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Merge tag 'gcc-plugins-v4.12-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git...
[linux/fpc-iii.git] / mm / huge_memory.c
bloba84909cf20d36b3d84f00d8529127f78f6b5981d
1 /*
2 * Copyright (C) 2009 Red Hat, Inc.
3 *
4 * This work is licensed under the terms of the GNU GPL, version 2. See
5 * the COPYING file in the top-level directory.
6 */
7
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10 #include <linux/mm.h>
11 #include <linux/sched.h>
12 #include <linux/sched/coredump.h>
13 #include <linux/sched/numa_balancing.h>
14 #include <linux/highmem.h>
15 #include <linux/hugetlb.h>
16 #include <linux/mmu_notifier.h>
17 #include <linux/rmap.h>
18 #include <linux/swap.h>
19 #include <linux/shrinker.h>
20 #include <linux/mm_inline.h>
21 #include <linux/swapops.h>
22 #include <linux/dax.h>
23 #include <linux/khugepaged.h>
24 #include <linux/freezer.h>
25 #include <linux/pfn_t.h>
26 #include <linux/mman.h>
27 #include <linux/memremap.h>
28 #include <linux/pagemap.h>
29 #include <linux/debugfs.h>
30 #include <linux/migrate.h>
31 #include <linux/hashtable.h>
32 #include <linux/userfaultfd_k.h>
33 #include <linux/page_idle.h>
34 #include <linux/shmem_fs.h>
35
36 #include <asm/tlb.h>
37 #include <asm/pgalloc.h>
38 #include "internal.h"
39
40 /*
41 * By default transparent hugepage support is disabled in order that avoid
42 * to risk increase the memory footprint of applications without a guaranteed
43 * benefit. When transparent hugepage support is enabled, is for all mappings,
44 * and khugepaged scans all mappings.
45 * Defrag is invoked by khugepaged hugepage allocations and by page faults
46 * for all hugepage allocations.
47 */
48 unsigned long transparent_hugepage_flags __read_mostly =
49 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
50 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
51 #endif
52 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
53 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
54 #endif
55 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
56 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
57 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
58
59 static struct shrinker deferred_split_shrinker;
60
61 static atomic_t huge_zero_refcount;
62 struct page *huge_zero_page __read_mostly;
63
64 static struct page *get_huge_zero_page(void)
65 {
66 struct page *zero_page;
67 retry:
68 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
69 return READ_ONCE(huge_zero_page);
70
71 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
72 HPAGE_PMD_ORDER);
73 if (!zero_page) {
74 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
75 return NULL;
76 }
77 count_vm_event(THP_ZERO_PAGE_ALLOC);
78 preempt_disable();
79 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
80 preempt_enable();
81 __free_pages(zero_page, compound_order(zero_page));
82 goto retry;
83 }
84
85 /* We take additional reference here. It will be put back by shrinker */
86 atomic_set(&huge_zero_refcount, 2);
87 preempt_enable();
88 return READ_ONCE(huge_zero_page);
89 }
90
91 static void put_huge_zero_page(void)
92 {
93 /*
94 * Counter should never go to zero here. Only shrinker can put
95 * last reference.
96 */
97 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
98 }
99
100 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
101 {
102 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
103 return READ_ONCE(huge_zero_page);
104
105 if (!get_huge_zero_page())
106 return NULL;
107
108 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
109 put_huge_zero_page();
110
111 return READ_ONCE(huge_zero_page);
112 }
113
114 void mm_put_huge_zero_page(struct mm_struct *mm)
115 {
116 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
117 put_huge_zero_page();
118 }
119
120 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
121 struct shrink_control *sc)
122 {
123 /* we can free zero page only if last reference remains */
124 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
125 }
126
127 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
128 struct shrink_control *sc)
129 {
130 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
131 struct page *zero_page = xchg(&huge_zero_page, NULL);
132 BUG_ON(zero_page == NULL);
133 __free_pages(zero_page, compound_order(zero_page));
134 return HPAGE_PMD_NR;
135 }
136
137 return 0;
138 }
139
140 static struct shrinker huge_zero_page_shrinker = {
141 .count_objects = shrink_huge_zero_page_count,
142 .scan_objects = shrink_huge_zero_page_scan,
143 .seeks = DEFAULT_SEEKS,
144 };
145
146 #ifdef CONFIG_SYSFS
147 static ssize_t enabled_show(struct kobject *kobj,
148 struct kobj_attribute *attr, char *buf)
149 {
150 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
151 return sprintf(buf, "[always] madvise never\n");
152 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
153 return sprintf(buf, "always [madvise] never\n");
154 else
155 return sprintf(buf, "always madvise [never]\n");
156 }
157
158 static ssize_t enabled_store(struct kobject *kobj,
159 struct kobj_attribute *attr,
160 const char *buf, size_t count)
161 {
162 ssize_t ret = count;
163
164 if (!memcmp("always", buf,
165 min(sizeof("always")-1, count))) {
166 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
167 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
168 } else if (!memcmp("madvise", buf,
169 min(sizeof("madvise")-1, count))) {
170 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
171 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
172 } else if (!memcmp("never", buf,
173 min(sizeof("never")-1, count))) {
174 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
175 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
176 } else
177 ret = -EINVAL;
178
179 if (ret > 0) {
180 int err = start_stop_khugepaged();
181 if (err)
182 ret = err;
183 }
184 return ret;
185 }
186 static struct kobj_attribute enabled_attr =
187 __ATTR(enabled, 0644, enabled_show, enabled_store);
188
189 ssize_t single_hugepage_flag_show(struct kobject *kobj,
190 struct kobj_attribute *attr, char *buf,
191 enum transparent_hugepage_flag flag)
192 {
193 return sprintf(buf, "%d\n",
194 !!test_bit(flag, &transparent_hugepage_flags));
195 }
196
197 ssize_t single_hugepage_flag_store(struct kobject *kobj,
198 struct kobj_attribute *attr,
199 const char *buf, size_t count,
200 enum transparent_hugepage_flag flag)
201 {
202 unsigned long value;
203 int ret;
204
205 ret = kstrtoul(buf, 10, &value);
206 if (ret < 0)
207 return ret;
208 if (value > 1)
209 return -EINVAL;
210
211 if (value)
212 set_bit(flag, &transparent_hugepage_flags);
213 else
214 clear_bit(flag, &transparent_hugepage_flags);
215
216 return count;
217 }
218
219 static ssize_t defrag_show(struct kobject *kobj,
220 struct kobj_attribute *attr, char *buf)
221 {
222 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
223 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
224 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
225 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
226 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
227 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
228 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
229 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
230 return sprintf(buf, "always defer defer+madvise madvise [never]\n");
231 }
232
233 static ssize_t defrag_store(struct kobject *kobj,
234 struct kobj_attribute *attr,
235 const char *buf, size_t count)
236 {
237 if (!memcmp("always", buf,
238 min(sizeof("always")-1, count))) {
239 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
240 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
241 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
242 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
243 } else if (!memcmp("defer+madvise", buf,
244 min(sizeof("defer+madvise")-1, count))) {
245 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
246 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
247 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
248 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
249 } else if (!memcmp("defer", buf,
250 min(sizeof("defer")-1, count))) {
251 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
252 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
253 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
254 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
255 } else if (!memcmp("madvise", buf,
256 min(sizeof("madvise")-1, count))) {
257 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
258 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
259 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
260 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
261 } else if (!memcmp("never", buf,
262 min(sizeof("never")-1, count))) {
263 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
264 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
265 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
266 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
267 } else
268 return -EINVAL;
269
270 return count;
271 }
272 static struct kobj_attribute defrag_attr =
273 __ATTR(defrag, 0644, defrag_show, defrag_store);
274
275 static ssize_t use_zero_page_show(struct kobject *kobj,
276 struct kobj_attribute *attr, char *buf)
277 {
278 return single_hugepage_flag_show(kobj, attr, buf,
279 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
280 }
281 static ssize_t use_zero_page_store(struct kobject *kobj,
282 struct kobj_attribute *attr, const char *buf, size_t count)
283 {
284 return single_hugepage_flag_store(kobj, attr, buf, count,
285 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
286 }
287 static struct kobj_attribute use_zero_page_attr =
288 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
289
290 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
291 struct kobj_attribute *attr, char *buf)
292 {
293 return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
294 }
295 static struct kobj_attribute hpage_pmd_size_attr =
296 __ATTR_RO(hpage_pmd_size);
297
298 #ifdef CONFIG_DEBUG_VM
299 static ssize_t debug_cow_show(struct kobject *kobj,
300 struct kobj_attribute *attr, char *buf)
301 {
302 return single_hugepage_flag_show(kobj, attr, buf,
303 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
304 }
305 static ssize_t debug_cow_store(struct kobject *kobj,
306 struct kobj_attribute *attr,
307 const char *buf, size_t count)
308 {
309 return single_hugepage_flag_store(kobj, attr, buf, count,
310 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
311 }
312 static struct kobj_attribute debug_cow_attr =
313 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
314 #endif /* CONFIG_DEBUG_VM */
315
316 static struct attribute *hugepage_attr[] = {
317 &enabled_attr.attr,
318 &defrag_attr.attr,
319 &use_zero_page_attr.attr,
320 &hpage_pmd_size_attr.attr,
321 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
322 &shmem_enabled_attr.attr,
323 #endif
324 #ifdef CONFIG_DEBUG_VM
325 &debug_cow_attr.attr,
326 #endif
327 NULL,
328 };
329
330 static struct attribute_group hugepage_attr_group = {
331 .attrs = hugepage_attr,
332 };
333
334 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
335 {
336 int err;
337
338 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
339 if (unlikely(!*hugepage_kobj)) {
340 pr_err("failed to create transparent hugepage kobject\n");
341 return -ENOMEM;
342 }
343
344 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
345 if (err) {
346 pr_err("failed to register transparent hugepage group\n");
347 goto delete_obj;
348 }
349
350 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
351 if (err) {
352 pr_err("failed to register transparent hugepage group\n");
353 goto remove_hp_group;
354 }
355
356 return 0;
357
358 remove_hp_group:
359 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
360 delete_obj:
361 kobject_put(*hugepage_kobj);
362 return err;
363 }
364
365 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
366 {
367 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
368 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
369 kobject_put(hugepage_kobj);
370 }
371 #else
372 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
373 {
374 return 0;
375 }
376
377 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
378 {
379 }
380 #endif /* CONFIG_SYSFS */
381
382 static int __init hugepage_init(void)
383 {
384 int err;
385 struct kobject *hugepage_kobj;
386
387 if (!has_transparent_hugepage()) {
388 transparent_hugepage_flags = 0;
389 return -EINVAL;
390 }
391
392 /*
393 * hugepages can't be allocated by the buddy allocator
394 */
395 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
396 /*
397 * we use page->mapping and page->index in second tail page
398 * as list_head: assuming THP order >= 2
399 */
400 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
401
402 err = hugepage_init_sysfs(&hugepage_kobj);
403 if (err)
404 goto err_sysfs;
405
406 err = khugepaged_init();
407 if (err)
408 goto err_slab;
409
410 err = register_shrinker(&huge_zero_page_shrinker);
411 if (err)
412 goto err_hzp_shrinker;
413 err = register_shrinker(&deferred_split_shrinker);
414 if (err)
415 goto err_split_shrinker;
416
417 /*
418 * By default disable transparent hugepages on smaller systems,
419 * where the extra memory used could hurt more than TLB overhead
420 * is likely to save. The admin can still enable it through /sys.
421 */
422 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
423 transparent_hugepage_flags = 0;
424 return 0;
425 }
426
427 err = start_stop_khugepaged();
428 if (err)
429 goto err_khugepaged;
430
431 return 0;
432 err_khugepaged:
433 unregister_shrinker(&deferred_split_shrinker);
434 err_split_shrinker:
435 unregister_shrinker(&huge_zero_page_shrinker);
436 err_hzp_shrinker:
437 khugepaged_destroy();
438 err_slab:
439 hugepage_exit_sysfs(hugepage_kobj);
440 err_sysfs:
441 return err;
442 }
443 subsys_initcall(hugepage_init);
444
445 static int __init setup_transparent_hugepage(char *str)
446 {
447 int ret = 0;
448 if (!str)
449 goto out;
450 if (!strcmp(str, "always")) {
451 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
452 &transparent_hugepage_flags);
453 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
454 &transparent_hugepage_flags);
455 ret = 1;
456 } else if (!strcmp(str, "madvise")) {
457 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
458 &transparent_hugepage_flags);
459 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
460 &transparent_hugepage_flags);
461 ret = 1;
462 } else if (!strcmp(str, "never")) {
463 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
464 &transparent_hugepage_flags);
465 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
466 &transparent_hugepage_flags);
467 ret = 1;
468 }
469 out:
470 if (!ret)
471 pr_warn("transparent_hugepage= cannot parse, ignored\n");
472 return ret;
473 }
474 __setup("transparent_hugepage=", setup_transparent_hugepage);
475
476 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
477 {
478 if (likely(vma->vm_flags & VM_WRITE))
479 pmd = pmd_mkwrite(pmd);
480 return pmd;
481 }
482
483 static inline struct list_head *page_deferred_list(struct page *page)
484 {
485 /*
486 * ->lru in the tail pages is occupied by compound_head.
487 * Let's use ->mapping + ->index in the second tail page as list_head.
488 */
489 return (struct list_head *)&page[2].mapping;
490 }
491
492 void prep_transhuge_page(struct page *page)
493 {
494 /*
495 * we use page->mapping and page->indexlru in second tail page
496 * as list_head: assuming THP order >= 2
497 */
498
499 INIT_LIST_HEAD(page_deferred_list(page));
500 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
501 }
502
503 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
504 loff_t off, unsigned long flags, unsigned long size)
505 {
506 unsigned long addr;
507 loff_t off_end = off + len;
508 loff_t off_align = round_up(off, size);
509 unsigned long len_pad;
510
511 if (off_end <= off_align || (off_end - off_align) < size)
512 return 0;
513
514 len_pad = len + size;
515 if (len_pad < len || (off + len_pad) < off)
516 return 0;
517
518 addr = current->mm->get_unmapped_area(filp, 0, len_pad,
519 off >> PAGE_SHIFT, flags);
520 if (IS_ERR_VALUE(addr))
521 return 0;
522
523 addr += (off - addr) & (size - 1);
524 return addr;
525 }
526
527 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
528 unsigned long len, unsigned long pgoff, unsigned long flags)
529 {
530 loff_t off = (loff_t)pgoff << PAGE_SHIFT;
531
532 if (addr)
533 goto out;
534 if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
535 goto out;
536
537 addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
538 if (addr)
539 return addr;
540
541 out:
542 return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
543 }
544 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
545
546 static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,
547 gfp_t gfp)
548 {
549 struct vm_area_struct *vma = vmf->vma;
550 struct mem_cgroup *memcg;
551 pgtable_t pgtable;
552 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
553
554 VM_BUG_ON_PAGE(!PageCompound(page), page);
555
556 if (mem_cgroup_try_charge(page, vma->vm_mm, gfp, &memcg, true)) {
557 put_page(page);
558 count_vm_event(THP_FAULT_FALLBACK);
559 return VM_FAULT_FALLBACK;
560 }
561
562 pgtable = pte_alloc_one(vma->vm_mm, haddr);
563 if (unlikely(!pgtable)) {
564 mem_cgroup_cancel_charge(page, memcg, true);
565 put_page(page);
566 return VM_FAULT_OOM;
567 }
568
569 clear_huge_page(page, haddr, HPAGE_PMD_NR);
570 /*
571 * The memory barrier inside __SetPageUptodate makes sure that
572 * clear_huge_page writes become visible before the set_pmd_at()
573 * write.
574 */
575 __SetPageUptodate(page);
576
577 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
578 if (unlikely(!pmd_none(*vmf->pmd))) {
579 spin_unlock(vmf->ptl);
580 mem_cgroup_cancel_charge(page, memcg, true);
581 put_page(page);
582 pte_free(vma->vm_mm, pgtable);
583 } else {
584 pmd_t entry;
585
586 /* Deliver the page fault to userland */
587 if (userfaultfd_missing(vma)) {
588 int ret;
589
590 spin_unlock(vmf->ptl);
591 mem_cgroup_cancel_charge(page, memcg, true);
592 put_page(page);
593 pte_free(vma->vm_mm, pgtable);
594 ret = handle_userfault(vmf, VM_UFFD_MISSING);
595 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
596 return ret;
597 }
598
599 entry = mk_huge_pmd(page, vma->vm_page_prot);
600 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
601 page_add_new_anon_rmap(page, vma, haddr, true);
602 mem_cgroup_commit_charge(page, memcg, false, true);
603 lru_cache_add_active_or_unevictable(page, vma);
604 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
605 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
606 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
607 atomic_long_inc(&vma->vm_mm->nr_ptes);
608 spin_unlock(vmf->ptl);
609 count_vm_event(THP_FAULT_ALLOC);
610 }
611
612 return 0;
613 }
614
615 /*
616 * always: directly stall for all thp allocations
617 * defer: wake kswapd and fail if not immediately available
618 * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
619 * fail if not immediately available
620 * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
621 * available
622 * never: never stall for any thp allocation
623 */
624 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
625 {
626 const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
627
628 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
629 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
630 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
631 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
632 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
633 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
634 __GFP_KSWAPD_RECLAIM);
635 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
636 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
637 0);
638 return GFP_TRANSHUGE_LIGHT;
639 }
640
641 /* Caller must hold page table lock. */
642 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
643 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
644 struct page *zero_page)
645 {
646 pmd_t entry;
647 if (!pmd_none(*pmd))
648 return false;
649 entry = mk_pmd(zero_page, vma->vm_page_prot);
650 entry = pmd_mkhuge(entry);
651 if (pgtable)
652 pgtable_trans_huge_deposit(mm, pmd, pgtable);
653 set_pmd_at(mm, haddr, pmd, entry);
654 atomic_long_inc(&mm->nr_ptes);
655 return true;
656 }
657
658 int do_huge_pmd_anonymous_page(struct vm_fault *vmf)
659 {
660 struct vm_area_struct *vma = vmf->vma;
661 gfp_t gfp;
662 struct page *page;
663 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
664
665 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
666 return VM_FAULT_FALLBACK;
667 if (unlikely(anon_vma_prepare(vma)))
668 return VM_FAULT_OOM;
669 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
670 return VM_FAULT_OOM;
671 if (!(vmf->flags & FAULT_FLAG_WRITE) &&
672 !mm_forbids_zeropage(vma->vm_mm) &&
673 transparent_hugepage_use_zero_page()) {
674 pgtable_t pgtable;
675 struct page *zero_page;
676 bool set;
677 int ret;
678 pgtable = pte_alloc_one(vma->vm_mm, haddr);
679 if (unlikely(!pgtable))
680 return VM_FAULT_OOM;
681 zero_page = mm_get_huge_zero_page(vma->vm_mm);
682 if (unlikely(!zero_page)) {
683 pte_free(vma->vm_mm, pgtable);
684 count_vm_event(THP_FAULT_FALLBACK);
685 return VM_FAULT_FALLBACK;
686 }
687 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
688 ret = 0;
689 set = false;
690 if (pmd_none(*vmf->pmd)) {
691 if (userfaultfd_missing(vma)) {
692 spin_unlock(vmf->ptl);
693 ret = handle_userfault(vmf, VM_UFFD_MISSING);
694 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
695 } else {
696 set_huge_zero_page(pgtable, vma->vm_mm, vma,
697 haddr, vmf->pmd, zero_page);
698 spin_unlock(vmf->ptl);
699 set = true;
700 }
701 } else
702 spin_unlock(vmf->ptl);
703 if (!set)
704 pte_free(vma->vm_mm, pgtable);
705 return ret;
706 }
707 gfp = alloc_hugepage_direct_gfpmask(vma);
708 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
709 if (unlikely(!page)) {
710 count_vm_event(THP_FAULT_FALLBACK);
711 return VM_FAULT_FALLBACK;
712 }
713 prep_transhuge_page(page);
714 return __do_huge_pmd_anonymous_page(vmf, page, gfp);
715 }
716
717 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
718 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
719 pgtable_t pgtable)
720 {
721 struct mm_struct *mm = vma->vm_mm;
722 pmd_t entry;
723 spinlock_t *ptl;
724
725 ptl = pmd_lock(mm, pmd);
726 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
727 if (pfn_t_devmap(pfn))
728 entry = pmd_mkdevmap(entry);
729 if (write) {
730 entry = pmd_mkyoung(pmd_mkdirty(entry));
731 entry = maybe_pmd_mkwrite(entry, vma);
732 }
733
734 if (pgtable) {
735 pgtable_trans_huge_deposit(mm, pmd, pgtable);
736 atomic_long_inc(&mm->nr_ptes);
737 }
738
739 set_pmd_at(mm, addr, pmd, entry);
740 update_mmu_cache_pmd(vma, addr, pmd);
741 spin_unlock(ptl);
742 }
743
744 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
745 pmd_t *pmd, pfn_t pfn, bool write)
746 {
747 pgprot_t pgprot = vma->vm_page_prot;
748 pgtable_t pgtable = NULL;
749 /*
750 * If we had pmd_special, we could avoid all these restrictions,
751 * but we need to be consistent with PTEs and architectures that
752 * can't support a 'special' bit.
753 */
754 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
755 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
756 (VM_PFNMAP|VM_MIXEDMAP));
757 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
758 BUG_ON(!pfn_t_devmap(pfn));
759
760 if (addr < vma->vm_start || addr >= vma->vm_end)
761 return VM_FAULT_SIGBUS;
762
763 if (arch_needs_pgtable_deposit()) {
764 pgtable = pte_alloc_one(vma->vm_mm, addr);
765 if (!pgtable)
766 return VM_FAULT_OOM;
767 }
768
769 track_pfn_insert(vma, &pgprot, pfn);
770
771 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
772 return VM_FAULT_NOPAGE;
773 }
774 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
775
776 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
777 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
778 {
779 if (likely(vma->vm_flags & VM_WRITE))
780 pud = pud_mkwrite(pud);
781 return pud;
782 }
783
784 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
785 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
786 {
787 struct mm_struct *mm = vma->vm_mm;
788 pud_t entry;
789 spinlock_t *ptl;
790
791 ptl = pud_lock(mm, pud);
792 entry = pud_mkhuge(pfn_t_pud(pfn, prot));
793 if (pfn_t_devmap(pfn))
794 entry = pud_mkdevmap(entry);
795 if (write) {
796 entry = pud_mkyoung(pud_mkdirty(entry));
797 entry = maybe_pud_mkwrite(entry, vma);
798 }
799 set_pud_at(mm, addr, pud, entry);
800 update_mmu_cache_pud(vma, addr, pud);
801 spin_unlock(ptl);
802 }
803
804 int vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
805 pud_t *pud, pfn_t pfn, bool write)
806 {
807 pgprot_t pgprot = vma->vm_page_prot;
808 /*
809 * If we had pud_special, we could avoid all these restrictions,
810 * but we need to be consistent with PTEs and architectures that
811 * can't support a 'special' bit.
812 */
813 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
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 BUG_ON(!pfn_t_devmap(pfn));
818
819 if (addr < vma->vm_start || addr >= vma->vm_end)
820 return VM_FAULT_SIGBUS;
821
822 track_pfn_insert(vma, &pgprot, pfn);
823
824 insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
825 return VM_FAULT_NOPAGE;
826 }
827 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
828 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
829
830 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
831 pmd_t *pmd)
832 {
833 pmd_t _pmd;
834
835 /*
836 * We should set the dirty bit only for FOLL_WRITE but for now
837 * the dirty bit in the pmd is meaningless. And if the dirty
838 * bit will become meaningful and we'll only set it with
839 * FOLL_WRITE, an atomic set_bit will be required on the pmd to
840 * set the young bit, instead of the current set_pmd_at.
841 */
842 _pmd = pmd_mkyoung(pmd_mkdirty(*pmd));
843 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
844 pmd, _pmd, 1))
845 update_mmu_cache_pmd(vma, addr, pmd);
846 }
847
848 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
849 pmd_t *pmd, int flags)
850 {
851 unsigned long pfn = pmd_pfn(*pmd);
852 struct mm_struct *mm = vma->vm_mm;
853 struct dev_pagemap *pgmap;
854 struct page *page;
855
856 assert_spin_locked(pmd_lockptr(mm, pmd));
857
858 /*
859 * When we COW a devmap PMD entry, we split it into PTEs, so we should
860 * not be in this function with `flags & FOLL_COW` set.
861 */
862 WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
863
864 if (flags & FOLL_WRITE && !pmd_write(*pmd))
865 return NULL;
866
867 if (pmd_present(*pmd) && pmd_devmap(*pmd))
868 /* pass */;
869 else
870 return NULL;
871
872 if (flags & FOLL_TOUCH)
873 touch_pmd(vma, addr, pmd);
874
875 /*
876 * device mapped pages can only be returned if the
877 * caller will manage the page reference count.
878 */
879 if (!(flags & FOLL_GET))
880 return ERR_PTR(-EEXIST);
881
882 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
883 pgmap = get_dev_pagemap(pfn, NULL);
884 if (!pgmap)
885 return ERR_PTR(-EFAULT);
886 page = pfn_to_page(pfn);
887 get_page(page);
888 put_dev_pagemap(pgmap);
889
890 return page;
891 }
892
893 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
894 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
895 struct vm_area_struct *vma)
896 {
897 spinlock_t *dst_ptl, *src_ptl;
898 struct page *src_page;
899 pmd_t pmd;
900 pgtable_t pgtable = NULL;
901 int ret = -ENOMEM;
902
903 /* Skip if can be re-fill on fault */
904 if (!vma_is_anonymous(vma))
905 return 0;
906
907 pgtable = pte_alloc_one(dst_mm, addr);
908 if (unlikely(!pgtable))
909 goto out;
910
911 dst_ptl = pmd_lock(dst_mm, dst_pmd);
912 src_ptl = pmd_lockptr(src_mm, src_pmd);
913 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
914
915 ret = -EAGAIN;
916 pmd = *src_pmd;
917 if (unlikely(!pmd_trans_huge(pmd))) {
918 pte_free(dst_mm, pgtable);
919 goto out_unlock;
920 }
921 /*
922 * When page table lock is held, the huge zero pmd should not be
923 * under splitting since we don't split the page itself, only pmd to
924 * a page table.
925 */
926 if (is_huge_zero_pmd(pmd)) {
927 struct page *zero_page;
928 /*
929 * get_huge_zero_page() will never allocate a new page here,
930 * since we already have a zero page to copy. It just takes a
931 * reference.
932 */
933 zero_page = mm_get_huge_zero_page(dst_mm);
934 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
935 zero_page);
936 ret = 0;
937 goto out_unlock;
938 }
939
940 src_page = pmd_page(pmd);
941 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
942 get_page(src_page);
943 page_dup_rmap(src_page, true);
944 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
945 atomic_long_inc(&dst_mm->nr_ptes);
946 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
947
948 pmdp_set_wrprotect(src_mm, addr, src_pmd);
949 pmd = pmd_mkold(pmd_wrprotect(pmd));
950 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
951
952 ret = 0;
953 out_unlock:
954 spin_unlock(src_ptl);
955 spin_unlock(dst_ptl);
956 out:
957 return ret;
958 }
959
960 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
961 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
962 pud_t *pud)
963 {
964 pud_t _pud;
965
966 /*
967 * We should set the dirty bit only for FOLL_WRITE but for now
968 * the dirty bit in the pud is meaningless. And if the dirty
969 * bit will become meaningful and we'll only set it with
970 * FOLL_WRITE, an atomic set_bit will be required on the pud to
971 * set the young bit, instead of the current set_pud_at.
972 */
973 _pud = pud_mkyoung(pud_mkdirty(*pud));
974 if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
975 pud, _pud, 1))
976 update_mmu_cache_pud(vma, addr, pud);
977 }
978
979 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
980 pud_t *pud, int flags)
981 {
982 unsigned long pfn = pud_pfn(*pud);
983 struct mm_struct *mm = vma->vm_mm;
984 struct dev_pagemap *pgmap;
985 struct page *page;
986
987 assert_spin_locked(pud_lockptr(mm, pud));
988
989 if (flags & FOLL_WRITE && !pud_write(*pud))
990 return NULL;
991
992 if (pud_present(*pud) && pud_devmap(*pud))
993 /* pass */;
994 else
995 return NULL;
996
997 if (flags & FOLL_TOUCH)
998 touch_pud(vma, addr, pud);
999
1000 /*
1001 * device mapped pages can only be returned if the
1002 * caller will manage the page reference count.
1003 */
1004 if (!(flags & FOLL_GET))
1005 return ERR_PTR(-EEXIST);
1006
1007 pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1008 pgmap = get_dev_pagemap(pfn, NULL);
1009 if (!pgmap)
1010 return ERR_PTR(-EFAULT);
1011 page = pfn_to_page(pfn);
1012 get_page(page);
1013 put_dev_pagemap(pgmap);
1014
1015 return page;
1016 }
1017
1018 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1019 pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1020 struct vm_area_struct *vma)
1021 {
1022 spinlock_t *dst_ptl, *src_ptl;
1023 pud_t pud;
1024 int ret;
1025
1026 dst_ptl = pud_lock(dst_mm, dst_pud);
1027 src_ptl = pud_lockptr(src_mm, src_pud);
1028 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1029
1030 ret = -EAGAIN;
1031 pud = *src_pud;
1032 if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1033 goto out_unlock;
1034
1035 /*
1036 * When page table lock is held, the huge zero pud should not be
1037 * under splitting since we don't split the page itself, only pud to
1038 * a page table.
1039 */
1040 if (is_huge_zero_pud(pud)) {
1041 /* No huge zero pud yet */
1042 }
1043
1044 pudp_set_wrprotect(src_mm, addr, src_pud);
1045 pud = pud_mkold(pud_wrprotect(pud));
1046 set_pud_at(dst_mm, addr, dst_pud, pud);
1047
1048 ret = 0;
1049 out_unlock:
1050 spin_unlock(src_ptl);
1051 spin_unlock(dst_ptl);
1052 return ret;
1053 }
1054
1055 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1056 {
1057 pud_t entry;
1058 unsigned long haddr;
1059 bool write = vmf->flags & FAULT_FLAG_WRITE;
1060
1061 vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1062 if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1063 goto unlock;
1064
1065 entry = pud_mkyoung(orig_pud);
1066 if (write)
1067 entry = pud_mkdirty(entry);
1068 haddr = vmf->address & HPAGE_PUD_MASK;
1069 if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1070 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1071
1072 unlock:
1073 spin_unlock(vmf->ptl);
1074 }
1075 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1076
1077 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1078 {
1079 pmd_t entry;
1080 unsigned long haddr;
1081 bool write = vmf->flags & FAULT_FLAG_WRITE;
1082
1083 vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1084 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1085 goto unlock;
1086
1087 entry = pmd_mkyoung(orig_pmd);
1088 if (write)
1089 entry = pmd_mkdirty(entry);
1090 haddr = vmf->address & HPAGE_PMD_MASK;
1091 if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1092 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1093
1094 unlock:
1095 spin_unlock(vmf->ptl);
1096 }
1097
1098 static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,
1099 struct page *page)
1100 {
1101 struct vm_area_struct *vma = vmf->vma;
1102 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1103 struct mem_cgroup *memcg;
1104 pgtable_t pgtable;
1105 pmd_t _pmd;
1106 int ret = 0, i;
1107 struct page **pages;
1108 unsigned long mmun_start; /* For mmu_notifiers */
1109 unsigned long mmun_end; /* For mmu_notifiers */
1110
1111 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1112 GFP_KERNEL);
1113 if (unlikely(!pages)) {
1114 ret |= VM_FAULT_OOM;
1115 goto out;
1116 }
1117
1118 for (i = 0; i < HPAGE_PMD_NR; i++) {
1119 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1120 vmf->address, page_to_nid(page));
1121 if (unlikely(!pages[i] ||
1122 mem_cgroup_try_charge(pages[i], vma->vm_mm,
1123 GFP_KERNEL, &memcg, false))) {
1124 if (pages[i])
1125 put_page(pages[i]);
1126 while (--i >= 0) {
1127 memcg = (void *)page_private(pages[i]);
1128 set_page_private(pages[i], 0);
1129 mem_cgroup_cancel_charge(pages[i], memcg,
1130 false);
1131 put_page(pages[i]);
1132 }
1133 kfree(pages);
1134 ret |= VM_FAULT_OOM;
1135 goto out;
1136 }
1137 set_page_private(pages[i], (unsigned long)memcg);
1138 }
1139
1140 for (i = 0; i < HPAGE_PMD_NR; i++) {
1141 copy_user_highpage(pages[i], page + i,
1142 haddr + PAGE_SIZE * i, vma);
1143 __SetPageUptodate(pages[i]);
1144 cond_resched();
1145 }
1146
1147 mmun_start = haddr;
1148 mmun_end = haddr + HPAGE_PMD_SIZE;
1149 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1150
1151 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1152 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1153 goto out_free_pages;
1154 VM_BUG_ON_PAGE(!PageHead(page), page);
1155
1156 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1157 /* leave pmd empty until pte is filled */
1158
1159 pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1160 pmd_populate(vma->vm_mm, &_pmd, pgtable);
1161
1162 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1163 pte_t entry;
1164 entry = mk_pte(pages[i], vma->vm_page_prot);
1165 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1166 memcg = (void *)page_private(pages[i]);
1167 set_page_private(pages[i], 0);
1168 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1169 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1170 lru_cache_add_active_or_unevictable(pages[i], vma);
1171 vmf->pte = pte_offset_map(&_pmd, haddr);
1172 VM_BUG_ON(!pte_none(*vmf->pte));
1173 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1174 pte_unmap(vmf->pte);
1175 }
1176 kfree(pages);
1177
1178 smp_wmb(); /* make pte visible before pmd */
1179 pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1180 page_remove_rmap(page, true);
1181 spin_unlock(vmf->ptl);
1182
1183 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1184
1185 ret |= VM_FAULT_WRITE;
1186 put_page(page);
1187
1188 out:
1189 return ret;
1190
1191 out_free_pages:
1192 spin_unlock(vmf->ptl);
1193 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1194 for (i = 0; i < HPAGE_PMD_NR; i++) {
1195 memcg = (void *)page_private(pages[i]);
1196 set_page_private(pages[i], 0);
1197 mem_cgroup_cancel_charge(pages[i], memcg, false);
1198 put_page(pages[i]);
1199 }
1200 kfree(pages);
1201 goto out;
1202 }
1203
1204 int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1205 {
1206 struct vm_area_struct *vma = vmf->vma;
1207 struct page *page = NULL, *new_page;
1208 struct mem_cgroup *memcg;
1209 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1210 unsigned long mmun_start; /* For mmu_notifiers */
1211 unsigned long mmun_end; /* For mmu_notifiers */
1212 gfp_t huge_gfp; /* for allocation and charge */
1213 int ret = 0;
1214
1215 vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1216 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1217 if (is_huge_zero_pmd(orig_pmd))
1218 goto alloc;
1219 spin_lock(vmf->ptl);
1220 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1221 goto out_unlock;
1222
1223 page = pmd_page(orig_pmd);
1224 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1225 /*
1226 * We can only reuse the page if nobody else maps the huge page or it's
1227 * part.
1228 */
1229 if (page_trans_huge_mapcount(page, NULL) == 1) {
1230 pmd_t entry;
1231 entry = pmd_mkyoung(orig_pmd);
1232 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1233 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
1234 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1235 ret |= VM_FAULT_WRITE;
1236 goto out_unlock;
1237 }
1238 get_page(page);
1239 spin_unlock(vmf->ptl);
1240 alloc:
1241 if (transparent_hugepage_enabled(vma) &&
1242 !transparent_hugepage_debug_cow()) {
1243 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1244 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1245 } else
1246 new_page = NULL;
1247
1248 if (likely(new_page)) {
1249 prep_transhuge_page(new_page);
1250 } else {
1251 if (!page) {
1252 split_huge_pmd(vma, vmf->pmd, vmf->address);
1253 ret |= VM_FAULT_FALLBACK;
1254 } else {
1255 ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1256 if (ret & VM_FAULT_OOM) {
1257 split_huge_pmd(vma, vmf->pmd, vmf->address);
1258 ret |= VM_FAULT_FALLBACK;
1259 }
1260 put_page(page);
1261 }
1262 count_vm_event(THP_FAULT_FALLBACK);
1263 goto out;
1264 }
1265
1266 if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
1267 huge_gfp, &memcg, true))) {
1268 put_page(new_page);
1269 split_huge_pmd(vma, vmf->pmd, vmf->address);
1270 if (page)
1271 put_page(page);
1272 ret |= VM_FAULT_FALLBACK;
1273 count_vm_event(THP_FAULT_FALLBACK);
1274 goto out;
1275 }
1276
1277 count_vm_event(THP_FAULT_ALLOC);
1278
1279 if (!page)
1280 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1281 else
1282 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1283 __SetPageUptodate(new_page);
1284
1285 mmun_start = haddr;
1286 mmun_end = haddr + HPAGE_PMD_SIZE;
1287 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1288
1289 spin_lock(vmf->ptl);
1290 if (page)
1291 put_page(page);
1292 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1293 spin_unlock(vmf->ptl);
1294 mem_cgroup_cancel_charge(new_page, memcg, true);
1295 put_page(new_page);
1296 goto out_mn;
1297 } else {
1298 pmd_t entry;
1299 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1300 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1301 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1302 page_add_new_anon_rmap(new_page, vma, haddr, true);
1303 mem_cgroup_commit_charge(new_page, memcg, false, true);
1304 lru_cache_add_active_or_unevictable(new_page, vma);
1305 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1306 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1307 if (!page) {
1308 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1309 } else {
1310 VM_BUG_ON_PAGE(!PageHead(page), page);
1311 page_remove_rmap(page, true);
1312 put_page(page);
1313 }
1314 ret |= VM_FAULT_WRITE;
1315 }
1316 spin_unlock(vmf->ptl);
1317 out_mn:
1318 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1319 out:
1320 return ret;
1321 out_unlock:
1322 spin_unlock(vmf->ptl);
1323 return ret;
1324 }
1325
1326 /*
1327 * FOLL_FORCE can write to even unwritable pmd's, but only
1328 * after we've gone through a COW cycle and they are dirty.
1329 */
1330 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1331 {
1332 return pmd_write(pmd) ||
1333 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1334 }
1335
1336 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1337 unsigned long addr,
1338 pmd_t *pmd,
1339 unsigned int flags)
1340 {
1341 struct mm_struct *mm = vma->vm_mm;
1342 struct page *page = NULL;
1343
1344 assert_spin_locked(pmd_lockptr(mm, pmd));
1345
1346 if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1347 goto out;
1348
1349 /* Avoid dumping huge zero page */
1350 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1351 return ERR_PTR(-EFAULT);
1352
1353 /* Full NUMA hinting faults to serialise migration in fault paths */
1354 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1355 goto out;
1356
1357 page = pmd_page(*pmd);
1358 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1359 if (flags & FOLL_TOUCH)
1360 touch_pmd(vma, addr, pmd);
1361 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1362 /*
1363 * We don't mlock() pte-mapped THPs. This way we can avoid
1364 * leaking mlocked pages into non-VM_LOCKED VMAs.
1365 *
1366 * For anon THP:
1367 *
1368 * In most cases the pmd is the only mapping of the page as we
1369 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1370 * writable private mappings in populate_vma_page_range().
1371 *
1372 * The only scenario when we have the page shared here is if we
1373 * mlocking read-only mapping shared over fork(). We skip
1374 * mlocking such pages.
1375 *
1376 * For file THP:
1377 *
1378 * We can expect PageDoubleMap() to be stable under page lock:
1379 * for file pages we set it in page_add_file_rmap(), which
1380 * requires page to be locked.
1381 */
1382
1383 if (PageAnon(page) && compound_mapcount(page) != 1)
1384 goto skip_mlock;
1385 if (PageDoubleMap(page) || !page->mapping)
1386 goto skip_mlock;
1387 if (!trylock_page(page))
1388 goto skip_mlock;
1389 lru_add_drain();
1390 if (page->mapping && !PageDoubleMap(page))
1391 mlock_vma_page(page);
1392 unlock_page(page);
1393 }
1394 skip_mlock:
1395 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1396 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1397 if (flags & FOLL_GET)
1398 get_page(page);
1399
1400 out:
1401 return page;
1402 }
1403
1404 /* NUMA hinting page fault entry point for trans huge pmds */
1405 int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1406 {
1407 struct vm_area_struct *vma = vmf->vma;
1408 struct anon_vma *anon_vma = NULL;
1409 struct page *page;
1410 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1411 int page_nid = -1, this_nid = numa_node_id();
1412 int target_nid, last_cpupid = -1;
1413 bool page_locked;
1414 bool migrated = false;
1415 bool was_writable;
1416 int flags = 0;
1417
1418 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1419 if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1420 goto out_unlock;
1421
1422 /*
1423 * If there are potential migrations, wait for completion and retry
1424 * without disrupting NUMA hinting information. Do not relock and
1425 * check_same as the page may no longer be mapped.
1426 */
1427 if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1428 page = pmd_page(*vmf->pmd);
1429 spin_unlock(vmf->ptl);
1430 wait_on_page_locked(page);
1431 goto out;
1432 }
1433
1434 page = pmd_page(pmd);
1435 BUG_ON(is_huge_zero_page(page));
1436 page_nid = page_to_nid(page);
1437 last_cpupid = page_cpupid_last(page);
1438 count_vm_numa_event(NUMA_HINT_FAULTS);
1439 if (page_nid == this_nid) {
1440 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1441 flags |= TNF_FAULT_LOCAL;
1442 }
1443
1444 /* See similar comment in do_numa_page for explanation */
1445 if (!pmd_savedwrite(pmd))
1446 flags |= TNF_NO_GROUP;
1447
1448 /*
1449 * Acquire the page lock to serialise THP migrations but avoid dropping
1450 * page_table_lock if at all possible
1451 */
1452 page_locked = trylock_page(page);
1453 target_nid = mpol_misplaced(page, vma, haddr);
1454 if (target_nid == -1) {
1455 /* If the page was locked, there are no parallel migrations */
1456 if (page_locked)
1457 goto clear_pmdnuma;
1458 }
1459
1460 /* Migration could have started since the pmd_trans_migrating check */
1461 if (!page_locked) {
1462 spin_unlock(vmf->ptl);
1463 wait_on_page_locked(page);
1464 page_nid = -1;
1465 goto out;
1466 }
1467
1468 /*
1469 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1470 * to serialises splits
1471 */
1472 get_page(page);
1473 spin_unlock(vmf->ptl);
1474 anon_vma = page_lock_anon_vma_read(page);
1475
1476 /* Confirm the PMD did not change while page_table_lock was released */
1477 spin_lock(vmf->ptl);
1478 if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1479 unlock_page(page);
1480 put_page(page);
1481 page_nid = -1;
1482 goto out_unlock;
1483 }
1484
1485 /* Bail if we fail to protect against THP splits for any reason */
1486 if (unlikely(!anon_vma)) {
1487 put_page(page);
1488 page_nid = -1;
1489 goto clear_pmdnuma;
1490 }
1491
1492 /*
1493 * Migrate the THP to the requested node, returns with page unlocked
1494 * and access rights restored.
1495 */
1496 spin_unlock(vmf->ptl);
1497 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1498 vmf->pmd, pmd, vmf->address, page, target_nid);
1499 if (migrated) {
1500 flags |= TNF_MIGRATED;
1501 page_nid = target_nid;
1502 } else
1503 flags |= TNF_MIGRATE_FAIL;
1504
1505 goto out;
1506 clear_pmdnuma:
1507 BUG_ON(!PageLocked(page));
1508 was_writable = pmd_savedwrite(pmd);
1509 pmd = pmd_modify(pmd, vma->vm_page_prot);
1510 pmd = pmd_mkyoung(pmd);
1511 if (was_writable)
1512 pmd = pmd_mkwrite(pmd);
1513 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1514 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1515 unlock_page(page);
1516 out_unlock:
1517 spin_unlock(vmf->ptl);
1518
1519 out:
1520 if (anon_vma)
1521 page_unlock_anon_vma_read(anon_vma);
1522
1523 if (page_nid != -1)
1524 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1525 flags);
1526
1527 return 0;
1528 }
1529
1530 /*
1531 * Return true if we do MADV_FREE successfully on entire pmd page.
1532 * Otherwise, return false.
1533 */
1534 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1535 pmd_t *pmd, unsigned long addr, unsigned long next)
1536 {
1537 spinlock_t *ptl;
1538 pmd_t orig_pmd;
1539 struct page *page;
1540 struct mm_struct *mm = tlb->mm;
1541 bool ret = false;
1542
1543 tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1544
1545 ptl = pmd_trans_huge_lock(pmd, vma);
1546 if (!ptl)
1547 goto out_unlocked;
1548
1549 orig_pmd = *pmd;
1550 if (is_huge_zero_pmd(orig_pmd))
1551 goto out;
1552
1553 page = pmd_page(orig_pmd);
1554 /*
1555 * If other processes are mapping this page, we couldn't discard
1556 * the page unless they all do MADV_FREE so let's skip the page.
1557 */
1558 if (page_mapcount(page) != 1)
1559 goto out;
1560
1561 if (!trylock_page(page))
1562 goto out;
1563
1564 /*
1565 * If user want to discard part-pages of THP, split it so MADV_FREE
1566 * will deactivate only them.
1567 */
1568 if (next - addr != HPAGE_PMD_SIZE) {
1569 get_page(page);
1570 spin_unlock(ptl);
1571 split_huge_page(page);
1572 put_page(page);
1573 unlock_page(page);
1574 goto out_unlocked;
1575 }
1576
1577 if (PageDirty(page))
1578 ClearPageDirty(page);
1579 unlock_page(page);
1580
1581 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1582 pmdp_invalidate(vma, addr, pmd);
1583 orig_pmd = pmd_mkold(orig_pmd);
1584 orig_pmd = pmd_mkclean(orig_pmd);
1585
1586 set_pmd_at(mm, addr, pmd, orig_pmd);
1587 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1588 }
1589
1590 mark_page_lazyfree(page);
1591 ret = true;
1592 out:
1593 spin_unlock(ptl);
1594 out_unlocked:
1595 return ret;
1596 }
1597
1598 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1599 {
1600 pgtable_t pgtable;
1601
1602 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1603 pte_free(mm, pgtable);
1604 atomic_long_dec(&mm->nr_ptes);
1605 }
1606
1607 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1608 pmd_t *pmd, unsigned long addr)
1609 {
1610 pmd_t orig_pmd;
1611 spinlock_t *ptl;
1612
1613 tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1614
1615 ptl = __pmd_trans_huge_lock(pmd, vma);
1616 if (!ptl)
1617 return 0;
1618 /*
1619 * For architectures like ppc64 we look at deposited pgtable
1620 * when calling pmdp_huge_get_and_clear. So do the
1621 * pgtable_trans_huge_withdraw after finishing pmdp related
1622 * operations.
1623 */
1624 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1625 tlb->fullmm);
1626 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1627 if (vma_is_dax(vma)) {
1628 if (arch_needs_pgtable_deposit())
1629 zap_deposited_table(tlb->mm, pmd);
1630 spin_unlock(ptl);
1631 if (is_huge_zero_pmd(orig_pmd))
1632 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1633 } else if (is_huge_zero_pmd(orig_pmd)) {
1634 zap_deposited_table(tlb->mm, pmd);
1635 spin_unlock(ptl);
1636 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1637 } else {
1638 struct page *page = pmd_page(orig_pmd);
1639 page_remove_rmap(page, true);
1640 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1641 VM_BUG_ON_PAGE(!PageHead(page), page);
1642 if (PageAnon(page)) {
1643 zap_deposited_table(tlb->mm, pmd);
1644 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1645 } else {
1646 if (arch_needs_pgtable_deposit())
1647 zap_deposited_table(tlb->mm, pmd);
1648 add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1649 }
1650 spin_unlock(ptl);
1651 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1652 }
1653 return 1;
1654 }
1655
1656 #ifndef pmd_move_must_withdraw
1657 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1658 spinlock_t *old_pmd_ptl,
1659 struct vm_area_struct *vma)
1660 {
1661 /*
1662 * With split pmd lock we also need to move preallocated
1663 * PTE page table if new_pmd is on different PMD page table.
1664 *
1665 * We also don't deposit and withdraw tables for file pages.
1666 */
1667 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1668 }
1669 #endif
1670
1671 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1672 unsigned long new_addr, unsigned long old_end,
1673 pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush)
1674 {
1675 spinlock_t *old_ptl, *new_ptl;
1676 pmd_t pmd;
1677 struct mm_struct *mm = vma->vm_mm;
1678 bool force_flush = false;
1679
1680 if ((old_addr & ~HPAGE_PMD_MASK) ||
1681 (new_addr & ~HPAGE_PMD_MASK) ||
1682 old_end - old_addr < HPAGE_PMD_SIZE)
1683 return false;
1684
1685 /*
1686 * The destination pmd shouldn't be established, free_pgtables()
1687 * should have release it.
1688 */
1689 if (WARN_ON(!pmd_none(*new_pmd))) {
1690 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1691 return false;
1692 }
1693
1694 /*
1695 * We don't have to worry about the ordering of src and dst
1696 * ptlocks because exclusive mmap_sem prevents deadlock.
1697 */
1698 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1699 if (old_ptl) {
1700 new_ptl = pmd_lockptr(mm, new_pmd);
1701 if (new_ptl != old_ptl)
1702 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1703 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1704 if (pmd_present(pmd) && pmd_dirty(pmd))
1705 force_flush = true;
1706 VM_BUG_ON(!pmd_none(*new_pmd));
1707
1708 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1709 pgtable_t pgtable;
1710 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1711 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1712 }
1713 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1714 if (new_ptl != old_ptl)
1715 spin_unlock(new_ptl);
1716 if (force_flush)
1717 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1718 else
1719 *need_flush = true;
1720 spin_unlock(old_ptl);
1721 return true;
1722 }
1723 return false;
1724 }
1725
1726 /*
1727 * Returns
1728 * - 0 if PMD could not be locked
1729 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1730 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1731 */
1732 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1733 unsigned long addr, pgprot_t newprot, int prot_numa)
1734 {
1735 struct mm_struct *mm = vma->vm_mm;
1736 spinlock_t *ptl;
1737 pmd_t entry;
1738 bool preserve_write;
1739 int ret;
1740
1741 ptl = __pmd_trans_huge_lock(pmd, vma);
1742 if (!ptl)
1743 return 0;
1744
1745 preserve_write = prot_numa && pmd_write(*pmd);
1746 ret = 1;
1747
1748 /*
1749 * Avoid trapping faults against the zero page. The read-only
1750 * data is likely to be read-cached on the local CPU and
1751 * local/remote hits to the zero page are not interesting.
1752 */
1753 if (prot_numa && is_huge_zero_pmd(*pmd))
1754 goto unlock;
1755
1756 if (prot_numa && pmd_protnone(*pmd))
1757 goto unlock;
1758
1759 /*
1760 * In case prot_numa, we are under down_read(mmap_sem). It's critical
1761 * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1762 * which is also under down_read(mmap_sem):
1763 *
1764 * CPU0: CPU1:
1765 * change_huge_pmd(prot_numa=1)
1766 * pmdp_huge_get_and_clear_notify()
1767 * madvise_dontneed()
1768 * zap_pmd_range()
1769 * pmd_trans_huge(*pmd) == 0 (without ptl)
1770 * // skip the pmd
1771 * set_pmd_at();
1772 * // pmd is re-established
1773 *
1774 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1775 * which may break userspace.
1776 *
1777 * pmdp_invalidate() is required to make sure we don't miss
1778 * dirty/young flags set by hardware.
1779 */
1780 entry = *pmd;
1781 pmdp_invalidate(vma, addr, pmd);
1782
1783 /*
1784 * Recover dirty/young flags. It relies on pmdp_invalidate to not
1785 * corrupt them.
1786 */
1787 if (pmd_dirty(*pmd))
1788 entry = pmd_mkdirty(entry);
1789 if (pmd_young(*pmd))
1790 entry = pmd_mkyoung(entry);
1791
1792 entry = pmd_modify(entry, newprot);
1793 if (preserve_write)
1794 entry = pmd_mk_savedwrite(entry);
1795 ret = HPAGE_PMD_NR;
1796 set_pmd_at(mm, addr, pmd, entry);
1797 BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1798 unlock:
1799 spin_unlock(ptl);
1800 return ret;
1801 }
1802
1803 /*
1804 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1805 *
1806 * Note that if it returns page table lock pointer, this routine returns without
1807 * unlocking page table lock. So callers must unlock it.
1808 */
1809 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1810 {
1811 spinlock_t *ptl;
1812 ptl = pmd_lock(vma->vm_mm, pmd);
1813 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1814 return ptl;
1815 spin_unlock(ptl);
1816 return NULL;
1817 }
1818
1819 /*
1820 * Returns true if a given pud maps a thp, false otherwise.
1821 *
1822 * Note that if it returns true, this routine returns without unlocking page
1823 * table lock. So callers must unlock it.
1824 */
1825 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1826 {
1827 spinlock_t *ptl;
1828
1829 ptl = pud_lock(vma->vm_mm, pud);
1830 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1831 return ptl;
1832 spin_unlock(ptl);
1833 return NULL;
1834 }
1835
1836 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1837 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1838 pud_t *pud, unsigned long addr)
1839 {
1840 pud_t orig_pud;
1841 spinlock_t *ptl;
1842
1843 ptl = __pud_trans_huge_lock(pud, vma);
1844 if (!ptl)
1845 return 0;
1846 /*
1847 * For architectures like ppc64 we look at deposited pgtable
1848 * when calling pudp_huge_get_and_clear. So do the
1849 * pgtable_trans_huge_withdraw after finishing pudp related
1850 * operations.
1851 */
1852 orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1853 tlb->fullmm);
1854 tlb_remove_pud_tlb_entry(tlb, pud, addr);
1855 if (vma_is_dax(vma)) {
1856 spin_unlock(ptl);
1857 /* No zero page support yet */
1858 } else {
1859 /* No support for anonymous PUD pages yet */
1860 BUG();
1861 }
1862 return 1;
1863 }
1864
1865 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
1866 unsigned long haddr)
1867 {
1868 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
1869 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1870 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
1871 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
1872
1873 count_vm_event(THP_SPLIT_PUD);
1874
1875 pudp_huge_clear_flush_notify(vma, haddr, pud);
1876 }
1877
1878 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
1879 unsigned long address)
1880 {
1881 spinlock_t *ptl;
1882 struct mm_struct *mm = vma->vm_mm;
1883 unsigned long haddr = address & HPAGE_PUD_MASK;
1884
1885 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
1886 ptl = pud_lock(mm, pud);
1887 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
1888 goto out;
1889 __split_huge_pud_locked(vma, pud, haddr);
1890
1891 out:
1892 spin_unlock(ptl);
1893 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PUD_SIZE);
1894 }
1895 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1896
1897 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
1898 unsigned long haddr, pmd_t *pmd)
1899 {
1900 struct mm_struct *mm = vma->vm_mm;
1901 pgtable_t pgtable;
1902 pmd_t _pmd;
1903 int i;
1904
1905 /* leave pmd empty until pte is filled */
1906 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1907
1908 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1909 pmd_populate(mm, &_pmd, pgtable);
1910
1911 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1912 pte_t *pte, entry;
1913 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1914 entry = pte_mkspecial(entry);
1915 pte = pte_offset_map(&_pmd, haddr);
1916 VM_BUG_ON(!pte_none(*pte));
1917 set_pte_at(mm, haddr, pte, entry);
1918 pte_unmap(pte);
1919 }
1920 smp_wmb(); /* make pte visible before pmd */
1921 pmd_populate(mm, pmd, pgtable);
1922 }
1923
1924 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
1925 unsigned long haddr, bool freeze)
1926 {
1927 struct mm_struct *mm = vma->vm_mm;
1928 struct page *page;
1929 pgtable_t pgtable;
1930 pmd_t _pmd;
1931 bool young, write, dirty, soft_dirty;
1932 unsigned long addr;
1933 int i;
1934
1935 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
1936 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1937 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
1938 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
1939
1940 count_vm_event(THP_SPLIT_PMD);
1941
1942 if (!vma_is_anonymous(vma)) {
1943 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1944 /*
1945 * We are going to unmap this huge page. So
1946 * just go ahead and zap it
1947 */
1948 if (arch_needs_pgtable_deposit())
1949 zap_deposited_table(mm, pmd);
1950 if (vma_is_dax(vma))
1951 return;
1952 page = pmd_page(_pmd);
1953 if (!PageReferenced(page) && pmd_young(_pmd))
1954 SetPageReferenced(page);
1955 page_remove_rmap(page, true);
1956 put_page(page);
1957 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1958 return;
1959 } else if (is_huge_zero_pmd(*pmd)) {
1960 return __split_huge_zero_page_pmd(vma, haddr, pmd);
1961 }
1962
1963 page = pmd_page(*pmd);
1964 VM_BUG_ON_PAGE(!page_count(page), page);
1965 page_ref_add(page, HPAGE_PMD_NR - 1);
1966 write = pmd_write(*pmd);
1967 young = pmd_young(*pmd);
1968 dirty = pmd_dirty(*pmd);
1969 soft_dirty = pmd_soft_dirty(*pmd);
1970
1971 pmdp_huge_split_prepare(vma, haddr, pmd);
1972 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1973 pmd_populate(mm, &_pmd, pgtable);
1974
1975 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
1976 pte_t entry, *pte;
1977 /*
1978 * Note that NUMA hinting access restrictions are not
1979 * transferred to avoid any possibility of altering
1980 * permissions across VMAs.
1981 */
1982 if (freeze) {
1983 swp_entry_t swp_entry;
1984 swp_entry = make_migration_entry(page + i, write);
1985 entry = swp_entry_to_pte(swp_entry);
1986 if (soft_dirty)
1987 entry = pte_swp_mksoft_dirty(entry);
1988 } else {
1989 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
1990 entry = maybe_mkwrite(entry, vma);
1991 if (!write)
1992 entry = pte_wrprotect(entry);
1993 if (!young)
1994 entry = pte_mkold(entry);
1995 if (soft_dirty)
1996 entry = pte_mksoft_dirty(entry);
1997 }
1998 if (dirty)
1999 SetPageDirty(page + i);
2000 pte = pte_offset_map(&_pmd, addr);
2001 BUG_ON(!pte_none(*pte));
2002 set_pte_at(mm, addr, pte, entry);
2003 atomic_inc(&page[i]._mapcount);
2004 pte_unmap(pte);
2005 }
2006
2007 /*
2008 * Set PG_double_map before dropping compound_mapcount to avoid
2009 * false-negative page_mapped().
2010 */
2011 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2012 for (i = 0; i < HPAGE_PMD_NR; i++)
2013 atomic_inc(&page[i]._mapcount);
2014 }
2015
2016 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2017 /* Last compound_mapcount is gone. */
2018 __dec_node_page_state(page, NR_ANON_THPS);
2019 if (TestClearPageDoubleMap(page)) {
2020 /* No need in mapcount reference anymore */
2021 for (i = 0; i < HPAGE_PMD_NR; i++)
2022 atomic_dec(&page[i]._mapcount);
2023 }
2024 }
2025
2026 smp_wmb(); /* make pte visible before pmd */
2027 /*
2028 * Up to this point the pmd is present and huge and userland has the
2029 * whole access to the hugepage during the split (which happens in
2030 * place). If we overwrite the pmd with the not-huge version pointing
2031 * to the pte here (which of course we could if all CPUs were bug
2032 * free), userland could trigger a small page size TLB miss on the
2033 * small sized TLB while the hugepage TLB entry is still established in
2034 * the huge TLB. Some CPU doesn't like that.
2035 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2036 * 383 on page 93. Intel should be safe but is also warns that it's
2037 * only safe if the permission and cache attributes of the two entries
2038 * loaded in the two TLB is identical (which should be the case here).
2039 * But it is generally safer to never allow small and huge TLB entries
2040 * for the same virtual address to be loaded simultaneously. So instead
2041 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2042 * current pmd notpresent (atomically because here the pmd_trans_huge
2043 * and pmd_trans_splitting must remain set at all times on the pmd
2044 * until the split is complete for this pmd), then we flush the SMP TLB
2045 * and finally we write the non-huge version of the pmd entry with
2046 * pmd_populate.
2047 */
2048 pmdp_invalidate(vma, haddr, pmd);
2049 pmd_populate(mm, pmd, pgtable);
2050
2051 if (freeze) {
2052 for (i = 0; i < HPAGE_PMD_NR; i++) {
2053 page_remove_rmap(page + i, false);
2054 put_page(page + i);
2055 }
2056 }
2057 }
2058
2059 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2060 unsigned long address, bool freeze, struct page *page)
2061 {
2062 spinlock_t *ptl;
2063 struct mm_struct *mm = vma->vm_mm;
2064 unsigned long haddr = address & HPAGE_PMD_MASK;
2065
2066 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2067 ptl = pmd_lock(mm, pmd);
2068
2069 /*
2070 * If caller asks to setup a migration entries, we need a page to check
2071 * pmd against. Otherwise we can end up replacing wrong page.
2072 */
2073 VM_BUG_ON(freeze && !page);
2074 if (page && page != pmd_page(*pmd))
2075 goto out;
2076
2077 if (pmd_trans_huge(*pmd)) {
2078 page = pmd_page(*pmd);
2079 if (PageMlocked(page))
2080 clear_page_mlock(page);
2081 } else if (!pmd_devmap(*pmd))
2082 goto out;
2083 __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2084 out:
2085 spin_unlock(ptl);
2086 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
2087 }
2088
2089 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2090 bool freeze, struct page *page)
2091 {
2092 pgd_t *pgd;
2093 p4d_t *p4d;
2094 pud_t *pud;
2095 pmd_t *pmd;
2096
2097 pgd = pgd_offset(vma->vm_mm, address);
2098 if (!pgd_present(*pgd))
2099 return;
2100
2101 p4d = p4d_offset(pgd, address);
2102 if (!p4d_present(*p4d))
2103 return;
2104
2105 pud = pud_offset(p4d, address);
2106 if (!pud_present(*pud))
2107 return;
2108
2109 pmd = pmd_offset(pud, address);
2110
2111 __split_huge_pmd(vma, pmd, address, freeze, page);
2112 }
2113
2114 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2115 unsigned long start,
2116 unsigned long end,
2117 long adjust_next)
2118 {
2119 /*
2120 * If the new start address isn't hpage aligned and it could
2121 * previously contain an hugepage: check if we need to split
2122 * an huge pmd.
2123 */
2124 if (start & ~HPAGE_PMD_MASK &&
2125 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2126 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2127 split_huge_pmd_address(vma, start, false, NULL);
2128
2129 /*
2130 * If the new end address isn't hpage aligned and it could
2131 * previously contain an hugepage: check if we need to split
2132 * an huge pmd.
2133 */
2134 if (end & ~HPAGE_PMD_MASK &&
2135 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2136 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2137 split_huge_pmd_address(vma, end, false, NULL);
2138
2139 /*
2140 * If we're also updating the vma->vm_next->vm_start, if the new
2141 * vm_next->vm_start isn't page aligned and it could previously
2142 * contain an hugepage: check if we need to split an huge pmd.
2143 */
2144 if (adjust_next > 0) {
2145 struct vm_area_struct *next = vma->vm_next;
2146 unsigned long nstart = next->vm_start;
2147 nstart += adjust_next << PAGE_SHIFT;
2148 if (nstart & ~HPAGE_PMD_MASK &&
2149 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2150 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2151 split_huge_pmd_address(next, nstart, false, NULL);
2152 }
2153 }
2154
2155 static void freeze_page(struct page *page)
2156 {
2157 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2158 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2159 bool unmap_success;
2160
2161 VM_BUG_ON_PAGE(!PageHead(page), page);
2162
2163 if (PageAnon(page))
2164 ttu_flags |= TTU_MIGRATION;
2165
2166 unmap_success = try_to_unmap(page, ttu_flags);
2167 VM_BUG_ON_PAGE(!unmap_success, page);
2168 }
2169
2170 static void unfreeze_page(struct page *page)
2171 {
2172 int i;
2173 if (PageTransHuge(page)) {
2174 remove_migration_ptes(page, page, true);
2175 } else {
2176 for (i = 0; i < HPAGE_PMD_NR; i++)
2177 remove_migration_ptes(page + i, page + i, true);
2178 }
2179 }
2180
2181 static void __split_huge_page_tail(struct page *head, int tail,
2182 struct lruvec *lruvec, struct list_head *list)
2183 {
2184 struct page *page_tail = head + tail;
2185
2186 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2187 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
2188
2189 /*
2190 * tail_page->_refcount is zero and not changing from under us. But
2191 * get_page_unless_zero() may be running from under us on the
2192 * tail_page. If we used atomic_set() below instead of atomic_inc() or
2193 * atomic_add(), we would then run atomic_set() concurrently with
2194 * get_page_unless_zero(), and atomic_set() is implemented in C not
2195 * using locked ops. spin_unlock on x86 sometime uses locked ops
2196 * because of PPro errata 66, 92, so unless somebody can guarantee
2197 * atomic_set() here would be safe on all archs (and not only on x86),
2198 * it's safer to use atomic_inc()/atomic_add().
2199 */
2200 if (PageAnon(head)) {
2201 page_ref_inc(page_tail);
2202 } else {
2203 /* Additional pin to radix tree */
2204 page_ref_add(page_tail, 2);
2205 }
2206
2207 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2208 page_tail->flags |= (head->flags &
2209 ((1L << PG_referenced) |
2210 (1L << PG_swapbacked) |
2211 (1L << PG_mlocked) |
2212 (1L << PG_uptodate) |
2213 (1L << PG_active) |
2214 (1L << PG_locked) |
2215 (1L << PG_unevictable) |
2216 (1L << PG_dirty)));
2217
2218 /*
2219 * After clearing PageTail the gup refcount can be released.
2220 * Page flags also must be visible before we make the page non-compound.
2221 */
2222 smp_wmb();
2223
2224 clear_compound_head(page_tail);
2225
2226 if (page_is_young(head))
2227 set_page_young(page_tail);
2228 if (page_is_idle(head))
2229 set_page_idle(page_tail);
2230
2231 /* ->mapping in first tail page is compound_mapcount */
2232 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2233 page_tail);
2234 page_tail->mapping = head->mapping;
2235
2236 page_tail->index = head->index + tail;
2237 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2238 lru_add_page_tail(head, page_tail, lruvec, list);
2239 }
2240
2241 static void __split_huge_page(struct page *page, struct list_head *list,
2242 unsigned long flags)
2243 {
2244 struct page *head = compound_head(page);
2245 struct zone *zone = page_zone(head);
2246 struct lruvec *lruvec;
2247 pgoff_t end = -1;
2248 int i;
2249
2250 lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2251
2252 /* complete memcg works before add pages to LRU */
2253 mem_cgroup_split_huge_fixup(head);
2254
2255 if (!PageAnon(page))
2256 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
2257
2258 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2259 __split_huge_page_tail(head, i, lruvec, list);
2260 /* Some pages can be beyond i_size: drop them from page cache */
2261 if (head[i].index >= end) {
2262 __ClearPageDirty(head + i);
2263 __delete_from_page_cache(head + i, NULL);
2264 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2265 shmem_uncharge(head->mapping->host, 1);
2266 put_page(head + i);
2267 }
2268 }
2269
2270 ClearPageCompound(head);
2271 /* See comment in __split_huge_page_tail() */
2272 if (PageAnon(head)) {
2273 page_ref_inc(head);
2274 } else {
2275 /* Additional pin to radix tree */
2276 page_ref_add(head, 2);
2277 spin_unlock(&head->mapping->tree_lock);
2278 }
2279
2280 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2281
2282 unfreeze_page(head);
2283
2284 for (i = 0; i < HPAGE_PMD_NR; i++) {
2285 struct page *subpage = head + i;
2286 if (subpage == page)
2287 continue;
2288 unlock_page(subpage);
2289
2290 /*
2291 * Subpages may be freed if there wasn't any mapping
2292 * like if add_to_swap() is running on a lru page that
2293 * had its mapping zapped. And freeing these pages
2294 * requires taking the lru_lock so we do the put_page
2295 * of the tail pages after the split is complete.
2296 */
2297 put_page(subpage);
2298 }
2299 }
2300
2301 int total_mapcount(struct page *page)
2302 {
2303 int i, compound, ret;
2304
2305 VM_BUG_ON_PAGE(PageTail(page), page);
2306
2307 if (likely(!PageCompound(page)))
2308 return atomic_read(&page->_mapcount) + 1;
2309
2310 compound = compound_mapcount(page);
2311 if (PageHuge(page))
2312 return compound;
2313 ret = compound;
2314 for (i = 0; i < HPAGE_PMD_NR; i++)
2315 ret += atomic_read(&page[i]._mapcount) + 1;
2316 /* File pages has compound_mapcount included in _mapcount */
2317 if (!PageAnon(page))
2318 return ret - compound * HPAGE_PMD_NR;
2319 if (PageDoubleMap(page))
2320 ret -= HPAGE_PMD_NR;
2321 return ret;
2322 }
2323
2324 /*
2325 * This calculates accurately how many mappings a transparent hugepage
2326 * has (unlike page_mapcount() which isn't fully accurate). This full
2327 * accuracy is primarily needed to know if copy-on-write faults can
2328 * reuse the page and change the mapping to read-write instead of
2329 * copying them. At the same time this returns the total_mapcount too.
2330 *
2331 * The function returns the highest mapcount any one of the subpages
2332 * has. If the return value is one, even if different processes are
2333 * mapping different subpages of the transparent hugepage, they can
2334 * all reuse it, because each process is reusing a different subpage.
2335 *
2336 * The total_mapcount is instead counting all virtual mappings of the
2337 * subpages. If the total_mapcount is equal to "one", it tells the
2338 * caller all mappings belong to the same "mm" and in turn the
2339 * anon_vma of the transparent hugepage can become the vma->anon_vma
2340 * local one as no other process may be mapping any of the subpages.
2341 *
2342 * It would be more accurate to replace page_mapcount() with
2343 * page_trans_huge_mapcount(), however we only use
2344 * page_trans_huge_mapcount() in the copy-on-write faults where we
2345 * need full accuracy to avoid breaking page pinning, because
2346 * page_trans_huge_mapcount() is slower than page_mapcount().
2347 */
2348 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2349 {
2350 int i, ret, _total_mapcount, mapcount;
2351
2352 /* hugetlbfs shouldn't call it */
2353 VM_BUG_ON_PAGE(PageHuge(page), page);
2354
2355 if (likely(!PageTransCompound(page))) {
2356 mapcount = atomic_read(&page->_mapcount) + 1;
2357 if (total_mapcount)
2358 *total_mapcount = mapcount;
2359 return mapcount;
2360 }
2361
2362 page = compound_head(page);
2363
2364 _total_mapcount = ret = 0;
2365 for (i = 0; i < HPAGE_PMD_NR; i++) {
2366 mapcount = atomic_read(&page[i]._mapcount) + 1;
2367 ret = max(ret, mapcount);
2368 _total_mapcount += mapcount;
2369 }
2370 if (PageDoubleMap(page)) {
2371 ret -= 1;
2372 _total_mapcount -= HPAGE_PMD_NR;
2373 }
2374 mapcount = compound_mapcount(page);
2375 ret += mapcount;
2376 _total_mapcount += mapcount;
2377 if (total_mapcount)
2378 *total_mapcount = _total_mapcount;
2379 return ret;
2380 }
2381
2382 /*
2383 * This function splits huge page into normal pages. @page can point to any
2384 * subpage of huge page to split. Split doesn't change the position of @page.
2385 *
2386 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2387 * The huge page must be locked.
2388 *
2389 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2390 *
2391 * Both head page and tail pages will inherit mapping, flags, and so on from
2392 * the hugepage.
2393 *
2394 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2395 * they are not mapped.
2396 *
2397 * Returns 0 if the hugepage is split successfully.
2398 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2399 * us.
2400 */
2401 int split_huge_page_to_list(struct page *page, struct list_head *list)
2402 {
2403 struct page *head = compound_head(page);
2404 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2405 struct anon_vma *anon_vma = NULL;
2406 struct address_space *mapping = NULL;
2407 int count, mapcount, extra_pins, ret;
2408 bool mlocked;
2409 unsigned long flags;
2410
2411 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2412 VM_BUG_ON_PAGE(!PageLocked(page), page);
2413 VM_BUG_ON_PAGE(!PageCompound(page), page);
2414
2415 if (PageAnon(head)) {
2416 /*
2417 * The caller does not necessarily hold an mmap_sem that would
2418 * prevent the anon_vma disappearing so we first we take a
2419 * reference to it and then lock the anon_vma for write. This
2420 * is similar to page_lock_anon_vma_read except the write lock
2421 * is taken to serialise against parallel split or collapse
2422 * operations.
2423 */
2424 anon_vma = page_get_anon_vma(head);
2425 if (!anon_vma) {
2426 ret = -EBUSY;
2427 goto out;
2428 }
2429 extra_pins = 0;
2430 mapping = NULL;
2431 anon_vma_lock_write(anon_vma);
2432 } else {
2433 mapping = head->mapping;
2434
2435 /* Truncated ? */
2436 if (!mapping) {
2437 ret = -EBUSY;
2438 goto out;
2439 }
2440
2441 /* Addidional pins from radix tree */
2442 extra_pins = HPAGE_PMD_NR;
2443 anon_vma = NULL;
2444 i_mmap_lock_read(mapping);
2445 }
2446
2447 /*
2448 * Racy check if we can split the page, before freeze_page() will
2449 * split PMDs
2450 */
2451 if (total_mapcount(head) != page_count(head) - extra_pins - 1) {
2452 ret = -EBUSY;
2453 goto out_unlock;
2454 }
2455
2456 mlocked = PageMlocked(page);
2457 freeze_page(head);
2458 VM_BUG_ON_PAGE(compound_mapcount(head), head);
2459
2460 /* Make sure the page is not on per-CPU pagevec as it takes pin */
2461 if (mlocked)
2462 lru_add_drain();
2463
2464 /* prevent PageLRU to go away from under us, and freeze lru stats */
2465 spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2466
2467 if (mapping) {
2468 void **pslot;
2469
2470 spin_lock(&mapping->tree_lock);
2471 pslot = radix_tree_lookup_slot(&mapping->page_tree,
2472 page_index(head));
2473 /*
2474 * Check if the head page is present in radix tree.
2475 * We assume all tail are present too, if head is there.
2476 */
2477 if (radix_tree_deref_slot_protected(pslot,
2478 &mapping->tree_lock) != head)
2479 goto fail;
2480 }
2481
2482 /* Prevent deferred_split_scan() touching ->_refcount */
2483 spin_lock(&pgdata->split_queue_lock);
2484 count = page_count(head);
2485 mapcount = total_mapcount(head);
2486 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2487 if (!list_empty(page_deferred_list(head))) {
2488 pgdata->split_queue_len--;
2489 list_del(page_deferred_list(head));
2490 }
2491 if (mapping)
2492 __dec_node_page_state(page, NR_SHMEM_THPS);
2493 spin_unlock(&pgdata->split_queue_lock);
2494 __split_huge_page(page, list, flags);
2495 ret = 0;
2496 } else {
2497 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2498 pr_alert("total_mapcount: %u, page_count(): %u\n",
2499 mapcount, count);
2500 if (PageTail(page))
2501 dump_page(head, NULL);
2502 dump_page(page, "total_mapcount(head) > 0");
2503 BUG();
2504 }
2505 spin_unlock(&pgdata->split_queue_lock);
2506 fail: if (mapping)
2507 spin_unlock(&mapping->tree_lock);
2508 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2509 unfreeze_page(head);
2510 ret = -EBUSY;
2511 }
2512
2513 out_unlock:
2514 if (anon_vma) {
2515 anon_vma_unlock_write(anon_vma);
2516 put_anon_vma(anon_vma);
2517 }
2518 if (mapping)
2519 i_mmap_unlock_read(mapping);
2520 out:
2521 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2522 return ret;
2523 }
2524
2525 void free_transhuge_page(struct page *page)
2526 {
2527 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2528 unsigned long flags;
2529
2530 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2531 if (!list_empty(page_deferred_list(page))) {
2532 pgdata->split_queue_len--;
2533 list_del(page_deferred_list(page));
2534 }
2535 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2536 free_compound_page(page);
2537 }
2538
2539 void deferred_split_huge_page(struct page *page)
2540 {
2541 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2542 unsigned long flags;
2543
2544 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2545
2546 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2547 if (list_empty(page_deferred_list(page))) {
2548 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2549 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2550 pgdata->split_queue_len++;
2551 }
2552 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2553 }
2554
2555 static unsigned long deferred_split_count(struct shrinker *shrink,
2556 struct shrink_control *sc)
2557 {
2558 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2559 return ACCESS_ONCE(pgdata->split_queue_len);
2560 }
2561
2562 static unsigned long deferred_split_scan(struct shrinker *shrink,
2563 struct shrink_control *sc)
2564 {
2565 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2566 unsigned long flags;
2567 LIST_HEAD(list), *pos, *next;
2568 struct page *page;
2569 int split = 0;
2570
2571 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2572 /* Take pin on all head pages to avoid freeing them under us */
2573 list_for_each_safe(pos, next, &pgdata->split_queue) {
2574 page = list_entry((void *)pos, struct page, mapping);
2575 page = compound_head(page);
2576 if (get_page_unless_zero(page)) {
2577 list_move(page_deferred_list(page), &list);
2578 } else {
2579 /* We lost race with put_compound_page() */
2580 list_del_init(page_deferred_list(page));
2581 pgdata->split_queue_len--;
2582 }
2583 if (!--sc->nr_to_scan)
2584 break;
2585 }
2586 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2587
2588 list_for_each_safe(pos, next, &list) {
2589 page = list_entry((void *)pos, struct page, mapping);
2590 lock_page(page);
2591 /* split_huge_page() removes page from list on success */
2592 if (!split_huge_page(page))
2593 split++;
2594 unlock_page(page);
2595 put_page(page);
2596 }
2597
2598 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2599 list_splice_tail(&list, &pgdata->split_queue);
2600 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2601
2602 /*
2603 * Stop shrinker if we didn't split any page, but the queue is empty.
2604 * This can happen if pages were freed under us.
2605 */
2606 if (!split && list_empty(&pgdata->split_queue))
2607 return SHRINK_STOP;
2608 return split;
2609 }
2610
2611 static struct shrinker deferred_split_shrinker = {
2612 .count_objects = deferred_split_count,
2613 .scan_objects = deferred_split_scan,
2614 .seeks = DEFAULT_SEEKS,
2615 .flags = SHRINKER_NUMA_AWARE,
2616 };
2617
2618 #ifdef CONFIG_DEBUG_FS
2619 static int split_huge_pages_set(void *data, u64 val)
2620 {
2621 struct zone *zone;
2622 struct page *page;
2623 unsigned long pfn, max_zone_pfn;
2624 unsigned long total = 0, split = 0;
2625
2626 if (val != 1)
2627 return -EINVAL;
2628
2629 for_each_populated_zone(zone) {
2630 max_zone_pfn = zone_end_pfn(zone);
2631 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2632 if (!pfn_valid(pfn))
2633 continue;
2634
2635 page = pfn_to_page(pfn);
2636 if (!get_page_unless_zero(page))
2637 continue;
2638
2639 if (zone != page_zone(page))
2640 goto next;
2641
2642 if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2643 goto next;
2644
2645 total++;
2646 lock_page(page);
2647 if (!split_huge_page(page))
2648 split++;
2649 unlock_page(page);
2650 next:
2651 put_page(page);
2652 }
2653 }
2654
2655 pr_info("%lu of %lu THP split\n", split, total);
2656
2657 return 0;
2658 }
2659 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2660 "%llu\n");
2661
2662 static int __init split_huge_pages_debugfs(void)
2663 {
2664 void *ret;
2665
2666 ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2667 &split_huge_pages_fops);
2668 if (!ret)
2669 pr_warn("Failed to create split_huge_pages in debugfs");
2670 return 0;
2671 }
2672 late_initcall(split_huge_pages_debugfs);
2673 #endif
Linux with added FPC-III support