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PCI: Disable MPS configuration by default
[linux-btrfs-devel.git] / mm / huge_memory.c
blobe2d1587be269bf475a5ce2c05e6d10d9648a2121
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 spin_unlock(&khugepaged_mm_lock);
1600
1601 if (free) {
1602 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1603 free_mm_slot(mm_slot);
1604 mmdrop(mm);
1605 } else if (mm_slot) {
1606 /*
1607 * This is required to serialize against
1608 * khugepaged_test_exit() (which is guaranteed to run
1609 * under mmap sem read mode). Stop here (after we
1610 * return all pagetables will be destroyed) until
1611 * khugepaged has finished working on the pagetables
1612 * under the mmap_sem.
1613 */
1614 down_write(&mm->mmap_sem);
1615 up_write(&mm->mmap_sem);
1616 }
1617 }
1618
1619 static void release_pte_page(struct page *page)
1620 {
1621 /* 0 stands for page_is_file_cache(page) == false */
1622 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1623 unlock_page(page);
1624 putback_lru_page(page);
1625 }
1626
1627 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1628 {
1629 while (--_pte >= pte) {
1630 pte_t pteval = *_pte;
1631 if (!pte_none(pteval))
1632 release_pte_page(pte_page(pteval));
1633 }
1634 }
1635
1636 static void release_all_pte_pages(pte_t *pte)
1637 {
1638 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1639 }
1640
1641 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1642 unsigned long address,
1643 pte_t *pte)
1644 {
1645 struct page *page;
1646 pte_t *_pte;
1647 int referenced = 0, isolated = 0, none = 0;
1648 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1649 _pte++, address += PAGE_SIZE) {
1650 pte_t pteval = *_pte;
1651 if (pte_none(pteval)) {
1652 if (++none <= khugepaged_max_ptes_none)
1653 continue;
1654 else {
1655 release_pte_pages(pte, _pte);
1656 goto out;
1657 }
1658 }
1659 if (!pte_present(pteval) || !pte_write(pteval)) {
1660 release_pte_pages(pte, _pte);
1661 goto out;
1662 }
1663 page = vm_normal_page(vma, address, pteval);
1664 if (unlikely(!page)) {
1665 release_pte_pages(pte, _pte);
1666 goto out;
1667 }
1668 VM_BUG_ON(PageCompound(page));
1669 BUG_ON(!PageAnon(page));
1670 VM_BUG_ON(!PageSwapBacked(page));
1671
1672 /* cannot use mapcount: can't collapse if there's a gup pin */
1673 if (page_count(page) != 1) {
1674 release_pte_pages(pte, _pte);
1675 goto out;
1676 }
1677 /*
1678 * We can do it before isolate_lru_page because the
1679 * page can't be freed from under us. NOTE: PG_lock
1680 * is needed to serialize against split_huge_page
1681 * when invoked from the VM.
1682 */
1683 if (!trylock_page(page)) {
1684 release_pte_pages(pte, _pte);
1685 goto out;
1686 }
1687 /*
1688 * Isolate the page to avoid collapsing an hugepage
1689 * currently in use by the VM.
1690 */
1691 if (isolate_lru_page(page)) {
1692 unlock_page(page);
1693 release_pte_pages(pte, _pte);
1694 goto out;
1695 }
1696 /* 0 stands for page_is_file_cache(page) == false */
1697 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1698 VM_BUG_ON(!PageLocked(page));
1699 VM_BUG_ON(PageLRU(page));
1700
1701 /* If there is no mapped pte young don't collapse the page */
1702 if (pte_young(pteval) || PageReferenced(page) ||
1703 mmu_notifier_test_young(vma->vm_mm, address))
1704 referenced = 1;
1705 }
1706 if (unlikely(!referenced))
1707 release_all_pte_pages(pte);
1708 else
1709 isolated = 1;
1710 out:
1711 return isolated;
1712 }
1713
1714 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1715 struct vm_area_struct *vma,
1716 unsigned long address,
1717 spinlock_t *ptl)
1718 {
1719 pte_t *_pte;
1720 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1721 pte_t pteval = *_pte;
1722 struct page *src_page;
1723
1724 if (pte_none(pteval)) {
1725 clear_user_highpage(page, address);
1726 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1727 } else {
1728 src_page = pte_page(pteval);
1729 copy_user_highpage(page, src_page, address, vma);
1730 VM_BUG_ON(page_mapcount(src_page) != 1);
1731 VM_BUG_ON(page_count(src_page) != 2);
1732 release_pte_page(src_page);
1733 /*
1734 * ptl mostly unnecessary, but preempt has to
1735 * be disabled to update the per-cpu stats
1736 * inside page_remove_rmap().
1737 */
1738 spin_lock(ptl);
1739 /*
1740 * paravirt calls inside pte_clear here are
1741 * superfluous.
1742 */
1743 pte_clear(vma->vm_mm, address, _pte);
1744 page_remove_rmap(src_page);
1745 spin_unlock(ptl);
1746 free_page_and_swap_cache(src_page);
1747 }
1748
1749 address += PAGE_SIZE;
1750 page++;
1751 }
1752 }
1753
1754 static void collapse_huge_page(struct mm_struct *mm,
1755 unsigned long address,
1756 struct page **hpage,
1757 struct vm_area_struct *vma,
1758 int node)
1759 {
1760 pgd_t *pgd;
1761 pud_t *pud;
1762 pmd_t *pmd, _pmd;
1763 pte_t *pte;
1764 pgtable_t pgtable;
1765 struct page *new_page;
1766 spinlock_t *ptl;
1767 int isolated;
1768 unsigned long hstart, hend;
1769
1770 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1771 #ifndef CONFIG_NUMA
1772 up_read(&mm->mmap_sem);
1773 VM_BUG_ON(!*hpage);
1774 new_page = *hpage;
1775 #else
1776 VM_BUG_ON(*hpage);
1777 /*
1778 * Allocate the page while the vma is still valid and under
1779 * the mmap_sem read mode so there is no memory allocation
1780 * later when we take the mmap_sem in write mode. This is more
1781 * friendly behavior (OTOH it may actually hide bugs) to
1782 * filesystems in userland with daemons allocating memory in
1783 * the userland I/O paths. Allocating memory with the
1784 * mmap_sem in read mode is good idea also to allow greater
1785 * scalability.
1786 */
1787 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1788 node, __GFP_OTHER_NODE);
1789
1790 /*
1791 * After allocating the hugepage, release the mmap_sem read lock in
1792 * preparation for taking it in write mode.
1793 */
1794 up_read(&mm->mmap_sem);
1795 if (unlikely(!new_page)) {
1796 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1797 *hpage = ERR_PTR(-ENOMEM);
1798 return;
1799 }
1800 #endif
1801
1802 count_vm_event(THP_COLLAPSE_ALLOC);
1803 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1804 #ifdef CONFIG_NUMA
1805 put_page(new_page);
1806 #endif
1807 return;
1808 }
1809
1810 /*
1811 * Prevent all access to pagetables with the exception of
1812 * gup_fast later hanlded by the ptep_clear_flush and the VM
1813 * handled by the anon_vma lock + PG_lock.
1814 */
1815 down_write(&mm->mmap_sem);
1816 if (unlikely(khugepaged_test_exit(mm)))
1817 goto out;
1818
1819 vma = find_vma(mm, address);
1820 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1821 hend = vma->vm_end & HPAGE_PMD_MASK;
1822 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1823 goto out;
1824
1825 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1826 (vma->vm_flags & VM_NOHUGEPAGE))
1827 goto out;
1828
1829 if (!vma->anon_vma || vma->vm_ops)
1830 goto out;
1831 if (is_vma_temporary_stack(vma))
1832 goto out;
1833 /*
1834 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1835 * true too, verify it here.
1836 */
1837 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1838
1839 pgd = pgd_offset(mm, address);
1840 if (!pgd_present(*pgd))
1841 goto out;
1842
1843 pud = pud_offset(pgd, address);
1844 if (!pud_present(*pud))
1845 goto out;
1846
1847 pmd = pmd_offset(pud, address);
1848 /* pmd can't go away or become huge under us */
1849 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1850 goto out;
1851
1852 anon_vma_lock(vma->anon_vma);
1853
1854 pte = pte_offset_map(pmd, address);
1855 ptl = pte_lockptr(mm, pmd);
1856
1857 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1858 /*
1859 * After this gup_fast can't run anymore. This also removes
1860 * any huge TLB entry from the CPU so we won't allow
1861 * huge and small TLB entries for the same virtual address
1862 * to avoid the risk of CPU bugs in that area.
1863 */
1864 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1865 spin_unlock(&mm->page_table_lock);
1866
1867 spin_lock(ptl);
1868 isolated = __collapse_huge_page_isolate(vma, address, pte);
1869 spin_unlock(ptl);
1870
1871 if (unlikely(!isolated)) {
1872 pte_unmap(pte);
1873 spin_lock(&mm->page_table_lock);
1874 BUG_ON(!pmd_none(*pmd));
1875 set_pmd_at(mm, address, pmd, _pmd);
1876 spin_unlock(&mm->page_table_lock);
1877 anon_vma_unlock(vma->anon_vma);
1878 goto out;
1879 }
1880
1881 /*
1882 * All pages are isolated and locked so anon_vma rmap
1883 * can't run anymore.
1884 */
1885 anon_vma_unlock(vma->anon_vma);
1886
1887 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1888 pte_unmap(pte);
1889 __SetPageUptodate(new_page);
1890 pgtable = pmd_pgtable(_pmd);
1891 VM_BUG_ON(page_count(pgtable) != 1);
1892 VM_BUG_ON(page_mapcount(pgtable) != 0);
1893
1894 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1895 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1896 _pmd = pmd_mkhuge(_pmd);
1897
1898 /*
1899 * spin_lock() below is not the equivalent of smp_wmb(), so
1900 * this is needed to avoid the copy_huge_page writes to become
1901 * visible after the set_pmd_at() write.
1902 */
1903 smp_wmb();
1904
1905 spin_lock(&mm->page_table_lock);
1906 BUG_ON(!pmd_none(*pmd));
1907 page_add_new_anon_rmap(new_page, vma, address);
1908 set_pmd_at(mm, address, pmd, _pmd);
1909 update_mmu_cache(vma, address, entry);
1910 prepare_pmd_huge_pte(pgtable, mm);
1911 mm->nr_ptes--;
1912 spin_unlock(&mm->page_table_lock);
1913
1914 #ifndef CONFIG_NUMA
1915 *hpage = NULL;
1916 #endif
1917 khugepaged_pages_collapsed++;
1918 out_up_write:
1919 up_write(&mm->mmap_sem);
1920 return;
1921
1922 out:
1923 mem_cgroup_uncharge_page(new_page);
1924 #ifdef CONFIG_NUMA
1925 put_page(new_page);
1926 #endif
1927 goto out_up_write;
1928 }
1929
1930 static int khugepaged_scan_pmd(struct mm_struct *mm,
1931 struct vm_area_struct *vma,
1932 unsigned long address,
1933 struct page **hpage)
1934 {
1935 pgd_t *pgd;
1936 pud_t *pud;
1937 pmd_t *pmd;
1938 pte_t *pte, *_pte;
1939 int ret = 0, referenced = 0, none = 0;
1940 struct page *page;
1941 unsigned long _address;
1942 spinlock_t *ptl;
1943 int node = -1;
1944
1945 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1946
1947 pgd = pgd_offset(mm, address);
1948 if (!pgd_present(*pgd))
1949 goto out;
1950
1951 pud = pud_offset(pgd, address);
1952 if (!pud_present(*pud))
1953 goto out;
1954
1955 pmd = pmd_offset(pud, address);
1956 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1957 goto out;
1958
1959 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1960 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1961 _pte++, _address += PAGE_SIZE) {
1962 pte_t pteval = *_pte;
1963 if (pte_none(pteval)) {
1964 if (++none <= khugepaged_max_ptes_none)
1965 continue;
1966 else
1967 goto out_unmap;
1968 }
1969 if (!pte_present(pteval) || !pte_write(pteval))
1970 goto out_unmap;
1971 page = vm_normal_page(vma, _address, pteval);
1972 if (unlikely(!page))
1973 goto out_unmap;
1974 /*
1975 * Chose the node of the first page. This could
1976 * be more sophisticated and look at more pages,
1977 * but isn't for now.
1978 */
1979 if (node == -1)
1980 node = page_to_nid(page);
1981 VM_BUG_ON(PageCompound(page));
1982 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
1983 goto out_unmap;
1984 /* cannot use mapcount: can't collapse if there's a gup pin */
1985 if (page_count(page) != 1)
1986 goto out_unmap;
1987 if (pte_young(pteval) || PageReferenced(page) ||
1988 mmu_notifier_test_young(vma->vm_mm, address))
1989 referenced = 1;
1990 }
1991 if (referenced)
1992 ret = 1;
1993 out_unmap:
1994 pte_unmap_unlock(pte, ptl);
1995 if (ret)
1996 /* collapse_huge_page will return with the mmap_sem released */
1997 collapse_huge_page(mm, address, hpage, vma, node);
1998 out:
1999 return ret;
2000 }
2001
2002 static void collect_mm_slot(struct mm_slot *mm_slot)
2003 {
2004 struct mm_struct *mm = mm_slot->mm;
2005
2006 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2007
2008 if (khugepaged_test_exit(mm)) {
2009 /* free mm_slot */
2010 hlist_del(&mm_slot->hash);
2011 list_del(&mm_slot->mm_node);
2012
2013 /*
2014 * Not strictly needed because the mm exited already.
2015 *
2016 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2017 */
2018
2019 /* khugepaged_mm_lock actually not necessary for the below */
2020 free_mm_slot(mm_slot);
2021 mmdrop(mm);
2022 }
2023 }
2024
2025 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2026 struct page **hpage)
2027 {
2028 struct mm_slot *mm_slot;
2029 struct mm_struct *mm;
2030 struct vm_area_struct *vma;
2031 int progress = 0;
2032
2033 VM_BUG_ON(!pages);
2034 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2035
2036 if (khugepaged_scan.mm_slot)
2037 mm_slot = khugepaged_scan.mm_slot;
2038 else {
2039 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2040 struct mm_slot, mm_node);
2041 khugepaged_scan.address = 0;
2042 khugepaged_scan.mm_slot = mm_slot;
2043 }
2044 spin_unlock(&khugepaged_mm_lock);
2045
2046 mm = mm_slot->mm;
2047 down_read(&mm->mmap_sem);
2048 if (unlikely(khugepaged_test_exit(mm)))
2049 vma = NULL;
2050 else
2051 vma = find_vma(mm, khugepaged_scan.address);
2052
2053 progress++;
2054 for (; vma; vma = vma->vm_next) {
2055 unsigned long hstart, hend;
2056
2057 cond_resched();
2058 if (unlikely(khugepaged_test_exit(mm))) {
2059 progress++;
2060 break;
2061 }
2062
2063 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2064 !khugepaged_always()) ||
2065 (vma->vm_flags & VM_NOHUGEPAGE)) {
2066 skip:
2067 progress++;
2068 continue;
2069 }
2070 if (!vma->anon_vma || vma->vm_ops)
2071 goto skip;
2072 if (is_vma_temporary_stack(vma))
2073 goto skip;
2074 /*
2075 * If is_pfn_mapping() is true is_learn_pfn_mapping()
2076 * must be true too, verify it here.
2077 */
2078 VM_BUG_ON(is_linear_pfn_mapping(vma) ||
2079 vma->vm_flags & VM_NO_THP);
2080
2081 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2082 hend = vma->vm_end & HPAGE_PMD_MASK;
2083 if (hstart >= hend)
2084 goto skip;
2085 if (khugepaged_scan.address > hend)
2086 goto skip;
2087 if (khugepaged_scan.address < hstart)
2088 khugepaged_scan.address = hstart;
2089 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2090
2091 while (khugepaged_scan.address < hend) {
2092 int ret;
2093 cond_resched();
2094 if (unlikely(khugepaged_test_exit(mm)))
2095 goto breakouterloop;
2096
2097 VM_BUG_ON(khugepaged_scan.address < hstart ||
2098 khugepaged_scan.address + HPAGE_PMD_SIZE >
2099 hend);
2100 ret = khugepaged_scan_pmd(mm, vma,
2101 khugepaged_scan.address,
2102 hpage);
2103 /* move to next address */
2104 khugepaged_scan.address += HPAGE_PMD_SIZE;
2105 progress += HPAGE_PMD_NR;
2106 if (ret)
2107 /* we released mmap_sem so break loop */
2108 goto breakouterloop_mmap_sem;
2109 if (progress >= pages)
2110 goto breakouterloop;
2111 }
2112 }
2113 breakouterloop:
2114 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2115 breakouterloop_mmap_sem:
2116
2117 spin_lock(&khugepaged_mm_lock);
2118 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2119 /*
2120 * Release the current mm_slot if this mm is about to die, or
2121 * if we scanned all vmas of this mm.
2122 */
2123 if (khugepaged_test_exit(mm) || !vma) {
2124 /*
2125 * Make sure that if mm_users is reaching zero while
2126 * khugepaged runs here, khugepaged_exit will find
2127 * mm_slot not pointing to the exiting mm.
2128 */
2129 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2130 khugepaged_scan.mm_slot = list_entry(
2131 mm_slot->mm_node.next,
2132 struct mm_slot, mm_node);
2133 khugepaged_scan.address = 0;
2134 } else {
2135 khugepaged_scan.mm_slot = NULL;
2136 khugepaged_full_scans++;
2137 }
2138
2139 collect_mm_slot(mm_slot);
2140 }
2141
2142 return progress;
2143 }
2144
2145 static int khugepaged_has_work(void)
2146 {
2147 return !list_empty(&khugepaged_scan.mm_head) &&
2148 khugepaged_enabled();
2149 }
2150
2151 static int khugepaged_wait_event(void)
2152 {
2153 return !list_empty(&khugepaged_scan.mm_head) ||
2154 !khugepaged_enabled();
2155 }
2156
2157 static void khugepaged_do_scan(struct page **hpage)
2158 {
2159 unsigned int progress = 0, pass_through_head = 0;
2160 unsigned int pages = khugepaged_pages_to_scan;
2161
2162 barrier(); /* write khugepaged_pages_to_scan to local stack */
2163
2164 while (progress < pages) {
2165 cond_resched();
2166
2167 #ifndef CONFIG_NUMA
2168 if (!*hpage) {
2169 *hpage = alloc_hugepage(khugepaged_defrag());
2170 if (unlikely(!*hpage)) {
2171 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2172 break;
2173 }
2174 count_vm_event(THP_COLLAPSE_ALLOC);
2175 }
2176 #else
2177 if (IS_ERR(*hpage))
2178 break;
2179 #endif
2180
2181 if (unlikely(kthread_should_stop() || freezing(current)))
2182 break;
2183
2184 spin_lock(&khugepaged_mm_lock);
2185 if (!khugepaged_scan.mm_slot)
2186 pass_through_head++;
2187 if (khugepaged_has_work() &&
2188 pass_through_head < 2)
2189 progress += khugepaged_scan_mm_slot(pages - progress,
2190 hpage);
2191 else
2192 progress = pages;
2193 spin_unlock(&khugepaged_mm_lock);
2194 }
2195 }
2196
2197 static void khugepaged_alloc_sleep(void)
2198 {
2199 DEFINE_WAIT(wait);
2200 add_wait_queue(&khugepaged_wait, &wait);
2201 schedule_timeout_interruptible(
2202 msecs_to_jiffies(
2203 khugepaged_alloc_sleep_millisecs));
2204 remove_wait_queue(&khugepaged_wait, &wait);
2205 }
2206
2207 #ifndef CONFIG_NUMA
2208 static struct page *khugepaged_alloc_hugepage(void)
2209 {
2210 struct page *hpage;
2211
2212 do {
2213 hpage = alloc_hugepage(khugepaged_defrag());
2214 if (!hpage) {
2215 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
2216 khugepaged_alloc_sleep();
2217 } else
2218 count_vm_event(THP_COLLAPSE_ALLOC);
2219 } while (unlikely(!hpage) &&
2220 likely(khugepaged_enabled()));
2221 return hpage;
2222 }
2223 #endif
2224
2225 static void khugepaged_loop(void)
2226 {
2227 struct page *hpage;
2228
2229 #ifdef CONFIG_NUMA
2230 hpage = NULL;
2231 #endif
2232 while (likely(khugepaged_enabled())) {
2233 #ifndef CONFIG_NUMA
2234 hpage = khugepaged_alloc_hugepage();
2235 if (unlikely(!hpage))
2236 break;
2237 #else
2238 if (IS_ERR(hpage)) {
2239 khugepaged_alloc_sleep();
2240 hpage = NULL;
2241 }
2242 #endif
2243
2244 khugepaged_do_scan(&hpage);
2245 #ifndef CONFIG_NUMA
2246 if (hpage)
2247 put_page(hpage);
2248 #endif
2249 try_to_freeze();
2250 if (unlikely(kthread_should_stop()))
2251 break;
2252 if (khugepaged_has_work()) {
2253 DEFINE_WAIT(wait);
2254 if (!khugepaged_scan_sleep_millisecs)
2255 continue;
2256 add_wait_queue(&khugepaged_wait, &wait);
2257 schedule_timeout_interruptible(
2258 msecs_to_jiffies(
2259 khugepaged_scan_sleep_millisecs));
2260 remove_wait_queue(&khugepaged_wait, &wait);
2261 } else if (khugepaged_enabled())
2262 wait_event_freezable(khugepaged_wait,
2263 khugepaged_wait_event());
2264 }
2265 }
2266
2267 static int khugepaged(void *none)
2268 {
2269 struct mm_slot *mm_slot;
2270
2271 set_freezable();
2272 set_user_nice(current, 19);
2273
2274 /* serialize with start_khugepaged() */
2275 mutex_lock(&khugepaged_mutex);
2276
2277 for (;;) {
2278 mutex_unlock(&khugepaged_mutex);
2279 VM_BUG_ON(khugepaged_thread != current);
2280 khugepaged_loop();
2281 VM_BUG_ON(khugepaged_thread != current);
2282
2283 mutex_lock(&khugepaged_mutex);
2284 if (!khugepaged_enabled())
2285 break;
2286 if (unlikely(kthread_should_stop()))
2287 break;
2288 }
2289
2290 spin_lock(&khugepaged_mm_lock);
2291 mm_slot = khugepaged_scan.mm_slot;
2292 khugepaged_scan.mm_slot = NULL;
2293 if (mm_slot)
2294 collect_mm_slot(mm_slot);
2295 spin_unlock(&khugepaged_mm_lock);
2296
2297 khugepaged_thread = NULL;
2298 mutex_unlock(&khugepaged_mutex);
2299
2300 return 0;
2301 }
2302
2303 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2304 {
2305 struct page *page;
2306
2307 spin_lock(&mm->page_table_lock);
2308 if (unlikely(!pmd_trans_huge(*pmd))) {
2309 spin_unlock(&mm->page_table_lock);
2310 return;
2311 }
2312 page = pmd_page(*pmd);
2313 VM_BUG_ON(!page_count(page));
2314 get_page(page);
2315 spin_unlock(&mm->page_table_lock);
2316
2317 split_huge_page(page);
2318
2319 put_page(page);
2320 BUG_ON(pmd_trans_huge(*pmd));
2321 }
2322
2323 static void split_huge_page_address(struct mm_struct *mm,
2324 unsigned long address)
2325 {
2326 pgd_t *pgd;
2327 pud_t *pud;
2328 pmd_t *pmd;
2329
2330 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2331
2332 pgd = pgd_offset(mm, address);
2333 if (!pgd_present(*pgd))
2334 return;
2335
2336 pud = pud_offset(pgd, address);
2337 if (!pud_present(*pud))
2338 return;
2339
2340 pmd = pmd_offset(pud, address);
2341 if (!pmd_present(*pmd))
2342 return;
2343 /*
2344 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2345 * materialize from under us.
2346 */
2347 split_huge_page_pmd(mm, pmd);
2348 }
2349
2350 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2351 unsigned long start,
2352 unsigned long end,
2353 long adjust_next)
2354 {
2355 /*
2356 * If the new start address isn't hpage aligned and it could
2357 * previously contain an hugepage: check if we need to split
2358 * an huge pmd.
2359 */
2360 if (start & ~HPAGE_PMD_MASK &&
2361 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2362 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2363 split_huge_page_address(vma->vm_mm, start);
2364
2365 /*
2366 * If the new end address isn't hpage aligned and it could
2367 * previously contain an hugepage: check if we need to split
2368 * an huge pmd.
2369 */
2370 if (end & ~HPAGE_PMD_MASK &&
2371 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2372 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2373 split_huge_page_address(vma->vm_mm, end);
2374
2375 /*
2376 * If we're also updating the vma->vm_next->vm_start, if the new
2377 * vm_next->vm_start isn't page aligned and it could previously
2378 * contain an hugepage: check if we need to split an huge pmd.
2379 */
2380 if (adjust_next > 0) {
2381 struct vm_area_struct *next = vma->vm_next;
2382 unsigned long nstart = next->vm_start;
2383 nstart += adjust_next << PAGE_SHIFT;
2384 if (nstart & ~HPAGE_PMD_MASK &&
2385 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2386 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2387 split_huge_page_address(next->vm_mm, nstart);
2388 }
2389 }
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