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1 | /* | |
2 | * Copyright (C) 2009 Red Hat, Inc. | |
3 | * | |
4 | * This work is licensed under the terms of the GNU GPL, version 2. See | |
5 | * the COPYING file in the top-level directory. | |
6 | */ | |
7 | ||
8 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt | |
9 | ||
10 | #include <linux/mm.h> | |
11 | #include <linux/sched.h> | |
12 | #include <linux/highmem.h> | |
13 | #include <linux/hugetlb.h> | |
14 | #include <linux/mmu_notifier.h> | |
15 | #include <linux/rmap.h> | |
16 | #include <linux/swap.h> | |
17 | #include <linux/shrinker.h> | |
18 | #include <linux/mm_inline.h> | |
19 | #include <linux/swapops.h> | |
20 | #include <linux/dax.h> | |
21 | #include <linux/khugepaged.h> | |
22 | #include <linux/freezer.h> | |
23 | #include <linux/pfn_t.h> | |
24 | #include <linux/mman.h> | |
25 | #include <linux/memremap.h> | |
26 | #include <linux/pagemap.h> | |
27 | #include <linux/debugfs.h> | |
28 | #include <linux/migrate.h> | |
29 | #include <linux/hashtable.h> | |
30 | #include <linux/userfaultfd_k.h> | |
31 | #include <linux/page_idle.h> | |
32 | #include <linux/shmem_fs.h> | |
33 | ||
34 | #include <asm/tlb.h> | |
35 | #include <asm/pgalloc.h> | |
36 | #include "internal.h" | |
37 | ||
38 | /* | |
39 | * By default transparent hugepage support is disabled in order that avoid | |
40 | * to risk increase the memory footprint of applications without a guaranteed | |
41 | * benefit. When transparent hugepage support is enabled, is for all mappings, | |
42 | * and khugepaged scans all mappings. | |
43 | * Defrag is invoked by khugepaged hugepage allocations and by page faults | |
44 | * for all hugepage allocations. | |
45 | */ | |
46 | unsigned long transparent_hugepage_flags __read_mostly = | |
47 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS | |
48 | (1<<TRANSPARENT_HUGEPAGE_FLAG)| | |
49 | #endif | |
50 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE | |
51 | (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| | |
52 | #endif | |
53 | (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)| | |
54 | (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| | |
55 | (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); | |
56 | ||
57 | static struct shrinker deferred_split_shrinker; | |
58 | ||
59 | static atomic_t huge_zero_refcount; | |
60 | struct page *huge_zero_page __read_mostly; | |
61 | ||
62 | static struct page *get_huge_zero_page(void) | |
63 | { | |
64 | struct page *zero_page; | |
65 | retry: | |
66 | if (likely(atomic_inc_not_zero(&huge_zero_refcount))) | |
67 | return READ_ONCE(huge_zero_page); | |
68 | ||
69 | zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, | |
70 | HPAGE_PMD_ORDER); | |
71 | if (!zero_page) { | |
72 | count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); | |
73 | return NULL; | |
74 | } | |
75 | count_vm_event(THP_ZERO_PAGE_ALLOC); | |
76 | preempt_disable(); | |
77 | if (cmpxchg(&huge_zero_page, NULL, zero_page)) { | |
78 | preempt_enable(); | |
79 | __free_pages(zero_page, compound_order(zero_page)); | |
80 | goto retry; | |
81 | } | |
82 | ||
83 | /* We take additional reference here. It will be put back by shrinker */ | |
84 | atomic_set(&huge_zero_refcount, 2); | |
85 | preempt_enable(); | |
86 | return READ_ONCE(huge_zero_page); | |
87 | } | |
88 | ||
89 | static void put_huge_zero_page(void) | |
90 | { | |
91 | /* | |
92 | * Counter should never go to zero here. Only shrinker can put | |
93 | * last reference. | |
94 | */ | |
95 | BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); | |
96 | } | |
97 | ||
98 | struct page *mm_get_huge_zero_page(struct mm_struct *mm) | |
99 | { | |
100 | if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) | |
101 | return READ_ONCE(huge_zero_page); | |
102 | ||
103 | if (!get_huge_zero_page()) | |
104 | return NULL; | |
105 | ||
106 | if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) | |
107 | put_huge_zero_page(); | |
108 | ||
109 | return READ_ONCE(huge_zero_page); | |
110 | } | |
111 | ||
112 | void mm_put_huge_zero_page(struct mm_struct *mm) | |
113 | { | |
114 | if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags)) | |
115 | put_huge_zero_page(); | |
116 | } | |
117 | ||
118 | static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink, | |
119 | struct shrink_control *sc) | |
120 | { | |
121 | /* we can free zero page only if last reference remains */ | |
122 | return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; | |
123 | } | |
124 | ||
125 | static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink, | |
126 | struct shrink_control *sc) | |
127 | { | |
128 | if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { | |
129 | struct page *zero_page = xchg(&huge_zero_page, NULL); | |
130 | BUG_ON(zero_page == NULL); | |
131 | __free_pages(zero_page, compound_order(zero_page)); | |
132 | return HPAGE_PMD_NR; | |
133 | } | |
134 | ||
135 | return 0; | |
136 | } | |
137 | ||
138 | static struct shrinker huge_zero_page_shrinker = { | |
139 | .count_objects = shrink_huge_zero_page_count, | |
140 | .scan_objects = shrink_huge_zero_page_scan, | |
141 | .seeks = DEFAULT_SEEKS, | |
142 | }; | |
143 | ||
144 | #ifdef CONFIG_SYSFS | |
145 | ||
146 | static ssize_t triple_flag_store(struct kobject *kobj, | |
147 | struct kobj_attribute *attr, | |
148 | const char *buf, size_t count, | |
149 | enum transparent_hugepage_flag enabled, | |
150 | enum transparent_hugepage_flag deferred, | |
151 | enum transparent_hugepage_flag req_madv) | |
152 | { | |
153 | if (!memcmp("defer", buf, | |
154 | min(sizeof("defer")-1, count))) { | |
155 | if (enabled == deferred) | |
156 | return -EINVAL; | |
157 | clear_bit(enabled, &transparent_hugepage_flags); | |
158 | clear_bit(req_madv, &transparent_hugepage_flags); | |
159 | set_bit(deferred, &transparent_hugepage_flags); | |
160 | } else if (!memcmp("always", buf, | |
161 | min(sizeof("always")-1, count))) { | |
162 | clear_bit(deferred, &transparent_hugepage_flags); | |
163 | clear_bit(req_madv, &transparent_hugepage_flags); | |
164 | set_bit(enabled, &transparent_hugepage_flags); | |
165 | } else if (!memcmp("madvise", buf, | |
166 | min(sizeof("madvise")-1, count))) { | |
167 | clear_bit(enabled, &transparent_hugepage_flags); | |
168 | clear_bit(deferred, &transparent_hugepage_flags); | |
169 | set_bit(req_madv, &transparent_hugepage_flags); | |
170 | } else if (!memcmp("never", buf, | |
171 | min(sizeof("never")-1, count))) { | |
172 | clear_bit(enabled, &transparent_hugepage_flags); | |
173 | clear_bit(req_madv, &transparent_hugepage_flags); | |
174 | clear_bit(deferred, &transparent_hugepage_flags); | |
175 | } else | |
176 | return -EINVAL; | |
177 | ||
178 | return count; | |
179 | } | |
180 | ||
181 | static ssize_t enabled_show(struct kobject *kobj, | |
182 | struct kobj_attribute *attr, char *buf) | |
183 | { | |
184 | if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) | |
185 | return sprintf(buf, "[always] madvise never\n"); | |
186 | else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)) | |
187 | return sprintf(buf, "always [madvise] never\n"); | |
188 | else | |
189 | return sprintf(buf, "always madvise [never]\n"); | |
190 | } | |
191 | ||
192 | static ssize_t enabled_store(struct kobject *kobj, | |
193 | struct kobj_attribute *attr, | |
194 | const char *buf, size_t count) | |
195 | { | |
196 | ssize_t ret; | |
197 | ||
198 | ret = triple_flag_store(kobj, attr, buf, count, | |
199 | TRANSPARENT_HUGEPAGE_FLAG, | |
200 | TRANSPARENT_HUGEPAGE_FLAG, | |
201 | TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); | |
202 | ||
203 | if (ret > 0) { | |
204 | int err = start_stop_khugepaged(); | |
205 | if (err) | |
206 | ret = err; | |
207 | } | |
208 | ||
209 | return ret; | |
210 | } | |
211 | static struct kobj_attribute enabled_attr = | |
212 | __ATTR(enabled, 0644, enabled_show, enabled_store); | |
213 | ||
214 | ssize_t single_hugepage_flag_show(struct kobject *kobj, | |
215 | struct kobj_attribute *attr, char *buf, | |
216 | enum transparent_hugepage_flag flag) | |
217 | { | |
218 | return sprintf(buf, "%d\n", | |
219 | !!test_bit(flag, &transparent_hugepage_flags)); | |
220 | } | |
221 | ||
222 | ssize_t single_hugepage_flag_store(struct kobject *kobj, | |
223 | struct kobj_attribute *attr, | |
224 | const char *buf, size_t count, | |
225 | enum transparent_hugepage_flag flag) | |
226 | { | |
227 | unsigned long value; | |
228 | int ret; | |
229 | ||
230 | ret = kstrtoul(buf, 10, &value); | |
231 | if (ret < 0) | |
232 | return ret; | |
233 | if (value > 1) | |
234 | return -EINVAL; | |
235 | ||
236 | if (value) | |
237 | set_bit(flag, &transparent_hugepage_flags); | |
238 | else | |
239 | clear_bit(flag, &transparent_hugepage_flags); | |
240 | ||
241 | return count; | |
242 | } | |
243 | ||
244 | /* | |
245 | * Currently defrag only disables __GFP_NOWAIT for allocation. A blind | |
246 | * __GFP_REPEAT is too aggressive, it's never worth swapping tons of | |
247 | * memory just to allocate one more hugepage. | |
248 | */ | |
249 | static ssize_t defrag_show(struct kobject *kobj, | |
250 | struct kobj_attribute *attr, char *buf) | |
251 | { | |
252 | if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) | |
253 | return sprintf(buf, "[always] defer madvise never\n"); | |
254 | if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) | |
255 | return sprintf(buf, "always [defer] madvise never\n"); | |
256 | else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) | |
257 | return sprintf(buf, "always defer [madvise] never\n"); | |
258 | else | |
259 | return sprintf(buf, "always defer madvise [never]\n"); | |
260 | ||
261 | } | |
262 | static ssize_t defrag_store(struct kobject *kobj, | |
263 | struct kobj_attribute *attr, | |
264 | const char *buf, size_t count) | |
265 | { | |
266 | return triple_flag_store(kobj, attr, buf, count, | |
267 | TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, | |
268 | TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, | |
269 | TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); | |
270 | } | |
271 | static struct kobj_attribute defrag_attr = | |
272 | __ATTR(defrag, 0644, defrag_show, defrag_store); | |
273 | ||
274 | static ssize_t use_zero_page_show(struct kobject *kobj, | |
275 | struct kobj_attribute *attr, char *buf) | |
276 | { | |
277 | return single_hugepage_flag_show(kobj, attr, buf, | |
278 | TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); | |
279 | } | |
280 | static ssize_t use_zero_page_store(struct kobject *kobj, | |
281 | struct kobj_attribute *attr, const char *buf, size_t count) | |
282 | { | |
283 | return single_hugepage_flag_store(kobj, attr, buf, count, | |
284 | TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); | |
285 | } | |
286 | static struct kobj_attribute use_zero_page_attr = | |
287 | __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); | |
288 | ||
289 | static ssize_t hpage_pmd_size_show(struct kobject *kobj, | |
290 | struct kobj_attribute *attr, char *buf) | |
291 | { | |
292 | return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE); | |
293 | } | |
294 | static struct kobj_attribute hpage_pmd_size_attr = | |
295 | __ATTR_RO(hpage_pmd_size); | |
296 | ||
297 | #ifdef CONFIG_DEBUG_VM | |
298 | static ssize_t debug_cow_show(struct kobject *kobj, | |
299 | struct kobj_attribute *attr, char *buf) | |
300 | { | |
301 | return single_hugepage_flag_show(kobj, attr, buf, | |
302 | TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); | |
303 | } | |
304 | static ssize_t debug_cow_store(struct kobject *kobj, | |
305 | struct kobj_attribute *attr, | |
306 | const char *buf, size_t count) | |
307 | { | |
308 | return single_hugepage_flag_store(kobj, attr, buf, count, | |
309 | TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG); | |
310 | } | |
311 | static struct kobj_attribute debug_cow_attr = | |
312 | __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store); | |
313 | #endif /* CONFIG_DEBUG_VM */ | |
314 | ||
315 | static struct attribute *hugepage_attr[] = { | |
316 | &enabled_attr.attr, | |
317 | &defrag_attr.attr, | |
318 | &use_zero_page_attr.attr, | |
319 | &hpage_pmd_size_attr.attr, | |
320 | #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE) | |
321 | &shmem_enabled_attr.attr, | |
322 | #endif | |
323 | #ifdef CONFIG_DEBUG_VM | |
324 | &debug_cow_attr.attr, | |
325 | #endif | |
326 | NULL, | |
327 | }; | |
328 | ||
329 | static struct attribute_group hugepage_attr_group = { | |
330 | .attrs = hugepage_attr, | |
331 | }; | |
332 | ||
333 | static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj) | |
334 | { | |
335 | int err; | |
336 | ||
337 | *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); | |
338 | if (unlikely(!*hugepage_kobj)) { | |
339 | pr_err("failed to create transparent hugepage kobject\n"); | |
340 | return -ENOMEM; | |
341 | } | |
342 | ||
343 | err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group); | |
344 | if (err) { | |
345 | pr_err("failed to register transparent hugepage group\n"); | |
346 | goto delete_obj; | |
347 | } | |
348 | ||
349 | err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group); | |
350 | if (err) { | |
351 | pr_err("failed to register transparent hugepage group\n"); | |
352 | goto remove_hp_group; | |
353 | } | |
354 | ||
355 | return 0; | |
356 | ||
357 | remove_hp_group: | |
358 | sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group); | |
359 | delete_obj: | |
360 | kobject_put(*hugepage_kobj); | |
361 | return err; | |
362 | } | |
363 | ||
364 | static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj) | |
365 | { | |
366 | sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group); | |
367 | sysfs_remove_group(hugepage_kobj, &hugepage_attr_group); | |
368 | kobject_put(hugepage_kobj); | |
369 | } | |
370 | #else | |
371 | static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj) | |
372 | { | |
373 | return 0; | |
374 | } | |
375 | ||
376 | static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj) | |
377 | { | |
378 | } | |
379 | #endif /* CONFIG_SYSFS */ | |
380 | ||
381 | static int __init hugepage_init(void) | |
382 | { | |
383 | int err; | |
384 | struct kobject *hugepage_kobj; | |
385 | ||
386 | if (!has_transparent_hugepage()) { | |
387 | transparent_hugepage_flags = 0; | |
388 | return -EINVAL; | |
389 | } | |
390 | ||
391 | /* | |
392 | * hugepages can't be allocated by the buddy allocator | |
393 | */ | |
394 | MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER); | |
395 | /* | |
396 | * we use page->mapping and page->index in second tail page | |
397 | * as list_head: assuming THP order >= 2 | |
398 | */ | |
399 | MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); | |
400 | ||
401 | err = hugepage_init_sysfs(&hugepage_kobj); | |
402 | if (err) | |
403 | goto err_sysfs; | |
404 | ||
405 | err = khugepaged_init(); | |
406 | if (err) | |
407 | goto err_slab; | |
408 | ||
409 | err = register_shrinker(&huge_zero_page_shrinker); | |
410 | if (err) | |
411 | goto err_hzp_shrinker; | |
412 | err = register_shrinker(&deferred_split_shrinker); | |
413 | if (err) | |
414 | goto err_split_shrinker; | |
415 | ||
416 | /* | |
417 | * By default disable transparent hugepages on smaller systems, | |
418 | * where the extra memory used could hurt more than TLB overhead | |
419 | * is likely to save. The admin can still enable it through /sys. | |
420 | */ | |
421 | if (totalram_pages < (512 << (20 - PAGE_SHIFT))) { | |
422 | transparent_hugepage_flags = 0; | |
423 | return 0; | |
424 | } | |
425 | ||
426 | err = start_stop_khugepaged(); | |
427 | if (err) | |
428 | goto err_khugepaged; | |
429 | ||
430 | return 0; | |
431 | err_khugepaged: | |
432 | unregister_shrinker(&deferred_split_shrinker); | |
433 | err_split_shrinker: | |
434 | unregister_shrinker(&huge_zero_page_shrinker); | |
435 | err_hzp_shrinker: | |
436 | khugepaged_destroy(); | |
437 | err_slab: | |
438 | hugepage_exit_sysfs(hugepage_kobj); | |
439 | err_sysfs: | |
440 | return err; | |
441 | } | |
442 | subsys_initcall(hugepage_init); | |
443 | ||
444 | static int __init setup_transparent_hugepage(char *str) | |
445 | { | |
446 | int ret = 0; | |
447 | if (!str) | |
448 | goto out; | |
449 | if (!strcmp(str, "always")) { | |
450 | set_bit(TRANSPARENT_HUGEPAGE_FLAG, | |
451 | &transparent_hugepage_flags); | |
452 | clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, | |
453 | &transparent_hugepage_flags); | |
454 | ret = 1; | |
455 | } else if (!strcmp(str, "madvise")) { | |
456 | clear_bit(TRANSPARENT_HUGEPAGE_FLAG, | |
457 | &transparent_hugepage_flags); | |
458 | set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, | |
459 | &transparent_hugepage_flags); | |
460 | ret = 1; | |
461 | } else if (!strcmp(str, "never")) { | |
462 | clear_bit(TRANSPARENT_HUGEPAGE_FLAG, | |
463 | &transparent_hugepage_flags); | |
464 | clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, | |
465 | &transparent_hugepage_flags); | |
466 | ret = 1; | |
467 | } | |
468 | out: | |
469 | if (!ret) | |
470 | pr_warn("transparent_hugepage= cannot parse, ignored\n"); | |
471 | return ret; | |
472 | } | |
473 | __setup("transparent_hugepage=", setup_transparent_hugepage); | |
474 | ||
475 | pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma) | |
476 | { | |
477 | if (likely(vma->vm_flags & VM_WRITE)) | |
478 | pmd = pmd_mkwrite(pmd); | |
479 | return pmd; | |
480 | } | |
481 | ||
482 | static inline struct list_head *page_deferred_list(struct page *page) | |
483 | { | |
484 | /* | |
485 | * ->lru in the tail pages is occupied by compound_head. | |
486 | * Let's use ->mapping + ->index in the second tail page as list_head. | |
487 | */ | |
488 | return (struct list_head *)&page[2].mapping; | |
489 | } | |
490 | ||
491 | void prep_transhuge_page(struct page *page) | |
492 | { | |
493 | /* | |
494 | * we use page->mapping and page->indexlru in second tail page | |
495 | * as list_head: assuming THP order >= 2 | |
496 | */ | |
497 | ||
498 | INIT_LIST_HEAD(page_deferred_list(page)); | |
499 | set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR); | |
500 | } | |
501 | ||
502 | unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len, | |
503 | loff_t off, unsigned long flags, unsigned long size) | |
504 | { | |
505 | unsigned long addr; | |
506 | loff_t off_end = off + len; | |
507 | loff_t off_align = round_up(off, size); | |
508 | unsigned long len_pad; | |
509 | ||
510 | if (off_end <= off_align || (off_end - off_align) < size) | |
511 | return 0; | |
512 | ||
513 | len_pad = len + size; | |
514 | if (len_pad < len || (off + len_pad) < off) | |
515 | return 0; | |
516 | ||
517 | addr = current->mm->get_unmapped_area(filp, 0, len_pad, | |
518 | off >> PAGE_SHIFT, flags); | |
519 | if (IS_ERR_VALUE(addr)) | |
520 | return 0; | |
521 | ||
522 | addr += (off - addr) & (size - 1); | |
523 | return addr; | |
524 | } | |
525 | ||
526 | unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, | |
527 | unsigned long len, unsigned long pgoff, unsigned long flags) | |
528 | { | |
529 | loff_t off = (loff_t)pgoff << PAGE_SHIFT; | |
530 | ||
531 | if (addr) | |
532 | goto out; | |
533 | if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD)) | |
534 | goto out; | |
535 | ||
536 | addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE); | |
537 | if (addr) | |
538 | return addr; | |
539 | ||
540 | out: | |
541 | return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags); | |
542 | } | |
543 | EXPORT_SYMBOL_GPL(thp_get_unmapped_area); | |
544 | ||
545 | static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page, | |
546 | gfp_t gfp) | |
547 | { | |
548 | struct vm_area_struct *vma = vmf->vma; | |
549 | struct mem_cgroup *memcg; | |
550 | pgtable_t pgtable; | |
551 | unsigned long haddr = vmf->address & HPAGE_PMD_MASK; | |
552 | ||
553 | VM_BUG_ON_PAGE(!PageCompound(page), page); | |
554 | ||
555 | if (mem_cgroup_try_charge(page, vma->vm_mm, gfp, &memcg, true)) { | |
556 | put_page(page); | |
557 | count_vm_event(THP_FAULT_FALLBACK); | |
558 | return VM_FAULT_FALLBACK; | |
559 | } | |
560 | ||
561 | pgtable = pte_alloc_one(vma->vm_mm, haddr); | |
562 | if (unlikely(!pgtable)) { | |
563 | mem_cgroup_cancel_charge(page, memcg, true); | |
564 | put_page(page); | |
565 | return VM_FAULT_OOM; | |
566 | } | |
567 | ||
568 | clear_huge_page(page, haddr, HPAGE_PMD_NR); | |
569 | /* | |
570 | * The memory barrier inside __SetPageUptodate makes sure that | |
571 | * clear_huge_page writes become visible before the set_pmd_at() | |
572 | * write. | |
573 | */ | |
574 | __SetPageUptodate(page); | |
575 | ||
576 | vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); | |
577 | if (unlikely(!pmd_none(*vmf->pmd))) { | |
578 | spin_unlock(vmf->ptl); | |
579 | mem_cgroup_cancel_charge(page, memcg, true); | |
580 | put_page(page); | |
581 | pte_free(vma->vm_mm, pgtable); | |
582 | } else { | |
583 | pmd_t entry; | |
584 | ||
585 | /* Deliver the page fault to userland */ | |
586 | if (userfaultfd_missing(vma)) { | |
587 | int ret; | |
588 | ||
589 | spin_unlock(vmf->ptl); | |
590 | mem_cgroup_cancel_charge(page, memcg, true); | |
591 | put_page(page); | |
592 | pte_free(vma->vm_mm, pgtable); | |
593 | ret = handle_userfault(vmf, VM_UFFD_MISSING); | |
594 | VM_BUG_ON(ret & VM_FAULT_FALLBACK); | |
595 | return ret; | |
596 | } | |
597 | ||
598 | entry = mk_huge_pmd(page, vma->vm_page_prot); | |
599 | entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); | |
600 | page_add_new_anon_rmap(page, vma, haddr, true); | |
601 | mem_cgroup_commit_charge(page, memcg, false, true); | |
602 | lru_cache_add_active_or_unevictable(page, vma); | |
603 | pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable); | |
604 | set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); | |
605 | add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); | |
606 | atomic_long_inc(&vma->vm_mm->nr_ptes); | |
607 | spin_unlock(vmf->ptl); | |
608 | count_vm_event(THP_FAULT_ALLOC); | |
609 | } | |
610 | ||
611 | return 0; | |
612 | } | |
613 | ||
614 | /* | |
615 | * If THP defrag is set to always then directly reclaim/compact as necessary | |
616 | * If set to defer then do only background reclaim/compact and defer to khugepaged | |
617 | * If set to madvise and the VMA is flagged then directly reclaim/compact | |
618 | * When direct reclaim/compact is allowed, don't retry except for flagged VMA's | |
619 | */ | |
620 | static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma) | |
621 | { | |
622 | bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE); | |
623 | ||
624 | if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, | |
625 | &transparent_hugepage_flags) && vma_madvised) | |
626 | return GFP_TRANSHUGE; | |
627 | else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, | |
628 | &transparent_hugepage_flags)) | |
629 | return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM; | |
630 | else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, | |
631 | &transparent_hugepage_flags)) | |
632 | return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY); | |
633 | ||
634 | return GFP_TRANSHUGE_LIGHT; | |
635 | } | |
636 | ||
637 | /* Caller must hold page table lock. */ | |
638 | static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, | |
639 | struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, | |
640 | struct page *zero_page) | |
641 | { | |
642 | pmd_t entry; | |
643 | if (!pmd_none(*pmd)) | |
644 | return false; | |
645 | entry = mk_pmd(zero_page, vma->vm_page_prot); | |
646 | entry = pmd_mkhuge(entry); | |
647 | if (pgtable) | |
648 | pgtable_trans_huge_deposit(mm, pmd, pgtable); | |
649 | set_pmd_at(mm, haddr, pmd, entry); | |
650 | atomic_long_inc(&mm->nr_ptes); | |
651 | return true; | |
652 | } | |
653 | ||
654 | int do_huge_pmd_anonymous_page(struct vm_fault *vmf) | |
655 | { | |
656 | struct vm_area_struct *vma = vmf->vma; | |
657 | gfp_t gfp; | |
658 | struct page *page; | |
659 | unsigned long haddr = vmf->address & HPAGE_PMD_MASK; | |
660 | ||
661 | if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end) | |
662 | return VM_FAULT_FALLBACK; | |
663 | if (unlikely(anon_vma_prepare(vma))) | |
664 | return VM_FAULT_OOM; | |
665 | if (unlikely(khugepaged_enter(vma, vma->vm_flags))) | |
666 | return VM_FAULT_OOM; | |
667 | if (!(vmf->flags & FAULT_FLAG_WRITE) && | |
668 | !mm_forbids_zeropage(vma->vm_mm) && | |
669 | transparent_hugepage_use_zero_page()) { | |
670 | pgtable_t pgtable; | |
671 | struct page *zero_page; | |
672 | bool set; | |
673 | int ret; | |
674 | pgtable = pte_alloc_one(vma->vm_mm, haddr); | |
675 | if (unlikely(!pgtable)) | |
676 | return VM_FAULT_OOM; | |
677 | zero_page = mm_get_huge_zero_page(vma->vm_mm); | |
678 | if (unlikely(!zero_page)) { | |
679 | pte_free(vma->vm_mm, pgtable); | |
680 | count_vm_event(THP_FAULT_FALLBACK); | |
681 | return VM_FAULT_FALLBACK; | |
682 | } | |
683 | vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); | |
684 | ret = 0; | |
685 | set = false; | |
686 | if (pmd_none(*vmf->pmd)) { | |
687 | if (userfaultfd_missing(vma)) { | |
688 | spin_unlock(vmf->ptl); | |
689 | ret = handle_userfault(vmf, VM_UFFD_MISSING); | |
690 | VM_BUG_ON(ret & VM_FAULT_FALLBACK); | |
691 | } else { | |
692 | set_huge_zero_page(pgtable, vma->vm_mm, vma, | |
693 | haddr, vmf->pmd, zero_page); | |
694 | spin_unlock(vmf->ptl); | |
695 | set = true; | |
696 | } | |
697 | } else | |
698 | spin_unlock(vmf->ptl); | |
699 | if (!set) | |
700 | pte_free(vma->vm_mm, pgtable); | |
701 | return ret; | |
702 | } | |
703 | gfp = alloc_hugepage_direct_gfpmask(vma); | |
704 | page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); | |
705 | if (unlikely(!page)) { | |
706 | count_vm_event(THP_FAULT_FALLBACK); | |
707 | return VM_FAULT_FALLBACK; | |
708 | } | |
709 | prep_transhuge_page(page); | |
710 | return __do_huge_pmd_anonymous_page(vmf, page, gfp); | |
711 | } | |
712 | ||
713 | static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, | |
714 | pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write) | |
715 | { | |
716 | struct mm_struct *mm = vma->vm_mm; | |
717 | pmd_t entry; | |
718 | spinlock_t *ptl; | |
719 | ||
720 | ptl = pmd_lock(mm, pmd); | |
721 | entry = pmd_mkhuge(pfn_t_pmd(pfn, prot)); | |
722 | if (pfn_t_devmap(pfn)) | |
723 | entry = pmd_mkdevmap(entry); | |
724 | if (write) { | |
725 | entry = pmd_mkyoung(pmd_mkdirty(entry)); | |
726 | entry = maybe_pmd_mkwrite(entry, vma); | |
727 | } | |
728 | set_pmd_at(mm, addr, pmd, entry); | |
729 | update_mmu_cache_pmd(vma, addr, pmd); | |
730 | spin_unlock(ptl); | |
731 | } | |
732 | ||
733 | int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, | |
734 | pmd_t *pmd, pfn_t pfn, bool write) | |
735 | { | |
736 | pgprot_t pgprot = vma->vm_page_prot; | |
737 | /* | |
738 | * If we had pmd_special, we could avoid all these restrictions, | |
739 | * but we need to be consistent with PTEs and architectures that | |
740 | * can't support a 'special' bit. | |
741 | */ | |
742 | BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))); | |
743 | BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) == | |
744 | (VM_PFNMAP|VM_MIXEDMAP)); | |
745 | BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags)); | |
746 | BUG_ON(!pfn_t_devmap(pfn)); | |
747 | ||
748 | if (addr < vma->vm_start || addr >= vma->vm_end) | |
749 | return VM_FAULT_SIGBUS; | |
750 | ||
751 | track_pfn_insert(vma, &pgprot, pfn); | |
752 | ||
753 | insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write); | |
754 | return VM_FAULT_NOPAGE; | |
755 | } | |
756 | EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd); | |
757 | ||
758 | static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, | |
759 | pmd_t *pmd) | |
760 | { | |
761 | pmd_t _pmd; | |
762 | ||
763 | /* | |
764 | * We should set the dirty bit only for FOLL_WRITE but for now | |
765 | * the dirty bit in the pmd is meaningless. And if the dirty | |
766 | * bit will become meaningful and we'll only set it with | |
767 | * FOLL_WRITE, an atomic set_bit will be required on the pmd to | |
768 | * set the young bit, instead of the current set_pmd_at. | |
769 | */ | |
770 | _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); | |
771 | if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, | |
772 | pmd, _pmd, 1)) | |
773 | update_mmu_cache_pmd(vma, addr, pmd); | |
774 | } | |
775 | ||
776 | struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, | |
777 | pmd_t *pmd, int flags) | |
778 | { | |
779 | unsigned long pfn = pmd_pfn(*pmd); | |
780 | struct mm_struct *mm = vma->vm_mm; | |
781 | struct dev_pagemap *pgmap; | |
782 | struct page *page; | |
783 | ||
784 | assert_spin_locked(pmd_lockptr(mm, pmd)); | |
785 | ||
786 | if (flags & FOLL_WRITE && !pmd_write(*pmd)) | |
787 | return NULL; | |
788 | ||
789 | if (pmd_present(*pmd) && pmd_devmap(*pmd)) | |
790 | /* pass */; | |
791 | else | |
792 | return NULL; | |
793 | ||
794 | if (flags & FOLL_TOUCH) | |
795 | touch_pmd(vma, addr, pmd); | |
796 | ||
797 | /* | |
798 | * device mapped pages can only be returned if the | |
799 | * caller will manage the page reference count. | |
800 | */ | |
801 | if (!(flags & FOLL_GET)) | |
802 | return ERR_PTR(-EEXIST); | |
803 | ||
804 | pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT; | |
805 | pgmap = get_dev_pagemap(pfn, NULL); | |
806 | if (!pgmap) | |
807 | return ERR_PTR(-EFAULT); | |
808 | page = pfn_to_page(pfn); | |
809 | get_page(page); | |
810 | put_dev_pagemap(pgmap); | |
811 | ||
812 | return page; | |
813 | } | |
814 | ||
815 | int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, | |
816 | pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, | |
817 | struct vm_area_struct *vma) | |
818 | { | |
819 | spinlock_t *dst_ptl, *src_ptl; | |
820 | struct page *src_page; | |
821 | pmd_t pmd; | |
822 | pgtable_t pgtable = NULL; | |
823 | int ret = -ENOMEM; | |
824 | ||
825 | /* Skip if can be re-fill on fault */ | |
826 | if (!vma_is_anonymous(vma)) | |
827 | return 0; | |
828 | ||
829 | pgtable = pte_alloc_one(dst_mm, addr); | |
830 | if (unlikely(!pgtable)) | |
831 | goto out; | |
832 | ||
833 | dst_ptl = pmd_lock(dst_mm, dst_pmd); | |
834 | src_ptl = pmd_lockptr(src_mm, src_pmd); | |
835 | spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); | |
836 | ||
837 | ret = -EAGAIN; | |
838 | pmd = *src_pmd; | |
839 | if (unlikely(!pmd_trans_huge(pmd))) { | |
840 | pte_free(dst_mm, pgtable); | |
841 | goto out_unlock; | |
842 | } | |
843 | /* | |
844 | * When page table lock is held, the huge zero pmd should not be | |
845 | * under splitting since we don't split the page itself, only pmd to | |
846 | * a page table. | |
847 | */ | |
848 | if (is_huge_zero_pmd(pmd)) { | |
849 | struct page *zero_page; | |
850 | /* | |
851 | * get_huge_zero_page() will never allocate a new page here, | |
852 | * since we already have a zero page to copy. It just takes a | |
853 | * reference. | |
854 | */ | |
855 | zero_page = mm_get_huge_zero_page(dst_mm); | |
856 | set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, | |
857 | zero_page); | |
858 | ret = 0; | |
859 | goto out_unlock; | |
860 | } | |
861 | ||
862 | src_page = pmd_page(pmd); | |
863 | VM_BUG_ON_PAGE(!PageHead(src_page), src_page); | |
864 | get_page(src_page); | |
865 | page_dup_rmap(src_page, true); | |
866 | add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR); | |
867 | atomic_long_inc(&dst_mm->nr_ptes); | |
868 | pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); | |
869 | ||
870 | pmdp_set_wrprotect(src_mm, addr, src_pmd); | |
871 | pmd = pmd_mkold(pmd_wrprotect(pmd)); | |
872 | set_pmd_at(dst_mm, addr, dst_pmd, pmd); | |
873 | ||
874 | ret = 0; | |
875 | out_unlock: | |
876 | spin_unlock(src_ptl); | |
877 | spin_unlock(dst_ptl); | |
878 | out: | |
879 | return ret; | |
880 | } | |
881 | ||
882 | void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd) | |
883 | { | |
884 | pmd_t entry; | |
885 | unsigned long haddr; | |
886 | bool write = vmf->flags & FAULT_FLAG_WRITE; | |
887 | ||
888 | vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd); | |
889 | if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) | |
890 | goto unlock; | |
891 | ||
892 | entry = pmd_mkyoung(orig_pmd); | |
893 | if (write) | |
894 | entry = pmd_mkdirty(entry); | |
895 | haddr = vmf->address & HPAGE_PMD_MASK; | |
896 | if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write)) | |
897 | update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd); | |
898 | ||
899 | unlock: | |
900 | spin_unlock(vmf->ptl); | |
901 | } | |
902 | ||
903 | static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd, | |
904 | struct page *page) | |
905 | { | |
906 | struct vm_area_struct *vma = vmf->vma; | |
907 | unsigned long haddr = vmf->address & HPAGE_PMD_MASK; | |
908 | struct mem_cgroup *memcg; | |
909 | pgtable_t pgtable; | |
910 | pmd_t _pmd; | |
911 | int ret = 0, i; | |
912 | struct page **pages; | |
913 | unsigned long mmun_start; /* For mmu_notifiers */ | |
914 | unsigned long mmun_end; /* For mmu_notifiers */ | |
915 | ||
916 | pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR, | |
917 | GFP_KERNEL); | |
918 | if (unlikely(!pages)) { | |
919 | ret |= VM_FAULT_OOM; | |
920 | goto out; | |
921 | } | |
922 | ||
923 | for (i = 0; i < HPAGE_PMD_NR; i++) { | |
924 | pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma, | |
925 | vmf->address, page_to_nid(page)); | |
926 | if (unlikely(!pages[i] || | |
927 | mem_cgroup_try_charge(pages[i], vma->vm_mm, | |
928 | GFP_KERNEL, &memcg, false))) { | |
929 | if (pages[i]) | |
930 | put_page(pages[i]); | |
931 | while (--i >= 0) { | |
932 | memcg = (void *)page_private(pages[i]); | |
933 | set_page_private(pages[i], 0); | |
934 | mem_cgroup_cancel_charge(pages[i], memcg, | |
935 | false); | |
936 | put_page(pages[i]); | |
937 | } | |
938 | kfree(pages); | |
939 | ret |= VM_FAULT_OOM; | |
940 | goto out; | |
941 | } | |
942 | set_page_private(pages[i], (unsigned long)memcg); | |
943 | } | |
944 | ||
945 | for (i = 0; i < HPAGE_PMD_NR; i++) { | |
946 | copy_user_highpage(pages[i], page + i, | |
947 | haddr + PAGE_SIZE * i, vma); | |
948 | __SetPageUptodate(pages[i]); | |
949 | cond_resched(); | |
950 | } | |
951 | ||
952 | mmun_start = haddr; | |
953 | mmun_end = haddr + HPAGE_PMD_SIZE; | |
954 | mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end); | |
955 | ||
956 | vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); | |
957 | if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) | |
958 | goto out_free_pages; | |
959 | VM_BUG_ON_PAGE(!PageHead(page), page); | |
960 | ||
961 | pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd); | |
962 | /* leave pmd empty until pte is filled */ | |
963 | ||
964 | pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd); | |
965 | pmd_populate(vma->vm_mm, &_pmd, pgtable); | |
966 | ||
967 | for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { | |
968 | pte_t entry; | |
969 | entry = mk_pte(pages[i], vma->vm_page_prot); | |
970 | entry = maybe_mkwrite(pte_mkdirty(entry), vma); | |
971 | memcg = (void *)page_private(pages[i]); | |
972 | set_page_private(pages[i], 0); | |
973 | page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false); | |
974 | mem_cgroup_commit_charge(pages[i], memcg, false, false); | |
975 | lru_cache_add_active_or_unevictable(pages[i], vma); | |
976 | vmf->pte = pte_offset_map(&_pmd, haddr); | |
977 | VM_BUG_ON(!pte_none(*vmf->pte)); | |
978 | set_pte_at(vma->vm_mm, haddr, vmf->pte, entry); | |
979 | pte_unmap(vmf->pte); | |
980 | } | |
981 | kfree(pages); | |
982 | ||
983 | smp_wmb(); /* make pte visible before pmd */ | |
984 | pmd_populate(vma->vm_mm, vmf->pmd, pgtable); | |
985 | page_remove_rmap(page, true); | |
986 | spin_unlock(vmf->ptl); | |
987 | ||
988 | mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); | |
989 | ||
990 | ret |= VM_FAULT_WRITE; | |
991 | put_page(page); | |
992 | ||
993 | out: | |
994 | return ret; | |
995 | ||
996 | out_free_pages: | |
997 | spin_unlock(vmf->ptl); | |
998 | mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); | |
999 | for (i = 0; i < HPAGE_PMD_NR; i++) { | |
1000 | memcg = (void *)page_private(pages[i]); | |
1001 | set_page_private(pages[i], 0); | |
1002 | mem_cgroup_cancel_charge(pages[i], memcg, false); | |
1003 | put_page(pages[i]); | |
1004 | } | |
1005 | kfree(pages); | |
1006 | goto out; | |
1007 | } | |
1008 | ||
1009 | int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) | |
1010 | { | |
1011 | struct vm_area_struct *vma = vmf->vma; | |
1012 | struct page *page = NULL, *new_page; | |
1013 | struct mem_cgroup *memcg; | |
1014 | unsigned long haddr = vmf->address & HPAGE_PMD_MASK; | |
1015 | unsigned long mmun_start; /* For mmu_notifiers */ | |
1016 | unsigned long mmun_end; /* For mmu_notifiers */ | |
1017 | gfp_t huge_gfp; /* for allocation and charge */ | |
1018 | int ret = 0; | |
1019 | ||
1020 | vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd); | |
1021 | VM_BUG_ON_VMA(!vma->anon_vma, vma); | |
1022 | if (is_huge_zero_pmd(orig_pmd)) | |
1023 | goto alloc; | |
1024 | spin_lock(vmf->ptl); | |
1025 | if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) | |
1026 | goto out_unlock; | |
1027 | ||
1028 | page = pmd_page(orig_pmd); | |
1029 | VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); | |
1030 | /* | |
1031 | * We can only reuse the page if nobody else maps the huge page or it's | |
1032 | * part. | |
1033 | */ | |
1034 | if (page_trans_huge_mapcount(page, NULL) == 1) { | |
1035 | pmd_t entry; | |
1036 | entry = pmd_mkyoung(orig_pmd); | |
1037 | entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); | |
1038 | if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1)) | |
1039 | update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); | |
1040 | ret |= VM_FAULT_WRITE; | |
1041 | goto out_unlock; | |
1042 | } | |
1043 | get_page(page); | |
1044 | spin_unlock(vmf->ptl); | |
1045 | alloc: | |
1046 | if (transparent_hugepage_enabled(vma) && | |
1047 | !transparent_hugepage_debug_cow()) { | |
1048 | huge_gfp = alloc_hugepage_direct_gfpmask(vma); | |
1049 | new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER); | |
1050 | } else | |
1051 | new_page = NULL; | |
1052 | ||
1053 | if (likely(new_page)) { | |
1054 | prep_transhuge_page(new_page); | |
1055 | } else { | |
1056 | if (!page) { | |
1057 | split_huge_pmd(vma, vmf->pmd, vmf->address); | |
1058 | ret |= VM_FAULT_FALLBACK; | |
1059 | } else { | |
1060 | ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page); | |
1061 | if (ret & VM_FAULT_OOM) { | |
1062 | split_huge_pmd(vma, vmf->pmd, vmf->address); | |
1063 | ret |= VM_FAULT_FALLBACK; | |
1064 | } | |
1065 | put_page(page); | |
1066 | } | |
1067 | count_vm_event(THP_FAULT_FALLBACK); | |
1068 | goto out; | |
1069 | } | |
1070 | ||
1071 | if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm, | |
1072 | huge_gfp, &memcg, true))) { | |
1073 | put_page(new_page); | |
1074 | split_huge_pmd(vma, vmf->pmd, vmf->address); | |
1075 | if (page) | |
1076 | put_page(page); | |
1077 | ret |= VM_FAULT_FALLBACK; | |
1078 | count_vm_event(THP_FAULT_FALLBACK); | |
1079 | goto out; | |
1080 | } | |
1081 | ||
1082 | count_vm_event(THP_FAULT_ALLOC); | |
1083 | ||
1084 | if (!page) | |
1085 | clear_huge_page(new_page, haddr, HPAGE_PMD_NR); | |
1086 | else | |
1087 | copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); | |
1088 | __SetPageUptodate(new_page); | |
1089 | ||
1090 | mmun_start = haddr; | |
1091 | mmun_end = haddr + HPAGE_PMD_SIZE; | |
1092 | mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end); | |
1093 | ||
1094 | spin_lock(vmf->ptl); | |
1095 | if (page) | |
1096 | put_page(page); | |
1097 | if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { | |
1098 | spin_unlock(vmf->ptl); | |
1099 | mem_cgroup_cancel_charge(new_page, memcg, true); | |
1100 | put_page(new_page); | |
1101 | goto out_mn; | |
1102 | } else { | |
1103 | pmd_t entry; | |
1104 | entry = mk_huge_pmd(new_page, vma->vm_page_prot); | |
1105 | entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); | |
1106 | pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd); | |
1107 | page_add_new_anon_rmap(new_page, vma, haddr, true); | |
1108 | mem_cgroup_commit_charge(new_page, memcg, false, true); | |
1109 | lru_cache_add_active_or_unevictable(new_page, vma); | |
1110 | set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry); | |
1111 | update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); | |
1112 | if (!page) { | |
1113 | add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR); | |
1114 | } else { | |
1115 | VM_BUG_ON_PAGE(!PageHead(page), page); | |
1116 | page_remove_rmap(page, true); | |
1117 | put_page(page); | |
1118 | } | |
1119 | ret |= VM_FAULT_WRITE; | |
1120 | } | |
1121 | spin_unlock(vmf->ptl); | |
1122 | out_mn: | |
1123 | mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); | |
1124 | out: | |
1125 | return ret; | |
1126 | out_unlock: | |
1127 | spin_unlock(vmf->ptl); | |
1128 | return ret; | |
1129 | } | |
1130 | ||
1131 | struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, | |
1132 | unsigned long addr, | |
1133 | pmd_t *pmd, | |
1134 | unsigned int flags) | |
1135 | { | |
1136 | struct mm_struct *mm = vma->vm_mm; | |
1137 | struct page *page = NULL; | |
1138 | ||
1139 | assert_spin_locked(pmd_lockptr(mm, pmd)); | |
1140 | ||
1141 | if (flags & FOLL_WRITE && !pmd_write(*pmd)) | |
1142 | goto out; | |
1143 | ||
1144 | /* Avoid dumping huge zero page */ | |
1145 | if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd)) | |
1146 | return ERR_PTR(-EFAULT); | |
1147 | ||
1148 | /* Full NUMA hinting faults to serialise migration in fault paths */ | |
1149 | if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) | |
1150 | goto out; | |
1151 | ||
1152 | page = pmd_page(*pmd); | |
1153 | VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); | |
1154 | if (flags & FOLL_TOUCH) | |
1155 | touch_pmd(vma, addr, pmd); | |
1156 | if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { | |
1157 | /* | |
1158 | * We don't mlock() pte-mapped THPs. This way we can avoid | |
1159 | * leaking mlocked pages into non-VM_LOCKED VMAs. | |
1160 | * | |
1161 | * For anon THP: | |
1162 | * | |
1163 | * In most cases the pmd is the only mapping of the page as we | |
1164 | * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for | |
1165 | * writable private mappings in populate_vma_page_range(). | |
1166 | * | |
1167 | * The only scenario when we have the page shared here is if we | |
1168 | * mlocking read-only mapping shared over fork(). We skip | |
1169 | * mlocking such pages. | |
1170 | * | |
1171 | * For file THP: | |
1172 | * | |
1173 | * We can expect PageDoubleMap() to be stable under page lock: | |
1174 | * for file pages we set it in page_add_file_rmap(), which | |
1175 | * requires page to be locked. | |
1176 | */ | |
1177 | ||
1178 | if (PageAnon(page) && compound_mapcount(page) != 1) | |
1179 | goto skip_mlock; | |
1180 | if (PageDoubleMap(page) || !page->mapping) | |
1181 | goto skip_mlock; | |
1182 | if (!trylock_page(page)) | |
1183 | goto skip_mlock; | |
1184 | lru_add_drain(); | |
1185 | if (page->mapping && !PageDoubleMap(page)) | |
1186 | mlock_vma_page(page); | |
1187 | unlock_page(page); | |
1188 | } | |
1189 | skip_mlock: | |
1190 | page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; | |
1191 | VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page); | |
1192 | if (flags & FOLL_GET) | |
1193 | get_page(page); | |
1194 | ||
1195 | out: | |
1196 | return page; | |
1197 | } | |
1198 | ||
1199 | /* NUMA hinting page fault entry point for trans huge pmds */ | |
1200 | int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd) | |
1201 | { | |
1202 | struct vm_area_struct *vma = vmf->vma; | |
1203 | struct anon_vma *anon_vma = NULL; | |
1204 | struct page *page; | |
1205 | unsigned long haddr = vmf->address & HPAGE_PMD_MASK; | |
1206 | int page_nid = -1, this_nid = numa_node_id(); | |
1207 | int target_nid, last_cpupid = -1; | |
1208 | bool page_locked; | |
1209 | bool migrated = false; | |
1210 | bool was_writable; | |
1211 | int flags = 0; | |
1212 | ||
1213 | vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); | |
1214 | if (unlikely(!pmd_same(pmd, *vmf->pmd))) | |
1215 | goto out_unlock; | |
1216 | ||
1217 | /* | |
1218 | * If there are potential migrations, wait for completion and retry | |
1219 | * without disrupting NUMA hinting information. Do not relock and | |
1220 | * check_same as the page may no longer be mapped. | |
1221 | */ | |
1222 | if (unlikely(pmd_trans_migrating(*vmf->pmd))) { | |
1223 | page = pmd_page(*vmf->pmd); | |
1224 | spin_unlock(vmf->ptl); | |
1225 | wait_on_page_locked(page); | |
1226 | goto out; | |
1227 | } | |
1228 | ||
1229 | page = pmd_page(pmd); | |
1230 | BUG_ON(is_huge_zero_page(page)); | |
1231 | page_nid = page_to_nid(page); | |
1232 | last_cpupid = page_cpupid_last(page); | |
1233 | count_vm_numa_event(NUMA_HINT_FAULTS); | |
1234 | if (page_nid == this_nid) { | |
1235 | count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL); | |
1236 | flags |= TNF_FAULT_LOCAL; | |
1237 | } | |
1238 | ||
1239 | /* See similar comment in do_numa_page for explanation */ | |
1240 | if (!pmd_write(pmd)) | |
1241 | flags |= TNF_NO_GROUP; | |
1242 | ||
1243 | /* | |
1244 | * Acquire the page lock to serialise THP migrations but avoid dropping | |
1245 | * page_table_lock if at all possible | |
1246 | */ | |
1247 | page_locked = trylock_page(page); | |
1248 | target_nid = mpol_misplaced(page, vma, haddr); | |
1249 | if (target_nid == -1) { | |
1250 | /* If the page was locked, there are no parallel migrations */ | |
1251 | if (page_locked) | |
1252 | goto clear_pmdnuma; | |
1253 | } | |
1254 | ||
1255 | /* Migration could have started since the pmd_trans_migrating check */ | |
1256 | if (!page_locked) { | |
1257 | spin_unlock(vmf->ptl); | |
1258 | wait_on_page_locked(page); | |
1259 | page_nid = -1; | |
1260 | goto out; | |
1261 | } | |
1262 | ||
1263 | /* | |
1264 | * Page is misplaced. Page lock serialises migrations. Acquire anon_vma | |
1265 | * to serialises splits | |
1266 | */ | |
1267 | get_page(page); | |
1268 | spin_unlock(vmf->ptl); | |
1269 | anon_vma = page_lock_anon_vma_read(page); | |
1270 | ||
1271 | /* Confirm the PMD did not change while page_table_lock was released */ | |
1272 | spin_lock(vmf->ptl); | |
1273 | if (unlikely(!pmd_same(pmd, *vmf->pmd))) { | |
1274 | unlock_page(page); | |
1275 | put_page(page); | |
1276 | page_nid = -1; | |
1277 | goto out_unlock; | |
1278 | } | |
1279 | ||
1280 | /* Bail if we fail to protect against THP splits for any reason */ | |
1281 | if (unlikely(!anon_vma)) { | |
1282 | put_page(page); | |
1283 | page_nid = -1; | |
1284 | goto clear_pmdnuma; | |
1285 | } | |
1286 | ||
1287 | /* | |
1288 | * Migrate the THP to the requested node, returns with page unlocked | |
1289 | * and access rights restored. | |
1290 | */ | |
1291 | spin_unlock(vmf->ptl); | |
1292 | migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma, | |
1293 | vmf->pmd, pmd, vmf->address, page, target_nid); | |
1294 | if (migrated) { | |
1295 | flags |= TNF_MIGRATED; | |
1296 | page_nid = target_nid; | |
1297 | } else | |
1298 | flags |= TNF_MIGRATE_FAIL; | |
1299 | ||
1300 | goto out; | |
1301 | clear_pmdnuma: | |
1302 | BUG_ON(!PageLocked(page)); | |
1303 | was_writable = pmd_write(pmd); | |
1304 | pmd = pmd_modify(pmd, vma->vm_page_prot); | |
1305 | pmd = pmd_mkyoung(pmd); | |
1306 | if (was_writable) | |
1307 | pmd = pmd_mkwrite(pmd); | |
1308 | set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd); | |
1309 | update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); | |
1310 | unlock_page(page); | |
1311 | out_unlock: | |
1312 | spin_unlock(vmf->ptl); | |
1313 | ||
1314 | out: | |
1315 | if (anon_vma) | |
1316 | page_unlock_anon_vma_read(anon_vma); | |
1317 | ||
1318 | if (page_nid != -1) | |
1319 | task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, | |
1320 | vmf->flags); | |
1321 | ||
1322 | return 0; | |
1323 | } | |
1324 | ||
1325 | /* | |
1326 | * Return true if we do MADV_FREE successfully on entire pmd page. | |
1327 | * Otherwise, return false. | |
1328 | */ | |
1329 | bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, | |
1330 | pmd_t *pmd, unsigned long addr, unsigned long next) | |
1331 | { | |
1332 | spinlock_t *ptl; | |
1333 | pmd_t orig_pmd; | |
1334 | struct page *page; | |
1335 | struct mm_struct *mm = tlb->mm; | |
1336 | bool ret = false; | |
1337 | ||
1338 | tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE); | |
1339 | ||
1340 | ptl = pmd_trans_huge_lock(pmd, vma); | |
1341 | if (!ptl) | |
1342 | goto out_unlocked; | |
1343 | ||
1344 | orig_pmd = *pmd; | |
1345 | if (is_huge_zero_pmd(orig_pmd)) | |
1346 | goto out; | |
1347 | ||
1348 | page = pmd_page(orig_pmd); | |
1349 | /* | |
1350 | * If other processes are mapping this page, we couldn't discard | |
1351 | * the page unless they all do MADV_FREE so let's skip the page. | |
1352 | */ | |
1353 | if (page_mapcount(page) != 1) | |
1354 | goto out; | |
1355 | ||
1356 | if (!trylock_page(page)) | |
1357 | goto out; | |
1358 | ||
1359 | /* | |
1360 | * If user want to discard part-pages of THP, split it so MADV_FREE | |
1361 | * will deactivate only them. | |
1362 | */ | |
1363 | if (next - addr != HPAGE_PMD_SIZE) { | |
1364 | get_page(page); | |
1365 | spin_unlock(ptl); | |
1366 | split_huge_page(page); | |
1367 | put_page(page); | |
1368 | unlock_page(page); | |
1369 | goto out_unlocked; | |
1370 | } | |
1371 | ||
1372 | if (PageDirty(page)) | |
1373 | ClearPageDirty(page); | |
1374 | unlock_page(page); | |
1375 | ||
1376 | if (PageActive(page)) | |
1377 | deactivate_page(page); | |
1378 | ||
1379 | if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { | |
1380 | orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, | |
1381 | tlb->fullmm); | |
1382 | orig_pmd = pmd_mkold(orig_pmd); | |
1383 | orig_pmd = pmd_mkclean(orig_pmd); | |
1384 | ||
1385 | set_pmd_at(mm, addr, pmd, orig_pmd); | |
1386 | tlb_remove_pmd_tlb_entry(tlb, pmd, addr); | |
1387 | } | |
1388 | ret = true; | |
1389 | out: | |
1390 | spin_unlock(ptl); | |
1391 | out_unlocked: | |
1392 | return ret; | |
1393 | } | |
1394 | ||
1395 | static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd) | |
1396 | { | |
1397 | pgtable_t pgtable; | |
1398 | ||
1399 | pgtable = pgtable_trans_huge_withdraw(mm, pmd); | |
1400 | pte_free(mm, pgtable); | |
1401 | atomic_long_dec(&mm->nr_ptes); | |
1402 | } | |
1403 | ||
1404 | int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, | |
1405 | pmd_t *pmd, unsigned long addr) | |
1406 | { | |
1407 | pmd_t orig_pmd; | |
1408 | spinlock_t *ptl; | |
1409 | ||
1410 | tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE); | |
1411 | ||
1412 | ptl = __pmd_trans_huge_lock(pmd, vma); | |
1413 | if (!ptl) | |
1414 | return 0; | |
1415 | /* | |
1416 | * For architectures like ppc64 we look at deposited pgtable | |
1417 | * when calling pmdp_huge_get_and_clear. So do the | |
1418 | * pgtable_trans_huge_withdraw after finishing pmdp related | |
1419 | * operations. | |
1420 | */ | |
1421 | orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, | |
1422 | tlb->fullmm); | |
1423 | tlb_remove_pmd_tlb_entry(tlb, pmd, addr); | |
1424 | if (vma_is_dax(vma)) { | |
1425 | spin_unlock(ptl); | |
1426 | if (is_huge_zero_pmd(orig_pmd)) | |
1427 | tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); | |
1428 | } else if (is_huge_zero_pmd(orig_pmd)) { | |
1429 | pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd)); | |
1430 | atomic_long_dec(&tlb->mm->nr_ptes); | |
1431 | spin_unlock(ptl); | |
1432 | tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); | |
1433 | } else { | |
1434 | struct page *page = pmd_page(orig_pmd); | |
1435 | page_remove_rmap(page, true); | |
1436 | VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); | |
1437 | VM_BUG_ON_PAGE(!PageHead(page), page); | |
1438 | if (PageAnon(page)) { | |
1439 | pgtable_t pgtable; | |
1440 | pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd); | |
1441 | pte_free(tlb->mm, pgtable); | |
1442 | atomic_long_dec(&tlb->mm->nr_ptes); | |
1443 | add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); | |
1444 | } else { | |
1445 | if (arch_needs_pgtable_deposit()) | |
1446 | zap_deposited_table(tlb->mm, pmd); | |
1447 | add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR); | |
1448 | } | |
1449 | spin_unlock(ptl); | |
1450 | tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE); | |
1451 | } | |
1452 | return 1; | |
1453 | } | |
1454 | ||
1455 | #ifndef pmd_move_must_withdraw | |
1456 | static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl, | |
1457 | spinlock_t *old_pmd_ptl, | |
1458 | struct vm_area_struct *vma) | |
1459 | { | |
1460 | /* | |
1461 | * With split pmd lock we also need to move preallocated | |
1462 | * PTE page table if new_pmd is on different PMD page table. | |
1463 | * | |
1464 | * We also don't deposit and withdraw tables for file pages. | |
1465 | */ | |
1466 | return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma); | |
1467 | } | |
1468 | #endif | |
1469 | ||
1470 | bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr, | |
1471 | unsigned long new_addr, unsigned long old_end, | |
1472 | pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush) | |
1473 | { | |
1474 | spinlock_t *old_ptl, *new_ptl; | |
1475 | pmd_t pmd; | |
1476 | struct mm_struct *mm = vma->vm_mm; | |
1477 | bool force_flush = false; | |
1478 | ||
1479 | if ((old_addr & ~HPAGE_PMD_MASK) || | |
1480 | (new_addr & ~HPAGE_PMD_MASK) || | |
1481 | old_end - old_addr < HPAGE_PMD_SIZE) | |
1482 | return false; | |
1483 | ||
1484 | /* | |
1485 | * The destination pmd shouldn't be established, free_pgtables() | |
1486 | * should have release it. | |
1487 | */ | |
1488 | if (WARN_ON(!pmd_none(*new_pmd))) { | |
1489 | VM_BUG_ON(pmd_trans_huge(*new_pmd)); | |
1490 | return false; | |
1491 | } | |
1492 | ||
1493 | /* | |
1494 | * We don't have to worry about the ordering of src and dst | |
1495 | * ptlocks because exclusive mmap_sem prevents deadlock. | |
1496 | */ | |
1497 | old_ptl = __pmd_trans_huge_lock(old_pmd, vma); | |
1498 | if (old_ptl) { | |
1499 | new_ptl = pmd_lockptr(mm, new_pmd); | |
1500 | if (new_ptl != old_ptl) | |
1501 | spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); | |
1502 | pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd); | |
1503 | if (pmd_present(pmd) && pmd_dirty(pmd)) | |
1504 | force_flush = true; | |
1505 | VM_BUG_ON(!pmd_none(*new_pmd)); | |
1506 | ||
1507 | if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) { | |
1508 | pgtable_t pgtable; | |
1509 | pgtable = pgtable_trans_huge_withdraw(mm, old_pmd); | |
1510 | pgtable_trans_huge_deposit(mm, new_pmd, pgtable); | |
1511 | } | |
1512 | set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd)); | |
1513 | if (new_ptl != old_ptl) | |
1514 | spin_unlock(new_ptl); | |
1515 | if (force_flush) | |
1516 | flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE); | |
1517 | else | |
1518 | *need_flush = true; | |
1519 | spin_unlock(old_ptl); | |
1520 | return true; | |
1521 | } | |
1522 | return false; | |
1523 | } | |
1524 | ||
1525 | /* | |
1526 | * Returns | |
1527 | * - 0 if PMD could not be locked | |
1528 | * - 1 if PMD was locked but protections unchange and TLB flush unnecessary | |
1529 | * - HPAGE_PMD_NR is protections changed and TLB flush necessary | |
1530 | */ | |
1531 | int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, | |
1532 | unsigned long addr, pgprot_t newprot, int prot_numa) | |
1533 | { | |
1534 | struct mm_struct *mm = vma->vm_mm; | |
1535 | spinlock_t *ptl; | |
1536 | int ret = 0; | |
1537 | ||
1538 | ptl = __pmd_trans_huge_lock(pmd, vma); | |
1539 | if (ptl) { | |
1540 | pmd_t entry; | |
1541 | bool preserve_write = prot_numa && pmd_write(*pmd); | |
1542 | ret = 1; | |
1543 | ||
1544 | /* | |
1545 | * Avoid trapping faults against the zero page. The read-only | |
1546 | * data is likely to be read-cached on the local CPU and | |
1547 | * local/remote hits to the zero page are not interesting. | |
1548 | */ | |
1549 | if (prot_numa && is_huge_zero_pmd(*pmd)) { | |
1550 | spin_unlock(ptl); | |
1551 | return ret; | |
1552 | } | |
1553 | ||
1554 | if (!prot_numa || !pmd_protnone(*pmd)) { | |
1555 | entry = pmdp_huge_get_and_clear_notify(mm, addr, pmd); | |
1556 | entry = pmd_modify(entry, newprot); | |
1557 | if (preserve_write) | |
1558 | entry = pmd_mkwrite(entry); | |
1559 | ret = HPAGE_PMD_NR; | |
1560 | set_pmd_at(mm, addr, pmd, entry); | |
1561 | BUG_ON(vma_is_anonymous(vma) && !preserve_write && | |
1562 | pmd_write(entry)); | |
1563 | } | |
1564 | spin_unlock(ptl); | |
1565 | } | |
1566 | ||
1567 | return ret; | |
1568 | } | |
1569 | ||
1570 | /* | |
1571 | * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise. | |
1572 | * | |
1573 | * Note that if it returns page table lock pointer, this routine returns without | |
1574 | * unlocking page table lock. So callers must unlock it. | |
1575 | */ | |
1576 | spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) | |
1577 | { | |
1578 | spinlock_t *ptl; | |
1579 | ptl = pmd_lock(vma->vm_mm, pmd); | |
1580 | if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd))) | |
1581 | return ptl; | |
1582 | spin_unlock(ptl); | |
1583 | return NULL; | |
1584 | } | |
1585 | ||
1586 | static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, | |
1587 | unsigned long haddr, pmd_t *pmd) | |
1588 | { | |
1589 | struct mm_struct *mm = vma->vm_mm; | |
1590 | pgtable_t pgtable; | |
1591 | pmd_t _pmd; | |
1592 | int i; | |
1593 | ||
1594 | /* leave pmd empty until pte is filled */ | |
1595 | pmdp_huge_clear_flush_notify(vma, haddr, pmd); | |
1596 | ||
1597 | pgtable = pgtable_trans_huge_withdraw(mm, pmd); | |
1598 | pmd_populate(mm, &_pmd, pgtable); | |
1599 | ||
1600 | for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { | |
1601 | pte_t *pte, entry; | |
1602 | entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); | |
1603 | entry = pte_mkspecial(entry); | |
1604 | pte = pte_offset_map(&_pmd, haddr); | |
1605 | VM_BUG_ON(!pte_none(*pte)); | |
1606 | set_pte_at(mm, haddr, pte, entry); | |
1607 | pte_unmap(pte); | |
1608 | } | |
1609 | smp_wmb(); /* make pte visible before pmd */ | |
1610 | pmd_populate(mm, pmd, pgtable); | |
1611 | } | |
1612 | ||
1613 | static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, | |
1614 | unsigned long haddr, bool freeze) | |
1615 | { | |
1616 | struct mm_struct *mm = vma->vm_mm; | |
1617 | struct page *page; | |
1618 | pgtable_t pgtable; | |
1619 | pmd_t _pmd; | |
1620 | bool young, write, dirty, soft_dirty; | |
1621 | unsigned long addr; | |
1622 | int i; | |
1623 | ||
1624 | VM_BUG_ON(haddr & ~HPAGE_PMD_MASK); | |
1625 | VM_BUG_ON_VMA(vma->vm_start > haddr, vma); | |
1626 | VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma); | |
1627 | VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)); | |
1628 | ||
1629 | count_vm_event(THP_SPLIT_PMD); | |
1630 | ||
1631 | if (!vma_is_anonymous(vma)) { | |
1632 | _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd); | |
1633 | /* | |
1634 | * We are going to unmap this huge page. So | |
1635 | * just go ahead and zap it | |
1636 | */ | |
1637 | if (arch_needs_pgtable_deposit()) | |
1638 | zap_deposited_table(mm, pmd); | |
1639 | if (vma_is_dax(vma)) | |
1640 | return; | |
1641 | page = pmd_page(_pmd); | |
1642 | if (!PageReferenced(page) && pmd_young(_pmd)) | |
1643 | SetPageReferenced(page); | |
1644 | page_remove_rmap(page, true); | |
1645 | put_page(page); | |
1646 | add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR); | |
1647 | return; | |
1648 | } else if (is_huge_zero_pmd(*pmd)) { | |
1649 | return __split_huge_zero_page_pmd(vma, haddr, pmd); | |
1650 | } | |
1651 | ||
1652 | page = pmd_page(*pmd); | |
1653 | VM_BUG_ON_PAGE(!page_count(page), page); | |
1654 | page_ref_add(page, HPAGE_PMD_NR - 1); | |
1655 | write = pmd_write(*pmd); | |
1656 | young = pmd_young(*pmd); | |
1657 | dirty = pmd_dirty(*pmd); | |
1658 | soft_dirty = pmd_soft_dirty(*pmd); | |
1659 | ||
1660 | pmdp_huge_split_prepare(vma, haddr, pmd); | |
1661 | pgtable = pgtable_trans_huge_withdraw(mm, pmd); | |
1662 | pmd_populate(mm, &_pmd, pgtable); | |
1663 | ||
1664 | for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) { | |
1665 | pte_t entry, *pte; | |
1666 | /* | |
1667 | * Note that NUMA hinting access restrictions are not | |
1668 | * transferred to avoid any possibility of altering | |
1669 | * permissions across VMAs. | |
1670 | */ | |
1671 | if (freeze) { | |
1672 | swp_entry_t swp_entry; | |
1673 | swp_entry = make_migration_entry(page + i, write); | |
1674 | entry = swp_entry_to_pte(swp_entry); | |
1675 | if (soft_dirty) | |
1676 | entry = pte_swp_mksoft_dirty(entry); | |
1677 | } else { | |
1678 | entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); | |
1679 | entry = maybe_mkwrite(entry, vma); | |
1680 | if (!write) | |
1681 | entry = pte_wrprotect(entry); | |
1682 | if (!young) | |
1683 | entry = pte_mkold(entry); | |
1684 | if (soft_dirty) | |
1685 | entry = pte_mksoft_dirty(entry); | |
1686 | } | |
1687 | if (dirty) | |
1688 | SetPageDirty(page + i); | |
1689 | pte = pte_offset_map(&_pmd, addr); | |
1690 | BUG_ON(!pte_none(*pte)); | |
1691 | set_pte_at(mm, addr, pte, entry); | |
1692 | atomic_inc(&page[i]._mapcount); | |
1693 | pte_unmap(pte); | |
1694 | } | |
1695 | ||
1696 | /* | |
1697 | * Set PG_double_map before dropping compound_mapcount to avoid | |
1698 | * false-negative page_mapped(). | |
1699 | */ | |
1700 | if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) { | |
1701 | for (i = 0; i < HPAGE_PMD_NR; i++) | |
1702 | atomic_inc(&page[i]._mapcount); | |
1703 | } | |
1704 | ||
1705 | if (atomic_add_negative(-1, compound_mapcount_ptr(page))) { | |
1706 | /* Last compound_mapcount is gone. */ | |
1707 | __dec_node_page_state(page, NR_ANON_THPS); | |
1708 | if (TestClearPageDoubleMap(page)) { | |
1709 | /* No need in mapcount reference anymore */ | |
1710 | for (i = 0; i < HPAGE_PMD_NR; i++) | |
1711 | atomic_dec(&page[i]._mapcount); | |
1712 | } | |
1713 | } | |
1714 | ||
1715 | smp_wmb(); /* make pte visible before pmd */ | |
1716 | /* | |
1717 | * Up to this point the pmd is present and huge and userland has the | |
1718 | * whole access to the hugepage during the split (which happens in | |
1719 | * place). If we overwrite the pmd with the not-huge version pointing | |
1720 | * to the pte here (which of course we could if all CPUs were bug | |
1721 | * free), userland could trigger a small page size TLB miss on the | |
1722 | * small sized TLB while the hugepage TLB entry is still established in | |
1723 | * the huge TLB. Some CPU doesn't like that. | |
1724 | * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum | |
1725 | * 383 on page 93. Intel should be safe but is also warns that it's | |
1726 | * only safe if the permission and cache attributes of the two entries | |
1727 | * loaded in the two TLB is identical (which should be the case here). | |
1728 | * But it is generally safer to never allow small and huge TLB entries | |
1729 | * for the same virtual address to be loaded simultaneously. So instead | |
1730 | * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the | |
1731 | * current pmd notpresent (atomically because here the pmd_trans_huge | |
1732 | * and pmd_trans_splitting must remain set at all times on the pmd | |
1733 | * until the split is complete for this pmd), then we flush the SMP TLB | |
1734 | * and finally we write the non-huge version of the pmd entry with | |
1735 | * pmd_populate. | |
1736 | */ | |
1737 | pmdp_invalidate(vma, haddr, pmd); | |
1738 | pmd_populate(mm, pmd, pgtable); | |
1739 | ||
1740 | if (freeze) { | |
1741 | for (i = 0; i < HPAGE_PMD_NR; i++) { | |
1742 | page_remove_rmap(page + i, false); | |
1743 | put_page(page + i); | |
1744 | } | |
1745 | } | |
1746 | } | |
1747 | ||
1748 | void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, | |
1749 | unsigned long address, bool freeze, struct page *page) | |
1750 | { | |
1751 | spinlock_t *ptl; | |
1752 | struct mm_struct *mm = vma->vm_mm; | |
1753 | unsigned long haddr = address & HPAGE_PMD_MASK; | |
1754 | ||
1755 | mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE); | |
1756 | ptl = pmd_lock(mm, pmd); | |
1757 | ||
1758 | /* | |
1759 | * If caller asks to setup a migration entries, we need a page to check | |
1760 | * pmd against. Otherwise we can end up replacing wrong page. | |
1761 | */ | |
1762 | VM_BUG_ON(freeze && !page); | |
1763 | if (page && page != pmd_page(*pmd)) | |
1764 | goto out; | |
1765 | ||
1766 | if (pmd_trans_huge(*pmd)) { | |
1767 | page = pmd_page(*pmd); | |
1768 | if (PageMlocked(page)) | |
1769 | clear_page_mlock(page); | |
1770 | } else if (!pmd_devmap(*pmd)) | |
1771 | goto out; | |
1772 | __split_huge_pmd_locked(vma, pmd, haddr, freeze); | |
1773 | out: | |
1774 | spin_unlock(ptl); | |
1775 | mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE); | |
1776 | } | |
1777 | ||
1778 | void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, | |
1779 | bool freeze, struct page *page) | |
1780 | { | |
1781 | pgd_t *pgd; | |
1782 | pud_t *pud; | |
1783 | pmd_t *pmd; | |
1784 | ||
1785 | pgd = pgd_offset(vma->vm_mm, address); | |
1786 | if (!pgd_present(*pgd)) | |
1787 | return; | |
1788 | ||
1789 | pud = pud_offset(pgd, address); | |
1790 | if (!pud_present(*pud)) | |
1791 | return; | |
1792 | ||
1793 | pmd = pmd_offset(pud, address); | |
1794 | ||
1795 | __split_huge_pmd(vma, pmd, address, freeze, page); | |
1796 | } | |
1797 | ||
1798 | void vma_adjust_trans_huge(struct vm_area_struct *vma, | |
1799 | unsigned long start, | |
1800 | unsigned long end, | |
1801 | long adjust_next) | |
1802 | { | |
1803 | /* | |
1804 | * If the new start address isn't hpage aligned and it could | |
1805 | * previously contain an hugepage: check if we need to split | |
1806 | * an huge pmd. | |
1807 | */ | |
1808 | if (start & ~HPAGE_PMD_MASK && | |
1809 | (start & HPAGE_PMD_MASK) >= vma->vm_start && | |
1810 | (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) | |
1811 | split_huge_pmd_address(vma, start, false, NULL); | |
1812 | ||
1813 | /* | |
1814 | * If the new end address isn't hpage aligned and it could | |
1815 | * previously contain an hugepage: check if we need to split | |
1816 | * an huge pmd. | |
1817 | */ | |
1818 | if (end & ~HPAGE_PMD_MASK && | |
1819 | (end & HPAGE_PMD_MASK) >= vma->vm_start && | |
1820 | (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) | |
1821 | split_huge_pmd_address(vma, end, false, NULL); | |
1822 | ||
1823 | /* | |
1824 | * If we're also updating the vma->vm_next->vm_start, if the new | |
1825 | * vm_next->vm_start isn't page aligned and it could previously | |
1826 | * contain an hugepage: check if we need to split an huge pmd. | |
1827 | */ | |
1828 | if (adjust_next > 0) { | |
1829 | struct vm_area_struct *next = vma->vm_next; | |
1830 | unsigned long nstart = next->vm_start; | |
1831 | nstart += adjust_next << PAGE_SHIFT; | |
1832 | if (nstart & ~HPAGE_PMD_MASK && | |
1833 | (nstart & HPAGE_PMD_MASK) >= next->vm_start && | |
1834 | (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) | |
1835 | split_huge_pmd_address(next, nstart, false, NULL); | |
1836 | } | |
1837 | } | |
1838 | ||
1839 | static void freeze_page(struct page *page) | |
1840 | { | |
1841 | enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | | |
1842 | TTU_RMAP_LOCKED; | |
1843 | int i, ret; | |
1844 | ||
1845 | VM_BUG_ON_PAGE(!PageHead(page), page); | |
1846 | ||
1847 | if (PageAnon(page)) | |
1848 | ttu_flags |= TTU_MIGRATION; | |
1849 | ||
1850 | /* We only need TTU_SPLIT_HUGE_PMD once */ | |
1851 | ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD); | |
1852 | for (i = 1; !ret && i < HPAGE_PMD_NR; i++) { | |
1853 | /* Cut short if the page is unmapped */ | |
1854 | if (page_count(page) == 1) | |
1855 | return; | |
1856 | ||
1857 | ret = try_to_unmap(page + i, ttu_flags); | |
1858 | } | |
1859 | VM_BUG_ON_PAGE(ret, page + i - 1); | |
1860 | } | |
1861 | ||
1862 | static void unfreeze_page(struct page *page) | |
1863 | { | |
1864 | int i; | |
1865 | ||
1866 | for (i = 0; i < HPAGE_PMD_NR; i++) | |
1867 | remove_migration_ptes(page + i, page + i, true); | |
1868 | } | |
1869 | ||
1870 | static void __split_huge_page_tail(struct page *head, int tail, | |
1871 | struct lruvec *lruvec, struct list_head *list) | |
1872 | { | |
1873 | struct page *page_tail = head + tail; | |
1874 | ||
1875 | VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); | |
1876 | VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail); | |
1877 | ||
1878 | /* | |
1879 | * tail_page->_refcount is zero and not changing from under us. But | |
1880 | * get_page_unless_zero() may be running from under us on the | |
1881 | * tail_page. If we used atomic_set() below instead of atomic_inc() or | |
1882 | * atomic_add(), we would then run atomic_set() concurrently with | |
1883 | * get_page_unless_zero(), and atomic_set() is implemented in C not | |
1884 | * using locked ops. spin_unlock on x86 sometime uses locked ops | |
1885 | * because of PPro errata 66, 92, so unless somebody can guarantee | |
1886 | * atomic_set() here would be safe on all archs (and not only on x86), | |
1887 | * it's safer to use atomic_inc()/atomic_add(). | |
1888 | */ | |
1889 | if (PageAnon(head)) { | |
1890 | page_ref_inc(page_tail); | |
1891 | } else { | |
1892 | /* Additional pin to radix tree */ | |
1893 | page_ref_add(page_tail, 2); | |
1894 | } | |
1895 | ||
1896 | page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; | |
1897 | page_tail->flags |= (head->flags & | |
1898 | ((1L << PG_referenced) | | |
1899 | (1L << PG_swapbacked) | | |
1900 | (1L << PG_mlocked) | | |
1901 | (1L << PG_uptodate) | | |
1902 | (1L << PG_active) | | |
1903 | (1L << PG_locked) | | |
1904 | (1L << PG_unevictable) | | |
1905 | (1L << PG_dirty))); | |
1906 | ||
1907 | /* | |
1908 | * After clearing PageTail the gup refcount can be released. | |
1909 | * Page flags also must be visible before we make the page non-compound. | |
1910 | */ | |
1911 | smp_wmb(); | |
1912 | ||
1913 | clear_compound_head(page_tail); | |
1914 | ||
1915 | if (page_is_young(head)) | |
1916 | set_page_young(page_tail); | |
1917 | if (page_is_idle(head)) | |
1918 | set_page_idle(page_tail); | |
1919 | ||
1920 | /* ->mapping in first tail page is compound_mapcount */ | |
1921 | VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING, | |
1922 | page_tail); | |
1923 | page_tail->mapping = head->mapping; | |
1924 | ||
1925 | page_tail->index = head->index + tail; | |
1926 | page_cpupid_xchg_last(page_tail, page_cpupid_last(head)); | |
1927 | lru_add_page_tail(head, page_tail, lruvec, list); | |
1928 | } | |
1929 | ||
1930 | static void __split_huge_page(struct page *page, struct list_head *list, | |
1931 | unsigned long flags) | |
1932 | { | |
1933 | struct page *head = compound_head(page); | |
1934 | struct zone *zone = page_zone(head); | |
1935 | struct lruvec *lruvec; | |
1936 | pgoff_t end = -1; | |
1937 | int i; | |
1938 | ||
1939 | lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat); | |
1940 | ||
1941 | /* complete memcg works before add pages to LRU */ | |
1942 | mem_cgroup_split_huge_fixup(head); | |
1943 | ||
1944 | if (!PageAnon(page)) | |
1945 | end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE); | |
1946 | ||
1947 | for (i = HPAGE_PMD_NR - 1; i >= 1; i--) { | |
1948 | __split_huge_page_tail(head, i, lruvec, list); | |
1949 | /* Some pages can be beyond i_size: drop them from page cache */ | |
1950 | if (head[i].index >= end) { | |
1951 | __ClearPageDirty(head + i); | |
1952 | __delete_from_page_cache(head + i, NULL); | |
1953 | if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head)) | |
1954 | shmem_uncharge(head->mapping->host, 1); | |
1955 | put_page(head + i); | |
1956 | } | |
1957 | } | |
1958 | ||
1959 | ClearPageCompound(head); | |
1960 | /* See comment in __split_huge_page_tail() */ | |
1961 | if (PageAnon(head)) { | |
1962 | page_ref_inc(head); | |
1963 | } else { | |
1964 | /* Additional pin to radix tree */ | |
1965 | page_ref_add(head, 2); | |
1966 | spin_unlock(&head->mapping->tree_lock); | |
1967 | } | |
1968 | ||
1969 | spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags); | |
1970 | ||
1971 | unfreeze_page(head); | |
1972 | ||
1973 | for (i = 0; i < HPAGE_PMD_NR; i++) { | |
1974 | struct page *subpage = head + i; | |
1975 | if (subpage == page) | |
1976 | continue; | |
1977 | unlock_page(subpage); | |
1978 | ||
1979 | /* | |
1980 | * Subpages may be freed if there wasn't any mapping | |
1981 | * like if add_to_swap() is running on a lru page that | |
1982 | * had its mapping zapped. And freeing these pages | |
1983 | * requires taking the lru_lock so we do the put_page | |
1984 | * of the tail pages after the split is complete. | |
1985 | */ | |
1986 | put_page(subpage); | |
1987 | } | |
1988 | } | |
1989 | ||
1990 | int total_mapcount(struct page *page) | |
1991 | { | |
1992 | int i, compound, ret; | |
1993 | ||
1994 | VM_BUG_ON_PAGE(PageTail(page), page); | |
1995 | ||
1996 | if (likely(!PageCompound(page))) | |
1997 | return atomic_read(&page->_mapcount) + 1; | |
1998 | ||
1999 | compound = compound_mapcount(page); | |
2000 | if (PageHuge(page)) | |
2001 | return compound; | |
2002 | ret = compound; | |
2003 | for (i = 0; i < HPAGE_PMD_NR; i++) | |
2004 | ret += atomic_read(&page[i]._mapcount) + 1; | |
2005 | /* File pages has compound_mapcount included in _mapcount */ | |
2006 | if (!PageAnon(page)) | |
2007 | return ret - compound * HPAGE_PMD_NR; | |
2008 | if (PageDoubleMap(page)) | |
2009 | ret -= HPAGE_PMD_NR; | |
2010 | return ret; | |
2011 | } | |
2012 | ||
2013 | /* | |
2014 | * This calculates accurately how many mappings a transparent hugepage | |
2015 | * has (unlike page_mapcount() which isn't fully accurate). This full | |
2016 | * accuracy is primarily needed to know if copy-on-write faults can | |
2017 | * reuse the page and change the mapping to read-write instead of | |
2018 | * copying them. At the same time this returns the total_mapcount too. | |
2019 | * | |
2020 | * The function returns the highest mapcount any one of the subpages | |
2021 | * has. If the return value is one, even if different processes are | |
2022 | * mapping different subpages of the transparent hugepage, they can | |
2023 | * all reuse it, because each process is reusing a different subpage. | |
2024 | * | |
2025 | * The total_mapcount is instead counting all virtual mappings of the | |
2026 | * subpages. If the total_mapcount is equal to "one", it tells the | |
2027 | * caller all mappings belong to the same "mm" and in turn the | |
2028 | * anon_vma of the transparent hugepage can become the vma->anon_vma | |
2029 | * local one as no other process may be mapping any of the subpages. | |
2030 | * | |
2031 | * It would be more accurate to replace page_mapcount() with | |
2032 | * page_trans_huge_mapcount(), however we only use | |
2033 | * page_trans_huge_mapcount() in the copy-on-write faults where we | |
2034 | * need full accuracy to avoid breaking page pinning, because | |
2035 | * page_trans_huge_mapcount() is slower than page_mapcount(). | |
2036 | */ | |
2037 | int page_trans_huge_mapcount(struct page *page, int *total_mapcount) | |
2038 | { | |
2039 | int i, ret, _total_mapcount, mapcount; | |
2040 | ||
2041 | /* hugetlbfs shouldn't call it */ | |
2042 | VM_BUG_ON_PAGE(PageHuge(page), page); | |
2043 | ||
2044 | if (likely(!PageTransCompound(page))) { | |
2045 | mapcount = atomic_read(&page->_mapcount) + 1; | |
2046 | if (total_mapcount) | |
2047 | *total_mapcount = mapcount; | |
2048 | return mapcount; | |
2049 | } | |
2050 | ||
2051 | page = compound_head(page); | |
2052 | ||
2053 | _total_mapcount = ret = 0; | |
2054 | for (i = 0; i < HPAGE_PMD_NR; i++) { | |
2055 | mapcount = atomic_read(&page[i]._mapcount) + 1; | |
2056 | ret = max(ret, mapcount); | |
2057 | _total_mapcount += mapcount; | |
2058 | } | |
2059 | if (PageDoubleMap(page)) { | |
2060 | ret -= 1; | |
2061 | _total_mapcount -= HPAGE_PMD_NR; | |
2062 | } | |
2063 | mapcount = compound_mapcount(page); | |
2064 | ret += mapcount; | |
2065 | _total_mapcount += mapcount; | |
2066 | if (total_mapcount) | |
2067 | *total_mapcount = _total_mapcount; | |
2068 | return ret; | |
2069 | } | |
2070 | ||
2071 | /* | |
2072 | * This function splits huge page into normal pages. @page can point to any | |
2073 | * subpage of huge page to split. Split doesn't change the position of @page. | |
2074 | * | |
2075 | * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. | |
2076 | * The huge page must be locked. | |
2077 | * | |
2078 | * If @list is null, tail pages will be added to LRU list, otherwise, to @list. | |
2079 | * | |
2080 | * Both head page and tail pages will inherit mapping, flags, and so on from | |
2081 | * the hugepage. | |
2082 | * | |
2083 | * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if | |
2084 | * they are not mapped. | |
2085 | * | |
2086 | * Returns 0 if the hugepage is split successfully. | |
2087 | * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under | |
2088 | * us. | |
2089 | */ | |
2090 | int split_huge_page_to_list(struct page *page, struct list_head *list) | |
2091 | { | |
2092 | struct page *head = compound_head(page); | |
2093 | struct pglist_data *pgdata = NODE_DATA(page_to_nid(head)); | |
2094 | struct anon_vma *anon_vma = NULL; | |
2095 | struct address_space *mapping = NULL; | |
2096 | int count, mapcount, extra_pins, ret; | |
2097 | bool mlocked; | |
2098 | unsigned long flags; | |
2099 | ||
2100 | VM_BUG_ON_PAGE(is_huge_zero_page(page), page); | |
2101 | VM_BUG_ON_PAGE(!PageLocked(page), page); | |
2102 | VM_BUG_ON_PAGE(!PageSwapBacked(page), page); | |
2103 | VM_BUG_ON_PAGE(!PageCompound(page), page); | |
2104 | ||
2105 | if (PageAnon(head)) { | |
2106 | /* | |
2107 | * The caller does not necessarily hold an mmap_sem that would | |
2108 | * prevent the anon_vma disappearing so we first we take a | |
2109 | * reference to it and then lock the anon_vma for write. This | |
2110 | * is similar to page_lock_anon_vma_read except the write lock | |
2111 | * is taken to serialise against parallel split or collapse | |
2112 | * operations. | |
2113 | */ | |
2114 | anon_vma = page_get_anon_vma(head); | |
2115 | if (!anon_vma) { | |
2116 | ret = -EBUSY; | |
2117 | goto out; | |
2118 | } | |
2119 | extra_pins = 0; | |
2120 | mapping = NULL; | |
2121 | anon_vma_lock_write(anon_vma); | |
2122 | } else { | |
2123 | mapping = head->mapping; | |
2124 | ||
2125 | /* Truncated ? */ | |
2126 | if (!mapping) { | |
2127 | ret = -EBUSY; | |
2128 | goto out; | |
2129 | } | |
2130 | ||
2131 | /* Addidional pins from radix tree */ | |
2132 | extra_pins = HPAGE_PMD_NR; | |
2133 | anon_vma = NULL; | |
2134 | i_mmap_lock_read(mapping); | |
2135 | } | |
2136 | ||
2137 | /* | |
2138 | * Racy check if we can split the page, before freeze_page() will | |
2139 | * split PMDs | |
2140 | */ | |
2141 | if (total_mapcount(head) != page_count(head) - extra_pins - 1) { | |
2142 | ret = -EBUSY; | |
2143 | goto out_unlock; | |
2144 | } | |
2145 | ||
2146 | mlocked = PageMlocked(page); | |
2147 | freeze_page(head); | |
2148 | VM_BUG_ON_PAGE(compound_mapcount(head), head); | |
2149 | ||
2150 | /* Make sure the page is not on per-CPU pagevec as it takes pin */ | |
2151 | if (mlocked) | |
2152 | lru_add_drain(); | |
2153 | ||
2154 | /* prevent PageLRU to go away from under us, and freeze lru stats */ | |
2155 | spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags); | |
2156 | ||
2157 | if (mapping) { | |
2158 | void **pslot; | |
2159 | ||
2160 | spin_lock(&mapping->tree_lock); | |
2161 | pslot = radix_tree_lookup_slot(&mapping->page_tree, | |
2162 | page_index(head)); | |
2163 | /* | |
2164 | * Check if the head page is present in radix tree. | |
2165 | * We assume all tail are present too, if head is there. | |
2166 | */ | |
2167 | if (radix_tree_deref_slot_protected(pslot, | |
2168 | &mapping->tree_lock) != head) | |
2169 | goto fail; | |
2170 | } | |
2171 | ||
2172 | /* Prevent deferred_split_scan() touching ->_refcount */ | |
2173 | spin_lock(&pgdata->split_queue_lock); | |
2174 | count = page_count(head); | |
2175 | mapcount = total_mapcount(head); | |
2176 | if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) { | |
2177 | if (!list_empty(page_deferred_list(head))) { | |
2178 | pgdata->split_queue_len--; | |
2179 | list_del(page_deferred_list(head)); | |
2180 | } | |
2181 | if (mapping) | |
2182 | __dec_node_page_state(page, NR_SHMEM_THPS); | |
2183 | spin_unlock(&pgdata->split_queue_lock); | |
2184 | __split_huge_page(page, list, flags); | |
2185 | ret = 0; | |
2186 | } else { | |
2187 | if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) { | |
2188 | pr_alert("total_mapcount: %u, page_count(): %u\n", | |
2189 | mapcount, count); | |
2190 | if (PageTail(page)) | |
2191 | dump_page(head, NULL); | |
2192 | dump_page(page, "total_mapcount(head) > 0"); | |
2193 | BUG(); | |
2194 | } | |
2195 | spin_unlock(&pgdata->split_queue_lock); | |
2196 | fail: if (mapping) | |
2197 | spin_unlock(&mapping->tree_lock); | |
2198 | spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags); | |
2199 | unfreeze_page(head); | |
2200 | ret = -EBUSY; | |
2201 | } | |
2202 | ||
2203 | out_unlock: | |
2204 | if (anon_vma) { | |
2205 | anon_vma_unlock_write(anon_vma); | |
2206 | put_anon_vma(anon_vma); | |
2207 | } | |
2208 | if (mapping) | |
2209 | i_mmap_unlock_read(mapping); | |
2210 | out: | |
2211 | count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED); | |
2212 | return ret; | |
2213 | } | |
2214 | ||
2215 | void free_transhuge_page(struct page *page) | |
2216 | { | |
2217 | struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); | |
2218 | unsigned long flags; | |
2219 | ||
2220 | spin_lock_irqsave(&pgdata->split_queue_lock, flags); | |
2221 | if (!list_empty(page_deferred_list(page))) { | |
2222 | pgdata->split_queue_len--; | |
2223 | list_del(page_deferred_list(page)); | |
2224 | } | |
2225 | spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); | |
2226 | free_compound_page(page); | |
2227 | } | |
2228 | ||
2229 | void deferred_split_huge_page(struct page *page) | |
2230 | { | |
2231 | struct pglist_data *pgdata = NODE_DATA(page_to_nid(page)); | |
2232 | unsigned long flags; | |
2233 | ||
2234 | VM_BUG_ON_PAGE(!PageTransHuge(page), page); | |
2235 | ||
2236 | spin_lock_irqsave(&pgdata->split_queue_lock, flags); | |
2237 | if (list_empty(page_deferred_list(page))) { | |
2238 | count_vm_event(THP_DEFERRED_SPLIT_PAGE); | |
2239 | list_add_tail(page_deferred_list(page), &pgdata->split_queue); | |
2240 | pgdata->split_queue_len++; | |
2241 | } | |
2242 | spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); | |
2243 | } | |
2244 | ||
2245 | static unsigned long deferred_split_count(struct shrinker *shrink, | |
2246 | struct shrink_control *sc) | |
2247 | { | |
2248 | struct pglist_data *pgdata = NODE_DATA(sc->nid); | |
2249 | return ACCESS_ONCE(pgdata->split_queue_len); | |
2250 | } | |
2251 | ||
2252 | static unsigned long deferred_split_scan(struct shrinker *shrink, | |
2253 | struct shrink_control *sc) | |
2254 | { | |
2255 | struct pglist_data *pgdata = NODE_DATA(sc->nid); | |
2256 | unsigned long flags; | |
2257 | LIST_HEAD(list), *pos, *next; | |
2258 | struct page *page; | |
2259 | int split = 0; | |
2260 | ||
2261 | spin_lock_irqsave(&pgdata->split_queue_lock, flags); | |
2262 | /* Take pin on all head pages to avoid freeing them under us */ | |
2263 | list_for_each_safe(pos, next, &pgdata->split_queue) { | |
2264 | page = list_entry((void *)pos, struct page, mapping); | |
2265 | page = compound_head(page); | |
2266 | if (get_page_unless_zero(page)) { | |
2267 | list_move(page_deferred_list(page), &list); | |
2268 | } else { | |
2269 | /* We lost race with put_compound_page() */ | |
2270 | list_del_init(page_deferred_list(page)); | |
2271 | pgdata->split_queue_len--; | |
2272 | } | |
2273 | if (!--sc->nr_to_scan) | |
2274 | break; | |
2275 | } | |
2276 | spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); | |
2277 | ||
2278 | list_for_each_safe(pos, next, &list) { | |
2279 | page = list_entry((void *)pos, struct page, mapping); | |
2280 | lock_page(page); | |
2281 | /* split_huge_page() removes page from list on success */ | |
2282 | if (!split_huge_page(page)) | |
2283 | split++; | |
2284 | unlock_page(page); | |
2285 | put_page(page); | |
2286 | } | |
2287 | ||
2288 | spin_lock_irqsave(&pgdata->split_queue_lock, flags); | |
2289 | list_splice_tail(&list, &pgdata->split_queue); | |
2290 | spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); | |
2291 | ||
2292 | /* | |
2293 | * Stop shrinker if we didn't split any page, but the queue is empty. | |
2294 | * This can happen if pages were freed under us. | |
2295 | */ | |
2296 | if (!split && list_empty(&pgdata->split_queue)) | |
2297 | return SHRINK_STOP; | |
2298 | return split; | |
2299 | } | |
2300 | ||
2301 | static struct shrinker deferred_split_shrinker = { | |
2302 | .count_objects = deferred_split_count, | |
2303 | .scan_objects = deferred_split_scan, | |
2304 | .seeks = DEFAULT_SEEKS, | |
2305 | .flags = SHRINKER_NUMA_AWARE, | |
2306 | }; | |
2307 | ||
2308 | #ifdef CONFIG_DEBUG_FS | |
2309 | static int split_huge_pages_set(void *data, u64 val) | |
2310 | { | |
2311 | struct zone *zone; | |
2312 | struct page *page; | |
2313 | unsigned long pfn, max_zone_pfn; | |
2314 | unsigned long total = 0, split = 0; | |
2315 | ||
2316 | if (val != 1) | |
2317 | return -EINVAL; | |
2318 | ||
2319 | for_each_populated_zone(zone) { | |
2320 | max_zone_pfn = zone_end_pfn(zone); | |
2321 | for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) { | |
2322 | if (!pfn_valid(pfn)) | |
2323 | continue; | |
2324 | ||
2325 | page = pfn_to_page(pfn); | |
2326 | if (!get_page_unless_zero(page)) | |
2327 | continue; | |
2328 | ||
2329 | if (zone != page_zone(page)) | |
2330 | goto next; | |
2331 | ||
2332 | if (!PageHead(page) || PageHuge(page) || !PageLRU(page)) | |
2333 | goto next; | |
2334 | ||
2335 | total++; | |
2336 | lock_page(page); | |
2337 | if (!split_huge_page(page)) | |
2338 | split++; | |
2339 | unlock_page(page); | |
2340 | next: | |
2341 | put_page(page); | |
2342 | } | |
2343 | } | |
2344 | ||
2345 | pr_info("%lu of %lu THP split\n", split, total); | |
2346 | ||
2347 | return 0; | |
2348 | } | |
2349 | DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set, | |
2350 | "%llu\n"); | |
2351 | ||
2352 | static int __init split_huge_pages_debugfs(void) | |
2353 | { | |
2354 | void *ret; | |
2355 | ||
2356 | ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL, | |
2357 | &split_huge_pages_fops); | |
2358 | if (!ret) | |
2359 | pr_warn("Failed to create split_huge_pages in debugfs"); | |
2360 | return 0; | |
2361 | } | |
2362 | late_initcall(split_huge_pages_debugfs); | |
2363 | #endif |