }
1417
1418 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1419 unsigned long old_addr,
1420 unsigned long new_addr, unsigned long old_end,
1421 pmd_t *old_pmd, pmd_t *new_pmd)
1422 {
1423 int ret = 0;
1424 pmd_t pmd;
1425
1426 struct mm_struct *mm = vma->vm_mm;
1427
1428 if ((old_addr & ~HPAGE_PMD_MASK) ||
1429 (new_addr & ~HPAGE_PMD_MASK) ||
1430 old_end - old_addr < HPAGE_PMD_SIZE ||
1431 (new_vma->vm_flags & VM_NOHUGEPAGE))
1432 goto out;
1433
1434 /*
1435 * The destination pmd shouldn't be established, free_pgtables()
1436 * should have release it.
1437 */
1438 if (WARN_ON(!pmd_none(*new_pmd))) {
1439 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1440 goto out;
1441 }
1442
1443 ret = __pmd_trans_huge_lock(old_pmd, vma);
1444 if (ret == 1) {
1445 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1446 VM_BUG_ON(!pmd_none(*new_pmd));
1447 set_pmd_at(mm, new_addr, new_pmd, pmd);
1448 spin_unlock(&mm->page_table_lock);
1449 }
1450 out:
1451 return ret;
1452 }
1453
1454 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1455 unsigned long addr, pgprot_t newprot, int prot_numa)
1456 {
1457 struct mm_struct *mm = vma->vm_mm;
1458 int ret = 0;
1459
1460 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1461 pmd_t entry;
1462 entry = pmdp_get_and_clear(mm, addr, pmd);
1463 if (!prot_numa) {
1464 entry = pmd_modify(entry, newprot);
1465 BUG_ON(pmd_write(entry));
1466 } else {
1467 struct page *page = pmd_page(*pmd);
1468
1469 /* only check non-shared pages */
1470 if (page_mapcount(page) == 1 &&
1471 !pmd_numa(*pmd)) {
1472 entry = pmd_mknuma(entry);
1473 }
1474 }
1475 set_pmd_at(mm, addr, pmd, entry);
1476 spin_unlock(&vma->vm_mm->page_table_lock);
1477 ret = 1;
1478 }
1479
1480 return ret;
1481 }
1482
1483 /*
1484 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1485 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1486 *
1487 * Note that if it returns 1, this routine returns without unlocking page
1488 * table locks. So callers must unlock them.
1489 */
1490 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1491 {
1492 spin_lock(&vma->vm_mm->page_table_lock);
1493 if (likely(pmd_trans_huge(*pmd))) {
1494 if (unlikely(pmd_trans_splitting(*pmd))) {
1495 spin_unlock(&vma->vm_mm->page_table_lock);
1496 wait_split_huge_page(vma->anon_vma, pmd);
1497 return -1;
1498 } else {
1499 /* Thp mapped by 'pmd' is stable, so we can
1500 * handle it as it is. */
1501 return 1;
1502 }
1503 }
1504 spin_unlock(&vma->vm_mm->page_table_lock);
1505 return 0;
1506 }
1507
1508 pmd_t *page_check_address_pmd(struct page *page,
1509 struct mm_struct *mm,
1510 unsigned long address,
1511 enum page_check_address_pmd_flag flag)
1512 {
1513 pmd_t *pmd, *ret = NULL;
1514
1515 if (address & ~HPAGE_PMD_MASK)
1516 goto out;
1517
1518 pmd = mm_find_pmd(mm, address);
1519 if (!pmd)
1520 goto out;
1521 if (pmd_none(*pmd))
1522 goto out;
1523 if (pmd_page(*pmd) != page)
1524 goto out;
1525 /*
1526 * split_vma() may create temporary aliased mappings. There is
1527 * no risk as long as all huge pmd are found and have their
1528 * splitting bit set before __split_huge_page_refcount
1529 * runs. Finding the same huge pmd more than once during the
1530 * same rmap walk is not a problem.
1531 */
1532 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1533 pmd_trans_splitting(*pmd))
1534 goto out;
1535 if (pmd_trans_huge(*pmd)) {
1536 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1537 !pmd_trans_splitting(*pmd));
1538 ret = pmd;
1539 }
1540 out:
1541 return ret;
1542 }
1543
1544 static int __split_huge_page_splitting(struct page *page,
1545 struct vm_area_struct *vma,
1546 unsigned long address)
1547 {
1548 struct mm_struct *mm = vma->vm_mm;
1549 pmd_t *pmd;
1550 int ret = 0;
1551 /* For mmu_notifiers */
1552 const unsigned long mmun_start = address;
1553 const unsigned long mmun_end = address + HPAGE_PMD_SIZE;
1554
1555 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1556 spin_lock(&mm->page_table_lock);
1557 pmd = page_check_address_pmd(page, mm, address,
1558 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1559 if (pmd) {
1560 /*
1561 * We can't temporarily set the pmd to null in order
1562 * to split it, the pmd must remain marked huge at all
1563 * times or the VM won't take the pmd_trans_huge paths
1564 * and it won't wait on the anon_vma->root->rwsem to
1565 * serialize against split_huge_page*.
1566 */
1567 pmdp_splitting_flush(vma, address, pmd);
1568 ret = 1;
1569 }
1570 spin_unlock(&mm->page_table_lock);
1571 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1572
1573 return ret;
1574 }
1575
1576 static void __split_huge_page_refcount(struct page *page)
1577 {
1578 int i;
1579 struct zone *zone = page_zone(page);
1580 struct lruvec *lruvec;
1581 int tail_count = 0;
1582
1583 /* prevent PageLRU to go away from under us, and freeze lru stats */
1584 spin_lock_irq(&zone->lru_lock);
1585 lruvec = mem_cgroup_page_lruvec(page, zone);
1586
1587 compound_lock(page);
1588 /* complete memcg works before add pages to LRU */
1589 mem_cgroup_split_huge_fixup(page);
1590
1591 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1592 struct page *page_tail = page + i;
1593
1594 /* tail_page->_mapcount cannot change */
1595 BUG_ON(page_mapcount(page_tail) < 0);
1596 tail_count += page_mapcount(page_tail);
1597 /* check for overflow */
1598 BUG_ON(tail_count < 0);
1599 BUG_ON(atomic_read(&page_tail->_count) != 0);
1600 /*
1601 * tail_page->_count is zero and not changing from
1602 * under us. But get_page_unless_zero() may be running
1603 * from under us on the tail_page. If we used
1604 * atomic_set() below instead of atomic_add(), we
1605 * would then run atomic_set() concurrently with
1606 * get_page_unless_zero(), and atomic_set() is
1607 * implemented in C not using locked ops. spin_unlock
1608 * on x86 sometime uses locked ops because of PPro
1609 * errata 66, 92, so unless somebody can guarantee
1610 * atomic_set() here would be safe on all archs (and
1611 * not only on x86), it's safer to use atomic_add().
1612 */
1613 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1614 &page_tail->_count);
1615
1616 /* after clearing PageTail the gup refcount can be released */
1617 smp_mb();
1618
1619 /*
1620 * retain hwpoison flag of the poisoned tail page:
1621 * fix for the unsuitable process killed on Guest Machine(KVM)
1622 * by the memory-failure.
1623 */
1624 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1625 page_tail->flags |= (page->flags &
1626 ((1L << PG_referenced) |
1627 (1L << PG_swapbacked) |
1628 (1L << PG_mlocked) |
1629 (1L << PG_uptodate)));
1630 page_tail->flags |= (1L << PG_dirty);
1631
1632 /* clear PageTail before overwriting first_page */
1633 smp_wmb();
1634
1635 /*
1636 * __split_huge_page_splitting() already set the
1637 * splitting bit in all pmd that could map this
1638 * hugepage, that will ensure no CPU can alter the
1639 * mapcount on the head page. The mapcount is only
1640 * accounted in the head page and it has to be
1641 * transferred to all tail pages in the below code. So
1642 * for this code to be safe, the split the mapcount
1643 * can't change. But that doesn't mean userland can't
1644 * keep changing and reading the page contents while
1645 * we transfer the mapcount, so the pmd splitting
1646 * status is achieved setting a reserved bit in the
1647 * pmd, not by clearing the present bit.
1648 */
1649 page_tail->_mapcount = page->_mapcount;
1650
1651 BUG_ON(page_tail->mapping);
1652 page_tail->mapping = page->mapping;
1653
1654 page_tail->index = page->index + i;
1655 page_xchg_last_nid(page_tail, page_last_nid(page));
1656
1657 BUG_ON(!PageAnon(page_tail));
1658 BUG_ON(!PageUptodate(page_tail));
1659 BUG_ON(!PageDirty(page_tail));
1660 BUG_ON(!PageSwapBacked(page_tail));
1661
1662 lru_add_page_tail(page, page_tail, lruvec);
1663 }
1664 atomic_sub(tail_count, &page->_count);
1665 BUG_ON(atomic_read(&page->_count) <= 0);
1666
1667 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1668 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1669
1670 ClearPageCompound(page);
1671 compound_unlock(page);
1672 spin_unlock_irq(&zone->lru_lock);
1673
1674 for (i = 1; i < HPAGE_PMD_NR; i++) {
1675 struct page *page_tail = page + i;
1676 BUG_ON(page_count(page_tail) <= 0);
1677 /*
1678 * Tail pages may be freed if there wasn't any mapping
1679 * like if add_to_swap() is running on a lru page that
1680 * had its mapping zapped. And freeing these pages
1681 * requires taking the lru_lock so we do the put_page
1682 * of the tail pages after the split is complete.
1683 */
1684 put_page(page_tail);
1685 }
1686
1687 /*
1688 * Only the head page (now become a regular page) is required
1689 * to be pinned by the caller.
1690 */
1691 BUG_ON(page_count(page) <= 0);
1692 }
1693
1694 static int __split_huge_page_map(struct page *page,
1695 struct vm_area_struct *vma,
1696 unsigned long address)
1697 {
1698 struct mm_struct *mm = vma->vm_mm;
1699 pmd_t *pmd, _pmd;
1700 int ret = 0, i;
1701 pgtable_t pgtable;
1702 unsigned long haddr;
1703
1704 spin_lock(&mm->page_table_lock);
1705 pmd = page_check_address_pmd(page, mm, address,
1706 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1707 if (pmd) {
1708 pgtable = pgtable_trans_huge_withdraw(mm);
1709 pmd_populate(mm, &_pmd, pgtable);
1710
1711 haddr = address;
1712 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1713 pte_t *pte, entry;
1714 BUG_ON(PageCompound(page+i));
1715 entry = mk_pte(page + i, vma->vm_page_prot);
1716 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1717 if (!pmd_write(*pmd))
1718 entry = pte_wrprotect(entry);
1719 else
1720 BUG_ON(page_mapcount(page) != 1);
1721 if (!pmd_young(*pmd))
1722 entry = pte_mkold(entry);
1723 if (pmd_numa(*pmd))
1724 entry = pte_mknuma(entry);
1725 pte = pte_offset_map(&_pmd, haddr);
1726 BUG_ON(!pte_none(*pte));
1727 set_pte_at(mm, haddr, pte, entry);
1728 pte_unmap(pte);
1729 }
1730
1731 smp_wmb(); /* make pte visible before pmd */
1732 /*
1733 * Up to this point the pmd is present and huge and
1734 * userland has the whole access to the hugepage
1735 * during the split (which happens in place). If we
1736 * overwrite the pmd with the not-huge version
1737 * pointing to the pte here (which of course we could
1738 * if all CPUs were bug free), userland could trigger
1739 * a small page size TLB miss on the small sized TLB
1740 * while the hugepage TLB entry is still established
1741 * in the huge TLB. Some CPU doesn't like that. See
1742 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1743 * Erratum 383 on page 93. Intel should be safe but is
1744 * also warns that it's only safe if the permission
1745 * and cache attributes of the two entries loaded in
1746 * the two TLB is identical (which should be the case
1747 * here). But it is generally safer to never allow
1748 * small and huge TLB entries for the same virtual
1749 * address to be loaded simultaneously. So instead of
1750 * doing "pmd_populate(); flush_tlb_range();" we first
1751 * mark the current pmd notpresent (atomically because
1752 * here the pmd_trans_huge and pmd_trans_splitting
1753 * must remain set at all times on the pmd until the
1754 * split is complete for this pmd), then we flush the
1755 * SMP TLB and finally we write the non-huge version
1756 * of the pmd entry with pmd_populate.
1757 */
1758 pmdp_invalidate(vma, address, pmd);
1759 pmd_populate(mm, pmd, pgtable);
1760 ret = 1;
1761 }
1762 spin_unlock(&mm->page_table_lock);
1763
1764 return ret;
1765 }
1766
1767 /* must be called with anon_vma->root->rwsem held */
1768 static void __split_huge_page(struct page *page,
1769 struct anon_vma *anon_vma)
1770 {
1771 int mapcount, mapcount2;
1772 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1773 struct anon_vma_chain *avc;
1774
1775 BUG_ON(!PageHead(page));
1776 BUG_ON(PageTail(page));
1777
1778 mapcount = 0;
1779 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1780 struct vm_area_struct *vma = avc->vma;
1781 unsigned long addr = vma_address(page, vma);
1782 BUG_ON(is_vma_temporary_stack(vma));
1783 mapcount += __split_huge_page_splitting(page, vma, addr);
1784 }
1785 /*
1786 * It is critical that new vmas are added to the tail of the
1787 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1788 * and establishes a child pmd before
1789 * __split_huge_page_splitting() freezes the parent pmd (so if
1790 * we fail to prevent copy_huge_pmd() from running until the
1791 * whole __split_huge_page() is complete), we will still see
1792 * the newly established pmd of the child later during the
1793 * walk, to be able to set it as pmd_trans_splitting too.
1794 */
1795 if (mapcount != page_mapcount(page))
1796 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1797 mapcount, page_mapcount(page));
1798 BUG_ON(mapcount != page_mapcount(page));
1799
1800 __split_huge_page_refcount(page);
1801
1802 mapcount2 = 0;
1803 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1804 struct vm_area_struct *vma = avc->vma;
1805 unsigned long addr = vma_address(page, vma);
1806 BUG_ON(is_vma_temporary_stack(vma));
1807 mapcount2 += __split_huge_page_map(page, vma, addr);
1808 }
1809 if (mapcount != mapcount2)
1810 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1811 mapcount, mapcount2, page_mapcount(page));
1812 BUG_ON(mapcount != mapcount2);
1813 }
1814
1815 int split_huge_page(struct page *page)
1816 {
1817 struct anon_vma *anon_vma;
1818 int ret = 1;
1819
1820 BUG_ON(is_huge_zero_pfn(page_to_pfn(page)));
1821 BUG_ON(!PageAnon(page));
1822 anon_vma = page_lock_anon_vma_read(page);
1823 if (!anon_vma)
1824 goto out;
1825 ret = 0;
1826 if (!PageCompound(page))
1827 goto out_unlock;
1828
1829 BUG_ON(!PageSwapBacked(page));
1830 __split_huge_page(page, anon_vma);
1831 count_vm_event(THP_SPLIT);
1832
1833 BUG_ON(PageCompound(page));
1834 out_unlock:
1835 page_unlock_anon_vma_read(anon_vma);
1836 out:
1837 return ret;
1838 }
1839
1840 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1841
1842 int hugepage_madvise(struct vm_area_struct *vma,
1843 unsigned long *vm_flags, int advice)
1844 {
1845 struct mm_struct *mm = vma->vm_mm;
1846
1847 switch (advice) {
1848 case MADV_HUGEPAGE:
1849 /*
1850 * Be somewhat over-protective like KSM for now!
1851 */
1852 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1853 return -EINVAL;
1854 if (mm->def_flags & VM_NOHUGEPAGE)
1855 return -EINVAL;
1856 *vm_flags &= ~VM_NOHUGEPAGE;
1857 *vm_flags |= VM_HUGEPAGE;
1858 /*
1859 * If the vma become good for khugepaged to scan,
1860 * register it here without waiting a page fault that
1861 * may not happen any time soon.
1862 */
1863 if (unlikely(khugepaged_enter_vma_merge(vma)))
1864 return -ENOMEM;
1865 break;
1866 case MADV_NOHUGEPAGE:
1867 /*
1868 * Be somewhat over-protective like KSM for now!
1869 */
1870 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1871 return -EINVAL;
1872 *vm_flags &= ~VM_HUGEPAGE;
1873 *vm_flags |= VM_NOHUGEPAGE;
1874 /*
1875 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1876 * this vma even if we leave the mm registered in khugepaged if
1877 * it got registered before VM_NOHUGEPAGE was set.
1878 */
1879 break;
1880 }
1881
1882 return 0;
1883 }
1884
1885 static int __init khugepaged_slab_init(void)
1886 {
1887 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1888 sizeof(struct mm_slot),
1889 __alignof__(struct mm_slot), 0, NULL);
1890 if (!mm_slot_cache)
1891 return -ENOMEM;
1892
1893 return 0;
1894 }
1895
1896 static void __init khugepaged_slab_free(void)
1897 {
1898 kmem_cache_destroy(mm_slot_cache);
1899 mm_slot_cache = NULL;
1900 }
1901
1902 static inline struct mm_slot *alloc_mm_slot(void)
1903 {
1904 if (!mm_slot_cache) /* initialization failed */
1905 return NULL;
1906 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1907 }
1908
1909 static inline void free_mm_slot(struct mm_slot *mm_slot)
1910 {
1911 kmem_cache_free(mm_slot_cache, mm_slot);
1912 }
1913
1914 static int __init mm_slots_hash_init(void)
1915 {
1916 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1917 GFP_KERNEL);
1918 if (!mm_slots_hash)
1919 return -ENOMEM;
1920 return 0;
1921 }
1922
1923 #if 0
1924 static void __init mm_slots_hash_free(void)
1925 {
1926 kfree(mm_slots_hash);
1927 mm_slots_hash = NULL;
1928 }
1929 #endif
1930
1931 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1932 {
1933 struct mm_slot *mm_slot;
1934 struct hlist_head *bucket;
1935 struct hlist_node *node;
1936
1937 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1938 % MM_SLOTS_HASH_HEADS];
1939 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1940 if (mm == mm_slot->mm)
1941 return mm_slot;
1942 }
1943 return NULL;
1944 }
1945
1946 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1947 struct mm_slot *mm_slot)
1948 {
1949 struct hlist_head *bucket;
1950
1951 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1952 % MM_SLOTS_HASH_HEADS];
1953 mm_slot->mm = mm;
1954 hlist_add_head(&mm_slot->hash, bucket);
1955 }
1956
1957 static inline int khugepaged_test_exit(struct mm_struct *mm)
1958 {
1959 return atomic_read(&mm->mm_users) == 0;
1960 }
1961
1962 int __khugepaged_enter(struct mm_struct *mm)
1963 {
1964 struct mm_slot *mm_slot;
1965 int wakeup;
1966
1967 mm_slot = alloc_mm_slot();
1968 if (!mm_slot)
1969 return -ENOMEM;
1970
1971 /* __khugepaged_exit() must not run from under us */
1972 VM_BUG_ON(khugepaged_test_exit(mm));
1973 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1974 free_mm_slot(mm_slot);
1975 return 0;
1976 }
1977
1978 spin_lock(&khugepaged_mm_lock);
1979 insert_to_mm_slots_hash(mm, mm_slot);
1980 /*
1981 * Insert just behind the scanning cursor, to let the area settle
1982 * down a little.
1983 */
1984 wakeup = list_empty(&khugepaged_scan.mm_head);
1985 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1986 spin_unlock(&khugepaged_mm_lock);
1987
1988 atomic_inc(&mm->mm_count);
1989 if (wakeup)
1990 wake_up_interruptible(&khugepaged_wait);
1991
1992 return 0;
1993 }
1994
1995 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1996 {
1997 unsigned long hstart, hend;
1998 if (!vma->anon_vma)
1999 /*
2000 * Not yet faulted in so we will register later in the
2001 * page fault if needed.
2002 */
2003 return 0;
2004 if (vma->vm_ops)
2005 /* khugepaged not yet working on file or special mappings */
2006 return 0;
2007 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2008 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2009 hend = vma->vm_end & HPAGE_PMD_MASK;
2010 if (hstart < hend)
2011 return khugepaged_enter(vma);
2012 return 0;
2013 }
2014
2015 void __khugepaged_exit(struct mm_struct *mm)
2016 {
2017 struct mm_slot *mm_slot;
2018 int free = 0;
2019
2020 spin_lock(&khugepaged_mm_lock);
2021 mm_slot = get_mm_slot(mm);
2022 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
2023 hlist_del(&mm_slot->hash);
2024 list_del(&mm_slot->mm_node);
2025 free = 1;
2026 }
2027 spin_unlock(&khugepaged_mm_lock);
2028
2029 if (free) {
2030 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2031 free_mm_slot(mm_slot);
2032 mmdrop(mm);
2033 } else if (mm_slot) {
2034 /*
2035 * This is required to serialize against
2036 * khugepaged_test_exit() (which is guaranteed to run
2037 * under mmap sem read mode). Stop here (after we
2038 * return all pagetables will be destroyed) until
2039 * khugepaged has finished working on the pagetables
2040 * under the mmap_sem.
2041 */
2042 down_write(&mm->mmap_sem);
2043 up_write(&mm->mmap_sem);
2044 }
2045 }
2046
2047 static void release_pte_page(struct page *page)
2048 {
2049 /* 0 stands for page_is_file_cache(page) == false */
2050 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
2051 unlock_page(page);
2052 putback_lru_page(page);
2053 }
2054
2055 static void release_pte_pages(pte_t *pte, pte_t *_pte)
2056 {
2057 while (--_pte >= pte) {
2058 pte_t pteval = *_pte;
2059 if (!pte_none(pteval))
2060 release_pte_page(pte_page(pteval));
2061 }
2062 }
2063
2064 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
2065 unsigned long address,
2066 pte_t *pte)
2067 {
2068 struct page *page;
2069 pte_t *_pte;
2070 int referenced = 0, none = 0;
2071 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
2072 _pte++, address += PAGE_SIZE) {
2073 pte_t pteval = *_pte;
2074 if (pte_none(pteval)) {
2075 if (++none <= khugepaged_max_ptes_none)
2076 continue;
2077 else
2078 goto out;
2079 }
2080 if (!pte_present(pteval) || !pte_write(pteval))
2081 goto out;
2082 page = vm_normal_page(vma, address, pteval);
2083 if (unlikely(!page))
2084 goto out;
2085
2086 VM_BUG_ON(PageCompound(page));
2087 BUG_ON(!PageAnon(page));
2088 VM_BUG_ON(!PageSwapBacked(page));
2089
2090 /* cannot use mapcount: can't collapse if there's a gup pin */
2091 if (page_count(page) != 1)
2092 goto out;
2093 /*
2094 * We can do it before isolate_lru_page because the
2095 * page can't be freed from under us. NOTE: PG_lock
2096 * is needed to serialize against split_huge_page
2097 * when invoked from the VM.
2098 */
2099 if (!trylock_page(page))
2100 goto out;
2101 /*
2102 * Isolate the page to avoid collapsing an hugepage
2103 * currently in use by the VM.
2104 */
2105 if (isolate_lru_page(page)) {
2106 unlock_page(page);
2107 goto out;
2108 }
2109 /* 0 stands for page_is_file_cache(page) == false */
2110 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
2111 VM_BUG_ON(!PageLocked(page));
2112 VM_BUG_ON(PageLRU(page));
2113
2114 /* If there is no mapped pte young don't collapse the page */
2115 if (pte_young(pteval) || PageReferenced(page) ||
2116 mmu_notifier_test_young(vma->vm_mm, address))
2117 referenced = 1;
2118 }
2119 if (likely(referenced))
2120 return 1;
2121 out:
2122 release_pte_pages(pte, _pte);
2123 return 0;
2124 }
2125
2126 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
2127 struct vm_area_struct *vma,
2128 unsigned long address,
2129 spinlock_t *ptl)
2130 {
2131 pte_t *_pte;
2132 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
2133 pte_t pteval = *_pte;
2134 struct page *src_page;
2135
2136 if (pte_none(pteval)) {
2137 clear_user_highpage(page, address);
2138 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
2139 } else {
2140 src_page = pte_page(pteval);
2141 copy_user_highpage(page, src_page, address, vma);
2142 VM_BUG_ON(page_mapcount(src_page) != 1);
2143 release_pte_page(src_page);
2144 /*
2145 * ptl mostly unnecessary, but preempt has to
2146 * be disabled to update the per-cpu stats
2147 * inside page_remove_rmap().
2148 */
2149 spin_lock(ptl);
2150 /*
2151 * paravirt calls inside pte_clear here are
2152 * superfluous.
2153 */
2154 pte_clear(vma->vm_mm, address, _pte);
2155 page_remove_rmap(src_page);
2156 spin_unlock(ptl);
2157 free_page_and_swap_cache(src_page);
2158 }
2159
2160 address += PAGE_SIZE;
2161 page++;
2162 }
2163 }
2164
2165 static void khugepaged_alloc_sleep(void)
2166 {
2167 wait_event_freezable_timeout(khugepaged_wait, false,
2168 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
2169 }
2170
2171 #ifdef CONFIG_NUMA
2172 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2173 {
2174 if (IS_ERR(*hpage)) {
2175 if (!*wait)
2176 return false;
2177
2178 *wait = false;
2179 *hpage = NULL;
2180 khugepaged_alloc_sleep();
2181 } else if (*hpage) {
2182 put_page(*hpage);
2183 *hpage = NULL;
2184 }
2185
2186 return true;
2187 }
2188
2189 static struct page
2190 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2191 struct vm_area_struct *vma, unsigned long address,
2192 int node)
2193 {
2194 VM_BUG_ON(*hpage);
2195 /*
2196 * Allocate the page while the vma is still valid and under
2197 * the mmap_sem read mode so there is no memory allocation
2198 * later when we take the mmap_sem in write mode. This is more
2199 * friendly behavior (OTOH it may actually hide bugs) to
2200 * filesystems in userland with daemons allocating memory in
2201 * the userland I/O paths. Allocating memory with the
2202 * mmap_sem in read mode is good idea also to allow greater
2203 * scalability.
2204 */
2205 *hpage = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
2206 node, __GFP_OTHER_NODE);
2207
2208 /*
2209 * After allocating the hugepage, release the mmap_sem read lock in
2210 * preparation for taking it in write mode.
2211 */
2212 up_read(&mm->mmap_sem);
2213 if (unlikely(!*hpage)) {
2214 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2215 *hpage = ERR_PTR(-ENOMEM);
2216 return NULL;
2217 }
2218
2219 count_vm_event(THP_COLLAPSE_ALLOC);
2220 return *hpage;
2221 }
2222 #else
2223 static struct page *khugepaged_alloc_hugepage(bool *wait)
2224 {
2225 struct page *hpage;
2226
2227 do {
2228 hpage = alloc_hugepage(khugepaged_defrag());
2229 if (!hpage) {
2230 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2231 if (!*wait)
2232 return NULL;
2233
2234 *wait = false;
2235 khugepaged_alloc_sleep();
2236 } else
2237 count_vm_event(THP_COLLAPSE_ALLOC);
2238 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
2239
2240 return hpage;
2241 }
2242
2243 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
2244 {
2245 if (!*hpage)
2246 *hpage = khugepaged_alloc_hugepage(wait);
2247
2248 if (unlikely(!*hpage))
2249 return false;
2250
2251 return true;
2252 }
2253
2254 static struct page
2255 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
2256 struct vm_area_struct *vma, unsigned long address,
2257 int node)
2258 {
2259 up_read(&mm->mmap_sem);
2260 VM_BUG_ON(!*hpage);
2261 return *hpage;
2262 }
2263 #endif
2264
2265 static bool hugepage_vma_check(struct vm_area_struct *vma)
2266 {
2267 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
2268 (vma->vm_flags & VM_NOHUGEPAGE))
2269 return false;
2270
2271 if (!vma->anon_vma || vma->vm_ops)
2272 return false;
2273 if (is_vma_temporary_stack(vma))
2274 return false;
2275 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2276 return true;
2277 }
2278
2279 static void collapse_huge_page(struct mm_struct *mm,
2280 unsigned long address,
2281 struct page **hpage,
2282 struct vm_area_struct *vma,
2283 int node)
2284 {
2285 pmd_t *pmd, _pmd;
2286 pte_t *pte;
2287 pgtable_t pgtable;
2288 struct page *new_page;
2289 spinlock_t *ptl;
2290 int isolated;
2291 unsigned long hstart, hend;
2292 unsigned long mmun_start; /* For mmu_notifiers */
2293 unsigned long mmun_end; /* For mmu_notifiers */
2294
2295 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2296
2297 /* release the mmap_sem read lock. */
2298 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
2299 if (!new_page)
2300 return;
2301
2302 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
2303 return;
2304
2305 /*
2306 * Prevent all access to pagetables with the exception of
2307 * gup_fast later hanlded by the ptep_clear_flush and the VM
2308 * handled by the anon_vma lock + PG_lock.
2309 */
2310 down_write(&mm->mmap_sem);
2311 if (unlikely(khugepaged_test_exit(mm)))
2312 goto out;
2313
2314 vma = find_vma(mm, address);
2315 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2316 hend = vma->vm_end & HPAGE_PMD_MASK;
2317 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
2318 goto out;
2319 if (!hugepage_vma_check(vma))
2320 goto out;
2321 pmd = mm_find_pmd(mm, address);
2322 if (!pmd)
2323 goto out;
2324 if (pmd_trans_huge(*pmd))
2325 goto out;
2326
2327 anon_vma_lock_write(vma->anon_vma);
2328
2329 pte = pte_offset_map(pmd, address);
2330 ptl = pte_lockptr(mm, pmd);
2331
2332 mmun_start = address;
2333 mmun_end = address + HPAGE_PMD_SIZE;
2334 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2335 spin_lock(&mm->page_table_lock); /* probably unnecessary */
2336 /*
2337 * After this gup_fast can't run anymore. This also removes
2338 * any huge TLB entry from the CPU so we won't allow
2339 * huge and small TLB entries for the same virtual address
2340 * to avoid the risk of CPU bugs in that area.
2341 */
2342 _pmd = pmdp_clear_flush(vma, address, pmd);
2343 spin_unlock(&mm->page_table_lock);
2344 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2345
2346 spin_lock(ptl);
2347 isolated = __collapse_huge_page_isolate(vma, address, pte);
2348 spin_unlock(ptl);
2349
2350 if (unlikely(!isolated)) {
2351 pte_unmap(pte);
2352 spin_lock(&mm->page_table_lock);
2353 BUG_ON(!pmd_none(*pmd));
2354 set_pmd_at(mm, address, pmd, _pmd);
2355 spin_unlock(&mm->page_table_lock);
2356 anon_vma_unlock(vma->anon_vma);
2357 goto out;
2358 }
2359
2360 /*
2361 * All pages are isolated and locked so anon_vma rmap
2362 * can't run anymore.
2363 */
2364 anon_vma_unlock(vma->anon_vma);
2365
2366 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
2367 pte_unmap(pte);
2368 __SetPageUptodate(new_page);
2369 pgtable = pmd_pgtable(_pmd);
2370
2371 _pmd = mk_huge_pmd(new_page, vma);
2372
2373 /*
2374 * spin_lock() below is not the equivalent of smp_wmb(), so
2375 * this is needed to avoid the copy_huge_page writes to become
2376 * visible after the set_pmd_at() write.
2377 */
2378 smp_wmb();
2379
2380 spin_lock(&mm->page_table_lock);
2381 BUG_ON(!pmd_none(*pmd));
2382 page_add_new_anon_rmap(new_page, vma, address);
2383 set_pmd_at(mm, address, pmd, _pmd);
2384 update_mmu_cache_pmd(vma, address, pmd);
2385 pgtable_trans_huge_deposit(mm, pgtable);
2386 spin_unlock(&mm->page_table_lock);
2387
2388 *hpage = NULL;
2389
2390 khugepaged_pages_collapsed++;
2391 out_up_write:
2392 up_write(&mm->mmap_sem);
2393 return;
2394
2395 out:
2396 mem_cgroup_uncharge_page(new_page);
2397 goto out_up_write;
2398 }
2399
2400 static int khugepaged_scan_pmd(struct mm_struct *mm,
2401 struct vm_area_struct *vma,
2402 unsigned long address,
2403 struct page **hpage)
2404 {
2405 pmd_t *pmd;
2406 pte_t *pte, *_pte;
2407 int ret = 0, referenced = 0, none = 0;
2408 struct page *page;
2409 unsigned long _address;
2410 spinlock_t *ptl;
2411 int node = -1;
2412
2413 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2414
2415 pmd = mm_find_pmd(mm, address);
2416 if (!pmd)
2417 goto out;
2418 if (pmd_trans_huge(*pmd))
2419 goto out;
2420
2421 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2422 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2423 _pte++, _address += PAGE_SIZE) {
2424 pte_t pteval = *_pte;
2425 if (pte_none(pteval)) {
2426 if (++none <= khugepaged_max_ptes_none)
2427 continue;
2428 else
2429 goto out_unmap;
2430 }
2431 if (!pte_present(pteval) || !pte_write(pteval))
2432 goto out_unmap;
2433 page = vm_normal_page(vma, _address, pteval);
2434 if (unlikely(!page))
2435 goto out_unmap;
2436 /*
2437 * Chose the node of the first page. This could
2438 * be more sophisticated and look at more pages,
2439 * but isn't for now.
2440 */
2441 if (node == -1)
2442 node = page_to_nid(page);
2443 VM_BUG_ON(PageCompound(page));
2444 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2445 goto out_unmap;
2446 /* cannot use mapcount: can't collapse if there's a gup pin */
2447 if (page_count(page) != 1)
2448 goto out_unmap;
2449 if (pte_young(pteval) || PageReferenced(page) ||
2450 mmu_notifier_test_young(vma->vm_mm, address))
2451 referenced = 1;
2452 }
2453 if (referenced)
2454 ret = 1;
2455 out_unmap:
2456 pte_unmap_unlock(pte, ptl);
2457 if (ret)
2458 /* collapse_huge_page will return with the mmap_sem released */
2459 collapse_huge_page(mm, address, hpage, vma, node);
2460 out:
2461 return ret;
2462 }
2463
2464 static void collect_mm_slot(struct mm_slot *mm_slot)
2465 {
2466 struct mm_struct *mm = mm_slot->mm;
2467
2468 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2469
2470 if (khugepaged_test_exit(mm)) {
2471 /* free mm_slot */
2472 hlist_del(&mm_slot->hash);
2473 list_del(&mm_slot->mm_node);
2474
2475 /*
2476 * Not strictly needed because the mm exited already.
2477 *
2478 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2479 */
2480
2481 /* khugepaged_mm_lock actually not necessary for the below */
2482 free_mm_slot(mm_slot);
2483 mmdrop(mm);
2484 }
2485 }
2486
2487 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2488 struct page **hpage)
2489 __releases(&khugepaged_mm_lock)
2490 __acquires(&khugepaged_mm_lock)
2491 {
2492 struct mm_slot *mm_slot;
2493 struct mm_struct *mm;
2494 struct vm_area_struct *vma;
2495 int progress = 0;
2496
2497 VM_BUG_ON(!pages);
2498 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2499
2500 if (khugepaged_scan.mm_slot)
2501 mm_slot = khugepaged_scan.mm_slot;
2502 else {
2503 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2504 struct mm_slot, mm_node);
2505 khugepaged_scan.address = 0;
2506 khugepaged_scan.mm_slot = mm_slot;
2507 }
2508 spin_unlock(&khugepaged_mm_lock);
2509
2510 mm = mm_slot->mm;
2511 down_read(&mm->mmap_sem);
2512 if (unlikely(khugepaged_test_exit(mm)))
2513 vma = NULL;
2514 else
2515 vma = find_vma(mm, khugepaged_scan.address);
2516
2517 progress++;
2518 for (; vma; vma = vma->vm_next) {
2519 unsigned long hstart, hend;
2520
2521 cond_resched();
2522 if (unlikely(khugepaged_test_exit(mm))) {
2523 progress++;
2524 break;
2525 }
2526 if (!hugepage_vma_check(vma)) {
2527 skip:
2528 progress++;
2529 continue;
2530 }
2531 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2532 hend = vma->vm_end & HPAGE_PMD_MASK;
2533 if (hstart >= hend)
2534 goto skip;
2535 if (khugepaged_scan.address > hend)
2536 goto skip;
2537 if (khugepaged_scan.address < hstart)
2538 khugepaged_scan.address = hstart;
2539 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2540
2541 while (khugepaged_scan.address < hend) {
2542 int ret;
2543 cond_resched();
2544 if (unlikely(khugepaged_test_exit(mm)))
2545 goto breakouterloop;
2546
2547 VM_BUG_ON(khugepaged_scan.address < hstart ||
2548 khugepaged_scan.address + HPAGE_PMD_SIZE >
2549 hend);
2550 ret = khugepaged_scan_pmd(mm, vma,
2551 khugepaged_scan.address,
2552 hpage);
2553 /* move to next address */
2554 khugepaged_scan.address += HPAGE_PMD_SIZE;
2555 progress += HPAGE_PMD_NR;
2556 if (ret)
2557 /* we released mmap_sem so break loop */
2558 goto breakouterloop_mmap_sem;
2559 if (progress >= pages)
2560 goto breakouterloop;
2561 }
2562 }
2563 breakouterloop:
2564 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2565 breakouterloop_mmap_sem:
2566
2567 spin_lock(&khugepaged_mm_lock);
2568 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2569 /*
2570 * Release the current mm_slot if this mm is about to die, or
2571 * if we scanned all vmas of this mm.
2572 */
2573 if (khugepaged_test_exit(mm) || !vma) {
2574 /*
2575 * Make sure that if mm_users is reaching zero while
2576 * khugepaged runs here, khugepaged_exit will find
2577 * mm_slot not pointing to the exiting mm.
2578 */
2579 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2580 khugepaged_scan.mm_slot = list_entry(
2581 mm_slot->mm_node.next,
2582 struct mm_slot, mm_node);
2583 khugepaged_scan.address = 0;
2584 } else {
2585 khugepaged_scan.mm_slot = NULL;
2586 khugepaged_full_scans++;
2587 }
2588
2589 collect_mm_slot(mm_slot);
2590 }
2591
2592 return progress;
2593 }
2594
2595 static int khugepaged_has_work(void)
2596 {
2597 return !list_empty(&khugepaged_scan.mm_head) &&
2598 khugepaged_enabled();
2599 }
2600
2601 static int khugepaged_wait_event(void)
2602 {
2603 return !list_empty(&khugepaged_scan.mm_head) ||
2604 kthread_should_stop();
2605 }
2606
2607 static void khugepaged_do_scan(void)
2608 {
2609 struct page *hpage = NULL;
2610 unsigned int progress = 0, pass_through_head = 0;
2611 unsigned int pages = khugepaged_pages_to_scan;
2612 bool wait = true;
2613
2614 barrier(); /* write khugepaged_pages_to_scan to local stack */
2615
2616 while (progress < pages) {
2617 if (!khugepaged_prealloc_page(&hpage, &wait))
2618 break;
2619
2620 cond_resched();
2621
2622 if (unlikely(kthread_should_stop() || freezing(current)))
2623 break;
2624
2625 spin_lock(&khugepaged_mm_lock);
2626 if (!khugepaged_scan.mm_slot)
2627 pass_through_head++;
2628 if (khugepaged_has_work() &&
2629 pass_through_head < 2)
2630 progress += khugepaged_scan_mm_slot(pages - progress,
2631 &hpage);
2632 else
2633 progress = pages;
2634 spin_unlock(&khugepaged_mm_lock);
2635 }
2636
2637 if (!IS_ERR_OR_NULL(hpage))
2638 put_page(hpage);
2639 }
2640
2641 static void khugepaged_wait_work(void)
2642 {
2643 try_to_freeze();
2644
2645 if (khugepaged_has_work()) {
2646 if (!khugepaged_scan_sleep_millisecs)
2647 return;
2648
2649 wait_event_freezable_timeout(khugepaged_wait,
2650 kthread_should_stop(),
2651 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2652 return;
2653 }
2654
2655 if (khugepaged_enabled())
2656 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2657 }
2658
2659 static int khugepaged(void *none)
2660 {
2661 struct mm_slot *mm_slot;
2662
2663 set_freezable();
2664 set_user_nice(current, 19);
2665
2666 while (!kthread_should_stop()) {
2667 khugepaged_do_scan();
2668 khugepaged_wait_work();
2669 }
2670
2671 spin_lock(&khugepaged_mm_lock);
2672 mm_slot = khugepaged_scan.mm_slot;
2673 khugepaged_scan.mm_slot = NULL;
2674 if (mm_slot)
2675 collect_mm_slot(mm_slot);
2676 spin_unlock(&khugepaged_mm_lock);
2677 return 0;
2678 }
2679
2680 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2681 unsigned long haddr, pmd_t *pmd)
2682 {
2683 struct mm_struct *mm = vma->vm_mm;
2684 pgtable_t pgtable;
2685 pmd_t _pmd;
2686 int i;
2687
2688 pmdp_clear_flush(vma, haddr, pmd);
2689 /* leave pmd empty until pte is filled */
2690
2691 pgtable = pgtable_trans_huge_withdraw(mm);
2692 pmd_populate(mm, &_pmd, pgtable);
2693
2694 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2695 pte_t *pte, entry;
2696 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2697 entry = pte_mkspecial(entry);
2698 pte = pte_offset_map(&_pmd, haddr);
2699 VM_BUG_ON(!pte_none(*pte));
2700 set_pte_at(mm, haddr, pte, entry);
2701 pte_unmap(pte);
2702 }
2703 smp_wmb(); /* make pte visible before pmd */
2704 pmd_populate(mm, pmd, pgtable);
2705 put_huge_zero_page();
2706 }
2707
2708 void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address,
2709 pmd_t *pmd)
2710 {
2711 struct page *page;
2712 struct mm_struct *mm = vma->vm_mm;
2713 unsigned long haddr = address & HPAGE_PMD_MASK;
2714 unsigned long mmun_start; /* For mmu_notifiers */
2715 unsigned long mmun_end; /* For mmu_notifiers */
2716
2717 BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE);
2718
2719 mmun_start = haddr;
2720 mmun_end = haddr + HPAGE_PMD_SIZE;
2721 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
2722 spin_lock(&mm->page_table_lock);
2723 if (unlikely(!pmd_trans_huge(*pmd))) {
2724 spin_unlock(&mm->page_table_lock);
2725 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2726 return;
2727 }
2728 if (is_huge_zero_pmd(*pmd)) {
2729 __split_huge_zero_page_pmd(vma, haddr, pmd);
2730 spin_unlock(&mm->page_table_lock);
2731 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2732 return;
2733 }
2734 page = pmd_page(*pmd);
2735 VM_BUG_ON(!page_count(page));
2736 get_page(page);
2737 spin_unlock(&mm->page_table_lock);
2738 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2739
2740 split_huge_page(page);
2741
2742 put_page(page);
2743 BUG_ON(pmd_trans_huge(*pmd));
2744 }
2745
2746 void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address,
2747 pmd_t *pmd)
2748 {
2749 struct vm_area_struct *vma;
2750
2751 vma = find_vma(mm, address);
2752 BUG_ON(vma == NULL);
2753 split_huge_page_pmd(vma, address, pmd);
2754 }
2755
2756 static void split_huge_page_address(struct mm_struct *mm,
2757 unsigned long address)
2758 {
2759 pmd_t *pmd;
2760
2761 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2762
2763 pmd = mm_find_pmd(mm, address);
2764 if (!pmd)
2765 return;
2766 /*
2767 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2768 * materialize from under us.
2769 */
2770 split_huge_page_pmd_mm(mm, address, pmd);
2771 }
2772
2773 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2774 unsigned long start,
2775 unsigned long end,
2776 long adjust_next)
2777 {
2778 /*
2779 * If the new start address isn't hpage aligned and it could
2780 * previously contain an hugepage: check if we need to split
2781 * an huge pmd.
2782 */
2783 if (start & ~HPAGE_PMD_MASK &&
2784 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2785 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2786 split_huge_page_address(vma->vm_mm, start);
2787
2788 /*
2789 * If the new end address isn't hpage aligned and it could
2790 * previously contain an hugepage: check if we need to split
2791 * an huge pmd.
2792 */
2793 if (end & ~HPAGE_PMD_MASK &&
2794 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2795 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2796 split_huge_page_address(vma->vm_mm, end);
2797
2798 /*
2799 * If we're also updating the vma->vm_next->vm_start, if the new
2800 * vm_next->vm_start isn't page aligned and it could previously
2801 * contain an hugepage: check if we need to split an huge pmd.
2802 */
2803 if (adjust_next > 0) {
2804 struct vm_area_struct *next = vma->vm_next;
2805 unsigned long nstart = next->vm_start;
2806 nstart += adjust_next << PAGE_SHIFT;
2807 if (nstart & ~HPAGE_PMD_MASK &&
2808 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2809 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2810 split_huge_page_address(next->vm_mm, nstart);
2811 }
2812 }
CJK support for tty framebuffer vt