1 // SPDX-License-Identifier: GPL-2.0
2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
3
4 #include <linux/mm.h>
5 #include <linux/sched.h>
6 #include <linux/sched/mm.h>
7 #include <linux/sched/coredump.h>
8 #include <linux/mmu_notifier.h>
9 #include <linux/rmap.h>
10 #include <linux/swap.h>
11 #include <linux/mm_inline.h>
12 #include <linux/kthread.h>
13 #include <linux/khugepaged.h>
14 #include <linux/freezer.h>
15 #include <linux/mman.h>
16 #include <linux/hashtable.h>
17 #include <linux/userfaultfd_k.h>
18 #include <linux/page_idle.h>
19 #include <linux/swapops.h>
20 #include <linux/shmem_fs.h>
21
22 #include <asm/tlb.h>
23 #include <asm/pgalloc.h>
24 #include "internal.h"
25
26 enum scan_result {
27 SCAN_FAIL,
28 SCAN_SUCCEED,
29 SCAN_PMD_NULL,
30 SCAN_EXCEED_NONE_PTE,
31 SCAN_EXCEED_SWAP_PTE,
32 SCAN_EXCEED_SHARED_PTE,
33 SCAN_PTE_NON_PRESENT,
34 SCAN_PTE_UFFD_WP,
35 SCAN_PAGE_RO,
36 SCAN_LACK_REFERENCED_PAGE,
37 SCAN_PAGE_NULL,
38 SCAN_SCAN_ABORT,
39 SCAN_PAGE_COUNT,
40 SCAN_PAGE_LRU,
41 SCAN_PAGE_LOCK,
42 SCAN_PAGE_ANON,
43 SCAN_PAGE_COMPOUND,
44 SCAN_ANY_PROCESS,
45 SCAN_VMA_NULL,
46 SCAN_VMA_CHECK,
47 SCAN_ADDRESS_RANGE,
48 SCAN_SWAP_CACHE_PAGE,
49 SCAN_DEL_PAGE_LRU,
50 SCAN_ALLOC_HUGE_PAGE_FAIL,
51 SCAN_CGROUP_CHARGE_FAIL,
52 SCAN_TRUNCATED,
53 SCAN_PAGE_HAS_PRIVATE,
54 };
55
56 #define CREATE_TRACE_POINTS
57 #include <trace/events/huge_memory.h>
58
59 static struct task_struct *khugepaged_thread __read_mostly;
60 static DEFINE_MUTEX(khugepaged_mutex);
61
62 /* default scan 8*512 pte (or vmas) every 30 second */
63 static unsigned int khugepaged_pages_to_scan __read_mostly;
64 static unsigned int khugepaged_pages_collapsed;
65 static unsigned int khugepaged_full_scans;
66 static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
67 /* during fragmentation poll the hugepage allocator once every minute */
68 static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
69 static unsigned long khugepaged_sleep_expire;
70 static DEFINE_SPINLOCK(khugepaged_mm_lock);
71 static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
72 /*
73 * default collapse hugepages if there is at least one pte mapped like
74 * it would have happened if the vma was large enough during page
75 * fault.
76 */
77 static unsigned int khugepaged_max_ptes_none __read_mostly;
78 static unsigned int khugepaged_max_ptes_swap __read_mostly;
79 static unsigned int khugepaged_max_ptes_shared __read_mostly;
80
81 #define MM_SLOTS_HASH_BITS 10
82 static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
83
84 static struct kmem_cache *mm_slot_cache __read_mostly;
85
86 #define MAX_PTE_MAPPED_THP 8
87
88 /**
89 * struct mm_slot - hash lookup from mm to mm_slot
90 * @hash: hash collision list
91 * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
92 * @mm: the mm that this information is valid for
93 */
94 struct mm_slot {
95 struct hlist_node hash;
96 struct list_head mm_node;
97 struct mm_struct *mm;
98
99 /* pte-mapped THP in this mm */
100 int nr_pte_mapped_thp;
101 unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP];
102 };
103
104 /**
105 * struct khugepaged_scan - cursor for scanning
106 * @mm_head: the head of the mm list to scan
107 * @mm_slot: the current mm_slot we are scanning
108 * @address: the next address inside that to be scanned
109 *
110 * There is only the one khugepaged_scan instance of this cursor structure.
111 */
112 struct khugepaged_scan {
113 struct list_head mm_head;
114 struct mm_slot *mm_slot;
115 unsigned long address;
116 };
117
118 static struct khugepaged_scan khugepaged_scan = {
119 .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
120 };
121
122 #ifdef CONFIG_SYSFS
scan_sleep_millisecs_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)123 static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
124 struct kobj_attribute *attr,
125 char *buf)
126 {
127 return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
128 }
129
scan_sleep_millisecs_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)130 static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
131 struct kobj_attribute *attr,
132 const char *buf, size_t count)
133 {
134 unsigned long msecs;
135 int err;
136
137 err = kstrtoul(buf, 10, &msecs);
138 if (err || msecs > UINT_MAX)
139 return -EINVAL;
140
141 khugepaged_scan_sleep_millisecs = msecs;
142 khugepaged_sleep_expire = 0;
143 wake_up_interruptible(&khugepaged_wait);
144
145 return count;
146 }
147 static struct kobj_attribute scan_sleep_millisecs_attr =
148 __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
149 scan_sleep_millisecs_store);
150
alloc_sleep_millisecs_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)151 static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
152 struct kobj_attribute *attr,
153 char *buf)
154 {
155 return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
156 }
157
alloc_sleep_millisecs_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)158 static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
159 struct kobj_attribute *attr,
160 const char *buf, size_t count)
161 {
162 unsigned long msecs;
163 int err;
164
165 err = kstrtoul(buf, 10, &msecs);
166 if (err || msecs > UINT_MAX)
167 return -EINVAL;
168
169 khugepaged_alloc_sleep_millisecs = msecs;
170 khugepaged_sleep_expire = 0;
171 wake_up_interruptible(&khugepaged_wait);
172
173 return count;
174 }
175 static struct kobj_attribute alloc_sleep_millisecs_attr =
176 __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
177 alloc_sleep_millisecs_store);
178
pages_to_scan_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)179 static ssize_t pages_to_scan_show(struct kobject *kobj,
180 struct kobj_attribute *attr,
181 char *buf)
182 {
183 return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
184 }
pages_to_scan_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)185 static ssize_t pages_to_scan_store(struct kobject *kobj,
186 struct kobj_attribute *attr,
187 const char *buf, size_t count)
188 {
189 int err;
190 unsigned long pages;
191
192 err = kstrtoul(buf, 10, &pages);
193 if (err || !pages || pages > UINT_MAX)
194 return -EINVAL;
195
196 khugepaged_pages_to_scan = pages;
197
198 return count;
199 }
200 static struct kobj_attribute pages_to_scan_attr =
201 __ATTR(pages_to_scan, 0644, pages_to_scan_show,
202 pages_to_scan_store);
203
pages_collapsed_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)204 static ssize_t pages_collapsed_show(struct kobject *kobj,
205 struct kobj_attribute *attr,
206 char *buf)
207 {
208 return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
209 }
210 static struct kobj_attribute pages_collapsed_attr =
211 __ATTR_RO(pages_collapsed);
212
full_scans_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)213 static ssize_t full_scans_show(struct kobject *kobj,
214 struct kobj_attribute *attr,
215 char *buf)
216 {
217 return sprintf(buf, "%u\n", khugepaged_full_scans);
218 }
219 static struct kobj_attribute full_scans_attr =
220 __ATTR_RO(full_scans);
221
khugepaged_defrag_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)222 static ssize_t khugepaged_defrag_show(struct kobject *kobj,
223 struct kobj_attribute *attr, char *buf)
224 {
225 return single_hugepage_flag_show(kobj, attr, buf,
226 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
227 }
khugepaged_defrag_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)228 static ssize_t khugepaged_defrag_store(struct kobject *kobj,
229 struct kobj_attribute *attr,
230 const char *buf, size_t count)
231 {
232 return single_hugepage_flag_store(kobj, attr, buf, count,
233 TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
234 }
235 static struct kobj_attribute khugepaged_defrag_attr =
236 __ATTR(defrag, 0644, khugepaged_defrag_show,
237 khugepaged_defrag_store);
238
239 /*
240 * max_ptes_none controls if khugepaged should collapse hugepages over
241 * any unmapped ptes in turn potentially increasing the memory
242 * footprint of the vmas. When max_ptes_none is 0 khugepaged will not
243 * reduce the available free memory in the system as it
244 * runs. Increasing max_ptes_none will instead potentially reduce the
245 * free memory in the system during the khugepaged scan.
246 */
khugepaged_max_ptes_none_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)247 static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
248 struct kobj_attribute *attr,
249 char *buf)
250 {
251 return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
252 }
khugepaged_max_ptes_none_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)253 static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
254 struct kobj_attribute *attr,
255 const char *buf, size_t count)
256 {
257 int err;
258 unsigned long max_ptes_none;
259
260 err = kstrtoul(buf, 10, &max_ptes_none);
261 if (err || max_ptes_none > HPAGE_PMD_NR-1)
262 return -EINVAL;
263
264 khugepaged_max_ptes_none = max_ptes_none;
265
266 return count;
267 }
268 static struct kobj_attribute khugepaged_max_ptes_none_attr =
269 __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
270 khugepaged_max_ptes_none_store);
271
khugepaged_max_ptes_swap_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)272 static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
273 struct kobj_attribute *attr,
274 char *buf)
275 {
276 return sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
277 }
278
khugepaged_max_ptes_swap_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)279 static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
280 struct kobj_attribute *attr,
281 const char *buf, size_t count)
282 {
283 int err;
284 unsigned long max_ptes_swap;
285
286 err = kstrtoul(buf, 10, &max_ptes_swap);
287 if (err || max_ptes_swap > HPAGE_PMD_NR-1)
288 return -EINVAL;
289
290 khugepaged_max_ptes_swap = max_ptes_swap;
291
292 return count;
293 }
294
295 static struct kobj_attribute khugepaged_max_ptes_swap_attr =
296 __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
297 khugepaged_max_ptes_swap_store);
298
khugepaged_max_ptes_shared_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)299 static ssize_t khugepaged_max_ptes_shared_show(struct kobject *kobj,
300 struct kobj_attribute *attr,
301 char *buf)
302 {
303 return sprintf(buf, "%u\n", khugepaged_max_ptes_shared);
304 }
305
khugepaged_max_ptes_shared_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)306 static ssize_t khugepaged_max_ptes_shared_store(struct kobject *kobj,
307 struct kobj_attribute *attr,
308 const char *buf, size_t count)
309 {
310 int err;
311 unsigned long max_ptes_shared;
312
313 err = kstrtoul(buf, 10, &max_ptes_shared);
314 if (err || max_ptes_shared > HPAGE_PMD_NR-1)
315 return -EINVAL;
316
317 khugepaged_max_ptes_shared = max_ptes_shared;
318
319 return count;
320 }
321
322 static struct kobj_attribute khugepaged_max_ptes_shared_attr =
323 __ATTR(max_ptes_shared, 0644, khugepaged_max_ptes_shared_show,
324 khugepaged_max_ptes_shared_store);
325
326 static struct attribute *khugepaged_attr[] = {
327 &khugepaged_defrag_attr.attr,
328 &khugepaged_max_ptes_none_attr.attr,
329 &khugepaged_max_ptes_swap_attr.attr,
330 &khugepaged_max_ptes_shared_attr.attr,
331 &pages_to_scan_attr.attr,
332 &pages_collapsed_attr.attr,
333 &full_scans_attr.attr,
334 &scan_sleep_millisecs_attr.attr,
335 &alloc_sleep_millisecs_attr.attr,
336 NULL,
337 };
338
339 struct attribute_group khugepaged_attr_group = {
340 .attrs = khugepaged_attr,
341 .name = "khugepaged",
342 };
343 #endif /* CONFIG_SYSFS */
344
hugepage_madvise(struct vm_area_struct * vma,unsigned long * vm_flags,int advice)345 int hugepage_madvise(struct vm_area_struct *vma,
346 unsigned long *vm_flags, int advice)
347 {
348 switch (advice) {
349 case MADV_HUGEPAGE:
350 #ifdef CONFIG_S390
351 /*
352 * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
353 * can't handle this properly after s390_enable_sie, so we simply
354 * ignore the madvise to prevent qemu from causing a SIGSEGV.
355 */
356 if (mm_has_pgste(vma->vm_mm))
357 return 0;
358 #endif
359 *vm_flags &= ~VM_NOHUGEPAGE;
360 *vm_flags |= VM_HUGEPAGE;
361 /*
362 * If the vma become good for khugepaged to scan,
363 * register it here without waiting a page fault that
364 * may not happen any time soon.
365 */
366 if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
367 khugepaged_enter_vma_merge(vma, *vm_flags))
368 return -ENOMEM;
369 break;
370 case MADV_NOHUGEPAGE:
371 *vm_flags &= ~VM_HUGEPAGE;
372 *vm_flags |= VM_NOHUGEPAGE;
373 /*
374 * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
375 * this vma even if we leave the mm registered in khugepaged if
376 * it got registered before VM_NOHUGEPAGE was set.
377 */
378 break;
379 }
380
381 return 0;
382 }
383
khugepaged_init(void)384 int __init khugepaged_init(void)
385 {
386 mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
387 sizeof(struct mm_slot),
388 __alignof__(struct mm_slot), 0, NULL);
389 if (!mm_slot_cache)
390 return -ENOMEM;
391
392 khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
393 khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
394 khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
395 khugepaged_max_ptes_shared = HPAGE_PMD_NR / 2;
396
397 return 0;
398 }
399
khugepaged_destroy(void)400 void __init khugepaged_destroy(void)
401 {
402 kmem_cache_destroy(mm_slot_cache);
403 }
404
alloc_mm_slot(void)405 static inline struct mm_slot *alloc_mm_slot(void)
406 {
407 if (!mm_slot_cache) /* initialization failed */
408 return NULL;
409 return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
410 }
411
free_mm_slot(struct mm_slot * mm_slot)412 static inline void free_mm_slot(struct mm_slot *mm_slot)
413 {
414 kmem_cache_free(mm_slot_cache, mm_slot);
415 }
416
get_mm_slot(struct mm_struct * mm)417 static struct mm_slot *get_mm_slot(struct mm_struct *mm)
418 {
419 struct mm_slot *mm_slot;
420
421 hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
422 if (mm == mm_slot->mm)
423 return mm_slot;
424
425 return NULL;
426 }
427
insert_to_mm_slots_hash(struct mm_struct * mm,struct mm_slot * mm_slot)428 static void insert_to_mm_slots_hash(struct mm_struct *mm,
429 struct mm_slot *mm_slot)
430 {
431 mm_slot->mm = mm;
432 hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
433 }
434
khugepaged_test_exit(struct mm_struct * mm)435 static inline int khugepaged_test_exit(struct mm_struct *mm)
436 {
437 return atomic_read(&mm->mm_users) == 0;
438 }
439
hugepage_vma_check(struct vm_area_struct * vma,unsigned long vm_flags)440 static bool hugepage_vma_check(struct vm_area_struct *vma,
441 unsigned long vm_flags)
442 {
443 if (!transhuge_vma_enabled(vma, vm_flags))
444 return false;
445
446 if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) -
447 vma->vm_pgoff, HPAGE_PMD_NR))
448 return false;
449
450 /* Enabled via shmem mount options or sysfs settings. */
451 if (shmem_file(vma->vm_file))
452 return shmem_huge_enabled(vma);
453
454 /* THP settings require madvise. */
455 if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always())
456 return false;
457
458 /* Only regular file is valid */
459 if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file &&
460 (vm_flags & VM_DENYWRITE)) {
461 struct inode *inode = vma->vm_file->f_inode;
462
463 return S_ISREG(inode->i_mode);
464 }
465
466 if (!vma->anon_vma || vma->vm_ops)
467 return false;
468 if (vma_is_temporary_stack(vma))
469 return false;
470 return !(vm_flags & VM_NO_KHUGEPAGED);
471 }
472
__khugepaged_enter(struct mm_struct * mm)473 int __khugepaged_enter(struct mm_struct *mm)
474 {
475 struct mm_slot *mm_slot;
476 int wakeup;
477
478 mm_slot = alloc_mm_slot();
479 if (!mm_slot)
480 return -ENOMEM;
481
482 /* __khugepaged_exit() must not run from under us */
483 VM_BUG_ON_MM(atomic_read(&mm->mm_users) == 0, mm);
484 if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
485 free_mm_slot(mm_slot);
486 return 0;
487 }
488
489 spin_lock(&khugepaged_mm_lock);
490 insert_to_mm_slots_hash(mm, mm_slot);
491 /*
492 * Insert just behind the scanning cursor, to let the area settle
493 * down a little.
494 */
495 wakeup = list_empty(&khugepaged_scan.mm_head);
496 list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
497 spin_unlock(&khugepaged_mm_lock);
498
499 mmgrab(mm);
500 if (wakeup)
501 wake_up_interruptible(&khugepaged_wait);
502
503 return 0;
504 }
505
khugepaged_enter_vma_merge(struct vm_area_struct * vma,unsigned long vm_flags)506 int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
507 unsigned long vm_flags)
508 {
509 unsigned long hstart, hend;
510
511 /*
512 * khugepaged only supports read-only files for non-shmem files.
513 * khugepaged does not yet work on special mappings. And
514 * file-private shmem THP is not supported.
515 */
516 if (!hugepage_vma_check(vma, vm_flags))
517 return 0;
518
519 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
520 hend = vma->vm_end & HPAGE_PMD_MASK;
521 if (hstart < hend)
522 return khugepaged_enter(vma, vm_flags);
523 return 0;
524 }
525
__khugepaged_exit(struct mm_struct * mm)526 void __khugepaged_exit(struct mm_struct *mm)
527 {
528 struct mm_slot *mm_slot;
529 int free = 0;
530
531 spin_lock(&khugepaged_mm_lock);
532 mm_slot = get_mm_slot(mm);
533 if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
534 hash_del(&mm_slot->hash);
535 list_del(&mm_slot->mm_node);
536 free = 1;
537 }
538 spin_unlock(&khugepaged_mm_lock);
539
540 if (free) {
541 clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
542 free_mm_slot(mm_slot);
543 mmdrop(mm);
544 } else if (mm_slot) {
545 /*
546 * This is required to serialize against
547 * khugepaged_test_exit() (which is guaranteed to run
548 * under mmap sem read mode). Stop here (after we
549 * return all pagetables will be destroyed) until
550 * khugepaged has finished working on the pagetables
551 * under the mmap_lock.
552 */
553 mmap_write_lock(mm);
554 mmap_write_unlock(mm);
555 }
556 }
557
release_pte_page(struct page * page)558 static void release_pte_page(struct page *page)
559 {
560 mod_node_page_state(page_pgdat(page),
561 NR_ISOLATED_ANON + page_is_file_lru(page),
562 -compound_nr(page));
563 unlock_page(page);
564 putback_lru_page(page);
565 }
566
release_pte_pages(pte_t * pte,pte_t * _pte,struct list_head * compound_pagelist)567 static void release_pte_pages(pte_t *pte, pte_t *_pte,
568 struct list_head *compound_pagelist)
569 {
570 struct page *page, *tmp;
571
572 while (--_pte >= pte) {
573 pte_t pteval = *_pte;
574
575 page = pte_page(pteval);
576 if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)) &&
577 !PageCompound(page))
578 release_pte_page(page);
579 }
580
581 list_for_each_entry_safe(page, tmp, compound_pagelist, lru) {
582 list_del(&page->lru);
583 release_pte_page(page);
584 }
585 }
586
is_refcount_suitable(struct page * page)587 static bool is_refcount_suitable(struct page *page)
588 {
589 int expected_refcount;
590
591 expected_refcount = total_mapcount(page);
592 if (PageSwapCache(page))
593 expected_refcount += compound_nr(page);
594
595 return page_count(page) == expected_refcount;
596 }
597
__collapse_huge_page_isolate(struct vm_area_struct * vma,unsigned long address,pte_t * pte,struct list_head * compound_pagelist)598 static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
599 unsigned long address,
600 pte_t *pte,
601 struct list_head *compound_pagelist)
602 {
603 struct page *page = NULL;
604 pte_t *_pte;
605 int none_or_zero = 0, shared = 0, result = 0, referenced = 0;
606 bool writable = false;
607
608 for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
609 _pte++, address += PAGE_SIZE) {
610 pte_t pteval = *_pte;
611 if (pte_none(pteval) || (pte_present(pteval) &&
612 is_zero_pfn(pte_pfn(pteval)))) {
613 if (!userfaultfd_armed(vma) &&
614 ++none_or_zero <= khugepaged_max_ptes_none) {
615 continue;
616 } else {
617 result = SCAN_EXCEED_NONE_PTE;
618 goto out;
619 }
620 }
621 if (!pte_present(pteval)) {
622 result = SCAN_PTE_NON_PRESENT;
623 goto out;
624 }
625 page = vm_normal_page(vma, address, pteval);
626 if (unlikely(!page)) {
627 result = SCAN_PAGE_NULL;
628 goto out;
629 }
630
631 VM_BUG_ON_PAGE(!PageAnon(page), page);
632
633 if (page_mapcount(page) > 1 &&
634 ++shared > khugepaged_max_ptes_shared) {
635 result = SCAN_EXCEED_SHARED_PTE;
636 goto out;
637 }
638
639 if (PageCompound(page)) {
640 struct page *p;
641 page = compound_head(page);
642
643 /*
644 * Check if we have dealt with the compound page
645 * already
646 */
647 list_for_each_entry(p, compound_pagelist, lru) {
648 if (page == p)
649 goto next;
650 }
651 }
652
653 /*
654 * We can do it before isolate_lru_page because the
655 * page can't be freed from under us. NOTE: PG_lock
656 * is needed to serialize against split_huge_page
657 * when invoked from the VM.
658 */
659 if (!trylock_page(page)) {
660 result = SCAN_PAGE_LOCK;
661 goto out;
662 }
663
664 /*
665 * Check if the page has any GUP (or other external) pins.
666 *
667 * The page table that maps the page has been already unlinked
668 * from the page table tree and this process cannot get
669 * an additinal pin on the page.
670 *
671 * New pins can come later if the page is shared across fork,
672 * but not from this process. The other process cannot write to
673 * the page, only trigger CoW.
674 */
675 if (!is_refcount_suitable(page)) {
676 unlock_page(page);
677 result = SCAN_PAGE_COUNT;
678 goto out;
679 }
680 if (!pte_write(pteval) && PageSwapCache(page) &&
681 !reuse_swap_page(page, NULL)) {
682 /*
683 * Page is in the swap cache and cannot be re-used.
684 * It cannot be collapsed into a THP.
685 */
686 unlock_page(page);
687 result = SCAN_SWAP_CACHE_PAGE;
688 goto out;
689 }
690
691 /*
692 * Isolate the page to avoid collapsing an hugepage
693 * currently in use by the VM.
694 */
695 if (isolate_lru_page(page)) {
696 unlock_page(page);
697 result = SCAN_DEL_PAGE_LRU;
698 goto out;
699 }
700 mod_node_page_state(page_pgdat(page),
701 NR_ISOLATED_ANON + page_is_file_lru(page),
702 compound_nr(page));
703 VM_BUG_ON_PAGE(!PageLocked(page), page);
704 VM_BUG_ON_PAGE(PageLRU(page), page);
705
706 if (PageCompound(page))
707 list_add_tail(&page->lru, compound_pagelist);
708 next:
709 /* There should be enough young pte to collapse the page */
710 if (pte_young(pteval) ||
711 page_is_young(page) || PageReferenced(page) ||
712 mmu_notifier_test_young(vma->vm_mm, address))
713 referenced++;
714
715 if (pte_write(pteval))
716 writable = true;
717 }
718
719 if (unlikely(!writable)) {
720 result = SCAN_PAGE_RO;
721 } else if (unlikely(!referenced)) {
722 result = SCAN_LACK_REFERENCED_PAGE;
723 } else {
724 result = SCAN_SUCCEED;
725 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
726 referenced, writable, result);
727 return 1;
728 }
729 out:
730 release_pte_pages(pte, _pte, compound_pagelist);
731 trace_mm_collapse_huge_page_isolate(page, none_or_zero,
732 referenced, writable, result);
733 return 0;
734 }
735
__collapse_huge_page_copy(pte_t * pte,struct page * page,struct vm_area_struct * vma,unsigned long address,spinlock_t * ptl,struct list_head * compound_pagelist)736 static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
737 struct vm_area_struct *vma,
738 unsigned long address,
739 spinlock_t *ptl,
740 struct list_head *compound_pagelist)
741 {
742 struct page *src_page, *tmp;
743 pte_t *_pte;
744 for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
745 _pte++, page++, address += PAGE_SIZE) {
746 pte_t pteval = *_pte;
747
748 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
749 clear_user_highpage(page, address);
750 add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
751 if (is_zero_pfn(pte_pfn(pteval))) {
752 /*
753 * ptl mostly unnecessary.
754 */
755 spin_lock(ptl);
756 /*
757 * paravirt calls inside pte_clear here are
758 * superfluous.
759 */
760 pte_clear(vma->vm_mm, address, _pte);
761 spin_unlock(ptl);
762 }
763 } else {
764 src_page = pte_page(pteval);
765 copy_user_highpage(page, src_page, address, vma);
766 if (!PageCompound(src_page))
767 release_pte_page(src_page);
768 /*
769 * ptl mostly unnecessary, but preempt has to
770 * be disabled to update the per-cpu stats
771 * inside page_remove_rmap().
772 */
773 spin_lock(ptl);
774 /*
775 * paravirt calls inside pte_clear here are
776 * superfluous.
777 */
778 pte_clear(vma->vm_mm, address, _pte);
779 page_remove_rmap(src_page, false);
780 spin_unlock(ptl);
781 free_page_and_swap_cache(src_page);
782 }
783 }
784
785 list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
786 list_del(&src_page->lru);
787 release_pte_page(src_page);
788 }
789 }
790
khugepaged_alloc_sleep(void)791 static void khugepaged_alloc_sleep(void)
792 {
793 DEFINE_WAIT(wait);
794
795 add_wait_queue(&khugepaged_wait, &wait);
796 freezable_schedule_timeout_interruptible(
797 msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
798 remove_wait_queue(&khugepaged_wait, &wait);
799 }
800
801 static int khugepaged_node_load[MAX_NUMNODES];
802
khugepaged_scan_abort(int nid)803 static bool khugepaged_scan_abort(int nid)
804 {
805 int i;
806
807 /*
808 * If node_reclaim_mode is disabled, then no extra effort is made to
809 * allocate memory locally.
810 */
811 if (!node_reclaim_mode)
812 return false;
813
814 /* If there is a count for this node already, it must be acceptable */
815 if (khugepaged_node_load[nid])
816 return false;
817
818 for (i = 0; i < MAX_NUMNODES; i++) {
819 if (!khugepaged_node_load[i])
820 continue;
821 if (node_distance(nid, i) > node_reclaim_distance)
822 return true;
823 }
824 return false;
825 }
826
827 /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
alloc_hugepage_khugepaged_gfpmask(void)828 static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
829 {
830 return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT;
831 }
832
833 #ifdef CONFIG_NUMA
khugepaged_find_target_node(void)834 static int khugepaged_find_target_node(void)
835 {
836 static int last_khugepaged_target_node = NUMA_NO_NODE;
837 int nid, target_node = 0, max_value = 0;
838
839 /* find first node with max normal pages hit */
840 for (nid = 0; nid < MAX_NUMNODES; nid++)
841 if (khugepaged_node_load[nid] > max_value) {
842 max_value = khugepaged_node_load[nid];
843 target_node = nid;
844 }
845
846 /* do some balance if several nodes have the same hit record */
847 if (target_node <= last_khugepaged_target_node)
848 for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
849 nid++)
850 if (max_value == khugepaged_node_load[nid]) {
851 target_node = nid;
852 break;
853 }
854
855 last_khugepaged_target_node = target_node;
856 return target_node;
857 }
858
khugepaged_prealloc_page(struct page ** hpage,bool * wait)859 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
860 {
861 if (IS_ERR(*hpage)) {
862 if (!*wait)
863 return false;
864
865 *wait = false;
866 *hpage = NULL;
867 khugepaged_alloc_sleep();
868 } else if (*hpage) {
869 put_page(*hpage);
870 *hpage = NULL;
871 }
872
873 return true;
874 }
875
876 static struct page *
khugepaged_alloc_page(struct page ** hpage,gfp_t gfp,int node)877 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
878 {
879 VM_BUG_ON_PAGE(*hpage, *hpage);
880
881 *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
882 if (unlikely(!*hpage)) {
883 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
884 *hpage = ERR_PTR(-ENOMEM);
885 return NULL;
886 }
887
888 prep_transhuge_page(*hpage);
889 count_vm_event(THP_COLLAPSE_ALLOC);
890 return *hpage;
891 }
892 #else
khugepaged_find_target_node(void)893 static int khugepaged_find_target_node(void)
894 {
895 return 0;
896 }
897
alloc_khugepaged_hugepage(void)898 static inline struct page *alloc_khugepaged_hugepage(void)
899 {
900 struct page *page;
901
902 page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
903 HPAGE_PMD_ORDER);
904 if (page)
905 prep_transhuge_page(page);
906 return page;
907 }
908
khugepaged_alloc_hugepage(bool * wait)909 static struct page *khugepaged_alloc_hugepage(bool *wait)
910 {
911 struct page *hpage;
912
913 do {
914 hpage = alloc_khugepaged_hugepage();
915 if (!hpage) {
916 count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
917 if (!*wait)
918 return NULL;
919
920 *wait = false;
921 khugepaged_alloc_sleep();
922 } else
923 count_vm_event(THP_COLLAPSE_ALLOC);
924 } while (unlikely(!hpage) && likely(khugepaged_enabled()));
925
926 return hpage;
927 }
928
khugepaged_prealloc_page(struct page ** hpage,bool * wait)929 static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
930 {
931 /*
932 * If the hpage allocated earlier was briefly exposed in page cache
933 * before collapse_file() failed, it is possible that racing lookups
934 * have not yet completed, and would then be unpleasantly surprised by
935 * finding the hpage reused for the same mapping at a different offset.
936 * Just release the previous allocation if there is any danger of that.
937 */
938 if (*hpage && page_count(*hpage) > 1) {
939 put_page(*hpage);
940 *hpage = NULL;
941 }
942
943 if (!*hpage)
944 *hpage = khugepaged_alloc_hugepage(wait);
945
946 if (unlikely(!*hpage))
947 return false;
948
949 return true;
950 }
951
952 static struct page *
khugepaged_alloc_page(struct page ** hpage,gfp_t gfp,int node)953 khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
954 {
955 VM_BUG_ON(!*hpage);
956
957 return *hpage;
958 }
959 #endif
960
961 /*
962 * If mmap_lock temporarily dropped, revalidate vma
963 * before taking mmap_lock.
964 * Return 0 if succeeds, otherwise return none-zero
965 * value (scan code).
966 */
967
hugepage_vma_revalidate(struct mm_struct * mm,unsigned long address,struct vm_area_struct ** vmap)968 static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
969 struct vm_area_struct **vmap)
970 {
971 struct vm_area_struct *vma;
972 unsigned long hstart, hend;
973
974 if (unlikely(khugepaged_test_exit(mm)))
975 return SCAN_ANY_PROCESS;
976
977 *vmap = vma = find_vma(mm, address);
978 if (!vma)
979 return SCAN_VMA_NULL;
980
981 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
982 hend = vma->vm_end & HPAGE_PMD_MASK;
983 if (address < hstart || address + HPAGE_PMD_SIZE > hend)
984 return SCAN_ADDRESS_RANGE;
985 if (!hugepage_vma_check(vma, vma->vm_flags))
986 return SCAN_VMA_CHECK;
987 /* Anon VMA expected */
988 if (!vma->anon_vma || vma->vm_ops)
989 return SCAN_VMA_CHECK;
990 return 0;
991 }
992
993 /*
994 * Bring missing pages in from swap, to complete THP collapse.
995 * Only done if khugepaged_scan_pmd believes it is worthwhile.
996 *
997 * Called and returns without pte mapped or spinlocks held,
998 * but with mmap_lock held to protect against vma changes.
999 */
1000
__collapse_huge_page_swapin(struct mm_struct * mm,struct vm_area_struct * vma,unsigned long address,pmd_t * pmd,int referenced)1001 static bool __collapse_huge_page_swapin(struct mm_struct *mm,
1002 struct vm_area_struct *vma,
1003 unsigned long address, pmd_t *pmd,
1004 int referenced)
1005 {
1006 int swapped_in = 0;
1007 vm_fault_t ret = 0;
1008 struct vm_fault vmf = {
1009 .vma = vma,
1010 .address = address,
1011 .flags = FAULT_FLAG_ALLOW_RETRY,
1012 .pmd = pmd,
1013 .pgoff = linear_page_index(vma, address),
1014 };
1015
1016 vmf.pte = pte_offset_map(pmd, address);
1017 for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE;
1018 vmf.pte++, vmf.address += PAGE_SIZE) {
1019 vmf.orig_pte = *vmf.pte;
1020 if (!is_swap_pte(vmf.orig_pte))
1021 continue;
1022 swapped_in++;
1023 ret = do_swap_page(&vmf);
1024
1025 /* do_swap_page returns VM_FAULT_RETRY with released mmap_lock */
1026 if (ret & VM_FAULT_RETRY) {
1027 mmap_read_lock(mm);
1028 if (hugepage_vma_revalidate(mm, address, &vmf.vma)) {
1029 /* vma is no longer available, don't continue to swapin */
1030 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
1031 return false;
1032 }
1033 /* check if the pmd is still valid */
1034 if (mm_find_pmd(mm, address) != pmd) {
1035 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
1036 return false;
1037 }
1038 }
1039 if (ret & VM_FAULT_ERROR) {
1040 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
1041 return false;
1042 }
1043 /* pte is unmapped now, we need to map it */
1044 vmf.pte = pte_offset_map(pmd, vmf.address);
1045 }
1046 vmf.pte--;
1047 pte_unmap(vmf.pte);
1048
1049 /* Drain LRU add pagevec to remove extra pin on the swapped in pages */
1050 if (swapped_in)
1051 lru_add_drain();
1052
1053 trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
1054 return true;
1055 }
1056
collapse_huge_page(struct mm_struct * mm,unsigned long address,struct page ** hpage,int node,int referenced,int unmapped)1057 static void collapse_huge_page(struct mm_struct *mm,
1058 unsigned long address,
1059 struct page **hpage,
1060 int node, int referenced, int unmapped)
1061 {
1062 LIST_HEAD(compound_pagelist);
1063 pmd_t *pmd, _pmd;
1064 pte_t *pte;
1065 pgtable_t pgtable;
1066 struct page *new_page;
1067 spinlock_t *pmd_ptl, *pte_ptl;
1068 int isolated = 0, result = 0;
1069 struct vm_area_struct *vma;
1070 struct mmu_notifier_range range;
1071 gfp_t gfp;
1072
1073 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1074
1075 /* Only allocate from the target node */
1076 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
1077
1078 /*
1079 * Before allocating the hugepage, release the mmap_lock read lock.
1080 * The allocation can take potentially a long time if it involves
1081 * sync compaction, and we do not need to hold the mmap_lock during
1082 * that. We will recheck the vma after taking it again in write mode.
1083 */
1084 mmap_read_unlock(mm);
1085 new_page = khugepaged_alloc_page(hpage, gfp, node);
1086 if (!new_page) {
1087 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
1088 goto out_nolock;
1089 }
1090
1091 if (unlikely(mem_cgroup_charge(new_page, mm, gfp))) {
1092 result = SCAN_CGROUP_CHARGE_FAIL;
1093 goto out_nolock;
1094 }
1095 count_memcg_page_event(new_page, THP_COLLAPSE_ALLOC);
1096
1097 mmap_read_lock(mm);
1098 result = hugepage_vma_revalidate(mm, address, &vma);
1099 if (result) {
1100 mmap_read_unlock(mm);
1101 goto out_nolock;
1102 }
1103
1104 pmd = mm_find_pmd(mm, address);
1105 if (!pmd) {
1106 result = SCAN_PMD_NULL;
1107 mmap_read_unlock(mm);
1108 goto out_nolock;
1109 }
1110
1111 /*
1112 * __collapse_huge_page_swapin always returns with mmap_lock locked.
1113 * If it fails, we release mmap_lock and jump out_nolock.
1114 * Continuing to collapse causes inconsistency.
1115 */
1116 if (unmapped && !__collapse_huge_page_swapin(mm, vma, address,
1117 pmd, referenced)) {
1118 mmap_read_unlock(mm);
1119 goto out_nolock;
1120 }
1121
1122 mmap_read_unlock(mm);
1123 /*
1124 * Prevent all access to pagetables with the exception of
1125 * gup_fast later handled by the ptep_clear_flush and the VM
1126 * handled by the anon_vma lock + PG_lock.
1127 */
1128 mmap_write_lock(mm);
1129 result = hugepage_vma_revalidate(mm, address, &vma);
1130 if (result)
1131 goto out;
1132 /* check if the pmd is still valid */
1133 if (mm_find_pmd(mm, address) != pmd)
1134 goto out;
1135
1136 anon_vma_lock_write(vma->anon_vma);
1137
1138 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm,
1139 address, address + HPAGE_PMD_SIZE);
1140 mmu_notifier_invalidate_range_start(&range);
1141
1142 pte = pte_offset_map(pmd, address);
1143 pte_ptl = pte_lockptr(mm, pmd);
1144
1145 pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
1146 /*
1147 * After this gup_fast can't run anymore. This also removes
1148 * any huge TLB entry from the CPU so we won't allow
1149 * huge and small TLB entries for the same virtual address
1150 * to avoid the risk of CPU bugs in that area.
1151 */
1152 _pmd = pmdp_collapse_flush(vma, address, pmd);
1153 spin_unlock(pmd_ptl);
1154 mmu_notifier_invalidate_range_end(&range);
1155
1156 spin_lock(pte_ptl);
1157 isolated = __collapse_huge_page_isolate(vma, address, pte,
1158 &compound_pagelist);
1159 spin_unlock(pte_ptl);
1160
1161 if (unlikely(!isolated)) {
1162 pte_unmap(pte);
1163 spin_lock(pmd_ptl);
1164 BUG_ON(!pmd_none(*pmd));
1165 /*
1166 * We can only use set_pmd_at when establishing
1167 * hugepmds and never for establishing regular pmds that
1168 * points to regular pagetables. Use pmd_populate for that
1169 */
1170 pmd_populate(mm, pmd, pmd_pgtable(_pmd));
1171 spin_unlock(pmd_ptl);
1172 anon_vma_unlock_write(vma->anon_vma);
1173 result = SCAN_FAIL;
1174 goto out;
1175 }
1176
1177 /*
1178 * All pages are isolated and locked so anon_vma rmap
1179 * can't run anymore.
1180 */
1181 anon_vma_unlock_write(vma->anon_vma);
1182
1183 __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl,
1184 &compound_pagelist);
1185 pte_unmap(pte);
1186 __SetPageUptodate(new_page);
1187 pgtable = pmd_pgtable(_pmd);
1188
1189 _pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
1190 _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
1191
1192 /*
1193 * spin_lock() below is not the equivalent of smp_wmb(), so
1194 * this is needed to avoid the copy_huge_page writes to become
1195 * visible after the set_pmd_at() write.
1196 */
1197 smp_wmb();
1198
1199 spin_lock(pmd_ptl);
1200 BUG_ON(!pmd_none(*pmd));
1201 page_add_new_anon_rmap(new_page, vma, address, true);
1202 lru_cache_add_inactive_or_unevictable(new_page, vma);
1203 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1204 set_pmd_at(mm, address, pmd, _pmd);
1205 update_mmu_cache_pmd(vma, address, pmd);
1206 spin_unlock(pmd_ptl);
1207
1208 *hpage = NULL;
1209
1210 khugepaged_pages_collapsed++;
1211 result = SCAN_SUCCEED;
1212 out_up_write:
1213 mmap_write_unlock(mm);
1214 out_nolock:
1215 if (!IS_ERR_OR_NULL(*hpage))
1216 mem_cgroup_uncharge(*hpage);
1217 trace_mm_collapse_huge_page(mm, isolated, result);
1218 return;
1219 out:
1220 goto out_up_write;
1221 }
1222
khugepaged_scan_pmd(struct mm_struct * mm,struct vm_area_struct * vma,unsigned long address,struct page ** hpage)1223 static int khugepaged_scan_pmd(struct mm_struct *mm,
1224 struct vm_area_struct *vma,
1225 unsigned long address,
1226 struct page **hpage)
1227 {
1228 pmd_t *pmd;
1229 pte_t *pte, *_pte;
1230 int ret = 0, result = 0, referenced = 0;
1231 int none_or_zero = 0, shared = 0;
1232 struct page *page = NULL;
1233 unsigned long _address;
1234 spinlock_t *ptl;
1235 int node = NUMA_NO_NODE, unmapped = 0;
1236 bool writable = false;
1237
1238 VM_BUG_ON(address & ~HPAGE_PMD_MASK);
1239
1240 pmd = mm_find_pmd(mm, address);
1241 if (!pmd) {
1242 result = SCAN_PMD_NULL;
1243 goto out;
1244 }
1245
1246 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1247 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
1248 for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
1249 _pte++, _address += PAGE_SIZE) {
1250 pte_t pteval = *_pte;
1251 if (is_swap_pte(pteval)) {
1252 if (++unmapped <= khugepaged_max_ptes_swap) {
1253 /*
1254 * Always be strict with uffd-wp
1255 * enabled swap entries. Please see
1256 * comment below for pte_uffd_wp().
1257 */
1258 if (pte_swp_uffd_wp(pteval)) {
1259 result = SCAN_PTE_UFFD_WP;
1260 goto out_unmap;
1261 }
1262 continue;
1263 } else {
1264 result = SCAN_EXCEED_SWAP_PTE;
1265 goto out_unmap;
1266 }
1267 }
1268 if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
1269 if (!userfaultfd_armed(vma) &&
1270 ++none_or_zero <= khugepaged_max_ptes_none) {
1271 continue;
1272 } else {
1273 result = SCAN_EXCEED_NONE_PTE;
1274 goto out_unmap;
1275 }
1276 }
1277 if (!pte_present(pteval)) {
1278 result = SCAN_PTE_NON_PRESENT;
1279 goto out_unmap;
1280 }
1281 if (pte_uffd_wp(pteval)) {
1282 /*
1283 * Don't collapse the page if any of the small
1284 * PTEs are armed with uffd write protection.
1285 * Here we can also mark the new huge pmd as
1286 * write protected if any of the small ones is
1287 * marked but that could bring uknown
1288 * userfault messages that falls outside of
1289 * the registered range. So, just be simple.
1290 */
1291 result = SCAN_PTE_UFFD_WP;
1292 goto out_unmap;
1293 }
1294 if (pte_write(pteval))
1295 writable = true;
1296
1297 page = vm_normal_page(vma, _address, pteval);
1298 if (unlikely(!page)) {
1299 result = SCAN_PAGE_NULL;
1300 goto out_unmap;
1301 }
1302
1303 if (page_mapcount(page) > 1 &&
1304 ++shared > khugepaged_max_ptes_shared) {
1305 result = SCAN_EXCEED_SHARED_PTE;
1306 goto out_unmap;
1307 }
1308
1309 page = compound_head(page);
1310
1311 /*
1312 * Record which node the original page is from and save this
1313 * information to khugepaged_node_load[].
1314 * Khupaged will allocate hugepage from the node has the max
1315 * hit record.
1316 */
1317 node = page_to_nid(page);
1318 if (khugepaged_scan_abort(node)) {
1319 result = SCAN_SCAN_ABORT;
1320 goto out_unmap;
1321 }
1322 khugepaged_node_load[node]++;
1323 if (!PageLRU(page)) {
1324 result = SCAN_PAGE_LRU;
1325 goto out_unmap;
1326 }
1327 if (PageLocked(page)) {
1328 result = SCAN_PAGE_LOCK;
1329 goto out_unmap;
1330 }
1331 if (!PageAnon(page)) {
1332 result = SCAN_PAGE_ANON;
1333 goto out_unmap;
1334 }
1335
1336 /*
1337 * Check if the page has any GUP (or other external) pins.
1338 *
1339 * Here the check is racy it may see totmal_mapcount > refcount
1340 * in some cases.
1341 * For example, one process with one forked child process.
1342 * The parent has the PMD split due to MADV_DONTNEED, then
1343 * the child is trying unmap the whole PMD, but khugepaged
1344 * may be scanning the parent between the child has
1345 * PageDoubleMap flag cleared and dec the mapcount. So
1346 * khugepaged may see total_mapcount > refcount.
1347 *
1348 * But such case is ephemeral we could always retry collapse
1349 * later. However it may report false positive if the page
1350 * has excessive GUP pins (i.e. 512). Anyway the same check
1351 * will be done again later the risk seems low.
1352 */
1353 if (!is_refcount_suitable(page)) {
1354 result = SCAN_PAGE_COUNT;
1355 goto out_unmap;
1356 }
1357 if (pte_young(pteval) ||
1358 page_is_young(page) || PageReferenced(page) ||
1359 mmu_notifier_test_young(vma->vm_mm, address))
1360 referenced++;
1361 }
1362 if (!writable) {
1363 result = SCAN_PAGE_RO;
1364 } else if (!referenced || (unmapped && referenced < HPAGE_PMD_NR/2)) {
1365 result = SCAN_LACK_REFERENCED_PAGE;
1366 } else {
1367 result = SCAN_SUCCEED;
1368 ret = 1;
1369 }
1370 out_unmap:
1371 pte_unmap_unlock(pte, ptl);
1372 if (ret) {
1373 node = khugepaged_find_target_node();
1374 /* collapse_huge_page will return with the mmap_lock released */
1375 collapse_huge_page(mm, address, hpage, node,
1376 referenced, unmapped);
1377 }
1378 out:
1379 trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
1380 none_or_zero, result, unmapped);
1381 return ret;
1382 }
1383
collect_mm_slot(struct mm_slot * mm_slot)1384 static void collect_mm_slot(struct mm_slot *mm_slot)
1385 {
1386 struct mm_struct *mm = mm_slot->mm;
1387
1388 lockdep_assert_held(&khugepaged_mm_lock);
1389
1390 if (khugepaged_test_exit(mm)) {
1391 /* free mm_slot */
1392 hash_del(&mm_slot->hash);
1393 list_del(&mm_slot->mm_node);
1394
1395 /*
1396 * Not strictly needed because the mm exited already.
1397 *
1398 * clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
1399 */
1400
1401 /* khugepaged_mm_lock actually not necessary for the below */
1402 free_mm_slot(mm_slot);
1403 mmdrop(mm);
1404 }
1405 }
1406
1407 #ifdef CONFIG_SHMEM
1408 /*
1409 * Notify khugepaged that given addr of the mm is pte-mapped THP. Then
1410 * khugepaged should try to collapse the page table.
1411 */
khugepaged_add_pte_mapped_thp(struct mm_struct * mm,unsigned long addr)1412 static int khugepaged_add_pte_mapped_thp(struct mm_struct *mm,
1413 unsigned long addr)
1414 {
1415 struct mm_slot *mm_slot;
1416
1417 VM_BUG_ON(addr & ~HPAGE_PMD_MASK);
1418
1419 spin_lock(&khugepaged_mm_lock);
1420 mm_slot = get_mm_slot(mm);
1421 if (likely(mm_slot && mm_slot->nr_pte_mapped_thp < MAX_PTE_MAPPED_THP))
1422 mm_slot->pte_mapped_thp[mm_slot->nr_pte_mapped_thp++] = addr;
1423 spin_unlock(&khugepaged_mm_lock);
1424 return 0;
1425 }
1426
1427 /**
1428 * Try to collapse a pte-mapped THP for mm at address haddr.
1429 *
1430 * This function checks whether all the PTEs in the PMD are pointing to the
1431 * right THP. If so, retract the page table so the THP can refault in with
1432 * as pmd-mapped.
1433 */
collapse_pte_mapped_thp(struct mm_struct * mm,unsigned long addr)1434 void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr)
1435 {
1436 unsigned long haddr = addr & HPAGE_PMD_MASK;
1437 struct vm_area_struct *vma = find_vma(mm, haddr);
1438 struct page *hpage;
1439 pte_t *start_pte, *pte;
1440 pmd_t *pmd, _pmd;
1441 spinlock_t *ptl;
1442 int count = 0;
1443 int i;
1444
1445 if (!vma || !vma->vm_file ||
1446 vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE)
1447 return;
1448
1449 /*
1450 * This vm_flags may not have VM_HUGEPAGE if the page was not
1451 * collapsed by this mm. But we can still collapse if the page is
1452 * the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check()
1453 * will not fail the vma for missing VM_HUGEPAGE
1454 */
1455 if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE))
1456 return;
1457
1458 hpage = find_lock_page(vma->vm_file->f_mapping,
1459 linear_page_index(vma, haddr));
1460 if (!hpage)
1461 return;
1462
1463 if (!PageHead(hpage))
1464 goto drop_hpage;
1465
1466 pmd = mm_find_pmd(mm, haddr);
1467 if (!pmd)
1468 goto drop_hpage;
1469
1470 start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl);
1471
1472 /* step 1: check all mapped PTEs are to the right huge page */
1473 for (i = 0, addr = haddr, pte = start_pte;
1474 i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) {
1475 struct page *page;
1476
1477 /* empty pte, skip */
1478 if (pte_none(*pte))
1479 continue;
1480
1481 /* page swapped out, abort */
1482 if (!pte_present(*pte))
1483 goto abort;
1484
1485 page = vm_normal_page(vma, addr, *pte);
1486
1487 /*
1488 * Note that uprobe, debugger, or MAP_PRIVATE may change the
1489 * page table, but the new page will not be a subpage of hpage.
1490 */
1491 if (hpage + i != page)
1492 goto abort;
1493 count++;
1494 }
1495
1496 /* step 2: adjust rmap */
1497 for (i = 0, addr = haddr, pte = start_pte;
1498 i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) {
1499 struct page *page;
1500
1501 if (pte_none(*pte))
1502 continue;
1503 page = vm_normal_page(vma, addr, *pte);
1504 page_remove_rmap(page, false);
1505 }
1506
1507 pte_unmap_unlock(start_pte, ptl);
1508
1509 /* step 3: set proper refcount and mm_counters. */
1510 if (count) {
1511 page_ref_sub(hpage, count);
1512 add_mm_counter(vma->vm_mm, mm_counter_file(hpage), -count);
1513 }
1514
1515 /* step 4: collapse pmd */
1516 ptl = pmd_lock(vma->vm_mm, pmd);
1517 _pmd = pmdp_collapse_flush(vma, haddr, pmd);
1518 spin_unlock(ptl);
1519 mm_dec_nr_ptes(mm);
1520 pte_free(mm, pmd_pgtable(_pmd));
1521
1522 drop_hpage:
1523 unlock_page(hpage);
1524 put_page(hpage);
1525 return;
1526
1527 abort:
1528 pte_unmap_unlock(start_pte, ptl);
1529 goto drop_hpage;
1530 }
1531
khugepaged_collapse_pte_mapped_thps(struct mm_slot * mm_slot)1532 static int khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot)
1533 {
1534 struct mm_struct *mm = mm_slot->mm;
1535 int i;
1536
1537 if (likely(mm_slot->nr_pte_mapped_thp == 0))
1538 return 0;
1539
1540 if (!mmap_write_trylock(mm))
1541 return -EBUSY;
1542
1543 if (unlikely(khugepaged_test_exit(mm)))
1544 goto out;
1545
1546 for (i = 0; i < mm_slot->nr_pte_mapped_thp; i++)
1547 collapse_pte_mapped_thp(mm, mm_slot->pte_mapped_thp[i]);
1548
1549 out:
1550 mm_slot->nr_pte_mapped_thp = 0;
1551 mmap_write_unlock(mm);
1552 return 0;
1553 }
1554
retract_page_tables(struct address_space * mapping,pgoff_t pgoff)1555 static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
1556 {
1557 struct vm_area_struct *vma;
1558 struct mm_struct *mm;
1559 unsigned long addr;
1560 pmd_t *pmd, _pmd;
1561
1562 i_mmap_lock_write(mapping);
1563 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
1564 /*
1565 * Check vma->anon_vma to exclude MAP_PRIVATE mappings that
1566 * got written to. These VMAs are likely not worth investing
1567 * mmap_write_lock(mm) as PMD-mapping is likely to be split
1568 * later.
1569 *
1570 * Not that vma->anon_vma check is racy: it can be set up after
1571 * the check but before we took mmap_lock by the fault path.
1572 * But page lock would prevent establishing any new ptes of the
1573 * page, so we are safe.
1574 *
1575 * An alternative would be drop the check, but check that page
1576 * table is clear before calling pmdp_collapse_flush() under
1577 * ptl. It has higher chance to recover THP for the VMA, but
1578 * has higher cost too.
1579 */
1580 if (vma->anon_vma)
1581 continue;
1582 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
1583 if (addr & ~HPAGE_PMD_MASK)
1584 continue;
1585 if (vma->vm_end < addr + HPAGE_PMD_SIZE)
1586 continue;
1587 mm = vma->vm_mm;
1588 pmd = mm_find_pmd(mm, addr);
1589 if (!pmd)
1590 continue;
1591 /*
1592 * We need exclusive mmap_lock to retract page table.
1593 *
1594 * We use trylock due to lock inversion: we need to acquire
1595 * mmap_lock while holding page lock. Fault path does it in
1596 * reverse order. Trylock is a way to avoid deadlock.
1597 */
1598 if (mmap_write_trylock(mm)) {
1599 if (!khugepaged_test_exit(mm)) {
1600 spinlock_t *ptl = pmd_lock(mm, pmd);
1601 /* assume page table is clear */
1602 _pmd = pmdp_collapse_flush(vma, addr, pmd);
1603 spin_unlock(ptl);
1604 mm_dec_nr_ptes(mm);
1605 pte_free(mm, pmd_pgtable(_pmd));
1606 }
1607 mmap_write_unlock(mm);
1608 } else {
1609 /* Try again later */
1610 khugepaged_add_pte_mapped_thp(mm, addr);
1611 }
1612 }
1613 i_mmap_unlock_write(mapping);
1614 }
1615
1616 /**
1617 * collapse_file - collapse filemap/tmpfs/shmem pages into huge one.
1618 *
1619 * Basic scheme is simple, details are more complex:
1620 * - allocate and lock a new huge page;
1621 * - scan page cache replacing old pages with the new one
1622 * + swap/gup in pages if necessary;
1623 * + fill in gaps;
1624 * + keep old pages around in case rollback is required;
1625 * - if replacing succeeds:
1626 * + copy data over;
1627 * + free old pages;
1628 * + unlock huge page;
1629 * - if replacing failed;
1630 * + put all pages back and unfreeze them;
1631 * + restore gaps in the page cache;
1632 * + unlock and free huge page;
1633 */
collapse_file(struct mm_struct * mm,struct file * file,pgoff_t start,struct page ** hpage,int node)1634 static void collapse_file(struct mm_struct *mm,
1635 struct file *file, pgoff_t start,
1636 struct page **hpage, int node)
1637 {
1638 struct address_space *mapping = file->f_mapping;
1639 gfp_t gfp;
1640 struct page *new_page;
1641 pgoff_t index, end = start + HPAGE_PMD_NR;
1642 LIST_HEAD(pagelist);
1643 XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
1644 int nr_none = 0, result = SCAN_SUCCEED;
1645 bool is_shmem = shmem_file(file);
1646
1647 VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem);
1648 VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
1649
1650 /* Only allocate from the target node */
1651 gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
1652
1653 new_page = khugepaged_alloc_page(hpage, gfp, node);
1654 if (!new_page) {
1655 result = SCAN_ALLOC_HUGE_PAGE_FAIL;
1656 goto out;
1657 }
1658
1659 if (unlikely(mem_cgroup_charge(new_page, mm, gfp))) {
1660 result = SCAN_CGROUP_CHARGE_FAIL;
1661 goto out;
1662 }
1663 count_memcg_page_event(new_page, THP_COLLAPSE_ALLOC);
1664
1665 /* This will be less messy when we use multi-index entries */
1666 do {
1667 xas_lock_irq(&xas);
1668 xas_create_range(&xas);
1669 if (!xas_error(&xas))
1670 break;
1671 xas_unlock_irq(&xas);
1672 if (!xas_nomem(&xas, GFP_KERNEL)) {
1673 result = SCAN_FAIL;
1674 goto out;
1675 }
1676 } while (1);
1677
1678 __SetPageLocked(new_page);
1679 if (is_shmem)
1680 __SetPageSwapBacked(new_page);
1681 new_page->index = start;
1682 new_page->mapping = mapping;
1683
1684 /*
1685 * At this point the new_page is locked and not up-to-date.
1686 * It's safe to insert it into the page cache, because nobody would
1687 * be able to map it or use it in another way until we unlock it.
1688 */
1689
1690 xas_set(&xas, start);
1691 for (index = start; index < end; index++) {
1692 struct page *page = xas_next(&xas);
1693
1694 VM_BUG_ON(index != xas.xa_index);
1695 if (is_shmem) {
1696 if (!page) {
1697 /*
1698 * Stop if extent has been truncated or
1699 * hole-punched, and is now completely
1700 * empty.
1701 */
1702 if (index == start) {
1703 if (!xas_next_entry(&xas, end - 1)) {
1704 result = SCAN_TRUNCATED;
1705 goto xa_locked;
1706 }
1707 xas_set(&xas, index);
1708 }
1709 if (!shmem_charge(mapping->host, 1)) {
1710 result = SCAN_FAIL;
1711 goto xa_locked;
1712 }
1713 xas_store(&xas, new_page);
1714 nr_none++;
1715 continue;
1716 }
1717
1718 if (xa_is_value(page) || !PageUptodate(page)) {
1719 xas_unlock_irq(&xas);
1720 /* swap in or instantiate fallocated page */
1721 if (shmem_getpage(mapping->host, index, &page,
1722 SGP_NOHUGE)) {
1723 result = SCAN_FAIL;
1724 goto xa_unlocked;
1725 }
1726 } else if (trylock_page(page)) {
1727 get_page(page);
1728 xas_unlock_irq(&xas);
1729 } else {
1730 result = SCAN_PAGE_LOCK;
1731 goto xa_locked;
1732 }
1733 } else { /* !is_shmem */
1734 if (!page || xa_is_value(page)) {
1735 xas_unlock_irq(&xas);
1736 page_cache_sync_readahead(mapping, &file->f_ra,
1737 file, index,
1738 end - index);
1739 /* drain pagevecs to help isolate_lru_page() */
1740 lru_add_drain();
1741 page = find_lock_page(mapping, index);
1742 if (unlikely(page == NULL)) {
1743 result = SCAN_FAIL;
1744 goto xa_unlocked;
1745 }
1746 } else if (PageDirty(page)) {
1747 /*
1748 * khugepaged only works on read-only fd,
1749 * so this page is dirty because it hasn't
1750 * been flushed since first write. There
1751 * won't be new dirty pages.
1752 *
1753 * Trigger async flush here and hope the
1754 * writeback is done when khugepaged
1755 * revisits this page.
1756 *
1757 * This is a one-off situation. We are not
1758 * forcing writeback in loop.
1759 */
1760 xas_unlock_irq(&xas);
1761 filemap_flush(mapping);
1762 result = SCAN_FAIL;
1763 goto xa_unlocked;
1764 } else if (PageWriteback(page)) {
1765 xas_unlock_irq(&xas);
1766 result = SCAN_FAIL;
1767 goto xa_unlocked;
1768 } else if (trylock_page(page)) {
1769 get_page(page);
1770 xas_unlock_irq(&xas);
1771 } else {
1772 result = SCAN_PAGE_LOCK;
1773 goto xa_locked;
1774 }
1775 }
1776
1777 /*
1778 * The page must be locked, so we can drop the i_pages lock
1779 * without racing with truncate.
1780 */
1781 VM_BUG_ON_PAGE(!PageLocked(page), page);
1782
1783 /* make sure the page is up to date */
1784 if (unlikely(!PageUptodate(page))) {
1785 result = SCAN_FAIL;
1786 goto out_unlock;
1787 }
1788
1789 /*
1790 * If file was truncated then extended, or hole-punched, before
1791 * we locked the first page, then a THP might be there already.
1792 */
1793 if (PageTransCompound(page)) {
1794 result = SCAN_PAGE_COMPOUND;
1795 goto out_unlock;
1796 }
1797
1798 if (page_mapping(page) != mapping) {
1799 result = SCAN_TRUNCATED;
1800 goto out_unlock;
1801 }
1802
1803 if (!is_shmem && (PageDirty(page) ||
1804 PageWriteback(page))) {
1805 /*
1806 * khugepaged only works on read-only fd, so this
1807 * page is dirty because it hasn't been flushed
1808 * since first write.
1809 */
1810 result = SCAN_FAIL;
1811 goto out_unlock;
1812 }
1813
1814 if (isolate_lru_page(page)) {
1815 result = SCAN_DEL_PAGE_LRU;
1816 goto out_unlock;
1817 }
1818
1819 if (page_has_private(page) &&
1820 !try_to_release_page(page, GFP_KERNEL)) {
1821 result = SCAN_PAGE_HAS_PRIVATE;
1822 putback_lru_page(page);
1823 goto out_unlock;
1824 }
1825
1826 if (page_mapped(page))
1827 unmap_mapping_pages(mapping, index, 1, false);
1828
1829 xas_lock_irq(&xas);
1830 xas_set(&xas, index);
1831
1832 VM_BUG_ON_PAGE(page != xas_load(&xas), page);
1833 VM_BUG_ON_PAGE(page_mapped(page), page);
1834
1835 /*
1836 * The page is expected to have page_count() == 3:
1837 * - we hold a pin on it;
1838 * - one reference from page cache;
1839 * - one from isolate_lru_page;
1840 */
1841 if (!page_ref_freeze(page, 3)) {
1842 result = SCAN_PAGE_COUNT;
1843 xas_unlock_irq(&xas);
1844 putback_lru_page(page);
1845 goto out_unlock;
1846 }
1847
1848 /*
1849 * Add the page to the list to be able to undo the collapse if
1850 * something go wrong.
1851 */
1852 list_add_tail(&page->lru, &pagelist);
1853
1854 /* Finally, replace with the new page. */
1855 xas_store(&xas, new_page);
1856 continue;
1857 out_unlock:
1858 unlock_page(page);
1859 put_page(page);
1860 goto xa_unlocked;
1861 }
1862
1863 if (is_shmem)
1864 __inc_node_page_state(new_page, NR_SHMEM_THPS);
1865 else {
1866 __inc_node_page_state(new_page, NR_FILE_THPS);
1867 filemap_nr_thps_inc(mapping);
1868 }
1869
1870 if (nr_none) {
1871 __mod_lruvec_page_state(new_page, NR_FILE_PAGES, nr_none);
1872 if (is_shmem)
1873 __mod_lruvec_page_state(new_page, NR_SHMEM, nr_none);
1874 }
1875
1876 xa_locked:
1877 xas_unlock_irq(&xas);
1878 xa_unlocked:
1879
1880 if (result == SCAN_SUCCEED) {
1881 struct page *page, *tmp;
1882
1883 /*
1884 * Replacing old pages with new one has succeeded, now we
1885 * need to copy the content and free the old pages.
1886 */
1887 index = start;
1888 list_for_each_entry_safe(page, tmp, &pagelist, lru) {
1889 while (index < page->index) {
1890 clear_highpage(new_page + (index % HPAGE_PMD_NR));
1891 index++;
1892 }
1893 copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
1894 page);
1895 list_del(&page->lru);
1896 page->mapping = NULL;
1897 page_ref_unfreeze(page, 1);
1898 ClearPageActive(page);
1899 ClearPageUnevictable(page);
1900 unlock_page(page);
1901 put_page(page);
1902 index++;
1903 }
1904 while (index < end) {
1905 clear_highpage(new_page + (index % HPAGE_PMD_NR));
1906 index++;
1907 }
1908
1909 SetPageUptodate(new_page);
1910 page_ref_add(new_page, HPAGE_PMD_NR - 1);
1911 if (is_shmem)
1912 set_page_dirty(new_page);
1913 lru_cache_add(new_page);
1914
1915 /*
1916 * Remove pte page tables, so we can re-fault the page as huge.
1917 */
1918 retract_page_tables(mapping, start);
1919 *hpage = NULL;
1920
1921 khugepaged_pages_collapsed++;
1922 } else {
1923 struct page *page;
1924
1925 /* Something went wrong: roll back page cache changes */
1926 xas_lock_irq(&xas);
1927 mapping->nrpages -= nr_none;
1928
1929 if (is_shmem)
1930 shmem_uncharge(mapping->host, nr_none);
1931
1932 xas_set(&xas, start);
1933 xas_for_each(&xas, page, end - 1) {
1934 page = list_first_entry_or_null(&pagelist,
1935 struct page, lru);
1936 if (!page || xas.xa_index < page->index) {
1937 if (!nr_none)
1938 break;
1939 nr_none--;
1940 /* Put holes back where they were */
1941 xas_store(&xas, NULL);
1942 continue;
1943 }
1944
1945 VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
1946
1947 /* Unfreeze the page. */
1948 list_del(&page->lru);
1949 page_ref_unfreeze(page, 2);
1950 xas_store(&xas, page);
1951 xas_pause(&xas);
1952 xas_unlock_irq(&xas);
1953 unlock_page(page);
1954 putback_lru_page(page);
1955 xas_lock_irq(&xas);
1956 }
1957 VM_BUG_ON(nr_none);
1958 xas_unlock_irq(&xas);
1959
1960 new_page->mapping = NULL;
1961 }
1962
1963 unlock_page(new_page);
1964 out:
1965 VM_BUG_ON(!list_empty(&pagelist));
1966 if (!IS_ERR_OR_NULL(*hpage))
1967 mem_cgroup_uncharge(*hpage);
1968 /* TODO: tracepoints */
1969 }
1970
khugepaged_scan_file(struct mm_struct * mm,struct file * file,pgoff_t start,struct page ** hpage)1971 static void khugepaged_scan_file(struct mm_struct *mm,
1972 struct file *file, pgoff_t start, struct page **hpage)
1973 {
1974 struct page *page = NULL;
1975 struct address_space *mapping = file->f_mapping;
1976 XA_STATE(xas, &mapping->i_pages, start);
1977 int present, swap;
1978 int node = NUMA_NO_NODE;
1979 int result = SCAN_SUCCEED;
1980
1981 present = 0;
1982 swap = 0;
1983 memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
1984 rcu_read_lock();
1985 xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) {
1986 if (xas_retry(&xas, page))
1987 continue;
1988
1989 if (xa_is_value(page)) {
1990 if (++swap > khugepaged_max_ptes_swap) {
1991 result = SCAN_EXCEED_SWAP_PTE;
1992 break;
1993 }
1994 continue;
1995 }
1996
1997 if (PageTransCompound(page)) {
1998 result = SCAN_PAGE_COMPOUND;
1999 break;
2000 }
2001
2002 node = page_to_nid(page);
2003 if (khugepaged_scan_abort(node)) {
2004 result = SCAN_SCAN_ABORT;
2005 break;
2006 }
2007 khugepaged_node_load[node]++;
2008
2009 if (!PageLRU(page)) {
2010 result = SCAN_PAGE_LRU;
2011 break;
2012 }
2013
2014 if (page_count(page) !=
2015 1 + page_mapcount(page) + page_has_private(page)) {
2016 result = SCAN_PAGE_COUNT;
2017 break;
2018 }
2019
2020 /*
2021 * We probably should check if the page is referenced here, but
2022 * nobody would transfer pte_young() to PageReferenced() for us.
2023 * And rmap walk here is just too costly...
2024 */
2025
2026 present++;
2027
2028 if (need_resched()) {
2029 xas_pause(&xas);
2030 cond_resched_rcu();
2031 }
2032 }
2033 rcu_read_unlock();
2034
2035 if (result == SCAN_SUCCEED) {
2036 if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
2037 result = SCAN_EXCEED_NONE_PTE;
2038 } else {
2039 node = khugepaged_find_target_node();
2040 collapse_file(mm, file, start, hpage, node);
2041 }
2042 }
2043
2044 /* TODO: tracepoints */
2045 }
2046 #else
khugepaged_scan_file(struct mm_struct * mm,struct file * file,pgoff_t start,struct page ** hpage)2047 static void khugepaged_scan_file(struct mm_struct *mm,
2048 struct file *file, pgoff_t start, struct page **hpage)
2049 {
2050 BUILD_BUG();
2051 }
2052
khugepaged_collapse_pte_mapped_thps(struct mm_slot * mm_slot)2053 static int khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot)
2054 {
2055 return 0;
2056 }
2057 #endif
2058
khugepaged_scan_mm_slot(unsigned int pages,struct page ** hpage)2059 static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
2060 struct page **hpage)
2061 __releases(&khugepaged_mm_lock)
2062 __acquires(&khugepaged_mm_lock)
2063 {
2064 struct mm_slot *mm_slot;
2065 struct mm_struct *mm;
2066 struct vm_area_struct *vma;
2067 int progress = 0;
2068
2069 VM_BUG_ON(!pages);
2070 lockdep_assert_held(&khugepaged_mm_lock);
2071
2072 if (khugepaged_scan.mm_slot)
2073 mm_slot = khugepaged_scan.mm_slot;
2074 else {
2075 mm_slot = list_entry(khugepaged_scan.mm_head.next,
2076 struct mm_slot, mm_node);
2077 khugepaged_scan.address = 0;
2078 khugepaged_scan.mm_slot = mm_slot;
2079 }
2080 spin_unlock(&khugepaged_mm_lock);
2081 khugepaged_collapse_pte_mapped_thps(mm_slot);
2082
2083 mm = mm_slot->mm;
2084 /*
2085 * Don't wait for semaphore (to avoid long wait times). Just move to
2086 * the next mm on the list.
2087 */
2088 vma = NULL;
2089 if (unlikely(!mmap_read_trylock(mm)))
2090 goto breakouterloop_mmap_lock;
2091 if (likely(!khugepaged_test_exit(mm)))
2092 vma = find_vma(mm, khugepaged_scan.address);
2093
2094 progress++;
2095 for (; vma; vma = vma->vm_next) {
2096 unsigned long hstart, hend;
2097
2098 cond_resched();
2099 if (unlikely(khugepaged_test_exit(mm))) {
2100 progress++;
2101 break;
2102 }
2103 if (!hugepage_vma_check(vma, vma->vm_flags)) {
2104 skip:
2105 progress++;
2106 continue;
2107 }
2108 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
2109 hend = vma->vm_end & HPAGE_PMD_MASK;
2110 if (hstart >= hend)
2111 goto skip;
2112 if (khugepaged_scan.address > hend)
2113 goto skip;
2114 if (khugepaged_scan.address < hstart)
2115 khugepaged_scan.address = hstart;
2116 VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
2117 if (shmem_file(vma->vm_file) && !shmem_huge_enabled(vma))
2118 goto skip;
2119
2120 while (khugepaged_scan.address < hend) {
2121 int ret;
2122 cond_resched();
2123 if (unlikely(khugepaged_test_exit(mm)))
2124 goto breakouterloop;
2125
2126 VM_BUG_ON(khugepaged_scan.address < hstart ||
2127 khugepaged_scan.address + HPAGE_PMD_SIZE >
2128 hend);
2129 if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) {
2130 struct file *file = get_file(vma->vm_file);
2131 pgoff_t pgoff = linear_page_index(vma,
2132 khugepaged_scan.address);
2133
2134 mmap_read_unlock(mm);
2135 ret = 1;
2136 khugepaged_scan_file(mm, file, pgoff, hpage);
2137 fput(file);
2138 } else {
2139 ret = khugepaged_scan_pmd(mm, vma,
2140 khugepaged_scan.address,
2141 hpage);
2142 }
2143 /* move to next address */
2144 khugepaged_scan.address += HPAGE_PMD_SIZE;
2145 progress += HPAGE_PMD_NR;
2146 if (ret)
2147 /* we released mmap_lock so break loop */
2148 goto breakouterloop_mmap_lock;
2149 if (progress >= pages)
2150 goto breakouterloop;
2151 }
2152 }
2153 breakouterloop:
2154 mmap_read_unlock(mm); /* exit_mmap will destroy ptes after this */
2155 breakouterloop_mmap_lock:
2156
2157 spin_lock(&khugepaged_mm_lock);
2158 VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
2159 /*
2160 * Release the current mm_slot if this mm is about to die, or
2161 * if we scanned all vmas of this mm.
2162 */
2163 if (khugepaged_test_exit(mm) || !vma) {
2164 /*
2165 * Make sure that if mm_users is reaching zero while
2166 * khugepaged runs here, khugepaged_exit will find
2167 * mm_slot not pointing to the exiting mm.
2168 */
2169 if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
2170 khugepaged_scan.mm_slot = list_entry(
2171 mm_slot->mm_node.next,
2172 struct mm_slot, mm_node);
2173 khugepaged_scan.address = 0;
2174 } else {
2175 khugepaged_scan.mm_slot = NULL;
2176 khugepaged_full_scans++;
2177 }
2178
2179 collect_mm_slot(mm_slot);
2180 }
2181
2182 return progress;
2183 }
2184
khugepaged_has_work(void)2185 static int khugepaged_has_work(void)
2186 {
2187 return !list_empty(&khugepaged_scan.mm_head) &&
2188 khugepaged_enabled();
2189 }
2190
khugepaged_wait_event(void)2191 static int khugepaged_wait_event(void)
2192 {
2193 return !list_empty(&khugepaged_scan.mm_head) ||
2194 kthread_should_stop();
2195 }
2196
khugepaged_do_scan(void)2197 static void khugepaged_do_scan(void)
2198 {
2199 struct page *hpage = NULL;
2200 unsigned int progress = 0, pass_through_head = 0;
2201 unsigned int pages = khugepaged_pages_to_scan;
2202 bool wait = true;
2203
2204 barrier(); /* write khugepaged_pages_to_scan to local stack */
2205
2206 lru_add_drain_all();
2207
2208 while (progress < pages) {
2209 if (!khugepaged_prealloc_page(&hpage, &wait))
2210 break;
2211
2212 cond_resched();
2213
2214 if (unlikely(kthread_should_stop() || try_to_freeze()))
2215 break;
2216
2217 spin_lock(&khugepaged_mm_lock);
2218 if (!khugepaged_scan.mm_slot)
2219 pass_through_head++;
2220 if (khugepaged_has_work() &&
2221 pass_through_head < 2)
2222 progress += khugepaged_scan_mm_slot(pages - progress,
2223 &hpage);
2224 else
2225 progress = pages;
2226 spin_unlock(&khugepaged_mm_lock);
2227 }
2228
2229 if (!IS_ERR_OR_NULL(hpage))
2230 put_page(hpage);
2231 }
2232
khugepaged_should_wakeup(void)2233 static bool khugepaged_should_wakeup(void)
2234 {
2235 return kthread_should_stop() ||
2236 time_after_eq(jiffies, khugepaged_sleep_expire);
2237 }
2238
khugepaged_wait_work(void)2239 static void khugepaged_wait_work(void)
2240 {
2241 if (khugepaged_has_work()) {
2242 const unsigned long scan_sleep_jiffies =
2243 msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
2244
2245 if (!scan_sleep_jiffies)
2246 return;
2247
2248 khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
2249 wait_event_freezable_timeout(khugepaged_wait,
2250 khugepaged_should_wakeup(),
2251 scan_sleep_jiffies);
2252 return;
2253 }
2254
2255 if (khugepaged_enabled())
2256 wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
2257 }
2258
khugepaged(void * none)2259 static int khugepaged(void *none)
2260 {
2261 struct mm_slot *mm_slot;
2262
2263 set_freezable();
2264 set_user_nice(current, MAX_NICE);
2265
2266 while (!kthread_should_stop()) {
2267 khugepaged_do_scan();
2268 khugepaged_wait_work();
2269 }
2270
2271 spin_lock(&khugepaged_mm_lock);
2272 mm_slot = khugepaged_scan.mm_slot;
2273 khugepaged_scan.mm_slot = NULL;
2274 if (mm_slot)
2275 collect_mm_slot(mm_slot);
2276 spin_unlock(&khugepaged_mm_lock);
2277 return 0;
2278 }
2279
set_recommended_min_free_kbytes(void)2280 static void set_recommended_min_free_kbytes(void)
2281 {
2282 struct zone *zone;
2283 int nr_zones = 0;
2284 unsigned long recommended_min;
2285
2286 for_each_populated_zone(zone) {
2287 /*
2288 * We don't need to worry about fragmentation of
2289 * ZONE_MOVABLE since it only has movable pages.
2290 */
2291 if (zone_idx(zone) > gfp_zone(GFP_USER))
2292 continue;
2293
2294 nr_zones++;
2295 }
2296
2297 /* Ensure 2 pageblocks are free to assist fragmentation avoidance */
2298 recommended_min = pageblock_nr_pages * nr_zones * 2;
2299
2300 /*
2301 * Make sure that on average at least two pageblocks are almost free
2302 * of another type, one for a migratetype to fall back to and a
2303 * second to avoid subsequent fallbacks of other types There are 3
2304 * MIGRATE_TYPES we care about.
2305 */
2306 recommended_min += pageblock_nr_pages * nr_zones *
2307 MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
2308
2309 /* don't ever allow to reserve more than 5% of the lowmem */
2310 recommended_min = min(recommended_min,
2311 (unsigned long) nr_free_buffer_pages() / 20);
2312 recommended_min <<= (PAGE_SHIFT-10);
2313
2314 if (recommended_min > min_free_kbytes) {
2315 if (user_min_free_kbytes >= 0)
2316 pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
2317 min_free_kbytes, recommended_min);
2318
2319 min_free_kbytes = recommended_min;
2320 }
2321 setup_per_zone_wmarks();
2322 }
2323
start_stop_khugepaged(void)2324 int start_stop_khugepaged(void)
2325 {
2326 int err = 0;
2327
2328 mutex_lock(&khugepaged_mutex);
2329 if (khugepaged_enabled()) {
2330 if (!khugepaged_thread)
2331 khugepaged_thread = kthread_run(khugepaged, NULL,
2332 "khugepaged");
2333 if (IS_ERR(khugepaged_thread)) {
2334 pr_err("khugepaged: kthread_run(khugepaged) failed\n");
2335 err = PTR_ERR(khugepaged_thread);
2336 khugepaged_thread = NULL;
2337 goto fail;
2338 }
2339
2340 if (!list_empty(&khugepaged_scan.mm_head))
2341 wake_up_interruptible(&khugepaged_wait);
2342
2343 set_recommended_min_free_kbytes();
2344 } else if (khugepaged_thread) {
2345 kthread_stop(khugepaged_thread);
2346 khugepaged_thread = NULL;
2347 }
2348 fail:
2349 mutex_unlock(&khugepaged_mutex);
2350 return err;
2351 }
2352
khugepaged_min_free_kbytes_update(void)2353 void khugepaged_min_free_kbytes_update(void)
2354 {
2355 mutex_lock(&khugepaged_mutex);
2356 if (khugepaged_enabled() && khugepaged_thread)
2357 set_recommended_min_free_kbytes();
2358 mutex_unlock(&khugepaged_mutex);
2359 }
2360