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h8300: Add missing closing parenthesis in flat_get_addr_from_rp()
[linux/fpc-iii.git] / mm / huge_memory.c
blob86975dec0ba160feadfb8aa0d13b8f2be943638d
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 if (!get_page_unless_zero(page))
1430 goto out_unlock;
1431 spin_unlock(vmf->ptl);
1432 wait_on_page_locked(page);
1433 put_page(page);
1434 goto out;
1435 }
1436
1437 page = pmd_page(pmd);
1438 BUG_ON(is_huge_zero_page(page));
1439 page_nid = page_to_nid(page);
1440 last_cpupid = page_cpupid_last(page);
1441 count_vm_numa_event(NUMA_HINT_FAULTS);
1442 if (page_nid == this_nid) {
1443 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1444 flags |= TNF_FAULT_LOCAL;
1445 }
1446
1447 /* See similar comment in do_numa_page for explanation */
1448 if (!pmd_savedwrite(pmd))
1449 flags |= TNF_NO_GROUP;
1450
1451 /*
1452 * Acquire the page lock to serialise THP migrations but avoid dropping
1453 * page_table_lock if at all possible
1454 */
1455 page_locked = trylock_page(page);
1456 target_nid = mpol_misplaced(page, vma, haddr);
1457 if (target_nid == -1) {
1458 /* If the page was locked, there are no parallel migrations */
1459 if (page_locked)
1460 goto clear_pmdnuma;
1461 }
1462
1463 /* Migration could have started since the pmd_trans_migrating check */
1464 if (!page_locked) {
1465 page_nid = -1;
1466 if (!get_page_unless_zero(page))
1467 goto out_unlock;
1468 spin_unlock(vmf->ptl);
1469 wait_on_page_locked(page);
1470 put_page(page);
1471 goto out;
1472 }
1473
1474 /*
1475 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1476 * to serialises splits
1477 */
1478 get_page(page);
1479 spin_unlock(vmf->ptl);
1480 anon_vma = page_lock_anon_vma_read(page);
1481
1482 /* Confirm the PMD did not change while page_table_lock was released */
1483 spin_lock(vmf->ptl);
1484 if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1485 unlock_page(page);
1486 put_page(page);
1487 page_nid = -1;
1488 goto out_unlock;
1489 }
1490
1491 /* Bail if we fail to protect against THP splits for any reason */
1492 if (unlikely(!anon_vma)) {
1493 put_page(page);
1494 page_nid = -1;
1495 goto clear_pmdnuma;
1496 }
1497
1498 /*
1499 * Migrate the THP to the requested node, returns with page unlocked
1500 * and access rights restored.
1501 */
1502 spin_unlock(vmf->ptl);
1503 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1504 vmf->pmd, pmd, vmf->address, page, target_nid);
1505 if (migrated) {
1506 flags |= TNF_MIGRATED;
1507 page_nid = target_nid;
1508 } else
1509 flags |= TNF_MIGRATE_FAIL;
1510
1511 goto out;
1512 clear_pmdnuma:
1513 BUG_ON(!PageLocked(page));
1514 was_writable = pmd_savedwrite(pmd);
1515 pmd = pmd_modify(pmd, vma->vm_page_prot);
1516 pmd = pmd_mkyoung(pmd);
1517 if (was_writable)
1518 pmd = pmd_mkwrite(pmd);
1519 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1520 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1521 unlock_page(page);
1522 out_unlock:
1523 spin_unlock(vmf->ptl);
1524
1525 out:
1526 if (anon_vma)
1527 page_unlock_anon_vma_read(anon_vma);
1528
1529 if (page_nid != -1)
1530 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1531 flags);
1532
1533 return 0;
1534 }
1535
1536 /*
1537 * Return true if we do MADV_FREE successfully on entire pmd page.
1538 * Otherwise, return false.
1539 */
1540 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1541 pmd_t *pmd, unsigned long addr, unsigned long next)
1542 {
1543 spinlock_t *ptl;
1544 pmd_t orig_pmd;
1545 struct page *page;
1546 struct mm_struct *mm = tlb->mm;
1547 bool ret = false;
1548
1549 tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1550
1551 ptl = pmd_trans_huge_lock(pmd, vma);
1552 if (!ptl)
1553 goto out_unlocked;
1554
1555 orig_pmd = *pmd;
1556 if (is_huge_zero_pmd(orig_pmd))
1557 goto out;
1558
1559 page = pmd_page(orig_pmd);
1560 /*
1561 * If other processes are mapping this page, we couldn't discard
1562 * the page unless they all do MADV_FREE so let's skip the page.
1563 */
1564 if (page_mapcount(page) != 1)
1565 goto out;
1566
1567 if (!trylock_page(page))
1568 goto out;
1569
1570 /*
1571 * If user want to discard part-pages of THP, split it so MADV_FREE
1572 * will deactivate only them.
1573 */
1574 if (next - addr != HPAGE_PMD_SIZE) {
1575 get_page(page);
1576 spin_unlock(ptl);
1577 split_huge_page(page);
1578 unlock_page(page);
1579 put_page(page);
1580 goto out_unlocked;
1581 }
1582
1583 if (PageDirty(page))
1584 ClearPageDirty(page);
1585 unlock_page(page);
1586
1587 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1588 pmdp_invalidate(vma, addr, pmd);
1589 orig_pmd = pmd_mkold(orig_pmd);
1590 orig_pmd = pmd_mkclean(orig_pmd);
1591
1592 set_pmd_at(mm, addr, pmd, orig_pmd);
1593 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1594 }
1595
1596 mark_page_lazyfree(page);
1597 ret = true;
1598 out:
1599 spin_unlock(ptl);
1600 out_unlocked:
1601 return ret;
1602 }
1603
1604 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1605 {
1606 pgtable_t pgtable;
1607
1608 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1609 pte_free(mm, pgtable);
1610 atomic_long_dec(&mm->nr_ptes);
1611 }
1612
1613 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1614 pmd_t *pmd, unsigned long addr)
1615 {
1616 pmd_t orig_pmd;
1617 spinlock_t *ptl;
1618
1619 tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1620
1621 ptl = __pmd_trans_huge_lock(pmd, vma);
1622 if (!ptl)
1623 return 0;
1624 /*
1625 * For architectures like ppc64 we look at deposited pgtable
1626 * when calling pmdp_huge_get_and_clear. So do the
1627 * pgtable_trans_huge_withdraw after finishing pmdp related
1628 * operations.
1629 */
1630 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1631 tlb->fullmm);
1632 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1633 if (vma_is_dax(vma)) {
1634 if (arch_needs_pgtable_deposit())
1635 zap_deposited_table(tlb->mm, pmd);
1636 spin_unlock(ptl);
1637 if (is_huge_zero_pmd(orig_pmd))
1638 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1639 } else if (is_huge_zero_pmd(orig_pmd)) {
1640 zap_deposited_table(tlb->mm, pmd);
1641 spin_unlock(ptl);
1642 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1643 } else {
1644 struct page *page = pmd_page(orig_pmd);
1645 page_remove_rmap(page, true);
1646 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1647 VM_BUG_ON_PAGE(!PageHead(page), page);
1648 if (PageAnon(page)) {
1649 zap_deposited_table(tlb->mm, pmd);
1650 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1651 } else {
1652 if (arch_needs_pgtable_deposit())
1653 zap_deposited_table(tlb->mm, pmd);
1654 add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1655 }
1656 spin_unlock(ptl);
1657 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1658 }
1659 return 1;
1660 }
1661
1662 #ifndef pmd_move_must_withdraw
1663 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1664 spinlock_t *old_pmd_ptl,
1665 struct vm_area_struct *vma)
1666 {
1667 /*
1668 * With split pmd lock we also need to move preallocated
1669 * PTE page table if new_pmd is on different PMD page table.
1670 *
1671 * We also don't deposit and withdraw tables for file pages.
1672 */
1673 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1674 }
1675 #endif
1676
1677 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1678 unsigned long new_addr, unsigned long old_end,
1679 pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush)
1680 {
1681 spinlock_t *old_ptl, *new_ptl;
1682 pmd_t pmd;
1683 struct mm_struct *mm = vma->vm_mm;
1684 bool force_flush = false;
1685
1686 if ((old_addr & ~HPAGE_PMD_MASK) ||
1687 (new_addr & ~HPAGE_PMD_MASK) ||
1688 old_end - old_addr < HPAGE_PMD_SIZE)
1689 return false;
1690
1691 /*
1692 * The destination pmd shouldn't be established, free_pgtables()
1693 * should have release it.
1694 */
1695 if (WARN_ON(!pmd_none(*new_pmd))) {
1696 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1697 return false;
1698 }
1699
1700 /*
1701 * We don't have to worry about the ordering of src and dst
1702 * ptlocks because exclusive mmap_sem prevents deadlock.
1703 */
1704 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1705 if (old_ptl) {
1706 new_ptl = pmd_lockptr(mm, new_pmd);
1707 if (new_ptl != old_ptl)
1708 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1709 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1710 if (pmd_present(pmd) && pmd_dirty(pmd))
1711 force_flush = true;
1712 VM_BUG_ON(!pmd_none(*new_pmd));
1713
1714 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1715 pgtable_t pgtable;
1716 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1717 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1718 }
1719 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1720 if (new_ptl != old_ptl)
1721 spin_unlock(new_ptl);
1722 if (force_flush)
1723 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1724 else
1725 *need_flush = true;
1726 spin_unlock(old_ptl);
1727 return true;
1728 }
1729 return false;
1730 }
1731
1732 /*
1733 * Returns
1734 * - 0 if PMD could not be locked
1735 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1736 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1737 */
1738 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1739 unsigned long addr, pgprot_t newprot, int prot_numa)
1740 {
1741 struct mm_struct *mm = vma->vm_mm;
1742 spinlock_t *ptl;
1743 pmd_t entry;
1744 bool preserve_write;
1745 int ret;
1746
1747 ptl = __pmd_trans_huge_lock(pmd, vma);
1748 if (!ptl)
1749 return 0;
1750
1751 preserve_write = prot_numa && pmd_write(*pmd);
1752 ret = 1;
1753
1754 /*
1755 * Avoid trapping faults against the zero page. The read-only
1756 * data is likely to be read-cached on the local CPU and
1757 * local/remote hits to the zero page are not interesting.
1758 */
1759 if (prot_numa && is_huge_zero_pmd(*pmd))
1760 goto unlock;
1761
1762 if (prot_numa && pmd_protnone(*pmd))
1763 goto unlock;
1764
1765 /*
1766 * In case prot_numa, we are under down_read(mmap_sem). It's critical
1767 * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1768 * which is also under down_read(mmap_sem):
1769 *
1770 * CPU0: CPU1:
1771 * change_huge_pmd(prot_numa=1)
1772 * pmdp_huge_get_and_clear_notify()
1773 * madvise_dontneed()
1774 * zap_pmd_range()
1775 * pmd_trans_huge(*pmd) == 0 (without ptl)
1776 * // skip the pmd
1777 * set_pmd_at();
1778 * // pmd is re-established
1779 *
1780 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1781 * which may break userspace.
1782 *
1783 * pmdp_invalidate() is required to make sure we don't miss
1784 * dirty/young flags set by hardware.
1785 */
1786 entry = *pmd;
1787 pmdp_invalidate(vma, addr, pmd);
1788
1789 /*
1790 * Recover dirty/young flags. It relies on pmdp_invalidate to not
1791 * corrupt them.
1792 */
1793 if (pmd_dirty(*pmd))
1794 entry = pmd_mkdirty(entry);
1795 if (pmd_young(*pmd))
1796 entry = pmd_mkyoung(entry);
1797
1798 entry = pmd_modify(entry, newprot);
1799 if (preserve_write)
1800 entry = pmd_mk_savedwrite(entry);
1801 ret = HPAGE_PMD_NR;
1802 set_pmd_at(mm, addr, pmd, entry);
1803 BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1804 unlock:
1805 spin_unlock(ptl);
1806 return ret;
1807 }
1808
1809 /*
1810 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1811 *
1812 * Note that if it returns page table lock pointer, this routine returns without
1813 * unlocking page table lock. So callers must unlock it.
1814 */
1815 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1816 {
1817 spinlock_t *ptl;
1818 ptl = pmd_lock(vma->vm_mm, pmd);
1819 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1820 return ptl;
1821 spin_unlock(ptl);
1822 return NULL;
1823 }
1824
1825 /*
1826 * Returns true if a given pud maps a thp, false otherwise.
1827 *
1828 * Note that if it returns true, this routine returns without unlocking page
1829 * table lock. So callers must unlock it.
1830 */
1831 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1832 {
1833 spinlock_t *ptl;
1834
1835 ptl = pud_lock(vma->vm_mm, pud);
1836 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1837 return ptl;
1838 spin_unlock(ptl);
1839 return NULL;
1840 }
1841
1842 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1843 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1844 pud_t *pud, unsigned long addr)
1845 {
1846 pud_t orig_pud;
1847 spinlock_t *ptl;
1848
1849 ptl = __pud_trans_huge_lock(pud, vma);
1850 if (!ptl)
1851 return 0;
1852 /*
1853 * For architectures like ppc64 we look at deposited pgtable
1854 * when calling pudp_huge_get_and_clear. So do the
1855 * pgtable_trans_huge_withdraw after finishing pudp related
1856 * operations.
1857 */
1858 orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1859 tlb->fullmm);
1860 tlb_remove_pud_tlb_entry(tlb, pud, addr);
1861 if (vma_is_dax(vma)) {
1862 spin_unlock(ptl);
1863 /* No zero page support yet */
1864 } else {
1865 /* No support for anonymous PUD pages yet */
1866 BUG();
1867 }
1868 return 1;
1869 }
1870
1871 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
1872 unsigned long haddr)
1873 {
1874 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
1875 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1876 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
1877 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
1878
1879 count_vm_event(THP_SPLIT_PUD);
1880
1881 pudp_huge_clear_flush_notify(vma, haddr, pud);
1882 }
1883
1884 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
1885 unsigned long address)
1886 {
1887 spinlock_t *ptl;
1888 struct mm_struct *mm = vma->vm_mm;
1889 unsigned long haddr = address & HPAGE_PUD_MASK;
1890
1891 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
1892 ptl = pud_lock(mm, pud);
1893 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
1894 goto out;
1895 __split_huge_pud_locked(vma, pud, haddr);
1896
1897 out:
1898 spin_unlock(ptl);
1899 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PUD_SIZE);
1900 }
1901 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1902
1903 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
1904 unsigned long haddr, pmd_t *pmd)
1905 {
1906 struct mm_struct *mm = vma->vm_mm;
1907 pgtable_t pgtable;
1908 pmd_t _pmd;
1909 int i;
1910
1911 /* leave pmd empty until pte is filled */
1912 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1913
1914 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1915 pmd_populate(mm, &_pmd, pgtable);
1916
1917 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1918 pte_t *pte, entry;
1919 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1920 entry = pte_mkspecial(entry);
1921 pte = pte_offset_map(&_pmd, haddr);
1922 VM_BUG_ON(!pte_none(*pte));
1923 set_pte_at(mm, haddr, pte, entry);
1924 pte_unmap(pte);
1925 }
1926 smp_wmb(); /* make pte visible before pmd */
1927 pmd_populate(mm, pmd, pgtable);
1928 }
1929
1930 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
1931 unsigned long haddr, bool freeze)
1932 {
1933 struct mm_struct *mm = vma->vm_mm;
1934 struct page *page;
1935 pgtable_t pgtable;
1936 pmd_t _pmd;
1937 bool young, write, dirty, soft_dirty;
1938 unsigned long addr;
1939 int i;
1940
1941 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
1942 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1943 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
1944 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
1945
1946 count_vm_event(THP_SPLIT_PMD);
1947
1948 if (!vma_is_anonymous(vma)) {
1949 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1950 /*
1951 * We are going to unmap this huge page. So
1952 * just go ahead and zap it
1953 */
1954 if (arch_needs_pgtable_deposit())
1955 zap_deposited_table(mm, pmd);
1956 if (vma_is_dax(vma))
1957 return;
1958 page = pmd_page(_pmd);
1959 if (!PageReferenced(page) && pmd_young(_pmd))
1960 SetPageReferenced(page);
1961 page_remove_rmap(page, true);
1962 put_page(page);
1963 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1964 return;
1965 } else if (is_huge_zero_pmd(*pmd)) {
1966 return __split_huge_zero_page_pmd(vma, haddr, pmd);
1967 }
1968
1969 page = pmd_page(*pmd);
1970 VM_BUG_ON_PAGE(!page_count(page), page);
1971 page_ref_add(page, HPAGE_PMD_NR - 1);
1972 write = pmd_write(*pmd);
1973 young = pmd_young(*pmd);
1974 dirty = pmd_dirty(*pmd);
1975 soft_dirty = pmd_soft_dirty(*pmd);
1976
1977 pmdp_huge_split_prepare(vma, haddr, pmd);
1978 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1979 pmd_populate(mm, &_pmd, pgtable);
1980
1981 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
1982 pte_t entry, *pte;
1983 /*
1984 * Note that NUMA hinting access restrictions are not
1985 * transferred to avoid any possibility of altering
1986 * permissions across VMAs.
1987 */
1988 if (freeze) {
1989 swp_entry_t swp_entry;
1990 swp_entry = make_migration_entry(page + i, write);
1991 entry = swp_entry_to_pte(swp_entry);
1992 if (soft_dirty)
1993 entry = pte_swp_mksoft_dirty(entry);
1994 } else {
1995 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
1996 entry = maybe_mkwrite(entry, vma);
1997 if (!write)
1998 entry = pte_wrprotect(entry);
1999 if (!young)
2000 entry = pte_mkold(entry);
2001 if (soft_dirty)
2002 entry = pte_mksoft_dirty(entry);
2003 }
2004 if (dirty)
2005 SetPageDirty(page + i);
2006 pte = pte_offset_map(&_pmd, addr);
2007 BUG_ON(!pte_none(*pte));
2008 set_pte_at(mm, addr, pte, entry);
2009 atomic_inc(&page[i]._mapcount);
2010 pte_unmap(pte);
2011 }
2012
2013 /*
2014 * Set PG_double_map before dropping compound_mapcount to avoid
2015 * false-negative page_mapped().
2016 */
2017 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2018 for (i = 0; i < HPAGE_PMD_NR; i++)
2019 atomic_inc(&page[i]._mapcount);
2020 }
2021
2022 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2023 /* Last compound_mapcount is gone. */
2024 __dec_node_page_state(page, NR_ANON_THPS);
2025 if (TestClearPageDoubleMap(page)) {
2026 /* No need in mapcount reference anymore */
2027 for (i = 0; i < HPAGE_PMD_NR; i++)
2028 atomic_dec(&page[i]._mapcount);
2029 }
2030 }
2031
2032 smp_wmb(); /* make pte visible before pmd */
2033 /*
2034 * Up to this point the pmd is present and huge and userland has the
2035 * whole access to the hugepage during the split (which happens in
2036 * place). If we overwrite the pmd with the not-huge version pointing
2037 * to the pte here (which of course we could if all CPUs were bug
2038 * free), userland could trigger a small page size TLB miss on the
2039 * small sized TLB while the hugepage TLB entry is still established in
2040 * the huge TLB. Some CPU doesn't like that.
2041 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2042 * 383 on page 93. Intel should be safe but is also warns that it's
2043 * only safe if the permission and cache attributes of the two entries
2044 * loaded in the two TLB is identical (which should be the case here).
2045 * But it is generally safer to never allow small and huge TLB entries
2046 * for the same virtual address to be loaded simultaneously. So instead
2047 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2048 * current pmd notpresent (atomically because here the pmd_trans_huge
2049 * and pmd_trans_splitting must remain set at all times on the pmd
2050 * until the split is complete for this pmd), then we flush the SMP TLB
2051 * and finally we write the non-huge version of the pmd entry with
2052 * pmd_populate.
2053 */
2054 pmdp_invalidate(vma, haddr, pmd);
2055 pmd_populate(mm, pmd, pgtable);
2056
2057 if (freeze) {
2058 for (i = 0; i < HPAGE_PMD_NR; i++) {
2059 page_remove_rmap(page + i, false);
2060 put_page(page + i);
2061 }
2062 }
2063 }
2064
2065 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2066 unsigned long address, bool freeze, struct page *page)
2067 {
2068 spinlock_t *ptl;
2069 struct mm_struct *mm = vma->vm_mm;
2070 unsigned long haddr = address & HPAGE_PMD_MASK;
2071
2072 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2073 ptl = pmd_lock(mm, pmd);
2074
2075 /*
2076 * If caller asks to setup a migration entries, we need a page to check
2077 * pmd against. Otherwise we can end up replacing wrong page.
2078 */
2079 VM_BUG_ON(freeze && !page);
2080 if (page && page != pmd_page(*pmd))
2081 goto out;
2082
2083 if (pmd_trans_huge(*pmd)) {
2084 page = pmd_page(*pmd);
2085 if (PageMlocked(page))
2086 clear_page_mlock(page);
2087 } else if (!pmd_devmap(*pmd))
2088 goto out;
2089 __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2090 out:
2091 spin_unlock(ptl);
2092 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
2093 }
2094
2095 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2096 bool freeze, struct page *page)
2097 {
2098 pgd_t *pgd;
2099 p4d_t *p4d;
2100 pud_t *pud;
2101 pmd_t *pmd;
2102
2103 pgd = pgd_offset(vma->vm_mm, address);
2104 if (!pgd_present(*pgd))
2105 return;
2106
2107 p4d = p4d_offset(pgd, address);
2108 if (!p4d_present(*p4d))
2109 return;
2110
2111 pud = pud_offset(p4d, address);
2112 if (!pud_present(*pud))
2113 return;
2114
2115 pmd = pmd_offset(pud, address);
2116
2117 __split_huge_pmd(vma, pmd, address, freeze, page);
2118 }
2119
2120 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2121 unsigned long start,
2122 unsigned long end,
2123 long adjust_next)
2124 {
2125 /*
2126 * If the new start address isn't hpage aligned and it could
2127 * previously contain an hugepage: check if we need to split
2128 * an huge pmd.
2129 */
2130 if (start & ~HPAGE_PMD_MASK &&
2131 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2132 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2133 split_huge_pmd_address(vma, start, false, NULL);
2134
2135 /*
2136 * If the new end address isn't hpage aligned and it could
2137 * previously contain an hugepage: check if we need to split
2138 * an huge pmd.
2139 */
2140 if (end & ~HPAGE_PMD_MASK &&
2141 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2142 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2143 split_huge_pmd_address(vma, end, false, NULL);
2144
2145 /*
2146 * If we're also updating the vma->vm_next->vm_start, if the new
2147 * vm_next->vm_start isn't page aligned and it could previously
2148 * contain an hugepage: check if we need to split an huge pmd.
2149 */
2150 if (adjust_next > 0) {
2151 struct vm_area_struct *next = vma->vm_next;
2152 unsigned long nstart = next->vm_start;
2153 nstart += adjust_next << PAGE_SHIFT;
2154 if (nstart & ~HPAGE_PMD_MASK &&
2155 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2156 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2157 split_huge_pmd_address(next, nstart, false, NULL);
2158 }
2159 }
2160
2161 static void freeze_page(struct page *page)
2162 {
2163 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2164 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2165 bool unmap_success;
2166
2167 VM_BUG_ON_PAGE(!PageHead(page), page);
2168
2169 if (PageAnon(page))
2170 ttu_flags |= TTU_MIGRATION;
2171
2172 unmap_success = try_to_unmap(page, ttu_flags);
2173 VM_BUG_ON_PAGE(!unmap_success, page);
2174 }
2175
2176 static void unfreeze_page(struct page *page)
2177 {
2178 int i;
2179 if (PageTransHuge(page)) {
2180 remove_migration_ptes(page, page, true);
2181 } else {
2182 for (i = 0; i < HPAGE_PMD_NR; i++)
2183 remove_migration_ptes(page + i, page + i, true);
2184 }
2185 }
2186
2187 static void __split_huge_page_tail(struct page *head, int tail,
2188 struct lruvec *lruvec, struct list_head *list)
2189 {
2190 struct page *page_tail = head + tail;
2191
2192 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2193 VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
2194
2195 /*
2196 * tail_page->_refcount is zero and not changing from under us. But
2197 * get_page_unless_zero() may be running from under us on the
2198 * tail_page. If we used atomic_set() below instead of atomic_inc() or
2199 * atomic_add(), we would then run atomic_set() concurrently with
2200 * get_page_unless_zero(), and atomic_set() is implemented in C not
2201 * using locked ops. spin_unlock on x86 sometime uses locked ops
2202 * because of PPro errata 66, 92, so unless somebody can guarantee
2203 * atomic_set() here would be safe on all archs (and not only on x86),
2204 * it's safer to use atomic_inc()/atomic_add().
2205 */
2206 if (PageAnon(head) && !PageSwapCache(head)) {
2207 page_ref_inc(page_tail);
2208 } else {
2209 /* Additional pin to radix tree */
2210 page_ref_add(page_tail, 2);
2211 }
2212
2213 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2214 page_tail->flags |= (head->flags &
2215 ((1L << PG_referenced) |
2216 (1L << PG_swapbacked) |
2217 (1L << PG_swapcache) |
2218 (1L << PG_mlocked) |
2219 (1L << PG_uptodate) |
2220 (1L << PG_active) |
2221 (1L << PG_locked) |
2222 (1L << PG_unevictable) |
2223 (1L << PG_dirty)));
2224
2225 /*
2226 * After clearing PageTail the gup refcount can be released.
2227 * Page flags also must be visible before we make the page non-compound.
2228 */
2229 smp_wmb();
2230
2231 clear_compound_head(page_tail);
2232
2233 if (page_is_young(head))
2234 set_page_young(page_tail);
2235 if (page_is_idle(head))
2236 set_page_idle(page_tail);
2237
2238 /* ->mapping in first tail page is compound_mapcount */
2239 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2240 page_tail);
2241 page_tail->mapping = head->mapping;
2242
2243 page_tail->index = head->index + tail;
2244 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2245 lru_add_page_tail(head, page_tail, lruvec, list);
2246 }
2247
2248 static void __split_huge_page(struct page *page, struct list_head *list,
2249 unsigned long flags)
2250 {
2251 struct page *head = compound_head(page);
2252 struct zone *zone = page_zone(head);
2253 struct lruvec *lruvec;
2254 pgoff_t end = -1;
2255 int i;
2256
2257 lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2258
2259 /* complete memcg works before add pages to LRU */
2260 mem_cgroup_split_huge_fixup(head);
2261
2262 if (!PageAnon(page))
2263 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
2264
2265 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2266 __split_huge_page_tail(head, i, lruvec, list);
2267 /* Some pages can be beyond i_size: drop them from page cache */
2268 if (head[i].index >= end) {
2269 __ClearPageDirty(head + i);
2270 __delete_from_page_cache(head + i, NULL);
2271 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2272 shmem_uncharge(head->mapping->host, 1);
2273 put_page(head + i);
2274 }
2275 }
2276
2277 ClearPageCompound(head);
2278 /* See comment in __split_huge_page_tail() */
2279 if (PageAnon(head)) {
2280 /* Additional pin to radix tree of swap cache */
2281 if (PageSwapCache(head))
2282 page_ref_add(head, 2);
2283 else
2284 page_ref_inc(head);
2285 } else {
2286 /* Additional pin to radix tree */
2287 page_ref_add(head, 2);
2288 spin_unlock(&head->mapping->tree_lock);
2289 }
2290
2291 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2292
2293 unfreeze_page(head);
2294
2295 for (i = 0; i < HPAGE_PMD_NR; i++) {
2296 struct page *subpage = head + i;
2297 if (subpage == page)
2298 continue;
2299 unlock_page(subpage);
2300
2301 /*
2302 * Subpages may be freed if there wasn't any mapping
2303 * like if add_to_swap() is running on a lru page that
2304 * had its mapping zapped. And freeing these pages
2305 * requires taking the lru_lock so we do the put_page
2306 * of the tail pages after the split is complete.
2307 */
2308 put_page(subpage);
2309 }
2310 }
2311
2312 int total_mapcount(struct page *page)
2313 {
2314 int i, compound, ret;
2315
2316 VM_BUG_ON_PAGE(PageTail(page), page);
2317
2318 if (likely(!PageCompound(page)))
2319 return atomic_read(&page->_mapcount) + 1;
2320
2321 compound = compound_mapcount(page);
2322 if (PageHuge(page))
2323 return compound;
2324 ret = compound;
2325 for (i = 0; i < HPAGE_PMD_NR; i++)
2326 ret += atomic_read(&page[i]._mapcount) + 1;
2327 /* File pages has compound_mapcount included in _mapcount */
2328 if (!PageAnon(page))
2329 return ret - compound * HPAGE_PMD_NR;
2330 if (PageDoubleMap(page))
2331 ret -= HPAGE_PMD_NR;
2332 return ret;
2333 }
2334
2335 /*
2336 * This calculates accurately how many mappings a transparent hugepage
2337 * has (unlike page_mapcount() which isn't fully accurate). This full
2338 * accuracy is primarily needed to know if copy-on-write faults can
2339 * reuse the page and change the mapping to read-write instead of
2340 * copying them. At the same time this returns the total_mapcount too.
2341 *
2342 * The function returns the highest mapcount any one of the subpages
2343 * has. If the return value is one, even if different processes are
2344 * mapping different subpages of the transparent hugepage, they can
2345 * all reuse it, because each process is reusing a different subpage.
2346 *
2347 * The total_mapcount is instead counting all virtual mappings of the
2348 * subpages. If the total_mapcount is equal to "one", it tells the
2349 * caller all mappings belong to the same "mm" and in turn the
2350 * anon_vma of the transparent hugepage can become the vma->anon_vma
2351 * local one as no other process may be mapping any of the subpages.
2352 *
2353 * It would be more accurate to replace page_mapcount() with
2354 * page_trans_huge_mapcount(), however we only use
2355 * page_trans_huge_mapcount() in the copy-on-write faults where we
2356 * need full accuracy to avoid breaking page pinning, because
2357 * page_trans_huge_mapcount() is slower than page_mapcount().
2358 */
2359 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2360 {
2361 int i, ret, _total_mapcount, mapcount;
2362
2363 /* hugetlbfs shouldn't call it */
2364 VM_BUG_ON_PAGE(PageHuge(page), page);
2365
2366 if (likely(!PageTransCompound(page))) {
2367 mapcount = atomic_read(&page->_mapcount) + 1;
2368 if (total_mapcount)
2369 *total_mapcount = mapcount;
2370 return mapcount;
2371 }
2372
2373 page = compound_head(page);
2374
2375 _total_mapcount = ret = 0;
2376 for (i = 0; i < HPAGE_PMD_NR; i++) {
2377 mapcount = atomic_read(&page[i]._mapcount) + 1;
2378 ret = max(ret, mapcount);
2379 _total_mapcount += mapcount;
2380 }
2381 if (PageDoubleMap(page)) {
2382 ret -= 1;
2383 _total_mapcount -= HPAGE_PMD_NR;
2384 }
2385 mapcount = compound_mapcount(page);
2386 ret += mapcount;
2387 _total_mapcount += mapcount;
2388 if (total_mapcount)
2389 *total_mapcount = _total_mapcount;
2390 return ret;
2391 }
2392
2393 /* Racy check whether the huge page can be split */
2394 bool can_split_huge_page(struct page *page, int *pextra_pins)
2395 {
2396 int extra_pins;
2397
2398 /* Additional pins from radix tree */
2399 if (PageAnon(page))
2400 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2401 else
2402 extra_pins = HPAGE_PMD_NR;
2403 if (pextra_pins)
2404 *pextra_pins = extra_pins;
2405 return total_mapcount(page) == page_count(page) - extra_pins - 1;
2406 }
2407
2408 /*
2409 * This function splits huge page into normal pages. @page can point to any
2410 * subpage of huge page to split. Split doesn't change the position of @page.
2411 *
2412 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2413 * The huge page must be locked.
2414 *
2415 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2416 *
2417 * Both head page and tail pages will inherit mapping, flags, and so on from
2418 * the hugepage.
2419 *
2420 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2421 * they are not mapped.
2422 *
2423 * Returns 0 if the hugepage is split successfully.
2424 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2425 * us.
2426 */
2427 int split_huge_page_to_list(struct page *page, struct list_head *list)
2428 {
2429 struct page *head = compound_head(page);
2430 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2431 struct anon_vma *anon_vma = NULL;
2432 struct address_space *mapping = NULL;
2433 int count, mapcount, extra_pins, ret;
2434 bool mlocked;
2435 unsigned long flags;
2436
2437 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2438 VM_BUG_ON_PAGE(!PageLocked(page), page);
2439 VM_BUG_ON_PAGE(!PageCompound(page), page);
2440
2441 if (PageAnon(head)) {
2442 /*
2443 * The caller does not necessarily hold an mmap_sem that would
2444 * prevent the anon_vma disappearing so we first we take a
2445 * reference to it and then lock the anon_vma for write. This
2446 * is similar to page_lock_anon_vma_read except the write lock
2447 * is taken to serialise against parallel split or collapse
2448 * operations.
2449 */
2450 anon_vma = page_get_anon_vma(head);
2451 if (!anon_vma) {
2452 ret = -EBUSY;
2453 goto out;
2454 }
2455 mapping = NULL;
2456 anon_vma_lock_write(anon_vma);
2457 } else {
2458 mapping = head->mapping;
2459
2460 /* Truncated ? */
2461 if (!mapping) {
2462 ret = -EBUSY;
2463 goto out;
2464 }
2465
2466 anon_vma = NULL;
2467 i_mmap_lock_read(mapping);
2468 }
2469
2470 /*
2471 * Racy check if we can split the page, before freeze_page() will
2472 * split PMDs
2473 */
2474 if (!can_split_huge_page(head, &extra_pins)) {
2475 ret = -EBUSY;
2476 goto out_unlock;
2477 }
2478
2479 mlocked = PageMlocked(page);
2480 freeze_page(head);
2481 VM_BUG_ON_PAGE(compound_mapcount(head), head);
2482
2483 /* Make sure the page is not on per-CPU pagevec as it takes pin */
2484 if (mlocked)
2485 lru_add_drain();
2486
2487 /* prevent PageLRU to go away from under us, and freeze lru stats */
2488 spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2489
2490 if (mapping) {
2491 void **pslot;
2492
2493 spin_lock(&mapping->tree_lock);
2494 pslot = radix_tree_lookup_slot(&mapping->page_tree,
2495 page_index(head));
2496 /*
2497 * Check if the head page is present in radix tree.
2498 * We assume all tail are present too, if head is there.
2499 */
2500 if (radix_tree_deref_slot_protected(pslot,
2501 &mapping->tree_lock) != head)
2502 goto fail;
2503 }
2504
2505 /* Prevent deferred_split_scan() touching ->_refcount */
2506 spin_lock(&pgdata->split_queue_lock);
2507 count = page_count(head);
2508 mapcount = total_mapcount(head);
2509 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2510 if (!list_empty(page_deferred_list(head))) {
2511 pgdata->split_queue_len--;
2512 list_del(page_deferred_list(head));
2513 }
2514 if (mapping)
2515 __dec_node_page_state(page, NR_SHMEM_THPS);
2516 spin_unlock(&pgdata->split_queue_lock);
2517 __split_huge_page(page, list, flags);
2518 ret = 0;
2519 } else {
2520 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2521 pr_alert("total_mapcount: %u, page_count(): %u\n",
2522 mapcount, count);
2523 if (PageTail(page))
2524 dump_page(head, NULL);
2525 dump_page(page, "total_mapcount(head) > 0");
2526 BUG();
2527 }
2528 spin_unlock(&pgdata->split_queue_lock);
2529 fail: if (mapping)
2530 spin_unlock(&mapping->tree_lock);
2531 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2532 unfreeze_page(head);
2533 ret = -EBUSY;
2534 }
2535
2536 out_unlock:
2537 if (anon_vma) {
2538 anon_vma_unlock_write(anon_vma);
2539 put_anon_vma(anon_vma);
2540 }
2541 if (mapping)
2542 i_mmap_unlock_read(mapping);
2543 out:
2544 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2545 return ret;
2546 }
2547
2548 void free_transhuge_page(struct page *page)
2549 {
2550 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2551 unsigned long flags;
2552
2553 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2554 if (!list_empty(page_deferred_list(page))) {
2555 pgdata->split_queue_len--;
2556 list_del(page_deferred_list(page));
2557 }
2558 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2559 free_compound_page(page);
2560 }
2561
2562 void deferred_split_huge_page(struct page *page)
2563 {
2564 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2565 unsigned long flags;
2566
2567 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2568
2569 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2570 if (list_empty(page_deferred_list(page))) {
2571 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2572 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2573 pgdata->split_queue_len++;
2574 }
2575 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2576 }
2577
2578 static unsigned long deferred_split_count(struct shrinker *shrink,
2579 struct shrink_control *sc)
2580 {
2581 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2582 return ACCESS_ONCE(pgdata->split_queue_len);
2583 }
2584
2585 static unsigned long deferred_split_scan(struct shrinker *shrink,
2586 struct shrink_control *sc)
2587 {
2588 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2589 unsigned long flags;
2590 LIST_HEAD(list), *pos, *next;
2591 struct page *page;
2592 int split = 0;
2593
2594 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2595 /* Take pin on all head pages to avoid freeing them under us */
2596 list_for_each_safe(pos, next, &pgdata->split_queue) {
2597 page = list_entry((void *)pos, struct page, mapping);
2598 page = compound_head(page);
2599 if (get_page_unless_zero(page)) {
2600 list_move(page_deferred_list(page), &list);
2601 } else {
2602 /* We lost race with put_compound_page() */
2603 list_del_init(page_deferred_list(page));
2604 pgdata->split_queue_len--;
2605 }
2606 if (!--sc->nr_to_scan)
2607 break;
2608 }
2609 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2610
2611 list_for_each_safe(pos, next, &list) {
2612 page = list_entry((void *)pos, struct page, mapping);
2613 lock_page(page);
2614 /* split_huge_page() removes page from list on success */
2615 if (!split_huge_page(page))
2616 split++;
2617 unlock_page(page);
2618 put_page(page);
2619 }
2620
2621 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2622 list_splice_tail(&list, &pgdata->split_queue);
2623 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2624
2625 /*
2626 * Stop shrinker if we didn't split any page, but the queue is empty.
2627 * This can happen if pages were freed under us.
2628 */
2629 if (!split && list_empty(&pgdata->split_queue))
2630 return SHRINK_STOP;
2631 return split;
2632 }
2633
2634 static struct shrinker deferred_split_shrinker = {
2635 .count_objects = deferred_split_count,
2636 .scan_objects = deferred_split_scan,
2637 .seeks = DEFAULT_SEEKS,
2638 .flags = SHRINKER_NUMA_AWARE,
2639 };
2640
2641 #ifdef CONFIG_DEBUG_FS
2642 static int split_huge_pages_set(void *data, u64 val)
2643 {
2644 struct zone *zone;
2645 struct page *page;
2646 unsigned long pfn, max_zone_pfn;
2647 unsigned long total = 0, split = 0;
2648
2649 if (val != 1)
2650 return -EINVAL;
2651
2652 for_each_populated_zone(zone) {
2653 max_zone_pfn = zone_end_pfn(zone);
2654 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2655 if (!pfn_valid(pfn))
2656 continue;
2657
2658 page = pfn_to_page(pfn);
2659 if (!get_page_unless_zero(page))
2660 continue;
2661
2662 if (zone != page_zone(page))
2663 goto next;
2664
2665 if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2666 goto next;
2667
2668 total++;
2669 lock_page(page);
2670 if (!split_huge_page(page))
2671 split++;
2672 unlock_page(page);
2673 next:
2674 put_page(page);
2675 }
2676 }
2677
2678 pr_info("%lu of %lu THP split\n", split, total);
2679
2680 return 0;
2681 }
2682 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2683 "%llu\n");
2684
2685 static int __init split_huge_pages_debugfs(void)
2686 {
2687 void *ret;
2688
2689 ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2690 &split_huge_pages_fops);
2691 if (!ret)
2692 pr_warn("Failed to create split_huge_pages in debugfs");
2693 return 0;
2694 }
2695 late_initcall(split_huge_pages_debugfs);
2696 #endif
Linux with added FPC-III support