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drm/nouveau: unpin pushbuffer bo before destroying it
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / mm / huge_memory.c
blob40f17c34b4153fab93b4f1a2685dee0b8cac4da8
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 <linux/pagemap.h>
21 #include <asm/tlb.h>
22 #include <asm/pgalloc.h>
23 #include "internal.h"
24
25 /*
26 * By default transparent hugepage support is enabled for all mappings
27 * and khugepaged scans all mappings. Defrag is only invoked by
28 * khugepaged hugepage allocations and by page faults inside
29 * MADV_HUGEPAGE regions to avoid the risk of slowing down short lived
30 * allocations.
31 */
32 unsigned long transparent_hugepage_flags __read_mostly =
33 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
34 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
35 #endif
36 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
37 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
38 #endif
39 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
40 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
41
42 /* default scan 8*512 pte (or vmas) every 30 second */
43 static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
44 static unsigned int khugepaged_pages_collapsed;
45 static unsigned int khugepaged_full_scans;
46 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
47 /* during fragmentation poll the hugepage allocator once every minute */
48 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
49 static struct task_struct *khugepaged_thread __read_mostly;
50 static DEFINE_MUTEX(khugepaged_mutex);
51 static DEFINE_SPINLOCK(khugepaged_mm_lock);
52 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
53 /*
54 * default collapse hugepages if there is at least one pte mapped like
55 * it would have happened if the vma was large enough during page
56 * fault.
57 */
58 static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
59
60 static int khugepaged(void *none);
61 static int mm_slots_hash_init(void);
62 static int khugepaged_slab_init(void);
63 static void khugepaged_slab_free(void);
64
65 #define MM_SLOTS_HASH_HEADS 1024
66 static struct hlist_head *mm_slots_hash __read_mostly;
67 static struct kmem_cache *mm_slot_cache __read_mostly;
68
69 /**
70 * struct mm_slot - hash lookup from mm to mm_slot
71 * @hash: hash collision list
72 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
73 * @mm: the mm that this information is valid for
74 */
75 struct mm_slot {
76 struct hlist_node hash;
77 struct list_head mm_node;
78 struct mm_struct *mm;
79 };
80
81 /**
82 * struct khugepaged_scan - cursor for scanning
83 * @mm_head: the head of the mm list to scan
84 * @mm_slot: the current mm_slot we are scanning
85 * @address: the next address inside that to be scanned
86 *
87 * There is only the one khugepaged_scan instance of this cursor structure.
88 */
89 struct khugepaged_scan {
90 struct list_head mm_head;
91 struct mm_slot *mm_slot;
92 unsigned long address;
93 };
94 static struct khugepaged_scan khugepaged_scan = {
95 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
96 };
97
98
99 static int set_recommended_min_free_kbytes(void)
100 {
101 struct zone *zone;
102 int nr_zones = 0;
103 unsigned long recommended_min;
104 extern int min_free_kbytes;
105
106 if (!khugepaged_enabled())
107 return 0;
108
109 for_each_populated_zone(zone)
110 nr_zones++;
111
112 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
113 recommended_min = pageblock_nr_pages * nr_zones * 2;
114
115 /*
116 * Make sure that on average at least two pageblocks are almost free
117 * of another type, one for a migratetype to fall back to and a
118 * second to avoid subsequent fallbacks of other types There are 3
119 * MIGRATE_TYPES we care about.
120 */
121 recommended_min += pageblock_nr_pages * nr_zones *
122 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
123
124 /* don't ever allow to reserve more than 5% of the lowmem */
125 recommended_min = min(recommended_min,
126 (unsigned long) nr_free_buffer_pages() / 20);
127 recommended_min <<= (PAGE_SHIFT-10);
128
129 if (recommended_min > min_free_kbytes)
130 min_free_kbytes = recommended_min;
131 setup_per_zone_wmarks();
132 return 0;
133 }
134 late_initcall(set_recommended_min_free_kbytes);
135
136 static int start_khugepaged(void)
137 {
138 int err = 0;
139 if (khugepaged_enabled()) {
140 if (!khugepaged_thread)
141 khugepaged_thread = kthread_run(khugepaged, NULL,
142 "khugepaged");
143 if (unlikely(IS_ERR(khugepaged_thread))) {
144 printk(KERN_ERR
145 "khugepaged: kthread_run(khugepaged) failed\n");
146 err = PTR_ERR(khugepaged_thread);
147 khugepaged_thread = NULL;
148 }
149
150 if (!list_empty(&khugepaged_scan.mm_head))
151 wake_up_interruptible(&khugepaged_wait);
152
153 set_recommended_min_free_kbytes();
154 } else if (khugepaged_thread) {
155 kthread_stop(khugepaged_thread);
156 khugepaged_thread = NULL;
157 }
158
159 return err;
160 }
161
162 #ifdef CONFIG_SYSFS
163
164 static ssize_t double_flag_show(struct kobject *kobj,
165 struct kobj_attribute *attr, char *buf,
166 enum transparent_hugepage_flag enabled,
167 enum transparent_hugepage_flag req_madv)
168 {
169 if (test_bit(enabled, &transparent_hugepage_flags)) {
170 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
171 return sprintf(buf, "[always] madvise never\n");
172 } else if (test_bit(req_madv, &transparent_hugepage_flags))
173 return sprintf(buf, "always [madvise] never\n");
174 else
175 return sprintf(buf, "always madvise [never]\n");
176 }
177 static ssize_t double_flag_store(struct kobject *kobj,
178 struct kobj_attribute *attr,
179 const char *buf, size_t count,
180 enum transparent_hugepage_flag enabled,
181 enum transparent_hugepage_flag req_madv)
182 {
183 if (!memcmp("always", buf,
184 min(sizeof("always")-1, count))) {
185 set_bit(enabled, &transparent_hugepage_flags);
186 clear_bit(req_madv, &transparent_hugepage_flags);
187 } else if (!memcmp("madvise", buf,
188 min(sizeof("madvise")-1, count))) {
189 clear_bit(enabled, &transparent_hugepage_flags);
190 set_bit(req_madv, &transparent_hugepage_flags);
191 } else if (!memcmp("never", buf,
192 min(sizeof("never")-1, count))) {
193 clear_bit(enabled, &transparent_hugepage_flags);
194 clear_bit(req_madv, &transparent_hugepage_flags);
195 } else
196 return -EINVAL;
197
198 return count;
199 }
200
201 static ssize_t enabled_show(struct kobject *kobj,
202 struct kobj_attribute *attr, char *buf)
203 {
204 return double_flag_show(kobj, attr, buf,
205 TRANSPARENT_HUGEPAGE_FLAG,
206 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
207 }
208 static ssize_t enabled_store(struct kobject *kobj,
209 struct kobj_attribute *attr,
210 const char *buf, size_t count)
211 {
212 ssize_t ret;
213
214 ret = double_flag_store(kobj, attr, buf, count,
215 TRANSPARENT_HUGEPAGE_FLAG,
216 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
217
218 if (ret > 0) {
219 int err;
220
221 mutex_lock(&khugepaged_mutex);
222 err = start_khugepaged();
223 mutex_unlock(&khugepaged_mutex);
224
225 if (err)
226 ret = err;
227 }
228
229 return ret;
230 }
231 static struct kobj_attribute enabled_attr =
232 __ATTR(enabled, 0644, enabled_show, enabled_store);
233
234 static ssize_t single_flag_show(struct kobject *kobj,
235 struct kobj_attribute *attr, char *buf,
236 enum transparent_hugepage_flag flag)
237 {
238 return sprintf(buf, "%d\n",
239 !!test_bit(flag, &transparent_hugepage_flags));
240 }
241
242 static ssize_t single_flag_store(struct kobject *kobj,
243 struct kobj_attribute *attr,
244 const char *buf, size_t count,
245 enum transparent_hugepage_flag flag)
246 {
247 unsigned long value;
248 int ret;
249
250 ret = kstrtoul(buf, 10, &value);
251 if (ret < 0)
252 return ret;
253 if (value > 1)
254 return -EINVAL;
255
256 if (value)
257 set_bit(flag, &transparent_hugepage_flags);
258 else
259 clear_bit(flag, &transparent_hugepage_flags);
260
261 return count;
262 }
263
264 /*
265 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
266 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
267 * memory just to allocate one more hugepage.
268 */
269 static ssize_t defrag_show(struct kobject *kobj,
270 struct kobj_attribute *attr, char *buf)
271 {
272 return double_flag_show(kobj, attr, buf,
273 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
274 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
275 }
276 static ssize_t defrag_store(struct kobject *kobj,
277 struct kobj_attribute *attr,
278 const char *buf, size_t count)
279 {
280 return double_flag_store(kobj, attr, buf, count,
281 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
282 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
283 }
284 static struct kobj_attribute defrag_attr =
285 __ATTR(defrag, 0644, defrag_show, defrag_store);
286
287 #ifdef CONFIG_DEBUG_VM
288 static ssize_t debug_cow_show(struct kobject *kobj,
289 struct kobj_attribute *attr, char *buf)
290 {
291 return single_flag_show(kobj, attr, buf,
292 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
293 }
294 static ssize_t debug_cow_store(struct kobject *kobj,
295 struct kobj_attribute *attr,
296 const char *buf, size_t count)
297 {
298 return single_flag_store(kobj, attr, buf, count,
299 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
300 }
301 static struct kobj_attribute debug_cow_attr =
302 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
303 #endif /* CONFIG_DEBUG_VM */
304
305 static struct attribute *hugepage_attr[] = {
306 &enabled_attr.attr,
307 &defrag_attr.attr,
308 #ifdef CONFIG_DEBUG_VM
309 &debug_cow_attr.attr,
310 #endif
311 NULL,
312 };
313
314 static struct attribute_group hugepage_attr_group = {
315 .attrs = hugepage_attr,
316 };
317
318 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
319 struct kobj_attribute *attr,
320 char *buf)
321 {
322 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
323 }
324
325 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
326 struct kobj_attribute *attr,
327 const char *buf, size_t count)
328 {
329 unsigned long msecs;
330 int err;
331
332 err = strict_strtoul(buf, 10, &msecs);
333 if (err || msecs > UINT_MAX)
334 return -EINVAL;
335
336 khugepaged_scan_sleep_millisecs = msecs;
337 wake_up_interruptible(&khugepaged_wait);
338
339 return count;
340 }
341 static struct kobj_attribute scan_sleep_millisecs_attr =
342 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
343 scan_sleep_millisecs_store);
344
345 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
346 struct kobj_attribute *attr,
347 char *buf)
348 {
349 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
350 }
351
352 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
353 struct kobj_attribute *attr,
354 const char *buf, size_t count)
355 {
356 unsigned long msecs;
357 int err;
358
359 err = strict_strtoul(buf, 10, &msecs);
360 if (err || msecs > UINT_MAX)
361 return -EINVAL;
362
363 khugepaged_alloc_sleep_millisecs = msecs;
364 wake_up_interruptible(&khugepaged_wait);
365
366 return count;
367 }
368 static struct kobj_attribute alloc_sleep_millisecs_attr =
369 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
370 alloc_sleep_millisecs_store);
371
372 static ssize_t pages_to_scan_show(struct kobject *kobj,
373 struct kobj_attribute *attr,
374 char *buf)
375 {
376 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
377 }
378 static ssize_t pages_to_scan_store(struct kobject *kobj,
379 struct kobj_attribute *attr,
380 const char *buf, size_t count)
381 {
382 int err;
383 unsigned long pages;
384
385 err = strict_strtoul(buf, 10, &pages);
386 if (err || !pages || pages > UINT_MAX)
387 return -EINVAL;
388
389 khugepaged_pages_to_scan = pages;
390
391 return count;
392 }
393 static struct kobj_attribute pages_to_scan_attr =
394 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
395 pages_to_scan_store);
396
397 static ssize_t pages_collapsed_show(struct kobject *kobj,
398 struct kobj_attribute *attr,
399 char *buf)
400 {
401 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
402 }
403 static struct kobj_attribute pages_collapsed_attr =
404 __ATTR_RO(pages_collapsed);
405
406 static ssize_t full_scans_show(struct kobject *kobj,
407 struct kobj_attribute *attr,
408 char *buf)
409 {
410 return sprintf(buf, "%u\n", khugepaged_full_scans);
411 }
412 static struct kobj_attribute full_scans_attr =
413 __ATTR_RO(full_scans);
414
415 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
416 struct kobj_attribute *attr, char *buf)
417 {
418 return single_flag_show(kobj, attr, buf,
419 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
420 }
421 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
422 struct kobj_attribute *attr,
423 const char *buf, size_t count)
424 {
425 return single_flag_store(kobj, attr, buf, count,
426 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
427 }
428 static struct kobj_attribute khugepaged_defrag_attr =
429 __ATTR(defrag, 0644, khugepaged_defrag_show,
430 khugepaged_defrag_store);
431
432 /*
433 * max_ptes_none controls if khugepaged should collapse hugepages over
434 * any unmapped ptes in turn potentially increasing the memory
435 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
436 * reduce the available free memory in the system as it
437 * runs. Increasing max_ptes_none will instead potentially reduce the
438 * free memory in the system during the khugepaged scan.
439 */
440 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
441 struct kobj_attribute *attr,
442 char *buf)
443 {
444 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
445 }
446 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
447 struct kobj_attribute *attr,
448 const char *buf, size_t count)
449 {
450 int err;
451 unsigned long max_ptes_none;
452
453 err = strict_strtoul(buf, 10, &max_ptes_none);
454 if (err || max_ptes_none > HPAGE_PMD_NR-1)
455 return -EINVAL;
456
457 khugepaged_max_ptes_none = max_ptes_none;
458
459 return count;
460 }
461 static struct kobj_attribute khugepaged_max_ptes_none_attr =
462 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
463 khugepaged_max_ptes_none_store);
464
465 static struct attribute *khugepaged_attr[] = {
466 &khugepaged_defrag_attr.attr,
467 &khugepaged_max_ptes_none_attr.attr,
468 &pages_to_scan_attr.attr,
469 &pages_collapsed_attr.attr,
470 &full_scans_attr.attr,
471 &scan_sleep_millisecs_attr.attr,
472 &alloc_sleep_millisecs_attr.attr,
473 NULL,
474 };
475
476 static struct attribute_group khugepaged_attr_group = {
477 .attrs = khugepaged_attr,
478 .name = "khugepaged",
479 };
480
481 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
482 {
483 int err;
484
485 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
486 if (unlikely(!*hugepage_kobj)) {
487 printk(KERN_ERR "hugepage: failed kobject create\n");
488 return -ENOMEM;
489 }
490
491 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
492 if (err) {
493 printk(KERN_ERR "hugepage: failed register hugeage group\n");
494 goto delete_obj;
495 }
496
497 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
498 if (err) {
499 printk(KERN_ERR "hugepage: failed register hugeage group\n");
500 goto remove_hp_group;
501 }
502
503 return 0;
504
505 remove_hp_group:
506 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
507 delete_obj:
508 kobject_put(*hugepage_kobj);
509 return err;
510 }
511
512 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
513 {
514 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
515 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
516 kobject_put(hugepage_kobj);
517 }
518 #else
519 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
520 {
521 return 0;
522 }
523
524 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
525 {
526 }
527 #endif /* CONFIG_SYSFS */
528
529 static int __init hugepage_init(void)
530 {
531 int err;
532 struct kobject *hugepage_kobj;
533
534 if (!has_transparent_hugepage()) {
535 transparent_hugepage_flags = 0;
536 return -EINVAL;
537 }
538
539 err = hugepage_init_sysfs(&hugepage_kobj);
540 if (err)
541 return err;
542
543 err = khugepaged_slab_init();
544 if (err)
545 goto out;
546
547 err = mm_slots_hash_init();
548 if (err) {
549 khugepaged_slab_free();
550 goto out;
551 }
552
553 /*
554 * By default disable transparent hugepages on smaller systems,
555 * where the extra memory used could hurt more than TLB overhead
556 * is likely to save. The admin can still enable it through /sys.
557 */
558 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
559 transparent_hugepage_flags = 0;
560
561 start_khugepaged();
562
563 return 0;
564 out:
565 hugepage_exit_sysfs(hugepage_kobj);
566 return err;
567 }
568 module_init(hugepage_init)
569
570 static int __init setup_transparent_hugepage(char *str)
571 {
572 int ret = 0;
573 if (!str)
574 goto out;
575 if (!strcmp(str, "always")) {
576 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
577 &transparent_hugepage_flags);
578 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
579 &transparent_hugepage_flags);
580 ret = 1;
581 } else if (!strcmp(str, "madvise")) {
582 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
583 &transparent_hugepage_flags);
584 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
585 &transparent_hugepage_flags);
586 ret = 1;
587 } else if (!strcmp(str, "never")) {
588 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
589 &transparent_hugepage_flags);
590 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
591 &transparent_hugepage_flags);
592 ret = 1;
593 }
594 out:
595 if (!ret)
596 printk(KERN_WARNING
597 "transparent_hugepage= cannot parse, ignored\n");
598 return ret;
599 }
600 __setup("transparent_hugepage=", setup_transparent_hugepage);
601
602 static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
603 {
604 if (likely(vma->vm_flags & VM_WRITE))
605 pmd = pmd_mkwrite(pmd);
606 return pmd;
607 }
608
609 static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
610 struct vm_area_struct *vma,
611 unsigned long haddr, pmd_t *pmd,
612 struct page *page)
613 {
614 pgtable_t pgtable;
615
616 VM_BUG_ON(!PageCompound(page));
617 pgtable = pte_alloc_one(mm, haddr);
618 if (unlikely(!pgtable))
619 return VM_FAULT_OOM;
620
621 clear_huge_page(page, haddr, HPAGE_PMD_NR);
622 __SetPageUptodate(page);
623
624 spin_lock(&mm->page_table_lock);
625 if (unlikely(!pmd_none(*pmd))) {
626 spin_unlock(&mm->page_table_lock);
627 mem_cgroup_uncharge_page(page);
628 put_page(page);
629 pte_free(mm, pgtable);
630 } else {
631 pmd_t entry;
632 entry = mk_pmd(page, vma->vm_page_prot);
633 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
634 entry = pmd_mkhuge(entry);
635 /*
636 * The spinlocking to take the lru_lock inside
637 * page_add_new_anon_rmap() acts as a full memory
638 * barrier to be sure clear_huge_page writes become
639 * visible after the set_pmd_at() write.
640 */
641 page_add_new_anon_rmap(page, vma, haddr);
642 set_pmd_at(mm, haddr, pmd, entry);
643 pgtable_trans_huge_deposit(mm, pgtable);
644 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
645 mm->nr_ptes++;
646 spin_unlock(&mm->page_table_lock);
647 }
648
649 return 0;
650 }
651
652 static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
653 {
654 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
655 }
656
657 static inline struct page *alloc_hugepage_vma(int defrag,
658 struct vm_area_struct *vma,
659 unsigned long haddr, int nd,
660 gfp_t extra_gfp)
661 {
662 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
663 HPAGE_PMD_ORDER, vma, haddr, nd);
664 }
665
666 #ifndef CONFIG_NUMA
667 static inline struct page *alloc_hugepage(int defrag)
668 {
669 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
670 HPAGE_PMD_ORDER);
671 }
672 #endif
673
674 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
675 unsigned long address, pmd_t *pmd,
676 unsigned int flags)
677 {
678 struct page *page;
679 unsigned long haddr = address & HPAGE_PMD_MASK;
680 pte_t *pte;
681
682 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
683 if (unlikely(anon_vma_prepare(vma)))
684 return VM_FAULT_OOM;
685 if (unlikely(khugepaged_enter(vma)))
686 return VM_FAULT_OOM;
687 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
688 vma, haddr, numa_node_id(), 0);
689 if (unlikely(!page)) {
690 count_vm_event(THP_FAULT_FALLBACK);
691 goto out;
692 }
693 count_vm_event(THP_FAULT_ALLOC);
694 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
695 put_page(page);
696 goto out;
697 }
698 if (unlikely(__do_huge_pmd_anonymous_page(mm, vma, haddr, pmd,
699 page))) {
700 mem_cgroup_uncharge_page(page);
701 put_page(page);
702 goto out;
703 }
704
705 return 0;
706 }
707 out:
708 /*
709 * Use __pte_alloc instead of pte_alloc_map, because we can't
710 * run pte_offset_map on the pmd, if an huge pmd could
711 * materialize from under us from a different thread.
712 */
713 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
714 return VM_FAULT_OOM;
715 /* if an huge pmd materialized from under us just retry later */
716 if (unlikely(pmd_trans_huge(*pmd)))
717 return 0;
718 /*
719 * A regular pmd is established and it can't morph into a huge pmd
720 * from under us anymore at this point because we hold the mmap_sem
721 * read mode and khugepaged takes it in write mode. So now it's
722 * safe to run pte_offset_map().
723 */
724 pte = pte_offset_map(pmd, address);
725 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
726 }
727
728 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
729 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
730 struct vm_area_struct *vma)
731 {
732 struct page *src_page;
733 pmd_t pmd;
734 pgtable_t pgtable;
735 int ret;
736
737 ret = -ENOMEM;
738 pgtable = pte_alloc_one(dst_mm, addr);
739 if (unlikely(!pgtable))
740 goto out;
741
742 spin_lock(&dst_mm->page_table_lock);
743 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
744
745 ret = -EAGAIN;
746 pmd = *src_pmd;
747 if (unlikely(!pmd_trans_huge(pmd))) {
748 pte_free(dst_mm, pgtable);
749 goto out_unlock;
750 }
751 if (unlikely(pmd_trans_splitting(pmd))) {
752 /* split huge page running from under us */
753 spin_unlock(&src_mm->page_table_lock);
754 spin_unlock(&dst_mm->page_table_lock);
755 pte_free(dst_mm, pgtable);
756
757 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
758 goto out;
759 }
760 src_page = pmd_page(pmd);
761 VM_BUG_ON(!PageHead(src_page));
762 get_page(src_page);
763 page_dup_rmap(src_page);
764 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
765
766 pmdp_set_wrprotect(src_mm, addr, src_pmd);
767 pmd = pmd_mkold(pmd_wrprotect(pmd));
768 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
769 pgtable_trans_huge_deposit(dst_mm, pgtable);
770 dst_mm->nr_ptes++;
771
772 ret = 0;
773 out_unlock:
774 spin_unlock(&src_mm->page_table_lock);
775 spin_unlock(&dst_mm->page_table_lock);
776 out:
777 return ret;
778 }
779
780 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
781 struct vm_area_struct *vma,
782 unsigned long address,
783 pmd_t *pmd, pmd_t orig_pmd,
784 struct page *page,
785 unsigned long haddr)
786 {
787 pgtable_t pgtable;
788 pmd_t _pmd;
789 int ret = 0, i;
790 struct page **pages;
791 unsigned long mmun_start; /* For mmu_notifiers */
792 unsigned long mmun_end; /* For mmu_notifiers */
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_node(GFP_HIGHUSER_MOVABLE |
803 __GFP_OTHER_NODE,
804 vma, address, page_to_nid(page));
805 if (unlikely(!pages[i] ||
806 mem_cgroup_newpage_charge(pages[i], mm,
807 GFP_KERNEL))) {
808 if (pages[i])
809 put_page(pages[i]);
810 mem_cgroup_uncharge_start();
811 while (--i >= 0) {
812 mem_cgroup_uncharge_page(pages[i]);
813 put_page(pages[i]);
814 }
815 mem_cgroup_uncharge_end();
816 kfree(pages);
817 ret |= VM_FAULT_OOM;
818 goto out;
819 }
820 }
821
822 for (i = 0; i < HPAGE_PMD_NR; i++) {
823 copy_user_highpage(pages[i], page + i,
824 haddr + PAGE_SIZE * i, vma);
825 __SetPageUptodate(pages[i]);
826 cond_resched();
827 }
828
829 mmun_start = haddr;
830 mmun_end = haddr + HPAGE_PMD_SIZE;
831 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
832
833 spin_lock(&mm->page_table_lock);
834 if (unlikely(!pmd_same(*pmd, orig_pmd)))
835 goto out_free_pages;
836 VM_BUG_ON(!PageHead(page));
837
838 pmdp_clear_flush(vma, haddr, pmd);
839 /* leave pmd empty until pte is filled */
840
841 pgtable = pgtable_trans_huge_withdraw(mm);
842 pmd_populate(mm, &_pmd, pgtable);
843
844 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
845 pte_t *pte, entry;
846 entry = mk_pte(pages[i], vma->vm_page_prot);
847 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
848 page_add_new_anon_rmap(pages[i], vma, haddr);
849 pte = pte_offset_map(&_pmd, haddr);
850 VM_BUG_ON(!pte_none(*pte));
851 set_pte_at(mm, haddr, pte, entry);
852 pte_unmap(pte);
853 }
854 kfree(pages);
855
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 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
862
863 ret |= VM_FAULT_WRITE;
864 put_page(page);
865
866 out:
867 return ret;
868
869 out_free_pages:
870 spin_unlock(&mm->page_table_lock);
871 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
872 mem_cgroup_uncharge_start();
873 for (i = 0; i < HPAGE_PMD_NR; i++) {
874 mem_cgroup_uncharge_page(pages[i]);
875 put_page(pages[i]);
876 }
877 mem_cgroup_uncharge_end();
878 kfree(pages);
879 goto out;
880 }
881
882 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
883 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
884 {
885 int ret = 0;
886 struct page *page, *new_page;
887 unsigned long haddr;
888 unsigned long mmun_start; /* For mmu_notifiers */
889 unsigned long mmun_end; /* For mmu_notifiers */
890
891 VM_BUG_ON(!vma->anon_vma);
892 spin_lock(&mm->page_table_lock);
893 if (unlikely(!pmd_same(*pmd, orig_pmd)))
894 goto out_unlock;
895
896 page = pmd_page(orig_pmd);
897 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
898 haddr = address & HPAGE_PMD_MASK;
899 if (page_mapcount(page) == 1) {
900 pmd_t entry;
901 entry = pmd_mkyoung(orig_pmd);
902 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
903 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
904 update_mmu_cache_pmd(vma, address, pmd);
905 ret |= VM_FAULT_WRITE;
906 goto out_unlock;
907 }
908 get_page(page);
909 spin_unlock(&mm->page_table_lock);
910
911 if (transparent_hugepage_enabled(vma) &&
912 !transparent_hugepage_debug_cow())
913 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
914 vma, haddr, numa_node_id(), 0);
915 else
916 new_page = NULL;
917
918 if (unlikely(!new_page)) {
919 count_vm_event(THP_FAULT_FALLBACK);
920 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
921 pmd, orig_pmd, page, haddr);
922 if (ret & VM_FAULT_OOM)
923 split_huge_page(page);
924 put_page(page);
925 goto out;
926 }
927 count_vm_event(THP_FAULT_ALLOC);
928
929 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
930 put_page(new_page);
931 split_huge_page(page);
932 put_page(page);
933 ret |= VM_FAULT_OOM;
934 goto out;
935 }
936
937 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
938 __SetPageUptodate(new_page);
939
940 mmun_start = haddr;
941 mmun_end = haddr + HPAGE_PMD_SIZE;
942 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
943
944 spin_lock(&mm->page_table_lock);
945 put_page(page);
946 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
947 spin_unlock(&mm->page_table_lock);
948 mem_cgroup_uncharge_page(new_page);
949 put_page(new_page);
950 goto out_mn;
951 } else {
952 pmd_t entry;
953 VM_BUG_ON(!PageHead(page));
954 entry = mk_pmd(new_page, vma->vm_page_prot);
955 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
956 entry = pmd_mkhuge(entry);
957 pmdp_clear_flush(vma, haddr, pmd);
958 page_add_new_anon_rmap(new_page, vma, haddr);
959 set_pmd_at(mm, haddr, pmd, entry);
960 update_mmu_cache_pmd(vma, address, pmd);
961 page_remove_rmap(page);
962 put_page(page);
963 ret |= VM_FAULT_WRITE;
964 }
965 spin_unlock(&mm->page_table_lock);
966 out_mn:
967 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
968 out:
969 return ret;
970 out_unlock:
971 spin_unlock(&mm->page_table_lock);
972 return ret;
973 }
974
975 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
976 unsigned long addr,
977 pmd_t *pmd,
978 unsigned int flags)
979 {
980 struct mm_struct *mm = vma->vm_mm;
981 struct page *page = NULL;
982
983 assert_spin_locked(&mm->page_table_lock);
984
985 if (flags & FOLL_WRITE && !pmd_write(*pmd))
986 goto out;
987
988 page = pmd_page(*pmd);
989 VM_BUG_ON(!PageHead(page));
990 if (flags & FOLL_TOUCH) {
991 pmd_t _pmd;
992 /*
993 * We should set the dirty bit only for FOLL_WRITE but
994 * for now the dirty bit in the pmd is meaningless.
995 * And if the dirty bit will become meaningful and
996 * we'll only set it with FOLL_WRITE, an atomic
997 * set_bit will be required on the pmd to set the
998 * young bit, instead of the current set_pmd_at.
999 */
1000 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1001 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
1002 }
1003 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1004 if (page->mapping && trylock_page(page)) {
1005 lru_add_drain();
1006 if (page->mapping)
1007 mlock_vma_page(page);
1008 unlock_page(page);
1009 }
1010 }
1011 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1012 VM_BUG_ON(!PageCompound(page));
1013 if (flags & FOLL_GET)
1014 get_page_foll(page);
1015
1016 out:
1017 return page;
1018 }
1019
1020 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1021 pmd_t *pmd, unsigned long addr)
1022 {
1023 int ret = 0;
1024
1025 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1026 struct page *page;
1027 pgtable_t pgtable;
1028 pmd_t orig_pmd;
1029 pgtable = pgtable_trans_huge_withdraw(tlb->mm);
1030 orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
1031 page = pmd_page(orig_pmd);
1032 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1033 page_remove_rmap(page);
1034 VM_BUG_ON(page_mapcount(page) < 0);
1035 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1036 VM_BUG_ON(!PageHead(page));
1037 tlb->mm->nr_ptes--;
1038 spin_unlock(&tlb->mm->page_table_lock);
1039 tlb_remove_page(tlb, page);
1040 pte_free(tlb->mm, pgtable);
1041 ret = 1;
1042 }
1043 return ret;
1044 }
1045
1046 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1047 unsigned long addr, unsigned long end,
1048 unsigned char *vec)
1049 {
1050 int ret = 0;
1051
1052 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1053 /*
1054 * All logical pages in the range are present
1055 * if backed by a huge page.
1056 */
1057 spin_unlock(&vma->vm_mm->page_table_lock);
1058 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1059 ret = 1;
1060 }
1061
1062 return ret;
1063 }
1064
1065 int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1066 unsigned long old_addr,
1067 unsigned long new_addr, unsigned long old_end,
1068 pmd_t *old_pmd, pmd_t *new_pmd)
1069 {
1070 int ret = 0;
1071 pmd_t pmd;
1072
1073 struct mm_struct *mm = vma->vm_mm;
1074
1075 if ((old_addr & ~HPAGE_PMD_MASK) ||
1076 (new_addr & ~HPAGE_PMD_MASK) ||
1077 old_end - old_addr < HPAGE_PMD_SIZE ||
1078 (new_vma->vm_flags & VM_NOHUGEPAGE))
1079 goto out;
1080
1081 /*
1082 * The destination pmd shouldn't be established, free_pgtables()
1083 * should have release it.
1084 */
1085 if (WARN_ON(!pmd_none(*new_pmd))) {
1086 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1087 goto out;
1088 }
1089
1090 ret = __pmd_trans_huge_lock(old_pmd, vma);
1091 if (ret == 1) {
1092 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1093 VM_BUG_ON(!pmd_none(*new_pmd));
1094 set_pmd_at(mm, new_addr, new_pmd, pmd);
1095 spin_unlock(&mm->page_table_lock);
1096 }
1097 out:
1098 return ret;
1099 }
1100
1101 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1102 unsigned long addr, pgprot_t newprot)
1103 {
1104 struct mm_struct *mm = vma->vm_mm;
1105 int ret = 0;
1106
1107 if (__pmd_trans_huge_lock(pmd, vma) == 1) {
1108 pmd_t entry;
1109 entry = pmdp_get_and_clear(mm, addr, pmd);
1110 entry = pmd_modify(entry, newprot);
1111 set_pmd_at(mm, addr, pmd, entry);
1112 spin_unlock(&vma->vm_mm->page_table_lock);
1113 ret = 1;
1114 }
1115
1116 return ret;
1117 }
1118
1119 /*
1120 * Returns 1 if a given pmd maps a stable (not under splitting) thp.
1121 * Returns -1 if it maps a thp under splitting. Returns 0 otherwise.
1122 *
1123 * Note that if it returns 1, this routine returns without unlocking page
1124 * table locks. So callers must unlock them.
1125 */
1126 int __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1127 {
1128 spin_lock(&vma->vm_mm->page_table_lock);
1129 if (likely(pmd_trans_huge(*pmd))) {
1130 if (unlikely(pmd_trans_splitting(*pmd))) {
1131 spin_unlock(&vma->vm_mm->page_table_lock);
1132 wait_split_huge_page(vma->anon_vma, pmd);
1133 return -1;
1134 } else {
1135 /* Thp mapped by 'pmd' is stable, so we can
1136 * handle it as it is. */
1137 return 1;
1138 }
1139 }
1140 spin_unlock(&vma->vm_mm->page_table_lock);
1141 return 0;
1142 }
1143
1144 pmd_t *page_check_address_pmd(struct page *page,
1145 struct mm_struct *mm,
1146 unsigned long address,
1147 enum page_check_address_pmd_flag flag)
1148 {
1149 pgd_t *pgd;
1150 pud_t *pud;
1151 pmd_t *pmd, *ret = NULL;
1152
1153 if (address & ~HPAGE_PMD_MASK)
1154 goto out;
1155
1156 pgd = pgd_offset(mm, address);
1157 if (!pgd_present(*pgd))
1158 goto out;
1159
1160 pud = pud_offset(pgd, address);
1161 if (!pud_present(*pud))
1162 goto out;
1163
1164 pmd = pmd_offset(pud, address);
1165 if (pmd_none(*pmd))
1166 goto out;
1167 if (pmd_page(*pmd) != page)
1168 goto out;
1169 /*
1170 * split_vma() may create temporary aliased mappings. There is
1171 * no risk as long as all huge pmd are found and have their
1172 * splitting bit set before __split_huge_page_refcount
1173 * runs. Finding the same huge pmd more than once during the
1174 * same rmap walk is not a problem.
1175 */
1176 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1177 pmd_trans_splitting(*pmd))
1178 goto out;
1179 if (pmd_trans_huge(*pmd)) {
1180 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1181 !pmd_trans_splitting(*pmd));
1182 ret = pmd;
1183 }
1184 out:
1185 return ret;
1186 }
1187
1188 static int __split_huge_page_splitting(struct page *page,
1189 struct vm_area_struct *vma,
1190 unsigned long address)
1191 {
1192 struct mm_struct *mm = vma->vm_mm;
1193 pmd_t *pmd;
1194 int ret = 0;
1195 /* For mmu_notifiers */
1196 const unsigned long mmun_start = address;
1197 const unsigned long mmun_end = address + HPAGE_PMD_SIZE;
1198
1199 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1200 spin_lock(&mm->page_table_lock);
1201 pmd = page_check_address_pmd(page, mm, address,
1202 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1203 if (pmd) {
1204 /*
1205 * We can't temporarily set the pmd to null in order
1206 * to split it, the pmd must remain marked huge at all
1207 * times or the VM won't take the pmd_trans_huge paths
1208 * and it won't wait on the anon_vma->root->mutex to
1209 * serialize against split_huge_page*.
1210 */
1211 pmdp_splitting_flush(vma, address, pmd);
1212 ret = 1;
1213 }
1214 spin_unlock(&mm->page_table_lock);
1215 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
1216
1217 return ret;
1218 }
1219
1220 static void __split_huge_page_refcount(struct page *page)
1221 {
1222 int i;
1223 struct zone *zone = page_zone(page);
1224 struct lruvec *lruvec;
1225 int tail_count = 0;
1226
1227 /* prevent PageLRU to go away from under us, and freeze lru stats */
1228 spin_lock_irq(&zone->lru_lock);
1229 lruvec = mem_cgroup_page_lruvec(page, zone);
1230
1231 compound_lock(page);
1232 /* complete memcg works before add pages to LRU */
1233 mem_cgroup_split_huge_fixup(page);
1234
1235 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1236 struct page *page_tail = page + i;
1237
1238 /* tail_page->_mapcount cannot change */
1239 BUG_ON(page_mapcount(page_tail) < 0);
1240 tail_count += page_mapcount(page_tail);
1241 /* check for overflow */
1242 BUG_ON(tail_count < 0);
1243 BUG_ON(atomic_read(&page_tail->_count) != 0);
1244 /*
1245 * tail_page->_count is zero and not changing from
1246 * under us. But get_page_unless_zero() may be running
1247 * from under us on the tail_page. If we used
1248 * atomic_set() below instead of atomic_add(), we
1249 * would then run atomic_set() concurrently with
1250 * get_page_unless_zero(), and atomic_set() is
1251 * implemented in C not using locked ops. spin_unlock
1252 * on x86 sometime uses locked ops because of PPro
1253 * errata 66, 92, so unless somebody can guarantee
1254 * atomic_set() here would be safe on all archs (and
1255 * not only on x86), it's safer to use atomic_add().
1256 */
1257 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1258 &page_tail->_count);
1259
1260 /* after clearing PageTail the gup refcount can be released */
1261 smp_mb();
1262
1263 /*
1264 * retain hwpoison flag of the poisoned tail page:
1265 * fix for the unsuitable process killed on Guest Machine(KVM)
1266 * by the memory-failure.
1267 */
1268 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1269 page_tail->flags |= (page->flags &
1270 ((1L << PG_referenced) |
1271 (1L << PG_swapbacked) |
1272 (1L << PG_mlocked) |
1273 (1L << PG_uptodate)));
1274 page_tail->flags |= (1L << PG_dirty);
1275
1276 /* clear PageTail before overwriting first_page */
1277 smp_wmb();
1278
1279 /*
1280 * __split_huge_page_splitting() already set the
1281 * splitting bit in all pmd that could map this
1282 * hugepage, that will ensure no CPU can alter the
1283 * mapcount on the head page. The mapcount is only
1284 * accounted in the head page and it has to be
1285 * transferred to all tail pages in the below code. So
1286 * for this code to be safe, the split the mapcount
1287 * can't change. But that doesn't mean userland can't
1288 * keep changing and reading the page contents while
1289 * we transfer the mapcount, so the pmd splitting
1290 * status is achieved setting a reserved bit in the
1291 * pmd, not by clearing the present bit.
1292 */
1293 page_tail->_mapcount = page->_mapcount;
1294
1295 BUG_ON(page_tail->mapping);
1296 page_tail->mapping = page->mapping;
1297
1298 page_tail->index = page->index + i;
1299
1300 BUG_ON(!PageAnon(page_tail));
1301 BUG_ON(!PageUptodate(page_tail));
1302 BUG_ON(!PageDirty(page_tail));
1303 BUG_ON(!PageSwapBacked(page_tail));
1304
1305 lru_add_page_tail(page, page_tail, lruvec);
1306 }
1307 atomic_sub(tail_count, &page->_count);
1308 BUG_ON(atomic_read(&page->_count) <= 0);
1309
1310 __mod_zone_page_state(zone, NR_ANON_TRANSPARENT_HUGEPAGES, -1);
1311 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1312
1313 ClearPageCompound(page);
1314 compound_unlock(page);
1315 spin_unlock_irq(&zone->lru_lock);
1316
1317 for (i = 1; i < HPAGE_PMD_NR; i++) {
1318 struct page *page_tail = page + i;
1319 BUG_ON(page_count(page_tail) <= 0);
1320 /*
1321 * Tail pages may be freed if there wasn't any mapping
1322 * like if add_to_swap() is running on a lru page that
1323 * had its mapping zapped. And freeing these pages
1324 * requires taking the lru_lock so we do the put_page
1325 * of the tail pages after the split is complete.
1326 */
1327 put_page(page_tail);
1328 }
1329
1330 /*
1331 * Only the head page (now become a regular page) is required
1332 * to be pinned by the caller.
1333 */
1334 BUG_ON(page_count(page) <= 0);
1335 }
1336
1337 static int __split_huge_page_map(struct page *page,
1338 struct vm_area_struct *vma,
1339 unsigned long address)
1340 {
1341 struct mm_struct *mm = vma->vm_mm;
1342 pmd_t *pmd, _pmd;
1343 int ret = 0, i;
1344 pgtable_t pgtable;
1345 unsigned long haddr;
1346
1347 spin_lock(&mm->page_table_lock);
1348 pmd = page_check_address_pmd(page, mm, address,
1349 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1350 if (pmd) {
1351 pgtable = pgtable_trans_huge_withdraw(mm);
1352 pmd_populate(mm, &_pmd, pgtable);
1353
1354 haddr = address;
1355 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1356 pte_t *pte, entry;
1357 BUG_ON(PageCompound(page+i));
1358 entry = mk_pte(page + i, vma->vm_page_prot);
1359 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1360 if (!pmd_write(*pmd))
1361 entry = pte_wrprotect(entry);
1362 else
1363 BUG_ON(page_mapcount(page) != 1);
1364 if (!pmd_young(*pmd))
1365 entry = pte_mkold(entry);
1366 pte = pte_offset_map(&_pmd, haddr);
1367 BUG_ON(!pte_none(*pte));
1368 set_pte_at(mm, haddr, pte, entry);
1369 pte_unmap(pte);
1370 }
1371
1372 smp_wmb(); /* make pte visible before pmd */
1373 /*
1374 * Up to this point the pmd is present and huge and
1375 * userland has the whole access to the hugepage
1376 * during the split (which happens in place). If we
1377 * overwrite the pmd with the not-huge version
1378 * pointing to the pte here (which of course we could
1379 * if all CPUs were bug free), userland could trigger
1380 * a small page size TLB miss on the small sized TLB
1381 * while the hugepage TLB entry is still established
1382 * in the huge TLB. Some CPU doesn't like that. See
1383 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1384 * Erratum 383 on page 93. Intel should be safe but is
1385 * also warns that it's only safe if the permission
1386 * and cache attributes of the two entries loaded in
1387 * the two TLB is identical (which should be the case
1388 * here). But it is generally safer to never allow
1389 * small and huge TLB entries for the same virtual
1390 * address to be loaded simultaneously. So instead of
1391 * doing "pmd_populate(); flush_tlb_range();" we first
1392 * mark the current pmd notpresent (atomically because
1393 * here the pmd_trans_huge and pmd_trans_splitting
1394 * must remain set at all times on the pmd until the
1395 * split is complete for this pmd), then we flush the
1396 * SMP TLB and finally we write the non-huge version
1397 * of the pmd entry with pmd_populate.
1398 */
1399 pmdp_invalidate(vma, address, pmd);
1400 pmd_populate(mm, pmd, pgtable);
1401 ret = 1;
1402 }
1403 spin_unlock(&mm->page_table_lock);
1404
1405 return ret;
1406 }
1407
1408 /* must be called with anon_vma->root->mutex hold */
1409 static void __split_huge_page(struct page *page,
1410 struct anon_vma *anon_vma)
1411 {
1412 int mapcount, mapcount2;
1413 pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1414 struct anon_vma_chain *avc;
1415
1416 BUG_ON(!PageHead(page));
1417 BUG_ON(PageTail(page));
1418
1419 mapcount = 0;
1420 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1421 struct vm_area_struct *vma = avc->vma;
1422 unsigned long addr = vma_address(page, vma);
1423 BUG_ON(is_vma_temporary_stack(vma));
1424 mapcount += __split_huge_page_splitting(page, vma, addr);
1425 }
1426 /*
1427 * It is critical that new vmas are added to the tail of the
1428 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1429 * and establishes a child pmd before
1430 * __split_huge_page_splitting() freezes the parent pmd (so if
1431 * we fail to prevent copy_huge_pmd() from running until the
1432 * whole __split_huge_page() is complete), we will still see
1433 * the newly established pmd of the child later during the
1434 * walk, to be able to set it as pmd_trans_splitting too.
1435 */
1436 if (mapcount != page_mapcount(page))
1437 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1438 mapcount, page_mapcount(page));
1439 BUG_ON(mapcount != page_mapcount(page));
1440
1441 __split_huge_page_refcount(page);
1442
1443 mapcount2 = 0;
1444 anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
1445 struct vm_area_struct *vma = avc->vma;
1446 unsigned long addr = vma_address(page, vma);
1447 BUG_ON(is_vma_temporary_stack(vma));
1448 mapcount2 += __split_huge_page_map(page, vma, addr);
1449 }
1450 if (mapcount != mapcount2)
1451 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1452 mapcount, mapcount2, page_mapcount(page));
1453 BUG_ON(mapcount != mapcount2);
1454 }
1455
1456 int split_huge_page(struct page *page)
1457 {
1458 struct anon_vma *anon_vma;
1459 int ret = 1;
1460
1461 BUG_ON(!PageAnon(page));
1462 anon_vma = page_lock_anon_vma(page);
1463 if (!anon_vma)
1464 goto out;
1465 ret = 0;
1466 if (!PageCompound(page))
1467 goto out_unlock;
1468
1469 BUG_ON(!PageSwapBacked(page));
1470 __split_huge_page(page, anon_vma);
1471 count_vm_event(THP_SPLIT);
1472
1473 BUG_ON(PageCompound(page));
1474 out_unlock:
1475 page_unlock_anon_vma(anon_vma);
1476 out:
1477 return ret;
1478 }
1479
1480 #define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1481
1482 int hugepage_madvise(struct vm_area_struct *vma,
1483 unsigned long *vm_flags, int advice)
1484 {
1485 struct mm_struct *mm = vma->vm_mm;
1486
1487 switch (advice) {
1488 case MADV_HUGEPAGE:
1489 /*
1490 * Be somewhat over-protective like KSM for now!
1491 */
1492 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
1493 return -EINVAL;
1494 if (mm->def_flags & VM_NOHUGEPAGE)
1495 return -EINVAL;
1496 *vm_flags &= ~VM_NOHUGEPAGE;
1497 *vm_flags |= VM_HUGEPAGE;
1498 /*
1499 * If the vma become good for khugepaged to scan,
1500 * register it here without waiting a page fault that
1501 * may not happen any time soon.
1502 */
1503 if (unlikely(khugepaged_enter_vma_merge(vma)))
1504 return -ENOMEM;
1505 break;
1506 case MADV_NOHUGEPAGE:
1507 /*
1508 * Be somewhat over-protective like KSM for now!
1509 */
1510 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
1511 return -EINVAL;
1512 *vm_flags &= ~VM_HUGEPAGE;
1513 *vm_flags |= VM_NOHUGEPAGE;
1514 /*
1515 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1516 * this vma even if we leave the mm registered in khugepaged if
1517 * it got registered before VM_NOHUGEPAGE was set.
1518 */
1519 break;
1520 }
1521
1522 return 0;
1523 }
1524
1525 static int __init khugepaged_slab_init(void)
1526 {
1527 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1528 sizeof(struct mm_slot),
1529 __alignof__(struct mm_slot), 0, NULL);
1530 if (!mm_slot_cache)
1531 return -ENOMEM;
1532
1533 return 0;
1534 }
1535
1536 static void __init khugepaged_slab_free(void)
1537 {
1538 kmem_cache_destroy(mm_slot_cache);
1539 mm_slot_cache = NULL;
1540 }
1541
1542 static inline struct mm_slot *alloc_mm_slot(void)
1543 {
1544 if (!mm_slot_cache) /* initialization failed */
1545 return NULL;
1546 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1547 }
1548
1549 static inline void free_mm_slot(struct mm_slot *mm_slot)
1550 {
1551 kmem_cache_free(mm_slot_cache, mm_slot);
1552 }
1553
1554 static int __init mm_slots_hash_init(void)
1555 {
1556 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1557 GFP_KERNEL);
1558 if (!mm_slots_hash)
1559 return -ENOMEM;
1560 return 0;
1561 }
1562
1563 #if 0
1564 static void __init mm_slots_hash_free(void)
1565 {
1566 kfree(mm_slots_hash);
1567 mm_slots_hash = NULL;
1568 }
1569 #endif
1570
1571 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1572 {
1573 struct mm_slot *mm_slot;
1574 struct hlist_head *bucket;
1575 struct hlist_node *node;
1576
1577 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1578 % MM_SLOTS_HASH_HEADS];
1579 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1580 if (mm == mm_slot->mm)
1581 return mm_slot;
1582 }
1583 return NULL;
1584 }
1585
1586 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1587 struct mm_slot *mm_slot)
1588 {
1589 struct hlist_head *bucket;
1590
1591 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1592 % MM_SLOTS_HASH_HEADS];
1593 mm_slot->mm = mm;
1594 hlist_add_head(&mm_slot->hash, bucket);
1595 }
1596
1597 static inline int khugepaged_test_exit(struct mm_struct *mm)
1598 {
1599 return atomic_read(&mm->mm_users) == 0;
1600 }
1601
1602 int __khugepaged_enter(struct mm_struct *mm)
1603 {
1604 struct mm_slot *mm_slot;
1605 int wakeup;
1606
1607 mm_slot = alloc_mm_slot();
1608 if (!mm_slot)
1609 return -ENOMEM;
1610
1611 /* __khugepaged_exit() must not run from under us */
1612 VM_BUG_ON(khugepaged_test_exit(mm));
1613 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1614 free_mm_slot(mm_slot);
1615 return 0;
1616 }
1617
1618 spin_lock(&khugepaged_mm_lock);
1619 insert_to_mm_slots_hash(mm, mm_slot);
1620 /*
1621 * Insert just behind the scanning cursor, to let the area settle
1622 * down a little.
1623 */
1624 wakeup = list_empty(&khugepaged_scan.mm_head);
1625 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1626 spin_unlock(&khugepaged_mm_lock);
1627
1628 atomic_inc(&mm->mm_count);
1629 if (wakeup)
1630 wake_up_interruptible(&khugepaged_wait);
1631
1632 return 0;
1633 }
1634
1635 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1636 {
1637 unsigned long hstart, hend;
1638 if (!vma->anon_vma)
1639 /*
1640 * Not yet faulted in so we will register later in the
1641 * page fault if needed.
1642 */
1643 return 0;
1644 if (vma->vm_ops)
1645 /* khugepaged not yet working on file or special mappings */
1646 return 0;
1647 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1648 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1649 hend = vma->vm_end & HPAGE_PMD_MASK;
1650 if (hstart < hend)
1651 return khugepaged_enter(vma);
1652 return 0;
1653 }
1654
1655 void __khugepaged_exit(struct mm_struct *mm)
1656 {
1657 struct mm_slot *mm_slot;
1658 int free = 0;
1659
1660 spin_lock(&khugepaged_mm_lock);
1661 mm_slot = get_mm_slot(mm);
1662 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1663 hlist_del(&mm_slot->hash);
1664 list_del(&mm_slot->mm_node);
1665 free = 1;
1666 }
1667 spin_unlock(&khugepaged_mm_lock);
1668
1669 if (free) {
1670 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1671 free_mm_slot(mm_slot);
1672 mmdrop(mm);
1673 } else if (mm_slot) {
1674 /*
1675 * This is required to serialize against
1676 * khugepaged_test_exit() (which is guaranteed to run
1677 * under mmap sem read mode). Stop here (after we
1678 * return all pagetables will be destroyed) until
1679 * khugepaged has finished working on the pagetables
1680 * under the mmap_sem.
1681 */
1682 down_write(&mm->mmap_sem);
1683 up_write(&mm->mmap_sem);
1684 }
1685 }
1686
1687 static void release_pte_page(struct page *page)
1688 {
1689 /* 0 stands for page_is_file_cache(page) == false */
1690 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1691 unlock_page(page);
1692 putback_lru_page(page);
1693 }
1694
1695 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1696 {
1697 while (--_pte >= pte) {
1698 pte_t pteval = *_pte;
1699 if (!pte_none(pteval))
1700 release_pte_page(pte_page(pteval));
1701 }
1702 }
1703
1704 static void release_all_pte_pages(pte_t *pte)
1705 {
1706 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1707 }
1708
1709 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1710 unsigned long address,
1711 pte_t *pte)
1712 {
1713 struct page *page;
1714 pte_t *_pte;
1715 int referenced = 0, isolated = 0, none = 0;
1716 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1717 _pte++, address += PAGE_SIZE) {
1718 pte_t pteval = *_pte;
1719 if (pte_none(pteval)) {
1720 if (++none <= khugepaged_max_ptes_none)
1721 continue;
1722 else {
1723 release_pte_pages(pte, _pte);
1724 goto out;
1725 }
1726 }
1727 if (!pte_present(pteval) || !pte_write(pteval)) {
1728 release_pte_pages(pte, _pte);
1729 goto out;
1730 }
1731 page = vm_normal_page(vma, address, pteval);
1732 if (unlikely(!page)) {
1733 release_pte_pages(pte, _pte);
1734 goto out;
1735 }
1736 VM_BUG_ON(PageCompound(page));
1737 BUG_ON(!PageAnon(page));
1738 VM_BUG_ON(!PageSwapBacked(page));
1739
1740 /* cannot use mapcount: can't collapse if there's a gup pin */
1741 if (page_count(page) != 1) {
1742 release_pte_pages(pte, _pte);
1743 goto out;
1744 }
1745 /*
1746 * We can do it before isolate_lru_page because the
1747 * page can't be freed from under us. NOTE: PG_lock
1748 * is needed to serialize against split_huge_page
1749 * when invoked from the VM.
1750 */
1751 if (!trylock_page(page)) {
1752 release_pte_pages(pte, _pte);
1753 goto out;
1754 }
1755 /*
1756 * Isolate the page to avoid collapsing an hugepage
1757 * currently in use by the VM.
1758 */
1759 if (isolate_lru_page(page)) {
1760 unlock_page(page);
1761 release_pte_pages(pte, _pte);
1762 goto out;
1763 }
1764 /* 0 stands for page_is_file_cache(page) == false */
1765 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1766 VM_BUG_ON(!PageLocked(page));
1767 VM_BUG_ON(PageLRU(page));
1768
1769 /* If there is no mapped pte young don't collapse the page */
1770 if (pte_young(pteval) || PageReferenced(page) ||
1771 mmu_notifier_test_young(vma->vm_mm, address))
1772 referenced = 1;
1773 }
1774 if (unlikely(!referenced))
1775 release_all_pte_pages(pte);
1776 else
1777 isolated = 1;
1778 out:
1779 return isolated;
1780 }
1781
1782 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1783 struct vm_area_struct *vma,
1784 unsigned long address,
1785 spinlock_t *ptl)
1786 {
1787 pte_t *_pte;
1788 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1789 pte_t pteval = *_pte;
1790 struct page *src_page;
1791
1792 if (pte_none(pteval)) {
1793 clear_user_highpage(page, address);
1794 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1795 } else {
1796 src_page = pte_page(pteval);
1797 copy_user_highpage(page, src_page, address, vma);
1798 VM_BUG_ON(page_mapcount(src_page) != 1);
1799 release_pte_page(src_page);
1800 /*
1801 * ptl mostly unnecessary, but preempt has to
1802 * be disabled to update the per-cpu stats
1803 * inside page_remove_rmap().
1804 */
1805 spin_lock(ptl);
1806 /*
1807 * paravirt calls inside pte_clear here are
1808 * superfluous.
1809 */
1810 pte_clear(vma->vm_mm, address, _pte);
1811 page_remove_rmap(src_page);
1812 spin_unlock(ptl);
1813 free_page_and_swap_cache(src_page);
1814 }
1815
1816 address += PAGE_SIZE;
1817 page++;
1818 }
1819 }
1820
1821 static void khugepaged_alloc_sleep(void)
1822 {
1823 wait_event_freezable_timeout(khugepaged_wait, false,
1824 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
1825 }
1826
1827 #ifdef CONFIG_NUMA
1828 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
1829 {
1830 if (IS_ERR(*hpage)) {
1831 if (!*wait)
1832 return false;
1833
1834 *wait = false;
1835 *hpage = NULL;
1836 khugepaged_alloc_sleep();
1837 } else if (*hpage) {
1838 put_page(*hpage);
1839 *hpage = NULL;
1840 }
1841
1842 return true;
1843 }
1844
1845 static struct page
1846 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
1847 struct vm_area_struct *vma, unsigned long address,
1848 int node)
1849 {
1850 VM_BUG_ON(*hpage);
1851 /*
1852 * Allocate the page while the vma is still valid and under
1853 * the mmap_sem read mode so there is no memory allocation
1854 * later when we take the mmap_sem in write mode. This is more
1855 * friendly behavior (OTOH it may actually hide bugs) to
1856 * filesystems in userland with daemons allocating memory in
1857 * the userland I/O paths. Allocating memory with the
1858 * mmap_sem in read mode is good idea also to allow greater
1859 * scalability.
1860 */
1861 *hpage = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1862 node, __GFP_OTHER_NODE);
1863
1864 /*
1865 * After allocating the hugepage, release the mmap_sem read lock in
1866 * preparation for taking it in write mode.
1867 */
1868 up_read(&mm->mmap_sem);
1869 if (unlikely(!*hpage)) {
1870 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1871 *hpage = ERR_PTR(-ENOMEM);
1872 return NULL;
1873 }
1874
1875 count_vm_event(THP_COLLAPSE_ALLOC);
1876 return *hpage;
1877 }
1878 #else
1879 static struct page *khugepaged_alloc_hugepage(bool *wait)
1880 {
1881 struct page *hpage;
1882
1883 do {
1884 hpage = alloc_hugepage(khugepaged_defrag());
1885 if (!hpage) {
1886 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
1887 if (!*wait)
1888 return NULL;
1889
1890 *wait = false;
1891 khugepaged_alloc_sleep();
1892 } else
1893 count_vm_event(THP_COLLAPSE_ALLOC);
1894 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
1895
1896 return hpage;
1897 }
1898
1899 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
1900 {
1901 if (!*hpage)
1902 *hpage = khugepaged_alloc_hugepage(wait);
1903
1904 if (unlikely(!*hpage))
1905 return false;
1906
1907 return true;
1908 }
1909
1910 static struct page
1911 *khugepaged_alloc_page(struct page **hpage, struct mm_struct *mm,
1912 struct vm_area_struct *vma, unsigned long address,
1913 int node)
1914 {
1915 up_read(&mm->mmap_sem);
1916 VM_BUG_ON(!*hpage);
1917 return *hpage;
1918 }
1919 #endif
1920
1921 static void collapse_huge_page(struct mm_struct *mm,
1922 unsigned long address,
1923 struct page **hpage,
1924 struct vm_area_struct *vma,
1925 int node)
1926 {
1927 pgd_t *pgd;
1928 pud_t *pud;
1929 pmd_t *pmd, _pmd;
1930 pte_t *pte;
1931 pgtable_t pgtable;
1932 struct page *new_page;
1933 spinlock_t *ptl;
1934 int isolated;
1935 unsigned long hstart, hend;
1936 unsigned long mmun_start; /* For mmu_notifiers */
1937 unsigned long mmun_end; /* For mmu_notifiers */
1938
1939 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1940
1941 /* release the mmap_sem read lock. */
1942 new_page = khugepaged_alloc_page(hpage, mm, vma, address, node);
1943 if (!new_page)
1944 return;
1945
1946 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
1947 return;
1948
1949 /*
1950 * Prevent all access to pagetables with the exception of
1951 * gup_fast later hanlded by the ptep_clear_flush and the VM
1952 * handled by the anon_vma lock + PG_lock.
1953 */
1954 down_write(&mm->mmap_sem);
1955 if (unlikely(khugepaged_test_exit(mm)))
1956 goto out;
1957
1958 vma = find_vma(mm, address);
1959 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1960 hend = vma->vm_end & HPAGE_PMD_MASK;
1961 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1962 goto out;
1963
1964 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1965 (vma->vm_flags & VM_NOHUGEPAGE))
1966 goto out;
1967
1968 if (!vma->anon_vma || vma->vm_ops)
1969 goto out;
1970 if (is_vma_temporary_stack(vma))
1971 goto out;
1972 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
1973
1974 pgd = pgd_offset(mm, address);
1975 if (!pgd_present(*pgd))
1976 goto out;
1977
1978 pud = pud_offset(pgd, address);
1979 if (!pud_present(*pud))
1980 goto out;
1981
1982 pmd = pmd_offset(pud, address);
1983 /* pmd can't go away or become huge under us */
1984 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1985 goto out;
1986
1987 anon_vma_lock(vma->anon_vma);
1988
1989 pte = pte_offset_map(pmd, address);
1990 ptl = pte_lockptr(mm, pmd);
1991
1992 mmun_start = address;
1993 mmun_end = address + HPAGE_PMD_SIZE;
1994 mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
1995 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1996 /*
1997 * After this gup_fast can't run anymore. This also removes
1998 * any huge TLB entry from the CPU so we won't allow
1999 * huge and small TLB entries for the same virtual address
2000 * to avoid the risk of CPU bugs in that area.
2001 */
2002 _pmd = pmdp_clear_flush(vma, address, pmd);
2003 spin_unlock(&mm->page_table_lock);
2004 mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
2005
2006 spin_lock(ptl);
2007 isolated = __collapse_huge_page_isolate(vma, address, pte);
2008 spin_unlock(ptl);
2009
2010 if (unlikely(!isolated)) {
2011 pte_unmap(pte);
2012 spin_lock(&mm->page_table_lock);
2013 BUG_ON(!pmd_none(*pmd));
2014 set_pmd_at(mm, address, pmd, _pmd);
2015 spin_unlock(&mm->page_table_lock);
2016 anon_vma_unlock(vma->anon_vma);
2017 goto out;
2018 }
2019
2020 /*
2021 * All pages are isolated and locked so anon_vma rmap
2022 * can't run anymore.
2023 */
2024 anon_vma_unlock(vma->anon_vma);
2025
2026 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
2027 pte_unmap(pte);
2028 __SetPageUptodate(new_page);
2029 pgtable = pmd_pgtable(_pmd);
2030
2031 _pmd = mk_pmd(new_page, vma->vm_page_prot);
2032 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
2033 _pmd = pmd_mkhuge(_pmd);
2034
2035 /*
2036 * spin_lock() below is not the equivalent of smp_wmb(), so
2037 * this is needed to avoid the copy_huge_page writes to become
2038 * visible after the set_pmd_at() write.
2039 */
2040 smp_wmb();
2041
2042 spin_lock(&mm->page_table_lock);
2043 BUG_ON(!pmd_none(*pmd));
2044 page_add_new_anon_rmap(new_page, vma, address);
2045 set_pmd_at(mm, address, pmd, _pmd);
2046 update_mmu_cache_pmd(vma, address, pmd);
2047 pgtable_trans_huge_deposit(mm, pgtable);
2048 spin_unlock(&mm->page_table_lock);
2049
2050 *hpage = NULL;
2051
2052 khugepaged_pages_collapsed++;
2053 out_up_write:
2054 up_write(&mm->mmap_sem);
2055 return;
2056
2057 out:
2058 mem_cgroup_uncharge_page(new_page);
2059 goto out_up_write;
2060 }
2061
2062 static int khugepaged_scan_pmd(struct mm_struct *mm,
2063 struct vm_area_struct *vma,
2064 unsigned long address,
2065 struct page **hpage)
2066 {
2067 pgd_t *pgd;
2068 pud_t *pud;
2069 pmd_t *pmd;
2070 pte_t *pte, *_pte;
2071 int ret = 0, referenced = 0, none = 0;
2072 struct page *page;
2073 unsigned long _address;
2074 spinlock_t *ptl;
2075 int node = -1;
2076
2077 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2078
2079 pgd = pgd_offset(mm, address);
2080 if (!pgd_present(*pgd))
2081 goto out;
2082
2083 pud = pud_offset(pgd, address);
2084 if (!pud_present(*pud))
2085 goto out;
2086
2087 pmd = pmd_offset(pud, address);
2088 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
2089 goto out;
2090
2091 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2092 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2093 _pte++, _address += PAGE_SIZE) {
2094 pte_t pteval = *_pte;
2095 if (pte_none(pteval)) {
2096 if (++none <= khugepaged_max_ptes_none)
2097 continue;
2098 else
2099 goto out_unmap;
2100 }
2101 if (!pte_present(pteval) || !pte_write(pteval))
2102 goto out_unmap;
2103 page = vm_normal_page(vma, _address, pteval);
2104 if (unlikely(!page))
2105 goto out_unmap;
2106 /*
2107 * Chose the node of the first page. This could
2108 * be more sophisticated and look at more pages,
2109 * but isn't for now.
2110 */
2111 if (node == -1)
2112 node = page_to_nid(page);
2113 VM_BUG_ON(PageCompound(page));
2114 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2115 goto out_unmap;
2116 /* cannot use mapcount: can't collapse if there's a gup pin */
2117 if (page_count(page) != 1)
2118 goto out_unmap;
2119 if (pte_young(pteval) || PageReferenced(page) ||
2120 mmu_notifier_test_young(vma->vm_mm, address))
2121 referenced = 1;
2122 }
2123 if (referenced)
2124 ret = 1;
2125 out_unmap:
2126 pte_unmap_unlock(pte, ptl);
2127 if (ret)
2128 /* collapse_huge_page will return with the mmap_sem released */
2129 collapse_huge_page(mm, address, hpage, vma, node);
2130 out:
2131 return ret;
2132 }
2133
2134 static void collect_mm_slot(struct mm_slot *mm_slot)
2135 {
2136 struct mm_struct *mm = mm_slot->mm;
2137
2138 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2139
2140 if (khugepaged_test_exit(mm)) {
2141 /* free mm_slot */
2142 hlist_del(&mm_slot->hash);
2143 list_del(&mm_slot->mm_node);
2144
2145 /*
2146 * Not strictly needed because the mm exited already.
2147 *
2148 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2149 */
2150
2151 /* khugepaged_mm_lock actually not necessary for the below */
2152 free_mm_slot(mm_slot);
2153 mmdrop(mm);
2154 }
2155 }
2156
2157 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2158 struct page **hpage)
2159 __releases(&khugepaged_mm_lock)
2160 __acquires(&khugepaged_mm_lock)
2161 {
2162 struct mm_slot *mm_slot;
2163 struct mm_struct *mm;
2164 struct vm_area_struct *vma;
2165 int progress = 0;
2166
2167 VM_BUG_ON(!pages);
2168 VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
2169
2170 if (khugepaged_scan.mm_slot)
2171 mm_slot = khugepaged_scan.mm_slot;
2172 else {
2173 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2174 struct mm_slot, mm_node);
2175 khugepaged_scan.address = 0;
2176 khugepaged_scan.mm_slot = mm_slot;
2177 }
2178 spin_unlock(&khugepaged_mm_lock);
2179
2180 mm = mm_slot->mm;
2181 down_read(&mm->mmap_sem);
2182 if (unlikely(khugepaged_test_exit(mm)))
2183 vma = NULL;
2184 else
2185 vma = find_vma(mm, khugepaged_scan.address);
2186
2187 progress++;
2188 for (; vma; vma = vma->vm_next) {
2189 unsigned long hstart, hend;
2190
2191 cond_resched();
2192 if (unlikely(khugepaged_test_exit(mm))) {
2193 progress++;
2194 break;
2195 }
2196
2197 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2198 !khugepaged_always()) ||
2199 (vma->vm_flags & VM_NOHUGEPAGE)) {
2200 skip:
2201 progress++;
2202 continue;
2203 }
2204 if (!vma->anon_vma || vma->vm_ops)
2205 goto skip;
2206 if (is_vma_temporary_stack(vma))
2207 goto skip;
2208 VM_BUG_ON(vma->vm_flags & VM_NO_THP);
2209
2210 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2211 hend = vma->vm_end & HPAGE_PMD_MASK;
2212 if (hstart >= hend)
2213 goto skip;
2214 if (khugepaged_scan.address > hend)
2215 goto skip;
2216 if (khugepaged_scan.address < hstart)
2217 khugepaged_scan.address = hstart;
2218 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2219
2220 while (khugepaged_scan.address < hend) {
2221 int ret;
2222 cond_resched();
2223 if (unlikely(khugepaged_test_exit(mm)))
2224 goto breakouterloop;
2225
2226 VM_BUG_ON(khugepaged_scan.address < hstart ||
2227 khugepaged_scan.address + HPAGE_PMD_SIZE >
2228 hend);
2229 ret = khugepaged_scan_pmd(mm, vma,
2230 khugepaged_scan.address,
2231 hpage);
2232 /* move to next address */
2233 khugepaged_scan.address += HPAGE_PMD_SIZE;
2234 progress += HPAGE_PMD_NR;
2235 if (ret)
2236 /* we released mmap_sem so break loop */
2237 goto breakouterloop_mmap_sem;
2238 if (progress >= pages)
2239 goto breakouterloop;
2240 }
2241 }
2242 breakouterloop:
2243 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2244 breakouterloop_mmap_sem:
2245
2246 spin_lock(&khugepaged_mm_lock);
2247 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2248 /*
2249 * Release the current mm_slot if this mm is about to die, or
2250 * if we scanned all vmas of this mm.
2251 */
2252 if (khugepaged_test_exit(mm) || !vma) {
2253 /*
2254 * Make sure that if mm_users is reaching zero while
2255 * khugepaged runs here, khugepaged_exit will find
2256 * mm_slot not pointing to the exiting mm.
2257 */
2258 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2259 khugepaged_scan.mm_slot = list_entry(
2260 mm_slot->mm_node.next,
2261 struct mm_slot, mm_node);
2262 khugepaged_scan.address = 0;
2263 } else {
2264 khugepaged_scan.mm_slot = NULL;
2265 khugepaged_full_scans++;
2266 }
2267
2268 collect_mm_slot(mm_slot);
2269 }
2270
2271 return progress;
2272 }
2273
2274 static int khugepaged_has_work(void)
2275 {
2276 return !list_empty(&khugepaged_scan.mm_head) &&
2277 khugepaged_enabled();
2278 }
2279
2280 static int khugepaged_wait_event(void)
2281 {
2282 return !list_empty(&khugepaged_scan.mm_head) ||
2283 kthread_should_stop();
2284 }
2285
2286 static void khugepaged_do_scan(void)
2287 {
2288 struct page *hpage = NULL;
2289 unsigned int progress = 0, pass_through_head = 0;
2290 unsigned int pages = khugepaged_pages_to_scan;
2291 bool wait = true;
2292
2293 barrier(); /* write khugepaged_pages_to_scan to local stack */
2294
2295 while (progress < pages) {
2296 if (!khugepaged_prealloc_page(&hpage, &wait))
2297 break;
2298
2299 cond_resched();
2300
2301 if (unlikely(kthread_should_stop() || freezing(current)))
2302 break;
2303
2304 spin_lock(&khugepaged_mm_lock);
2305 if (!khugepaged_scan.mm_slot)
2306 pass_through_head++;
2307 if (khugepaged_has_work() &&
2308 pass_through_head < 2)
2309 progress += khugepaged_scan_mm_slot(pages - progress,
2310 &hpage);
2311 else
2312 progress = pages;
2313 spin_unlock(&khugepaged_mm_lock);
2314 }
2315
2316 if (!IS_ERR_OR_NULL(hpage))
2317 put_page(hpage);
2318 }
2319
2320 static void khugepaged_wait_work(void)
2321 {
2322 try_to_freeze();
2323
2324 if (khugepaged_has_work()) {
2325 if (!khugepaged_scan_sleep_millisecs)
2326 return;
2327
2328 wait_event_freezable_timeout(khugepaged_wait,
2329 kthread_should_stop(),
2330 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
2331 return;
2332 }
2333
2334 if (khugepaged_enabled())
2335 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2336 }
2337
2338 static int khugepaged(void *none)
2339 {
2340 struct mm_slot *mm_slot;
2341
2342 set_freezable();
2343 set_user_nice(current, 19);
2344
2345 while (!kthread_should_stop()) {
2346 khugepaged_do_scan();
2347 khugepaged_wait_work();
2348 }
2349
2350 spin_lock(&khugepaged_mm_lock);
2351 mm_slot = khugepaged_scan.mm_slot;
2352 khugepaged_scan.mm_slot = NULL;
2353 if (mm_slot)
2354 collect_mm_slot(mm_slot);
2355 spin_unlock(&khugepaged_mm_lock);
2356 return 0;
2357 }
2358
2359 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2360 {
2361 struct page *page;
2362
2363 spin_lock(&mm->page_table_lock);
2364 if (unlikely(!pmd_trans_huge(*pmd))) {
2365 spin_unlock(&mm->page_table_lock);
2366 return;
2367 }
2368 page = pmd_page(*pmd);
2369 VM_BUG_ON(!page_count(page));
2370 get_page(page);
2371 spin_unlock(&mm->page_table_lock);
2372
2373 split_huge_page(page);
2374
2375 put_page(page);
2376 BUG_ON(pmd_trans_huge(*pmd));
2377 }
2378
2379 static void split_huge_page_address(struct mm_struct *mm,
2380 unsigned long address)
2381 {
2382 pgd_t *pgd;
2383 pud_t *pud;
2384 pmd_t *pmd;
2385
2386 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2387
2388 pgd = pgd_offset(mm, address);
2389 if (!pgd_present(*pgd))
2390 return;
2391
2392 pud = pud_offset(pgd, address);
2393 if (!pud_present(*pud))
2394 return;
2395
2396 pmd = pmd_offset(pud, address);
2397 if (!pmd_present(*pmd))
2398 return;
2399 /*
2400 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2401 * materialize from under us.
2402 */
2403 split_huge_page_pmd(mm, pmd);
2404 }
2405
2406 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2407 unsigned long start,
2408 unsigned long end,
2409 long adjust_next)
2410 {
2411 /*
2412 * If the new start address isn't hpage aligned and it could
2413 * previously contain an hugepage: check if we need to split
2414 * an huge pmd.
2415 */
2416 if (start & ~HPAGE_PMD_MASK &&
2417 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2418 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2419 split_huge_page_address(vma->vm_mm, start);
2420
2421 /*
2422 * If the new end address isn't hpage aligned and it could
2423 * previously contain an hugepage: check if we need to split
2424 * an huge pmd.
2425 */
2426 if (end & ~HPAGE_PMD_MASK &&
2427 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2428 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2429 split_huge_page_address(vma->vm_mm, end);
2430
2431 /*
2432 * If we're also updating the vma->vm_next->vm_start, if the new
2433 * vm_next->vm_start isn't page aligned and it could previously
2434 * contain an hugepage: check if we need to split an huge pmd.
2435 */
2436 if (adjust_next > 0) {
2437 struct vm_area_struct *next = vma->vm_next;
2438 unsigned long nstart = next->vm_start;
2439 nstart += adjust_next << PAGE_SHIFT;
2440 if (nstart & ~HPAGE_PMD_MASK &&
2441 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2442 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2443 split_huge_page_address(next->vm_mm, nstart);
2444 }
2445 }
Linux 2.6 ibm-acpi/thinkpad-acpi driver git tree