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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
b46e756f KS |
2 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
3 | ||
4 | #include <linux/mm.h> | |
5 | #include <linux/sched.h> | |
6e84f315 | 6 | #include <linux/sched/mm.h> |
f7ccbae4 | 7 | #include <linux/sched/coredump.h> |
b46e756f KS |
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> | |
f3f0e1d2 | 20 | #include <linux/shmem_fs.h> |
b46e756f KS |
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, | |
71a2c112 KS |
31 | SCAN_EXCEED_SWAP_PTE, |
32 | SCAN_EXCEED_SHARED_PTE, | |
b46e756f | 33 | SCAN_PTE_NON_PRESENT, |
e1e267c7 | 34 | SCAN_PTE_UFFD_WP, |
b46e756f | 35 | SCAN_PAGE_RO, |
0db501f7 | 36 | SCAN_LACK_REFERENCED_PAGE, |
b46e756f KS |
37 | SCAN_PAGE_NULL, |
38 | SCAN_SCAN_ABORT, | |
39 | SCAN_PAGE_COUNT, | |
40 | SCAN_PAGE_LRU, | |
41 | SCAN_PAGE_LOCK, | |
42 | SCAN_PAGE_ANON, | |
43 | SCAN_PAGE_COMPOUND, | |
44 | SCAN_ANY_PROCESS, | |
45 | SCAN_VMA_NULL, | |
46 | SCAN_VMA_CHECK, | |
47 | SCAN_ADDRESS_RANGE, | |
48 | SCAN_SWAP_CACHE_PAGE, | |
49 | SCAN_DEL_PAGE_LRU, | |
50 | SCAN_ALLOC_HUGE_PAGE_FAIL, | |
51 | SCAN_CGROUP_CHARGE_FAIL, | |
f3f0e1d2 | 52 | SCAN_TRUNCATED, |
99cb0dbd | 53 | SCAN_PAGE_HAS_PRIVATE, |
b46e756f KS |
54 | }; |
55 | ||
56 | #define CREATE_TRACE_POINTS | |
57 | #include <trace/events/huge_memory.h> | |
58 | ||
4aab2be0 VB |
59 | static struct task_struct *khugepaged_thread __read_mostly; |
60 | static DEFINE_MUTEX(khugepaged_mutex); | |
61 | ||
b46e756f KS |
62 | /* default scan 8*512 pte (or vmas) every 30 second */ |
63 | static unsigned int khugepaged_pages_to_scan __read_mostly; | |
64 | static unsigned int khugepaged_pages_collapsed; | |
65 | static unsigned int khugepaged_full_scans; | |
66 | static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000; | |
67 | /* during fragmentation poll the hugepage allocator once every minute */ | |
68 | static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000; | |
69 | static unsigned long khugepaged_sleep_expire; | |
70 | static DEFINE_SPINLOCK(khugepaged_mm_lock); | |
71 | static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait); | |
72 | /* | |
73 | * default collapse hugepages if there is at least one pte mapped like | |
74 | * it would have happened if the vma was large enough during page | |
75 | * fault. | |
76 | */ | |
77 | static unsigned int khugepaged_max_ptes_none __read_mostly; | |
78 | static unsigned int khugepaged_max_ptes_swap __read_mostly; | |
71a2c112 | 79 | static unsigned int khugepaged_max_ptes_shared __read_mostly; |
b46e756f KS |
80 | |
81 | #define MM_SLOTS_HASH_BITS 10 | |
82 | static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS); | |
83 | ||
84 | static struct kmem_cache *mm_slot_cache __read_mostly; | |
85 | ||
27e1f827 SL |
86 | #define MAX_PTE_MAPPED_THP 8 |
87 | ||
b46e756f KS |
88 | /** |
89 | * struct mm_slot - hash lookup from mm to mm_slot | |
90 | * @hash: hash collision list | |
91 | * @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head | |
92 | * @mm: the mm that this information is valid for | |
93 | */ | |
94 | struct mm_slot { | |
95 | struct hlist_node hash; | |
96 | struct list_head mm_node; | |
97 | struct mm_struct *mm; | |
27e1f827 SL |
98 | |
99 | /* pte-mapped THP in this mm */ | |
100 | int nr_pte_mapped_thp; | |
101 | unsigned long pte_mapped_thp[MAX_PTE_MAPPED_THP]; | |
b46e756f KS |
102 | }; |
103 | ||
104 | /** | |
105 | * struct khugepaged_scan - cursor for scanning | |
106 | * @mm_head: the head of the mm list to scan | |
107 | * @mm_slot: the current mm_slot we are scanning | |
108 | * @address: the next address inside that to be scanned | |
109 | * | |
110 | * There is only the one khugepaged_scan instance of this cursor structure. | |
111 | */ | |
112 | struct khugepaged_scan { | |
113 | struct list_head mm_head; | |
114 | struct mm_slot *mm_slot; | |
115 | unsigned long address; | |
116 | }; | |
117 | ||
118 | static struct khugepaged_scan khugepaged_scan = { | |
119 | .mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head), | |
120 | }; | |
121 | ||
e1465d12 | 122 | #ifdef CONFIG_SYSFS |
b46e756f KS |
123 | static ssize_t scan_sleep_millisecs_show(struct kobject *kobj, |
124 | struct kobj_attribute *attr, | |
125 | char *buf) | |
126 | { | |
127 | return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs); | |
128 | } | |
129 | ||
130 | static ssize_t scan_sleep_millisecs_store(struct kobject *kobj, | |
131 | struct kobj_attribute *attr, | |
132 | const char *buf, size_t count) | |
133 | { | |
134 | unsigned long msecs; | |
135 | int err; | |
136 | ||
137 | err = kstrtoul(buf, 10, &msecs); | |
138 | if (err || msecs > UINT_MAX) | |
139 | return -EINVAL; | |
140 | ||
141 | khugepaged_scan_sleep_millisecs = msecs; | |
142 | khugepaged_sleep_expire = 0; | |
143 | wake_up_interruptible(&khugepaged_wait); | |
144 | ||
145 | return count; | |
146 | } | |
147 | static struct kobj_attribute scan_sleep_millisecs_attr = | |
148 | __ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show, | |
149 | scan_sleep_millisecs_store); | |
150 | ||
151 | static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj, | |
152 | struct kobj_attribute *attr, | |
153 | char *buf) | |
154 | { | |
155 | return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs); | |
156 | } | |
157 | ||
158 | static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj, | |
159 | struct kobj_attribute *attr, | |
160 | const char *buf, size_t count) | |
161 | { | |
162 | unsigned long msecs; | |
163 | int err; | |
164 | ||
165 | err = kstrtoul(buf, 10, &msecs); | |
166 | if (err || msecs > UINT_MAX) | |
167 | return -EINVAL; | |
168 | ||
169 | khugepaged_alloc_sleep_millisecs = msecs; | |
170 | khugepaged_sleep_expire = 0; | |
171 | wake_up_interruptible(&khugepaged_wait); | |
172 | ||
173 | return count; | |
174 | } | |
175 | static struct kobj_attribute alloc_sleep_millisecs_attr = | |
176 | __ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show, | |
177 | alloc_sleep_millisecs_store); | |
178 | ||
179 | static ssize_t pages_to_scan_show(struct kobject *kobj, | |
180 | struct kobj_attribute *attr, | |
181 | char *buf) | |
182 | { | |
183 | return sprintf(buf, "%u\n", khugepaged_pages_to_scan); | |
184 | } | |
185 | static ssize_t pages_to_scan_store(struct kobject *kobj, | |
186 | struct kobj_attribute *attr, | |
187 | const char *buf, size_t count) | |
188 | { | |
189 | int err; | |
190 | unsigned long pages; | |
191 | ||
192 | err = kstrtoul(buf, 10, &pages); | |
193 | if (err || !pages || pages > UINT_MAX) | |
194 | return -EINVAL; | |
195 | ||
196 | khugepaged_pages_to_scan = pages; | |
197 | ||
198 | return count; | |
199 | } | |
200 | static struct kobj_attribute pages_to_scan_attr = | |
201 | __ATTR(pages_to_scan, 0644, pages_to_scan_show, | |
202 | pages_to_scan_store); | |
203 | ||
204 | static ssize_t pages_collapsed_show(struct kobject *kobj, | |
205 | struct kobj_attribute *attr, | |
206 | char *buf) | |
207 | { | |
208 | return sprintf(buf, "%u\n", khugepaged_pages_collapsed); | |
209 | } | |
210 | static struct kobj_attribute pages_collapsed_attr = | |
211 | __ATTR_RO(pages_collapsed); | |
212 | ||
213 | static ssize_t full_scans_show(struct kobject *kobj, | |
214 | struct kobj_attribute *attr, | |
215 | char *buf) | |
216 | { | |
217 | return sprintf(buf, "%u\n", khugepaged_full_scans); | |
218 | } | |
219 | static struct kobj_attribute full_scans_attr = | |
220 | __ATTR_RO(full_scans); | |
221 | ||
222 | static ssize_t khugepaged_defrag_show(struct kobject *kobj, | |
223 | struct kobj_attribute *attr, char *buf) | |
224 | { | |
225 | return single_hugepage_flag_show(kobj, attr, buf, | |
226 | TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); | |
227 | } | |
228 | static ssize_t khugepaged_defrag_store(struct kobject *kobj, | |
229 | struct kobj_attribute *attr, | |
230 | const char *buf, size_t count) | |
231 | { | |
232 | return single_hugepage_flag_store(kobj, attr, buf, count, | |
233 | TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); | |
234 | } | |
235 | static struct kobj_attribute khugepaged_defrag_attr = | |
236 | __ATTR(defrag, 0644, khugepaged_defrag_show, | |
237 | khugepaged_defrag_store); | |
238 | ||
239 | /* | |
240 | * max_ptes_none controls if khugepaged should collapse hugepages over | |
241 | * any unmapped ptes in turn potentially increasing the memory | |
242 | * footprint of the vmas. When max_ptes_none is 0 khugepaged will not | |
243 | * reduce the available free memory in the system as it | |
244 | * runs. Increasing max_ptes_none will instead potentially reduce the | |
245 | * free memory in the system during the khugepaged scan. | |
246 | */ | |
247 | static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj, | |
248 | struct kobj_attribute *attr, | |
249 | char *buf) | |
250 | { | |
251 | return sprintf(buf, "%u\n", khugepaged_max_ptes_none); | |
252 | } | |
253 | static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj, | |
254 | struct kobj_attribute *attr, | |
255 | const char *buf, size_t count) | |
256 | { | |
257 | int err; | |
258 | unsigned long max_ptes_none; | |
259 | ||
260 | err = kstrtoul(buf, 10, &max_ptes_none); | |
261 | if (err || max_ptes_none > HPAGE_PMD_NR-1) | |
262 | return -EINVAL; | |
263 | ||
264 | khugepaged_max_ptes_none = max_ptes_none; | |
265 | ||
266 | return count; | |
267 | } | |
268 | static struct kobj_attribute khugepaged_max_ptes_none_attr = | |
269 | __ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show, | |
270 | khugepaged_max_ptes_none_store); | |
271 | ||
272 | static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj, | |
273 | struct kobj_attribute *attr, | |
274 | char *buf) | |
275 | { | |
276 | return sprintf(buf, "%u\n", khugepaged_max_ptes_swap); | |
277 | } | |
278 | ||
279 | static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj, | |
280 | struct kobj_attribute *attr, | |
281 | const char *buf, size_t count) | |
282 | { | |
283 | int err; | |
284 | unsigned long max_ptes_swap; | |
285 | ||
286 | err = kstrtoul(buf, 10, &max_ptes_swap); | |
287 | if (err || max_ptes_swap > HPAGE_PMD_NR-1) | |
288 | return -EINVAL; | |
289 | ||
290 | khugepaged_max_ptes_swap = max_ptes_swap; | |
291 | ||
292 | return count; | |
293 | } | |
294 | ||
295 | static struct kobj_attribute khugepaged_max_ptes_swap_attr = | |
296 | __ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show, | |
297 | khugepaged_max_ptes_swap_store); | |
298 | ||
71a2c112 KS |
299 | static ssize_t khugepaged_max_ptes_shared_show(struct kobject *kobj, |
300 | struct kobj_attribute *attr, | |
301 | char *buf) | |
302 | { | |
303 | return sprintf(buf, "%u\n", khugepaged_max_ptes_shared); | |
304 | } | |
305 | ||
306 | static ssize_t khugepaged_max_ptes_shared_store(struct kobject *kobj, | |
307 | struct kobj_attribute *attr, | |
308 | const char *buf, size_t count) | |
309 | { | |
310 | int err; | |
311 | unsigned long max_ptes_shared; | |
312 | ||
313 | err = kstrtoul(buf, 10, &max_ptes_shared); | |
314 | if (err || max_ptes_shared > HPAGE_PMD_NR-1) | |
315 | return -EINVAL; | |
316 | ||
317 | khugepaged_max_ptes_shared = max_ptes_shared; | |
318 | ||
319 | return count; | |
320 | } | |
321 | ||
322 | static struct kobj_attribute khugepaged_max_ptes_shared_attr = | |
323 | __ATTR(max_ptes_shared, 0644, khugepaged_max_ptes_shared_show, | |
324 | khugepaged_max_ptes_shared_store); | |
325 | ||
b46e756f KS |
326 | static struct attribute *khugepaged_attr[] = { |
327 | &khugepaged_defrag_attr.attr, | |
328 | &khugepaged_max_ptes_none_attr.attr, | |
71a2c112 KS |
329 | &khugepaged_max_ptes_swap_attr.attr, |
330 | &khugepaged_max_ptes_shared_attr.attr, | |
b46e756f KS |
331 | &pages_to_scan_attr.attr, |
332 | &pages_collapsed_attr.attr, | |
333 | &full_scans_attr.attr, | |
334 | &scan_sleep_millisecs_attr.attr, | |
335 | &alloc_sleep_millisecs_attr.attr, | |
b46e756f KS |
336 | NULL, |
337 | }; | |
338 | ||
339 | struct attribute_group khugepaged_attr_group = { | |
340 | .attrs = khugepaged_attr, | |
341 | .name = "khugepaged", | |
342 | }; | |
e1465d12 | 343 | #endif /* CONFIG_SYSFS */ |
b46e756f | 344 | |
b46e756f KS |
345 | int hugepage_madvise(struct vm_area_struct *vma, |
346 | unsigned long *vm_flags, int advice) | |
347 | { | |
348 | switch (advice) { | |
349 | case MADV_HUGEPAGE: | |
350 | #ifdef CONFIG_S390 | |
351 | /* | |
352 | * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 | |
353 | * can't handle this properly after s390_enable_sie, so we simply | |
354 | * ignore the madvise to prevent qemu from causing a SIGSEGV. | |
355 | */ | |
356 | if (mm_has_pgste(vma->vm_mm)) | |
357 | return 0; | |
358 | #endif | |
359 | *vm_flags &= ~VM_NOHUGEPAGE; | |
360 | *vm_flags |= VM_HUGEPAGE; | |
361 | /* | |
362 | * If the vma become good for khugepaged to scan, | |
363 | * register it here without waiting a page fault that | |
364 | * may not happen any time soon. | |
365 | */ | |
366 | if (!(*vm_flags & VM_NO_KHUGEPAGED) && | |
367 | khugepaged_enter_vma_merge(vma, *vm_flags)) | |
368 | return -ENOMEM; | |
369 | break; | |
370 | case MADV_NOHUGEPAGE: | |
371 | *vm_flags &= ~VM_HUGEPAGE; | |
372 | *vm_flags |= VM_NOHUGEPAGE; | |
373 | /* | |
374 | * Setting VM_NOHUGEPAGE will prevent khugepaged from scanning | |
375 | * this vma even if we leave the mm registered in khugepaged if | |
376 | * it got registered before VM_NOHUGEPAGE was set. | |
377 | */ | |
378 | break; | |
379 | } | |
380 | ||
381 | return 0; | |
382 | } | |
383 | ||
384 | int __init khugepaged_init(void) | |
385 | { | |
386 | mm_slot_cache = kmem_cache_create("khugepaged_mm_slot", | |
387 | sizeof(struct mm_slot), | |
388 | __alignof__(struct mm_slot), 0, NULL); | |
389 | if (!mm_slot_cache) | |
390 | return -ENOMEM; | |
391 | ||
392 | khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; | |
393 | khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; | |
394 | khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8; | |
71a2c112 | 395 | khugepaged_max_ptes_shared = HPAGE_PMD_NR / 2; |
b46e756f KS |
396 | |
397 | return 0; | |
398 | } | |
399 | ||
400 | void __init khugepaged_destroy(void) | |
401 | { | |
402 | kmem_cache_destroy(mm_slot_cache); | |
403 | } | |
404 | ||
405 | static inline struct mm_slot *alloc_mm_slot(void) | |
406 | { | |
407 | if (!mm_slot_cache) /* initialization failed */ | |
408 | return NULL; | |
409 | return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL); | |
410 | } | |
411 | ||
412 | static inline void free_mm_slot(struct mm_slot *mm_slot) | |
413 | { | |
414 | kmem_cache_free(mm_slot_cache, mm_slot); | |
415 | } | |
416 | ||
417 | static struct mm_slot *get_mm_slot(struct mm_struct *mm) | |
418 | { | |
419 | struct mm_slot *mm_slot; | |
420 | ||
421 | hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm) | |
422 | if (mm == mm_slot->mm) | |
423 | return mm_slot; | |
424 | ||
425 | return NULL; | |
426 | } | |
427 | ||
428 | static void insert_to_mm_slots_hash(struct mm_struct *mm, | |
429 | struct mm_slot *mm_slot) | |
430 | { | |
431 | mm_slot->mm = mm; | |
432 | hash_add(mm_slots_hash, &mm_slot->hash, (long)mm); | |
433 | } | |
434 | ||
435 | static inline int khugepaged_test_exit(struct mm_struct *mm) | |
436 | { | |
4d45e75a | 437 | return atomic_read(&mm->mm_users) == 0; |
b46e756f KS |
438 | } |
439 | ||
50f8b92f SL |
440 | static bool hugepage_vma_check(struct vm_area_struct *vma, |
441 | unsigned long vm_flags) | |
c2231020 | 442 | { |
50f8b92f SL |
443 | if ((!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) || |
444 | (vm_flags & VM_NOHUGEPAGE) || | |
c2231020 YS |
445 | test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) |
446 | return false; | |
99cb0dbd SL |
447 | |
448 | if (shmem_file(vma->vm_file) || | |
449 | (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && | |
450 | vma->vm_file && | |
451 | (vm_flags & VM_DENYWRITE))) { | |
c2231020 YS |
452 | return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, |
453 | HPAGE_PMD_NR); | |
454 | } | |
455 | if (!vma->anon_vma || vma->vm_ops) | |
456 | return false; | |
222100ee | 457 | if (vma_is_temporary_stack(vma)) |
c2231020 | 458 | return false; |
50f8b92f | 459 | return !(vm_flags & VM_NO_KHUGEPAGED); |
c2231020 YS |
460 | } |
461 | ||
b46e756f KS |
462 | int __khugepaged_enter(struct mm_struct *mm) |
463 | { | |
464 | struct mm_slot *mm_slot; | |
465 | int wakeup; | |
466 | ||
467 | mm_slot = alloc_mm_slot(); | |
468 | if (!mm_slot) | |
469 | return -ENOMEM; | |
470 | ||
471 | /* __khugepaged_exit() must not run from under us */ | |
f3f99d63 | 472 | VM_BUG_ON_MM(atomic_read(&mm->mm_users) == 0, mm); |
b46e756f KS |
473 | if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) { |
474 | free_mm_slot(mm_slot); | |
475 | return 0; | |
476 | } | |
477 | ||
478 | spin_lock(&khugepaged_mm_lock); | |
479 | insert_to_mm_slots_hash(mm, mm_slot); | |
480 | /* | |
481 | * Insert just behind the scanning cursor, to let the area settle | |
482 | * down a little. | |
483 | */ | |
484 | wakeup = list_empty(&khugepaged_scan.mm_head); | |
485 | list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head); | |
486 | spin_unlock(&khugepaged_mm_lock); | |
487 | ||
f1f10076 | 488 | mmgrab(mm); |
b46e756f KS |
489 | if (wakeup) |
490 | wake_up_interruptible(&khugepaged_wait); | |
491 | ||
492 | return 0; | |
493 | } | |
494 | ||
495 | int khugepaged_enter_vma_merge(struct vm_area_struct *vma, | |
496 | unsigned long vm_flags) | |
497 | { | |
498 | unsigned long hstart, hend; | |
c2231020 YS |
499 | |
500 | /* | |
99cb0dbd SL |
501 | * khugepaged only supports read-only files for non-shmem files. |
502 | * khugepaged does not yet work on special mappings. And | |
503 | * file-private shmem THP is not supported. | |
c2231020 | 504 | */ |
50f8b92f | 505 | if (!hugepage_vma_check(vma, vm_flags)) |
b46e756f | 506 | return 0; |
c2231020 | 507 | |
b46e756f KS |
508 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; |
509 | hend = vma->vm_end & HPAGE_PMD_MASK; | |
510 | if (hstart < hend) | |
511 | return khugepaged_enter(vma, vm_flags); | |
512 | return 0; | |
513 | } | |
514 | ||
515 | void __khugepaged_exit(struct mm_struct *mm) | |
516 | { | |
517 | struct mm_slot *mm_slot; | |
518 | int free = 0; | |
519 | ||
520 | spin_lock(&khugepaged_mm_lock); | |
521 | mm_slot = get_mm_slot(mm); | |
522 | if (mm_slot && khugepaged_scan.mm_slot != mm_slot) { | |
523 | hash_del(&mm_slot->hash); | |
524 | list_del(&mm_slot->mm_node); | |
525 | free = 1; | |
526 | } | |
527 | spin_unlock(&khugepaged_mm_lock); | |
528 | ||
529 | if (free) { | |
530 | clear_bit(MMF_VM_HUGEPAGE, &mm->flags); | |
531 | free_mm_slot(mm_slot); | |
532 | mmdrop(mm); | |
533 | } else if (mm_slot) { | |
534 | /* | |
535 | * This is required to serialize against | |
536 | * khugepaged_test_exit() (which is guaranteed to run | |
537 | * under mmap sem read mode). Stop here (after we | |
538 | * return all pagetables will be destroyed) until | |
539 | * khugepaged has finished working on the pagetables | |
c1e8d7c6 | 540 | * under the mmap_lock. |
b46e756f | 541 | */ |
d8ed45c5 ML |
542 | mmap_write_lock(mm); |
543 | mmap_write_unlock(mm); | |
b46e756f KS |
544 | } |
545 | } | |
546 | ||
547 | static void release_pte_page(struct page *page) | |
548 | { | |
5503fbf2 KS |
549 | mod_node_page_state(page_pgdat(page), |
550 | NR_ISOLATED_ANON + page_is_file_lru(page), | |
551 | -compound_nr(page)); | |
b46e756f KS |
552 | unlock_page(page); |
553 | putback_lru_page(page); | |
554 | } | |
555 | ||
5503fbf2 KS |
556 | static void release_pte_pages(pte_t *pte, pte_t *_pte, |
557 | struct list_head *compound_pagelist) | |
b46e756f | 558 | { |
5503fbf2 KS |
559 | struct page *page, *tmp; |
560 | ||
b46e756f KS |
561 | while (--_pte >= pte) { |
562 | pte_t pteval = *_pte; | |
5503fbf2 KS |
563 | |
564 | page = pte_page(pteval); | |
565 | if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)) && | |
566 | !PageCompound(page)) | |
567 | release_pte_page(page); | |
568 | } | |
569 | ||
570 | list_for_each_entry_safe(page, tmp, compound_pagelist, lru) { | |
571 | list_del(&page->lru); | |
572 | release_pte_page(page); | |
b46e756f KS |
573 | } |
574 | } | |
575 | ||
9445689f KS |
576 | static bool is_refcount_suitable(struct page *page) |
577 | { | |
578 | int expected_refcount; | |
579 | ||
580 | expected_refcount = total_mapcount(page); | |
581 | if (PageSwapCache(page)) | |
582 | expected_refcount += compound_nr(page); | |
583 | ||
584 | return page_count(page) == expected_refcount; | |
585 | } | |
586 | ||
b46e756f KS |
587 | static int __collapse_huge_page_isolate(struct vm_area_struct *vma, |
588 | unsigned long address, | |
5503fbf2 KS |
589 | pte_t *pte, |
590 | struct list_head *compound_pagelist) | |
b46e756f KS |
591 | { |
592 | struct page *page = NULL; | |
593 | pte_t *_pte; | |
71a2c112 | 594 | int none_or_zero = 0, shared = 0, result = 0, referenced = 0; |
0db501f7 | 595 | bool writable = false; |
b46e756f KS |
596 | |
597 | for (_pte = pte; _pte < pte+HPAGE_PMD_NR; | |
598 | _pte++, address += PAGE_SIZE) { | |
599 | pte_t pteval = *_pte; | |
600 | if (pte_none(pteval) || (pte_present(pteval) && | |
601 | is_zero_pfn(pte_pfn(pteval)))) { | |
602 | if (!userfaultfd_armed(vma) && | |
603 | ++none_or_zero <= khugepaged_max_ptes_none) { | |
604 | continue; | |
605 | } else { | |
606 | result = SCAN_EXCEED_NONE_PTE; | |
607 | goto out; | |
608 | } | |
609 | } | |
610 | if (!pte_present(pteval)) { | |
611 | result = SCAN_PTE_NON_PRESENT; | |
612 | goto out; | |
613 | } | |
614 | page = vm_normal_page(vma, address, pteval); | |
615 | if (unlikely(!page)) { | |
616 | result = SCAN_PAGE_NULL; | |
617 | goto out; | |
618 | } | |
619 | ||
5503fbf2 KS |
620 | VM_BUG_ON_PAGE(!PageAnon(page), page); |
621 | ||
71a2c112 KS |
622 | if (page_mapcount(page) > 1 && |
623 | ++shared > khugepaged_max_ptes_shared) { | |
624 | result = SCAN_EXCEED_SHARED_PTE; | |
625 | goto out; | |
626 | } | |
627 | ||
fece2029 | 628 | if (PageCompound(page)) { |
5503fbf2 KS |
629 | struct page *p; |
630 | page = compound_head(page); | |
fece2029 | 631 | |
5503fbf2 KS |
632 | /* |
633 | * Check if we have dealt with the compound page | |
634 | * already | |
635 | */ | |
636 | list_for_each_entry(p, compound_pagelist, lru) { | |
637 | if (page == p) | |
638 | goto next; | |
639 | } | |
640 | } | |
b46e756f KS |
641 | |
642 | /* | |
643 | * We can do it before isolate_lru_page because the | |
644 | * page can't be freed from under us. NOTE: PG_lock | |
645 | * is needed to serialize against split_huge_page | |
646 | * when invoked from the VM. | |
647 | */ | |
648 | if (!trylock_page(page)) { | |
649 | result = SCAN_PAGE_LOCK; | |
650 | goto out; | |
651 | } | |
652 | ||
653 | /* | |
9445689f KS |
654 | * Check if the page has any GUP (or other external) pins. |
655 | * | |
656 | * The page table that maps the page has been already unlinked | |
657 | * from the page table tree and this process cannot get | |
658 | * an additinal pin on the page. | |
659 | * | |
660 | * New pins can come later if the page is shared across fork, | |
661 | * but not from this process. The other process cannot write to | |
662 | * the page, only trigger CoW. | |
b46e756f | 663 | */ |
9445689f | 664 | if (!is_refcount_suitable(page)) { |
b46e756f KS |
665 | unlock_page(page); |
666 | result = SCAN_PAGE_COUNT; | |
667 | goto out; | |
668 | } | |
5503fbf2 KS |
669 | if (!pte_write(pteval) && PageSwapCache(page) && |
670 | !reuse_swap_page(page, NULL)) { | |
b46e756f | 671 | /* |
5503fbf2 KS |
672 | * Page is in the swap cache and cannot be re-used. |
673 | * It cannot be collapsed into a THP. | |
b46e756f | 674 | */ |
5503fbf2 KS |
675 | unlock_page(page); |
676 | result = SCAN_SWAP_CACHE_PAGE; | |
677 | goto out; | |
b46e756f KS |
678 | } |
679 | ||
680 | /* | |
681 | * Isolate the page to avoid collapsing an hugepage | |
682 | * currently in use by the VM. | |
683 | */ | |
684 | if (isolate_lru_page(page)) { | |
685 | unlock_page(page); | |
686 | result = SCAN_DEL_PAGE_LRU; | |
687 | goto out; | |
688 | } | |
5503fbf2 KS |
689 | mod_node_page_state(page_pgdat(page), |
690 | NR_ISOLATED_ANON + page_is_file_lru(page), | |
691 | compound_nr(page)); | |
b46e756f KS |
692 | VM_BUG_ON_PAGE(!PageLocked(page), page); |
693 | VM_BUG_ON_PAGE(PageLRU(page), page); | |
694 | ||
5503fbf2 KS |
695 | if (PageCompound(page)) |
696 | list_add_tail(&page->lru, compound_pagelist); | |
697 | next: | |
0db501f7 | 698 | /* There should be enough young pte to collapse the page */ |
b46e756f KS |
699 | if (pte_young(pteval) || |
700 | page_is_young(page) || PageReferenced(page) || | |
701 | mmu_notifier_test_young(vma->vm_mm, address)) | |
0db501f7 | 702 | referenced++; |
5503fbf2 KS |
703 | |
704 | if (pte_write(pteval)) | |
705 | writable = true; | |
b46e756f KS |
706 | } |
707 | if (likely(writable)) { | |
708 | if (likely(referenced)) { | |
709 | result = SCAN_SUCCEED; | |
710 | trace_mm_collapse_huge_page_isolate(page, none_or_zero, | |
711 | referenced, writable, result); | |
712 | return 1; | |
713 | } | |
714 | } else { | |
715 | result = SCAN_PAGE_RO; | |
716 | } | |
717 | ||
718 | out: | |
5503fbf2 | 719 | release_pte_pages(pte, _pte, compound_pagelist); |
b46e756f KS |
720 | trace_mm_collapse_huge_page_isolate(page, none_or_zero, |
721 | referenced, writable, result); | |
722 | return 0; | |
723 | } | |
724 | ||
725 | static void __collapse_huge_page_copy(pte_t *pte, struct page *page, | |
726 | struct vm_area_struct *vma, | |
727 | unsigned long address, | |
5503fbf2 KS |
728 | spinlock_t *ptl, |
729 | struct list_head *compound_pagelist) | |
b46e756f | 730 | { |
5503fbf2 | 731 | struct page *src_page, *tmp; |
b46e756f | 732 | pte_t *_pte; |
338a16ba DR |
733 | for (_pte = pte; _pte < pte + HPAGE_PMD_NR; |
734 | _pte++, page++, address += PAGE_SIZE) { | |
b46e756f | 735 | pte_t pteval = *_pte; |
b46e756f KS |
736 | |
737 | if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { | |
738 | clear_user_highpage(page, address); | |
739 | add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1); | |
740 | if (is_zero_pfn(pte_pfn(pteval))) { | |
741 | /* | |
742 | * ptl mostly unnecessary. | |
743 | */ | |
744 | spin_lock(ptl); | |
745 | /* | |
746 | * paravirt calls inside pte_clear here are | |
747 | * superfluous. | |
748 | */ | |
749 | pte_clear(vma->vm_mm, address, _pte); | |
750 | spin_unlock(ptl); | |
751 | } | |
752 | } else { | |
753 | src_page = pte_page(pteval); | |
754 | copy_user_highpage(page, src_page, address, vma); | |
5503fbf2 KS |
755 | if (!PageCompound(src_page)) |
756 | release_pte_page(src_page); | |
b46e756f KS |
757 | /* |
758 | * ptl mostly unnecessary, but preempt has to | |
759 | * be disabled to update the per-cpu stats | |
760 | * inside page_remove_rmap(). | |
761 | */ | |
762 | spin_lock(ptl); | |
763 | /* | |
764 | * paravirt calls inside pte_clear here are | |
765 | * superfluous. | |
766 | */ | |
767 | pte_clear(vma->vm_mm, address, _pte); | |
768 | page_remove_rmap(src_page, false); | |
769 | spin_unlock(ptl); | |
770 | free_page_and_swap_cache(src_page); | |
771 | } | |
b46e756f | 772 | } |
5503fbf2 KS |
773 | |
774 | list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) { | |
775 | list_del(&src_page->lru); | |
776 | release_pte_page(src_page); | |
777 | } | |
b46e756f KS |
778 | } |
779 | ||
780 | static void khugepaged_alloc_sleep(void) | |
781 | { | |
782 | DEFINE_WAIT(wait); | |
783 | ||
784 | add_wait_queue(&khugepaged_wait, &wait); | |
785 | freezable_schedule_timeout_interruptible( | |
786 | msecs_to_jiffies(khugepaged_alloc_sleep_millisecs)); | |
787 | remove_wait_queue(&khugepaged_wait, &wait); | |
788 | } | |
789 | ||
790 | static int khugepaged_node_load[MAX_NUMNODES]; | |
791 | ||
792 | static bool khugepaged_scan_abort(int nid) | |
793 | { | |
794 | int i; | |
795 | ||
796 | /* | |
a5f5f91d | 797 | * If node_reclaim_mode is disabled, then no extra effort is made to |
b46e756f KS |
798 | * allocate memory locally. |
799 | */ | |
a5f5f91d | 800 | if (!node_reclaim_mode) |
b46e756f KS |
801 | return false; |
802 | ||
803 | /* If there is a count for this node already, it must be acceptable */ | |
804 | if (khugepaged_node_load[nid]) | |
805 | return false; | |
806 | ||
807 | for (i = 0; i < MAX_NUMNODES; i++) { | |
808 | if (!khugepaged_node_load[i]) | |
809 | continue; | |
a55c7454 | 810 | if (node_distance(nid, i) > node_reclaim_distance) |
b46e756f KS |
811 | return true; |
812 | } | |
813 | return false; | |
814 | } | |
815 | ||
816 | /* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ | |
817 | static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) | |
818 | { | |
25160354 | 819 | return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT; |
b46e756f KS |
820 | } |
821 | ||
822 | #ifdef CONFIG_NUMA | |
823 | static int khugepaged_find_target_node(void) | |
824 | { | |
825 | static int last_khugepaged_target_node = NUMA_NO_NODE; | |
826 | int nid, target_node = 0, max_value = 0; | |
827 | ||
828 | /* find first node with max normal pages hit */ | |
829 | for (nid = 0; nid < MAX_NUMNODES; nid++) | |
830 | if (khugepaged_node_load[nid] > max_value) { | |
831 | max_value = khugepaged_node_load[nid]; | |
832 | target_node = nid; | |
833 | } | |
834 | ||
835 | /* do some balance if several nodes have the same hit record */ | |
836 | if (target_node <= last_khugepaged_target_node) | |
837 | for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES; | |
838 | nid++) | |
839 | if (max_value == khugepaged_node_load[nid]) { | |
840 | target_node = nid; | |
841 | break; | |
842 | } | |
843 | ||
844 | last_khugepaged_target_node = target_node; | |
845 | return target_node; | |
846 | } | |
847 | ||
848 | static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) | |
849 | { | |
850 | if (IS_ERR(*hpage)) { | |
851 | if (!*wait) | |
852 | return false; | |
853 | ||
854 | *wait = false; | |
855 | *hpage = NULL; | |
856 | khugepaged_alloc_sleep(); | |
857 | } else if (*hpage) { | |
858 | put_page(*hpage); | |
859 | *hpage = NULL; | |
860 | } | |
861 | ||
862 | return true; | |
863 | } | |
864 | ||
865 | static struct page * | |
988ddb71 | 866 | khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) |
b46e756f KS |
867 | { |
868 | VM_BUG_ON_PAGE(*hpage, *hpage); | |
869 | ||
b46e756f KS |
870 | *hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER); |
871 | if (unlikely(!*hpage)) { | |
872 | count_vm_event(THP_COLLAPSE_ALLOC_FAILED); | |
873 | *hpage = ERR_PTR(-ENOMEM); | |
874 | return NULL; | |
875 | } | |
876 | ||
877 | prep_transhuge_page(*hpage); | |
878 | count_vm_event(THP_COLLAPSE_ALLOC); | |
879 | return *hpage; | |
880 | } | |
881 | #else | |
882 | static int khugepaged_find_target_node(void) | |
883 | { | |
884 | return 0; | |
885 | } | |
886 | ||
887 | static inline struct page *alloc_khugepaged_hugepage(void) | |
888 | { | |
889 | struct page *page; | |
890 | ||
891 | page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), | |
892 | HPAGE_PMD_ORDER); | |
893 | if (page) | |
894 | prep_transhuge_page(page); | |
895 | return page; | |
896 | } | |
897 | ||
898 | static struct page *khugepaged_alloc_hugepage(bool *wait) | |
899 | { | |
900 | struct page *hpage; | |
901 | ||
902 | do { | |
903 | hpage = alloc_khugepaged_hugepage(); | |
904 | if (!hpage) { | |
905 | count_vm_event(THP_COLLAPSE_ALLOC_FAILED); | |
906 | if (!*wait) | |
907 | return NULL; | |
908 | ||
909 | *wait = false; | |
910 | khugepaged_alloc_sleep(); | |
911 | } else | |
912 | count_vm_event(THP_COLLAPSE_ALLOC); | |
913 | } while (unlikely(!hpage) && likely(khugepaged_enabled())); | |
914 | ||
915 | return hpage; | |
916 | } | |
917 | ||
918 | static bool khugepaged_prealloc_page(struct page **hpage, bool *wait) | |
919 | { | |
033b5d77 HD |
920 | /* |
921 | * If the hpage allocated earlier was briefly exposed in page cache | |
922 | * before collapse_file() failed, it is possible that racing lookups | |
923 | * have not yet completed, and would then be unpleasantly surprised by | |
924 | * finding the hpage reused for the same mapping at a different offset. | |
925 | * Just release the previous allocation if there is any danger of that. | |
926 | */ | |
927 | if (*hpage && page_count(*hpage) > 1) { | |
928 | put_page(*hpage); | |
929 | *hpage = NULL; | |
930 | } | |
931 | ||
b46e756f KS |
932 | if (!*hpage) |
933 | *hpage = khugepaged_alloc_hugepage(wait); | |
934 | ||
935 | if (unlikely(!*hpage)) | |
936 | return false; | |
937 | ||
938 | return true; | |
939 | } | |
940 | ||
941 | static struct page * | |
988ddb71 | 942 | khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node) |
b46e756f | 943 | { |
b46e756f KS |
944 | VM_BUG_ON(!*hpage); |
945 | ||
946 | return *hpage; | |
947 | } | |
948 | #endif | |
949 | ||
b46e756f | 950 | /* |
c1e8d7c6 ML |
951 | * If mmap_lock temporarily dropped, revalidate vma |
952 | * before taking mmap_lock. | |
b46e756f KS |
953 | * Return 0 if succeeds, otherwise return none-zero |
954 | * value (scan code). | |
955 | */ | |
956 | ||
c131f751 KS |
957 | static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address, |
958 | struct vm_area_struct **vmap) | |
b46e756f KS |
959 | { |
960 | struct vm_area_struct *vma; | |
961 | unsigned long hstart, hend; | |
962 | ||
963 | if (unlikely(khugepaged_test_exit(mm))) | |
964 | return SCAN_ANY_PROCESS; | |
965 | ||
c131f751 | 966 | *vmap = vma = find_vma(mm, address); |
b46e756f KS |
967 | if (!vma) |
968 | return SCAN_VMA_NULL; | |
969 | ||
970 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; | |
971 | hend = vma->vm_end & HPAGE_PMD_MASK; | |
972 | if (address < hstart || address + HPAGE_PMD_SIZE > hend) | |
973 | return SCAN_ADDRESS_RANGE; | |
50f8b92f | 974 | if (!hugepage_vma_check(vma, vma->vm_flags)) |
b46e756f | 975 | return SCAN_VMA_CHECK; |
594cced1 KS |
976 | /* Anon VMA expected */ |
977 | if (!vma->anon_vma || vma->vm_ops) | |
978 | return SCAN_VMA_CHECK; | |
b46e756f KS |
979 | return 0; |
980 | } | |
981 | ||
982 | /* | |
983 | * Bring missing pages in from swap, to complete THP collapse. | |
984 | * Only done if khugepaged_scan_pmd believes it is worthwhile. | |
985 | * | |
986 | * Called and returns without pte mapped or spinlocks held, | |
c1e8d7c6 | 987 | * but with mmap_lock held to protect against vma changes. |
b46e756f KS |
988 | */ |
989 | ||
990 | static bool __collapse_huge_page_swapin(struct mm_struct *mm, | |
991 | struct vm_area_struct *vma, | |
0db501f7 EA |
992 | unsigned long address, pmd_t *pmd, |
993 | int referenced) | |
b46e756f | 994 | { |
2b740303 SJ |
995 | int swapped_in = 0; |
996 | vm_fault_t ret = 0; | |
82b0f8c3 | 997 | struct vm_fault vmf = { |
b46e756f KS |
998 | .vma = vma, |
999 | .address = address, | |
1000 | .flags = FAULT_FLAG_ALLOW_RETRY, | |
1001 | .pmd = pmd, | |
0721ec8b | 1002 | .pgoff = linear_page_index(vma, address), |
b46e756f KS |
1003 | }; |
1004 | ||
82b0f8c3 JK |
1005 | vmf.pte = pte_offset_map(pmd, address); |
1006 | for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE; | |
1007 | vmf.pte++, vmf.address += PAGE_SIZE) { | |
2994302b JK |
1008 | vmf.orig_pte = *vmf.pte; |
1009 | if (!is_swap_pte(vmf.orig_pte)) | |
b46e756f KS |
1010 | continue; |
1011 | swapped_in++; | |
2994302b | 1012 | ret = do_swap_page(&vmf); |
0db501f7 | 1013 | |
c1e8d7c6 | 1014 | /* do_swap_page returns VM_FAULT_RETRY with released mmap_lock */ |
b46e756f | 1015 | if (ret & VM_FAULT_RETRY) { |
d8ed45c5 | 1016 | mmap_read_lock(mm); |
82b0f8c3 | 1017 | if (hugepage_vma_revalidate(mm, address, &vmf.vma)) { |
47f863ea | 1018 | /* vma is no longer available, don't continue to swapin */ |
0db501f7 | 1019 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
b46e756f | 1020 | return false; |
47f863ea | 1021 | } |
b46e756f | 1022 | /* check if the pmd is still valid */ |
835152a2 SP |
1023 | if (mm_find_pmd(mm, address) != pmd) { |
1024 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); | |
b46e756f | 1025 | return false; |
835152a2 | 1026 | } |
b46e756f KS |
1027 | } |
1028 | if (ret & VM_FAULT_ERROR) { | |
0db501f7 | 1029 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0); |
b46e756f KS |
1030 | return false; |
1031 | } | |
1032 | /* pte is unmapped now, we need to map it */ | |
82b0f8c3 | 1033 | vmf.pte = pte_offset_map(pmd, vmf.address); |
b46e756f | 1034 | } |
82b0f8c3 JK |
1035 | vmf.pte--; |
1036 | pte_unmap(vmf.pte); | |
ae2c5d80 KS |
1037 | |
1038 | /* Drain LRU add pagevec to remove extra pin on the swapped in pages */ | |
1039 | if (swapped_in) | |
1040 | lru_add_drain(); | |
1041 | ||
0db501f7 | 1042 | trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1); |
b46e756f KS |
1043 | return true; |
1044 | } | |
1045 | ||
1046 | static void collapse_huge_page(struct mm_struct *mm, | |
1047 | unsigned long address, | |
1048 | struct page **hpage, | |
ffe945e6 | 1049 | int node, int referenced, int unmapped) |
b46e756f | 1050 | { |
5503fbf2 | 1051 | LIST_HEAD(compound_pagelist); |
b46e756f KS |
1052 | pmd_t *pmd, _pmd; |
1053 | pte_t *pte; | |
1054 | pgtable_t pgtable; | |
1055 | struct page *new_page; | |
1056 | spinlock_t *pmd_ptl, *pte_ptl; | |
1057 | int isolated = 0, result = 0; | |
c131f751 | 1058 | struct vm_area_struct *vma; |
ac46d4f3 | 1059 | struct mmu_notifier_range range; |
b46e756f KS |
1060 | gfp_t gfp; |
1061 | ||
1062 | VM_BUG_ON(address & ~HPAGE_PMD_MASK); | |
1063 | ||
1064 | /* Only allocate from the target node */ | |
41b6167e | 1065 | gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; |
b46e756f | 1066 | |
988ddb71 | 1067 | /* |
c1e8d7c6 | 1068 | * Before allocating the hugepage, release the mmap_lock read lock. |
988ddb71 | 1069 | * The allocation can take potentially a long time if it involves |
c1e8d7c6 | 1070 | * sync compaction, and we do not need to hold the mmap_lock during |
988ddb71 KS |
1071 | * that. We will recheck the vma after taking it again in write mode. |
1072 | */ | |
d8ed45c5 | 1073 | mmap_read_unlock(mm); |
988ddb71 | 1074 | new_page = khugepaged_alloc_page(hpage, gfp, node); |
b46e756f KS |
1075 | if (!new_page) { |
1076 | result = SCAN_ALLOC_HUGE_PAGE_FAIL; | |
1077 | goto out_nolock; | |
1078 | } | |
1079 | ||
d9eb1ea2 | 1080 | if (unlikely(mem_cgroup_charge(new_page, mm, gfp))) { |
b46e756f KS |
1081 | result = SCAN_CGROUP_CHARGE_FAIL; |
1082 | goto out_nolock; | |
1083 | } | |
9d82c694 | 1084 | count_memcg_page_event(new_page, THP_COLLAPSE_ALLOC); |
b46e756f | 1085 | |
d8ed45c5 | 1086 | mmap_read_lock(mm); |
c131f751 | 1087 | result = hugepage_vma_revalidate(mm, address, &vma); |
b46e756f | 1088 | if (result) { |
d8ed45c5 | 1089 | mmap_read_unlock(mm); |
b46e756f KS |
1090 | goto out_nolock; |
1091 | } | |
1092 | ||
1093 | pmd = mm_find_pmd(mm, address); | |
1094 | if (!pmd) { | |
1095 | result = SCAN_PMD_NULL; | |
d8ed45c5 | 1096 | mmap_read_unlock(mm); |
b46e756f KS |
1097 | goto out_nolock; |
1098 | } | |
1099 | ||
1100 | /* | |
c1e8d7c6 ML |
1101 | * __collapse_huge_page_swapin always returns with mmap_lock locked. |
1102 | * If it fails, we release mmap_lock and jump out_nolock. | |
b46e756f KS |
1103 | * Continuing to collapse causes inconsistency. |
1104 | */ | |
ffe945e6 KS |
1105 | if (unmapped && !__collapse_huge_page_swapin(mm, vma, address, |
1106 | pmd, referenced)) { | |
d8ed45c5 | 1107 | mmap_read_unlock(mm); |
b46e756f KS |
1108 | goto out_nolock; |
1109 | } | |
1110 | ||
d8ed45c5 | 1111 | mmap_read_unlock(mm); |
b46e756f KS |
1112 | /* |
1113 | * Prevent all access to pagetables with the exception of | |
1114 | * gup_fast later handled by the ptep_clear_flush and the VM | |
1115 | * handled by the anon_vma lock + PG_lock. | |
1116 | */ | |
d8ed45c5 | 1117 | mmap_write_lock(mm); |
c131f751 | 1118 | result = hugepage_vma_revalidate(mm, address, &vma); |
b46e756f KS |
1119 | if (result) |
1120 | goto out; | |
1121 | /* check if the pmd is still valid */ | |
1122 | if (mm_find_pmd(mm, address) != pmd) | |
1123 | goto out; | |
1124 | ||
1125 | anon_vma_lock_write(vma->anon_vma); | |
1126 | ||
7269f999 | 1127 | mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, |
6f4f13e8 | 1128 | address, address + HPAGE_PMD_SIZE); |
ac46d4f3 | 1129 | mmu_notifier_invalidate_range_start(&range); |
ec649c9d VS |
1130 | |
1131 | pte = pte_offset_map(pmd, address); | |
1132 | pte_ptl = pte_lockptr(mm, pmd); | |
1133 | ||
b46e756f KS |
1134 | pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */ |
1135 | /* | |
1136 | * After this gup_fast can't run anymore. This also removes | |
1137 | * any huge TLB entry from the CPU so we won't allow | |
1138 | * huge and small TLB entries for the same virtual address | |
1139 | * to avoid the risk of CPU bugs in that area. | |
1140 | */ | |
1141 | _pmd = pmdp_collapse_flush(vma, address, pmd); | |
1142 | spin_unlock(pmd_ptl); | |
ac46d4f3 | 1143 | mmu_notifier_invalidate_range_end(&range); |
b46e756f KS |
1144 | |
1145 | spin_lock(pte_ptl); | |
5503fbf2 KS |
1146 | isolated = __collapse_huge_page_isolate(vma, address, pte, |
1147 | &compound_pagelist); | |
b46e756f KS |
1148 | spin_unlock(pte_ptl); |
1149 | ||
1150 | if (unlikely(!isolated)) { | |
1151 | pte_unmap(pte); | |
1152 | spin_lock(pmd_ptl); | |
1153 | BUG_ON(!pmd_none(*pmd)); | |
1154 | /* | |
1155 | * We can only use set_pmd_at when establishing | |
1156 | * hugepmds and never for establishing regular pmds that | |
1157 | * points to regular pagetables. Use pmd_populate for that | |
1158 | */ | |
1159 | pmd_populate(mm, pmd, pmd_pgtable(_pmd)); | |
1160 | spin_unlock(pmd_ptl); | |
1161 | anon_vma_unlock_write(vma->anon_vma); | |
1162 | result = SCAN_FAIL; | |
1163 | goto out; | |
1164 | } | |
1165 | ||
1166 | /* | |
1167 | * All pages are isolated and locked so anon_vma rmap | |
1168 | * can't run anymore. | |
1169 | */ | |
1170 | anon_vma_unlock_write(vma->anon_vma); | |
1171 | ||
5503fbf2 KS |
1172 | __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl, |
1173 | &compound_pagelist); | |
b46e756f KS |
1174 | pte_unmap(pte); |
1175 | __SetPageUptodate(new_page); | |
1176 | pgtable = pmd_pgtable(_pmd); | |
1177 | ||
1178 | _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); | |
f55e1014 | 1179 | _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); |
b46e756f KS |
1180 | |
1181 | /* | |
1182 | * spin_lock() below is not the equivalent of smp_wmb(), so | |
1183 | * this is needed to avoid the copy_huge_page writes to become | |
1184 | * visible after the set_pmd_at() write. | |
1185 | */ | |
1186 | smp_wmb(); | |
1187 | ||
1188 | spin_lock(pmd_ptl); | |
1189 | BUG_ON(!pmd_none(*pmd)); | |
be5d0a74 | 1190 | page_add_new_anon_rmap(new_page, vma, address, true); |
b518154e | 1191 | lru_cache_add_inactive_or_unevictable(new_page, vma); |
b46e756f KS |
1192 | pgtable_trans_huge_deposit(mm, pmd, pgtable); |
1193 | set_pmd_at(mm, address, pmd, _pmd); | |
1194 | update_mmu_cache_pmd(vma, address, pmd); | |
1195 | spin_unlock(pmd_ptl); | |
1196 | ||
1197 | *hpage = NULL; | |
1198 | ||
1199 | khugepaged_pages_collapsed++; | |
1200 | result = SCAN_SUCCEED; | |
1201 | out_up_write: | |
d8ed45c5 | 1202 | mmap_write_unlock(mm); |
b46e756f | 1203 | out_nolock: |
9d82c694 JW |
1204 | if (!IS_ERR_OR_NULL(*hpage)) |
1205 | mem_cgroup_uncharge(*hpage); | |
b46e756f KS |
1206 | trace_mm_collapse_huge_page(mm, isolated, result); |
1207 | return; | |
1208 | out: | |
b46e756f KS |
1209 | goto out_up_write; |
1210 | } | |
1211 | ||
1212 | static int khugepaged_scan_pmd(struct mm_struct *mm, | |
1213 | struct vm_area_struct *vma, | |
1214 | unsigned long address, | |
1215 | struct page **hpage) | |
1216 | { | |
1217 | pmd_t *pmd; | |
1218 | pte_t *pte, *_pte; | |
71a2c112 KS |
1219 | int ret = 0, result = 0, referenced = 0; |
1220 | int none_or_zero = 0, shared = 0; | |
b46e756f KS |
1221 | struct page *page = NULL; |
1222 | unsigned long _address; | |
1223 | spinlock_t *ptl; | |
1224 | int node = NUMA_NO_NODE, unmapped = 0; | |
0db501f7 | 1225 | bool writable = false; |
b46e756f KS |
1226 | |
1227 | VM_BUG_ON(address & ~HPAGE_PMD_MASK); | |
1228 | ||
1229 | pmd = mm_find_pmd(mm, address); | |
1230 | if (!pmd) { | |
1231 | result = SCAN_PMD_NULL; | |
1232 | goto out; | |
1233 | } | |
1234 | ||
1235 | memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); | |
1236 | pte = pte_offset_map_lock(mm, pmd, address, &ptl); | |
1237 | for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR; | |
1238 | _pte++, _address += PAGE_SIZE) { | |
1239 | pte_t pteval = *_pte; | |
1240 | if (is_swap_pte(pteval)) { | |
1241 | if (++unmapped <= khugepaged_max_ptes_swap) { | |
e1e267c7 PX |
1242 | /* |
1243 | * Always be strict with uffd-wp | |
1244 | * enabled swap entries. Please see | |
1245 | * comment below for pte_uffd_wp(). | |
1246 | */ | |
1247 | if (pte_swp_uffd_wp(pteval)) { | |
1248 | result = SCAN_PTE_UFFD_WP; | |
1249 | goto out_unmap; | |
1250 | } | |
b46e756f KS |
1251 | continue; |
1252 | } else { | |
1253 | result = SCAN_EXCEED_SWAP_PTE; | |
1254 | goto out_unmap; | |
1255 | } | |
1256 | } | |
1257 | if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { | |
1258 | if (!userfaultfd_armed(vma) && | |
1259 | ++none_or_zero <= khugepaged_max_ptes_none) { | |
1260 | continue; | |
1261 | } else { | |
1262 | result = SCAN_EXCEED_NONE_PTE; | |
1263 | goto out_unmap; | |
1264 | } | |
1265 | } | |
1266 | if (!pte_present(pteval)) { | |
1267 | result = SCAN_PTE_NON_PRESENT; | |
1268 | goto out_unmap; | |
1269 | } | |
e1e267c7 PX |
1270 | if (pte_uffd_wp(pteval)) { |
1271 | /* | |
1272 | * Don't collapse the page if any of the small | |
1273 | * PTEs are armed with uffd write protection. | |
1274 | * Here we can also mark the new huge pmd as | |
1275 | * write protected if any of the small ones is | |
1276 | * marked but that could bring uknown | |
1277 | * userfault messages that falls outside of | |
1278 | * the registered range. So, just be simple. | |
1279 | */ | |
1280 | result = SCAN_PTE_UFFD_WP; | |
1281 | goto out_unmap; | |
1282 | } | |
b46e756f KS |
1283 | if (pte_write(pteval)) |
1284 | writable = true; | |
1285 | ||
1286 | page = vm_normal_page(vma, _address, pteval); | |
1287 | if (unlikely(!page)) { | |
1288 | result = SCAN_PAGE_NULL; | |
1289 | goto out_unmap; | |
1290 | } | |
1291 | ||
71a2c112 KS |
1292 | if (page_mapcount(page) > 1 && |
1293 | ++shared > khugepaged_max_ptes_shared) { | |
1294 | result = SCAN_EXCEED_SHARED_PTE; | |
1295 | goto out_unmap; | |
1296 | } | |
1297 | ||
5503fbf2 | 1298 | page = compound_head(page); |
b46e756f KS |
1299 | |
1300 | /* | |
1301 | * Record which node the original page is from and save this | |
1302 | * information to khugepaged_node_load[]. | |
1303 | * Khupaged will allocate hugepage from the node has the max | |
1304 | * hit record. | |
1305 | */ | |
1306 | node = page_to_nid(page); | |
1307 | if (khugepaged_scan_abort(node)) { | |
1308 | result = SCAN_SCAN_ABORT; | |
1309 | goto out_unmap; | |
1310 | } | |
1311 | khugepaged_node_load[node]++; | |
1312 | if (!PageLRU(page)) { | |
1313 | result = SCAN_PAGE_LRU; | |
1314 | goto out_unmap; | |
1315 | } | |
1316 | if (PageLocked(page)) { | |
1317 | result = SCAN_PAGE_LOCK; | |
1318 | goto out_unmap; | |
1319 | } | |
1320 | if (!PageAnon(page)) { | |
1321 | result = SCAN_PAGE_ANON; | |
1322 | goto out_unmap; | |
1323 | } | |
1324 | ||
1325 | /* | |
9445689f KS |
1326 | * Check if the page has any GUP (or other external) pins. |
1327 | * | |
1328 | * Here the check is racy it may see totmal_mapcount > refcount | |
1329 | * in some cases. | |
1330 | * For example, one process with one forked child process. | |
1331 | * The parent has the PMD split due to MADV_DONTNEED, then | |
1332 | * the child is trying unmap the whole PMD, but khugepaged | |
1333 | * may be scanning the parent between the child has | |
1334 | * PageDoubleMap flag cleared and dec the mapcount. So | |
1335 | * khugepaged may see total_mapcount > refcount. | |
1336 | * | |
1337 | * But such case is ephemeral we could always retry collapse | |
1338 | * later. However it may report false positive if the page | |
1339 | * has excessive GUP pins (i.e. 512). Anyway the same check | |
1340 | * will be done again later the risk seems low. | |
b46e756f | 1341 | */ |
9445689f | 1342 | if (!is_refcount_suitable(page)) { |
b46e756f KS |
1343 | result = SCAN_PAGE_COUNT; |
1344 | goto out_unmap; | |
1345 | } | |
1346 | if (pte_young(pteval) || | |
1347 | page_is_young(page) || PageReferenced(page) || | |
1348 | mmu_notifier_test_young(vma->vm_mm, address)) | |
0db501f7 | 1349 | referenced++; |
b46e756f | 1350 | } |
ffe945e6 | 1351 | if (!writable) { |
b46e756f | 1352 | result = SCAN_PAGE_RO; |
ffe945e6 KS |
1353 | } else if (!referenced || (unmapped && referenced < HPAGE_PMD_NR/2)) { |
1354 | result = SCAN_LACK_REFERENCED_PAGE; | |
1355 | } else { | |
1356 | result = SCAN_SUCCEED; | |
1357 | ret = 1; | |
b46e756f KS |
1358 | } |
1359 | out_unmap: | |
1360 | pte_unmap_unlock(pte, ptl); | |
1361 | if (ret) { | |
1362 | node = khugepaged_find_target_node(); | |
c1e8d7c6 | 1363 | /* collapse_huge_page will return with the mmap_lock released */ |
ffe945e6 KS |
1364 | collapse_huge_page(mm, address, hpage, node, |
1365 | referenced, unmapped); | |
b46e756f KS |
1366 | } |
1367 | out: | |
1368 | trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced, | |
1369 | none_or_zero, result, unmapped); | |
1370 | return ret; | |
1371 | } | |
1372 | ||
1373 | static void collect_mm_slot(struct mm_slot *mm_slot) | |
1374 | { | |
1375 | struct mm_struct *mm = mm_slot->mm; | |
1376 | ||
35f3aa39 | 1377 | lockdep_assert_held(&khugepaged_mm_lock); |
b46e756f KS |
1378 | |
1379 | if (khugepaged_test_exit(mm)) { | |
1380 | /* free mm_slot */ | |
1381 | hash_del(&mm_slot->hash); | |
1382 | list_del(&mm_slot->mm_node); | |
1383 | ||
1384 | /* | |
1385 | * Not strictly needed because the mm exited already. | |
1386 | * | |
1387 | * clear_bit(MMF_VM_HUGEPAGE, &mm->flags); | |
1388 | */ | |
1389 | ||
1390 | /* khugepaged_mm_lock actually not necessary for the below */ | |
1391 | free_mm_slot(mm_slot); | |
1392 | mmdrop(mm); | |
1393 | } | |
1394 | } | |
1395 | ||
396bcc52 | 1396 | #ifdef CONFIG_SHMEM |
27e1f827 SL |
1397 | /* |
1398 | * Notify khugepaged that given addr of the mm is pte-mapped THP. Then | |
1399 | * khugepaged should try to collapse the page table. | |
1400 | */ | |
1401 | static int khugepaged_add_pte_mapped_thp(struct mm_struct *mm, | |
1402 | unsigned long addr) | |
1403 | { | |
1404 | struct mm_slot *mm_slot; | |
1405 | ||
1406 | VM_BUG_ON(addr & ~HPAGE_PMD_MASK); | |
1407 | ||
1408 | spin_lock(&khugepaged_mm_lock); | |
1409 | mm_slot = get_mm_slot(mm); | |
1410 | if (likely(mm_slot && mm_slot->nr_pte_mapped_thp < MAX_PTE_MAPPED_THP)) | |
1411 | mm_slot->pte_mapped_thp[mm_slot->nr_pte_mapped_thp++] = addr; | |
1412 | spin_unlock(&khugepaged_mm_lock); | |
1413 | return 0; | |
1414 | } | |
1415 | ||
1416 | /** | |
1417 | * Try to collapse a pte-mapped THP for mm at address haddr. | |
1418 | * | |
1419 | * This function checks whether all the PTEs in the PMD are pointing to the | |
1420 | * right THP. If so, retract the page table so the THP can refault in with | |
1421 | * as pmd-mapped. | |
1422 | */ | |
1423 | void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) | |
1424 | { | |
1425 | unsigned long haddr = addr & HPAGE_PMD_MASK; | |
1426 | struct vm_area_struct *vma = find_vma(mm, haddr); | |
119a5fc1 | 1427 | struct page *hpage; |
27e1f827 SL |
1428 | pte_t *start_pte, *pte; |
1429 | pmd_t *pmd, _pmd; | |
1430 | spinlock_t *ptl; | |
1431 | int count = 0; | |
1432 | int i; | |
1433 | ||
1434 | if (!vma || !vma->vm_file || | |
1435 | vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE) | |
1436 | return; | |
1437 | ||
1438 | /* | |
1439 | * This vm_flags may not have VM_HUGEPAGE if the page was not | |
1440 | * collapsed by this mm. But we can still collapse if the page is | |
1441 | * the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check() | |
1442 | * will not fail the vma for missing VM_HUGEPAGE | |
1443 | */ | |
1444 | if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE)) | |
1445 | return; | |
1446 | ||
119a5fc1 HD |
1447 | hpage = find_lock_page(vma->vm_file->f_mapping, |
1448 | linear_page_index(vma, haddr)); | |
1449 | if (!hpage) | |
1450 | return; | |
1451 | ||
1452 | if (!PageHead(hpage)) | |
1453 | goto drop_hpage; | |
1454 | ||
27e1f827 SL |
1455 | pmd = mm_find_pmd(mm, haddr); |
1456 | if (!pmd) | |
119a5fc1 | 1457 | goto drop_hpage; |
27e1f827 SL |
1458 | |
1459 | start_pte = pte_offset_map_lock(mm, pmd, haddr, &ptl); | |
1460 | ||
1461 | /* step 1: check all mapped PTEs are to the right huge page */ | |
1462 | for (i = 0, addr = haddr, pte = start_pte; | |
1463 | i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) { | |
1464 | struct page *page; | |
1465 | ||
1466 | /* empty pte, skip */ | |
1467 | if (pte_none(*pte)) | |
1468 | continue; | |
1469 | ||
1470 | /* page swapped out, abort */ | |
1471 | if (!pte_present(*pte)) | |
1472 | goto abort; | |
1473 | ||
1474 | page = vm_normal_page(vma, addr, *pte); | |
1475 | ||
27e1f827 | 1476 | /* |
119a5fc1 HD |
1477 | * Note that uprobe, debugger, or MAP_PRIVATE may change the |
1478 | * page table, but the new page will not be a subpage of hpage. | |
27e1f827 | 1479 | */ |
119a5fc1 | 1480 | if (hpage + i != page) |
27e1f827 SL |
1481 | goto abort; |
1482 | count++; | |
1483 | } | |
1484 | ||
1485 | /* step 2: adjust rmap */ | |
1486 | for (i = 0, addr = haddr, pte = start_pte; | |
1487 | i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) { | |
1488 | struct page *page; | |
1489 | ||
1490 | if (pte_none(*pte)) | |
1491 | continue; | |
1492 | page = vm_normal_page(vma, addr, *pte); | |
1493 | page_remove_rmap(page, false); | |
1494 | } | |
1495 | ||
1496 | pte_unmap_unlock(start_pte, ptl); | |
1497 | ||
1498 | /* step 3: set proper refcount and mm_counters. */ | |
119a5fc1 | 1499 | if (count) { |
27e1f827 SL |
1500 | page_ref_sub(hpage, count); |
1501 | add_mm_counter(vma->vm_mm, mm_counter_file(hpage), -count); | |
1502 | } | |
1503 | ||
1504 | /* step 4: collapse pmd */ | |
1505 | ptl = pmd_lock(vma->vm_mm, pmd); | |
723a80da | 1506 | _pmd = pmdp_collapse_flush(vma, haddr, pmd); |
27e1f827 SL |
1507 | spin_unlock(ptl); |
1508 | mm_dec_nr_ptes(mm); | |
1509 | pte_free(mm, pmd_pgtable(_pmd)); | |
119a5fc1 HD |
1510 | |
1511 | drop_hpage: | |
1512 | unlock_page(hpage); | |
1513 | put_page(hpage); | |
27e1f827 SL |
1514 | return; |
1515 | ||
1516 | abort: | |
1517 | pte_unmap_unlock(start_pte, ptl); | |
119a5fc1 | 1518 | goto drop_hpage; |
27e1f827 SL |
1519 | } |
1520 | ||
1521 | static int khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot) | |
1522 | { | |
1523 | struct mm_struct *mm = mm_slot->mm; | |
1524 | int i; | |
1525 | ||
1526 | if (likely(mm_slot->nr_pte_mapped_thp == 0)) | |
1527 | return 0; | |
1528 | ||
d8ed45c5 | 1529 | if (!mmap_write_trylock(mm)) |
27e1f827 SL |
1530 | return -EBUSY; |
1531 | ||
1532 | if (unlikely(khugepaged_test_exit(mm))) | |
1533 | goto out; | |
1534 | ||
1535 | for (i = 0; i < mm_slot->nr_pte_mapped_thp; i++) | |
1536 | collapse_pte_mapped_thp(mm, mm_slot->pte_mapped_thp[i]); | |
1537 | ||
1538 | out: | |
1539 | mm_slot->nr_pte_mapped_thp = 0; | |
d8ed45c5 | 1540 | mmap_write_unlock(mm); |
27e1f827 SL |
1541 | return 0; |
1542 | } | |
1543 | ||
f3f0e1d2 KS |
1544 | static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) |
1545 | { | |
1546 | struct vm_area_struct *vma; | |
18e77600 | 1547 | struct mm_struct *mm; |
f3f0e1d2 KS |
1548 | unsigned long addr; |
1549 | pmd_t *pmd, _pmd; | |
1550 | ||
1551 | i_mmap_lock_write(mapping); | |
1552 | vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { | |
27e1f827 SL |
1553 | /* |
1554 | * Check vma->anon_vma to exclude MAP_PRIVATE mappings that | |
1555 | * got written to. These VMAs are likely not worth investing | |
3e4e28c5 | 1556 | * mmap_write_lock(mm) as PMD-mapping is likely to be split |
27e1f827 SL |
1557 | * later. |
1558 | * | |
1559 | * Not that vma->anon_vma check is racy: it can be set up after | |
c1e8d7c6 | 1560 | * the check but before we took mmap_lock by the fault path. |
27e1f827 SL |
1561 | * But page lock would prevent establishing any new ptes of the |
1562 | * page, so we are safe. | |
1563 | * | |
1564 | * An alternative would be drop the check, but check that page | |
1565 | * table is clear before calling pmdp_collapse_flush() under | |
1566 | * ptl. It has higher chance to recover THP for the VMA, but | |
1567 | * has higher cost too. | |
1568 | */ | |
f3f0e1d2 KS |
1569 | if (vma->anon_vma) |
1570 | continue; | |
1571 | addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT); | |
1572 | if (addr & ~HPAGE_PMD_MASK) | |
1573 | continue; | |
1574 | if (vma->vm_end < addr + HPAGE_PMD_SIZE) | |
1575 | continue; | |
18e77600 HD |
1576 | mm = vma->vm_mm; |
1577 | pmd = mm_find_pmd(mm, addr); | |
f3f0e1d2 KS |
1578 | if (!pmd) |
1579 | continue; | |
1580 | /* | |
c1e8d7c6 | 1581 | * We need exclusive mmap_lock to retract page table. |
27e1f827 SL |
1582 | * |
1583 | * We use trylock due to lock inversion: we need to acquire | |
c1e8d7c6 | 1584 | * mmap_lock while holding page lock. Fault path does it in |
27e1f827 | 1585 | * reverse order. Trylock is a way to avoid deadlock. |
f3f0e1d2 | 1586 | */ |
18e77600 HD |
1587 | if (mmap_write_trylock(mm)) { |
1588 | if (!khugepaged_test_exit(mm)) { | |
1589 | spinlock_t *ptl = pmd_lock(mm, pmd); | |
1590 | /* assume page table is clear */ | |
1591 | _pmd = pmdp_collapse_flush(vma, addr, pmd); | |
1592 | spin_unlock(ptl); | |
1593 | mm_dec_nr_ptes(mm); | |
1594 | pte_free(mm, pmd_pgtable(_pmd)); | |
1595 | } | |
1596 | mmap_write_unlock(mm); | |
27e1f827 SL |
1597 | } else { |
1598 | /* Try again later */ | |
18e77600 | 1599 | khugepaged_add_pte_mapped_thp(mm, addr); |
f3f0e1d2 KS |
1600 | } |
1601 | } | |
1602 | i_mmap_unlock_write(mapping); | |
1603 | } | |
1604 | ||
1605 | /** | |
99cb0dbd | 1606 | * collapse_file - collapse filemap/tmpfs/shmem pages into huge one. |
f3f0e1d2 KS |
1607 | * |
1608 | * Basic scheme is simple, details are more complex: | |
87c460a0 | 1609 | * - allocate and lock a new huge page; |
77da9389 | 1610 | * - scan page cache replacing old pages with the new one |
99cb0dbd | 1611 | * + swap/gup in pages if necessary; |
f3f0e1d2 | 1612 | * + fill in gaps; |
77da9389 MW |
1613 | * + keep old pages around in case rollback is required; |
1614 | * - if replacing succeeds: | |
f3f0e1d2 KS |
1615 | * + copy data over; |
1616 | * + free old pages; | |
87c460a0 | 1617 | * + unlock huge page; |
f3f0e1d2 KS |
1618 | * - if replacing failed; |
1619 | * + put all pages back and unfreeze them; | |
77da9389 | 1620 | * + restore gaps in the page cache; |
87c460a0 | 1621 | * + unlock and free huge page; |
f3f0e1d2 | 1622 | */ |
579c571e SL |
1623 | static void collapse_file(struct mm_struct *mm, |
1624 | struct file *file, pgoff_t start, | |
f3f0e1d2 KS |
1625 | struct page **hpage, int node) |
1626 | { | |
579c571e | 1627 | struct address_space *mapping = file->f_mapping; |
f3f0e1d2 | 1628 | gfp_t gfp; |
77da9389 | 1629 | struct page *new_page; |
f3f0e1d2 KS |
1630 | pgoff_t index, end = start + HPAGE_PMD_NR; |
1631 | LIST_HEAD(pagelist); | |
77da9389 | 1632 | XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); |
f3f0e1d2 | 1633 | int nr_none = 0, result = SCAN_SUCCEED; |
99cb0dbd | 1634 | bool is_shmem = shmem_file(file); |
f3f0e1d2 | 1635 | |
99cb0dbd | 1636 | VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); |
f3f0e1d2 KS |
1637 | VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); |
1638 | ||
1639 | /* Only allocate from the target node */ | |
41b6167e | 1640 | gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE; |
f3f0e1d2 KS |
1641 | |
1642 | new_page = khugepaged_alloc_page(hpage, gfp, node); | |
1643 | if (!new_page) { | |
1644 | result = SCAN_ALLOC_HUGE_PAGE_FAIL; | |
1645 | goto out; | |
1646 | } | |
1647 | ||
d9eb1ea2 | 1648 | if (unlikely(mem_cgroup_charge(new_page, mm, gfp))) { |
f3f0e1d2 KS |
1649 | result = SCAN_CGROUP_CHARGE_FAIL; |
1650 | goto out; | |
1651 | } | |
9d82c694 | 1652 | count_memcg_page_event(new_page, THP_COLLAPSE_ALLOC); |
f3f0e1d2 | 1653 | |
95feeabb HD |
1654 | /* This will be less messy when we use multi-index entries */ |
1655 | do { | |
1656 | xas_lock_irq(&xas); | |
1657 | xas_create_range(&xas); | |
1658 | if (!xas_error(&xas)) | |
1659 | break; | |
1660 | xas_unlock_irq(&xas); | |
1661 | if (!xas_nomem(&xas, GFP_KERNEL)) { | |
95feeabb HD |
1662 | result = SCAN_FAIL; |
1663 | goto out; | |
1664 | } | |
1665 | } while (1); | |
1666 | ||
042a3082 | 1667 | __SetPageLocked(new_page); |
99cb0dbd SL |
1668 | if (is_shmem) |
1669 | __SetPageSwapBacked(new_page); | |
f3f0e1d2 KS |
1670 | new_page->index = start; |
1671 | new_page->mapping = mapping; | |
f3f0e1d2 | 1672 | |
f3f0e1d2 | 1673 | /* |
87c460a0 HD |
1674 | * At this point the new_page is locked and not up-to-date. |
1675 | * It's safe to insert it into the page cache, because nobody would | |
1676 | * be able to map it or use it in another way until we unlock it. | |
f3f0e1d2 KS |
1677 | */ |
1678 | ||
77da9389 MW |
1679 | xas_set(&xas, start); |
1680 | for (index = start; index < end; index++) { | |
1681 | struct page *page = xas_next(&xas); | |
1682 | ||
1683 | VM_BUG_ON(index != xas.xa_index); | |
99cb0dbd SL |
1684 | if (is_shmem) { |
1685 | if (!page) { | |
1686 | /* | |
1687 | * Stop if extent has been truncated or | |
1688 | * hole-punched, and is now completely | |
1689 | * empty. | |
1690 | */ | |
1691 | if (index == start) { | |
1692 | if (!xas_next_entry(&xas, end - 1)) { | |
1693 | result = SCAN_TRUNCATED; | |
1694 | goto xa_locked; | |
1695 | } | |
1696 | xas_set(&xas, index); | |
1697 | } | |
1698 | if (!shmem_charge(mapping->host, 1)) { | |
1699 | result = SCAN_FAIL; | |
042a3082 | 1700 | goto xa_locked; |
701270fa | 1701 | } |
99cb0dbd SL |
1702 | xas_store(&xas, new_page); |
1703 | nr_none++; | |
1704 | continue; | |
701270fa | 1705 | } |
99cb0dbd SL |
1706 | |
1707 | if (xa_is_value(page) || !PageUptodate(page)) { | |
1708 | xas_unlock_irq(&xas); | |
1709 | /* swap in or instantiate fallocated page */ | |
1710 | if (shmem_getpage(mapping->host, index, &page, | |
1711 | SGP_NOHUGE)) { | |
1712 | result = SCAN_FAIL; | |
1713 | goto xa_unlocked; | |
1714 | } | |
1715 | } else if (trylock_page(page)) { | |
1716 | get_page(page); | |
1717 | xas_unlock_irq(&xas); | |
1718 | } else { | |
1719 | result = SCAN_PAGE_LOCK; | |
042a3082 | 1720 | goto xa_locked; |
77da9389 | 1721 | } |
99cb0dbd SL |
1722 | } else { /* !is_shmem */ |
1723 | if (!page || xa_is_value(page)) { | |
1724 | xas_unlock_irq(&xas); | |
1725 | page_cache_sync_readahead(mapping, &file->f_ra, | |
1726 | file, index, | |
e5a59d30 | 1727 | end - index); |
99cb0dbd SL |
1728 | /* drain pagevecs to help isolate_lru_page() */ |
1729 | lru_add_drain(); | |
1730 | page = find_lock_page(mapping, index); | |
1731 | if (unlikely(page == NULL)) { | |
1732 | result = SCAN_FAIL; | |
1733 | goto xa_unlocked; | |
1734 | } | |
75f36069 SL |
1735 | } else if (PageDirty(page)) { |
1736 | /* | |
1737 | * khugepaged only works on read-only fd, | |
1738 | * so this page is dirty because it hasn't | |
1739 | * been flushed since first write. There | |
1740 | * won't be new dirty pages. | |
1741 | * | |
1742 | * Trigger async flush here and hope the | |
1743 | * writeback is done when khugepaged | |
1744 | * revisits this page. | |
1745 | * | |
1746 | * This is a one-off situation. We are not | |
1747 | * forcing writeback in loop. | |
1748 | */ | |
1749 | xas_unlock_irq(&xas); | |
1750 | filemap_flush(mapping); | |
1751 | result = SCAN_FAIL; | |
1752 | goto xa_unlocked; | |
99cb0dbd SL |
1753 | } else if (trylock_page(page)) { |
1754 | get_page(page); | |
1755 | xas_unlock_irq(&xas); | |
1756 | } else { | |
1757 | result = SCAN_PAGE_LOCK; | |
1758 | goto xa_locked; | |
f3f0e1d2 | 1759 | } |
f3f0e1d2 KS |
1760 | } |
1761 | ||
1762 | /* | |
b93b0163 | 1763 | * The page must be locked, so we can drop the i_pages lock |
f3f0e1d2 KS |
1764 | * without racing with truncate. |
1765 | */ | |
1766 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
4655e5e5 SL |
1767 | |
1768 | /* make sure the page is up to date */ | |
1769 | if (unlikely(!PageUptodate(page))) { | |
1770 | result = SCAN_FAIL; | |
1771 | goto out_unlock; | |
1772 | } | |
06a5e126 HD |
1773 | |
1774 | /* | |
1775 | * If file was truncated then extended, or hole-punched, before | |
1776 | * we locked the first page, then a THP might be there already. | |
1777 | */ | |
1778 | if (PageTransCompound(page)) { | |
1779 | result = SCAN_PAGE_COMPOUND; | |
1780 | goto out_unlock; | |
1781 | } | |
f3f0e1d2 KS |
1782 | |
1783 | if (page_mapping(page) != mapping) { | |
1784 | result = SCAN_TRUNCATED; | |
1785 | goto out_unlock; | |
1786 | } | |
f3f0e1d2 | 1787 | |
4655e5e5 SL |
1788 | if (!is_shmem && PageDirty(page)) { |
1789 | /* | |
1790 | * khugepaged only works on read-only fd, so this | |
1791 | * page is dirty because it hasn't been flushed | |
1792 | * since first write. | |
1793 | */ | |
1794 | result = SCAN_FAIL; | |
1795 | goto out_unlock; | |
1796 | } | |
1797 | ||
f3f0e1d2 KS |
1798 | if (isolate_lru_page(page)) { |
1799 | result = SCAN_DEL_PAGE_LRU; | |
042a3082 | 1800 | goto out_unlock; |
f3f0e1d2 KS |
1801 | } |
1802 | ||
99cb0dbd SL |
1803 | if (page_has_private(page) && |
1804 | !try_to_release_page(page, GFP_KERNEL)) { | |
1805 | result = SCAN_PAGE_HAS_PRIVATE; | |
2f33a706 | 1806 | putback_lru_page(page); |
99cb0dbd SL |
1807 | goto out_unlock; |
1808 | } | |
1809 | ||
f3f0e1d2 | 1810 | if (page_mapped(page)) |
977fbdcd | 1811 | unmap_mapping_pages(mapping, index, 1, false); |
f3f0e1d2 | 1812 | |
77da9389 MW |
1813 | xas_lock_irq(&xas); |
1814 | xas_set(&xas, index); | |
f3f0e1d2 | 1815 | |
77da9389 | 1816 | VM_BUG_ON_PAGE(page != xas_load(&xas), page); |
f3f0e1d2 KS |
1817 | VM_BUG_ON_PAGE(page_mapped(page), page); |
1818 | ||
1819 | /* | |
1820 | * The page is expected to have page_count() == 3: | |
1821 | * - we hold a pin on it; | |
77da9389 | 1822 | * - one reference from page cache; |
f3f0e1d2 KS |
1823 | * - one from isolate_lru_page; |
1824 | */ | |
1825 | if (!page_ref_freeze(page, 3)) { | |
1826 | result = SCAN_PAGE_COUNT; | |
042a3082 HD |
1827 | xas_unlock_irq(&xas); |
1828 | putback_lru_page(page); | |
1829 | goto out_unlock; | |
f3f0e1d2 KS |
1830 | } |
1831 | ||
1832 | /* | |
1833 | * Add the page to the list to be able to undo the collapse if | |
1834 | * something go wrong. | |
1835 | */ | |
1836 | list_add_tail(&page->lru, &pagelist); | |
1837 | ||
1838 | /* Finally, replace with the new page. */ | |
4101196b | 1839 | xas_store(&xas, new_page); |
f3f0e1d2 | 1840 | continue; |
f3f0e1d2 KS |
1841 | out_unlock: |
1842 | unlock_page(page); | |
1843 | put_page(page); | |
042a3082 | 1844 | goto xa_unlocked; |
f3f0e1d2 KS |
1845 | } |
1846 | ||
99cb0dbd SL |
1847 | if (is_shmem) |
1848 | __inc_node_page_state(new_page, NR_SHMEM_THPS); | |
09d91cda | 1849 | else { |
99cb0dbd | 1850 | __inc_node_page_state(new_page, NR_FILE_THPS); |
09d91cda SL |
1851 | filemap_nr_thps_inc(mapping); |
1852 | } | |
99cb0dbd | 1853 | |
042a3082 | 1854 | if (nr_none) { |
9d82c694 | 1855 | __mod_lruvec_page_state(new_page, NR_FILE_PAGES, nr_none); |
99cb0dbd | 1856 | if (is_shmem) |
9d82c694 | 1857 | __mod_lruvec_page_state(new_page, NR_SHMEM, nr_none); |
042a3082 HD |
1858 | } |
1859 | ||
1860 | xa_locked: | |
1861 | xas_unlock_irq(&xas); | |
77da9389 | 1862 | xa_unlocked: |
042a3082 | 1863 | |
f3f0e1d2 | 1864 | if (result == SCAN_SUCCEED) { |
77da9389 | 1865 | struct page *page, *tmp; |
f3f0e1d2 KS |
1866 | |
1867 | /* | |
77da9389 MW |
1868 | * Replacing old pages with new one has succeeded, now we |
1869 | * need to copy the content and free the old pages. | |
f3f0e1d2 | 1870 | */ |
2af8ff29 | 1871 | index = start; |
f3f0e1d2 | 1872 | list_for_each_entry_safe(page, tmp, &pagelist, lru) { |
2af8ff29 HD |
1873 | while (index < page->index) { |
1874 | clear_highpage(new_page + (index % HPAGE_PMD_NR)); | |
1875 | index++; | |
1876 | } | |
f3f0e1d2 KS |
1877 | copy_highpage(new_page + (page->index % HPAGE_PMD_NR), |
1878 | page); | |
1879 | list_del(&page->lru); | |
f3f0e1d2 | 1880 | page->mapping = NULL; |
042a3082 | 1881 | page_ref_unfreeze(page, 1); |
f3f0e1d2 KS |
1882 | ClearPageActive(page); |
1883 | ClearPageUnevictable(page); | |
042a3082 | 1884 | unlock_page(page); |
f3f0e1d2 | 1885 | put_page(page); |
2af8ff29 HD |
1886 | index++; |
1887 | } | |
1888 | while (index < end) { | |
1889 | clear_highpage(new_page + (index % HPAGE_PMD_NR)); | |
1890 | index++; | |
f3f0e1d2 KS |
1891 | } |
1892 | ||
f3f0e1d2 | 1893 | SetPageUptodate(new_page); |
87c460a0 | 1894 | page_ref_add(new_page, HPAGE_PMD_NR - 1); |
6058eaec | 1895 | if (is_shmem) |
99cb0dbd | 1896 | set_page_dirty(new_page); |
6058eaec | 1897 | lru_cache_add(new_page); |
f3f0e1d2 | 1898 | |
042a3082 HD |
1899 | /* |
1900 | * Remove pte page tables, so we can re-fault the page as huge. | |
1901 | */ | |
1902 | retract_page_tables(mapping, start); | |
f3f0e1d2 | 1903 | *hpage = NULL; |
87aa7529 YS |
1904 | |
1905 | khugepaged_pages_collapsed++; | |
f3f0e1d2 | 1906 | } else { |
77da9389 | 1907 | struct page *page; |
aaa52e34 | 1908 | |
77da9389 | 1909 | /* Something went wrong: roll back page cache changes */ |
77da9389 | 1910 | xas_lock_irq(&xas); |
aaa52e34 | 1911 | mapping->nrpages -= nr_none; |
99cb0dbd SL |
1912 | |
1913 | if (is_shmem) | |
1914 | shmem_uncharge(mapping->host, nr_none); | |
aaa52e34 | 1915 | |
77da9389 MW |
1916 | xas_set(&xas, start); |
1917 | xas_for_each(&xas, page, end - 1) { | |
f3f0e1d2 KS |
1918 | page = list_first_entry_or_null(&pagelist, |
1919 | struct page, lru); | |
77da9389 | 1920 | if (!page || xas.xa_index < page->index) { |
f3f0e1d2 KS |
1921 | if (!nr_none) |
1922 | break; | |
f3f0e1d2 | 1923 | nr_none--; |
59749e6c | 1924 | /* Put holes back where they were */ |
77da9389 | 1925 | xas_store(&xas, NULL); |
f3f0e1d2 KS |
1926 | continue; |
1927 | } | |
1928 | ||
77da9389 | 1929 | VM_BUG_ON_PAGE(page->index != xas.xa_index, page); |
f3f0e1d2 KS |
1930 | |
1931 | /* Unfreeze the page. */ | |
1932 | list_del(&page->lru); | |
1933 | page_ref_unfreeze(page, 2); | |
77da9389 MW |
1934 | xas_store(&xas, page); |
1935 | xas_pause(&xas); | |
1936 | xas_unlock_irq(&xas); | |
f3f0e1d2 | 1937 | unlock_page(page); |
042a3082 | 1938 | putback_lru_page(page); |
77da9389 | 1939 | xas_lock_irq(&xas); |
f3f0e1d2 KS |
1940 | } |
1941 | VM_BUG_ON(nr_none); | |
77da9389 | 1942 | xas_unlock_irq(&xas); |
f3f0e1d2 | 1943 | |
f3f0e1d2 KS |
1944 | new_page->mapping = NULL; |
1945 | } | |
042a3082 HD |
1946 | |
1947 | unlock_page(new_page); | |
f3f0e1d2 KS |
1948 | out: |
1949 | VM_BUG_ON(!list_empty(&pagelist)); | |
9d82c694 JW |
1950 | if (!IS_ERR_OR_NULL(*hpage)) |
1951 | mem_cgroup_uncharge(*hpage); | |
f3f0e1d2 KS |
1952 | /* TODO: tracepoints */ |
1953 | } | |
1954 | ||
579c571e SL |
1955 | static void khugepaged_scan_file(struct mm_struct *mm, |
1956 | struct file *file, pgoff_t start, struct page **hpage) | |
f3f0e1d2 KS |
1957 | { |
1958 | struct page *page = NULL; | |
579c571e | 1959 | struct address_space *mapping = file->f_mapping; |
85b392db | 1960 | XA_STATE(xas, &mapping->i_pages, start); |
f3f0e1d2 KS |
1961 | int present, swap; |
1962 | int node = NUMA_NO_NODE; | |
1963 | int result = SCAN_SUCCEED; | |
1964 | ||
1965 | present = 0; | |
1966 | swap = 0; | |
1967 | memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load)); | |
1968 | rcu_read_lock(); | |
85b392db MW |
1969 | xas_for_each(&xas, page, start + HPAGE_PMD_NR - 1) { |
1970 | if (xas_retry(&xas, page)) | |
f3f0e1d2 | 1971 | continue; |
f3f0e1d2 | 1972 | |
85b392db | 1973 | if (xa_is_value(page)) { |
f3f0e1d2 KS |
1974 | if (++swap > khugepaged_max_ptes_swap) { |
1975 | result = SCAN_EXCEED_SWAP_PTE; | |
1976 | break; | |
1977 | } | |
1978 | continue; | |
1979 | } | |
1980 | ||
1981 | if (PageTransCompound(page)) { | |
1982 | result = SCAN_PAGE_COMPOUND; | |
1983 | break; | |
1984 | } | |
1985 | ||
1986 | node = page_to_nid(page); | |
1987 | if (khugepaged_scan_abort(node)) { | |
1988 | result = SCAN_SCAN_ABORT; | |
1989 | break; | |
1990 | } | |
1991 | khugepaged_node_load[node]++; | |
1992 | ||
1993 | if (!PageLRU(page)) { | |
1994 | result = SCAN_PAGE_LRU; | |
1995 | break; | |
1996 | } | |
1997 | ||
99cb0dbd SL |
1998 | if (page_count(page) != |
1999 | 1 + page_mapcount(page) + page_has_private(page)) { | |
f3f0e1d2 KS |
2000 | result = SCAN_PAGE_COUNT; |
2001 | break; | |
2002 | } | |
2003 | ||
2004 | /* | |
2005 | * We probably should check if the page is referenced here, but | |
2006 | * nobody would transfer pte_young() to PageReferenced() for us. | |
2007 | * And rmap walk here is just too costly... | |
2008 | */ | |
2009 | ||
2010 | present++; | |
2011 | ||
2012 | if (need_resched()) { | |
85b392db | 2013 | xas_pause(&xas); |
f3f0e1d2 | 2014 | cond_resched_rcu(); |
f3f0e1d2 KS |
2015 | } |
2016 | } | |
2017 | rcu_read_unlock(); | |
2018 | ||
2019 | if (result == SCAN_SUCCEED) { | |
2020 | if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) { | |
2021 | result = SCAN_EXCEED_NONE_PTE; | |
2022 | } else { | |
2023 | node = khugepaged_find_target_node(); | |
579c571e | 2024 | collapse_file(mm, file, start, hpage, node); |
f3f0e1d2 KS |
2025 | } |
2026 | } | |
2027 | ||
2028 | /* TODO: tracepoints */ | |
2029 | } | |
2030 | #else | |
579c571e SL |
2031 | static void khugepaged_scan_file(struct mm_struct *mm, |
2032 | struct file *file, pgoff_t start, struct page **hpage) | |
f3f0e1d2 KS |
2033 | { |
2034 | BUILD_BUG(); | |
2035 | } | |
27e1f827 SL |
2036 | |
2037 | static int khugepaged_collapse_pte_mapped_thps(struct mm_slot *mm_slot) | |
2038 | { | |
2039 | return 0; | |
2040 | } | |
f3f0e1d2 KS |
2041 | #endif |
2042 | ||
b46e756f KS |
2043 | static unsigned int khugepaged_scan_mm_slot(unsigned int pages, |
2044 | struct page **hpage) | |
2045 | __releases(&khugepaged_mm_lock) | |
2046 | __acquires(&khugepaged_mm_lock) | |
2047 | { | |
2048 | struct mm_slot *mm_slot; | |
2049 | struct mm_struct *mm; | |
2050 | struct vm_area_struct *vma; | |
2051 | int progress = 0; | |
2052 | ||
2053 | VM_BUG_ON(!pages); | |
35f3aa39 | 2054 | lockdep_assert_held(&khugepaged_mm_lock); |
b46e756f KS |
2055 | |
2056 | if (khugepaged_scan.mm_slot) | |
2057 | mm_slot = khugepaged_scan.mm_slot; | |
2058 | else { | |
2059 | mm_slot = list_entry(khugepaged_scan.mm_head.next, | |
2060 | struct mm_slot, mm_node); | |
2061 | khugepaged_scan.address = 0; | |
2062 | khugepaged_scan.mm_slot = mm_slot; | |
2063 | } | |
2064 | spin_unlock(&khugepaged_mm_lock); | |
27e1f827 | 2065 | khugepaged_collapse_pte_mapped_thps(mm_slot); |
b46e756f KS |
2066 | |
2067 | mm = mm_slot->mm; | |
3b454ad3 YS |
2068 | /* |
2069 | * Don't wait for semaphore (to avoid long wait times). Just move to | |
2070 | * the next mm on the list. | |
2071 | */ | |
2072 | vma = NULL; | |
d8ed45c5 | 2073 | if (unlikely(!mmap_read_trylock(mm))) |
c1e8d7c6 | 2074 | goto breakouterloop_mmap_lock; |
3b454ad3 | 2075 | if (likely(!khugepaged_test_exit(mm))) |
b46e756f KS |
2076 | vma = find_vma(mm, khugepaged_scan.address); |
2077 | ||
2078 | progress++; | |
2079 | for (; vma; vma = vma->vm_next) { | |
2080 | unsigned long hstart, hend; | |
2081 | ||
2082 | cond_resched(); | |
2083 | if (unlikely(khugepaged_test_exit(mm))) { | |
2084 | progress++; | |
2085 | break; | |
2086 | } | |
50f8b92f | 2087 | if (!hugepage_vma_check(vma, vma->vm_flags)) { |
b46e756f KS |
2088 | skip: |
2089 | progress++; | |
2090 | continue; | |
2091 | } | |
2092 | hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; | |
2093 | hend = vma->vm_end & HPAGE_PMD_MASK; | |
2094 | if (hstart >= hend) | |
2095 | goto skip; | |
2096 | if (khugepaged_scan.address > hend) | |
2097 | goto skip; | |
2098 | if (khugepaged_scan.address < hstart) | |
2099 | khugepaged_scan.address = hstart; | |
2100 | VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK); | |
396bcc52 MWO |
2101 | if (shmem_file(vma->vm_file) && !shmem_huge_enabled(vma)) |
2102 | goto skip; | |
b46e756f KS |
2103 | |
2104 | while (khugepaged_scan.address < hend) { | |
2105 | int ret; | |
2106 | cond_resched(); | |
2107 | if (unlikely(khugepaged_test_exit(mm))) | |
2108 | goto breakouterloop; | |
2109 | ||
2110 | VM_BUG_ON(khugepaged_scan.address < hstart || | |
2111 | khugepaged_scan.address + HPAGE_PMD_SIZE > | |
2112 | hend); | |
99cb0dbd | 2113 | if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) { |
396bcc52 | 2114 | struct file *file = get_file(vma->vm_file); |
f3f0e1d2 KS |
2115 | pgoff_t pgoff = linear_page_index(vma, |
2116 | khugepaged_scan.address); | |
99cb0dbd | 2117 | |
d8ed45c5 | 2118 | mmap_read_unlock(mm); |
f3f0e1d2 | 2119 | ret = 1; |
579c571e | 2120 | khugepaged_scan_file(mm, file, pgoff, hpage); |
f3f0e1d2 KS |
2121 | fput(file); |
2122 | } else { | |
2123 | ret = khugepaged_scan_pmd(mm, vma, | |
2124 | khugepaged_scan.address, | |
2125 | hpage); | |
2126 | } | |
b46e756f KS |
2127 | /* move to next address */ |
2128 | khugepaged_scan.address += HPAGE_PMD_SIZE; | |
2129 | progress += HPAGE_PMD_NR; | |
2130 | if (ret) | |
c1e8d7c6 ML |
2131 | /* we released mmap_lock so break loop */ |
2132 | goto breakouterloop_mmap_lock; | |
b46e756f KS |
2133 | if (progress >= pages) |
2134 | goto breakouterloop; | |
2135 | } | |
2136 | } | |
2137 | breakouterloop: | |
d8ed45c5 | 2138 | mmap_read_unlock(mm); /* exit_mmap will destroy ptes after this */ |
c1e8d7c6 | 2139 | breakouterloop_mmap_lock: |
b46e756f KS |
2140 | |
2141 | spin_lock(&khugepaged_mm_lock); | |
2142 | VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot); | |
2143 | /* | |
2144 | * Release the current mm_slot if this mm is about to die, or | |
2145 | * if we scanned all vmas of this mm. | |
2146 | */ | |
2147 | if (khugepaged_test_exit(mm) || !vma) { | |
2148 | /* | |
2149 | * Make sure that if mm_users is reaching zero while | |
2150 | * khugepaged runs here, khugepaged_exit will find | |
2151 | * mm_slot not pointing to the exiting mm. | |
2152 | */ | |
2153 | if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) { | |
2154 | khugepaged_scan.mm_slot = list_entry( | |
2155 | mm_slot->mm_node.next, | |
2156 | struct mm_slot, mm_node); | |
2157 | khugepaged_scan.address = 0; | |
2158 | } else { | |
2159 | khugepaged_scan.mm_slot = NULL; | |
2160 | khugepaged_full_scans++; | |
2161 | } | |
2162 | ||
2163 | collect_mm_slot(mm_slot); | |
2164 | } | |
2165 | ||
2166 | return progress; | |
2167 | } | |
2168 | ||
2169 | static int khugepaged_has_work(void) | |
2170 | { | |
2171 | return !list_empty(&khugepaged_scan.mm_head) && | |
2172 | khugepaged_enabled(); | |
2173 | } | |
2174 | ||
2175 | static int khugepaged_wait_event(void) | |
2176 | { | |
2177 | return !list_empty(&khugepaged_scan.mm_head) || | |
2178 | kthread_should_stop(); | |
2179 | } | |
2180 | ||
2181 | static void khugepaged_do_scan(void) | |
2182 | { | |
2183 | struct page *hpage = NULL; | |
2184 | unsigned int progress = 0, pass_through_head = 0; | |
2185 | unsigned int pages = khugepaged_pages_to_scan; | |
2186 | bool wait = true; | |
2187 | ||
2188 | barrier(); /* write khugepaged_pages_to_scan to local stack */ | |
2189 | ||
a980df33 KS |
2190 | lru_add_drain_all(); |
2191 | ||
b46e756f KS |
2192 | while (progress < pages) { |
2193 | if (!khugepaged_prealloc_page(&hpage, &wait)) | |
2194 | break; | |
2195 | ||
2196 | cond_resched(); | |
2197 | ||
2198 | if (unlikely(kthread_should_stop() || try_to_freeze())) | |
2199 | break; | |
2200 | ||
2201 | spin_lock(&khugepaged_mm_lock); | |
2202 | if (!khugepaged_scan.mm_slot) | |
2203 | pass_through_head++; | |
2204 | if (khugepaged_has_work() && | |
2205 | pass_through_head < 2) | |
2206 | progress += khugepaged_scan_mm_slot(pages - progress, | |
2207 | &hpage); | |
2208 | else | |
2209 | progress = pages; | |
2210 | spin_unlock(&khugepaged_mm_lock); | |
2211 | } | |
2212 | ||
2213 | if (!IS_ERR_OR_NULL(hpage)) | |
2214 | put_page(hpage); | |
2215 | } | |
2216 | ||
2217 | static bool khugepaged_should_wakeup(void) | |
2218 | { | |
2219 | return kthread_should_stop() || | |
2220 | time_after_eq(jiffies, khugepaged_sleep_expire); | |
2221 | } | |
2222 | ||
2223 | static void khugepaged_wait_work(void) | |
2224 | { | |
2225 | if (khugepaged_has_work()) { | |
2226 | const unsigned long scan_sleep_jiffies = | |
2227 | msecs_to_jiffies(khugepaged_scan_sleep_millisecs); | |
2228 | ||
2229 | if (!scan_sleep_jiffies) | |
2230 | return; | |
2231 | ||
2232 | khugepaged_sleep_expire = jiffies + scan_sleep_jiffies; | |
2233 | wait_event_freezable_timeout(khugepaged_wait, | |
2234 | khugepaged_should_wakeup(), | |
2235 | scan_sleep_jiffies); | |
2236 | return; | |
2237 | } | |
2238 | ||
2239 | if (khugepaged_enabled()) | |
2240 | wait_event_freezable(khugepaged_wait, khugepaged_wait_event()); | |
2241 | } | |
2242 | ||
2243 | static int khugepaged(void *none) | |
2244 | { | |
2245 | struct mm_slot *mm_slot; | |
2246 | ||
2247 | set_freezable(); | |
2248 | set_user_nice(current, MAX_NICE); | |
2249 | ||
2250 | while (!kthread_should_stop()) { | |
2251 | khugepaged_do_scan(); | |
2252 | khugepaged_wait_work(); | |
2253 | } | |
2254 | ||
2255 | spin_lock(&khugepaged_mm_lock); | |
2256 | mm_slot = khugepaged_scan.mm_slot; | |
2257 | khugepaged_scan.mm_slot = NULL; | |
2258 | if (mm_slot) | |
2259 | collect_mm_slot(mm_slot); | |
2260 | spin_unlock(&khugepaged_mm_lock); | |
2261 | return 0; | |
2262 | } | |
2263 | ||
2264 | static void set_recommended_min_free_kbytes(void) | |
2265 | { | |
2266 | struct zone *zone; | |
2267 | int nr_zones = 0; | |
2268 | unsigned long recommended_min; | |
2269 | ||
b7d349c7 JK |
2270 | for_each_populated_zone(zone) { |
2271 | /* | |
2272 | * We don't need to worry about fragmentation of | |
2273 | * ZONE_MOVABLE since it only has movable pages. | |
2274 | */ | |
2275 | if (zone_idx(zone) > gfp_zone(GFP_USER)) | |
2276 | continue; | |
2277 | ||
b46e756f | 2278 | nr_zones++; |
b7d349c7 | 2279 | } |
b46e756f KS |
2280 | |
2281 | /* Ensure 2 pageblocks are free to assist fragmentation avoidance */ | |
2282 | recommended_min = pageblock_nr_pages * nr_zones * 2; | |
2283 | ||
2284 | /* | |
2285 | * Make sure that on average at least two pageblocks are almost free | |
2286 | * of another type, one for a migratetype to fall back to and a | |
2287 | * second to avoid subsequent fallbacks of other types There are 3 | |
2288 | * MIGRATE_TYPES we care about. | |
2289 | */ | |
2290 | recommended_min += pageblock_nr_pages * nr_zones * | |
2291 | MIGRATE_PCPTYPES * MIGRATE_PCPTYPES; | |
2292 | ||
2293 | /* don't ever allow to reserve more than 5% of the lowmem */ | |
2294 | recommended_min = min(recommended_min, | |
2295 | (unsigned long) nr_free_buffer_pages() / 20); | |
2296 | recommended_min <<= (PAGE_SHIFT-10); | |
2297 | ||
2298 | if (recommended_min > min_free_kbytes) { | |
2299 | if (user_min_free_kbytes >= 0) | |
2300 | pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", | |
2301 | min_free_kbytes, recommended_min); | |
2302 | ||
2303 | min_free_kbytes = recommended_min; | |
2304 | } | |
2305 | setup_per_zone_wmarks(); | |
2306 | } | |
2307 | ||
2308 | int start_stop_khugepaged(void) | |
2309 | { | |
b46e756f KS |
2310 | int err = 0; |
2311 | ||
2312 | mutex_lock(&khugepaged_mutex); | |
2313 | if (khugepaged_enabled()) { | |
2314 | if (!khugepaged_thread) | |
2315 | khugepaged_thread = kthread_run(khugepaged, NULL, | |
2316 | "khugepaged"); | |
2317 | if (IS_ERR(khugepaged_thread)) { | |
2318 | pr_err("khugepaged: kthread_run(khugepaged) failed\n"); | |
2319 | err = PTR_ERR(khugepaged_thread); | |
2320 | khugepaged_thread = NULL; | |
2321 | goto fail; | |
2322 | } | |
2323 | ||
2324 | if (!list_empty(&khugepaged_scan.mm_head)) | |
2325 | wake_up_interruptible(&khugepaged_wait); | |
2326 | ||
2327 | set_recommended_min_free_kbytes(); | |
2328 | } else if (khugepaged_thread) { | |
2329 | kthread_stop(khugepaged_thread); | |
2330 | khugepaged_thread = NULL; | |
2331 | } | |
2332 | fail: | |
2333 | mutex_unlock(&khugepaged_mutex); | |
2334 | return err; | |
2335 | } | |
4aab2be0 VB |
2336 | |
2337 | void khugepaged_min_free_kbytes_update(void) | |
2338 | { | |
2339 | mutex_lock(&khugepaged_mutex); | |
2340 | if (khugepaged_enabled() && khugepaged_thread) | |
2341 | set_recommended_min_free_kbytes(); | |
2342 | mutex_unlock(&khugepaged_mutex); | |
2343 | } |