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staging: brcm80211: remove unused module from softmac driver
[zen-stable.git] / mm / huge_memory.c
blob3e29781ee7628b2c3efdd0fde5d639f2d765b18f
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 if (test_bit(flag, &transparent_hugepage_flags))
248 return sprintf(buf, "[yes] no\n");
249 else
250 return sprintf(buf, "yes [no]\n");
251 }
252 static ssize_t single_flag_store(struct kobject *kobj,
253 struct kobj_attribute *attr,
254 const char *buf, size_t count,
255 enum transparent_hugepage_flag flag)
256 {
257 if (!memcmp("yes", buf,
258 min(sizeof("yes")-1, count))) {
259 set_bit(flag, &transparent_hugepage_flags);
260 } else if (!memcmp("no", buf,
261 min(sizeof("no")-1, count))) {
262 clear_bit(flag, &transparent_hugepage_flags);
263 } else
264 return -EINVAL;
265
266 return count;
267 }
268
269 /*
270 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
271 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
272 * memory just to allocate one more hugepage.
273 */
274 static ssize_t defrag_show(struct kobject *kobj,
275 struct kobj_attribute *attr, char *buf)
276 {
277 return double_flag_show(kobj, attr, buf,
278 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
279 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
280 }
281 static ssize_t defrag_store(struct kobject *kobj,
282 struct kobj_attribute *attr,
283 const char *buf, size_t count)
284 {
285 return double_flag_store(kobj, attr, buf, count,
286 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
287 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
288 }
289 static struct kobj_attribute defrag_attr =
290 __ATTR(defrag, 0644, defrag_show, defrag_store);
291
292 #ifdef CONFIG_DEBUG_VM
293 static ssize_t debug_cow_show(struct kobject *kobj,
294 struct kobj_attribute *attr, char *buf)
295 {
296 return single_flag_show(kobj, attr, buf,
297 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
298 }
299 static ssize_t debug_cow_store(struct kobject *kobj,
300 struct kobj_attribute *attr,
301 const char *buf, size_t count)
302 {
303 return single_flag_store(kobj, attr, buf, count,
304 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
305 }
306 static struct kobj_attribute debug_cow_attr =
307 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
308 #endif /* CONFIG_DEBUG_VM */
309
310 static struct attribute *hugepage_attr[] = {
311 &enabled_attr.attr,
312 &defrag_attr.attr,
313 #ifdef CONFIG_DEBUG_VM
314 &debug_cow_attr.attr,
315 #endif
316 NULL,
317 };
318
319 static struct attribute_group hugepage_attr_group = {
320 .attrs = hugepage_attr,
321 };
322
323 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
324 struct kobj_attribute *attr,
325 char *buf)
326 {
327 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
328 }
329
330 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
331 struct kobj_attribute *attr,
332 const char *buf, size_t count)
333 {
334 unsigned long msecs;
335 int err;
336
337 err = strict_strtoul(buf, 10, &msecs);
338 if (err || msecs > UINT_MAX)
339 return -EINVAL;
340
341 khugepaged_scan_sleep_millisecs = msecs;
342 wake_up_interruptible(&khugepaged_wait);
343
344 return count;
345 }
346 static struct kobj_attribute scan_sleep_millisecs_attr =
347 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
348 scan_sleep_millisecs_store);
349
350 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
351 struct kobj_attribute *attr,
352 char *buf)
353 {
354 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
355 }
356
357 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
358 struct kobj_attribute *attr,
359 const char *buf, size_t count)
360 {
361 unsigned long msecs;
362 int err;
363
364 err = strict_strtoul(buf, 10, &msecs);
365 if (err || msecs > UINT_MAX)
366 return -EINVAL;
367
368 khugepaged_alloc_sleep_millisecs = msecs;
369 wake_up_interruptible(&khugepaged_wait);
370
371 return count;
372 }
373 static struct kobj_attribute alloc_sleep_millisecs_attr =
374 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
375 alloc_sleep_millisecs_store);
376
377 static ssize_t pages_to_scan_show(struct kobject *kobj,
378 struct kobj_attribute *attr,
379 char *buf)
380 {
381 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
382 }
383 static ssize_t pages_to_scan_store(struct kobject *kobj,
384 struct kobj_attribute *attr,
385 const char *buf, size_t count)
386 {
387 int err;
388 unsigned long pages;
389
390 err = strict_strtoul(buf, 10, &pages);
391 if (err || !pages || pages > UINT_MAX)
392 return -EINVAL;
393
394 khugepaged_pages_to_scan = pages;
395
396 return count;
397 }
398 static struct kobj_attribute pages_to_scan_attr =
399 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
400 pages_to_scan_store);
401
402 static ssize_t pages_collapsed_show(struct kobject *kobj,
403 struct kobj_attribute *attr,
404 char *buf)
405 {
406 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
407 }
408 static struct kobj_attribute pages_collapsed_attr =
409 __ATTR_RO(pages_collapsed);
410
411 static ssize_t full_scans_show(struct kobject *kobj,
412 struct kobj_attribute *attr,
413 char *buf)
414 {
415 return sprintf(buf, "%u\n", khugepaged_full_scans);
416 }
417 static struct kobj_attribute full_scans_attr =
418 __ATTR_RO(full_scans);
419
420 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
421 struct kobj_attribute *attr, char *buf)
422 {
423 return single_flag_show(kobj, attr, buf,
424 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
425 }
426 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
427 struct kobj_attribute *attr,
428 const char *buf, size_t count)
429 {
430 return single_flag_store(kobj, attr, buf, count,
431 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
432 }
433 static struct kobj_attribute khugepaged_defrag_attr =
434 __ATTR(defrag, 0644, khugepaged_defrag_show,
435 khugepaged_defrag_store);
436
437 /*
438 * max_ptes_none controls if khugepaged should collapse hugepages over
439 * any unmapped ptes in turn potentially increasing the memory
440 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
441 * reduce the available free memory in the system as it
442 * runs. Increasing max_ptes_none will instead potentially reduce the
443 * free memory in the system during the khugepaged scan.
444 */
445 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
446 struct kobj_attribute *attr,
447 char *buf)
448 {
449 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
450 }
451 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
452 struct kobj_attribute *attr,
453 const char *buf, size_t count)
454 {
455 int err;
456 unsigned long max_ptes_none;
457
458 err = strict_strtoul(buf, 10, &max_ptes_none);
459 if (err || max_ptes_none > HPAGE_PMD_NR-1)
460 return -EINVAL;
461
462 khugepaged_max_ptes_none = max_ptes_none;
463
464 return count;
465 }
466 static struct kobj_attribute khugepaged_max_ptes_none_attr =
467 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
468 khugepaged_max_ptes_none_store);
469
470 static struct attribute *khugepaged_attr[] = {
471 &khugepaged_defrag_attr.attr,
472 &khugepaged_max_ptes_none_attr.attr,
473 &pages_to_scan_attr.attr,
474 &pages_collapsed_attr.attr,
475 &full_scans_attr.attr,
476 &scan_sleep_millisecs_attr.attr,
477 &alloc_sleep_millisecs_attr.attr,
478 NULL,
479 };
480
481 static struct attribute_group khugepaged_attr_group = {
482 .attrs = khugepaged_attr,
483 .name = "khugepaged",
484 };
485 #endif /* CONFIG_SYSFS */
486
487 static int __init hugepage_init(void)
488 {
489 int err;
490 #ifdef CONFIG_SYSFS
491 static struct kobject *hugepage_kobj;
492 #endif
493
494 err = -EINVAL;
495 if (!has_transparent_hugepage()) {
496 transparent_hugepage_flags = 0;
497 goto out;
498 }
499
500 #ifdef CONFIG_SYSFS
501 err = -ENOMEM;
502 hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
503 if (unlikely(!hugepage_kobj)) {
504 printk(KERN_ERR "hugepage: failed kobject create\n");
505 goto out;
506 }
507
508 err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group);
509 if (err) {
510 printk(KERN_ERR "hugepage: failed register hugeage group\n");
511 goto out;
512 }
513
514 err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group);
515 if (err) {
516 printk(KERN_ERR "hugepage: failed register hugeage group\n");
517 goto out;
518 }
519 #endif
520
521 err = khugepaged_slab_init();
522 if (err)
523 goto out;
524
525 err = mm_slots_hash_init();
526 if (err) {
527 khugepaged_slab_free();
528 goto out;
529 }
530
531 /*
532 * By default disable transparent hugepages on smaller systems,
533 * where the extra memory used could hurt more than TLB overhead
534 * is likely to save. The admin can still enable it through /sys.
535 */
536 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
537 transparent_hugepage_flags = 0;
538
539 start_khugepaged();
540
541 set_recommended_min_free_kbytes();
542
543 out:
544 return err;
545 }
546 module_init(hugepage_init)
547
548 static int __init setup_transparent_hugepage(char *str)
549 {
550 int ret = 0;
551 if (!str)
552 goto out;
553 if (!strcmp(str, "always")) {
554 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
555 &transparent_hugepage_flags);
556 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
557 &transparent_hugepage_flags);
558 ret = 1;
559 } else if (!strcmp(str, "madvise")) {
560 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
561 &transparent_hugepage_flags);
562 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
563 &transparent_hugepage_flags);
564 ret = 1;
565 } else if (!strcmp(str, "never")) {
566 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
567 &transparent_hugepage_flags);
568 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
569 &transparent_hugepage_flags);
570 ret = 1;
571 }
572 out:
573 if (!ret)
574 printk(KERN_WARNING
575 "transparent_hugepage= cannot parse, ignored\n");
576 return ret;
577 }
578 __setup("transparent_hugepage=", setup_transparent_hugepage);
579
580 static void prepare_pmd_huge_pte(pgtable_t pgtable,
581 struct mm_struct *mm)
582 {
583 assert_spin_locked(&mm->page_table_lock);
584
585 /* FIFO */
586 if (!mm->pmd_huge_pte)
587 INIT_LIST_HEAD(&pgtable->lru);
588 else
589 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
590 mm->pmd_huge_pte = pgtable;
591 }
592
593 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
594 {
595 if (likely(vma->vm_flags & VM_WRITE))
596 pmd = pmd_mkwrite(pmd);
597 return pmd;
598 }
599
600 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
601 struct vm_area_struct *vma,
602 unsigned long haddr, pmd_t *pmd,
603 struct page *page)
604 {
605 int ret = 0;
606 pgtable_t pgtable;
607
608 VM_BUG_ON(!PageCompound(page));
609 pgtable = pte_alloc_one(mm, haddr);
610 if (unlikely(!pgtable)) {
611 mem_cgroup_uncharge_page(page);
612 put_page(page);
613 return VM_FAULT_OOM;
614 }
615
616 clear_huge_page(page, haddr, HPAGE_PMD_NR);
617 __SetPageUptodate(page);
618
619 spin_lock(&mm->page_table_lock);
620 if (unlikely(!pmd_none(*pmd))) {
621 spin_unlock(&mm->page_table_lock);
622 mem_cgroup_uncharge_page(page);
623 put_page(page);
624 pte_free(mm, pgtable);
625 } else {
626 pmd_t entry;
627 entry = mk_pmd(page, vma->vm_page_prot);
628 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
629 entry = pmd_mkhuge(entry);
630 /*
631 * The spinlocking to take the lru_lock inside
632 * page_add_new_anon_rmap() acts as a full memory
633 * barrier to be sure clear_huge_page writes become
634 * visible after the set_pmd_at() write.
635 */
636 page_add_new_anon_rmap(page, vma, haddr);
637 set_pmd_at(mm, haddr, pmd, entry);
638 prepare_pmd_huge_pte(pgtable, mm);
639 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
640 spin_unlock(&mm->page_table_lock);
641 }
642
643 return ret;
644 }
645
646 static inline gfp_t alloc_hugepage_gfpmask(int defrag)
647 {
648 return GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT);
649 }
650
651 static inline struct page *alloc_hugepage_vma(int defrag,
652 struct vm_area_struct *vma,
653 unsigned long haddr)
654 {
655 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag),
656 HPAGE_PMD_ORDER, vma, haddr);
657 }
658
659 #ifndef CONFIG_NUMA
660 static inline struct page *alloc_hugepage(int defrag)
661 {
662 return alloc_pages(alloc_hugepage_gfpmask(defrag),
663 HPAGE_PMD_ORDER);
664 }
665 #endif
666
667 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
668 unsigned long address, pmd_t *pmd,
669 unsigned int flags)
670 {
671 struct page *page;
672 unsigned long haddr = address & HPAGE_PMD_MASK;
673 pte_t *pte;
674
675 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
676 if (unlikely(anon_vma_prepare(vma)))
677 return VM_FAULT_OOM;
678 if (unlikely(khugepaged_enter(vma)))
679 return VM_FAULT_OOM;
680 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
681 vma, haddr);
682 if (unlikely(!page))
683 goto out;
684 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
685 put_page(page);
686 goto out;
687 }
688
689 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
690 }
691 out:
692 /*
693 * Use __pte_alloc instead of pte_alloc_map, because we can't
694 * run pte_offset_map on the pmd, if an huge pmd could
695 * materialize from under us from a different thread.
696 */
697 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
698 return VM_FAULT_OOM;
699 /* if an huge pmd materialized from under us just retry later */
700 if (unlikely(pmd_trans_huge(*pmd)))
701 return 0;
702 /*
703 * A regular pmd is established and it can't morph into a huge pmd
704 * from under us anymore at this point because we hold the mmap_sem
705 * read mode and khugepaged takes it in write mode. So now it's
706 * safe to run pte_offset_map().
707 */
708 pte = pte_offset_map(pmd, address);
709 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
710 }
711
712 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
713 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
714 struct vm_area_struct *vma)
715 {
716 struct page *src_page;
717 pmd_t pmd;
718 pgtable_t pgtable;
719 int ret;
720
721 ret = -ENOMEM;
722 pgtable = pte_alloc_one(dst_mm, addr);
723 if (unlikely(!pgtable))
724 goto out;
725
726 spin_lock(&dst_mm->page_table_lock);
727 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
728
729 ret = -EAGAIN;
730 pmd = *src_pmd;
731 if (unlikely(!pmd_trans_huge(pmd))) {
732 pte_free(dst_mm, pgtable);
733 goto out_unlock;
734 }
735 if (unlikely(pmd_trans_splitting(pmd))) {
736 /* split huge page running from under us */
737 spin_unlock(&src_mm->page_table_lock);
738 spin_unlock(&dst_mm->page_table_lock);
739 pte_free(dst_mm, pgtable);
740
741 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
742 goto out;
743 }
744 src_page = pmd_page(pmd);
745 VM_BUG_ON(!PageHead(src_page));
746 get_page(src_page);
747 page_dup_rmap(src_page);
748 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
749
750 pmdp_set_wrprotect(src_mm, addr, src_pmd);
751 pmd = pmd_mkold(pmd_wrprotect(pmd));
752 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
753 prepare_pmd_huge_pte(pgtable, dst_mm);
754
755 ret = 0;
756 out_unlock:
757 spin_unlock(&src_mm->page_table_lock);
758 spin_unlock(&dst_mm->page_table_lock);
759 out:
760 return ret;
761 }
762
763 /* no "address" argument so destroys page coloring of some arch */
764 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
765 {
766 pgtable_t pgtable;
767
768 assert_spin_locked(&mm->page_table_lock);
769
770 /* FIFO */
771 pgtable = mm->pmd_huge_pte;
772 if (list_empty(&pgtable->lru))
773 mm->pmd_huge_pte = NULL;
774 else {
775 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
776 struct page, lru);
777 list_del(&pgtable->lru);
778 }
779 return pgtable;
780 }
781
782 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
783 struct vm_area_struct *vma,
784 unsigned long address,
785 pmd_t *pmd, pmd_t orig_pmd,
786 struct page *page,
787 unsigned long haddr)
788 {
789 pgtable_t pgtable;
790 pmd_t _pmd;
791 int ret = 0, i;
792 struct page **pages;
793
794 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
795 GFP_KERNEL);
796 if (unlikely(!pages)) {
797 ret |= VM_FAULT_OOM;
798 goto out;
799 }
800
801 for (i = 0; i < HPAGE_PMD_NR; i++) {
802 pages[i] = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
803 vma, address);
804 if (unlikely(!pages[i] ||
805 mem_cgroup_newpage_charge(pages[i], mm,
806 GFP_KERNEL))) {
807 if (pages[i])
808 put_page(pages[i]);
809 mem_cgroup_uncharge_start();
810 while (--i >= 0) {
811 mem_cgroup_uncharge_page(pages[i]);
812 put_page(pages[i]);
813 }
814 mem_cgroup_uncharge_end();
815 kfree(pages);
816 ret |= VM_FAULT_OOM;
817 goto out;
818 }
819 }
820
821 for (i = 0; i < HPAGE_PMD_NR; i++) {
822 copy_user_highpage(pages[i], page + i,
823 haddr + PAGE_SHIFT*i, vma);
824 __SetPageUptodate(pages[i]);
825 cond_resched();
826 }
827
828 spin_lock(&mm->page_table_lock);
829 if (unlikely(!pmd_same(*pmd, orig_pmd)))
830 goto out_free_pages;
831 VM_BUG_ON(!PageHead(page));
832
833 pmdp_clear_flush_notify(vma, haddr, pmd);
834 /* leave pmd empty until pte is filled */
835
836 pgtable = get_pmd_huge_pte(mm);
837 pmd_populate(mm, &_pmd, pgtable);
838
839 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
840 pte_t *pte, entry;
841 entry = mk_pte(pages[i], vma->vm_page_prot);
842 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
843 page_add_new_anon_rmap(pages[i], vma, haddr);
844 pte = pte_offset_map(&_pmd, haddr);
845 VM_BUG_ON(!pte_none(*pte));
846 set_pte_at(mm, haddr, pte, entry);
847 pte_unmap(pte);
848 }
849 kfree(pages);
850
851 mm->nr_ptes++;
852 smp_wmb(); /* make pte visible before pmd */
853 pmd_populate(mm, pmd, pgtable);
854 page_remove_rmap(page);
855 spin_unlock(&mm->page_table_lock);
856
857 ret |= VM_FAULT_WRITE;
858 put_page(page);
859
860 out:
861 return ret;
862
863 out_free_pages:
864 spin_unlock(&mm->page_table_lock);
865 mem_cgroup_uncharge_start();
866 for (i = 0; i < HPAGE_PMD_NR; i++) {
867 mem_cgroup_uncharge_page(pages[i]);
868 put_page(pages[i]);
869 }
870 mem_cgroup_uncharge_end();
871 kfree(pages);
872 goto out;
873 }
874
875 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
876 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
877 {
878 int ret = 0;
879 struct page *page, *new_page;
880 unsigned long haddr;
881
882 VM_BUG_ON(!vma->anon_vma);
883 spin_lock(&mm->page_table_lock);
884 if (unlikely(!pmd_same(*pmd, orig_pmd)))
885 goto out_unlock;
886
887 page = pmd_page(orig_pmd);
888 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
889 haddr = address & HPAGE_PMD_MASK;
890 if (page_mapcount(page) == 1) {
891 pmd_t entry;
892 entry = pmd_mkyoung(orig_pmd);
893 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
894 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
895 update_mmu_cache(vma, address, entry);
896 ret |= VM_FAULT_WRITE;
897 goto out_unlock;
898 }
899 get_page(page);
900 spin_unlock(&mm->page_table_lock);
901
902 if (transparent_hugepage_enabled(vma) &&
903 !transparent_hugepage_debug_cow())
904 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
905 vma, haddr);
906 else
907 new_page = NULL;
908
909 if (unlikely(!new_page)) {
910 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
911 pmd, orig_pmd, page, haddr);
912 put_page(page);
913 goto out;
914 }
915
916 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
917 put_page(new_page);
918 put_page(page);
919 ret |= VM_FAULT_OOM;
920 goto out;
921 }
922
923 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
924 __SetPageUptodate(new_page);
925
926 spin_lock(&mm->page_table_lock);
927 put_page(page);
928 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
929 mem_cgroup_uncharge_page(new_page);
930 put_page(new_page);
931 } else {
932 pmd_t entry;
933 VM_BUG_ON(!PageHead(page));
934 entry = mk_pmd(new_page, vma->vm_page_prot);
935 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
936 entry = pmd_mkhuge(entry);
937 pmdp_clear_flush_notify(vma, haddr, pmd);
938 page_add_new_anon_rmap(new_page, vma, haddr);
939 set_pmd_at(mm, haddr, pmd, entry);
940 update_mmu_cache(vma, address, entry);
941 page_remove_rmap(page);
942 put_page(page);
943 ret |= VM_FAULT_WRITE;
944 }
945 out_unlock:
946 spin_unlock(&mm->page_table_lock);
947 out:
948 return ret;
949 }
950
951 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
952 unsigned long addr,
953 pmd_t *pmd,
954 unsigned int flags)
955 {
956 struct page *page = NULL;
957
958 assert_spin_locked(&mm->page_table_lock);
959
960 if (flags & FOLL_WRITE && !pmd_write(*pmd))
961 goto out;
962
963 page = pmd_page(*pmd);
964 VM_BUG_ON(!PageHead(page));
965 if (flags & FOLL_TOUCH) {
966 pmd_t _pmd;
967 /*
968 * We should set the dirty bit only for FOLL_WRITE but
969 * for now the dirty bit in the pmd is meaningless.
970 * And if the dirty bit will become meaningful and
971 * we'll only set it with FOLL_WRITE, an atomic
972 * set_bit will be required on the pmd to set the
973 * young bit, instead of the current set_pmd_at.
974 */
975 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
976 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
977 }
978 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
979 VM_BUG_ON(!PageCompound(page));
980 if (flags & FOLL_GET)
981 get_page(page);
982
983 out:
984 return page;
985 }
986
987 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
988 pmd_t *pmd)
989 {
990 int ret = 0;
991
992 spin_lock(&tlb->mm->page_table_lock);
993 if (likely(pmd_trans_huge(*pmd))) {
994 if (unlikely(pmd_trans_splitting(*pmd))) {
995 spin_unlock(&tlb->mm->page_table_lock);
996 wait_split_huge_page(vma->anon_vma,
997 pmd);
998 } else {
999 struct page *page;
1000 pgtable_t pgtable;
1001 pgtable = get_pmd_huge_pte(tlb->mm);
1002 page = pmd_page(*pmd);
1003 pmd_clear(pmd);
1004 page_remove_rmap(page);
1005 VM_BUG_ON(page_mapcount(page) < 0);
1006 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1007 VM_BUG_ON(!PageHead(page));
1008 spin_unlock(&tlb->mm->page_table_lock);
1009 tlb_remove_page(tlb, page);
1010 pte_free(tlb->mm, pgtable);
1011 ret = 1;
1012 }
1013 } else
1014 spin_unlock(&tlb->mm->page_table_lock);
1015
1016 return ret;
1017 }
1018
1019 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1020 unsigned long addr, unsigned long end,
1021 unsigned char *vec)
1022 {
1023 int ret = 0;
1024
1025 spin_lock(&vma->vm_mm->page_table_lock);
1026 if (likely(pmd_trans_huge(*pmd))) {
1027 ret = !pmd_trans_splitting(*pmd);
1028 spin_unlock(&vma->vm_mm->page_table_lock);
1029 if (unlikely(!ret))
1030 wait_split_huge_page(vma->anon_vma, pmd);
1031 else {
1032 /*
1033 * All logical pages in the range are present
1034 * if backed by a huge page.
1035 */
1036 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1037 }
1038 } else
1039 spin_unlock(&vma->vm_mm->page_table_lock);
1040
1041 return ret;
1042 }
1043
1044 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1045 unsigned long addr, pgprot_t newprot)
1046 {
1047 struct mm_struct *mm = vma->vm_mm;
1048 int ret = 0;
1049
1050 spin_lock(&mm->page_table_lock);
1051 if (likely(pmd_trans_huge(*pmd))) {
1052 if (unlikely(pmd_trans_splitting(*pmd))) {
1053 spin_unlock(&mm->page_table_lock);
1054 wait_split_huge_page(vma->anon_vma, pmd);
1055 } else {
1056 pmd_t entry;
1057
1058 entry = pmdp_get_and_clear(mm, addr, pmd);
1059 entry = pmd_modify(entry, newprot);
1060 set_pmd_at(mm, addr, pmd, entry);
1061 spin_unlock(&vma->vm_mm->page_table_lock);
1062 flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
1063 ret = 1;
1064 }
1065 } else
1066 spin_unlock(&vma->vm_mm->page_table_lock);
1067
1068 return ret;
1069 }
1070
1071 pmd_t *page_check_address_pmd(struct page *page,
1072 struct mm_struct *mm,
1073 unsigned long address,
1074 enum page_check_address_pmd_flag flag)
1075 {
1076 pgd_t *pgd;
1077 pud_t *pud;
1078 pmd_t *pmd, *ret = NULL;
1079
1080 if (address & ~HPAGE_PMD_MASK)
1081 goto out;
1082
1083 pgd = pgd_offset(mm, address);
1084 if (!pgd_present(*pgd))
1085 goto out;
1086
1087 pud = pud_offset(pgd, address);
1088 if (!pud_present(*pud))
1089 goto out;
1090
1091 pmd = pmd_offset(pud, address);
1092 if (pmd_none(*pmd))
1093 goto out;
1094 if (pmd_page(*pmd) != page)
1095 goto out;
1096 /*
1097 * split_vma() may create temporary aliased mappings. There is
1098 * no risk as long as all huge pmd are found and have their
1099 * splitting bit set before __split_huge_page_refcount
1100 * runs. Finding the same huge pmd more than once during the
1101 * same rmap walk is not a problem.
1102 */
1103 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1104 pmd_trans_splitting(*pmd))
1105 goto out;
1106 if (pmd_trans_huge(*pmd)) {
1107 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1108 !pmd_trans_splitting(*pmd));
1109 ret = pmd;
1110 }
1111 out:
1112 return ret;
1113 }
1114
1115 static int __split_huge_page_splitting(struct page *page,
1116 struct vm_area_struct *vma,
1117 unsigned long address)
1118 {
1119 struct mm_struct *mm = vma->vm_mm;
1120 pmd_t *pmd;
1121 int ret = 0;
1122
1123 spin_lock(&mm->page_table_lock);
1124 pmd = page_check_address_pmd(page, mm, address,
1125 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1126 if (pmd) {
1127 /*
1128 * We can't temporarily set the pmd to null in order
1129 * to split it, the pmd must remain marked huge at all
1130 * times or the VM won't take the pmd_trans_huge paths
1131 * and it won't wait on the anon_vma->root->lock to
1132 * serialize against split_huge_page*.
1133 */
1134 pmdp_splitting_flush_notify(vma, address, pmd);
1135 ret = 1;
1136 }
1137 spin_unlock(&mm->page_table_lock);
1138
1139 return ret;
1140 }
1141
1142 static void __split_huge_page_refcount(struct page *page)
1143 {
1144 int i;
1145 unsigned long head_index = page->index;
1146 struct zone *zone = page_zone(page);
1147 int zonestat;
1148
1149 /* prevent PageLRU to go away from under us, and freeze lru stats */
1150 spin_lock_irq(&zone->lru_lock);
1151 compound_lock(page);
1152
1153 for (i = 1; i < HPAGE_PMD_NR; i++) {
1154 struct page *page_tail = page + i;
1155
1156 /* tail_page->_count cannot change */
1157 atomic_sub(atomic_read(&page_tail->_count), &page->_count);
1158 BUG_ON(page_count(page) <= 0);
1159 atomic_add(page_mapcount(page) + 1, &page_tail->_count);
1160 BUG_ON(atomic_read(&page_tail->_count) <= 0);
1161
1162 /* after clearing PageTail the gup refcount can be released */
1163 smp_mb();
1164
1165 /*
1166 * retain hwpoison flag of the poisoned tail page:
1167 * fix for the unsuitable process killed on Guest Machine(KVM)
1168 * by the memory-failure.
1169 */
1170 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1171 page_tail->flags |= (page->flags &
1172 ((1L << PG_referenced) |
1173 (1L << PG_swapbacked) |
1174 (1L << PG_mlocked) |
1175 (1L << PG_uptodate)));
1176 page_tail->flags |= (1L << PG_dirty);
1177
1178 /*
1179 * 1) clear PageTail before overwriting first_page
1180 * 2) clear PageTail before clearing PageHead for VM_BUG_ON
1181 */
1182 smp_wmb();
1183
1184 /*
1185 * __split_huge_page_splitting() already set the
1186 * splitting bit in all pmd that could map this
1187 * hugepage, that will ensure no CPU can alter the
1188 * mapcount on the head page. The mapcount is only
1189 * accounted in the head page and it has to be
1190 * transferred to all tail pages in the below code. So
1191 * for this code to be safe, the split the mapcount
1192 * can't change. But that doesn't mean userland can't
1193 * keep changing and reading the page contents while
1194 * we transfer the mapcount, so the pmd splitting
1195 * status is achieved setting a reserved bit in the
1196 * pmd, not by clearing the present bit.
1197 */
1198 BUG_ON(page_mapcount(page_tail));
1199 page_tail->_mapcount = page->_mapcount;
1200
1201 BUG_ON(page_tail->mapping);
1202 page_tail->mapping = page->mapping;
1203
1204 page_tail->index = ++head_index;
1205
1206 BUG_ON(!PageAnon(page_tail));
1207 BUG_ON(!PageUptodate(page_tail));
1208 BUG_ON(!PageDirty(page_tail));
1209 BUG_ON(!PageSwapBacked(page_tail));
1210
1211 mem_cgroup_split_huge_fixup(page, page_tail);
1212
1213 lru_add_page_tail(zone, page, page_tail);
1214 }
1215
1216 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1217 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1218
1219 /*
1220 * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics,
1221 * so adjust those appropriately if this page is on the LRU.
1222 */
1223 if (PageLRU(page)) {
1224 zonestat = NR_LRU_BASE + page_lru(page);
1225 __mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1));
1226 }
1227
1228 ClearPageCompound(page);
1229 compound_unlock(page);
1230 spin_unlock_irq(&zone->lru_lock);
1231
1232 for (i = 1; i < HPAGE_PMD_NR; i++) {
1233 struct page *page_tail = page + i;
1234 BUG_ON(page_count(page_tail) <= 0);
1235 /*
1236 * Tail pages may be freed if there wasn't any mapping
1237 * like if add_to_swap() is running on a lru page that
1238 * had its mapping zapped. And freeing these pages
1239 * requires taking the lru_lock so we do the put_page
1240 * of the tail pages after the split is complete.
1241 */
1242 put_page(page_tail);
1243 }
1244
1245 /*
1246 * Only the head page (now become a regular page) is required
1247 * to be pinned by the caller.
1248 */
1249 BUG_ON(page_count(page) <= 0);
1250 }
1251
1252 static int __split_huge_page_map(struct page *page,
1253 struct vm_area_struct *vma,
1254 unsigned long address)
1255 {
1256 struct mm_struct *mm = vma->vm_mm;
1257 pmd_t *pmd, _pmd;
1258 int ret = 0, i;
1259 pgtable_t pgtable;
1260 unsigned long haddr;
1261
1262 spin_lock(&mm->page_table_lock);
1263 pmd = page_check_address_pmd(page, mm, address,
1264 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1265 if (pmd) {
1266 pgtable = get_pmd_huge_pte(mm);
1267 pmd_populate(mm, &_pmd, pgtable);
1268
1269 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1270 i++, haddr += PAGE_SIZE) {
1271 pte_t *pte, entry;
1272 BUG_ON(PageCompound(page+i));
1273 entry = mk_pte(page + i, vma->vm_page_prot);
1274 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1275 if (!pmd_write(*pmd))
1276 entry = pte_wrprotect(entry);
1277 else
1278 BUG_ON(page_mapcount(page) != 1);
1279 if (!pmd_young(*pmd))
1280 entry = pte_mkold(entry);
1281 pte = pte_offset_map(&_pmd, haddr);
1282 BUG_ON(!pte_none(*pte));
1283 set_pte_at(mm, haddr, pte, entry);
1284 pte_unmap(pte);
1285 }
1286
1287 mm->nr_ptes++;
1288 smp_wmb(); /* make pte visible before pmd */
1289 /*
1290 * Up to this point the pmd is present and huge and
1291 * userland has the whole access to the hugepage
1292 * during the split (which happens in place). If we
1293 * overwrite the pmd with the not-huge version
1294 * pointing to the pte here (which of course we could
1295 * if all CPUs were bug free), userland could trigger
1296 * a small page size TLB miss on the small sized TLB
1297 * while the hugepage TLB entry is still established
1298 * in the huge TLB. Some CPU doesn't like that. See
1299 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1300 * Erratum 383 on page 93. Intel should be safe but is
1301 * also warns that it's only safe if the permission
1302 * and cache attributes of the two entries loaded in
1303 * the two TLB is identical (which should be the case
1304 * here). But it is generally safer to never allow
1305 * small and huge TLB entries for the same virtual
1306 * address to be loaded simultaneously. So instead of
1307 * doing "pmd_populate(); flush_tlb_range();" we first
1308 * mark the current pmd notpresent (atomically because
1309 * here the pmd_trans_huge and pmd_trans_splitting
1310 * must remain set at all times on the pmd until the
1311 * split is complete for this pmd), then we flush the
1312 * SMP TLB and finally we write the non-huge version
1313 * of the pmd entry with pmd_populate.
1314 */
1315 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1316 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1317 pmd_populate(mm, pmd, pgtable);
1318 ret = 1;
1319 }
1320 spin_unlock(&mm->page_table_lock);
1321
1322 return ret;
1323 }
1324
1325 /* must be called with anon_vma->root->lock hold */
1326 static void __split_huge_page(struct page *page,
1327 struct anon_vma *anon_vma)
1328 {
1329 int mapcount, mapcount2;
1330 struct anon_vma_chain *avc;
1331
1332 BUG_ON(!PageHead(page));
1333 BUG_ON(PageTail(page));
1334
1335 mapcount = 0;
1336 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1337 struct vm_area_struct *vma = avc->vma;
1338 unsigned long addr = vma_address(page, vma);
1339 BUG_ON(is_vma_temporary_stack(vma));
1340 if (addr == -EFAULT)
1341 continue;
1342 mapcount += __split_huge_page_splitting(page, vma, addr);
1343 }
1344 /*
1345 * It is critical that new vmas are added to the tail of the
1346 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1347 * and establishes a child pmd before
1348 * __split_huge_page_splitting() freezes the parent pmd (so if
1349 * we fail to prevent copy_huge_pmd() from running until the
1350 * whole __split_huge_page() is complete), we will still see
1351 * the newly established pmd of the child later during the
1352 * walk, to be able to set it as pmd_trans_splitting too.
1353 */
1354 if (mapcount != page_mapcount(page))
1355 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1356 mapcount, page_mapcount(page));
1357 BUG_ON(mapcount != page_mapcount(page));
1358
1359 __split_huge_page_refcount(page);
1360
1361 mapcount2 = 0;
1362 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1363 struct vm_area_struct *vma = avc->vma;
1364 unsigned long addr = vma_address(page, vma);
1365 BUG_ON(is_vma_temporary_stack(vma));
1366 if (addr == -EFAULT)
1367 continue;
1368 mapcount2 += __split_huge_page_map(page, vma, addr);
1369 }
1370 if (mapcount != mapcount2)
1371 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1372 mapcount, mapcount2, page_mapcount(page));
1373 BUG_ON(mapcount != mapcount2);
1374 }
1375
1376 int split_huge_page(struct page *page)
1377 {
1378 struct anon_vma *anon_vma;
1379 int ret = 1;
1380
1381 BUG_ON(!PageAnon(page));
1382 anon_vma = page_lock_anon_vma(page);
1383 if (!anon_vma)
1384 goto out;
1385 ret = 0;
1386 if (!PageCompound(page))
1387 goto out_unlock;
1388
1389 BUG_ON(!PageSwapBacked(page));
1390 __split_huge_page(page, anon_vma);
1391
1392 BUG_ON(PageCompound(page));
1393 out_unlock:
1394 page_unlock_anon_vma(anon_vma);
1395 out:
1396 return ret;
1397 }
1398
1399 int hugepage_madvise(struct vm_area_struct *vma,
1400 unsigned long *vm_flags, int advice)
1401 {
1402 switch (advice) {
1403 case MADV_HUGEPAGE:
1404 /*
1405 * Be somewhat over-protective like KSM for now!
1406 */
1407 if (*vm_flags & (VM_HUGEPAGE |
1408 VM_SHARED | VM_MAYSHARE |
1409 VM_PFNMAP | VM_IO | VM_DONTEXPAND |
1410 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
1411 VM_MIXEDMAP | VM_SAO))
1412 return -EINVAL;
1413 *vm_flags &= ~VM_NOHUGEPAGE;
1414 *vm_flags |= VM_HUGEPAGE;
1415 /*
1416 * If the vma become good for khugepaged to scan,
1417 * register it here without waiting a page fault that
1418 * may not happen any time soon.
1419 */
1420 if (unlikely(khugepaged_enter_vma_merge(vma)))
1421 return -ENOMEM;
1422 break;
1423 case MADV_NOHUGEPAGE:
1424 /*
1425 * Be somewhat over-protective like KSM for now!
1426 */
1427 if (*vm_flags & (VM_NOHUGEPAGE |
1428 VM_SHARED | VM_MAYSHARE |
1429 VM_PFNMAP | VM_IO | VM_DONTEXPAND |
1430 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
1431 VM_MIXEDMAP | VM_SAO))
1432 return -EINVAL;
1433 *vm_flags &= ~VM_HUGEPAGE;
1434 *vm_flags |= VM_NOHUGEPAGE;
1435 /*
1436 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1437 * this vma even if we leave the mm registered in khugepaged if
1438 * it got registered before VM_NOHUGEPAGE was set.
1439 */
1440 break;
1441 }
1442
1443 return 0;
1444 }
1445
1446 static int __init khugepaged_slab_init(void)
1447 {
1448 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1449 sizeof(struct mm_slot),
1450 __alignof__(struct mm_slot), 0, NULL);
1451 if (!mm_slot_cache)
1452 return -ENOMEM;
1453
1454 return 0;
1455 }
1456
1457 static void __init khugepaged_slab_free(void)
1458 {
1459 kmem_cache_destroy(mm_slot_cache);
1460 mm_slot_cache = NULL;
1461 }
1462
1463 static inline struct mm_slot *alloc_mm_slot(void)
1464 {
1465 if (!mm_slot_cache) /* initialization failed */
1466 return NULL;
1467 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1468 }
1469
1470 static inline void free_mm_slot(struct mm_slot *mm_slot)
1471 {
1472 kmem_cache_free(mm_slot_cache, mm_slot);
1473 }
1474
1475 static int __init mm_slots_hash_init(void)
1476 {
1477 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1478 GFP_KERNEL);
1479 if (!mm_slots_hash)
1480 return -ENOMEM;
1481 return 0;
1482 }
1483
1484 #if 0
1485 static void __init mm_slots_hash_free(void)
1486 {
1487 kfree(mm_slots_hash);
1488 mm_slots_hash = NULL;
1489 }
1490 #endif
1491
1492 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1493 {
1494 struct mm_slot *mm_slot;
1495 struct hlist_head *bucket;
1496 struct hlist_node *node;
1497
1498 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1499 % MM_SLOTS_HASH_HEADS];
1500 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1501 if (mm == mm_slot->mm)
1502 return mm_slot;
1503 }
1504 return NULL;
1505 }
1506
1507 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1508 struct mm_slot *mm_slot)
1509 {
1510 struct hlist_head *bucket;
1511
1512 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1513 % MM_SLOTS_HASH_HEADS];
1514 mm_slot->mm = mm;
1515 hlist_add_head(&mm_slot->hash, bucket);
1516 }
1517
1518 static inline int khugepaged_test_exit(struct mm_struct *mm)
1519 {
1520 return atomic_read(&mm->mm_users) == 0;
1521 }
1522
1523 int __khugepaged_enter(struct mm_struct *mm)
1524 {
1525 struct mm_slot *mm_slot;
1526 int wakeup;
1527
1528 mm_slot = alloc_mm_slot();
1529 if (!mm_slot)
1530 return -ENOMEM;
1531
1532 /* __khugepaged_exit() must not run from under us */
1533 VM_BUG_ON(khugepaged_test_exit(mm));
1534 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1535 free_mm_slot(mm_slot);
1536 return 0;
1537 }
1538
1539 spin_lock(&khugepaged_mm_lock);
1540 insert_to_mm_slots_hash(mm, mm_slot);
1541 /*
1542 * Insert just behind the scanning cursor, to let the area settle
1543 * down a little.
1544 */
1545 wakeup = list_empty(&khugepaged_scan.mm_head);
1546 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1547 spin_unlock(&khugepaged_mm_lock);
1548
1549 atomic_inc(&mm->mm_count);
1550 if (wakeup)
1551 wake_up_interruptible(&khugepaged_wait);
1552
1553 return 0;
1554 }
1555
1556 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1557 {
1558 unsigned long hstart, hend;
1559 if (!vma->anon_vma)
1560 /*
1561 * Not yet faulted in so we will register later in the
1562 * page fault if needed.
1563 */
1564 return 0;
1565 if (vma->vm_file || vma->vm_ops)
1566 /* khugepaged not yet working on file or special mappings */
1567 return 0;
1568 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1569 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1570 hend = vma->vm_end & HPAGE_PMD_MASK;
1571 if (hstart < hend)
1572 return khugepaged_enter(vma);
1573 return 0;
1574 }
1575
1576 void __khugepaged_exit(struct mm_struct *mm)
1577 {
1578 struct mm_slot *mm_slot;
1579 int free = 0;
1580
1581 spin_lock(&khugepaged_mm_lock);
1582 mm_slot = get_mm_slot(mm);
1583 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1584 hlist_del(&mm_slot->hash);
1585 list_del(&mm_slot->mm_node);
1586 free = 1;
1587 }
1588
1589 if (free) {
1590 spin_unlock(&khugepaged_mm_lock);
1591 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1592 free_mm_slot(mm_slot);
1593 mmdrop(mm);
1594 } else if (mm_slot) {
1595 spin_unlock(&khugepaged_mm_lock);
1596 /*
1597 * This is required to serialize against
1598 * khugepaged_test_exit() (which is guaranteed to run
1599 * under mmap sem read mode). Stop here (after we
1600 * return all pagetables will be destroyed) until
1601 * khugepaged has finished working on the pagetables
1602 * under the mmap_sem.
1603 */
1604 down_write(&mm->mmap_sem);
1605 up_write(&mm->mmap_sem);
1606 } else
1607 spin_unlock(&khugepaged_mm_lock);
1608 }
1609
1610 static void release_pte_page(struct page *page)
1611 {
1612 /* 0 stands for page_is_file_cache(page) == false */
1613 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1614 unlock_page(page);
1615 putback_lru_page(page);
1616 }
1617
1618 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1619 {
1620 while (--_pte >= pte) {
1621 pte_t pteval = *_pte;
1622 if (!pte_none(pteval))
1623 release_pte_page(pte_page(pteval));
1624 }
1625 }
1626
1627 static void release_all_pte_pages(pte_t *pte)
1628 {
1629 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1630 }
1631
1632 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1633 unsigned long address,
1634 pte_t *pte)
1635 {
1636 struct page *page;
1637 pte_t *_pte;
1638 int referenced = 0, isolated = 0, none = 0;
1639 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1640 _pte++, address += PAGE_SIZE) {
1641 pte_t pteval = *_pte;
1642 if (pte_none(pteval)) {
1643 if (++none <= khugepaged_max_ptes_none)
1644 continue;
1645 else {
1646 release_pte_pages(pte, _pte);
1647 goto out;
1648 }
1649 }
1650 if (!pte_present(pteval) || !pte_write(pteval)) {
1651 release_pte_pages(pte, _pte);
1652 goto out;
1653 }
1654 page = vm_normal_page(vma, address, pteval);
1655 if (unlikely(!page)) {
1656 release_pte_pages(pte, _pte);
1657 goto out;
1658 }
1659 VM_BUG_ON(PageCompound(page));
1660 BUG_ON(!PageAnon(page));
1661 VM_BUG_ON(!PageSwapBacked(page));
1662
1663 /* cannot use mapcount: can't collapse if there's a gup pin */
1664 if (page_count(page) != 1) {
1665 release_pte_pages(pte, _pte);
1666 goto out;
1667 }
1668 /*
1669 * We can do it before isolate_lru_page because the
1670 * page can't be freed from under us. NOTE: PG_lock
1671 * is needed to serialize against split_huge_page
1672 * when invoked from the VM.
1673 */
1674 if (!trylock_page(page)) {
1675 release_pte_pages(pte, _pte);
1676 goto out;
1677 }
1678 /*
1679 * Isolate the page to avoid collapsing an hugepage
1680 * currently in use by the VM.
1681 */
1682 if (isolate_lru_page(page)) {
1683 unlock_page(page);
1684 release_pte_pages(pte, _pte);
1685 goto out;
1686 }
1687 /* 0 stands for page_is_file_cache(page) == false */
1688 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1689 VM_BUG_ON(!PageLocked(page));
1690 VM_BUG_ON(PageLRU(page));
1691
1692 /* If there is no mapped pte young don't collapse the page */
1693 if (pte_young(pteval) || PageReferenced(page) ||
1694 mmu_notifier_test_young(vma->vm_mm, address))
1695 referenced = 1;
1696 }
1697 if (unlikely(!referenced))
1698 release_all_pte_pages(pte);
1699 else
1700 isolated = 1;
1701 out:
1702 return isolated;
1703 }
1704
1705 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1706 struct vm_area_struct *vma,
1707 unsigned long address,
1708 spinlock_t *ptl)
1709 {
1710 pte_t *_pte;
1711 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1712 pte_t pteval = *_pte;
1713 struct page *src_page;
1714
1715 if (pte_none(pteval)) {
1716 clear_user_highpage(page, address);
1717 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1718 } else {
1719 src_page = pte_page(pteval);
1720 copy_user_highpage(page, src_page, address, vma);
1721 VM_BUG_ON(page_mapcount(src_page) != 1);
1722 VM_BUG_ON(page_count(src_page) != 2);
1723 release_pte_page(src_page);
1724 /*
1725 * ptl mostly unnecessary, but preempt has to
1726 * be disabled to update the per-cpu stats
1727 * inside page_remove_rmap().
1728 */
1729 spin_lock(ptl);
1730 /*
1731 * paravirt calls inside pte_clear here are
1732 * superfluous.
1733 */
1734 pte_clear(vma->vm_mm, address, _pte);
1735 page_remove_rmap(src_page);
1736 spin_unlock(ptl);
1737 free_page_and_swap_cache(src_page);
1738 }
1739
1740 address += PAGE_SIZE;
1741 page++;
1742 }
1743 }
1744
1745 static void collapse_huge_page(struct mm_struct *mm,
1746 unsigned long address,
1747 struct page **hpage,
1748 struct vm_area_struct *vma)
1749 {
1750 pgd_t *pgd;
1751 pud_t *pud;
1752 pmd_t *pmd, _pmd;
1753 pte_t *pte;
1754 pgtable_t pgtable;
1755 struct page *new_page;
1756 spinlock_t *ptl;
1757 int isolated;
1758 unsigned long hstart, hend;
1759
1760 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1761 #ifndef CONFIG_NUMA
1762 VM_BUG_ON(!*hpage);
1763 new_page = *hpage;
1764 #else
1765 VM_BUG_ON(*hpage);
1766 /*
1767 * Allocate the page while the vma is still valid and under
1768 * the mmap_sem read mode so there is no memory allocation
1769 * later when we take the mmap_sem in write mode. This is more
1770 * friendly behavior (OTOH it may actually hide bugs) to
1771 * filesystems in userland with daemons allocating memory in
1772 * the userland I/O paths. Allocating memory with the
1773 * mmap_sem in read mode is good idea also to allow greater
1774 * scalability.
1775 */
1776 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address);
1777 if (unlikely(!new_page)) {
1778 up_read(&mm->mmap_sem);
1779 *hpage = ERR_PTR(-ENOMEM);
1780 return;
1781 }
1782 #endif
1783 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1784 up_read(&mm->mmap_sem);
1785 put_page(new_page);
1786 return;
1787 }
1788
1789 /* after allocating the hugepage upgrade to mmap_sem write mode */
1790 up_read(&mm->mmap_sem);
1791
1792 /*
1793 * Prevent all access to pagetables with the exception of
1794 * gup_fast later hanlded by the ptep_clear_flush and the VM
1795 * handled by the anon_vma lock + PG_lock.
1796 */
1797 down_write(&mm->mmap_sem);
1798 if (unlikely(khugepaged_test_exit(mm)))
1799 goto out;
1800
1801 vma = find_vma(mm, address);
1802 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1803 hend = vma->vm_end & HPAGE_PMD_MASK;
1804 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1805 goto out;
1806
1807 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1808 (vma->vm_flags & VM_NOHUGEPAGE))
1809 goto out;
1810
1811 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
1812 if (!vma->anon_vma || vma->vm_ops || vma->vm_file)
1813 goto out;
1814 if (is_vma_temporary_stack(vma))
1815 goto out;
1816 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1817
1818 pgd = pgd_offset(mm, address);
1819 if (!pgd_present(*pgd))
1820 goto out;
1821
1822 pud = pud_offset(pgd, address);
1823 if (!pud_present(*pud))
1824 goto out;
1825
1826 pmd = pmd_offset(pud, address);
1827 /* pmd can't go away or become huge under us */
1828 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1829 goto out;
1830
1831 anon_vma_lock(vma->anon_vma);
1832
1833 pte = pte_offset_map(pmd, address);
1834 ptl = pte_lockptr(mm, pmd);
1835
1836 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1837 /*
1838 * After this gup_fast can't run anymore. This also removes
1839 * any huge TLB entry from the CPU so we won't allow
1840 * huge and small TLB entries for the same virtual address
1841 * to avoid the risk of CPU bugs in that area.
1842 */
1843 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1844 spin_unlock(&mm->page_table_lock);
1845
1846 spin_lock(ptl);
1847 isolated = __collapse_huge_page_isolate(vma, address, pte);
1848 spin_unlock(ptl);
1849
1850 if (unlikely(!isolated)) {
1851 pte_unmap(pte);
1852 spin_lock(&mm->page_table_lock);
1853 BUG_ON(!pmd_none(*pmd));
1854 set_pmd_at(mm, address, pmd, _pmd);
1855 spin_unlock(&mm->page_table_lock);
1856 anon_vma_unlock(vma->anon_vma);
1857 goto out;
1858 }
1859
1860 /*
1861 * All pages are isolated and locked so anon_vma rmap
1862 * can't run anymore.
1863 */
1864 anon_vma_unlock(vma->anon_vma);
1865
1866 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1867 pte_unmap(pte);
1868 __SetPageUptodate(new_page);
1869 pgtable = pmd_pgtable(_pmd);
1870 VM_BUG_ON(page_count(pgtable) != 1);
1871 VM_BUG_ON(page_mapcount(pgtable) != 0);
1872
1873 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1874 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1875 _pmd = pmd_mkhuge(_pmd);
1876
1877 /*
1878 * spin_lock() below is not the equivalent of smp_wmb(), so
1879 * this is needed to avoid the copy_huge_page writes to become
1880 * visible after the set_pmd_at() write.
1881 */
1882 smp_wmb();
1883
1884 spin_lock(&mm->page_table_lock);
1885 BUG_ON(!pmd_none(*pmd));
1886 page_add_new_anon_rmap(new_page, vma, address);
1887 set_pmd_at(mm, address, pmd, _pmd);
1888 update_mmu_cache(vma, address, entry);
1889 prepare_pmd_huge_pte(pgtable, mm);
1890 mm->nr_ptes--;
1891 spin_unlock(&mm->page_table_lock);
1892
1893 #ifndef CONFIG_NUMA
1894 *hpage = NULL;
1895 #endif
1896 khugepaged_pages_collapsed++;
1897 out_up_write:
1898 up_write(&mm->mmap_sem);
1899 return;
1900
1901 out:
1902 mem_cgroup_uncharge_page(new_page);
1903 #ifdef CONFIG_NUMA
1904 put_page(new_page);
1905 #endif
1906 goto out_up_write;
1907 }
1908
1909 static int khugepaged_scan_pmd(struct mm_struct *mm,
1910 struct vm_area_struct *vma,
1911 unsigned long address,
1912 struct page **hpage)
1913 {
1914 pgd_t *pgd;
1915 pud_t *pud;
1916 pmd_t *pmd;
1917 pte_t *pte, *_pte;
1918 int ret = 0, referenced = 0, none = 0;
1919 struct page *page;
1920 unsigned long _address;
1921 spinlock_t *ptl;
1922
1923 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1924
1925 pgd = pgd_offset(mm, address);
1926 if (!pgd_present(*pgd))
1927 goto out;
1928
1929 pud = pud_offset(pgd, address);
1930 if (!pud_present(*pud))
1931 goto out;
1932
1933 pmd = pmd_offset(pud, address);
1934 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1935 goto out;
1936
1937 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1938 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1939 _pte++, _address += PAGE_SIZE) {
1940 pte_t pteval = *_pte;
1941 if (pte_none(pteval)) {
1942 if (++none <= khugepaged_max_ptes_none)
1943 continue;
1944 else
1945 goto out_unmap;
1946 }
1947 if (!pte_present(pteval) || !pte_write(pteval))
1948 goto out_unmap;
1949 page = vm_normal_page(vma, _address, pteval);
1950 if (unlikely(!page))
1951 goto out_unmap;
1952 VM_BUG_ON(PageCompound(page));
1953 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
1954 goto out_unmap;
1955 /* cannot use mapcount: can't collapse if there's a gup pin */
1956 if (page_count(page) != 1)
1957 goto out_unmap;
1958 if (pte_young(pteval) || PageReferenced(page) ||
1959 mmu_notifier_test_young(vma->vm_mm, address))
1960 referenced = 1;
1961 }
1962 if (referenced)
1963 ret = 1;
1964 out_unmap:
1965 pte_unmap_unlock(pte, ptl);
1966 if (ret)
1967 /* collapse_huge_page will return with the mmap_sem released */
1968 collapse_huge_page(mm, address, hpage, vma);
1969 out:
1970 return ret;
1971 }
1972
1973 static void collect_mm_slot(struct mm_slot *mm_slot)
1974 {
1975 struct mm_struct *mm = mm_slot->mm;
1976
1977 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
1978
1979 if (khugepaged_test_exit(mm)) {
1980 /* free mm_slot */
1981 hlist_del(&mm_slot->hash);
1982 list_del(&mm_slot->mm_node);
1983
1984 /*
1985 * Not strictly needed because the mm exited already.
1986 *
1987 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1988 */
1989
1990 /* khugepaged_mm_lock actually not necessary for the below */
1991 free_mm_slot(mm_slot);
1992 mmdrop(mm);
1993 }
1994 }
1995
1996 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1997 struct page **hpage)
1998 {
1999 struct mm_slot *mm_slot;
2000 struct mm_struct *mm;
2001 struct vm_area_struct *vma;
2002 int progress = 0;
2003
2004 VM_BUG_ON(!pages);
2005 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2006
2007 if (khugepaged_scan.mm_slot)
2008 mm_slot = khugepaged_scan.mm_slot;
2009 else {
2010 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2011 struct mm_slot, mm_node);
2012 khugepaged_scan.address = 0;
2013 khugepaged_scan.mm_slot = mm_slot;
2014 }
2015 spin_unlock(&khugepaged_mm_lock);
2016
2017 mm = mm_slot->mm;
2018 down_read(&mm->mmap_sem);
2019 if (unlikely(khugepaged_test_exit(mm)))
2020 vma = NULL;
2021 else
2022 vma = find_vma(mm, khugepaged_scan.address);
2023
2024 progress++;
2025 for (; vma; vma = vma->vm_next) {
2026 unsigned long hstart, hend;
2027
2028 cond_resched();
2029 if (unlikely(khugepaged_test_exit(mm))) {
2030 progress++;
2031 break;
2032 }
2033
2034 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2035 !khugepaged_always()) ||
2036 (vma->vm_flags & VM_NOHUGEPAGE)) {
2037 skip:
2038 progress++;
2039 continue;
2040 }
2041 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
2042 if (!vma->anon_vma || vma->vm_ops || vma->vm_file)
2043 goto skip;
2044 if (is_vma_temporary_stack(vma))
2045 goto skip;
2046
2047 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
2048
2049 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2050 hend = vma->vm_end & HPAGE_PMD_MASK;
2051 if (hstart >= hend)
2052 goto skip;
2053 if (khugepaged_scan.address > hend)
2054 goto skip;
2055 if (khugepaged_scan.address < hstart)
2056 khugepaged_scan.address = hstart;
2057 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2058
2059 while (khugepaged_scan.address < hend) {
2060 int ret;
2061 cond_resched();
2062 if (unlikely(khugepaged_test_exit(mm)))
2063 goto breakouterloop;
2064
2065 VM_BUG_ON(khugepaged_scan.address < hstart ||
2066 khugepaged_scan.address + HPAGE_PMD_SIZE >
2067 hend);
2068 ret = khugepaged_scan_pmd(mm, vma,
2069 khugepaged_scan.address,
2070 hpage);
2071 /* move to next address */
2072 khugepaged_scan.address += HPAGE_PMD_SIZE;
2073 progress += HPAGE_PMD_NR;
2074 if (ret)
2075 /* we released mmap_sem so break loop */
2076 goto breakouterloop_mmap_sem;
2077 if (progress >= pages)
2078 goto breakouterloop;
2079 }
2080 }
2081 breakouterloop:
2082 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2083 breakouterloop_mmap_sem:
2084
2085 spin_lock(&khugepaged_mm_lock);
2086 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2087 /*
2088 * Release the current mm_slot if this mm is about to die, or
2089 * if we scanned all vmas of this mm.
2090 */
2091 if (khugepaged_test_exit(mm) || !vma) {
2092 /*
2093 * Make sure that if mm_users is reaching zero while
2094 * khugepaged runs here, khugepaged_exit will find
2095 * mm_slot not pointing to the exiting mm.
2096 */
2097 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2098 khugepaged_scan.mm_slot = list_entry(
2099 mm_slot->mm_node.next,
2100 struct mm_slot, mm_node);
2101 khugepaged_scan.address = 0;
2102 } else {
2103 khugepaged_scan.mm_slot = NULL;
2104 khugepaged_full_scans++;
2105 }
2106
2107 collect_mm_slot(mm_slot);
2108 }
2109
2110 return progress;
2111 }
2112
2113 static int khugepaged_has_work(void)
2114 {
2115 return !list_empty(&khugepaged_scan.mm_head) &&
2116 khugepaged_enabled();
2117 }
2118
2119 static int khugepaged_wait_event(void)
2120 {
2121 return !list_empty(&khugepaged_scan.mm_head) ||
2122 !khugepaged_enabled();
2123 }
2124
2125 static void khugepaged_do_scan(struct page **hpage)
2126 {
2127 unsigned int progress = 0, pass_through_head = 0;
2128 unsigned int pages = khugepaged_pages_to_scan;
2129
2130 barrier(); /* write khugepaged_pages_to_scan to local stack */
2131
2132 while (progress < pages) {
2133 cond_resched();
2134
2135 #ifndef CONFIG_NUMA
2136 if (!*hpage) {
2137 *hpage = alloc_hugepage(khugepaged_defrag());
2138 if (unlikely(!*hpage))
2139 break;
2140 }
2141 #else
2142 if (IS_ERR(*hpage))
2143 break;
2144 #endif
2145
2146 if (unlikely(kthread_should_stop() || freezing(current)))
2147 break;
2148
2149 spin_lock(&khugepaged_mm_lock);
2150 if (!khugepaged_scan.mm_slot)
2151 pass_through_head++;
2152 if (khugepaged_has_work() &&
2153 pass_through_head < 2)
2154 progress += khugepaged_scan_mm_slot(pages - progress,
2155 hpage);
2156 else
2157 progress = pages;
2158 spin_unlock(&khugepaged_mm_lock);
2159 }
2160 }
2161
2162 static void khugepaged_alloc_sleep(void)
2163 {
2164 DEFINE_WAIT(wait);
2165 add_wait_queue(&khugepaged_wait, &wait);
2166 schedule_timeout_interruptible(
2167 msecs_to_jiffies(
2168 khugepaged_alloc_sleep_millisecs));
2169 remove_wait_queue(&khugepaged_wait, &wait);
2170 }
2171
2172 #ifndef CONFIG_NUMA
2173 static struct page *khugepaged_alloc_hugepage(void)
2174 {
2175 struct page *hpage;
2176
2177 do {
2178 hpage = alloc_hugepage(khugepaged_defrag());
2179 if (!hpage)
2180 khugepaged_alloc_sleep();
2181 } while (unlikely(!hpage) &&
2182 likely(khugepaged_enabled()));
2183 return hpage;
2184 }
2185 #endif
2186
2187 static void khugepaged_loop(void)
2188 {
2189 struct page *hpage;
2190
2191 #ifdef CONFIG_NUMA
2192 hpage = NULL;
2193 #endif
2194 while (likely(khugepaged_enabled())) {
2195 #ifndef CONFIG_NUMA
2196 hpage = khugepaged_alloc_hugepage();
2197 if (unlikely(!hpage))
2198 break;
2199 #else
2200 if (IS_ERR(hpage)) {
2201 khugepaged_alloc_sleep();
2202 hpage = NULL;
2203 }
2204 #endif
2205
2206 khugepaged_do_scan(&hpage);
2207 #ifndef CONFIG_NUMA
2208 if (hpage)
2209 put_page(hpage);
2210 #endif
2211 try_to_freeze();
2212 if (unlikely(kthread_should_stop()))
2213 break;
2214 if (khugepaged_has_work()) {
2215 DEFINE_WAIT(wait);
2216 if (!khugepaged_scan_sleep_millisecs)
2217 continue;
2218 add_wait_queue(&khugepaged_wait, &wait);
2219 schedule_timeout_interruptible(
2220 msecs_to_jiffies(
2221 khugepaged_scan_sleep_millisecs));
2222 remove_wait_queue(&khugepaged_wait, &wait);
2223 } else if (khugepaged_enabled())
2224 wait_event_freezable(khugepaged_wait,
2225 khugepaged_wait_event());
2226 }
2227 }
2228
2229 static int khugepaged(void *none)
2230 {
2231 struct mm_slot *mm_slot;
2232
2233 set_freezable();
2234 set_user_nice(current, 19);
2235
2236 /* serialize with start_khugepaged() */
2237 mutex_lock(&khugepaged_mutex);
2238
2239 for (;;) {
2240 mutex_unlock(&khugepaged_mutex);
2241 VM_BUG_ON(khugepaged_thread != current);
2242 khugepaged_loop();
2243 VM_BUG_ON(khugepaged_thread != current);
2244
2245 mutex_lock(&khugepaged_mutex);
2246 if (!khugepaged_enabled())
2247 break;
2248 if (unlikely(kthread_should_stop()))
2249 break;
2250 }
2251
2252 spin_lock(&khugepaged_mm_lock);
2253 mm_slot = khugepaged_scan.mm_slot;
2254 khugepaged_scan.mm_slot = NULL;
2255 if (mm_slot)
2256 collect_mm_slot(mm_slot);
2257 spin_unlock(&khugepaged_mm_lock);
2258
2259 khugepaged_thread = NULL;
2260 mutex_unlock(&khugepaged_mutex);
2261
2262 return 0;
2263 }
2264
2265 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2266 {
2267 struct page *page;
2268
2269 spin_lock(&mm->page_table_lock);
2270 if (unlikely(!pmd_trans_huge(*pmd))) {
2271 spin_unlock(&mm->page_table_lock);
2272 return;
2273 }
2274 page = pmd_page(*pmd);
2275 VM_BUG_ON(!page_count(page));
2276 get_page(page);
2277 spin_unlock(&mm->page_table_lock);
2278
2279 split_huge_page(page);
2280
2281 put_page(page);
2282 BUG_ON(pmd_trans_huge(*pmd));
2283 }
2284
2285 static void split_huge_page_address(struct mm_struct *mm,
2286 unsigned long address)
2287 {
2288 pgd_t *pgd;
2289 pud_t *pud;
2290 pmd_t *pmd;
2291
2292 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2293
2294 pgd = pgd_offset(mm, address);
2295 if (!pgd_present(*pgd))
2296 return;
2297
2298 pud = pud_offset(pgd, address);
2299 if (!pud_present(*pud))
2300 return;
2301
2302 pmd = pmd_offset(pud, address);
2303 if (!pmd_present(*pmd))
2304 return;
2305 /*
2306 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2307 * materialize from under us.
2308 */
2309 split_huge_page_pmd(mm, pmd);
2310 }
2311
2312 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2313 unsigned long start,
2314 unsigned long end,
2315 long adjust_next)
2316 {
2317 /*
2318 * If the new start address isn't hpage aligned and it could
2319 * previously contain an hugepage: check if we need to split
2320 * an huge pmd.
2321 */
2322 if (start & ~HPAGE_PMD_MASK &&
2323 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2324 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2325 split_huge_page_address(vma->vm_mm, start);
2326
2327 /*
2328 * If the new end address isn't hpage aligned and it could
2329 * previously contain an hugepage: check if we need to split
2330 * an huge pmd.
2331 */
2332 if (end & ~HPAGE_PMD_MASK &&
2333 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2334 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2335 split_huge_page_address(vma->vm_mm, end);
2336
2337 /*
2338 * If we're also updating the vma->vm_next->vm_start, if the new
2339 * vm_next->vm_start isn't page aligned and it could previously
2340 * contain an hugepage: check if we need to split an huge pmd.
2341 */
2342 if (adjust_next > 0) {
2343 struct vm_area_struct *next = vma->vm_next;
2344 unsigned long nstart = next->vm_start;
2345 nstart += adjust_next << PAGE_SHIFT;
2346 if (nstart & ~HPAGE_PMD_MASK &&
2347 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2348 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2349 split_huge_page_address(next->vm_mm, nstart);
2350 }
2351 }