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thp: add numa awareness to hugepage allocations
[linux/fpc-iii.git] / mm / huge_memory.c
blobf6559e7711bd0c4316cde419cc49772e0d12d3c2
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 <asm/tlb.h>
19 #include <asm/pgalloc.h>
20 #include "internal.h"
21
22 /*
23 * By default transparent hugepage support is enabled for all mappings
24 * and khugepaged scans all mappings. Defrag is only invoked by
25 * khugepaged hugepage allocations and by page faults inside
26 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
27 * allocations.
28 */
29 unsigned long transparent_hugepage_flags __read_mostly =
30 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
31 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
32 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
33
34 /* default scan 8*512 pte (or vmas) every 30 second */
35 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
36 static unsigned int khugepaged_pages_collapsed;
37 static unsigned int khugepaged_full_scans;
38 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
39 /* during fragmentation poll the hugepage allocator once every minute */
40 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
41 static struct task_struct *khugepaged_thread __read_mostly;
42 static DEFINE_MUTEX(khugepaged_mutex);
43 static DEFINE_SPINLOCK(khugepaged_mm_lock);
44 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
45 /*
46 * default collapse hugepages if there is at least one pte mapped like
47 * it would have happened if the vma was large enough during page
48 * fault.
49 */
50 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
51
52 static int khugepaged(void *none);
53 static int mm_slots_hash_init(void);
54 static int khugepaged_slab_init(void);
55 static void khugepaged_slab_free(void);
56
57 #define MM_SLOTS_HASH_HEADS 1024
58 static struct hlist_head *mm_slots_hash __read_mostly;
59 static struct kmem_cache *mm_slot_cache __read_mostly;
60
61 /**
62 * struct mm_slot - hash lookup from mm to mm_slot
63 * @hash: hash collision list
64 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
65 * @mm: the mm that this information is valid for
66 */
67 struct mm_slot {
68 struct hlist_node hash;
69 struct list_head mm_node;
70 struct mm_struct *mm;
71 };
72
73 /**
74 * struct khugepaged_scan - cursor for scanning
75 * @mm_head: the head of the mm list to scan
76 * @mm_slot: the current mm_slot we are scanning
77 * @address: the next address inside that to be scanned
78 *
79 * There is only the one khugepaged_scan instance of this cursor structure.
80 */
81 struct khugepaged_scan {
82 struct list_head mm_head;
83 struct mm_slot *mm_slot;
84 unsigned long address;
85 } khugepaged_scan = {
86 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
87 };
88
89
90 static int set_recommended_min_free_kbytes(void)
91 {
92 struct zone *zone;
93 int nr_zones = 0;
94 unsigned long recommended_min;
95 extern int min_free_kbytes;
96
97 if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG,
98 &transparent_hugepage_flags) &&
99 !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
100 &transparent_hugepage_flags))
101 return 0;
102
103 for_each_populated_zone(zone)
104 nr_zones++;
105
106 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
107 recommended_min = pageblock_nr_pages * nr_zones * 2;
108
109 /*
110 * Make sure that on average at least two pageblocks are almost free
111 * of another type, one for a migratetype to fall back to and a
112 * second to avoid subsequent fallbacks of other types There are 3
113 * MIGRATE_TYPES we care about.
114 */
115 recommended_min += pageblock_nr_pages * nr_zones *
116 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
117
118 /* don't ever allow to reserve more than 5% of the lowmem */
119 recommended_min = min(recommended_min,
120 (unsigned long) nr_free_buffer_pages() / 20);
121 recommended_min <<= (PAGE_SHIFT-10);
122
123 if (recommended_min > min_free_kbytes)
124 min_free_kbytes = recommended_min;
125 setup_per_zone_wmarks();
126 return 0;
127 }
128 late_initcall(set_recommended_min_free_kbytes);
129
130 static int start_khugepaged(void)
131 {
132 int err = 0;
133 if (khugepaged_enabled()) {
134 int wakeup;
135 if (unlikely(!mm_slot_cache || !mm_slots_hash)) {
136 err = -ENOMEM;
137 goto out;
138 }
139 mutex_lock(&khugepaged_mutex);
140 if (!khugepaged_thread)
141 khugepaged_thread = kthread_run(khugepaged, NULL,
142 "khugepaged");
143 if (unlikely(IS_ERR(khugepaged_thread))) {
144 printk(KERN_ERR
145 "khugepaged: kthread_run(khugepaged) failed\n");
146 err = PTR_ERR(khugepaged_thread);
147 khugepaged_thread = NULL;
148 }
149 wakeup = !list_empty(&khugepaged_scan.mm_head);
150 mutex_unlock(&khugepaged_mutex);
151 if (wakeup)
152 wake_up_interruptible(&khugepaged_wait);
153
154 set_recommended_min_free_kbytes();
155 } else
156 /* wakeup to exit */
157 wake_up_interruptible(&khugepaged_wait);
158 out:
159 return err;
160 }
161
162 #ifdef CONFIG_SYSFS
163
164 static ssize_t double_flag_show(struct kobject *kobj,
165 struct kobj_attribute *attr, char *buf,
166 enum transparent_hugepage_flag enabled,
167 enum transparent_hugepage_flag req_madv)
168 {
169 if (test_bit(enabled, &transparent_hugepage_flags)) {
170 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
171 return sprintf(buf, "[always] madvise never\n");
172 } else if (test_bit(req_madv, &transparent_hugepage_flags))
173 return sprintf(buf, "always [madvise] never\n");
174 else
175 return sprintf(buf, "always madvise [never]\n");
176 }
177 static ssize_t double_flag_store(struct kobject *kobj,
178 struct kobj_attribute *attr,
179 const char *buf, size_t count,
180 enum transparent_hugepage_flag enabled,
181 enum transparent_hugepage_flag req_madv)
182 {
183 if (!memcmp("always", buf,
184 min(sizeof("always")-1, count))) {
185 set_bit(enabled, &transparent_hugepage_flags);
186 clear_bit(req_madv, &transparent_hugepage_flags);
187 } else if (!memcmp("madvise", buf,
188 min(sizeof("madvise")-1, count))) {
189 clear_bit(enabled, &transparent_hugepage_flags);
190 set_bit(req_madv, &transparent_hugepage_flags);
191 } else if (!memcmp("never", buf,
192 min(sizeof("never")-1, count))) {
193 clear_bit(enabled, &transparent_hugepage_flags);
194 clear_bit(req_madv, &transparent_hugepage_flags);
195 } else
196 return -EINVAL;
197
198 return count;
199 }
200
201 static ssize_t enabled_show(struct kobject *kobj,
202 struct kobj_attribute *attr, char *buf)
203 {
204 return double_flag_show(kobj, attr, buf,
205 TRANSPARENT_HUGEPAGE_FLAG,
206 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
207 }
208 static ssize_t enabled_store(struct kobject *kobj,
209 struct kobj_attribute *attr,
210 const char *buf, size_t count)
211 {
212 ssize_t ret;
213
214 ret = double_flag_store(kobj, attr, buf, count,
215 TRANSPARENT_HUGEPAGE_FLAG,
216 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
217
218 if (ret > 0) {
219 int err = start_khugepaged();
220 if (err)
221 ret = err;
222 }
223
224 if (ret > 0 &&
225 (test_bit(TRANSPARENT_HUGEPAGE_FLAG,
226 &transparent_hugepage_flags) ||
227 test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
228 &transparent_hugepage_flags)))
229 set_recommended_min_free_kbytes();
230
231 return ret;
232 }
233 static struct kobj_attribute enabled_attr =
234 __ATTR(enabled, 0644, enabled_show, enabled_store);
235
236 static ssize_t single_flag_show(struct kobject *kobj,
237 struct kobj_attribute *attr, char *buf,
238 enum transparent_hugepage_flag flag)
239 {
240 if (test_bit(flag, &transparent_hugepage_flags))
241 return sprintf(buf, "[yes] no\n");
242 else
243 return sprintf(buf, "yes [no]\n");
244 }
245 static ssize_t single_flag_store(struct kobject *kobj,
246 struct kobj_attribute *attr,
247 const char *buf, size_t count,
248 enum transparent_hugepage_flag flag)
249 {
250 if (!memcmp("yes", buf,
251 min(sizeof("yes")-1, count))) {
252 set_bit(flag, &transparent_hugepage_flags);
253 } else if (!memcmp("no", buf,
254 min(sizeof("no")-1, count))) {
255 clear_bit(flag, &transparent_hugepage_flags);
256 } else
257 return -EINVAL;
258
259 return count;
260 }
261
262 /*
263 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
264 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
265 * memory just to allocate one more hugepage.
266 */
267 static ssize_t defrag_show(struct kobject *kobj,
268 struct kobj_attribute *attr, char *buf)
269 {
270 return double_flag_show(kobj, attr, buf,
271 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
272 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
273 }
274 static ssize_t defrag_store(struct kobject *kobj,
275 struct kobj_attribute *attr,
276 const char *buf, size_t count)
277 {
278 return double_flag_store(kobj, attr, buf, count,
279 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
280 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
281 }
282 static struct kobj_attribute defrag_attr =
283 __ATTR(defrag, 0644, defrag_show, defrag_store);
284
285 #ifdef CONFIG_DEBUG_VM
286 static ssize_t debug_cow_show(struct kobject *kobj,
287 struct kobj_attribute *attr, char *buf)
288 {
289 return single_flag_show(kobj, attr, buf,
290 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
291 }
292 static ssize_t debug_cow_store(struct kobject *kobj,
293 struct kobj_attribute *attr,
294 const char *buf, size_t count)
295 {
296 return single_flag_store(kobj, attr, buf, count,
297 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
298 }
299 static struct kobj_attribute debug_cow_attr =
300 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
301 #endif /* CONFIG_DEBUG_VM */
302
303 static struct attribute *hugepage_attr[] = {
304 &enabled_attr.attr,
305 &defrag_attr.attr,
306 #ifdef CONFIG_DEBUG_VM
307 &debug_cow_attr.attr,
308 #endif
309 NULL,
310 };
311
312 static struct attribute_group hugepage_attr_group = {
313 .attrs = hugepage_attr,
314 };
315
316 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
317 struct kobj_attribute *attr,
318 char *buf)
319 {
320 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
321 }
322
323 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
324 struct kobj_attribute *attr,
325 const char *buf, size_t count)
326 {
327 unsigned long msecs;
328 int err;
329
330 err = strict_strtoul(buf, 10, &msecs);
331 if (err || msecs > UINT_MAX)
332 return -EINVAL;
333
334 khugepaged_scan_sleep_millisecs = msecs;
335 wake_up_interruptible(&khugepaged_wait);
336
337 return count;
338 }
339 static struct kobj_attribute scan_sleep_millisecs_attr =
340 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
341 scan_sleep_millisecs_store);
342
343 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
344 struct kobj_attribute *attr,
345 char *buf)
346 {
347 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
348 }
349
350 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
351 struct kobj_attribute *attr,
352 const char *buf, size_t count)
353 {
354 unsigned long msecs;
355 int err;
356
357 err = strict_strtoul(buf, 10, &msecs);
358 if (err || msecs > UINT_MAX)
359 return -EINVAL;
360
361 khugepaged_alloc_sleep_millisecs = msecs;
362 wake_up_interruptible(&khugepaged_wait);
363
364 return count;
365 }
366 static struct kobj_attribute alloc_sleep_millisecs_attr =
367 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
368 alloc_sleep_millisecs_store);
369
370 static ssize_t pages_to_scan_show(struct kobject *kobj,
371 struct kobj_attribute *attr,
372 char *buf)
373 {
374 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
375 }
376 static ssize_t pages_to_scan_store(struct kobject *kobj,
377 struct kobj_attribute *attr,
378 const char *buf, size_t count)
379 {
380 int err;
381 unsigned long pages;
382
383 err = strict_strtoul(buf, 10, &pages);
384 if (err || !pages || pages > UINT_MAX)
385 return -EINVAL;
386
387 khugepaged_pages_to_scan = pages;
388
389 return count;
390 }
391 static struct kobj_attribute pages_to_scan_attr =
392 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
393 pages_to_scan_store);
394
395 static ssize_t pages_collapsed_show(struct kobject *kobj,
396 struct kobj_attribute *attr,
397 char *buf)
398 {
399 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
400 }
401 static struct kobj_attribute pages_collapsed_attr =
402 __ATTR_RO(pages_collapsed);
403
404 static ssize_t full_scans_show(struct kobject *kobj,
405 struct kobj_attribute *attr,
406 char *buf)
407 {
408 return sprintf(buf, "%u\n", khugepaged_full_scans);
409 }
410 static struct kobj_attribute full_scans_attr =
411 __ATTR_RO(full_scans);
412
413 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
414 struct kobj_attribute *attr, char *buf)
415 {
416 return single_flag_show(kobj, attr, buf,
417 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
418 }
419 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
420 struct kobj_attribute *attr,
421 const char *buf, size_t count)
422 {
423 return single_flag_store(kobj, attr, buf, count,
424 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
425 }
426 static struct kobj_attribute khugepaged_defrag_attr =
427 __ATTR(defrag, 0644, khugepaged_defrag_show,
428 khugepaged_defrag_store);
429
430 /*
431 * max_ptes_none controls if khugepaged should collapse hugepages over
432 * any unmapped ptes in turn potentially increasing the memory
433 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
434 * reduce the available free memory in the system as it
435 * runs. Increasing max_ptes_none will instead potentially reduce the
436 * free memory in the system during the khugepaged scan.
437 */
438 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
439 struct kobj_attribute *attr,
440 char *buf)
441 {
442 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
443 }
444 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
445 struct kobj_attribute *attr,
446 const char *buf, size_t count)
447 {
448 int err;
449 unsigned long max_ptes_none;
450
451 err = strict_strtoul(buf, 10, &max_ptes_none);
452 if (err || max_ptes_none > HPAGE_PMD_NR-1)
453 return -EINVAL;
454
455 khugepaged_max_ptes_none = max_ptes_none;
456
457 return count;
458 }
459 static struct kobj_attribute khugepaged_max_ptes_none_attr =
460 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
461 khugepaged_max_ptes_none_store);
462
463 static struct attribute *khugepaged_attr[] = {
464 &khugepaged_defrag_attr.attr,
465 &khugepaged_max_ptes_none_attr.attr,
466 &pages_to_scan_attr.attr,
467 &pages_collapsed_attr.attr,
468 &full_scans_attr.attr,
469 &scan_sleep_millisecs_attr.attr,
470 &alloc_sleep_millisecs_attr.attr,
471 NULL,
472 };
473
474 static struct attribute_group khugepaged_attr_group = {
475 .attrs = khugepaged_attr,
476 .name = "khugepaged",
477 };
478 #endif /* CONFIG_SYSFS */
479
480 static int __init hugepage_init(void)
481 {
482 int err;
483 #ifdef CONFIG_SYSFS
484 static struct kobject *hugepage_kobj;
485
486 err = -ENOMEM;
487 hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
488 if (unlikely(!hugepage_kobj)) {
489 printk(KERN_ERR "hugepage: failed kobject create\n");
490 goto out;
491 }
492
493 err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group);
494 if (err) {
495 printk(KERN_ERR "hugepage: failed register hugeage group\n");
496 goto out;
497 }
498
499 err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group);
500 if (err) {
501 printk(KERN_ERR "hugepage: failed register hugeage group\n");
502 goto out;
503 }
504 #endif
505
506 err = khugepaged_slab_init();
507 if (err)
508 goto out;
509
510 err = mm_slots_hash_init();
511 if (err) {
512 khugepaged_slab_free();
513 goto out;
514 }
515
516 start_khugepaged();
517
518 set_recommended_min_free_kbytes();
519
520 out:
521 return err;
522 }
523 module_init(hugepage_init)
524
525 static int __init setup_transparent_hugepage(char *str)
526 {
527 int ret = 0;
528 if (!str)
529 goto out;
530 if (!strcmp(str, "always")) {
531 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
532 &transparent_hugepage_flags);
533 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
534 &transparent_hugepage_flags);
535 ret = 1;
536 } else if (!strcmp(str, "madvise")) {
537 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
538 &transparent_hugepage_flags);
539 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
540 &transparent_hugepage_flags);
541 ret = 1;
542 } else if (!strcmp(str, "never")) {
543 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
544 &transparent_hugepage_flags);
545 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
546 &transparent_hugepage_flags);
547 ret = 1;
548 }
549 out:
550 if (!ret)
551 printk(KERN_WARNING
552 "transparent_hugepage= cannot parse, ignored\n");
553 return ret;
554 }
555 __setup("transparent_hugepage=", setup_transparent_hugepage);
556
557 static void prepare_pmd_huge_pte(pgtable_t pgtable,
558 struct mm_struct *mm)
559 {
560 assert_spin_locked(&mm->page_table_lock);
561
562 /* FIFO */
563 if (!mm->pmd_huge_pte)
564 INIT_LIST_HEAD(&pgtable->lru);
565 else
566 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
567 mm->pmd_huge_pte = pgtable;
568 }
569
570 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
571 {
572 if (likely(vma->vm_flags & VM_WRITE))
573 pmd = pmd_mkwrite(pmd);
574 return pmd;
575 }
576
577 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
578 struct vm_area_struct *vma,
579 unsigned long haddr, pmd_t *pmd,
580 struct page *page)
581 {
582 int ret = 0;
583 pgtable_t pgtable;
584
585 VM_BUG_ON(!PageCompound(page));
586 pgtable = pte_alloc_one(mm, haddr);
587 if (unlikely(!pgtable)) {
588 mem_cgroup_uncharge_page(page);
589 put_page(page);
590 return VM_FAULT_OOM;
591 }
592
593 clear_huge_page(page, haddr, HPAGE_PMD_NR);
594 __SetPageUptodate(page);
595
596 spin_lock(&mm->page_table_lock);
597 if (unlikely(!pmd_none(*pmd))) {
598 spin_unlock(&mm->page_table_lock);
599 mem_cgroup_uncharge_page(page);
600 put_page(page);
601 pte_free(mm, pgtable);
602 } else {
603 pmd_t entry;
604 entry = mk_pmd(page, vma->vm_page_prot);
605 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
606 entry = pmd_mkhuge(entry);
607 /*
608 * The spinlocking to take the lru_lock inside
609 * page_add_new_anon_rmap() acts as a full memory
610 * barrier to be sure clear_huge_page writes become
611 * visible after the set_pmd_at() write.
612 */
613 page_add_new_anon_rmap(page, vma, haddr);
614 set_pmd_at(mm, haddr, pmd, entry);
615 prepare_pmd_huge_pte(pgtable, mm);
616 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
617 spin_unlock(&mm->page_table_lock);
618 }
619
620 return ret;
621 }
622
623 static inline gfp_t alloc_hugepage_gfpmask(int defrag)
624 {
625 return GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT);
626 }
627
628 static inline struct page *alloc_hugepage_vma(int defrag,
629 struct vm_area_struct *vma,
630 unsigned long haddr)
631 {
632 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag),
633 HPAGE_PMD_ORDER, vma, haddr);
634 }
635
636 #ifndef CONFIG_NUMA
637 static inline struct page *alloc_hugepage(int defrag)
638 {
639 return alloc_pages(alloc_hugepage_gfpmask(defrag),
640 HPAGE_PMD_ORDER);
641 }
642 #endif
643
644 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
645 unsigned long address, pmd_t *pmd,
646 unsigned int flags)
647 {
648 struct page *page;
649 unsigned long haddr = address & HPAGE_PMD_MASK;
650 pte_t *pte;
651
652 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
653 if (unlikely(anon_vma_prepare(vma)))
654 return VM_FAULT_OOM;
655 if (unlikely(khugepaged_enter(vma)))
656 return VM_FAULT_OOM;
657 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
658 vma, haddr);
659 if (unlikely(!page))
660 goto out;
661 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
662 put_page(page);
663 goto out;
664 }
665
666 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
667 }
668 out:
669 /*
670 * Use __pte_alloc instead of pte_alloc_map, because we can't
671 * run pte_offset_map on the pmd, if an huge pmd could
672 * materialize from under us from a different thread.
673 */
674 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
675 return VM_FAULT_OOM;
676 /* if an huge pmd materialized from under us just retry later */
677 if (unlikely(pmd_trans_huge(*pmd)))
678 return 0;
679 /*
680 * A regular pmd is established and it can't morph into a huge pmd
681 * from under us anymore at this point because we hold the mmap_sem
682 * read mode and khugepaged takes it in write mode. So now it's
683 * safe to run pte_offset_map().
684 */
685 pte = pte_offset_map(pmd, address);
686 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
687 }
688
689 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
690 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
691 struct vm_area_struct *vma)
692 {
693 struct page *src_page;
694 pmd_t pmd;
695 pgtable_t pgtable;
696 int ret;
697
698 ret = -ENOMEM;
699 pgtable = pte_alloc_one(dst_mm, addr);
700 if (unlikely(!pgtable))
701 goto out;
702
703 spin_lock(&dst_mm->page_table_lock);
704 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
705
706 ret = -EAGAIN;
707 pmd = *src_pmd;
708 if (unlikely(!pmd_trans_huge(pmd))) {
709 pte_free(dst_mm, pgtable);
710 goto out_unlock;
711 }
712 if (unlikely(pmd_trans_splitting(pmd))) {
713 /* split huge page running from under us */
714 spin_unlock(&src_mm->page_table_lock);
715 spin_unlock(&dst_mm->page_table_lock);
716 pte_free(dst_mm, pgtable);
717
718 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
719 goto out;
720 }
721 src_page = pmd_page(pmd);
722 VM_BUG_ON(!PageHead(src_page));
723 get_page(src_page);
724 page_dup_rmap(src_page);
725 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
726
727 pmdp_set_wrprotect(src_mm, addr, src_pmd);
728 pmd = pmd_mkold(pmd_wrprotect(pmd));
729 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
730 prepare_pmd_huge_pte(pgtable, dst_mm);
731
732 ret = 0;
733 out_unlock:
734 spin_unlock(&src_mm->page_table_lock);
735 spin_unlock(&dst_mm->page_table_lock);
736 out:
737 return ret;
738 }
739
740 /* no "address" argument so destroys page coloring of some arch */
741 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
742 {
743 pgtable_t pgtable;
744
745 assert_spin_locked(&mm->page_table_lock);
746
747 /* FIFO */
748 pgtable = mm->pmd_huge_pte;
749 if (list_empty(&pgtable->lru))
750 mm->pmd_huge_pte = NULL;
751 else {
752 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
753 struct page, lru);
754 list_del(&pgtable->lru);
755 }
756 return pgtable;
757 }
758
759 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
760 struct vm_area_struct *vma,
761 unsigned long address,
762 pmd_t *pmd, pmd_t orig_pmd,
763 struct page *page,
764 unsigned long haddr)
765 {
766 pgtable_t pgtable;
767 pmd_t _pmd;
768 int ret = 0, i;
769 struct page **pages;
770
771 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
772 GFP_KERNEL);
773 if (unlikely(!pages)) {
774 ret |= VM_FAULT_OOM;
775 goto out;
776 }
777
778 for (i = 0; i < HPAGE_PMD_NR; i++) {
779 pages[i] = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
780 vma, address);
781 if (unlikely(!pages[i] ||
782 mem_cgroup_newpage_charge(pages[i], mm,
783 GFP_KERNEL))) {
784 if (pages[i])
785 put_page(pages[i]);
786 mem_cgroup_uncharge_start();
787 while (--i >= 0) {
788 mem_cgroup_uncharge_page(pages[i]);
789 put_page(pages[i]);
790 }
791 mem_cgroup_uncharge_end();
792 kfree(pages);
793 ret |= VM_FAULT_OOM;
794 goto out;
795 }
796 }
797
798 for (i = 0; i < HPAGE_PMD_NR; i++) {
799 copy_user_highpage(pages[i], page + i,
800 haddr + PAGE_SHIFT*i, vma);
801 __SetPageUptodate(pages[i]);
802 cond_resched();
803 }
804
805 spin_lock(&mm->page_table_lock);
806 if (unlikely(!pmd_same(*pmd, orig_pmd)))
807 goto out_free_pages;
808 VM_BUG_ON(!PageHead(page));
809
810 pmdp_clear_flush_notify(vma, haddr, pmd);
811 /* leave pmd empty until pte is filled */
812
813 pgtable = get_pmd_huge_pte(mm);
814 pmd_populate(mm, &_pmd, pgtable);
815
816 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
817 pte_t *pte, entry;
818 entry = mk_pte(pages[i], vma->vm_page_prot);
819 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
820 page_add_new_anon_rmap(pages[i], vma, haddr);
821 pte = pte_offset_map(&_pmd, haddr);
822 VM_BUG_ON(!pte_none(*pte));
823 set_pte_at(mm, haddr, pte, entry);
824 pte_unmap(pte);
825 }
826 kfree(pages);
827
828 mm->nr_ptes++;
829 smp_wmb(); /* make pte visible before pmd */
830 pmd_populate(mm, pmd, pgtable);
831 page_remove_rmap(page);
832 spin_unlock(&mm->page_table_lock);
833
834 ret |= VM_FAULT_WRITE;
835 put_page(page);
836
837 out:
838 return ret;
839
840 out_free_pages:
841 spin_unlock(&mm->page_table_lock);
842 mem_cgroup_uncharge_start();
843 for (i = 0; i < HPAGE_PMD_NR; i++) {
844 mem_cgroup_uncharge_page(pages[i]);
845 put_page(pages[i]);
846 }
847 mem_cgroup_uncharge_end();
848 kfree(pages);
849 goto out;
850 }
851
852 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
853 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
854 {
855 int ret = 0;
856 struct page *page, *new_page;
857 unsigned long haddr;
858
859 VM_BUG_ON(!vma->anon_vma);
860 spin_lock(&mm->page_table_lock);
861 if (unlikely(!pmd_same(*pmd, orig_pmd)))
862 goto out_unlock;
863
864 page = pmd_page(orig_pmd);
865 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
866 haddr = address & HPAGE_PMD_MASK;
867 if (page_mapcount(page) == 1) {
868 pmd_t entry;
869 entry = pmd_mkyoung(orig_pmd);
870 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
871 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
872 update_mmu_cache(vma, address, entry);
873 ret |= VM_FAULT_WRITE;
874 goto out_unlock;
875 }
876 get_page(page);
877 spin_unlock(&mm->page_table_lock);
878
879 if (transparent_hugepage_enabled(vma) &&
880 !transparent_hugepage_debug_cow())
881 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
882 vma, haddr);
883 else
884 new_page = NULL;
885
886 if (unlikely(!new_page)) {
887 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
888 pmd, orig_pmd, page, haddr);
889 put_page(page);
890 goto out;
891 }
892
893 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
894 put_page(new_page);
895 put_page(page);
896 ret |= VM_FAULT_OOM;
897 goto out;
898 }
899
900 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
901 __SetPageUptodate(new_page);
902
903 spin_lock(&mm->page_table_lock);
904 put_page(page);
905 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
906 mem_cgroup_uncharge_page(new_page);
907 put_page(new_page);
908 } else {
909 pmd_t entry;
910 VM_BUG_ON(!PageHead(page));
911 entry = mk_pmd(new_page, vma->vm_page_prot);
912 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
913 entry = pmd_mkhuge(entry);
914 pmdp_clear_flush_notify(vma, haddr, pmd);
915 page_add_new_anon_rmap(new_page, vma, haddr);
916 set_pmd_at(mm, haddr, pmd, entry);
917 update_mmu_cache(vma, address, entry);
918 page_remove_rmap(page);
919 put_page(page);
920 ret |= VM_FAULT_WRITE;
921 }
922 out_unlock:
923 spin_unlock(&mm->page_table_lock);
924 out:
925 return ret;
926 }
927
928 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
929 unsigned long addr,
930 pmd_t *pmd,
931 unsigned int flags)
932 {
933 struct page *page = NULL;
934
935 assert_spin_locked(&mm->page_table_lock);
936
937 if (flags & FOLL_WRITE && !pmd_write(*pmd))
938 goto out;
939
940 page = pmd_page(*pmd);
941 VM_BUG_ON(!PageHead(page));
942 if (flags & FOLL_TOUCH) {
943 pmd_t _pmd;
944 /*
945 * We should set the dirty bit only for FOLL_WRITE but
946 * for now the dirty bit in the pmd is meaningless.
947 * And if the dirty bit will become meaningful and
948 * we'll only set it with FOLL_WRITE, an atomic
949 * set_bit will be required on the pmd to set the
950 * young bit, instead of the current set_pmd_at.
951 */
952 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
953 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
954 }
955 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
956 VM_BUG_ON(!PageCompound(page));
957 if (flags & FOLL_GET)
958 get_page(page);
959
960 out:
961 return page;
962 }
963
964 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
965 pmd_t *pmd)
966 {
967 int ret = 0;
968
969 spin_lock(&tlb->mm->page_table_lock);
970 if (likely(pmd_trans_huge(*pmd))) {
971 if (unlikely(pmd_trans_splitting(*pmd))) {
972 spin_unlock(&tlb->mm->page_table_lock);
973 wait_split_huge_page(vma->anon_vma,
974 pmd);
975 } else {
976 struct page *page;
977 pgtable_t pgtable;
978 pgtable = get_pmd_huge_pte(tlb->mm);
979 page = pmd_page(*pmd);
980 pmd_clear(pmd);
981 page_remove_rmap(page);
982 VM_BUG_ON(page_mapcount(page) < 0);
983 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
984 VM_BUG_ON(!PageHead(page));
985 spin_unlock(&tlb->mm->page_table_lock);
986 tlb_remove_page(tlb, page);
987 pte_free(tlb->mm, pgtable);
988 ret = 1;
989 }
990 } else
991 spin_unlock(&tlb->mm->page_table_lock);
992
993 return ret;
994 }
995
996 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
997 unsigned long addr, unsigned long end,
998 unsigned char *vec)
999 {
1000 int ret = 0;
1001
1002 spin_lock(&vma->vm_mm->page_table_lock);
1003 if (likely(pmd_trans_huge(*pmd))) {
1004 ret = !pmd_trans_splitting(*pmd);
1005 spin_unlock(&vma->vm_mm->page_table_lock);
1006 if (unlikely(!ret))
1007 wait_split_huge_page(vma->anon_vma, pmd);
1008 else {
1009 /*
1010 * All logical pages in the range are present
1011 * if backed by a huge page.
1012 */
1013 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1014 }
1015 } else
1016 spin_unlock(&vma->vm_mm->page_table_lock);
1017
1018 return ret;
1019 }
1020
1021 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1022 unsigned long addr, pgprot_t newprot)
1023 {
1024 struct mm_struct *mm = vma->vm_mm;
1025 int ret = 0;
1026
1027 spin_lock(&mm->page_table_lock);
1028 if (likely(pmd_trans_huge(*pmd))) {
1029 if (unlikely(pmd_trans_splitting(*pmd))) {
1030 spin_unlock(&mm->page_table_lock);
1031 wait_split_huge_page(vma->anon_vma, pmd);
1032 } else {
1033 pmd_t entry;
1034
1035 entry = pmdp_get_and_clear(mm, addr, pmd);
1036 entry = pmd_modify(entry, newprot);
1037 set_pmd_at(mm, addr, pmd, entry);
1038 spin_unlock(&vma->vm_mm->page_table_lock);
1039 flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
1040 ret = 1;
1041 }
1042 } else
1043 spin_unlock(&vma->vm_mm->page_table_lock);
1044
1045 return ret;
1046 }
1047
1048 pmd_t *page_check_address_pmd(struct page *page,
1049 struct mm_struct *mm,
1050 unsigned long address,
1051 enum page_check_address_pmd_flag flag)
1052 {
1053 pgd_t *pgd;
1054 pud_t *pud;
1055 pmd_t *pmd, *ret = NULL;
1056
1057 if (address & ~HPAGE_PMD_MASK)
1058 goto out;
1059
1060 pgd = pgd_offset(mm, address);
1061 if (!pgd_present(*pgd))
1062 goto out;
1063
1064 pud = pud_offset(pgd, address);
1065 if (!pud_present(*pud))
1066 goto out;
1067
1068 pmd = pmd_offset(pud, address);
1069 if (pmd_none(*pmd))
1070 goto out;
1071 if (pmd_page(*pmd) != page)
1072 goto out;
1073 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1074 pmd_trans_splitting(*pmd));
1075 if (pmd_trans_huge(*pmd)) {
1076 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1077 !pmd_trans_splitting(*pmd));
1078 ret = pmd;
1079 }
1080 out:
1081 return ret;
1082 }
1083
1084 static int __split_huge_page_splitting(struct page *page,
1085 struct vm_area_struct *vma,
1086 unsigned long address)
1087 {
1088 struct mm_struct *mm = vma->vm_mm;
1089 pmd_t *pmd;
1090 int ret = 0;
1091
1092 spin_lock(&mm->page_table_lock);
1093 pmd = page_check_address_pmd(page, mm, address,
1094 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1095 if (pmd) {
1096 /*
1097 * We can't temporarily set the pmd to null in order
1098 * to split it, the pmd must remain marked huge at all
1099 * times or the VM won't take the pmd_trans_huge paths
1100 * and it won't wait on the anon_vma->root->lock to
1101 * serialize against split_huge_page*.
1102 */
1103 pmdp_splitting_flush_notify(vma, address, pmd);
1104 ret = 1;
1105 }
1106 spin_unlock(&mm->page_table_lock);
1107
1108 return ret;
1109 }
1110
1111 static void __split_huge_page_refcount(struct page *page)
1112 {
1113 int i;
1114 unsigned long head_index = page->index;
1115 struct zone *zone = page_zone(page);
1116
1117 /* prevent PageLRU to go away from under us, and freeze lru stats */
1118 spin_lock_irq(&zone->lru_lock);
1119 compound_lock(page);
1120
1121 for (i = 1; i < HPAGE_PMD_NR; i++) {
1122 struct page *page_tail = page + i;
1123
1124 /* tail_page->_count cannot change */
1125 atomic_sub(atomic_read(&page_tail->_count), &page->_count);
1126 BUG_ON(page_count(page) <= 0);
1127 atomic_add(page_mapcount(page) + 1, &page_tail->_count);
1128 BUG_ON(atomic_read(&page_tail->_count) <= 0);
1129
1130 /* after clearing PageTail the gup refcount can be released */
1131 smp_mb();
1132
1133 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
1134 page_tail->flags |= (page->flags &
1135 ((1L << PG_referenced) |
1136 (1L << PG_swapbacked) |
1137 (1L << PG_mlocked) |
1138 (1L << PG_uptodate)));
1139 page_tail->flags |= (1L << PG_dirty);
1140
1141 /*
1142 * 1) clear PageTail before overwriting first_page
1143 * 2) clear PageTail before clearing PageHead for VM_BUG_ON
1144 */
1145 smp_wmb();
1146
1147 /*
1148 * __split_huge_page_splitting() already set the
1149 * splitting bit in all pmd that could map this
1150 * hugepage, that will ensure no CPU can alter the
1151 * mapcount on the head page. The mapcount is only
1152 * accounted in the head page and it has to be
1153 * transferred to all tail pages in the below code. So
1154 * for this code to be safe, the split the mapcount
1155 * can't change. But that doesn't mean userland can't
1156 * keep changing and reading the page contents while
1157 * we transfer the mapcount, so the pmd splitting
1158 * status is achieved setting a reserved bit in the
1159 * pmd, not by clearing the present bit.
1160 */
1161 BUG_ON(page_mapcount(page_tail));
1162 page_tail->_mapcount = page->_mapcount;
1163
1164 BUG_ON(page_tail->mapping);
1165 page_tail->mapping = page->mapping;
1166
1167 page_tail->index = ++head_index;
1168
1169 BUG_ON(!PageAnon(page_tail));
1170 BUG_ON(!PageUptodate(page_tail));
1171 BUG_ON(!PageDirty(page_tail));
1172 BUG_ON(!PageSwapBacked(page_tail));
1173
1174 lru_add_page_tail(zone, page, page_tail);
1175 }
1176
1177 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1178 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1179
1180 ClearPageCompound(page);
1181 compound_unlock(page);
1182 spin_unlock_irq(&zone->lru_lock);
1183
1184 for (i = 1; i < HPAGE_PMD_NR; i++) {
1185 struct page *page_tail = page + i;
1186 BUG_ON(page_count(page_tail) <= 0);
1187 /*
1188 * Tail pages may be freed if there wasn't any mapping
1189 * like if add_to_swap() is running on a lru page that
1190 * had its mapping zapped. And freeing these pages
1191 * requires taking the lru_lock so we do the put_page
1192 * of the tail pages after the split is complete.
1193 */
1194 put_page(page_tail);
1195 }
1196
1197 /*
1198 * Only the head page (now become a regular page) is required
1199 * to be pinned by the caller.
1200 */
1201 BUG_ON(page_count(page) <= 0);
1202 }
1203
1204 static int __split_huge_page_map(struct page *page,
1205 struct vm_area_struct *vma,
1206 unsigned long address)
1207 {
1208 struct mm_struct *mm = vma->vm_mm;
1209 pmd_t *pmd, _pmd;
1210 int ret = 0, i;
1211 pgtable_t pgtable;
1212 unsigned long haddr;
1213
1214 spin_lock(&mm->page_table_lock);
1215 pmd = page_check_address_pmd(page, mm, address,
1216 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1217 if (pmd) {
1218 pgtable = get_pmd_huge_pte(mm);
1219 pmd_populate(mm, &_pmd, pgtable);
1220
1221 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1222 i++, haddr += PAGE_SIZE) {
1223 pte_t *pte, entry;
1224 BUG_ON(PageCompound(page+i));
1225 entry = mk_pte(page + i, vma->vm_page_prot);
1226 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1227 if (!pmd_write(*pmd))
1228 entry = pte_wrprotect(entry);
1229 else
1230 BUG_ON(page_mapcount(page) != 1);
1231 if (!pmd_young(*pmd))
1232 entry = pte_mkold(entry);
1233 pte = pte_offset_map(&_pmd, haddr);
1234 BUG_ON(!pte_none(*pte));
1235 set_pte_at(mm, haddr, pte, entry);
1236 pte_unmap(pte);
1237 }
1238
1239 mm->nr_ptes++;
1240 smp_wmb(); /* make pte visible before pmd */
1241 /*
1242 * Up to this point the pmd is present and huge and
1243 * userland has the whole access to the hugepage
1244 * during the split (which happens in place). If we
1245 * overwrite the pmd with the not-huge version
1246 * pointing to the pte here (which of course we could
1247 * if all CPUs were bug free), userland could trigger
1248 * a small page size TLB miss on the small sized TLB
1249 * while the hugepage TLB entry is still established
1250 * in the huge TLB. Some CPU doesn't like that. See
1251 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1252 * Erratum 383 on page 93. Intel should be safe but is
1253 * also warns that it's only safe if the permission
1254 * and cache attributes of the two entries loaded in
1255 * the two TLB is identical (which should be the case
1256 * here). But it is generally safer to never allow
1257 * small and huge TLB entries for the same virtual
1258 * address to be loaded simultaneously. So instead of
1259 * doing "pmd_populate(); flush_tlb_range();" we first
1260 * mark the current pmd notpresent (atomically because
1261 * here the pmd_trans_huge and pmd_trans_splitting
1262 * must remain set at all times on the pmd until the
1263 * split is complete for this pmd), then we flush the
1264 * SMP TLB and finally we write the non-huge version
1265 * of the pmd entry with pmd_populate.
1266 */
1267 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1268 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1269 pmd_populate(mm, pmd, pgtable);
1270 ret = 1;
1271 }
1272 spin_unlock(&mm->page_table_lock);
1273
1274 return ret;
1275 }
1276
1277 /* must be called with anon_vma->root->lock hold */
1278 static void __split_huge_page(struct page *page,
1279 struct anon_vma *anon_vma)
1280 {
1281 int mapcount, mapcount2;
1282 struct anon_vma_chain *avc;
1283
1284 BUG_ON(!PageHead(page));
1285 BUG_ON(PageTail(page));
1286
1287 mapcount = 0;
1288 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1289 struct vm_area_struct *vma = avc->vma;
1290 unsigned long addr = vma_address(page, vma);
1291 BUG_ON(is_vma_temporary_stack(vma));
1292 if (addr == -EFAULT)
1293 continue;
1294 mapcount += __split_huge_page_splitting(page, vma, addr);
1295 }
1296 /*
1297 * It is critical that new vmas are added to the tail of the
1298 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1299 * and establishes a child pmd before
1300 * __split_huge_page_splitting() freezes the parent pmd (so if
1301 * we fail to prevent copy_huge_pmd() from running until the
1302 * whole __split_huge_page() is complete), we will still see
1303 * the newly established pmd of the child later during the
1304 * walk, to be able to set it as pmd_trans_splitting too.
1305 */
1306 if (mapcount != page_mapcount(page))
1307 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1308 mapcount, page_mapcount(page));
1309 BUG_ON(mapcount != page_mapcount(page));
1310
1311 __split_huge_page_refcount(page);
1312
1313 mapcount2 = 0;
1314 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1315 struct vm_area_struct *vma = avc->vma;
1316 unsigned long addr = vma_address(page, vma);
1317 BUG_ON(is_vma_temporary_stack(vma));
1318 if (addr == -EFAULT)
1319 continue;
1320 mapcount2 += __split_huge_page_map(page, vma, addr);
1321 }
1322 if (mapcount != mapcount2)
1323 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1324 mapcount, mapcount2, page_mapcount(page));
1325 BUG_ON(mapcount != mapcount2);
1326 }
1327
1328 int split_huge_page(struct page *page)
1329 {
1330 struct anon_vma *anon_vma;
1331 int ret = 1;
1332
1333 BUG_ON(!PageAnon(page));
1334 anon_vma = page_lock_anon_vma(page);
1335 if (!anon_vma)
1336 goto out;
1337 ret = 0;
1338 if (!PageCompound(page))
1339 goto out_unlock;
1340
1341 BUG_ON(!PageSwapBacked(page));
1342 __split_huge_page(page, anon_vma);
1343
1344 BUG_ON(PageCompound(page));
1345 out_unlock:
1346 page_unlock_anon_vma(anon_vma);
1347 out:
1348 return ret;
1349 }
1350
1351 int hugepage_madvise(unsigned long *vm_flags)
1352 {
1353 /*
1354 * Be somewhat over-protective like KSM for now!
1355 */
1356 if (*vm_flags & (VM_HUGEPAGE | VM_SHARED | VM_MAYSHARE |
1357 VM_PFNMAP | VM_IO | VM_DONTEXPAND |
1358 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
1359 VM_MIXEDMAP | VM_SAO))
1360 return -EINVAL;
1361
1362 *vm_flags |= VM_HUGEPAGE;
1363
1364 return 0;
1365 }
1366
1367 static int __init khugepaged_slab_init(void)
1368 {
1369 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1370 sizeof(struct mm_slot),
1371 __alignof__(struct mm_slot), 0, NULL);
1372 if (!mm_slot_cache)
1373 return -ENOMEM;
1374
1375 return 0;
1376 }
1377
1378 static void __init khugepaged_slab_free(void)
1379 {
1380 kmem_cache_destroy(mm_slot_cache);
1381 mm_slot_cache = NULL;
1382 }
1383
1384 static inline struct mm_slot *alloc_mm_slot(void)
1385 {
1386 if (!mm_slot_cache) /* initialization failed */
1387 return NULL;
1388 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1389 }
1390
1391 static inline void free_mm_slot(struct mm_slot *mm_slot)
1392 {
1393 kmem_cache_free(mm_slot_cache, mm_slot);
1394 }
1395
1396 static int __init mm_slots_hash_init(void)
1397 {
1398 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1399 GFP_KERNEL);
1400 if (!mm_slots_hash)
1401 return -ENOMEM;
1402 return 0;
1403 }
1404
1405 #if 0
1406 static void __init mm_slots_hash_free(void)
1407 {
1408 kfree(mm_slots_hash);
1409 mm_slots_hash = NULL;
1410 }
1411 #endif
1412
1413 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1414 {
1415 struct mm_slot *mm_slot;
1416 struct hlist_head *bucket;
1417 struct hlist_node *node;
1418
1419 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1420 % MM_SLOTS_HASH_HEADS];
1421 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1422 if (mm == mm_slot->mm)
1423 return mm_slot;
1424 }
1425 return NULL;
1426 }
1427
1428 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1429 struct mm_slot *mm_slot)
1430 {
1431 struct hlist_head *bucket;
1432
1433 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1434 % MM_SLOTS_HASH_HEADS];
1435 mm_slot->mm = mm;
1436 hlist_add_head(&mm_slot->hash, bucket);
1437 }
1438
1439 static inline int khugepaged_test_exit(struct mm_struct *mm)
1440 {
1441 return atomic_read(&mm->mm_users) == 0;
1442 }
1443
1444 int __khugepaged_enter(struct mm_struct *mm)
1445 {
1446 struct mm_slot *mm_slot;
1447 int wakeup;
1448
1449 mm_slot = alloc_mm_slot();
1450 if (!mm_slot)
1451 return -ENOMEM;
1452
1453 /* __khugepaged_exit() must not run from under us */
1454 VM_BUG_ON(khugepaged_test_exit(mm));
1455 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1456 free_mm_slot(mm_slot);
1457 return 0;
1458 }
1459
1460 spin_lock(&khugepaged_mm_lock);
1461 insert_to_mm_slots_hash(mm, mm_slot);
1462 /*
1463 * Insert just behind the scanning cursor, to let the area settle
1464 * down a little.
1465 */
1466 wakeup = list_empty(&khugepaged_scan.mm_head);
1467 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1468 spin_unlock(&khugepaged_mm_lock);
1469
1470 atomic_inc(&mm->mm_count);
1471 if (wakeup)
1472 wake_up_interruptible(&khugepaged_wait);
1473
1474 return 0;
1475 }
1476
1477 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1478 {
1479 unsigned long hstart, hend;
1480 if (!vma->anon_vma)
1481 /*
1482 * Not yet faulted in so we will register later in the
1483 * page fault if needed.
1484 */
1485 return 0;
1486 if (vma->vm_file || vma->vm_ops)
1487 /* khugepaged not yet working on file or special mappings */
1488 return 0;
1489 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1490 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1491 hend = vma->vm_end & HPAGE_PMD_MASK;
1492 if (hstart < hend)
1493 return khugepaged_enter(vma);
1494 return 0;
1495 }
1496
1497 void __khugepaged_exit(struct mm_struct *mm)
1498 {
1499 struct mm_slot *mm_slot;
1500 int free = 0;
1501
1502 spin_lock(&khugepaged_mm_lock);
1503 mm_slot = get_mm_slot(mm);
1504 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1505 hlist_del(&mm_slot->hash);
1506 list_del(&mm_slot->mm_node);
1507 free = 1;
1508 }
1509
1510 if (free) {
1511 spin_unlock(&khugepaged_mm_lock);
1512 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1513 free_mm_slot(mm_slot);
1514 mmdrop(mm);
1515 } else if (mm_slot) {
1516 spin_unlock(&khugepaged_mm_lock);
1517 /*
1518 * This is required to serialize against
1519 * khugepaged_test_exit() (which is guaranteed to run
1520 * under mmap sem read mode). Stop here (after we
1521 * return all pagetables will be destroyed) until
1522 * khugepaged has finished working on the pagetables
1523 * under the mmap_sem.
1524 */
1525 down_write(&mm->mmap_sem);
1526 up_write(&mm->mmap_sem);
1527 } else
1528 spin_unlock(&khugepaged_mm_lock);
1529 }
1530
1531 static void release_pte_page(struct page *page)
1532 {
1533 /* 0 stands for page_is_file_cache(page) == false */
1534 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1535 unlock_page(page);
1536 putback_lru_page(page);
1537 }
1538
1539 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1540 {
1541 while (--_pte >= pte) {
1542 pte_t pteval = *_pte;
1543 if (!pte_none(pteval))
1544 release_pte_page(pte_page(pteval));
1545 }
1546 }
1547
1548 static void release_all_pte_pages(pte_t *pte)
1549 {
1550 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1551 }
1552
1553 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1554 unsigned long address,
1555 pte_t *pte)
1556 {
1557 struct page *page;
1558 pte_t *_pte;
1559 int referenced = 0, isolated = 0, none = 0;
1560 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1561 _pte++, address += PAGE_SIZE) {
1562 pte_t pteval = *_pte;
1563 if (pte_none(pteval)) {
1564 if (++none <= khugepaged_max_ptes_none)
1565 continue;
1566 else {
1567 release_pte_pages(pte, _pte);
1568 goto out;
1569 }
1570 }
1571 if (!pte_present(pteval) || !pte_write(pteval)) {
1572 release_pte_pages(pte, _pte);
1573 goto out;
1574 }
1575 page = vm_normal_page(vma, address, pteval);
1576 if (unlikely(!page)) {
1577 release_pte_pages(pte, _pte);
1578 goto out;
1579 }
1580 VM_BUG_ON(PageCompound(page));
1581 BUG_ON(!PageAnon(page));
1582 VM_BUG_ON(!PageSwapBacked(page));
1583
1584 /* cannot use mapcount: can't collapse if there's a gup pin */
1585 if (page_count(page) != 1) {
1586 release_pte_pages(pte, _pte);
1587 goto out;
1588 }
1589 /*
1590 * We can do it before isolate_lru_page because the
1591 * page can't be freed from under us. NOTE: PG_lock
1592 * is needed to serialize against split_huge_page
1593 * when invoked from the VM.
1594 */
1595 if (!trylock_page(page)) {
1596 release_pte_pages(pte, _pte);
1597 goto out;
1598 }
1599 /*
1600 * Isolate the page to avoid collapsing an hugepage
1601 * currently in use by the VM.
1602 */
1603 if (isolate_lru_page(page)) {
1604 unlock_page(page);
1605 release_pte_pages(pte, _pte);
1606 goto out;
1607 }
1608 /* 0 stands for page_is_file_cache(page) == false */
1609 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1610 VM_BUG_ON(!PageLocked(page));
1611 VM_BUG_ON(PageLRU(page));
1612
1613 /* If there is no mapped pte young don't collapse the page */
1614 if (pte_young(pteval))
1615 referenced = 1;
1616 }
1617 if (unlikely(!referenced))
1618 release_all_pte_pages(pte);
1619 else
1620 isolated = 1;
1621 out:
1622 return isolated;
1623 }
1624
1625 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1626 struct vm_area_struct *vma,
1627 unsigned long address,
1628 spinlock_t *ptl)
1629 {
1630 pte_t *_pte;
1631 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1632 pte_t pteval = *_pte;
1633 struct page *src_page;
1634
1635 if (pte_none(pteval)) {
1636 clear_user_highpage(page, address);
1637 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1638 } else {
1639 src_page = pte_page(pteval);
1640 copy_user_highpage(page, src_page, address, vma);
1641 VM_BUG_ON(page_mapcount(src_page) != 1);
1642 VM_BUG_ON(page_count(src_page) != 2);
1643 release_pte_page(src_page);
1644 /*
1645 * ptl mostly unnecessary, but preempt has to
1646 * be disabled to update the per-cpu stats
1647 * inside page_remove_rmap().
1648 */
1649 spin_lock(ptl);
1650 /*
1651 * paravirt calls inside pte_clear here are
1652 * superfluous.
1653 */
1654 pte_clear(vma->vm_mm, address, _pte);
1655 page_remove_rmap(src_page);
1656 spin_unlock(ptl);
1657 free_page_and_swap_cache(src_page);
1658 }
1659
1660 address += PAGE_SIZE;
1661 page++;
1662 }
1663 }
1664
1665 static void collapse_huge_page(struct mm_struct *mm,
1666 unsigned long address,
1667 struct page **hpage)
1668 {
1669 struct vm_area_struct *vma;
1670 pgd_t *pgd;
1671 pud_t *pud;
1672 pmd_t *pmd, _pmd;
1673 pte_t *pte;
1674 pgtable_t pgtable;
1675 struct page *new_page;
1676 spinlock_t *ptl;
1677 int isolated;
1678 unsigned long hstart, hend;
1679
1680 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1681 #ifndef CONFIG_NUMA
1682 VM_BUG_ON(!*hpage);
1683 #else
1684 VM_BUG_ON(*hpage);
1685 #endif
1686
1687 /*
1688 * Prevent all access to pagetables with the exception of
1689 * gup_fast later hanlded by the ptep_clear_flush and the VM
1690 * handled by the anon_vma lock + PG_lock.
1691 */
1692 down_write(&mm->mmap_sem);
1693 if (unlikely(khugepaged_test_exit(mm)))
1694 goto out;
1695
1696 vma = find_vma(mm, address);
1697 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1698 hend = vma->vm_end & HPAGE_PMD_MASK;
1699 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1700 goto out;
1701
1702 if (!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always())
1703 goto out;
1704
1705 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
1706 if (!vma->anon_vma || vma->vm_ops || vma->vm_file)
1707 goto out;
1708 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1709
1710 pgd = pgd_offset(mm, address);
1711 if (!pgd_present(*pgd))
1712 goto out;
1713
1714 pud = pud_offset(pgd, address);
1715 if (!pud_present(*pud))
1716 goto out;
1717
1718 pmd = pmd_offset(pud, address);
1719 /* pmd can't go away or become huge under us */
1720 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1721 goto out;
1722
1723 #ifndef CONFIG_NUMA
1724 new_page = *hpage;
1725 #else
1726 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address);
1727 if (unlikely(!new_page)) {
1728 *hpage = ERR_PTR(-ENOMEM);
1729 goto out;
1730 }
1731 #endif
1732 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
1733 goto out_put_page;
1734
1735 anon_vma_lock(vma->anon_vma);
1736
1737 pte = pte_offset_map(pmd, address);
1738 ptl = pte_lockptr(mm, pmd);
1739
1740 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1741 /*
1742 * After this gup_fast can't run anymore. This also removes
1743 * any huge TLB entry from the CPU so we won't allow
1744 * huge and small TLB entries for the same virtual address
1745 * to avoid the risk of CPU bugs in that area.
1746 */
1747 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1748 spin_unlock(&mm->page_table_lock);
1749
1750 spin_lock(ptl);
1751 isolated = __collapse_huge_page_isolate(vma, address, pte);
1752 spin_unlock(ptl);
1753 pte_unmap(pte);
1754
1755 if (unlikely(!isolated)) {
1756 spin_lock(&mm->page_table_lock);
1757 BUG_ON(!pmd_none(*pmd));
1758 set_pmd_at(mm, address, pmd, _pmd);
1759 spin_unlock(&mm->page_table_lock);
1760 anon_vma_unlock(vma->anon_vma);
1761 mem_cgroup_uncharge_page(new_page);
1762 goto out_put_page;
1763 }
1764
1765 /*
1766 * All pages are isolated and locked so anon_vma rmap
1767 * can't run anymore.
1768 */
1769 anon_vma_unlock(vma->anon_vma);
1770
1771 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1772 __SetPageUptodate(new_page);
1773 pgtable = pmd_pgtable(_pmd);
1774 VM_BUG_ON(page_count(pgtable) != 1);
1775 VM_BUG_ON(page_mapcount(pgtable) != 0);
1776
1777 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1778 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1779 _pmd = pmd_mkhuge(_pmd);
1780
1781 /*
1782 * spin_lock() below is not the equivalent of smp_wmb(), so
1783 * this is needed to avoid the copy_huge_page writes to become
1784 * visible after the set_pmd_at() write.
1785 */
1786 smp_wmb();
1787
1788 spin_lock(&mm->page_table_lock);
1789 BUG_ON(!pmd_none(*pmd));
1790 page_add_new_anon_rmap(new_page, vma, address);
1791 set_pmd_at(mm, address, pmd, _pmd);
1792 update_mmu_cache(vma, address, entry);
1793 prepare_pmd_huge_pte(pgtable, mm);
1794 mm->nr_ptes--;
1795 spin_unlock(&mm->page_table_lock);
1796
1797 #ifndef CONFIG_NUMA
1798 *hpage = NULL;
1799 #endif
1800 khugepaged_pages_collapsed++;
1801 out:
1802 up_write(&mm->mmap_sem);
1803 return;
1804
1805 out_put_page:
1806 #ifdef CONFIG_NUMA
1807 put_page(new_page);
1808 #endif
1809 goto out;
1810 }
1811
1812 static int khugepaged_scan_pmd(struct mm_struct *mm,
1813 struct vm_area_struct *vma,
1814 unsigned long address,
1815 struct page **hpage)
1816 {
1817 pgd_t *pgd;
1818 pud_t *pud;
1819 pmd_t *pmd;
1820 pte_t *pte, *_pte;
1821 int ret = 0, referenced = 0, none = 0;
1822 struct page *page;
1823 unsigned long _address;
1824 spinlock_t *ptl;
1825
1826 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1827
1828 pgd = pgd_offset(mm, address);
1829 if (!pgd_present(*pgd))
1830 goto out;
1831
1832 pud = pud_offset(pgd, address);
1833 if (!pud_present(*pud))
1834 goto out;
1835
1836 pmd = pmd_offset(pud, address);
1837 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1838 goto out;
1839
1840 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1841 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1842 _pte++, _address += PAGE_SIZE) {
1843 pte_t pteval = *_pte;
1844 if (pte_none(pteval)) {
1845 if (++none <= khugepaged_max_ptes_none)
1846 continue;
1847 else
1848 goto out_unmap;
1849 }
1850 if (!pte_present(pteval) || !pte_write(pteval))
1851 goto out_unmap;
1852 page = vm_normal_page(vma, _address, pteval);
1853 if (unlikely(!page))
1854 goto out_unmap;
1855 VM_BUG_ON(PageCompound(page));
1856 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
1857 goto out_unmap;
1858 /* cannot use mapcount: can't collapse if there's a gup pin */
1859 if (page_count(page) != 1)
1860 goto out_unmap;
1861 if (pte_young(pteval))
1862 referenced = 1;
1863 }
1864 if (referenced)
1865 ret = 1;
1866 out_unmap:
1867 pte_unmap_unlock(pte, ptl);
1868 if (ret) {
1869 up_read(&mm->mmap_sem);
1870 collapse_huge_page(mm, address, hpage);
1871 }
1872 out:
1873 return ret;
1874 }
1875
1876 static void collect_mm_slot(struct mm_slot *mm_slot)
1877 {
1878 struct mm_struct *mm = mm_slot->mm;
1879
1880 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
1881
1882 if (khugepaged_test_exit(mm)) {
1883 /* free mm_slot */
1884 hlist_del(&mm_slot->hash);
1885 list_del(&mm_slot->mm_node);
1886
1887 /*
1888 * Not strictly needed because the mm exited already.
1889 *
1890 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1891 */
1892
1893 /* khugepaged_mm_lock actually not necessary for the below */
1894 free_mm_slot(mm_slot);
1895 mmdrop(mm);
1896 }
1897 }
1898
1899 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1900 struct page **hpage)
1901 {
1902 struct mm_slot *mm_slot;
1903 struct mm_struct *mm;
1904 struct vm_area_struct *vma;
1905 int progress = 0;
1906
1907 VM_BUG_ON(!pages);
1908 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
1909
1910 if (khugepaged_scan.mm_slot)
1911 mm_slot = khugepaged_scan.mm_slot;
1912 else {
1913 mm_slot = list_entry(khugepaged_scan.mm_head.next,
1914 struct mm_slot, mm_node);
1915 khugepaged_scan.address = 0;
1916 khugepaged_scan.mm_slot = mm_slot;
1917 }
1918 spin_unlock(&khugepaged_mm_lock);
1919
1920 mm = mm_slot->mm;
1921 down_read(&mm->mmap_sem);
1922 if (unlikely(khugepaged_test_exit(mm)))
1923 vma = NULL;
1924 else
1925 vma = find_vma(mm, khugepaged_scan.address);
1926
1927 progress++;
1928 for (; vma; vma = vma->vm_next) {
1929 unsigned long hstart, hend;
1930
1931 cond_resched();
1932 if (unlikely(khugepaged_test_exit(mm))) {
1933 progress++;
1934 break;
1935 }
1936
1937 if (!(vma->vm_flags & VM_HUGEPAGE) &&
1938 !khugepaged_always()) {
1939 progress++;
1940 continue;
1941 }
1942
1943 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
1944 if (!vma->anon_vma || vma->vm_ops || vma->vm_file) {
1945 khugepaged_scan.address = vma->vm_end;
1946 progress++;
1947 continue;
1948 }
1949 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1950
1951 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1952 hend = vma->vm_end & HPAGE_PMD_MASK;
1953 if (hstart >= hend) {
1954 progress++;
1955 continue;
1956 }
1957 if (khugepaged_scan.address < hstart)
1958 khugepaged_scan.address = hstart;
1959 if (khugepaged_scan.address > hend) {
1960 khugepaged_scan.address = hend + HPAGE_PMD_SIZE;
1961 progress++;
1962 continue;
1963 }
1964 BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
1965
1966 while (khugepaged_scan.address < hend) {
1967 int ret;
1968 cond_resched();
1969 if (unlikely(khugepaged_test_exit(mm)))
1970 goto breakouterloop;
1971
1972 VM_BUG_ON(khugepaged_scan.address < hstart ||
1973 khugepaged_scan.address + HPAGE_PMD_SIZE >
1974 hend);
1975 ret = khugepaged_scan_pmd(mm, vma,
1976 khugepaged_scan.address,
1977 hpage);
1978 /* move to next address */
1979 khugepaged_scan.address += HPAGE_PMD_SIZE;
1980 progress += HPAGE_PMD_NR;
1981 if (ret)
1982 /* we released mmap_sem so break loop */
1983 goto breakouterloop_mmap_sem;
1984 if (progress >= pages)
1985 goto breakouterloop;
1986 }
1987 }
1988 breakouterloop:
1989 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
1990 breakouterloop_mmap_sem:
1991
1992 spin_lock(&khugepaged_mm_lock);
1993 BUG_ON(khugepaged_scan.mm_slot != mm_slot);
1994 /*
1995 * Release the current mm_slot if this mm is about to die, or
1996 * if we scanned all vmas of this mm.
1997 */
1998 if (khugepaged_test_exit(mm) || !vma) {
1999 /*
2000 * Make sure that if mm_users is reaching zero while
2001 * khugepaged runs here, khugepaged_exit will find
2002 * mm_slot not pointing to the exiting mm.
2003 */
2004 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2005 khugepaged_scan.mm_slot = list_entry(
2006 mm_slot->mm_node.next,
2007 struct mm_slot, mm_node);
2008 khugepaged_scan.address = 0;
2009 } else {
2010 khugepaged_scan.mm_slot = NULL;
2011 khugepaged_full_scans++;
2012 }
2013
2014 collect_mm_slot(mm_slot);
2015 }
2016
2017 return progress;
2018 }
2019
2020 static int khugepaged_has_work(void)
2021 {
2022 return !list_empty(&khugepaged_scan.mm_head) &&
2023 khugepaged_enabled();
2024 }
2025
2026 static int khugepaged_wait_event(void)
2027 {
2028 return !list_empty(&khugepaged_scan.mm_head) ||
2029 !khugepaged_enabled();
2030 }
2031
2032 static void khugepaged_do_scan(struct page **hpage)
2033 {
2034 unsigned int progress = 0, pass_through_head = 0;
2035 unsigned int pages = khugepaged_pages_to_scan;
2036
2037 barrier(); /* write khugepaged_pages_to_scan to local stack */
2038
2039 while (progress < pages) {
2040 cond_resched();
2041
2042 #ifndef CONFIG_NUMA
2043 if (!*hpage) {
2044 *hpage = alloc_hugepage(khugepaged_defrag());
2045 if (unlikely(!*hpage))
2046 break;
2047 }
2048 #else
2049 if (IS_ERR(*hpage))
2050 break;
2051 #endif
2052
2053 spin_lock(&khugepaged_mm_lock);
2054 if (!khugepaged_scan.mm_slot)
2055 pass_through_head++;
2056 if (khugepaged_has_work() &&
2057 pass_through_head < 2)
2058 progress += khugepaged_scan_mm_slot(pages - progress,
2059 hpage);
2060 else
2061 progress = pages;
2062 spin_unlock(&khugepaged_mm_lock);
2063 }
2064 }
2065
2066 static void khugepaged_alloc_sleep(void)
2067 {
2068 DEFINE_WAIT(wait);
2069 add_wait_queue(&khugepaged_wait, &wait);
2070 schedule_timeout_interruptible(
2071 msecs_to_jiffies(
2072 khugepaged_alloc_sleep_millisecs));
2073 remove_wait_queue(&khugepaged_wait, &wait);
2074 }
2075
2076 #ifndef CONFIG_NUMA
2077 static struct page *khugepaged_alloc_hugepage(void)
2078 {
2079 struct page *hpage;
2080
2081 do {
2082 hpage = alloc_hugepage(khugepaged_defrag());
2083 if (!hpage)
2084 khugepaged_alloc_sleep();
2085 } while (unlikely(!hpage) &&
2086 likely(khugepaged_enabled()));
2087 return hpage;
2088 }
2089 #endif
2090
2091 static void khugepaged_loop(void)
2092 {
2093 struct page *hpage;
2094
2095 #ifdef CONFIG_NUMA
2096 hpage = NULL;
2097 #endif
2098 while (likely(khugepaged_enabled())) {
2099 #ifndef CONFIG_NUMA
2100 hpage = khugepaged_alloc_hugepage();
2101 if (unlikely(!hpage))
2102 break;
2103 #else
2104 if (IS_ERR(hpage)) {
2105 khugepaged_alloc_sleep();
2106 hpage = NULL;
2107 }
2108 #endif
2109
2110 khugepaged_do_scan(&hpage);
2111 #ifndef CONFIG_NUMA
2112 if (hpage)
2113 put_page(hpage);
2114 #endif
2115 if (khugepaged_has_work()) {
2116 DEFINE_WAIT(wait);
2117 if (!khugepaged_scan_sleep_millisecs)
2118 continue;
2119 add_wait_queue(&khugepaged_wait, &wait);
2120 schedule_timeout_interruptible(
2121 msecs_to_jiffies(
2122 khugepaged_scan_sleep_millisecs));
2123 remove_wait_queue(&khugepaged_wait, &wait);
2124 } else if (khugepaged_enabled())
2125 wait_event_interruptible(khugepaged_wait,
2126 khugepaged_wait_event());
2127 }
2128 }
2129
2130 static int khugepaged(void *none)
2131 {
2132 struct mm_slot *mm_slot;
2133
2134 set_user_nice(current, 19);
2135
2136 /* serialize with start_khugepaged() */
2137 mutex_lock(&khugepaged_mutex);
2138
2139 for (;;) {
2140 mutex_unlock(&khugepaged_mutex);
2141 BUG_ON(khugepaged_thread != current);
2142 khugepaged_loop();
2143 BUG_ON(khugepaged_thread != current);
2144
2145 mutex_lock(&khugepaged_mutex);
2146 if (!khugepaged_enabled())
2147 break;
2148 }
2149
2150 spin_lock(&khugepaged_mm_lock);
2151 mm_slot = khugepaged_scan.mm_slot;
2152 khugepaged_scan.mm_slot = NULL;
2153 if (mm_slot)
2154 collect_mm_slot(mm_slot);
2155 spin_unlock(&khugepaged_mm_lock);
2156
2157 khugepaged_thread = NULL;
2158 mutex_unlock(&khugepaged_mutex);
2159
2160 return 0;
2161 }
2162
2163 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2164 {
2165 struct page *page;
2166
2167 spin_lock(&mm->page_table_lock);
2168 if (unlikely(!pmd_trans_huge(*pmd))) {
2169 spin_unlock(&mm->page_table_lock);
2170 return;
2171 }
2172 page = pmd_page(*pmd);
2173 VM_BUG_ON(!page_count(page));
2174 get_page(page);
2175 spin_unlock(&mm->page_table_lock);
2176
2177 split_huge_page(page);
2178
2179 put_page(page);
2180 BUG_ON(pmd_trans_huge(*pmd));
2181 }
Linux with added FPC-III support