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thp: fix PARAVIRT x86 32bit noPAE
[linux-2.6.git] / mm / huge_memory.c
blobe187454d82f666a70bab08762ca92cd60b8f848c
1 /*
2 * Copyright (C) 2009 Red Hat, Inc.
3 *
4 * This work is licensed under the terms of the GNU GPL, version 2. See
5 * the COPYING file in the top-level directory.
6 */
7
8 #include <linux/mm.h>
9 #include <linux/sched.h>
10 #include <linux/highmem.h>
11 #include <linux/hugetlb.h>
12 #include <linux/mmu_notifier.h>
13 #include <linux/rmap.h>
14 #include <linux/swap.h>
15 #include <linux/mm_inline.h>
16 #include <linux/kthread.h>
17 #include <linux/khugepaged.h>
18 #include <linux/freezer.h>
19 #include <linux/mman.h>
20 #include <asm/tlb.h>
21 #include <asm/pgalloc.h>
22 #include "internal.h"
23
24 /*
25 * By default transparent hugepage support is enabled for all mappings
26 * and khugepaged scans all mappings. Defrag is only invoked by
27 * khugepaged hugepage allocations and by page faults inside
28 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
29 * allocations.
30 */
31 unsigned long transparent_hugepage_flags __read_mostly =
32 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
33 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
34 #endif
35 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
36 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
37 #endif
38 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
39 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
40
41 /* default scan 8*512 pte (or vmas) every 30 second */
42 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
43 static unsigned int khugepaged_pages_collapsed;
44 static unsigned int khugepaged_full_scans;
45 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
46 /* during fragmentation poll the hugepage allocator once every minute */
47 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
48 static struct task_struct *khugepaged_thread __read_mostly;
49 static DEFINE_MUTEX(khugepaged_mutex);
50 static DEFINE_SPINLOCK(khugepaged_mm_lock);
51 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
52 /*
53 * default collapse hugepages if there is at least one pte mapped like
54 * it would have happened if the vma was large enough during page
55 * fault.
56 */
57 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
58
59 static int khugepaged(void *none);
60 static int mm_slots_hash_init(void);
61 static int khugepaged_slab_init(void);
62 static void khugepaged_slab_free(void);
63
64 #define MM_SLOTS_HASH_HEADS 1024
65 static struct hlist_head *mm_slots_hash __read_mostly;
66 static struct kmem_cache *mm_slot_cache __read_mostly;
67
68 /**
69 * struct mm_slot - hash lookup from mm to mm_slot
70 * @hash: hash collision list
71 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
72 * @mm: the mm that this information is valid for
73 */
74 struct mm_slot {
75 struct hlist_node hash;
76 struct list_head mm_node;
77 struct mm_struct *mm;
78 };
79
80 /**
81 * struct khugepaged_scan - cursor for scanning
82 * @mm_head: the head of the mm list to scan
83 * @mm_slot: the current mm_slot we are scanning
84 * @address: the next address inside that to be scanned
85 *
86 * There is only the one khugepaged_scan instance of this cursor structure.
87 */
88 struct khugepaged_scan {
89 struct list_head mm_head;
90 struct mm_slot *mm_slot;
91 unsigned long address;
92 } khugepaged_scan = {
93 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
94 };
95
96
97 static int set_recommended_min_free_kbytes(void)
98 {
99 struct zone *zone;
100 int nr_zones = 0;
101 unsigned long recommended_min;
102 extern int min_free_kbytes;
103
104 if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG,
105 &transparent_hugepage_flags) &&
106 !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
107 &transparent_hugepage_flags))
108 return 0;
109
110 for_each_populated_zone(zone)
111 nr_zones++;
112
113 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
114 recommended_min = pageblock_nr_pages * nr_zones * 2;
115
116 /*
117 * Make sure that on average at least two pageblocks are almost free
118 * of another type, one for a migratetype to fall back to and a
119 * second to avoid subsequent fallbacks of other types There are 3
120 * MIGRATE_TYPES we care about.
121 */
122 recommended_min += pageblock_nr_pages * nr_zones *
123 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
124
125 /* don't ever allow to reserve more than 5% of the lowmem */
126 recommended_min = min(recommended_min,
127 (unsigned long) nr_free_buffer_pages() / 20);
128 recommended_min <<= (PAGE_SHIFT-10);
129
130 if (recommended_min > min_free_kbytes)
131 min_free_kbytes = recommended_min;
132 setup_per_zone_wmarks();
133 return 0;
134 }
135 late_initcall(set_recommended_min_free_kbytes);
136
137 static int start_khugepaged(void)
138 {
139 int err = 0;
140 if (khugepaged_enabled()) {
141 int wakeup;
142 if (unlikely(!mm_slot_cache || !mm_slots_hash)) {
143 err = -ENOMEM;
144 goto out;
145 }
146 mutex_lock(&khugepaged_mutex);
147 if (!khugepaged_thread)
148 khugepaged_thread = kthread_run(khugepaged, NULL,
149 "khugepaged");
150 if (unlikely(IS_ERR(khugepaged_thread))) {
151 printk(KERN_ERR
152 "khugepaged: kthread_run(khugepaged) failed\n");
153 err = PTR_ERR(khugepaged_thread);
154 khugepaged_thread = NULL;
155 }
156 wakeup = !list_empty(&khugepaged_scan.mm_head);
157 mutex_unlock(&khugepaged_mutex);
158 if (wakeup)
159 wake_up_interruptible(&khugepaged_wait);
160
161 set_recommended_min_free_kbytes();
162 } else
163 /* wakeup to exit */
164 wake_up_interruptible(&khugepaged_wait);
165 out:
166 return err;
167 }
168
169 #ifdef CONFIG_SYSFS
170
171 static ssize_t double_flag_show(struct kobject *kobj,
172 struct kobj_attribute *attr, char *buf,
173 enum transparent_hugepage_flag enabled,
174 enum transparent_hugepage_flag req_madv)
175 {
176 if (test_bit(enabled, &transparent_hugepage_flags)) {
177 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
178 return sprintf(buf, "[always] madvise never\n");
179 } else if (test_bit(req_madv, &transparent_hugepage_flags))
180 return sprintf(buf, "always [madvise] never\n");
181 else
182 return sprintf(buf, "always madvise [never]\n");
183 }
184 static ssize_t double_flag_store(struct kobject *kobj,
185 struct kobj_attribute *attr,
186 const char *buf, size_t count,
187 enum transparent_hugepage_flag enabled,
188 enum transparent_hugepage_flag req_madv)
189 {
190 if (!memcmp("always", buf,
191 min(sizeof("always")-1, count))) {
192 set_bit(enabled, &transparent_hugepage_flags);
193 clear_bit(req_madv, &transparent_hugepage_flags);
194 } else if (!memcmp("madvise", buf,
195 min(sizeof("madvise")-1, count))) {
196 clear_bit(enabled, &transparent_hugepage_flags);
197 set_bit(req_madv, &transparent_hugepage_flags);
198 } else if (!memcmp("never", buf,
199 min(sizeof("never")-1, count))) {
200 clear_bit(enabled, &transparent_hugepage_flags);
201 clear_bit(req_madv, &transparent_hugepage_flags);
202 } else
203 return -EINVAL;
204
205 return count;
206 }
207
208 static ssize_t enabled_show(struct kobject *kobj,
209 struct kobj_attribute *attr, char *buf)
210 {
211 return double_flag_show(kobj, attr, buf,
212 TRANSPARENT_HUGEPAGE_FLAG,
213 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
214 }
215 static ssize_t enabled_store(struct kobject *kobj,
216 struct kobj_attribute *attr,
217 const char *buf, size_t count)
218 {
219 ssize_t ret;
220
221 ret = double_flag_store(kobj, attr, buf, count,
222 TRANSPARENT_HUGEPAGE_FLAG,
223 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
224
225 if (ret > 0) {
226 int err = start_khugepaged();
227 if (err)
228 ret = err;
229 }
230
231 if (ret > 0 &&
232 (test_bit(TRANSPARENT_HUGEPAGE_FLAG,
233 &transparent_hugepage_flags) ||
234 test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
235 &transparent_hugepage_flags)))
236 set_recommended_min_free_kbytes();
237
238 return ret;
239 }
240 static struct kobj_attribute enabled_attr =
241 __ATTR(enabled, 0644, enabled_show, enabled_store);
242
243 static ssize_t single_flag_show(struct kobject *kobj,
244 struct kobj_attribute *attr, char *buf,
245 enum transparent_hugepage_flag flag)
246 {
247 if (test_bit(flag, &transparent_hugepage_flags))
248 return sprintf(buf, "[yes] no\n");
249 else
250 return sprintf(buf, "yes [no]\n");
251 }
252 static ssize_t single_flag_store(struct kobject *kobj,
253 struct kobj_attribute *attr,
254 const char *buf, size_t count,
255 enum transparent_hugepage_flag flag)
256 {
257 if (!memcmp("yes", buf,
258 min(sizeof("yes")-1, count))) {
259 set_bit(flag, &transparent_hugepage_flags);
260 } else if (!memcmp("no", buf,
261 min(sizeof("no")-1, count))) {
262 clear_bit(flag, &transparent_hugepage_flags);
263 } else
264 return -EINVAL;
265
266 return count;
267 }
268
269 /*
270 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
271 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
272 * memory just to allocate one more hugepage.
273 */
274 static ssize_t defrag_show(struct kobject *kobj,
275 struct kobj_attribute *attr, char *buf)
276 {
277 return double_flag_show(kobj, attr, buf,
278 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
279 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
280 }
281 static ssize_t defrag_store(struct kobject *kobj,
282 struct kobj_attribute *attr,
283 const char *buf, size_t count)
284 {
285 return double_flag_store(kobj, attr, buf, count,
286 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
287 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
288 }
289 static struct kobj_attribute defrag_attr =
290 __ATTR(defrag, 0644, defrag_show, defrag_store);
291
292 #ifdef CONFIG_DEBUG_VM
293 static ssize_t debug_cow_show(struct kobject *kobj,
294 struct kobj_attribute *attr, char *buf)
295 {
296 return single_flag_show(kobj, attr, buf,
297 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
298 }
299 static ssize_t debug_cow_store(struct kobject *kobj,
300 struct kobj_attribute *attr,
301 const char *buf, size_t count)
302 {
303 return single_flag_store(kobj, attr, buf, count,
304 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
305 }
306 static struct kobj_attribute debug_cow_attr =
307 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
308 #endif /* CONFIG_DEBUG_VM */
309
310 static struct attribute *hugepage_attr[] = {
311 &enabled_attr.attr,
312 &defrag_attr.attr,
313 #ifdef CONFIG_DEBUG_VM
314 &debug_cow_attr.attr,
315 #endif
316 NULL,
317 };
318
319 static struct attribute_group hugepage_attr_group = {
320 .attrs = hugepage_attr,
321 };
322
323 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
324 struct kobj_attribute *attr,
325 char *buf)
326 {
327 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
328 }
329
330 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
331 struct kobj_attribute *attr,
332 const char *buf, size_t count)
333 {
334 unsigned long msecs;
335 int err;
336
337 err = strict_strtoul(buf, 10, &msecs);
338 if (err || msecs > UINT_MAX)
339 return -EINVAL;
340
341 khugepaged_scan_sleep_millisecs = msecs;
342 wake_up_interruptible(&khugepaged_wait);
343
344 return count;
345 }
346 static struct kobj_attribute scan_sleep_millisecs_attr =
347 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
348 scan_sleep_millisecs_store);
349
350 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
351 struct kobj_attribute *attr,
352 char *buf)
353 {
354 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
355 }
356
357 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
358 struct kobj_attribute *attr,
359 const char *buf, size_t count)
360 {
361 unsigned long msecs;
362 int err;
363
364 err = strict_strtoul(buf, 10, &msecs);
365 if (err || msecs > UINT_MAX)
366 return -EINVAL;
367
368 khugepaged_alloc_sleep_millisecs = msecs;
369 wake_up_interruptible(&khugepaged_wait);
370
371 return count;
372 }
373 static struct kobj_attribute alloc_sleep_millisecs_attr =
374 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
375 alloc_sleep_millisecs_store);
376
377 static ssize_t pages_to_scan_show(struct kobject *kobj,
378 struct kobj_attribute *attr,
379 char *buf)
380 {
381 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
382 }
383 static ssize_t pages_to_scan_store(struct kobject *kobj,
384 struct kobj_attribute *attr,
385 const char *buf, size_t count)
386 {
387 int err;
388 unsigned long pages;
389
390 err = strict_strtoul(buf, 10, &pages);
391 if (err || !pages || pages > UINT_MAX)
392 return -EINVAL;
393
394 khugepaged_pages_to_scan = pages;
395
396 return count;
397 }
398 static struct kobj_attribute pages_to_scan_attr =
399 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
400 pages_to_scan_store);
401
402 static ssize_t pages_collapsed_show(struct kobject *kobj,
403 struct kobj_attribute *attr,
404 char *buf)
405 {
406 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
407 }
408 static struct kobj_attribute pages_collapsed_attr =
409 __ATTR_RO(pages_collapsed);
410
411 static ssize_t full_scans_show(struct kobject *kobj,
412 struct kobj_attribute *attr,
413 char *buf)
414 {
415 return sprintf(buf, "%u\n", khugepaged_full_scans);
416 }
417 static struct kobj_attribute full_scans_attr =
418 __ATTR_RO(full_scans);
419
420 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
421 struct kobj_attribute *attr, char *buf)
422 {
423 return single_flag_show(kobj, attr, buf,
424 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
425 }
426 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
427 struct kobj_attribute *attr,
428 const char *buf, size_t count)
429 {
430 return single_flag_store(kobj, attr, buf, count,
431 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
432 }
433 static struct kobj_attribute khugepaged_defrag_attr =
434 __ATTR(defrag, 0644, khugepaged_defrag_show,
435 khugepaged_defrag_store);
436
437 /*
438 * max_ptes_none controls if khugepaged should collapse hugepages over
439 * any unmapped ptes in turn potentially increasing the memory
440 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
441 * reduce the available free memory in the system as it
442 * runs. Increasing max_ptes_none will instead potentially reduce the
443 * free memory in the system during the khugepaged scan.
444 */
445 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
446 struct kobj_attribute *attr,
447 char *buf)
448 {
449 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
450 }
451 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
452 struct kobj_attribute *attr,
453 const char *buf, size_t count)
454 {
455 int err;
456 unsigned long max_ptes_none;
457
458 err = strict_strtoul(buf, 10, &max_ptes_none);
459 if (err || max_ptes_none > HPAGE_PMD_NR-1)
460 return -EINVAL;
461
462 khugepaged_max_ptes_none = max_ptes_none;
463
464 return count;
465 }
466 static struct kobj_attribute khugepaged_max_ptes_none_attr =
467 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
468 khugepaged_max_ptes_none_store);
469
470 static struct attribute *khugepaged_attr[] = {
471 &khugepaged_defrag_attr.attr,
472 &khugepaged_max_ptes_none_attr.attr,
473 &pages_to_scan_attr.attr,
474 &pages_collapsed_attr.attr,
475 &full_scans_attr.attr,
476 &scan_sleep_millisecs_attr.attr,
477 &alloc_sleep_millisecs_attr.attr,
478 NULL,
479 };
480
481 static struct attribute_group khugepaged_attr_group = {
482 .attrs = khugepaged_attr,
483 .name = "khugepaged",
484 };
485 #endif /* CONFIG_SYSFS */
486
487 static int __init hugepage_init(void)
488 {
489 int err;
490 #ifdef CONFIG_SYSFS
491 static struct kobject *hugepage_kobj;
492 #endif
493
494 err = -EINVAL;
495 if (!has_transparent_hugepage()) {
496 transparent_hugepage_flags = 0;
497 goto out;
498 }
499
500 #ifdef CONFIG_SYSFS
501 err = -ENOMEM;
502 hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
503 if (unlikely(!hugepage_kobj)) {
504 printk(KERN_ERR "hugepage: failed kobject create\n");
505 goto out;
506 }
507
508 err = sysfs_create_group(hugepage_kobj, &hugepage_attr_group);
509 if (err) {
510 printk(KERN_ERR "hugepage: failed register hugeage group\n");
511 goto out;
512 }
513
514 err = sysfs_create_group(hugepage_kobj, &khugepaged_attr_group);
515 if (err) {
516 printk(KERN_ERR "hugepage: failed register hugeage group\n");
517 goto out;
518 }
519 #endif
520
521 err = khugepaged_slab_init();
522 if (err)
523 goto out;
524
525 err = mm_slots_hash_init();
526 if (err) {
527 khugepaged_slab_free();
528 goto out;
529 }
530
531 /*
532 * By default disable transparent hugepages on smaller systems,
533 * where the extra memory used could hurt more than TLB overhead
534 * is likely to save. The admin can still enable it through /sys.
535 */
536 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
537 transparent_hugepage_flags = 0;
538
539 start_khugepaged();
540
541 set_recommended_min_free_kbytes();
542
543 out:
544 return err;
545 }
546 module_init(hugepage_init)
547
548 static int __init setup_transparent_hugepage(char *str)
549 {
550 int ret = 0;
551 if (!str)
552 goto out;
553 if (!strcmp(str, "always")) {
554 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
555 &transparent_hugepage_flags);
556 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
557 &transparent_hugepage_flags);
558 ret = 1;
559 } else if (!strcmp(str, "madvise")) {
560 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
561 &transparent_hugepage_flags);
562 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
563 &transparent_hugepage_flags);
564 ret = 1;
565 } else if (!strcmp(str, "never")) {
566 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
567 &transparent_hugepage_flags);
568 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
569 &transparent_hugepage_flags);
570 ret = 1;
571 }
572 out:
573 if (!ret)
574 printk(KERN_WARNING
575 "transparent_hugepage= cannot parse, ignored\n");
576 return ret;
577 }
578 __setup("transparent_hugepage=", setup_transparent_hugepage);
579
580 static void prepare_pmd_huge_pte(pgtable_t pgtable,
581 struct mm_struct *mm)
582 {
583 assert_spin_locked(&mm->page_table_lock);
584
585 /* FIFO */
586 if (!mm->pmd_huge_pte)
587 INIT_LIST_HEAD(&pgtable->lru);
588 else
589 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
590 mm->pmd_huge_pte = pgtable;
591 }
592
593 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
594 {
595 if (likely(vma->vm_flags & VM_WRITE))
596 pmd = pmd_mkwrite(pmd);
597 return pmd;
598 }
599
600 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
601 struct vm_area_struct *vma,
602 unsigned long haddr, pmd_t *pmd,
603 struct page *page)
604 {
605 int ret = 0;
606 pgtable_t pgtable;
607
608 VM_BUG_ON(!PageCompound(page));
609 pgtable = pte_alloc_one(mm, haddr);
610 if (unlikely(!pgtable)) {
611 mem_cgroup_uncharge_page(page);
612 put_page(page);
613 return VM_FAULT_OOM;
614 }
615
616 clear_huge_page(page, haddr, HPAGE_PMD_NR);
617 __SetPageUptodate(page);
618
619 spin_lock(&mm->page_table_lock);
620 if (unlikely(!pmd_none(*pmd))) {
621 spin_unlock(&mm->page_table_lock);
622 mem_cgroup_uncharge_page(page);
623 put_page(page);
624 pte_free(mm, pgtable);
625 } else {
626 pmd_t entry;
627 entry = mk_pmd(page, vma->vm_page_prot);
628 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
629 entry = pmd_mkhuge(entry);
630 /*
631 * The spinlocking to take the lru_lock inside
632 * page_add_new_anon_rmap() acts as a full memory
633 * barrier to be sure clear_huge_page writes become
634 * visible after the set_pmd_at() write.
635 */
636 page_add_new_anon_rmap(page, vma, haddr);
637 set_pmd_at(mm, haddr, pmd, entry);
638 prepare_pmd_huge_pte(pgtable, mm);
639 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
640 spin_unlock(&mm->page_table_lock);
641 }
642
643 return ret;
644 }
645
646 static inline gfp_t alloc_hugepage_gfpmask(int defrag)
647 {
648 return GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT);
649 }
650
651 static inline struct page *alloc_hugepage_vma(int defrag,
652 struct vm_area_struct *vma,
653 unsigned long haddr)
654 {
655 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag),
656 HPAGE_PMD_ORDER, vma, haddr);
657 }
658
659 #ifndef CONFIG_NUMA
660 static inline struct page *alloc_hugepage(int defrag)
661 {
662 return alloc_pages(alloc_hugepage_gfpmask(defrag),
663 HPAGE_PMD_ORDER);
664 }
665 #endif
666
667 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
668 unsigned long address, pmd_t *pmd,
669 unsigned int flags)
670 {
671 struct page *page;
672 unsigned long haddr = address & HPAGE_PMD_MASK;
673 pte_t *pte;
674
675 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
676 if (unlikely(anon_vma_prepare(vma)))
677 return VM_FAULT_OOM;
678 if (unlikely(khugepaged_enter(vma)))
679 return VM_FAULT_OOM;
680 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
681 vma, haddr);
682 if (unlikely(!page))
683 goto out;
684 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
685 put_page(page);
686 goto out;
687 }
688
689 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
690 }
691 out:
692 /*
693 * Use __pte_alloc instead of pte_alloc_map, because we can't
694 * run pte_offset_map on the pmd, if an huge pmd could
695 * materialize from under us from a different thread.
696 */
697 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
698 return VM_FAULT_OOM;
699 /* if an huge pmd materialized from under us just retry later */
700 if (unlikely(pmd_trans_huge(*pmd)))
701 return 0;
702 /*
703 * A regular pmd is established and it can't morph into a huge pmd
704 * from under us anymore at this point because we hold the mmap_sem
705 * read mode and khugepaged takes it in write mode. So now it's
706 * safe to run pte_offset_map().
707 */
708 pte = pte_offset_map(pmd, address);
709 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
710 }
711
712 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
713 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
714 struct vm_area_struct *vma)
715 {
716 struct page *src_page;
717 pmd_t pmd;
718 pgtable_t pgtable;
719 int ret;
720
721 ret = -ENOMEM;
722 pgtable = pte_alloc_one(dst_mm, addr);
723 if (unlikely(!pgtable))
724 goto out;
725
726 spin_lock(&dst_mm->page_table_lock);
727 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
728
729 ret = -EAGAIN;
730 pmd = *src_pmd;
731 if (unlikely(!pmd_trans_huge(pmd))) {
732 pte_free(dst_mm, pgtable);
733 goto out_unlock;
734 }
735 if (unlikely(pmd_trans_splitting(pmd))) {
736 /* split huge page running from under us */
737 spin_unlock(&src_mm->page_table_lock);
738 spin_unlock(&dst_mm->page_table_lock);
739 pte_free(dst_mm, pgtable);
740
741 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
742 goto out;
743 }
744 src_page = pmd_page(pmd);
745 VM_BUG_ON(!PageHead(src_page));
746 get_page(src_page);
747 page_dup_rmap(src_page);
748 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
749
750 pmdp_set_wrprotect(src_mm, addr, src_pmd);
751 pmd = pmd_mkold(pmd_wrprotect(pmd));
752 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
753 prepare_pmd_huge_pte(pgtable, dst_mm);
754
755 ret = 0;
756 out_unlock:
757 spin_unlock(&src_mm->page_table_lock);
758 spin_unlock(&dst_mm->page_table_lock);
759 out:
760 return ret;
761 }
762
763 /* no "address" argument so destroys page coloring of some arch */
764 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
765 {
766 pgtable_t pgtable;
767
768 assert_spin_locked(&mm->page_table_lock);
769
770 /* FIFO */
771 pgtable = mm->pmd_huge_pte;
772 if (list_empty(&pgtable->lru))
773 mm->pmd_huge_pte = NULL;
774 else {
775 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
776 struct page, lru);
777 list_del(&pgtable->lru);
778 }
779 return pgtable;
780 }
781
782 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
783 struct vm_area_struct *vma,
784 unsigned long address,
785 pmd_t *pmd, pmd_t orig_pmd,
786 struct page *page,
787 unsigned long haddr)
788 {
789 pgtable_t pgtable;
790 pmd_t _pmd;
791 int ret = 0, i;
792 struct page **pages;
793
794 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
795 GFP_KERNEL);
796 if (unlikely(!pages)) {
797 ret |= VM_FAULT_OOM;
798 goto out;
799 }
800
801 for (i = 0; i < HPAGE_PMD_NR; i++) {
802 pages[i] = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
803 vma, address);
804 if (unlikely(!pages[i] ||
805 mem_cgroup_newpage_charge(pages[i], mm,
806 GFP_KERNEL))) {
807 if (pages[i])
808 put_page(pages[i]);
809 mem_cgroup_uncharge_start();
810 while (--i >= 0) {
811 mem_cgroup_uncharge_page(pages[i]);
812 put_page(pages[i]);
813 }
814 mem_cgroup_uncharge_end();
815 kfree(pages);
816 ret |= VM_FAULT_OOM;
817 goto out;
818 }
819 }
820
821 for (i = 0; i < HPAGE_PMD_NR; i++) {
822 copy_user_highpage(pages[i], page + i,
823 haddr + PAGE_SHIFT*i, vma);
824 __SetPageUptodate(pages[i]);
825 cond_resched();
826 }
827
828 spin_lock(&mm->page_table_lock);
829 if (unlikely(!pmd_same(*pmd, orig_pmd)))
830 goto out_free_pages;
831 VM_BUG_ON(!PageHead(page));
832
833 pmdp_clear_flush_notify(vma, haddr, pmd);
834 /* leave pmd empty until pte is filled */
835
836 pgtable = get_pmd_huge_pte(mm);
837 pmd_populate(mm, &_pmd, pgtable);
838
839 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
840 pte_t *pte, entry;
841 entry = mk_pte(pages[i], vma->vm_page_prot);
842 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
843 page_add_new_anon_rmap(pages[i], vma, haddr);
844 pte = pte_offset_map(&_pmd, haddr);
845 VM_BUG_ON(!pte_none(*pte));
846 set_pte_at(mm, haddr, pte, entry);
847 pte_unmap(pte);
848 }
849 kfree(pages);
850
851 mm->nr_ptes++;
852 smp_wmb(); /* make pte visible before pmd */
853 pmd_populate(mm, pmd, pgtable);
854 page_remove_rmap(page);
855 spin_unlock(&mm->page_table_lock);
856
857 ret |= VM_FAULT_WRITE;
858 put_page(page);
859
860 out:
861 return ret;
862
863 out_free_pages:
864 spin_unlock(&mm->page_table_lock);
865 mem_cgroup_uncharge_start();
866 for (i = 0; i < HPAGE_PMD_NR; i++) {
867 mem_cgroup_uncharge_page(pages[i]);
868 put_page(pages[i]);
869 }
870 mem_cgroup_uncharge_end();
871 kfree(pages);
872 goto out;
873 }
874
875 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
876 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
877 {
878 int ret = 0;
879 struct page *page, *new_page;
880 unsigned long haddr;
881
882 VM_BUG_ON(!vma->anon_vma);
883 spin_lock(&mm->page_table_lock);
884 if (unlikely(!pmd_same(*pmd, orig_pmd)))
885 goto out_unlock;
886
887 page = pmd_page(orig_pmd);
888 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
889 haddr = address & HPAGE_PMD_MASK;
890 if (page_mapcount(page) == 1) {
891 pmd_t entry;
892 entry = pmd_mkyoung(orig_pmd);
893 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
894 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
895 update_mmu_cache(vma, address, entry);
896 ret |= VM_FAULT_WRITE;
897 goto out_unlock;
898 }
899 get_page(page);
900 spin_unlock(&mm->page_table_lock);
901
902 if (transparent_hugepage_enabled(vma) &&
903 !transparent_hugepage_debug_cow())
904 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
905 vma, haddr);
906 else
907 new_page = NULL;
908
909 if (unlikely(!new_page)) {
910 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
911 pmd, orig_pmd, page, haddr);
912 put_page(page);
913 goto out;
914 }
915
916 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
917 put_page(new_page);
918 put_page(page);
919 ret |= VM_FAULT_OOM;
920 goto out;
921 }
922
923 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
924 __SetPageUptodate(new_page);
925
926 spin_lock(&mm->page_table_lock);
927 put_page(page);
928 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
929 mem_cgroup_uncharge_page(new_page);
930 put_page(new_page);
931 } else {
932 pmd_t entry;
933 VM_BUG_ON(!PageHead(page));
934 entry = mk_pmd(new_page, vma->vm_page_prot);
935 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
936 entry = pmd_mkhuge(entry);
937 pmdp_clear_flush_notify(vma, haddr, pmd);
938 page_add_new_anon_rmap(new_page, vma, haddr);
939 set_pmd_at(mm, haddr, pmd, entry);
940 update_mmu_cache(vma, address, entry);
941 page_remove_rmap(page);
942 put_page(page);
943 ret |= VM_FAULT_WRITE;
944 }
945 out_unlock:
946 spin_unlock(&mm->page_table_lock);
947 out:
948 return ret;
949 }
950
951 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
952 unsigned long addr,
953 pmd_t *pmd,
954 unsigned int flags)
955 {
956 struct page *page = NULL;
957
958 assert_spin_locked(&mm->page_table_lock);
959
960 if (flags & FOLL_WRITE && !pmd_write(*pmd))
961 goto out;
962
963 page = pmd_page(*pmd);
964 VM_BUG_ON(!PageHead(page));
965 if (flags & FOLL_TOUCH) {
966 pmd_t _pmd;
967 /*
968 * We should set the dirty bit only for FOLL_WRITE but
969 * for now the dirty bit in the pmd is meaningless.
970 * And if the dirty bit will become meaningful and
971 * we'll only set it with FOLL_WRITE, an atomic
972 * set_bit will be required on the pmd to set the
973 * young bit, instead of the current set_pmd_at.
974 */
975 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
976 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
977 }
978 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
979 VM_BUG_ON(!PageCompound(page));
980 if (flags & FOLL_GET)
981 get_page(page);
982
983 out:
984 return page;
985 }
986
987 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
988 pmd_t *pmd)
989 {
990 int ret = 0;
991
992 spin_lock(&tlb->mm->page_table_lock);
993 if (likely(pmd_trans_huge(*pmd))) {
994 if (unlikely(pmd_trans_splitting(*pmd))) {
995 spin_unlock(&tlb->mm->page_table_lock);
996 wait_split_huge_page(vma->anon_vma,
997 pmd);
998 } else {
999 struct page *page;
1000 pgtable_t pgtable;
1001 pgtable = get_pmd_huge_pte(tlb->mm);
1002 page = pmd_page(*pmd);
1003 pmd_clear(pmd);
1004 page_remove_rmap(page);
1005 VM_BUG_ON(page_mapcount(page) < 0);
1006 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1007 VM_BUG_ON(!PageHead(page));
1008 spin_unlock(&tlb->mm->page_table_lock);
1009 tlb_remove_page(tlb, page);
1010 pte_free(tlb->mm, pgtable);
1011 ret = 1;
1012 }
1013 } else
1014 spin_unlock(&tlb->mm->page_table_lock);
1015
1016 return ret;
1017 }
1018
1019 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1020 unsigned long addr, unsigned long end,
1021 unsigned char *vec)
1022 {
1023 int ret = 0;
1024
1025 spin_lock(&vma->vm_mm->page_table_lock);
1026 if (likely(pmd_trans_huge(*pmd))) {
1027 ret = !pmd_trans_splitting(*pmd);
1028 spin_unlock(&vma->vm_mm->page_table_lock);
1029 if (unlikely(!ret))
1030 wait_split_huge_page(vma->anon_vma, pmd);
1031 else {
1032 /*
1033 * All logical pages in the range are present
1034 * if backed by a huge page.
1035 */
1036 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1037 }
1038 } else
1039 spin_unlock(&vma->vm_mm->page_table_lock);
1040
1041 return ret;
1042 }
1043
1044 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1045 unsigned long addr, pgprot_t newprot)
1046 {
1047 struct mm_struct *mm = vma->vm_mm;
1048 int ret = 0;
1049
1050 spin_lock(&mm->page_table_lock);
1051 if (likely(pmd_trans_huge(*pmd))) {
1052 if (unlikely(pmd_trans_splitting(*pmd))) {
1053 spin_unlock(&mm->page_table_lock);
1054 wait_split_huge_page(vma->anon_vma, pmd);
1055 } else {
1056 pmd_t entry;
1057
1058 entry = pmdp_get_and_clear(mm, addr, pmd);
1059 entry = pmd_modify(entry, newprot);
1060 set_pmd_at(mm, addr, pmd, entry);
1061 spin_unlock(&vma->vm_mm->page_table_lock);
1062 flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
1063 ret = 1;
1064 }
1065 } else
1066 spin_unlock(&vma->vm_mm->page_table_lock);
1067
1068 return ret;
1069 }
1070
1071 pmd_t *page_check_address_pmd(struct page *page,
1072 struct mm_struct *mm,
1073 unsigned long address,
1074 enum page_check_address_pmd_flag flag)
1075 {
1076 pgd_t *pgd;
1077 pud_t *pud;
1078 pmd_t *pmd, *ret = NULL;
1079
1080 if (address & ~HPAGE_PMD_MASK)
1081 goto out;
1082
1083 pgd = pgd_offset(mm, address);
1084 if (!pgd_present(*pgd))
1085 goto out;
1086
1087 pud = pud_offset(pgd, address);
1088 if (!pud_present(*pud))
1089 goto out;
1090
1091 pmd = pmd_offset(pud, address);
1092 if (pmd_none(*pmd))
1093 goto out;
1094 if (pmd_page(*pmd) != page)
1095 goto out;
1096 /*
1097 * split_vma() may create temporary aliased mappings. There is
1098 * no risk as long as all huge pmd are found and have their
1099 * splitting bit set before __split_huge_page_refcount
1100 * runs. Finding the same huge pmd more than once during the
1101 * same rmap walk is not a problem.
1102 */
1103 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1104 pmd_trans_splitting(*pmd))
1105 goto out;
1106 if (pmd_trans_huge(*pmd)) {
1107 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1108 !pmd_trans_splitting(*pmd));
1109 ret = pmd;
1110 }
1111 out:
1112 return ret;
1113 }
1114
1115 static int __split_huge_page_splitting(struct page *page,
1116 struct vm_area_struct *vma,
1117 unsigned long address)
1118 {
1119 struct mm_struct *mm = vma->vm_mm;
1120 pmd_t *pmd;
1121 int ret = 0;
1122
1123 spin_lock(&mm->page_table_lock);
1124 pmd = page_check_address_pmd(page, mm, address,
1125 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1126 if (pmd) {
1127 /*
1128 * We can't temporarily set the pmd to null in order
1129 * to split it, the pmd must remain marked huge at all
1130 * times or the VM won't take the pmd_trans_huge paths
1131 * and it won't wait on the anon_vma->root->lock to
1132 * serialize against split_huge_page*.
1133 */
1134 pmdp_splitting_flush_notify(vma, address, pmd);
1135 ret = 1;
1136 }
1137 spin_unlock(&mm->page_table_lock);
1138
1139 return ret;
1140 }
1141
1142 static void __split_huge_page_refcount(struct page *page)
1143 {
1144 int i;
1145 unsigned long head_index = page->index;
1146 struct zone *zone = page_zone(page);
1147 int zonestat;
1148
1149 /* prevent PageLRU to go away from under us, and freeze lru stats */
1150 spin_lock_irq(&zone->lru_lock);
1151 compound_lock(page);
1152
1153 for (i = 1; i < HPAGE_PMD_NR; i++) {
1154 struct page *page_tail = page + i;
1155
1156 /* tail_page->_count cannot change */
1157 atomic_sub(atomic_read(&page_tail->_count), &page->_count);
1158 BUG_ON(page_count(page) <= 0);
1159 atomic_add(page_mapcount(page) + 1, &page_tail->_count);
1160 BUG_ON(atomic_read(&page_tail->_count) <= 0);
1161
1162 /* after clearing PageTail the gup refcount can be released */
1163 smp_mb();
1164
1165 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
1166 page_tail->flags |= (page->flags &
1167 ((1L << PG_referenced) |
1168 (1L << PG_swapbacked) |
1169 (1L << PG_mlocked) |
1170 (1L << PG_uptodate)));
1171 page_tail->flags |= (1L << PG_dirty);
1172
1173 /*
1174 * 1) clear PageTail before overwriting first_page
1175 * 2) clear PageTail before clearing PageHead for VM_BUG_ON
1176 */
1177 smp_wmb();
1178
1179 /*
1180 * __split_huge_page_splitting() already set the
1181 * splitting bit in all pmd that could map this
1182 * hugepage, that will ensure no CPU can alter the
1183 * mapcount on the head page. The mapcount is only
1184 * accounted in the head page and it has to be
1185 * transferred to all tail pages in the below code. So
1186 * for this code to be safe, the split the mapcount
1187 * can't change. But that doesn't mean userland can't
1188 * keep changing and reading the page contents while
1189 * we transfer the mapcount, so the pmd splitting
1190 * status is achieved setting a reserved bit in the
1191 * pmd, not by clearing the present bit.
1192 */
1193 BUG_ON(page_mapcount(page_tail));
1194 page_tail->_mapcount = page->_mapcount;
1195
1196 BUG_ON(page_tail->mapping);
1197 page_tail->mapping = page->mapping;
1198
1199 page_tail->index = ++head_index;
1200
1201 BUG_ON(!PageAnon(page_tail));
1202 BUG_ON(!PageUptodate(page_tail));
1203 BUG_ON(!PageDirty(page_tail));
1204 BUG_ON(!PageSwapBacked(page_tail));
1205
1206 mem_cgroup_split_huge_fixup(page, page_tail);
1207
1208 lru_add_page_tail(zone, page, page_tail);
1209 }
1210
1211 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1212 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1213
1214 /*
1215 * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics,
1216 * so adjust those appropriately if this page is on the LRU.
1217 */
1218 if (PageLRU(page)) {
1219 zonestat = NR_LRU_BASE + page_lru(page);
1220 __mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1));
1221 }
1222
1223 ClearPageCompound(page);
1224 compound_unlock(page);
1225 spin_unlock_irq(&zone->lru_lock);
1226
1227 for (i = 1; i < HPAGE_PMD_NR; i++) {
1228 struct page *page_tail = page + i;
1229 BUG_ON(page_count(page_tail) <= 0);
1230 /*
1231 * Tail pages may be freed if there wasn't any mapping
1232 * like if add_to_swap() is running on a lru page that
1233 * had its mapping zapped. And freeing these pages
1234 * requires taking the lru_lock so we do the put_page
1235 * of the tail pages after the split is complete.
1236 */
1237 put_page(page_tail);
1238 }
1239
1240 /*
1241 * Only the head page (now become a regular page) is required
1242 * to be pinned by the caller.
1243 */
1244 BUG_ON(page_count(page) <= 0);
1245 }
1246
1247 static int __split_huge_page_map(struct page *page,
1248 struct vm_area_struct *vma,
1249 unsigned long address)
1250 {
1251 struct mm_struct *mm = vma->vm_mm;
1252 pmd_t *pmd, _pmd;
1253 int ret = 0, i;
1254 pgtable_t pgtable;
1255 unsigned long haddr;
1256
1257 spin_lock(&mm->page_table_lock);
1258 pmd = page_check_address_pmd(page, mm, address,
1259 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1260 if (pmd) {
1261 pgtable = get_pmd_huge_pte(mm);
1262 pmd_populate(mm, &_pmd, pgtable);
1263
1264 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1265 i++, haddr += PAGE_SIZE) {
1266 pte_t *pte, entry;
1267 BUG_ON(PageCompound(page+i));
1268 entry = mk_pte(page + i, vma->vm_page_prot);
1269 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1270 if (!pmd_write(*pmd))
1271 entry = pte_wrprotect(entry);
1272 else
1273 BUG_ON(page_mapcount(page) != 1);
1274 if (!pmd_young(*pmd))
1275 entry = pte_mkold(entry);
1276 pte = pte_offset_map(&_pmd, haddr);
1277 BUG_ON(!pte_none(*pte));
1278 set_pte_at(mm, haddr, pte, entry);
1279 pte_unmap(pte);
1280 }
1281
1282 mm->nr_ptes++;
1283 smp_wmb(); /* make pte visible before pmd */
1284 /*
1285 * Up to this point the pmd is present and huge and
1286 * userland has the whole access to the hugepage
1287 * during the split (which happens in place). If we
1288 * overwrite the pmd with the not-huge version
1289 * pointing to the pte here (which of course we could
1290 * if all CPUs were bug free), userland could trigger
1291 * a small page size TLB miss on the small sized TLB
1292 * while the hugepage TLB entry is still established
1293 * in the huge TLB. Some CPU doesn't like that. See
1294 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1295 * Erratum 383 on page 93. Intel should be safe but is
1296 * also warns that it's only safe if the permission
1297 * and cache attributes of the two entries loaded in
1298 * the two TLB is identical (which should be the case
1299 * here). But it is generally safer to never allow
1300 * small and huge TLB entries for the same virtual
1301 * address to be loaded simultaneously. So instead of
1302 * doing "pmd_populate(); flush_tlb_range();" we first
1303 * mark the current pmd notpresent (atomically because
1304 * here the pmd_trans_huge and pmd_trans_splitting
1305 * must remain set at all times on the pmd until the
1306 * split is complete for this pmd), then we flush the
1307 * SMP TLB and finally we write the non-huge version
1308 * of the pmd entry with pmd_populate.
1309 */
1310 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1311 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1312 pmd_populate(mm, pmd, pgtable);
1313 ret = 1;
1314 }
1315 spin_unlock(&mm->page_table_lock);
1316
1317 return ret;
1318 }
1319
1320 /* must be called with anon_vma->root->lock hold */
1321 static void __split_huge_page(struct page *page,
1322 struct anon_vma *anon_vma)
1323 {
1324 int mapcount, mapcount2;
1325 struct anon_vma_chain *avc;
1326
1327 BUG_ON(!PageHead(page));
1328 BUG_ON(PageTail(page));
1329
1330 mapcount = 0;
1331 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1332 struct vm_area_struct *vma = avc->vma;
1333 unsigned long addr = vma_address(page, vma);
1334 BUG_ON(is_vma_temporary_stack(vma));
1335 if (addr == -EFAULT)
1336 continue;
1337 mapcount += __split_huge_page_splitting(page, vma, addr);
1338 }
1339 /*
1340 * It is critical that new vmas are added to the tail of the
1341 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1342 * and establishes a child pmd before
1343 * __split_huge_page_splitting() freezes the parent pmd (so if
1344 * we fail to prevent copy_huge_pmd() from running until the
1345 * whole __split_huge_page() is complete), we will still see
1346 * the newly established pmd of the child later during the
1347 * walk, to be able to set it as pmd_trans_splitting too.
1348 */
1349 if (mapcount != page_mapcount(page))
1350 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1351 mapcount, page_mapcount(page));
1352 BUG_ON(mapcount != page_mapcount(page));
1353
1354 __split_huge_page_refcount(page);
1355
1356 mapcount2 = 0;
1357 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1358 struct vm_area_struct *vma = avc->vma;
1359 unsigned long addr = vma_address(page, vma);
1360 BUG_ON(is_vma_temporary_stack(vma));
1361 if (addr == -EFAULT)
1362 continue;
1363 mapcount2 += __split_huge_page_map(page, vma, addr);
1364 }
1365 if (mapcount != mapcount2)
1366 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1367 mapcount, mapcount2, page_mapcount(page));
1368 BUG_ON(mapcount != mapcount2);
1369 }
1370
1371 int split_huge_page(struct page *page)
1372 {
1373 struct anon_vma *anon_vma;
1374 int ret = 1;
1375
1376 BUG_ON(!PageAnon(page));
1377 anon_vma = page_lock_anon_vma(page);
1378 if (!anon_vma)
1379 goto out;
1380 ret = 0;
1381 if (!PageCompound(page))
1382 goto out_unlock;
1383
1384 BUG_ON(!PageSwapBacked(page));
1385 __split_huge_page(page, anon_vma);
1386
1387 BUG_ON(PageCompound(page));
1388 out_unlock:
1389 page_unlock_anon_vma(anon_vma);
1390 out:
1391 return ret;
1392 }
1393
1394 int hugepage_madvise(struct vm_area_struct *vma,
1395 unsigned long *vm_flags, int advice)
1396 {
1397 switch (advice) {
1398 case MADV_HUGEPAGE:
1399 /*
1400 * Be somewhat over-protective like KSM for now!
1401 */
1402 if (*vm_flags & (VM_HUGEPAGE |
1403 VM_SHARED | VM_MAYSHARE |
1404 VM_PFNMAP | VM_IO | VM_DONTEXPAND |
1405 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
1406 VM_MIXEDMAP | VM_SAO))
1407 return -EINVAL;
1408 *vm_flags &= ~VM_NOHUGEPAGE;
1409 *vm_flags |= VM_HUGEPAGE;
1410 /*
1411 * If the vma become good for khugepaged to scan,
1412 * register it here without waiting a page fault that
1413 * may not happen any time soon.
1414 */
1415 if (unlikely(khugepaged_enter_vma_merge(vma)))
1416 return -ENOMEM;
1417 break;
1418 case MADV_NOHUGEPAGE:
1419 /*
1420 * Be somewhat over-protective like KSM for now!
1421 */
1422 if (*vm_flags & (VM_NOHUGEPAGE |
1423 VM_SHARED | VM_MAYSHARE |
1424 VM_PFNMAP | VM_IO | VM_DONTEXPAND |
1425 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
1426 VM_MIXEDMAP | VM_SAO))
1427 return -EINVAL;
1428 *vm_flags &= ~VM_HUGEPAGE;
1429 *vm_flags |= VM_NOHUGEPAGE;
1430 /*
1431 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1432 * this vma even if we leave the mm registered in khugepaged if
1433 * it got registered before VM_NOHUGEPAGE was set.
1434 */
1435 break;
1436 }
1437
1438 return 0;
1439 }
1440
1441 static int __init khugepaged_slab_init(void)
1442 {
1443 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1444 sizeof(struct mm_slot),
1445 __alignof__(struct mm_slot), 0, NULL);
1446 if (!mm_slot_cache)
1447 return -ENOMEM;
1448
1449 return 0;
1450 }
1451
1452 static void __init khugepaged_slab_free(void)
1453 {
1454 kmem_cache_destroy(mm_slot_cache);
1455 mm_slot_cache = NULL;
1456 }
1457
1458 static inline struct mm_slot *alloc_mm_slot(void)
1459 {
1460 if (!mm_slot_cache) /* initialization failed */
1461 return NULL;
1462 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1463 }
1464
1465 static inline void free_mm_slot(struct mm_slot *mm_slot)
1466 {
1467 kmem_cache_free(mm_slot_cache, mm_slot);
1468 }
1469
1470 static int __init mm_slots_hash_init(void)
1471 {
1472 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1473 GFP_KERNEL);
1474 if (!mm_slots_hash)
1475 return -ENOMEM;
1476 return 0;
1477 }
1478
1479 #if 0
1480 static void __init mm_slots_hash_free(void)
1481 {
1482 kfree(mm_slots_hash);
1483 mm_slots_hash = NULL;
1484 }
1485 #endif
1486
1487 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1488 {
1489 struct mm_slot *mm_slot;
1490 struct hlist_head *bucket;
1491 struct hlist_node *node;
1492
1493 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1494 % MM_SLOTS_HASH_HEADS];
1495 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1496 if (mm == mm_slot->mm)
1497 return mm_slot;
1498 }
1499 return NULL;
1500 }
1501
1502 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1503 struct mm_slot *mm_slot)
1504 {
1505 struct hlist_head *bucket;
1506
1507 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1508 % MM_SLOTS_HASH_HEADS];
1509 mm_slot->mm = mm;
1510 hlist_add_head(&mm_slot->hash, bucket);
1511 }
1512
1513 static inline int khugepaged_test_exit(struct mm_struct *mm)
1514 {
1515 return atomic_read(&mm->mm_users) == 0;
1516 }
1517
1518 int __khugepaged_enter(struct mm_struct *mm)
1519 {
1520 struct mm_slot *mm_slot;
1521 int wakeup;
1522
1523 mm_slot = alloc_mm_slot();
1524 if (!mm_slot)
1525 return -ENOMEM;
1526
1527 /* __khugepaged_exit() must not run from under us */
1528 VM_BUG_ON(khugepaged_test_exit(mm));
1529 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1530 free_mm_slot(mm_slot);
1531 return 0;
1532 }
1533
1534 spin_lock(&khugepaged_mm_lock);
1535 insert_to_mm_slots_hash(mm, mm_slot);
1536 /*
1537 * Insert just behind the scanning cursor, to let the area settle
1538 * down a little.
1539 */
1540 wakeup = list_empty(&khugepaged_scan.mm_head);
1541 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1542 spin_unlock(&khugepaged_mm_lock);
1543
1544 atomic_inc(&mm->mm_count);
1545 if (wakeup)
1546 wake_up_interruptible(&khugepaged_wait);
1547
1548 return 0;
1549 }
1550
1551 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1552 {
1553 unsigned long hstart, hend;
1554 if (!vma->anon_vma)
1555 /*
1556 * Not yet faulted in so we will register later in the
1557 * page fault if needed.
1558 */
1559 return 0;
1560 if (vma->vm_file || vma->vm_ops)
1561 /* khugepaged not yet working on file or special mappings */
1562 return 0;
1563 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1564 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1565 hend = vma->vm_end & HPAGE_PMD_MASK;
1566 if (hstart < hend)
1567 return khugepaged_enter(vma);
1568 return 0;
1569 }
1570
1571 void __khugepaged_exit(struct mm_struct *mm)
1572 {
1573 struct mm_slot *mm_slot;
1574 int free = 0;
1575
1576 spin_lock(&khugepaged_mm_lock);
1577 mm_slot = get_mm_slot(mm);
1578 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1579 hlist_del(&mm_slot->hash);
1580 list_del(&mm_slot->mm_node);
1581 free = 1;
1582 }
1583
1584 if (free) {
1585 spin_unlock(&khugepaged_mm_lock);
1586 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1587 free_mm_slot(mm_slot);
1588 mmdrop(mm);
1589 } else if (mm_slot) {
1590 spin_unlock(&khugepaged_mm_lock);
1591 /*
1592 * This is required to serialize against
1593 * khugepaged_test_exit() (which is guaranteed to run
1594 * under mmap sem read mode). Stop here (after we
1595 * return all pagetables will be destroyed) until
1596 * khugepaged has finished working on the pagetables
1597 * under the mmap_sem.
1598 */
1599 down_write(&mm->mmap_sem);
1600 up_write(&mm->mmap_sem);
1601 } else
1602 spin_unlock(&khugepaged_mm_lock);
1603 }
1604
1605 static void release_pte_page(struct page *page)
1606 {
1607 /* 0 stands for page_is_file_cache(page) == false */
1608 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1609 unlock_page(page);
1610 putback_lru_page(page);
1611 }
1612
1613 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1614 {
1615 while (--_pte >= pte) {
1616 pte_t pteval = *_pte;
1617 if (!pte_none(pteval))
1618 release_pte_page(pte_page(pteval));
1619 }
1620 }
1621
1622 static void release_all_pte_pages(pte_t *pte)
1623 {
1624 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1625 }
1626
1627 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1628 unsigned long address,
1629 pte_t *pte)
1630 {
1631 struct page *page;
1632 pte_t *_pte;
1633 int referenced = 0, isolated = 0, none = 0;
1634 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1635 _pte++, address += PAGE_SIZE) {
1636 pte_t pteval = *_pte;
1637 if (pte_none(pteval)) {
1638 if (++none <= khugepaged_max_ptes_none)
1639 continue;
1640 else {
1641 release_pte_pages(pte, _pte);
1642 goto out;
1643 }
1644 }
1645 if (!pte_present(pteval) || !pte_write(pteval)) {
1646 release_pte_pages(pte, _pte);
1647 goto out;
1648 }
1649 page = vm_normal_page(vma, address, pteval);
1650 if (unlikely(!page)) {
1651 release_pte_pages(pte, _pte);
1652 goto out;
1653 }
1654 VM_BUG_ON(PageCompound(page));
1655 BUG_ON(!PageAnon(page));
1656 VM_BUG_ON(!PageSwapBacked(page));
1657
1658 /* cannot use mapcount: can't collapse if there's a gup pin */
1659 if (page_count(page) != 1) {
1660 release_pte_pages(pte, _pte);
1661 goto out;
1662 }
1663 /*
1664 * We can do it before isolate_lru_page because the
1665 * page can't be freed from under us. NOTE: PG_lock
1666 * is needed to serialize against split_huge_page
1667 * when invoked from the VM.
1668 */
1669 if (!trylock_page(page)) {
1670 release_pte_pages(pte, _pte);
1671 goto out;
1672 }
1673 /*
1674 * Isolate the page to avoid collapsing an hugepage
1675 * currently in use by the VM.
1676 */
1677 if (isolate_lru_page(page)) {
1678 unlock_page(page);
1679 release_pte_pages(pte, _pte);
1680 goto out;
1681 }
1682 /* 0 stands for page_is_file_cache(page) == false */
1683 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1684 VM_BUG_ON(!PageLocked(page));
1685 VM_BUG_ON(PageLRU(page));
1686
1687 /* If there is no mapped pte young don't collapse the page */
1688 if (pte_young(pteval) || PageReferenced(page) ||
1689 mmu_notifier_test_young(vma->vm_mm, address))
1690 referenced = 1;
1691 }
1692 if (unlikely(!referenced))
1693 release_all_pte_pages(pte);
1694 else
1695 isolated = 1;
1696 out:
1697 return isolated;
1698 }
1699
1700 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1701 struct vm_area_struct *vma,
1702 unsigned long address,
1703 spinlock_t *ptl)
1704 {
1705 pte_t *_pte;
1706 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1707 pte_t pteval = *_pte;
1708 struct page *src_page;
1709
1710 if (pte_none(pteval)) {
1711 clear_user_highpage(page, address);
1712 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1713 } else {
1714 src_page = pte_page(pteval);
1715 copy_user_highpage(page, src_page, address, vma);
1716 VM_BUG_ON(page_mapcount(src_page) != 1);
1717 VM_BUG_ON(page_count(src_page) != 2);
1718 release_pte_page(src_page);
1719 /*
1720 * ptl mostly unnecessary, but preempt has to
1721 * be disabled to update the per-cpu stats
1722 * inside page_remove_rmap().
1723 */
1724 spin_lock(ptl);
1725 /*
1726 * paravirt calls inside pte_clear here are
1727 * superfluous.
1728 */
1729 pte_clear(vma->vm_mm, address, _pte);
1730 page_remove_rmap(src_page);
1731 spin_unlock(ptl);
1732 free_page_and_swap_cache(src_page);
1733 }
1734
1735 address += PAGE_SIZE;
1736 page++;
1737 }
1738 }
1739
1740 static void collapse_huge_page(struct mm_struct *mm,
1741 unsigned long address,
1742 struct page **hpage,
1743 struct vm_area_struct *vma)
1744 {
1745 pgd_t *pgd;
1746 pud_t *pud;
1747 pmd_t *pmd, _pmd;
1748 pte_t *pte;
1749 pgtable_t pgtable;
1750 struct page *new_page;
1751 spinlock_t *ptl;
1752 int isolated;
1753 unsigned long hstart, hend;
1754
1755 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1756 #ifndef CONFIG_NUMA
1757 VM_BUG_ON(!*hpage);
1758 new_page = *hpage;
1759 #else
1760 VM_BUG_ON(*hpage);
1761 /*
1762 * Allocate the page while the vma is still valid and under
1763 * the mmap_sem read mode so there is no memory allocation
1764 * later when we take the mmap_sem in write mode. This is more
1765 * friendly behavior (OTOH it may actually hide bugs) to
1766 * filesystems in userland with daemons allocating memory in
1767 * the userland I/O paths. Allocating memory with the
1768 * mmap_sem in read mode is good idea also to allow greater
1769 * scalability.
1770 */
1771 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address);
1772 if (unlikely(!new_page)) {
1773 up_read(&mm->mmap_sem);
1774 *hpage = ERR_PTR(-ENOMEM);
1775 return;
1776 }
1777 #endif
1778 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1779 up_read(&mm->mmap_sem);
1780 put_page(new_page);
1781 return;
1782 }
1783
1784 /* after allocating the hugepage upgrade to mmap_sem write mode */
1785 up_read(&mm->mmap_sem);
1786
1787 /*
1788 * Prevent all access to pagetables with the exception of
1789 * gup_fast later hanlded by the ptep_clear_flush and the VM
1790 * handled by the anon_vma lock + PG_lock.
1791 */
1792 down_write(&mm->mmap_sem);
1793 if (unlikely(khugepaged_test_exit(mm)))
1794 goto out;
1795
1796 vma = find_vma(mm, address);
1797 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1798 hend = vma->vm_end & HPAGE_PMD_MASK;
1799 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1800 goto out;
1801
1802 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1803 (vma->vm_flags & VM_NOHUGEPAGE))
1804 goto out;
1805
1806 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
1807 if (!vma->anon_vma || vma->vm_ops || vma->vm_file)
1808 goto out;
1809 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1810
1811 pgd = pgd_offset(mm, address);
1812 if (!pgd_present(*pgd))
1813 goto out;
1814
1815 pud = pud_offset(pgd, address);
1816 if (!pud_present(*pud))
1817 goto out;
1818
1819 pmd = pmd_offset(pud, address);
1820 /* pmd can't go away or become huge under us */
1821 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1822 goto out;
1823
1824 anon_vma_lock(vma->anon_vma);
1825
1826 pte = pte_offset_map(pmd, address);
1827 ptl = pte_lockptr(mm, pmd);
1828
1829 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1830 /*
1831 * After this gup_fast can't run anymore. This also removes
1832 * any huge TLB entry from the CPU so we won't allow
1833 * huge and small TLB entries for the same virtual address
1834 * to avoid the risk of CPU bugs in that area.
1835 */
1836 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1837 spin_unlock(&mm->page_table_lock);
1838
1839 spin_lock(ptl);
1840 isolated = __collapse_huge_page_isolate(vma, address, pte);
1841 spin_unlock(ptl);
1842
1843 if (unlikely(!isolated)) {
1844 pte_unmap(pte);
1845 spin_lock(&mm->page_table_lock);
1846 BUG_ON(!pmd_none(*pmd));
1847 set_pmd_at(mm, address, pmd, _pmd);
1848 spin_unlock(&mm->page_table_lock);
1849 anon_vma_unlock(vma->anon_vma);
1850 mem_cgroup_uncharge_page(new_page);
1851 goto out;
1852 }
1853
1854 /*
1855 * All pages are isolated and locked so anon_vma rmap
1856 * can't run anymore.
1857 */
1858 anon_vma_unlock(vma->anon_vma);
1859
1860 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1861 pte_unmap(pte);
1862 __SetPageUptodate(new_page);
1863 pgtable = pmd_pgtable(_pmd);
1864 VM_BUG_ON(page_count(pgtable) != 1);
1865 VM_BUG_ON(page_mapcount(pgtable) != 0);
1866
1867 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1868 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1869 _pmd = pmd_mkhuge(_pmd);
1870
1871 /*
1872 * spin_lock() below is not the equivalent of smp_wmb(), so
1873 * this is needed to avoid the copy_huge_page writes to become
1874 * visible after the set_pmd_at() write.
1875 */
1876 smp_wmb();
1877
1878 spin_lock(&mm->page_table_lock);
1879 BUG_ON(!pmd_none(*pmd));
1880 page_add_new_anon_rmap(new_page, vma, address);
1881 set_pmd_at(mm, address, pmd, _pmd);
1882 update_mmu_cache(vma, address, entry);
1883 prepare_pmd_huge_pte(pgtable, mm);
1884 mm->nr_ptes--;
1885 spin_unlock(&mm->page_table_lock);
1886
1887 #ifndef CONFIG_NUMA
1888 *hpage = NULL;
1889 #endif
1890 khugepaged_pages_collapsed++;
1891 out_up_write:
1892 up_write(&mm->mmap_sem);
1893 return;
1894
1895 out:
1896 #ifdef CONFIG_NUMA
1897 put_page(new_page);
1898 #endif
1899 goto out_up_write;
1900 }
1901
1902 static int khugepaged_scan_pmd(struct mm_struct *mm,
1903 struct vm_area_struct *vma,
1904 unsigned long address,
1905 struct page **hpage)
1906 {
1907 pgd_t *pgd;
1908 pud_t *pud;
1909 pmd_t *pmd;
1910 pte_t *pte, *_pte;
1911 int ret = 0, referenced = 0, none = 0;
1912 struct page *page;
1913 unsigned long _address;
1914 spinlock_t *ptl;
1915
1916 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1917
1918 pgd = pgd_offset(mm, address);
1919 if (!pgd_present(*pgd))
1920 goto out;
1921
1922 pud = pud_offset(pgd, address);
1923 if (!pud_present(*pud))
1924 goto out;
1925
1926 pmd = pmd_offset(pud, address);
1927 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1928 goto out;
1929
1930 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1931 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1932 _pte++, _address += PAGE_SIZE) {
1933 pte_t pteval = *_pte;
1934 if (pte_none(pteval)) {
1935 if (++none <= khugepaged_max_ptes_none)
1936 continue;
1937 else
1938 goto out_unmap;
1939 }
1940 if (!pte_present(pteval) || !pte_write(pteval))
1941 goto out_unmap;
1942 page = vm_normal_page(vma, _address, pteval);
1943 if (unlikely(!page))
1944 goto out_unmap;
1945 VM_BUG_ON(PageCompound(page));
1946 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
1947 goto out_unmap;
1948 /* cannot use mapcount: can't collapse if there's a gup pin */
1949 if (page_count(page) != 1)
1950 goto out_unmap;
1951 if (pte_young(pteval) || PageReferenced(page) ||
1952 mmu_notifier_test_young(vma->vm_mm, address))
1953 referenced = 1;
1954 }
1955 if (referenced)
1956 ret = 1;
1957 out_unmap:
1958 pte_unmap_unlock(pte, ptl);
1959 if (ret)
1960 /* collapse_huge_page will return with the mmap_sem released */
1961 collapse_huge_page(mm, address, hpage, vma);
1962 out:
1963 return ret;
1964 }
1965
1966 static void collect_mm_slot(struct mm_slot *mm_slot)
1967 {
1968 struct mm_struct *mm = mm_slot->mm;
1969
1970 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
1971
1972 if (khugepaged_test_exit(mm)) {
1973 /* free mm_slot */
1974 hlist_del(&mm_slot->hash);
1975 list_del(&mm_slot->mm_node);
1976
1977 /*
1978 * Not strictly needed because the mm exited already.
1979 *
1980 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1981 */
1982
1983 /* khugepaged_mm_lock actually not necessary for the below */
1984 free_mm_slot(mm_slot);
1985 mmdrop(mm);
1986 }
1987 }
1988
1989 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
1990 struct page **hpage)
1991 {
1992 struct mm_slot *mm_slot;
1993 struct mm_struct *mm;
1994 struct vm_area_struct *vma;
1995 int progress = 0;
1996
1997 VM_BUG_ON(!pages);
1998 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
1999
2000 if (khugepaged_scan.mm_slot)
2001 mm_slot = khugepaged_scan.mm_slot;
2002 else {
2003 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2004 struct mm_slot, mm_node);
2005 khugepaged_scan.address = 0;
2006 khugepaged_scan.mm_slot = mm_slot;
2007 }
2008 spin_unlock(&khugepaged_mm_lock);
2009
2010 mm = mm_slot->mm;
2011 down_read(&mm->mmap_sem);
2012 if (unlikely(khugepaged_test_exit(mm)))
2013 vma = NULL;
2014 else
2015 vma = find_vma(mm, khugepaged_scan.address);
2016
2017 progress++;
2018 for (; vma; vma = vma->vm_next) {
2019 unsigned long hstart, hend;
2020
2021 cond_resched();
2022 if (unlikely(khugepaged_test_exit(mm))) {
2023 progress++;
2024 break;
2025 }
2026
2027 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2028 !khugepaged_always()) ||
2029 (vma->vm_flags & VM_NOHUGEPAGE)) {
2030 progress++;
2031 continue;
2032 }
2033
2034 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
2035 if (!vma->anon_vma || vma->vm_ops || vma->vm_file) {
2036 khugepaged_scan.address = vma->vm_end;
2037 progress++;
2038 continue;
2039 }
2040 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
2041
2042 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2043 hend = vma->vm_end & HPAGE_PMD_MASK;
2044 if (hstart >= hend) {
2045 progress++;
2046 continue;
2047 }
2048 if (khugepaged_scan.address < hstart)
2049 khugepaged_scan.address = hstart;
2050 if (khugepaged_scan.address > hend) {
2051 khugepaged_scan.address = hend + HPAGE_PMD_SIZE;
2052 progress++;
2053 continue;
2054 }
2055 BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2056
2057 while (khugepaged_scan.address < hend) {
2058 int ret;
2059 cond_resched();
2060 if (unlikely(khugepaged_test_exit(mm)))
2061 goto breakouterloop;
2062
2063 VM_BUG_ON(khugepaged_scan.address < hstart ||
2064 khugepaged_scan.address + HPAGE_PMD_SIZE >
2065 hend);
2066 ret = khugepaged_scan_pmd(mm, vma,
2067 khugepaged_scan.address,
2068 hpage);
2069 /* move to next address */
2070 khugepaged_scan.address += HPAGE_PMD_SIZE;
2071 progress += HPAGE_PMD_NR;
2072 if (ret)
2073 /* we released mmap_sem so break loop */
2074 goto breakouterloop_mmap_sem;
2075 if (progress >= pages)
2076 goto breakouterloop;
2077 }
2078 }
2079 breakouterloop:
2080 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2081 breakouterloop_mmap_sem:
2082
2083 spin_lock(&khugepaged_mm_lock);
2084 BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2085 /*
2086 * Release the current mm_slot if this mm is about to die, or
2087 * if we scanned all vmas of this mm.
2088 */
2089 if (khugepaged_test_exit(mm) || !vma) {
2090 /*
2091 * Make sure that if mm_users is reaching zero while
2092 * khugepaged runs here, khugepaged_exit will find
2093 * mm_slot not pointing to the exiting mm.
2094 */
2095 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2096 khugepaged_scan.mm_slot = list_entry(
2097 mm_slot->mm_node.next,
2098 struct mm_slot, mm_node);
2099 khugepaged_scan.address = 0;
2100 } else {
2101 khugepaged_scan.mm_slot = NULL;
2102 khugepaged_full_scans++;
2103 }
2104
2105 collect_mm_slot(mm_slot);
2106 }
2107
2108 return progress;
2109 }
2110
2111 static int khugepaged_has_work(void)
2112 {
2113 return !list_empty(&khugepaged_scan.mm_head) &&
2114 khugepaged_enabled();
2115 }
2116
2117 static int khugepaged_wait_event(void)
2118 {
2119 return !list_empty(&khugepaged_scan.mm_head) ||
2120 !khugepaged_enabled();
2121 }
2122
2123 static void khugepaged_do_scan(struct page **hpage)
2124 {
2125 unsigned int progress = 0, pass_through_head = 0;
2126 unsigned int pages = khugepaged_pages_to_scan;
2127
2128 barrier(); /* write khugepaged_pages_to_scan to local stack */
2129
2130 while (progress < pages) {
2131 cond_resched();
2132
2133 #ifndef CONFIG_NUMA
2134 if (!*hpage) {
2135 *hpage = alloc_hugepage(khugepaged_defrag());
2136 if (unlikely(!*hpage))
2137 break;
2138 }
2139 #else
2140 if (IS_ERR(*hpage))
2141 break;
2142 #endif
2143
2144 if (unlikely(kthread_should_stop() || freezing(current)))
2145 break;
2146
2147 spin_lock(&khugepaged_mm_lock);
2148 if (!khugepaged_scan.mm_slot)
2149 pass_through_head++;
2150 if (khugepaged_has_work() &&
2151 pass_through_head < 2)
2152 progress += khugepaged_scan_mm_slot(pages - progress,
2153 hpage);
2154 else
2155 progress = pages;
2156 spin_unlock(&khugepaged_mm_lock);
2157 }
2158 }
2159
2160 static void khugepaged_alloc_sleep(void)
2161 {
2162 DEFINE_WAIT(wait);
2163 add_wait_queue(&khugepaged_wait, &wait);
2164 schedule_timeout_interruptible(
2165 msecs_to_jiffies(
2166 khugepaged_alloc_sleep_millisecs));
2167 remove_wait_queue(&khugepaged_wait, &wait);
2168 }
2169
2170 #ifndef CONFIG_NUMA
2171 static struct page *khugepaged_alloc_hugepage(void)
2172 {
2173 struct page *hpage;
2174
2175 do {
2176 hpage = alloc_hugepage(khugepaged_defrag());
2177 if (!hpage)
2178 khugepaged_alloc_sleep();
2179 } while (unlikely(!hpage) &&
2180 likely(khugepaged_enabled()));
2181 return hpage;
2182 }
2183 #endif
2184
2185 static void khugepaged_loop(void)
2186 {
2187 struct page *hpage;
2188
2189 #ifdef CONFIG_NUMA
2190 hpage = NULL;
2191 #endif
2192 while (likely(khugepaged_enabled())) {
2193 #ifndef CONFIG_NUMA
2194 hpage = khugepaged_alloc_hugepage();
2195 if (unlikely(!hpage))
2196 break;
2197 #else
2198 if (IS_ERR(hpage)) {
2199 khugepaged_alloc_sleep();
2200 hpage = NULL;
2201 }
2202 #endif
2203
2204 khugepaged_do_scan(&hpage);
2205 #ifndef CONFIG_NUMA
2206 if (hpage)
2207 put_page(hpage);
2208 #endif
2209 try_to_freeze();
2210 if (unlikely(kthread_should_stop()))
2211 break;
2212 if (khugepaged_has_work()) {
2213 DEFINE_WAIT(wait);
2214 if (!khugepaged_scan_sleep_millisecs)
2215 continue;
2216 add_wait_queue(&khugepaged_wait, &wait);
2217 schedule_timeout_interruptible(
2218 msecs_to_jiffies(
2219 khugepaged_scan_sleep_millisecs));
2220 remove_wait_queue(&khugepaged_wait, &wait);
2221 } else if (khugepaged_enabled())
2222 wait_event_freezable(khugepaged_wait,
2223 khugepaged_wait_event());
2224 }
2225 }
2226
2227 static int khugepaged(void *none)
2228 {
2229 struct mm_slot *mm_slot;
2230
2231 set_freezable();
2232 set_user_nice(current, 19);
2233
2234 /* serialize with start_khugepaged() */
2235 mutex_lock(&khugepaged_mutex);
2236
2237 for (;;) {
2238 mutex_unlock(&khugepaged_mutex);
2239 BUG_ON(khugepaged_thread != current);
2240 khugepaged_loop();
2241 BUG_ON(khugepaged_thread != current);
2242
2243 mutex_lock(&khugepaged_mutex);
2244 if (!khugepaged_enabled())
2245 break;
2246 if (unlikely(kthread_should_stop()))
2247 break;
2248 }
2249
2250 spin_lock(&khugepaged_mm_lock);
2251 mm_slot = khugepaged_scan.mm_slot;
2252 khugepaged_scan.mm_slot = NULL;
2253 if (mm_slot)
2254 collect_mm_slot(mm_slot);
2255 spin_unlock(&khugepaged_mm_lock);
2256
2257 khugepaged_thread = NULL;
2258 mutex_unlock(&khugepaged_mutex);
2259
2260 return 0;
2261 }
2262
2263 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2264 {
2265 struct page *page;
2266
2267 spin_lock(&mm->page_table_lock);
2268 if (unlikely(!pmd_trans_huge(*pmd))) {
2269 spin_unlock(&mm->page_table_lock);
2270 return;
2271 }
2272 page = pmd_page(*pmd);
2273 VM_BUG_ON(!page_count(page));
2274 get_page(page);
2275 spin_unlock(&mm->page_table_lock);
2276
2277 split_huge_page(page);
2278
2279 put_page(page);
2280 BUG_ON(pmd_trans_huge(*pmd));
2281 }
2282
2283 static void split_huge_page_address(struct mm_struct *mm,
2284 unsigned long address)
2285 {
2286 pgd_t *pgd;
2287 pud_t *pud;
2288 pmd_t *pmd;
2289
2290 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2291
2292 pgd = pgd_offset(mm, address);
2293 if (!pgd_present(*pgd))
2294 return;
2295
2296 pud = pud_offset(pgd, address);
2297 if (!pud_present(*pud))
2298 return;
2299
2300 pmd = pmd_offset(pud, address);
2301 if (!pmd_present(*pmd))
2302 return;
2303 /*
2304 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2305 * materialize from under us.
2306 */
2307 split_huge_page_pmd(mm, pmd);
2308 }
2309
2310 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2311 unsigned long start,
2312 unsigned long end,
2313 long adjust_next)
2314 {
2315 /*
2316 * If the new start address isn't hpage aligned and it could
2317 * previously contain an hugepage: check if we need to split
2318 * an huge pmd.
2319 */
2320 if (start & ~HPAGE_PMD_MASK &&
2321 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2322 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2323 split_huge_page_address(vma->vm_mm, start);
2324
2325 /*
2326 * If the new end address isn't hpage aligned and it could
2327 * previously contain an hugepage: check if we need to split
2328 * an huge pmd.
2329 */
2330 if (end & ~HPAGE_PMD_MASK &&
2331 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2332 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2333 split_huge_page_address(vma->vm_mm, end);
2334
2335 /*
2336 * If we're also updating the vma->vm_next->vm_start, if the new
2337 * vm_next->vm_start isn't page aligned and it could previously
2338 * contain an hugepage: check if we need to split an huge pmd.
2339 */
2340 if (adjust_next > 0) {
2341 struct vm_area_struct *next = vma->vm_next;
2342 unsigned long nstart = next->vm_start;
2343 nstart += adjust_next << PAGE_SHIFT;
2344 if (nstart & ~HPAGE_PMD_MASK &&
2345 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2346 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2347 split_huge_page_address(next->vm_mm, nstart);
2348 }
2349 }
Linus' kernel tree