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rapidio: fix default routing initialization
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / mm / huge_memory.c
blob56cac93f155d1f80082c90cf570576f67d4e2811
1 /*
2 * Copyright (C) 2009 Red Hat, Inc.
3 *
4 * This work is licensed under the terms of the GNU GPL, version 2. See
5 * the COPYING file in the top-level directory.
6 */
7
8 #include <linux/mm.h>
9 #include <linux/sched.h>
10 #include <linux/highmem.h>
11 #include <linux/hugetlb.h>
12 #include <linux/mmu_notifier.h>
13 #include <linux/rmap.h>
14 #include <linux/swap.h>
15 #include <linux/mm_inline.h>
16 #include <linux/kthread.h>
17 #include <linux/khugepaged.h>
18 #include <linux/freezer.h>
19 #include <linux/mman.h>
20 #include <asm/tlb.h>
21 #include <asm/pgalloc.h>
22 #include "internal.h"
23
24 /*
25 * By default transparent hugepage support is enabled for all mappings
26 * and khugepaged scans all mappings. Defrag is only invoked by
27 * khugepaged hugepage allocations and by page faults inside
28 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
29 * allocations.
30 */
31 unsigned long transparent_hugepage_flags __read_mostly =
32 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
33 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
34 #endif
35 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
36 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
37 #endif
38 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
39 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
40
41 /* default scan 8*512 pte (or vmas) every 30 second */
42 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
43 static unsigned int khugepaged_pages_collapsed;
44 static unsigned int khugepaged_full_scans;
45 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
46 /* during fragmentation poll the hugepage allocator once every minute */
47 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
48 static struct task_struct *khugepaged_thread __read_mostly;
49 static DEFINE_MUTEX(khugepaged_mutex);
50 static DEFINE_SPINLOCK(khugepaged_mm_lock);
51 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
52 /*
53 * default collapse hugepages if there is at least one pte mapped like
54 * it would have happened if the vma was large enough during page
55 * fault.
56 */
57 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
58
59 static int khugepaged(void *none);
60 static int mm_slots_hash_init(void);
61 static int khugepaged_slab_init(void);
62 static void khugepaged_slab_free(void);
63
64 #define MM_SLOTS_HASH_HEADS 1024
65 static struct hlist_head *mm_slots_hash __read_mostly;
66 static struct kmem_cache *mm_slot_cache __read_mostly;
67
68 /**
69 * struct mm_slot - hash lookup from mm to mm_slot
70 * @hash: hash collision list
71 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
72 * @mm: the mm that this information is valid for
73 */
74 struct mm_slot {
75 struct hlist_node hash;
76 struct list_head mm_node;
77 struct mm_struct *mm;
78 };
79
80 /**
81 * struct khugepaged_scan - cursor for scanning
82 * @mm_head: the head of the mm list to scan
83 * @mm_slot: the current mm_slot we are scanning
84 * @address: the next address inside that to be scanned
85 *
86 * There is only the one khugepaged_scan instance of this cursor structure.
87 */
88 struct khugepaged_scan {
89 struct list_head mm_head;
90 struct mm_slot *mm_slot;
91 unsigned long address;
92 } khugepaged_scan = {
93 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
94 };
95
96
97 static int set_recommended_min_free_kbytes(void)
98 {
99 struct zone *zone;
100 int nr_zones = 0;
101 unsigned long recommended_min;
102 extern int min_free_kbytes;
103
104 if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG,
105 &transparent_hugepage_flags) &&
106 !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
107 &transparent_hugepage_flags))
108 return 0;
109
110 for_each_populated_zone(zone)
111 nr_zones++;
112
113 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
114 recommended_min = pageblock_nr_pages * nr_zones * 2;
115
116 /*
117 * Make sure that on average at least two pageblocks are almost free
118 * of another type, one for a migratetype to fall back to and a
119 * second to avoid subsequent fallbacks of other types There are 3
120 * MIGRATE_TYPES we care about.
121 */
122 recommended_min += pageblock_nr_pages * nr_zones *
123 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
124
125 /* don't ever allow to reserve more than 5% of the lowmem */
126 recommended_min = min(recommended_min,
127 (unsigned long) nr_free_buffer_pages() / 20);
128 recommended_min <<= (PAGE_SHIFT-10);
129
130 if (recommended_min > min_free_kbytes)
131 min_free_kbytes = recommended_min;
132 setup_per_zone_wmarks();
133 return 0;
134 }
135 late_initcall(set_recommended_min_free_kbytes);
136
137 static int start_khugepaged(void)
138 {
139 int err = 0;
140 if (khugepaged_enabled()) {
141 int wakeup;
142 if (unlikely(!mm_slot_cache || !mm_slots_hash)) {
143 err = -ENOMEM;
144 goto out;
145 }
146 mutex_lock(&khugepaged_mutex);
147 if (!khugepaged_thread)
148 khugepaged_thread = kthread_run(khugepaged, NULL,
149 "khugepaged");
150 if (unlikely(IS_ERR(khugepaged_thread))) {
151 printk(KERN_ERR
152 "khugepaged: kthread_run(khugepaged) failed\n");
153 err = PTR_ERR(khugepaged_thread);
154 khugepaged_thread = NULL;
155 }
156 wakeup = !list_empty(&khugepaged_scan.mm_head);
157 mutex_unlock(&khugepaged_mutex);
158 if (wakeup)
159 wake_up_interruptible(&khugepaged_wait);
160
161 set_recommended_min_free_kbytes();
162 } else
163 /* wakeup to exit */
164 wake_up_interruptible(&khugepaged_wait);
165 out:
166 return err;
167 }
168
169 #ifdef CONFIG_SYSFS
170
171 static ssize_t double_flag_show(struct kobject *kobj,
172 struct kobj_attribute *attr, char *buf,
173 enum transparent_hugepage_flag enabled,
174 enum transparent_hugepage_flag req_madv)
175 {
176 if (test_bit(enabled, &transparent_hugepage_flags)) {
177 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
178 return sprintf(buf, "[always] madvise never\n");
179 } else if (test_bit(req_madv, &transparent_hugepage_flags))
180 return sprintf(buf, "always [madvise] never\n");
181 else
182 return sprintf(buf, "always madvise [never]\n");
183 }
184 static ssize_t double_flag_store(struct kobject *kobj,
185 struct kobj_attribute *attr,
186 const char *buf, size_t count,
187 enum transparent_hugepage_flag enabled,
188 enum transparent_hugepage_flag req_madv)
189 {
190 if (!memcmp("always", buf,
191 min(sizeof("always")-1, count))) {
192 set_bit(enabled, &transparent_hugepage_flags);
193 clear_bit(req_madv, &transparent_hugepage_flags);
194 } else if (!memcmp("madvise", buf,
195 min(sizeof("madvise")-1, count))) {
196 clear_bit(enabled, &transparent_hugepage_flags);
197 set_bit(req_madv, &transparent_hugepage_flags);
198 } else if (!memcmp("never", buf,
199 min(sizeof("never")-1, count))) {
200 clear_bit(enabled, &transparent_hugepage_flags);
201 clear_bit(req_madv, &transparent_hugepage_flags);
202 } else
203 return -EINVAL;
204
205 return count;
206 }
207
208 static ssize_t enabled_show(struct kobject *kobj,
209 struct kobj_attribute *attr, char *buf)
210 {
211 return double_flag_show(kobj, attr, buf,
212 TRANSPARENT_HUGEPAGE_FLAG,
213 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
214 }
215 static ssize_t enabled_store(struct kobject *kobj,
216 struct kobj_attribute *attr,
217 const char *buf, size_t count)
218 {
219 ssize_t ret;
220
221 ret = double_flag_store(kobj, attr, buf, count,
222 TRANSPARENT_HUGEPAGE_FLAG,
223 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
224
225 if (ret > 0) {
226 int err = start_khugepaged();
227 if (err)
228 ret = err;
229 }
230
231 if (ret > 0 &&
232 (test_bit(TRANSPARENT_HUGEPAGE_FLAG,
233 &transparent_hugepage_flags) ||
234 test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
235 &transparent_hugepage_flags)))
236 set_recommended_min_free_kbytes();
237
238 return ret;
239 }
240 static struct kobj_attribute enabled_attr =
241 __ATTR(enabled, 0644, enabled_show, enabled_store);
242
243 static ssize_t single_flag_show(struct kobject *kobj,
244 struct kobj_attribute *attr, char *buf,
245 enum transparent_hugepage_flag flag)
246 {
247 return sprintf(buf, "%d\n",
248 !!test_bit(flag, &transparent_hugepage_flags));
249 }
250
251 static ssize_t single_flag_store(struct kobject *kobj,
252 struct kobj_attribute *attr,
253 const char *buf, size_t count,
254 enum transparent_hugepage_flag flag)
255 {
256 unsigned long value;
257 int ret;
258
259 ret = kstrtoul(buf, 10, &value);
260 if (ret < 0)
261 return ret;
262 if (value > 1)
263 return -EINVAL;
264
265 if (value)
266 set_bit(flag, &transparent_hugepage_flags);
267 else
268 clear_bit(flag, &transparent_hugepage_flags);
269
270 return count;
271 }
272
273 /*
274 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
275 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
276 * memory just to allocate one more hugepage.
277 */
278 static ssize_t defrag_show(struct kobject *kobj,
279 struct kobj_attribute *attr, char *buf)
280 {
281 return double_flag_show(kobj, attr, buf,
282 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
283 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
284 }
285 static ssize_t defrag_store(struct kobject *kobj,
286 struct kobj_attribute *attr,
287 const char *buf, size_t count)
288 {
289 return double_flag_store(kobj, attr, buf, count,
290 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
291 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
292 }
293 static struct kobj_attribute defrag_attr =
294 __ATTR(defrag, 0644, defrag_show, defrag_store);
295
296 #ifdef CONFIG_DEBUG_VM
297 static ssize_t debug_cow_show(struct kobject *kobj,
298 struct kobj_attribute *attr, char *buf)
299 {
300 return single_flag_show(kobj, attr, buf,
301 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
302 }
303 static ssize_t debug_cow_store(struct kobject *kobj,
304 struct kobj_attribute *attr,
305 const char *buf, size_t count)
306 {
307 return single_flag_store(kobj, attr, buf, count,
308 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
309 }
310 static struct kobj_attribute debug_cow_attr =
311 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
312 #endif /* CONFIG_DEBUG_VM */
313
314 static struct attribute *hugepage_attr[] = {
315 &enabled_attr.attr,
316 &defrag_attr.attr,
317 #ifdef CONFIG_DEBUG_VM
318 &debug_cow_attr.attr,
319 #endif
320 NULL,
321 };
322
323 static struct attribute_group hugepage_attr_group = {
324 .attrs = hugepage_attr,
325 };
326
327 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
328 struct kobj_attribute *attr,
329 char *buf)
330 {
331 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
332 }
333
334 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
335 struct kobj_attribute *attr,
336 const char *buf, size_t count)
337 {
338 unsigned long msecs;
339 int err;
340
341 err = strict_strtoul(buf, 10, &msecs);
342 if (err || msecs > UINT_MAX)
343 return -EINVAL;
344
345 khugepaged_scan_sleep_millisecs = msecs;
346 wake_up_interruptible(&khugepaged_wait);
347
348 return count;
349 }
350 static struct kobj_attribute scan_sleep_millisecs_attr =
351 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
352 scan_sleep_millisecs_store);
353
354 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
355 struct kobj_attribute *attr,
356 char *buf)
357 {
358 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
359 }
360
361 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
362 struct kobj_attribute *attr,
363 const char *buf, size_t count)
364 {
365 unsigned long msecs;
366 int err;
367
368 err = strict_strtoul(buf, 10, &msecs);
369 if (err || msecs > UINT_MAX)
370 return -EINVAL;
371
372 khugepaged_alloc_sleep_millisecs = msecs;
373 wake_up_interruptible(&khugepaged_wait);
374
375 return count;
376 }
377 static struct kobj_attribute alloc_sleep_millisecs_attr =
378 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
379 alloc_sleep_millisecs_store);
380
381 static ssize_t pages_to_scan_show(struct kobject *kobj,
382 struct kobj_attribute *attr,
383 char *buf)
384 {
385 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
386 }
387 static ssize_t pages_to_scan_store(struct kobject *kobj,
388 struct kobj_attribute *attr,
389 const char *buf, size_t count)
390 {
391 int err;
392 unsigned long pages;
393
394 err = strict_strtoul(buf, 10, &pages);
395 if (err || !pages || pages > UINT_MAX)
396 return -EINVAL;
397
398 khugepaged_pages_to_scan = pages;
399
400 return count;
401 }
402 static struct kobj_attribute pages_to_scan_attr =
403 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
404 pages_to_scan_store);
405
406 static ssize_t pages_collapsed_show(struct kobject *kobj,
407 struct kobj_attribute *attr,
408 char *buf)
409 {
410 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
411 }
412 static struct kobj_attribute pages_collapsed_attr =
413 __ATTR_RO(pages_collapsed);
414
415 static ssize_t full_scans_show(struct kobject *kobj,
416 struct kobj_attribute *attr,
417 char *buf)
418 {
419 return sprintf(buf, "%u\n", khugepaged_full_scans);
420 }
421 static struct kobj_attribute full_scans_attr =
422 __ATTR_RO(full_scans);
423
424 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
425 struct kobj_attribute *attr, char *buf)
426 {
427 return single_flag_show(kobj, attr, buf,
428 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
429 }
430 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
431 struct kobj_attribute *attr,
432 const char *buf, size_t count)
433 {
434 return single_flag_store(kobj, attr, buf, count,
435 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
436 }
437 static struct kobj_attribute khugepaged_defrag_attr =
438 __ATTR(defrag, 0644, khugepaged_defrag_show,
439 khugepaged_defrag_store);
440
441 /*
442 * max_ptes_none controls if khugepaged should collapse hugepages over
443 * any unmapped ptes in turn potentially increasing the memory
444 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
445 * reduce the available free memory in the system as it
446 * runs. Increasing max_ptes_none will instead potentially reduce the
447 * free memory in the system during the khugepaged scan.
448 */
449 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
450 struct kobj_attribute *attr,
451 char *buf)
452 {
453 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
454 }
455 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
456 struct kobj_attribute *attr,
457 const char *buf, size_t count)
458 {
459 int err;
460 unsigned long max_ptes_none;
461
462 err = strict_strtoul(buf, 10, &max_ptes_none);
463 if (err || max_ptes_none > HPAGE_PMD_NR-1)
464 return -EINVAL;
465
466 khugepaged_max_ptes_none = max_ptes_none;
467
468 return count;
469 }
470 static struct kobj_attribute khugepaged_max_ptes_none_attr =
471 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
472 khugepaged_max_ptes_none_store);
473
474 static struct attribute *khugepaged_attr[] = {
475 &khugepaged_defrag_attr.attr,
476 &khugepaged_max_ptes_none_attr.attr,
477 &pages_to_scan_attr.attr,
478 &pages_collapsed_attr.attr,
479 &full_scans_attr.attr,
480 &scan_sleep_millisecs_attr.attr,
481 &alloc_sleep_millisecs_attr.attr,
482 NULL,
483 };
484
485 static struct attribute_group khugepaged_attr_group = {
486 .attrs = khugepaged_attr,
487 .name = "khugepaged",
488 };
489 #endif /* CONFIG_SYSFS */
490
491 static int __init hugepage_init(void)
492 {
493 int err;
494 #ifdef CONFIG_SYSFS
495 static struct kobject *hugepage_kobj;
496 #endif
497
498 err = -EINVAL;
499 if (!has_transparent_hugepage()) {
500 transparent_hugepage_flags = 0;
501 goto out;
502 }
503
504 #ifdef CONFIG_SYSFS
505 err = -ENOMEM;
506 hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
507 if (unlikely(!hugepage_kobj)) {
508 printk(KERN_ERR "hugepage: failed kobject create\n");
509 goto out;
510 }
511
512 err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group);
513 if (err) {
514 printk(KERN_ERR "hugepage: failed register hugeage group\n");
515 goto out;
516 }
517
518 err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group);
519 if (err) {
520 printk(KERN_ERR "hugepage: failed register hugeage group\n");
521 goto out;
522 }
523 #endif
524
525 err = khugepaged_slab_init();
526 if (err)
527 goto out;
528
529 err = mm_slots_hash_init();
530 if (err) {
531 khugepaged_slab_free();
532 goto out;
533 }
534
535 /*
536 * By default disable transparent hugepages on smaller systems,
537 * where the extra memory used could hurt more than TLB overhead
538 * is likely to save. The admin can still enable it through /sys.
539 */
540 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
541 transparent_hugepage_flags = 0;
542
543 start_khugepaged();
544
545 set_recommended_min_free_kbytes();
546
547 out:
548 return err;
549 }
550 module_init(hugepage_init)
551
552 static int __init setup_transparent_hugepage(char *str)
553 {
554 int ret = 0;
555 if (!str)
556 goto out;
557 if (!strcmp(str, "always")) {
558 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
559 &transparent_hugepage_flags);
560 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
561 &transparent_hugepage_flags);
562 ret = 1;
563 } else if (!strcmp(str, "madvise")) {
564 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
565 &transparent_hugepage_flags);
566 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
567 &transparent_hugepage_flags);
568 ret = 1;
569 } else if (!strcmp(str, "never")) {
570 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
571 &transparent_hugepage_flags);
572 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
573 &transparent_hugepage_flags);
574 ret = 1;
575 }
576 out:
577 if (!ret)
578 printk(KERN_WARNING
579 "transparent_hugepage= cannot parse, ignored\n");
580 return ret;
581 }
582 __setup("transparent_hugepage=", setup_transparent_hugepage);
583
584 static void prepare_pmd_huge_pte(pgtable_t pgtable,
585 struct mm_struct *mm)
586 {
587 assert_spin_locked(&mm->page_table_lock);
588
589 /* FIFO */
590 if (!mm->pmd_huge_pte)
591 INIT_LIST_HEAD(&pgtable->lru);
592 else
593 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
594 mm->pmd_huge_pte = pgtable;
595 }
596
597 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
598 {
599 if (likely(vma->vm_flags & VM_WRITE))
600 pmd = pmd_mkwrite(pmd);
601 return pmd;
602 }
603
604 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
605 struct vm_area_struct *vma,
606 unsigned long haddr, pmd_t *pmd,
607 struct page *page)
608 {
609 int ret = 0;
610 pgtable_t pgtable;
611
612 VM_BUG_ON(!PageCompound(page));
613 pgtable = pte_alloc_one(mm, haddr);
614 if (unlikely(!pgtable)) {
615 mem_cgroup_uncharge_page(page);
616 put_page(page);
617 return VM_FAULT_OOM;
618 }
619
620 clear_huge_page(page, haddr, HPAGE_PMD_NR);
621 __SetPageUptodate(page);
622
623 spin_lock(&mm->page_table_lock);
624 if (unlikely(!pmd_none(*pmd))) {
625 spin_unlock(&mm->page_table_lock);
626 mem_cgroup_uncharge_page(page);
627 put_page(page);
628 pte_free(mm, pgtable);
629 } else {
630 pmd_t entry;
631 entry = mk_pmd(page, vma->vm_page_prot);
632 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
633 entry = pmd_mkhuge(entry);
634 /*
635 * The spinlocking to take the lru_lock inside
636 * page_add_new_anon_rmap() acts as a full memory
637 * barrier to be sure clear_huge_page writes become
638 * visible after the set_pmd_at() write.
639 */
640 page_add_new_anon_rmap(page, vma, haddr);
641 set_pmd_at(mm, haddr, pmd, entry);
642 prepare_pmd_huge_pte(pgtable, mm);
643 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
644 spin_unlock(&mm->page_table_lock);
645 }
646
647 return ret;
648 }
649
650 static inline gfp_t alloc_hugepage_gfpmask(int defrag)
651 {
652 return GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT);
653 }
654
655 static inline struct page *alloc_hugepage_vma(int defrag,
656 struct vm_area_struct *vma,
657 unsigned long haddr, int nd)
658 {
659 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag),
660 HPAGE_PMD_ORDER, vma, haddr, nd);
661 }
662
663 #ifndef CONFIG_NUMA
664 static inline struct page *alloc_hugepage(int defrag)
665 {
666 return alloc_pages(alloc_hugepage_gfpmask(defrag),
667 HPAGE_PMD_ORDER);
668 }
669 #endif
670
671 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
672 unsigned long address, pmd_t *pmd,
673 unsigned int flags)
674 {
675 struct page *page;
676 unsigned long haddr = address & HPAGE_PMD_MASK;
677 pte_t *pte;
678
679 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
680 if (unlikely(anon_vma_prepare(vma)))
681 return VM_FAULT_OOM;
682 if (unlikely(khugepaged_enter(vma)))
683 return VM_FAULT_OOM;
684 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
685 vma, haddr, numa_node_id());
686 if (unlikely(!page))
687 goto out;
688 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
689 put_page(page);
690 goto out;
691 }
692
693 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
694 }
695 out:
696 /*
697 * Use __pte_alloc instead of pte_alloc_map, because we can't
698 * run pte_offset_map on the pmd, if an huge pmd could
699 * materialize from under us from a different thread.
700 */
701 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
702 return VM_FAULT_OOM;
703 /* if an huge pmd materialized from under us just retry later */
704 if (unlikely(pmd_trans_huge(*pmd)))
705 return 0;
706 /*
707 * A regular pmd is established and it can't morph into a huge pmd
708 * from under us anymore at this point because we hold the mmap_sem
709 * read mode and khugepaged takes it in write mode. So now it's
710 * safe to run pte_offset_map().
711 */
712 pte = pte_offset_map(pmd, address);
713 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
714 }
715
716 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
717 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
718 struct vm_area_struct *vma)
719 {
720 struct page *src_page;
721 pmd_t pmd;
722 pgtable_t pgtable;
723 int ret;
724
725 ret = -ENOMEM;
726 pgtable = pte_alloc_one(dst_mm, addr);
727 if (unlikely(!pgtable))
728 goto out;
729
730 spin_lock(&dst_mm->page_table_lock);
731 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
732
733 ret = -EAGAIN;
734 pmd = *src_pmd;
735 if (unlikely(!pmd_trans_huge(pmd))) {
736 pte_free(dst_mm, pgtable);
737 goto out_unlock;
738 }
739 if (unlikely(pmd_trans_splitting(pmd))) {
740 /* split huge page running from under us */
741 spin_unlock(&src_mm->page_table_lock);
742 spin_unlock(&dst_mm->page_table_lock);
743 pte_free(dst_mm, pgtable);
744
745 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
746 goto out;
747 }
748 src_page = pmd_page(pmd);
749 VM_BUG_ON(!PageHead(src_page));
750 get_page(src_page);
751 page_dup_rmap(src_page);
752 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
753
754 pmdp_set_wrprotect(src_mm, addr, src_pmd);
755 pmd = pmd_mkold(pmd_wrprotect(pmd));
756 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
757 prepare_pmd_huge_pte(pgtable, dst_mm);
758
759 ret = 0;
760 out_unlock:
761 spin_unlock(&src_mm->page_table_lock);
762 spin_unlock(&dst_mm->page_table_lock);
763 out:
764 return ret;
765 }
766
767 /* no "address" argument so destroys page coloring of some arch */
768 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
769 {
770 pgtable_t pgtable;
771
772 assert_spin_locked(&mm->page_table_lock);
773
774 /* FIFO */
775 pgtable = mm->pmd_huge_pte;
776 if (list_empty(&pgtable->lru))
777 mm->pmd_huge_pte = NULL;
778 else {
779 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
780 struct page, lru);
781 list_del(&pgtable->lru);
782 }
783 return pgtable;
784 }
785
786 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
787 struct vm_area_struct *vma,
788 unsigned long address,
789 pmd_t *pmd, pmd_t orig_pmd,
790 struct page *page,
791 unsigned long haddr)
792 {
793 pgtable_t pgtable;
794 pmd_t _pmd;
795 int ret = 0, i;
796 struct page **pages;
797
798 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
799 GFP_KERNEL);
800 if (unlikely(!pages)) {
801 ret |= VM_FAULT_OOM;
802 goto out;
803 }
804
805 for (i = 0; i < HPAGE_PMD_NR; i++) {
806 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE,
807 vma, address, page_to_nid(page));
808 if (unlikely(!pages[i] ||
809 mem_cgroup_newpage_charge(pages[i], mm,
810 GFP_KERNEL))) {
811 if (pages[i])
812 put_page(pages[i]);
813 mem_cgroup_uncharge_start();
814 while (--i >= 0) {
815 mem_cgroup_uncharge_page(pages[i]);
816 put_page(pages[i]);
817 }
818 mem_cgroup_uncharge_end();
819 kfree(pages);
820 ret |= VM_FAULT_OOM;
821 goto out;
822 }
823 }
824
825 for (i = 0; i < HPAGE_PMD_NR; i++) {
826 copy_user_highpage(pages[i], page + i,
827 haddr + PAGE_SHIFT*i, vma);
828 __SetPageUptodate(pages[i]);
829 cond_resched();
830 }
831
832 spin_lock(&mm->page_table_lock);
833 if (unlikely(!pmd_same(*pmd, orig_pmd)))
834 goto out_free_pages;
835 VM_BUG_ON(!PageHead(page));
836
837 pmdp_clear_flush_notify(vma, haddr, pmd);
838 /* leave pmd empty until pte is filled */
839
840 pgtable = get_pmd_huge_pte(mm);
841 pmd_populate(mm, &_pmd, pgtable);
842
843 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
844 pte_t *pte, entry;
845 entry = mk_pte(pages[i], vma->vm_page_prot);
846 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
847 page_add_new_anon_rmap(pages[i], vma, haddr);
848 pte = pte_offset_map(&_pmd, haddr);
849 VM_BUG_ON(!pte_none(*pte));
850 set_pte_at(mm, haddr, pte, entry);
851 pte_unmap(pte);
852 }
853 kfree(pages);
854
855 mm->nr_ptes++;
856 smp_wmb(); /* make pte visible before pmd */
857 pmd_populate(mm, pmd, pgtable);
858 page_remove_rmap(page);
859 spin_unlock(&mm->page_table_lock);
860
861 ret |= VM_FAULT_WRITE;
862 put_page(page);
863
864 out:
865 return ret;
866
867 out_free_pages:
868 spin_unlock(&mm->page_table_lock);
869 mem_cgroup_uncharge_start();
870 for (i = 0; i < HPAGE_PMD_NR; i++) {
871 mem_cgroup_uncharge_page(pages[i]);
872 put_page(pages[i]);
873 }
874 mem_cgroup_uncharge_end();
875 kfree(pages);
876 goto out;
877 }
878
879 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
880 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
881 {
882 int ret = 0;
883 struct page *page, *new_page;
884 unsigned long haddr;
885
886 VM_BUG_ON(!vma->anon_vma);
887 spin_lock(&mm->page_table_lock);
888 if (unlikely(!pmd_same(*pmd, orig_pmd)))
889 goto out_unlock;
890
891 page = pmd_page(orig_pmd);
892 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
893 haddr = address & HPAGE_PMD_MASK;
894 if (page_mapcount(page) == 1) {
895 pmd_t entry;
896 entry = pmd_mkyoung(orig_pmd);
897 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
898 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
899 update_mmu_cache(vma, address, entry);
900 ret |= VM_FAULT_WRITE;
901 goto out_unlock;
902 }
903 get_page(page);
904 spin_unlock(&mm->page_table_lock);
905
906 if (transparent_hugepage_enabled(vma) &&
907 !transparent_hugepage_debug_cow())
908 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
909 vma, haddr, numa_node_id());
910 else
911 new_page = NULL;
912
913 if (unlikely(!new_page)) {
914 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
915 pmd, orig_pmd, page, haddr);
916 put_page(page);
917 goto out;
918 }
919
920 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
921 put_page(new_page);
922 put_page(page);
923 ret |= VM_FAULT_OOM;
924 goto out;
925 }
926
927 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
928 __SetPageUptodate(new_page);
929
930 spin_lock(&mm->page_table_lock);
931 put_page(page);
932 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
933 mem_cgroup_uncharge_page(new_page);
934 put_page(new_page);
935 } else {
936 pmd_t entry;
937 VM_BUG_ON(!PageHead(page));
938 entry = mk_pmd(new_page, vma->vm_page_prot);
939 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
940 entry = pmd_mkhuge(entry);
941 pmdp_clear_flush_notify(vma, haddr, pmd);
942 page_add_new_anon_rmap(new_page, vma, haddr);
943 set_pmd_at(mm, haddr, pmd, entry);
944 update_mmu_cache(vma, address, entry);
945 page_remove_rmap(page);
946 put_page(page);
947 ret |= VM_FAULT_WRITE;
948 }
949 out_unlock:
950 spin_unlock(&mm->page_table_lock);
951 out:
952 return ret;
953 }
954
955 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
956 unsigned long addr,
957 pmd_t *pmd,
958 unsigned int flags)
959 {
960 struct page *page = NULL;
961
962 assert_spin_locked(&mm->page_table_lock);
963
964 if (flags & FOLL_WRITE && !pmd_write(*pmd))
965 goto out;
966
967 page = pmd_page(*pmd);
968 VM_BUG_ON(!PageHead(page));
969 if (flags & FOLL_TOUCH) {
970 pmd_t _pmd;
971 /*
972 * We should set the dirty bit only for FOLL_WRITE but
973 * for now the dirty bit in the pmd is meaningless.
974 * And if the dirty bit will become meaningful and
975 * we'll only set it with FOLL_WRITE, an atomic
976 * set_bit will be required on the pmd to set the
977 * young bit, instead of the current set_pmd_at.
978 */
979 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
980 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
981 }
982 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
983 VM_BUG_ON(!PageCompound(page));
984 if (flags & FOLL_GET)
985 get_page(page);
986
987 out:
988 return page;
989 }
990
991 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
992 pmd_t *pmd)
993 {
994 int ret = 0;
995
996 spin_lock(&tlb->mm->page_table_lock);
997 if (likely(pmd_trans_huge(*pmd))) {
998 if (unlikely(pmd_trans_splitting(*pmd))) {
999 spin_unlock(&tlb->mm->page_table_lock);
1000 wait_split_huge_page(vma->anon_vma,
1001 pmd);
1002 } else {
1003 struct page *page;
1004 pgtable_t pgtable;
1005 pgtable = get_pmd_huge_pte(tlb->mm);
1006 page = pmd_page(*pmd);
1007 pmd_clear(pmd);
1008 page_remove_rmap(page);
1009 VM_BUG_ON(page_mapcount(page) < 0);
1010 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1011 VM_BUG_ON(!PageHead(page));
1012 spin_unlock(&tlb->mm->page_table_lock);
1013 tlb_remove_page(tlb, page);
1014 pte_free(tlb->mm, pgtable);
1015 ret = 1;
1016 }
1017 } else
1018 spin_unlock(&tlb->mm->page_table_lock);
1019
1020 return ret;
1021 }
1022
1023 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1024 unsigned long addr, unsigned long end,
1025 unsigned char *vec)
1026 {
1027 int ret = 0;
1028
1029 spin_lock(&vma->vm_mm->page_table_lock);
1030 if (likely(pmd_trans_huge(*pmd))) {
1031 ret = !pmd_trans_splitting(*pmd);
1032 spin_unlock(&vma->vm_mm->page_table_lock);
1033 if (unlikely(!ret))
1034 wait_split_huge_page(vma->anon_vma, pmd);
1035 else {
1036 /*
1037 * All logical pages in the range are present
1038 * if backed by a huge page.
1039 */
1040 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1041 }
1042 } else
1043 spin_unlock(&vma->vm_mm->page_table_lock);
1044
1045 return ret;
1046 }
1047
1048 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1049 unsigned long addr, pgprot_t newprot)
1050 {
1051 struct mm_struct *mm = vma->vm_mm;
1052 int ret = 0;
1053
1054 spin_lock(&mm->page_table_lock);
1055 if (likely(pmd_trans_huge(*pmd))) {
1056 if (unlikely(pmd_trans_splitting(*pmd))) {
1057 spin_unlock(&mm->page_table_lock);
1058 wait_split_huge_page(vma->anon_vma, pmd);
1059 } else {
1060 pmd_t entry;
1061
1062 entry = pmdp_get_and_clear(mm, addr, pmd);
1063 entry = pmd_modify(entry, newprot);
1064 set_pmd_at(mm, addr, pmd, entry);
1065 spin_unlock(&vma->vm_mm->page_table_lock);
1066 flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
1067 ret = 1;
1068 }
1069 } else
1070 spin_unlock(&vma->vm_mm->page_table_lock);
1071
1072 return ret;
1073 }
1074
1075 pmd_t *page_check_address_pmd(struct page *page,
1076 struct mm_struct *mm,
1077 unsigned long address,
1078 enum page_check_address_pmd_flag flag)
1079 {
1080 pgd_t *pgd;
1081 pud_t *pud;
1082 pmd_t *pmd, *ret = NULL;
1083
1084 if (address & ~HPAGE_PMD_MASK)
1085 goto out;
1086
1087 pgd = pgd_offset(mm, address);
1088 if (!pgd_present(*pgd))
1089 goto out;
1090
1091 pud = pud_offset(pgd, address);
1092 if (!pud_present(*pud))
1093 goto out;
1094
1095 pmd = pmd_offset(pud, address);
1096 if (pmd_none(*pmd))
1097 goto out;
1098 if (pmd_page(*pmd) != page)
1099 goto out;
1100 /*
1101 * split_vma() may create temporary aliased mappings. There is
1102 * no risk as long as all huge pmd are found and have their
1103 * splitting bit set before __split_huge_page_refcount
1104 * runs. Finding the same huge pmd more than once during the
1105 * same rmap walk is not a problem.
1106 */
1107 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1108 pmd_trans_splitting(*pmd))
1109 goto out;
1110 if (pmd_trans_huge(*pmd)) {
1111 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1112 !pmd_trans_splitting(*pmd));
1113 ret = pmd;
1114 }
1115 out:
1116 return ret;
1117 }
1118
1119 static int __split_huge_page_splitting(struct page *page,
1120 struct vm_area_struct *vma,
1121 unsigned long address)
1122 {
1123 struct mm_struct *mm = vma->vm_mm;
1124 pmd_t *pmd;
1125 int ret = 0;
1126
1127 spin_lock(&mm->page_table_lock);
1128 pmd = page_check_address_pmd(page, mm, address,
1129 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1130 if (pmd) {
1131 /*
1132 * We can't temporarily set the pmd to null in order
1133 * to split it, the pmd must remain marked huge at all
1134 * times or the VM won't take the pmd_trans_huge paths
1135 * and it won't wait on the anon_vma->root->lock to
1136 * serialize against split_huge_page*.
1137 */
1138 pmdp_splitting_flush_notify(vma, address, pmd);
1139 ret = 1;
1140 }
1141 spin_unlock(&mm->page_table_lock);
1142
1143 return ret;
1144 }
1145
1146 static void __split_huge_page_refcount(struct page *page)
1147 {
1148 int i;
1149 unsigned long head_index = page->index;
1150 struct zone *zone = page_zone(page);
1151 int zonestat;
1152
1153 /* prevent PageLRU to go away from under us, and freeze lru stats */
1154 spin_lock_irq(&zone->lru_lock);
1155 compound_lock(page);
1156
1157 for (i = 1; i < HPAGE_PMD_NR; i++) {
1158 struct page *page_tail = page + i;
1159
1160 /* tail_page->_count cannot change */
1161 atomic_sub(atomic_read(&page_tail->_count), &page->_count);
1162 BUG_ON(page_count(page) <= 0);
1163 atomic_add(page_mapcount(page) + 1, &page_tail->_count);
1164 BUG_ON(atomic_read(&page_tail->_count) <= 0);
1165
1166 /* after clearing PageTail the gup refcount can be released */
1167 smp_mb();
1168
1169 /*
1170 * retain hwpoison flag of the poisoned tail page:
1171 * fix for the unsuitable process killed on Guest Machine(KVM)
1172 * by the memory-failure.
1173 */
1174 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1175 page_tail->flags |= (page->flags &
1176 ((1L << PG_referenced) |
1177 (1L << PG_swapbacked) |
1178 (1L << PG_mlocked) |
1179 (1L << PG_uptodate)));
1180 page_tail->flags |= (1L << PG_dirty);
1181
1182 /*
1183 * 1) clear PageTail before overwriting first_page
1184 * 2) clear PageTail before clearing PageHead for VM_BUG_ON
1185 */
1186 smp_wmb();
1187
1188 /*
1189 * __split_huge_page_splitting() already set the
1190 * splitting bit in all pmd that could map this
1191 * hugepage, that will ensure no CPU can alter the
1192 * mapcount on the head page. The mapcount is only
1193 * accounted in the head page and it has to be
1194 * transferred to all tail pages in the below code. So
1195 * for this code to be safe, the split the mapcount
1196 * can't change. But that doesn't mean userland can't
1197 * keep changing and reading the page contents while
1198 * we transfer the mapcount, so the pmd splitting
1199 * status is achieved setting a reserved bit in the
1200 * pmd, not by clearing the present bit.
1201 */
1202 BUG_ON(page_mapcount(page_tail));
1203 page_tail->_mapcount = page->_mapcount;
1204
1205 BUG_ON(page_tail->mapping);
1206 page_tail->mapping = page->mapping;
1207
1208 page_tail->index = ++head_index;
1209
1210 BUG_ON(!PageAnon(page_tail));
1211 BUG_ON(!PageUptodate(page_tail));
1212 BUG_ON(!PageDirty(page_tail));
1213 BUG_ON(!PageSwapBacked(page_tail));
1214
1215 mem_cgroup_split_huge_fixup(page, page_tail);
1216
1217 lru_add_page_tail(zone, page, page_tail);
1218 }
1219
1220 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1221 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1222
1223 /*
1224 * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics,
1225 * so adjust those appropriately if this page is on the LRU.
1226 */
1227 if (PageLRU(page)) {
1228 zonestat = NR_LRU_BASE + page_lru(page);
1229 __mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1));
1230 }
1231
1232 ClearPageCompound(page);
1233 compound_unlock(page);
1234 spin_unlock_irq(&zone->lru_lock);
1235
1236 for (i = 1; i < HPAGE_PMD_NR; i++) {
1237 struct page *page_tail = page + i;
1238 BUG_ON(page_count(page_tail) <= 0);
1239 /*
1240 * Tail pages may be freed if there wasn't any mapping
1241 * like if add_to_swap() is running on a lru page that
1242 * had its mapping zapped. And freeing these pages
1243 * requires taking the lru_lock so we do the put_page
1244 * of the tail pages after the split is complete.
1245 */
1246 put_page(page_tail);
1247 }
1248
1249 /*
1250 * Only the head page (now become a regular page) is required
1251 * to be pinned by the caller.
1252 */
1253 BUG_ON(page_count(page) <= 0);
1254 }
1255
1256 static int __split_huge_page_map(struct page *page,
1257 struct vm_area_struct *vma,
1258 unsigned long address)
1259 {
1260 struct mm_struct *mm = vma->vm_mm;
1261 pmd_t *pmd, _pmd;
1262 int ret = 0, i;
1263 pgtable_t pgtable;
1264 unsigned long haddr;
1265
1266 spin_lock(&mm->page_table_lock);
1267 pmd = page_check_address_pmd(page, mm, address,
1268 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1269 if (pmd) {
1270 pgtable = get_pmd_huge_pte(mm);
1271 pmd_populate(mm, &_pmd, pgtable);
1272
1273 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1274 i++, haddr += PAGE_SIZE) {
1275 pte_t *pte, entry;
1276 BUG_ON(PageCompound(page+i));
1277 entry = mk_pte(page + i, vma->vm_page_prot);
1278 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1279 if (!pmd_write(*pmd))
1280 entry = pte_wrprotect(entry);
1281 else
1282 BUG_ON(page_mapcount(page) != 1);
1283 if (!pmd_young(*pmd))
1284 entry = pte_mkold(entry);
1285 pte = pte_offset_map(&_pmd, haddr);
1286 BUG_ON(!pte_none(*pte));
1287 set_pte_at(mm, haddr, pte, entry);
1288 pte_unmap(pte);
1289 }
1290
1291 mm->nr_ptes++;
1292 smp_wmb(); /* make pte visible before pmd */
1293 /*
1294 * Up to this point the pmd is present and huge and
1295 * userland has the whole access to the hugepage
1296 * during the split (which happens in place). If we
1297 * overwrite the pmd with the not-huge version
1298 * pointing to the pte here (which of course we could
1299 * if all CPUs were bug free), userland could trigger
1300 * a small page size TLB miss on the small sized TLB
1301 * while the hugepage TLB entry is still established
1302 * in the huge TLB. Some CPU doesn't like that. See
1303 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1304 * Erratum 383 on page 93. Intel should be safe but is
1305 * also warns that it's only safe if the permission
1306 * and cache attributes of the two entries loaded in
1307 * the two TLB is identical (which should be the case
1308 * here). But it is generally safer to never allow
1309 * small and huge TLB entries for the same virtual
1310 * address to be loaded simultaneously. So instead of
1311 * doing "pmd_populate(); flush_tlb_range();" we first
1312 * mark the current pmd notpresent (atomically because
1313 * here the pmd_trans_huge and pmd_trans_splitting
1314 * must remain set at all times on the pmd until the
1315 * split is complete for this pmd), then we flush the
1316 * SMP TLB and finally we write the non-huge version
1317 * of the pmd entry with pmd_populate.
1318 */
1319 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1320 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1321 pmd_populate(mm, pmd, pgtable);
1322 ret = 1;
1323 }
1324 spin_unlock(&mm->page_table_lock);
1325
1326 return ret;
1327 }
1328
1329 /* must be called with anon_vma->root->lock hold */
1330 static void __split_huge_page(struct page *page,
1331 struct anon_vma *anon_vma)
1332 {
1333 int mapcount, mapcount2;
1334 struct anon_vma_chain *avc;
1335
1336 BUG_ON(!PageHead(page));
1337 BUG_ON(PageTail(page));
1338
1339 mapcount = 0;
1340 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1341 struct vm_area_struct *vma = avc->vma;
1342 unsigned long addr = vma_address(page, vma);
1343 BUG_ON(is_vma_temporary_stack(vma));
1344 if (addr == -EFAULT)
1345 continue;
1346 mapcount += __split_huge_page_splitting(page, vma, addr);
1347 }
1348 /*
1349 * It is critical that new vmas are added to the tail of the
1350 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1351 * and establishes a child pmd before
1352 * __split_huge_page_splitting() freezes the parent pmd (so if
1353 * we fail to prevent copy_huge_pmd() from running until the
1354 * whole __split_huge_page() is complete), we will still see
1355 * the newly established pmd of the child later during the
1356 * walk, to be able to set it as pmd_trans_splitting too.
1357 */
1358 if (mapcount != page_mapcount(page))
1359 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1360 mapcount, page_mapcount(page));
1361 BUG_ON(mapcount != page_mapcount(page));
1362
1363 __split_huge_page_refcount(page);
1364
1365 mapcount2 = 0;
1366 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1367 struct vm_area_struct *vma = avc->vma;
1368 unsigned long addr = vma_address(page, vma);
1369 BUG_ON(is_vma_temporary_stack(vma));
1370 if (addr == -EFAULT)
1371 continue;
1372 mapcount2 += __split_huge_page_map(page, vma, addr);
1373 }
1374 if (mapcount != mapcount2)
1375 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1376 mapcount, mapcount2, page_mapcount(page));
1377 BUG_ON(mapcount != mapcount2);
1378 }
1379
1380 int split_huge_page(struct page *page)
1381 {
1382 struct anon_vma *anon_vma;
1383 int ret = 1;
1384
1385 BUG_ON(!PageAnon(page));
1386 anon_vma = page_lock_anon_vma(page);
1387 if (!anon_vma)
1388 goto out;
1389 ret = 0;
1390 if (!PageCompound(page))
1391 goto out_unlock;
1392
1393 BUG_ON(!PageSwapBacked(page));
1394 __split_huge_page(page, anon_vma);
1395
1396 BUG_ON(PageCompound(page));
1397 out_unlock:
1398 page_unlock_anon_vma(anon_vma);
1399 out:
1400 return ret;
1401 }
1402
1403 #define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \
1404 VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1405
1406 int hugepage_madvise(struct vm_area_struct *vma,
1407 unsigned long *vm_flags, int advice)
1408 {
1409 switch (advice) {
1410 case MADV_HUGEPAGE:
1411 /*
1412 * Be somewhat over-protective like KSM for now!
1413 */
1414 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1415 return -EINVAL;
1416 *vm_flags &= ~VM_NOHUGEPAGE;
1417 *vm_flags |= VM_HUGEPAGE;
1418 /*
1419 * If the vma become good for khugepaged to scan,
1420 * register it here without waiting a page fault that
1421 * may not happen any time soon.
1422 */
1423 if (unlikely(khugepaged_enter_vma_merge(vma)))
1424 return -ENOMEM;
1425 break;
1426 case MADV_NOHUGEPAGE:
1427 /*
1428 * Be somewhat over-protective like KSM for now!
1429 */
1430 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1431 return -EINVAL;
1432 *vm_flags &= ~VM_HUGEPAGE;
1433 *vm_flags |= VM_NOHUGEPAGE;
1434 /*
1435 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1436 * this vma even if we leave the mm registered in khugepaged if
1437 * it got registered before VM_NOHUGEPAGE was set.
1438 */
1439 break;
1440 }
1441
1442 return 0;
1443 }
1444
1445 static int __init khugepaged_slab_init(void)
1446 {
1447 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1448 sizeof(struct mm_slot),
1449 __alignof__(struct mm_slot), 0, NULL);
1450 if (!mm_slot_cache)
1451 return -ENOMEM;
1452
1453 return 0;
1454 }
1455
1456 static void __init khugepaged_slab_free(void)
1457 {
1458 kmem_cache_destroy(mm_slot_cache);
1459 mm_slot_cache = NULL;
1460 }
1461
1462 static inline struct mm_slot *alloc_mm_slot(void)
1463 {
1464 if (!mm_slot_cache) /* initialization failed */
1465 return NULL;
1466 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1467 }
1468
1469 static inline void free_mm_slot(struct mm_slot *mm_slot)
1470 {
1471 kmem_cache_free(mm_slot_cache, mm_slot);
1472 }
1473
1474 static int __init mm_slots_hash_init(void)
1475 {
1476 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1477 GFP_KERNEL);
1478 if (!mm_slots_hash)
1479 return -ENOMEM;
1480 return 0;
1481 }
1482
1483 #if 0
1484 static void __init mm_slots_hash_free(void)
1485 {
1486 kfree(mm_slots_hash);
1487 mm_slots_hash = NULL;
1488 }
1489 #endif
1490
1491 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1492 {
1493 struct mm_slot *mm_slot;
1494 struct hlist_head *bucket;
1495 struct hlist_node *node;
1496
1497 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1498 % MM_SLOTS_HASH_HEADS];
1499 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1500 if (mm == mm_slot->mm)
1501 return mm_slot;
1502 }
1503 return NULL;
1504 }
1505
1506 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1507 struct mm_slot *mm_slot)
1508 {
1509 struct hlist_head *bucket;
1510
1511 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1512 % MM_SLOTS_HASH_HEADS];
1513 mm_slot->mm = mm;
1514 hlist_add_head(&mm_slot->hash, bucket);
1515 }
1516
1517 static inline int khugepaged_test_exit(struct mm_struct *mm)
1518 {
1519 return atomic_read(&mm->mm_users) == 0;
1520 }
1521
1522 int __khugepaged_enter(struct mm_struct *mm)
1523 {
1524 struct mm_slot *mm_slot;
1525 int wakeup;
1526
1527 mm_slot = alloc_mm_slot();
1528 if (!mm_slot)
1529 return -ENOMEM;
1530
1531 /* __khugepaged_exit() must not run from under us */
1532 VM_BUG_ON(khugepaged_test_exit(mm));
1533 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1534 free_mm_slot(mm_slot);
1535 return 0;
1536 }
1537
1538 spin_lock(&khugepaged_mm_lock);
1539 insert_to_mm_slots_hash(mm, mm_slot);
1540 /*
1541 * Insert just behind the scanning cursor, to let the area settle
1542 * down a little.
1543 */
1544 wakeup = list_empty(&khugepaged_scan.mm_head);
1545 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1546 spin_unlock(&khugepaged_mm_lock);
1547
1548 atomic_inc(&mm->mm_count);
1549 if (wakeup)
1550 wake_up_interruptible(&khugepaged_wait);
1551
1552 return 0;
1553 }
1554
1555 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1556 {
1557 unsigned long hstart, hend;
1558 if (!vma->anon_vma)
1559 /*
1560 * Not yet faulted in so we will register later in the
1561 * page fault if needed.
1562 */
1563 return 0;
1564 if (vma->vm_ops)
1565 /* khugepaged not yet working on file or special mappings */
1566 return 0;
1567 /*
1568 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1569 * true too, verify it here.
1570 */
1571 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1572 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1573 hend = vma->vm_end & HPAGE_PMD_MASK;
1574 if (hstart < hend)
1575 return khugepaged_enter(vma);
1576 return 0;
1577 }
1578
1579 void __khugepaged_exit(struct mm_struct *mm)
1580 {
1581 struct mm_slot *mm_slot;
1582 int free = 0;
1583
1584 spin_lock(&khugepaged_mm_lock);
1585 mm_slot = get_mm_slot(mm);
1586 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1587 hlist_del(&mm_slot->hash);
1588 list_del(&mm_slot->mm_node);
1589 free = 1;
1590 }
1591
1592 if (free) {
1593 spin_unlock(&khugepaged_mm_lock);
1594 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1595 free_mm_slot(mm_slot);
1596 mmdrop(mm);
1597 } else if (mm_slot) {
1598 spin_unlock(&khugepaged_mm_lock);
1599 /*
1600 * This is required to serialize against
1601 * khugepaged_test_exit() (which is guaranteed to run
1602 * under mmap sem read mode). Stop here (after we
1603 * return all pagetables will be destroyed) until
1604 * khugepaged has finished working on the pagetables
1605 * under the mmap_sem.
1606 */
1607 down_write(&mm->mmap_sem);
1608 up_write(&mm->mmap_sem);
1609 } else
1610 spin_unlock(&khugepaged_mm_lock);
1611 }
1612
1613 static void release_pte_page(struct page *page)
1614 {
1615 /* 0 stands for page_is_file_cache(page) == false */
1616 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1617 unlock_page(page);
1618 putback_lru_page(page);
1619 }
1620
1621 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1622 {
1623 while (--_pte >= pte) {
1624 pte_t pteval = *_pte;
1625 if (!pte_none(pteval))
1626 release_pte_page(pte_page(pteval));
1627 }
1628 }
1629
1630 static void release_all_pte_pages(pte_t *pte)
1631 {
1632 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1633 }
1634
1635 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1636 unsigned long address,
1637 pte_t *pte)
1638 {
1639 struct page *page;
1640 pte_t *_pte;
1641 int referenced = 0, isolated = 0, none = 0;
1642 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1643 _pte++, address += PAGE_SIZE) {
1644 pte_t pteval = *_pte;
1645 if (pte_none(pteval)) {
1646 if (++none <= khugepaged_max_ptes_none)
1647 continue;
1648 else {
1649 release_pte_pages(pte, _pte);
1650 goto out;
1651 }
1652 }
1653 if (!pte_present(pteval) || !pte_write(pteval)) {
1654 release_pte_pages(pte, _pte);
1655 goto out;
1656 }
1657 page = vm_normal_page(vma, address, pteval);
1658 if (unlikely(!page)) {
1659 release_pte_pages(pte, _pte);
1660 goto out;
1661 }
1662 VM_BUG_ON(PageCompound(page));
1663 BUG_ON(!PageAnon(page));
1664 VM_BUG_ON(!PageSwapBacked(page));
1665
1666 /* cannot use mapcount: can't collapse if there's a gup pin */
1667 if (page_count(page) != 1) {
1668 release_pte_pages(pte, _pte);
1669 goto out;
1670 }
1671 /*
1672 * We can do it before isolate_lru_page because the
1673 * page can't be freed from under us. NOTE: PG_lock
1674 * is needed to serialize against split_huge_page
1675 * when invoked from the VM.
1676 */
1677 if (!trylock_page(page)) {
1678 release_pte_pages(pte, _pte);
1679 goto out;
1680 }
1681 /*
1682 * Isolate the page to avoid collapsing an hugepage
1683 * currently in use by the VM.
1684 */
1685 if (isolate_lru_page(page)) {
1686 unlock_page(page);
1687 release_pte_pages(pte, _pte);
1688 goto out;
1689 }
1690 /* 0 stands for page_is_file_cache(page) == false */
1691 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1692 VM_BUG_ON(!PageLocked(page));
1693 VM_BUG_ON(PageLRU(page));
1694
1695 /* If there is no mapped pte young don't collapse the page */
1696 if (pte_young(pteval) || PageReferenced(page) ||
1697 mmu_notifier_test_young(vma->vm_mm, address))
1698 referenced = 1;
1699 }
1700 if (unlikely(!referenced))
1701 release_all_pte_pages(pte);
1702 else
1703 isolated = 1;
1704 out:
1705 return isolated;
1706 }
1707
1708 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1709 struct vm_area_struct *vma,
1710 unsigned long address,
1711 spinlock_t *ptl)
1712 {
1713 pte_t *_pte;
1714 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1715 pte_t pteval = *_pte;
1716 struct page *src_page;
1717
1718 if (pte_none(pteval)) {
1719 clear_user_highpage(page, address);
1720 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1721 } else {
1722 src_page = pte_page(pteval);
1723 copy_user_highpage(page, src_page, address, vma);
1724 VM_BUG_ON(page_mapcount(src_page) != 1);
1725 VM_BUG_ON(page_count(src_page) != 2);
1726 release_pte_page(src_page);
1727 /*
1728 * ptl mostly unnecessary, but preempt has to
1729 * be disabled to update the per-cpu stats
1730 * inside page_remove_rmap().
1731 */
1732 spin_lock(ptl);
1733 /*
1734 * paravirt calls inside pte_clear here are
1735 * superfluous.
1736 */
1737 pte_clear(vma->vm_mm, address, _pte);
1738 page_remove_rmap(src_page);
1739 spin_unlock(ptl);
1740 free_page_and_swap_cache(src_page);
1741 }
1742
1743 address += PAGE_SIZE;
1744 page++;
1745 }
1746 }
1747
1748 static void collapse_huge_page(struct mm_struct *mm,
1749 unsigned long address,
1750 struct page **hpage,
1751 struct vm_area_struct *vma,
1752 int node)
1753 {
1754 pgd_t *pgd;
1755 pud_t *pud;
1756 pmd_t *pmd, _pmd;
1757 pte_t *pte;
1758 pgtable_t pgtable;
1759 struct page *new_page;
1760 spinlock_t *ptl;
1761 int isolated;
1762 unsigned long hstart, hend;
1763
1764 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1765 #ifndef CONFIG_NUMA
1766 VM_BUG_ON(!*hpage);
1767 new_page = *hpage;
1768 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1769 up_read(&mm->mmap_sem);
1770 return;
1771 }
1772 #else
1773 VM_BUG_ON(*hpage);
1774 /*
1775 * Allocate the page while the vma is still valid and under
1776 * the mmap_sem read mode so there is no memory allocation
1777 * later when we take the mmap_sem in write mode. This is more
1778 * friendly behavior (OTOH it may actually hide bugs) to
1779 * filesystems in userland with daemons allocating memory in
1780 * the userland I/O paths. Allocating memory with the
1781 * mmap_sem in read mode is good idea also to allow greater
1782 * scalability.
1783 */
1784 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1785 node);
1786 if (unlikely(!new_page)) {
1787 up_read(&mm->mmap_sem);
1788 *hpage = ERR_PTR(-ENOMEM);
1789 return;
1790 }
1791 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1792 up_read(&mm->mmap_sem);
1793 put_page(new_page);
1794 return;
1795 }
1796 #endif
1797
1798 /* after allocating the hugepage upgrade to mmap_sem write mode */
1799 up_read(&mm->mmap_sem);
1800
1801 /*
1802 * Prevent all access to pagetables with the exception of
1803 * gup_fast later hanlded by the ptep_clear_flush and the VM
1804 * handled by the anon_vma lock + PG_lock.
1805 */
1806 down_write(&mm->mmap_sem);
1807 if (unlikely(khugepaged_test_exit(mm)))
1808 goto out;
1809
1810 vma = find_vma(mm, address);
1811 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1812 hend = vma->vm_end & HPAGE_PMD_MASK;
1813 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1814 goto out;
1815
1816 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1817 (vma->vm_flags & VM_NOHUGEPAGE))
1818 goto out;
1819
1820 if (!vma->anon_vma || vma->vm_ops)
1821 goto out;
1822 if (is_vma_temporary_stack(vma))
1823 goto out;
1824 /*
1825 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1826 * true too, verify it here.
1827 */
1828 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
1829
1830 pgd = pgd_offset(mm, address);
1831 if (!pgd_present(*pgd))
1832 goto out;
1833
1834 pud = pud_offset(pgd, address);
1835 if (!pud_present(*pud))
1836 goto out;
1837
1838 pmd = pmd_offset(pud, address);
1839 /* pmd can't go away or become huge under us */
1840 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1841 goto out;
1842
1843 anon_vma_lock(vma->anon_vma);
1844
1845 pte = pte_offset_map(pmd, address);
1846 ptl = pte_lockptr(mm, pmd);
1847
1848 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1849 /*
1850 * After this gup_fast can't run anymore. This also removes
1851 * any huge TLB entry from the CPU so we won't allow
1852 * huge and small TLB entries for the same virtual address
1853 * to avoid the risk of CPU bugs in that area.
1854 */
1855 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1856 spin_unlock(&mm->page_table_lock);
1857
1858 spin_lock(ptl);
1859 isolated = __collapse_huge_page_isolate(vma, address, pte);
1860 spin_unlock(ptl);
1861
1862 if (unlikely(!isolated)) {
1863 pte_unmap(pte);
1864 spin_lock(&mm->page_table_lock);
1865 BUG_ON(!pmd_none(*pmd));
1866 set_pmd_at(mm, address, pmd, _pmd);
1867 spin_unlock(&mm->page_table_lock);
1868 anon_vma_unlock(vma->anon_vma);
1869 goto out;
1870 }
1871
1872 /*
1873 * All pages are isolated and locked so anon_vma rmap
1874 * can't run anymore.
1875 */
1876 anon_vma_unlock(vma->anon_vma);
1877
1878 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1879 pte_unmap(pte);
1880 __SetPageUptodate(new_page);
1881 pgtable = pmd_pgtable(_pmd);
1882 VM_BUG_ON(page_count(pgtable) != 1);
1883 VM_BUG_ON(page_mapcount(pgtable) != 0);
1884
1885 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1886 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1887 _pmd = pmd_mkhuge(_pmd);
1888
1889 /*
1890 * spin_lock() below is not the equivalent of smp_wmb(), so
1891 * this is needed to avoid the copy_huge_page writes to become
1892 * visible after the set_pmd_at() write.
1893 */
1894 smp_wmb();
1895
1896 spin_lock(&mm->page_table_lock);
1897 BUG_ON(!pmd_none(*pmd));
1898 page_add_new_anon_rmap(new_page, vma, address);
1899 set_pmd_at(mm, address, pmd, _pmd);
1900 update_mmu_cache(vma, address, entry);
1901 prepare_pmd_huge_pte(pgtable, mm);
1902 mm->nr_ptes--;
1903 spin_unlock(&mm->page_table_lock);
1904
1905 #ifndef CONFIG_NUMA
1906 *hpage = NULL;
1907 #endif
1908 khugepaged_pages_collapsed++;
1909 out_up_write:
1910 up_write(&mm->mmap_sem);
1911 return;
1912
1913 out:
1914 mem_cgroup_uncharge_page(new_page);
1915 #ifdef CONFIG_NUMA
1916 put_page(new_page);
1917 #endif
1918 goto out_up_write;
1919 }
1920
1921 static int khugepaged_scan_pmd(struct mm_struct *mm,
1922 struct vm_area_struct *vma,
1923 unsigned long address,
1924 struct page **hpage)
1925 {
1926 pgd_t *pgd;
1927 pud_t *pud;
1928 pmd_t *pmd;
1929 pte_t *pte, *_pte;
1930 int ret = 0, referenced = 0, none = 0;
1931 struct page *page;
1932 unsigned long _address;
1933 spinlock_t *ptl;
1934 int node = -1;
1935
1936 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1937
1938 pgd = pgd_offset(mm, address);
1939 if (!pgd_present(*pgd))
1940 goto out;
1941
1942 pud = pud_offset(pgd, address);
1943 if (!pud_present(*pud))
1944 goto out;
1945
1946 pmd = pmd_offset(pud, address);
1947 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1948 goto out;
1949
1950 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1951 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1952 _pte++, _address += PAGE_SIZE) {
1953 pte_t pteval = *_pte;
1954 if (pte_none(pteval)) {
1955 if (++none <= khugepaged_max_ptes_none)
1956 continue;
1957 else
1958 goto out_unmap;
1959 }
1960 if (!pte_present(pteval) || !pte_write(pteval))
1961 goto out_unmap;
1962 page = vm_normal_page(vma, _address, pteval);
1963 if (unlikely(!page))
1964 goto out_unmap;
1965 /*
1966 * Chose the node of the first page. This could
1967 * be more sophisticated and look at more pages,
1968 * but isn't for now.
1969 */
1970 if (node == -1)
1971 node = page_to_nid(page);
1972 VM_BUG_ON(PageCompound(page));
1973 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
1974 goto out_unmap;
1975 /* cannot use mapcount: can't collapse if there's a gup pin */
1976 if (page_count(page) != 1)
1977 goto out_unmap;
1978 if (pte_young(pteval) || PageReferenced(page) ||
1979 mmu_notifier_test_young(vma->vm_mm, address))
1980 referenced = 1;
1981 }
1982 if (referenced)
1983 ret = 1;
1984 out_unmap:
1985 pte_unmap_unlock(pte, ptl);
1986 if (ret)
1987 /* collapse_huge_page will return with the mmap_sem released */
1988 collapse_huge_page(mm, address, hpage, vma, node);
1989 out:
1990 return ret;
1991 }
1992
1993 static void collect_mm_slot(struct mm_slot *mm_slot)
1994 {
1995 struct mm_struct *mm = mm_slot->mm;
1996
1997 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
1998
1999 if (khugepaged_test_exit(mm)) {
2000 /* free mm_slot */
2001 hlist_del(&mm_slot->hash);
2002 list_del(&mm_slot->mm_node);
2003
2004 /*
2005 * Not strictly needed because the mm exited already.
2006 *
2007 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2008 */
2009
2010 /* khugepaged_mm_lock actually not necessary for the below */
2011 free_mm_slot(mm_slot);
2012 mmdrop(mm);
2013 }
2014 }
2015
2016 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2017 struct page **hpage)
2018 {
2019 struct mm_slot *mm_slot;
2020 struct mm_struct *mm;
2021 struct vm_area_struct *vma;
2022 int progress = 0;
2023
2024 VM_BUG_ON(!pages);
2025 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2026
2027 if (khugepaged_scan.mm_slot)
2028 mm_slot = khugepaged_scan.mm_slot;
2029 else {
2030 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2031 struct mm_slot, mm_node);
2032 khugepaged_scan.address = 0;
2033 khugepaged_scan.mm_slot = mm_slot;
2034 }
2035 spin_unlock(&khugepaged_mm_lock);
2036
2037 mm = mm_slot->mm;
2038 down_read(&mm->mmap_sem);
2039 if (unlikely(khugepaged_test_exit(mm)))
2040 vma = NULL;
2041 else
2042 vma = find_vma(mm, khugepaged_scan.address);
2043
2044 progress++;
2045 for (; vma; vma = vma->vm_next) {
2046 unsigned long hstart, hend;
2047
2048 cond_resched();
2049 if (unlikely(khugepaged_test_exit(mm))) {
2050 progress++;
2051 break;
2052 }
2053
2054 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2055 !khugepaged_always()) ||
2056 (vma->vm_flags & VM_NOHUGEPAGE)) {
2057 skip:
2058 progress++;
2059 continue;
2060 }
2061 if (!vma->anon_vma || vma->vm_ops)
2062 goto skip;
2063 if (is_vma_temporary_stack(vma))
2064 goto skip;
2065 /*
2066 * If is_pfn_mapping() is true is_learn_pfn_mapping()
2067 * must be true too, verify it here.
2068 */
2069 VM_BUG_ON(is_linear_pfn_mapping(vma) ||
2070 vma->vm_flags & VM_NO_THP);
2071
2072 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2073 hend = vma->vm_end & HPAGE_PMD_MASK;
2074 if (hstart >= hend)
2075 goto skip;
2076 if (khugepaged_scan.address > hend)
2077 goto skip;
2078 if (khugepaged_scan.address < hstart)
2079 khugepaged_scan.address = hstart;
2080 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2081
2082 while (khugepaged_scan.address < hend) {
2083 int ret;
2084 cond_resched();
2085 if (unlikely(khugepaged_test_exit(mm)))
2086 goto breakouterloop;
2087
2088 VM_BUG_ON(khugepaged_scan.address < hstart ||
2089 khugepaged_scan.address + HPAGE_PMD_SIZE >
2090 hend);
2091 ret = khugepaged_scan_pmd(mm, vma,
2092 khugepaged_scan.address,
2093 hpage);
2094 /* move to next address */
2095 khugepaged_scan.address += HPAGE_PMD_SIZE;
2096 progress += HPAGE_PMD_NR;
2097 if (ret)
2098 /* we released mmap_sem so break loop */
2099 goto breakouterloop_mmap_sem;
2100 if (progress >= pages)
2101 goto breakouterloop;
2102 }
2103 }
2104 breakouterloop:
2105 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2106 breakouterloop_mmap_sem:
2107
2108 spin_lock(&khugepaged_mm_lock);
2109 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2110 /*
2111 * Release the current mm_slot if this mm is about to die, or
2112 * if we scanned all vmas of this mm.
2113 */
2114 if (khugepaged_test_exit(mm) || !vma) {
2115 /*
2116 * Make sure that if mm_users is reaching zero while
2117 * khugepaged runs here, khugepaged_exit will find
2118 * mm_slot not pointing to the exiting mm.
2119 */
2120 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2121 khugepaged_scan.mm_slot = list_entry(
2122 mm_slot->mm_node.next,
2123 struct mm_slot, mm_node);
2124 khugepaged_scan.address = 0;
2125 } else {
2126 khugepaged_scan.mm_slot = NULL;
2127 khugepaged_full_scans++;
2128 }
2129
2130 collect_mm_slot(mm_slot);
2131 }
2132
2133 return progress;
2134 }
2135
2136 static int khugepaged_has_work(void)
2137 {
2138 return !list_empty(&khugepaged_scan.mm_head) &&
2139 khugepaged_enabled();
2140 }
2141
2142 static int khugepaged_wait_event(void)
2143 {
2144 return !list_empty(&khugepaged_scan.mm_head) ||
2145 !khugepaged_enabled();
2146 }
2147
2148 static void khugepaged_do_scan(struct page **hpage)
2149 {
2150 unsigned int progress = 0, pass_through_head = 0;
2151 unsigned int pages = khugepaged_pages_to_scan;
2152
2153 barrier(); /* write khugepaged_pages_to_scan to local stack */
2154
2155 while (progress < pages) {
2156 cond_resched();
2157
2158 #ifndef CONFIG_NUMA
2159 if (!*hpage) {
2160 *hpage = alloc_hugepage(khugepaged_defrag());
2161 if (unlikely(!*hpage))
2162 break;
2163 }
2164 #else
2165 if (IS_ERR(*hpage))
2166 break;
2167 #endif
2168
2169 if (unlikely(kthread_should_stop() || freezing(current)))
2170 break;
2171
2172 spin_lock(&khugepaged_mm_lock);
2173 if (!khugepaged_scan.mm_slot)
2174 pass_through_head++;
2175 if (khugepaged_has_work() &&
2176 pass_through_head < 2)
2177 progress += khugepaged_scan_mm_slot(pages - progress,
2178 hpage);
2179 else
2180 progress = pages;
2181 spin_unlock(&khugepaged_mm_lock);
2182 }
2183 }
2184
2185 static void khugepaged_alloc_sleep(void)
2186 {
2187 DEFINE_WAIT(wait);
2188 add_wait_queue(&khugepaged_wait, &wait);
2189 schedule_timeout_interruptible(
2190 msecs_to_jiffies(
2191 khugepaged_alloc_sleep_millisecs));
2192 remove_wait_queue(&khugepaged_wait, &wait);
2193 }
2194
2195 #ifndef CONFIG_NUMA
2196 static struct page *khugepaged_alloc_hugepage(void)
2197 {
2198 struct page *hpage;
2199
2200 do {
2201 hpage = alloc_hugepage(khugepaged_defrag());
2202 if (!hpage)
2203 khugepaged_alloc_sleep();
2204 } while (unlikely(!hpage) &&
2205 likely(khugepaged_enabled()));
2206 return hpage;
2207 }
2208 #endif
2209
2210 static void khugepaged_loop(void)
2211 {
2212 struct page *hpage;
2213
2214 #ifdef CONFIG_NUMA
2215 hpage = NULL;
2216 #endif
2217 while (likely(khugepaged_enabled())) {
2218 #ifndef CONFIG_NUMA
2219 hpage = khugepaged_alloc_hugepage();
2220 if (unlikely(!hpage))
2221 break;
2222 #else
2223 if (IS_ERR(hpage)) {
2224 khugepaged_alloc_sleep();
2225 hpage = NULL;
2226 }
2227 #endif
2228
2229 khugepaged_do_scan(&hpage);
2230 #ifndef CONFIG_NUMA
2231 if (hpage)
2232 put_page(hpage);
2233 #endif
2234 try_to_freeze();
2235 if (unlikely(kthread_should_stop()))
2236 break;
2237 if (khugepaged_has_work()) {
2238 DEFINE_WAIT(wait);
2239 if (!khugepaged_scan_sleep_millisecs)
2240 continue;
2241 add_wait_queue(&khugepaged_wait, &wait);
2242 schedule_timeout_interruptible(
2243 msecs_to_jiffies(
2244 khugepaged_scan_sleep_millisecs));
2245 remove_wait_queue(&khugepaged_wait, &wait);
2246 } else if (khugepaged_enabled())
2247 wait_event_freezable(khugepaged_wait,
2248 khugepaged_wait_event());
2249 }
2250 }
2251
2252 static int khugepaged(void *none)
2253 {
2254 struct mm_slot *mm_slot;
2255
2256 set_freezable();
2257 set_user_nice(current, 19);
2258
2259 /* serialize with start_khugepaged() */
2260 mutex_lock(&khugepaged_mutex);
2261
2262 for (;;) {
2263 mutex_unlock(&khugepaged_mutex);
2264 VM_BUG_ON(khugepaged_thread != current);
2265 khugepaged_loop();
2266 VM_BUG_ON(khugepaged_thread != current);
2267
2268 mutex_lock(&khugepaged_mutex);
2269 if (!khugepaged_enabled())
2270 break;
2271 if (unlikely(kthread_should_stop()))
2272 break;
2273 }
2274
2275 spin_lock(&khugepaged_mm_lock);
2276 mm_slot = khugepaged_scan.mm_slot;
2277 khugepaged_scan.mm_slot = NULL;
2278 if (mm_slot)
2279 collect_mm_slot(mm_slot);
2280 spin_unlock(&khugepaged_mm_lock);
2281
2282 khugepaged_thread = NULL;
2283 mutex_unlock(&khugepaged_mutex);
2284
2285 return 0;
2286 }
2287
2288 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2289 {
2290 struct page *page;
2291
2292 spin_lock(&mm->page_table_lock);
2293 if (unlikely(!pmd_trans_huge(*pmd))) {
2294 spin_unlock(&mm->page_table_lock);
2295 return;
2296 }
2297 page = pmd_page(*pmd);
2298 VM_BUG_ON(!page_count(page));
2299 get_page(page);
2300 spin_unlock(&mm->page_table_lock);
2301
2302 split_huge_page(page);
2303
2304 put_page(page);
2305 BUG_ON(pmd_trans_huge(*pmd));
2306 }
2307
2308 static void split_huge_page_address(struct mm_struct *mm,
2309 unsigned long address)
2310 {
2311 pgd_t *pgd;
2312 pud_t *pud;
2313 pmd_t *pmd;
2314
2315 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2316
2317 pgd = pgd_offset(mm, address);
2318 if (!pgd_present(*pgd))
2319 return;
2320
2321 pud = pud_offset(pgd, address);
2322 if (!pud_present(*pud))
2323 return;
2324
2325 pmd = pmd_offset(pud, address);
2326 if (!pmd_present(*pmd))
2327 return;
2328 /*
2329 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2330 * materialize from under us.
2331 */
2332 split_huge_page_pmd(mm, pmd);
2333 }
2334
2335 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2336 unsigned long start,
2337 unsigned long end,
2338 long adjust_next)
2339 {
2340 /*
2341 * If the new start address isn't hpage aligned and it could
2342 * previously contain an hugepage: check if we need to split
2343 * an huge pmd.
2344 */
2345 if (start & ~HPAGE_PMD_MASK &&
2346 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2347 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2348 split_huge_page_address(vma->vm_mm, start);
2349
2350 /*
2351 * If the new end address isn't hpage aligned and it could
2352 * previously contain an hugepage: check if we need to split
2353 * an huge pmd.
2354 */
2355 if (end & ~HPAGE_PMD_MASK &&
2356 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2357 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2358 split_huge_page_address(vma->vm_mm, end);
2359
2360 /*
2361 * If we're also updating the vma->vm_next->vm_start, if the new
2362 * vm_next->vm_start isn't page aligned and it could previously
2363 * contain an hugepage: check if we need to split an huge pmd.
2364 */
2365 if (adjust_next > 0) {
2366 struct vm_area_struct *next = vma->vm_next;
2367 unsigned long nstart = next->vm_start;
2368 nstart += adjust_next << PAGE_SHIFT;
2369 if (nstart & ~HPAGE_PMD_MASK &&
2370 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2371 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2372 split_huge_page_address(next->vm_mm, nstart);
2373 }
2374 }
Linux 2.6 ibm-acpi/thinkpad-acpi driver git tree