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b46e756f KS |
1 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
2 | ||
3 | #include <linux/mm.h> | |
4 | #include <linux/sched.h> | |
6e84f315 | 5 | #include <linux/sched/mm.h> |
f7ccbae4 | 6 | #include <linux/sched/coredump.h> |
b46e756f KS |
7 | #include <linux/mmu_notifier.h> |
8 | #include <linux/rmap.h> | |
9 | #include <linux/swap.h> | |
10 | #include <linux/mm_inline.h> | |
11 | #include <linux/kthread.h> | |
12 | #include <linux/khugepaged.h> | |
13 | #include <linux/freezer.h> | |
14 | #include <linux/mman.h> | |
15 | #include <linux/hashtable.h> | |
16 | #include <linux/userfaultfd_k.h> | |
17 | #include <linux/page_idle.h> | |
18 | #include <linux/swapops.h> | |
f3f0e1d2 | 19 | #include <linux/shmem_fs.h> |
b46e756f KS |
20 | |
21 | #include <asm/tlb.h> | |
22 | #include <asm/pgalloc.h> | |
23 | #include "internal.h" | |
24 | ||
25 | enum scan_result { | |
26 | SCAN_FAIL, | |
27 | SCAN_SUCCEED, | |
28 | SCAN_PMD_NULL, | |
29 | SCAN_EXCEED_NONE_PTE, | |
30 | SCAN_PTE_NON_PRESENT, | |
31 | SCAN_PAGE_RO, | |
0db501f7 | 32 | SCAN_LACK_REFERENCED_PAGE, |
b46e756f KS |
33 | SCAN_PAGE_NULL, |
34 | SCAN_SCAN_ABORT, | |
35 | SCAN_PAGE_COUNT, | |
36 | SCAN_PAGE_LRU, | |
37 | SCAN_PAGE_LOCK, | |
38 | SCAN_PAGE_ANON, | |
39 | SCAN_PAGE_COMPOUND, | |
40 | SCAN_ANY_PROCESS, | |
41 | SCAN_VMA_NULL, | |
42 | SCAN_VMA_CHECK, | |
43 | SCAN_ADDRESS_RANGE, | |
44 | SCAN_SWAP_CACHE_PAGE, | |
45 | SCAN_DEL_PAGE_LRU, | |
46 | SCAN_ALLOC_HUGE_PAGE_FAIL, | |
47 | SCAN_CGROUP_CHARGE_FAIL, | |
f3f0e1d2 KS |
48 | SCAN_EXCEED_SWAP_PTE, |
49 | SCAN_TRUNCATED, | |
b46e756f KS |
50 | }; |
51 | ||
52 | #define CREATE_TRACE_POINTS | |
53 | #include <trace/events/huge_memory.h> | |
54 | ||
55 | /* default scan 8*512 pte (or vmas) every 30 second */ | |
56 | static unsigned int khugepaged_pages_to_scan __read_mostly; | |
57 | static unsigned int khugepaged_pages_collapsed; | |
58 | static unsigned int khugepaged_full_scans; | |
59 | static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; | |
60 | /* during fragmentation poll the hugepage allocator once every minute */ | |
61 | static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; | |
62 | static unsigned long khugepaged_sleep_expire; | |
63 | static DEFINE_SPINLOCK(khugepaged_mm_lock); | |
64 | static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); | |
65 | /* | |
66 | * default collapse hugepages if there is at least one pte mapped like | |
67 | * it would have happened if the vma was large enough during page | |
68 | * fault. | |
69 | */ | |
70 | static unsigned int khugepaged_max_ptes_none __read_mostly; | |
71 | static unsigned int khugepaged_max_ptes_swap __read_mostly; | |
72 | ||
73 | #define MM_SLOTS_HASH_BITS 10 | |
74 | static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); | |
75 | ||
76 | static struct kmem_cache *mm_slot_cache __read_mostly; | |
77 | ||
78 | /** | |
79 | * struct mm_slot - hash lookup from mm to mm_slot | |
80 | * @hash: hash collision list | |
81 | * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head | |
82 | * @mm: the mm that this information is valid for | |
83 | */ | |
84 | struct mm_slot { | |
85 | struct hlist_node hash; | |
86 | struct list_head mm_node; | |
87 | struct mm_struct *mm; | |
88 | }; | |
89 | ||
90 | /** | |
91 | * struct khugepaged_scan - cursor for scanning | |
92 | * @mm_head: the head of the mm list to scan | |
93 | * @mm_slot: the current mm_slot we are scanning | |
94 | * @address: the next address inside that to be scanned | |
95 | * | |
96 | * There is only the one khugepaged_scan instance of this cursor structure. | |
97 | */ | |
98 | struct khugepaged_scan { | |
99 | struct list_head mm_head; | |
100 | struct mm_slot *mm_slot; | |
101 | unsigned long address; | |
102 | }; | |
103 | ||
104 | static struct khugepaged_scan khugepaged_scan = { | |
105 | .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), | |
106 | }; | |
107 | ||
e1465d12 | 108 | #ifdef CONFIG_SYSFS |
b46e756f KS |
109 | static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, |
110 | struct kobj_attribute *attr, | |
111 | char *buf) | |
112 | { | |
113 | return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); | |
114 | } | |
115 | ||
116 | static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, | |
117 | struct kobj_attribute *attr, | |
118 | const char *buf, size_t count) | |
119 | { | |
120 | unsigned long msecs; | |
121 | int err; | |
122 | ||
123 | err = kstrtoul(buf, 10, &msecs); | |
124 | if (err || msecs > UINT_MAX) | |
125 | return -EINVAL; | |
126 | ||
127 | khugepaged_scan_sleep_millisecs = msecs; | |
128 | khugepaged_sleep_expire = 0; | |
129 | wake_up_interruptible(&khugepaged_wait); | |
130 | ||
131 | return count; | |
132 | } | |
133 | static struct kobj_attribute scan_sleep_millisecs_attr = | |
134 | __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, | |
135 | scan_sleep_millisecs_store); | |
136 | ||
137 | static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, | |
138 | struct kobj_attribute *attr, | |
139 | char *buf) | |
140 | { | |
141 | return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); | |
142 | } | |
143 | ||
144 | static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, | |
145 | struct kobj_attribute *attr, | |
146 | const char *buf, size_t count) | |
147 | { | |
148 | unsigned long msecs; | |
149 | int err; | |
150 | ||
151 | err = kstrtoul(buf, 10, &msecs); | |
152 | if (err || msecs > UINT_MAX) | |
153 | return -EINVAL; | |
154 | ||
155 | khugepaged_alloc_sleep_millisecs = msecs; | |
156 | khugepaged_sleep_expire = 0; | |
157 | wake_up_interruptible(&khugepaged_wait); | |
158 | ||
159 | return count; | |
160 | } | |
161 | static struct kobj_attribute alloc_sleep_millisecs_attr = | |
162 | __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, | |
163 | alloc_sleep_millisecs_store); | |
164 | ||
165 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
166 | struct kobj_attribute *attr, | |
167 | char *buf) | |
168 | { | |
169 | return sprintf(buf, "%u\n", khugepaged_pages_to_scan); | |
170 | } | |
171 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
172 | struct kobj_attribute *attr, | |
173 | const char *buf, size_t count) | |
174 | { | |
175 | int err; | |
176 | unsigned long pages; | |
177 | ||
178 | err = kstrtoul(buf, 10, &pages); | |
179 | if (err || !pages || pages > UINT_MAX) | |
180 | return -EINVAL; | |
181 | ||
182 | khugepaged_pages_to_scan = pages; | |
183 | ||
184 | return count; | |
185 | } | |
186 | static struct kobj_attribute pages_to_scan_attr = | |
187 | __ATTR(pages_to_scan, 0644, pages_to_scan_show, | |
188 | pages_to_scan_store); | |
189 | ||
190 | static ssize_t pages_collapsed_show(struct kobject *kobj, | |
191 | struct kobj_attribute *attr, | |
192 | char *buf) | |
193 | { | |
194 | return sprintf(buf, "%u\n", khugepaged_pages_collapsed); | |
195 | } | |
196 | static struct kobj_attribute pages_collapsed_attr = | |
197 | __ATTR_RO(pages_collapsed); | |
198 | ||
199 | static ssize_t full_scans_show(struct kobject *kobj, | |
200 | struct kobj_attribute *attr, | |
201 | char *buf) | |
202 | { | |
203 | return sprintf(buf, "%u\n", khugepaged_full_scans); | |
204 | } | |
205 | static struct kobj_attribute full_scans_attr = | |
206 | __ATTR_RO(full_scans); | |
207 | ||
208 | static ssize_t khugepaged_defrag_show(struct kobject *kobj, | |
209 | struct kobj_attribute *attr, char *buf) | |
210 | { | |
211 | return single_hugepage_flag_show(kobj, attr, buf, | |
212 | TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); | |
213 | } | |
214 | static ssize_t khugepaged_defrag_store(struct kobject *kobj, | |
215 | struct kobj_attribute *attr, | |
216 | const char *buf, size_t count) | |
217 | { | |
218 | return single_hugepage_flag_store(kobj, attr, buf, count, | |
219 | TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); | |
220 | } | |
221 | static struct kobj_attribute khugepaged_defrag_attr = | |
222 | __ATTR(defrag, 0644, khugepaged_defrag_show, | |
223 | khugepaged_defrag_store); | |
224 | ||
225 | /* | |
226 | * max_ptes_none controls if khugepaged should collapse hugepages over | |
227 | * any unmapped ptes in turn potentially increasing the memory | |
228 | * footprint of the vmas. When max_ptes_none is 0 khugepaged will not | |
229 | * reduce the available free memory in the system as it | |
230 | * runs. Increasing max_ptes_none will instead potentially reduce the | |
231 | * free memory in the system during the khugepaged scan. | |
232 | */ | |
233 | static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, | |
234 | struct kobj_attribute *attr, | |
235 | char *buf) | |
236 | { | |
237 | return sprintf(buf, "%u\n", khugepaged_max_ptes_none); | |
238 | } | |
239 | static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, | |
240 | struct kobj_attribute *attr, | |
241 | const char *buf, size_t count) | |
242 | { | |
243 | int err; | |
244 | unsigned long max_ptes_none; | |
245 | ||
246 | err = kstrtoul(buf, 10, &max_ptes_none); | |
247 | if (err || max_ptes_none > HPAGE_PMD_NR-1) | |
248 | return -EINVAL; | |
249 | ||
250 | khugepaged_max_ptes_none = max_ptes_none; | |
251 | ||
252 | return count; | |
253 | } | |
254 | static struct kobj_attribute khugepaged_max_ptes_none_attr = | |
255 | __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, | |
256 | khugepaged_max_ptes_none_store); | |
257 | ||
258 | static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj, | |
259 | struct kobj_attribute *attr, | |
260 | char *buf) | |
261 | { | |
262 | return sprintf(buf, "%u\n", khugepaged_max_ptes_swap); | |
263 | } | |
264 | ||
265 | static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj, | |
266 | struct kobj_attribute *attr, | |
267 | const char *buf, size_t count) | |
268 | { | |
269 | int err; | |
270 | unsigned long max_ptes_swap; | |
271 | ||
272 | err = kstrtoul(buf, 10, &max_ptes_swap); | |
273 | if (err || max_ptes_swap > HPAGE_PMD_NR-1) | |
274 | return -EINVAL; | |
275 | ||
276 | khugepaged_max_ptes_swap = max_ptes_swap; | |
277 | ||
278 | return count; | |
279 | } | |
280 | ||
281 | static struct kobj_attribute khugepaged_max_ptes_swap_attr = | |
282 | __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show, | |
283 | khugepaged_max_ptes_swap_store); | |
284 | ||
285 | static struct attribute *khugepaged_attr[] = { | |
286 | &khugepaged_defrag_attr.attr, | |
287 | &khugepaged_max_ptes_none_attr.attr, | |
288 | &pages_to_scan_attr.attr, | |
289 | &pages_collapsed_attr.attr, | |
290 | &full_scans_attr.attr, | |
291 | &scan_sleep_millisecs_attr.attr, | |
292 | &alloc_sleep_millisecs_attr.attr, | |
293 | &khugepaged_max_ptes_swap_attr.attr, | |
294 | NULL, | |
295 | }; | |
296 | ||
297 | struct attribute_group khugepaged_attr_group = { | |
298 | .attrs = khugepaged_attr, | |
299 | .name = "khugepaged", | |
300 | }; | |
e1465d12 | 301 | #endif /* CONFIG_SYSFS */ |
b46e756f | 302 | |
f3f0e1d2 | 303 | #define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB) |
b46e756f KS |
304 | |
305 | int hugepage_madvise(struct vm_area_struct *vma, | |
306 | unsigned long *vm_flags, int advice) | |
307 | { | |
308 | switch (advice) { | |
309 | case MADV_HUGEPAGE: | |
310 | #ifdef CONFIG_S390 | |
311 | /* | |
312 | * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 | |
313 | * can't handle this properly after s390_enable_sie, so we simply | |
314 | * ignore the madvise to prevent qemu from causing a SIGSEGV. | |
315 | */ | |
316 | if (mm_has_pgste(vma->vm_mm)) | |
317 | return 0; | |
318 | #endif | |
319 | *vm_flags &= ~VM_NOHUGEPAGE; | |
320 | *vm_flags |= VM_HUGEPAGE; | |
321 | /* | |
322 | * If the vma become good for khugepaged to scan, | |
323 | * register it here without waiting a page fault that | |
324 | * may not happen any time soon. | |
325 | */ | |
326 | if (!(*vm_flags & VM_NO_KHUGEPAGED) && | |
327 | khugepaged_enter_vma_merge(vma, *vm_flags)) | |
328 | return -ENOMEM; | |
329 | break; | |
330 | case MADV_NOHUGEPAGE: | |
331 | *vm_flags &= ~VM_HUGEPAGE; | |
332 | *vm_flags |= VM_NOHUGEPAGE; | |
333 | /* | |
334 | * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning | |
335 | * this vma even if we leave the mm registered in khugepaged if | |
336 | * it got registered before VM_NOHUGEPAGE was set. | |
337 | */ | |
338 | break; | |
339 | } | |
340 | ||
341 | return 0; | |
342 | } | |
343 | ||
344 | int __init khugepaged_init(void) | |
345 | { | |
346 | mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", | |
347 | sizeof(struct mm_slot), | |
348 | __alignof__(struct mm_slot), 0, NULL); | |
349 | if (!mm_slot_cache) | |
350 | return -ENOMEM; | |
351 | ||
352 | khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; | |
353 | khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; | |
354 | khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; | |
355 | ||
356 | return 0; | |
357 | } | |
358 | ||
359 | void __init khugepaged_destroy(void) | |
360 | { | |
361 | kmem_cache_destroy(mm_slot_cache); | |
362 | } | |
363 | ||
364 | static inline struct mm_slot *alloc_mm_slot(void) | |
365 | { | |
366 | if (!mm_slot_cache) /* initialization failed */ | |
367 | return NULL; | |
368 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
369 | } | |
370 | ||
371 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
372 | { | |
373 | kmem_cache_free(mm_slot_cache, mm_slot); | |
374 | } | |
375 | ||
376 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) | |
377 | { | |
378 | struct mm_slot *mm_slot; | |
379 | ||
380 | hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) | |
381 | if (mm == mm_slot->mm) | |
382 | return mm_slot; | |
383 | ||
384 | return NULL; | |
385 | } | |
386 | ||
387 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
388 | struct mm_slot *mm_slot) | |
389 | { | |
390 | mm_slot->mm = mm; | |
391 | hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); | |
392 | } | |
393 | ||
394 | static inline int khugepaged_test_exit(struct mm_struct *mm) | |
395 | { | |
396 | return atomic_read(&mm->mm_users) == 0; | |
397 | } | |
398 | ||
399 | int __khugepaged_enter(struct mm_struct *mm) | |
400 | { | |
401 | struct mm_slot *mm_slot; | |
402 | int wakeup; | |
403 | ||
404 | mm_slot = alloc_mm_slot(); | |
405 | if (!mm_slot) | |
406 | return -ENOMEM; | |
407 | ||
408 | /* __khugepaged_exit() must not run from under us */ | |
409 | VM_BUG_ON_MM(khugepaged_test_exit(mm), mm); | |
410 | if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { | |
411 | free_mm_slot(mm_slot); | |
412 | return 0; | |
413 | } | |
414 | ||
415 | spin_lock(&khugepaged_mm_lock); | |
416 | insert_to_mm_slots_hash(mm, mm_slot); | |
417 | /* | |
418 | * Insert just behind the scanning cursor, to let the area settle | |
419 | * down a little. | |
420 | */ | |
421 | wakeup = list_empty(&khugepaged_scan.mm_head); | |
422 | list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); | |
423 | spin_unlock(&khugepaged_mm_lock); | |
424 | ||
f1f10076 | 425 | mmgrab(mm); |
b46e756f KS |
426 | if (wakeup) |
427 | wake_up_interruptible(&khugepaged_wait); | |
428 | ||
429 | return 0; | |
430 | } | |
431 | ||
432 | int khugepaged_enter_vma_merge(struct vm_area_struct *vma, | |
433 | unsigned long vm_flags) | |
434 | { | |
435 | unsigned long hstart, hend; | |
436 | if (!vma->anon_vma) | |
437 | /* | |
438 | * Not yet faulted in so we will register later in the | |
439 | * page fault if needed. | |
440 | */ | |
441 | return 0; | |
442 | if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED)) | |
443 | /* khugepaged not yet working on file or special mappings */ | |
444 | return 0; | |
445 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; | |
446 | hend = vma->vm_end & HPAGE_PMD_MASK; | |
447 | if (hstart < hend) | |
448 | return khugepaged_enter(vma, vm_flags); | |
449 | return 0; | |
450 | } | |
451 | ||
452 | void __khugepaged_exit(struct mm_struct *mm) | |
453 | { | |
454 | struct mm_slot *mm_slot; | |
455 | int free = 0; | |
456 | ||
457 | spin_lock(&khugepaged_mm_lock); | |
458 | mm_slot = get_mm_slot(mm); | |
459 | if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { | |
460 | hash_del(&mm_slot->hash); | |
461 | list_del(&mm_slot->mm_node); | |
462 | free = 1; | |
463 | } | |
464 | spin_unlock(&khugepaged_mm_lock); | |
465 | ||
466 | if (free) { | |
467 | clear_bit(MMF_VM_HUGEPAGE, &mm->flags); | |
468 | free_mm_slot(mm_slot); | |
469 | mmdrop(mm); | |
470 | } else if (mm_slot) { | |
471 | /* | |
472 | * This is required to serialize against | |
473 | * khugepaged_test_exit() (which is guaranteed to run | |
474 | * under mmap sem read mode). Stop here (after we | |
475 | * return all pagetables will be destroyed) until | |
476 | * khugepaged has finished working on the pagetables | |
477 | * under the mmap_sem. | |
478 | */ | |
479 | down_write(&mm->mmap_sem); | |
480 | up_write(&mm->mmap_sem); | |
481 | } | |
482 | } | |
483 | ||
484 | static void release_pte_page(struct page *page) | |
485 | { | |
d44d363f | 486 | dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); |
b46e756f KS |
487 | unlock_page(page); |
488 | putback_lru_page(page); | |
489 | } | |
490 | ||
491 | static void release_pte_pages(pte_t *pte, pte_t *_pte) | |
492 | { | |
493 | while (--_pte >= pte) { | |
494 | pte_t pteval = *_pte; | |
495 | if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval))) | |
496 | release_pte_page(pte_page(pteval)); | |
497 | } | |
498 | } | |
499 | ||
500 | static int __collapse_huge_page_isolate(struct vm_area_struct *vma, | |
501 | unsigned long address, | |
502 | pte_t *pte) | |
503 | { | |
504 | struct page *page = NULL; | |
505 | pte_t *_pte; | |
0db501f7 EA |
506 | int none_or_zero = 0, result = 0, referenced = 0; |
507 | bool writable = false; | |
b46e756f KS |
508 | |
509 | for (_pte = pte; _pte < pte+HPAGE_PMD_NR; | |
510 | _pte++, address += PAGE_SIZE) { | |
511 | pte_t pteval = *_pte; | |
512 | if (pte_none(pteval) || (pte_present(pteval) && | |
513 | is_zero_pfn(pte_pfn(pteval)))) { | |
514 | if (!userfaultfd_armed(vma) && | |
515 | ++none_or_zero <= khugepaged_max_ptes_none) { | |
516 | continue; | |
517 | } else { | |
518 | result = SCAN_EXCEED_NONE_PTE; | |
519 | goto out; | |
520 | } | |
521 | } | |
522 | if (!pte_present(pteval)) { | |
523 | result = SCAN_PTE_NON_PRESENT; | |
524 | goto out; | |
525 | } | |
526 | page = vm_normal_page(vma, address, pteval); | |
527 | if (unlikely(!page)) { | |
528 | result = SCAN_PAGE_NULL; | |
529 | goto out; | |
530 | } | |
531 | ||
532 | VM_BUG_ON_PAGE(PageCompound(page), page); | |
533 | VM_BUG_ON_PAGE(!PageAnon(page), page); | |
b46e756f KS |
534 | |
535 | /* | |
536 | * We can do it before isolate_lru_page because the | |
537 | * page can't be freed from under us. NOTE: PG_lock | |
538 | * is needed to serialize against split_huge_page | |
539 | * when invoked from the VM. | |
540 | */ | |
541 | if (!trylock_page(page)) { | |
542 | result = SCAN_PAGE_LOCK; | |
543 | goto out; | |
544 | } | |
545 | ||
546 | /* | |
547 | * cannot use mapcount: can't collapse if there's a gup pin. | |
548 | * The page must only be referenced by the scanned process | |
549 | * and page swap cache. | |
550 | */ | |
2948be5a | 551 | if (page_count(page) != 1 + PageSwapCache(page)) { |
b46e756f KS |
552 | unlock_page(page); |
553 | result = SCAN_PAGE_COUNT; | |
554 | goto out; | |
555 | } | |
556 | if (pte_write(pteval)) { | |
557 | writable = true; | |
558 | } else { | |
559 | if (PageSwapCache(page) && | |
560 | !reuse_swap_page(page, NULL)) { | |
561 | unlock_page(page); | |
562 | result = SCAN_SWAP_CACHE_PAGE; | |
563 | goto out; | |
564 | } | |
565 | /* | |
566 | * Page is not in the swap cache. It can be collapsed | |
567 | * into a THP. | |
568 | */ | |
569 | } | |
570 | ||
571 | /* | |
572 | * Isolate the page to avoid collapsing an hugepage | |
573 | * currently in use by the VM. | |
574 | */ | |
575 | if (isolate_lru_page(page)) { | |
576 | unlock_page(page); | |
577 | result = SCAN_DEL_PAGE_LRU; | |
578 | goto out; | |
579 | } | |
d44d363f SL |
580 | inc_node_page_state(page, |
581 | NR_ISOLATED_ANON + page_is_file_cache(page)); | |
b46e756f KS |
582 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
583 | VM_BUG_ON_PAGE(PageLRU(page), page); | |
584 | ||
0db501f7 | 585 | /* There should be enough young pte to collapse the page */ |
b46e756f KS |
586 | if (pte_young(pteval) || |
587 | page_is_young(page) || PageReferenced(page) || | |
588 | mmu_notifier_test_young(vma->vm_mm, address)) | |
0db501f7 | 589 | referenced++; |
b46e756f KS |
590 | } |
591 | if (likely(writable)) { | |
592 | if (likely(referenced)) { | |
593 | result = SCAN_SUCCEED; | |
594 | trace_mm_collapse_huge_page_isolate(page, none_or_zero, | |
595 | referenced, writable, result); | |
596 | return 1; | |
597 | } | |
598 | } else { | |
599 | result = SCAN_PAGE_RO; | |
600 | } | |
601 | ||
602 | out: | |
603 | release_pte_pages(pte, _pte); | |
604 | trace_mm_collapse_huge_page_isolate(page, none_or_zero, | |
605 | referenced, writable, result); | |
606 | return 0; | |
607 | } | |
608 | ||
609 | static void __collapse_huge_page_copy(pte_t *pte, struct page *page, | |
610 | struct vm_area_struct *vma, | |
611 | unsigned long address, | |
612 | spinlock_t *ptl) | |
613 | { | |
614 | pte_t *_pte; | |
338a16ba DR |
615 | for (_pte = pte; _pte < pte + HPAGE_PMD_NR; |
616 | _pte++, page++, address += PAGE_SIZE) { | |
b46e756f KS |
617 | pte_t pteval = *_pte; |
618 | struct page *src_page; | |
619 | ||
620 | if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { | |
621 | clear_user_highpage(page, address); | |
622 | add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); | |
623 | if (is_zero_pfn(pte_pfn(pteval))) { | |
624 | /* | |
625 | * ptl mostly unnecessary. | |
626 | */ | |
627 | spin_lock(ptl); | |
628 | /* | |
629 | * paravirt calls inside pte_clear here are | |
630 | * superfluous. | |
631 | */ | |
632 | pte_clear(vma->vm_mm, address, _pte); | |
633 | spin_unlock(ptl); | |
634 | } | |
635 | } else { | |
636 | src_page = pte_page(pteval); | |
637 | copy_user_highpage(page, src_page, address, vma); | |
638 | VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page); | |
639 | release_pte_page(src_page); | |
640 | /* | |
641 | * ptl mostly unnecessary, but preempt has to | |
642 | * be disabled to update the per-cpu stats | |
643 | * inside page_remove_rmap(). | |
644 | */ | |
645 | spin_lock(ptl); | |
646 | /* | |
647 | * paravirt calls inside pte_clear here are | |
648 | * superfluous. | |
649 | */ | |
650 | pte_clear(vma->vm_mm, address, _pte); | |
651 | page_remove_rmap(src_page, false); | |
652 | spin_unlock(ptl); | |
653 | free_page_and_swap_cache(src_page); | |
654 | } | |
b46e756f KS |
655 | } |
656 | } | |
657 | ||
658 | static void khugepaged_alloc_sleep(void) | |
659 | { | |
660 | DEFINE_WAIT(wait); | |
661 | ||
662 | add_wait_queue(&khugepaged_wait, &wait); | |
663 | freezable_schedule_timeout_interruptible( | |
664 | msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); | |
665 | remove_wait_queue(&khugepaged_wait, &wait); | |
666 | } | |
667 | ||
668 | static int khugepaged_node_load[MAX_NUMNODES]; | |
669 | ||
670 | static bool khugepaged_scan_abort(int nid) | |
671 | { | |
672 | int i; | |
673 | ||
674 | /* | |
a5f5f91d | 675 | * If node_reclaim_mode is disabled, then no extra effort is made to |
b46e756f KS |
676 | * allocate memory locally. |
677 | */ | |
a5f5f91d | 678 | if (!node_reclaim_mode) |
b46e756f KS |
679 | return false; |
680 | ||
681 | /* If there is a count for this node already, it must be acceptable */ | |
682 | if (khugepaged_node_load[nid]) | |
683 | return false; | |
684 | ||
685 | for (i = 0; i < MAX_NUMNODES; i++) { | |
686 | if (!khugepaged_node_load[i]) | |
687 | continue; | |
688 | if (node_distance(nid, i) > RECLAIM_DISTANCE) | |
689 | return true; | |
690 | } | |
691 | return false; | |
692 | } | |
693 | ||
694 | /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ | |
695 | static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) | |
696 | { | |
25160354 | 697 | return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT; |
b46e756f KS |
698 | } |
699 | ||
700 | #ifdef CONFIG_NUMA | |
701 | static int khugepaged_find_target_node(void) | |
702 | { | |
703 | static int last_khugepaged_target_node = NUMA_NO_NODE; | |
704 | int nid, target_node = 0, max_value = 0; | |
705 | ||
706 | /* find first node with max normal pages hit */ | |
707 | for (nid = 0; nid < MAX_NUMNODES; nid++) | |
708 | if (khugepaged_node_load[nid] > max_value) { | |
709 | max_value = khugepaged_node_load[nid]; | |
710 | target_node = nid; | |
711 | } | |
712 | ||
713 | /* do some balance if several nodes have the same hit record */ | |
714 | if (target_node <= last_khugepaged_target_node) | |
715 | for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; | |
716 | nid++) | |
717 | if (max_value == khugepaged_node_load[nid]) { | |
718 | target_node = nid; | |
719 | break; | |
720 | } | |
721 | ||
722 | last_khugepaged_target_node = target_node; | |
723 | return target_node; | |
724 | } | |
725 | ||
726 | static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) | |
727 | { | |
728 | if (IS_ERR(*hpage)) { | |
729 | if (!*wait) | |
730 | return false; | |
731 | ||
732 | *wait = false; | |
733 | *hpage = NULL; | |
734 | khugepaged_alloc_sleep(); | |
735 | } else if (*hpage) { | |
736 | put_page(*hpage); | |
737 | *hpage = NULL; | |
738 | } | |
739 | ||
740 | return true; | |
741 | } | |
742 | ||
743 | static struct page * | |
988ddb71 | 744 | khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) |
b46e756f KS |
745 | { |
746 | VM_BUG_ON_PAGE(*hpage, *hpage); | |
747 | ||
b46e756f KS |
748 | *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); |
749 | if (unlikely(!*hpage)) { | |
750 | count_vm_event(THP_COLLAPSE_ALLOC_FAILED); | |
751 | *hpage = ERR_PTR(-ENOMEM); | |
752 | return NULL; | |
753 | } | |
754 | ||
755 | prep_transhuge_page(*hpage); | |
756 | count_vm_event(THP_COLLAPSE_ALLOC); | |
757 | return *hpage; | |
758 | } | |
759 | #else | |
760 | static int khugepaged_find_target_node(void) | |
761 | { | |
762 | return 0; | |
763 | } | |
764 | ||
765 | static inline struct page *alloc_khugepaged_hugepage(void) | |
766 | { | |
767 | struct page *page; | |
768 | ||
769 | page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), | |
770 | HPAGE_PMD_ORDER); | |
771 | if (page) | |
772 | prep_transhuge_page(page); | |
773 | return page; | |
774 | } | |
775 | ||
776 | static struct page *khugepaged_alloc_hugepage(bool *wait) | |
777 | { | |
778 | struct page *hpage; | |
779 | ||
780 | do { | |
781 | hpage = alloc_khugepaged_hugepage(); | |
782 | if (!hpage) { | |
783 | count_vm_event(THP_COLLAPSE_ALLOC_FAILED); | |
784 | if (!*wait) | |
785 | return NULL; | |
786 | ||
787 | *wait = false; | |
788 | khugepaged_alloc_sleep(); | |
789 | } else | |
790 | count_vm_event(THP_COLLAPSE_ALLOC); | |
791 | } while (unlikely(!hpage) && likely(khugepaged_enabled())); | |
792 | ||
793 | return hpage; | |
794 | } | |
795 | ||
796 | static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) | |
797 | { | |
798 | if (!*hpage) | |
799 | *hpage = khugepaged_alloc_hugepage(wait); | |
800 | ||
801 | if (unlikely(!*hpage)) | |
802 | return false; | |
803 | ||
804 | return true; | |
805 | } | |
806 | ||
807 | static struct page * | |
988ddb71 | 808 | khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) |
b46e756f | 809 | { |
b46e756f KS |
810 | VM_BUG_ON(!*hpage); |
811 | ||
812 | return *hpage; | |
813 | } | |
814 | #endif | |
815 | ||
816 | static bool hugepage_vma_check(struct vm_area_struct *vma) | |
817 | { | |
818 | if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || | |
819 | (vma->vm_flags & VM_NOHUGEPAGE)) | |
820 | return false; | |
f3f0e1d2 | 821 | if (shmem_file(vma->vm_file)) { |
e496cf3d KS |
822 | if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) |
823 | return false; | |
f3f0e1d2 KS |
824 | return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, |
825 | HPAGE_PMD_NR); | |
826 | } | |
b46e756f KS |
827 | if (!vma->anon_vma || vma->vm_ops) |
828 | return false; | |
829 | if (is_vma_temporary_stack(vma)) | |
830 | return false; | |
831 | return !(vma->vm_flags & VM_NO_KHUGEPAGED); | |
832 | } | |
833 | ||
834 | /* | |
835 | * If mmap_sem temporarily dropped, revalidate vma | |
836 | * before taking mmap_sem. | |
837 | * Return 0 if succeeds, otherwise return none-zero | |
838 | * value (scan code). | |
839 | */ | |
840 | ||
c131f751 KS |
841 | static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, |
842 | struct vm_area_struct **vmap) | |
b46e756f KS |
843 | { |
844 | struct vm_area_struct *vma; | |
845 | unsigned long hstart, hend; | |
846 | ||
847 | if (unlikely(khugepaged_test_exit(mm))) | |
848 | return SCAN_ANY_PROCESS; | |
849 | ||
c131f751 | 850 | *vmap = vma = find_vma(mm, address); |
b46e756f KS |
851 | if (!vma) |
852 | return SCAN_VMA_NULL; | |
853 | ||
854 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; | |
855 | hend = vma->vm_end & HPAGE_PMD_MASK; | |
856 | if (address < hstart || address + HPAGE_PMD_SIZE > hend) | |
857 | return SCAN_ADDRESS_RANGE; | |
858 | if (!hugepage_vma_check(vma)) | |
859 | return SCAN_VMA_CHECK; | |
860 | return 0; | |
861 | } | |
862 | ||
863 | /* | |
864 | * Bring missing pages in from swap, to complete THP collapse. | |
865 | * Only done if khugepaged_scan_pmd believes it is worthwhile. | |
866 | * | |
867 | * Called and returns without pte mapped or spinlocks held, | |
868 | * but with mmap_sem held to protect against vma changes. | |
869 | */ | |
870 | ||
871 | static bool __collapse_huge_page_swapin(struct mm_struct *mm, | |
872 | struct vm_area_struct *vma, | |
0db501f7 EA |
873 | unsigned long address, pmd_t *pmd, |
874 | int referenced) | |
b46e756f | 875 | { |
b46e756f | 876 | int swapped_in = 0, ret = 0; |
82b0f8c3 | 877 | struct vm_fault vmf = { |
b46e756f KS |
878 | .vma = vma, |
879 | .address = address, | |
880 | .flags = FAULT_FLAG_ALLOW_RETRY, | |
881 | .pmd = pmd, | |
0721ec8b | 882 | .pgoff = linear_page_index(vma, address), |
b46e756f KS |
883 | }; |
884 | ||
982785c6 EA |
885 | /* we only decide to swapin, if there is enough young ptes */ |
886 | if (referenced < HPAGE_PMD_NR/2) { | |
887 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); | |
888 | return false; | |
889 | } | |
82b0f8c3 JK |
890 | vmf.pte = pte_offset_map(pmd, address); |
891 | for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; | |
892 | vmf.pte++, vmf.address += PAGE_SIZE) { | |
2994302b JK |
893 | vmf.orig_pte = *vmf.pte; |
894 | if (!is_swap_pte(vmf.orig_pte)) | |
b46e756f KS |
895 | continue; |
896 | swapped_in++; | |
2994302b | 897 | ret = do_swap_page(&vmf); |
0db501f7 | 898 | |
b46e756f KS |
899 | /* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */ |
900 | if (ret & VM_FAULT_RETRY) { | |
901 | down_read(&mm->mmap_sem); | |
82b0f8c3 | 902 | if (hugepage_vma_revalidate(mm, address, &vmf.vma)) { |
47f863ea | 903 | /* vma is no longer available, don't continue to swapin */ |
0db501f7 | 904 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
b46e756f | 905 | return false; |
47f863ea | 906 | } |
b46e756f | 907 | /* check if the pmd is still valid */ |
835152a2 SP |
908 | if (mm_find_pmd(mm, address) != pmd) { |
909 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); | |
b46e756f | 910 | return false; |
835152a2 | 911 | } |
b46e756f KS |
912 | } |
913 | if (ret & VM_FAULT_ERROR) { | |
0db501f7 | 914 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
b46e756f KS |
915 | return false; |
916 | } | |
917 | /* pte is unmapped now, we need to map it */ | |
82b0f8c3 | 918 | vmf.pte = pte_offset_map(pmd, vmf.address); |
b46e756f | 919 | } |
82b0f8c3 JK |
920 | vmf.pte--; |
921 | pte_unmap(vmf.pte); | |
0db501f7 | 922 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); |
b46e756f KS |
923 | return true; |
924 | } | |
925 | ||
926 | static void collapse_huge_page(struct mm_struct *mm, | |
927 | unsigned long address, | |
928 | struct page **hpage, | |
0db501f7 | 929 | int node, int referenced) |
b46e756f KS |
930 | { |
931 | pmd_t *pmd, _pmd; | |
932 | pte_t *pte; | |
933 | pgtable_t pgtable; | |
934 | struct page *new_page; | |
935 | spinlock_t *pmd_ptl, *pte_ptl; | |
936 | int isolated = 0, result = 0; | |
937 | struct mem_cgroup *memcg; | |
c131f751 | 938 | struct vm_area_struct *vma; |
b46e756f KS |
939 | unsigned long mmun_start; /* For mmu_notifiers */ |
940 | unsigned long mmun_end; /* For mmu_notifiers */ | |
941 | gfp_t gfp; | |
942 | ||
943 | VM_BUG_ON(address & ~HPAGE_PMD_MASK); | |
944 | ||
945 | /* Only allocate from the target node */ | |
41b6167e | 946 | gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; |
b46e756f | 947 | |
988ddb71 KS |
948 | /* |
949 | * Before allocating the hugepage, release the mmap_sem read lock. | |
950 | * The allocation can take potentially a long time if it involves | |
951 | * sync compaction, and we do not need to hold the mmap_sem during | |
952 | * that. We will recheck the vma after taking it again in write mode. | |
953 | */ | |
954 | up_read(&mm->mmap_sem); | |
955 | new_page = khugepaged_alloc_page(hpage, gfp, node); | |
b46e756f KS |
956 | if (!new_page) { |
957 | result = SCAN_ALLOC_HUGE_PAGE_FAIL; | |
958 | goto out_nolock; | |
959 | } | |
960 | ||
961 | if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { | |
962 | result = SCAN_CGROUP_CHARGE_FAIL; | |
963 | goto out_nolock; | |
964 | } | |
965 | ||
966 | down_read(&mm->mmap_sem); | |
c131f751 | 967 | result = hugepage_vma_revalidate(mm, address, &vma); |
b46e756f KS |
968 | if (result) { |
969 | mem_cgroup_cancel_charge(new_page, memcg, true); | |
970 | up_read(&mm->mmap_sem); | |
971 | goto out_nolock; | |
972 | } | |
973 | ||
974 | pmd = mm_find_pmd(mm, address); | |
975 | if (!pmd) { | |
976 | result = SCAN_PMD_NULL; | |
977 | mem_cgroup_cancel_charge(new_page, memcg, true); | |
978 | up_read(&mm->mmap_sem); | |
979 | goto out_nolock; | |
980 | } | |
981 | ||
982 | /* | |
983 | * __collapse_huge_page_swapin always returns with mmap_sem locked. | |
47f863ea | 984 | * If it fails, we release mmap_sem and jump out_nolock. |
b46e756f KS |
985 | * Continuing to collapse causes inconsistency. |
986 | */ | |
0db501f7 | 987 | if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) { |
b46e756f KS |
988 | mem_cgroup_cancel_charge(new_page, memcg, true); |
989 | up_read(&mm->mmap_sem); | |
990 | goto out_nolock; | |
991 | } | |
992 | ||
993 | up_read(&mm->mmap_sem); | |
994 | /* | |
995 | * Prevent all access to pagetables with the exception of | |
996 | * gup_fast later handled by the ptep_clear_flush and the VM | |
997 | * handled by the anon_vma lock + PG_lock. | |
998 | */ | |
999 | down_write(&mm->mmap_sem); | |
c131f751 | 1000 | result = hugepage_vma_revalidate(mm, address, &vma); |
b46e756f KS |
1001 | if (result) |
1002 | goto out; | |
1003 | /* check if the pmd is still valid */ | |
1004 | if (mm_find_pmd(mm, address) != pmd) | |
1005 | goto out; | |
1006 | ||
1007 | anon_vma_lock_write(vma->anon_vma); | |
1008 | ||
1009 | pte = pte_offset_map(pmd, address); | |
1010 | pte_ptl = pte_lockptr(mm, pmd); | |
1011 | ||
1012 | mmun_start = address; | |
1013 | mmun_end = address + HPAGE_PMD_SIZE; | |
1014 | mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); | |
1015 | pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ | |
1016 | /* | |
1017 | * After this gup_fast can't run anymore. This also removes | |
1018 | * any huge TLB entry from the CPU so we won't allow | |
1019 | * huge and small TLB entries for the same virtual address | |
1020 | * to avoid the risk of CPU bugs in that area. | |
1021 | */ | |
1022 | _pmd = pmdp_collapse_flush(vma, address, pmd); | |
1023 | spin_unlock(pmd_ptl); | |
1024 | mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); | |
1025 | ||
1026 | spin_lock(pte_ptl); | |
1027 | isolated = __collapse_huge_page_isolate(vma, address, pte); | |
1028 | spin_unlock(pte_ptl); | |
1029 | ||
1030 | if (unlikely(!isolated)) { | |
1031 | pte_unmap(pte); | |
1032 | spin_lock(pmd_ptl); | |
1033 | BUG_ON(!pmd_none(*pmd)); | |
1034 | /* | |
1035 | * We can only use set_pmd_at when establishing | |
1036 | * hugepmds and never for establishing regular pmds that | |
1037 | * points to regular pagetables. Use pmd_populate for that | |
1038 | */ | |
1039 | pmd_populate(mm, pmd, pmd_pgtable(_pmd)); | |
1040 | spin_unlock(pmd_ptl); | |
1041 | anon_vma_unlock_write(vma->anon_vma); | |
1042 | result = SCAN_FAIL; | |
1043 | goto out; | |
1044 | } | |
1045 | ||
1046 | /* | |
1047 | * All pages are isolated and locked so anon_vma rmap | |
1048 | * can't run anymore. | |
1049 | */ | |
1050 | anon_vma_unlock_write(vma->anon_vma); | |
1051 | ||
1052 | __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl); | |
1053 | pte_unmap(pte); | |
1054 | __SetPageUptodate(new_page); | |
1055 | pgtable = pmd_pgtable(_pmd); | |
1056 | ||
1057 | _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); | |
1058 | _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); | |
1059 | ||
1060 | /* | |
1061 | * spin_lock() below is not the equivalent of smp_wmb(), so | |
1062 | * this is needed to avoid the copy_huge_page writes to become | |
1063 | * visible after the set_pmd_at() write. | |
1064 | */ | |
1065 | smp_wmb(); | |
1066 | ||
1067 | spin_lock(pmd_ptl); | |
1068 | BUG_ON(!pmd_none(*pmd)); | |
1069 | page_add_new_anon_rmap(new_page, vma, address, true); | |
1070 | mem_cgroup_commit_charge(new_page, memcg, false, true); | |
1071 | lru_cache_add_active_or_unevictable(new_page, vma); | |
1072 | pgtable_trans_huge_deposit(mm, pmd, pgtable); | |
1073 | set_pmd_at(mm, address, pmd, _pmd); | |
1074 | update_mmu_cache_pmd(vma, address, pmd); | |
1075 | spin_unlock(pmd_ptl); | |
1076 | ||
1077 | *hpage = NULL; | |
1078 | ||
1079 | khugepaged_pages_collapsed++; | |
1080 | result = SCAN_SUCCEED; | |
1081 | out_up_write: | |
1082 | up_write(&mm->mmap_sem); | |
1083 | out_nolock: | |
1084 | trace_mm_collapse_huge_page(mm, isolated, result); | |
1085 | return; | |
1086 | out: | |
1087 | mem_cgroup_cancel_charge(new_page, memcg, true); | |
1088 | goto out_up_write; | |
1089 | } | |
1090 | ||
1091 | static int khugepaged_scan_pmd(struct mm_struct *mm, | |
1092 | struct vm_area_struct *vma, | |
1093 | unsigned long address, | |
1094 | struct page **hpage) | |
1095 | { | |
1096 | pmd_t *pmd; | |
1097 | pte_t *pte, *_pte; | |
0db501f7 | 1098 | int ret = 0, none_or_zero = 0, result = 0, referenced = 0; |
b46e756f KS |
1099 | struct page *page = NULL; |
1100 | unsigned long _address; | |
1101 | spinlock_t *ptl; | |
1102 | int node = NUMA_NO_NODE, unmapped = 0; | |
0db501f7 | 1103 | bool writable = false; |
b46e756f KS |
1104 | |
1105 | VM_BUG_ON(address & ~HPAGE_PMD_MASK); | |
1106 | ||
1107 | pmd = mm_find_pmd(mm, address); | |
1108 | if (!pmd) { | |
1109 | result = SCAN_PMD_NULL; | |
1110 | goto out; | |
1111 | } | |
1112 | ||
1113 | memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); | |
1114 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); | |
1115 | for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; | |
1116 | _pte++, _address += PAGE_SIZE) { | |
1117 | pte_t pteval = *_pte; | |
1118 | if (is_swap_pte(pteval)) { | |
1119 | if (++unmapped <= khugepaged_max_ptes_swap) { | |
1120 | continue; | |
1121 | } else { | |
1122 | result = SCAN_EXCEED_SWAP_PTE; | |
1123 | goto out_unmap; | |
1124 | } | |
1125 | } | |
1126 | if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { | |
1127 | if (!userfaultfd_armed(vma) && | |
1128 | ++none_or_zero <= khugepaged_max_ptes_none) { | |
1129 | continue; | |
1130 | } else { | |
1131 | result = SCAN_EXCEED_NONE_PTE; | |
1132 | goto out_unmap; | |
1133 | } | |
1134 | } | |
1135 | if (!pte_present(pteval)) { | |
1136 | result = SCAN_PTE_NON_PRESENT; | |
1137 | goto out_unmap; | |
1138 | } | |
1139 | if (pte_write(pteval)) | |
1140 | writable = true; | |
1141 | ||
1142 | page = vm_normal_page(vma, _address, pteval); | |
1143 | if (unlikely(!page)) { | |
1144 | result = SCAN_PAGE_NULL; | |
1145 | goto out_unmap; | |
1146 | } | |
1147 | ||
1148 | /* TODO: teach khugepaged to collapse THP mapped with pte */ | |
1149 | if (PageCompound(page)) { | |
1150 | result = SCAN_PAGE_COMPOUND; | |
1151 | goto out_unmap; | |
1152 | } | |
1153 | ||
1154 | /* | |
1155 | * Record which node the original page is from and save this | |
1156 | * information to khugepaged_node_load[]. | |
1157 | * Khupaged will allocate hugepage from the node has the max | |
1158 | * hit record. | |
1159 | */ | |
1160 | node = page_to_nid(page); | |
1161 | if (khugepaged_scan_abort(node)) { | |
1162 | result = SCAN_SCAN_ABORT; | |
1163 | goto out_unmap; | |
1164 | } | |
1165 | khugepaged_node_load[node]++; | |
1166 | if (!PageLRU(page)) { | |
1167 | result = SCAN_PAGE_LRU; | |
1168 | goto out_unmap; | |
1169 | } | |
1170 | if (PageLocked(page)) { | |
1171 | result = SCAN_PAGE_LOCK; | |
1172 | goto out_unmap; | |
1173 | } | |
1174 | if (!PageAnon(page)) { | |
1175 | result = SCAN_PAGE_ANON; | |
1176 | goto out_unmap; | |
1177 | } | |
1178 | ||
1179 | /* | |
1180 | * cannot use mapcount: can't collapse if there's a gup pin. | |
1181 | * The page must only be referenced by the scanned process | |
1182 | * and page swap cache. | |
1183 | */ | |
2948be5a | 1184 | if (page_count(page) != 1 + PageSwapCache(page)) { |
b46e756f KS |
1185 | result = SCAN_PAGE_COUNT; |
1186 | goto out_unmap; | |
1187 | } | |
1188 | if (pte_young(pteval) || | |
1189 | page_is_young(page) || PageReferenced(page) || | |
1190 | mmu_notifier_test_young(vma->vm_mm, address)) | |
0db501f7 | 1191 | referenced++; |
b46e756f KS |
1192 | } |
1193 | if (writable) { | |
1194 | if (referenced) { | |
1195 | result = SCAN_SUCCEED; | |
1196 | ret = 1; | |
1197 | } else { | |
0db501f7 | 1198 | result = SCAN_LACK_REFERENCED_PAGE; |
b46e756f KS |
1199 | } |
1200 | } else { | |
1201 | result = SCAN_PAGE_RO; | |
1202 | } | |
1203 | out_unmap: | |
1204 | pte_unmap_unlock(pte, ptl); | |
1205 | if (ret) { | |
1206 | node = khugepaged_find_target_node(); | |
1207 | /* collapse_huge_page will return with the mmap_sem released */ | |
c131f751 | 1208 | collapse_huge_page(mm, address, hpage, node, referenced); |
b46e756f KS |
1209 | } |
1210 | out: | |
1211 | trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, | |
1212 | none_or_zero, result, unmapped); | |
1213 | return ret; | |
1214 | } | |
1215 | ||
1216 | static void collect_mm_slot(struct mm_slot *mm_slot) | |
1217 | { | |
1218 | struct mm_struct *mm = mm_slot->mm; | |
1219 | ||
1220 | VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); | |
1221 | ||
1222 | if (khugepaged_test_exit(mm)) { | |
1223 | /* free mm_slot */ | |
1224 | hash_del(&mm_slot->hash); | |
1225 | list_del(&mm_slot->mm_node); | |
1226 | ||
1227 | /* | |
1228 | * Not strictly needed because the mm exited already. | |
1229 | * | |
1230 | * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); | |
1231 | */ | |
1232 | ||
1233 | /* khugepaged_mm_lock actually not necessary for the below */ | |
1234 | free_mm_slot(mm_slot); | |
1235 | mmdrop(mm); | |
1236 | } | |
1237 | } | |
1238 | ||
e496cf3d | 1239 | #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) |
f3f0e1d2 KS |
1240 | static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) |
1241 | { | |
1242 | struct vm_area_struct *vma; | |
1243 | unsigned long addr; | |
1244 | pmd_t *pmd, _pmd; | |
1245 | ||
1246 | i_mmap_lock_write(mapping); | |
1247 | vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { | |
1248 | /* probably overkill */ | |
1249 | if (vma->anon_vma) | |
1250 | continue; | |
1251 | addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); | |
1252 | if (addr & ~HPAGE_PMD_MASK) | |
1253 | continue; | |
1254 | if (vma->vm_end < addr + HPAGE_PMD_SIZE) | |
1255 | continue; | |
1256 | pmd = mm_find_pmd(vma->vm_mm, addr); | |
1257 | if (!pmd) | |
1258 | continue; | |
1259 | /* | |
1260 | * We need exclusive mmap_sem to retract page table. | |
1261 | * If trylock fails we would end up with pte-mapped THP after | |
1262 | * re-fault. Not ideal, but it's more important to not disturb | |
1263 | * the system too much. | |
1264 | */ | |
1265 | if (down_write_trylock(&vma->vm_mm->mmap_sem)) { | |
1266 | spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd); | |
1267 | /* assume page table is clear */ | |
1268 | _pmd = pmdp_collapse_flush(vma, addr, pmd); | |
1269 | spin_unlock(ptl); | |
1270 | up_write(&vma->vm_mm->mmap_sem); | |
d670ffd8 AK |
1271 | atomic_long_dec(&vma->vm_mm->nr_ptes); |
1272 | pte_free(vma->vm_mm, pmd_pgtable(_pmd)); | |
f3f0e1d2 KS |
1273 | } |
1274 | } | |
1275 | i_mmap_unlock_write(mapping); | |
1276 | } | |
1277 | ||
1278 | /** | |
1279 | * collapse_shmem - collapse small tmpfs/shmem pages into huge one. | |
1280 | * | |
1281 | * Basic scheme is simple, details are more complex: | |
1282 | * - allocate and freeze a new huge page; | |
1283 | * - scan over radix tree replacing old pages the new one | |
1284 | * + swap in pages if necessary; | |
1285 | * + fill in gaps; | |
1286 | * + keep old pages around in case if rollback is required; | |
1287 | * - if replacing succeed: | |
1288 | * + copy data over; | |
1289 | * + free old pages; | |
1290 | * + unfreeze huge page; | |
1291 | * - if replacing failed; | |
1292 | * + put all pages back and unfreeze them; | |
1293 | * + restore gaps in the radix-tree; | |
1294 | * + free huge page; | |
1295 | */ | |
1296 | static void collapse_shmem(struct mm_struct *mm, | |
1297 | struct address_space *mapping, pgoff_t start, | |
1298 | struct page **hpage, int node) | |
1299 | { | |
1300 | gfp_t gfp; | |
1301 | struct page *page, *new_page, *tmp; | |
1302 | struct mem_cgroup *memcg; | |
1303 | pgoff_t index, end = start + HPAGE_PMD_NR; | |
1304 | LIST_HEAD(pagelist); | |
1305 | struct radix_tree_iter iter; | |
1306 | void **slot; | |
1307 | int nr_none = 0, result = SCAN_SUCCEED; | |
1308 | ||
1309 | VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); | |
1310 | ||
1311 | /* Only allocate from the target node */ | |
41b6167e | 1312 | gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; |
f3f0e1d2 KS |
1313 | |
1314 | new_page = khugepaged_alloc_page(hpage, gfp, node); | |
1315 | if (!new_page) { | |
1316 | result = SCAN_ALLOC_HUGE_PAGE_FAIL; | |
1317 | goto out; | |
1318 | } | |
1319 | ||
1320 | if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) { | |
1321 | result = SCAN_CGROUP_CHARGE_FAIL; | |
1322 | goto out; | |
1323 | } | |
1324 | ||
1325 | new_page->index = start; | |
1326 | new_page->mapping = mapping; | |
1327 | __SetPageSwapBacked(new_page); | |
1328 | __SetPageLocked(new_page); | |
1329 | BUG_ON(!page_ref_freeze(new_page, 1)); | |
1330 | ||
1331 | ||
1332 | /* | |
1333 | * At this point the new_page is 'frozen' (page_count() is zero), locked | |
1334 | * and not up-to-date. It's safe to insert it into radix tree, because | |
1335 | * nobody would be able to map it or use it in other way until we | |
1336 | * unfreeze it. | |
1337 | */ | |
1338 | ||
1339 | index = start; | |
1340 | spin_lock_irq(&mapping->tree_lock); | |
1341 | radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { | |
1342 | int n = min(iter.index, end) - index; | |
1343 | ||
1344 | /* | |
1345 | * Handle holes in the radix tree: charge it from shmem and | |
1346 | * insert relevant subpage of new_page into the radix-tree. | |
1347 | */ | |
1348 | if (n && !shmem_charge(mapping->host, n)) { | |
1349 | result = SCAN_FAIL; | |
1350 | break; | |
1351 | } | |
1352 | nr_none += n; | |
1353 | for (; index < min(iter.index, end); index++) { | |
1354 | radix_tree_insert(&mapping->page_tree, index, | |
1355 | new_page + (index % HPAGE_PMD_NR)); | |
1356 | } | |
1357 | ||
1358 | /* We are done. */ | |
1359 | if (index >= end) | |
1360 | break; | |
1361 | ||
1362 | page = radix_tree_deref_slot_protected(slot, | |
1363 | &mapping->tree_lock); | |
1364 | if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) { | |
1365 | spin_unlock_irq(&mapping->tree_lock); | |
1366 | /* swap in or instantiate fallocated page */ | |
1367 | if (shmem_getpage(mapping->host, index, &page, | |
1368 | SGP_NOHUGE)) { | |
1369 | result = SCAN_FAIL; | |
1370 | goto tree_unlocked; | |
1371 | } | |
1372 | spin_lock_irq(&mapping->tree_lock); | |
1373 | } else if (trylock_page(page)) { | |
1374 | get_page(page); | |
1375 | } else { | |
1376 | result = SCAN_PAGE_LOCK; | |
1377 | break; | |
1378 | } | |
1379 | ||
1380 | /* | |
1381 | * The page must be locked, so we can drop the tree_lock | |
1382 | * without racing with truncate. | |
1383 | */ | |
1384 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
1385 | VM_BUG_ON_PAGE(!PageUptodate(page), page); | |
1386 | VM_BUG_ON_PAGE(PageTransCompound(page), page); | |
1387 | ||
1388 | if (page_mapping(page) != mapping) { | |
1389 | result = SCAN_TRUNCATED; | |
1390 | goto out_unlock; | |
1391 | } | |
1392 | spin_unlock_irq(&mapping->tree_lock); | |
1393 | ||
1394 | if (isolate_lru_page(page)) { | |
1395 | result = SCAN_DEL_PAGE_LRU; | |
1396 | goto out_isolate_failed; | |
1397 | } | |
1398 | ||
1399 | if (page_mapped(page)) | |
1400 | unmap_mapping_range(mapping, index << PAGE_SHIFT, | |
1401 | PAGE_SIZE, 0); | |
1402 | ||
1403 | spin_lock_irq(&mapping->tree_lock); | |
1404 | ||
91a45f71 JW |
1405 | slot = radix_tree_lookup_slot(&mapping->page_tree, index); |
1406 | VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot, | |
1407 | &mapping->tree_lock), page); | |
f3f0e1d2 KS |
1408 | VM_BUG_ON_PAGE(page_mapped(page), page); |
1409 | ||
1410 | /* | |
1411 | * The page is expected to have page_count() == 3: | |
1412 | * - we hold a pin on it; | |
1413 | * - one reference from radix tree; | |
1414 | * - one from isolate_lru_page; | |
1415 | */ | |
1416 | if (!page_ref_freeze(page, 3)) { | |
1417 | result = SCAN_PAGE_COUNT; | |
1418 | goto out_lru; | |
1419 | } | |
1420 | ||
1421 | /* | |
1422 | * Add the page to the list to be able to undo the collapse if | |
1423 | * something go wrong. | |
1424 | */ | |
1425 | list_add_tail(&page->lru, &pagelist); | |
1426 | ||
1427 | /* Finally, replace with the new page. */ | |
6d75f366 | 1428 | radix_tree_replace_slot(&mapping->page_tree, slot, |
f3f0e1d2 KS |
1429 | new_page + (index % HPAGE_PMD_NR)); |
1430 | ||
148deab2 | 1431 | slot = radix_tree_iter_resume(slot, &iter); |
f3f0e1d2 KS |
1432 | index++; |
1433 | continue; | |
1434 | out_lru: | |
1435 | spin_unlock_irq(&mapping->tree_lock); | |
1436 | putback_lru_page(page); | |
1437 | out_isolate_failed: | |
1438 | unlock_page(page); | |
1439 | put_page(page); | |
1440 | goto tree_unlocked; | |
1441 | out_unlock: | |
1442 | unlock_page(page); | |
1443 | put_page(page); | |
1444 | break; | |
1445 | } | |
1446 | ||
1447 | /* | |
1448 | * Handle hole in radix tree at the end of the range. | |
1449 | * This code only triggers if there's nothing in radix tree | |
1450 | * beyond 'end'. | |
1451 | */ | |
1452 | if (result == SCAN_SUCCEED && index < end) { | |
1453 | int n = end - index; | |
1454 | ||
1455 | if (!shmem_charge(mapping->host, n)) { | |
1456 | result = SCAN_FAIL; | |
1457 | goto tree_locked; | |
1458 | } | |
1459 | ||
1460 | for (; index < end; index++) { | |
1461 | radix_tree_insert(&mapping->page_tree, index, | |
1462 | new_page + (index % HPAGE_PMD_NR)); | |
1463 | } | |
1464 | nr_none += n; | |
1465 | } | |
1466 | ||
1467 | tree_locked: | |
1468 | spin_unlock_irq(&mapping->tree_lock); | |
1469 | tree_unlocked: | |
1470 | ||
1471 | if (result == SCAN_SUCCEED) { | |
1472 | unsigned long flags; | |
1473 | struct zone *zone = page_zone(new_page); | |
1474 | ||
1475 | /* | |
1476 | * Replacing old pages with new one has succeed, now we need to | |
1477 | * copy the content and free old pages. | |
1478 | */ | |
1479 | list_for_each_entry_safe(page, tmp, &pagelist, lru) { | |
1480 | copy_highpage(new_page + (page->index % HPAGE_PMD_NR), | |
1481 | page); | |
1482 | list_del(&page->lru); | |
1483 | unlock_page(page); | |
1484 | page_ref_unfreeze(page, 1); | |
1485 | page->mapping = NULL; | |
1486 | ClearPageActive(page); | |
1487 | ClearPageUnevictable(page); | |
1488 | put_page(page); | |
1489 | } | |
1490 | ||
1491 | local_irq_save(flags); | |
11fb9989 | 1492 | __inc_node_page_state(new_page, NR_SHMEM_THPS); |
f3f0e1d2 | 1493 | if (nr_none) { |
11fb9989 MG |
1494 | __mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none); |
1495 | __mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none); | |
f3f0e1d2 KS |
1496 | } |
1497 | local_irq_restore(flags); | |
1498 | ||
1499 | /* | |
1500 | * Remove pte page tables, so we can re-faulti | |
1501 | * the page as huge. | |
1502 | */ | |
1503 | retract_page_tables(mapping, start); | |
1504 | ||
1505 | /* Everything is ready, let's unfreeze the new_page */ | |
1506 | set_page_dirty(new_page); | |
1507 | SetPageUptodate(new_page); | |
1508 | page_ref_unfreeze(new_page, HPAGE_PMD_NR); | |
1509 | mem_cgroup_commit_charge(new_page, memcg, false, true); | |
1510 | lru_cache_add_anon(new_page); | |
1511 | unlock_page(new_page); | |
1512 | ||
1513 | *hpage = NULL; | |
1514 | } else { | |
1515 | /* Something went wrong: rollback changes to the radix-tree */ | |
1516 | shmem_uncharge(mapping->host, nr_none); | |
1517 | spin_lock_irq(&mapping->tree_lock); | |
1518 | radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, | |
1519 | start) { | |
1520 | if (iter.index >= end) | |
1521 | break; | |
1522 | page = list_first_entry_or_null(&pagelist, | |
1523 | struct page, lru); | |
1524 | if (!page || iter.index < page->index) { | |
1525 | if (!nr_none) | |
1526 | break; | |
f3f0e1d2 | 1527 | nr_none--; |
59749e6c JW |
1528 | /* Put holes back where they were */ |
1529 | radix_tree_delete(&mapping->page_tree, | |
1530 | iter.index); | |
f3f0e1d2 KS |
1531 | continue; |
1532 | } | |
1533 | ||
1534 | VM_BUG_ON_PAGE(page->index != iter.index, page); | |
1535 | ||
1536 | /* Unfreeze the page. */ | |
1537 | list_del(&page->lru); | |
1538 | page_ref_unfreeze(page, 2); | |
6d75f366 JW |
1539 | radix_tree_replace_slot(&mapping->page_tree, |
1540 | slot, page); | |
148deab2 | 1541 | slot = radix_tree_iter_resume(slot, &iter); |
f3f0e1d2 KS |
1542 | spin_unlock_irq(&mapping->tree_lock); |
1543 | putback_lru_page(page); | |
1544 | unlock_page(page); | |
1545 | spin_lock_irq(&mapping->tree_lock); | |
1546 | } | |
1547 | VM_BUG_ON(nr_none); | |
1548 | spin_unlock_irq(&mapping->tree_lock); | |
1549 | ||
1550 | /* Unfreeze new_page, caller would take care about freeing it */ | |
1551 | page_ref_unfreeze(new_page, 1); | |
1552 | mem_cgroup_cancel_charge(new_page, memcg, true); | |
1553 | unlock_page(new_page); | |
1554 | new_page->mapping = NULL; | |
1555 | } | |
1556 | out: | |
1557 | VM_BUG_ON(!list_empty(&pagelist)); | |
1558 | /* TODO: tracepoints */ | |
1559 | } | |
1560 | ||
1561 | static void khugepaged_scan_shmem(struct mm_struct *mm, | |
1562 | struct address_space *mapping, | |
1563 | pgoff_t start, struct page **hpage) | |
1564 | { | |
1565 | struct page *page = NULL; | |
1566 | struct radix_tree_iter iter; | |
1567 | void **slot; | |
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 | radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { | |
1577 | if (iter.index >= start + HPAGE_PMD_NR) | |
1578 | break; | |
1579 | ||
1580 | page = radix_tree_deref_slot(slot); | |
1581 | if (radix_tree_deref_retry(page)) { | |
1582 | slot = radix_tree_iter_retry(&iter); | |
1583 | continue; | |
1584 | } | |
1585 | ||
1586 | if (radix_tree_exception(page)) { | |
1587 | if (++swap > khugepaged_max_ptes_swap) { | |
1588 | result = SCAN_EXCEED_SWAP_PTE; | |
1589 | break; | |
1590 | } | |
1591 | continue; | |
1592 | } | |
1593 | ||
1594 | if (PageTransCompound(page)) { | |
1595 | result = SCAN_PAGE_COMPOUND; | |
1596 | break; | |
1597 | } | |
1598 | ||
1599 | node = page_to_nid(page); | |
1600 | if (khugepaged_scan_abort(node)) { | |
1601 | result = SCAN_SCAN_ABORT; | |
1602 | break; | |
1603 | } | |
1604 | khugepaged_node_load[node]++; | |
1605 | ||
1606 | if (!PageLRU(page)) { | |
1607 | result = SCAN_PAGE_LRU; | |
1608 | break; | |
1609 | } | |
1610 | ||
1611 | if (page_count(page) != 1 + page_mapcount(page)) { | |
1612 | result = SCAN_PAGE_COUNT; | |
1613 | break; | |
1614 | } | |
1615 | ||
1616 | /* | |
1617 | * We probably should check if the page is referenced here, but | |
1618 | * nobody would transfer pte_young() to PageReferenced() for us. | |
1619 | * And rmap walk here is just too costly... | |
1620 | */ | |
1621 | ||
1622 | present++; | |
1623 | ||
1624 | if (need_resched()) { | |
148deab2 | 1625 | slot = radix_tree_iter_resume(slot, &iter); |
f3f0e1d2 | 1626 | cond_resched_rcu(); |
f3f0e1d2 KS |
1627 | } |
1628 | } | |
1629 | rcu_read_unlock(); | |
1630 | ||
1631 | if (result == SCAN_SUCCEED) { | |
1632 | if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { | |
1633 | result = SCAN_EXCEED_NONE_PTE; | |
1634 | } else { | |
1635 | node = khugepaged_find_target_node(); | |
1636 | collapse_shmem(mm, mapping, start, hpage, node); | |
1637 | } | |
1638 | } | |
1639 | ||
1640 | /* TODO: tracepoints */ | |
1641 | } | |
1642 | #else | |
1643 | static void khugepaged_scan_shmem(struct mm_struct *mm, | |
1644 | struct address_space *mapping, | |
1645 | pgoff_t start, struct page **hpage) | |
1646 | { | |
1647 | BUILD_BUG(); | |
1648 | } | |
1649 | #endif | |
1650 | ||
b46e756f KS |
1651 | static unsigned int khugepaged_scan_mm_slot(unsigned int pages, |
1652 | struct page **hpage) | |
1653 | __releases(&khugepaged_mm_lock) | |
1654 | __acquires(&khugepaged_mm_lock) | |
1655 | { | |
1656 | struct mm_slot *mm_slot; | |
1657 | struct mm_struct *mm; | |
1658 | struct vm_area_struct *vma; | |
1659 | int progress = 0; | |
1660 | ||
1661 | VM_BUG_ON(!pages); | |
1662 | VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock)); | |
1663 | ||
1664 | if (khugepaged_scan.mm_slot) | |
1665 | mm_slot = khugepaged_scan.mm_slot; | |
1666 | else { | |
1667 | mm_slot = list_entry(khugepaged_scan.mm_head.next, | |
1668 | struct mm_slot, mm_node); | |
1669 | khugepaged_scan.address = 0; | |
1670 | khugepaged_scan.mm_slot = mm_slot; | |
1671 | } | |
1672 | spin_unlock(&khugepaged_mm_lock); | |
1673 | ||
1674 | mm = mm_slot->mm; | |
1675 | down_read(&mm->mmap_sem); | |
1676 | if (unlikely(khugepaged_test_exit(mm))) | |
1677 | vma = NULL; | |
1678 | else | |
1679 | vma = find_vma(mm, khugepaged_scan.address); | |
1680 | ||
1681 | progress++; | |
1682 | for (; vma; vma = vma->vm_next) { | |
1683 | unsigned long hstart, hend; | |
1684 | ||
1685 | cond_resched(); | |
1686 | if (unlikely(khugepaged_test_exit(mm))) { | |
1687 | progress++; | |
1688 | break; | |
1689 | } | |
1690 | if (!hugepage_vma_check(vma)) { | |
1691 | skip: | |
1692 | progress++; | |
1693 | continue; | |
1694 | } | |
1695 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; | |
1696 | hend = vma->vm_end & HPAGE_PMD_MASK; | |
1697 | if (hstart >= hend) | |
1698 | goto skip; | |
1699 | if (khugepaged_scan.address > hend) | |
1700 | goto skip; | |
1701 | if (khugepaged_scan.address < hstart) | |
1702 | khugepaged_scan.address = hstart; | |
1703 | VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); | |
1704 | ||
1705 | while (khugepaged_scan.address < hend) { | |
1706 | int ret; | |
1707 | cond_resched(); | |
1708 | if (unlikely(khugepaged_test_exit(mm))) | |
1709 | goto breakouterloop; | |
1710 | ||
1711 | VM_BUG_ON(khugepaged_scan.address < hstart || | |
1712 | khugepaged_scan.address + HPAGE_PMD_SIZE > | |
1713 | hend); | |
f3f0e1d2 | 1714 | if (shmem_file(vma->vm_file)) { |
e496cf3d | 1715 | struct file *file; |
f3f0e1d2 KS |
1716 | pgoff_t pgoff = linear_page_index(vma, |
1717 | khugepaged_scan.address); | |
e496cf3d KS |
1718 | if (!shmem_huge_enabled(vma)) |
1719 | goto skip; | |
1720 | file = get_file(vma->vm_file); | |
f3f0e1d2 KS |
1721 | up_read(&mm->mmap_sem); |
1722 | ret = 1; | |
1723 | khugepaged_scan_shmem(mm, file->f_mapping, | |
1724 | pgoff, hpage); | |
1725 | fput(file); | |
1726 | } else { | |
1727 | ret = khugepaged_scan_pmd(mm, vma, | |
1728 | khugepaged_scan.address, | |
1729 | hpage); | |
1730 | } | |
b46e756f KS |
1731 | /* move to next address */ |
1732 | khugepaged_scan.address += HPAGE_PMD_SIZE; | |
1733 | progress += HPAGE_PMD_NR; | |
1734 | if (ret) | |
1735 | /* we released mmap_sem so break loop */ | |
1736 | goto breakouterloop_mmap_sem; | |
1737 | if (progress >= pages) | |
1738 | goto breakouterloop; | |
1739 | } | |
1740 | } | |
1741 | breakouterloop: | |
1742 | up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */ | |
1743 | breakouterloop_mmap_sem: | |
1744 | ||
1745 | spin_lock(&khugepaged_mm_lock); | |
1746 | VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); | |
1747 | /* | |
1748 | * Release the current mm_slot if this mm is about to die, or | |
1749 | * if we scanned all vmas of this mm. | |
1750 | */ | |
1751 | if (khugepaged_test_exit(mm) || !vma) { | |
1752 | /* | |
1753 | * Make sure that if mm_users is reaching zero while | |
1754 | * khugepaged runs here, khugepaged_exit will find | |
1755 | * mm_slot not pointing to the exiting mm. | |
1756 | */ | |
1757 | if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { | |
1758 | khugepaged_scan.mm_slot = list_entry( | |
1759 | mm_slot->mm_node.next, | |
1760 | struct mm_slot, mm_node); | |
1761 | khugepaged_scan.address = 0; | |
1762 | } else { | |
1763 | khugepaged_scan.mm_slot = NULL; | |
1764 | khugepaged_full_scans++; | |
1765 | } | |
1766 | ||
1767 | collect_mm_slot(mm_slot); | |
1768 | } | |
1769 | ||
1770 | return progress; | |
1771 | } | |
1772 | ||
1773 | static int khugepaged_has_work(void) | |
1774 | { | |
1775 | return !list_empty(&khugepaged_scan.mm_head) && | |
1776 | khugepaged_enabled(); | |
1777 | } | |
1778 | ||
1779 | static int khugepaged_wait_event(void) | |
1780 | { | |
1781 | return !list_empty(&khugepaged_scan.mm_head) || | |
1782 | kthread_should_stop(); | |
1783 | } | |
1784 | ||
1785 | static void khugepaged_do_scan(void) | |
1786 | { | |
1787 | struct page *hpage = NULL; | |
1788 | unsigned int progress = 0, pass_through_head = 0; | |
1789 | unsigned int pages = khugepaged_pages_to_scan; | |
1790 | bool wait = true; | |
1791 | ||
1792 | barrier(); /* write khugepaged_pages_to_scan to local stack */ | |
1793 | ||
1794 | while (progress < pages) { | |
1795 | if (!khugepaged_prealloc_page(&hpage, &wait)) | |
1796 | break; | |
1797 | ||
1798 | cond_resched(); | |
1799 | ||
1800 | if (unlikely(kthread_should_stop() || try_to_freeze())) | |
1801 | break; | |
1802 | ||
1803 | spin_lock(&khugepaged_mm_lock); | |
1804 | if (!khugepaged_scan.mm_slot) | |
1805 | pass_through_head++; | |
1806 | if (khugepaged_has_work() && | |
1807 | pass_through_head < 2) | |
1808 | progress += khugepaged_scan_mm_slot(pages - progress, | |
1809 | &hpage); | |
1810 | else | |
1811 | progress = pages; | |
1812 | spin_unlock(&khugepaged_mm_lock); | |
1813 | } | |
1814 | ||
1815 | if (!IS_ERR_OR_NULL(hpage)) | |
1816 | put_page(hpage); | |
1817 | } | |
1818 | ||
1819 | static bool khugepaged_should_wakeup(void) | |
1820 | { | |
1821 | return kthread_should_stop() || | |
1822 | time_after_eq(jiffies, khugepaged_sleep_expire); | |
1823 | } | |
1824 | ||
1825 | static void khugepaged_wait_work(void) | |
1826 | { | |
1827 | if (khugepaged_has_work()) { | |
1828 | const unsigned long scan_sleep_jiffies = | |
1829 | msecs_to_jiffies(khugepaged_scan_sleep_millisecs); | |
1830 | ||
1831 | if (!scan_sleep_jiffies) | |
1832 | return; | |
1833 | ||
1834 | khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; | |
1835 | wait_event_freezable_timeout(khugepaged_wait, | |
1836 | khugepaged_should_wakeup(), | |
1837 | scan_sleep_jiffies); | |
1838 | return; | |
1839 | } | |
1840 | ||
1841 | if (khugepaged_enabled()) | |
1842 | wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); | |
1843 | } | |
1844 | ||
1845 | static int khugepaged(void *none) | |
1846 | { | |
1847 | struct mm_slot *mm_slot; | |
1848 | ||
1849 | set_freezable(); | |
1850 | set_user_nice(current, MAX_NICE); | |
1851 | ||
1852 | while (!kthread_should_stop()) { | |
1853 | khugepaged_do_scan(); | |
1854 | khugepaged_wait_work(); | |
1855 | } | |
1856 | ||
1857 | spin_lock(&khugepaged_mm_lock); | |
1858 | mm_slot = khugepaged_scan.mm_slot; | |
1859 | khugepaged_scan.mm_slot = NULL; | |
1860 | if (mm_slot) | |
1861 | collect_mm_slot(mm_slot); | |
1862 | spin_unlock(&khugepaged_mm_lock); | |
1863 | return 0; | |
1864 | } | |
1865 | ||
1866 | static void set_recommended_min_free_kbytes(void) | |
1867 | { | |
1868 | struct zone *zone; | |
1869 | int nr_zones = 0; | |
1870 | unsigned long recommended_min; | |
1871 | ||
1872 | for_each_populated_zone(zone) | |
1873 | nr_zones++; | |
1874 | ||
1875 | /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ | |
1876 | recommended_min = pageblock_nr_pages * nr_zones * 2; | |
1877 | ||
1878 | /* | |
1879 | * Make sure that on average at least two pageblocks are almost free | |
1880 | * of another type, one for a migratetype to fall back to and a | |
1881 | * second to avoid subsequent fallbacks of other types There are 3 | |
1882 | * MIGRATE_TYPES we care about. | |
1883 | */ | |
1884 | recommended_min += pageblock_nr_pages * nr_zones * | |
1885 | MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; | |
1886 | ||
1887 | /* don't ever allow to reserve more than 5% of the lowmem */ | |
1888 | recommended_min = min(recommended_min, | |
1889 | (unsigned long) nr_free_buffer_pages() / 20); | |
1890 | recommended_min <<= (PAGE_SHIFT-10); | |
1891 | ||
1892 | if (recommended_min > min_free_kbytes) { | |
1893 | if (user_min_free_kbytes >= 0) | |
1894 | pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", | |
1895 | min_free_kbytes, recommended_min); | |
1896 | ||
1897 | min_free_kbytes = recommended_min; | |
1898 | } | |
1899 | setup_per_zone_wmarks(); | |
1900 | } | |
1901 | ||
1902 | int start_stop_khugepaged(void) | |
1903 | { | |
1904 | static struct task_struct *khugepaged_thread __read_mostly; | |
1905 | static DEFINE_MUTEX(khugepaged_mutex); | |
1906 | int err = 0; | |
1907 | ||
1908 | mutex_lock(&khugepaged_mutex); | |
1909 | if (khugepaged_enabled()) { | |
1910 | if (!khugepaged_thread) | |
1911 | khugepaged_thread = kthread_run(khugepaged, NULL, | |
1912 | "khugepaged"); | |
1913 | if (IS_ERR(khugepaged_thread)) { | |
1914 | pr_err("khugepaged: kthread_run(khugepaged) failed\n"); | |
1915 | err = PTR_ERR(khugepaged_thread); | |
1916 | khugepaged_thread = NULL; | |
1917 | goto fail; | |
1918 | } | |
1919 | ||
1920 | if (!list_empty(&khugepaged_scan.mm_head)) | |
1921 | wake_up_interruptible(&khugepaged_wait); | |
1922 | ||
1923 | set_recommended_min_free_kbytes(); | |
1924 | } else if (khugepaged_thread) { | |
1925 | kthread_stop(khugepaged_thread); | |
1926 | khugepaged_thread = NULL; | |
1927 | } | |
1928 | fail: | |
1929 | mutex_unlock(&khugepaged_mutex); | |
1930 | return err; | |
1931 | } |