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_PTE_NON_PRESENT, |
32 | SCAN_PAGE_RO, |
33 | SCAN_LACK_REFERENCED_PAGE, |
34 | SCAN_PAGE_NULL, |
35 | SCAN_SCAN_ABORT, |
36 | SCAN_PAGE_COUNT, |
37 | SCAN_PAGE_LRU, |
38 | SCAN_PAGE_LOCK, |
39 | SCAN_PAGE_ANON, |
40 | SCAN_PAGE_COMPOUND, |
41 | SCAN_ANY_PROCESS, |
42 | SCAN_VMA_NULL, |
43 | SCAN_VMA_CHECK, |
44 | SCAN_ADDRESS_RANGE, |
45 | SCAN_SWAP_CACHE_PAGE, |
46 | SCAN_DEL_PAGE_LRU, |
47 | SCAN_ALLOC_HUGE_PAGE_FAIL, |
48 | SCAN_CGROUP_CHARGE_FAIL, |
49 | SCAN_EXCEED_SWAP_PTE, |
50 | SCAN_TRUNCATED, |
51 | }; |
52 | |
53 | #define CREATE_TRACE_POINTS |
54 | #include <trace/events/huge_memory.h> |
55 | |
56 | /* default scan 8*512 pte (or vmas) every 30 second */ |
57 | static unsigned int khugepaged_pages_to_scan __read_mostly; |
58 | static unsigned int khugepaged_pages_collapsed; |
59 | static unsigned int khugepaged_full_scans; |
60 | static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; |
61 | /* during fragmentation poll the hugepage allocator once every minute */ |
62 | static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; |
63 | static unsigned long khugepaged_sleep_expire; |
64 | static DEFINE_SPINLOCK(khugepaged_mm_lock); |
65 | static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); |
66 | /* |
67 | * default collapse hugepages if there is at least one pte mapped like |
68 | * it would have happened if the vma was large enough during page |
69 | * fault. |
70 | */ |
71 | static unsigned int khugepaged_max_ptes_none __read_mostly; |
72 | static unsigned int khugepaged_max_ptes_swap __read_mostly; |
73 | |
74 | #define MM_SLOTS_HASH_BITS 10 |
75 | static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); |
76 | |
77 | static struct kmem_cache *mm_slot_cache __read_mostly; |
78 | |
79 | /** |
80 | * struct mm_slot - hash lookup from mm to mm_slot |
81 | * @hash: hash collision list |
82 | * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head |
83 | * @mm: the mm that this information is valid for |
84 | */ |
85 | struct mm_slot { |
86 | struct hlist_node hash; |
87 | struct list_head mm_node; |
88 | struct mm_struct *mm; |
89 | }; |
90 | |
91 | /** |
92 | * struct khugepaged_scan - cursor for scanning |
93 | * @mm_head: the head of the mm list to scan |
94 | * @mm_slot: the current mm_slot we are scanning |
95 | * @address: the next address inside that to be scanned |
96 | * |
97 | * There is only the one khugepaged_scan instance of this cursor structure. |
98 | */ |
99 | struct khugepaged_scan { |
100 | struct list_head mm_head; |
101 | struct mm_slot *mm_slot; |
102 | unsigned long address; |
103 | }; |
104 | |
105 | static struct khugepaged_scan khugepaged_scan = { |
106 | .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), |
107 | }; |
108 | |
109 | #ifdef CONFIG_SYSFS |
110 | static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, |
111 | struct kobj_attribute *attr, |
112 | char *buf) |
113 | { |
114 | return sprintf(buf, "%u\n" , khugepaged_scan_sleep_millisecs); |
115 | } |
116 | |
117 | static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, |
118 | struct kobj_attribute *attr, |
119 | const char *buf, size_t count) |
120 | { |
121 | unsigned long msecs; |
122 | int err; |
123 | |
124 | err = kstrtoul(buf, 10, &msecs); |
125 | if (err || msecs > UINT_MAX) |
126 | return -EINVAL; |
127 | |
128 | khugepaged_scan_sleep_millisecs = msecs; |
129 | khugepaged_sleep_expire = 0; |
130 | wake_up_interruptible(&khugepaged_wait); |
131 | |
132 | return count; |
133 | } |
134 | static struct kobj_attribute scan_sleep_millisecs_attr = |
135 | __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, |
136 | scan_sleep_millisecs_store); |
137 | |
138 | static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, |
139 | struct kobj_attribute *attr, |
140 | char *buf) |
141 | { |
142 | return sprintf(buf, "%u\n" , khugepaged_alloc_sleep_millisecs); |
143 | } |
144 | |
145 | static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, |
146 | struct kobj_attribute *attr, |
147 | const char *buf, size_t count) |
148 | { |
149 | unsigned long msecs; |
150 | int err; |
151 | |
152 | err = kstrtoul(buf, 10, &msecs); |
153 | if (err || msecs > UINT_MAX) |
154 | return -EINVAL; |
155 | |
156 | khugepaged_alloc_sleep_millisecs = msecs; |
157 | khugepaged_sleep_expire = 0; |
158 | wake_up_interruptible(&khugepaged_wait); |
159 | |
160 | return count; |
161 | } |
162 | static struct kobj_attribute alloc_sleep_millisecs_attr = |
163 | __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, |
164 | alloc_sleep_millisecs_store); |
165 | |
166 | static ssize_t pages_to_scan_show(struct kobject *kobj, |
167 | struct kobj_attribute *attr, |
168 | char *buf) |
169 | { |
170 | return sprintf(buf, "%u\n" , khugepaged_pages_to_scan); |
171 | } |
172 | static ssize_t pages_to_scan_store(struct kobject *kobj, |
173 | struct kobj_attribute *attr, |
174 | const char *buf, size_t count) |
175 | { |
176 | int err; |
177 | unsigned long pages; |
178 | |
179 | err = kstrtoul(buf, 10, &pages); |
180 | if (err || !pages || pages > UINT_MAX) |
181 | return -EINVAL; |
182 | |
183 | khugepaged_pages_to_scan = pages; |
184 | |
185 | return count; |
186 | } |
187 | static struct kobj_attribute pages_to_scan_attr = |
188 | __ATTR(pages_to_scan, 0644, pages_to_scan_show, |
189 | pages_to_scan_store); |
190 | |
191 | static ssize_t pages_collapsed_show(struct kobject *kobj, |
192 | struct kobj_attribute *attr, |
193 | char *buf) |
194 | { |
195 | return sprintf(buf, "%u\n" , khugepaged_pages_collapsed); |
196 | } |
197 | static struct kobj_attribute pages_collapsed_attr = |
198 | __ATTR_RO(pages_collapsed); |
199 | |
200 | static ssize_t full_scans_show(struct kobject *kobj, |
201 | struct kobj_attribute *attr, |
202 | char *buf) |
203 | { |
204 | return sprintf(buf, "%u\n" , khugepaged_full_scans); |
205 | } |
206 | static struct kobj_attribute full_scans_attr = |
207 | __ATTR_RO(full_scans); |
208 | |
209 | static ssize_t khugepaged_defrag_show(struct kobject *kobj, |
210 | struct kobj_attribute *attr, char *buf) |
211 | { |
212 | return single_hugepage_flag_show(kobj, attr, buf, |
213 | TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); |
214 | } |
215 | static ssize_t khugepaged_defrag_store(struct kobject *kobj, |
216 | struct kobj_attribute *attr, |
217 | const char *buf, size_t count) |
218 | { |
219 | return single_hugepage_flag_store(kobj, attr, buf, count, |
220 | TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); |
221 | } |
222 | static struct kobj_attribute khugepaged_defrag_attr = |
223 | __ATTR(defrag, 0644, khugepaged_defrag_show, |
224 | khugepaged_defrag_store); |
225 | |
226 | /* |
227 | * max_ptes_none controls if khugepaged should collapse hugepages over |
228 | * any unmapped ptes in turn potentially increasing the memory |
229 | * footprint of the vmas. When max_ptes_none is 0 khugepaged will not |
230 | * reduce the available free memory in the system as it |
231 | * runs. Increasing max_ptes_none will instead potentially reduce the |
232 | * free memory in the system during the khugepaged scan. |
233 | */ |
234 | static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, |
235 | struct kobj_attribute *attr, |
236 | char *buf) |
237 | { |
238 | return sprintf(buf, "%u\n" , khugepaged_max_ptes_none); |
239 | } |
240 | static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, |
241 | struct kobj_attribute *attr, |
242 | const char *buf, size_t count) |
243 | { |
244 | int err; |
245 | unsigned long max_ptes_none; |
246 | |
247 | err = kstrtoul(buf, 10, &max_ptes_none); |
248 | if (err || max_ptes_none > HPAGE_PMD_NR-1) |
249 | return -EINVAL; |
250 | |
251 | khugepaged_max_ptes_none = max_ptes_none; |
252 | |
253 | return count; |
254 | } |
255 | static struct kobj_attribute khugepaged_max_ptes_none_attr = |
256 | __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, |
257 | khugepaged_max_ptes_none_store); |
258 | |
259 | static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj, |
260 | struct kobj_attribute *attr, |
261 | char *buf) |
262 | { |
263 | return sprintf(buf, "%u\n" , khugepaged_max_ptes_swap); |
264 | } |
265 | |
266 | static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj, |
267 | struct kobj_attribute *attr, |
268 | const char *buf, size_t count) |
269 | { |
270 | int err; |
271 | unsigned long max_ptes_swap; |
272 | |
273 | err = kstrtoul(buf, 10, &max_ptes_swap); |
274 | if (err || max_ptes_swap > HPAGE_PMD_NR-1) |
275 | return -EINVAL; |
276 | |
277 | khugepaged_max_ptes_swap = max_ptes_swap; |
278 | |
279 | return count; |
280 | } |
281 | |
282 | static struct kobj_attribute khugepaged_max_ptes_swap_attr = |
283 | __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show, |
284 | khugepaged_max_ptes_swap_store); |
285 | |
286 | static struct attribute *khugepaged_attr[] = { |
287 | &khugepaged_defrag_attr.attr, |
288 | &khugepaged_max_ptes_none_attr.attr, |
289 | &pages_to_scan_attr.attr, |
290 | &pages_collapsed_attr.attr, |
291 | &full_scans_attr.attr, |
292 | &scan_sleep_millisecs_attr.attr, |
293 | &alloc_sleep_millisecs_attr.attr, |
294 | &khugepaged_max_ptes_swap_attr.attr, |
295 | NULL, |
296 | }; |
297 | |
298 | struct attribute_group khugepaged_attr_group = { |
299 | .attrs = khugepaged_attr, |
300 | .name = "khugepaged" , |
301 | }; |
302 | #endif /* CONFIG_SYSFS */ |
303 | |
304 | #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB) |
305 | |
306 | int hugepage_madvise(struct vm_area_struct *vma, |
307 | unsigned long *vm_flags, int advice) |
308 | { |
309 | switch (advice) { |
310 | case MADV_HUGEPAGE: |
311 | #ifdef CONFIG_S390 |
312 | /* |
313 | * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 |
314 | * can't handle this properly after s390_enable_sie, so we simply |
315 | * ignore the madvise to prevent qemu from causing a SIGSEGV. |
316 | */ |
317 | if (mm_has_pgste(vma->vm_mm)) |
318 | return 0; |
319 | #endif |
320 | *vm_flags &= ~VM_NOHUGEPAGE; |
321 | *vm_flags |= VM_HUGEPAGE; |
322 | /* |
323 | * If the vma become good for khugepaged to scan, |
324 | * register it here without waiting a page fault that |
325 | * may not happen any time soon. |
326 | */ |
327 | if (!(*vm_flags & VM_NO_KHUGEPAGED) && |
328 | khugepaged_enter_vma_merge(vma, *vm_flags)) |
329 | return -ENOMEM; |
330 | break; |
331 | case MADV_NOHUGEPAGE: |
332 | *vm_flags &= ~VM_HUGEPAGE; |
333 | *vm_flags |= VM_NOHUGEPAGE; |
334 | /* |
335 | * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning |
336 | * this vma even if we leave the mm registered in khugepaged if |
337 | * it got registered before VM_NOHUGEPAGE was set. |
338 | */ |
339 | break; |
340 | } |
341 | |
342 | return 0; |
343 | } |
344 | |
345 | int __init khugepaged_init(void) |
346 | { |
347 | mm_slot_cache = kmem_cache_create("khugepaged_mm_slot" , |
348 | sizeof(struct mm_slot), |
349 | __alignof__(struct mm_slot), 0, NULL); |
350 | if (!mm_slot_cache) |
351 | return -ENOMEM; |
352 | |
353 | khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; |
354 | khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; |
355 | khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; |
356 | |
357 | return 0; |
358 | } |
359 | |
360 | void __init khugepaged_destroy(void) |
361 | { |
362 | kmem_cache_destroy(mm_slot_cache); |
363 | } |
364 | |
365 | static inline struct mm_slot *alloc_mm_slot(void) |
366 | { |
367 | if (!mm_slot_cache) /* initialization failed */ |
368 | return NULL; |
369 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); |
370 | } |
371 | |
372 | static inline void free_mm_slot(struct mm_slot *mm_slot) |
373 | { |
374 | kmem_cache_free(mm_slot_cache, mm_slot); |
375 | } |
376 | |
377 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) |
378 | { |
379 | struct mm_slot *mm_slot; |
380 | |
381 | hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) |
382 | if (mm == mm_slot->mm) |
383 | return mm_slot; |
384 | |
385 | return NULL; |
386 | } |
387 | |
388 | static void insert_to_mm_slots_hash(struct mm_struct *mm, |
389 | struct mm_slot *mm_slot) |
390 | { |
391 | mm_slot->mm = mm; |
392 | hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); |
393 | } |
394 | |
395 | static inline int khugepaged_test_exit(struct mm_struct *mm) |
396 | { |
397 | return atomic_read(&mm->mm_users) == 0; |
398 | } |
399 | |
400 | static bool hugepage_vma_check(struct vm_area_struct *vma, |
401 | unsigned long vm_flags) |
402 | { |
403 | if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || |
404 | (vm_flags & VM_NOHUGEPAGE) || |
405 | test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) |
406 | return false; |
407 | if (shmem_file(vma->vm_file)) { |
408 | if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) |
409 | return false; |
410 | return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, |
411 | HPAGE_PMD_NR); |
412 | } |
413 | if (!vma->anon_vma || vma->vm_ops) |
414 | return false; |
415 | if (is_vma_temporary_stack(vma)) |
416 | return false; |
417 | return !(vm_flags & VM_NO_KHUGEPAGED); |
418 | } |
419 | |
420 | int __khugepaged_enter(struct mm_struct *mm) |
421 | { |
422 | struct mm_slot *mm_slot; |
423 | int wakeup; |
424 | |
425 | mm_slot = alloc_mm_slot(); |
426 | if (!mm_slot) |
427 | return -ENOMEM; |
428 | |
429 | /* __khugepaged_exit() must not run from under us */ |
430 | VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); |
431 | if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { |
432 | free_mm_slot(mm_slot); |
433 | return 0; |
434 | } |
435 | |
436 | spin_lock(&khugepaged_mm_lock); |
437 | insert_to_mm_slots_hash(mm, mm_slot); |
438 | /* |
439 | * Insert just behind the scanning cursor, to let the area settle |
440 | * down a little. |
441 | */ |
442 | wakeup = list_empty(&khugepaged_scan.mm_head); |
443 | list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); |
444 | spin_unlock(&khugepaged_mm_lock); |
445 | |
446 | mmgrab(mm); |
447 | if (wakeup) |
448 | wake_up_interruptible(&khugepaged_wait); |
449 | |
450 | return 0; |
451 | } |
452 | |
453 | int khugepaged_enter_vma_merge(struct vm_area_struct *vma, |
454 | unsigned long vm_flags) |
455 | { |
456 | unsigned long hstart, hend; |
457 | |
458 | /* |
459 | * khugepaged does not yet work on non-shmem files or special |
460 | * mappings. And file-private shmem THP is not supported. |
461 | */ |
462 | if (!hugepage_vma_check(vma, vm_flags)) |
463 | return 0; |
464 | |
465 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; |
466 | hend = vma->vm_end & HPAGE_PMD_MASK; |
467 | if (hstart < hend) |
468 | return khugepaged_enter(vma, vm_flags); |
469 | return 0; |
470 | } |
471 | |
472 | void __khugepaged_exit(struct mm_struct *mm) |
473 | { |
474 | struct mm_slot *mm_slot; |
475 | int free = 0; |
476 | |
477 | spin_lock(&khugepaged_mm_lock); |
478 | mm_slot = get_mm_slot(mm); |
479 | if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { |
480 | hash_del(&mm_slot->hash); |
481 | list_del(&mm_slot->mm_node); |
482 | free = 1; |
483 | } |
484 | spin_unlock(&khugepaged_mm_lock); |
485 | |
486 | if (free) { |
487 | clear_bit(MMF_VM_HUGEPAGE, &mm->flags); |
488 | free_mm_slot(mm_slot); |
489 | mmdrop(mm); |
490 | } else if (mm_slot) { |
491 | /* |
492 | * This is required to serialize against |
493 | * khugepaged_test_exit() (which is guaranteed to run |
494 | * under mmap sem read mode). Stop here (after we |
495 | * return all pagetables will be destroyed) until |
496 | * khugepaged has finished working on the pagetables |
497 | * under the mmap_sem. |
498 | */ |
499 | down_write(&mm->mmap_sem); |
500 | up_write(&mm->mmap_sem); |
501 | } |
502 | } |
503 | |
504 | static void release_pte_page(struct page *page) |
505 | { |
506 | dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); |
507 | unlock_page(page); |
508 | putback_lru_page(page); |
509 | } |
510 | |
511 | static void release_pte_pages(pte_t *pte, pte_t *_pte) |
512 | { |
513 | while (--_pte >= pte) { |
514 | pte_t pteval = *_pte; |
515 | if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) |
516 | release_pte_page(pte_page(pteval)); |
517 | } |
518 | } |
519 | |
520 | static int __collapse_huge_page_isolate(struct vm_area_struct *vma, |
521 | unsigned long address, |
522 | pte_t *pte) |
523 | { |
524 | struct page *page = NULL; |
525 | pte_t *_pte; |
526 | int none_or_zero = 0, result = 0, referenced = 0; |
527 | bool writable = false; |
528 | |
529 | for (_pte = pte; _pte < pte+HPAGE_PMD_NR; |
530 | _pte++, address += PAGE_SIZE) { |
531 | pte_t pteval = *_pte; |
532 | if (pte_none(pteval) || (pte_present(pteval) && |
533 | is_zero_pfn(pte_pfn(pteval)))) { |
534 | if (!userfaultfd_armed(vma) && |
535 | ++none_or_zero <= khugepaged_max_ptes_none) { |
536 | continue; |
537 | } else { |
538 | result = SCAN_EXCEED_NONE_PTE; |
539 | goto out; |
540 | } |
541 | } |
542 | if (!pte_present(pteval)) { |
543 | result = SCAN_PTE_NON_PRESENT; |
544 | goto out; |
545 | } |
546 | page = vm_normal_page(vma, address, pteval); |
547 | if (unlikely(!page)) { |
548 | result = SCAN_PAGE_NULL; |
549 | goto out; |
550 | } |
551 | |
552 | /* TODO: teach khugepaged to collapse THP mapped with pte */ |
553 | if (PageCompound(page)) { |
554 | result = SCAN_PAGE_COMPOUND; |
555 | goto out; |
556 | } |
557 | |
558 | VM_BUG_ON_PAGE(!PageAnon(page), page); |
559 | |
560 | /* |
561 | * We can do it before isolate_lru_page because the |
562 | * page can't be freed from under us. NOTE: PG_lock |
563 | * is needed to serialize against split_huge_page |
564 | * when invoked from the VM. |
565 | */ |
566 | if (!trylock_page(page)) { |
567 | result = SCAN_PAGE_LOCK; |
568 | goto out; |
569 | } |
570 | |
571 | /* |
572 | * cannot use mapcount: can't collapse if there's a gup pin. |
573 | * The page must only be referenced by the scanned process |
574 | * and page swap cache. |
575 | */ |
576 | if (page_count(page) != 1 + PageSwapCache(page)) { |
577 | unlock_page(page); |
578 | result = SCAN_PAGE_COUNT; |
579 | goto out; |
580 | } |
581 | if (pte_write(pteval)) { |
582 | writable = true; |
583 | } else { |
584 | if (PageSwapCache(page) && |
585 | !reuse_swap_page(page, NULL)) { |
586 | unlock_page(page); |
587 | result = SCAN_SWAP_CACHE_PAGE; |
588 | goto out; |
589 | } |
590 | /* |
591 | * Page is not in the swap cache. It can be collapsed |
592 | * into a THP. |
593 | */ |
594 | } |
595 | |
596 | /* |
597 | * Isolate the page to avoid collapsing an hugepage |
598 | * currently in use by the VM. |
599 | */ |
600 | if (isolate_lru_page(page)) { |
601 | unlock_page(page); |
602 | result = SCAN_DEL_PAGE_LRU; |
603 | goto out; |
604 | } |
605 | inc_node_page_state(page, |
606 | NR_ISOLATED_ANON + page_is_file_cache(page)); |
607 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
608 | VM_BUG_ON_PAGE(PageLRU(page), page); |
609 | |
610 | /* There should be enough young pte to collapse the page */ |
611 | if (pte_young(pteval) || |
612 | page_is_young(page) || PageReferenced(page) || |
613 | mmu_notifier_test_young(vma->vm_mm, address)) |
614 | referenced++; |
615 | } |
616 | if (likely(writable)) { |
617 | if (likely(referenced)) { |
618 | result = SCAN_SUCCEED; |
619 | trace_mm_collapse_huge_page_isolate(page, none_or_zero, |
620 | referenced, writable, result); |
621 | return 1; |
622 | } |
623 | } else { |
624 | result = SCAN_PAGE_RO; |
625 | } |
626 | |
627 | out: |
628 | release_pte_pages(pte, _pte); |
629 | trace_mm_collapse_huge_page_isolate(page, none_or_zero, |
630 | referenced, writable, result); |
631 | return 0; |
632 | } |
633 | |
634 | static void __collapse_huge_page_copy(pte_t *pte, struct page *page, |
635 | struct vm_area_struct *vma, |
636 | unsigned long address, |
637 | spinlock_t *ptl) |
638 | { |
639 | pte_t *_pte; |
640 | for (_pte = pte; _pte < pte + HPAGE_PMD_NR; |
641 | _pte++, page++, address += PAGE_SIZE) { |
642 | pte_t pteval = *_pte; |
643 | struct page *src_page; |
644 | |
645 | if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { |
646 | clear_user_highpage(page, address); |
647 | add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); |
648 | if (is_zero_pfn(pte_pfn(pteval))) { |
649 | /* |
650 | * ptl mostly unnecessary. |
651 | */ |
652 | spin_lock(ptl); |
653 | /* |
654 | * paravirt calls inside pte_clear here are |
655 | * superfluous. |
656 | */ |
657 | pte_clear(vma->vm_mm, address, _pte); |
658 | spin_unlock(ptl); |
659 | } |
660 | } else { |
661 | src_page = pte_page(pteval); |
662 | copy_user_highpage(page, src_page, address, vma); |
663 | VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); |
664 | release_pte_page(src_page); |
665 | /* |
666 | * ptl mostly unnecessary, but preempt has to |
667 | * be disabled to update the per-cpu stats |
668 | * inside page_remove_rmap(). |
669 | */ |
670 | spin_lock(ptl); |
671 | /* |
672 | * paravirt calls inside pte_clear here are |
673 | * superfluous. |
674 | */ |
675 | pte_clear(vma->vm_mm, address, _pte); |
676 | page_remove_rmap(src_page, false); |
677 | spin_unlock(ptl); |
678 | free_page_and_swap_cache(src_page); |
679 | } |
680 | } |
681 | } |
682 | |
683 | static void khugepaged_alloc_sleep(void) |
684 | { |
685 | DEFINE_WAIT(wait); |
686 | |
687 | add_wait_queue(&khugepaged_wait, &wait); |
688 | freezable_schedule_timeout_interruptible( |
689 | msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); |
690 | remove_wait_queue(&khugepaged_wait, &wait); |
691 | } |
692 | |
693 | static int khugepaged_node_load[MAX_NUMNODES]; |
694 | |
695 | static bool khugepaged_scan_abort(int nid) |
696 | { |
697 | int i; |
698 | |
699 | /* |
700 | * If node_reclaim_mode is disabled, then no extra effort is made to |
701 | * allocate memory locally. |
702 | */ |
703 | if (!node_reclaim_mode) |
704 | return false; |
705 | |
706 | /* If there is a count for this node already, it must be acceptable */ |
707 | if (khugepaged_node_load[nid]) |
708 | return false; |
709 | |
710 | for (i = 0; i < MAX_NUMNODES; i++) { |
711 | if (!khugepaged_node_load[i]) |
712 | continue; |
713 | if (node_distance(nid, i) > RECLAIM_DISTANCE) |
714 | return true; |
715 | } |
716 | return false; |
717 | } |
718 | |
719 | /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ |
720 | static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) |
721 | { |
722 | return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT; |
723 | } |
724 | |
725 | #ifdef CONFIG_NUMA |
726 | static int khugepaged_find_target_node(void) |
727 | { |
728 | static int last_khugepaged_target_node = NUMA_NO_NODE; |
729 | int nid, target_node = 0, max_value = 0; |
730 | |
731 | /* find first node with max normal pages hit */ |
732 | for (nid = 0; nid < MAX_NUMNODES; nid++) |
733 | if (khugepaged_node_load[nid] > max_value) { |
734 | max_value = khugepaged_node_load[nid]; |
735 | target_node = nid; |
736 | } |
737 | |
738 | /* do some balance if several nodes have the same hit record */ |
739 | if (target_node <= last_khugepaged_target_node) |
740 | for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; |
741 | nid++) |
742 | if (max_value == khugepaged_node_load[nid]) { |
743 | target_node = nid; |
744 | break; |
745 | } |
746 | |
747 | last_khugepaged_target_node = target_node; |
748 | return target_node; |
749 | } |
750 | |
751 | static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) |
752 | { |
753 | if (IS_ERR(*hpage)) { |
754 | if (!*wait) |
755 | return false; |
756 | |
757 | *wait = false; |
758 | *hpage = NULL; |
759 | khugepaged_alloc_sleep(); |
760 | } else if (*hpage) { |
761 | put_page(*hpage); |
762 | *hpage = NULL; |
763 | } |
764 | |
765 | return true; |
766 | } |
767 | |
768 | static struct page * |
769 | khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) |
770 | { |
771 | VM_BUG_ON_PAGE(*hpage, *hpage); |
772 | |
773 | *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); |
774 | if (unlikely(!*hpage)) { |
775 | count_vm_event(THP_COLLAPSE_ALLOC_FAILED); |
776 | *hpage = ERR_PTR(-ENOMEM); |
777 | return NULL; |
778 | } |
779 | |
780 | prep_transhuge_page(*hpage); |
781 | count_vm_event(THP_COLLAPSE_ALLOC); |
782 | return *hpage; |
783 | } |
784 | #else |
785 | static int khugepaged_find_target_node(void) |
786 | { |
787 | return 0; |
788 | } |
789 | |
790 | static inline struct page *alloc_khugepaged_hugepage(void) |
791 | { |
792 | struct page *page; |
793 | |
794 | page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), |
795 | HPAGE_PMD_ORDER); |
796 | if (page) |
797 | prep_transhuge_page(page); |
798 | return page; |
799 | } |
800 | |
801 | static struct page *khugepaged_alloc_hugepage(bool *wait) |
802 | { |
803 | struct page *hpage; |
804 | |
805 | do { |
806 | hpage = alloc_khugepaged_hugepage(); |
807 | if (!hpage) { |
808 | count_vm_event(THP_COLLAPSE_ALLOC_FAILED); |
809 | if (!*wait) |
810 | return NULL; |
811 | |
812 | *wait = false; |
813 | khugepaged_alloc_sleep(); |
814 | } else |
815 | count_vm_event(THP_COLLAPSE_ALLOC); |
816 | } while (unlikely(!hpage) && likely(khugepaged_enabled())); |
817 | |
818 | return hpage; |
819 | } |
820 | |
821 | static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) |
822 | { |
823 | if (!*hpage) |
824 | *hpage = khugepaged_alloc_hugepage(wait); |
825 | |
826 | if (unlikely(!*hpage)) |
827 | return false; |
828 | |
829 | return true; |
830 | } |
831 | |
832 | static struct page * |
833 | khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) |
834 | { |
835 | VM_BUG_ON(!*hpage); |
836 | |
837 | return *hpage; |
838 | } |
839 | #endif |
840 | |
841 | /* |
842 | * If mmap_sem temporarily dropped, revalidate vma |
843 | * before taking mmap_sem. |
844 | * Return 0 if succeeds, otherwise return none-zero |
845 | * value (scan code). |
846 | */ |
847 | |
848 | static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, |
849 | struct vm_area_struct **vmap) |
850 | { |
851 | struct vm_area_struct *vma; |
852 | unsigned long hstart, hend; |
853 | |
854 | if (unlikely(khugepaged_test_exit(mm))) |
855 | return SCAN_ANY_PROCESS; |
856 | |
857 | *vmap = vma = find_vma(mm, address); |
858 | if (!vma) |
859 | return SCAN_VMA_NULL; |
860 | |
861 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; |
862 | hend = vma->vm_end & HPAGE_PMD_MASK; |
863 | if (address < hstart || address + HPAGE_PMD_SIZE > hend) |
864 | return SCAN_ADDRESS_RANGE; |
865 | if (!hugepage_vma_check(vma, vma->vm_flags)) |
866 | return SCAN_VMA_CHECK; |
867 | return 0; |
868 | } |
869 | |
870 | /* |
871 | * Bring missing pages in from swap, to complete THP collapse. |
872 | * Only done if khugepaged_scan_pmd believes it is worthwhile. |
873 | * |
874 | * Called and returns without pte mapped or spinlocks held, |
875 | * but with mmap_sem held to protect against vma changes. |
876 | */ |
877 | |
878 | static bool __collapse_huge_page_swapin(struct mm_struct *mm, |
879 | struct vm_area_struct *vma, |
880 | unsigned long address, pmd_t *pmd, |
881 | int referenced) |
882 | { |
883 | int swapped_in = 0; |
884 | vm_fault_t ret = 0; |
885 | struct vm_fault vmf = { |
886 | .vma = vma, |
887 | .address = address, |
888 | .flags = FAULT_FLAG_ALLOW_RETRY, |
889 | .pmd = pmd, |
890 | .pgoff = linear_page_index(vma, address), |
891 | }; |
892 | |
893 | /* we only decide to swapin, if there is enough young ptes */ |
894 | if (referenced < HPAGE_PMD_NR/2) { |
895 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
896 | return false; |
897 | } |
898 | vmf.pte = pte_offset_map(pmd, address); |
899 | for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; |
900 | vmf.pte++, vmf.address += PAGE_SIZE) { |
901 | vmf.orig_pte = *vmf.pte; |
902 | if (!is_swap_pte(vmf.orig_pte)) |
903 | continue; |
904 | swapped_in++; |
905 | ret = do_swap_page(&vmf); |
906 | |
907 | /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */ |
908 | if (ret & VM_FAULT_RETRY) { |
909 | down_read(&mm->mmap_sem); |
910 | if (hugepage_vma_revalidate(mm, address, &vmf.vma)) { |
911 | /* vma is no longer available, don't continue to swapin */ |
912 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
913 | return false; |
914 | } |
915 | /* check if the pmd is still valid */ |
916 | if (mm_find_pmd(mm, address) != pmd) { |
917 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
918 | return false; |
919 | } |
920 | } |
921 | if (ret & VM_FAULT_ERROR) { |
922 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
923 | return false; |
924 | } |
925 | /* pte is unmapped now, we need to map it */ |
926 | vmf.pte = pte_offset_map(pmd, vmf.address); |
927 | } |
928 | vmf.pte--; |
929 | pte_unmap(vmf.pte); |
930 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); |
931 | return true; |
932 | } |
933 | |
934 | static void collapse_huge_page(struct mm_struct *mm, |
935 | unsigned long address, |
936 | struct page **hpage, |
937 | int node, int referenced) |
938 | { |
939 | pmd_t *pmd, _pmd; |
940 | pte_t *pte; |
941 | pgtable_t pgtable; |
942 | struct page *new_page; |
943 | spinlock_t *pmd_ptl, *pte_ptl; |
944 | int isolated = 0, result = 0; |
945 | struct mem_cgroup *memcg; |
946 | struct vm_area_struct *vma; |
947 | struct mmu_notifier_range range; |
948 | gfp_t gfp; |
949 | |
950 | VM_BUG_ON(address & ~HPAGE_PMD_MASK); |
951 | |
952 | /* Only allocate from the target node */ |
953 | gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; |
954 | |
955 | /* |
956 | * Before allocating the hugepage, release the mmap_sem read lock. |
957 | * The allocation can take potentially a long time if it involves |
958 | * sync compaction, and we do not need to hold the mmap_sem during |
959 | * that. We will recheck the vma after taking it again in write mode. |
960 | */ |
961 | up_read(&mm->mmap_sem); |
962 | new_page = khugepaged_alloc_page(hpage, gfp, node); |
963 | if (!new_page) { |
964 | result = SCAN_ALLOC_HUGE_PAGE_FAIL; |
965 | goto out_nolock; |
966 | } |
967 | |
968 | if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { |
969 | result = SCAN_CGROUP_CHARGE_FAIL; |
970 | goto out_nolock; |
971 | } |
972 | |
973 | down_read(&mm->mmap_sem); |
974 | result = hugepage_vma_revalidate(mm, address, &vma); |
975 | if (result) { |
976 | mem_cgroup_cancel_charge(new_page, memcg, true); |
977 | up_read(&mm->mmap_sem); |
978 | goto out_nolock; |
979 | } |
980 | |
981 | pmd = mm_find_pmd(mm, address); |
982 | if (!pmd) { |
983 | result = SCAN_PMD_NULL; |
984 | mem_cgroup_cancel_charge(new_page, memcg, true); |
985 | up_read(&mm->mmap_sem); |
986 | goto out_nolock; |
987 | } |
988 | |
989 | /* |
990 | * __collapse_huge_page_swapin always returns with mmap_sem locked. |
991 | * If it fails, we release mmap_sem and jump out_nolock. |
992 | * Continuing to collapse causes inconsistency. |
993 | */ |
994 | if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) { |
995 | mem_cgroup_cancel_charge(new_page, memcg, true); |
996 | up_read(&mm->mmap_sem); |
997 | goto out_nolock; |
998 | } |
999 | |
1000 | up_read(&mm->mmap_sem); |
1001 | /* |
1002 | * Prevent all access to pagetables with the exception of |
1003 | * gup_fast later handled by the ptep_clear_flush and the VM |
1004 | * handled by the anon_vma lock + PG_lock. |
1005 | */ |
1006 | down_write(&mm->mmap_sem); |
1007 | result = hugepage_vma_revalidate(mm, address, &vma); |
1008 | if (result) |
1009 | goto out; |
1010 | /* check if the pmd is still valid */ |
1011 | if (mm_find_pmd(mm, address) != pmd) |
1012 | goto out; |
1013 | |
1014 | anon_vma_lock_write(vma->anon_vma); |
1015 | |
1016 | pte = pte_offset_map(pmd, address); |
1017 | pte_ptl = pte_lockptr(mm, pmd); |
1018 | |
1019 | mmu_notifier_range_init(&range, mm, address, address + HPAGE_PMD_SIZE); |
1020 | mmu_notifier_invalidate_range_start(&range); |
1021 | pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ |
1022 | /* |
1023 | * After this gup_fast can't run anymore. This also removes |
1024 | * any huge TLB entry from the CPU so we won't allow |
1025 | * huge and small TLB entries for the same virtual address |
1026 | * to avoid the risk of CPU bugs in that area. |
1027 | */ |
1028 | _pmd = pmdp_collapse_flush(vma, address, pmd); |
1029 | spin_unlock(pmd_ptl); |
1030 | mmu_notifier_invalidate_range_end(&range); |
1031 | |
1032 | spin_lock(pte_ptl); |
1033 | isolated = __collapse_huge_page_isolate(vma, address, pte); |
1034 | spin_unlock(pte_ptl); |
1035 | |
1036 | if (unlikely(!isolated)) { |
1037 | pte_unmap(pte); |
1038 | spin_lock(pmd_ptl); |
1039 | BUG_ON(!pmd_none(*pmd)); |
1040 | /* |
1041 | * We can only use set_pmd_at when establishing |
1042 | * hugepmds and never for establishing regular pmds that |
1043 | * points to regular pagetables. Use pmd_populate for that |
1044 | */ |
1045 | pmd_populate(mm, pmd, pmd_pgtable(_pmd)); |
1046 | spin_unlock(pmd_ptl); |
1047 | anon_vma_unlock_write(vma->anon_vma); |
1048 | result = SCAN_FAIL; |
1049 | goto out; |
1050 | } |
1051 | |
1052 | /* |
1053 | * All pages are isolated and locked so anon_vma rmap |
1054 | * can't run anymore. |
1055 | */ |
1056 | anon_vma_unlock_write(vma->anon_vma); |
1057 | |
1058 | __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); |
1059 | pte_unmap(pte); |
1060 | __SetPageUptodate(new_page); |
1061 | pgtable = pmd_pgtable(_pmd); |
1062 | |
1063 | _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); |
1064 | _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); |
1065 | |
1066 | /* |
1067 | * spin_lock() below is not the equivalent of smp_wmb(), so |
1068 | * this is needed to avoid the copy_huge_page writes to become |
1069 | * visible after the set_pmd_at() write. |
1070 | */ |
1071 | smp_wmb(); |
1072 | |
1073 | spin_lock(pmd_ptl); |
1074 | BUG_ON(!pmd_none(*pmd)); |
1075 | page_add_new_anon_rmap(new_page, vma, address, true); |
1076 | mem_cgroup_commit_charge(new_page, memcg, false, true); |
1077 | count_memcg_events(memcg, THP_COLLAPSE_ALLOC, 1); |
1078 | lru_cache_add_active_or_unevictable(new_page, vma); |
1079 | pgtable_trans_huge_deposit(mm, pmd, pgtable); |
1080 | set_pmd_at(mm, address, pmd, _pmd); |
1081 | update_mmu_cache_pmd(vma, address, pmd); |
1082 | spin_unlock(pmd_ptl); |
1083 | |
1084 | *hpage = NULL; |
1085 | |
1086 | khugepaged_pages_collapsed++; |
1087 | result = SCAN_SUCCEED; |
1088 | out_up_write: |
1089 | up_write(&mm->mmap_sem); |
1090 | out_nolock: |
1091 | trace_mm_collapse_huge_page(mm, isolated, result); |
1092 | return; |
1093 | out: |
1094 | mem_cgroup_cancel_charge(new_page, memcg, true); |
1095 | goto out_up_write; |
1096 | } |
1097 | |
1098 | static int khugepaged_scan_pmd(struct mm_struct *mm, |
1099 | struct vm_area_struct *vma, |
1100 | unsigned long address, |
1101 | struct page **hpage) |
1102 | { |
1103 | pmd_t *pmd; |
1104 | pte_t *pte, *_pte; |
1105 | int ret = 0, none_or_zero = 0, result = 0, referenced = 0; |
1106 | struct page *page = NULL; |
1107 | unsigned long _address; |
1108 | spinlock_t *ptl; |
1109 | int node = NUMA_NO_NODE, unmapped = 0; |
1110 | bool writable = false; |
1111 | |
1112 | VM_BUG_ON(address & ~HPAGE_PMD_MASK); |
1113 | |
1114 | pmd = mm_find_pmd(mm, address); |
1115 | if (!pmd) { |
1116 | result = SCAN_PMD_NULL; |
1117 | goto out; |
1118 | } |
1119 | |
1120 | memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); |
1121 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); |
1122 | for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; |
1123 | _pte++, _address += PAGE_SIZE) { |
1124 | pte_t pteval = *_pte; |
1125 | if (is_swap_pte(pteval)) { |
1126 | if (++unmapped <= khugepaged_max_ptes_swap) { |
1127 | continue; |
1128 | } else { |
1129 | result = SCAN_EXCEED_SWAP_PTE; |
1130 | goto out_unmap; |
1131 | } |
1132 | } |
1133 | if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { |
1134 | if (!userfaultfd_armed(vma) && |
1135 | ++none_or_zero <= khugepaged_max_ptes_none) { |
1136 | continue; |
1137 | } else { |
1138 | result = SCAN_EXCEED_NONE_PTE; |
1139 | goto out_unmap; |
1140 | } |
1141 | } |
1142 | if (!pte_present(pteval)) { |
1143 | result = SCAN_PTE_NON_PRESENT; |
1144 | goto out_unmap; |
1145 | } |
1146 | if (pte_write(pteval)) |
1147 | writable = true; |
1148 | |
1149 | page = vm_normal_page(vma, _address, pteval); |
1150 | if (unlikely(!page)) { |
1151 | result = SCAN_PAGE_NULL; |
1152 | goto out_unmap; |
1153 | } |
1154 | |
1155 | /* TODO: teach khugepaged to collapse THP mapped with pte */ |
1156 | if (PageCompound(page)) { |
1157 | result = SCAN_PAGE_COMPOUND; |
1158 | goto out_unmap; |
1159 | } |
1160 | |
1161 | /* |
1162 | * Record which node the original page is from and save this |
1163 | * information to khugepaged_node_load[]. |
1164 | * Khupaged will allocate hugepage from the node has the max |
1165 | * hit record. |
1166 | */ |
1167 | node = page_to_nid(page); |
1168 | if (khugepaged_scan_abort(node)) { |
1169 | result = SCAN_SCAN_ABORT; |
1170 | goto out_unmap; |
1171 | } |
1172 | khugepaged_node_load[node]++; |
1173 | if (!PageLRU(page)) { |
1174 | result = SCAN_PAGE_LRU; |
1175 | goto out_unmap; |
1176 | } |
1177 | if (PageLocked(page)) { |
1178 | result = SCAN_PAGE_LOCK; |
1179 | goto out_unmap; |
1180 | } |
1181 | if (!PageAnon(page)) { |
1182 | result = SCAN_PAGE_ANON; |
1183 | goto out_unmap; |
1184 | } |
1185 | |
1186 | /* |
1187 | * cannot use mapcount: can't collapse if there's a gup pin. |
1188 | * The page must only be referenced by the scanned process |
1189 | * and page swap cache. |
1190 | */ |
1191 | if (page_count(page) != 1 + PageSwapCache(page)) { |
1192 | result = SCAN_PAGE_COUNT; |
1193 | goto out_unmap; |
1194 | } |
1195 | if (pte_young(pteval) || |
1196 | page_is_young(page) || PageReferenced(page) || |
1197 | mmu_notifier_test_young(vma->vm_mm, address)) |
1198 | referenced++; |
1199 | } |
1200 | if (writable) { |
1201 | if (referenced) { |
1202 | result = SCAN_SUCCEED; |
1203 | ret = 1; |
1204 | } else { |
1205 | result = SCAN_LACK_REFERENCED_PAGE; |
1206 | } |
1207 | } else { |
1208 | result = SCAN_PAGE_RO; |
1209 | } |
1210 | out_unmap: |
1211 | pte_unmap_unlock(pte, ptl); |
1212 | if (ret) { |
1213 | node = khugepaged_find_target_node(); |
1214 | /* collapse_huge_page will return with the mmap_sem released */ |
1215 | collapse_huge_page(mm, address, hpage, node, referenced); |
1216 | } |
1217 | out: |
1218 | trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, |
1219 | none_or_zero, result, unmapped); |
1220 | return ret; |
1221 | } |
1222 | |
1223 | static void collect_mm_slot(struct mm_slot *mm_slot) |
1224 | { |
1225 | struct mm_struct *mm = mm_slot->mm; |
1226 | |
1227 | lockdep_assert_held(&khugepaged_mm_lock); |
1228 | |
1229 | if (khugepaged_test_exit(mm)) { |
1230 | /* free mm_slot */ |
1231 | hash_del(&mm_slot->hash); |
1232 | list_del(&mm_slot->mm_node); |
1233 | |
1234 | /* |
1235 | * Not strictly needed because the mm exited already. |
1236 | * |
1237 | * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); |
1238 | */ |
1239 | |
1240 | /* khugepaged_mm_lock actually not necessary for the below */ |
1241 | free_mm_slot(mm_slot); |
1242 | mmdrop(mm); |
1243 | } |
1244 | } |
1245 | |
1246 | #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) |
1247 | static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) |
1248 | { |
1249 | struct vm_area_struct *vma; |
1250 | unsigned long addr; |
1251 | pmd_t *pmd, _pmd; |
1252 | |
1253 | i_mmap_lock_write(mapping); |
1254 | vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { |
1255 | /* probably overkill */ |
1256 | if (vma->anon_vma) |
1257 | continue; |
1258 | addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); |
1259 | if (addr & ~HPAGE_PMD_MASK) |
1260 | continue; |
1261 | if (vma->vm_end < addr + HPAGE_PMD_SIZE) |
1262 | continue; |
1263 | pmd = mm_find_pmd(vma->vm_mm, addr); |
1264 | if (!pmd) |
1265 | continue; |
1266 | /* |
1267 | * We need exclusive mmap_sem to retract page table. |
1268 | * If trylock fails we would end up with pte-mapped THP after |
1269 | * re-fault. Not ideal, but it's more important to not disturb |
1270 | * the system too much. |
1271 | */ |
1272 | if (down_write_trylock(&vma->vm_mm->mmap_sem)) { |
1273 | spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd); |
1274 | /* assume page table is clear */ |
1275 | _pmd = pmdp_collapse_flush(vma, addr, pmd); |
1276 | spin_unlock(ptl); |
1277 | up_write(&vma->vm_mm->mmap_sem); |
1278 | mm_dec_nr_ptes(vma->vm_mm); |
1279 | pte_free(vma->vm_mm, pmd_pgtable(_pmd)); |
1280 | } |
1281 | } |
1282 | i_mmap_unlock_write(mapping); |
1283 | } |
1284 | |
1285 | /** |
1286 | * collapse_shmem - collapse small tmpfs/shmem pages into huge one. |
1287 | * |
1288 | * Basic scheme is simple, details are more complex: |
1289 | * - allocate and lock a new huge page; |
1290 | * - scan page cache replacing old pages with the new one |
1291 | * + swap in pages if necessary; |
1292 | * + fill in gaps; |
1293 | * + keep old pages around in case rollback is required; |
1294 | * - if replacing succeeds: |
1295 | * + copy data over; |
1296 | * + free old pages; |
1297 | * + unlock huge page; |
1298 | * - if replacing failed; |
1299 | * + put all pages back and unfreeze them; |
1300 | * + restore gaps in the page cache; |
1301 | * + unlock and free huge page; |
1302 | */ |
1303 | static void collapse_shmem(struct mm_struct *mm, |
1304 | struct address_space *mapping, pgoff_t start, |
1305 | struct page **hpage, int node) |
1306 | { |
1307 | gfp_t gfp; |
1308 | struct page *new_page; |
1309 | struct mem_cgroup *memcg; |
1310 | pgoff_t index, end = start + HPAGE_PMD_NR; |
1311 | LIST_HEAD(pagelist); |
1312 | XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); |
1313 | int nr_none = 0, result = SCAN_SUCCEED; |
1314 | |
1315 | VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); |
1316 | |
1317 | /* Only allocate from the target node */ |
1318 | gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; |
1319 | |
1320 | new_page = khugepaged_alloc_page(hpage, gfp, node); |
1321 | if (!new_page) { |
1322 | result = SCAN_ALLOC_HUGE_PAGE_FAIL; |
1323 | goto out; |
1324 | } |
1325 | |
1326 | if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { |
1327 | result = SCAN_CGROUP_CHARGE_FAIL; |
1328 | goto out; |
1329 | } |
1330 | |
1331 | /* This will be less messy when we use multi-index entries */ |
1332 | do { |
1333 | xas_lock_irq(&xas); |
1334 | xas_create_range(&xas); |
1335 | if (!xas_error(&xas)) |
1336 | break; |
1337 | xas_unlock_irq(&xas); |
1338 | if (!xas_nomem(&xas, GFP_KERNEL)) { |
1339 | mem_cgroup_cancel_charge(new_page, memcg, true); |
1340 | result = SCAN_FAIL; |
1341 | goto out; |
1342 | } |
1343 | } while (1); |
1344 | |
1345 | __SetPageLocked(new_page); |
1346 | __SetPageSwapBacked(new_page); |
1347 | new_page->index = start; |
1348 | new_page->mapping = mapping; |
1349 | |
1350 | /* |
1351 | * At this point the new_page is locked and not up-to-date. |
1352 | * It's safe to insert it into the page cache, because nobody would |
1353 | * be able to map it or use it in another way until we unlock it. |
1354 | */ |
1355 | |
1356 | xas_set(&xas, start); |
1357 | for (index = start; index < end; index++) { |
1358 | struct page *page = xas_next(&xas); |
1359 | |
1360 | VM_BUG_ON(index != xas.xa_index); |
1361 | if (!page) { |
1362 | /* |
1363 | * Stop if extent has been truncated or hole-punched, |
1364 | * and is now completely empty. |
1365 | */ |
1366 | if (index == start) { |
1367 | if (!xas_next_entry(&xas, end - 1)) { |
1368 | result = SCAN_TRUNCATED; |
1369 | goto xa_locked; |
1370 | } |
1371 | xas_set(&xas, index); |
1372 | } |
1373 | if (!shmem_charge(mapping->host, 1)) { |
1374 | result = SCAN_FAIL; |
1375 | goto xa_locked; |
1376 | } |
1377 | xas_store(&xas, new_page + (index % HPAGE_PMD_NR)); |
1378 | nr_none++; |
1379 | continue; |
1380 | } |
1381 | |
1382 | if (xa_is_value(page) || !PageUptodate(page)) { |
1383 | xas_unlock_irq(&xas); |
1384 | /* swap in or instantiate fallocated page */ |
1385 | if (shmem_getpage(mapping->host, index, &page, |
1386 | SGP_NOHUGE)) { |
1387 | result = SCAN_FAIL; |
1388 | goto xa_unlocked; |
1389 | } |
1390 | } else if (trylock_page(page)) { |
1391 | get_page(page); |
1392 | xas_unlock_irq(&xas); |
1393 | } else { |
1394 | result = SCAN_PAGE_LOCK; |
1395 | goto xa_locked; |
1396 | } |
1397 | |
1398 | /* |
1399 | * The page must be locked, so we can drop the i_pages lock |
1400 | * without racing with truncate. |
1401 | */ |
1402 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
1403 | VM_BUG_ON_PAGE(!PageUptodate(page), page); |
1404 | |
1405 | /* |
1406 | * If file was truncated then extended, or hole-punched, before |
1407 | * we locked the first page, then a THP might be there already. |
1408 | */ |
1409 | if (PageTransCompound(page)) { |
1410 | result = SCAN_PAGE_COMPOUND; |
1411 | goto out_unlock; |
1412 | } |
1413 | |
1414 | if (page_mapping(page) != mapping) { |
1415 | result = SCAN_TRUNCATED; |
1416 | goto out_unlock; |
1417 | } |
1418 | |
1419 | if (isolate_lru_page(page)) { |
1420 | result = SCAN_DEL_PAGE_LRU; |
1421 | goto out_unlock; |
1422 | } |
1423 | |
1424 | if (page_mapped(page)) |
1425 | unmap_mapping_pages(mapping, index, 1, false); |
1426 | |
1427 | xas_lock_irq(&xas); |
1428 | xas_set(&xas, index); |
1429 | |
1430 | VM_BUG_ON_PAGE(page != xas_load(&xas), page); |
1431 | VM_BUG_ON_PAGE(page_mapped(page), page); |
1432 | |
1433 | /* |
1434 | * The page is expected to have page_count() == 3: |
1435 | * - we hold a pin on it; |
1436 | * - one reference from page cache; |
1437 | * - one from isolate_lru_page; |
1438 | */ |
1439 | if (!page_ref_freeze(page, 3)) { |
1440 | result = SCAN_PAGE_COUNT; |
1441 | xas_unlock_irq(&xas); |
1442 | putback_lru_page(page); |
1443 | goto out_unlock; |
1444 | } |
1445 | |
1446 | /* |
1447 | * Add the page to the list to be able to undo the collapse if |
1448 | * something go wrong. |
1449 | */ |
1450 | list_add_tail(&page->lru, &pagelist); |
1451 | |
1452 | /* Finally, replace with the new page. */ |
1453 | xas_store(&xas, new_page + (index % HPAGE_PMD_NR)); |
1454 | continue; |
1455 | out_unlock: |
1456 | unlock_page(page); |
1457 | put_page(page); |
1458 | goto xa_unlocked; |
1459 | } |
1460 | |
1461 | __inc_node_page_state(new_page, NR_SHMEM_THPS); |
1462 | if (nr_none) { |
1463 | struct zone *zone = page_zone(new_page); |
1464 | |
1465 | __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none); |
1466 | __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none); |
1467 | } |
1468 | |
1469 | xa_locked: |
1470 | xas_unlock_irq(&xas); |
1471 | xa_unlocked: |
1472 | |
1473 | if (result == SCAN_SUCCEED) { |
1474 | struct page *page, *tmp; |
1475 | |
1476 | /* |
1477 | * Replacing old pages with new one has succeeded, now we |
1478 | * need to copy the content and free the old pages. |
1479 | */ |
1480 | index = start; |
1481 | list_for_each_entry_safe(page, tmp, &pagelist, lru) { |
1482 | while (index < page->index) { |
1483 | clear_highpage(new_page + (index % HPAGE_PMD_NR)); |
1484 | index++; |
1485 | } |
1486 | copy_highpage(new_page + (page->index % HPAGE_PMD_NR), |
1487 | page); |
1488 | list_del(&page->lru); |
1489 | page->mapping = NULL; |
1490 | page_ref_unfreeze(page, 1); |
1491 | ClearPageActive(page); |
1492 | ClearPageUnevictable(page); |
1493 | unlock_page(page); |
1494 | put_page(page); |
1495 | index++; |
1496 | } |
1497 | while (index < end) { |
1498 | clear_highpage(new_page + (index % HPAGE_PMD_NR)); |
1499 | index++; |
1500 | } |
1501 | |
1502 | SetPageUptodate(new_page); |
1503 | page_ref_add(new_page, HPAGE_PMD_NR - 1); |
1504 | set_page_dirty(new_page); |
1505 | mem_cgroup_commit_charge(new_page, memcg, false, true); |
1506 | count_memcg_events(memcg, THP_COLLAPSE_ALLOC, 1); |
1507 | lru_cache_add_anon(new_page); |
1508 | |
1509 | /* |
1510 | * Remove pte page tables, so we can re-fault the page as huge. |
1511 | */ |
1512 | retract_page_tables(mapping, start); |
1513 | *hpage = NULL; |
1514 | |
1515 | khugepaged_pages_collapsed++; |
1516 | } else { |
1517 | struct page *page; |
1518 | |
1519 | /* Something went wrong: roll back page cache changes */ |
1520 | xas_lock_irq(&xas); |
1521 | mapping->nrpages -= nr_none; |
1522 | shmem_uncharge(mapping->host, nr_none); |
1523 | |
1524 | xas_set(&xas, start); |
1525 | xas_for_each(&xas, page, end - 1) { |
1526 | page = list_first_entry_or_null(&pagelist, |
1527 | struct page, lru); |
1528 | if (!page || xas.xa_index < page->index) { |
1529 | if (!nr_none) |
1530 | break; |
1531 | nr_none--; |
1532 | /* Put holes back where they were */ |
1533 | xas_store(&xas, NULL); |
1534 | continue; |
1535 | } |
1536 | |
1537 | VM_BUG_ON_PAGE(page->index != xas.xa_index, page); |
1538 | |
1539 | /* Unfreeze the page. */ |
1540 | list_del(&page->lru); |
1541 | page_ref_unfreeze(page, 2); |
1542 | xas_store(&xas, page); |
1543 | xas_pause(&xas); |
1544 | xas_unlock_irq(&xas); |
1545 | unlock_page(page); |
1546 | putback_lru_page(page); |
1547 | xas_lock_irq(&xas); |
1548 | } |
1549 | VM_BUG_ON(nr_none); |
1550 | xas_unlock_irq(&xas); |
1551 | |
1552 | mem_cgroup_cancel_charge(new_page, memcg, true); |
1553 | new_page->mapping = NULL; |
1554 | } |
1555 | |
1556 | unlock_page(new_page); |
1557 | out: |
1558 | VM_BUG_ON(!list_empty(&pagelist)); |
1559 | /* TODO: tracepoints */ |
1560 | } |
1561 | |
1562 | static void khugepaged_scan_shmem(struct mm_struct *mm, |
1563 | struct address_space *mapping, |
1564 | pgoff_t start, struct page **hpage) |
1565 | { |
1566 | struct page *page = NULL; |
1567 | XA_STATE(xas, &mapping->i_pages, start); |
1568 | int present, swap; |
1569 | int node = NUMA_NO_NODE; |
1570 | int result = SCAN_SUCCEED; |
1571 | |
1572 | present = 0; |
1573 | swap = 0; |
1574 | memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); |
1575 | rcu_read_lock(); |
1576 | xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) { |
1577 | if (xas_retry(&xas, page)) |
1578 | continue; |
1579 | |
1580 | if (xa_is_value(page)) { |
1581 | if (++swap > khugepaged_max_ptes_swap) { |
1582 | result = SCAN_EXCEED_SWAP_PTE; |
1583 | break; |
1584 | } |
1585 | continue; |
1586 | } |
1587 | |
1588 | if (PageTransCompound(page)) { |
1589 | result = SCAN_PAGE_COMPOUND; |
1590 | break; |
1591 | } |
1592 | |
1593 | node = page_to_nid(page); |
1594 | if (khugepaged_scan_abort(node)) { |
1595 | result = SCAN_SCAN_ABORT; |
1596 | break; |
1597 | } |
1598 | khugepaged_node_load[node]++; |
1599 | |
1600 | if (!PageLRU(page)) { |
1601 | result = SCAN_PAGE_LRU; |
1602 | break; |
1603 | } |
1604 | |
1605 | if (page_count(page) != 1 + page_mapcount(page)) { |
1606 | result = SCAN_PAGE_COUNT; |
1607 | break; |
1608 | } |
1609 | |
1610 | /* |
1611 | * We probably should check if the page is referenced here, but |
1612 | * nobody would transfer pte_young() to PageReferenced() for us. |
1613 | * And rmap walk here is just too costly... |
1614 | */ |
1615 | |
1616 | present++; |
1617 | |
1618 | if (need_resched()) { |
1619 | xas_pause(&xas); |
1620 | cond_resched_rcu(); |
1621 | } |
1622 | } |
1623 | rcu_read_unlock(); |
1624 | |
1625 | if (result == SCAN_SUCCEED) { |
1626 | if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { |
1627 | result = SCAN_EXCEED_NONE_PTE; |
1628 | } else { |
1629 | node = khugepaged_find_target_node(); |
1630 | collapse_shmem(mm, mapping, start, hpage, node); |
1631 | } |
1632 | } |
1633 | |
1634 | /* TODO: tracepoints */ |
1635 | } |
1636 | #else |
1637 | static void khugepaged_scan_shmem(struct mm_struct *mm, |
1638 | struct address_space *mapping, |
1639 | pgoff_t start, struct page **hpage) |
1640 | { |
1641 | BUILD_BUG(); |
1642 | } |
1643 | #endif |
1644 | |
1645 | static unsigned int khugepaged_scan_mm_slot(unsigned int pages, |
1646 | struct page **hpage) |
1647 | __releases(&khugepaged_mm_lock) |
1648 | __acquires(&khugepaged_mm_lock) |
1649 | { |
1650 | struct mm_slot *mm_slot; |
1651 | struct mm_struct *mm; |
1652 | struct vm_area_struct *vma; |
1653 | int progress = 0; |
1654 | |
1655 | VM_BUG_ON(!pages); |
1656 | lockdep_assert_held(&khugepaged_mm_lock); |
1657 | |
1658 | if (khugepaged_scan.mm_slot) |
1659 | mm_slot = khugepaged_scan.mm_slot; |
1660 | else { |
1661 | mm_slot = list_entry(khugepaged_scan.mm_head.next, |
1662 | struct mm_slot, mm_node); |
1663 | khugepaged_scan.address = 0; |
1664 | khugepaged_scan.mm_slot = mm_slot; |
1665 | } |
1666 | spin_unlock(&khugepaged_mm_lock); |
1667 | |
1668 | mm = mm_slot->mm; |
1669 | /* |
1670 | * Don't wait for semaphore (to avoid long wait times). Just move to |
1671 | * the next mm on the list. |
1672 | */ |
1673 | vma = NULL; |
1674 | if (unlikely(!down_read_trylock(&mm->mmap_sem))) |
1675 | goto breakouterloop_mmap_sem; |
1676 | if (likely(!khugepaged_test_exit(mm))) |
1677 | vma = find_vma(mm, khugepaged_scan.address); |
1678 | |
1679 | progress++; |
1680 | for (; vma; vma = vma->vm_next) { |
1681 | unsigned long hstart, hend; |
1682 | |
1683 | cond_resched(); |
1684 | if (unlikely(khugepaged_test_exit(mm))) { |
1685 | progress++; |
1686 | break; |
1687 | } |
1688 | if (!hugepage_vma_check(vma, vma->vm_flags)) { |
1689 | skip: |
1690 | progress++; |
1691 | continue; |
1692 | } |
1693 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; |
1694 | hend = vma->vm_end & HPAGE_PMD_MASK; |
1695 | if (hstart >= hend) |
1696 | goto skip; |
1697 | if (khugepaged_scan.address > hend) |
1698 | goto skip; |
1699 | if (khugepaged_scan.address < hstart) |
1700 | khugepaged_scan.address = hstart; |
1701 | VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); |
1702 | |
1703 | while (khugepaged_scan.address < hend) { |
1704 | int ret; |
1705 | cond_resched(); |
1706 | if (unlikely(khugepaged_test_exit(mm))) |
1707 | goto breakouterloop; |
1708 | |
1709 | VM_BUG_ON(khugepaged_scan.address < hstart || |
1710 | khugepaged_scan.address + HPAGE_PMD_SIZE > |
1711 | hend); |
1712 | if (shmem_file(vma->vm_file)) { |
1713 | struct file *file; |
1714 | pgoff_t pgoff = linear_page_index(vma, |
1715 | khugepaged_scan.address); |
1716 | if (!shmem_huge_enabled(vma)) |
1717 | goto skip; |
1718 | file = get_file(vma->vm_file); |
1719 | up_read(&mm->mmap_sem); |
1720 | ret = 1; |
1721 | khugepaged_scan_shmem(mm, file->f_mapping, |
1722 | pgoff, hpage); |
1723 | fput(file); |
1724 | } else { |
1725 | ret = khugepaged_scan_pmd(mm, vma, |
1726 | khugepaged_scan.address, |
1727 | hpage); |
1728 | } |
1729 | /* move to next address */ |
1730 | khugepaged_scan.address += HPAGE_PMD_SIZE; |
1731 | progress += HPAGE_PMD_NR; |
1732 | if (ret) |
1733 | /* we released mmap_sem so break loop */ |
1734 | goto breakouterloop_mmap_sem; |
1735 | if (progress >= pages) |
1736 | goto breakouterloop; |
1737 | } |
1738 | } |
1739 | breakouterloop: |
1740 | up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ |
1741 | breakouterloop_mmap_sem: |
1742 | |
1743 | spin_lock(&khugepaged_mm_lock); |
1744 | VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); |
1745 | /* |
1746 | * Release the current mm_slot if this mm is about to die, or |
1747 | * if we scanned all vmas of this mm. |
1748 | */ |
1749 | if (khugepaged_test_exit(mm) || !vma) { |
1750 | /* |
1751 | * Make sure that if mm_users is reaching zero while |
1752 | * khugepaged runs here, khugepaged_exit will find |
1753 | * mm_slot not pointing to the exiting mm. |
1754 | */ |
1755 | if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { |
1756 | khugepaged_scan.mm_slot = list_entry( |
1757 | mm_slot->mm_node.next, |
1758 | struct mm_slot, mm_node); |
1759 | khugepaged_scan.address = 0; |
1760 | } else { |
1761 | khugepaged_scan.mm_slot = NULL; |
1762 | khugepaged_full_scans++; |
1763 | } |
1764 | |
1765 | collect_mm_slot(mm_slot); |
1766 | } |
1767 | |
1768 | return progress; |
1769 | } |
1770 | |
1771 | static int khugepaged_has_work(void) |
1772 | { |
1773 | return !list_empty(&khugepaged_scan.mm_head) && |
1774 | khugepaged_enabled(); |
1775 | } |
1776 | |
1777 | static int khugepaged_wait_event(void) |
1778 | { |
1779 | return !list_empty(&khugepaged_scan.mm_head) || |
1780 | kthread_should_stop(); |
1781 | } |
1782 | |
1783 | static void khugepaged_do_scan(void) |
1784 | { |
1785 | struct page *hpage = NULL; |
1786 | unsigned int progress = 0, pass_through_head = 0; |
1787 | unsigned int pages = khugepaged_pages_to_scan; |
1788 | bool wait = true; |
1789 | |
1790 | barrier(); /* write khugepaged_pages_to_scan to local stack */ |
1791 | |
1792 | while (progress < pages) { |
1793 | if (!khugepaged_prealloc_page(&hpage, &wait)) |
1794 | break; |
1795 | |
1796 | cond_resched(); |
1797 | |
1798 | if (unlikely(kthread_should_stop() || try_to_freeze())) |
1799 | break; |
1800 | |
1801 | spin_lock(&khugepaged_mm_lock); |
1802 | if (!khugepaged_scan.mm_slot) |
1803 | pass_through_head++; |
1804 | if (khugepaged_has_work() && |
1805 | pass_through_head < 2) |
1806 | progress += khugepaged_scan_mm_slot(pages - progress, |
1807 | &hpage); |
1808 | else |
1809 | progress = pages; |
1810 | spin_unlock(&khugepaged_mm_lock); |
1811 | } |
1812 | |
1813 | if (!IS_ERR_OR_NULL(hpage)) |
1814 | put_page(hpage); |
1815 | } |
1816 | |
1817 | static bool khugepaged_should_wakeup(void) |
1818 | { |
1819 | return kthread_should_stop() || |
1820 | time_after_eq(jiffies, khugepaged_sleep_expire); |
1821 | } |
1822 | |
1823 | static void khugepaged_wait_work(void) |
1824 | { |
1825 | if (khugepaged_has_work()) { |
1826 | const unsigned long scan_sleep_jiffies = |
1827 | msecs_to_jiffies(khugepaged_scan_sleep_millisecs); |
1828 | |
1829 | if (!scan_sleep_jiffies) |
1830 | return; |
1831 | |
1832 | khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; |
1833 | wait_event_freezable_timeout(khugepaged_wait, |
1834 | khugepaged_should_wakeup(), |
1835 | scan_sleep_jiffies); |
1836 | return; |
1837 | } |
1838 | |
1839 | if (khugepaged_enabled()) |
1840 | wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); |
1841 | } |
1842 | |
1843 | static int khugepaged(void *none) |
1844 | { |
1845 | struct mm_slot *mm_slot; |
1846 | |
1847 | set_freezable(); |
1848 | set_user_nice(current, MAX_NICE); |
1849 | |
1850 | while (!kthread_should_stop()) { |
1851 | khugepaged_do_scan(); |
1852 | khugepaged_wait_work(); |
1853 | } |
1854 | |
1855 | spin_lock(&khugepaged_mm_lock); |
1856 | mm_slot = khugepaged_scan.mm_slot; |
1857 | khugepaged_scan.mm_slot = NULL; |
1858 | if (mm_slot) |
1859 | collect_mm_slot(mm_slot); |
1860 | spin_unlock(&khugepaged_mm_lock); |
1861 | return 0; |
1862 | } |
1863 | |
1864 | static void set_recommended_min_free_kbytes(void) |
1865 | { |
1866 | struct zone *zone; |
1867 | int nr_zones = 0; |
1868 | unsigned long recommended_min; |
1869 | |
1870 | for_each_populated_zone(zone) { |
1871 | /* |
1872 | * We don't need to worry about fragmentation of |
1873 | * ZONE_MOVABLE since it only has movable pages. |
1874 | */ |
1875 | if (zone_idx(zone) > gfp_zone(GFP_USER)) |
1876 | continue; |
1877 | |
1878 | nr_zones++; |
1879 | } |
1880 | |
1881 | /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ |
1882 | recommended_min = pageblock_nr_pages * nr_zones * 2; |
1883 | |
1884 | /* |
1885 | * Make sure that on average at least two pageblocks are almost free |
1886 | * of another type, one for a migratetype to fall back to and a |
1887 | * second to avoid subsequent fallbacks of other types There are 3 |
1888 | * MIGRATE_TYPES we care about. |
1889 | */ |
1890 | recommended_min += pageblock_nr_pages * nr_zones * |
1891 | MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; |
1892 | |
1893 | /* don't ever allow to reserve more than 5% of the lowmem */ |
1894 | recommended_min = min(recommended_min, |
1895 | (unsigned long) nr_free_buffer_pages() / 20); |
1896 | recommended_min <<= (PAGE_SHIFT-10); |
1897 | |
1898 | if (recommended_min > min_free_kbytes) { |
1899 | if (user_min_free_kbytes >= 0) |
1900 | pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n" , |
1901 | min_free_kbytes, recommended_min); |
1902 | |
1903 | min_free_kbytes = recommended_min; |
1904 | } |
1905 | setup_per_zone_wmarks(); |
1906 | } |
1907 | |
1908 | int start_stop_khugepaged(void) |
1909 | { |
1910 | static struct task_struct *khugepaged_thread __read_mostly; |
1911 | static DEFINE_MUTEX(khugepaged_mutex); |
1912 | int err = 0; |
1913 | |
1914 | mutex_lock(&khugepaged_mutex); |
1915 | if (khugepaged_enabled()) { |
1916 | if (!khugepaged_thread) |
1917 | khugepaged_thread = kthread_run(khugepaged, NULL, |
1918 | "khugepaged" ); |
1919 | if (IS_ERR(khugepaged_thread)) { |
1920 | pr_err("khugepaged: kthread_run(khugepaged) failed\n" ); |
1921 | err = PTR_ERR(khugepaged_thread); |
1922 | khugepaged_thread = NULL; |
1923 | goto fail; |
1924 | } |
1925 | |
1926 | if (!list_empty(&khugepaged_scan.mm_head)) |
1927 | wake_up_interruptible(&khugepaged_wait); |
1928 | |
1929 | set_recommended_min_free_kbytes(); |
1930 | } else if (khugepaged_thread) { |
1931 | kthread_stop(khugepaged_thread); |
1932 | khugepaged_thread = NULL; |
1933 | } |
1934 | fail: |
1935 | mutex_unlock(&khugepaged_mutex); |
1936 | return err; |
1937 | } |
1938 | |