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ethtool: Change ETHTOOL_PHYS_ID implementation to allow dropping RTNL
[linux/fpc-iii.git] / mm / huge_memory.c
blob0a619e0e2e0bd26da68b26948f065e1be72a8aa0
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, gfp_t extra_gfp)
647 {
648 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
649 }
650
651 static inline struct page *alloc_hugepage_vma(int defrag,
652 struct vm_area_struct *vma,
653 unsigned long haddr, int nd,
654 gfp_t extra_gfp)
655 {
656 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
657 HPAGE_PMD_ORDER, vma, haddr, nd);
658 }
659
660 #ifndef CONFIG_NUMA
661 static inline struct page *alloc_hugepage(int defrag)
662 {
663 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
664 HPAGE_PMD_ORDER);
665 }
666 #endif
667
668 int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
669 unsigned long address, pmd_t *pmd,
670 unsigned int flags)
671 {
672 struct page *page;
673 unsigned long haddr = address & HPAGE_PMD_MASK;
674 pte_t *pte;
675
676 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
677 if (unlikely(anon_vma_prepare(vma)))
678 return VM_FAULT_OOM;
679 if (unlikely(khugepaged_enter(vma)))
680 return VM_FAULT_OOM;
681 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
682 vma, haddr, numa_node_id(), 0);
683 if (unlikely(!page))
684 goto out;
685 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
686 put_page(page);
687 goto out;
688 }
689
690 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
691 }
692 out:
693 /*
694 * Use __pte_alloc instead of pte_alloc_map, because we can't
695 * run pte_offset_map on the pmd, if an huge pmd could
696 * materialize from under us from a different thread.
697 */
698 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
699 return VM_FAULT_OOM;
700 /* if an huge pmd materialized from under us just retry later */
701 if (unlikely(pmd_trans_huge(*pmd)))
702 return 0;
703 /*
704 * A regular pmd is established and it can't morph into a huge pmd
705 * from under us anymore at this point because we hold the mmap_sem
706 * read mode and khugepaged takes it in write mode. So now it's
707 * safe to run pte_offset_map().
708 */
709 pte = pte_offset_map(pmd, address);
710 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
711 }
712
713 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
714 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
715 struct vm_area_struct *vma)
716 {
717 struct page *src_page;
718 pmd_t pmd;
719 pgtable_t pgtable;
720 int ret;
721
722 ret = -ENOMEM;
723 pgtable = pte_alloc_one(dst_mm, addr);
724 if (unlikely(!pgtable))
725 goto out;
726
727 spin_lock(&dst_mm->page_table_lock);
728 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
729
730 ret = -EAGAIN;
731 pmd = *src_pmd;
732 if (unlikely(!pmd_trans_huge(pmd))) {
733 pte_free(dst_mm, pgtable);
734 goto out_unlock;
735 }
736 if (unlikely(pmd_trans_splitting(pmd))) {
737 /* split huge page running from under us */
738 spin_unlock(&src_mm->page_table_lock);
739 spin_unlock(&dst_mm->page_table_lock);
740 pte_free(dst_mm, pgtable);
741
742 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
743 goto out;
744 }
745 src_page = pmd_page(pmd);
746 VM_BUG_ON(!PageHead(src_page));
747 get_page(src_page);
748 page_dup_rmap(src_page);
749 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
750
751 pmdp_set_wrprotect(src_mm, addr, src_pmd);
752 pmd = pmd_mkold(pmd_wrprotect(pmd));
753 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
754 prepare_pmd_huge_pte(pgtable, dst_mm);
755
756 ret = 0;
757 out_unlock:
758 spin_unlock(&src_mm->page_table_lock);
759 spin_unlock(&dst_mm->page_table_lock);
760 out:
761 return ret;
762 }
763
764 /* no "address" argument so destroys page coloring of some arch */
765 pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
766 {
767 pgtable_t pgtable;
768
769 assert_spin_locked(&mm->page_table_lock);
770
771 /* FIFO */
772 pgtable = mm->pmd_huge_pte;
773 if (list_empty(&pgtable->lru))
774 mm->pmd_huge_pte = NULL;
775 else {
776 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
777 struct page, lru);
778 list_del(&pgtable->lru);
779 }
780 return pgtable;
781 }
782
783 static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
784 struct vm_area_struct *vma,
785 unsigned long address,
786 pmd_t *pmd, pmd_t orig_pmd,
787 struct page *page,
788 unsigned long haddr)
789 {
790 pgtable_t pgtable;
791 pmd_t _pmd;
792 int ret = 0, i;
793 struct page **pages;
794
795 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
796 GFP_KERNEL);
797 if (unlikely(!pages)) {
798 ret |= VM_FAULT_OOM;
799 goto out;
800 }
801
802 for (i = 0; i < HPAGE_PMD_NR; i++) {
803 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
804 __GFP_OTHER_NODE,
805 vma, address, page_to_nid(page));
806 if (unlikely(!pages[i] ||
807 mem_cgroup_newpage_charge(pages[i], mm,
808 GFP_KERNEL))) {
809 if (pages[i])
810 put_page(pages[i]);
811 mem_cgroup_uncharge_start();
812 while (--i >= 0) {
813 mem_cgroup_uncharge_page(pages[i]);
814 put_page(pages[i]);
815 }
816 mem_cgroup_uncharge_end();
817 kfree(pages);
818 ret |= VM_FAULT_OOM;
819 goto out;
820 }
821 }
822
823 for (i = 0; i < HPAGE_PMD_NR; i++) {
824 copy_user_highpage(pages[i], page + i,
825 haddr + PAGE_SHIFT*i, vma);
826 __SetPageUptodate(pages[i]);
827 cond_resched();
828 }
829
830 spin_lock(&mm->page_table_lock);
831 if (unlikely(!pmd_same(*pmd, orig_pmd)))
832 goto out_free_pages;
833 VM_BUG_ON(!PageHead(page));
834
835 pmdp_clear_flush_notify(vma, haddr, pmd);
836 /* leave pmd empty until pte is filled */
837
838 pgtable = get_pmd_huge_pte(mm);
839 pmd_populate(mm, &_pmd, pgtable);
840
841 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
842 pte_t *pte, entry;
843 entry = mk_pte(pages[i], vma->vm_page_prot);
844 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
845 page_add_new_anon_rmap(pages[i], vma, haddr);
846 pte = pte_offset_map(&_pmd, haddr);
847 VM_BUG_ON(!pte_none(*pte));
848 set_pte_at(mm, haddr, pte, entry);
849 pte_unmap(pte);
850 }
851 kfree(pages);
852
853 mm->nr_ptes++;
854 smp_wmb(); /* make pte visible before pmd */
855 pmd_populate(mm, pmd, pgtable);
856 page_remove_rmap(page);
857 spin_unlock(&mm->page_table_lock);
858
859 ret |= VM_FAULT_WRITE;
860 put_page(page);
861
862 out:
863 return ret;
864
865 out_free_pages:
866 spin_unlock(&mm->page_table_lock);
867 mem_cgroup_uncharge_start();
868 for (i = 0; i < HPAGE_PMD_NR; i++) {
869 mem_cgroup_uncharge_page(pages[i]);
870 put_page(pages[i]);
871 }
872 mem_cgroup_uncharge_end();
873 kfree(pages);
874 goto out;
875 }
876
877 int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
878 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
879 {
880 int ret = 0;
881 struct page *page, *new_page;
882 unsigned long haddr;
883
884 VM_BUG_ON(!vma->anon_vma);
885 spin_lock(&mm->page_table_lock);
886 if (unlikely(!pmd_same(*pmd, orig_pmd)))
887 goto out_unlock;
888
889 page = pmd_page(orig_pmd);
890 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
891 haddr = address & HPAGE_PMD_MASK;
892 if (page_mapcount(page) == 1) {
893 pmd_t entry;
894 entry = pmd_mkyoung(orig_pmd);
895 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
896 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
897 update_mmu_cache(vma, address, entry);
898 ret |= VM_FAULT_WRITE;
899 goto out_unlock;
900 }
901 get_page(page);
902 spin_unlock(&mm->page_table_lock);
903
904 if (transparent_hugepage_enabled(vma) &&
905 !transparent_hugepage_debug_cow())
906 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
907 vma, haddr, numa_node_id(), 0);
908 else
909 new_page = NULL;
910
911 if (unlikely(!new_page)) {
912 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
913 pmd, orig_pmd, page, haddr);
914 put_page(page);
915 goto out;
916 }
917
918 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
919 put_page(new_page);
920 put_page(page);
921 ret |= VM_FAULT_OOM;
922 goto out;
923 }
924
925 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
926 __SetPageUptodate(new_page);
927
928 spin_lock(&mm->page_table_lock);
929 put_page(page);
930 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
931 mem_cgroup_uncharge_page(new_page);
932 put_page(new_page);
933 } else {
934 pmd_t entry;
935 VM_BUG_ON(!PageHead(page));
936 entry = mk_pmd(new_page, vma->vm_page_prot);
937 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
938 entry = pmd_mkhuge(entry);
939 pmdp_clear_flush_notify(vma, haddr, pmd);
940 page_add_new_anon_rmap(new_page, vma, haddr);
941 set_pmd_at(mm, haddr, pmd, entry);
942 update_mmu_cache(vma, address, entry);
943 page_remove_rmap(page);
944 put_page(page);
945 ret |= VM_FAULT_WRITE;
946 }
947 out_unlock:
948 spin_unlock(&mm->page_table_lock);
949 out:
950 return ret;
951 }
952
953 struct page *follow_trans_huge_pmd(struct mm_struct *mm,
954 unsigned long addr,
955 pmd_t *pmd,
956 unsigned int flags)
957 {
958 struct page *page = NULL;
959
960 assert_spin_locked(&mm->page_table_lock);
961
962 if (flags & FOLL_WRITE && !pmd_write(*pmd))
963 goto out;
964
965 page = pmd_page(*pmd);
966 VM_BUG_ON(!PageHead(page));
967 if (flags & FOLL_TOUCH) {
968 pmd_t _pmd;
969 /*
970 * We should set the dirty bit only for FOLL_WRITE but
971 * for now the dirty bit in the pmd is meaningless.
972 * And if the dirty bit will become meaningful and
973 * we'll only set it with FOLL_WRITE, an atomic
974 * set_bit will be required on the pmd to set the
975 * young bit, instead of the current set_pmd_at.
976 */
977 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
978 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
979 }
980 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
981 VM_BUG_ON(!PageCompound(page));
982 if (flags & FOLL_GET)
983 get_page(page);
984
985 out:
986 return page;
987 }
988
989 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
990 pmd_t *pmd)
991 {
992 int ret = 0;
993
994 spin_lock(&tlb->mm->page_table_lock);
995 if (likely(pmd_trans_huge(*pmd))) {
996 if (unlikely(pmd_trans_splitting(*pmd))) {
997 spin_unlock(&tlb->mm->page_table_lock);
998 wait_split_huge_page(vma->anon_vma,
999 pmd);
1000 } else {
1001 struct page *page;
1002 pgtable_t pgtable;
1003 pgtable = get_pmd_huge_pte(tlb->mm);
1004 page = pmd_page(*pmd);
1005 pmd_clear(pmd);
1006 page_remove_rmap(page);
1007 VM_BUG_ON(page_mapcount(page) < 0);
1008 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1009 VM_BUG_ON(!PageHead(page));
1010 spin_unlock(&tlb->mm->page_table_lock);
1011 tlb_remove_page(tlb, page);
1012 pte_free(tlb->mm, pgtable);
1013 ret = 1;
1014 }
1015 } else
1016 spin_unlock(&tlb->mm->page_table_lock);
1017
1018 return ret;
1019 }
1020
1021 int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1022 unsigned long addr, unsigned long end,
1023 unsigned char *vec)
1024 {
1025 int ret = 0;
1026
1027 spin_lock(&vma->vm_mm->page_table_lock);
1028 if (likely(pmd_trans_huge(*pmd))) {
1029 ret = !pmd_trans_splitting(*pmd);
1030 spin_unlock(&vma->vm_mm->page_table_lock);
1031 if (unlikely(!ret))
1032 wait_split_huge_page(vma->anon_vma, pmd);
1033 else {
1034 /*
1035 * All logical pages in the range are present
1036 * if backed by a huge page.
1037 */
1038 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1039 }
1040 } else
1041 spin_unlock(&vma->vm_mm->page_table_lock);
1042
1043 return ret;
1044 }
1045
1046 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1047 unsigned long addr, pgprot_t newprot)
1048 {
1049 struct mm_struct *mm = vma->vm_mm;
1050 int ret = 0;
1051
1052 spin_lock(&mm->page_table_lock);
1053 if (likely(pmd_trans_huge(*pmd))) {
1054 if (unlikely(pmd_trans_splitting(*pmd))) {
1055 spin_unlock(&mm->page_table_lock);
1056 wait_split_huge_page(vma->anon_vma, pmd);
1057 } else {
1058 pmd_t entry;
1059
1060 entry = pmdp_get_and_clear(mm, addr, pmd);
1061 entry = pmd_modify(entry, newprot);
1062 set_pmd_at(mm, addr, pmd, entry);
1063 spin_unlock(&vma->vm_mm->page_table_lock);
1064 flush_tlb_range(vma, addr, addr + HPAGE_PMD_SIZE);
1065 ret = 1;
1066 }
1067 } else
1068 spin_unlock(&vma->vm_mm->page_table_lock);
1069
1070 return ret;
1071 }
1072
1073 pmd_t *page_check_address_pmd(struct page *page,
1074 struct mm_struct *mm,
1075 unsigned long address,
1076 enum page_check_address_pmd_flag flag)
1077 {
1078 pgd_t *pgd;
1079 pud_t *pud;
1080 pmd_t *pmd, *ret = NULL;
1081
1082 if (address & ~HPAGE_PMD_MASK)
1083 goto out;
1084
1085 pgd = pgd_offset(mm, address);
1086 if (!pgd_present(*pgd))
1087 goto out;
1088
1089 pud = pud_offset(pgd, address);
1090 if (!pud_present(*pud))
1091 goto out;
1092
1093 pmd = pmd_offset(pud, address);
1094 if (pmd_none(*pmd))
1095 goto out;
1096 if (pmd_page(*pmd) != page)
1097 goto out;
1098 /*
1099 * split_vma() may create temporary aliased mappings. There is
1100 * no risk as long as all huge pmd are found and have their
1101 * splitting bit set before __split_huge_page_refcount
1102 * runs. Finding the same huge pmd more than once during the
1103 * same rmap walk is not a problem.
1104 */
1105 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1106 pmd_trans_splitting(*pmd))
1107 goto out;
1108 if (pmd_trans_huge(*pmd)) {
1109 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1110 !pmd_trans_splitting(*pmd));
1111 ret = pmd;
1112 }
1113 out:
1114 return ret;
1115 }
1116
1117 static int __split_huge_page_splitting(struct page *page,
1118 struct vm_area_struct *vma,
1119 unsigned long address)
1120 {
1121 struct mm_struct *mm = vma->vm_mm;
1122 pmd_t *pmd;
1123 int ret = 0;
1124
1125 spin_lock(&mm->page_table_lock);
1126 pmd = page_check_address_pmd(page, mm, address,
1127 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1128 if (pmd) {
1129 /*
1130 * We can't temporarily set the pmd to null in order
1131 * to split it, the pmd must remain marked huge at all
1132 * times or the VM won't take the pmd_trans_huge paths
1133 * and it won't wait on the anon_vma->root->lock to
1134 * serialize against split_huge_page*.
1135 */
1136 pmdp_splitting_flush_notify(vma, address, pmd);
1137 ret = 1;
1138 }
1139 spin_unlock(&mm->page_table_lock);
1140
1141 return ret;
1142 }
1143
1144 static void __split_huge_page_refcount(struct page *page)
1145 {
1146 int i;
1147 unsigned long head_index = page->index;
1148 struct zone *zone = page_zone(page);
1149 int zonestat;
1150
1151 /* prevent PageLRU to go away from under us, and freeze lru stats */
1152 spin_lock_irq(&zone->lru_lock);
1153 compound_lock(page);
1154
1155 for (i = 1; i < HPAGE_PMD_NR; i++) {
1156 struct page *page_tail = page + i;
1157
1158 /* tail_page->_count cannot change */
1159 atomic_sub(atomic_read(&page_tail->_count), &page->_count);
1160 BUG_ON(page_count(page) <= 0);
1161 atomic_add(page_mapcount(page) + 1, &page_tail->_count);
1162 BUG_ON(atomic_read(&page_tail->_count) <= 0);
1163
1164 /* after clearing PageTail the gup refcount can be released */
1165 smp_mb();
1166
1167 /*
1168 * retain hwpoison flag of the poisoned tail page:
1169 * fix for the unsuitable process killed on Guest Machine(KVM)
1170 * by the memory-failure.
1171 */
1172 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
1173 page_tail->flags |= (page->flags &
1174 ((1L << PG_referenced) |
1175 (1L << PG_swapbacked) |
1176 (1L << PG_mlocked) |
1177 (1L << PG_uptodate)));
1178 page_tail->flags |= (1L << PG_dirty);
1179
1180 /*
1181 * 1) clear PageTail before overwriting first_page
1182 * 2) clear PageTail before clearing PageHead for VM_BUG_ON
1183 */
1184 smp_wmb();
1185
1186 /*
1187 * __split_huge_page_splitting() already set the
1188 * splitting bit in all pmd that could map this
1189 * hugepage, that will ensure no CPU can alter the
1190 * mapcount on the head page. The mapcount is only
1191 * accounted in the head page and it has to be
1192 * transferred to all tail pages in the below code. So
1193 * for this code to be safe, the split the mapcount
1194 * can't change. But that doesn't mean userland can't
1195 * keep changing and reading the page contents while
1196 * we transfer the mapcount, so the pmd splitting
1197 * status is achieved setting a reserved bit in the
1198 * pmd, not by clearing the present bit.
1199 */
1200 BUG_ON(page_mapcount(page_tail));
1201 page_tail->_mapcount = page->_mapcount;
1202
1203 BUG_ON(page_tail->mapping);
1204 page_tail->mapping = page->mapping;
1205
1206 page_tail->index = ++head_index;
1207
1208 BUG_ON(!PageAnon(page_tail));
1209 BUG_ON(!PageUptodate(page_tail));
1210 BUG_ON(!PageDirty(page_tail));
1211 BUG_ON(!PageSwapBacked(page_tail));
1212
1213 mem_cgroup_split_huge_fixup(page, page_tail);
1214
1215 lru_add_page_tail(zone, page, page_tail);
1216 }
1217
1218 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1219 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1220
1221 /*
1222 * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics,
1223 * so adjust those appropriately if this page is on the LRU.
1224 */
1225 if (PageLRU(page)) {
1226 zonestat = NR_LRU_BASE + page_lru(page);
1227 __mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1));
1228 }
1229
1230 ClearPageCompound(page);
1231 compound_unlock(page);
1232 spin_unlock_irq(&zone->lru_lock);
1233
1234 for (i = 1; i < HPAGE_PMD_NR; i++) {
1235 struct page *page_tail = page + i;
1236 BUG_ON(page_count(page_tail) <= 0);
1237 /*
1238 * Tail pages may be freed if there wasn't any mapping
1239 * like if add_to_swap() is running on a lru page that
1240 * had its mapping zapped. And freeing these pages
1241 * requires taking the lru_lock so we do the put_page
1242 * of the tail pages after the split is complete.
1243 */
1244 put_page(page_tail);
1245 }
1246
1247 /*
1248 * Only the head page (now become a regular page) is required
1249 * to be pinned by the caller.
1250 */
1251 BUG_ON(page_count(page) <= 0);
1252 }
1253
1254 static int __split_huge_page_map(struct page *page,
1255 struct vm_area_struct *vma,
1256 unsigned long address)
1257 {
1258 struct mm_struct *mm = vma->vm_mm;
1259 pmd_t *pmd, _pmd;
1260 int ret = 0, i;
1261 pgtable_t pgtable;
1262 unsigned long haddr;
1263
1264 spin_lock(&mm->page_table_lock);
1265 pmd = page_check_address_pmd(page, mm, address,
1266 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1267 if (pmd) {
1268 pgtable = get_pmd_huge_pte(mm);
1269 pmd_populate(mm, &_pmd, pgtable);
1270
1271 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1272 i++, haddr += PAGE_SIZE) {
1273 pte_t *pte, entry;
1274 BUG_ON(PageCompound(page+i));
1275 entry = mk_pte(page + i, vma->vm_page_prot);
1276 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1277 if (!pmd_write(*pmd))
1278 entry = pte_wrprotect(entry);
1279 else
1280 BUG_ON(page_mapcount(page) != 1);
1281 if (!pmd_young(*pmd))
1282 entry = pte_mkold(entry);
1283 pte = pte_offset_map(&_pmd, haddr);
1284 BUG_ON(!pte_none(*pte));
1285 set_pte_at(mm, haddr, pte, entry);
1286 pte_unmap(pte);
1287 }
1288
1289 mm->nr_ptes++;
1290 smp_wmb(); /* make pte visible before pmd */
1291 /*
1292 * Up to this point the pmd is present and huge and
1293 * userland has the whole access to the hugepage
1294 * during the split (which happens in place). If we
1295 * overwrite the pmd with the not-huge version
1296 * pointing to the pte here (which of course we could
1297 * if all CPUs were bug free), userland could trigger
1298 * a small page size TLB miss on the small sized TLB
1299 * while the hugepage TLB entry is still established
1300 * in the huge TLB. Some CPU doesn't like that. See
1301 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1302 * Erratum 383 on page 93. Intel should be safe but is
1303 * also warns that it's only safe if the permission
1304 * and cache attributes of the two entries loaded in
1305 * the two TLB is identical (which should be the case
1306 * here). But it is generally safer to never allow
1307 * small and huge TLB entries for the same virtual
1308 * address to be loaded simultaneously. So instead of
1309 * doing "pmd_populate(); flush_tlb_range();" we first
1310 * mark the current pmd notpresent (atomically because
1311 * here the pmd_trans_huge and pmd_trans_splitting
1312 * must remain set at all times on the pmd until the
1313 * split is complete for this pmd), then we flush the
1314 * SMP TLB and finally we write the non-huge version
1315 * of the pmd entry with pmd_populate.
1316 */
1317 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1318 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1319 pmd_populate(mm, pmd, pgtable);
1320 ret = 1;
1321 }
1322 spin_unlock(&mm->page_table_lock);
1323
1324 return ret;
1325 }
1326
1327 /* must be called with anon_vma->root->lock hold */
1328 static void __split_huge_page(struct page *page,
1329 struct anon_vma *anon_vma)
1330 {
1331 int mapcount, mapcount2;
1332 struct anon_vma_chain *avc;
1333
1334 BUG_ON(!PageHead(page));
1335 BUG_ON(PageTail(page));
1336
1337 mapcount = 0;
1338 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1339 struct vm_area_struct *vma = avc->vma;
1340 unsigned long addr = vma_address(page, vma);
1341 BUG_ON(is_vma_temporary_stack(vma));
1342 if (addr == -EFAULT)
1343 continue;
1344 mapcount += __split_huge_page_splitting(page, vma, addr);
1345 }
1346 /*
1347 * It is critical that new vmas are added to the tail of the
1348 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1349 * and establishes a child pmd before
1350 * __split_huge_page_splitting() freezes the parent pmd (so if
1351 * we fail to prevent copy_huge_pmd() from running until the
1352 * whole __split_huge_page() is complete), we will still see
1353 * the newly established pmd of the child later during the
1354 * walk, to be able to set it as pmd_trans_splitting too.
1355 */
1356 if (mapcount != page_mapcount(page))
1357 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1358 mapcount, page_mapcount(page));
1359 BUG_ON(mapcount != page_mapcount(page));
1360
1361 __split_huge_page_refcount(page);
1362
1363 mapcount2 = 0;
1364 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1365 struct vm_area_struct *vma = avc->vma;
1366 unsigned long addr = vma_address(page, vma);
1367 BUG_ON(is_vma_temporary_stack(vma));
1368 if (addr == -EFAULT)
1369 continue;
1370 mapcount2 += __split_huge_page_map(page, vma, addr);
1371 }
1372 if (mapcount != mapcount2)
1373 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1374 mapcount, mapcount2, page_mapcount(page));
1375 BUG_ON(mapcount != mapcount2);
1376 }
1377
1378 int split_huge_page(struct page *page)
1379 {
1380 struct anon_vma *anon_vma;
1381 int ret = 1;
1382
1383 BUG_ON(!PageAnon(page));
1384 anon_vma = page_lock_anon_vma(page);
1385 if (!anon_vma)
1386 goto out;
1387 ret = 0;
1388 if (!PageCompound(page))
1389 goto out_unlock;
1390
1391 BUG_ON(!PageSwapBacked(page));
1392 __split_huge_page(page, anon_vma);
1393
1394 BUG_ON(PageCompound(page));
1395 out_unlock:
1396 page_unlock_anon_vma(anon_vma);
1397 out:
1398 return ret;
1399 }
1400
1401 int hugepage_madvise(struct vm_area_struct *vma,
1402 unsigned long *vm_flags, int advice)
1403 {
1404 switch (advice) {
1405 case MADV_HUGEPAGE:
1406 /*
1407 * Be somewhat over-protective like KSM for now!
1408 */
1409 if (*vm_flags & (VM_HUGEPAGE |
1410 VM_SHARED | VM_MAYSHARE |
1411 VM_PFNMAP | VM_IO | VM_DONTEXPAND |
1412 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
1413 VM_MIXEDMAP | VM_SAO))
1414 return -EINVAL;
1415 *vm_flags &= ~VM_NOHUGEPAGE;
1416 *vm_flags |= VM_HUGEPAGE;
1417 /*
1418 * If the vma become good for khugepaged to scan,
1419 * register it here without waiting a page fault that
1420 * may not happen any time soon.
1421 */
1422 if (unlikely(khugepaged_enter_vma_merge(vma)))
1423 return -ENOMEM;
1424 break;
1425 case MADV_NOHUGEPAGE:
1426 /*
1427 * Be somewhat over-protective like KSM for now!
1428 */
1429 if (*vm_flags & (VM_NOHUGEPAGE |
1430 VM_SHARED | VM_MAYSHARE |
1431 VM_PFNMAP | VM_IO | VM_DONTEXPAND |
1432 VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE |
1433 VM_MIXEDMAP | VM_SAO))
1434 return -EINVAL;
1435 *vm_flags &= ~VM_HUGEPAGE;
1436 *vm_flags |= VM_NOHUGEPAGE;
1437 /*
1438 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1439 * this vma even if we leave the mm registered in khugepaged if
1440 * it got registered before VM_NOHUGEPAGE was set.
1441 */
1442 break;
1443 }
1444
1445 return 0;
1446 }
1447
1448 static int __init khugepaged_slab_init(void)
1449 {
1450 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1451 sizeof(struct mm_slot),
1452 __alignof__(struct mm_slot), 0, NULL);
1453 if (!mm_slot_cache)
1454 return -ENOMEM;
1455
1456 return 0;
1457 }
1458
1459 static void __init khugepaged_slab_free(void)
1460 {
1461 kmem_cache_destroy(mm_slot_cache);
1462 mm_slot_cache = NULL;
1463 }
1464
1465 static inline struct mm_slot *alloc_mm_slot(void)
1466 {
1467 if (!mm_slot_cache) /* initialization failed */
1468 return NULL;
1469 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1470 }
1471
1472 static inline void free_mm_slot(struct mm_slot *mm_slot)
1473 {
1474 kmem_cache_free(mm_slot_cache, mm_slot);
1475 }
1476
1477 static int __init mm_slots_hash_init(void)
1478 {
1479 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1480 GFP_KERNEL);
1481 if (!mm_slots_hash)
1482 return -ENOMEM;
1483 return 0;
1484 }
1485
1486 #if 0
1487 static void __init mm_slots_hash_free(void)
1488 {
1489 kfree(mm_slots_hash);
1490 mm_slots_hash = NULL;
1491 }
1492 #endif
1493
1494 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1495 {
1496 struct mm_slot *mm_slot;
1497 struct hlist_head *bucket;
1498 struct hlist_node *node;
1499
1500 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1501 % MM_SLOTS_HASH_HEADS];
1502 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1503 if (mm == mm_slot->mm)
1504 return mm_slot;
1505 }
1506 return NULL;
1507 }
1508
1509 static void insert_to_mm_slots_hash(struct mm_struct *mm,
1510 struct mm_slot *mm_slot)
1511 {
1512 struct hlist_head *bucket;
1513
1514 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1515 % MM_SLOTS_HASH_HEADS];
1516 mm_slot->mm = mm;
1517 hlist_add_head(&mm_slot->hash, bucket);
1518 }
1519
1520 static inline int khugepaged_test_exit(struct mm_struct *mm)
1521 {
1522 return atomic_read(&mm->mm_users) == 0;
1523 }
1524
1525 int __khugepaged_enter(struct mm_struct *mm)
1526 {
1527 struct mm_slot *mm_slot;
1528 int wakeup;
1529
1530 mm_slot = alloc_mm_slot();
1531 if (!mm_slot)
1532 return -ENOMEM;
1533
1534 /* __khugepaged_exit() must not run from under us */
1535 VM_BUG_ON(khugepaged_test_exit(mm));
1536 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1537 free_mm_slot(mm_slot);
1538 return 0;
1539 }
1540
1541 spin_lock(&khugepaged_mm_lock);
1542 insert_to_mm_slots_hash(mm, mm_slot);
1543 /*
1544 * Insert just behind the scanning cursor, to let the area settle
1545 * down a little.
1546 */
1547 wakeup = list_empty(&khugepaged_scan.mm_head);
1548 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1549 spin_unlock(&khugepaged_mm_lock);
1550
1551 atomic_inc(&mm->mm_count);
1552 if (wakeup)
1553 wake_up_interruptible(&khugepaged_wait);
1554
1555 return 0;
1556 }
1557
1558 int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1559 {
1560 unsigned long hstart, hend;
1561 if (!vma->anon_vma)
1562 /*
1563 * Not yet faulted in so we will register later in the
1564 * page fault if needed.
1565 */
1566 return 0;
1567 if (vma->vm_file || vma->vm_ops)
1568 /* khugepaged not yet working on file or special mappings */
1569 return 0;
1570 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1571 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1572 hend = vma->vm_end & HPAGE_PMD_MASK;
1573 if (hstart < hend)
1574 return khugepaged_enter(vma);
1575 return 0;
1576 }
1577
1578 void __khugepaged_exit(struct mm_struct *mm)
1579 {
1580 struct mm_slot *mm_slot;
1581 int free = 0;
1582
1583 spin_lock(&khugepaged_mm_lock);
1584 mm_slot = get_mm_slot(mm);
1585 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1586 hlist_del(&mm_slot->hash);
1587 list_del(&mm_slot->mm_node);
1588 free = 1;
1589 }
1590
1591 if (free) {
1592 spin_unlock(&khugepaged_mm_lock);
1593 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1594 free_mm_slot(mm_slot);
1595 mmdrop(mm);
1596 } else if (mm_slot) {
1597 spin_unlock(&khugepaged_mm_lock);
1598 /*
1599 * This is required to serialize against
1600 * khugepaged_test_exit() (which is guaranteed to run
1601 * under mmap sem read mode). Stop here (after we
1602 * return all pagetables will be destroyed) until
1603 * khugepaged has finished working on the pagetables
1604 * under the mmap_sem.
1605 */
1606 down_write(&mm->mmap_sem);
1607 up_write(&mm->mmap_sem);
1608 } else
1609 spin_unlock(&khugepaged_mm_lock);
1610 }
1611
1612 static void release_pte_page(struct page *page)
1613 {
1614 /* 0 stands for page_is_file_cache(page) == false */
1615 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1616 unlock_page(page);
1617 putback_lru_page(page);
1618 }
1619
1620 static void release_pte_pages(pte_t *pte, pte_t *_pte)
1621 {
1622 while (--_pte >= pte) {
1623 pte_t pteval = *_pte;
1624 if (!pte_none(pteval))
1625 release_pte_page(pte_page(pteval));
1626 }
1627 }
1628
1629 static void release_all_pte_pages(pte_t *pte)
1630 {
1631 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1632 }
1633
1634 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1635 unsigned long address,
1636 pte_t *pte)
1637 {
1638 struct page *page;
1639 pte_t *_pte;
1640 int referenced = 0, isolated = 0, none = 0;
1641 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1642 _pte++, address += PAGE_SIZE) {
1643 pte_t pteval = *_pte;
1644 if (pte_none(pteval)) {
1645 if (++none <= khugepaged_max_ptes_none)
1646 continue;
1647 else {
1648 release_pte_pages(pte, _pte);
1649 goto out;
1650 }
1651 }
1652 if (!pte_present(pteval) || !pte_write(pteval)) {
1653 release_pte_pages(pte, _pte);
1654 goto out;
1655 }
1656 page = vm_normal_page(vma, address, pteval);
1657 if (unlikely(!page)) {
1658 release_pte_pages(pte, _pte);
1659 goto out;
1660 }
1661 VM_BUG_ON(PageCompound(page));
1662 BUG_ON(!PageAnon(page));
1663 VM_BUG_ON(!PageSwapBacked(page));
1664
1665 /* cannot use mapcount: can't collapse if there's a gup pin */
1666 if (page_count(page) != 1) {
1667 release_pte_pages(pte, _pte);
1668 goto out;
1669 }
1670 /*
1671 * We can do it before isolate_lru_page because the
1672 * page can't be freed from under us. NOTE: PG_lock
1673 * is needed to serialize against split_huge_page
1674 * when invoked from the VM.
1675 */
1676 if (!trylock_page(page)) {
1677 release_pte_pages(pte, _pte);
1678 goto out;
1679 }
1680 /*
1681 * Isolate the page to avoid collapsing an hugepage
1682 * currently in use by the VM.
1683 */
1684 if (isolate_lru_page(page)) {
1685 unlock_page(page);
1686 release_pte_pages(pte, _pte);
1687 goto out;
1688 }
1689 /* 0 stands for page_is_file_cache(page) == false */
1690 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1691 VM_BUG_ON(!PageLocked(page));
1692 VM_BUG_ON(PageLRU(page));
1693
1694 /* If there is no mapped pte young don't collapse the page */
1695 if (pte_young(pteval) || PageReferenced(page) ||
1696 mmu_notifier_test_young(vma->vm_mm, address))
1697 referenced = 1;
1698 }
1699 if (unlikely(!referenced))
1700 release_all_pte_pages(pte);
1701 else
1702 isolated = 1;
1703 out:
1704 return isolated;
1705 }
1706
1707 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1708 struct vm_area_struct *vma,
1709 unsigned long address,
1710 spinlock_t *ptl)
1711 {
1712 pte_t *_pte;
1713 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1714 pte_t pteval = *_pte;
1715 struct page *src_page;
1716
1717 if (pte_none(pteval)) {
1718 clear_user_highpage(page, address);
1719 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1720 } else {
1721 src_page = pte_page(pteval);
1722 copy_user_highpage(page, src_page, address, vma);
1723 VM_BUG_ON(page_mapcount(src_page) != 1);
1724 VM_BUG_ON(page_count(src_page) != 2);
1725 release_pte_page(src_page);
1726 /*
1727 * ptl mostly unnecessary, but preempt has to
1728 * be disabled to update the per-cpu stats
1729 * inside page_remove_rmap().
1730 */
1731 spin_lock(ptl);
1732 /*
1733 * paravirt calls inside pte_clear here are
1734 * superfluous.
1735 */
1736 pte_clear(vma->vm_mm, address, _pte);
1737 page_remove_rmap(src_page);
1738 spin_unlock(ptl);
1739 free_page_and_swap_cache(src_page);
1740 }
1741
1742 address += PAGE_SIZE;
1743 page++;
1744 }
1745 }
1746
1747 static void collapse_huge_page(struct mm_struct *mm,
1748 unsigned long address,
1749 struct page **hpage,
1750 struct vm_area_struct *vma,
1751 int node)
1752 {
1753 pgd_t *pgd;
1754 pud_t *pud;
1755 pmd_t *pmd, _pmd;
1756 pte_t *pte;
1757 pgtable_t pgtable;
1758 struct page *new_page;
1759 spinlock_t *ptl;
1760 int isolated;
1761 unsigned long hstart, hend;
1762
1763 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1764 #ifndef CONFIG_NUMA
1765 VM_BUG_ON(!*hpage);
1766 new_page = *hpage;
1767 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1768 up_read(&mm->mmap_sem);
1769 return;
1770 }
1771 #else
1772 VM_BUG_ON(*hpage);
1773 /*
1774 * Allocate the page while the vma is still valid and under
1775 * the mmap_sem read mode so there is no memory allocation
1776 * later when we take the mmap_sem in write mode. This is more
1777 * friendly behavior (OTOH it may actually hide bugs) to
1778 * filesystems in userland with daemons allocating memory in
1779 * the userland I/O paths. Allocating memory with the
1780 * mmap_sem in read mode is good idea also to allow greater
1781 * scalability.
1782 */
1783 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
1784 node, __GFP_OTHER_NODE);
1785 if (unlikely(!new_page)) {
1786 up_read(&mm->mmap_sem);
1787 *hpage = ERR_PTR(-ENOMEM);
1788 return;
1789 }
1790 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
1791 up_read(&mm->mmap_sem);
1792 put_page(new_page);
1793 return;
1794 }
1795 #endif
1796
1797 /* after allocating the hugepage upgrade to mmap_sem write mode */
1798 up_read(&mm->mmap_sem);
1799
1800 /*
1801 * Prevent all access to pagetables with the exception of
1802 * gup_fast later hanlded by the ptep_clear_flush and the VM
1803 * handled by the anon_vma lock + PG_lock.
1804 */
1805 down_write(&mm->mmap_sem);
1806 if (unlikely(khugepaged_test_exit(mm)))
1807 goto out;
1808
1809 vma = find_vma(mm, address);
1810 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1811 hend = vma->vm_end & HPAGE_PMD_MASK;
1812 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1813 goto out;
1814
1815 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1816 (vma->vm_flags & VM_NOHUGEPAGE))
1817 goto out;
1818
1819 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
1820 if (!vma->anon_vma || vma->vm_ops || vma->vm_file)
1821 goto out;
1822 if (is_vma_temporary_stack(vma))
1823 goto out;
1824 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
1825
1826 pgd = pgd_offset(mm, address);
1827 if (!pgd_present(*pgd))
1828 goto out;
1829
1830 pud = pud_offset(pgd, address);
1831 if (!pud_present(*pud))
1832 goto out;
1833
1834 pmd = pmd_offset(pud, address);
1835 /* pmd can't go away or become huge under us */
1836 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1837 goto out;
1838
1839 anon_vma_lock(vma->anon_vma);
1840
1841 pte = pte_offset_map(pmd, address);
1842 ptl = pte_lockptr(mm, pmd);
1843
1844 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1845 /*
1846 * After this gup_fast can't run anymore. This also removes
1847 * any huge TLB entry from the CPU so we won't allow
1848 * huge and small TLB entries for the same virtual address
1849 * to avoid the risk of CPU bugs in that area.
1850 */
1851 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1852 spin_unlock(&mm->page_table_lock);
1853
1854 spin_lock(ptl);
1855 isolated = __collapse_huge_page_isolate(vma, address, pte);
1856 spin_unlock(ptl);
1857
1858 if (unlikely(!isolated)) {
1859 pte_unmap(pte);
1860 spin_lock(&mm->page_table_lock);
1861 BUG_ON(!pmd_none(*pmd));
1862 set_pmd_at(mm, address, pmd, _pmd);
1863 spin_unlock(&mm->page_table_lock);
1864 anon_vma_unlock(vma->anon_vma);
1865 goto out;
1866 }
1867
1868 /*
1869 * All pages are isolated and locked so anon_vma rmap
1870 * can't run anymore.
1871 */
1872 anon_vma_unlock(vma->anon_vma);
1873
1874 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
1875 pte_unmap(pte);
1876 __SetPageUptodate(new_page);
1877 pgtable = pmd_pgtable(_pmd);
1878 VM_BUG_ON(page_count(pgtable) != 1);
1879 VM_BUG_ON(page_mapcount(pgtable) != 0);
1880
1881 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1882 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1883 _pmd = pmd_mkhuge(_pmd);
1884
1885 /*
1886 * spin_lock() below is not the equivalent of smp_wmb(), so
1887 * this is needed to avoid the copy_huge_page writes to become
1888 * visible after the set_pmd_at() write.
1889 */
1890 smp_wmb();
1891
1892 spin_lock(&mm->page_table_lock);
1893 BUG_ON(!pmd_none(*pmd));
1894 page_add_new_anon_rmap(new_page, vma, address);
1895 set_pmd_at(mm, address, pmd, _pmd);
1896 update_mmu_cache(vma, address, entry);
1897 prepare_pmd_huge_pte(pgtable, mm);
1898 mm->nr_ptes--;
1899 spin_unlock(&mm->page_table_lock);
1900
1901 #ifndef CONFIG_NUMA
1902 *hpage = NULL;
1903 #endif
1904 khugepaged_pages_collapsed++;
1905 out_up_write:
1906 up_write(&mm->mmap_sem);
1907 return;
1908
1909 out:
1910 mem_cgroup_uncharge_page(new_page);
1911 #ifdef CONFIG_NUMA
1912 put_page(new_page);
1913 #endif
1914 goto out_up_write;
1915 }
1916
1917 static int khugepaged_scan_pmd(struct mm_struct *mm,
1918 struct vm_area_struct *vma,
1919 unsigned long address,
1920 struct page **hpage)
1921 {
1922 pgd_t *pgd;
1923 pud_t *pud;
1924 pmd_t *pmd;
1925 pte_t *pte, *_pte;
1926 int ret = 0, referenced = 0, none = 0;
1927 struct page *page;
1928 unsigned long _address;
1929 spinlock_t *ptl;
1930 int node = -1;
1931
1932 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1933
1934 pgd = pgd_offset(mm, address);
1935 if (!pgd_present(*pgd))
1936 goto out;
1937
1938 pud = pud_offset(pgd, address);
1939 if (!pud_present(*pud))
1940 goto out;
1941
1942 pmd = pmd_offset(pud, address);
1943 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1944 goto out;
1945
1946 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1947 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1948 _pte++, _address += PAGE_SIZE) {
1949 pte_t pteval = *_pte;
1950 if (pte_none(pteval)) {
1951 if (++none <= khugepaged_max_ptes_none)
1952 continue;
1953 else
1954 goto out_unmap;
1955 }
1956 if (!pte_present(pteval) || !pte_write(pteval))
1957 goto out_unmap;
1958 page = vm_normal_page(vma, _address, pteval);
1959 if (unlikely(!page))
1960 goto out_unmap;
1961 /*
1962 * Chose the node of the first page. This could
1963 * be more sophisticated and look at more pages,
1964 * but isn't for now.
1965 */
1966 if (node == -1)
1967 node = page_to_nid(page);
1968 VM_BUG_ON(PageCompound(page));
1969 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
1970 goto out_unmap;
1971 /* cannot use mapcount: can't collapse if there's a gup pin */
1972 if (page_count(page) != 1)
1973 goto out_unmap;
1974 if (pte_young(pteval) || PageReferenced(page) ||
1975 mmu_notifier_test_young(vma->vm_mm, address))
1976 referenced = 1;
1977 }
1978 if (referenced)
1979 ret = 1;
1980 out_unmap:
1981 pte_unmap_unlock(pte, ptl);
1982 if (ret)
1983 /* collapse_huge_page will return with the mmap_sem released */
1984 collapse_huge_page(mm, address, hpage, vma, node);
1985 out:
1986 return ret;
1987 }
1988
1989 static void collect_mm_slot(struct mm_slot *mm_slot)
1990 {
1991 struct mm_struct *mm = mm_slot->mm;
1992
1993 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
1994
1995 if (khugepaged_test_exit(mm)) {
1996 /* free mm_slot */
1997 hlist_del(&mm_slot->hash);
1998 list_del(&mm_slot->mm_node);
1999
2000 /*
2001 * Not strictly needed because the mm exited already.
2002 *
2003 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2004 */
2005
2006 /* khugepaged_mm_lock actually not necessary for the below */
2007 free_mm_slot(mm_slot);
2008 mmdrop(mm);
2009 }
2010 }
2011
2012 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2013 struct page **hpage)
2014 {
2015 struct mm_slot *mm_slot;
2016 struct mm_struct *mm;
2017 struct vm_area_struct *vma;
2018 int progress = 0;
2019
2020 VM_BUG_ON(!pages);
2021 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2022
2023 if (khugepaged_scan.mm_slot)
2024 mm_slot = khugepaged_scan.mm_slot;
2025 else {
2026 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2027 struct mm_slot, mm_node);
2028 khugepaged_scan.address = 0;
2029 khugepaged_scan.mm_slot = mm_slot;
2030 }
2031 spin_unlock(&khugepaged_mm_lock);
2032
2033 mm = mm_slot->mm;
2034 down_read(&mm->mmap_sem);
2035 if (unlikely(khugepaged_test_exit(mm)))
2036 vma = NULL;
2037 else
2038 vma = find_vma(mm, khugepaged_scan.address);
2039
2040 progress++;
2041 for (; vma; vma = vma->vm_next) {
2042 unsigned long hstart, hend;
2043
2044 cond_resched();
2045 if (unlikely(khugepaged_test_exit(mm))) {
2046 progress++;
2047 break;
2048 }
2049
2050 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2051 !khugepaged_always()) ||
2052 (vma->vm_flags & VM_NOHUGEPAGE)) {
2053 skip:
2054 progress++;
2055 continue;
2056 }
2057 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
2058 if (!vma->anon_vma || vma->vm_ops || vma->vm_file)
2059 goto skip;
2060 if (is_vma_temporary_stack(vma))
2061 goto skip;
2062
2063 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
2064
2065 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2066 hend = vma->vm_end & HPAGE_PMD_MASK;
2067 if (hstart >= hend)
2068 goto skip;
2069 if (khugepaged_scan.address > hend)
2070 goto skip;
2071 if (khugepaged_scan.address < hstart)
2072 khugepaged_scan.address = hstart;
2073 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2074
2075 while (khugepaged_scan.address < hend) {
2076 int ret;
2077 cond_resched();
2078 if (unlikely(khugepaged_test_exit(mm)))
2079 goto breakouterloop;
2080
2081 VM_BUG_ON(khugepaged_scan.address < hstart ||
2082 khugepaged_scan.address + HPAGE_PMD_SIZE >
2083 hend);
2084 ret = khugepaged_scan_pmd(mm, vma,
2085 khugepaged_scan.address,
2086 hpage);
2087 /* move to next address */
2088 khugepaged_scan.address += HPAGE_PMD_SIZE;
2089 progress += HPAGE_PMD_NR;
2090 if (ret)
2091 /* we released mmap_sem so break loop */
2092 goto breakouterloop_mmap_sem;
2093 if (progress >= pages)
2094 goto breakouterloop;
2095 }
2096 }
2097 breakouterloop:
2098 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2099 breakouterloop_mmap_sem:
2100
2101 spin_lock(&khugepaged_mm_lock);
2102 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2103 /*
2104 * Release the current mm_slot if this mm is about to die, or
2105 * if we scanned all vmas of this mm.
2106 */
2107 if (khugepaged_test_exit(mm) || !vma) {
2108 /*
2109 * Make sure that if mm_users is reaching zero while
2110 * khugepaged runs here, khugepaged_exit will find
2111 * mm_slot not pointing to the exiting mm.
2112 */
2113 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2114 khugepaged_scan.mm_slot = list_entry(
2115 mm_slot->mm_node.next,
2116 struct mm_slot, mm_node);
2117 khugepaged_scan.address = 0;
2118 } else {
2119 khugepaged_scan.mm_slot = NULL;
2120 khugepaged_full_scans++;
2121 }
2122
2123 collect_mm_slot(mm_slot);
2124 }
2125
2126 return progress;
2127 }
2128
2129 static int khugepaged_has_work(void)
2130 {
2131 return !list_empty(&khugepaged_scan.mm_head) &&
2132 khugepaged_enabled();
2133 }
2134
2135 static int khugepaged_wait_event(void)
2136 {
2137 return !list_empty(&khugepaged_scan.mm_head) ||
2138 !khugepaged_enabled();
2139 }
2140
2141 static void khugepaged_do_scan(struct page **hpage)
2142 {
2143 unsigned int progress = 0, pass_through_head = 0;
2144 unsigned int pages = khugepaged_pages_to_scan;
2145
2146 barrier(); /* write khugepaged_pages_to_scan to local stack */
2147
2148 while (progress < pages) {
2149 cond_resched();
2150
2151 #ifndef CONFIG_NUMA
2152 if (!*hpage) {
2153 *hpage = alloc_hugepage(khugepaged_defrag());
2154 if (unlikely(!*hpage))
2155 break;
2156 }
2157 #else
2158 if (IS_ERR(*hpage))
2159 break;
2160 #endif
2161
2162 if (unlikely(kthread_should_stop() || freezing(current)))
2163 break;
2164
2165 spin_lock(&khugepaged_mm_lock);
2166 if (!khugepaged_scan.mm_slot)
2167 pass_through_head++;
2168 if (khugepaged_has_work() &&
2169 pass_through_head < 2)
2170 progress += khugepaged_scan_mm_slot(pages - progress,
2171 hpage);
2172 else
2173 progress = pages;
2174 spin_unlock(&khugepaged_mm_lock);
2175 }
2176 }
2177
2178 static void khugepaged_alloc_sleep(void)
2179 {
2180 DEFINE_WAIT(wait);
2181 add_wait_queue(&khugepaged_wait, &wait);
2182 schedule_timeout_interruptible(
2183 msecs_to_jiffies(
2184 khugepaged_alloc_sleep_millisecs));
2185 remove_wait_queue(&khugepaged_wait, &wait);
2186 }
2187
2188 #ifndef CONFIG_NUMA
2189 static struct page *khugepaged_alloc_hugepage(void)
2190 {
2191 struct page *hpage;
2192
2193 do {
2194 hpage = alloc_hugepage(khugepaged_defrag());
2195 if (!hpage)
2196 khugepaged_alloc_sleep();
2197 } while (unlikely(!hpage) &&
2198 likely(khugepaged_enabled()));
2199 return hpage;
2200 }
2201 #endif
2202
2203 static void khugepaged_loop(void)
2204 {
2205 struct page *hpage;
2206
2207 #ifdef CONFIG_NUMA
2208 hpage = NULL;
2209 #endif
2210 while (likely(khugepaged_enabled())) {
2211 #ifndef CONFIG_NUMA
2212 hpage = khugepaged_alloc_hugepage();
2213 if (unlikely(!hpage))
2214 break;
2215 #else
2216 if (IS_ERR(hpage)) {
2217 khugepaged_alloc_sleep();
2218 hpage = NULL;
2219 }
2220 #endif
2221
2222 khugepaged_do_scan(&hpage);
2223 #ifndef CONFIG_NUMA
2224 if (hpage)
2225 put_page(hpage);
2226 #endif
2227 try_to_freeze();
2228 if (unlikely(kthread_should_stop()))
2229 break;
2230 if (khugepaged_has_work()) {
2231 DEFINE_WAIT(wait);
2232 if (!khugepaged_scan_sleep_millisecs)
2233 continue;
2234 add_wait_queue(&khugepaged_wait, &wait);
2235 schedule_timeout_interruptible(
2236 msecs_to_jiffies(
2237 khugepaged_scan_sleep_millisecs));
2238 remove_wait_queue(&khugepaged_wait, &wait);
2239 } else if (khugepaged_enabled())
2240 wait_event_freezable(khugepaged_wait,
2241 khugepaged_wait_event());
2242 }
2243 }
2244
2245 static int khugepaged(void *none)
2246 {
2247 struct mm_slot *mm_slot;
2248
2249 set_freezable();
2250 set_user_nice(current, 19);
2251
2252 /* serialize with start_khugepaged() */
2253 mutex_lock(&khugepaged_mutex);
2254
2255 for (;;) {
2256 mutex_unlock(&khugepaged_mutex);
2257 VM_BUG_ON(khugepaged_thread != current);
2258 khugepaged_loop();
2259 VM_BUG_ON(khugepaged_thread != current);
2260
2261 mutex_lock(&khugepaged_mutex);
2262 if (!khugepaged_enabled())
2263 break;
2264 if (unlikely(kthread_should_stop()))
2265 break;
2266 }
2267
2268 spin_lock(&khugepaged_mm_lock);
2269 mm_slot = khugepaged_scan.mm_slot;
2270 khugepaged_scan.mm_slot = NULL;
2271 if (mm_slot)
2272 collect_mm_slot(mm_slot);
2273 spin_unlock(&khugepaged_mm_lock);
2274
2275 khugepaged_thread = NULL;
2276 mutex_unlock(&khugepaged_mutex);
2277
2278 return 0;
2279 }
2280
2281 void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2282 {
2283 struct page *page;
2284
2285 spin_lock(&mm->page_table_lock);
2286 if (unlikely(!pmd_trans_huge(*pmd))) {
2287 spin_unlock(&mm->page_table_lock);
2288 return;
2289 }
2290 page = pmd_page(*pmd);
2291 VM_BUG_ON(!page_count(page));
2292 get_page(page);
2293 spin_unlock(&mm->page_table_lock);
2294
2295 split_huge_page(page);
2296
2297 put_page(page);
2298 BUG_ON(pmd_trans_huge(*pmd));
2299 }
2300
2301 static void split_huge_page_address(struct mm_struct *mm,
2302 unsigned long address)
2303 {
2304 pgd_t *pgd;
2305 pud_t *pud;
2306 pmd_t *pmd;
2307
2308 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2309
2310 pgd = pgd_offset(mm, address);
2311 if (!pgd_present(*pgd))
2312 return;
2313
2314 pud = pud_offset(pgd, address);
2315 if (!pud_present(*pud))
2316 return;
2317
2318 pmd = pmd_offset(pud, address);
2319 if (!pmd_present(*pmd))
2320 return;
2321 /*
2322 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2323 * materialize from under us.
2324 */
2325 split_huge_page_pmd(mm, pmd);
2326 }
2327
2328 void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2329 unsigned long start,
2330 unsigned long end,
2331 long adjust_next)
2332 {
2333 /*
2334 * If the new start address isn't hpage aligned and it could
2335 * previously contain an hugepage: check if we need to split
2336 * an huge pmd.
2337 */
2338 if (start & ~HPAGE_PMD_MASK &&
2339 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2340 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2341 split_huge_page_address(vma->vm_mm, start);
2342
2343 /*
2344 * If the new end address isn't hpage aligned and it could
2345 * previously contain an hugepage: check if we need to split
2346 * an huge pmd.
2347 */
2348 if (end & ~HPAGE_PMD_MASK &&
2349 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2350 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2351 split_huge_page_address(vma->vm_mm, end);
2352
2353 /*
2354 * If we're also updating the vma->vm_next->vm_start, if the new
2355 * vm_next->vm_start isn't page aligned and it could previously
2356 * contain an hugepage: check if we need to split an huge pmd.
2357 */
2358 if (adjust_next > 0) {
2359 struct vm_area_struct *next = vma->vm_next;
2360 unsigned long nstart = next->vm_start;
2361 nstart += adjust_next << PAGE_SHIFT;
2362 if (nstart & ~HPAGE_PMD_MASK &&
2363 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2364 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2365 split_huge_page_address(next->vm_mm, nstart);
2366 }
2367 }
Linux with added FPC-III support