xref: /openbmc/linux/mm/huge_memory.c (revision 81d67439)
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/mm_inline.h>
16 #include <linux/kthread.h>
17 #include <linux/khugepaged.h>
18 #include <linux/freezer.h>
19 #include <linux/mman.h>
20 #include <asm/tlb.h>
21 #include <asm/pgalloc.h>
22 #include "internal.h"
23 
24 /*
25  * By default transparent hugepage support is enabled for all mappings
26  * and khugepaged scans all mappings. Defrag is only invoked by
27  * khugepaged hugepage allocations and by page faults inside
28  * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
29  * allocations.
30  */
31 unsigned long transparent_hugepage_flags __read_mostly =
32 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
33 	(1<<TRANSPARENT_HUGEPAGE_FLAG)|
34 #endif
35 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
36 	(1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
37 #endif
38 	(1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
39 	(1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
40 
41 /* default scan 8*512 pte (or vmas) every 30 second */
42 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
43 static unsigned int khugepaged_pages_collapsed;
44 static unsigned int khugepaged_full_scans;
45 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
46 /* during fragmentation poll the hugepage allocator once every minute */
47 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
48 static struct task_struct *khugepaged_thread __read_mostly;
49 static DEFINE_MUTEX(khugepaged_mutex);
50 static DEFINE_SPINLOCK(khugepaged_mm_lock);
51 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
52 /*
53  * default collapse hugepages if there is at least one pte mapped like
54  * it would have happened if the vma was large enough during page
55  * fault.
56  */
57 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
58 
59 static int khugepaged(void *none);
60 static int mm_slots_hash_init(void);
61 static int khugepaged_slab_init(void);
62 static void khugepaged_slab_free(void);
63 
64 #define MM_SLOTS_HASH_HEADS 1024
65 static struct hlist_head *mm_slots_hash __read_mostly;
66 static struct kmem_cache *mm_slot_cache __read_mostly;
67 
68 /**
69  * struct mm_slot - hash lookup from mm to mm_slot
70  * @hash: hash collision list
71  * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
72  * @mm: the mm that this information is valid for
73  */
74 struct mm_slot {
75 	struct hlist_node hash;
76 	struct list_head mm_node;
77 	struct mm_struct *mm;
78 };
79 
80 /**
81  * struct khugepaged_scan - cursor for scanning
82  * @mm_head: the head of the mm list to scan
83  * @mm_slot: the current mm_slot we are scanning
84  * @address: the next address inside that to be scanned
85  *
86  * There is only the one khugepaged_scan instance of this cursor structure.
87  */
88 struct khugepaged_scan {
89 	struct list_head mm_head;
90 	struct mm_slot *mm_slot;
91 	unsigned long address;
92 } khugepaged_scan = {
93 	.mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
94 };
95 
96 
97 static int set_recommended_min_free_kbytes(void)
98 {
99 	struct zone *zone;
100 	int nr_zones = 0;
101 	unsigned long recommended_min;
102 	extern int min_free_kbytes;
103 
104 	if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG,
105 		      &transparent_hugepage_flags) &&
106 	    !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
107 		      &transparent_hugepage_flags))
108 		return 0;
109 
110 	for_each_populated_zone(zone)
111 		nr_zones++;
112 
113 	/* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
114 	recommended_min = pageblock_nr_pages * nr_zones * 2;
115 
116 	/*
117 	 * Make sure that on average at least two pageblocks are almost free
118 	 * of another type, one for a migratetype to fall back to and a
119 	 * second to avoid subsequent fallbacks of other types There are 3
120 	 * MIGRATE_TYPES we care about.
121 	 */
122 	recommended_min += pageblock_nr_pages * nr_zones *
123 			   MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
124 
125 	/* don't ever allow to reserve more than 5% of the lowmem */
126 	recommended_min = min(recommended_min,
127 			      (unsigned long) nr_free_buffer_pages() / 20);
128 	recommended_min <<= (PAGE_SHIFT-10);
129 
130 	if (recommended_min > min_free_kbytes)
131 		min_free_kbytes = recommended_min;
132 	setup_per_zone_wmarks();
133 	return 0;
134 }
135 late_initcall(set_recommended_min_free_kbytes);
136 
137 static int start_khugepaged(void)
138 {
139 	int err = 0;
140 	if (khugepaged_enabled()) {
141 		int wakeup;
142 		if (unlikely(!mm_slot_cache || !mm_slots_hash)) {
143 			err = -ENOMEM;
144 			goto out;
145 		}
146 		mutex_lock(&khugepaged_mutex);
147 		if (!khugepaged_thread)
148 			khugepaged_thread = kthread_run(khugepaged, NULL,
149 							"khugepaged");
150 		if (unlikely(IS_ERR(khugepaged_thread))) {
151 			printk(KERN_ERR
152 			       "khugepaged: kthread_run(khugepaged) failed\n");
153 			err = PTR_ERR(khugepaged_thread);
154 			khugepaged_thread = NULL;
155 		}
156 		wakeup = !list_empty(&khugepaged_scan.mm_head);
157 		mutex_unlock(&khugepaged_mutex);
158 		if (wakeup)
159 			wake_up_interruptible(&khugepaged_wait);
160 
161 		set_recommended_min_free_kbytes();
162 	} else
163 		/* wakeup to exit */
164 		wake_up_interruptible(&khugepaged_wait);
165 out:
166 	return err;
167 }
168 
169 #ifdef CONFIG_SYSFS
170 
171 static ssize_t double_flag_show(struct kobject *kobj,
172 				struct kobj_attribute *attr, char *buf,
173 				enum transparent_hugepage_flag enabled,
174 				enum transparent_hugepage_flag req_madv)
175 {
176 	if (test_bit(enabled, &transparent_hugepage_flags)) {
177 		VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
178 		return sprintf(buf, "[always] madvise never\n");
179 	} else if (test_bit(req_madv, &transparent_hugepage_flags))
180 		return sprintf(buf, "always [madvise] never\n");
181 	else
182 		return sprintf(buf, "always madvise [never]\n");
183 }
184 static ssize_t double_flag_store(struct kobject *kobj,
185 				 struct kobj_attribute *attr,
186 				 const char *buf, size_t count,
187 				 enum transparent_hugepage_flag enabled,
188 				 enum transparent_hugepage_flag req_madv)
189 {
190 	if (!memcmp("always", buf,
191 		    min(sizeof("always")-1, count))) {
192 		set_bit(enabled, &transparent_hugepage_flags);
193 		clear_bit(req_madv, &transparent_hugepage_flags);
194 	} else if (!memcmp("madvise", buf,
195 			   min(sizeof("madvise")-1, count))) {
196 		clear_bit(enabled, &transparent_hugepage_flags);
197 		set_bit(req_madv, &transparent_hugepage_flags);
198 	} else if (!memcmp("never", buf,
199 			   min(sizeof("never")-1, count))) {
200 		clear_bit(enabled, &transparent_hugepage_flags);
201 		clear_bit(req_madv, &transparent_hugepage_flags);
202 	} else
203 		return -EINVAL;
204 
205 	return count;
206 }
207 
208 static ssize_t enabled_show(struct kobject *kobj,
209 			    struct kobj_attribute *attr, char *buf)
210 {
211 	return double_flag_show(kobj, attr, buf,
212 				TRANSPARENT_HUGEPAGE_FLAG,
213 				TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
214 }
215 static ssize_t enabled_store(struct kobject *kobj,
216 			     struct kobj_attribute *attr,
217 			     const char *buf, size_t count)
218 {
219 	ssize_t ret;
220 
221 	ret = double_flag_store(kobj, attr, buf, count,
222 				TRANSPARENT_HUGEPAGE_FLAG,
223 				TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
224 
225 	if (ret > 0) {
226 		int err = start_khugepaged();
227 		if (err)
228 			ret = err;
229 	}
230 
231 	if (ret > 0 &&
232 	    (test_bit(TRANSPARENT_HUGEPAGE_FLAG,
233 		      &transparent_hugepage_flags) ||
234 	     test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
235 		      &transparent_hugepage_flags)))
236 		set_recommended_min_free_kbytes();
237 
238 	return ret;
239 }
240 static struct kobj_attribute enabled_attr =
241 	__ATTR(enabled, 0644, enabled_show, enabled_store);
242 
243 static ssize_t single_flag_show(struct kobject *kobj,
244 				struct kobj_attribute *attr, char *buf,
245 				enum transparent_hugepage_flag flag)
246 {
247 	return sprintf(buf, "%d\n",
248 		       !!test_bit(flag, &transparent_hugepage_flags));
249 }
250 
251 static ssize_t single_flag_store(struct kobject *kobj,
252 				 struct kobj_attribute *attr,
253 				 const char *buf, size_t count,
254 				 enum transparent_hugepage_flag flag)
255 {
256 	unsigned long value;
257 	int ret;
258 
259 	ret = kstrtoul(buf, 10, &value);
260 	if (ret < 0)
261 		return ret;
262 	if (value > 1)
263 		return -EINVAL;
264 
265 	if (value)
266 		set_bit(flag, &transparent_hugepage_flags);
267 	else
268 		clear_bit(flag, &transparent_hugepage_flags);
269 
270 	return count;
271 }
272 
273 /*
274  * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
275  * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
276  * memory just to allocate one more hugepage.
277  */
278 static ssize_t defrag_show(struct kobject *kobj,
279 			   struct kobj_attribute *attr, char *buf)
280 {
281 	return double_flag_show(kobj, attr, buf,
282 				TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
283 				TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
284 }
285 static ssize_t defrag_store(struct kobject *kobj,
286 			    struct kobj_attribute *attr,
287 			    const char *buf, size_t count)
288 {
289 	return double_flag_store(kobj, attr, buf, count,
290 				 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
291 				 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
292 }
293 static struct kobj_attribute defrag_attr =
294 	__ATTR(defrag, 0644, defrag_show, defrag_store);
295 
296 #ifdef CONFIG_DEBUG_VM
297 static ssize_t debug_cow_show(struct kobject *kobj,
298 				struct kobj_attribute *attr, char *buf)
299 {
300 	return single_flag_show(kobj, attr, buf,
301 				TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
302 }
303 static ssize_t debug_cow_store(struct kobject *kobj,
304 			       struct kobj_attribute *attr,
305 			       const char *buf, size_t count)
306 {
307 	return single_flag_store(kobj, attr, buf, count,
308 				 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
309 }
310 static struct kobj_attribute debug_cow_attr =
311 	__ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
312 #endif /* CONFIG_DEBUG_VM */
313 
314 static struct attribute *hugepage_attr[] = {
315 	&enabled_attr.attr,
316 	&defrag_attr.attr,
317 #ifdef CONFIG_DEBUG_VM
318 	&debug_cow_attr.attr,
319 #endif
320 	NULL,
321 };
322 
323 static struct attribute_group hugepage_attr_group = {
324 	.attrs = hugepage_attr,
325 };
326 
327 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
328 					 struct kobj_attribute *attr,
329 					 char *buf)
330 {
331 	return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
332 }
333 
334 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
335 					  struct kobj_attribute *attr,
336 					  const char *buf, size_t count)
337 {
338 	unsigned long msecs;
339 	int err;
340 
341 	err = strict_strtoul(buf, 10, &msecs);
342 	if (err || msecs > UINT_MAX)
343 		return -EINVAL;
344 
345 	khugepaged_scan_sleep_millisecs = msecs;
346 	wake_up_interruptible(&khugepaged_wait);
347 
348 	return count;
349 }
350 static struct kobj_attribute scan_sleep_millisecs_attr =
351 	__ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
352 	       scan_sleep_millisecs_store);
353 
354 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
355 					  struct kobj_attribute *attr,
356 					  char *buf)
357 {
358 	return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
359 }
360 
361 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
362 					   struct kobj_attribute *attr,
363 					   const char *buf, size_t count)
364 {
365 	unsigned long msecs;
366 	int err;
367 
368 	err = strict_strtoul(buf, 10, &msecs);
369 	if (err || msecs > UINT_MAX)
370 		return -EINVAL;
371 
372 	khugepaged_alloc_sleep_millisecs = msecs;
373 	wake_up_interruptible(&khugepaged_wait);
374 
375 	return count;
376 }
377 static struct kobj_attribute alloc_sleep_millisecs_attr =
378 	__ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
379 	       alloc_sleep_millisecs_store);
380 
381 static ssize_t pages_to_scan_show(struct kobject *kobj,
382 				  struct kobj_attribute *attr,
383 				  char *buf)
384 {
385 	return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
386 }
387 static ssize_t pages_to_scan_store(struct kobject *kobj,
388 				   struct kobj_attribute *attr,
389 				   const char *buf, size_t count)
390 {
391 	int err;
392 	unsigned long pages;
393 
394 	err = strict_strtoul(buf, 10, &pages);
395 	if (err || !pages || pages > UINT_MAX)
396 		return -EINVAL;
397 
398 	khugepaged_pages_to_scan = pages;
399 
400 	return count;
401 }
402 static struct kobj_attribute pages_to_scan_attr =
403 	__ATTR(pages_to_scan, 0644, pages_to_scan_show,
404 	       pages_to_scan_store);
405 
406 static ssize_t pages_collapsed_show(struct kobject *kobj,
407 				    struct kobj_attribute *attr,
408 				    char *buf)
409 {
410 	return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
411 }
412 static struct kobj_attribute pages_collapsed_attr =
413 	__ATTR_RO(pages_collapsed);
414 
415 static ssize_t full_scans_show(struct kobject *kobj,
416 			       struct kobj_attribute *attr,
417 			       char *buf)
418 {
419 	return sprintf(buf, "%u\n", khugepaged_full_scans);
420 }
421 static struct kobj_attribute full_scans_attr =
422 	__ATTR_RO(full_scans);
423 
424 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
425 				      struct kobj_attribute *attr, char *buf)
426 {
427 	return single_flag_show(kobj, attr, buf,
428 				TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
429 }
430 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
431 				       struct kobj_attribute *attr,
432 				       const char *buf, size_t count)
433 {
434 	return single_flag_store(kobj, attr, buf, count,
435 				 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
436 }
437 static struct kobj_attribute khugepaged_defrag_attr =
438 	__ATTR(defrag, 0644, khugepaged_defrag_show,
439 	       khugepaged_defrag_store);
440 
441 /*
442  * max_ptes_none controls if khugepaged should collapse hugepages over
443  * any unmapped ptes in turn potentially increasing the memory
444  * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
445  * reduce the available free memory in the system as it
446  * runs. Increasing max_ptes_none will instead potentially reduce the
447  * free memory in the system during the khugepaged scan.
448  */
449 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
450 					     struct kobj_attribute *attr,
451 					     char *buf)
452 {
453 	return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
454 }
455 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
456 					      struct kobj_attribute *attr,
457 					      const char *buf, size_t count)
458 {
459 	int err;
460 	unsigned long max_ptes_none;
461 
462 	err = strict_strtoul(buf, 10, &max_ptes_none);
463 	if (err || max_ptes_none > HPAGE_PMD_NR-1)
464 		return -EINVAL;
465 
466 	khugepaged_max_ptes_none = max_ptes_none;
467 
468 	return count;
469 }
470 static struct kobj_attribute khugepaged_max_ptes_none_attr =
471 	__ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
472 	       khugepaged_max_ptes_none_store);
473 
474 static struct attribute *khugepaged_attr[] = {
475 	&khugepaged_defrag_attr.attr,
476 	&khugepaged_max_ptes_none_attr.attr,
477 	&pages_to_scan_attr.attr,
478 	&pages_collapsed_attr.attr,
479 	&full_scans_attr.attr,
480 	&scan_sleep_millisecs_attr.attr,
481 	&alloc_sleep_millisecs_attr.attr,
482 	NULL,
483 };
484 
485 static struct attribute_group khugepaged_attr_group = {
486 	.attrs = khugepaged_attr,
487 	.name = "khugepaged",
488 };
489 #endif /* CONFIG_SYSFS */
490 
491 static int __init hugepage_init(void)
492 {
493 	int err;
494 #ifdef CONFIG_SYSFS
495 	static struct kobject *hugepage_kobj;
496 #endif
497 
498 	err = -EINVAL;
499 	if (!has_transparent_hugepage()) {
500 		transparent_hugepage_flags = 0;
501 		goto out;
502 	}
503 
504 #ifdef CONFIG_SYSFS
505 	err = -ENOMEM;
506 	hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
507 	if (unlikely(!hugepage_kobj)) {
508 		printk(KERN_ERR "hugepage: failed kobject create\n");
509 		goto out;
510 	}
511 
512 	err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group);
513 	if (err) {
514 		printk(KERN_ERR "hugepage: failed register hugeage group\n");
515 		goto out;
516 	}
517 
518 	err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group);
519 	if (err) {
520 		printk(KERN_ERR "hugepage: failed register hugeage group\n");
521 		goto out;
522 	}
523 #endif
524 
525 	err = khugepaged_slab_init();
526 	if (err)
527 		goto out;
528 
529 	err = mm_slots_hash_init();
530 	if (err) {
531 		khugepaged_slab_free();
532 		goto out;
533 	}
534 
535 	/*
536 	 * By default disable transparent hugepages on smaller systems,
537 	 * where the extra memory used could hurt more than TLB overhead
538 	 * is likely to save.  The admin can still enable it through /sys.
539 	 */
540 	if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
541 		transparent_hugepage_flags = 0;
542 
543 	start_khugepaged();
544 
545 	set_recommended_min_free_kbytes();
546 
547 out:
548 	return err;
549 }
550 module_init(hugepage_init)
551 
552 static int __init setup_transparent_hugepage(char *str)
553 {
554 	int ret = 0;
555 	if (!str)
556 		goto out;
557 	if (!strcmp(str, "always")) {
558 		set_bit(TRANSPARENT_HUGEPAGE_FLAG,
559 			&transparent_hugepage_flags);
560 		clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
561 			  &transparent_hugepage_flags);
562 		ret = 1;
563 	} else if (!strcmp(str, "madvise")) {
564 		clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
565 			  &transparent_hugepage_flags);
566 		set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
567 			&transparent_hugepage_flags);
568 		ret = 1;
569 	} else if (!strcmp(str, "never")) {
570 		clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
571 			  &transparent_hugepage_flags);
572 		clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
573 			  &transparent_hugepage_flags);
574 		ret = 1;
575 	}
576 out:
577 	if (!ret)
578 		printk(KERN_WARNING
579 		       "transparent_hugepage= cannot parse, ignored\n");
580 	return ret;
581 }
582 __setup("transparent_hugepage=", setup_transparent_hugepage);
583 
584 static void prepare_pmd_huge_pte(pgtable_t pgtable,
585 				 struct mm_struct *mm)
586 {
587 	assert_spin_locked(&mm->page_table_lock);
588 
589 	/* FIFO */
590 	if (!mm->pmd_huge_pte)
591 		INIT_LIST_HEAD(&pgtable->lru);
592 	else
593 		list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
594 	mm->pmd_huge_pte = pgtable;
595 }
596 
597 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
598 {
599 	if (likely(vma->vm_flags & VM_WRITE))
600 		pmd = pmd_mkwrite(pmd);
601 	return pmd;
602 }
603 
604 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
605 					struct vm_area_struct *vma,
606 					unsigned long haddr, pmd_t *pmd,
607 					struct page *page)
608 {
609 	int ret = 0;
610 	pgtable_t pgtable;
611 
612 	VM_BUG_ON(!PageCompound(page));
613 	pgtable = pte_alloc_one(mm, haddr);
614 	if (unlikely(!pgtable)) {
615 		mem_cgroup_uncharge_page(page);
616 		put_page(page);
617 		return VM_FAULT_OOM;
618 	}
619 
620 	clear_huge_page(page, haddr, HPAGE_PMD_NR);
621 	__SetPageUptodate(page);
622 
623 	spin_lock(&mm->page_table_lock);
624 	if (unlikely(!pmd_none(*pmd))) {
625 		spin_unlock(&mm->page_table_lock);
626 		mem_cgroup_uncharge_page(page);
627 		put_page(page);
628 		pte_free(mm, pgtable);
629 	} else {
630 		pmd_t entry;
631 		entry = mk_pmd(page, vma->vm_page_prot);
632 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
633 		entry = pmd_mkhuge(entry);
634 		/*
635 		 * The spinlocking to take the lru_lock inside
636 		 * page_add_new_anon_rmap() acts as a full memory
637 		 * barrier to be sure clear_huge_page writes become
638 		 * visible after the set_pmd_at() write.
639 		 */
640 		page_add_new_anon_rmap(page, vma, haddr);
641 		set_pmd_at(mm, haddr, pmd, entry);
642 		prepare_pmd_huge_pte(pgtable, mm);
643 		add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
644 		spin_unlock(&mm->page_table_lock);
645 	}
646 
647 	return ret;
648 }
649 
650 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
651 {
652 	return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
653 }
654 
655 static inline struct page *alloc_hugepage_vma(int defrag,
656 					      struct vm_area_struct *vma,
657 					      unsigned long haddr, int nd,
658 					      gfp_t extra_gfp)
659 {
660 	return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
661 			       HPAGE_PMD_ORDER, vma, haddr, nd);
662 }
663 
664 #ifndef CONFIG_NUMA
665 static inline struct page *alloc_hugepage(int defrag)
666 {
667 	return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
668 			   HPAGE_PMD_ORDER);
669 }
670 #endif
671 
672 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
673 			       unsigned long address, pmd_t *pmd,
674 			       unsigned int flags)
675 {
676 	struct page *page;
677 	unsigned long haddr = address & HPAGE_PMD_MASK;
678 	pte_t *pte;
679 
680 	if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
681 		if (unlikely(anon_vma_prepare(vma)))
682 			return VM_FAULT_OOM;
683 		if (unlikely(khugepaged_enter(vma)))
684 			return VM_FAULT_OOM;
685 		page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
686 					  vma, haddr, numa_node_id(), 0);
687 		if (unlikely(!page)) {
688 			count_vm_event(THP_FAULT_FALLBACK);
689 			goto out;
690 		}
691 		count_vm_event(THP_FAULT_ALLOC);
692 		if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
693 			put_page(page);
694 			goto out;
695 		}
696 
697 		return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
698 	}
699 out:
700 	/*
701 	 * Use __pte_alloc instead of pte_alloc_map, because we can't
702 	 * run pte_offset_map on the pmd, if an huge pmd could
703 	 * materialize from under us from a different thread.
704 	 */
705 	if (unlikely(__pte_alloc(mm, vma, pmd, address)))
706 		return VM_FAULT_OOM;
707 	/* if an huge pmd materialized from under us just retry later */
708 	if (unlikely(pmd_trans_huge(*pmd)))
709 		return 0;
710 	/*
711 	 * A regular pmd is established and it can't morph into a huge pmd
712 	 * from under us anymore at this point because we hold the mmap_sem
713 	 * read mode and khugepaged takes it in write mode. So now it's
714 	 * safe to run pte_offset_map().
715 	 */
716 	pte = pte_offset_map(pmd, address);
717 	return handle_pte_fault(mm, vma, address, pte, pmd, flags);
718 }
719 
720 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
721 		  pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
722 		  struct vm_area_struct *vma)
723 {
724 	struct page *src_page;
725 	pmd_t pmd;
726 	pgtable_t pgtable;
727 	int ret;
728 
729 	ret = -ENOMEM;
730 	pgtable = pte_alloc_one(dst_mm, addr);
731 	if (unlikely(!pgtable))
732 		goto out;
733 
734 	spin_lock(&dst_mm->page_table_lock);
735 	spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
736 
737 	ret = -EAGAIN;
738 	pmd = *src_pmd;
739 	if (unlikely(!pmd_trans_huge(pmd))) {
740 		pte_free(dst_mm, pgtable);
741 		goto out_unlock;
742 	}
743 	if (unlikely(pmd_trans_splitting(pmd))) {
744 		/* split huge page running from under us */
745 		spin_unlock(&src_mm->page_table_lock);
746 		spin_unlock(&dst_mm->page_table_lock);
747 		pte_free(dst_mm, pgtable);
748 
749 		wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
750 		goto out;
751 	}
752 	src_page = pmd_page(pmd);
753 	VM_BUG_ON(!PageHead(src_page));
754 	get_page(src_page);
755 	page_dup_rmap(src_page);
756 	add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
757 
758 	pmdp_set_wrprotect(src_mm, addr, src_pmd);
759 	pmd = pmd_mkold(pmd_wrprotect(pmd));
760 	set_pmd_at(dst_mm, addr, dst_pmd, pmd);
761 	prepare_pmd_huge_pte(pgtable, dst_mm);
762 
763 	ret = 0;
764 out_unlock:
765 	spin_unlock(&src_mm->page_table_lock);
766 	spin_unlock(&dst_mm->page_table_lock);
767 out:
768 	return ret;
769 }
770 
771 /* no "address" argument so destroys page coloring of some arch */
772 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
773 {
774 	pgtable_t pgtable;
775 
776 	assert_spin_locked(&mm->page_table_lock);
777 
778 	/* FIFO */
779 	pgtable = mm->pmd_huge_pte;
780 	if (list_empty(&pgtable->lru))
781 		mm->pmd_huge_pte = NULL;
782 	else {
783 		mm->pmd_huge_pte = list_entry(pgtable->lru.next,
784 					      struct page, lru);
785 		list_del(&pgtable->lru);
786 	}
787 	return pgtable;
788 }
789 
790 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
791 					struct vm_area_struct *vma,
792 					unsigned long address,
793 					pmd_t *pmd, pmd_t orig_pmd,
794 					struct page *page,
795 					unsigned long haddr)
796 {
797 	pgtable_t pgtable;
798 	pmd_t _pmd;
799 	int ret = 0, i;
800 	struct page **pages;
801 
802 	pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
803 			GFP_KERNEL);
804 	if (unlikely(!pages)) {
805 		ret |= VM_FAULT_OOM;
806 		goto out;
807 	}
808 
809 	for (i = 0; i < HPAGE_PMD_NR; i++) {
810 		pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
811 					       __GFP_OTHER_NODE,
812 					       vma, address, page_to_nid(page));
813 		if (unlikely(!pages[i] ||
814 			     mem_cgroup_newpage_charge(pages[i], mm,
815 						       GFP_KERNEL))) {
816 			if (pages[i])
817 				put_page(pages[i]);
818 			mem_cgroup_uncharge_start();
819 			while (--i >= 0) {
820 				mem_cgroup_uncharge_page(pages[i]);
821 				put_page(pages[i]);
822 			}
823 			mem_cgroup_uncharge_end();
824 			kfree(pages);
825 			ret |= VM_FAULT_OOM;
826 			goto out;
827 		}
828 	}
829 
830 	for (i = 0; i < HPAGE_PMD_NR; i++) {
831 		copy_user_highpage(pages[i], page + i,
832 				   haddr + PAGE_SHIFT*i, vma);
833 		__SetPageUptodate(pages[i]);
834 		cond_resched();
835 	}
836 
837 	spin_lock(&mm->page_table_lock);
838 	if (unlikely(!pmd_same(*pmd, orig_pmd)))
839 		goto out_free_pages;
840 	VM_BUG_ON(!PageHead(page));
841 
842 	pmdp_clear_flush_notify(vma, haddr, pmd);
843 	/* leave pmd empty until pte is filled */
844 
845 	pgtable = get_pmd_huge_pte(mm);
846 	pmd_populate(mm, &_pmd, pgtable);
847 
848 	for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
849 		pte_t *pte, entry;
850 		entry = mk_pte(pages[i], vma->vm_page_prot);
851 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
852 		page_add_new_anon_rmap(pages[i], vma, haddr);
853 		pte = pte_offset_map(&_pmd, haddr);
854 		VM_BUG_ON(!pte_none(*pte));
855 		set_pte_at(mm, haddr, pte, entry);
856 		pte_unmap(pte);
857 	}
858 	kfree(pages);
859 
860 	mm->nr_ptes++;
861 	smp_wmb(); /* make pte visible before pmd */
862 	pmd_populate(mm, pmd, pgtable);
863 	page_remove_rmap(page);
864 	spin_unlock(&mm->page_table_lock);
865 
866 	ret |= VM_FAULT_WRITE;
867 	put_page(page);
868 
869 out:
870 	return ret;
871 
872 out_free_pages:
873 	spin_unlock(&mm->page_table_lock);
874 	mem_cgroup_uncharge_start();
875 	for (i = 0; i < HPAGE_PMD_NR; i++) {
876 		mem_cgroup_uncharge_page(pages[i]);
877 		put_page(pages[i]);
878 	}
879 	mem_cgroup_uncharge_end();
880 	kfree(pages);
881 	goto out;
882 }
883 
884 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
885 			unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
886 {
887 	int ret = 0;
888 	struct page *page, *new_page;
889 	unsigned long haddr;
890 
891 	VM_BUG_ON(!vma->anon_vma);
892 	spin_lock(&mm->page_table_lock);
893 	if (unlikely(!pmd_same(*pmd, orig_pmd)))
894 		goto out_unlock;
895 
896 	page = pmd_page(orig_pmd);
897 	VM_BUG_ON(!PageCompound(page) || !PageHead(page));
898 	haddr = address & HPAGE_PMD_MASK;
899 	if (page_mapcount(page) == 1) {
900 		pmd_t entry;
901 		entry = pmd_mkyoung(orig_pmd);
902 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
903 		if (pmdp_set_access_flags(vma, haddr, pmd, entry,  1))
904 			update_mmu_cache(vma, address, entry);
905 		ret |= VM_FAULT_WRITE;
906 		goto out_unlock;
907 	}
908 	get_page(page);
909 	spin_unlock(&mm->page_table_lock);
910 
911 	if (transparent_hugepage_enabled(vma) &&
912 	    !transparent_hugepage_debug_cow())
913 		new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
914 					      vma, haddr, numa_node_id(), 0);
915 	else
916 		new_page = NULL;
917 
918 	if (unlikely(!new_page)) {
919 		count_vm_event(THP_FAULT_FALLBACK);
920 		ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
921 						   pmd, orig_pmd, page, haddr);
922 		put_page(page);
923 		goto out;
924 	}
925 	count_vm_event(THP_FAULT_ALLOC);
926 
927 	if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
928 		put_page(new_page);
929 		put_page(page);
930 		ret |= VM_FAULT_OOM;
931 		goto out;
932 	}
933 
934 	copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
935 	__SetPageUptodate(new_page);
936 
937 	spin_lock(&mm->page_table_lock);
938 	put_page(page);
939 	if (unlikely(!pmd_same(*pmd, orig_pmd))) {
940 		mem_cgroup_uncharge_page(new_page);
941 		put_page(new_page);
942 	} else {
943 		pmd_t entry;
944 		VM_BUG_ON(!PageHead(page));
945 		entry = mk_pmd(new_page, vma->vm_page_prot);
946 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
947 		entry = pmd_mkhuge(entry);
948 		pmdp_clear_flush_notify(vma, haddr, pmd);
949 		page_add_new_anon_rmap(new_page, vma, haddr);
950 		set_pmd_at(mm, haddr, pmd, entry);
951 		update_mmu_cache(vma, address, entry);
952 		page_remove_rmap(page);
953 		put_page(page);
954 		ret |= VM_FAULT_WRITE;
955 	}
956 out_unlock:
957 	spin_unlock(&mm->page_table_lock);
958 out:
959 	return ret;
960 }
961 
962 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
963 				   unsigned long addr,
964 				   pmd_t *pmd,
965 				   unsigned int flags)
966 {
967 	struct page *page = NULL;
968 
969 	assert_spin_locked(&mm->page_table_lock);
970 
971 	if (flags & FOLL_WRITE && !pmd_write(*pmd))
972 		goto out;
973 
974 	page = pmd_page(*pmd);
975 	VM_BUG_ON(!PageHead(page));
976 	if (flags & FOLL_TOUCH) {
977 		pmd_t _pmd;
978 		/*
979 		 * We should set the dirty bit only for FOLL_WRITE but
980 		 * for now the dirty bit in the pmd is meaningless.
981 		 * And if the dirty bit will become meaningful and
982 		 * we'll only set it with FOLL_WRITE, an atomic
983 		 * set_bit will be required on the pmd to set the
984 		 * young bit, instead of the current set_pmd_at.
985 		 */
986 		_pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
987 		set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
988 	}
989 	page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
990 	VM_BUG_ON(!PageCompound(page));
991 	if (flags & FOLL_GET)
992 		get_page(page);
993 
994 out:
995 	return page;
996 }
997 
998 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
999 		 pmd_t *pmd)
1000 {
1001 	int ret = 0;
1002 
1003 	spin_lock(&tlb->mm->page_table_lock);
1004 	if (likely(pmd_trans_huge(*pmd))) {
1005 		if (unlikely(pmd_trans_splitting(*pmd))) {
1006 			spin_unlock(&tlb->mm->page_table_lock);
1007 			wait_split_huge_page(vma->anon_vma,
1008 					     pmd);
1009 		} else {
1010 			struct page *page;
1011 			pgtable_t pgtable;
1012 			pgtable = get_pmd_huge_pte(tlb->mm);
1013 			page = pmd_page(*pmd);
1014 			pmd_clear(pmd);
1015 			page_remove_rmap(page);
1016 			VM_BUG_ON(page_mapcount(page) < 0);
1017 			add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1018 			VM_BUG_ON(!PageHead(page));
1019 			spin_unlock(&tlb->mm->page_table_lock);
1020 			tlb_remove_page(tlb, page);
1021 			pte_free(tlb->mm, pgtable);
1022 			ret = 1;
1023 		}
1024 	} else
1025 		spin_unlock(&tlb->mm->page_table_lock);
1026 
1027 	return ret;
1028 }
1029 
1030 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1031 		unsigned long addr, unsigned long end,
1032 		unsigned char *vec)
1033 {
1034 	int ret = 0;
1035 
1036 	spin_lock(&vma->vm_mm->page_table_lock);
1037 	if (likely(pmd_trans_huge(*pmd))) {
1038 		ret = !pmd_trans_splitting(*pmd);
1039 		spin_unlock(&vma->vm_mm->page_table_lock);
1040 		if (unlikely(!ret))
1041 			wait_split_huge_page(vma->anon_vma, pmd);
1042 		else {
1043 			/*
1044 			 * All logical pages in the range are present
1045 			 * if backed by a huge page.
1046 			 */
1047 			memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1048 		}
1049 	} else
1050 		spin_unlock(&vma->vm_mm->page_table_lock);
1051 
1052 	return ret;
1053 }
1054 
1055 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1056 		unsigned long addr, pgprot_t newprot)
1057 {
1058 	struct mm_struct *mm = vma->vm_mm;
1059 	int ret = 0;
1060 
1061 	spin_lock(&mm->page_table_lock);
1062 	if (likely(pmd_trans_huge(*pmd))) {
1063 		if (unlikely(pmd_trans_splitting(*pmd))) {
1064 			spin_unlock(&mm->page_table_lock);
1065 			wait_split_huge_page(vma->anon_vma, pmd);
1066 		} else {
1067 			pmd_t entry;
1068 
1069 			entry = pmdp_get_and_clear(mm, addr, pmd);
1070 			entry = pmd_modify(entry, newprot);
1071 			set_pmd_at(mm, addr, pmd, entry);
1072 			spin_unlock(&vma->vm_mm->page_table_lock);
1073 			flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
1074 			ret = 1;
1075 		}
1076 	} else
1077 		spin_unlock(&vma->vm_mm->page_table_lock);
1078 
1079 	return ret;
1080 }
1081 
1082 pmd_t *page_check_address_pmd(struct page *page,
1083 			      struct mm_struct *mm,
1084 			      unsigned long address,
1085 			      enum page_check_address_pmd_flag flag)
1086 {
1087 	pgd_t *pgd;
1088 	pud_t *pud;
1089 	pmd_t *pmd, *ret = NULL;
1090 
1091 	if (address & ~HPAGE_PMD_MASK)
1092 		goto out;
1093 
1094 	pgd = pgd_offset(mm, address);
1095 	if (!pgd_present(*pgd))
1096 		goto out;
1097 
1098 	pud = pud_offset(pgd, address);
1099 	if (!pud_present(*pud))
1100 		goto out;
1101 
1102 	pmd = pmd_offset(pud, address);
1103 	if (pmd_none(*pmd))
1104 		goto out;
1105 	if (pmd_page(*pmd) != page)
1106 		goto out;
1107 	/*
1108 	 * split_vma() may create temporary aliased mappings. There is
1109 	 * no risk as long as all huge pmd are found and have their
1110 	 * splitting bit set before __split_huge_page_refcount
1111 	 * runs. Finding the same huge pmd more than once during the
1112 	 * same rmap walk is not a problem.
1113 	 */
1114 	if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1115 	    pmd_trans_splitting(*pmd))
1116 		goto out;
1117 	if (pmd_trans_huge(*pmd)) {
1118 		VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1119 			  !pmd_trans_splitting(*pmd));
1120 		ret = pmd;
1121 	}
1122 out:
1123 	return ret;
1124 }
1125 
1126 static int __split_huge_page_splitting(struct page *page,
1127 				       struct vm_area_struct *vma,
1128 				       unsigned long address)
1129 {
1130 	struct mm_struct *mm = vma->vm_mm;
1131 	pmd_t *pmd;
1132 	int ret = 0;
1133 
1134 	spin_lock(&mm->page_table_lock);
1135 	pmd = page_check_address_pmd(page, mm, address,
1136 				     PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1137 	if (pmd) {
1138 		/*
1139 		 * We can't temporarily set the pmd to null in order
1140 		 * to split it, the pmd must remain marked huge at all
1141 		 * times or the VM won't take the pmd_trans_huge paths
1142 		 * and it won't wait on the anon_vma->root->mutex to
1143 		 * serialize against split_huge_page*.
1144 		 */
1145 		pmdp_splitting_flush_notify(vma, address, pmd);
1146 		ret = 1;
1147 	}
1148 	spin_unlock(&mm->page_table_lock);
1149 
1150 	return ret;
1151 }
1152 
1153 static void __split_huge_page_refcount(struct page *page)
1154 {
1155 	int i;
1156 	unsigned long head_index = page->index;
1157 	struct zone *zone = page_zone(page);
1158 	int zonestat;
1159 
1160 	/* prevent PageLRU to go away from under us, and freeze lru stats */
1161 	spin_lock_irq(&zone->lru_lock);
1162 	compound_lock(page);
1163 
1164 	for (i = 1; i < HPAGE_PMD_NR; i++) {
1165 		struct page *page_tail = page + i;
1166 
1167 		/* tail_page->_count cannot change */
1168 		atomic_sub(atomic_read(&page_tail->_count), &page->_count);
1169 		BUG_ON(page_count(page) <= 0);
1170 		atomic_add(page_mapcount(page) + 1, &page_tail->_count);
1171 		BUG_ON(atomic_read(&page_tail->_count) <= 0);
1172 
1173 		/* after clearing PageTail the gup refcount can be released */
1174 		smp_mb();
1175 
1176 		/*
1177 		 * retain hwpoison flag of the poisoned tail page:
1178 		 *   fix for the unsuitable process killed on Guest Machine(KVM)
1179 		 *   by the memory-failure.
1180 		 */
1181 		page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1182 		page_tail->flags |= (page->flags &
1183 				     ((1L << PG_referenced) |
1184 				      (1L << PG_swapbacked) |
1185 				      (1L << PG_mlocked) |
1186 				      (1L << PG_uptodate)));
1187 		page_tail->flags |= (1L << PG_dirty);
1188 
1189 		/*
1190 		 * 1) clear PageTail before overwriting first_page
1191 		 * 2) clear PageTail before clearing PageHead for VM_BUG_ON
1192 		 */
1193 		smp_wmb();
1194 
1195 		/*
1196 		 * __split_huge_page_splitting() already set the
1197 		 * splitting bit in all pmd that could map this
1198 		 * hugepage, that will ensure no CPU can alter the
1199 		 * mapcount on the head page. The mapcount is only
1200 		 * accounted in the head page and it has to be
1201 		 * transferred to all tail pages in the below code. So
1202 		 * for this code to be safe, the split the mapcount
1203 		 * can't change. But that doesn't mean userland can't
1204 		 * keep changing and reading the page contents while
1205 		 * we transfer the mapcount, so the pmd splitting
1206 		 * status is achieved setting a reserved bit in the
1207 		 * pmd, not by clearing the present bit.
1208 		*/
1209 		BUG_ON(page_mapcount(page_tail));
1210 		page_tail->_mapcount = page->_mapcount;
1211 
1212 		BUG_ON(page_tail->mapping);
1213 		page_tail->mapping = page->mapping;
1214 
1215 		page_tail->index = ++head_index;
1216 
1217 		BUG_ON(!PageAnon(page_tail));
1218 		BUG_ON(!PageUptodate(page_tail));
1219 		BUG_ON(!PageDirty(page_tail));
1220 		BUG_ON(!PageSwapBacked(page_tail));
1221 
1222 		mem_cgroup_split_huge_fixup(page, page_tail);
1223 
1224 		lru_add_page_tail(zone, page, page_tail);
1225 	}
1226 
1227 	__dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1228 	__mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1229 
1230 	/*
1231 	 * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics,
1232 	 * so adjust those appropriately if this page is on the LRU.
1233 	 */
1234 	if (PageLRU(page)) {
1235 		zonestat = NR_LRU_BASE + page_lru(page);
1236 		__mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1));
1237 	}
1238 
1239 	ClearPageCompound(page);
1240 	compound_unlock(page);
1241 	spin_unlock_irq(&zone->lru_lock);
1242 
1243 	for (i = 1; i < HPAGE_PMD_NR; i++) {
1244 		struct page *page_tail = page + i;
1245 		BUG_ON(page_count(page_tail) <= 0);
1246 		/*
1247 		 * Tail pages may be freed if there wasn't any mapping
1248 		 * like if add_to_swap() is running on a lru page that
1249 		 * had its mapping zapped. And freeing these pages
1250 		 * requires taking the lru_lock so we do the put_page
1251 		 * of the tail pages after the split is complete.
1252 		 */
1253 		put_page(page_tail);
1254 	}
1255 
1256 	/*
1257 	 * Only the head page (now become a regular page) is required
1258 	 * to be pinned by the caller.
1259 	 */
1260 	BUG_ON(page_count(page) <= 0);
1261 }
1262 
1263 static int __split_huge_page_map(struct page *page,
1264 				 struct vm_area_struct *vma,
1265 				 unsigned long address)
1266 {
1267 	struct mm_struct *mm = vma->vm_mm;
1268 	pmd_t *pmd, _pmd;
1269 	int ret = 0, i;
1270 	pgtable_t pgtable;
1271 	unsigned long haddr;
1272 
1273 	spin_lock(&mm->page_table_lock);
1274 	pmd = page_check_address_pmd(page, mm, address,
1275 				     PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1276 	if (pmd) {
1277 		pgtable = get_pmd_huge_pte(mm);
1278 		pmd_populate(mm, &_pmd, pgtable);
1279 
1280 		for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1281 		     i++, haddr += PAGE_SIZE) {
1282 			pte_t *pte, entry;
1283 			BUG_ON(PageCompound(page+i));
1284 			entry = mk_pte(page + i, vma->vm_page_prot);
1285 			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1286 			if (!pmd_write(*pmd))
1287 				entry = pte_wrprotect(entry);
1288 			else
1289 				BUG_ON(page_mapcount(page) != 1);
1290 			if (!pmd_young(*pmd))
1291 				entry = pte_mkold(entry);
1292 			pte = pte_offset_map(&_pmd, haddr);
1293 			BUG_ON(!pte_none(*pte));
1294 			set_pte_at(mm, haddr, pte, entry);
1295 			pte_unmap(pte);
1296 		}
1297 
1298 		mm->nr_ptes++;
1299 		smp_wmb(); /* make pte visible before pmd */
1300 		/*
1301 		 * Up to this point the pmd is present and huge and
1302 		 * userland has the whole access to the hugepage
1303 		 * during the split (which happens in place). If we
1304 		 * overwrite the pmd with the not-huge version
1305 		 * pointing to the pte here (which of course we could
1306 		 * if all CPUs were bug free), userland could trigger
1307 		 * a small page size TLB miss on the small sized TLB
1308 		 * while the hugepage TLB entry is still established
1309 		 * in the huge TLB. Some CPU doesn't like that. See
1310 		 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1311 		 * Erratum 383 on page 93. Intel should be safe but is
1312 		 * also warns that it's only safe if the permission
1313 		 * and cache attributes of the two entries loaded in
1314 		 * the two TLB is identical (which should be the case
1315 		 * here). But it is generally safer to never allow
1316 		 * small and huge TLB entries for the same virtual
1317 		 * address to be loaded simultaneously. So instead of
1318 		 * doing "pmd_populate(); flush_tlb_range();" we first
1319 		 * mark the current pmd notpresent (atomically because
1320 		 * here the pmd_trans_huge and pmd_trans_splitting
1321 		 * must remain set at all times on the pmd until the
1322 		 * split is complete for this pmd), then we flush the
1323 		 * SMP TLB and finally we write the non-huge version
1324 		 * of the pmd entry with pmd_populate.
1325 		 */
1326 		set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1327 		flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1328 		pmd_populate(mm, pmd, pgtable);
1329 		ret = 1;
1330 	}
1331 	spin_unlock(&mm->page_table_lock);
1332 
1333 	return ret;
1334 }
1335 
1336 /* must be called with anon_vma->root->mutex hold */
1337 static void __split_huge_page(struct page *page,
1338 			      struct anon_vma *anon_vma)
1339 {
1340 	int mapcount, mapcount2;
1341 	struct anon_vma_chain *avc;
1342 
1343 	BUG_ON(!PageHead(page));
1344 	BUG_ON(PageTail(page));
1345 
1346 	mapcount = 0;
1347 	list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1348 		struct vm_area_struct *vma = avc->vma;
1349 		unsigned long addr = vma_address(page, vma);
1350 		BUG_ON(is_vma_temporary_stack(vma));
1351 		if (addr == -EFAULT)
1352 			continue;
1353 		mapcount += __split_huge_page_splitting(page, vma, addr);
1354 	}
1355 	/*
1356 	 * It is critical that new vmas are added to the tail of the
1357 	 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1358 	 * and establishes a child pmd before
1359 	 * __split_huge_page_splitting() freezes the parent pmd (so if
1360 	 * we fail to prevent copy_huge_pmd() from running until the
1361 	 * whole __split_huge_page() is complete), we will still see
1362 	 * the newly established pmd of the child later during the
1363 	 * walk, to be able to set it as pmd_trans_splitting too.
1364 	 */
1365 	if (mapcount != page_mapcount(page))
1366 		printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1367 		       mapcount, page_mapcount(page));
1368 	BUG_ON(mapcount != page_mapcount(page));
1369 
1370 	__split_huge_page_refcount(page);
1371 
1372 	mapcount2 = 0;
1373 	list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1374 		struct vm_area_struct *vma = avc->vma;
1375 		unsigned long addr = vma_address(page, vma);
1376 		BUG_ON(is_vma_temporary_stack(vma));
1377 		if (addr == -EFAULT)
1378 			continue;
1379 		mapcount2 += __split_huge_page_map(page, vma, addr);
1380 	}
1381 	if (mapcount != mapcount2)
1382 		printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1383 		       mapcount, mapcount2, page_mapcount(page));
1384 	BUG_ON(mapcount != mapcount2);
1385 }
1386 
1387 int split_huge_page(struct page *page)
1388 {
1389 	struct anon_vma *anon_vma;
1390 	int ret = 1;
1391 
1392 	BUG_ON(!PageAnon(page));
1393 	anon_vma = page_lock_anon_vma(page);
1394 	if (!anon_vma)
1395 		goto out;
1396 	ret = 0;
1397 	if (!PageCompound(page))
1398 		goto out_unlock;
1399 
1400 	BUG_ON(!PageSwapBacked(page));
1401 	__split_huge_page(page, anon_vma);
1402 	count_vm_event(THP_SPLIT);
1403 
1404 	BUG_ON(PageCompound(page));
1405 out_unlock:
1406 	page_unlock_anon_vma(anon_vma);
1407 out:
1408 	return ret;
1409 }
1410 
1411 #define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \
1412 		   VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1413 
1414 int hugepage_madvise(struct vm_area_struct *vma,
1415 		     unsigned long *vm_flags, int advice)
1416 {
1417 	switch (advice) {
1418 	case MADV_HUGEPAGE:
1419 		/*
1420 		 * Be somewhat over-protective like KSM for now!
1421 		 */
1422 		if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1423 			return -EINVAL;
1424 		*vm_flags &= ~VM_NOHUGEPAGE;
1425 		*vm_flags |= VM_HUGEPAGE;
1426 		/*
1427 		 * If the vma become good for khugepaged to scan,
1428 		 * register it here without waiting a page fault that
1429 		 * may not happen any time soon.
1430 		 */
1431 		if (unlikely(khugepaged_enter_vma_merge(vma)))
1432 			return -ENOMEM;
1433 		break;
1434 	case MADV_NOHUGEPAGE:
1435 		/*
1436 		 * Be somewhat over-protective like KSM for now!
1437 		 */
1438 		if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1439 			return -EINVAL;
1440 		*vm_flags &= ~VM_HUGEPAGE;
1441 		*vm_flags |= VM_NOHUGEPAGE;
1442 		/*
1443 		 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1444 		 * this vma even if we leave the mm registered in khugepaged if
1445 		 * it got registered before VM_NOHUGEPAGE was set.
1446 		 */
1447 		break;
1448 	}
1449 
1450 	return 0;
1451 }
1452 
1453 static int __init khugepaged_slab_init(void)
1454 {
1455 	mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1456 					  sizeof(struct mm_slot),
1457 					  __alignof__(struct mm_slot), 0, NULL);
1458 	if (!mm_slot_cache)
1459 		return -ENOMEM;
1460 
1461 	return 0;
1462 }
1463 
1464 static void __init khugepaged_slab_free(void)
1465 {
1466 	kmem_cache_destroy(mm_slot_cache);
1467 	mm_slot_cache = NULL;
1468 }
1469 
1470 static inline struct mm_slot *alloc_mm_slot(void)
1471 {
1472 	if (!mm_slot_cache)	/* initialization failed */
1473 		return NULL;
1474 	return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1475 }
1476 
1477 static inline void free_mm_slot(struct mm_slot *mm_slot)
1478 {
1479 	kmem_cache_free(mm_slot_cache, mm_slot);
1480 }
1481 
1482 static int __init mm_slots_hash_init(void)
1483 {
1484 	mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1485 				GFP_KERNEL);
1486 	if (!mm_slots_hash)
1487 		return -ENOMEM;
1488 	return 0;
1489 }
1490 
1491 #if 0
1492 static void __init mm_slots_hash_free(void)
1493 {
1494 	kfree(mm_slots_hash);
1495 	mm_slots_hash = NULL;
1496 }
1497 #endif
1498 
1499 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1500 {
1501 	struct mm_slot *mm_slot;
1502 	struct hlist_head *bucket;
1503 	struct hlist_node *node;
1504 
1505 	bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1506 				% MM_SLOTS_HASH_HEADS];
1507 	hlist_for_each_entry(mm_slot, node, bucket, hash) {
1508 		if (mm == mm_slot->mm)
1509 			return mm_slot;
1510 	}
1511 	return NULL;
1512 }
1513 
1514 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1515 				    struct mm_slot *mm_slot)
1516 {
1517 	struct hlist_head *bucket;
1518 
1519 	bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1520 				% MM_SLOTS_HASH_HEADS];
1521 	mm_slot->mm = mm;
1522 	hlist_add_head(&mm_slot->hash, bucket);
1523 }
1524 
1525 static inline int khugepaged_test_exit(struct mm_struct *mm)
1526 {
1527 	return atomic_read(&mm->mm_users) == 0;
1528 }
1529 
1530 int __khugepaged_enter(struct mm_struct *mm)
1531 {
1532 	struct mm_slot *mm_slot;
1533 	int wakeup;
1534 
1535 	mm_slot = alloc_mm_slot();
1536 	if (!mm_slot)
1537 		return -ENOMEM;
1538 
1539 	/* __khugepaged_exit() must not run from under us */
1540 	VM_BUG_ON(khugepaged_test_exit(mm));
1541 	if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1542 		free_mm_slot(mm_slot);
1543 		return 0;
1544 	}
1545 
1546 	spin_lock(&khugepaged_mm_lock);
1547 	insert_to_mm_slots_hash(mm, mm_slot);
1548 	/*
1549 	 * Insert just behind the scanning cursor, to let the area settle
1550 	 * down a little.
1551 	 */
1552 	wakeup = list_empty(&khugepaged_scan.mm_head);
1553 	list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1554 	spin_unlock(&khugepaged_mm_lock);
1555 
1556 	atomic_inc(&mm->mm_count);
1557 	if (wakeup)
1558 		wake_up_interruptible(&khugepaged_wait);
1559 
1560 	return 0;
1561 }
1562 
1563 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1564 {
1565 	unsigned long hstart, hend;
1566 	if (!vma->anon_vma)
1567 		/*
1568 		 * Not yet faulted in so we will register later in the
1569 		 * page fault if needed.
1570 		 */
1571 		return 0;
1572 	if (vma->vm_ops)
1573 		/* khugepaged not yet working on file or special mappings */
1574 		return 0;
1575 	/*
1576 	 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1577 	 * true too, verify it here.
1578 	 */
1579 	VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1580 	hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1581 	hend = vma->vm_end & HPAGE_PMD_MASK;
1582 	if (hstart < hend)
1583 		return khugepaged_enter(vma);
1584 	return 0;
1585 }
1586 
1587 void __khugepaged_exit(struct mm_struct *mm)
1588 {
1589 	struct mm_slot *mm_slot;
1590 	int free = 0;
1591 
1592 	spin_lock(&khugepaged_mm_lock);
1593 	mm_slot = get_mm_slot(mm);
1594 	if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1595 		hlist_del(&mm_slot->hash);
1596 		list_del(&mm_slot->mm_node);
1597 		free = 1;
1598 	}
1599 
1600 	if (free) {
1601 		spin_unlock(&khugepaged_mm_lock);
1602 		clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1603 		free_mm_slot(mm_slot);
1604 		mmdrop(mm);
1605 	} else if (mm_slot) {
1606 		spin_unlock(&khugepaged_mm_lock);
1607 		/*
1608 		 * This is required to serialize against
1609 		 * khugepaged_test_exit() (which is guaranteed to run
1610 		 * under mmap sem read mode). Stop here (after we
1611 		 * return all pagetables will be destroyed) until
1612 		 * khugepaged has finished working on the pagetables
1613 		 * under the mmap_sem.
1614 		 */
1615 		down_write(&mm->mmap_sem);
1616 		up_write(&mm->mmap_sem);
1617 	} else
1618 		spin_unlock(&khugepaged_mm_lock);
1619 }
1620 
1621 static void release_pte_page(struct page *page)
1622 {
1623 	/* 0 stands for page_is_file_cache(page) == false */
1624 	dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1625 	unlock_page(page);
1626 	putback_lru_page(page);
1627 }
1628 
1629 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1630 {
1631 	while (--_pte >= pte) {
1632 		pte_t pteval = *_pte;
1633 		if (!pte_none(pteval))
1634 			release_pte_page(pte_page(pteval));
1635 	}
1636 }
1637 
1638 static void release_all_pte_pages(pte_t *pte)
1639 {
1640 	release_pte_pages(pte, pte + HPAGE_PMD_NR);
1641 }
1642 
1643 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1644 					unsigned long address,
1645 					pte_t *pte)
1646 {
1647 	struct page *page;
1648 	pte_t *_pte;
1649 	int referenced = 0, isolated = 0, none = 0;
1650 	for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1651 	     _pte++, address += PAGE_SIZE) {
1652 		pte_t pteval = *_pte;
1653 		if (pte_none(pteval)) {
1654 			if (++none <= khugepaged_max_ptes_none)
1655 				continue;
1656 			else {
1657 				release_pte_pages(pte, _pte);
1658 				goto out;
1659 			}
1660 		}
1661 		if (!pte_present(pteval) || !pte_write(pteval)) {
1662 			release_pte_pages(pte, _pte);
1663 			goto out;
1664 		}
1665 		page = vm_normal_page(vma, address, pteval);
1666 		if (unlikely(!page)) {
1667 			release_pte_pages(pte, _pte);
1668 			goto out;
1669 		}
1670 		VM_BUG_ON(PageCompound(page));
1671 		BUG_ON(!PageAnon(page));
1672 		VM_BUG_ON(!PageSwapBacked(page));
1673 
1674 		/* cannot use mapcount: can't collapse if there's a gup pin */
1675 		if (page_count(page) != 1) {
1676 			release_pte_pages(pte, _pte);
1677 			goto out;
1678 		}
1679 		/*
1680 		 * We can do it before isolate_lru_page because the
1681 		 * page can't be freed from under us. NOTE: PG_lock
1682 		 * is needed to serialize against split_huge_page
1683 		 * when invoked from the VM.
1684 		 */
1685 		if (!trylock_page(page)) {
1686 			release_pte_pages(pte, _pte);
1687 			goto out;
1688 		}
1689 		/*
1690 		 * Isolate the page to avoid collapsing an hugepage
1691 		 * currently in use by the VM.
1692 		 */
1693 		if (isolate_lru_page(page)) {
1694 			unlock_page(page);
1695 			release_pte_pages(pte, _pte);
1696 			goto out;
1697 		}
1698 		/* 0 stands for page_is_file_cache(page) == false */
1699 		inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1700 		VM_BUG_ON(!PageLocked(page));
1701 		VM_BUG_ON(PageLRU(page));
1702 
1703 		/* If there is no mapped pte young don't collapse the page */
1704 		if (pte_young(pteval) || PageReferenced(page) ||
1705 		    mmu_notifier_test_young(vma->vm_mm, address))
1706 			referenced = 1;
1707 	}
1708 	if (unlikely(!referenced))
1709 		release_all_pte_pages(pte);
1710 	else
1711 		isolated = 1;
1712 out:
1713 	return isolated;
1714 }
1715 
1716 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1717 				      struct vm_area_struct *vma,
1718 				      unsigned long address,
1719 				      spinlock_t *ptl)
1720 {
1721 	pte_t *_pte;
1722 	for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1723 		pte_t pteval = *_pte;
1724 		struct page *src_page;
1725 
1726 		if (pte_none(pteval)) {
1727 			clear_user_highpage(page, address);
1728 			add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1729 		} else {
1730 			src_page = pte_page(pteval);
1731 			copy_user_highpage(page, src_page, address, vma);
1732 			VM_BUG_ON(page_mapcount(src_page) != 1);
1733 			VM_BUG_ON(page_count(src_page) != 2);
1734 			release_pte_page(src_page);
1735 			/*
1736 			 * ptl mostly unnecessary, but preempt has to
1737 			 * be disabled to update the per-cpu stats
1738 			 * inside page_remove_rmap().
1739 			 */
1740 			spin_lock(ptl);
1741 			/*
1742 			 * paravirt calls inside pte_clear here are
1743 			 * superfluous.
1744 			 */
1745 			pte_clear(vma->vm_mm, address, _pte);
1746 			page_remove_rmap(src_page);
1747 			spin_unlock(ptl);
1748 			free_page_and_swap_cache(src_page);
1749 		}
1750 
1751 		address += PAGE_SIZE;
1752 		page++;
1753 	}
1754 }
1755 
1756 static void collapse_huge_page(struct mm_struct *mm,
1757 			       unsigned long address,
1758 			       struct page **hpage,
1759 			       struct vm_area_struct *vma,
1760 			       int node)
1761 {
1762 	pgd_t *pgd;
1763 	pud_t *pud;
1764 	pmd_t *pmd, _pmd;
1765 	pte_t *pte;
1766 	pgtable_t pgtable;
1767 	struct page *new_page;
1768 	spinlock_t *ptl;
1769 	int isolated;
1770 	unsigned long hstart, hend;
1771 
1772 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1773 #ifndef CONFIG_NUMA
1774 	up_read(&mm->mmap_sem);
1775 	VM_BUG_ON(!*hpage);
1776 	new_page = *hpage;
1777 #else
1778 	VM_BUG_ON(*hpage);
1779 	/*
1780 	 * Allocate the page while the vma is still valid and under
1781 	 * the mmap_sem read mode so there is no memory allocation
1782 	 * later when we take the mmap_sem in write mode. This is more
1783 	 * friendly behavior (OTOH it may actually hide bugs) to
1784 	 * filesystems in userland with daemons allocating memory in
1785 	 * the userland I/O paths.  Allocating memory with the
1786 	 * mmap_sem in read mode is good idea also to allow greater
1787 	 * scalability.
1788 	 */
1789 	new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1790 				      node, __GFP_OTHER_NODE);
1791 
1792 	/*
1793 	 * After allocating the hugepage, release the mmap_sem read lock in
1794 	 * preparation for taking it in write mode.
1795 	 */
1796 	up_read(&mm->mmap_sem);
1797 	if (unlikely(!new_page)) {
1798 		count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1799 		*hpage = ERR_PTR(-ENOMEM);
1800 		return;
1801 	}
1802 #endif
1803 
1804 	count_vm_event(THP_COLLAPSE_ALLOC);
1805 	if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1806 #ifdef CONFIG_NUMA
1807 		put_page(new_page);
1808 #endif
1809 		return;
1810 	}
1811 
1812 	/*
1813 	 * Prevent all access to pagetables with the exception of
1814 	 * gup_fast later hanlded by the ptep_clear_flush and the VM
1815 	 * handled by the anon_vma lock + PG_lock.
1816 	 */
1817 	down_write(&mm->mmap_sem);
1818 	if (unlikely(khugepaged_test_exit(mm)))
1819 		goto out;
1820 
1821 	vma = find_vma(mm, address);
1822 	hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1823 	hend = vma->vm_end & HPAGE_PMD_MASK;
1824 	if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1825 		goto out;
1826 
1827 	if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1828 	    (vma->vm_flags & VM_NOHUGEPAGE))
1829 		goto out;
1830 
1831 	if (!vma->anon_vma || vma->vm_ops)
1832 		goto out;
1833 	if (is_vma_temporary_stack(vma))
1834 		goto out;
1835 	/*
1836 	 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1837 	 * true too, verify it here.
1838 	 */
1839 	VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1840 
1841 	pgd = pgd_offset(mm, address);
1842 	if (!pgd_present(*pgd))
1843 		goto out;
1844 
1845 	pud = pud_offset(pgd, address);
1846 	if (!pud_present(*pud))
1847 		goto out;
1848 
1849 	pmd = pmd_offset(pud, address);
1850 	/* pmd can't go away or become huge under us */
1851 	if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1852 		goto out;
1853 
1854 	anon_vma_lock(vma->anon_vma);
1855 
1856 	pte = pte_offset_map(pmd, address);
1857 	ptl = pte_lockptr(mm, pmd);
1858 
1859 	spin_lock(&mm->page_table_lock); /* probably unnecessary */
1860 	/*
1861 	 * After this gup_fast can't run anymore. This also removes
1862 	 * any huge TLB entry from the CPU so we won't allow
1863 	 * huge and small TLB entries for the same virtual address
1864 	 * to avoid the risk of CPU bugs in that area.
1865 	 */
1866 	_pmd = pmdp_clear_flush_notify(vma, address, pmd);
1867 	spin_unlock(&mm->page_table_lock);
1868 
1869 	spin_lock(ptl);
1870 	isolated = __collapse_huge_page_isolate(vma, address, pte);
1871 	spin_unlock(ptl);
1872 
1873 	if (unlikely(!isolated)) {
1874 		pte_unmap(pte);
1875 		spin_lock(&mm->page_table_lock);
1876 		BUG_ON(!pmd_none(*pmd));
1877 		set_pmd_at(mm, address, pmd, _pmd);
1878 		spin_unlock(&mm->page_table_lock);
1879 		anon_vma_unlock(vma->anon_vma);
1880 		goto out;
1881 	}
1882 
1883 	/*
1884 	 * All pages are isolated and locked so anon_vma rmap
1885 	 * can't run anymore.
1886 	 */
1887 	anon_vma_unlock(vma->anon_vma);
1888 
1889 	__collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1890 	pte_unmap(pte);
1891 	__SetPageUptodate(new_page);
1892 	pgtable = pmd_pgtable(_pmd);
1893 	VM_BUG_ON(page_count(pgtable) != 1);
1894 	VM_BUG_ON(page_mapcount(pgtable) != 0);
1895 
1896 	_pmd = mk_pmd(new_page, vma->vm_page_prot);
1897 	_pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1898 	_pmd = pmd_mkhuge(_pmd);
1899 
1900 	/*
1901 	 * spin_lock() below is not the equivalent of smp_wmb(), so
1902 	 * this is needed to avoid the copy_huge_page writes to become
1903 	 * visible after the set_pmd_at() write.
1904 	 */
1905 	smp_wmb();
1906 
1907 	spin_lock(&mm->page_table_lock);
1908 	BUG_ON(!pmd_none(*pmd));
1909 	page_add_new_anon_rmap(new_page, vma, address);
1910 	set_pmd_at(mm, address, pmd, _pmd);
1911 	update_mmu_cache(vma, address, entry);
1912 	prepare_pmd_huge_pte(pgtable, mm);
1913 	mm->nr_ptes--;
1914 	spin_unlock(&mm->page_table_lock);
1915 
1916 #ifndef CONFIG_NUMA
1917 	*hpage = NULL;
1918 #endif
1919 	khugepaged_pages_collapsed++;
1920 out_up_write:
1921 	up_write(&mm->mmap_sem);
1922 	return;
1923 
1924 out:
1925 	mem_cgroup_uncharge_page(new_page);
1926 #ifdef CONFIG_NUMA
1927 	put_page(new_page);
1928 #endif
1929 	goto out_up_write;
1930 }
1931 
1932 static int khugepaged_scan_pmd(struct mm_struct *mm,
1933 			       struct vm_area_struct *vma,
1934 			       unsigned long address,
1935 			       struct page **hpage)
1936 {
1937 	pgd_t *pgd;
1938 	pud_t *pud;
1939 	pmd_t *pmd;
1940 	pte_t *pte, *_pte;
1941 	int ret = 0, referenced = 0, none = 0;
1942 	struct page *page;
1943 	unsigned long _address;
1944 	spinlock_t *ptl;
1945 	int node = -1;
1946 
1947 	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1948 
1949 	pgd = pgd_offset(mm, address);
1950 	if (!pgd_present(*pgd))
1951 		goto out;
1952 
1953 	pud = pud_offset(pgd, address);
1954 	if (!pud_present(*pud))
1955 		goto out;
1956 
1957 	pmd = pmd_offset(pud, address);
1958 	if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1959 		goto out;
1960 
1961 	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1962 	for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1963 	     _pte++, _address += PAGE_SIZE) {
1964 		pte_t pteval = *_pte;
1965 		if (pte_none(pteval)) {
1966 			if (++none <= khugepaged_max_ptes_none)
1967 				continue;
1968 			else
1969 				goto out_unmap;
1970 		}
1971 		if (!pte_present(pteval) || !pte_write(pteval))
1972 			goto out_unmap;
1973 		page = vm_normal_page(vma, _address, pteval);
1974 		if (unlikely(!page))
1975 			goto out_unmap;
1976 		/*
1977 		 * Chose the node of the first page. This could
1978 		 * be more sophisticated and look at more pages,
1979 		 * but isn't for now.
1980 		 */
1981 		if (node == -1)
1982 			node = page_to_nid(page);
1983 		VM_BUG_ON(PageCompound(page));
1984 		if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
1985 			goto out_unmap;
1986 		/* cannot use mapcount: can't collapse if there's a gup pin */
1987 		if (page_count(page) != 1)
1988 			goto out_unmap;
1989 		if (pte_young(pteval) || PageReferenced(page) ||
1990 		    mmu_notifier_test_young(vma->vm_mm, address))
1991 			referenced = 1;
1992 	}
1993 	if (referenced)
1994 		ret = 1;
1995 out_unmap:
1996 	pte_unmap_unlock(pte, ptl);
1997 	if (ret)
1998 		/* collapse_huge_page will return with the mmap_sem released */
1999 		collapse_huge_page(mm, address, hpage, vma, node);
2000 out:
2001 	return ret;
2002 }
2003 
2004 static void collect_mm_slot(struct mm_slot *mm_slot)
2005 {
2006 	struct mm_struct *mm = mm_slot->mm;
2007 
2008 	VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2009 
2010 	if (khugepaged_test_exit(mm)) {
2011 		/* free mm_slot */
2012 		hlist_del(&mm_slot->hash);
2013 		list_del(&mm_slot->mm_node);
2014 
2015 		/*
2016 		 * Not strictly needed because the mm exited already.
2017 		 *
2018 		 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2019 		 */
2020 
2021 		/* khugepaged_mm_lock actually not necessary for the below */
2022 		free_mm_slot(mm_slot);
2023 		mmdrop(mm);
2024 	}
2025 }
2026 
2027 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2028 					    struct page **hpage)
2029 {
2030 	struct mm_slot *mm_slot;
2031 	struct mm_struct *mm;
2032 	struct vm_area_struct *vma;
2033 	int progress = 0;
2034 
2035 	VM_BUG_ON(!pages);
2036 	VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2037 
2038 	if (khugepaged_scan.mm_slot)
2039 		mm_slot = khugepaged_scan.mm_slot;
2040 	else {
2041 		mm_slot = list_entry(khugepaged_scan.mm_head.next,
2042 				     struct mm_slot, mm_node);
2043 		khugepaged_scan.address = 0;
2044 		khugepaged_scan.mm_slot = mm_slot;
2045 	}
2046 	spin_unlock(&khugepaged_mm_lock);
2047 
2048 	mm = mm_slot->mm;
2049 	down_read(&mm->mmap_sem);
2050 	if (unlikely(khugepaged_test_exit(mm)))
2051 		vma = NULL;
2052 	else
2053 		vma = find_vma(mm, khugepaged_scan.address);
2054 
2055 	progress++;
2056 	for (; vma; vma = vma->vm_next) {
2057 		unsigned long hstart, hend;
2058 
2059 		cond_resched();
2060 		if (unlikely(khugepaged_test_exit(mm))) {
2061 			progress++;
2062 			break;
2063 		}
2064 
2065 		if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2066 		     !khugepaged_always()) ||
2067 		    (vma->vm_flags & VM_NOHUGEPAGE)) {
2068 		skip:
2069 			progress++;
2070 			continue;
2071 		}
2072 		if (!vma->anon_vma || vma->vm_ops)
2073 			goto skip;
2074 		if (is_vma_temporary_stack(vma))
2075 			goto skip;
2076 		/*
2077 		 * If is_pfn_mapping() is true is_learn_pfn_mapping()
2078 		 * must be true too, verify it here.
2079 		 */
2080 		VM_BUG_ON(is_linear_pfn_mapping(vma) ||
2081 			  vma->vm_flags & VM_NO_THP);
2082 
2083 		hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2084 		hend = vma->vm_end & HPAGE_PMD_MASK;
2085 		if (hstart >= hend)
2086 			goto skip;
2087 		if (khugepaged_scan.address > hend)
2088 			goto skip;
2089 		if (khugepaged_scan.address < hstart)
2090 			khugepaged_scan.address = hstart;
2091 		VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2092 
2093 		while (khugepaged_scan.address < hend) {
2094 			int ret;
2095 			cond_resched();
2096 			if (unlikely(khugepaged_test_exit(mm)))
2097 				goto breakouterloop;
2098 
2099 			VM_BUG_ON(khugepaged_scan.address < hstart ||
2100 				  khugepaged_scan.address + HPAGE_PMD_SIZE >
2101 				  hend);
2102 			ret = khugepaged_scan_pmd(mm, vma,
2103 						  khugepaged_scan.address,
2104 						  hpage);
2105 			/* move to next address */
2106 			khugepaged_scan.address += HPAGE_PMD_SIZE;
2107 			progress += HPAGE_PMD_NR;
2108 			if (ret)
2109 				/* we released mmap_sem so break loop */
2110 				goto breakouterloop_mmap_sem;
2111 			if (progress >= pages)
2112 				goto breakouterloop;
2113 		}
2114 	}
2115 breakouterloop:
2116 	up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2117 breakouterloop_mmap_sem:
2118 
2119 	spin_lock(&khugepaged_mm_lock);
2120 	VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2121 	/*
2122 	 * Release the current mm_slot if this mm is about to die, or
2123 	 * if we scanned all vmas of this mm.
2124 	 */
2125 	if (khugepaged_test_exit(mm) || !vma) {
2126 		/*
2127 		 * Make sure that if mm_users is reaching zero while
2128 		 * khugepaged runs here, khugepaged_exit will find
2129 		 * mm_slot not pointing to the exiting mm.
2130 		 */
2131 		if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2132 			khugepaged_scan.mm_slot = list_entry(
2133 				mm_slot->mm_node.next,
2134 				struct mm_slot, mm_node);
2135 			khugepaged_scan.address = 0;
2136 		} else {
2137 			khugepaged_scan.mm_slot = NULL;
2138 			khugepaged_full_scans++;
2139 		}
2140 
2141 		collect_mm_slot(mm_slot);
2142 	}
2143 
2144 	return progress;
2145 }
2146 
2147 static int khugepaged_has_work(void)
2148 {
2149 	return !list_empty(&khugepaged_scan.mm_head) &&
2150 		khugepaged_enabled();
2151 }
2152 
2153 static int khugepaged_wait_event(void)
2154 {
2155 	return !list_empty(&khugepaged_scan.mm_head) ||
2156 		!khugepaged_enabled();
2157 }
2158 
2159 static void khugepaged_do_scan(struct page **hpage)
2160 {
2161 	unsigned int progress = 0, pass_through_head = 0;
2162 	unsigned int pages = khugepaged_pages_to_scan;
2163 
2164 	barrier(); /* write khugepaged_pages_to_scan to local stack */
2165 
2166 	while (progress < pages) {
2167 		cond_resched();
2168 
2169 #ifndef CONFIG_NUMA
2170 		if (!*hpage) {
2171 			*hpage = alloc_hugepage(khugepaged_defrag());
2172 			if (unlikely(!*hpage)) {
2173 				count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2174 				break;
2175 			}
2176 			count_vm_event(THP_COLLAPSE_ALLOC);
2177 		}
2178 #else
2179 		if (IS_ERR(*hpage))
2180 			break;
2181 #endif
2182 
2183 		if (unlikely(kthread_should_stop() || freezing(current)))
2184 			break;
2185 
2186 		spin_lock(&khugepaged_mm_lock);
2187 		if (!khugepaged_scan.mm_slot)
2188 			pass_through_head++;
2189 		if (khugepaged_has_work() &&
2190 		    pass_through_head < 2)
2191 			progress += khugepaged_scan_mm_slot(pages - progress,
2192 							    hpage);
2193 		else
2194 			progress = pages;
2195 		spin_unlock(&khugepaged_mm_lock);
2196 	}
2197 }
2198 
2199 static void khugepaged_alloc_sleep(void)
2200 {
2201 	DEFINE_WAIT(wait);
2202 	add_wait_queue(&khugepaged_wait, &wait);
2203 	schedule_timeout_interruptible(
2204 		msecs_to_jiffies(
2205 			khugepaged_alloc_sleep_millisecs));
2206 	remove_wait_queue(&khugepaged_wait, &wait);
2207 }
2208 
2209 #ifndef CONFIG_NUMA
2210 static struct page *khugepaged_alloc_hugepage(void)
2211 {
2212 	struct page *hpage;
2213 
2214 	do {
2215 		hpage = alloc_hugepage(khugepaged_defrag());
2216 		if (!hpage) {
2217 			count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2218 			khugepaged_alloc_sleep();
2219 		} else
2220 			count_vm_event(THP_COLLAPSE_ALLOC);
2221 	} while (unlikely(!hpage) &&
2222 		 likely(khugepaged_enabled()));
2223 	return hpage;
2224 }
2225 #endif
2226 
2227 static void khugepaged_loop(void)
2228 {
2229 	struct page *hpage;
2230 
2231 #ifdef CONFIG_NUMA
2232 	hpage = NULL;
2233 #endif
2234 	while (likely(khugepaged_enabled())) {
2235 #ifndef CONFIG_NUMA
2236 		hpage = khugepaged_alloc_hugepage();
2237 		if (unlikely(!hpage))
2238 			break;
2239 #else
2240 		if (IS_ERR(hpage)) {
2241 			khugepaged_alloc_sleep();
2242 			hpage = NULL;
2243 		}
2244 #endif
2245 
2246 		khugepaged_do_scan(&hpage);
2247 #ifndef CONFIG_NUMA
2248 		if (hpage)
2249 			put_page(hpage);
2250 #endif
2251 		try_to_freeze();
2252 		if (unlikely(kthread_should_stop()))
2253 			break;
2254 		if (khugepaged_has_work()) {
2255 			DEFINE_WAIT(wait);
2256 			if (!khugepaged_scan_sleep_millisecs)
2257 				continue;
2258 			add_wait_queue(&khugepaged_wait, &wait);
2259 			schedule_timeout_interruptible(
2260 				msecs_to_jiffies(
2261 					khugepaged_scan_sleep_millisecs));
2262 			remove_wait_queue(&khugepaged_wait, &wait);
2263 		} else if (khugepaged_enabled())
2264 			wait_event_freezable(khugepaged_wait,
2265 					     khugepaged_wait_event());
2266 	}
2267 }
2268 
2269 static int khugepaged(void *none)
2270 {
2271 	struct mm_slot *mm_slot;
2272 
2273 	set_freezable();
2274 	set_user_nice(current, 19);
2275 
2276 	/* serialize with start_khugepaged() */
2277 	mutex_lock(&khugepaged_mutex);
2278 
2279 	for (;;) {
2280 		mutex_unlock(&khugepaged_mutex);
2281 		VM_BUG_ON(khugepaged_thread != current);
2282 		khugepaged_loop();
2283 		VM_BUG_ON(khugepaged_thread != current);
2284 
2285 		mutex_lock(&khugepaged_mutex);
2286 		if (!khugepaged_enabled())
2287 			break;
2288 		if (unlikely(kthread_should_stop()))
2289 			break;
2290 	}
2291 
2292 	spin_lock(&khugepaged_mm_lock);
2293 	mm_slot = khugepaged_scan.mm_slot;
2294 	khugepaged_scan.mm_slot = NULL;
2295 	if (mm_slot)
2296 		collect_mm_slot(mm_slot);
2297 	spin_unlock(&khugepaged_mm_lock);
2298 
2299 	khugepaged_thread = NULL;
2300 	mutex_unlock(&khugepaged_mutex);
2301 
2302 	return 0;
2303 }
2304 
2305 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2306 {
2307 	struct page *page;
2308 
2309 	spin_lock(&mm->page_table_lock);
2310 	if (unlikely(!pmd_trans_huge(*pmd))) {
2311 		spin_unlock(&mm->page_table_lock);
2312 		return;
2313 	}
2314 	page = pmd_page(*pmd);
2315 	VM_BUG_ON(!page_count(page));
2316 	get_page(page);
2317 	spin_unlock(&mm->page_table_lock);
2318 
2319 	split_huge_page(page);
2320 
2321 	put_page(page);
2322 	BUG_ON(pmd_trans_huge(*pmd));
2323 }
2324 
2325 static void split_huge_page_address(struct mm_struct *mm,
2326 				    unsigned long address)
2327 {
2328 	pgd_t *pgd;
2329 	pud_t *pud;
2330 	pmd_t *pmd;
2331 
2332 	VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2333 
2334 	pgd = pgd_offset(mm, address);
2335 	if (!pgd_present(*pgd))
2336 		return;
2337 
2338 	pud = pud_offset(pgd, address);
2339 	if (!pud_present(*pud))
2340 		return;
2341 
2342 	pmd = pmd_offset(pud, address);
2343 	if (!pmd_present(*pmd))
2344 		return;
2345 	/*
2346 	 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2347 	 * materialize from under us.
2348 	 */
2349 	split_huge_page_pmd(mm, pmd);
2350 }
2351 
2352 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2353 			     unsigned long start,
2354 			     unsigned long end,
2355 			     long adjust_next)
2356 {
2357 	/*
2358 	 * If the new start address isn't hpage aligned and it could
2359 	 * previously contain an hugepage: check if we need to split
2360 	 * an huge pmd.
2361 	 */
2362 	if (start & ~HPAGE_PMD_MASK &&
2363 	    (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2364 	    (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2365 		split_huge_page_address(vma->vm_mm, start);
2366 
2367 	/*
2368 	 * If the new end address isn't hpage aligned and it could
2369 	 * previously contain an hugepage: check if we need to split
2370 	 * an huge pmd.
2371 	 */
2372 	if (end & ~HPAGE_PMD_MASK &&
2373 	    (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2374 	    (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2375 		split_huge_page_address(vma->vm_mm, end);
2376 
2377 	/*
2378 	 * If we're also updating the vma->vm_next->vm_start, if the new
2379 	 * vm_next->vm_start isn't page aligned and it could previously
2380 	 * contain an hugepage: check if we need to split an huge pmd.
2381 	 */
2382 	if (adjust_next > 0) {
2383 		struct vm_area_struct *next = vma->vm_next;
2384 		unsigned long nstart = next->vm_start;
2385 		nstart += adjust_next << PAGE_SHIFT;
2386 		if (nstart & ~HPAGE_PMD_MASK &&
2387 		    (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2388 		    (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2389 			split_huge_page_address(next->vm_mm, nstart);
2390 	}
2391 }
2392