xref: /openbmc/linux/mm/huge_memory.c (revision 19deb7695e072deaff025e03de40c61b525bd57e)
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 (!memcmp("always", buf,
181 		    min(sizeof("always")-1, count))) {
182 		clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
183 		set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
184 	} else if (!memcmp("madvise", buf,
185 			   min(sizeof("madvise")-1, count))) {
186 		clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
187 		set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
188 	} else if (!memcmp("never", buf,
189 			   min(sizeof("never")-1, count))) {
190 		clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
191 		clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
192 	} else
193 		ret = -EINVAL;
194 
195 	if (ret > 0) {
196 		int err = start_stop_khugepaged();
197 		if (err)
198 			ret = err;
199 	}
200 	return ret;
201 }
202 static struct kobj_attribute enabled_attr =
203 	__ATTR(enabled, 0644, enabled_show, enabled_store);
204 
205 ssize_t single_hugepage_flag_show(struct kobject *kobj,
206 				struct kobj_attribute *attr, char *buf,
207 				enum transparent_hugepage_flag flag)
208 {
209 	return sprintf(buf, "%d\n",
210 		       !!test_bit(flag, &transparent_hugepage_flags));
211 }
212 
213 ssize_t single_hugepage_flag_store(struct kobject *kobj,
214 				 struct kobj_attribute *attr,
215 				 const char *buf, size_t count,
216 				 enum transparent_hugepage_flag flag)
217 {
218 	unsigned long value;
219 	int ret;
220 
221 	ret = kstrtoul(buf, 10, &value);
222 	if (ret < 0)
223 		return ret;
224 	if (value > 1)
225 		return -EINVAL;
226 
227 	if (value)
228 		set_bit(flag, &transparent_hugepage_flags);
229 	else
230 		clear_bit(flag, &transparent_hugepage_flags);
231 
232 	return count;
233 }
234 
235 static ssize_t defrag_show(struct kobject *kobj,
236 			   struct kobj_attribute *attr, char *buf)
237 {
238 	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
239 		return sprintf(buf, "[always] defer defer+madvise madvise never\n");
240 	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
241 		return sprintf(buf, "always [defer] defer+madvise madvise never\n");
242 	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
243 		return sprintf(buf, "always defer [defer+madvise] madvise never\n");
244 	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
245 		return sprintf(buf, "always defer defer+madvise [madvise] never\n");
246 	return sprintf(buf, "always defer defer+madvise madvise [never]\n");
247 }
248 
249 static ssize_t defrag_store(struct kobject *kobj,
250 			    struct kobj_attribute *attr,
251 			    const char *buf, size_t count)
252 {
253 	if (!memcmp("always", buf,
254 		    min(sizeof("always")-1, count))) {
255 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
256 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
257 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
258 		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
259 	} else if (!memcmp("defer+madvise", buf,
260 		    min(sizeof("defer+madvise")-1, count))) {
261 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
262 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
263 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
264 		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
265 	} else if (!memcmp("defer", buf,
266 		    min(sizeof("defer")-1, count))) {
267 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
268 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
269 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
270 		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
271 	} else if (!memcmp("madvise", buf,
272 			   min(sizeof("madvise")-1, count))) {
273 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
274 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
275 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
276 		set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
277 	} else if (!memcmp("never", buf,
278 			   min(sizeof("never")-1, count))) {
279 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
280 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
281 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
282 		clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
283 	} else
284 		return -EINVAL;
285 
286 	return count;
287 }
288 static struct kobj_attribute defrag_attr =
289 	__ATTR(defrag, 0644, defrag_show, defrag_store);
290 
291 static ssize_t use_zero_page_show(struct kobject *kobj,
292 		struct kobj_attribute *attr, char *buf)
293 {
294 	return single_hugepage_flag_show(kobj, attr, buf,
295 				TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
296 }
297 static ssize_t use_zero_page_store(struct kobject *kobj,
298 		struct kobj_attribute *attr, const char *buf, size_t count)
299 {
300 	return single_hugepage_flag_store(kobj, attr, buf, count,
301 				 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
302 }
303 static struct kobj_attribute use_zero_page_attr =
304 	__ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
305 
306 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
307 		struct kobj_attribute *attr, char *buf)
308 {
309 	return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
310 }
311 static struct kobj_attribute hpage_pmd_size_attr =
312 	__ATTR_RO(hpage_pmd_size);
313 
314 #ifdef CONFIG_DEBUG_VM
315 static ssize_t debug_cow_show(struct kobject *kobj,
316 				struct kobj_attribute *attr, char *buf)
317 {
318 	return single_hugepage_flag_show(kobj, attr, buf,
319 				TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
320 }
321 static ssize_t debug_cow_store(struct kobject *kobj,
322 			       struct kobj_attribute *attr,
323 			       const char *buf, size_t count)
324 {
325 	return single_hugepage_flag_store(kobj, attr, buf, count,
326 				 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
327 }
328 static struct kobj_attribute debug_cow_attr =
329 	__ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
330 #endif /* CONFIG_DEBUG_VM */
331 
332 static struct attribute *hugepage_attr[] = {
333 	&enabled_attr.attr,
334 	&defrag_attr.attr,
335 	&use_zero_page_attr.attr,
336 	&hpage_pmd_size_attr.attr,
337 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
338 	&shmem_enabled_attr.attr,
339 #endif
340 #ifdef CONFIG_DEBUG_VM
341 	&debug_cow_attr.attr,
342 #endif
343 	NULL,
344 };
345 
346 static const struct attribute_group hugepage_attr_group = {
347 	.attrs = hugepage_attr,
348 };
349 
350 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
351 {
352 	int err;
353 
354 	*hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
355 	if (unlikely(!*hugepage_kobj)) {
356 		pr_err("failed to create transparent hugepage kobject\n");
357 		return -ENOMEM;
358 	}
359 
360 	err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
361 	if (err) {
362 		pr_err("failed to register transparent hugepage group\n");
363 		goto delete_obj;
364 	}
365 
366 	err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
367 	if (err) {
368 		pr_err("failed to register transparent hugepage group\n");
369 		goto remove_hp_group;
370 	}
371 
372 	return 0;
373 
374 remove_hp_group:
375 	sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
376 delete_obj:
377 	kobject_put(*hugepage_kobj);
378 	return err;
379 }
380 
381 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
382 {
383 	sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
384 	sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
385 	kobject_put(hugepage_kobj);
386 }
387 #else
388 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
389 {
390 	return 0;
391 }
392 
393 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
394 {
395 }
396 #endif /* CONFIG_SYSFS */
397 
398 static int __init hugepage_init(void)
399 {
400 	int err;
401 	struct kobject *hugepage_kobj;
402 
403 	if (!has_transparent_hugepage()) {
404 		transparent_hugepage_flags = 0;
405 		return -EINVAL;
406 	}
407 
408 	/*
409 	 * hugepages can't be allocated by the buddy allocator
410 	 */
411 	MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
412 	/*
413 	 * we use page->mapping and page->index in second tail page
414 	 * as list_head: assuming THP order >= 2
415 	 */
416 	MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
417 
418 	err = hugepage_init_sysfs(&hugepage_kobj);
419 	if (err)
420 		goto err_sysfs;
421 
422 	err = khugepaged_init();
423 	if (err)
424 		goto err_slab;
425 
426 	err = register_shrinker(&huge_zero_page_shrinker);
427 	if (err)
428 		goto err_hzp_shrinker;
429 	err = register_shrinker(&deferred_split_shrinker);
430 	if (err)
431 		goto err_split_shrinker;
432 
433 	/*
434 	 * By default disable transparent hugepages on smaller systems,
435 	 * where the extra memory used could hurt more than TLB overhead
436 	 * is likely to save.  The admin can still enable it through /sys.
437 	 */
438 	if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
439 		transparent_hugepage_flags = 0;
440 		return 0;
441 	}
442 
443 	err = start_stop_khugepaged();
444 	if (err)
445 		goto err_khugepaged;
446 
447 	return 0;
448 err_khugepaged:
449 	unregister_shrinker(&deferred_split_shrinker);
450 err_split_shrinker:
451 	unregister_shrinker(&huge_zero_page_shrinker);
452 err_hzp_shrinker:
453 	khugepaged_destroy();
454 err_slab:
455 	hugepage_exit_sysfs(hugepage_kobj);
456 err_sysfs:
457 	return err;
458 }
459 subsys_initcall(hugepage_init);
460 
461 static int __init setup_transparent_hugepage(char *str)
462 {
463 	int ret = 0;
464 	if (!str)
465 		goto out;
466 	if (!strcmp(str, "always")) {
467 		set_bit(TRANSPARENT_HUGEPAGE_FLAG,
468 			&transparent_hugepage_flags);
469 		clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
470 			  &transparent_hugepage_flags);
471 		ret = 1;
472 	} else if (!strcmp(str, "madvise")) {
473 		clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
474 			  &transparent_hugepage_flags);
475 		set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
476 			&transparent_hugepage_flags);
477 		ret = 1;
478 	} else if (!strcmp(str, "never")) {
479 		clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
480 			  &transparent_hugepage_flags);
481 		clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
482 			  &transparent_hugepage_flags);
483 		ret = 1;
484 	}
485 out:
486 	if (!ret)
487 		pr_warn("transparent_hugepage= cannot parse, ignored\n");
488 	return ret;
489 }
490 __setup("transparent_hugepage=", setup_transparent_hugepage);
491 
492 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
493 {
494 	if (likely(vma->vm_flags & VM_WRITE))
495 		pmd = pmd_mkwrite(pmd);
496 	return pmd;
497 }
498 
499 static inline struct list_head *page_deferred_list(struct page *page)
500 {
501 	/* ->lru in the tail pages is occupied by compound_head. */
502 	return &page[2].deferred_list;
503 }
504 
505 void prep_transhuge_page(struct page *page)
506 {
507 	/*
508 	 * we use page->mapping and page->indexlru in second tail page
509 	 * as list_head: assuming THP order >= 2
510 	 */
511 
512 	INIT_LIST_HEAD(page_deferred_list(page));
513 	set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
514 }
515 
516 static unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
517 		loff_t off, unsigned long flags, unsigned long size)
518 {
519 	unsigned long addr;
520 	loff_t off_end = off + len;
521 	loff_t off_align = round_up(off, size);
522 	unsigned long len_pad;
523 
524 	if (off_end <= off_align || (off_end - off_align) < size)
525 		return 0;
526 
527 	len_pad = len + size;
528 	if (len_pad < len || (off + len_pad) < off)
529 		return 0;
530 
531 	addr = current->mm->get_unmapped_area(filp, 0, len_pad,
532 					      off >> PAGE_SHIFT, flags);
533 	if (IS_ERR_VALUE(addr))
534 		return 0;
535 
536 	addr += (off - addr) & (size - 1);
537 	return addr;
538 }
539 
540 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
541 		unsigned long len, unsigned long pgoff, unsigned long flags)
542 {
543 	loff_t off = (loff_t)pgoff << PAGE_SHIFT;
544 
545 	if (addr)
546 		goto out;
547 	if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
548 		goto out;
549 
550 	addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
551 	if (addr)
552 		return addr;
553 
554  out:
555 	return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
556 }
557 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
558 
559 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
560 			struct page *page, gfp_t gfp)
561 {
562 	struct vm_area_struct *vma = vmf->vma;
563 	struct mem_cgroup *memcg;
564 	pgtable_t pgtable;
565 	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
566 	vm_fault_t ret = 0;
567 
568 	VM_BUG_ON_PAGE(!PageCompound(page), page);
569 
570 	if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
571 		put_page(page);
572 		count_vm_event(THP_FAULT_FALLBACK);
573 		return VM_FAULT_FALLBACK;
574 	}
575 
576 	pgtable = pte_alloc_one(vma->vm_mm);
577 	if (unlikely(!pgtable)) {
578 		ret = VM_FAULT_OOM;
579 		goto release;
580 	}
581 
582 	clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
583 	/*
584 	 * The memory barrier inside __SetPageUptodate makes sure that
585 	 * clear_huge_page writes become visible before the set_pmd_at()
586 	 * write.
587 	 */
588 	__SetPageUptodate(page);
589 
590 	vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
591 	if (unlikely(!pmd_none(*vmf->pmd))) {
592 		goto unlock_release;
593 	} else {
594 		pmd_t entry;
595 
596 		ret = check_stable_address_space(vma->vm_mm);
597 		if (ret)
598 			goto unlock_release;
599 
600 		/* Deliver the page fault to userland */
601 		if (userfaultfd_missing(vma)) {
602 			vm_fault_t ret2;
603 
604 			spin_unlock(vmf->ptl);
605 			mem_cgroup_cancel_charge(page, memcg, true);
606 			put_page(page);
607 			pte_free(vma->vm_mm, pgtable);
608 			ret2 = handle_userfault(vmf, VM_UFFD_MISSING);
609 			VM_BUG_ON(ret2 & VM_FAULT_FALLBACK);
610 			return ret2;
611 		}
612 
613 		entry = mk_huge_pmd(page, vma->vm_page_prot);
614 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
615 		page_add_new_anon_rmap(page, vma, haddr, true);
616 		mem_cgroup_commit_charge(page, memcg, false, true);
617 		lru_cache_add_active_or_unevictable(page, vma);
618 		pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
619 		set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
620 		add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
621 		mm_inc_nr_ptes(vma->vm_mm);
622 		spin_unlock(vmf->ptl);
623 		count_vm_event(THP_FAULT_ALLOC);
624 		count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
625 	}
626 
627 	return 0;
628 unlock_release:
629 	spin_unlock(vmf->ptl);
630 release:
631 	if (pgtable)
632 		pte_free(vma->vm_mm, pgtable);
633 	mem_cgroup_cancel_charge(page, memcg, true);
634 	put_page(page);
635 	return ret;
636 
637 }
638 
639 /*
640  * always: directly stall for all thp allocations
641  * defer: wake kswapd and fail if not immediately available
642  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
643  *		  fail if not immediately available
644  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
645  *	    available
646  * never: never stall for any thp allocation
647  */
648 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
649 {
650 	const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
651 
652 	/* Always do synchronous compaction */
653 	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
654 		return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
655 
656 	/* Kick kcompactd and fail quickly */
657 	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
658 		return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
659 
660 	/* Synchronous compaction if madvised, otherwise kick kcompactd */
661 	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
662 		return GFP_TRANSHUGE_LIGHT |
663 			(vma_madvised ? __GFP_DIRECT_RECLAIM :
664 					__GFP_KSWAPD_RECLAIM);
665 
666 	/* Only do synchronous compaction if madvised */
667 	if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
668 		return GFP_TRANSHUGE_LIGHT |
669 		       (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
670 
671 	return GFP_TRANSHUGE_LIGHT;
672 }
673 
674 /* Caller must hold page table lock. */
675 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
676 		struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
677 		struct page *zero_page)
678 {
679 	pmd_t entry;
680 	if (!pmd_none(*pmd))
681 		return false;
682 	entry = mk_pmd(zero_page, vma->vm_page_prot);
683 	entry = pmd_mkhuge(entry);
684 	if (pgtable)
685 		pgtable_trans_huge_deposit(mm, pmd, pgtable);
686 	set_pmd_at(mm, haddr, pmd, entry);
687 	mm_inc_nr_ptes(mm);
688 	return true;
689 }
690 
691 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
692 {
693 	struct vm_area_struct *vma = vmf->vma;
694 	gfp_t gfp;
695 	struct page *page;
696 	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
697 
698 	if (!transhuge_vma_suitable(vma, haddr))
699 		return VM_FAULT_FALLBACK;
700 	if (unlikely(anon_vma_prepare(vma)))
701 		return VM_FAULT_OOM;
702 	if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
703 		return VM_FAULT_OOM;
704 	if (!(vmf->flags & FAULT_FLAG_WRITE) &&
705 			!mm_forbids_zeropage(vma->vm_mm) &&
706 			transparent_hugepage_use_zero_page()) {
707 		pgtable_t pgtable;
708 		struct page *zero_page;
709 		bool set;
710 		vm_fault_t ret;
711 		pgtable = pte_alloc_one(vma->vm_mm);
712 		if (unlikely(!pgtable))
713 			return VM_FAULT_OOM;
714 		zero_page = mm_get_huge_zero_page(vma->vm_mm);
715 		if (unlikely(!zero_page)) {
716 			pte_free(vma->vm_mm, pgtable);
717 			count_vm_event(THP_FAULT_FALLBACK);
718 			return VM_FAULT_FALLBACK;
719 		}
720 		vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
721 		ret = 0;
722 		set = false;
723 		if (pmd_none(*vmf->pmd)) {
724 			ret = check_stable_address_space(vma->vm_mm);
725 			if (ret) {
726 				spin_unlock(vmf->ptl);
727 			} else if (userfaultfd_missing(vma)) {
728 				spin_unlock(vmf->ptl);
729 				ret = handle_userfault(vmf, VM_UFFD_MISSING);
730 				VM_BUG_ON(ret & VM_FAULT_FALLBACK);
731 			} else {
732 				set_huge_zero_page(pgtable, vma->vm_mm, vma,
733 						   haddr, vmf->pmd, zero_page);
734 				spin_unlock(vmf->ptl);
735 				set = true;
736 			}
737 		} else
738 			spin_unlock(vmf->ptl);
739 		if (!set)
740 			pte_free(vma->vm_mm, pgtable);
741 		return ret;
742 	}
743 	gfp = alloc_hugepage_direct_gfpmask(vma);
744 	page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
745 	if (unlikely(!page)) {
746 		count_vm_event(THP_FAULT_FALLBACK);
747 		return VM_FAULT_FALLBACK;
748 	}
749 	prep_transhuge_page(page);
750 	return __do_huge_pmd_anonymous_page(vmf, page, gfp);
751 }
752 
753 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
754 		pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
755 		pgtable_t pgtable)
756 {
757 	struct mm_struct *mm = vma->vm_mm;
758 	pmd_t entry;
759 	spinlock_t *ptl;
760 
761 	ptl = pmd_lock(mm, pmd);
762 	if (!pmd_none(*pmd)) {
763 		if (write) {
764 			if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
765 				WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
766 				goto out_unlock;
767 			}
768 			entry = pmd_mkyoung(*pmd);
769 			entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
770 			if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
771 				update_mmu_cache_pmd(vma, addr, pmd);
772 		}
773 
774 		goto out_unlock;
775 	}
776 
777 	entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
778 	if (pfn_t_devmap(pfn))
779 		entry = pmd_mkdevmap(entry);
780 	if (write) {
781 		entry = pmd_mkyoung(pmd_mkdirty(entry));
782 		entry = maybe_pmd_mkwrite(entry, vma);
783 	}
784 
785 	if (pgtable) {
786 		pgtable_trans_huge_deposit(mm, pmd, pgtable);
787 		mm_inc_nr_ptes(mm);
788 		pgtable = NULL;
789 	}
790 
791 	set_pmd_at(mm, addr, pmd, entry);
792 	update_mmu_cache_pmd(vma, addr, pmd);
793 
794 out_unlock:
795 	spin_unlock(ptl);
796 	if (pgtable)
797 		pte_free(mm, pgtable);
798 }
799 
800 vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write)
801 {
802 	unsigned long addr = vmf->address & PMD_MASK;
803 	struct vm_area_struct *vma = vmf->vma;
804 	pgprot_t pgprot = vma->vm_page_prot;
805 	pgtable_t pgtable = NULL;
806 
807 	/*
808 	 * If we had pmd_special, we could avoid all these restrictions,
809 	 * but we need to be consistent with PTEs and architectures that
810 	 * can't support a 'special' bit.
811 	 */
812 	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
813 			!pfn_t_devmap(pfn));
814 	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
815 						(VM_PFNMAP|VM_MIXEDMAP));
816 	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
817 
818 	if (addr < vma->vm_start || addr >= vma->vm_end)
819 		return VM_FAULT_SIGBUS;
820 
821 	if (arch_needs_pgtable_deposit()) {
822 		pgtable = pte_alloc_one(vma->vm_mm);
823 		if (!pgtable)
824 			return VM_FAULT_OOM;
825 	}
826 
827 	track_pfn_insert(vma, &pgprot, pfn);
828 
829 	insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
830 	return VM_FAULT_NOPAGE;
831 }
832 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
833 
834 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
835 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
836 {
837 	if (likely(vma->vm_flags & VM_WRITE))
838 		pud = pud_mkwrite(pud);
839 	return pud;
840 }
841 
842 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
843 		pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
844 {
845 	struct mm_struct *mm = vma->vm_mm;
846 	pud_t entry;
847 	spinlock_t *ptl;
848 
849 	ptl = pud_lock(mm, pud);
850 	if (!pud_none(*pud)) {
851 		if (write) {
852 			if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
853 				WARN_ON_ONCE(!is_huge_zero_pud(*pud));
854 				goto out_unlock;
855 			}
856 			entry = pud_mkyoung(*pud);
857 			entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
858 			if (pudp_set_access_flags(vma, addr, pud, entry, 1))
859 				update_mmu_cache_pud(vma, addr, pud);
860 		}
861 		goto out_unlock;
862 	}
863 
864 	entry = pud_mkhuge(pfn_t_pud(pfn, prot));
865 	if (pfn_t_devmap(pfn))
866 		entry = pud_mkdevmap(entry);
867 	if (write) {
868 		entry = pud_mkyoung(pud_mkdirty(entry));
869 		entry = maybe_pud_mkwrite(entry, vma);
870 	}
871 	set_pud_at(mm, addr, pud, entry);
872 	update_mmu_cache_pud(vma, addr, pud);
873 
874 out_unlock:
875 	spin_unlock(ptl);
876 }
877 
878 vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
879 {
880 	unsigned long addr = vmf->address & PUD_MASK;
881 	struct vm_area_struct *vma = vmf->vma;
882 	pgprot_t pgprot = vma->vm_page_prot;
883 
884 	/*
885 	 * If we had pud_special, we could avoid all these restrictions,
886 	 * but we need to be consistent with PTEs and architectures that
887 	 * can't support a 'special' bit.
888 	 */
889 	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
890 			!pfn_t_devmap(pfn));
891 	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
892 						(VM_PFNMAP|VM_MIXEDMAP));
893 	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
894 
895 	if (addr < vma->vm_start || addr >= vma->vm_end)
896 		return VM_FAULT_SIGBUS;
897 
898 	track_pfn_insert(vma, &pgprot, pfn);
899 
900 	insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
901 	return VM_FAULT_NOPAGE;
902 }
903 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
904 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
905 
906 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
907 		pmd_t *pmd, int flags)
908 {
909 	pmd_t _pmd;
910 
911 	_pmd = pmd_mkyoung(*pmd);
912 	if (flags & FOLL_WRITE)
913 		_pmd = pmd_mkdirty(_pmd);
914 	if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
915 				pmd, _pmd, flags & FOLL_WRITE))
916 		update_mmu_cache_pmd(vma, addr, pmd);
917 }
918 
919 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
920 		pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
921 {
922 	unsigned long pfn = pmd_pfn(*pmd);
923 	struct mm_struct *mm = vma->vm_mm;
924 	struct page *page;
925 
926 	assert_spin_locked(pmd_lockptr(mm, pmd));
927 
928 	/*
929 	 * When we COW a devmap PMD entry, we split it into PTEs, so we should
930 	 * not be in this function with `flags & FOLL_COW` set.
931 	 */
932 	WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
933 
934 	if (flags & FOLL_WRITE && !pmd_write(*pmd))
935 		return NULL;
936 
937 	if (pmd_present(*pmd) && pmd_devmap(*pmd))
938 		/* pass */;
939 	else
940 		return NULL;
941 
942 	if (flags & FOLL_TOUCH)
943 		touch_pmd(vma, addr, pmd, flags);
944 
945 	/*
946 	 * device mapped pages can only be returned if the
947 	 * caller will manage the page reference count.
948 	 */
949 	if (!(flags & FOLL_GET))
950 		return ERR_PTR(-EEXIST);
951 
952 	pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
953 	*pgmap = get_dev_pagemap(pfn, *pgmap);
954 	if (!*pgmap)
955 		return ERR_PTR(-EFAULT);
956 	page = pfn_to_page(pfn);
957 	get_page(page);
958 
959 	return page;
960 }
961 
962 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
963 		  pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
964 		  struct vm_area_struct *vma)
965 {
966 	spinlock_t *dst_ptl, *src_ptl;
967 	struct page *src_page;
968 	pmd_t pmd;
969 	pgtable_t pgtable = NULL;
970 	int ret = -ENOMEM;
971 
972 	/* Skip if can be re-fill on fault */
973 	if (!vma_is_anonymous(vma))
974 		return 0;
975 
976 	pgtable = pte_alloc_one(dst_mm);
977 	if (unlikely(!pgtable))
978 		goto out;
979 
980 	dst_ptl = pmd_lock(dst_mm, dst_pmd);
981 	src_ptl = pmd_lockptr(src_mm, src_pmd);
982 	spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
983 
984 	ret = -EAGAIN;
985 	pmd = *src_pmd;
986 
987 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
988 	if (unlikely(is_swap_pmd(pmd))) {
989 		swp_entry_t entry = pmd_to_swp_entry(pmd);
990 
991 		VM_BUG_ON(!is_pmd_migration_entry(pmd));
992 		if (is_write_migration_entry(entry)) {
993 			make_migration_entry_read(&entry);
994 			pmd = swp_entry_to_pmd(entry);
995 			if (pmd_swp_soft_dirty(*src_pmd))
996 				pmd = pmd_swp_mksoft_dirty(pmd);
997 			set_pmd_at(src_mm, addr, src_pmd, pmd);
998 		}
999 		add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1000 		mm_inc_nr_ptes(dst_mm);
1001 		pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1002 		set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1003 		ret = 0;
1004 		goto out_unlock;
1005 	}
1006 #endif
1007 
1008 	if (unlikely(!pmd_trans_huge(pmd))) {
1009 		pte_free(dst_mm, pgtable);
1010 		goto out_unlock;
1011 	}
1012 	/*
1013 	 * When page table lock is held, the huge zero pmd should not be
1014 	 * under splitting since we don't split the page itself, only pmd to
1015 	 * a page table.
1016 	 */
1017 	if (is_huge_zero_pmd(pmd)) {
1018 		struct page *zero_page;
1019 		/*
1020 		 * get_huge_zero_page() will never allocate a new page here,
1021 		 * since we already have a zero page to copy. It just takes a
1022 		 * reference.
1023 		 */
1024 		zero_page = mm_get_huge_zero_page(dst_mm);
1025 		set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1026 				zero_page);
1027 		ret = 0;
1028 		goto out_unlock;
1029 	}
1030 
1031 	src_page = pmd_page(pmd);
1032 	VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1033 	get_page(src_page);
1034 	page_dup_rmap(src_page, true);
1035 	add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1036 	mm_inc_nr_ptes(dst_mm);
1037 	pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1038 
1039 	pmdp_set_wrprotect(src_mm, addr, src_pmd);
1040 	pmd = pmd_mkold(pmd_wrprotect(pmd));
1041 	set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1042 
1043 	ret = 0;
1044 out_unlock:
1045 	spin_unlock(src_ptl);
1046 	spin_unlock(dst_ptl);
1047 out:
1048 	return ret;
1049 }
1050 
1051 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1052 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1053 		pud_t *pud, int flags)
1054 {
1055 	pud_t _pud;
1056 
1057 	_pud = pud_mkyoung(*pud);
1058 	if (flags & FOLL_WRITE)
1059 		_pud = pud_mkdirty(_pud);
1060 	if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1061 				pud, _pud, flags & FOLL_WRITE))
1062 		update_mmu_cache_pud(vma, addr, pud);
1063 }
1064 
1065 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1066 		pud_t *pud, int flags, struct dev_pagemap **pgmap)
1067 {
1068 	unsigned long pfn = pud_pfn(*pud);
1069 	struct mm_struct *mm = vma->vm_mm;
1070 	struct page *page;
1071 
1072 	assert_spin_locked(pud_lockptr(mm, pud));
1073 
1074 	if (flags & FOLL_WRITE && !pud_write(*pud))
1075 		return NULL;
1076 
1077 	if (pud_present(*pud) && pud_devmap(*pud))
1078 		/* pass */;
1079 	else
1080 		return NULL;
1081 
1082 	if (flags & FOLL_TOUCH)
1083 		touch_pud(vma, addr, pud, flags);
1084 
1085 	/*
1086 	 * device mapped pages can only be returned if the
1087 	 * caller will manage the page reference count.
1088 	 */
1089 	if (!(flags & FOLL_GET))
1090 		return ERR_PTR(-EEXIST);
1091 
1092 	pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1093 	*pgmap = get_dev_pagemap(pfn, *pgmap);
1094 	if (!*pgmap)
1095 		return ERR_PTR(-EFAULT);
1096 	page = pfn_to_page(pfn);
1097 	get_page(page);
1098 
1099 	return page;
1100 }
1101 
1102 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1103 		  pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1104 		  struct vm_area_struct *vma)
1105 {
1106 	spinlock_t *dst_ptl, *src_ptl;
1107 	pud_t pud;
1108 	int ret;
1109 
1110 	dst_ptl = pud_lock(dst_mm, dst_pud);
1111 	src_ptl = pud_lockptr(src_mm, src_pud);
1112 	spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1113 
1114 	ret = -EAGAIN;
1115 	pud = *src_pud;
1116 	if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1117 		goto out_unlock;
1118 
1119 	/*
1120 	 * When page table lock is held, the huge zero pud should not be
1121 	 * under splitting since we don't split the page itself, only pud to
1122 	 * a page table.
1123 	 */
1124 	if (is_huge_zero_pud(pud)) {
1125 		/* No huge zero pud yet */
1126 	}
1127 
1128 	pudp_set_wrprotect(src_mm, addr, src_pud);
1129 	pud = pud_mkold(pud_wrprotect(pud));
1130 	set_pud_at(dst_mm, addr, dst_pud, pud);
1131 
1132 	ret = 0;
1133 out_unlock:
1134 	spin_unlock(src_ptl);
1135 	spin_unlock(dst_ptl);
1136 	return ret;
1137 }
1138 
1139 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1140 {
1141 	pud_t entry;
1142 	unsigned long haddr;
1143 	bool write = vmf->flags & FAULT_FLAG_WRITE;
1144 
1145 	vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1146 	if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1147 		goto unlock;
1148 
1149 	entry = pud_mkyoung(orig_pud);
1150 	if (write)
1151 		entry = pud_mkdirty(entry);
1152 	haddr = vmf->address & HPAGE_PUD_MASK;
1153 	if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1154 		update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1155 
1156 unlock:
1157 	spin_unlock(vmf->ptl);
1158 }
1159 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1160 
1161 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1162 {
1163 	pmd_t entry;
1164 	unsigned long haddr;
1165 	bool write = vmf->flags & FAULT_FLAG_WRITE;
1166 
1167 	vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1168 	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1169 		goto unlock;
1170 
1171 	entry = pmd_mkyoung(orig_pmd);
1172 	if (write)
1173 		entry = pmd_mkdirty(entry);
1174 	haddr = vmf->address & HPAGE_PMD_MASK;
1175 	if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1176 		update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1177 
1178 unlock:
1179 	spin_unlock(vmf->ptl);
1180 }
1181 
1182 static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
1183 			pmd_t orig_pmd, struct page *page)
1184 {
1185 	struct vm_area_struct *vma = vmf->vma;
1186 	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1187 	struct mem_cgroup *memcg;
1188 	pgtable_t pgtable;
1189 	pmd_t _pmd;
1190 	int i;
1191 	vm_fault_t ret = 0;
1192 	struct page **pages;
1193 	struct mmu_notifier_range range;
1194 
1195 	pages = kmalloc_array(HPAGE_PMD_NR, sizeof(struct page *),
1196 			      GFP_KERNEL);
1197 	if (unlikely(!pages)) {
1198 		ret |= VM_FAULT_OOM;
1199 		goto out;
1200 	}
1201 
1202 	for (i = 0; i < HPAGE_PMD_NR; i++) {
1203 		pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1204 					       vmf->address, page_to_nid(page));
1205 		if (unlikely(!pages[i] ||
1206 			     mem_cgroup_try_charge_delay(pages[i], vma->vm_mm,
1207 				     GFP_KERNEL, &memcg, false))) {
1208 			if (pages[i])
1209 				put_page(pages[i]);
1210 			while (--i >= 0) {
1211 				memcg = (void *)page_private(pages[i]);
1212 				set_page_private(pages[i], 0);
1213 				mem_cgroup_cancel_charge(pages[i], memcg,
1214 						false);
1215 				put_page(pages[i]);
1216 			}
1217 			kfree(pages);
1218 			ret |= VM_FAULT_OOM;
1219 			goto out;
1220 		}
1221 		set_page_private(pages[i], (unsigned long)memcg);
1222 	}
1223 
1224 	for (i = 0; i < HPAGE_PMD_NR; i++) {
1225 		copy_user_highpage(pages[i], page + i,
1226 				   haddr + PAGE_SIZE * i, vma);
1227 		__SetPageUptodate(pages[i]);
1228 		cond_resched();
1229 	}
1230 
1231 	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1232 				haddr, haddr + HPAGE_PMD_SIZE);
1233 	mmu_notifier_invalidate_range_start(&range);
1234 
1235 	vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1236 	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1237 		goto out_free_pages;
1238 	VM_BUG_ON_PAGE(!PageHead(page), page);
1239 
1240 	/*
1241 	 * Leave pmd empty until pte is filled note we must notify here as
1242 	 * concurrent CPU thread might write to new page before the call to
1243 	 * mmu_notifier_invalidate_range_end() happens which can lead to a
1244 	 * device seeing memory write in different order than CPU.
1245 	 *
1246 	 * See Documentation/vm/mmu_notifier.rst
1247 	 */
1248 	pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1249 
1250 	pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1251 	pmd_populate(vma->vm_mm, &_pmd, pgtable);
1252 
1253 	for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1254 		pte_t entry;
1255 		entry = mk_pte(pages[i], vma->vm_page_prot);
1256 		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1257 		memcg = (void *)page_private(pages[i]);
1258 		set_page_private(pages[i], 0);
1259 		page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1260 		mem_cgroup_commit_charge(pages[i], memcg, false, false);
1261 		lru_cache_add_active_or_unevictable(pages[i], vma);
1262 		vmf->pte = pte_offset_map(&_pmd, haddr);
1263 		VM_BUG_ON(!pte_none(*vmf->pte));
1264 		set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1265 		pte_unmap(vmf->pte);
1266 	}
1267 	kfree(pages);
1268 
1269 	smp_wmb(); /* make pte visible before pmd */
1270 	pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1271 	page_remove_rmap(page, true);
1272 	spin_unlock(vmf->ptl);
1273 
1274 	/*
1275 	 * No need to double call mmu_notifier->invalidate_range() callback as
1276 	 * the above pmdp_huge_clear_flush_notify() did already call it.
1277 	 */
1278 	mmu_notifier_invalidate_range_only_end(&range);
1279 
1280 	ret |= VM_FAULT_WRITE;
1281 	put_page(page);
1282 
1283 out:
1284 	return ret;
1285 
1286 out_free_pages:
1287 	spin_unlock(vmf->ptl);
1288 	mmu_notifier_invalidate_range_end(&range);
1289 	for (i = 0; i < HPAGE_PMD_NR; i++) {
1290 		memcg = (void *)page_private(pages[i]);
1291 		set_page_private(pages[i], 0);
1292 		mem_cgroup_cancel_charge(pages[i], memcg, false);
1293 		put_page(pages[i]);
1294 	}
1295 	kfree(pages);
1296 	goto out;
1297 }
1298 
1299 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1300 {
1301 	struct vm_area_struct *vma = vmf->vma;
1302 	struct page *page = NULL, *new_page;
1303 	struct mem_cgroup *memcg;
1304 	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1305 	struct mmu_notifier_range range;
1306 	gfp_t huge_gfp;			/* for allocation and charge */
1307 	vm_fault_t ret = 0;
1308 
1309 	vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1310 	VM_BUG_ON_VMA(!vma->anon_vma, vma);
1311 	if (is_huge_zero_pmd(orig_pmd))
1312 		goto alloc;
1313 	spin_lock(vmf->ptl);
1314 	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1315 		goto out_unlock;
1316 
1317 	page = pmd_page(orig_pmd);
1318 	VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1319 	/*
1320 	 * We can only reuse the page if nobody else maps the huge page or it's
1321 	 * part.
1322 	 */
1323 	if (!trylock_page(page)) {
1324 		get_page(page);
1325 		spin_unlock(vmf->ptl);
1326 		lock_page(page);
1327 		spin_lock(vmf->ptl);
1328 		if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1329 			unlock_page(page);
1330 			put_page(page);
1331 			goto out_unlock;
1332 		}
1333 		put_page(page);
1334 	}
1335 	if (reuse_swap_page(page, NULL)) {
1336 		pmd_t entry;
1337 		entry = pmd_mkyoung(orig_pmd);
1338 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1339 		if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1340 			update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1341 		ret |= VM_FAULT_WRITE;
1342 		unlock_page(page);
1343 		goto out_unlock;
1344 	}
1345 	unlock_page(page);
1346 	get_page(page);
1347 	spin_unlock(vmf->ptl);
1348 alloc:
1349 	if (__transparent_hugepage_enabled(vma) &&
1350 	    !transparent_hugepage_debug_cow()) {
1351 		huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1352 		new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1353 	} else
1354 		new_page = NULL;
1355 
1356 	if (likely(new_page)) {
1357 		prep_transhuge_page(new_page);
1358 	} else {
1359 		if (!page) {
1360 			split_huge_pmd(vma, vmf->pmd, vmf->address);
1361 			ret |= VM_FAULT_FALLBACK;
1362 		} else {
1363 			ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1364 			if (ret & VM_FAULT_OOM) {
1365 				split_huge_pmd(vma, vmf->pmd, vmf->address);
1366 				ret |= VM_FAULT_FALLBACK;
1367 			}
1368 			put_page(page);
1369 		}
1370 		count_vm_event(THP_FAULT_FALLBACK);
1371 		goto out;
1372 	}
1373 
1374 	if (unlikely(mem_cgroup_try_charge_delay(new_page, vma->vm_mm,
1375 					huge_gfp, &memcg, true))) {
1376 		put_page(new_page);
1377 		split_huge_pmd(vma, vmf->pmd, vmf->address);
1378 		if (page)
1379 			put_page(page);
1380 		ret |= VM_FAULT_FALLBACK;
1381 		count_vm_event(THP_FAULT_FALLBACK);
1382 		goto out;
1383 	}
1384 
1385 	count_vm_event(THP_FAULT_ALLOC);
1386 	count_memcg_events(memcg, THP_FAULT_ALLOC, 1);
1387 
1388 	if (!page)
1389 		clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1390 	else
1391 		copy_user_huge_page(new_page, page, vmf->address,
1392 				    vma, HPAGE_PMD_NR);
1393 	__SetPageUptodate(new_page);
1394 
1395 	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1396 				haddr, haddr + HPAGE_PMD_SIZE);
1397 	mmu_notifier_invalidate_range_start(&range);
1398 
1399 	spin_lock(vmf->ptl);
1400 	if (page)
1401 		put_page(page);
1402 	if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1403 		spin_unlock(vmf->ptl);
1404 		mem_cgroup_cancel_charge(new_page, memcg, true);
1405 		put_page(new_page);
1406 		goto out_mn;
1407 	} else {
1408 		pmd_t entry;
1409 		entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1410 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1411 		pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1412 		page_add_new_anon_rmap(new_page, vma, haddr, true);
1413 		mem_cgroup_commit_charge(new_page, memcg, false, true);
1414 		lru_cache_add_active_or_unevictable(new_page, vma);
1415 		set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1416 		update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1417 		if (!page) {
1418 			add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1419 		} else {
1420 			VM_BUG_ON_PAGE(!PageHead(page), page);
1421 			page_remove_rmap(page, true);
1422 			put_page(page);
1423 		}
1424 		ret |= VM_FAULT_WRITE;
1425 	}
1426 	spin_unlock(vmf->ptl);
1427 out_mn:
1428 	/*
1429 	 * No need to double call mmu_notifier->invalidate_range() callback as
1430 	 * the above pmdp_huge_clear_flush_notify() did already call it.
1431 	 */
1432 	mmu_notifier_invalidate_range_only_end(&range);
1433 out:
1434 	return ret;
1435 out_unlock:
1436 	spin_unlock(vmf->ptl);
1437 	return ret;
1438 }
1439 
1440 /*
1441  * FOLL_FORCE can write to even unwritable pmd's, but only
1442  * after we've gone through a COW cycle and they are dirty.
1443  */
1444 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1445 {
1446 	return pmd_write(pmd) ||
1447 	       ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1448 }
1449 
1450 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1451 				   unsigned long addr,
1452 				   pmd_t *pmd,
1453 				   unsigned int flags)
1454 {
1455 	struct mm_struct *mm = vma->vm_mm;
1456 	struct page *page = NULL;
1457 
1458 	assert_spin_locked(pmd_lockptr(mm, pmd));
1459 
1460 	if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1461 		goto out;
1462 
1463 	/* Avoid dumping huge zero page */
1464 	if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1465 		return ERR_PTR(-EFAULT);
1466 
1467 	/* Full NUMA hinting faults to serialise migration in fault paths */
1468 	if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1469 		goto out;
1470 
1471 	page = pmd_page(*pmd);
1472 	VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1473 	if (flags & FOLL_TOUCH)
1474 		touch_pmd(vma, addr, pmd, flags);
1475 	if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1476 		/*
1477 		 * We don't mlock() pte-mapped THPs. This way we can avoid
1478 		 * leaking mlocked pages into non-VM_LOCKED VMAs.
1479 		 *
1480 		 * For anon THP:
1481 		 *
1482 		 * In most cases the pmd is the only mapping of the page as we
1483 		 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1484 		 * writable private mappings in populate_vma_page_range().
1485 		 *
1486 		 * The only scenario when we have the page shared here is if we
1487 		 * mlocking read-only mapping shared over fork(). We skip
1488 		 * mlocking such pages.
1489 		 *
1490 		 * For file THP:
1491 		 *
1492 		 * We can expect PageDoubleMap() to be stable under page lock:
1493 		 * for file pages we set it in page_add_file_rmap(), which
1494 		 * requires page to be locked.
1495 		 */
1496 
1497 		if (PageAnon(page) && compound_mapcount(page) != 1)
1498 			goto skip_mlock;
1499 		if (PageDoubleMap(page) || !page->mapping)
1500 			goto skip_mlock;
1501 		if (!trylock_page(page))
1502 			goto skip_mlock;
1503 		lru_add_drain();
1504 		if (page->mapping && !PageDoubleMap(page))
1505 			mlock_vma_page(page);
1506 		unlock_page(page);
1507 	}
1508 skip_mlock:
1509 	page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1510 	VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1511 	if (flags & FOLL_GET)
1512 		get_page(page);
1513 
1514 out:
1515 	return page;
1516 }
1517 
1518 /* NUMA hinting page fault entry point for trans huge pmds */
1519 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1520 {
1521 	struct vm_area_struct *vma = vmf->vma;
1522 	struct anon_vma *anon_vma = NULL;
1523 	struct page *page;
1524 	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1525 	int page_nid = NUMA_NO_NODE, this_nid = numa_node_id();
1526 	int target_nid, last_cpupid = -1;
1527 	bool page_locked;
1528 	bool migrated = false;
1529 	bool was_writable;
1530 	int flags = 0;
1531 
1532 	vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1533 	if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1534 		goto out_unlock;
1535 
1536 	/*
1537 	 * If there are potential migrations, wait for completion and retry
1538 	 * without disrupting NUMA hinting information. Do not relock and
1539 	 * check_same as the page may no longer be mapped.
1540 	 */
1541 	if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1542 		page = pmd_page(*vmf->pmd);
1543 		if (!get_page_unless_zero(page))
1544 			goto out_unlock;
1545 		spin_unlock(vmf->ptl);
1546 		put_and_wait_on_page_locked(page);
1547 		goto out;
1548 	}
1549 
1550 	page = pmd_page(pmd);
1551 	BUG_ON(is_huge_zero_page(page));
1552 	page_nid = page_to_nid(page);
1553 	last_cpupid = page_cpupid_last(page);
1554 	count_vm_numa_event(NUMA_HINT_FAULTS);
1555 	if (page_nid == this_nid) {
1556 		count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1557 		flags |= TNF_FAULT_LOCAL;
1558 	}
1559 
1560 	/* See similar comment in do_numa_page for explanation */
1561 	if (!pmd_savedwrite(pmd))
1562 		flags |= TNF_NO_GROUP;
1563 
1564 	/*
1565 	 * Acquire the page lock to serialise THP migrations but avoid dropping
1566 	 * page_table_lock if at all possible
1567 	 */
1568 	page_locked = trylock_page(page);
1569 	target_nid = mpol_misplaced(page, vma, haddr);
1570 	if (target_nid == NUMA_NO_NODE) {
1571 		/* If the page was locked, there are no parallel migrations */
1572 		if (page_locked)
1573 			goto clear_pmdnuma;
1574 	}
1575 
1576 	/* Migration could have started since the pmd_trans_migrating check */
1577 	if (!page_locked) {
1578 		page_nid = NUMA_NO_NODE;
1579 		if (!get_page_unless_zero(page))
1580 			goto out_unlock;
1581 		spin_unlock(vmf->ptl);
1582 		put_and_wait_on_page_locked(page);
1583 		goto out;
1584 	}
1585 
1586 	/*
1587 	 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1588 	 * to serialises splits
1589 	 */
1590 	get_page(page);
1591 	spin_unlock(vmf->ptl);
1592 	anon_vma = page_lock_anon_vma_read(page);
1593 
1594 	/* Confirm the PMD did not change while page_table_lock was released */
1595 	spin_lock(vmf->ptl);
1596 	if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1597 		unlock_page(page);
1598 		put_page(page);
1599 		page_nid = NUMA_NO_NODE;
1600 		goto out_unlock;
1601 	}
1602 
1603 	/* Bail if we fail to protect against THP splits for any reason */
1604 	if (unlikely(!anon_vma)) {
1605 		put_page(page);
1606 		page_nid = NUMA_NO_NODE;
1607 		goto clear_pmdnuma;
1608 	}
1609 
1610 	/*
1611 	 * Since we took the NUMA fault, we must have observed the !accessible
1612 	 * bit. Make sure all other CPUs agree with that, to avoid them
1613 	 * modifying the page we're about to migrate.
1614 	 *
1615 	 * Must be done under PTL such that we'll observe the relevant
1616 	 * inc_tlb_flush_pending().
1617 	 *
1618 	 * We are not sure a pending tlb flush here is for a huge page
1619 	 * mapping or not. Hence use the tlb range variant
1620 	 */
1621 	if (mm_tlb_flush_pending(vma->vm_mm)) {
1622 		flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1623 		/*
1624 		 * change_huge_pmd() released the pmd lock before
1625 		 * invalidating the secondary MMUs sharing the primary
1626 		 * MMU pagetables (with ->invalidate_range()). The
1627 		 * mmu_notifier_invalidate_range_end() (which
1628 		 * internally calls ->invalidate_range()) in
1629 		 * change_pmd_range() will run after us, so we can't
1630 		 * rely on it here and we need an explicit invalidate.
1631 		 */
1632 		mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1633 					      haddr + HPAGE_PMD_SIZE);
1634 	}
1635 
1636 	/*
1637 	 * Migrate the THP to the requested node, returns with page unlocked
1638 	 * and access rights restored.
1639 	 */
1640 	spin_unlock(vmf->ptl);
1641 
1642 	migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1643 				vmf->pmd, pmd, vmf->address, page, target_nid);
1644 	if (migrated) {
1645 		flags |= TNF_MIGRATED;
1646 		page_nid = target_nid;
1647 	} else
1648 		flags |= TNF_MIGRATE_FAIL;
1649 
1650 	goto out;
1651 clear_pmdnuma:
1652 	BUG_ON(!PageLocked(page));
1653 	was_writable = pmd_savedwrite(pmd);
1654 	pmd = pmd_modify(pmd, vma->vm_page_prot);
1655 	pmd = pmd_mkyoung(pmd);
1656 	if (was_writable)
1657 		pmd = pmd_mkwrite(pmd);
1658 	set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1659 	update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1660 	unlock_page(page);
1661 out_unlock:
1662 	spin_unlock(vmf->ptl);
1663 
1664 out:
1665 	if (anon_vma)
1666 		page_unlock_anon_vma_read(anon_vma);
1667 
1668 	if (page_nid != NUMA_NO_NODE)
1669 		task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1670 				flags);
1671 
1672 	return 0;
1673 }
1674 
1675 /*
1676  * Return true if we do MADV_FREE successfully on entire pmd page.
1677  * Otherwise, return false.
1678  */
1679 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1680 		pmd_t *pmd, unsigned long addr, unsigned long next)
1681 {
1682 	spinlock_t *ptl;
1683 	pmd_t orig_pmd;
1684 	struct page *page;
1685 	struct mm_struct *mm = tlb->mm;
1686 	bool ret = false;
1687 
1688 	tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1689 
1690 	ptl = pmd_trans_huge_lock(pmd, vma);
1691 	if (!ptl)
1692 		goto out_unlocked;
1693 
1694 	orig_pmd = *pmd;
1695 	if (is_huge_zero_pmd(orig_pmd))
1696 		goto out;
1697 
1698 	if (unlikely(!pmd_present(orig_pmd))) {
1699 		VM_BUG_ON(thp_migration_supported() &&
1700 				  !is_pmd_migration_entry(orig_pmd));
1701 		goto out;
1702 	}
1703 
1704 	page = pmd_page(orig_pmd);
1705 	/*
1706 	 * If other processes are mapping this page, we couldn't discard
1707 	 * the page unless they all do MADV_FREE so let's skip the page.
1708 	 */
1709 	if (page_mapcount(page) != 1)
1710 		goto out;
1711 
1712 	if (!trylock_page(page))
1713 		goto out;
1714 
1715 	/*
1716 	 * If user want to discard part-pages of THP, split it so MADV_FREE
1717 	 * will deactivate only them.
1718 	 */
1719 	if (next - addr != HPAGE_PMD_SIZE) {
1720 		get_page(page);
1721 		spin_unlock(ptl);
1722 		split_huge_page(page);
1723 		unlock_page(page);
1724 		put_page(page);
1725 		goto out_unlocked;
1726 	}
1727 
1728 	if (PageDirty(page))
1729 		ClearPageDirty(page);
1730 	unlock_page(page);
1731 
1732 	if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1733 		pmdp_invalidate(vma, addr, pmd);
1734 		orig_pmd = pmd_mkold(orig_pmd);
1735 		orig_pmd = pmd_mkclean(orig_pmd);
1736 
1737 		set_pmd_at(mm, addr, pmd, orig_pmd);
1738 		tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1739 	}
1740 
1741 	mark_page_lazyfree(page);
1742 	ret = true;
1743 out:
1744 	spin_unlock(ptl);
1745 out_unlocked:
1746 	return ret;
1747 }
1748 
1749 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1750 {
1751 	pgtable_t pgtable;
1752 
1753 	pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1754 	pte_free(mm, pgtable);
1755 	mm_dec_nr_ptes(mm);
1756 }
1757 
1758 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1759 		 pmd_t *pmd, unsigned long addr)
1760 {
1761 	pmd_t orig_pmd;
1762 	spinlock_t *ptl;
1763 
1764 	tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1765 
1766 	ptl = __pmd_trans_huge_lock(pmd, vma);
1767 	if (!ptl)
1768 		return 0;
1769 	/*
1770 	 * For architectures like ppc64 we look at deposited pgtable
1771 	 * when calling pmdp_huge_get_and_clear. So do the
1772 	 * pgtable_trans_huge_withdraw after finishing pmdp related
1773 	 * operations.
1774 	 */
1775 	orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1776 			tlb->fullmm);
1777 	tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1778 	if (vma_is_dax(vma)) {
1779 		if (arch_needs_pgtable_deposit())
1780 			zap_deposited_table(tlb->mm, pmd);
1781 		spin_unlock(ptl);
1782 		if (is_huge_zero_pmd(orig_pmd))
1783 			tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1784 	} else if (is_huge_zero_pmd(orig_pmd)) {
1785 		zap_deposited_table(tlb->mm, pmd);
1786 		spin_unlock(ptl);
1787 		tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1788 	} else {
1789 		struct page *page = NULL;
1790 		int flush_needed = 1;
1791 
1792 		if (pmd_present(orig_pmd)) {
1793 			page = pmd_page(orig_pmd);
1794 			page_remove_rmap(page, true);
1795 			VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1796 			VM_BUG_ON_PAGE(!PageHead(page), page);
1797 		} else if (thp_migration_supported()) {
1798 			swp_entry_t entry;
1799 
1800 			VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1801 			entry = pmd_to_swp_entry(orig_pmd);
1802 			page = pfn_to_page(swp_offset(entry));
1803 			flush_needed = 0;
1804 		} else
1805 			WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1806 
1807 		if (PageAnon(page)) {
1808 			zap_deposited_table(tlb->mm, pmd);
1809 			add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1810 		} else {
1811 			if (arch_needs_pgtable_deposit())
1812 				zap_deposited_table(tlb->mm, pmd);
1813 			add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1814 		}
1815 
1816 		spin_unlock(ptl);
1817 		if (flush_needed)
1818 			tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1819 	}
1820 	return 1;
1821 }
1822 
1823 #ifndef pmd_move_must_withdraw
1824 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1825 					 spinlock_t *old_pmd_ptl,
1826 					 struct vm_area_struct *vma)
1827 {
1828 	/*
1829 	 * With split pmd lock we also need to move preallocated
1830 	 * PTE page table if new_pmd is on different PMD page table.
1831 	 *
1832 	 * We also don't deposit and withdraw tables for file pages.
1833 	 */
1834 	return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1835 }
1836 #endif
1837 
1838 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1839 {
1840 #ifdef CONFIG_MEM_SOFT_DIRTY
1841 	if (unlikely(is_pmd_migration_entry(pmd)))
1842 		pmd = pmd_swp_mksoft_dirty(pmd);
1843 	else if (pmd_present(pmd))
1844 		pmd = pmd_mksoft_dirty(pmd);
1845 #endif
1846 	return pmd;
1847 }
1848 
1849 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1850 		  unsigned long new_addr, unsigned long old_end,
1851 		  pmd_t *old_pmd, pmd_t *new_pmd)
1852 {
1853 	spinlock_t *old_ptl, *new_ptl;
1854 	pmd_t pmd;
1855 	struct mm_struct *mm = vma->vm_mm;
1856 	bool force_flush = false;
1857 
1858 	if ((old_addr & ~HPAGE_PMD_MASK) ||
1859 	    (new_addr & ~HPAGE_PMD_MASK) ||
1860 	    old_end - old_addr < HPAGE_PMD_SIZE)
1861 		return false;
1862 
1863 	/*
1864 	 * The destination pmd shouldn't be established, free_pgtables()
1865 	 * should have release it.
1866 	 */
1867 	if (WARN_ON(!pmd_none(*new_pmd))) {
1868 		VM_BUG_ON(pmd_trans_huge(*new_pmd));
1869 		return false;
1870 	}
1871 
1872 	/*
1873 	 * We don't have to worry about the ordering of src and dst
1874 	 * ptlocks because exclusive mmap_sem prevents deadlock.
1875 	 */
1876 	old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1877 	if (old_ptl) {
1878 		new_ptl = pmd_lockptr(mm, new_pmd);
1879 		if (new_ptl != old_ptl)
1880 			spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1881 		pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1882 		if (pmd_present(pmd))
1883 			force_flush = true;
1884 		VM_BUG_ON(!pmd_none(*new_pmd));
1885 
1886 		if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1887 			pgtable_t pgtable;
1888 			pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1889 			pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1890 		}
1891 		pmd = move_soft_dirty_pmd(pmd);
1892 		set_pmd_at(mm, new_addr, new_pmd, pmd);
1893 		if (force_flush)
1894 			flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1895 		if (new_ptl != old_ptl)
1896 			spin_unlock(new_ptl);
1897 		spin_unlock(old_ptl);
1898 		return true;
1899 	}
1900 	return false;
1901 }
1902 
1903 /*
1904  * Returns
1905  *  - 0 if PMD could not be locked
1906  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1907  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1908  */
1909 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1910 		unsigned long addr, pgprot_t newprot, int prot_numa)
1911 {
1912 	struct mm_struct *mm = vma->vm_mm;
1913 	spinlock_t *ptl;
1914 	pmd_t entry;
1915 	bool preserve_write;
1916 	int ret;
1917 
1918 	ptl = __pmd_trans_huge_lock(pmd, vma);
1919 	if (!ptl)
1920 		return 0;
1921 
1922 	preserve_write = prot_numa && pmd_write(*pmd);
1923 	ret = 1;
1924 
1925 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1926 	if (is_swap_pmd(*pmd)) {
1927 		swp_entry_t entry = pmd_to_swp_entry(*pmd);
1928 
1929 		VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1930 		if (is_write_migration_entry(entry)) {
1931 			pmd_t newpmd;
1932 			/*
1933 			 * A protection check is difficult so
1934 			 * just be safe and disable write
1935 			 */
1936 			make_migration_entry_read(&entry);
1937 			newpmd = swp_entry_to_pmd(entry);
1938 			if (pmd_swp_soft_dirty(*pmd))
1939 				newpmd = pmd_swp_mksoft_dirty(newpmd);
1940 			set_pmd_at(mm, addr, pmd, newpmd);
1941 		}
1942 		goto unlock;
1943 	}
1944 #endif
1945 
1946 	/*
1947 	 * Avoid trapping faults against the zero page. The read-only
1948 	 * data is likely to be read-cached on the local CPU and
1949 	 * local/remote hits to the zero page are not interesting.
1950 	 */
1951 	if (prot_numa && is_huge_zero_pmd(*pmd))
1952 		goto unlock;
1953 
1954 	if (prot_numa && pmd_protnone(*pmd))
1955 		goto unlock;
1956 
1957 	/*
1958 	 * In case prot_numa, we are under down_read(mmap_sem). It's critical
1959 	 * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1960 	 * which is also under down_read(mmap_sem):
1961 	 *
1962 	 *	CPU0:				CPU1:
1963 	 *				change_huge_pmd(prot_numa=1)
1964 	 *				 pmdp_huge_get_and_clear_notify()
1965 	 * madvise_dontneed()
1966 	 *  zap_pmd_range()
1967 	 *   pmd_trans_huge(*pmd) == 0 (without ptl)
1968 	 *   // skip the pmd
1969 	 *				 set_pmd_at();
1970 	 *				 // pmd is re-established
1971 	 *
1972 	 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1973 	 * which may break userspace.
1974 	 *
1975 	 * pmdp_invalidate() is required to make sure we don't miss
1976 	 * dirty/young flags set by hardware.
1977 	 */
1978 	entry = pmdp_invalidate(vma, addr, pmd);
1979 
1980 	entry = pmd_modify(entry, newprot);
1981 	if (preserve_write)
1982 		entry = pmd_mk_savedwrite(entry);
1983 	ret = HPAGE_PMD_NR;
1984 	set_pmd_at(mm, addr, pmd, entry);
1985 	BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1986 unlock:
1987 	spin_unlock(ptl);
1988 	return ret;
1989 }
1990 
1991 /*
1992  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1993  *
1994  * Note that if it returns page table lock pointer, this routine returns without
1995  * unlocking page table lock. So callers must unlock it.
1996  */
1997 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1998 {
1999 	spinlock_t *ptl;
2000 	ptl = pmd_lock(vma->vm_mm, pmd);
2001 	if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
2002 			pmd_devmap(*pmd)))
2003 		return ptl;
2004 	spin_unlock(ptl);
2005 	return NULL;
2006 }
2007 
2008 /*
2009  * Returns true if a given pud maps a thp, false otherwise.
2010  *
2011  * Note that if it returns true, this routine returns without unlocking page
2012  * table lock. So callers must unlock it.
2013  */
2014 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
2015 {
2016 	spinlock_t *ptl;
2017 
2018 	ptl = pud_lock(vma->vm_mm, pud);
2019 	if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
2020 		return ptl;
2021 	spin_unlock(ptl);
2022 	return NULL;
2023 }
2024 
2025 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
2026 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
2027 		 pud_t *pud, unsigned long addr)
2028 {
2029 	spinlock_t *ptl;
2030 
2031 	ptl = __pud_trans_huge_lock(pud, vma);
2032 	if (!ptl)
2033 		return 0;
2034 	/*
2035 	 * For architectures like ppc64 we look at deposited pgtable
2036 	 * when calling pudp_huge_get_and_clear. So do the
2037 	 * pgtable_trans_huge_withdraw after finishing pudp related
2038 	 * operations.
2039 	 */
2040 	pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
2041 	tlb_remove_pud_tlb_entry(tlb, pud, addr);
2042 	if (vma_is_dax(vma)) {
2043 		spin_unlock(ptl);
2044 		/* No zero page support yet */
2045 	} else {
2046 		/* No support for anonymous PUD pages yet */
2047 		BUG();
2048 	}
2049 	return 1;
2050 }
2051 
2052 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2053 		unsigned long haddr)
2054 {
2055 	VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2056 	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2057 	VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2058 	VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2059 
2060 	count_vm_event(THP_SPLIT_PUD);
2061 
2062 	pudp_huge_clear_flush_notify(vma, haddr, pud);
2063 }
2064 
2065 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2066 		unsigned long address)
2067 {
2068 	spinlock_t *ptl;
2069 	struct mmu_notifier_range range;
2070 
2071 	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2072 				address & HPAGE_PUD_MASK,
2073 				(address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2074 	mmu_notifier_invalidate_range_start(&range);
2075 	ptl = pud_lock(vma->vm_mm, pud);
2076 	if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2077 		goto out;
2078 	__split_huge_pud_locked(vma, pud, range.start);
2079 
2080 out:
2081 	spin_unlock(ptl);
2082 	/*
2083 	 * No need to double call mmu_notifier->invalidate_range() callback as
2084 	 * the above pudp_huge_clear_flush_notify() did already call it.
2085 	 */
2086 	mmu_notifier_invalidate_range_only_end(&range);
2087 }
2088 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2089 
2090 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2091 		unsigned long haddr, pmd_t *pmd)
2092 {
2093 	struct mm_struct *mm = vma->vm_mm;
2094 	pgtable_t pgtable;
2095 	pmd_t _pmd;
2096 	int i;
2097 
2098 	/*
2099 	 * Leave pmd empty until pte is filled note that it is fine to delay
2100 	 * notification until mmu_notifier_invalidate_range_end() as we are
2101 	 * replacing a zero pmd write protected page with a zero pte write
2102 	 * protected page.
2103 	 *
2104 	 * See Documentation/vm/mmu_notifier.rst
2105 	 */
2106 	pmdp_huge_clear_flush(vma, haddr, pmd);
2107 
2108 	pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2109 	pmd_populate(mm, &_pmd, pgtable);
2110 
2111 	for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2112 		pte_t *pte, entry;
2113 		entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2114 		entry = pte_mkspecial(entry);
2115 		pte = pte_offset_map(&_pmd, haddr);
2116 		VM_BUG_ON(!pte_none(*pte));
2117 		set_pte_at(mm, haddr, pte, entry);
2118 		pte_unmap(pte);
2119 	}
2120 	smp_wmb(); /* make pte visible before pmd */
2121 	pmd_populate(mm, pmd, pgtable);
2122 }
2123 
2124 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2125 		unsigned long haddr, bool freeze)
2126 {
2127 	struct mm_struct *mm = vma->vm_mm;
2128 	struct page *page;
2129 	pgtable_t pgtable;
2130 	pmd_t old_pmd, _pmd;
2131 	bool young, write, soft_dirty, pmd_migration = false;
2132 	unsigned long addr;
2133 	int i;
2134 
2135 	VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2136 	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2137 	VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2138 	VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2139 				&& !pmd_devmap(*pmd));
2140 
2141 	count_vm_event(THP_SPLIT_PMD);
2142 
2143 	if (!vma_is_anonymous(vma)) {
2144 		_pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2145 		/*
2146 		 * We are going to unmap this huge page. So
2147 		 * just go ahead and zap it
2148 		 */
2149 		if (arch_needs_pgtable_deposit())
2150 			zap_deposited_table(mm, pmd);
2151 		if (vma_is_dax(vma))
2152 			return;
2153 		page = pmd_page(_pmd);
2154 		if (!PageDirty(page) && pmd_dirty(_pmd))
2155 			set_page_dirty(page);
2156 		if (!PageReferenced(page) && pmd_young(_pmd))
2157 			SetPageReferenced(page);
2158 		page_remove_rmap(page, true);
2159 		put_page(page);
2160 		add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2161 		return;
2162 	} else if (is_huge_zero_pmd(*pmd)) {
2163 		/*
2164 		 * FIXME: Do we want to invalidate secondary mmu by calling
2165 		 * mmu_notifier_invalidate_range() see comments below inside
2166 		 * __split_huge_pmd() ?
2167 		 *
2168 		 * We are going from a zero huge page write protected to zero
2169 		 * small page also write protected so it does not seems useful
2170 		 * to invalidate secondary mmu at this time.
2171 		 */
2172 		return __split_huge_zero_page_pmd(vma, haddr, pmd);
2173 	}
2174 
2175 	/*
2176 	 * Up to this point the pmd is present and huge and userland has the
2177 	 * whole access to the hugepage during the split (which happens in
2178 	 * place). If we overwrite the pmd with the not-huge version pointing
2179 	 * to the pte here (which of course we could if all CPUs were bug
2180 	 * free), userland could trigger a small page size TLB miss on the
2181 	 * small sized TLB while the hugepage TLB entry is still established in
2182 	 * the huge TLB. Some CPU doesn't like that.
2183 	 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2184 	 * 383 on page 93. Intel should be safe but is also warns that it's
2185 	 * only safe if the permission and cache attributes of the two entries
2186 	 * loaded in the two TLB is identical (which should be the case here).
2187 	 * But it is generally safer to never allow small and huge TLB entries
2188 	 * for the same virtual address to be loaded simultaneously. So instead
2189 	 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2190 	 * current pmd notpresent (atomically because here the pmd_trans_huge
2191 	 * must remain set at all times on the pmd until the split is complete
2192 	 * for this pmd), then we flush the SMP TLB and finally we write the
2193 	 * non-huge version of the pmd entry with pmd_populate.
2194 	 */
2195 	old_pmd = pmdp_invalidate(vma, haddr, pmd);
2196 
2197 	pmd_migration = is_pmd_migration_entry(old_pmd);
2198 	if (unlikely(pmd_migration)) {
2199 		swp_entry_t entry;
2200 
2201 		entry = pmd_to_swp_entry(old_pmd);
2202 		page = pfn_to_page(swp_offset(entry));
2203 		write = is_write_migration_entry(entry);
2204 		young = false;
2205 		soft_dirty = pmd_swp_soft_dirty(old_pmd);
2206 	} else {
2207 		page = pmd_page(old_pmd);
2208 		if (pmd_dirty(old_pmd))
2209 			SetPageDirty(page);
2210 		write = pmd_write(old_pmd);
2211 		young = pmd_young(old_pmd);
2212 		soft_dirty = pmd_soft_dirty(old_pmd);
2213 	}
2214 	VM_BUG_ON_PAGE(!page_count(page), page);
2215 	page_ref_add(page, HPAGE_PMD_NR - 1);
2216 
2217 	/*
2218 	 * Withdraw the table only after we mark the pmd entry invalid.
2219 	 * This's critical for some architectures (Power).
2220 	 */
2221 	pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2222 	pmd_populate(mm, &_pmd, pgtable);
2223 
2224 	for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2225 		pte_t entry, *pte;
2226 		/*
2227 		 * Note that NUMA hinting access restrictions are not
2228 		 * transferred to avoid any possibility of altering
2229 		 * permissions across VMAs.
2230 		 */
2231 		if (freeze || pmd_migration) {
2232 			swp_entry_t swp_entry;
2233 			swp_entry = make_migration_entry(page + i, write);
2234 			entry = swp_entry_to_pte(swp_entry);
2235 			if (soft_dirty)
2236 				entry = pte_swp_mksoft_dirty(entry);
2237 		} else {
2238 			entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2239 			entry = maybe_mkwrite(entry, vma);
2240 			if (!write)
2241 				entry = pte_wrprotect(entry);
2242 			if (!young)
2243 				entry = pte_mkold(entry);
2244 			if (soft_dirty)
2245 				entry = pte_mksoft_dirty(entry);
2246 		}
2247 		pte = pte_offset_map(&_pmd, addr);
2248 		BUG_ON(!pte_none(*pte));
2249 		set_pte_at(mm, addr, pte, entry);
2250 		atomic_inc(&page[i]._mapcount);
2251 		pte_unmap(pte);
2252 	}
2253 
2254 	/*
2255 	 * Set PG_double_map before dropping compound_mapcount to avoid
2256 	 * false-negative page_mapped().
2257 	 */
2258 	if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2259 		for (i = 0; i < HPAGE_PMD_NR; i++)
2260 			atomic_inc(&page[i]._mapcount);
2261 	}
2262 
2263 	if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2264 		/* Last compound_mapcount is gone. */
2265 		__dec_node_page_state(page, NR_ANON_THPS);
2266 		if (TestClearPageDoubleMap(page)) {
2267 			/* No need in mapcount reference anymore */
2268 			for (i = 0; i < HPAGE_PMD_NR; i++)
2269 				atomic_dec(&page[i]._mapcount);
2270 		}
2271 	}
2272 
2273 	smp_wmb(); /* make pte visible before pmd */
2274 	pmd_populate(mm, pmd, pgtable);
2275 
2276 	if (freeze) {
2277 		for (i = 0; i < HPAGE_PMD_NR; i++) {
2278 			page_remove_rmap(page + i, false);
2279 			put_page(page + i);
2280 		}
2281 	}
2282 }
2283 
2284 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2285 		unsigned long address, bool freeze, struct page *page)
2286 {
2287 	spinlock_t *ptl;
2288 	struct mmu_notifier_range range;
2289 
2290 	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2291 				address & HPAGE_PMD_MASK,
2292 				(address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2293 	mmu_notifier_invalidate_range_start(&range);
2294 	ptl = pmd_lock(vma->vm_mm, pmd);
2295 
2296 	/*
2297 	 * If caller asks to setup a migration entries, we need a page to check
2298 	 * pmd against. Otherwise we can end up replacing wrong page.
2299 	 */
2300 	VM_BUG_ON(freeze && !page);
2301 	if (page && page != pmd_page(*pmd))
2302 	        goto out;
2303 
2304 	if (pmd_trans_huge(*pmd)) {
2305 		page = pmd_page(*pmd);
2306 		if (PageMlocked(page))
2307 			clear_page_mlock(page);
2308 	} else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2309 		goto out;
2310 	__split_huge_pmd_locked(vma, pmd, range.start, freeze);
2311 out:
2312 	spin_unlock(ptl);
2313 	/*
2314 	 * No need to double call mmu_notifier->invalidate_range() callback.
2315 	 * They are 3 cases to consider inside __split_huge_pmd_locked():
2316 	 *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2317 	 *  2) __split_huge_zero_page_pmd() read only zero page and any write
2318 	 *    fault will trigger a flush_notify before pointing to a new page
2319 	 *    (it is fine if the secondary mmu keeps pointing to the old zero
2320 	 *    page in the meantime)
2321 	 *  3) Split a huge pmd into pte pointing to the same page. No need
2322 	 *     to invalidate secondary tlb entry they are all still valid.
2323 	 *     any further changes to individual pte will notify. So no need
2324 	 *     to call mmu_notifier->invalidate_range()
2325 	 */
2326 	mmu_notifier_invalidate_range_only_end(&range);
2327 }
2328 
2329 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2330 		bool freeze, struct page *page)
2331 {
2332 	pgd_t *pgd;
2333 	p4d_t *p4d;
2334 	pud_t *pud;
2335 	pmd_t *pmd;
2336 
2337 	pgd = pgd_offset(vma->vm_mm, address);
2338 	if (!pgd_present(*pgd))
2339 		return;
2340 
2341 	p4d = p4d_offset(pgd, address);
2342 	if (!p4d_present(*p4d))
2343 		return;
2344 
2345 	pud = pud_offset(p4d, address);
2346 	if (!pud_present(*pud))
2347 		return;
2348 
2349 	pmd = pmd_offset(pud, address);
2350 
2351 	__split_huge_pmd(vma, pmd, address, freeze, page);
2352 }
2353 
2354 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2355 			     unsigned long start,
2356 			     unsigned long end,
2357 			     long adjust_next)
2358 {
2359 	/*
2360 	 * If the new start address isn't hpage aligned and it could
2361 	 * previously contain an hugepage: check if we need to split
2362 	 * an huge pmd.
2363 	 */
2364 	if (start & ~HPAGE_PMD_MASK &&
2365 	    (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2366 	    (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2367 		split_huge_pmd_address(vma, start, false, NULL);
2368 
2369 	/*
2370 	 * If the new end address isn't hpage aligned and it could
2371 	 * previously contain an hugepage: check if we need to split
2372 	 * an huge pmd.
2373 	 */
2374 	if (end & ~HPAGE_PMD_MASK &&
2375 	    (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2376 	    (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2377 		split_huge_pmd_address(vma, end, false, NULL);
2378 
2379 	/*
2380 	 * If we're also updating the vma->vm_next->vm_start, if the new
2381 	 * vm_next->vm_start isn't page aligned and it could previously
2382 	 * contain an hugepage: check if we need to split an huge pmd.
2383 	 */
2384 	if (adjust_next > 0) {
2385 		struct vm_area_struct *next = vma->vm_next;
2386 		unsigned long nstart = next->vm_start;
2387 		nstart += adjust_next << PAGE_SHIFT;
2388 		if (nstart & ~HPAGE_PMD_MASK &&
2389 		    (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2390 		    (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2391 			split_huge_pmd_address(next, nstart, false, NULL);
2392 	}
2393 }
2394 
2395 static void unmap_page(struct page *page)
2396 {
2397 	enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2398 		TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2399 	bool unmap_success;
2400 
2401 	VM_BUG_ON_PAGE(!PageHead(page), page);
2402 
2403 	if (PageAnon(page))
2404 		ttu_flags |= TTU_SPLIT_FREEZE;
2405 
2406 	unmap_success = try_to_unmap(page, ttu_flags);
2407 	VM_BUG_ON_PAGE(!unmap_success, page);
2408 }
2409 
2410 static void remap_page(struct page *page)
2411 {
2412 	int i;
2413 	if (PageTransHuge(page)) {
2414 		remove_migration_ptes(page, page, true);
2415 	} else {
2416 		for (i = 0; i < HPAGE_PMD_NR; i++)
2417 			remove_migration_ptes(page + i, page + i, true);
2418 	}
2419 }
2420 
2421 static void __split_huge_page_tail(struct page *head, int tail,
2422 		struct lruvec *lruvec, struct list_head *list)
2423 {
2424 	struct page *page_tail = head + tail;
2425 
2426 	VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2427 
2428 	/*
2429 	 * Clone page flags before unfreezing refcount.
2430 	 *
2431 	 * After successful get_page_unless_zero() might follow flags change,
2432 	 * for exmaple lock_page() which set PG_waiters.
2433 	 */
2434 	page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2435 	page_tail->flags |= (head->flags &
2436 			((1L << PG_referenced) |
2437 			 (1L << PG_swapbacked) |
2438 			 (1L << PG_swapcache) |
2439 			 (1L << PG_mlocked) |
2440 			 (1L << PG_uptodate) |
2441 			 (1L << PG_active) |
2442 			 (1L << PG_workingset) |
2443 			 (1L << PG_locked) |
2444 			 (1L << PG_unevictable) |
2445 			 (1L << PG_dirty)));
2446 
2447 	/* ->mapping in first tail page is compound_mapcount */
2448 	VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2449 			page_tail);
2450 	page_tail->mapping = head->mapping;
2451 	page_tail->index = head->index + tail;
2452 
2453 	/* Page flags must be visible before we make the page non-compound. */
2454 	smp_wmb();
2455 
2456 	/*
2457 	 * Clear PageTail before unfreezing page refcount.
2458 	 *
2459 	 * After successful get_page_unless_zero() might follow put_page()
2460 	 * which needs correct compound_head().
2461 	 */
2462 	clear_compound_head(page_tail);
2463 
2464 	/* Finally unfreeze refcount. Additional reference from page cache. */
2465 	page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2466 					  PageSwapCache(head)));
2467 
2468 	if (page_is_young(head))
2469 		set_page_young(page_tail);
2470 	if (page_is_idle(head))
2471 		set_page_idle(page_tail);
2472 
2473 	page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2474 
2475 	/*
2476 	 * always add to the tail because some iterators expect new
2477 	 * pages to show after the currently processed elements - e.g.
2478 	 * migrate_pages
2479 	 */
2480 	lru_add_page_tail(head, page_tail, lruvec, list);
2481 }
2482 
2483 static void __split_huge_page(struct page *page, struct list_head *list,
2484 		pgoff_t end, unsigned long flags)
2485 {
2486 	struct page *head = compound_head(page);
2487 	pg_data_t *pgdat = page_pgdat(head);
2488 	struct lruvec *lruvec;
2489 	int i;
2490 
2491 	lruvec = mem_cgroup_page_lruvec(head, pgdat);
2492 
2493 	/* complete memcg works before add pages to LRU */
2494 	mem_cgroup_split_huge_fixup(head);
2495 
2496 	for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2497 		__split_huge_page_tail(head, i, lruvec, list);
2498 		/* Some pages can be beyond i_size: drop them from page cache */
2499 		if (head[i].index >= end) {
2500 			ClearPageDirty(head + i);
2501 			__delete_from_page_cache(head + i, NULL);
2502 			if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2503 				shmem_uncharge(head->mapping->host, 1);
2504 			put_page(head + i);
2505 		}
2506 	}
2507 
2508 	ClearPageCompound(head);
2509 
2510 	split_page_owner(head, HPAGE_PMD_ORDER);
2511 
2512 	/* See comment in __split_huge_page_tail() */
2513 	if (PageAnon(head)) {
2514 		/* Additional pin to swap cache */
2515 		if (PageSwapCache(head))
2516 			page_ref_add(head, 2);
2517 		else
2518 			page_ref_inc(head);
2519 	} else {
2520 		/* Additional pin to page cache */
2521 		page_ref_add(head, 2);
2522 		xa_unlock(&head->mapping->i_pages);
2523 	}
2524 
2525 	spin_unlock_irqrestore(&pgdat->lru_lock, flags);
2526 
2527 	remap_page(head);
2528 
2529 	for (i = 0; i < HPAGE_PMD_NR; i++) {
2530 		struct page *subpage = head + i;
2531 		if (subpage == page)
2532 			continue;
2533 		unlock_page(subpage);
2534 
2535 		/*
2536 		 * Subpages may be freed if there wasn't any mapping
2537 		 * like if add_to_swap() is running on a lru page that
2538 		 * had its mapping zapped. And freeing these pages
2539 		 * requires taking the lru_lock so we do the put_page
2540 		 * of the tail pages after the split is complete.
2541 		 */
2542 		put_page(subpage);
2543 	}
2544 }
2545 
2546 int total_mapcount(struct page *page)
2547 {
2548 	int i, compound, ret;
2549 
2550 	VM_BUG_ON_PAGE(PageTail(page), page);
2551 
2552 	if (likely(!PageCompound(page)))
2553 		return atomic_read(&page->_mapcount) + 1;
2554 
2555 	compound = compound_mapcount(page);
2556 	if (PageHuge(page))
2557 		return compound;
2558 	ret = compound;
2559 	for (i = 0; i < HPAGE_PMD_NR; i++)
2560 		ret += atomic_read(&page[i]._mapcount) + 1;
2561 	/* File pages has compound_mapcount included in _mapcount */
2562 	if (!PageAnon(page))
2563 		return ret - compound * HPAGE_PMD_NR;
2564 	if (PageDoubleMap(page))
2565 		ret -= HPAGE_PMD_NR;
2566 	return ret;
2567 }
2568 
2569 /*
2570  * This calculates accurately how many mappings a transparent hugepage
2571  * has (unlike page_mapcount() which isn't fully accurate). This full
2572  * accuracy is primarily needed to know if copy-on-write faults can
2573  * reuse the page and change the mapping to read-write instead of
2574  * copying them. At the same time this returns the total_mapcount too.
2575  *
2576  * The function returns the highest mapcount any one of the subpages
2577  * has. If the return value is one, even if different processes are
2578  * mapping different subpages of the transparent hugepage, they can
2579  * all reuse it, because each process is reusing a different subpage.
2580  *
2581  * The total_mapcount is instead counting all virtual mappings of the
2582  * subpages. If the total_mapcount is equal to "one", it tells the
2583  * caller all mappings belong to the same "mm" and in turn the
2584  * anon_vma of the transparent hugepage can become the vma->anon_vma
2585  * local one as no other process may be mapping any of the subpages.
2586  *
2587  * It would be more accurate to replace page_mapcount() with
2588  * page_trans_huge_mapcount(), however we only use
2589  * page_trans_huge_mapcount() in the copy-on-write faults where we
2590  * need full accuracy to avoid breaking page pinning, because
2591  * page_trans_huge_mapcount() is slower than page_mapcount().
2592  */
2593 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2594 {
2595 	int i, ret, _total_mapcount, mapcount;
2596 
2597 	/* hugetlbfs shouldn't call it */
2598 	VM_BUG_ON_PAGE(PageHuge(page), page);
2599 
2600 	if (likely(!PageTransCompound(page))) {
2601 		mapcount = atomic_read(&page->_mapcount) + 1;
2602 		if (total_mapcount)
2603 			*total_mapcount = mapcount;
2604 		return mapcount;
2605 	}
2606 
2607 	page = compound_head(page);
2608 
2609 	_total_mapcount = ret = 0;
2610 	for (i = 0; i < HPAGE_PMD_NR; i++) {
2611 		mapcount = atomic_read(&page[i]._mapcount) + 1;
2612 		ret = max(ret, mapcount);
2613 		_total_mapcount += mapcount;
2614 	}
2615 	if (PageDoubleMap(page)) {
2616 		ret -= 1;
2617 		_total_mapcount -= HPAGE_PMD_NR;
2618 	}
2619 	mapcount = compound_mapcount(page);
2620 	ret += mapcount;
2621 	_total_mapcount += mapcount;
2622 	if (total_mapcount)
2623 		*total_mapcount = _total_mapcount;
2624 	return ret;
2625 }
2626 
2627 /* Racy check whether the huge page can be split */
2628 bool can_split_huge_page(struct page *page, int *pextra_pins)
2629 {
2630 	int extra_pins;
2631 
2632 	/* Additional pins from page cache */
2633 	if (PageAnon(page))
2634 		extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2635 	else
2636 		extra_pins = HPAGE_PMD_NR;
2637 	if (pextra_pins)
2638 		*pextra_pins = extra_pins;
2639 	return total_mapcount(page) == page_count(page) - extra_pins - 1;
2640 }
2641 
2642 /*
2643  * This function splits huge page into normal pages. @page can point to any
2644  * subpage of huge page to split. Split doesn't change the position of @page.
2645  *
2646  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2647  * The huge page must be locked.
2648  *
2649  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2650  *
2651  * Both head page and tail pages will inherit mapping, flags, and so on from
2652  * the hugepage.
2653  *
2654  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2655  * they are not mapped.
2656  *
2657  * Returns 0 if the hugepage is split successfully.
2658  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2659  * us.
2660  */
2661 int split_huge_page_to_list(struct page *page, struct list_head *list)
2662 {
2663 	struct page *head = compound_head(page);
2664 	struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2665 	struct anon_vma *anon_vma = NULL;
2666 	struct address_space *mapping = NULL;
2667 	int count, mapcount, extra_pins, ret;
2668 	bool mlocked;
2669 	unsigned long flags;
2670 	pgoff_t end;
2671 
2672 	VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2673 	VM_BUG_ON_PAGE(!PageLocked(page), page);
2674 	VM_BUG_ON_PAGE(!PageCompound(page), page);
2675 
2676 	if (PageWriteback(page))
2677 		return -EBUSY;
2678 
2679 	if (PageAnon(head)) {
2680 		/*
2681 		 * The caller does not necessarily hold an mmap_sem that would
2682 		 * prevent the anon_vma disappearing so we first we take a
2683 		 * reference to it and then lock the anon_vma for write. This
2684 		 * is similar to page_lock_anon_vma_read except the write lock
2685 		 * is taken to serialise against parallel split or collapse
2686 		 * operations.
2687 		 */
2688 		anon_vma = page_get_anon_vma(head);
2689 		if (!anon_vma) {
2690 			ret = -EBUSY;
2691 			goto out;
2692 		}
2693 		end = -1;
2694 		mapping = NULL;
2695 		anon_vma_lock_write(anon_vma);
2696 	} else {
2697 		mapping = head->mapping;
2698 
2699 		/* Truncated ? */
2700 		if (!mapping) {
2701 			ret = -EBUSY;
2702 			goto out;
2703 		}
2704 
2705 		anon_vma = NULL;
2706 		i_mmap_lock_read(mapping);
2707 
2708 		/*
2709 		 *__split_huge_page() may need to trim off pages beyond EOF:
2710 		 * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2711 		 * which cannot be nested inside the page tree lock. So note
2712 		 * end now: i_size itself may be changed at any moment, but
2713 		 * head page lock is good enough to serialize the trimming.
2714 		 */
2715 		end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2716 	}
2717 
2718 	/*
2719 	 * Racy check if we can split the page, before unmap_page() will
2720 	 * split PMDs
2721 	 */
2722 	if (!can_split_huge_page(head, &extra_pins)) {
2723 		ret = -EBUSY;
2724 		goto out_unlock;
2725 	}
2726 
2727 	mlocked = PageMlocked(page);
2728 	unmap_page(head);
2729 	VM_BUG_ON_PAGE(compound_mapcount(head), head);
2730 
2731 	/* Make sure the page is not on per-CPU pagevec as it takes pin */
2732 	if (mlocked)
2733 		lru_add_drain();
2734 
2735 	/* prevent PageLRU to go away from under us, and freeze lru stats */
2736 	spin_lock_irqsave(&pgdata->lru_lock, flags);
2737 
2738 	if (mapping) {
2739 		XA_STATE(xas, &mapping->i_pages, page_index(head));
2740 
2741 		/*
2742 		 * Check if the head page is present in page cache.
2743 		 * We assume all tail are present too, if head is there.
2744 		 */
2745 		xa_lock(&mapping->i_pages);
2746 		if (xas_load(&xas) != head)
2747 			goto fail;
2748 	}
2749 
2750 	/* Prevent deferred_split_scan() touching ->_refcount */
2751 	spin_lock(&pgdata->split_queue_lock);
2752 	count = page_count(head);
2753 	mapcount = total_mapcount(head);
2754 	if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2755 		if (!list_empty(page_deferred_list(head))) {
2756 			pgdata->split_queue_len--;
2757 			list_del(page_deferred_list(head));
2758 		}
2759 		if (mapping)
2760 			__dec_node_page_state(page, NR_SHMEM_THPS);
2761 		spin_unlock(&pgdata->split_queue_lock);
2762 		__split_huge_page(page, list, end, flags);
2763 		if (PageSwapCache(head)) {
2764 			swp_entry_t entry = { .val = page_private(head) };
2765 
2766 			ret = split_swap_cluster(entry);
2767 		} else
2768 			ret = 0;
2769 	} else {
2770 		if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2771 			pr_alert("total_mapcount: %u, page_count(): %u\n",
2772 					mapcount, count);
2773 			if (PageTail(page))
2774 				dump_page(head, NULL);
2775 			dump_page(page, "total_mapcount(head) > 0");
2776 			BUG();
2777 		}
2778 		spin_unlock(&pgdata->split_queue_lock);
2779 fail:		if (mapping)
2780 			xa_unlock(&mapping->i_pages);
2781 		spin_unlock_irqrestore(&pgdata->lru_lock, flags);
2782 		remap_page(head);
2783 		ret = -EBUSY;
2784 	}
2785 
2786 out_unlock:
2787 	if (anon_vma) {
2788 		anon_vma_unlock_write(anon_vma);
2789 		put_anon_vma(anon_vma);
2790 	}
2791 	if (mapping)
2792 		i_mmap_unlock_read(mapping);
2793 out:
2794 	count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2795 	return ret;
2796 }
2797 
2798 void free_transhuge_page(struct page *page)
2799 {
2800 	struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2801 	unsigned long flags;
2802 
2803 	spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2804 	if (!list_empty(page_deferred_list(page))) {
2805 		pgdata->split_queue_len--;
2806 		list_del(page_deferred_list(page));
2807 	}
2808 	spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2809 	free_compound_page(page);
2810 }
2811 
2812 void deferred_split_huge_page(struct page *page)
2813 {
2814 	struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2815 	unsigned long flags;
2816 
2817 	VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2818 
2819 	spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2820 	if (list_empty(page_deferred_list(page))) {
2821 		count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2822 		list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2823 		pgdata->split_queue_len++;
2824 	}
2825 	spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2826 }
2827 
2828 static unsigned long deferred_split_count(struct shrinker *shrink,
2829 		struct shrink_control *sc)
2830 {
2831 	struct pglist_data *pgdata = NODE_DATA(sc->nid);
2832 	return READ_ONCE(pgdata->split_queue_len);
2833 }
2834 
2835 static unsigned long deferred_split_scan(struct shrinker *shrink,
2836 		struct shrink_control *sc)
2837 {
2838 	struct pglist_data *pgdata = NODE_DATA(sc->nid);
2839 	unsigned long flags;
2840 	LIST_HEAD(list), *pos, *next;
2841 	struct page *page;
2842 	int split = 0;
2843 
2844 	spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2845 	/* Take pin on all head pages to avoid freeing them under us */
2846 	list_for_each_safe(pos, next, &pgdata->split_queue) {
2847 		page = list_entry((void *)pos, struct page, mapping);
2848 		page = compound_head(page);
2849 		if (get_page_unless_zero(page)) {
2850 			list_move(page_deferred_list(page), &list);
2851 		} else {
2852 			/* We lost race with put_compound_page() */
2853 			list_del_init(page_deferred_list(page));
2854 			pgdata->split_queue_len--;
2855 		}
2856 		if (!--sc->nr_to_scan)
2857 			break;
2858 	}
2859 	spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2860 
2861 	list_for_each_safe(pos, next, &list) {
2862 		page = list_entry((void *)pos, struct page, mapping);
2863 		if (!trylock_page(page))
2864 			goto next;
2865 		/* split_huge_page() removes page from list on success */
2866 		if (!split_huge_page(page))
2867 			split++;
2868 		unlock_page(page);
2869 next:
2870 		put_page(page);
2871 	}
2872 
2873 	spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2874 	list_splice_tail(&list, &pgdata->split_queue);
2875 	spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2876 
2877 	/*
2878 	 * Stop shrinker if we didn't split any page, but the queue is empty.
2879 	 * This can happen if pages were freed under us.
2880 	 */
2881 	if (!split && list_empty(&pgdata->split_queue))
2882 		return SHRINK_STOP;
2883 	return split;
2884 }
2885 
2886 static struct shrinker deferred_split_shrinker = {
2887 	.count_objects = deferred_split_count,
2888 	.scan_objects = deferred_split_scan,
2889 	.seeks = DEFAULT_SEEKS,
2890 	.flags = SHRINKER_NUMA_AWARE,
2891 };
2892 
2893 #ifdef CONFIG_DEBUG_FS
2894 static int split_huge_pages_set(void *data, u64 val)
2895 {
2896 	struct zone *zone;
2897 	struct page *page;
2898 	unsigned long pfn, max_zone_pfn;
2899 	unsigned long total = 0, split = 0;
2900 
2901 	if (val != 1)
2902 		return -EINVAL;
2903 
2904 	for_each_populated_zone(zone) {
2905 		max_zone_pfn = zone_end_pfn(zone);
2906 		for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2907 			if (!pfn_valid(pfn))
2908 				continue;
2909 
2910 			page = pfn_to_page(pfn);
2911 			if (!get_page_unless_zero(page))
2912 				continue;
2913 
2914 			if (zone != page_zone(page))
2915 				goto next;
2916 
2917 			if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2918 				goto next;
2919 
2920 			total++;
2921 			lock_page(page);
2922 			if (!split_huge_page(page))
2923 				split++;
2924 			unlock_page(page);
2925 next:
2926 			put_page(page);
2927 		}
2928 	}
2929 
2930 	pr_info("%lu of %lu THP split\n", split, total);
2931 
2932 	return 0;
2933 }
2934 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2935 		"%llu\n");
2936 
2937 static int __init split_huge_pages_debugfs(void)
2938 {
2939 	debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2940 			    &split_huge_pages_fops);
2941 	return 0;
2942 }
2943 late_initcall(split_huge_pages_debugfs);
2944 #endif
2945 
2946 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2947 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2948 		struct page *page)
2949 {
2950 	struct vm_area_struct *vma = pvmw->vma;
2951 	struct mm_struct *mm = vma->vm_mm;
2952 	unsigned long address = pvmw->address;
2953 	pmd_t pmdval;
2954 	swp_entry_t entry;
2955 	pmd_t pmdswp;
2956 
2957 	if (!(pvmw->pmd && !pvmw->pte))
2958 		return;
2959 
2960 	flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2961 	pmdval = *pvmw->pmd;
2962 	pmdp_invalidate(vma, address, pvmw->pmd);
2963 	if (pmd_dirty(pmdval))
2964 		set_page_dirty(page);
2965 	entry = make_migration_entry(page, pmd_write(pmdval));
2966 	pmdswp = swp_entry_to_pmd(entry);
2967 	if (pmd_soft_dirty(pmdval))
2968 		pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2969 	set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2970 	page_remove_rmap(page, true);
2971 	put_page(page);
2972 }
2973 
2974 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2975 {
2976 	struct vm_area_struct *vma = pvmw->vma;
2977 	struct mm_struct *mm = vma->vm_mm;
2978 	unsigned long address = pvmw->address;
2979 	unsigned long mmun_start = address & HPAGE_PMD_MASK;
2980 	pmd_t pmde;
2981 	swp_entry_t entry;
2982 
2983 	if (!(pvmw->pmd && !pvmw->pte))
2984 		return;
2985 
2986 	entry = pmd_to_swp_entry(*pvmw->pmd);
2987 	get_page(new);
2988 	pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2989 	if (pmd_swp_soft_dirty(*pvmw->pmd))
2990 		pmde = pmd_mksoft_dirty(pmde);
2991 	if (is_write_migration_entry(entry))
2992 		pmde = maybe_pmd_mkwrite(pmde, vma);
2993 
2994 	flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2995 	if (PageAnon(new))
2996 		page_add_anon_rmap(new, vma, mmun_start, true);
2997 	else
2998 		page_add_file_rmap(new, true);
2999 	set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
3000 	if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
3001 		mlock_vma_page(new);
3002 	update_mmu_cache_pmd(vma, address, pvmw->pmd);
3003 }
3004 #endif
3005