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ext4: fix race between sync and completed io work
[linux-2.6-block.git] / mm / huge_memory.c
CommitLineData
71e3aac0
AA		 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>
ba76149f
AA		 15#include <linux/mm_inline.h>
16#include <linux/kthread.h>
17#include <linux/khugepaged.h>
878aee7d 18#include <linux/freezer.h>
a664b2d8 19#include <linux/mman.h>
71e3aac0
AA		 20#include <asm/tlb.h>
21#include <asm/pgalloc.h>
22#include "internal.h"
23
ba76149f
AA		 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 */
71e3aac0 31unsigned long transparent_hugepage_flags __read_mostly =
13ece886 32#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
ba76149f 33 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
13ece886
AA		 34#endif
35#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
36 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
37#endif
d39d33c3 38 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
ba76149f
AA		 39 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
40
41/* default scan 8*512 pte (or vmas) every 30 second */
42static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8;
43static unsigned int khugepaged_pages_collapsed;
44static unsigned int khugepaged_full_scans;
45static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
46/* during fragmentation poll the hugepage allocator once every minute */
47static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
48static struct task_struct *khugepaged_thread __read_mostly;
49static DEFINE_MUTEX(khugepaged_mutex);
50static DEFINE_SPINLOCK(khugepaged_mm_lock);
51static 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 */
57static unsigned int khugepaged_max_ptes_none __read_mostly = HPAGE_PMD_NR-1;
58
59static int khugepaged(void *none);
60static int mm_slots_hash_init(void);
61static int khugepaged_slab_init(void);
62static void khugepaged_slab_free(void);
63
64#define MM_SLOTS_HASH_HEADS 1024
65static struct hlist_head *mm_slots_hash __read_mostly;
66static 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 */
74struct 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 */
88struct khugepaged_scan {
89 struct list_head mm_head;
90 struct mm_slot *mm_slot;
91 unsigned long address;
2f1da642
HS		 92};
93static struct khugepaged_scan khugepaged_scan = {
ba76149f
AA		 94 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
95};
96
f000565a
AA		 97
98static int set_recommended_min_free_kbytes(void)
99{
100 struct zone *zone;
101 int nr_zones = 0;
102 unsigned long recommended_min;
103 extern int min_free_kbytes;
104
105 if (!test_bit(TRANSPARENT_HUGEPAGE_FLAG,
106 &transparent_hugepage_flags) &&
107 !test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
108 &transparent_hugepage_flags))
109 return 0;
110
111 for_each_populated_zone(zone)
112 nr_zones++;
113
114 /* Make sure at least 2 hugepages are free for MIGRATE_RESERVE */
115 recommended_min = pageblock_nr_pages * nr_zones * 2;
116
117 /*
118 * Make sure that on average at least two pageblocks are almost free
119 * of another type, one for a migratetype to fall back to and a
120 * second to avoid subsequent fallbacks of other types There are 3
121 * MIGRATE_TYPES we care about.
122 */
123 recommended_min += pageblock_nr_pages * nr_zones *
124 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
125
126 /* don't ever allow to reserve more than 5% of the lowmem */
127 recommended_min = min(recommended_min,
128 (unsigned long) nr_free_buffer_pages() / 20);
129 recommended_min <<= (PAGE_SHIFT-10);
130
131 if (recommended_min > min_free_kbytes)
132 min_free_kbytes = recommended_min;
133 setup_per_zone_wmarks();
134 return 0;
135}
136late_initcall(set_recommended_min_free_kbytes);
137
ba76149f
AA		 138static int start_khugepaged(void)
139{
140 int err = 0;
141 if (khugepaged_enabled()) {
142 int wakeup;
143 if (unlikely(!mm_slot_cache || !mm_slots_hash)) {
144 err = -ENOMEM;
145 goto out;
146 }
147 mutex_lock(&khugepaged_mutex);
148 if (!khugepaged_thread)
149 khugepaged_thread = kthread_run(khugepaged, NULL,
150 "khugepaged");
151 if (unlikely(IS_ERR(khugepaged_thread))) {
152 printk(KERN_ERR
153 "khugepaged: kthread_run(khugepaged) failed\n");
154 err = PTR_ERR(khugepaged_thread);
155 khugepaged_thread = NULL;
156 }
157 wakeup = !list_empty(&khugepaged_scan.mm_head);
158 mutex_unlock(&khugepaged_mutex);
159 if (wakeup)
160 wake_up_interruptible(&khugepaged_wait);
f000565a
AA		 161
162 set_recommended_min_free_kbytes();
ba76149f
AA		 163 } else
164 /* wakeup to exit */
165 wake_up_interruptible(&khugepaged_wait);
166out:
167 return err;
168}
71e3aac0
AA		 169
170#ifdef CONFIG_SYSFS
ba76149f 171
71e3aac0
AA		 172static ssize_t double_flag_show(struct kobject *kobj,
173 struct kobj_attribute *attr, char *buf,
174 enum transparent_hugepage_flag enabled,
175 enum transparent_hugepage_flag req_madv)
176{
177 if (test_bit(enabled, &transparent_hugepage_flags)) {
178 VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags));
179 return sprintf(buf, "[always] madvise never\n");
180 } else if (test_bit(req_madv, &transparent_hugepage_flags))
181 return sprintf(buf, "always [madvise] never\n");
182 else
183 return sprintf(buf, "always madvise [never]\n");
184}
185static ssize_t double_flag_store(struct kobject *kobj,
186 struct kobj_attribute *attr,
187 const char *buf, size_t count,
188 enum transparent_hugepage_flag enabled,
189 enum transparent_hugepage_flag req_madv)
190{
191 if (!memcmp("always", buf,
192 min(sizeof("always")-1, count))) {
193 set_bit(enabled, &transparent_hugepage_flags);
194 clear_bit(req_madv, &transparent_hugepage_flags);
195 } else if (!memcmp("madvise", buf,
196 min(sizeof("madvise")-1, count))) {
197 clear_bit(enabled, &transparent_hugepage_flags);
198 set_bit(req_madv, &transparent_hugepage_flags);
199 } else if (!memcmp("never", buf,
200 min(sizeof("never")-1, count))) {
201 clear_bit(enabled, &transparent_hugepage_flags);
202 clear_bit(req_madv, &transparent_hugepage_flags);
203 } else
204 return -EINVAL;
205
206 return count;
207}
208
209static ssize_t enabled_show(struct kobject *kobj,
210 struct kobj_attribute *attr, char *buf)
211{
212 return double_flag_show(kobj, attr, buf,
213 TRANSPARENT_HUGEPAGE_FLAG,
214 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
215}
216static ssize_t enabled_store(struct kobject *kobj,
217 struct kobj_attribute *attr,
218 const char *buf, size_t count)
219{
ba76149f
AA		 220 ssize_t ret;
221
222 ret = double_flag_store(kobj, attr, buf, count,
223 TRANSPARENT_HUGEPAGE_FLAG,
224 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
225
226 if (ret > 0) {
227 int err = start_khugepaged();
228 if (err)
229 ret = err;
230 }
231
f000565a
AA		 232 if (ret > 0 &&
233 (test_bit(TRANSPARENT_HUGEPAGE_FLAG,
234 &transparent_hugepage_flags) ||
235 test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
236 &transparent_hugepage_flags)))
237 set_recommended_min_free_kbytes();
238
ba76149f 239 return ret;
71e3aac0
AA		 240}
241static struct kobj_attribute enabled_attr =
242 __ATTR(enabled, 0644, enabled_show, enabled_store);
243
244static ssize_t single_flag_show(struct kobject *kobj,
245 struct kobj_attribute *attr, char *buf,
246 enum transparent_hugepage_flag flag)
247{
e27e6151
BH		 248 return sprintf(buf, "%d\n",
249 !!test_bit(flag, &transparent_hugepage_flags));
71e3aac0 250}
e27e6151 251
71e3aac0
AA		 252static 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{
e27e6151
BH		 257 unsigned long value;
258 int ret;
259
260 ret = kstrtoul(buf, 10, &value);
261 if (ret < 0)
262 return ret;
263 if (value > 1)
264 return -EINVAL;
265
266 if (value)
71e3aac0 267 set_bit(flag, &transparent_hugepage_flags);
e27e6151 268 else
71e3aac0 269 clear_bit(flag, &transparent_hugepage_flags);
71e3aac0
AA		 270
271 return count;
272}
273
274/*
275 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
276 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
277 * memory just to allocate one more hugepage.
278 */
279static ssize_t defrag_show(struct kobject *kobj,
280 struct kobj_attribute *attr, char *buf)
281{
282 return double_flag_show(kobj, attr, buf,
283 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
284 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
285}
286static ssize_t defrag_store(struct kobject *kobj,
287 struct kobj_attribute *attr,
288 const char *buf, size_t count)
289{
290 return double_flag_store(kobj, attr, buf, count,
291 TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
292 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
293}
294static struct kobj_attribute defrag_attr =
295 __ATTR(defrag, 0644, defrag_show, defrag_store);
296
297#ifdef CONFIG_DEBUG_VM
298static ssize_t debug_cow_show(struct kobject *kobj,
299 struct kobj_attribute *attr, char *buf)
300{
301 return single_flag_show(kobj, attr, buf,
302 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
303}
304static ssize_t debug_cow_store(struct kobject *kobj,
305 struct kobj_attribute *attr,
306 const char *buf, size_t count)
307{
308 return single_flag_store(kobj, attr, buf, count,
309 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
310}
311static struct kobj_attribute debug_cow_attr =
312 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
313#endif /* CONFIG_DEBUG_VM */
314
315static struct attribute *hugepage_attr[] = {
316 &enabled_attr.attr,
317 &defrag_attr.attr,
318#ifdef CONFIG_DEBUG_VM
319 &debug_cow_attr.attr,
320#endif
321 NULL,
322};
323
324static struct attribute_group hugepage_attr_group = {
325 .attrs = hugepage_attr,
ba76149f
AA		 326};
327
328static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
329 struct kobj_attribute *attr,
330 char *buf)
331{
332 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
333}
334
335static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
336 struct kobj_attribute *attr,
337 const char *buf, size_t count)
338{
339 unsigned long msecs;
340 int err;
341
342 err = strict_strtoul(buf, 10, &msecs);
343 if (err || msecs > UINT_MAX)
344 return -EINVAL;
345
346 khugepaged_scan_sleep_millisecs = msecs;
347 wake_up_interruptible(&khugepaged_wait);
348
349 return count;
350}
351static struct kobj_attribute scan_sleep_millisecs_attr =
352 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
353 scan_sleep_millisecs_store);
354
355static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
356 struct kobj_attribute *attr,
357 char *buf)
358{
359 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
360}
361
362static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
363 struct kobj_attribute *attr,
364 const char *buf, size_t count)
365{
366 unsigned long msecs;
367 int err;
368
369 err = strict_strtoul(buf, 10, &msecs);
370 if (err || msecs > UINT_MAX)
371 return -EINVAL;
372
373 khugepaged_alloc_sleep_millisecs = msecs;
374 wake_up_interruptible(&khugepaged_wait);
375
376 return count;
377}
378static struct kobj_attribute alloc_sleep_millisecs_attr =
379 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
380 alloc_sleep_millisecs_store);
381
382static ssize_t pages_to_scan_show(struct kobject *kobj,
383 struct kobj_attribute *attr,
384 char *buf)
385{
386 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
387}
388static ssize_t pages_to_scan_store(struct kobject *kobj,
389 struct kobj_attribute *attr,
390 const char *buf, size_t count)
391{
392 int err;
393 unsigned long pages;
394
395 err = strict_strtoul(buf, 10, &pages);
396 if (err || !pages || pages > UINT_MAX)
397 return -EINVAL;
398
399 khugepaged_pages_to_scan = pages;
400
401 return count;
402}
403static struct kobj_attribute pages_to_scan_attr =
404 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
405 pages_to_scan_store);
406
407static ssize_t pages_collapsed_show(struct kobject *kobj,
408 struct kobj_attribute *attr,
409 char *buf)
410{
411 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
412}
413static struct kobj_attribute pages_collapsed_attr =
414 __ATTR_RO(pages_collapsed);
415
416static ssize_t full_scans_show(struct kobject *kobj,
417 struct kobj_attribute *attr,
418 char *buf)
419{
420 return sprintf(buf, "%u\n", khugepaged_full_scans);
421}
422static struct kobj_attribute full_scans_attr =
423 __ATTR_RO(full_scans);
424
425static ssize_t khugepaged_defrag_show(struct kobject *kobj,
426 struct kobj_attribute *attr, char *buf)
427{
428 return single_flag_show(kobj, attr, buf,
429 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
430}
431static ssize_t khugepaged_defrag_store(struct kobject *kobj,
432 struct kobj_attribute *attr,
433 const char *buf, size_t count)
434{
435 return single_flag_store(kobj, attr, buf, count,
436 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
437}
438static struct kobj_attribute khugepaged_defrag_attr =
439 __ATTR(defrag, 0644, khugepaged_defrag_show,
440 khugepaged_defrag_store);
441
442/*
443 * max_ptes_none controls if khugepaged should collapse hugepages over
444 * any unmapped ptes in turn potentially increasing the memory
445 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
446 * reduce the available free memory in the system as it
447 * runs. Increasing max_ptes_none will instead potentially reduce the
448 * free memory in the system during the khugepaged scan.
449 */
450static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
451 struct kobj_attribute *attr,
452 char *buf)
453{
454 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
455}
456static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
457 struct kobj_attribute *attr,
458 const char *buf, size_t count)
459{
460 int err;
461 unsigned long max_ptes_none;
462
463 err = strict_strtoul(buf, 10, &max_ptes_none);
464 if (err || max_ptes_none > HPAGE_PMD_NR-1)
465 return -EINVAL;
466
467 khugepaged_max_ptes_none = max_ptes_none;
468
469 return count;
470}
471static struct kobj_attribute khugepaged_max_ptes_none_attr =
472 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
473 khugepaged_max_ptes_none_store);
474
475static struct attribute *khugepaged_attr[] = {
476 &khugepaged_defrag_attr.attr,
477 &khugepaged_max_ptes_none_attr.attr,
478 &pages_to_scan_attr.attr,
479 &pages_collapsed_attr.attr,
480 &full_scans_attr.attr,
481 &scan_sleep_millisecs_attr.attr,
482 &alloc_sleep_millisecs_attr.attr,
483 NULL,
484};
485
486static struct attribute_group khugepaged_attr_group = {
487 .attrs = khugepaged_attr,
488 .name = "khugepaged",
71e3aac0 489};
71e3aac0 490
569e5590 491static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
71e3aac0 492{
71e3aac0
AA		 493 int err;
494
569e5590
SL		 495 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
496 if (unlikely(!*hugepage_kobj)) {
ba76149f 497 printk(KERN_ERR "hugepage: failed kobject create\n");
569e5590 498 return -ENOMEM;
ba76149f
AA		 499 }
500
569e5590 501 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
ba76149f
AA		 502 if (err) {
503 printk(KERN_ERR "hugepage: failed register hugeage group\n");
569e5590 504 goto delete_obj;
ba76149f
AA		 505 }
506
569e5590 507 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
ba76149f
AA		 508 if (err) {
509 printk(KERN_ERR "hugepage: failed register hugeage group\n");
569e5590 510 goto remove_hp_group;
ba76149f 511 }
569e5590
SL		 512
513 return 0;
514
515remove_hp_group:
516 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
517delete_obj:
518 kobject_put(*hugepage_kobj);
519 return err;
520}
521
522static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
523{
524 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
525 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
526 kobject_put(hugepage_kobj);
527}
528#else
529static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
530{
531 return 0;
532}
533
534static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
535{
536}
537#endif /* CONFIG_SYSFS */
538
539static int __init hugepage_init(void)
540{
541 int err;
542 struct kobject *hugepage_kobj;
543
544 if (!has_transparent_hugepage()) {
545 transparent_hugepage_flags = 0;
546 return -EINVAL;
547 }
548
549 err = hugepage_init_sysfs(&hugepage_kobj);
550 if (err)
551 return err;
ba76149f
AA		 552
553 err = khugepaged_slab_init();
554 if (err)
555 goto out;
556
557 err = mm_slots_hash_init();
558 if (err) {
559 khugepaged_slab_free();
560 goto out;
561 }
562
97562cd2
RR		 563 /*
564 * By default disable transparent hugepages on smaller systems,
565 * where the extra memory used could hurt more than TLB overhead
566 * is likely to save. The admin can still enable it through /sys.
567 */
568 if (totalram_pages < (512 << (20 - PAGE_SHIFT)))
569 transparent_hugepage_flags = 0;
570
ba76149f
AA		 571 start_khugepaged();
572
f000565a
AA		 573 set_recommended_min_free_kbytes();
574
569e5590 575 return 0;
ba76149f 576out:
569e5590 577 hugepage_exit_sysfs(hugepage_kobj);
ba76149f 578 return err;
71e3aac0
AA		 579}
580module_init(hugepage_init)
581
582static int __init setup_transparent_hugepage(char *str)
583{
584 int ret = 0;
585 if (!str)
586 goto out;
587 if (!strcmp(str, "always")) {
588 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
589 &transparent_hugepage_flags);
590 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
591 &transparent_hugepage_flags);
592 ret = 1;
593 } else if (!strcmp(str, "madvise")) {
594 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
595 &transparent_hugepage_flags);
596 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
597 &transparent_hugepage_flags);
598 ret = 1;
599 } else if (!strcmp(str, "never")) {
600 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
601 &transparent_hugepage_flags);
602 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
603 &transparent_hugepage_flags);
604 ret = 1;
605 }
606out:
607 if (!ret)
608 printk(KERN_WARNING
609 "transparent_hugepage= cannot parse, ignored\n");
610 return ret;
611}
612__setup("transparent_hugepage=", setup_transparent_hugepage);
613
614static void prepare_pmd_huge_pte(pgtable_t pgtable,
615 struct mm_struct *mm)
616{
617 assert_spin_locked(&mm->page_table_lock);
618
619 /* FIFO */
620 if (!mm->pmd_huge_pte)
621 INIT_LIST_HEAD(&pgtable->lru);
622 else
623 list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
624 mm->pmd_huge_pte = pgtable;
625}
626
627static inline pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
628{
629 if (likely(vma->vm_flags & VM_WRITE))
630 pmd = pmd_mkwrite(pmd);
631 return pmd;
632}
633
634static int __do_huge_pmd_anonymous_page(struct mm_struct *mm,
635 struct vm_area_struct *vma,
636 unsigned long haddr, pmd_t *pmd,
637 struct page *page)
638{
639 int ret = 0;
640 pgtable_t pgtable;
641
642 VM_BUG_ON(!PageCompound(page));
643 pgtable = pte_alloc_one(mm, haddr);
644 if (unlikely(!pgtable)) {
b9bbfbe3 645 mem_cgroup_uncharge_page(page);
71e3aac0
AA		 646 put_page(page);
647 return VM_FAULT_OOM;
648 }
649
650 clear_huge_page(page, haddr, HPAGE_PMD_NR);
651 __SetPageUptodate(page);
652
653 spin_lock(&mm->page_table_lock);
654 if (unlikely(!pmd_none(*pmd))) {
655 spin_unlock(&mm->page_table_lock);
b9bbfbe3 656 mem_cgroup_uncharge_page(page);
71e3aac0
AA		 657 put_page(page);
658 pte_free(mm, pgtable);
659 } else {
660 pmd_t entry;
661 entry = mk_pmd(page, vma->vm_page_prot);
662 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
663 entry = pmd_mkhuge(entry);
664 /*
665 * The spinlocking to take the lru_lock inside
666 * page_add_new_anon_rmap() acts as a full memory
667 * barrier to be sure clear_huge_page writes become
668 * visible after the set_pmd_at() write.
669 */
670 page_add_new_anon_rmap(page, vma, haddr);
671 set_pmd_at(mm, haddr, pmd, entry);
672 prepare_pmd_huge_pte(pgtable, mm);
673 add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
674 spin_unlock(&mm->page_table_lock);
675 }
676
677 return ret;
678}
679
cc5d462f 680static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp)
0bbbc0b3 681{
cc5d462f 682 return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp;
0bbbc0b3
AA		 683}
684
685static inline struct page *alloc_hugepage_vma(int defrag,
686 struct vm_area_struct *vma,
cc5d462f
AK		 687 unsigned long haddr, int nd,
688 gfp_t extra_gfp)
0bbbc0b3 689{
cc5d462f 690 return alloc_pages_vma(alloc_hugepage_gfpmask(defrag, extra_gfp),
5c4b4be3 691 HPAGE_PMD_ORDER, vma, haddr, nd);
0bbbc0b3
AA		 692}
693
694#ifndef CONFIG_NUMA
71e3aac0
AA		 695static inline struct page *alloc_hugepage(int defrag)
696{
cc5d462f 697 return alloc_pages(alloc_hugepage_gfpmask(defrag, 0),
71e3aac0
AA		 698 HPAGE_PMD_ORDER);
699}
0bbbc0b3 700#endif
71e3aac0
AA		 701
702int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
703 unsigned long address, pmd_t *pmd,
704 unsigned int flags)
705{
706 struct page *page;
707 unsigned long haddr = address & HPAGE_PMD_MASK;
708 pte_t *pte;
709
710 if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
711 if (unlikely(anon_vma_prepare(vma)))
712 return VM_FAULT_OOM;
ba76149f
AA		 713 if (unlikely(khugepaged_enter(vma)))
714 return VM_FAULT_OOM;
0bbbc0b3 715 page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
cc5d462f 716 vma, haddr, numa_node_id(), 0);
81ab4201
AK		 717 if (unlikely(!page)) {
718 count_vm_event(THP_FAULT_FALLBACK);
71e3aac0 719 goto out;
81ab4201
AK		 720 }
721 count_vm_event(THP_FAULT_ALLOC);
b9bbfbe3
AA		 722 if (unlikely(mem_cgroup_newpage_charge(page, mm, GFP_KERNEL))) {
723 put_page(page);
724 goto out;
725 }
71e3aac0
AA		 726
727 return __do_huge_pmd_anonymous_page(mm, vma, haddr, pmd, page);
728 }
729out:
730 /*
731 * Use __pte_alloc instead of pte_alloc_map, because we can't
732 * run pte_offset_map on the pmd, if an huge pmd could
733 * materialize from under us from a different thread.
734 */
735 if (unlikely(__pte_alloc(mm, vma, pmd, address)))
736 return VM_FAULT_OOM;
737 /* if an huge pmd materialized from under us just retry later */
738 if (unlikely(pmd_trans_huge(*pmd)))
739 return 0;
740 /*
741 * A regular pmd is established and it can't morph into a huge pmd
742 * from under us anymore at this point because we hold the mmap_sem
743 * read mode and khugepaged takes it in write mode. So now it's
744 * safe to run pte_offset_map().
745 */
746 pte = pte_offset_map(pmd, address);
747 return handle_pte_fault(mm, vma, address, pte, pmd, flags);
748}
749
750int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
751 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
752 struct vm_area_struct *vma)
753{
754 struct page *src_page;
755 pmd_t pmd;
756 pgtable_t pgtable;
757 int ret;
758
759 ret = -ENOMEM;
760 pgtable = pte_alloc_one(dst_mm, addr);
761 if (unlikely(!pgtable))
762 goto out;
763
764 spin_lock(&dst_mm->page_table_lock);
765 spin_lock_nested(&src_mm->page_table_lock, SINGLE_DEPTH_NESTING);
766
767 ret = -EAGAIN;
768 pmd = *src_pmd;
769 if (unlikely(!pmd_trans_huge(pmd))) {
770 pte_free(dst_mm, pgtable);
771 goto out_unlock;
772 }
773 if (unlikely(pmd_trans_splitting(pmd))) {
774 /* split huge page running from under us */
775 spin_unlock(&src_mm->page_table_lock);
776 spin_unlock(&dst_mm->page_table_lock);
777 pte_free(dst_mm, pgtable);
778
779 wait_split_huge_page(vma->anon_vma, src_pmd); /* src_vma */
780 goto out;
781 }
782 src_page = pmd_page(pmd);
783 VM_BUG_ON(!PageHead(src_page));
784 get_page(src_page);
785 page_dup_rmap(src_page);
786 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
787
788 pmdp_set_wrprotect(src_mm, addr, src_pmd);
789 pmd = pmd_mkold(pmd_wrprotect(pmd));
790 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
791 prepare_pmd_huge_pte(pgtable, dst_mm);
792
793 ret = 0;
794out_unlock:
795 spin_unlock(&src_mm->page_table_lock);
796 spin_unlock(&dst_mm->page_table_lock);
797out:
798 return ret;
799}
800
801/* no "address" argument so destroys page coloring of some arch */
802pgtable_t get_pmd_huge_pte(struct mm_struct *mm)
803{
804 pgtable_t pgtable;
805
806 assert_spin_locked(&mm->page_table_lock);
807
808 /* FIFO */
809 pgtable = mm->pmd_huge_pte;
810 if (list_empty(&pgtable->lru))
811 mm->pmd_huge_pte = NULL;
812 else {
813 mm->pmd_huge_pte = list_entry(pgtable->lru.next,
814 struct page, lru);
815 list_del(&pgtable->lru);
816 }
817 return pgtable;
818}
819
820static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
821 struct vm_area_struct *vma,
822 unsigned long address,
823 pmd_t *pmd, pmd_t orig_pmd,
824 struct page *page,
825 unsigned long haddr)
826{
827 pgtable_t pgtable;
828 pmd_t _pmd;
829 int ret = 0, i;
830 struct page **pages;
831
832 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
833 GFP_KERNEL);
834 if (unlikely(!pages)) {
835 ret |= VM_FAULT_OOM;
836 goto out;
837 }
838
839 for (i = 0; i < HPAGE_PMD_NR; i++) {
cc5d462f
AK		 840 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
841 __GFP_OTHER_NODE,
19ee151e 842 vma, address, page_to_nid(page));
b9bbfbe3
AA		 843 if (unlikely(!pages[i] ||
844 mem_cgroup_newpage_charge(pages[i], mm,
845 GFP_KERNEL))) {
846 if (pages[i])
71e3aac0 847 put_page(pages[i]);
b9bbfbe3
AA		 848 mem_cgroup_uncharge_start();
849 while (--i >= 0) {
850 mem_cgroup_uncharge_page(pages[i]);
851 put_page(pages[i]);
852 }
853 mem_cgroup_uncharge_end();
71e3aac0
AA		 854 kfree(pages);
855 ret |= VM_FAULT_OOM;
856 goto out;
857 }
858 }
859
860 for (i = 0; i < HPAGE_PMD_NR; i++) {
861 copy_user_highpage(pages[i], page + i,
0089e485 862 haddr + PAGE_SIZE * i, vma);
71e3aac0
AA		 863 __SetPageUptodate(pages[i]);
864 cond_resched();
865 }
866
867 spin_lock(&mm->page_table_lock);
868 if (unlikely(!pmd_same(*pmd, orig_pmd)))
869 goto out_free_pages;
870 VM_BUG_ON(!PageHead(page));
871
872 pmdp_clear_flush_notify(vma, haddr, pmd);
873 /* leave pmd empty until pte is filled */
874
875 pgtable = get_pmd_huge_pte(mm);
876 pmd_populate(mm, &_pmd, pgtable);
877
878 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
879 pte_t *pte, entry;
880 entry = mk_pte(pages[i], vma->vm_page_prot);
881 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
882 page_add_new_anon_rmap(pages[i], vma, haddr);
883 pte = pte_offset_map(&_pmd, haddr);
884 VM_BUG_ON(!pte_none(*pte));
885 set_pte_at(mm, haddr, pte, entry);
886 pte_unmap(pte);
887 }
888 kfree(pages);
889
890 mm->nr_ptes++;
891 smp_wmb(); /* make pte visible before pmd */
892 pmd_populate(mm, pmd, pgtable);
893 page_remove_rmap(page);
894 spin_unlock(&mm->page_table_lock);
895
896 ret |= VM_FAULT_WRITE;
897 put_page(page);
898
899out:
900 return ret;
901
902out_free_pages:
903 spin_unlock(&mm->page_table_lock);
b9bbfbe3
AA		 904 mem_cgroup_uncharge_start();
905 for (i = 0; i < HPAGE_PMD_NR; i++) {
906 mem_cgroup_uncharge_page(pages[i]);
71e3aac0 907 put_page(pages[i]);
b9bbfbe3
AA		 908 }
909 mem_cgroup_uncharge_end();
71e3aac0
AA		 910 kfree(pages);
911 goto out;
912}
913
914int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
915 unsigned long address, pmd_t *pmd, pmd_t orig_pmd)
916{
917 int ret = 0;
918 struct page *page, *new_page;
919 unsigned long haddr;
920
921 VM_BUG_ON(!vma->anon_vma);
922 spin_lock(&mm->page_table_lock);
923 if (unlikely(!pmd_same(*pmd, orig_pmd)))
924 goto out_unlock;
925
926 page = pmd_page(orig_pmd);
927 VM_BUG_ON(!PageCompound(page) || !PageHead(page));
928 haddr = address & HPAGE_PMD_MASK;
929 if (page_mapcount(page) == 1) {
930 pmd_t entry;
931 entry = pmd_mkyoung(orig_pmd);
932 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
933 if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
934 update_mmu_cache(vma, address, entry);
935 ret |= VM_FAULT_WRITE;
936 goto out_unlock;
937 }
938 get_page(page);
939 spin_unlock(&mm->page_table_lock);
940
941 if (transparent_hugepage_enabled(vma) &&
942 !transparent_hugepage_debug_cow())
0bbbc0b3 943 new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma),
cc5d462f 944 vma, haddr, numa_node_id(), 0);
71e3aac0
AA		 945 else
946 new_page = NULL;
947
948 if (unlikely(!new_page)) {
81ab4201 949 count_vm_event(THP_FAULT_FALLBACK);
71e3aac0
AA		 950 ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
951 pmd, orig_pmd, page, haddr);
952 put_page(page);
953 goto out;
954 }
81ab4201 955 count_vm_event(THP_FAULT_ALLOC);
71e3aac0 956
b9bbfbe3
AA		 957 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
958 put_page(new_page);
959 put_page(page);
960 ret |= VM_FAULT_OOM;
961 goto out;
962 }
963
71e3aac0
AA		 964 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
965 __SetPageUptodate(new_page);
966
967 spin_lock(&mm->page_table_lock);
968 put_page(page);
b9bbfbe3
AA		 969 if (unlikely(!pmd_same(*pmd, orig_pmd))) {
970 mem_cgroup_uncharge_page(new_page);
71e3aac0 971 put_page(new_page);
b9bbfbe3 972 } else {
71e3aac0
AA		 973 pmd_t entry;
974 VM_BUG_ON(!PageHead(page));
975 entry = mk_pmd(new_page, vma->vm_page_prot);
976 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
977 entry = pmd_mkhuge(entry);
978 pmdp_clear_flush_notify(vma, haddr, pmd);
979 page_add_new_anon_rmap(new_page, vma, haddr);
980 set_pmd_at(mm, haddr, pmd, entry);
981 update_mmu_cache(vma, address, entry);
982 page_remove_rmap(page);
983 put_page(page);
984 ret |= VM_FAULT_WRITE;
985 }
986out_unlock:
987 spin_unlock(&mm->page_table_lock);
988out:
989 return ret;
990}
991
992struct page *follow_trans_huge_pmd(struct mm_struct *mm,
993 unsigned long addr,
994 pmd_t *pmd,
995 unsigned int flags)
996{
997 struct page *page = NULL;
998
999 assert_spin_locked(&mm->page_table_lock);
1000
1001 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1002 goto out;
1003
1004 page = pmd_page(*pmd);
1005 VM_BUG_ON(!PageHead(page));
1006 if (flags & FOLL_TOUCH) {
1007 pmd_t _pmd;
1008 /*
1009 * We should set the dirty bit only for FOLL_WRITE but
1010 * for now the dirty bit in the pmd is meaningless.
1011 * And if the dirty bit will become meaningful and
1012 * we'll only set it with FOLL_WRITE, an atomic
1013 * set_bit will be required on the pmd to set the
1014 * young bit, instead of the current set_pmd_at.
1015 */
1016 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
1017 set_pmd_at(mm, addr & HPAGE_PMD_MASK, pmd, _pmd);
1018 }
1019 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1020 VM_BUG_ON(!PageCompound(page));
1021 if (flags & FOLL_GET)
70b50f94 1022 get_page_foll(page);
71e3aac0
AA		 1023
1024out:
1025 return page;
1026}
1027
1028int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
f21760b1 1029 pmd_t *pmd, unsigned long addr)
71e3aac0
AA		 1030{
1031 int ret = 0;
1032
1033 spin_lock(&tlb->mm->page_table_lock);
1034 if (likely(pmd_trans_huge(*pmd))) {
1035 if (unlikely(pmd_trans_splitting(*pmd))) {
1036 spin_unlock(&tlb->mm->page_table_lock);
1037 wait_split_huge_page(vma->anon_vma,
1038 pmd);
1039 } else {
1040 struct page *page;
1041 pgtable_t pgtable;
1042 pgtable = get_pmd_huge_pte(tlb->mm);
1043 page = pmd_page(*pmd);
1044 pmd_clear(pmd);
f21760b1 1045 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
71e3aac0
AA		 1046 page_remove_rmap(page);
1047 VM_BUG_ON(page_mapcount(page) < 0);
1048 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1049 VM_BUG_ON(!PageHead(page));
1050 spin_unlock(&tlb->mm->page_table_lock);
1051 tlb_remove_page(tlb, page);
1052 pte_free(tlb->mm, pgtable);
1053 ret = 1;
1054 }
1055 } else
1056 spin_unlock(&tlb->mm->page_table_lock);
1057
1058 return ret;
1059}
1060
0ca1634d
JW		 1061int mincore_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1062 unsigned long addr, unsigned long end,
1063 unsigned char *vec)
1064{
1065 int ret = 0;
1066
1067 spin_lock(&vma->vm_mm->page_table_lock);
1068 if (likely(pmd_trans_huge(*pmd))) {
1069 ret = !pmd_trans_splitting(*pmd);
1070 spin_unlock(&vma->vm_mm->page_table_lock);
1071 if (unlikely(!ret))
1072 wait_split_huge_page(vma->anon_vma, pmd);
1073 else {
1074 /*
1075 * All logical pages in the range are present
1076 * if backed by a huge page.
1077 */
1078 memset(vec, 1, (end - addr) >> PAGE_SHIFT);
1079 }
1080 } else
1081 spin_unlock(&vma->vm_mm->page_table_lock);
1082
1083 return ret;
1084}
1085
37a1c49a
AA		 1086int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
1087 unsigned long old_addr,
1088 unsigned long new_addr, unsigned long old_end,
1089 pmd_t *old_pmd, pmd_t *new_pmd)
1090{
1091 int ret = 0;
1092 pmd_t pmd;
1093
1094 struct mm_struct *mm = vma->vm_mm;
1095
1096 if ((old_addr & ~HPAGE_PMD_MASK) ||
1097 (new_addr & ~HPAGE_PMD_MASK) ||
1098 old_end - old_addr < HPAGE_PMD_SIZE ||
1099 (new_vma->vm_flags & VM_NOHUGEPAGE))
1100 goto out;
1101
1102 /*
1103 * The destination pmd shouldn't be established, free_pgtables()
1104 * should have release it.
1105 */
1106 if (WARN_ON(!pmd_none(*new_pmd))) {
1107 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1108 goto out;
1109 }
1110
1111 spin_lock(&mm->page_table_lock);
1112 if (likely(pmd_trans_huge(*old_pmd))) {
1113 if (pmd_trans_splitting(*old_pmd)) {
1114 spin_unlock(&mm->page_table_lock);
1115 wait_split_huge_page(vma->anon_vma, old_pmd);
1116 ret = -1;
1117 } else {
1118 pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
1119 VM_BUG_ON(!pmd_none(*new_pmd));
1120 set_pmd_at(mm, new_addr, new_pmd, pmd);
1121 spin_unlock(&mm->page_table_lock);
1122 ret = 1;
1123 }
1124 } else {
1125 spin_unlock(&mm->page_table_lock);
1126 }
1127out:
1128 return ret;
1129}
1130
cd7548ab
JW		 1131int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1132 unsigned long addr, pgprot_t newprot)
1133{
1134 struct mm_struct *mm = vma->vm_mm;
1135 int ret = 0;
1136
1137 spin_lock(&mm->page_table_lock);
1138 if (likely(pmd_trans_huge(*pmd))) {
1139 if (unlikely(pmd_trans_splitting(*pmd))) {
1140 spin_unlock(&mm->page_table_lock);
1141 wait_split_huge_page(vma->anon_vma, pmd);
1142 } else {
1143 pmd_t entry;
1144
1145 entry = pmdp_get_and_clear(mm, addr, pmd);
1146 entry = pmd_modify(entry, newprot);
1147 set_pmd_at(mm, addr, pmd, entry);
1148 spin_unlock(&vma->vm_mm->page_table_lock);
cd7548ab
JW		 1149 ret = 1;
1150 }
1151 } else
1152 spin_unlock(&vma->vm_mm->page_table_lock);
1153
1154 return ret;
1155}
1156
71e3aac0
AA		 1157pmd_t *page_check_address_pmd(struct page *page,
1158 struct mm_struct *mm,
1159 unsigned long address,
1160 enum page_check_address_pmd_flag flag)
1161{
1162 pgd_t *pgd;
1163 pud_t *pud;
1164 pmd_t *pmd, *ret = NULL;
1165
1166 if (address & ~HPAGE_PMD_MASK)
1167 goto out;
1168
1169 pgd = pgd_offset(mm, address);
1170 if (!pgd_present(*pgd))
1171 goto out;
1172
1173 pud = pud_offset(pgd, address);
1174 if (!pud_present(*pud))
1175 goto out;
1176
1177 pmd = pmd_offset(pud, address);
1178 if (pmd_none(*pmd))
1179 goto out;
1180 if (pmd_page(*pmd) != page)
1181 goto out;
94fcc585
AA		 1182 /*
1183 * split_vma() may create temporary aliased mappings. There is
1184 * no risk as long as all huge pmd are found and have their
1185 * splitting bit set before __split_huge_page_refcount
1186 * runs. Finding the same huge pmd more than once during the
1187 * same rmap walk is not a problem.
1188 */
1189 if (flag == PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG &&
1190 pmd_trans_splitting(*pmd))
1191 goto out;
71e3aac0
AA		 1192 if (pmd_trans_huge(*pmd)) {
1193 VM_BUG_ON(flag == PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG &&
1194 !pmd_trans_splitting(*pmd));
1195 ret = pmd;
1196 }
1197out:
1198 return ret;
1199}
1200
1201static int __split_huge_page_splitting(struct page *page,
1202 struct vm_area_struct *vma,
1203 unsigned long address)
1204{
1205 struct mm_struct *mm = vma->vm_mm;
1206 pmd_t *pmd;
1207 int ret = 0;
1208
1209 spin_lock(&mm->page_table_lock);
1210 pmd = page_check_address_pmd(page, mm, address,
1211 PAGE_CHECK_ADDRESS_PMD_NOTSPLITTING_FLAG);
1212 if (pmd) {
1213 /*
1214 * We can't temporarily set the pmd to null in order
1215 * to split it, the pmd must remain marked huge at all
1216 * times or the VM won't take the pmd_trans_huge paths
2b575eb6 1217 * and it won't wait on the anon_vma->root->mutex to
71e3aac0
AA		 1218 * serialize against split_huge_page*.
1219 */
1220 pmdp_splitting_flush_notify(vma, address, pmd);
1221 ret = 1;
1222 }
1223 spin_unlock(&mm->page_table_lock);
1224
1225 return ret;
1226}
1227
1228static void __split_huge_page_refcount(struct page *page)
1229{
1230 int i;
71e3aac0 1231 struct zone *zone = page_zone(page);
70b50f94 1232 int tail_count = 0;
71e3aac0
AA		 1233
1234 /* prevent PageLRU to go away from under us, and freeze lru stats */
1235 spin_lock_irq(&zone->lru_lock);
1236 compound_lock(page);
e94c8a9c
KH		 1237 /* complete memcg works before add pages to LRU */
1238 mem_cgroup_split_huge_fixup(page);
71e3aac0 1239
45676885 1240 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
71e3aac0
AA		 1241 struct page *page_tail = page + i;
1242
70b50f94
AA		 1243 /* tail_page->_mapcount cannot change */
1244 BUG_ON(page_mapcount(page_tail) < 0);
1245 tail_count += page_mapcount(page_tail);
1246 /* check for overflow */
1247 BUG_ON(tail_count < 0);
1248 BUG_ON(atomic_read(&page_tail->_count) != 0);
1249 /*
1250 * tail_page->_count is zero and not changing from
1251 * under us. But get_page_unless_zero() may be running
1252 * from under us on the tail_page. If we used
1253 * atomic_set() below instead of atomic_add(), we
1254 * would then run atomic_set() concurrently with
1255 * get_page_unless_zero(), and atomic_set() is
1256 * implemented in C not using locked ops. spin_unlock
1257 * on x86 sometime uses locked ops because of PPro
1258 * errata 66, 92, so unless somebody can guarantee
1259 * atomic_set() here would be safe on all archs (and
1260 * not only on x86), it's safer to use atomic_add().
1261 */
1262 atomic_add(page_mapcount(page) + page_mapcount(page_tail) + 1,
1263 &page_tail->_count);
71e3aac0
AA		 1264
1265 /* after clearing PageTail the gup refcount can be released */
1266 smp_mb();
1267
a6d30ddd
JD		 1268 /*
1269 * retain hwpoison flag of the poisoned tail page:
1270 * fix for the unsuitable process killed on Guest Machine(KVM)
1271 * by the memory-failure.
1272 */
1273 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;
71e3aac0
AA		 1274 page_tail->flags |= (page->flags &
1275 ((1L << PG_referenced) |
1276 (1L << PG_swapbacked) |
1277 (1L << PG_mlocked) |
1278 (1L << PG_uptodate)));
1279 page_tail->flags |= (1L << PG_dirty);
1280
70b50f94 1281 /* clear PageTail before overwriting first_page */
71e3aac0
AA		 1282 smp_wmb();
1283
1284 /*
1285 * __split_huge_page_splitting() already set the
1286 * splitting bit in all pmd that could map this
1287 * hugepage, that will ensure no CPU can alter the
1288 * mapcount on the head page. The mapcount is only
1289 * accounted in the head page and it has to be
1290 * transferred to all tail pages in the below code. So
1291 * for this code to be safe, the split the mapcount
1292 * can't change. But that doesn't mean userland can't
1293 * keep changing and reading the page contents while
1294 * we transfer the mapcount, so the pmd splitting
1295 * status is achieved setting a reserved bit in the
1296 * pmd, not by clearing the present bit.
1297 */
71e3aac0
AA		 1298 page_tail->_mapcount = page->_mapcount;
1299
1300 BUG_ON(page_tail->mapping);
1301 page_tail->mapping = page->mapping;
1302
45676885 1303 page_tail->index = page->index + i;
71e3aac0
AA		 1304
1305 BUG_ON(!PageAnon(page_tail));
1306 BUG_ON(!PageUptodate(page_tail));
1307 BUG_ON(!PageDirty(page_tail));
1308 BUG_ON(!PageSwapBacked(page_tail));
1309
ca3e0214 1310
71e3aac0
AA		 1311 lru_add_page_tail(zone, page, page_tail);
1312 }
70b50f94
AA		 1313 atomic_sub(tail_count, &page->_count);
1314 BUG_ON(atomic_read(&page->_count) <= 0);
71e3aac0 1315
79134171
AA		 1316 __dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1317 __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
1318
71e3aac0
AA		 1319 ClearPageCompound(page);
1320 compound_unlock(page);
1321 spin_unlock_irq(&zone->lru_lock);
1322
1323 for (i = 1; i < HPAGE_PMD_NR; i++) {
1324 struct page *page_tail = page + i;
1325 BUG_ON(page_count(page_tail) <= 0);
1326 /*
1327 * Tail pages may be freed if there wasn't any mapping
1328 * like if add_to_swap() is running on a lru page that
1329 * had its mapping zapped. And freeing these pages
1330 * requires taking the lru_lock so we do the put_page
1331 * of the tail pages after the split is complete.
1332 */
1333 put_page(page_tail);
1334 }
1335
1336 /*
1337 * Only the head page (now become a regular page) is required
1338 * to be pinned by the caller.
1339 */
1340 BUG_ON(page_count(page) <= 0);
1341}
1342
1343static int __split_huge_page_map(struct page *page,
1344 struct vm_area_struct *vma,
1345 unsigned long address)
1346{
1347 struct mm_struct *mm = vma->vm_mm;
1348 pmd_t *pmd, _pmd;
1349 int ret = 0, i;
1350 pgtable_t pgtable;
1351 unsigned long haddr;
1352
1353 spin_lock(&mm->page_table_lock);
1354 pmd = page_check_address_pmd(page, mm, address,
1355 PAGE_CHECK_ADDRESS_PMD_SPLITTING_FLAG);
1356 if (pmd) {
1357 pgtable = get_pmd_huge_pte(mm);
1358 pmd_populate(mm, &_pmd, pgtable);
1359
1360 for (i = 0, haddr = address; i < HPAGE_PMD_NR;
1361 i++, haddr += PAGE_SIZE) {
1362 pte_t *pte, entry;
1363 BUG_ON(PageCompound(page+i));
1364 entry = mk_pte(page + i, vma->vm_page_prot);
1365 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1366 if (!pmd_write(*pmd))
1367 entry = pte_wrprotect(entry);
1368 else
1369 BUG_ON(page_mapcount(page) != 1);
1370 if (!pmd_young(*pmd))
1371 entry = pte_mkold(entry);
1372 pte = pte_offset_map(&_pmd, haddr);
1373 BUG_ON(!pte_none(*pte));
1374 set_pte_at(mm, haddr, pte, entry);
1375 pte_unmap(pte);
1376 }
1377
1378 mm->nr_ptes++;
1379 smp_wmb(); /* make pte visible before pmd */
1380 /*
1381 * Up to this point the pmd is present and huge and
1382 * userland has the whole access to the hugepage
1383 * during the split (which happens in place). If we
1384 * overwrite the pmd with the not-huge version
1385 * pointing to the pte here (which of course we could
1386 * if all CPUs were bug free), userland could trigger
1387 * a small page size TLB miss on the small sized TLB
1388 * while the hugepage TLB entry is still established
1389 * in the huge TLB. Some CPU doesn't like that. See
1390 * http://support.amd.com/us/Processor_TechDocs/41322.pdf,
1391 * Erratum 383 on page 93. Intel should be safe but is
1392 * also warns that it's only safe if the permission
1393 * and cache attributes of the two entries loaded in
1394 * the two TLB is identical (which should be the case
1395 * here). But it is generally safer to never allow
1396 * small and huge TLB entries for the same virtual
1397 * address to be loaded simultaneously. So instead of
1398 * doing "pmd_populate(); flush_tlb_range();" we first
1399 * mark the current pmd notpresent (atomically because
1400 * here the pmd_trans_huge and pmd_trans_splitting
1401 * must remain set at all times on the pmd until the
1402 * split is complete for this pmd), then we flush the
1403 * SMP TLB and finally we write the non-huge version
1404 * of the pmd entry with pmd_populate.
1405 */
1406 set_pmd_at(mm, address, pmd, pmd_mknotpresent(*pmd));
1407 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
1408 pmd_populate(mm, pmd, pgtable);
1409 ret = 1;
1410 }
1411 spin_unlock(&mm->page_table_lock);
1412
1413 return ret;
1414}
1415
2b575eb6 1416/* must be called with anon_vma->root->mutex hold */
71e3aac0
AA		 1417static void __split_huge_page(struct page *page,
1418 struct anon_vma *anon_vma)
1419{
1420 int mapcount, mapcount2;
1421 struct anon_vma_chain *avc;
1422
1423 BUG_ON(!PageHead(page));
1424 BUG_ON(PageTail(page));
1425
1426 mapcount = 0;
1427 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1428 struct vm_area_struct *vma = avc->vma;
1429 unsigned long addr = vma_address(page, vma);
1430 BUG_ON(is_vma_temporary_stack(vma));
1431 if (addr == -EFAULT)
1432 continue;
1433 mapcount += __split_huge_page_splitting(page, vma, addr);
1434 }
05759d38
AA		 1435 /*
1436 * It is critical that new vmas are added to the tail of the
1437 * anon_vma list. This guarantes that if copy_huge_pmd() runs
1438 * and establishes a child pmd before
1439 * __split_huge_page_splitting() freezes the parent pmd (so if
1440 * we fail to prevent copy_huge_pmd() from running until the
1441 * whole __split_huge_page() is complete), we will still see
1442 * the newly established pmd of the child later during the
1443 * walk, to be able to set it as pmd_trans_splitting too.
1444 */
1445 if (mapcount != page_mapcount(page))
1446 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1447 mapcount, page_mapcount(page));
71e3aac0
AA		 1448 BUG_ON(mapcount != page_mapcount(page));
1449
1450 __split_huge_page_refcount(page);
1451
1452 mapcount2 = 0;
1453 list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1454 struct vm_area_struct *vma = avc->vma;
1455 unsigned long addr = vma_address(page, vma);
1456 BUG_ON(is_vma_temporary_stack(vma));
1457 if (addr == -EFAULT)
1458 continue;
1459 mapcount2 += __split_huge_page_map(page, vma, addr);
1460 }
05759d38
AA		 1461 if (mapcount != mapcount2)
1462 printk(KERN_ERR "mapcount %d mapcount2 %d page_mapcount %d\n",
1463 mapcount, mapcount2, page_mapcount(page));
71e3aac0
AA		 1464 BUG_ON(mapcount != mapcount2);
1465}
1466
1467int split_huge_page(struct page *page)
1468{
1469 struct anon_vma *anon_vma;
1470 int ret = 1;
1471
1472 BUG_ON(!PageAnon(page));
1473 anon_vma = page_lock_anon_vma(page);
1474 if (!anon_vma)
1475 goto out;
1476 ret = 0;
1477 if (!PageCompound(page))
1478 goto out_unlock;
1479
1480 BUG_ON(!PageSwapBacked(page));
1481 __split_huge_page(page, anon_vma);
81ab4201 1482 count_vm_event(THP_SPLIT);
71e3aac0
AA		 1483
1484 BUG_ON(PageCompound(page));
1485out_unlock:
1486 page_unlock_anon_vma(anon_vma);
1487out:
1488 return ret;
1489}
1490
78f11a25
AA		 1491#define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \
1492 VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
1493
60ab3244
AA		 1494int hugepage_madvise(struct vm_area_struct *vma,
1495 unsigned long *vm_flags, int advice)
0af4e98b 1496{
a664b2d8
AA		 1497 switch (advice) {
1498 case MADV_HUGEPAGE:
1499 /*
1500 * Be somewhat over-protective like KSM for now!
1501 */
78f11a25 1502 if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP))
a664b2d8
AA		 1503 return -EINVAL;
1504 *vm_flags &= ~VM_NOHUGEPAGE;
1505 *vm_flags |= VM_HUGEPAGE;
60ab3244
AA		 1506 /*
1507 * If the vma become good for khugepaged to scan,
1508 * register it here without waiting a page fault that
1509 * may not happen any time soon.
1510 */
1511 if (unlikely(khugepaged_enter_vma_merge(vma)))
1512 return -ENOMEM;
a664b2d8
AA		 1513 break;
1514 case MADV_NOHUGEPAGE:
1515 /*
1516 * Be somewhat over-protective like KSM for now!
1517 */
78f11a25 1518 if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP))
a664b2d8
AA		 1519 return -EINVAL;
1520 *vm_flags &= ~VM_HUGEPAGE;
1521 *vm_flags |= VM_NOHUGEPAGE;
60ab3244
AA		 1522 /*
1523 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
1524 * this vma even if we leave the mm registered in khugepaged if
1525 * it got registered before VM_NOHUGEPAGE was set.
1526 */
a664b2d8
AA		 1527 break;
1528 }
0af4e98b
AA		 1529
1530 return 0;
1531}
1532
ba76149f
AA		 1533static int __init khugepaged_slab_init(void)
1534{
1535 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
1536 sizeof(struct mm_slot),
1537 __alignof__(struct mm_slot), 0, NULL);
1538 if (!mm_slot_cache)
1539 return -ENOMEM;
1540
1541 return 0;
1542}
1543
1544static void __init khugepaged_slab_free(void)
1545{
1546 kmem_cache_destroy(mm_slot_cache);
1547 mm_slot_cache = NULL;
1548}
1549
1550static inline struct mm_slot *alloc_mm_slot(void)
1551{
1552 if (!mm_slot_cache) /* initialization failed */
1553 return NULL;
1554 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
1555}
1556
1557static inline void free_mm_slot(struct mm_slot *mm_slot)
1558{
1559 kmem_cache_free(mm_slot_cache, mm_slot);
1560}
1561
1562static int __init mm_slots_hash_init(void)
1563{
1564 mm_slots_hash = kzalloc(MM_SLOTS_HASH_HEADS * sizeof(struct hlist_head),
1565 GFP_KERNEL);
1566 if (!mm_slots_hash)
1567 return -ENOMEM;
1568 return 0;
1569}
1570
1571#if 0
1572static void __init mm_slots_hash_free(void)
1573{
1574 kfree(mm_slots_hash);
1575 mm_slots_hash = NULL;
1576}
1577#endif
1578
1579static struct mm_slot *get_mm_slot(struct mm_struct *mm)
1580{
1581 struct mm_slot *mm_slot;
1582 struct hlist_head *bucket;
1583 struct hlist_node *node;
1584
1585 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1586 % MM_SLOTS_HASH_HEADS];
1587 hlist_for_each_entry(mm_slot, node, bucket, hash) {
1588 if (mm == mm_slot->mm)
1589 return mm_slot;
1590 }
1591 return NULL;
1592}
1593
1594static void insert_to_mm_slots_hash(struct mm_struct *mm,
1595 struct mm_slot *mm_slot)
1596{
1597 struct hlist_head *bucket;
1598
1599 bucket = &mm_slots_hash[((unsigned long)mm / sizeof(struct mm_struct))
1600 % MM_SLOTS_HASH_HEADS];
1601 mm_slot->mm = mm;
1602 hlist_add_head(&mm_slot->hash, bucket);
1603}
1604
1605static inline int khugepaged_test_exit(struct mm_struct *mm)
1606{
1607 return atomic_read(&mm->mm_users) == 0;
1608}
1609
1610int __khugepaged_enter(struct mm_struct *mm)
1611{
1612 struct mm_slot *mm_slot;
1613 int wakeup;
1614
1615 mm_slot = alloc_mm_slot();
1616 if (!mm_slot)
1617 return -ENOMEM;
1618
1619 /* __khugepaged_exit() must not run from under us */
1620 VM_BUG_ON(khugepaged_test_exit(mm));
1621 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
1622 free_mm_slot(mm_slot);
1623 return 0;
1624 }
1625
1626 spin_lock(&khugepaged_mm_lock);
1627 insert_to_mm_slots_hash(mm, mm_slot);
1628 /*
1629 * Insert just behind the scanning cursor, to let the area settle
1630 * down a little.
1631 */
1632 wakeup = list_empty(&khugepaged_scan.mm_head);
1633 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
1634 spin_unlock(&khugepaged_mm_lock);
1635
1636 atomic_inc(&mm->mm_count);
1637 if (wakeup)
1638 wake_up_interruptible(&khugepaged_wait);
1639
1640 return 0;
1641}
1642
1643int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
1644{
1645 unsigned long hstart, hend;
1646 if (!vma->anon_vma)
1647 /*
1648 * Not yet faulted in so we will register later in the
1649 * page fault if needed.
1650 */
1651 return 0;
78f11a25 1652 if (vma->vm_ops)
ba76149f
AA		 1653 /* khugepaged not yet working on file or special mappings */
1654 return 0;
78f11a25
AA		 1655 /*
1656 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1657 * true too, verify it here.
1658 */
1659 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
ba76149f
AA		 1660 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1661 hend = vma->vm_end & HPAGE_PMD_MASK;
1662 if (hstart < hend)
1663 return khugepaged_enter(vma);
1664 return 0;
1665}
1666
1667void __khugepaged_exit(struct mm_struct *mm)
1668{
1669 struct mm_slot *mm_slot;
1670 int free = 0;
1671
1672 spin_lock(&khugepaged_mm_lock);
1673 mm_slot = get_mm_slot(mm);
1674 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
1675 hlist_del(&mm_slot->hash);
1676 list_del(&mm_slot->mm_node);
1677 free = 1;
1678 }
d788e80a 1679 spin_unlock(&khugepaged_mm_lock);
ba76149f
AA		 1680
1681 if (free) {
ba76149f
AA		 1682 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1683 free_mm_slot(mm_slot);
1684 mmdrop(mm);
1685 } else if (mm_slot) {
ba76149f
AA		 1686 /*
1687 * This is required to serialize against
1688 * khugepaged_test_exit() (which is guaranteed to run
1689 * under mmap sem read mode). Stop here (after we
1690 * return all pagetables will be destroyed) until
1691 * khugepaged has finished working on the pagetables
1692 * under the mmap_sem.
1693 */
1694 down_write(&mm->mmap_sem);
1695 up_write(&mm->mmap_sem);
d788e80a 1696 }
ba76149f
AA		 1697}
1698
1699static void release_pte_page(struct page *page)
1700{
1701 /* 0 stands for page_is_file_cache(page) == false */
1702 dec_zone_page_state(page, NR_ISOLATED_ANON + 0);
1703 unlock_page(page);
1704 putback_lru_page(page);
1705}
1706
1707static void release_pte_pages(pte_t *pte, pte_t *_pte)
1708{
1709 while (--_pte >= pte) {
1710 pte_t pteval = *_pte;
1711 if (!pte_none(pteval))
1712 release_pte_page(pte_page(pteval));
1713 }
1714}
1715
1716static void release_all_pte_pages(pte_t *pte)
1717{
1718 release_pte_pages(pte, pte + HPAGE_PMD_NR);
1719}
1720
1721static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
1722 unsigned long address,
1723 pte_t *pte)
1724{
1725 struct page *page;
1726 pte_t *_pte;
1727 int referenced = 0, isolated = 0, none = 0;
1728 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
1729 _pte++, address += PAGE_SIZE) {
1730 pte_t pteval = *_pte;
1731 if (pte_none(pteval)) {
1732 if (++none <= khugepaged_max_ptes_none)
1733 continue;
1734 else {
1735 release_pte_pages(pte, _pte);
1736 goto out;
1737 }
1738 }
1739 if (!pte_present(pteval) || !pte_write(pteval)) {
1740 release_pte_pages(pte, _pte);
1741 goto out;
1742 }
1743 page = vm_normal_page(vma, address, pteval);
1744 if (unlikely(!page)) {
1745 release_pte_pages(pte, _pte);
1746 goto out;
1747 }
1748 VM_BUG_ON(PageCompound(page));
1749 BUG_ON(!PageAnon(page));
1750 VM_BUG_ON(!PageSwapBacked(page));
1751
1752 /* cannot use mapcount: can't collapse if there's a gup pin */
1753 if (page_count(page) != 1) {
1754 release_pte_pages(pte, _pte);
1755 goto out;
1756 }
1757 /*
1758 * We can do it before isolate_lru_page because the
1759 * page can't be freed from under us. NOTE: PG_lock
1760 * is needed to serialize against split_huge_page
1761 * when invoked from the VM.
1762 */
1763 if (!trylock_page(page)) {
1764 release_pte_pages(pte, _pte);
1765 goto out;
1766 }
1767 /*
1768 * Isolate the page to avoid collapsing an hugepage
1769 * currently in use by the VM.
1770 */
1771 if (isolate_lru_page(page)) {
1772 unlock_page(page);
1773 release_pte_pages(pte, _pte);
1774 goto out;
1775 }
1776 /* 0 stands for page_is_file_cache(page) == false */
1777 inc_zone_page_state(page, NR_ISOLATED_ANON + 0);
1778 VM_BUG_ON(!PageLocked(page));
1779 VM_BUG_ON(PageLRU(page));
1780
1781 /* If there is no mapped pte young don't collapse the page */
8ee53820
AA		 1782 if (pte_young(pteval) || PageReferenced(page) ||
1783 mmu_notifier_test_young(vma->vm_mm, address))
ba76149f
AA		 1784 referenced = 1;
1785 }
1786 if (unlikely(!referenced))
1787 release_all_pte_pages(pte);
1788 else
1789 isolated = 1;
1790out:
1791 return isolated;
1792}
1793
1794static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
1795 struct vm_area_struct *vma,
1796 unsigned long address,
1797 spinlock_t *ptl)
1798{
1799 pte_t *_pte;
1800 for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++) {
1801 pte_t pteval = *_pte;
1802 struct page *src_page;
1803
1804 if (pte_none(pteval)) {
1805 clear_user_highpage(page, address);
1806 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
1807 } else {
1808 src_page = pte_page(pteval);
1809 copy_user_highpage(page, src_page, address, vma);
1810 VM_BUG_ON(page_mapcount(src_page) != 1);
1811 VM_BUG_ON(page_count(src_page) != 2);
1812 release_pte_page(src_page);
1813 /*
1814 * ptl mostly unnecessary, but preempt has to
1815 * be disabled to update the per-cpu stats
1816 * inside page_remove_rmap().
1817 */
1818 spin_lock(ptl);
1819 /*
1820 * paravirt calls inside pte_clear here are
1821 * superfluous.
1822 */
1823 pte_clear(vma->vm_mm, address, _pte);
1824 page_remove_rmap(src_page);
1825 spin_unlock(ptl);
1826 free_page_and_swap_cache(src_page);
1827 }
1828
1829 address += PAGE_SIZE;
1830 page++;
1831 }
1832}
1833
1834static void collapse_huge_page(struct mm_struct *mm,
1835 unsigned long address,
ce83d217 1836 struct page **hpage,
5c4b4be3
AK		 1837 struct vm_area_struct *vma,
1838 int node)
ba76149f 1839{
ba76149f
AA		 1840 pgd_t *pgd;
1841 pud_t *pud;
1842 pmd_t *pmd, _pmd;
1843 pte_t *pte;
1844 pgtable_t pgtable;
1845 struct page *new_page;
1846 spinlock_t *ptl;
1847 int isolated;
1848 unsigned long hstart, hend;
1849
1850 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
0bbbc0b3 1851#ifndef CONFIG_NUMA
692e0b35 1852 up_read(&mm->mmap_sem);
ba76149f 1853 VM_BUG_ON(!*hpage);
ce83d217 1854 new_page = *hpage;
0bbbc0b3
AA		 1855#else
1856 VM_BUG_ON(*hpage);
ce83d217
AA		 1857 /*
1858 * Allocate the page while the vma is still valid and under
1859 * the mmap_sem read mode so there is no memory allocation
1860 * later when we take the mmap_sem in write mode. This is more
1861 * friendly behavior (OTOH it may actually hide bugs) to
1862 * filesystems in userland with daemons allocating memory in
1863 * the userland I/O paths. Allocating memory with the
1864 * mmap_sem in read mode is good idea also to allow greater
1865 * scalability.
1866 */
5c4b4be3 1867 new_page = alloc_hugepage_vma(khugepaged_defrag(), vma, address,
cc5d462f 1868 node, __GFP_OTHER_NODE);
692e0b35
AA		 1869
1870 /*
1871 * After allocating the hugepage, release the mmap_sem read lock in
1872 * preparation for taking it in write mode.
1873 */
1874 up_read(&mm->mmap_sem);
ce83d217 1875 if (unlikely(!new_page)) {
81ab4201 1876 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
ce83d217
AA		 1877 *hpage = ERR_PTR(-ENOMEM);
1878 return;
1879 }
692e0b35
AA		 1880#endif
1881
81ab4201 1882 count_vm_event(THP_COLLAPSE_ALLOC);
ce83d217 1883 if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) {
692e0b35 1884#ifdef CONFIG_NUMA
ce83d217 1885 put_page(new_page);
692e0b35 1886#endif
ce83d217
AA		 1887 return;
1888 }
ba76149f
AA		 1889
1890 /*
1891 * Prevent all access to pagetables with the exception of
1892 * gup_fast later hanlded by the ptep_clear_flush and the VM
1893 * handled by the anon_vma lock + PG_lock.
1894 */
1895 down_write(&mm->mmap_sem);
1896 if (unlikely(khugepaged_test_exit(mm)))
1897 goto out;
1898
1899 vma = find_vma(mm, address);
1900 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
1901 hend = vma->vm_end & HPAGE_PMD_MASK;
1902 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
1903 goto out;
1904
60ab3244
AA		 1905 if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
1906 (vma->vm_flags & VM_NOHUGEPAGE))
ba76149f
AA		 1907 goto out;
1908
78f11a25 1909 if (!vma->anon_vma || vma->vm_ops)
ba76149f 1910 goto out;
a7d6e4ec
AA		 1911 if (is_vma_temporary_stack(vma))
1912 goto out;
78f11a25
AA		 1913 /*
1914 * If is_pfn_mapping() is true is_learn_pfn_mapping() must be
1915 * true too, verify it here.
1916 */
1917 VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP);
ba76149f
AA		 1918
1919 pgd = pgd_offset(mm, address);
1920 if (!pgd_present(*pgd))
1921 goto out;
1922
1923 pud = pud_offset(pgd, address);
1924 if (!pud_present(*pud))
1925 goto out;
1926
1927 pmd = pmd_offset(pud, address);
1928 /* pmd can't go away or become huge under us */
1929 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
1930 goto out;
1931
ba76149f
AA		 1932 anon_vma_lock(vma->anon_vma);
1933
1934 pte = pte_offset_map(pmd, address);
1935 ptl = pte_lockptr(mm, pmd);
1936
1937 spin_lock(&mm->page_table_lock); /* probably unnecessary */
1938 /*
1939 * After this gup_fast can't run anymore. This also removes
1940 * any huge TLB entry from the CPU so we won't allow
1941 * huge and small TLB entries for the same virtual address
1942 * to avoid the risk of CPU bugs in that area.
1943 */
1944 _pmd = pmdp_clear_flush_notify(vma, address, pmd);
1945 spin_unlock(&mm->page_table_lock);
1946
1947 spin_lock(ptl);
1948 isolated = __collapse_huge_page_isolate(vma, address, pte);
1949 spin_unlock(ptl);
ba76149f
AA		 1950
1951 if (unlikely(!isolated)) {
453c7192 1952 pte_unmap(pte);
ba76149f
AA		 1953 spin_lock(&mm->page_table_lock);
1954 BUG_ON(!pmd_none(*pmd));
1955 set_pmd_at(mm, address, pmd, _pmd);
1956 spin_unlock(&mm->page_table_lock);
1957 anon_vma_unlock(vma->anon_vma);
ce83d217 1958 goto out;
ba76149f
AA		 1959 }
1960
1961 /*
1962 * All pages are isolated and locked so anon_vma rmap
1963 * can't run anymore.
1964 */
1965 anon_vma_unlock(vma->anon_vma);
1966
1967 __collapse_huge_page_copy(pte, new_page, vma, address, ptl);
453c7192 1968 pte_unmap(pte);
ba76149f
AA		 1969 __SetPageUptodate(new_page);
1970 pgtable = pmd_pgtable(_pmd);
1971 VM_BUG_ON(page_count(pgtable) != 1);
1972 VM_BUG_ON(page_mapcount(pgtable) != 0);
1973
1974 _pmd = mk_pmd(new_page, vma->vm_page_prot);
1975 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1976 _pmd = pmd_mkhuge(_pmd);
1977
1978 /*
1979 * spin_lock() below is not the equivalent of smp_wmb(), so
1980 * this is needed to avoid the copy_huge_page writes to become
1981 * visible after the set_pmd_at() write.
1982 */
1983 smp_wmb();
1984
1985 spin_lock(&mm->page_table_lock);
1986 BUG_ON(!pmd_none(*pmd));
1987 page_add_new_anon_rmap(new_page, vma, address);
1988 set_pmd_at(mm, address, pmd, _pmd);
35d8c7ad 1989 update_mmu_cache(vma, address, _pmd);
ba76149f
AA		 1990 prepare_pmd_huge_pte(pgtable, mm);
1991 mm->nr_ptes--;
1992 spin_unlock(&mm->page_table_lock);
1993
0bbbc0b3 1994#ifndef CONFIG_NUMA
ba76149f 1995 *hpage = NULL;
0bbbc0b3 1996#endif
ba76149f 1997 khugepaged_pages_collapsed++;
ce83d217 1998out_up_write:
ba76149f 1999 up_write(&mm->mmap_sem);
0bbbc0b3
AA		 2000 return;
2001
ce83d217 2002out:
678ff896 2003 mem_cgroup_uncharge_page(new_page);
0bbbc0b3
AA		 2004#ifdef CONFIG_NUMA
2005 put_page(new_page);
2006#endif
ce83d217 2007 goto out_up_write;
ba76149f
AA		 2008}
2009
2010static int khugepaged_scan_pmd(struct mm_struct *mm,
2011 struct vm_area_struct *vma,
2012 unsigned long address,
2013 struct page **hpage)
2014{
2015 pgd_t *pgd;
2016 pud_t *pud;
2017 pmd_t *pmd;
2018 pte_t *pte, *_pte;
2019 int ret = 0, referenced = 0, none = 0;
2020 struct page *page;
2021 unsigned long _address;
2022 spinlock_t *ptl;
5c4b4be3 2023 int node = -1;
ba76149f
AA		 2024
2025 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
2026
2027 pgd = pgd_offset(mm, address);
2028 if (!pgd_present(*pgd))
2029 goto out;
2030
2031 pud = pud_offset(pgd, address);
2032 if (!pud_present(*pud))
2033 goto out;
2034
2035 pmd = pmd_offset(pud, address);
2036 if (!pmd_present(*pmd) || pmd_trans_huge(*pmd))
2037 goto out;
2038
2039 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
2040 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
2041 _pte++, _address += PAGE_SIZE) {
2042 pte_t pteval = *_pte;
2043 if (pte_none(pteval)) {
2044 if (++none <= khugepaged_max_ptes_none)
2045 continue;
2046 else
2047 goto out_unmap;
2048 }
2049 if (!pte_present(pteval) || !pte_write(pteval))
2050 goto out_unmap;
2051 page = vm_normal_page(vma, _address, pteval);
2052 if (unlikely(!page))
2053 goto out_unmap;
5c4b4be3
AK		 2054 /*
2055 * Chose the node of the first page. This could
2056 * be more sophisticated and look at more pages,
2057 * but isn't for now.
2058 */
2059 if (node == -1)
2060 node = page_to_nid(page);
ba76149f
AA		 2061 VM_BUG_ON(PageCompound(page));
2062 if (!PageLRU(page) || PageLocked(page) || !PageAnon(page))
2063 goto out_unmap;
2064 /* cannot use mapcount: can't collapse if there's a gup pin */
2065 if (page_count(page) != 1)
2066 goto out_unmap;
8ee53820
AA		 2067 if (pte_young(pteval) || PageReferenced(page) ||
2068 mmu_notifier_test_young(vma->vm_mm, address))
ba76149f
AA		 2069 referenced = 1;
2070 }
2071 if (referenced)
2072 ret = 1;
2073out_unmap:
2074 pte_unmap_unlock(pte, ptl);
ce83d217
AA		 2075 if (ret)
2076 /* collapse_huge_page will return with the mmap_sem released */
5c4b4be3 2077 collapse_huge_page(mm, address, hpage, vma, node);
ba76149f
AA		 2078out:
2079 return ret;
2080}
2081
2082static void collect_mm_slot(struct mm_slot *mm_slot)
2083{
2084 struct mm_struct *mm = mm_slot->mm;
2085
2086 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2087
2088 if (khugepaged_test_exit(mm)) {
2089 /* free mm_slot */
2090 hlist_del(&mm_slot->hash);
2091 list_del(&mm_slot->mm_node);
2092
2093 /*
2094 * Not strictly needed because the mm exited already.
2095 *
2096 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
2097 */
2098
2099 /* khugepaged_mm_lock actually not necessary for the below */
2100 free_mm_slot(mm_slot);
2101 mmdrop(mm);
2102 }
2103}
2104
2105static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2106 struct page **hpage)
2f1da642
HS		 2107 __releases(&khugepaged_mm_lock)
2108 __acquires(&khugepaged_mm_lock)
ba76149f
AA		 2109{
2110 struct mm_slot *mm_slot;
2111 struct mm_struct *mm;
2112 struct vm_area_struct *vma;
2113 int progress = 0;
2114
2115 VM_BUG_ON(!pages);
2116 VM_BUG_ON(!spin_is_locked(&khugepaged_mm_lock));
2117
2118 if (khugepaged_scan.mm_slot)
2119 mm_slot = khugepaged_scan.mm_slot;
2120 else {
2121 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2122 struct mm_slot, mm_node);
2123 khugepaged_scan.address = 0;
2124 khugepaged_scan.mm_slot = mm_slot;
2125 }
2126 spin_unlock(&khugepaged_mm_lock);
2127
2128 mm = mm_slot->mm;
2129 down_read(&mm->mmap_sem);
2130 if (unlikely(khugepaged_test_exit(mm)))
2131 vma = NULL;
2132 else
2133 vma = find_vma(mm, khugepaged_scan.address);
2134
2135 progress++;
2136 for (; vma; vma = vma->vm_next) {
2137 unsigned long hstart, hend;
2138
2139 cond_resched();
2140 if (unlikely(khugepaged_test_exit(mm))) {
2141 progress++;
2142 break;
2143 }
2144
60ab3244
AA		 2145 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
2146 !khugepaged_always()) ||
2147 (vma->vm_flags & VM_NOHUGEPAGE)) {
a7d6e4ec 2148 skip:
ba76149f
AA		 2149 progress++;
2150 continue;
2151 }
78f11a25 2152 if (!vma->anon_vma || vma->vm_ops)
a7d6e4ec
AA		 2153 goto skip;
2154 if (is_vma_temporary_stack(vma))
2155 goto skip;
78f11a25
AA		 2156 /*
2157 * If is_pfn_mapping() is true is_learn_pfn_mapping()
2158 * must be true too, verify it here.
2159 */
2160 VM_BUG_ON(is_linear_pfn_mapping(vma) ||
2161 vma->vm_flags & VM_NO_THP);
ba76149f
AA		 2162
2163 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2164 hend = vma->vm_end & HPAGE_PMD_MASK;
a7d6e4ec
AA		 2165 if (hstart >= hend)
2166 goto skip;
2167 if (khugepaged_scan.address > hend)
2168 goto skip;
ba76149f
AA		 2169 if (khugepaged_scan.address < hstart)
2170 khugepaged_scan.address = hstart;
a7d6e4ec 2171 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
ba76149f
AA		 2172
2173 while (khugepaged_scan.address < hend) {
2174 int ret;
2175 cond_resched();
2176 if (unlikely(khugepaged_test_exit(mm)))
2177 goto breakouterloop;
2178
2179 VM_BUG_ON(khugepaged_scan.address < hstart ||
2180 khugepaged_scan.address + HPAGE_PMD_SIZE >
2181 hend);
2182 ret = khugepaged_scan_pmd(mm, vma,
2183 khugepaged_scan.address,
2184 hpage);
2185 /* move to next address */
2186 khugepaged_scan.address += HPAGE_PMD_SIZE;
2187 progress += HPAGE_PMD_NR;
2188 if (ret)
2189 /* we released mmap_sem so break loop */
2190 goto breakouterloop_mmap_sem;
2191 if (progress >= pages)
2192 goto breakouterloop;
2193 }
2194 }
2195breakouterloop:
2196 up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
2197breakouterloop_mmap_sem:
2198
2199 spin_lock(&khugepaged_mm_lock);
a7d6e4ec 2200 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
ba76149f
AA		 2201 /*
2202 * Release the current mm_slot if this mm is about to die, or
2203 * if we scanned all vmas of this mm.
2204 */
2205 if (khugepaged_test_exit(mm) || !vma) {
2206 /*
2207 * Make sure that if mm_users is reaching zero while
2208 * khugepaged runs here, khugepaged_exit will find
2209 * mm_slot not pointing to the exiting mm.
2210 */
2211 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2212 khugepaged_scan.mm_slot = list_entry(
2213 mm_slot->mm_node.next,
2214 struct mm_slot, mm_node);
2215 khugepaged_scan.address = 0;
2216 } else {
2217 khugepaged_scan.mm_slot = NULL;
2218 khugepaged_full_scans++;
2219 }
2220
2221 collect_mm_slot(mm_slot);
2222 }
2223
2224 return progress;
2225}
2226
2227static int khugepaged_has_work(void)
2228{
2229 return !list_empty(&khugepaged_scan.mm_head) &&
2230 khugepaged_enabled();
2231}
2232
2233static int khugepaged_wait_event(void)
2234{
2235 return !list_empty(&khugepaged_scan.mm_head) ||
2236 !khugepaged_enabled();
2237}
2238
2239static void khugepaged_do_scan(struct page **hpage)
2240{
2241 unsigned int progress = 0, pass_through_head = 0;
2242 unsigned int pages = khugepaged_pages_to_scan;
2243
2244 barrier(); /* write khugepaged_pages_to_scan to local stack */
2245
2246 while (progress < pages) {
2247 cond_resched();
2248
0bbbc0b3 2249#ifndef CONFIG_NUMA
ba76149f
AA		 2250 if (!*hpage) {
2251 *hpage = alloc_hugepage(khugepaged_defrag());
81ab4201
AK		 2252 if (unlikely(!*hpage)) {
2253 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
ba76149f 2254 break;
81ab4201
AK		 2255 }
2256 count_vm_event(THP_COLLAPSE_ALLOC);
ba76149f 2257 }
0bbbc0b3
AA		 2258#else
2259 if (IS_ERR(*hpage))
2260 break;
2261#endif
ba76149f 2262
878aee7d
AA		 2263 if (unlikely(kthread_should_stop() || freezing(current)))
2264 break;
2265
ba76149f
AA		 2266 spin_lock(&khugepaged_mm_lock);
2267 if (!khugepaged_scan.mm_slot)
2268 pass_through_head++;
2269 if (khugepaged_has_work() &&
2270 pass_through_head < 2)
2271 progress += khugepaged_scan_mm_slot(pages - progress,
2272 hpage);
2273 else
2274 progress = pages;
2275 spin_unlock(&khugepaged_mm_lock);
2276 }
2277}
2278
0bbbc0b3
AA		 2279static void khugepaged_alloc_sleep(void)
2280{
1dfb059b
AA		 2281 wait_event_freezable_timeout(khugepaged_wait, false,
2282 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
0bbbc0b3
AA		 2283}
2284
2285#ifndef CONFIG_NUMA
ba76149f
AA		 2286static struct page *khugepaged_alloc_hugepage(void)
2287{
2288 struct page *hpage;
2289
2290 do {
2291 hpage = alloc_hugepage(khugepaged_defrag());
81ab4201
AK		 2292 if (!hpage) {
2293 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
0bbbc0b3 2294 khugepaged_alloc_sleep();
81ab4201
AK		 2295 } else
2296 count_vm_event(THP_COLLAPSE_ALLOC);
ba76149f
AA		 2297 } while (unlikely(!hpage) &&
2298 likely(khugepaged_enabled()));
2299 return hpage;
2300}
0bbbc0b3 2301#endif
ba76149f
AA		 2302
2303static void khugepaged_loop(void)
2304{
2305 struct page *hpage;
2306
0bbbc0b3
AA		 2307#ifdef CONFIG_NUMA
2308 hpage = NULL;
2309#endif
ba76149f 2310 while (likely(khugepaged_enabled())) {
0bbbc0b3 2311#ifndef CONFIG_NUMA
ba76149f 2312 hpage = khugepaged_alloc_hugepage();
f300ea49 2313 if (unlikely(!hpage))
ba76149f 2314 break;
0bbbc0b3
AA		 2315#else
2316 if (IS_ERR(hpage)) {
2317 khugepaged_alloc_sleep();
2318 hpage = NULL;
2319 }
2320#endif
ba76149f
AA		 2321
2322 khugepaged_do_scan(&hpage);
0bbbc0b3 2323#ifndef CONFIG_NUMA
ba76149f
AA		 2324 if (hpage)
2325 put_page(hpage);
0bbbc0b3 2326#endif
878aee7d
AA		 2327 try_to_freeze();
2328 if (unlikely(kthread_should_stop()))
2329 break;
ba76149f 2330 if (khugepaged_has_work()) {
ba76149f
AA		 2331 if (!khugepaged_scan_sleep_millisecs)
2332 continue;
1dfb059b
AA		 2333 wait_event_freezable_timeout(khugepaged_wait, false,
2334 msecs_to_jiffies(khugepaged_scan_sleep_millisecs));
ba76149f 2335 } else if (khugepaged_enabled())
878aee7d
AA		 2336 wait_event_freezable(khugepaged_wait,
2337 khugepaged_wait_event());
ba76149f
AA		 2338 }
2339}
2340
2341static int khugepaged(void *none)
2342{
2343 struct mm_slot *mm_slot;
2344
878aee7d 2345 set_freezable();
ba76149f
AA		 2346 set_user_nice(current, 19);
2347
2348 /* serialize with start_khugepaged() */
2349 mutex_lock(&khugepaged_mutex);
2350
2351 for (;;) {
2352 mutex_unlock(&khugepaged_mutex);
a7d6e4ec 2353 VM_BUG_ON(khugepaged_thread != current);
ba76149f 2354 khugepaged_loop();
a7d6e4ec 2355 VM_BUG_ON(khugepaged_thread != current);
ba76149f
AA		 2356
2357 mutex_lock(&khugepaged_mutex);
2358 if (!khugepaged_enabled())
2359 break;
878aee7d
AA		 2360 if (unlikely(kthread_should_stop()))
2361 break;
ba76149f
AA		 2362 }
2363
2364 spin_lock(&khugepaged_mm_lock);
2365 mm_slot = khugepaged_scan.mm_slot;
2366 khugepaged_scan.mm_slot = NULL;
2367 if (mm_slot)
2368 collect_mm_slot(mm_slot);
2369 spin_unlock(&khugepaged_mm_lock);
2370
2371 khugepaged_thread = NULL;
2372 mutex_unlock(&khugepaged_mutex);
2373
2374 return 0;
2375}
2376
71e3aac0
AA		 2377void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd)
2378{
2379 struct page *page;
2380
2381 spin_lock(&mm->page_table_lock);
2382 if (unlikely(!pmd_trans_huge(*pmd))) {
2383 spin_unlock(&mm->page_table_lock);
2384 return;
2385 }
2386 page = pmd_page(*pmd);
2387 VM_BUG_ON(!page_count(page));
2388 get_page(page);
2389 spin_unlock(&mm->page_table_lock);
2390
2391 split_huge_page(page);
2392
2393 put_page(page);
2394 BUG_ON(pmd_trans_huge(*pmd));
2395}
94fcc585
AA		 2396
2397static void split_huge_page_address(struct mm_struct *mm,
2398 unsigned long address)
2399{
2400 pgd_t *pgd;
2401 pud_t *pud;
2402 pmd_t *pmd;
2403
2404 VM_BUG_ON(!(address & ~HPAGE_PMD_MASK));
2405
2406 pgd = pgd_offset(mm, address);
2407 if (!pgd_present(*pgd))
2408 return;
2409
2410 pud = pud_offset(pgd, address);
2411 if (!pud_present(*pud))
2412 return;
2413
2414 pmd = pmd_offset(pud, address);
2415 if (!pmd_present(*pmd))
2416 return;
2417 /*
2418 * Caller holds the mmap_sem write mode, so a huge pmd cannot
2419 * materialize from under us.
2420 */
2421 split_huge_page_pmd(mm, pmd);
2422}
2423
2424void __vma_adjust_trans_huge(struct vm_area_struct *vma,
2425 unsigned long start,
2426 unsigned long end,
2427 long adjust_next)
2428{
2429 /*
2430 * If the new start address isn't hpage aligned and it could
2431 * previously contain an hugepage: check if we need to split
2432 * an huge pmd.
2433 */
2434 if (start & ~HPAGE_PMD_MASK &&
2435 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2436 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2437 split_huge_page_address(vma->vm_mm, start);
2438
2439 /*
2440 * If the new end address isn't hpage aligned and it could
2441 * previously contain an hugepage: check if we need to split
2442 * an huge pmd.
2443 */
2444 if (end & ~HPAGE_PMD_MASK &&
2445 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2446 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2447 split_huge_page_address(vma->vm_mm, end);
2448
2449 /*
2450 * If we're also updating the vma->vm_next->vm_start, if the new
2451 * vm_next->vm_start isn't page aligned and it could previously
2452 * contain an hugepage: check if we need to split an huge pmd.
2453 */
2454 if (adjust_next > 0) {
2455 struct vm_area_struct *next = vma->vm_next;
2456 unsigned long nstart = next->vm_start;
2457 nstart += adjust_next << PAGE_SHIFT;
2458 if (nstart & ~HPAGE_PMD_MASK &&
2459 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2460 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2461 split_huge_page_address(next->vm_mm, nstart);
2462 }
2463}
Linux 6.x block layer and io_uring tree(s)