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net: fix ifindex collision during namespace removal
[linux/fpc-iii.git] / mm / huge_memory.c
blob7ea8da990b9de0b81cfeef42d336d3f185671a7f
1 /*
2 * Copyright (C) 2009 Red Hat, Inc.
3 *
4 * This work is licensed under the terms of the GNU GPL, version 2. See
5 * the COPYING file in the top-level directory.
6 */
7
8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10 #include <linux/mm.h>
11 #include <linux/sched.h>
12 #include <linux/highmem.h>
13 #include <linux/hugetlb.h>
14 #include <linux/mmu_notifier.h>
15 #include <linux/rmap.h>
16 #include <linux/swap.h>
17 #include <linux/shrinker.h>
18 #include <linux/mm_inline.h>
19 #include <linux/swapops.h>
20 #include <linux/dax.h>
21 #include <linux/khugepaged.h>
22 #include <linux/freezer.h>
23 #include <linux/pfn_t.h>
24 #include <linux/mman.h>
25 #include <linux/memremap.h>
26 #include <linux/pagemap.h>
27 #include <linux/debugfs.h>
28 #include <linux/migrate.h>
29 #include <linux/hashtable.h>
30 #include <linux/userfaultfd_k.h>
31 #include <linux/page_idle.h>
32 #include <linux/shmem_fs.h>
33
34 #include <asm/tlb.h>
35 #include <asm/pgalloc.h>
36 #include "internal.h"
37
38 /*
39 * By default transparent hugepage support is disabled in order that avoid
40 * to risk increase the memory footprint of applications without a guaranteed
41 * benefit. When transparent hugepage support is enabled, is for all mappings,
42 * and khugepaged scans all mappings.
43 * Defrag is invoked by khugepaged hugepage allocations and by page faults
44 * for all hugepage allocations.
45 */
46 unsigned long transparent_hugepage_flags __read_mostly =
47 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
48 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
49 #endif
50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
51 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
52 #endif
53 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
54 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
55 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
56
57 static struct shrinker deferred_split_shrinker;
58
59 static atomic_t huge_zero_refcount;
60 struct page *huge_zero_page __read_mostly;
61
62 static struct page *get_huge_zero_page(void)
63 {
64 struct page *zero_page;
65 retry:
66 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
67 return READ_ONCE(huge_zero_page);
68
69 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
70 HPAGE_PMD_ORDER);
71 if (!zero_page) {
72 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
73 return NULL;
74 }
75 count_vm_event(THP_ZERO_PAGE_ALLOC);
76 preempt_disable();
77 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
78 preempt_enable();
79 __free_pages(zero_page, compound_order(zero_page));
80 goto retry;
81 }
82
83 /* We take additional reference here. It will be put back by shrinker */
84 atomic_set(&huge_zero_refcount, 2);
85 preempt_enable();
86 return READ_ONCE(huge_zero_page);
87 }
88
89 static void put_huge_zero_page(void)
90 {
91 /*
92 * Counter should never go to zero here. Only shrinker can put
93 * last reference.
94 */
95 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
96 }
97
98 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
99 {
100 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
101 return READ_ONCE(huge_zero_page);
102
103 if (!get_huge_zero_page())
104 return NULL;
105
106 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
107 put_huge_zero_page();
108
109 return READ_ONCE(huge_zero_page);
110 }
111
112 void mm_put_huge_zero_page(struct mm_struct *mm)
113 {
114 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
115 put_huge_zero_page();
116 }
117
118 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
119 struct shrink_control *sc)
120 {
121 /* we can free zero page only if last reference remains */
122 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
123 }
124
125 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
126 struct shrink_control *sc)
127 {
128 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
129 struct page *zero_page = xchg(&huge_zero_page, NULL);
130 BUG_ON(zero_page == NULL);
131 __free_pages(zero_page, compound_order(zero_page));
132 return HPAGE_PMD_NR;
133 }
134
135 return 0;
136 }
137
138 static struct shrinker huge_zero_page_shrinker = {
139 .count_objects = shrink_huge_zero_page_count,
140 .scan_objects = shrink_huge_zero_page_scan,
141 .seeks = DEFAULT_SEEKS,
142 };
143
144 #ifdef CONFIG_SYSFS
145
146 static ssize_t triple_flag_store(struct kobject *kobj,
147 struct kobj_attribute *attr,
148 const char *buf, size_t count,
149 enum transparent_hugepage_flag enabled,
150 enum transparent_hugepage_flag deferred,
151 enum transparent_hugepage_flag req_madv)
152 {
153 if (!memcmp("defer", buf,
154 min(sizeof("defer")-1, count))) {
155 if (enabled == deferred)
156 return -EINVAL;
157 clear_bit(enabled, &transparent_hugepage_flags);
158 clear_bit(req_madv, &transparent_hugepage_flags);
159 set_bit(deferred, &transparent_hugepage_flags);
160 } else if (!memcmp("always", buf,
161 min(sizeof("always")-1, count))) {
162 clear_bit(deferred, &transparent_hugepage_flags);
163 clear_bit(req_madv, &transparent_hugepage_flags);
164 set_bit(enabled, &transparent_hugepage_flags);
165 } else if (!memcmp("madvise", buf,
166 min(sizeof("madvise")-1, count))) {
167 clear_bit(enabled, &transparent_hugepage_flags);
168 clear_bit(deferred, &transparent_hugepage_flags);
169 set_bit(req_madv, &transparent_hugepage_flags);
170 } else if (!memcmp("never", buf,
171 min(sizeof("never")-1, count))) {
172 clear_bit(enabled, &transparent_hugepage_flags);
173 clear_bit(req_madv, &transparent_hugepage_flags);
174 clear_bit(deferred, &transparent_hugepage_flags);
175 } else
176 return -EINVAL;
177
178 return count;
179 }
180
181 static ssize_t enabled_show(struct kobject *kobj,
182 struct kobj_attribute *attr, char *buf)
183 {
184 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
185 return sprintf(buf, "[always] madvise never\n");
186 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
187 return sprintf(buf, "always [madvise] never\n");
188 else
189 return sprintf(buf, "always madvise [never]\n");
190 }
191
192 static ssize_t enabled_store(struct kobject *kobj,
193 struct kobj_attribute *attr,
194 const char *buf, size_t count)
195 {
196 ssize_t ret;
197
198 ret = triple_flag_store(kobj, attr, buf, count,
199 TRANSPARENT_HUGEPAGE_FLAG,
200 TRANSPARENT_HUGEPAGE_FLAG,
201 TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG);
202
203 if (ret > 0) {
204 int err = start_stop_khugepaged();
205 if (err)
206 ret = err;
207 }
208
209 return ret;
210 }
211 static struct kobj_attribute enabled_attr =
212 __ATTR(enabled, 0644, enabled_show, enabled_store);
213
214 ssize_t single_hugepage_flag_show(struct kobject *kobj,
215 struct kobj_attribute *attr, char *buf,
216 enum transparent_hugepage_flag flag)
217 {
218 return sprintf(buf, "%d\n",
219 !!test_bit(flag, &transparent_hugepage_flags));
220 }
221
222 ssize_t single_hugepage_flag_store(struct kobject *kobj,
223 struct kobj_attribute *attr,
224 const char *buf, size_t count,
225 enum transparent_hugepage_flag flag)
226 {
227 unsigned long value;
228 int ret;
229
230 ret = kstrtoul(buf, 10, &value);
231 if (ret < 0)
232 return ret;
233 if (value > 1)
234 return -EINVAL;
235
236 if (value)
237 set_bit(flag, &transparent_hugepage_flags);
238 else
239 clear_bit(flag, &transparent_hugepage_flags);
240
241 return count;
242 }
243
244 /*
245 * Currently defrag only disables __GFP_NOWAIT for allocation. A blind
246 * __GFP_REPEAT is too aggressive, it's never worth swapping tons of
247 * memory just to allocate one more hugepage.
248 */
249 static ssize_t defrag_show(struct kobject *kobj,
250 struct kobj_attribute *attr, char *buf)
251 {
252 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
253 return sprintf(buf, "[always] defer madvise never\n");
254 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
255 return sprintf(buf, "always [defer] madvise never\n");
256 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
257 return sprintf(buf, "always defer [madvise] never\n");
258 else
259 return sprintf(buf, "always defer madvise [never]\n");
260
261 }
262 static ssize_t defrag_store(struct kobject *kobj,
263 struct kobj_attribute *attr,
264 const char *buf, size_t count)
265 {
266 return triple_flag_store(kobj, attr, buf, count,
267 TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
268 TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
269 TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG);
270 }
271 static struct kobj_attribute defrag_attr =
272 __ATTR(defrag, 0644, defrag_show, defrag_store);
273
274 static ssize_t use_zero_page_show(struct kobject *kobj,
275 struct kobj_attribute *attr, char *buf)
276 {
277 return single_hugepage_flag_show(kobj, attr, buf,
278 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
279 }
280 static ssize_t use_zero_page_store(struct kobject *kobj,
281 struct kobj_attribute *attr, const char *buf, size_t count)
282 {
283 return single_hugepage_flag_store(kobj, attr, buf, count,
284 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
285 }
286 static struct kobj_attribute use_zero_page_attr =
287 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
288 #ifdef CONFIG_DEBUG_VM
289 static ssize_t debug_cow_show(struct kobject *kobj,
290 struct kobj_attribute *attr, char *buf)
291 {
292 return single_hugepage_flag_show(kobj, attr, buf,
293 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
294 }
295 static ssize_t debug_cow_store(struct kobject *kobj,
296 struct kobj_attribute *attr,
297 const char *buf, size_t count)
298 {
299 return single_hugepage_flag_store(kobj, attr, buf, count,
300 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
301 }
302 static struct kobj_attribute debug_cow_attr =
303 __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
304 #endif /* CONFIG_DEBUG_VM */
305
306 static struct attribute *hugepage_attr[] = {
307 &enabled_attr.attr,
308 &defrag_attr.attr,
309 &use_zero_page_attr.attr,
310 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
311 &shmem_enabled_attr.attr,
312 #endif
313 #ifdef CONFIG_DEBUG_VM
314 &debug_cow_attr.attr,
315 #endif
316 NULL,
317 };
318
319 static struct attribute_group hugepage_attr_group = {
320 .attrs = hugepage_attr,
321 };
322
323 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
324 {
325 int err;
326
327 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
328 if (unlikely(!*hugepage_kobj)) {
329 pr_err("failed to create transparent hugepage kobject\n");
330 return -ENOMEM;
331 }
332
333 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
334 if (err) {
335 pr_err("failed to register transparent hugepage group\n");
336 goto delete_obj;
337 }
338
339 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
340 if (err) {
341 pr_err("failed to register transparent hugepage group\n");
342 goto remove_hp_group;
343 }
344
345 return 0;
346
347 remove_hp_group:
348 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
349 delete_obj:
350 kobject_put(*hugepage_kobj);
351 return err;
352 }
353
354 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
355 {
356 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
357 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
358 kobject_put(hugepage_kobj);
359 }
360 #else
361 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
362 {
363 return 0;
364 }
365
366 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
367 {
368 }
369 #endif /* CONFIG_SYSFS */
370
371 static int __init hugepage_init(void)
372 {
373 int err;
374 struct kobject *hugepage_kobj;
375
376 if (!has_transparent_hugepage()) {
377 transparent_hugepage_flags = 0;
378 return -EINVAL;
379 }
380
381 /*
382 * hugepages can't be allocated by the buddy allocator
383 */
384 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
385 /*
386 * we use page->mapping and page->index in second tail page
387 * as list_head: assuming THP order >= 2
388 */
389 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
390
391 err = hugepage_init_sysfs(&hugepage_kobj);
392 if (err)
393 goto err_sysfs;
394
395 err = khugepaged_init();
396 if (err)
397 goto err_slab;
398
399 err = register_shrinker(&huge_zero_page_shrinker);
400 if (err)
401 goto err_hzp_shrinker;
402 err = register_shrinker(&deferred_split_shrinker);
403 if (err)
404 goto err_split_shrinker;
405
406 /*
407 * By default disable transparent hugepages on smaller systems,
408 * where the extra memory used could hurt more than TLB overhead
409 * is likely to save. The admin can still enable it through /sys.
410 */
411 if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
412 transparent_hugepage_flags = 0;
413 return 0;
414 }
415
416 err = start_stop_khugepaged();
417 if (err)
418 goto err_khugepaged;
419
420 return 0;
421 err_khugepaged:
422 unregister_shrinker(&deferred_split_shrinker);
423 err_split_shrinker:
424 unregister_shrinker(&huge_zero_page_shrinker);
425 err_hzp_shrinker:
426 khugepaged_destroy();
427 err_slab:
428 hugepage_exit_sysfs(hugepage_kobj);
429 err_sysfs:
430 return err;
431 }
432 subsys_initcall(hugepage_init);
433
434 static int __init setup_transparent_hugepage(char *str)
435 {
436 int ret = 0;
437 if (!str)
438 goto out;
439 if (!strcmp(str, "always")) {
440 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
441 &transparent_hugepage_flags);
442 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
443 &transparent_hugepage_flags);
444 ret = 1;
445 } else if (!strcmp(str, "madvise")) {
446 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
447 &transparent_hugepage_flags);
448 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
449 &transparent_hugepage_flags);
450 ret = 1;
451 } else if (!strcmp(str, "never")) {
452 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
453 &transparent_hugepage_flags);
454 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
455 &transparent_hugepage_flags);
456 ret = 1;
457 }
458 out:
459 if (!ret)
460 pr_warn("transparent_hugepage= cannot parse, ignored\n");
461 return ret;
462 }
463 __setup("transparent_hugepage=", setup_transparent_hugepage);
464
465 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
466 {
467 if (likely(vma->vm_flags & VM_WRITE))
468 pmd = pmd_mkwrite(pmd);
469 return pmd;
470 }
471
472 static inline struct list_head *page_deferred_list(struct page *page)
473 {
474 /*
475 * ->lru in the tail pages is occupied by compound_head.
476 * Let's use ->mapping + ->index in the second tail page as list_head.
477 */
478 return (struct list_head *)&page[2].mapping;
479 }
480
481 void prep_transhuge_page(struct page *page)
482 {
483 /*
484 * we use page->mapping and page->indexlru in second tail page
485 * as list_head: assuming THP order >= 2
486 */
487
488 INIT_LIST_HEAD(page_deferred_list(page));
489 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
490 }
491
492 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
493 loff_t off, unsigned long flags, unsigned long size)
494 {
495 unsigned long addr;
496 loff_t off_end = off + len;
497 loff_t off_align = round_up(off, size);
498 unsigned long len_pad;
499
500 if (off_end <= off_align || (off_end - off_align) < size)
501 return 0;
502
503 len_pad = len + size;
504 if (len_pad < len || (off + len_pad) < off)
505 return 0;
506
507 addr = current->mm->get_unmapped_area(filp, 0, len_pad,
508 off >> PAGE_SHIFT, flags);
509 if (IS_ERR_VALUE(addr))
510 return 0;
511
512 addr += (off - addr) & (size - 1);
513 return addr;
514 }
515
516 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
517 unsigned long len, unsigned long pgoff, unsigned long flags)
518 {
519 loff_t off = (loff_t)pgoff << PAGE_SHIFT;
520
521 if (addr)
522 goto out;
523 if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
524 goto out;
525
526 addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
527 if (addr)
528 return addr;
529
530 out:
531 return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
532 }
533 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
534
535 static int __do_huge_pmd_anonymous_page(struct fault_env *fe, struct page *page,
536 gfp_t gfp)
537 {
538 struct vm_area_struct *vma = fe->vma;
539 struct mem_cgroup *memcg;
540 pgtable_t pgtable;
541 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
542
543 VM_BUG_ON_PAGE(!PageCompound(page), page);
544
545 if (mem_cgroup_try_charge(page, vma->vm_mm, gfp | __GFP_NORETRY, &memcg,
546 true)) {
547 put_page(page);
548 count_vm_event(THP_FAULT_FALLBACK);
549 return VM_FAULT_FALLBACK;
550 }
551
552 pgtable = pte_alloc_one(vma->vm_mm, haddr);
553 if (unlikely(!pgtable)) {
554 mem_cgroup_cancel_charge(page, memcg, true);
555 put_page(page);
556 return VM_FAULT_OOM;
557 }
558
559 clear_huge_page(page, haddr, HPAGE_PMD_NR);
560 /*
561 * The memory barrier inside __SetPageUptodate makes sure that
562 * clear_huge_page writes become visible before the set_pmd_at()
563 * write.
564 */
565 __SetPageUptodate(page);
566
567 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
568 if (unlikely(!pmd_none(*fe->pmd))) {
569 spin_unlock(fe->ptl);
570 mem_cgroup_cancel_charge(page, memcg, true);
571 put_page(page);
572 pte_free(vma->vm_mm, pgtable);
573 } else {
574 pmd_t entry;
575
576 /* Deliver the page fault to userland */
577 if (userfaultfd_missing(vma)) {
578 int ret;
579
580 spin_unlock(fe->ptl);
581 mem_cgroup_cancel_charge(page, memcg, true);
582 put_page(page);
583 pte_free(vma->vm_mm, pgtable);
584 ret = handle_userfault(fe, VM_UFFD_MISSING);
585 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
586 return ret;
587 }
588
589 entry = mk_huge_pmd(page, vma->vm_page_prot);
590 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
591 page_add_new_anon_rmap(page, vma, haddr, true);
592 mem_cgroup_commit_charge(page, memcg, false, true);
593 lru_cache_add_active_or_unevictable(page, vma);
594 pgtable_trans_huge_deposit(vma->vm_mm, fe->pmd, pgtable);
595 set_pmd_at(vma->vm_mm, haddr, fe->pmd, entry);
596 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
597 atomic_long_inc(&vma->vm_mm->nr_ptes);
598 spin_unlock(fe->ptl);
599 count_vm_event(THP_FAULT_ALLOC);
600 }
601
602 return 0;
603 }
604
605 /*
606 * If THP defrag is set to always then directly reclaim/compact as necessary
607 * If set to defer then do only background reclaim/compact and defer to khugepaged
608 * If set to madvise and the VMA is flagged then directly reclaim/compact
609 * When direct reclaim/compact is allowed, don't retry except for flagged VMA's
610 */
611 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
612 {
613 bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
614
615 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
616 &transparent_hugepage_flags) && vma_madvised)
617 return GFP_TRANSHUGE;
618 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
619 &transparent_hugepage_flags))
620 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
621 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
622 &transparent_hugepage_flags))
623 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
624
625 return GFP_TRANSHUGE_LIGHT;
626 }
627
628 /* Caller must hold page table lock. */
629 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
630 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
631 struct page *zero_page)
632 {
633 pmd_t entry;
634 if (!pmd_none(*pmd))
635 return false;
636 entry = mk_pmd(zero_page, vma->vm_page_prot);
637 entry = pmd_mkhuge(entry);
638 if (pgtable)
639 pgtable_trans_huge_deposit(mm, pmd, pgtable);
640 set_pmd_at(mm, haddr, pmd, entry);
641 atomic_long_inc(&mm->nr_ptes);
642 return true;
643 }
644
645 int do_huge_pmd_anonymous_page(struct fault_env *fe)
646 {
647 struct vm_area_struct *vma = fe->vma;
648 gfp_t gfp;
649 struct page *page;
650 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
651
652 if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
653 return VM_FAULT_FALLBACK;
654 if (unlikely(anon_vma_prepare(vma)))
655 return VM_FAULT_OOM;
656 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
657 return VM_FAULT_OOM;
658 if (!(fe->flags & FAULT_FLAG_WRITE) &&
659 !mm_forbids_zeropage(vma->vm_mm) &&
660 transparent_hugepage_use_zero_page()) {
661 pgtable_t pgtable;
662 struct page *zero_page;
663 bool set;
664 int ret;
665 pgtable = pte_alloc_one(vma->vm_mm, haddr);
666 if (unlikely(!pgtable))
667 return VM_FAULT_OOM;
668 zero_page = mm_get_huge_zero_page(vma->vm_mm);
669 if (unlikely(!zero_page)) {
670 pte_free(vma->vm_mm, pgtable);
671 count_vm_event(THP_FAULT_FALLBACK);
672 return VM_FAULT_FALLBACK;
673 }
674 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
675 ret = 0;
676 set = false;
677 if (pmd_none(*fe->pmd)) {
678 if (userfaultfd_missing(vma)) {
679 spin_unlock(fe->ptl);
680 ret = handle_userfault(fe, VM_UFFD_MISSING);
681 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
682 } else {
683 set_huge_zero_page(pgtable, vma->vm_mm, vma,
684 haddr, fe->pmd, zero_page);
685 spin_unlock(fe->ptl);
686 set = true;
687 }
688 } else
689 spin_unlock(fe->ptl);
690 if (!set)
691 pte_free(vma->vm_mm, pgtable);
692 return ret;
693 }
694 gfp = alloc_hugepage_direct_gfpmask(vma);
695 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
696 if (unlikely(!page)) {
697 count_vm_event(THP_FAULT_FALLBACK);
698 return VM_FAULT_FALLBACK;
699 }
700 prep_transhuge_page(page);
701 return __do_huge_pmd_anonymous_page(fe, page, gfp);
702 }
703
704 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
705 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write)
706 {
707 struct mm_struct *mm = vma->vm_mm;
708 pmd_t entry;
709 spinlock_t *ptl;
710
711 ptl = pmd_lock(mm, pmd);
712 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
713 if (pfn_t_devmap(pfn))
714 entry = pmd_mkdevmap(entry);
715 if (write) {
716 entry = pmd_mkyoung(pmd_mkdirty(entry));
717 entry = maybe_pmd_mkwrite(entry, vma);
718 }
719 set_pmd_at(mm, addr, pmd, entry);
720 update_mmu_cache_pmd(vma, addr, pmd);
721 spin_unlock(ptl);
722 }
723
724 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
725 pmd_t *pmd, pfn_t pfn, bool write)
726 {
727 pgprot_t pgprot = vma->vm_page_prot;
728 /*
729 * If we had pmd_special, we could avoid all these restrictions,
730 * but we need to be consistent with PTEs and architectures that
731 * can't support a 'special' bit.
732 */
733 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
734 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
735 (VM_PFNMAP|VM_MIXEDMAP));
736 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
737 BUG_ON(!pfn_t_devmap(pfn));
738
739 if (addr < vma->vm_start || addr >= vma->vm_end)
740 return VM_FAULT_SIGBUS;
741 if (track_pfn_insert(vma, &pgprot, pfn))
742 return VM_FAULT_SIGBUS;
743 insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write);
744 return VM_FAULT_NOPAGE;
745 }
746 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
747
748 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
749 pmd_t *pmd, int flags)
750 {
751 pmd_t _pmd;
752
753 _pmd = pmd_mkyoung(*pmd);
754 if (flags & FOLL_WRITE)
755 _pmd = pmd_mkdirty(_pmd);
756 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
757 pmd, _pmd, flags & FOLL_WRITE))
758 update_mmu_cache_pmd(vma, addr, pmd);
759 }
760
761 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
762 pmd_t *pmd, int flags)
763 {
764 unsigned long pfn = pmd_pfn(*pmd);
765 struct mm_struct *mm = vma->vm_mm;
766 struct dev_pagemap *pgmap;
767 struct page *page;
768
769 assert_spin_locked(pmd_lockptr(mm, pmd));
770
771 /*
772 * When we COW a devmap PMD entry, we split it into PTEs, so we should
773 * not be in this function with `flags & FOLL_COW` set.
774 */
775 WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
776
777 if (flags & FOLL_WRITE && !pmd_write(*pmd))
778 return NULL;
779
780 if (pmd_present(*pmd) && pmd_devmap(*pmd))
781 /* pass */;
782 else
783 return NULL;
784
785 if (flags & FOLL_TOUCH)
786 touch_pmd(vma, addr, pmd, flags);
787
788 /*
789 * device mapped pages can only be returned if the
790 * caller will manage the page reference count.
791 */
792 if (!(flags & FOLL_GET))
793 return ERR_PTR(-EEXIST);
794
795 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
796 pgmap = get_dev_pagemap(pfn, NULL);
797 if (!pgmap)
798 return ERR_PTR(-EFAULT);
799 page = pfn_to_page(pfn);
800 get_page(page);
801 put_dev_pagemap(pgmap);
802
803 return page;
804 }
805
806 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
807 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
808 struct vm_area_struct *vma)
809 {
810 spinlock_t *dst_ptl, *src_ptl;
811 struct page *src_page;
812 pmd_t pmd;
813 pgtable_t pgtable = NULL;
814 int ret = -ENOMEM;
815
816 /* Skip if can be re-fill on fault */
817 if (!vma_is_anonymous(vma))
818 return 0;
819
820 pgtable = pte_alloc_one(dst_mm, addr);
821 if (unlikely(!pgtable))
822 goto out;
823
824 dst_ptl = pmd_lock(dst_mm, dst_pmd);
825 src_ptl = pmd_lockptr(src_mm, src_pmd);
826 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
827
828 ret = -EAGAIN;
829 pmd = *src_pmd;
830 if (unlikely(!pmd_trans_huge(pmd))) {
831 pte_free(dst_mm, pgtable);
832 goto out_unlock;
833 }
834 /*
835 * When page table lock is held, the huge zero pmd should not be
836 * under splitting since we don't split the page itself, only pmd to
837 * a page table.
838 */
839 if (is_huge_zero_pmd(pmd)) {
840 struct page *zero_page;
841 /*
842 * get_huge_zero_page() will never allocate a new page here,
843 * since we already have a zero page to copy. It just takes a
844 * reference.
845 */
846 zero_page = mm_get_huge_zero_page(dst_mm);
847 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
848 zero_page);
849 ret = 0;
850 goto out_unlock;
851 }
852
853 src_page = pmd_page(pmd);
854 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
855 get_page(src_page);
856 page_dup_rmap(src_page, true);
857 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
858 atomic_long_inc(&dst_mm->nr_ptes);
859 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
860
861 pmdp_set_wrprotect(src_mm, addr, src_pmd);
862 pmd = pmd_mkold(pmd_wrprotect(pmd));
863 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
864
865 ret = 0;
866 out_unlock:
867 spin_unlock(src_ptl);
868 spin_unlock(dst_ptl);
869 out:
870 return ret;
871 }
872
873 void huge_pmd_set_accessed(struct fault_env *fe, pmd_t orig_pmd)
874 {
875 pmd_t entry;
876 unsigned long haddr;
877 bool write = fe->flags & FAULT_FLAG_WRITE;
878
879 fe->ptl = pmd_lock(fe->vma->vm_mm, fe->pmd);
880 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
881 goto unlock;
882
883 entry = pmd_mkyoung(orig_pmd);
884 if (write)
885 entry = pmd_mkdirty(entry);
886 haddr = fe->address & HPAGE_PMD_MASK;
887 if (pmdp_set_access_flags(fe->vma, haddr, fe->pmd, entry, write))
888 update_mmu_cache_pmd(fe->vma, fe->address, fe->pmd);
889
890 unlock:
891 spin_unlock(fe->ptl);
892 }
893
894 static int do_huge_pmd_wp_page_fallback(struct fault_env *fe, pmd_t orig_pmd,
895 struct page *page)
896 {
897 struct vm_area_struct *vma = fe->vma;
898 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
899 struct mem_cgroup *memcg;
900 pgtable_t pgtable;
901 pmd_t _pmd;
902 int ret = 0, i;
903 struct page **pages;
904 unsigned long mmun_start; /* For mmu_notifiers */
905 unsigned long mmun_end; /* For mmu_notifiers */
906
907 pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
908 GFP_KERNEL);
909 if (unlikely(!pages)) {
910 ret |= VM_FAULT_OOM;
911 goto out;
912 }
913
914 for (i = 0; i < HPAGE_PMD_NR; i++) {
915 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE |
916 __GFP_OTHER_NODE, vma,
917 fe->address, page_to_nid(page));
918 if (unlikely(!pages[i] ||
919 mem_cgroup_try_charge(pages[i], vma->vm_mm,
920 GFP_KERNEL, &memcg, false))) {
921 if (pages[i])
922 put_page(pages[i]);
923 while (--i >= 0) {
924 memcg = (void *)page_private(pages[i]);
925 set_page_private(pages[i], 0);
926 mem_cgroup_cancel_charge(pages[i], memcg,
927 false);
928 put_page(pages[i]);
929 }
930 kfree(pages);
931 ret |= VM_FAULT_OOM;
932 goto out;
933 }
934 set_page_private(pages[i], (unsigned long)memcg);
935 }
936
937 for (i = 0; i < HPAGE_PMD_NR; i++) {
938 copy_user_highpage(pages[i], page + i,
939 haddr + PAGE_SIZE * i, vma);
940 __SetPageUptodate(pages[i]);
941 cond_resched();
942 }
943
944 mmun_start = haddr;
945 mmun_end = haddr + HPAGE_PMD_SIZE;
946 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
947
948 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
949 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
950 goto out_free_pages;
951 VM_BUG_ON_PAGE(!PageHead(page), page);
952
953 pmdp_huge_clear_flush_notify(vma, haddr, fe->pmd);
954 /* leave pmd empty until pte is filled */
955
956 pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, fe->pmd);
957 pmd_populate(vma->vm_mm, &_pmd, pgtable);
958
959 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
960 pte_t entry;
961 entry = mk_pte(pages[i], vma->vm_page_prot);
962 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
963 memcg = (void *)page_private(pages[i]);
964 set_page_private(pages[i], 0);
965 page_add_new_anon_rmap(pages[i], fe->vma, haddr, false);
966 mem_cgroup_commit_charge(pages[i], memcg, false, false);
967 lru_cache_add_active_or_unevictable(pages[i], vma);
968 fe->pte = pte_offset_map(&_pmd, haddr);
969 VM_BUG_ON(!pte_none(*fe->pte));
970 set_pte_at(vma->vm_mm, haddr, fe->pte, entry);
971 pte_unmap(fe->pte);
972 }
973 kfree(pages);
974
975 smp_wmb(); /* make pte visible before pmd */
976 pmd_populate(vma->vm_mm, fe->pmd, pgtable);
977 page_remove_rmap(page, true);
978 spin_unlock(fe->ptl);
979
980 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
981
982 ret |= VM_FAULT_WRITE;
983 put_page(page);
984
985 out:
986 return ret;
987
988 out_free_pages:
989 spin_unlock(fe->ptl);
990 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
991 for (i = 0; i < HPAGE_PMD_NR; i++) {
992 memcg = (void *)page_private(pages[i]);
993 set_page_private(pages[i], 0);
994 mem_cgroup_cancel_charge(pages[i], memcg, false);
995 put_page(pages[i]);
996 }
997 kfree(pages);
998 goto out;
999 }
1000
1001 int do_huge_pmd_wp_page(struct fault_env *fe, pmd_t orig_pmd)
1002 {
1003 struct vm_area_struct *vma = fe->vma;
1004 struct page *page = NULL, *new_page;
1005 struct mem_cgroup *memcg;
1006 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1007 unsigned long mmun_start; /* For mmu_notifiers */
1008 unsigned long mmun_end; /* For mmu_notifiers */
1009 gfp_t huge_gfp; /* for allocation and charge */
1010 int ret = 0;
1011
1012 fe->ptl = pmd_lockptr(vma->vm_mm, fe->pmd);
1013 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1014 if (is_huge_zero_pmd(orig_pmd))
1015 goto alloc;
1016 spin_lock(fe->ptl);
1017 if (unlikely(!pmd_same(*fe->pmd, orig_pmd)))
1018 goto out_unlock;
1019
1020 page = pmd_page(orig_pmd);
1021 VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1022 /*
1023 * We can only reuse the page if nobody else maps the huge page or it's
1024 * part.
1025 */
1026 if (page_trans_huge_mapcount(page, NULL) == 1) {
1027 pmd_t entry;
1028 entry = pmd_mkyoung(orig_pmd);
1029 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1030 if (pmdp_set_access_flags(vma, haddr, fe->pmd, entry, 1))
1031 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1032 ret |= VM_FAULT_WRITE;
1033 goto out_unlock;
1034 }
1035 get_page(page);
1036 spin_unlock(fe->ptl);
1037 alloc:
1038 if (transparent_hugepage_enabled(vma) &&
1039 !transparent_hugepage_debug_cow()) {
1040 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1041 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1042 } else
1043 new_page = NULL;
1044
1045 if (likely(new_page)) {
1046 prep_transhuge_page(new_page);
1047 } else {
1048 if (!page) {
1049 split_huge_pmd(vma, fe->pmd, fe->address);
1050 ret |= VM_FAULT_FALLBACK;
1051 } else {
1052 ret = do_huge_pmd_wp_page_fallback(fe, orig_pmd, page);
1053 if (ret & VM_FAULT_OOM) {
1054 split_huge_pmd(vma, fe->pmd, fe->address);
1055 ret |= VM_FAULT_FALLBACK;
1056 }
1057 put_page(page);
1058 }
1059 count_vm_event(THP_FAULT_FALLBACK);
1060 goto out;
1061 }
1062
1063 if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
1064 huge_gfp | __GFP_NORETRY, &memcg, true))) {
1065 put_page(new_page);
1066 split_huge_pmd(vma, fe->pmd, fe->address);
1067 if (page)
1068 put_page(page);
1069 ret |= VM_FAULT_FALLBACK;
1070 count_vm_event(THP_FAULT_FALLBACK);
1071 goto out;
1072 }
1073
1074 count_vm_event(THP_FAULT_ALLOC);
1075
1076 if (!page)
1077 clear_huge_page(new_page, haddr, HPAGE_PMD_NR);
1078 else
1079 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1080 __SetPageUptodate(new_page);
1081
1082 mmun_start = haddr;
1083 mmun_end = haddr + HPAGE_PMD_SIZE;
1084 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1085
1086 spin_lock(fe->ptl);
1087 if (page)
1088 put_page(page);
1089 if (unlikely(!pmd_same(*fe->pmd, orig_pmd))) {
1090 spin_unlock(fe->ptl);
1091 mem_cgroup_cancel_charge(new_page, memcg, true);
1092 put_page(new_page);
1093 goto out_mn;
1094 } else {
1095 pmd_t entry;
1096 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1097 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1098 pmdp_huge_clear_flush_notify(vma, haddr, fe->pmd);
1099 page_add_new_anon_rmap(new_page, vma, haddr, true);
1100 mem_cgroup_commit_charge(new_page, memcg, false, true);
1101 lru_cache_add_active_or_unevictable(new_page, vma);
1102 set_pmd_at(vma->vm_mm, haddr, fe->pmd, entry);
1103 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1104 if (!page) {
1105 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1106 } else {
1107 VM_BUG_ON_PAGE(!PageHead(page), page);
1108 page_remove_rmap(page, true);
1109 put_page(page);
1110 }
1111 ret |= VM_FAULT_WRITE;
1112 }
1113 spin_unlock(fe->ptl);
1114 out_mn:
1115 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1116 out:
1117 return ret;
1118 out_unlock:
1119 spin_unlock(fe->ptl);
1120 return ret;
1121 }
1122
1123 /*
1124 * FOLL_FORCE can write to even unwritable pmd's, but only
1125 * after we've gone through a COW cycle and they are dirty.
1126 */
1127 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1128 {
1129 return pmd_write(pmd) ||
1130 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1131 }
1132
1133 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1134 unsigned long addr,
1135 pmd_t *pmd,
1136 unsigned int flags)
1137 {
1138 struct mm_struct *mm = vma->vm_mm;
1139 struct page *page = NULL;
1140
1141 assert_spin_locked(pmd_lockptr(mm, pmd));
1142
1143 if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1144 goto out;
1145
1146 /* Avoid dumping huge zero page */
1147 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1148 return ERR_PTR(-EFAULT);
1149
1150 /* Full NUMA hinting faults to serialise migration in fault paths */
1151 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1152 goto out;
1153
1154 page = pmd_page(*pmd);
1155 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1156 if (flags & FOLL_TOUCH)
1157 touch_pmd(vma, addr, pmd, flags);
1158 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1159 /*
1160 * We don't mlock() pte-mapped THPs. This way we can avoid
1161 * leaking mlocked pages into non-VM_LOCKED VMAs.
1162 *
1163 * For anon THP:
1164 *
1165 * In most cases the pmd is the only mapping of the page as we
1166 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1167 * writable private mappings in populate_vma_page_range().
1168 *
1169 * The only scenario when we have the page shared here is if we
1170 * mlocking read-only mapping shared over fork(). We skip
1171 * mlocking such pages.
1172 *
1173 * For file THP:
1174 *
1175 * We can expect PageDoubleMap() to be stable under page lock:
1176 * for file pages we set it in page_add_file_rmap(), which
1177 * requires page to be locked.
1178 */
1179
1180 if (PageAnon(page) && compound_mapcount(page) != 1)
1181 goto skip_mlock;
1182 if (PageDoubleMap(page) || !page->mapping)
1183 goto skip_mlock;
1184 if (!trylock_page(page))
1185 goto skip_mlock;
1186 lru_add_drain();
1187 if (page->mapping && !PageDoubleMap(page))
1188 mlock_vma_page(page);
1189 unlock_page(page);
1190 }
1191 skip_mlock:
1192 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1193 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1194 if (flags & FOLL_GET)
1195 get_page(page);
1196
1197 out:
1198 return page;
1199 }
1200
1201 /* NUMA hinting page fault entry point for trans huge pmds */
1202 int do_huge_pmd_numa_page(struct fault_env *fe, pmd_t pmd)
1203 {
1204 struct vm_area_struct *vma = fe->vma;
1205 struct anon_vma *anon_vma = NULL;
1206 struct page *page;
1207 unsigned long haddr = fe->address & HPAGE_PMD_MASK;
1208 int page_nid = -1, this_nid = numa_node_id();
1209 int target_nid, last_cpupid = -1;
1210 bool page_locked;
1211 bool migrated = false;
1212 bool was_writable;
1213 int flags = 0;
1214
1215 fe->ptl = pmd_lock(vma->vm_mm, fe->pmd);
1216 if (unlikely(!pmd_same(pmd, *fe->pmd)))
1217 goto out_unlock;
1218
1219 /*
1220 * If there are potential migrations, wait for completion and retry
1221 * without disrupting NUMA hinting information. Do not relock and
1222 * check_same as the page may no longer be mapped.
1223 */
1224 if (unlikely(pmd_trans_migrating(*fe->pmd))) {
1225 page = pmd_page(*fe->pmd);
1226 if (!get_page_unless_zero(page))
1227 goto out_unlock;
1228 spin_unlock(fe->ptl);
1229 wait_on_page_locked(page);
1230 put_page(page);
1231 goto out;
1232 }
1233
1234 page = pmd_page(pmd);
1235 BUG_ON(is_huge_zero_page(page));
1236 page_nid = page_to_nid(page);
1237 last_cpupid = page_cpupid_last(page);
1238 count_vm_numa_event(NUMA_HINT_FAULTS);
1239 if (page_nid == this_nid) {
1240 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1241 flags |= TNF_FAULT_LOCAL;
1242 }
1243
1244 /* See similar comment in do_numa_page for explanation */
1245 if (!pmd_write(pmd))
1246 flags |= TNF_NO_GROUP;
1247
1248 /*
1249 * Acquire the page lock to serialise THP migrations but avoid dropping
1250 * page_table_lock if at all possible
1251 */
1252 page_locked = trylock_page(page);
1253 target_nid = mpol_misplaced(page, vma, haddr);
1254 if (target_nid == -1) {
1255 /* If the page was locked, there are no parallel migrations */
1256 if (page_locked)
1257 goto clear_pmdnuma;
1258 }
1259
1260 /* Migration could have started since the pmd_trans_migrating check */
1261 if (!page_locked) {
1262 page_nid = -1;
1263 if (!get_page_unless_zero(page))
1264 goto out_unlock;
1265 spin_unlock(fe->ptl);
1266 wait_on_page_locked(page);
1267 put_page(page);
1268 goto out;
1269 }
1270
1271 /*
1272 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1273 * to serialises splits
1274 */
1275 get_page(page);
1276 spin_unlock(fe->ptl);
1277 anon_vma = page_lock_anon_vma_read(page);
1278
1279 /* Confirm the PMD did not change while page_table_lock was released */
1280 spin_lock(fe->ptl);
1281 if (unlikely(!pmd_same(pmd, *fe->pmd))) {
1282 unlock_page(page);
1283 put_page(page);
1284 page_nid = -1;
1285 goto out_unlock;
1286 }
1287
1288 /* Bail if we fail to protect against THP splits for any reason */
1289 if (unlikely(!anon_vma)) {
1290 put_page(page);
1291 page_nid = -1;
1292 goto clear_pmdnuma;
1293 }
1294
1295 /*
1296 * Migrate the THP to the requested node, returns with page unlocked
1297 * and access rights restored.
1298 */
1299 spin_unlock(fe->ptl);
1300 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1301 fe->pmd, pmd, fe->address, page, target_nid);
1302 if (migrated) {
1303 flags |= TNF_MIGRATED;
1304 page_nid = target_nid;
1305 } else
1306 flags |= TNF_MIGRATE_FAIL;
1307
1308 goto out;
1309 clear_pmdnuma:
1310 BUG_ON(!PageLocked(page));
1311 was_writable = pmd_write(pmd);
1312 pmd = pmd_modify(pmd, vma->vm_page_prot);
1313 pmd = pmd_mkyoung(pmd);
1314 if (was_writable)
1315 pmd = pmd_mkwrite(pmd);
1316 set_pmd_at(vma->vm_mm, haddr, fe->pmd, pmd);
1317 update_mmu_cache_pmd(vma, fe->address, fe->pmd);
1318 unlock_page(page);
1319 out_unlock:
1320 spin_unlock(fe->ptl);
1321
1322 out:
1323 if (anon_vma)
1324 page_unlock_anon_vma_read(anon_vma);
1325
1326 if (page_nid != -1)
1327 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, fe->flags);
1328
1329 return 0;
1330 }
1331
1332 /*
1333 * Return true if we do MADV_FREE successfully on entire pmd page.
1334 * Otherwise, return false.
1335 */
1336 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1337 pmd_t *pmd, unsigned long addr, unsigned long next)
1338 {
1339 spinlock_t *ptl;
1340 pmd_t orig_pmd;
1341 struct page *page;
1342 struct mm_struct *mm = tlb->mm;
1343 bool ret = false;
1344
1345 ptl = pmd_trans_huge_lock(pmd, vma);
1346 if (!ptl)
1347 goto out_unlocked;
1348
1349 orig_pmd = *pmd;
1350 if (is_huge_zero_pmd(orig_pmd))
1351 goto out;
1352
1353 page = pmd_page(orig_pmd);
1354 /*
1355 * If other processes are mapping this page, we couldn't discard
1356 * the page unless they all do MADV_FREE so let's skip the page.
1357 */
1358 if (page_mapcount(page) != 1)
1359 goto out;
1360
1361 if (!trylock_page(page))
1362 goto out;
1363
1364 /*
1365 * If user want to discard part-pages of THP, split it so MADV_FREE
1366 * will deactivate only them.
1367 */
1368 if (next - addr != HPAGE_PMD_SIZE) {
1369 get_page(page);
1370 spin_unlock(ptl);
1371 split_huge_page(page);
1372 unlock_page(page);
1373 put_page(page);
1374 goto out_unlocked;
1375 }
1376
1377 if (PageDirty(page))
1378 ClearPageDirty(page);
1379 unlock_page(page);
1380
1381 if (PageActive(page))
1382 deactivate_page(page);
1383
1384 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1385 pmdp_invalidate(vma, addr, pmd);
1386 orig_pmd = pmd_mkold(orig_pmd);
1387 orig_pmd = pmd_mkclean(orig_pmd);
1388
1389 set_pmd_at(mm, addr, pmd, orig_pmd);
1390 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1391 }
1392 ret = true;
1393 out:
1394 spin_unlock(ptl);
1395 out_unlocked:
1396 return ret;
1397 }
1398
1399 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1400 pmd_t *pmd, unsigned long addr)
1401 {
1402 pmd_t orig_pmd;
1403 spinlock_t *ptl;
1404
1405 ptl = __pmd_trans_huge_lock(pmd, vma);
1406 if (!ptl)
1407 return 0;
1408 /*
1409 * For architectures like ppc64 we look at deposited pgtable
1410 * when calling pmdp_huge_get_and_clear. So do the
1411 * pgtable_trans_huge_withdraw after finishing pmdp related
1412 * operations.
1413 */
1414 orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1415 tlb->fullmm);
1416 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1417 if (vma_is_dax(vma)) {
1418 spin_unlock(ptl);
1419 if (is_huge_zero_pmd(orig_pmd))
1420 tlb_remove_page(tlb, pmd_page(orig_pmd));
1421 } else if (is_huge_zero_pmd(orig_pmd)) {
1422 pte_free(tlb->mm, pgtable_trans_huge_withdraw(tlb->mm, pmd));
1423 atomic_long_dec(&tlb->mm->nr_ptes);
1424 spin_unlock(ptl);
1425 tlb_remove_page(tlb, pmd_page(orig_pmd));
1426 } else {
1427 struct page *page = pmd_page(orig_pmd);
1428 page_remove_rmap(page, true);
1429 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1430 VM_BUG_ON_PAGE(!PageHead(page), page);
1431 if (PageAnon(page)) {
1432 pgtable_t pgtable;
1433 pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd);
1434 pte_free(tlb->mm, pgtable);
1435 atomic_long_dec(&tlb->mm->nr_ptes);
1436 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1437 } else {
1438 add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1439 }
1440 spin_unlock(ptl);
1441 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1442 }
1443 return 1;
1444 }
1445
1446 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1447 unsigned long new_addr, unsigned long old_end,
1448 pmd_t *old_pmd, pmd_t *new_pmd)
1449 {
1450 spinlock_t *old_ptl, *new_ptl;
1451 pmd_t pmd;
1452 struct mm_struct *mm = vma->vm_mm;
1453 bool force_flush = false;
1454
1455 if ((old_addr & ~HPAGE_PMD_MASK) ||
1456 (new_addr & ~HPAGE_PMD_MASK) ||
1457 old_end - old_addr < HPAGE_PMD_SIZE)
1458 return false;
1459
1460 /*
1461 * The destination pmd shouldn't be established, free_pgtables()
1462 * should have release it.
1463 */
1464 if (WARN_ON(!pmd_none(*new_pmd))) {
1465 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1466 return false;
1467 }
1468
1469 /*
1470 * We don't have to worry about the ordering of src and dst
1471 * ptlocks because exclusive mmap_sem prevents deadlock.
1472 */
1473 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1474 if (old_ptl) {
1475 new_ptl = pmd_lockptr(mm, new_pmd);
1476 if (new_ptl != old_ptl)
1477 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1478 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1479 if (pmd_present(pmd))
1480 force_flush = true;
1481 VM_BUG_ON(!pmd_none(*new_pmd));
1482
1483 if (pmd_move_must_withdraw(new_ptl, old_ptl) &&
1484 vma_is_anonymous(vma)) {
1485 pgtable_t pgtable;
1486 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1487 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1488 }
1489 set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
1490 if (force_flush)
1491 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1492 if (new_ptl != old_ptl)
1493 spin_unlock(new_ptl);
1494 spin_unlock(old_ptl);
1495 return true;
1496 }
1497 return false;
1498 }
1499
1500 /*
1501 * Returns
1502 * - 0 if PMD could not be locked
1503 * - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1504 * - HPAGE_PMD_NR is protections changed and TLB flush necessary
1505 */
1506 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1507 unsigned long addr, pgprot_t newprot, int prot_numa)
1508 {
1509 struct mm_struct *mm = vma->vm_mm;
1510 spinlock_t *ptl;
1511 pmd_t entry;
1512 bool preserve_write;
1513 int ret;
1514
1515 ptl = __pmd_trans_huge_lock(pmd, vma);
1516 if (!ptl)
1517 return 0;
1518
1519 preserve_write = prot_numa && pmd_write(*pmd);
1520 ret = 1;
1521
1522 /*
1523 * Avoid trapping faults against the zero page. The read-only
1524 * data is likely to be read-cached on the local CPU and
1525 * local/remote hits to the zero page are not interesting.
1526 */
1527 if (prot_numa && is_huge_zero_pmd(*pmd))
1528 goto unlock;
1529
1530 if (prot_numa && pmd_protnone(*pmd))
1531 goto unlock;
1532
1533 /*
1534 * In case prot_numa, we are under down_read(mmap_sem). It's critical
1535 * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1536 * which is also under down_read(mmap_sem):
1537 *
1538 * CPU0: CPU1:
1539 * change_huge_pmd(prot_numa=1)
1540 * pmdp_huge_get_and_clear_notify()
1541 * madvise_dontneed()
1542 * zap_pmd_range()
1543 * pmd_trans_huge(*pmd) == 0 (without ptl)
1544 * // skip the pmd
1545 * set_pmd_at();
1546 * // pmd is re-established
1547 *
1548 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1549 * which may break userspace.
1550 *
1551 * pmdp_invalidate() is required to make sure we don't miss
1552 * dirty/young flags set by hardware.
1553 */
1554 entry = *pmd;
1555 pmdp_invalidate(vma, addr, pmd);
1556
1557 /*
1558 * Recover dirty/young flags. It relies on pmdp_invalidate to not
1559 * corrupt them.
1560 */
1561 if (pmd_dirty(*pmd))
1562 entry = pmd_mkdirty(entry);
1563 if (pmd_young(*pmd))
1564 entry = pmd_mkyoung(entry);
1565
1566 entry = pmd_modify(entry, newprot);
1567 if (preserve_write)
1568 entry = pmd_mkwrite(entry);
1569 ret = HPAGE_PMD_NR;
1570 set_pmd_at(mm, addr, pmd, entry);
1571 BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1572 unlock:
1573 spin_unlock(ptl);
1574 return ret;
1575 }
1576
1577 /*
1578 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1579 *
1580 * Note that if it returns page table lock pointer, this routine returns without
1581 * unlocking page table lock. So callers must unlock it.
1582 */
1583 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1584 {
1585 spinlock_t *ptl;
1586 ptl = pmd_lock(vma->vm_mm, pmd);
1587 if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
1588 return ptl;
1589 spin_unlock(ptl);
1590 return NULL;
1591 }
1592
1593 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
1594 unsigned long haddr, pmd_t *pmd)
1595 {
1596 struct mm_struct *mm = vma->vm_mm;
1597 pgtable_t pgtable;
1598 pmd_t _pmd;
1599 int i;
1600
1601 /* leave pmd empty until pte is filled */
1602 pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1603
1604 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1605 pmd_populate(mm, &_pmd, pgtable);
1606
1607 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1608 pte_t *pte, entry;
1609 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
1610 entry = pte_mkspecial(entry);
1611 pte = pte_offset_map(&_pmd, haddr);
1612 VM_BUG_ON(!pte_none(*pte));
1613 set_pte_at(mm, haddr, pte, entry);
1614 pte_unmap(pte);
1615 }
1616 smp_wmb(); /* make pte visible before pmd */
1617 pmd_populate(mm, pmd, pgtable);
1618 }
1619
1620 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
1621 unsigned long haddr, bool freeze)
1622 {
1623 struct mm_struct *mm = vma->vm_mm;
1624 struct page *page;
1625 pgtable_t pgtable;
1626 pmd_t _pmd;
1627 bool young, write, dirty, soft_dirty;
1628 unsigned long addr;
1629 int i;
1630
1631 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
1632 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1633 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
1634 VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
1635
1636 count_vm_event(THP_SPLIT_PMD);
1637
1638 if (!vma_is_anonymous(vma)) {
1639 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
1640 if (vma_is_dax(vma))
1641 return;
1642 page = pmd_page(_pmd);
1643 if (!PageDirty(page) && pmd_dirty(_pmd))
1644 set_page_dirty(page);
1645 if (!PageReferenced(page) && pmd_young(_pmd))
1646 SetPageReferenced(page);
1647 page_remove_rmap(page, true);
1648 put_page(page);
1649 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1650 return;
1651 } else if (is_huge_zero_pmd(*pmd)) {
1652 return __split_huge_zero_page_pmd(vma, haddr, pmd);
1653 }
1654
1655 page = pmd_page(*pmd);
1656 VM_BUG_ON_PAGE(!page_count(page), page);
1657 page_ref_add(page, HPAGE_PMD_NR - 1);
1658 write = pmd_write(*pmd);
1659 young = pmd_young(*pmd);
1660 dirty = pmd_dirty(*pmd);
1661 soft_dirty = pmd_soft_dirty(*pmd);
1662
1663 pmdp_huge_split_prepare(vma, haddr, pmd);
1664 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1665 pmd_populate(mm, &_pmd, pgtable);
1666
1667 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
1668 pte_t entry, *pte;
1669 /*
1670 * Note that NUMA hinting access restrictions are not
1671 * transferred to avoid any possibility of altering
1672 * permissions across VMAs.
1673 */
1674 if (freeze) {
1675 swp_entry_t swp_entry;
1676 swp_entry = make_migration_entry(page + i, write);
1677 entry = swp_entry_to_pte(swp_entry);
1678 if (soft_dirty)
1679 entry = pte_swp_mksoft_dirty(entry);
1680 } else {
1681 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
1682 entry = maybe_mkwrite(entry, vma);
1683 if (!write)
1684 entry = pte_wrprotect(entry);
1685 if (!young)
1686 entry = pte_mkold(entry);
1687 if (soft_dirty)
1688 entry = pte_mksoft_dirty(entry);
1689 }
1690 if (dirty)
1691 SetPageDirty(page + i);
1692 pte = pte_offset_map(&_pmd, addr);
1693 BUG_ON(!pte_none(*pte));
1694 set_pte_at(mm, addr, pte, entry);
1695 atomic_inc(&page[i]._mapcount);
1696 pte_unmap(pte);
1697 }
1698
1699 /*
1700 * Set PG_double_map before dropping compound_mapcount to avoid
1701 * false-negative page_mapped().
1702 */
1703 if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
1704 for (i = 0; i < HPAGE_PMD_NR; i++)
1705 atomic_inc(&page[i]._mapcount);
1706 }
1707
1708 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
1709 /* Last compound_mapcount is gone. */
1710 __dec_node_page_state(page, NR_ANON_THPS);
1711 if (TestClearPageDoubleMap(page)) {
1712 /* No need in mapcount reference anymore */
1713 for (i = 0; i < HPAGE_PMD_NR; i++)
1714 atomic_dec(&page[i]._mapcount);
1715 }
1716 }
1717
1718 smp_wmb(); /* make pte visible before pmd */
1719 /*
1720 * Up to this point the pmd is present and huge and userland has the
1721 * whole access to the hugepage during the split (which happens in
1722 * place). If we overwrite the pmd with the not-huge version pointing
1723 * to the pte here (which of course we could if all CPUs were bug
1724 * free), userland could trigger a small page size TLB miss on the
1725 * small sized TLB while the hugepage TLB entry is still established in
1726 * the huge TLB. Some CPU doesn't like that.
1727 * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
1728 * 383 on page 93. Intel should be safe but is also warns that it's
1729 * only safe if the permission and cache attributes of the two entries
1730 * loaded in the two TLB is identical (which should be the case here).
1731 * But it is generally safer to never allow small and huge TLB entries
1732 * for the same virtual address to be loaded simultaneously. So instead
1733 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
1734 * current pmd notpresent (atomically because here the pmd_trans_huge
1735 * and pmd_trans_splitting must remain set at all times on the pmd
1736 * until the split is complete for this pmd), then we flush the SMP TLB
1737 * and finally we write the non-huge version of the pmd entry with
1738 * pmd_populate.
1739 */
1740 pmdp_invalidate(vma, haddr, pmd);
1741 pmd_populate(mm, pmd, pgtable);
1742
1743 if (freeze) {
1744 for (i = 0; i < HPAGE_PMD_NR; i++) {
1745 page_remove_rmap(page + i, false);
1746 put_page(page + i);
1747 }
1748 }
1749 }
1750
1751 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1752 unsigned long address, bool freeze, struct page *page)
1753 {
1754 spinlock_t *ptl;
1755 struct mm_struct *mm = vma->vm_mm;
1756 unsigned long haddr = address & HPAGE_PMD_MASK;
1757
1758 mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
1759 ptl = pmd_lock(mm, pmd);
1760
1761 /*
1762 * If caller asks to setup a migration entries, we need a page to check
1763 * pmd against. Otherwise we can end up replacing wrong page.
1764 */
1765 VM_BUG_ON(freeze && !page);
1766 if (page && page != pmd_page(*pmd))
1767 goto out;
1768
1769 if (pmd_trans_huge(*pmd)) {
1770 page = pmd_page(*pmd);
1771 if (PageMlocked(page))
1772 clear_page_mlock(page);
1773 } else if (!pmd_devmap(*pmd))
1774 goto out;
1775 __split_huge_pmd_locked(vma, pmd, haddr, freeze);
1776 out:
1777 spin_unlock(ptl);
1778 mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
1779 }
1780
1781 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
1782 bool freeze, struct page *page)
1783 {
1784 pgd_t *pgd;
1785 pud_t *pud;
1786 pmd_t *pmd;
1787
1788 pgd = pgd_offset(vma->vm_mm, address);
1789 if (!pgd_present(*pgd))
1790 return;
1791
1792 pud = pud_offset(pgd, address);
1793 if (!pud_present(*pud))
1794 return;
1795
1796 pmd = pmd_offset(pud, address);
1797
1798 __split_huge_pmd(vma, pmd, address, freeze, page);
1799 }
1800
1801 void vma_adjust_trans_huge(struct vm_area_struct *vma,
1802 unsigned long start,
1803 unsigned long end,
1804 long adjust_next)
1805 {
1806 /*
1807 * If the new start address isn't hpage aligned and it could
1808 * previously contain an hugepage: check if we need to split
1809 * an huge pmd.
1810 */
1811 if (start & ~HPAGE_PMD_MASK &&
1812 (start & HPAGE_PMD_MASK) >= vma->vm_start &&
1813 (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
1814 split_huge_pmd_address(vma, start, false, NULL);
1815
1816 /*
1817 * If the new end address isn't hpage aligned and it could
1818 * previously contain an hugepage: check if we need to split
1819 * an huge pmd.
1820 */
1821 if (end & ~HPAGE_PMD_MASK &&
1822 (end & HPAGE_PMD_MASK) >= vma->vm_start &&
1823 (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
1824 split_huge_pmd_address(vma, end, false, NULL);
1825
1826 /*
1827 * If we're also updating the vma->vm_next->vm_start, if the new
1828 * vm_next->vm_start isn't page aligned and it could previously
1829 * contain an hugepage: check if we need to split an huge pmd.
1830 */
1831 if (adjust_next > 0) {
1832 struct vm_area_struct *next = vma->vm_next;
1833 unsigned long nstart = next->vm_start;
1834 nstart += adjust_next << PAGE_SHIFT;
1835 if (nstart & ~HPAGE_PMD_MASK &&
1836 (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
1837 (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
1838 split_huge_pmd_address(next, nstart, false, NULL);
1839 }
1840 }
1841
1842 static void unmap_page(struct page *page)
1843 {
1844 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
1845 TTU_RMAP_LOCKED;
1846 int i, ret;
1847
1848 VM_BUG_ON_PAGE(!PageHead(page), page);
1849
1850 if (PageAnon(page))
1851 ttu_flags |= TTU_MIGRATION;
1852
1853 /* We only need TTU_SPLIT_HUGE_PMD once */
1854 ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD);
1855 for (i = 1; !ret && i < HPAGE_PMD_NR; i++) {
1856 /* Cut short if the page is unmapped */
1857 if (page_count(page) == 1)
1858 return;
1859
1860 ret = try_to_unmap(page + i, ttu_flags);
1861 }
1862 VM_BUG_ON_PAGE(ret, page + i - 1);
1863 }
1864
1865 static void remap_page(struct page *page)
1866 {
1867 int i;
1868
1869 for (i = 0; i < HPAGE_PMD_NR; i++)
1870 remove_migration_ptes(page + i, page + i, true);
1871 }
1872
1873 static void __split_huge_page_tail(struct page *head, int tail,
1874 struct lruvec *lruvec, struct list_head *list)
1875 {
1876 struct page *page_tail = head + tail;
1877
1878 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
1879
1880 /*
1881 * Clone page flags before unfreezing refcount.
1882 *
1883 * After successful get_page_unless_zero() might follow flags change,
1884 * for exmaple lock_page() which set PG_waiters.
1885 */
1886 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
1887 page_tail->flags |= (head->flags &
1888 ((1L << PG_referenced) |
1889 (1L << PG_swapbacked) |
1890 (1L << PG_mlocked) |
1891 (1L << PG_uptodate) |
1892 (1L << PG_active) |
1893 (1L << PG_locked) |
1894 (1L << PG_unevictable) |
1895 (1L << PG_dirty)));
1896
1897 /* ->mapping in first tail page is compound_mapcount */
1898 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
1899 page_tail);
1900 page_tail->mapping = head->mapping;
1901 page_tail->index = head->index + tail;
1902
1903 /* Page flags must be visible before we make the page non-compound. */
1904 smp_wmb();
1905
1906 /*
1907 * Clear PageTail before unfreezing page refcount.
1908 *
1909 * After successful get_page_unless_zero() might follow put_page()
1910 * which needs correct compound_head().
1911 */
1912 clear_compound_head(page_tail);
1913
1914 /* Finally unfreeze refcount. Additional reference from page cache. */
1915 page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
1916 PageSwapCache(head)));
1917
1918 if (page_is_young(head))
1919 set_page_young(page_tail);
1920 if (page_is_idle(head))
1921 set_page_idle(page_tail);
1922
1923 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
1924 lru_add_page_tail(head, page_tail, lruvec, list);
1925 }
1926
1927 static void __split_huge_page(struct page *page, struct list_head *list,
1928 pgoff_t end, unsigned long flags)
1929 {
1930 struct page *head = compound_head(page);
1931 struct zone *zone = page_zone(head);
1932 struct lruvec *lruvec;
1933 int i;
1934
1935 lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
1936
1937 /* complete memcg works before add pages to LRU */
1938 mem_cgroup_split_huge_fixup(head);
1939
1940 for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
1941 __split_huge_page_tail(head, i, lruvec, list);
1942 /* Some pages can be beyond i_size: drop them from page cache */
1943 if (head[i].index >= end) {
1944 __ClearPageDirty(head + i);
1945 __delete_from_page_cache(head + i, NULL);
1946 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
1947 shmem_uncharge(head->mapping->host, 1);
1948 put_page(head + i);
1949 }
1950 }
1951
1952 ClearPageCompound(head);
1953 /* See comment in __split_huge_page_tail() */
1954 if (PageAnon(head)) {
1955 page_ref_inc(head);
1956 } else {
1957 /* Additional pin to radix tree */
1958 page_ref_add(head, 2);
1959 spin_unlock(&head->mapping->tree_lock);
1960 }
1961
1962 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
1963
1964 remap_page(head);
1965
1966 for (i = 0; i < HPAGE_PMD_NR; i++) {
1967 struct page *subpage = head + i;
1968 if (subpage == page)
1969 continue;
1970 unlock_page(subpage);
1971
1972 /*
1973 * Subpages may be freed if there wasn't any mapping
1974 * like if add_to_swap() is running on a lru page that
1975 * had its mapping zapped. And freeing these pages
1976 * requires taking the lru_lock so we do the put_page
1977 * of the tail pages after the split is complete.
1978 */
1979 put_page(subpage);
1980 }
1981 }
1982
1983 int total_mapcount(struct page *page)
1984 {
1985 int i, compound, ret;
1986
1987 VM_BUG_ON_PAGE(PageTail(page), page);
1988
1989 if (likely(!PageCompound(page)))
1990 return atomic_read(&page->_mapcount) + 1;
1991
1992 compound = compound_mapcount(page);
1993 if (PageHuge(page))
1994 return compound;
1995 ret = compound;
1996 for (i = 0; i < HPAGE_PMD_NR; i++)
1997 ret += atomic_read(&page[i]._mapcount) + 1;
1998 /* File pages has compound_mapcount included in _mapcount */
1999 if (!PageAnon(page))
2000 return ret - compound * HPAGE_PMD_NR;
2001 if (PageDoubleMap(page))
2002 ret -= HPAGE_PMD_NR;
2003 return ret;
2004 }
2005
2006 /*
2007 * This calculates accurately how many mappings a transparent hugepage
2008 * has (unlike page_mapcount() which isn't fully accurate). This full
2009 * accuracy is primarily needed to know if copy-on-write faults can
2010 * reuse the page and change the mapping to read-write instead of
2011 * copying them. At the same time this returns the total_mapcount too.
2012 *
2013 * The function returns the highest mapcount any one of the subpages
2014 * has. If the return value is one, even if different processes are
2015 * mapping different subpages of the transparent hugepage, they can
2016 * all reuse it, because each process is reusing a different subpage.
2017 *
2018 * The total_mapcount is instead counting all virtual mappings of the
2019 * subpages. If the total_mapcount is equal to "one", it tells the
2020 * caller all mappings belong to the same "mm" and in turn the
2021 * anon_vma of the transparent hugepage can become the vma->anon_vma
2022 * local one as no other process may be mapping any of the subpages.
2023 *
2024 * It would be more accurate to replace page_mapcount() with
2025 * page_trans_huge_mapcount(), however we only use
2026 * page_trans_huge_mapcount() in the copy-on-write faults where we
2027 * need full accuracy to avoid breaking page pinning, because
2028 * page_trans_huge_mapcount() is slower than page_mapcount().
2029 */
2030 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2031 {
2032 int i, ret, _total_mapcount, mapcount;
2033
2034 /* hugetlbfs shouldn't call it */
2035 VM_BUG_ON_PAGE(PageHuge(page), page);
2036
2037 if (likely(!PageTransCompound(page))) {
2038 mapcount = atomic_read(&page->_mapcount) + 1;
2039 if (total_mapcount)
2040 *total_mapcount = mapcount;
2041 return mapcount;
2042 }
2043
2044 page = compound_head(page);
2045
2046 _total_mapcount = ret = 0;
2047 for (i = 0; i < HPAGE_PMD_NR; i++) {
2048 mapcount = atomic_read(&page[i]._mapcount) + 1;
2049 ret = max(ret, mapcount);
2050 _total_mapcount += mapcount;
2051 }
2052 if (PageDoubleMap(page)) {
2053 ret -= 1;
2054 _total_mapcount -= HPAGE_PMD_NR;
2055 }
2056 mapcount = compound_mapcount(page);
2057 ret += mapcount;
2058 _total_mapcount += mapcount;
2059 if (total_mapcount)
2060 *total_mapcount = _total_mapcount;
2061 return ret;
2062 }
2063
2064 /*
2065 * This function splits huge page into normal pages. @page can point to any
2066 * subpage of huge page to split. Split doesn't change the position of @page.
2067 *
2068 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2069 * The huge page must be locked.
2070 *
2071 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2072 *
2073 * Both head page and tail pages will inherit mapping, flags, and so on from
2074 * the hugepage.
2075 *
2076 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2077 * they are not mapped.
2078 *
2079 * Returns 0 if the hugepage is split successfully.
2080 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2081 * us.
2082 */
2083 int split_huge_page_to_list(struct page *page, struct list_head *list)
2084 {
2085 struct page *head = compound_head(page);
2086 struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2087 struct anon_vma *anon_vma = NULL;
2088 struct address_space *mapping = NULL;
2089 int count, mapcount, extra_pins, ret;
2090 bool mlocked;
2091 unsigned long flags;
2092 pgoff_t end;
2093
2094 VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2095 VM_BUG_ON_PAGE(!PageLocked(page), page);
2096 VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
2097 VM_BUG_ON_PAGE(!PageCompound(page), page);
2098
2099 if (PageAnon(head)) {
2100 /*
2101 * The caller does not necessarily hold an mmap_sem that would
2102 * prevent the anon_vma disappearing so we first we take a
2103 * reference to it and then lock the anon_vma for write. This
2104 * is similar to page_lock_anon_vma_read except the write lock
2105 * is taken to serialise against parallel split or collapse
2106 * operations.
2107 */
2108 anon_vma = page_get_anon_vma(head);
2109 if (!anon_vma) {
2110 ret = -EBUSY;
2111 goto out;
2112 }
2113 extra_pins = 0;
2114 end = -1;
2115 mapping = NULL;
2116 anon_vma_lock_write(anon_vma);
2117 } else {
2118 mapping = head->mapping;
2119
2120 /* Truncated ? */
2121 if (!mapping) {
2122 ret = -EBUSY;
2123 goto out;
2124 }
2125
2126 /* Addidional pins from radix tree */
2127 extra_pins = HPAGE_PMD_NR;
2128 anon_vma = NULL;
2129 i_mmap_lock_read(mapping);
2130
2131 /*
2132 *__split_huge_page() may need to trim off pages beyond EOF:
2133 * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2134 * which cannot be nested inside the page tree lock. So note
2135 * end now: i_size itself may be changed at any moment, but
2136 * head page lock is good enough to serialize the trimming.
2137 */
2138 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2139 }
2140
2141 /*
2142 * Racy check if we can split the page, before unmap_page() will
2143 * split PMDs
2144 */
2145 if (total_mapcount(head) != page_count(head) - extra_pins - 1) {
2146 ret = -EBUSY;
2147 goto out_unlock;
2148 }
2149
2150 mlocked = PageMlocked(page);
2151 unmap_page(head);
2152 VM_BUG_ON_PAGE(compound_mapcount(head), head);
2153
2154 /* Make sure the page is not on per-CPU pagevec as it takes pin */
2155 if (mlocked)
2156 lru_add_drain();
2157
2158 /* prevent PageLRU to go away from under us, and freeze lru stats */
2159 spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2160
2161 if (mapping) {
2162 void **pslot;
2163
2164 spin_lock(&mapping->tree_lock);
2165 pslot = radix_tree_lookup_slot(&mapping->page_tree,
2166 page_index(head));
2167 /*
2168 * Check if the head page is present in radix tree.
2169 * We assume all tail are present too, if head is there.
2170 */
2171 if (radix_tree_deref_slot_protected(pslot,
2172 &mapping->tree_lock) != head)
2173 goto fail;
2174 }
2175
2176 /* Prevent deferred_split_scan() touching ->_refcount */
2177 spin_lock(&pgdata->split_queue_lock);
2178 count = page_count(head);
2179 mapcount = total_mapcount(head);
2180 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2181 if (!list_empty(page_deferred_list(head))) {
2182 pgdata->split_queue_len--;
2183 list_del(page_deferred_list(head));
2184 }
2185 if (mapping)
2186 __dec_node_page_state(page, NR_SHMEM_THPS);
2187 spin_unlock(&pgdata->split_queue_lock);
2188 __split_huge_page(page, list, end, flags);
2189 ret = 0;
2190 } else {
2191 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2192 pr_alert("total_mapcount: %u, page_count(): %u\n",
2193 mapcount, count);
2194 if (PageTail(page))
2195 dump_page(head, NULL);
2196 dump_page(page, "total_mapcount(head) > 0");
2197 BUG();
2198 }
2199 spin_unlock(&pgdata->split_queue_lock);
2200 fail: if (mapping)
2201 spin_unlock(&mapping->tree_lock);
2202 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2203 remap_page(head);
2204 ret = -EBUSY;
2205 }
2206
2207 out_unlock:
2208 if (anon_vma) {
2209 anon_vma_unlock_write(anon_vma);
2210 put_anon_vma(anon_vma);
2211 }
2212 if (mapping)
2213 i_mmap_unlock_read(mapping);
2214 out:
2215 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2216 return ret;
2217 }
2218
2219 void free_transhuge_page(struct page *page)
2220 {
2221 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2222 unsigned long flags;
2223
2224 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2225 if (!list_empty(page_deferred_list(page))) {
2226 pgdata->split_queue_len--;
2227 list_del(page_deferred_list(page));
2228 }
2229 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2230 free_compound_page(page);
2231 }
2232
2233 void deferred_split_huge_page(struct page *page)
2234 {
2235 struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2236 unsigned long flags;
2237
2238 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2239
2240 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2241 if (list_empty(page_deferred_list(page))) {
2242 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2243 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2244 pgdata->split_queue_len++;
2245 }
2246 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2247 }
2248
2249 static unsigned long deferred_split_count(struct shrinker *shrink,
2250 struct shrink_control *sc)
2251 {
2252 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2253 return ACCESS_ONCE(pgdata->split_queue_len);
2254 }
2255
2256 static unsigned long deferred_split_scan(struct shrinker *shrink,
2257 struct shrink_control *sc)
2258 {
2259 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2260 unsigned long flags;
2261 LIST_HEAD(list), *pos, *next;
2262 struct page *page;
2263 int split = 0;
2264
2265 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2266 /* Take pin on all head pages to avoid freeing them under us */
2267 list_for_each_safe(pos, next, &pgdata->split_queue) {
2268 page = list_entry((void *)pos, struct page, mapping);
2269 page = compound_head(page);
2270 if (get_page_unless_zero(page)) {
2271 list_move(page_deferred_list(page), &list);
2272 } else {
2273 /* We lost race with put_compound_page() */
2274 list_del_init(page_deferred_list(page));
2275 pgdata->split_queue_len--;
2276 }
2277 if (!--sc->nr_to_scan)
2278 break;
2279 }
2280 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2281
2282 list_for_each_safe(pos, next, &list) {
2283 page = list_entry((void *)pos, struct page, mapping);
2284 if (!trylock_page(page))
2285 goto next;
2286 /* split_huge_page() removes page from list on success */
2287 if (!split_huge_page(page))
2288 split++;
2289 unlock_page(page);
2290 next:
2291 put_page(page);
2292 }
2293
2294 spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2295 list_splice_tail(&list, &pgdata->split_queue);
2296 spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2297
2298 /*
2299 * Stop shrinker if we didn't split any page, but the queue is empty.
2300 * This can happen if pages were freed under us.
2301 */
2302 if (!split && list_empty(&pgdata->split_queue))
2303 return SHRINK_STOP;
2304 return split;
2305 }
2306
2307 static struct shrinker deferred_split_shrinker = {
2308 .count_objects = deferred_split_count,
2309 .scan_objects = deferred_split_scan,
2310 .seeks = DEFAULT_SEEKS,
2311 .flags = SHRINKER_NUMA_AWARE,
2312 };
2313
2314 #ifdef CONFIG_DEBUG_FS
2315 static int split_huge_pages_set(void *data, u64 val)
2316 {
2317 struct zone *zone;
2318 struct page *page;
2319 unsigned long pfn, max_zone_pfn;
2320 unsigned long total = 0, split = 0;
2321
2322 if (val != 1)
2323 return -EINVAL;
2324
2325 for_each_populated_zone(zone) {
2326 max_zone_pfn = zone_end_pfn(zone);
2327 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2328 if (!pfn_valid(pfn))
2329 continue;
2330
2331 page = pfn_to_page(pfn);
2332 if (!get_page_unless_zero(page))
2333 continue;
2334
2335 if (zone != page_zone(page))
2336 goto next;
2337
2338 if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2339 goto next;
2340
2341 total++;
2342 lock_page(page);
2343 if (!split_huge_page(page))
2344 split++;
2345 unlock_page(page);
2346 next:
2347 put_page(page);
2348 }
2349 }
2350
2351 pr_info("%lu of %lu THP split\n", split, total);
2352
2353 return 0;
2354 }
2355 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2356 "%llu\n");
2357
2358 static int __init split_huge_pages_debugfs(void)
2359 {
2360 void *ret;
2361
2362 ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2363 &split_huge_pages_fops);
2364 if (!ret)
2365 pr_warn("Failed to create split_huge_pages in debugfs");
2366 return 0;
2367 }
2368 late_initcall(split_huge_pages_debugfs);
2369 #endif
Linux with added FPC-III support