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Linux 5.7.7
[linux/fpc-iii.git] / mm / huge_memory.c
blobdddc863b3cbcf92d4d1c2f0e15052bf4bec15eda
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2009 Red Hat, Inc.
4 */
5
6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7
8 #include <linux/mm.h>
9 #include <linux/sched.h>
10 #include <linux/sched/coredump.h>
11 #include <linux/sched/numa_balancing.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 #include <linux/oom.h>
34 #include <linux/numa.h>
35 #include <linux/page_owner.h>
36
37 #include <asm/tlb.h>
38 #include <asm/pgalloc.h>
39 #include "internal.h"
40
41 /*
42 * By default, transparent hugepage support is disabled in order to avoid
43 * risking an increased memory footprint for applications that are not
44 * guaranteed to benefit from it. When transparent hugepage support is
45 * enabled, it is for all mappings, and khugepaged scans all mappings.
46 * Defrag is invoked by khugepaged hugepage allocations and by page faults
47 * for all hugepage allocations.
48 */
49 unsigned long transparent_hugepage_flags __read_mostly =
50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
51 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
52 #endif
53 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
54 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
55 #endif
56 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
57 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
58 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
59
60 static struct shrinker deferred_split_shrinker;
61
62 static atomic_t huge_zero_refcount;
63 struct page *huge_zero_page __read_mostly;
64
65 bool transparent_hugepage_enabled(struct vm_area_struct *vma)
66 {
67 /* The addr is used to check if the vma size fits */
68 unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE;
69
70 if (!transhuge_vma_suitable(vma, addr))
71 return false;
72 if (vma_is_anonymous(vma))
73 return __transparent_hugepage_enabled(vma);
74 if (vma_is_shmem(vma))
75 return shmem_huge_enabled(vma);
76
77 return false;
78 }
79
80 static struct page *get_huge_zero_page(void)
81 {
82 struct page *zero_page;
83 retry:
84 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
85 return READ_ONCE(huge_zero_page);
86
87 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
88 HPAGE_PMD_ORDER);
89 if (!zero_page) {
90 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
91 return NULL;
92 }
93 count_vm_event(THP_ZERO_PAGE_ALLOC);
94 preempt_disable();
95 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
96 preempt_enable();
97 __free_pages(zero_page, compound_order(zero_page));
98 goto retry;
99 }
100
101 /* We take additional reference here. It will be put back by shrinker */
102 atomic_set(&huge_zero_refcount, 2);
103 preempt_enable();
104 return READ_ONCE(huge_zero_page);
105 }
106
107 static void put_huge_zero_page(void)
108 {
109 /*
110 * Counter should never go to zero here. Only shrinker can put
111 * last reference.
112 */
113 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
114 }
115
116 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
117 {
118 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
119 return READ_ONCE(huge_zero_page);
120
121 if (!get_huge_zero_page())
122 return NULL;
123
124 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
125 put_huge_zero_page();
126
127 return READ_ONCE(huge_zero_page);
128 }
129
130 void mm_put_huge_zero_page(struct mm_struct *mm)
131 {
132 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
133 put_huge_zero_page();
134 }
135
136 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
137 struct shrink_control *sc)
138 {
139 /* we can free zero page only if last reference remains */
140 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
141 }
142
143 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
144 struct shrink_control *sc)
145 {
146 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
147 struct page *zero_page = xchg(&huge_zero_page, NULL);
148 BUG_ON(zero_page == NULL);
149 __free_pages(zero_page, compound_order(zero_page));
150 return HPAGE_PMD_NR;
151 }
152
153 return 0;
154 }
155
156 static struct shrinker huge_zero_page_shrinker = {
157 .count_objects = shrink_huge_zero_page_count,
158 .scan_objects = shrink_huge_zero_page_scan,
159 .seeks = DEFAULT_SEEKS,
160 };
161
162 #ifdef CONFIG_SYSFS
163 static ssize_t enabled_show(struct kobject *kobj,
164 struct kobj_attribute *attr, char *buf)
165 {
166 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
167 return sprintf(buf, "[always] madvise never\n");
168 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
169 return sprintf(buf, "always [madvise] never\n");
170 else
171 return sprintf(buf, "always madvise [never]\n");
172 }
173
174 static ssize_t enabled_store(struct kobject *kobj,
175 struct kobj_attribute *attr,
176 const char *buf, size_t count)
177 {
178 ssize_t ret = count;
179
180 if (sysfs_streq(buf, "always")) {
181 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
182 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
183 } else if (sysfs_streq(buf, "madvise")) {
184 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
185 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
186 } else if (sysfs_streq(buf, "never")) {
187 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
188 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
189 } else
190 ret = -EINVAL;
191
192 if (ret > 0) {
193 int err = start_stop_khugepaged();
194 if (err)
195 ret = err;
196 }
197 return ret;
198 }
199 static struct kobj_attribute enabled_attr =
200 __ATTR(enabled, 0644, enabled_show, enabled_store);
201
202 ssize_t single_hugepage_flag_show(struct kobject *kobj,
203 struct kobj_attribute *attr, char *buf,
204 enum transparent_hugepage_flag flag)
205 {
206 return sprintf(buf, "%d\n",
207 !!test_bit(flag, &transparent_hugepage_flags));
208 }
209
210 ssize_t single_hugepage_flag_store(struct kobject *kobj,
211 struct kobj_attribute *attr,
212 const char *buf, size_t count,
213 enum transparent_hugepage_flag flag)
214 {
215 unsigned long value;
216 int ret;
217
218 ret = kstrtoul(buf, 10, &value);
219 if (ret < 0)
220 return ret;
221 if (value > 1)
222 return -EINVAL;
223
224 if (value)
225 set_bit(flag, &transparent_hugepage_flags);
226 else
227 clear_bit(flag, &transparent_hugepage_flags);
228
229 return count;
230 }
231
232 static ssize_t defrag_show(struct kobject *kobj,
233 struct kobj_attribute *attr, char *buf)
234 {
235 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
236 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
237 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
238 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
239 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
240 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
241 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
242 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
243 return sprintf(buf, "always defer defer+madvise madvise [never]\n");
244 }
245
246 static ssize_t defrag_store(struct kobject *kobj,
247 struct kobj_attribute *attr,
248 const char *buf, size_t count)
249 {
250 if (sysfs_streq(buf, "always")) {
251 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
252 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
253 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
254 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
255 } else if (sysfs_streq(buf, "defer+madvise")) {
256 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
257 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
258 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
259 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
260 } else if (sysfs_streq(buf, "defer")) {
261 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
262 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
263 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
264 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
265 } else if (sysfs_streq(buf, "madvise")) {
266 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
267 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
268 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
269 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
270 } else if (sysfs_streq(buf, "never")) {
271 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
272 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
273 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
274 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
275 } else
276 return -EINVAL;
277
278 return count;
279 }
280 static struct kobj_attribute defrag_attr =
281 __ATTR(defrag, 0644, defrag_show, defrag_store);
282
283 static ssize_t use_zero_page_show(struct kobject *kobj,
284 struct kobj_attribute *attr, char *buf)
285 {
286 return single_hugepage_flag_show(kobj, attr, buf,
287 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
288 }
289 static ssize_t use_zero_page_store(struct kobject *kobj,
290 struct kobj_attribute *attr, const char *buf, size_t count)
291 {
292 return single_hugepage_flag_store(kobj, attr, buf, count,
293 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
294 }
295 static struct kobj_attribute use_zero_page_attr =
296 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
297
298 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
299 struct kobj_attribute *attr, char *buf)
300 {
301 return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
302 }
303 static struct kobj_attribute hpage_pmd_size_attr =
304 __ATTR_RO(hpage_pmd_size);
305
306 #ifdef CONFIG_DEBUG_VM
307 static ssize_t debug_cow_show(struct kobject *kobj,
308 struct kobj_attribute *attr, char *buf)
309 {
310 return single_hugepage_flag_show(kobj, attr, buf,
311 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
312 }
313 static ssize_t debug_cow_store(struct kobject *kobj,
314 struct kobj_attribute *attr,
315 const char *buf, size_t count)
316 {
317 return single_hugepage_flag_store(kobj, attr, buf, count,
318 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
319 }
320 static struct kobj_attribute debug_cow_attr =
321 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
322 #endif /* CONFIG_DEBUG_VM */
323
324 static struct attribute *hugepage_attr[] = {
325 &enabled_attr.attr,
326 &defrag_attr.attr,
327 &use_zero_page_attr.attr,
328 &hpage_pmd_size_attr.attr,
329 #ifdef CONFIG_SHMEM
330 &shmem_enabled_attr.attr,
331 #endif
332 #ifdef CONFIG_DEBUG_VM
333 &debug_cow_attr.attr,
334 #endif
335 NULL,
336 };
337
338 static const struct attribute_group hugepage_attr_group = {
339 .attrs = hugepage_attr,
340 };
341
342 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
343 {
344 int err;
345
346 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
347 if (unlikely(!*hugepage_kobj)) {
348 pr_err("failed to create transparent hugepage kobject\n");
349 return -ENOMEM;
350 }
351
352 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
353 if (err) {
354 pr_err("failed to register transparent hugepage group\n");
355 goto delete_obj;
356 }
357
358 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
359 if (err) {
360 pr_err("failed to register transparent hugepage group\n");
361 goto remove_hp_group;
362 }
363
364 return 0;
365
366 remove_hp_group:
367 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
368 delete_obj:
369 kobject_put(*hugepage_kobj);
370 return err;
371 }
372
373 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
374 {
375 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
376 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
377 kobject_put(hugepage_kobj);
378 }
379 #else
380 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
381 {
382 return 0;
383 }
384
385 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
386 {
387 }
388 #endif /* CONFIG_SYSFS */
389
390 static int __init hugepage_init(void)
391 {
392 int err;
393 struct kobject *hugepage_kobj;
394
395 if (!has_transparent_hugepage()) {
396 transparent_hugepage_flags = 0;
397 return -EINVAL;
398 }
399
400 /*
401 * hugepages can't be allocated by the buddy allocator
402 */
403 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
404 /*
405 * we use page->mapping and page->index in second tail page
406 * as list_head: assuming THP order >= 2
407 */
408 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
409
410 err = hugepage_init_sysfs(&hugepage_kobj);
411 if (err)
412 goto err_sysfs;
413
414 err = khugepaged_init();
415 if (err)
416 goto err_slab;
417
418 err = register_shrinker(&huge_zero_page_shrinker);
419 if (err)
420 goto err_hzp_shrinker;
421 err = register_shrinker(&deferred_split_shrinker);
422 if (err)
423 goto err_split_shrinker;
424
425 /*
426 * By default disable transparent hugepages on smaller systems,
427 * where the extra memory used could hurt more than TLB overhead
428 * is likely to save. The admin can still enable it through /sys.
429 */
430 if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
431 transparent_hugepage_flags = 0;
432 return 0;
433 }
434
435 err = start_stop_khugepaged();
436 if (err)
437 goto err_khugepaged;
438
439 return 0;
440 err_khugepaged:
441 unregister_shrinker(&deferred_split_shrinker);
442 err_split_shrinker:
443 unregister_shrinker(&huge_zero_page_shrinker);
444 err_hzp_shrinker:
445 khugepaged_destroy();
446 err_slab:
447 hugepage_exit_sysfs(hugepage_kobj);
448 err_sysfs:
449 return err;
450 }
451 subsys_initcall(hugepage_init);
452
453 static int __init setup_transparent_hugepage(char *str)
454 {
455 int ret = 0;
456 if (!str)
457 goto out;
458 if (!strcmp(str, "always")) {
459 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
460 &transparent_hugepage_flags);
461 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
462 &transparent_hugepage_flags);
463 ret = 1;
464 } else if (!strcmp(str, "madvise")) {
465 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
466 &transparent_hugepage_flags);
467 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
468 &transparent_hugepage_flags);
469 ret = 1;
470 } else if (!strcmp(str, "never")) {
471 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
472 &transparent_hugepage_flags);
473 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
474 &transparent_hugepage_flags);
475 ret = 1;
476 }
477 out:
478 if (!ret)
479 pr_warn("transparent_hugepage= cannot parse, ignored\n");
480 return ret;
481 }
482 __setup("transparent_hugepage=", setup_transparent_hugepage);
483
484 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
485 {
486 if (likely(vma->vm_flags & VM_WRITE))
487 pmd = pmd_mkwrite(pmd);
488 return pmd;
489 }
490
491 #ifdef CONFIG_MEMCG
492 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
493 {
494 struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
495 struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
496
497 if (memcg)
498 return &memcg->deferred_split_queue;
499 else
500 return &pgdat->deferred_split_queue;
501 }
502 #else
503 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
504 {
505 struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
506
507 return &pgdat->deferred_split_queue;
508 }
509 #endif
510
511 void prep_transhuge_page(struct page *page)
512 {
513 /*
514 * we use page->mapping and page->indexlru in second tail page
515 * as list_head: assuming THP order >= 2
516 */
517
518 INIT_LIST_HEAD(page_deferred_list(page));
519 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
520 }
521
522 bool is_transparent_hugepage(struct page *page)
523 {
524 if (!PageCompound(page))
525 return 0;
526
527 page = compound_head(page);
528 return is_huge_zero_page(page) ||
529 page[1].compound_dtor == TRANSHUGE_PAGE_DTOR;
530 }
531 EXPORT_SYMBOL_GPL(is_transparent_hugepage);
532
533 static unsigned long __thp_get_unmapped_area(struct file *filp,
534 unsigned long addr, unsigned long len,
535 loff_t off, unsigned long flags, unsigned long size)
536 {
537 loff_t off_end = off + len;
538 loff_t off_align = round_up(off, size);
539 unsigned long len_pad, ret;
540
541 if (off_end <= off_align || (off_end - off_align) < size)
542 return 0;
543
544 len_pad = len + size;
545 if (len_pad < len || (off + len_pad) < off)
546 return 0;
547
548 ret = current->mm->get_unmapped_area(filp, addr, len_pad,
549 off >> PAGE_SHIFT, flags);
550
551 /*
552 * The failure might be due to length padding. The caller will retry
553 * without the padding.
554 */
555 if (IS_ERR_VALUE(ret))
556 return 0;
557
558 /*
559 * Do not try to align to THP boundary if allocation at the address
560 * hint succeeds.
561 */
562 if (ret == addr)
563 return addr;
564
565 ret += (off - ret) & (size - 1);
566 return ret;
567 }
568
569 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
570 unsigned long len, unsigned long pgoff, unsigned long flags)
571 {
572 unsigned long ret;
573 loff_t off = (loff_t)pgoff << PAGE_SHIFT;
574
575 if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
576 goto out;
577
578 ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE);
579 if (ret)
580 return ret;
581 out:
582 return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
583 }
584 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
585
586 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
587 struct page *page, gfp_t gfp)
588 {
589 struct vm_area_struct *vma = vmf->vma;
590 struct mem_cgroup *memcg;
591 pgtable_t pgtable;
592 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
593 vm_fault_t ret = 0;
594
595 VM_BUG_ON_PAGE(!PageCompound(page), page);
596
597 if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
598 put_page(page);
599 count_vm_event(THP_FAULT_FALLBACK);
600 count_vm_event(THP_FAULT_FALLBACK_CHARGE);
601 return VM_FAULT_FALLBACK;
602 }
603
604 pgtable = pte_alloc_one(vma->vm_mm);
605 if (unlikely(!pgtable)) {
606 ret = VM_FAULT_OOM;
607 goto release;
608 }
609
610 clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
611 /*
612 * The memory barrier inside __SetPageUptodate makes sure that
613 * clear_huge_page writes become visible before the set_pmd_at()
614 * write.
615 */
616 __SetPageUptodate(page);
617
618 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
619 if (unlikely(!pmd_none(*vmf->pmd))) {
620 goto unlock_release;
621 } else {
622 pmd_t entry;
623
624 ret = check_stable_address_space(vma->vm_mm);
625 if (ret)
626 goto unlock_release;
627
628 /* Deliver the page fault to userland */
629 if (userfaultfd_missing(vma)) {
630 vm_fault_t ret2;
631
632 spin_unlock(vmf->ptl);
633 mem_cgroup_cancel_charge(page, memcg, true);
634 put_page(page);
635 pte_free(vma->vm_mm, pgtable);
636 ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
637 VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
638 return ret2;
639 }
640
641 entry = mk_huge_pmd(page, vma->vm_page_prot);
642 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
643 page_add_new_anon_rmap(page, vma, haddr, true);
644 mem_cgroup_commit_charge(page, memcg, false, true);
645 lru_cache_add_active_or_unevictable(page, vma);
646 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
647 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
648 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
649 mm_inc_nr_ptes(vma->vm_mm);
650 spin_unlock(vmf->ptl);
651 count_vm_event(THP_FAULT_ALLOC);
652 count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
653 }
654
655 return 0;
656 unlock_release:
657 spin_unlock(vmf->ptl);
658 release:
659 if (pgtable)
660 pte_free(vma->vm_mm, pgtable);
661 mem_cgroup_cancel_charge(page, memcg, true);
662 put_page(page);
663 return ret;
664
665 }
666
667 /*
668 * always: directly stall for all thp allocations
669 * defer: wake kswapd and fail if not immediately available
670 * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
671 * fail if not immediately available
672 * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
673 * available
674 * never: never stall for any thp allocation
675 */
676 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
677 {
678 const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
679
680 /* Always do synchronous compaction */
681 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
682 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
683
684 /* Kick kcompactd and fail quickly */
685 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
686 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
687
688 /* Synchronous compaction if madvised, otherwise kick kcompactd */
689 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
690 return GFP_TRANSHUGE_LIGHT |
691 (vma_madvised ? __GFP_DIRECT_RECLAIM :
692 __GFP_KSWAPD_RECLAIM);
693
694 /* Only do synchronous compaction if madvised */
695 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
696 return GFP_TRANSHUGE_LIGHT |
697 (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
698
699 return GFP_TRANSHUGE_LIGHT;
700 }
701
702 /* Caller must hold page table lock. */
703 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
704 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
705 struct page *zero_page)
706 {
707 pmd_t entry;
708 if (!pmd_none(*pmd))
709 return false;
710 entry = mk_pmd(zero_page, vma->vm_page_prot);
711 entry = pmd_mkhuge(entry);
712 if (pgtable)
713 pgtable_trans_huge_deposit(mm, pmd, pgtable);
714 set_pmd_at(mm, haddr, pmd, entry);
715 mm_inc_nr_ptes(mm);
716 return true;
717 }
718
719 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
720 {
721 struct vm_area_struct *vma = vmf->vma;
722 gfp_t gfp;
723 struct page *page;
724 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
725
726 if (!transhuge_vma_suitable(vma, haddr))
727 return VM_FAULT_FALLBACK;
728 if (unlikely(anon_vma_prepare(vma)))
729 return VM_FAULT_OOM;
730 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
731 return VM_FAULT_OOM;
732 if (!(vmf->flags & FAULT_FLAG_WRITE) &&
733 !mm_forbids_zeropage(vma->vm_mm) &&
734 transparent_hugepage_use_zero_page()) {
735 pgtable_t pgtable;
736 struct page *zero_page;
737 bool set;
738 vm_fault_t ret;
739 pgtable = pte_alloc_one(vma->vm_mm);
740 if (unlikely(!pgtable))
741 return VM_FAULT_OOM;
742 zero_page = mm_get_huge_zero_page(vma->vm_mm);
743 if (unlikely(!zero_page)) {
744 pte_free(vma->vm_mm, pgtable);
745 count_vm_event(THP_FAULT_FALLBACK);
746 return VM_FAULT_FALLBACK;
747 }
748 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
749 ret = 0;
750 set = false;
751 if (pmd_none(*vmf->pmd)) {
752 ret = check_stable_address_space(vma->vm_mm);
753 if (ret) {
754 spin_unlock(vmf->ptl);
755 } else if (userfaultfd_missing(vma)) {
756 spin_unlock(vmf->ptl);
757 ret = handle_userfault(vmf, VM_UFFD_MISSING);
758 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
759 } else {
760 set_huge_zero_page(pgtable, vma->vm_mm, vma,
761 haddr, vmf->pmd, zero_page);
762 spin_unlock(vmf->ptl);
763 set = true;
764 }
765 } else
766 spin_unlock(vmf->ptl);
767 if (!set)
768 pte_free(vma->vm_mm, pgtable);
769 return ret;
770 }
771 gfp = alloc_hugepage_direct_gfpmask(vma);
772 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
773 if (unlikely(!page)) {
774 count_vm_event(THP_FAULT_FALLBACK);
775 return VM_FAULT_FALLBACK;
776 }
777 prep_transhuge_page(page);
778 return __do_huge_pmd_anonymous_page(vmf, page, gfp);
779 }
780
781 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
782 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
783 pgtable_t pgtable)
784 {
785 struct mm_struct *mm = vma->vm_mm;
786 pmd_t entry;
787 spinlock_t *ptl;
788
789 ptl = pmd_lock(mm, pmd);
790 if (!pmd_none(*pmd)) {
791 if (write) {
792 if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
793 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
794 goto out_unlock;
795 }
796 entry = pmd_mkyoung(*pmd);
797 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
798 if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
799 update_mmu_cache_pmd(vma, addr, pmd);
800 }
801
802 goto out_unlock;
803 }
804
805 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
806 if (pfn_t_devmap(pfn))
807 entry = pmd_mkdevmap(entry);
808 if (write) {
809 entry = pmd_mkyoung(pmd_mkdirty(entry));
810 entry = maybe_pmd_mkwrite(entry, vma);
811 }
812
813 if (pgtable) {
814 pgtable_trans_huge_deposit(mm, pmd, pgtable);
815 mm_inc_nr_ptes(mm);
816 pgtable = NULL;
817 }
818
819 set_pmd_at(mm, addr, pmd, entry);
820 update_mmu_cache_pmd(vma, addr, pmd);
821
822 out_unlock:
823 spin_unlock(ptl);
824 if (pgtable)
825 pte_free(mm, pgtable);
826 }
827
828 /**
829 * vmf_insert_pfn_pmd_prot - insert a pmd size pfn
830 * @vmf: Structure describing the fault
831 * @pfn: pfn to insert
832 * @pgprot: page protection to use
833 * @write: whether it's a write fault
834 *
835 * Insert a pmd size pfn. See vmf_insert_pfn() for additional info and
836 * also consult the vmf_insert_mixed_prot() documentation when
837 * @pgprot != @vmf->vma->vm_page_prot.
838 *
839 * Return: vm_fault_t value.
840 */
841 vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, pfn_t pfn,
842 pgprot_t pgprot, bool write)
843 {
844 unsigned long addr = vmf->address & PMD_MASK;
845 struct vm_area_struct *vma = vmf->vma;
846 pgtable_t pgtable = NULL;
847
848 /*
849 * If we had pmd_special, we could avoid all these restrictions,
850 * but we need to be consistent with PTEs and architectures that
851 * can't support a 'special' bit.
852 */
853 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
854 !pfn_t_devmap(pfn));
855 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
856 (VM_PFNMAP|VM_MIXEDMAP));
857 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
858
859 if (addr < vma->vm_start || addr >= vma->vm_end)
860 return VM_FAULT_SIGBUS;
861
862 if (arch_needs_pgtable_deposit()) {
863 pgtable = pte_alloc_one(vma->vm_mm);
864 if (!pgtable)
865 return VM_FAULT_OOM;
866 }
867
868 track_pfn_insert(vma, &pgprot, pfn);
869
870 insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
871 return VM_FAULT_NOPAGE;
872 }
873 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd_prot);
874
875 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
876 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
877 {
878 if (likely(vma->vm_flags & VM_WRITE))
879 pud = pud_mkwrite(pud);
880 return pud;
881 }
882
883 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
884 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
885 {
886 struct mm_struct *mm = vma->vm_mm;
887 pud_t entry;
888 spinlock_t *ptl;
889
890 ptl = pud_lock(mm, pud);
891 if (!pud_none(*pud)) {
892 if (write) {
893 if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
894 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
895 goto out_unlock;
896 }
897 entry = pud_mkyoung(*pud);
898 entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
899 if (pudp_set_access_flags(vma, addr, pud, entry, 1))
900 update_mmu_cache_pud(vma, addr, pud);
901 }
902 goto out_unlock;
903 }
904
905 entry = pud_mkhuge(pfn_t_pud(pfn, prot));
906 if (pfn_t_devmap(pfn))
907 entry = pud_mkdevmap(entry);
908 if (write) {
909 entry = pud_mkyoung(pud_mkdirty(entry));
910 entry = maybe_pud_mkwrite(entry, vma);
911 }
912 set_pud_at(mm, addr, pud, entry);
913 update_mmu_cache_pud(vma, addr, pud);
914
915 out_unlock:
916 spin_unlock(ptl);
917 }
918
919 /**
920 * vmf_insert_pfn_pud_prot - insert a pud size pfn
921 * @vmf: Structure describing the fault
922 * @pfn: pfn to insert
923 * @pgprot: page protection to use
924 * @write: whether it's a write fault
925 *
926 * Insert a pud size pfn. See vmf_insert_pfn() for additional info and
927 * also consult the vmf_insert_mixed_prot() documentation when
928 * @pgprot != @vmf->vma->vm_page_prot.
929 *
930 * Return: vm_fault_t value.
931 */
932 vm_fault_t vmf_insert_pfn_pud_prot(struct vm_fault *vmf, pfn_t pfn,
933 pgprot_t pgprot, bool write)
934 {
935 unsigned long addr = vmf->address & PUD_MASK;
936 struct vm_area_struct *vma = vmf->vma;
937
938 /*
939 * If we had pud_special, we could avoid all these restrictions,
940 * but we need to be consistent with PTEs and architectures that
941 * can't support a 'special' bit.
942 */
943 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
944 !pfn_t_devmap(pfn));
945 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
946 (VM_PFNMAP|VM_MIXEDMAP));
947 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
948
949 if (addr < vma->vm_start || addr >= vma->vm_end)
950 return VM_FAULT_SIGBUS;
951
952 track_pfn_insert(vma, &pgprot, pfn);
953
954 insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
955 return VM_FAULT_NOPAGE;
956 }
957 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot);
958 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
959
960 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
961 pmd_t *pmd, int flags)
962 {
963 pmd_t _pmd;
964
965 _pmd = pmd_mkyoung(*pmd);
966 if (flags & FOLL_WRITE)
967 _pmd = pmd_mkdirty(_pmd);
968 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
969 pmd, _pmd, flags & FOLL_WRITE))
970 update_mmu_cache_pmd(vma, addr, pmd);
971 }
972
973 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
974 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
975 {
976 unsigned long pfn = pmd_pfn(*pmd);
977 struct mm_struct *mm = vma->vm_mm;
978 struct page *page;
979
980 assert_spin_locked(pmd_lockptr(mm, pmd));
981
982 /*
983 * When we COW a devmap PMD entry, we split it into PTEs, so we should
984 * not be in this function with `flags & FOLL_COW` set.
985 */
986 WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
987
988 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
989 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
990 (FOLL_PIN | FOLL_GET)))
991 return NULL;
992
993 if (flags & FOLL_WRITE && !pmd_write(*pmd))
994 return NULL;
995
996 if (pmd_present(*pmd) && pmd_devmap(*pmd))
997 /* pass */;
998 else
999 return NULL;
1000
1001 if (flags & FOLL_TOUCH)
1002 touch_pmd(vma, addr, pmd, flags);
1003
1004 /*
1005 * device mapped pages can only be returned if the
1006 * caller will manage the page reference count.
1007 */
1008 if (!(flags & (FOLL_GET | FOLL_PIN)))
1009 return ERR_PTR(-EEXIST);
1010
1011 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1012 *pgmap = get_dev_pagemap(pfn, *pgmap);
1013 if (!*pgmap)
1014 return ERR_PTR(-EFAULT);
1015 page = pfn_to_page(pfn);
1016 if (!try_grab_page(page, flags))
1017 page = ERR_PTR(-ENOMEM);
1018
1019 return page;
1020 }
1021
1022 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1023 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1024 struct vm_area_struct *vma)
1025 {
1026 spinlock_t *dst_ptl, *src_ptl;
1027 struct page *src_page;
1028 pmd_t pmd;
1029 pgtable_t pgtable = NULL;
1030 int ret = -ENOMEM;
1031
1032 /* Skip if can be re-fill on fault */
1033 if (!vma_is_anonymous(vma))
1034 return 0;
1035
1036 pgtable = pte_alloc_one(dst_mm);
1037 if (unlikely(!pgtable))
1038 goto out;
1039
1040 dst_ptl = pmd_lock(dst_mm, dst_pmd);
1041 src_ptl = pmd_lockptr(src_mm, src_pmd);
1042 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1043
1044 ret = -EAGAIN;
1045 pmd = *src_pmd;
1046
1047 /*
1048 * Make sure the _PAGE_UFFD_WP bit is cleared if the new VMA
1049 * does not have the VM_UFFD_WP, which means that the uffd
1050 * fork event is not enabled.
1051 */
1052 if (!(vma->vm_flags & VM_UFFD_WP))
1053 pmd = pmd_clear_uffd_wp(pmd);
1054
1055 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1056 if (unlikely(is_swap_pmd(pmd))) {
1057 swp_entry_t entry = pmd_to_swp_entry(pmd);
1058
1059 VM_BUG_ON(!is_pmd_migration_entry(pmd));
1060 if (is_write_migration_entry(entry)) {
1061 make_migration_entry_read(&entry);
1062 pmd = swp_entry_to_pmd(entry);
1063 if (pmd_swp_soft_dirty(*src_pmd))
1064 pmd = pmd_swp_mksoft_dirty(pmd);
1065 set_pmd_at(src_mm, addr, src_pmd, pmd);
1066 }
1067 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1068 mm_inc_nr_ptes(dst_mm);
1069 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1070 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1071 ret = 0;
1072 goto out_unlock;
1073 }
1074 #endif
1075
1076 if (unlikely(!pmd_trans_huge(pmd))) {
1077 pte_free(dst_mm, pgtable);
1078 goto out_unlock;
1079 }
1080 /*
1081 * When page table lock is held, the huge zero pmd should not be
1082 * under splitting since we don't split the page itself, only pmd to
1083 * a page table.
1084 */
1085 if (is_huge_zero_pmd(pmd)) {
1086 struct page *zero_page;
1087 /*
1088 * get_huge_zero_page() will never allocate a new page here,
1089 * since we already have a zero page to copy. It just takes a
1090 * reference.
1091 */
1092 zero_page = mm_get_huge_zero_page(dst_mm);
1093 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1094 zero_page);
1095 ret = 0;
1096 goto out_unlock;
1097 }
1098
1099 src_page = pmd_page(pmd);
1100 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1101 get_page(src_page);
1102 page_dup_rmap(src_page, true);
1103 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1104 mm_inc_nr_ptes(dst_mm);
1105 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1106
1107 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1108 pmd = pmd_mkold(pmd_wrprotect(pmd));
1109 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1110
1111 ret = 0;
1112 out_unlock:
1113 spin_unlock(src_ptl);
1114 spin_unlock(dst_ptl);
1115 out:
1116 return ret;
1117 }
1118
1119 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1120 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1121 pud_t *pud, int flags)
1122 {
1123 pud_t _pud;
1124
1125 _pud = pud_mkyoung(*pud);
1126 if (flags & FOLL_WRITE)
1127 _pud = pud_mkdirty(_pud);
1128 if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1129 pud, _pud, flags & FOLL_WRITE))
1130 update_mmu_cache_pud(vma, addr, pud);
1131 }
1132
1133 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1134 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1135 {
1136 unsigned long pfn = pud_pfn(*pud);
1137 struct mm_struct *mm = vma->vm_mm;
1138 struct page *page;
1139
1140 assert_spin_locked(pud_lockptr(mm, pud));
1141
1142 if (flags & FOLL_WRITE && !pud_write(*pud))
1143 return NULL;
1144
1145 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
1146 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
1147 (FOLL_PIN | FOLL_GET)))
1148 return NULL;
1149
1150 if (pud_present(*pud) && pud_devmap(*pud))
1151 /* pass */;
1152 else
1153 return NULL;
1154
1155 if (flags & FOLL_TOUCH)
1156 touch_pud(vma, addr, pud, flags);
1157
1158 /*
1159 * device mapped pages can only be returned if the
1160 * caller will manage the page reference count.
1161 *
1162 * At least one of FOLL_GET | FOLL_PIN must be set, so assert that here:
1163 */
1164 if (!(flags & (FOLL_GET | FOLL_PIN)))
1165 return ERR_PTR(-EEXIST);
1166
1167 pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1168 *pgmap = get_dev_pagemap(pfn, *pgmap);
1169 if (!*pgmap)
1170 return ERR_PTR(-EFAULT);
1171 page = pfn_to_page(pfn);
1172 if (!try_grab_page(page, flags))
1173 page = ERR_PTR(-ENOMEM);
1174
1175 return page;
1176 }
1177
1178 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1179 pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1180 struct vm_area_struct *vma)
1181 {
1182 spinlock_t *dst_ptl, *src_ptl;
1183 pud_t pud;
1184 int ret;
1185
1186 dst_ptl = pud_lock(dst_mm, dst_pud);
1187 src_ptl = pud_lockptr(src_mm, src_pud);
1188 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1189
1190 ret = -EAGAIN;
1191 pud = *src_pud;
1192 if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1193 goto out_unlock;
1194
1195 /*
1196 * When page table lock is held, the huge zero pud should not be
1197 * under splitting since we don't split the page itself, only pud to
1198 * a page table.
1199 */
1200 if (is_huge_zero_pud(pud)) {
1201 /* No huge zero pud yet */
1202 }
1203
1204 pudp_set_wrprotect(src_mm, addr, src_pud);
1205 pud = pud_mkold(pud_wrprotect(pud));
1206 set_pud_at(dst_mm, addr, dst_pud, pud);
1207
1208 ret = 0;
1209 out_unlock:
1210 spin_unlock(src_ptl);
1211 spin_unlock(dst_ptl);
1212 return ret;
1213 }
1214
1215 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1216 {
1217 pud_t entry;
1218 unsigned long haddr;
1219 bool write = vmf->flags & FAULT_FLAG_WRITE;
1220
1221 vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1222 if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1223 goto unlock;
1224
1225 entry = pud_mkyoung(orig_pud);
1226 if (write)
1227 entry = pud_mkdirty(entry);
1228 haddr = vmf->address & HPAGE_PUD_MASK;
1229 if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1230 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1231
1232 unlock:
1233 spin_unlock(vmf->ptl);
1234 }
1235 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1236
1237 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1238 {
1239 pmd_t entry;
1240 unsigned long haddr;
1241 bool write = vmf->flags & FAULT_FLAG_WRITE;
1242
1243 vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1244 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1245 goto unlock;
1246
1247 entry = pmd_mkyoung(orig_pmd);
1248 if (write)
1249 entry = pmd_mkdirty(entry);
1250 haddr = vmf->address & HPAGE_PMD_MASK;
1251 if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1252 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1253
1254 unlock:
1255 spin_unlock(vmf->ptl);
1256 }
1257
1258 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1259 pmd_t orig_pmd, struct page *page)
1260 {
1261 struct vm_area_struct *vma = vmf->vma;
1262 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1263 struct mem_cgroup *memcg;
1264 pgtable_t pgtable;
1265 pmd_t _pmd;
1266 int i;
1267 vm_fault_t ret = 0;
1268 struct page **pages;
1269 struct mmu_notifier_range range;
1270
1271 pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1272 GFP_KERNEL);
1273 if (unlikely(!pages)) {
1274 ret |= VM_FAULT_OOM;
1275 goto out;
1276 }
1277
1278 for (i = 0; i < HPAGE_PMD_NR; i++) {
1279 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1280 vmf->address, page_to_nid(page));
1281 if (unlikely(!pages[i] ||
1282 mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1283 GFP_KERNEL, &memcg, false))) {
1284 if (pages[i])
1285 put_page(pages[i]);
1286 while (--i >= 0) {
1287 memcg = (void *)page_private(pages[i]);
1288 set_page_private(pages[i], 0);
1289 mem_cgroup_cancel_charge(pages[i], memcg,
1290 false);
1291 put_page(pages[i]);
1292 }
1293 kfree(pages);
1294 ret |= VM_FAULT_OOM;
1295 goto out;
1296 }
1297 set_page_private(pages[i], (unsigned long)memcg);
1298 }
1299
1300 for (i = 0; i < HPAGE_PMD_NR; i++) {
1301 copy_user_highpage(pages[i], page + i,
1302 haddr + PAGE_SIZE * i, vma);
1303 __SetPageUptodate(pages[i]);
1304 cond_resched();
1305 }
1306
1307 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1308 haddr, haddr + HPAGE_PMD_SIZE);
1309 mmu_notifier_invalidate_range_start(&range);
1310
1311 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1312 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1313 goto out_free_pages;
1314 VM_BUG_ON_PAGE(!PageHead(page), page);
1315
1316 /*
1317 * Leave pmd empty until pte is filled note we must notify here as
1318 * concurrent CPU thread might write to new page before the call to
1319 * mmu_notifier_invalidate_range_end() happens which can lead to a
1320 * device seeing memory write in different order than CPU.
1321 *
1322 * See Documentation/vm/mmu_notifier.rst
1323 */
1324 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1325
1326 pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1327 pmd_populate(vma->vm_mm, &_pmd, pgtable);
1328
1329 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1330 pte_t entry;
1331 entry = mk_pte(pages[i], vma->vm_page_prot);
1332 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1333 memcg = (void *)page_private(pages[i]);
1334 set_page_private(pages[i], 0);
1335 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1336 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1337 lru_cache_add_active_or_unevictable(pages[i], vma);
1338 vmf->pte = pte_offset_map(&_pmd, haddr);
1339 VM_BUG_ON(!pte_none(*vmf->pte));
1340 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1341 pte_unmap(vmf->pte);
1342 }
1343 kfree(pages);
1344
1345 smp_wmb(); /* make pte visible before pmd */
1346 pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1347 page_remove_rmap(page, true);
1348 spin_unlock(vmf->ptl);
1349
1350 /*
1351 * No need to double call mmu_notifier->invalidate_range() callback as
1352 * the above pmdp_huge_clear_flush_notify() did already call it.
1353 */
1354 mmu_notifier_invalidate_range_only_end(&range);
1355
1356 ret |= VM_FAULT_WRITE;
1357 put_page(page);
1358
1359 out:
1360 return ret;
1361
1362 out_free_pages:
1363 spin_unlock(vmf->ptl);
1364 mmu_notifier_invalidate_range_end(&range);
1365 for (i = 0; i < HPAGE_PMD_NR; i++) {
1366 memcg = (void *)page_private(pages[i]);
1367 set_page_private(pages[i], 0);
1368 mem_cgroup_cancel_charge(pages[i], memcg, false);
1369 put_page(pages[i]);
1370 }
1371 kfree(pages);
1372 goto out;
1373 }
1374
1375 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1376 {
1377 struct vm_area_struct *vma = vmf->vma;
1378 struct page *page = NULL, *new_page;
1379 struct mem_cgroup *memcg;
1380 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1381 struct mmu_notifier_range range;
1382 gfp_t huge_gfp; /* for allocation and charge */
1383 vm_fault_t ret = 0;
1384
1385 vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1386 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1387 if (is_huge_zero_pmd(orig_pmd))
1388 goto alloc;
1389 spin_lock(vmf->ptl);
1390 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1391 goto out_unlock;
1392
1393 page = pmd_page(orig_pmd);
1394 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1395 /*
1396 * We can only reuse the page if nobody else maps the huge page or it's
1397 * part.
1398 */
1399 if (!trylock_page(page)) {
1400 get_page(page);
1401 spin_unlock(vmf->ptl);
1402 lock_page(page);
1403 spin_lock(vmf->ptl);
1404 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1405 unlock_page(page);
1406 put_page(page);
1407 goto out_unlock;
1408 }
1409 put_page(page);
1410 }
1411 if (reuse_swap_page(page, NULL)) {
1412 pmd_t entry;
1413 entry = pmd_mkyoung(orig_pmd);
1414 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1415 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
1416 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1417 ret |= VM_FAULT_WRITE;
1418 unlock_page(page);
1419 goto out_unlock;
1420 }
1421 unlock_page(page);
1422 get_page(page);
1423 spin_unlock(vmf->ptl);
1424 alloc:
1425 if (__transparent_hugepage_enabled(vma) &&
1426 !transparent_hugepage_debug_cow()) {
1427 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1428 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1429 } else
1430 new_page = NULL;
1431
1432 if (likely(new_page)) {
1433 prep_transhuge_page(new_page);
1434 } else {
1435 if (!page) {
1436 split_huge_pmd(vma, vmf->pmd, vmf->address);
1437 ret |= VM_FAULT_FALLBACK;
1438 } else {
1439 ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1440 if (ret & VM_FAULT_OOM) {
1441 split_huge_pmd(vma, vmf->pmd, vmf->address);
1442 ret |= VM_FAULT_FALLBACK;
1443 }
1444 put_page(page);
1445 }
1446 count_vm_event(THP_FAULT_FALLBACK);
1447 goto out;
1448 }
1449
1450 if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1451 huge_gfp, &memcg, true))) {
1452 put_page(new_page);
1453 split_huge_pmd(vma, vmf->pmd, vmf->address);
1454 if (page)
1455 put_page(page);
1456 ret |= VM_FAULT_FALLBACK;
1457 count_vm_event(THP_FAULT_FALLBACK);
1458 count_vm_event(THP_FAULT_FALLBACK_CHARGE);
1459 goto out;
1460 }
1461
1462 count_vm_event(THP_FAULT_ALLOC);
1463 count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
1464
1465 if (!page)
1466 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1467 else
1468 copy_user_huge_page(new_page, page, vmf->address,
1469 vma, HPAGE_PMD_NR);
1470 __SetPageUptodate(new_page);
1471
1472 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1473 haddr, haddr + HPAGE_PMD_SIZE);
1474 mmu_notifier_invalidate_range_start(&range);
1475
1476 spin_lock(vmf->ptl);
1477 if (page)
1478 put_page(page);
1479 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1480 spin_unlock(vmf->ptl);
1481 mem_cgroup_cancel_charge(new_page, memcg, true);
1482 put_page(new_page);
1483 goto out_mn;
1484 } else {
1485 pmd_t entry;
1486 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1487 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1488 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1489 page_add_new_anon_rmap(new_page, vma, haddr, true);
1490 mem_cgroup_commit_charge(new_page, memcg, false, true);
1491 lru_cache_add_active_or_unevictable(new_page, vma);
1492 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1493 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1494 if (!page) {
1495 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1496 } else {
1497 VM_BUG_ON_PAGE(!PageHead(page), page);
1498 page_remove_rmap(page, true);
1499 put_page(page);
1500 }
1501 ret |= VM_FAULT_WRITE;
1502 }
1503 spin_unlock(vmf->ptl);
1504 out_mn:
1505 /*
1506 * No need to double call mmu_notifier->invalidate_range() callback as
1507 * the above pmdp_huge_clear_flush_notify() did already call it.
1508 */
1509 mmu_notifier_invalidate_range_only_end(&range);
1510 out:
1511 return ret;
1512 out_unlock:
1513 spin_unlock(vmf->ptl);
1514 return ret;
1515 }
1516
1517 /*
1518 * FOLL_FORCE or a forced COW break can write even to unwritable pmd's,
1519 * but only after we've gone through a COW cycle and they are dirty.
1520 */
1521 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1522 {
1523 return pmd_write(pmd) || ((flags & FOLL_COW) && pmd_dirty(pmd));
1524 }
1525
1526 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1527 unsigned long addr,
1528 pmd_t *pmd,
1529 unsigned int flags)
1530 {
1531 struct mm_struct *mm = vma->vm_mm;
1532 struct page *page = NULL;
1533
1534 assert_spin_locked(pmd_lockptr(mm, pmd));
1535
1536 if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1537 goto out;
1538
1539 /* Avoid dumping huge zero page */
1540 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1541 return ERR_PTR(-EFAULT);
1542
1543 /* Full NUMA hinting faults to serialise migration in fault paths */
1544 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1545 goto out;
1546
1547 page = pmd_page(*pmd);
1548 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1549
1550 if (!try_grab_page(page, flags))
1551 return ERR_PTR(-ENOMEM);
1552
1553 if (flags & FOLL_TOUCH)
1554 touch_pmd(vma, addr, pmd, flags);
1555
1556 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1557 /*
1558 * We don't mlock() pte-mapped THPs. This way we can avoid
1559 * leaking mlocked pages into non-VM_LOCKED VMAs.
1560 *
1561 * For anon THP:
1562 *
1563 * In most cases the pmd is the only mapping of the page as we
1564 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1565 * writable private mappings in populate_vma_page_range().
1566 *
1567 * The only scenario when we have the page shared here is if we
1568 * mlocking read-only mapping shared over fork(). We skip
1569 * mlocking such pages.
1570 *
1571 * For file THP:
1572 *
1573 * We can expect PageDoubleMap() to be stable under page lock:
1574 * for file pages we set it in page_add_file_rmap(), which
1575 * requires page to be locked.
1576 */
1577
1578 if (PageAnon(page) && compound_mapcount(page) != 1)
1579 goto skip_mlock;
1580 if (PageDoubleMap(page) || !page->mapping)
1581 goto skip_mlock;
1582 if (!trylock_page(page))
1583 goto skip_mlock;
1584 lru_add_drain();
1585 if (page->mapping && !PageDoubleMap(page))
1586 mlock_vma_page(page);
1587 unlock_page(page);
1588 }
1589 skip_mlock:
1590 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1591 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1592
1593 out:
1594 return page;
1595 }
1596
1597 /* NUMA hinting page fault entry point for trans huge pmds */
1598 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1599 {
1600 struct vm_area_struct *vma = vmf->vma;
1601 struct anon_vma *anon_vma = NULL;
1602 struct page *page;
1603 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1604 int page_nid = NUMA_NO_NODE, this_nid = numa_node_id();
1605 int target_nid, last_cpupid = -1;
1606 bool page_locked;
1607 bool migrated = false;
1608 bool was_writable;
1609 int flags = 0;
1610
1611 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1612 if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1613 goto out_unlock;
1614
1615 /*
1616 * If there are potential migrations, wait for completion and retry
1617 * without disrupting NUMA hinting information. Do not relock and
1618 * check_same as the page may no longer be mapped.
1619 */
1620 if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1621 page = pmd_page(*vmf->pmd);
1622 if (!get_page_unless_zero(page))
1623 goto out_unlock;
1624 spin_unlock(vmf->ptl);
1625 put_and_wait_on_page_locked(page);
1626 goto out;
1627 }
1628
1629 page = pmd_page(pmd);
1630 BUG_ON(is_huge_zero_page(page));
1631 page_nid = page_to_nid(page);
1632 last_cpupid = page_cpupid_last(page);
1633 count_vm_numa_event(NUMA_HINT_FAULTS);
1634 if (page_nid == this_nid) {
1635 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1636 flags |= TNF_FAULT_LOCAL;
1637 }
1638
1639 /* See similar comment in do_numa_page for explanation */
1640 if (!pmd_savedwrite(pmd))
1641 flags |= TNF_NO_GROUP;
1642
1643 /*
1644 * Acquire the page lock to serialise THP migrations but avoid dropping
1645 * page_table_lock if at all possible
1646 */
1647 page_locked = trylock_page(page);
1648 target_nid = mpol_misplaced(page, vma, haddr);
1649 if (target_nid == NUMA_NO_NODE) {
1650 /* If the page was locked, there are no parallel migrations */
1651 if (page_locked)
1652 goto clear_pmdnuma;
1653 }
1654
1655 /* Migration could have started since the pmd_trans_migrating check */
1656 if (!page_locked) {
1657 page_nid = NUMA_NO_NODE;
1658 if (!get_page_unless_zero(page))
1659 goto out_unlock;
1660 spin_unlock(vmf->ptl);
1661 put_and_wait_on_page_locked(page);
1662 goto out;
1663 }
1664
1665 /*
1666 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1667 * to serialises splits
1668 */
1669 get_page(page);
1670 spin_unlock(vmf->ptl);
1671 anon_vma = page_lock_anon_vma_read(page);
1672
1673 /* Confirm the PMD did not change while page_table_lock was released */
1674 spin_lock(vmf->ptl);
1675 if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1676 unlock_page(page);
1677 put_page(page);
1678 page_nid = NUMA_NO_NODE;
1679 goto out_unlock;
1680 }
1681
1682 /* Bail if we fail to protect against THP splits for any reason */
1683 if (unlikely(!anon_vma)) {
1684 put_page(page);
1685 page_nid = NUMA_NO_NODE;
1686 goto clear_pmdnuma;
1687 }
1688
1689 /*
1690 * Since we took the NUMA fault, we must have observed the !accessible
1691 * bit. Make sure all other CPUs agree with that, to avoid them
1692 * modifying the page we're about to migrate.
1693 *
1694 * Must be done under PTL such that we'll observe the relevant
1695 * inc_tlb_flush_pending().
1696 *
1697 * We are not sure a pending tlb flush here is for a huge page
1698 * mapping or not. Hence use the tlb range variant
1699 */
1700 if (mm_tlb_flush_pending(vma->vm_mm)) {
1701 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1702 /*
1703 * change_huge_pmd() released the pmd lock before
1704 * invalidating the secondary MMUs sharing the primary
1705 * MMU pagetables (with ->invalidate_range()). The
1706 * mmu_notifier_invalidate_range_end() (which
1707 * internally calls ->invalidate_range()) in
1708 * change_pmd_range() will run after us, so we can't
1709 * rely on it here and we need an explicit invalidate.
1710 */
1711 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1712 haddr + HPAGE_PMD_SIZE);
1713 }
1714
1715 /*
1716 * Migrate the THP to the requested node, returns with page unlocked
1717 * and access rights restored.
1718 */
1719 spin_unlock(vmf->ptl);
1720
1721 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1722 vmf->pmd, pmd, vmf->address, page, target_nid);
1723 if (migrated) {
1724 flags |= TNF_MIGRATED;
1725 page_nid = target_nid;
1726 } else
1727 flags |= TNF_MIGRATE_FAIL;
1728
1729 goto out;
1730 clear_pmdnuma:
1731 BUG_ON(!PageLocked(page));
1732 was_writable = pmd_savedwrite(pmd);
1733 pmd = pmd_modify(pmd, vma->vm_page_prot);
1734 pmd = pmd_mkyoung(pmd);
1735 if (was_writable)
1736 pmd = pmd_mkwrite(pmd);
1737 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1738 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1739 unlock_page(page);
1740 out_unlock:
1741 spin_unlock(vmf->ptl);
1742
1743 out:
1744 if (anon_vma)
1745 page_unlock_anon_vma_read(anon_vma);
1746
1747 if (page_nid != NUMA_NO_NODE)
1748 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1749 flags);
1750
1751 return 0;
1752 }
1753
1754 /*
1755 * Return true if we do MADV_FREE successfully on entire pmd page.
1756 * Otherwise, return false.
1757 */
1758 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1759 pmd_t *pmd, unsigned long addr, unsigned long next)
1760 {
1761 spinlock_t *ptl;
1762 pmd_t orig_pmd;
1763 struct page *page;
1764 struct mm_struct *mm = tlb->mm;
1765 bool ret = false;
1766
1767 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1768
1769 ptl = pmd_trans_huge_lock(pmd, vma);
1770 if (!ptl)
1771 goto out_unlocked;
1772
1773 orig_pmd = *pmd;
1774 if (is_huge_zero_pmd(orig_pmd))
1775 goto out;
1776
1777 if (unlikely(!pmd_present(orig_pmd))) {
1778 VM_BUG_ON(thp_migration_supported() &&
1779 !is_pmd_migration_entry(orig_pmd));
1780 goto out;
1781 }
1782
1783 page = pmd_page(orig_pmd);
1784 /*
1785 * If other processes are mapping this page, we couldn't discard
1786 * the page unless they all do MADV_FREE so let's skip the page.
1787 */
1788 if (page_mapcount(page) != 1)
1789 goto out;
1790
1791 if (!trylock_page(page))
1792 goto out;
1793
1794 /*
1795 * If user want to discard part-pages of THP, split it so MADV_FREE
1796 * will deactivate only them.
1797 */
1798 if (next - addr != HPAGE_PMD_SIZE) {
1799 get_page(page);
1800 spin_unlock(ptl);
1801 split_huge_page(page);
1802 unlock_page(page);
1803 put_page(page);
1804 goto out_unlocked;
1805 }
1806
1807 if (PageDirty(page))
1808 ClearPageDirty(page);
1809 unlock_page(page);
1810
1811 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1812 pmdp_invalidate(vma, addr, pmd);
1813 orig_pmd = pmd_mkold(orig_pmd);
1814 orig_pmd = pmd_mkclean(orig_pmd);
1815
1816 set_pmd_at(mm, addr, pmd, orig_pmd);
1817 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1818 }
1819
1820 mark_page_lazyfree(page);
1821 ret = true;
1822 out:
1823 spin_unlock(ptl);
1824 out_unlocked:
1825 return ret;
1826 }
1827
1828 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1829 {
1830 pgtable_t pgtable;
1831
1832 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1833 pte_free(mm, pgtable);
1834 mm_dec_nr_ptes(mm);
1835 }
1836
1837 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1838 pmd_t *pmd, unsigned long addr)
1839 {
1840 pmd_t orig_pmd;
1841 spinlock_t *ptl;
1842
1843 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1844
1845 ptl = __pmd_trans_huge_lock(pmd, vma);
1846 if (!ptl)
1847 return 0;
1848 /*
1849 * For architectures like ppc64 we look at deposited pgtable
1850 * when calling pmdp_huge_get_and_clear. So do the
1851 * pgtable_trans_huge_withdraw after finishing pmdp related
1852 * operations.
1853 */
1854 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1855 tlb->fullmm);
1856 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1857 if (vma_is_special_huge(vma)) {
1858 if (arch_needs_pgtable_deposit())
1859 zap_deposited_table(tlb->mm, pmd);
1860 spin_unlock(ptl);
1861 if (is_huge_zero_pmd(orig_pmd))
1862 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1863 } else if (is_huge_zero_pmd(orig_pmd)) {
1864 zap_deposited_table(tlb->mm, pmd);
1865 spin_unlock(ptl);
1866 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1867 } else {
1868 struct page *page = NULL;
1869 int flush_needed = 1;
1870
1871 if (pmd_present(orig_pmd)) {
1872 page = pmd_page(orig_pmd);
1873 page_remove_rmap(page, true);
1874 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1875 VM_BUG_ON_PAGE(!PageHead(page), page);
1876 } else if (thp_migration_supported()) {
1877 swp_entry_t entry;
1878
1879 VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1880 entry = pmd_to_swp_entry(orig_pmd);
1881 page = pfn_to_page(swp_offset(entry));
1882 flush_needed = 0;
1883 } else
1884 WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1885
1886 if (PageAnon(page)) {
1887 zap_deposited_table(tlb->mm, pmd);
1888 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1889 } else {
1890 if (arch_needs_pgtable_deposit())
1891 zap_deposited_table(tlb->mm, pmd);
1892 add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1893 }
1894
1895 spin_unlock(ptl);
1896 if (flush_needed)
1897 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1898 }
1899 return 1;
1900 }
1901
1902 #ifndef pmd_move_must_withdraw
1903 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1904 spinlock_t *old_pmd_ptl,
1905 struct vm_area_struct *vma)
1906 {
1907 /*
1908 * With split pmd lock we also need to move preallocated
1909 * PTE page table if new_pmd is on different PMD page table.
1910 *
1911 * We also don't deposit and withdraw tables for file pages.
1912 */
1913 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1914 }
1915 #endif
1916
1917 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1918 {
1919 #ifdef CONFIG_MEM_SOFT_DIRTY
1920 if (unlikely(is_pmd_migration_entry(pmd)))
1921 pmd = pmd_swp_mksoft_dirty(pmd);
1922 else if (pmd_present(pmd))
1923 pmd = pmd_mksoft_dirty(pmd);
1924 #endif
1925 return pmd;
1926 }
1927
1928 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1929 unsigned long new_addr, unsigned long old_end,
1930 pmd_t *old_pmd, pmd_t *new_pmd)
1931 {
1932 spinlock_t *old_ptl, *new_ptl;
1933 pmd_t pmd;
1934 struct mm_struct *mm = vma->vm_mm;
1935 bool force_flush = false;
1936
1937 if ((old_addr & ~HPAGE_PMD_MASK) ||
1938 (new_addr & ~HPAGE_PMD_MASK) ||
1939 old_end - old_addr < HPAGE_PMD_SIZE)
1940 return false;
1941
1942 /*
1943 * The destination pmd shouldn't be established, free_pgtables()
1944 * should have release it.
1945 */
1946 if (WARN_ON(!pmd_none(*new_pmd))) {
1947 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1948 return false;
1949 }
1950
1951 /*
1952 * We don't have to worry about the ordering of src and dst
1953 * ptlocks because exclusive mmap_sem prevents deadlock.
1954 */
1955 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1956 if (old_ptl) {
1957 new_ptl = pmd_lockptr(mm, new_pmd);
1958 if (new_ptl != old_ptl)
1959 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1960 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1961 if (pmd_present(pmd))
1962 force_flush = true;
1963 VM_BUG_ON(!pmd_none(*new_pmd));
1964
1965 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1966 pgtable_t pgtable;
1967 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1968 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1969 }
1970 pmd = move_soft_dirty_pmd(pmd);
1971 set_pmd_at(mm, new_addr, new_pmd, pmd);
1972 if (force_flush)
1973 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1974 if (new_ptl != old_ptl)
1975 spin_unlock(new_ptl);
1976 spin_unlock(old_ptl);
1977 return true;
1978 }
1979 return false;
1980 }
1981
1982 /*
1983 * Returns
1984 * - 0 if PMD could not be locked
1985 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1986 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1987 */
1988 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1989 unsigned long addr, pgprot_t newprot, unsigned long cp_flags)
1990 {
1991 struct mm_struct *mm = vma->vm_mm;
1992 spinlock_t *ptl;
1993 pmd_t entry;
1994 bool preserve_write;
1995 int ret;
1996 bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
1997 bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
1998 bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
1999
2000 ptl = __pmd_trans_huge_lock(pmd, vma);
2001 if (!ptl)
2002 return 0;
2003
2004 preserve_write = prot_numa && pmd_write(*pmd);
2005 ret = 1;
2006
2007 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2008 if (is_swap_pmd(*pmd)) {
2009 swp_entry_t entry = pmd_to_swp_entry(*pmd);
2010
2011 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
2012 if (is_write_migration_entry(entry)) {
2013 pmd_t newpmd;
2014 /*
2015 * A protection check is difficult so
2016 * just be safe and disable write
2017 */
2018 make_migration_entry_read(&entry);
2019 newpmd = swp_entry_to_pmd(entry);
2020 if (pmd_swp_soft_dirty(*pmd))
2021 newpmd = pmd_swp_mksoft_dirty(newpmd);
2022 set_pmd_at(mm, addr, pmd, newpmd);
2023 }
2024 goto unlock;
2025 }
2026 #endif
2027
2028 /*
2029 * Avoid trapping faults against the zero page. The read-only
2030 * data is likely to be read-cached on the local CPU and
2031 * local/remote hits to the zero page are not interesting.
2032 */
2033 if (prot_numa && is_huge_zero_pmd(*pmd))
2034 goto unlock;
2035
2036 if (prot_numa && pmd_protnone(*pmd))
2037 goto unlock;
2038
2039 /*
2040 * In case prot_numa, we are under down_read(mmap_sem). It's critical
2041 * to not clear pmd intermittently to avoid race with MADV_DONTNEED
2042 * which is also under down_read(mmap_sem):
2043 *
2044 * CPU0: CPU1:
2045 * change_huge_pmd(prot_numa=1)
2046 * pmdp_huge_get_and_clear_notify()
2047 * madvise_dontneed()
2048 * zap_pmd_range()
2049 * pmd_trans_huge(*pmd) == 0 (without ptl)
2050 * // skip the pmd
2051 * set_pmd_at();
2052 * // pmd is re-established
2053 *
2054 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
2055 * which may break userspace.
2056 *
2057 * pmdp_invalidate() is required to make sure we don't miss
2058 * dirty/young flags set by hardware.
2059 */
2060 entry = pmdp_invalidate(vma, addr, pmd);
2061
2062 entry = pmd_modify(entry, newprot);
2063 if (preserve_write)
2064 entry = pmd_mk_savedwrite(entry);
2065 if (uffd_wp) {
2066 entry = pmd_wrprotect(entry);
2067 entry = pmd_mkuffd_wp(entry);
2068 } else if (uffd_wp_resolve) {
2069 /*
2070 * Leave the write bit to be handled by PF interrupt
2071 * handler, then things like COW could be properly
2072 * handled.
2073 */
2074 entry = pmd_clear_uffd_wp(entry);
2075 }
2076 ret = HPAGE_PMD_NR;
2077 set_pmd_at(mm, addr, pmd, entry);
2078 BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
2079 unlock:
2080 spin_unlock(ptl);
2081 return ret;
2082 }
2083
2084 /*
2085 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
2086 *
2087 * Note that if it returns page table lock pointer, this routine returns without
2088 * unlocking page table lock. So callers must unlock it.
2089 */
2090 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
2091 {
2092 spinlock_t *ptl;
2093 ptl = pmd_lock(vma->vm_mm, pmd);
2094 if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
2095 pmd_devmap(*pmd)))
2096 return ptl;
2097 spin_unlock(ptl);
2098 return NULL;
2099 }
2100
2101 /*
2102 * Returns true if a given pud maps a thp, false otherwise.
2103 *
2104 * Note that if it returns true, this routine returns without unlocking page
2105 * table lock. So callers must unlock it.
2106 */
2107 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
2108 {
2109 spinlock_t *ptl;
2110
2111 ptl = pud_lock(vma->vm_mm, pud);
2112 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
2113 return ptl;
2114 spin_unlock(ptl);
2115 return NULL;
2116 }
2117
2118 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
2119 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
2120 pud_t *pud, unsigned long addr)
2121 {
2122 spinlock_t *ptl;
2123
2124 ptl = __pud_trans_huge_lock(pud, vma);
2125 if (!ptl)
2126 return 0;
2127 /*
2128 * For architectures like ppc64 we look at deposited pgtable
2129 * when calling pudp_huge_get_and_clear. So do the
2130 * pgtable_trans_huge_withdraw after finishing pudp related
2131 * operations.
2132 */
2133 pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
2134 tlb_remove_pud_tlb_entry(tlb, pud, addr);
2135 if (vma_is_special_huge(vma)) {
2136 spin_unlock(ptl);
2137 /* No zero page support yet */
2138 } else {
2139 /* No support for anonymous PUD pages yet */
2140 BUG();
2141 }
2142 return 1;
2143 }
2144
2145 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2146 unsigned long haddr)
2147 {
2148 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2149 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2150 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2151 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2152
2153 count_vm_event(THP_SPLIT_PUD);
2154
2155 pudp_huge_clear_flush_notify(vma, haddr, pud);
2156 }
2157
2158 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2159 unsigned long address)
2160 {
2161 spinlock_t *ptl;
2162 struct mmu_notifier_range range;
2163
2164 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2165 address & HPAGE_PUD_MASK,
2166 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2167 mmu_notifier_invalidate_range_start(&range);
2168 ptl = pud_lock(vma->vm_mm, pud);
2169 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2170 goto out;
2171 __split_huge_pud_locked(vma, pud, range.start);
2172
2173 out:
2174 spin_unlock(ptl);
2175 /*
2176 * No need to double call mmu_notifier->invalidate_range() callback as
2177 * the above pudp_huge_clear_flush_notify() did already call it.
2178 */
2179 mmu_notifier_invalidate_range_only_end(&range);
2180 }
2181 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2182
2183 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2184 unsigned long haddr, pmd_t *pmd)
2185 {
2186 struct mm_struct *mm = vma->vm_mm;
2187 pgtable_t pgtable;
2188 pmd_t _pmd;
2189 int i;
2190
2191 /*
2192 * Leave pmd empty until pte is filled note that it is fine to delay
2193 * notification until mmu_notifier_invalidate_range_end() as we are
2194 * replacing a zero pmd write protected page with a zero pte write
2195 * protected page.
2196 *
2197 * See Documentation/vm/mmu_notifier.rst
2198 */
2199 pmdp_huge_clear_flush(vma, haddr, pmd);
2200
2201 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2202 pmd_populate(mm, &_pmd, pgtable);
2203
2204 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2205 pte_t *pte, entry;
2206 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2207 entry = pte_mkspecial(entry);
2208 pte = pte_offset_map(&_pmd, haddr);
2209 VM_BUG_ON(!pte_none(*pte));
2210 set_pte_at(mm, haddr, pte, entry);
2211 pte_unmap(pte);
2212 }
2213 smp_wmb(); /* make pte visible before pmd */
2214 pmd_populate(mm, pmd, pgtable);
2215 }
2216
2217 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2218 unsigned long haddr, bool freeze)
2219 {
2220 struct mm_struct *mm = vma->vm_mm;
2221 struct page *page;
2222 pgtable_t pgtable;
2223 pmd_t old_pmd, _pmd;
2224 bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false;
2225 unsigned long addr;
2226 int i;
2227
2228 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2229 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2230 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2231 VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2232 && !pmd_devmap(*pmd));
2233
2234 count_vm_event(THP_SPLIT_PMD);
2235
2236 if (!vma_is_anonymous(vma)) {
2237 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2238 /*
2239 * We are going to unmap this huge page. So
2240 * just go ahead and zap it
2241 */
2242 if (arch_needs_pgtable_deposit())
2243 zap_deposited_table(mm, pmd);
2244 if (vma_is_special_huge(vma))
2245 return;
2246 page = pmd_page(_pmd);
2247 if (!PageDirty(page) && pmd_dirty(_pmd))
2248 set_page_dirty(page);
2249 if (!PageReferenced(page) && pmd_young(_pmd))
2250 SetPageReferenced(page);
2251 page_remove_rmap(page, true);
2252 put_page(page);
2253 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2254 return;
2255 } else if (is_huge_zero_pmd(*pmd)) {
2256 /*
2257 * FIXME: Do we want to invalidate secondary mmu by calling
2258 * mmu_notifier_invalidate_range() see comments below inside
2259 * __split_huge_pmd() ?
2260 *
2261 * We are going from a zero huge page write protected to zero
2262 * small page also write protected so it does not seems useful
2263 * to invalidate secondary mmu at this time.
2264 */
2265 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2266 }
2267
2268 /*
2269 * Up to this point the pmd is present and huge and userland has the
2270 * whole access to the hugepage during the split (which happens in
2271 * place). If we overwrite the pmd with the not-huge version pointing
2272 * to the pte here (which of course we could if all CPUs were bug
2273 * free), userland could trigger a small page size TLB miss on the
2274 * small sized TLB while the hugepage TLB entry is still established in
2275 * the huge TLB. Some CPU doesn't like that.
2276 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2277 * 383 on page 93. Intel should be safe but is also warns that it's
2278 * only safe if the permission and cache attributes of the two entries
2279 * loaded in the two TLB is identical (which should be the case here).
2280 * But it is generally safer to never allow small and huge TLB entries
2281 * for the same virtual address to be loaded simultaneously. So instead
2282 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2283 * current pmd notpresent (atomically because here the pmd_trans_huge
2284 * must remain set at all times on the pmd until the split is complete
2285 * for this pmd), then we flush the SMP TLB and finally we write the
2286 * non-huge version of the pmd entry with pmd_populate.
2287 */
2288 old_pmd = pmdp_invalidate(vma, haddr, pmd);
2289
2290 pmd_migration = is_pmd_migration_entry(old_pmd);
2291 if (unlikely(pmd_migration)) {
2292 swp_entry_t entry;
2293
2294 entry = pmd_to_swp_entry(old_pmd);
2295 page = pfn_to_page(swp_offset(entry));
2296 write = is_write_migration_entry(entry);
2297 young = false;
2298 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2299 uffd_wp = pmd_swp_uffd_wp(old_pmd);
2300 } else {
2301 page = pmd_page(old_pmd);
2302 if (pmd_dirty(old_pmd))
2303 SetPageDirty(page);
2304 write = pmd_write(old_pmd);
2305 young = pmd_young(old_pmd);
2306 soft_dirty = pmd_soft_dirty(old_pmd);
2307 uffd_wp = pmd_uffd_wp(old_pmd);
2308 }
2309 VM_BUG_ON_PAGE(!page_count(page), page);
2310 page_ref_add(page, HPAGE_PMD_NR - 1);
2311
2312 /*
2313 * Withdraw the table only after we mark the pmd entry invalid.
2314 * This's critical for some architectures (Power).
2315 */
2316 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2317 pmd_populate(mm, &_pmd, pgtable);
2318
2319 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2320 pte_t entry, *pte;
2321 /*
2322 * Note that NUMA hinting access restrictions are not
2323 * transferred to avoid any possibility of altering
2324 * permissions across VMAs.
2325 */
2326 if (freeze || pmd_migration) {
2327 swp_entry_t swp_entry;
2328 swp_entry = make_migration_entry(page + i, write);
2329 entry = swp_entry_to_pte(swp_entry);
2330 if (soft_dirty)
2331 entry = pte_swp_mksoft_dirty(entry);
2332 if (uffd_wp)
2333 entry = pte_swp_mkuffd_wp(entry);
2334 } else {
2335 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2336 entry = maybe_mkwrite(entry, vma);
2337 if (!write)
2338 entry = pte_wrprotect(entry);
2339 if (!young)
2340 entry = pte_mkold(entry);
2341 if (soft_dirty)
2342 entry = pte_mksoft_dirty(entry);
2343 if (uffd_wp)
2344 entry = pte_mkuffd_wp(entry);
2345 }
2346 pte = pte_offset_map(&_pmd, addr);
2347 BUG_ON(!pte_none(*pte));
2348 set_pte_at(mm, addr, pte, entry);
2349 atomic_inc(&page[i]._mapcount);
2350 pte_unmap(pte);
2351 }
2352
2353 /*
2354 * Set PG_double_map before dropping compound_mapcount to avoid
2355 * false-negative page_mapped().
2356 */
2357 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2358 for (i = 0; i < HPAGE_PMD_NR; i++)
2359 atomic_inc(&page[i]._mapcount);
2360 }
2361
2362 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2363 /* Last compound_mapcount is gone. */
2364 __dec_node_page_state(page, NR_ANON_THPS);
2365 if (TestClearPageDoubleMap(page)) {
2366 /* No need in mapcount reference anymore */
2367 for (i = 0; i < HPAGE_PMD_NR; i++)
2368 atomic_dec(&page[i]._mapcount);
2369 }
2370 }
2371
2372 smp_wmb(); /* make pte visible before pmd */
2373 pmd_populate(mm, pmd, pgtable);
2374
2375 if (freeze) {
2376 for (i = 0; i < HPAGE_PMD_NR; i++) {
2377 page_remove_rmap(page + i, false);
2378 put_page(page + i);
2379 }
2380 }
2381 }
2382
2383 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2384 unsigned long address, bool freeze, struct page *page)
2385 {
2386 spinlock_t *ptl;
2387 struct mmu_notifier_range range;
2388 bool was_locked = false;
2389 pmd_t _pmd;
2390
2391 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2392 address & HPAGE_PMD_MASK,
2393 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2394 mmu_notifier_invalidate_range_start(&range);
2395 ptl = pmd_lock(vma->vm_mm, pmd);
2396
2397 /*
2398 * If caller asks to setup a migration entries, we need a page to check
2399 * pmd against. Otherwise we can end up replacing wrong page.
2400 */
2401 VM_BUG_ON(freeze && !page);
2402 if (page) {
2403 VM_WARN_ON_ONCE(!PageLocked(page));
2404 was_locked = true;
2405 if (page != pmd_page(*pmd))
2406 goto out;
2407 }
2408
2409 repeat:
2410 if (pmd_trans_huge(*pmd)) {
2411 if (!page) {
2412 page = pmd_page(*pmd);
2413 if (unlikely(!trylock_page(page))) {
2414 get_page(page);
2415 _pmd = *pmd;
2416 spin_unlock(ptl);
2417 lock_page(page);
2418 spin_lock(ptl);
2419 if (unlikely(!pmd_same(*pmd, _pmd))) {
2420 unlock_page(page);
2421 put_page(page);
2422 page = NULL;
2423 goto repeat;
2424 }
2425 put_page(page);
2426 }
2427 }
2428 if (PageMlocked(page))
2429 clear_page_mlock(page);
2430 } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2431 goto out;
2432 __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2433 out:
2434 spin_unlock(ptl);
2435 if (!was_locked && page)
2436 unlock_page(page);
2437 /*
2438 * No need to double call mmu_notifier->invalidate_range() callback.
2439 * They are 3 cases to consider inside __split_huge_pmd_locked():
2440 * 1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2441 * 2) __split_huge_zero_page_pmd() read only zero page and any write
2442 * fault will trigger a flush_notify before pointing to a new page
2443 * (it is fine if the secondary mmu keeps pointing to the old zero
2444 * page in the meantime)
2445 * 3) Split a huge pmd into pte pointing to the same page. No need
2446 * to invalidate secondary tlb entry they are all still valid.
2447 * any further changes to individual pte will notify. So no need
2448 * to call mmu_notifier->invalidate_range()
2449 */
2450 mmu_notifier_invalidate_range_only_end(&range);
2451 }
2452
2453 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2454 bool freeze, struct page *page)
2455 {
2456 pgd_t *pgd;
2457 p4d_t *p4d;
2458 pud_t *pud;
2459 pmd_t *pmd;
2460
2461 pgd = pgd_offset(vma->vm_mm, address);
2462 if (!pgd_present(*pgd))
2463 return;
2464
2465 p4d = p4d_offset(pgd, address);
2466 if (!p4d_present(*p4d))
2467 return;
2468
2469 pud = pud_offset(p4d, address);
2470 if (!pud_present(*pud))
2471 return;
2472
2473 pmd = pmd_offset(pud, address);
2474
2475 __split_huge_pmd(vma, pmd, address, freeze, page);
2476 }
2477
2478 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2479 unsigned long start,
2480 unsigned long end,
2481 long adjust_next)
2482 {
2483 /*
2484 * If the new start address isn't hpage aligned and it could
2485 * previously contain an hugepage: check if we need to split
2486 * an huge pmd.
2487 */
2488 if (start & ~HPAGE_PMD_MASK &&
2489 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2490 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2491 split_huge_pmd_address(vma, start, false, NULL);
2492
2493 /*
2494 * If the new end address isn't hpage aligned and it could
2495 * previously contain an hugepage: check if we need to split
2496 * an huge pmd.
2497 */
2498 if (end & ~HPAGE_PMD_MASK &&
2499 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2500 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2501 split_huge_pmd_address(vma, end, false, NULL);
2502
2503 /*
2504 * If we're also updating the vma->vm_next->vm_start, if the new
2505 * vm_next->vm_start isn't page aligned and it could previously
2506 * contain an hugepage: check if we need to split an huge pmd.
2507 */
2508 if (adjust_next > 0) {
2509 struct vm_area_struct *next = vma->vm_next;
2510 unsigned long nstart = next->vm_start;
2511 nstart += adjust_next << PAGE_SHIFT;
2512 if (nstart & ~HPAGE_PMD_MASK &&
2513 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2514 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2515 split_huge_pmd_address(next, nstart, false, NULL);
2516 }
2517 }
2518
2519 static void unmap_page(struct page *page)
2520 {
2521 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2522 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2523 bool unmap_success;
2524
2525 VM_BUG_ON_PAGE(!PageHead(page), page);
2526
2527 if (PageAnon(page))
2528 ttu_flags |= TTU_SPLIT_FREEZE;
2529
2530 unmap_success = try_to_unmap(page, ttu_flags);
2531 VM_BUG_ON_PAGE(!unmap_success, page);
2532 }
2533
2534 static void remap_page(struct page *page)
2535 {
2536 int i;
2537 if (PageTransHuge(page)) {
2538 remove_migration_ptes(page, page, true);
2539 } else {
2540 for (i = 0; i < HPAGE_PMD_NR; i++)
2541 remove_migration_ptes(page + i, page + i, true);
2542 }
2543 }
2544
2545 static void __split_huge_page_tail(struct page *head, int tail,
2546 struct lruvec *lruvec, struct list_head *list)
2547 {
2548 struct page *page_tail = head + tail;
2549
2550 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2551
2552 /*
2553 * Clone page flags before unfreezing refcount.
2554 *
2555 * After successful get_page_unless_zero() might follow flags change,
2556 * for exmaple lock_page() which set PG_waiters.
2557 */
2558 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2559 page_tail->flags |= (head->flags &
2560 ((1L << PG_referenced) |
2561 (1L << PG_swapbacked) |
2562 (1L << PG_swapcache) |
2563 (1L << PG_mlocked) |
2564 (1L << PG_uptodate) |
2565 (1L << PG_active) |
2566 (1L << PG_workingset) |
2567 (1L << PG_locked) |
2568 (1L << PG_unevictable) |
2569 (1L << PG_dirty)));
2570
2571 /* ->mapping in first tail page is compound_mapcount */
2572 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2573 page_tail);
2574 page_tail->mapping = head->mapping;
2575 page_tail->index = head->index + tail;
2576
2577 /* Page flags must be visible before we make the page non-compound. */
2578 smp_wmb();
2579
2580 /*
2581 * Clear PageTail before unfreezing page refcount.
2582 *
2583 * After successful get_page_unless_zero() might follow put_page()
2584 * which needs correct compound_head().
2585 */
2586 clear_compound_head(page_tail);
2587
2588 /* Finally unfreeze refcount. Additional reference from page cache. */
2589 page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2590 PageSwapCache(head)));
2591
2592 if (page_is_young(head))
2593 set_page_young(page_tail);
2594 if (page_is_idle(head))
2595 set_page_idle(page_tail);
2596
2597 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2598
2599 /*
2600 * always add to the tail because some iterators expect new
2601 * pages to show after the currently processed elements - e.g.
2602 * migrate_pages
2603 */
2604 lru_add_page_tail(head, page_tail, lruvec, list);
2605 }
2606
2607 static void __split_huge_page(struct page *page, struct list_head *list,
2608 pgoff_t end, unsigned long flags)
2609 {
2610 struct page *head = compound_head(page);
2611 pg_data_t *pgdat = page_pgdat(head);
2612 struct lruvec *lruvec;
2613 struct address_space *swap_cache = NULL;
2614 unsigned long offset = 0;
2615 int i;
2616
2617 lruvec = mem_cgroup_page_lruvec(head, pgdat);
2618
2619 /* complete memcg works before add pages to LRU */
2620 mem_cgroup_split_huge_fixup(head);
2621
2622 if (PageAnon(head) && PageSwapCache(head)) {
2623 swp_entry_t entry = { .val = page_private(head) };
2624
2625 offset = swp_offset(entry);
2626 swap_cache = swap_address_space(entry);
2627 xa_lock(&swap_cache->i_pages);
2628 }
2629
2630 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2631 __split_huge_page_tail(head, i, lruvec, list);
2632 /* Some pages can be beyond i_size: drop them from page cache */
2633 if (head[i].index >= end) {
2634 ClearPageDirty(head + i);
2635 __delete_from_page_cache(head + i, NULL);
2636 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2637 shmem_uncharge(head->mapping->host, 1);
2638 put_page(head + i);
2639 } else if (!PageAnon(page)) {
2640 __xa_store(&head->mapping->i_pages, head[i].index,
2641 head + i, 0);
2642 } else if (swap_cache) {
2643 __xa_store(&swap_cache->i_pages, offset + i,
2644 head + i, 0);
2645 }
2646 }
2647
2648 ClearPageCompound(head);
2649
2650 split_page_owner(head, HPAGE_PMD_ORDER);
2651
2652 /* See comment in __split_huge_page_tail() */
2653 if (PageAnon(head)) {
2654 /* Additional pin to swap cache */
2655 if (PageSwapCache(head)) {
2656 page_ref_add(head, 2);
2657 xa_unlock(&swap_cache->i_pages);
2658 } else {
2659 page_ref_inc(head);
2660 }
2661 } else {
2662 /* Additional pin to page cache */
2663 page_ref_add(head, 2);
2664 xa_unlock(&head->mapping->i_pages);
2665 }
2666
2667 spin_unlock_irqrestore(&pgdat->lru_lock, flags);
2668
2669 remap_page(head);
2670
2671 for (i = 0; i < HPAGE_PMD_NR; i++) {
2672 struct page *subpage = head + i;
2673 if (subpage == page)
2674 continue;
2675 unlock_page(subpage);
2676
2677 /*
2678 * Subpages may be freed if there wasn't any mapping
2679 * like if add_to_swap() is running on a lru page that
2680 * had its mapping zapped. And freeing these pages
2681 * requires taking the lru_lock so we do the put_page
2682 * of the tail pages after the split is complete.
2683 */
2684 put_page(subpage);
2685 }
2686 }
2687
2688 int total_mapcount(struct page *page)
2689 {
2690 int i, compound, ret;
2691
2692 VM_BUG_ON_PAGE(PageTail(page), page);
2693
2694 if (likely(!PageCompound(page)))
2695 return atomic_read(&page->_mapcount) + 1;
2696
2697 compound = compound_mapcount(page);
2698 if (PageHuge(page))
2699 return compound;
2700 ret = compound;
2701 for (i = 0; i < HPAGE_PMD_NR; i++)
2702 ret += atomic_read(&page[i]._mapcount) + 1;
2703 /* File pages has compound_mapcount included in _mapcount */
2704 if (!PageAnon(page))
2705 return ret - compound * HPAGE_PMD_NR;
2706 if (PageDoubleMap(page))
2707 ret -= HPAGE_PMD_NR;
2708 return ret;
2709 }
2710
2711 /*
2712 * This calculates accurately how many mappings a transparent hugepage
2713 * has (unlike page_mapcount() which isn't fully accurate). This full
2714 * accuracy is primarily needed to know if copy-on-write faults can
2715 * reuse the page and change the mapping to read-write instead of
2716 * copying them. At the same time this returns the total_mapcount too.
2717 *
2718 * The function returns the highest mapcount any one of the subpages
2719 * has. If the return value is one, even if different processes are
2720 * mapping different subpages of the transparent hugepage, they can
2721 * all reuse it, because each process is reusing a different subpage.
2722 *
2723 * The total_mapcount is instead counting all virtual mappings of the
2724 * subpages. If the total_mapcount is equal to "one", it tells the
2725 * caller all mappings belong to the same "mm" and in turn the
2726 * anon_vma of the transparent hugepage can become the vma->anon_vma
2727 * local one as no other process may be mapping any of the subpages.
2728 *
2729 * It would be more accurate to replace page_mapcount() with
2730 * page_trans_huge_mapcount(), however we only use
2731 * page_trans_huge_mapcount() in the copy-on-write faults where we
2732 * need full accuracy to avoid breaking page pinning, because
2733 * page_trans_huge_mapcount() is slower than page_mapcount().
2734 */
2735 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2736 {
2737 int i, ret, _total_mapcount, mapcount;
2738
2739 /* hugetlbfs shouldn't call it */
2740 VM_BUG_ON_PAGE(PageHuge(page), page);
2741
2742 if (likely(!PageTransCompound(page))) {
2743 mapcount = atomic_read(&page->_mapcount) + 1;
2744 if (total_mapcount)
2745 *total_mapcount = mapcount;
2746 return mapcount;
2747 }
2748
2749 page = compound_head(page);
2750
2751 _total_mapcount = ret = 0;
2752 for (i = 0; i < HPAGE_PMD_NR; i++) {
2753 mapcount = atomic_read(&page[i]._mapcount) + 1;
2754 ret = max(ret, mapcount);
2755 _total_mapcount += mapcount;
2756 }
2757 if (PageDoubleMap(page)) {
2758 ret -= 1;
2759 _total_mapcount -= HPAGE_PMD_NR;
2760 }
2761 mapcount = compound_mapcount(page);
2762 ret += mapcount;
2763 _total_mapcount += mapcount;
2764 if (total_mapcount)
2765 *total_mapcount = _total_mapcount;
2766 return ret;
2767 }
2768
2769 /* Racy check whether the huge page can be split */
2770 bool can_split_huge_page(struct page *page, int *pextra_pins)
2771 {
2772 int extra_pins;
2773
2774 /* Additional pins from page cache */
2775 if (PageAnon(page))
2776 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2777 else
2778 extra_pins = HPAGE_PMD_NR;
2779 if (pextra_pins)
2780 *pextra_pins = extra_pins;
2781 return total_mapcount(page) == page_count(page) - extra_pins - 1;
2782 }
2783
2784 /*
2785 * This function splits huge page into normal pages. @page can point to any
2786 * subpage of huge page to split. Split doesn't change the position of @page.
2787 *
2788 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2789 * The huge page must be locked.
2790 *
2791 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2792 *
2793 * Both head page and tail pages will inherit mapping, flags, and so on from
2794 * the hugepage.
2795 *
2796 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2797 * they are not mapped.
2798 *
2799 * Returns 0 if the hugepage is split successfully.
2800 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2801 * us.
2802 */
2803 int split_huge_page_to_list(struct page *page, struct list_head *list)
2804 {
2805 struct page *head = compound_head(page);
2806 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2807 struct deferred_split *ds_queue = get_deferred_split_queue(head);
2808 struct anon_vma *anon_vma = NULL;
2809 struct address_space *mapping = NULL;
2810 int count, mapcount, extra_pins, ret;
2811 bool mlocked;
2812 unsigned long flags;
2813 pgoff_t end;
2814
2815 VM_BUG_ON_PAGE(is_huge_zero_page(head), head);
2816 VM_BUG_ON_PAGE(!PageLocked(head), head);
2817 VM_BUG_ON_PAGE(!PageCompound(head), head);
2818
2819 if (PageWriteback(head))
2820 return -EBUSY;
2821
2822 if (PageAnon(head)) {
2823 /*
2824 * The caller does not necessarily hold an mmap_sem that would
2825 * prevent the anon_vma disappearing so we first we take a
2826 * reference to it and then lock the anon_vma for write. This
2827 * is similar to page_lock_anon_vma_read except the write lock
2828 * is taken to serialise against parallel split or collapse
2829 * operations.
2830 */
2831 anon_vma = page_get_anon_vma(head);
2832 if (!anon_vma) {
2833 ret = -EBUSY;
2834 goto out;
2835 }
2836 end = -1;
2837 mapping = NULL;
2838 anon_vma_lock_write(anon_vma);
2839 } else {
2840 mapping = head->mapping;
2841
2842 /* Truncated ? */
2843 if (!mapping) {
2844 ret = -EBUSY;
2845 goto out;
2846 }
2847
2848 anon_vma = NULL;
2849 i_mmap_lock_read(mapping);
2850
2851 /*
2852 *__split_huge_page() may need to trim off pages beyond EOF:
2853 * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2854 * which cannot be nested inside the page tree lock. So note
2855 * end now: i_size itself may be changed at any moment, but
2856 * head page lock is good enough to serialize the trimming.
2857 */
2858 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2859 }
2860
2861 /*
2862 * Racy check if we can split the page, before unmap_page() will
2863 * split PMDs
2864 */
2865 if (!can_split_huge_page(head, &extra_pins)) {
2866 ret = -EBUSY;
2867 goto out_unlock;
2868 }
2869
2870 mlocked = PageMlocked(head);
2871 unmap_page(head);
2872 VM_BUG_ON_PAGE(compound_mapcount(head), head);
2873
2874 /* Make sure the page is not on per-CPU pagevec as it takes pin */
2875 if (mlocked)
2876 lru_add_drain();
2877
2878 /* prevent PageLRU to go away from under us, and freeze lru stats */
2879 spin_lock_irqsave(&pgdata->lru_lock, flags);
2880
2881 if (mapping) {
2882 XA_STATE(xas, &mapping->i_pages, page_index(head));
2883
2884 /*
2885 * Check if the head page is present in page cache.
2886 * We assume all tail are present too, if head is there.
2887 */
2888 xa_lock(&mapping->i_pages);
2889 if (xas_load(&xas) != head)
2890 goto fail;
2891 }
2892
2893 /* Prevent deferred_split_scan() touching ->_refcount */
2894 spin_lock(&ds_queue->split_queue_lock);
2895 count = page_count(head);
2896 mapcount = total_mapcount(head);
2897 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2898 if (!list_empty(page_deferred_list(head))) {
2899 ds_queue->split_queue_len--;
2900 list_del(page_deferred_list(head));
2901 }
2902 spin_unlock(&ds_queue->split_queue_lock);
2903 if (mapping) {
2904 if (PageSwapBacked(head))
2905 __dec_node_page_state(head, NR_SHMEM_THPS);
2906 else
2907 __dec_node_page_state(head, NR_FILE_THPS);
2908 }
2909
2910 __split_huge_page(page, list, end, flags);
2911 if (PageSwapCache(head)) {
2912 swp_entry_t entry = { .val = page_private(head) };
2913
2914 ret = split_swap_cluster(entry);
2915 } else
2916 ret = 0;
2917 } else {
2918 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2919 pr_alert("total_mapcount: %u, page_count(): %u\n",
2920 mapcount, count);
2921 if (PageTail(page))
2922 dump_page(head, NULL);
2923 dump_page(page, "total_mapcount(head) > 0");
2924 BUG();
2925 }
2926 spin_unlock(&ds_queue->split_queue_lock);
2927 fail: if (mapping)
2928 xa_unlock(&mapping->i_pages);
2929 spin_unlock_irqrestore(&pgdata->lru_lock, flags);
2930 remap_page(head);
2931 ret = -EBUSY;
2932 }
2933
2934 out_unlock:
2935 if (anon_vma) {
2936 anon_vma_unlock_write(anon_vma);
2937 put_anon_vma(anon_vma);
2938 }
2939 if (mapping)
2940 i_mmap_unlock_read(mapping);
2941 out:
2942 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2943 return ret;
2944 }
2945
2946 void free_transhuge_page(struct page *page)
2947 {
2948 struct deferred_split *ds_queue = get_deferred_split_queue(page);
2949 unsigned long flags;
2950
2951 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2952 if (!list_empty(page_deferred_list(page))) {
2953 ds_queue->split_queue_len--;
2954 list_del(page_deferred_list(page));
2955 }
2956 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2957 free_compound_page(page);
2958 }
2959
2960 void deferred_split_huge_page(struct page *page)
2961 {
2962 struct deferred_split *ds_queue = get_deferred_split_queue(page);
2963 #ifdef CONFIG_MEMCG
2964 struct mem_cgroup *memcg = compound_head(page)->mem_cgroup;
2965 #endif
2966 unsigned long flags;
2967
2968 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2969
2970 /*
2971 * The try_to_unmap() in page reclaim path might reach here too,
2972 * this may cause a race condition to corrupt deferred split queue.
2973 * And, if page reclaim is already handling the same page, it is
2974 * unnecessary to handle it again in shrinker.
2975 *
2976 * Check PageSwapCache to determine if the page is being
2977 * handled by page reclaim since THP swap would add the page into
2978 * swap cache before calling try_to_unmap().
2979 */
2980 if (PageSwapCache(page))
2981 return;
2982
2983 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2984 if (list_empty(page_deferred_list(page))) {
2985 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2986 list_add_tail(page_deferred_list(page), &ds_queue->split_queue);
2987 ds_queue->split_queue_len++;
2988 #ifdef CONFIG_MEMCG
2989 if (memcg)
2990 memcg_set_shrinker_bit(memcg, page_to_nid(page),
2991 deferred_split_shrinker.id);
2992 #endif
2993 }
2994 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2995 }
2996
2997 static unsigned long deferred_split_count(struct shrinker *shrink,
2998 struct shrink_control *sc)
2999 {
3000 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3001 struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
3002
3003 #ifdef CONFIG_MEMCG
3004 if (sc->memcg)
3005 ds_queue = &sc->memcg->deferred_split_queue;
3006 #endif
3007 return READ_ONCE(ds_queue->split_queue_len);
3008 }
3009
3010 static unsigned long deferred_split_scan(struct shrinker *shrink,
3011 struct shrink_control *sc)
3012 {
3013 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3014 struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
3015 unsigned long flags;
3016 LIST_HEAD(list), *pos, *next;
3017 struct page *page;
3018 int split = 0;
3019
3020 #ifdef CONFIG_MEMCG
3021 if (sc->memcg)
3022 ds_queue = &sc->memcg->deferred_split_queue;
3023 #endif
3024
3025 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
3026 /* Take pin on all head pages to avoid freeing them under us */
3027 list_for_each_safe(pos, next, &ds_queue->split_queue) {
3028 page = list_entry((void *)pos, struct page, mapping);
3029 page = compound_head(page);
3030 if (get_page_unless_zero(page)) {
3031 list_move(page_deferred_list(page), &list);
3032 } else {
3033 /* We lost race with put_compound_page() */
3034 list_del_init(page_deferred_list(page));
3035 ds_queue->split_queue_len--;
3036 }
3037 if (!--sc->nr_to_scan)
3038 break;
3039 }
3040 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
3041
3042 list_for_each_safe(pos, next, &list) {
3043 page = list_entry((void *)pos, struct page, mapping);
3044 if (!trylock_page(page))
3045 goto next;
3046 /* split_huge_page() removes page from list on success */
3047 if (!split_huge_page(page))
3048 split++;
3049 unlock_page(page);
3050 next:
3051 put_page(page);
3052 }
3053
3054 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
3055 list_splice_tail(&list, &ds_queue->split_queue);
3056 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
3057
3058 /*
3059 * Stop shrinker if we didn't split any page, but the queue is empty.
3060 * This can happen if pages were freed under us.
3061 */
3062 if (!split && list_empty(&ds_queue->split_queue))
3063 return SHRINK_STOP;
3064 return split;
3065 }
3066
3067 static struct shrinker deferred_split_shrinker = {
3068 .count_objects = deferred_split_count,
3069 .scan_objects = deferred_split_scan,
3070 .seeks = DEFAULT_SEEKS,
3071 .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
3072 SHRINKER_NONSLAB,
3073 };
3074
3075 #ifdef CONFIG_DEBUG_FS
3076 static int split_huge_pages_set(void *data, u64 val)
3077 {
3078 struct zone *zone;
3079 struct page *page;
3080 unsigned long pfn, max_zone_pfn;
3081 unsigned long total = 0, split = 0;
3082
3083 if (val != 1)
3084 return -EINVAL;
3085
3086 for_each_populated_zone(zone) {
3087 max_zone_pfn = zone_end_pfn(zone);
3088 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
3089 if (!pfn_valid(pfn))
3090 continue;
3091
3092 page = pfn_to_page(pfn);
3093 if (!get_page_unless_zero(page))
3094 continue;
3095
3096 if (zone != page_zone(page))
3097 goto next;
3098
3099 if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
3100 goto next;
3101
3102 total++;
3103 lock_page(page);
3104 if (!split_huge_page(page))
3105 split++;
3106 unlock_page(page);
3107 next:
3108 put_page(page);
3109 }
3110 }
3111
3112 pr_info("%lu of %lu THP split\n", split, total);
3113
3114 return 0;
3115 }
3116 DEFINE_DEBUGFS_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
3117 "%llu\n");
3118
3119 static int __init split_huge_pages_debugfs(void)
3120 {
3121 debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3122 &split_huge_pages_fops);
3123 return 0;
3124 }
3125 late_initcall(split_huge_pages_debugfs);
3126 #endif
3127
3128 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
3129 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
3130 struct page *page)
3131 {
3132 struct vm_area_struct *vma = pvmw->vma;
3133 struct mm_struct *mm = vma->vm_mm;
3134 unsigned long address = pvmw->address;
3135 pmd_t pmdval;
3136 swp_entry_t entry;
3137 pmd_t pmdswp;
3138
3139 if (!(pvmw->pmd && !pvmw->pte))
3140 return;
3141
3142 flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
3143 pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
3144 if (pmd_dirty(pmdval))
3145 set_page_dirty(page);
3146 entry = make_migration_entry(page, pmd_write(pmdval));
3147 pmdswp = swp_entry_to_pmd(entry);
3148 if (pmd_soft_dirty(pmdval))
3149 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
3150 set_pmd_at(mm, address, pvmw->pmd, pmdswp);
3151 page_remove_rmap(page, true);
3152 put_page(page);
3153 }
3154
3155 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
3156 {
3157 struct vm_area_struct *vma = pvmw->vma;
3158 struct mm_struct *mm = vma->vm_mm;
3159 unsigned long address = pvmw->address;
3160 unsigned long mmun_start = address & HPAGE_PMD_MASK;
3161 pmd_t pmde;
3162 swp_entry_t entry;
3163
3164 if (!(pvmw->pmd && !pvmw->pte))
3165 return;
3166
3167 entry = pmd_to_swp_entry(*pvmw->pmd);
3168 get_page(new);
3169 pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
3170 if (pmd_swp_soft_dirty(*pvmw->pmd))
3171 pmde = pmd_mksoft_dirty(pmde);
3172 if (is_write_migration_entry(entry))
3173 pmde = maybe_pmd_mkwrite(pmde, vma);
3174
3175 flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
3176 if (PageAnon(new))
3177 page_add_anon_rmap(new, vma, mmun_start, true);
3178 else
3179 page_add_file_rmap(new, true);
3180 set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
3181 if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
3182 mlock_vma_page(new);
3183 update_mmu_cache_pmd(vma, address, pvmw->pmd);
3184 }
3185 #endif
Linux with added FPC-III support