1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2009 Red Hat, Inc.
4 */
5
6 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7
8 #include <linux/mm.h>
9 #include <linux/sched.h>
10 #include <linux/sched/mm.h>
11 #include <linux/sched/coredump.h>
12 #include <linux/sched/numa_balancing.h>
13 #include <linux/highmem.h>
14 #include <linux/hugetlb.h>
15 #include <linux/mmu_notifier.h>
16 #include <linux/rmap.h>
17 #include <linux/swap.h>
18 #include <linux/shrinker.h>
19 #include <linux/mm_inline.h>
20 #include <linux/swapops.h>
21 #include <linux/dax.h>
22 #include <linux/khugepaged.h>
23 #include <linux/freezer.h>
24 #include <linux/pfn_t.h>
25 #include <linux/mman.h>
26 #include <linux/memremap.h>
27 #include <linux/pagemap.h>
28 #include <linux/debugfs.h>
29 #include <linux/migrate.h>
30 #include <linux/hashtable.h>
31 #include <linux/userfaultfd_k.h>
32 #include <linux/page_idle.h>
33 #include <linux/shmem_fs.h>
34 #include <linux/oom.h>
35 #include <linux/numa.h>
36 #include <linux/page_owner.h>
37
38 #include <asm/tlb.h>
39 #include <asm/pgalloc.h>
40 #include "internal.h"
41
42 /*
43 * By default, transparent hugepage support is disabled in order to avoid
44 * risking an increased memory footprint for applications that are not
45 * guaranteed to benefit from it. When transparent hugepage support is
46 * enabled, it is for all mappings, and khugepaged scans all mappings.
47 * Defrag is invoked by khugepaged hugepage allocations and by page faults
48 * for all hugepage allocations.
49 */
50 unsigned long transparent_hugepage_flags __read_mostly =
51 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
52 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
53 #endif
54 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
55 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
56 #endif
57 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
58 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
59 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
60
61 static struct shrinker deferred_split_shrinker;
62
63 static atomic_t huge_zero_refcount;
64 struct page *huge_zero_page __read_mostly;
65
transparent_hugepage_enabled(struct vm_area_struct * vma)66 bool transparent_hugepage_enabled(struct vm_area_struct *vma)
67 {
68 /* The addr is used to check if the vma size fits */
69 unsigned long addr = (vma->vm_end & HPAGE_PMD_MASK) - HPAGE_PMD_SIZE;
70
71 if (!transhuge_vma_suitable(vma, addr))
72 return false;
73 if (vma_is_anonymous(vma))
74 return __transparent_hugepage_enabled(vma);
75 if (vma_is_shmem(vma))
76 return shmem_huge_enabled(vma);
77
78 return false;
79 }
80
get_huge_zero_page(void)81 static bool get_huge_zero_page(void)
82 {
83 struct page *zero_page;
84 retry:
85 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
86 return true;
87
88 zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
89 HPAGE_PMD_ORDER);
90 if (!zero_page) {
91 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
92 return false;
93 }
94 count_vm_event(THP_ZERO_PAGE_ALLOC);
95 preempt_disable();
96 if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
97 preempt_enable();
98 __free_pages(zero_page, compound_order(zero_page));
99 goto retry;
100 }
101
102 /* We take additional reference here. It will be put back by shrinker */
103 atomic_set(&huge_zero_refcount, 2);
104 preempt_enable();
105 return true;
106 }
107
put_huge_zero_page(void)108 static void put_huge_zero_page(void)
109 {
110 /*
111 * Counter should never go to zero here. Only shrinker can put
112 * last reference.
113 */
114 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
115 }
116
mm_get_huge_zero_page(struct mm_struct * mm)117 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
118 {
119 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
120 return READ_ONCE(huge_zero_page);
121
122 if (!get_huge_zero_page())
123 return NULL;
124
125 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
126 put_huge_zero_page();
127
128 return READ_ONCE(huge_zero_page);
129 }
130
mm_put_huge_zero_page(struct mm_struct * mm)131 void mm_put_huge_zero_page(struct mm_struct *mm)
132 {
133 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
134 put_huge_zero_page();
135 }
136
shrink_huge_zero_page_count(struct shrinker * shrink,struct shrink_control * sc)137 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
138 struct shrink_control *sc)
139 {
140 /* we can free zero page only if last reference remains */
141 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
142 }
143
shrink_huge_zero_page_scan(struct shrinker * shrink,struct shrink_control * sc)144 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
145 struct shrink_control *sc)
146 {
147 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
148 struct page *zero_page = xchg(&huge_zero_page, NULL);
149 BUG_ON(zero_page == NULL);
150 __free_pages(zero_page, compound_order(zero_page));
151 return HPAGE_PMD_NR;
152 }
153
154 return 0;
155 }
156
157 static struct shrinker huge_zero_page_shrinker = {
158 .count_objects = shrink_huge_zero_page_count,
159 .scan_objects = shrink_huge_zero_page_scan,
160 .seeks = DEFAULT_SEEKS,
161 };
162
163 #ifdef CONFIG_SYSFS
enabled_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)164 static ssize_t enabled_show(struct kobject *kobj,
165 struct kobj_attribute *attr, char *buf)
166 {
167 const char *output;
168
169 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
170 output = "[always] madvise never";
171 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
172 &transparent_hugepage_flags))
173 output = "always [madvise] never";
174 else
175 output = "always madvise [never]";
176
177 return sysfs_emit(buf, "%s\n", output);
178 }
179
enabled_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)180 static ssize_t enabled_store(struct kobject *kobj,
181 struct kobj_attribute *attr,
182 const char *buf, size_t count)
183 {
184 ssize_t ret = count;
185
186 if (sysfs_streq(buf, "always")) {
187 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
188 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
189 } else if (sysfs_streq(buf, "madvise")) {
190 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
191 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
192 } else if (sysfs_streq(buf, "never")) {
193 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
194 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
195 } else
196 ret = -EINVAL;
197
198 if (ret > 0) {
199 int err = start_stop_khugepaged();
200 if (err)
201 ret = err;
202 }
203 return ret;
204 }
205 static struct kobj_attribute enabled_attr =
206 __ATTR(enabled, 0644, enabled_show, enabled_store);
207
single_hugepage_flag_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf,enum transparent_hugepage_flag flag)208 ssize_t single_hugepage_flag_show(struct kobject *kobj,
209 struct kobj_attribute *attr, char *buf,
210 enum transparent_hugepage_flag flag)
211 {
212 return sysfs_emit(buf, "%d\n",
213 !!test_bit(flag, &transparent_hugepage_flags));
214 }
215
single_hugepage_flag_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count,enum transparent_hugepage_flag flag)216 ssize_t single_hugepage_flag_store(struct kobject *kobj,
217 struct kobj_attribute *attr,
218 const char *buf, size_t count,
219 enum transparent_hugepage_flag flag)
220 {
221 unsigned long value;
222 int ret;
223
224 ret = kstrtoul(buf, 10, &value);
225 if (ret < 0)
226 return ret;
227 if (value > 1)
228 return -EINVAL;
229
230 if (value)
231 set_bit(flag, &transparent_hugepage_flags);
232 else
233 clear_bit(flag, &transparent_hugepage_flags);
234
235 return count;
236 }
237
defrag_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)238 static ssize_t defrag_show(struct kobject *kobj,
239 struct kobj_attribute *attr, char *buf)
240 {
241 const char *output;
242
243 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
244 &transparent_hugepage_flags))
245 output = "[always] defer defer+madvise madvise never";
246 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
247 &transparent_hugepage_flags))
248 output = "always [defer] defer+madvise madvise never";
249 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG,
250 &transparent_hugepage_flags))
251 output = "always defer [defer+madvise] madvise never";
252 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
253 &transparent_hugepage_flags))
254 output = "always defer defer+madvise [madvise] never";
255 else
256 output = "always defer defer+madvise madvise [never]";
257
258 return sysfs_emit(buf, "%s\n", output);
259 }
260
defrag_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)261 static ssize_t defrag_store(struct kobject *kobj,
262 struct kobj_attribute *attr,
263 const char *buf, size_t count)
264 {
265 if (sysfs_streq(buf, "always")) {
266 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
267 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
268 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
269 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
270 } else if (sysfs_streq(buf, "defer+madvise")) {
271 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
272 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
273 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
274 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
275 } else if (sysfs_streq(buf, "defer")) {
276 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
277 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
278 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
279 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
280 } else if (sysfs_streq(buf, "madvise")) {
281 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
282 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
283 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
284 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
285 } else if (sysfs_streq(buf, "never")) {
286 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
287 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
288 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
289 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
290 } else
291 return -EINVAL;
292
293 return count;
294 }
295 static struct kobj_attribute defrag_attr =
296 __ATTR(defrag, 0644, defrag_show, defrag_store);
297
use_zero_page_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)298 static ssize_t use_zero_page_show(struct kobject *kobj,
299 struct kobj_attribute *attr, char *buf)
300 {
301 return single_hugepage_flag_show(kobj, attr, buf,
302 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
303 }
use_zero_page_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)304 static ssize_t use_zero_page_store(struct kobject *kobj,
305 struct kobj_attribute *attr, const char *buf, size_t count)
306 {
307 return single_hugepage_flag_store(kobj, attr, buf, count,
308 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
309 }
310 static struct kobj_attribute use_zero_page_attr =
311 __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
312
hpage_pmd_size_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)313 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
314 struct kobj_attribute *attr, char *buf)
315 {
316 return sysfs_emit(buf, "%lu\n", HPAGE_PMD_SIZE);
317 }
318 static struct kobj_attribute hpage_pmd_size_attr =
319 __ATTR_RO(hpage_pmd_size);
320
321 static struct attribute *hugepage_attr[] = {
322 &enabled_attr.attr,
323 &defrag_attr.attr,
324 &use_zero_page_attr.attr,
325 &hpage_pmd_size_attr.attr,
326 #ifdef CONFIG_SHMEM
327 &shmem_enabled_attr.attr,
328 #endif
329 NULL,
330 };
331
332 static const struct attribute_group hugepage_attr_group = {
333 .attrs = hugepage_attr,
334 };
335
hugepage_init_sysfs(struct kobject ** hugepage_kobj)336 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
337 {
338 int err;
339
340 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
341 if (unlikely(!*hugepage_kobj)) {
342 pr_err("failed to create transparent hugepage kobject\n");
343 return -ENOMEM;
344 }
345
346 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
347 if (err) {
348 pr_err("failed to register transparent hugepage group\n");
349 goto delete_obj;
350 }
351
352 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
353 if (err) {
354 pr_err("failed to register transparent hugepage group\n");
355 goto remove_hp_group;
356 }
357
358 return 0;
359
360 remove_hp_group:
361 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
362 delete_obj:
363 kobject_put(*hugepage_kobj);
364 return err;
365 }
366
hugepage_exit_sysfs(struct kobject * hugepage_kobj)367 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
368 {
369 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
370 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
371 kobject_put(hugepage_kobj);
372 }
373 #else
hugepage_init_sysfs(struct kobject ** hugepage_kobj)374 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
375 {
376 return 0;
377 }
378
hugepage_exit_sysfs(struct kobject * hugepage_kobj)379 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
380 {
381 }
382 #endif /* CONFIG_SYSFS */
383
hugepage_init(void)384 static int __init hugepage_init(void)
385 {
386 int err;
387 struct kobject *hugepage_kobj;
388
389 if (!has_transparent_hugepage()) {
390 /*
391 * Hardware doesn't support hugepages, hence disable
392 * DAX PMD support.
393 */
394 transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_NEVER_DAX;
395 return -EINVAL;
396 }
397
398 /*
399 * hugepages can't be allocated by the buddy allocator
400 */
401 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
402 /*
403 * we use page->mapping and page->index in second tail page
404 * as list_head: assuming THP order >= 2
405 */
406 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
407
408 err = hugepage_init_sysfs(&hugepage_kobj);
409 if (err)
410 goto err_sysfs;
411
412 err = khugepaged_init();
413 if (err)
414 goto err_slab;
415
416 err = register_shrinker(&huge_zero_page_shrinker);
417 if (err)
418 goto err_hzp_shrinker;
419 err = register_shrinker(&deferred_split_shrinker);
420 if (err)
421 goto err_split_shrinker;
422
423 /*
424 * By default disable transparent hugepages on smaller systems,
425 * where the extra memory used could hurt more than TLB overhead
426 * is likely to save. The admin can still enable it through /sys.
427 */
428 if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
429 transparent_hugepage_flags = 0;
430 return 0;
431 }
432
433 err = start_stop_khugepaged();
434 if (err)
435 goto err_khugepaged;
436
437 return 0;
438 err_khugepaged:
439 unregister_shrinker(&deferred_split_shrinker);
440 err_split_shrinker:
441 unregister_shrinker(&huge_zero_page_shrinker);
442 err_hzp_shrinker:
443 khugepaged_destroy();
444 err_slab:
445 hugepage_exit_sysfs(hugepage_kobj);
446 err_sysfs:
447 return err;
448 }
449 subsys_initcall(hugepage_init);
450
setup_transparent_hugepage(char * str)451 static int __init setup_transparent_hugepage(char *str)
452 {
453 int ret = 0;
454 if (!str)
455 goto out;
456 if (!strcmp(str, "always")) {
457 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
458 &transparent_hugepage_flags);
459 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
460 &transparent_hugepage_flags);
461 ret = 1;
462 } else if (!strcmp(str, "madvise")) {
463 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
464 &transparent_hugepage_flags);
465 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
466 &transparent_hugepage_flags);
467 ret = 1;
468 } else if (!strcmp(str, "never")) {
469 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
470 &transparent_hugepage_flags);
471 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
472 &transparent_hugepage_flags);
473 ret = 1;
474 }
475 out:
476 if (!ret)
477 pr_warn("transparent_hugepage= cannot parse, ignored\n");
478 return ret;
479 }
480 __setup("transparent_hugepage=", setup_transparent_hugepage);
481
maybe_pmd_mkwrite(pmd_t pmd,struct vm_area_struct * vma)482 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
483 {
484 if (likely(vma->vm_flags & VM_WRITE))
485 pmd = pmd_mkwrite(pmd);
486 return pmd;
487 }
488
489 #ifdef CONFIG_MEMCG
get_deferred_split_queue(struct page * page)490 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
491 {
492 struct mem_cgroup *memcg = page_memcg(compound_head(page));
493 struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
494
495 if (memcg)
496 return &memcg->deferred_split_queue;
497 else
498 return &pgdat->deferred_split_queue;
499 }
500 #else
get_deferred_split_queue(struct page * page)501 static inline struct deferred_split *get_deferred_split_queue(struct page *page)
502 {
503 struct pglist_data *pgdat = NODE_DATA(page_to_nid(page));
504
505 return &pgdat->deferred_split_queue;
506 }
507 #endif
508
prep_transhuge_page(struct page * page)509 void prep_transhuge_page(struct page *page)
510 {
511 /*
512 * we use page->mapping and page->indexlru in second tail page
513 * as list_head: assuming THP order >= 2
514 */
515
516 INIT_LIST_HEAD(page_deferred_list(page));
517 set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
518 }
519
is_transparent_hugepage(struct page * page)520 bool is_transparent_hugepage(struct page *page)
521 {
522 if (!PageCompound(page))
523 return false;
524
525 page = compound_head(page);
526 return is_huge_zero_page(page) ||
527 page[1].compound_dtor == TRANSHUGE_PAGE_DTOR;
528 }
529 EXPORT_SYMBOL_GPL(is_transparent_hugepage);
530
__thp_get_unmapped_area(struct file * filp,unsigned long addr,unsigned long len,loff_t off,unsigned long flags,unsigned long size)531 static unsigned long __thp_get_unmapped_area(struct file *filp,
532 unsigned long addr, unsigned long len,
533 loff_t off, unsigned long flags, unsigned long size)
534 {
535 loff_t off_end = off + len;
536 loff_t off_align = round_up(off, size);
537 unsigned long len_pad, ret;
538
539 if (off_end <= off_align || (off_end - off_align) < size)
540 return 0;
541
542 len_pad = len + size;
543 if (len_pad < len || (off + len_pad) < off)
544 return 0;
545
546 ret = current->mm->get_unmapped_area(filp, addr, len_pad,
547 off >> PAGE_SHIFT, flags);
548
549 /*
550 * The failure might be due to length padding. The caller will retry
551 * without the padding.
552 */
553 if (IS_ERR_VALUE(ret))
554 return 0;
555
556 /*
557 * Do not try to align to THP boundary if allocation at the address
558 * hint succeeds.
559 */
560 if (ret == addr)
561 return addr;
562
563 ret += (off - ret) & (size - 1);
564 return ret;
565 }
566
thp_get_unmapped_area(struct file * filp,unsigned long addr,unsigned long len,unsigned long pgoff,unsigned long flags)567 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
568 unsigned long len, unsigned long pgoff, unsigned long flags)
569 {
570 unsigned long ret;
571 loff_t off = (loff_t)pgoff << PAGE_SHIFT;
572
573 if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
574 goto out;
575
576 ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE);
577 if (ret)
578 return ret;
579 out:
580 return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
581 }
582 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
583
__do_huge_pmd_anonymous_page(struct vm_fault * vmf,struct page * page,gfp_t gfp)584 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
585 struct page *page, gfp_t gfp)
586 {
587 struct vm_area_struct *vma = vmf->vma;
588 pgtable_t pgtable;
589 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
590 vm_fault_t ret = 0;
591
592 VM_BUG_ON_PAGE(!PageCompound(page), page);
593
594 if (mem_cgroup_charge(page, vma->vm_mm, gfp)) {
595 put_page(page);
596 count_vm_event(THP_FAULT_FALLBACK);
597 count_vm_event(THP_FAULT_FALLBACK_CHARGE);
598 return VM_FAULT_FALLBACK;
599 }
600 cgroup_throttle_swaprate(page, gfp);
601
602 pgtable = pte_alloc_one(vma->vm_mm);
603 if (unlikely(!pgtable)) {
604 ret = VM_FAULT_OOM;
605 goto release;
606 }
607
608 clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
609 /*
610 * The memory barrier inside __SetPageUptodate makes sure that
611 * clear_huge_page writes become visible before the set_pmd_at()
612 * write.
613 */
614 __SetPageUptodate(page);
615
616 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
617 if (unlikely(!pmd_none(*vmf->pmd))) {
618 goto unlock_release;
619 } else {
620 pmd_t entry;
621
622 ret = check_stable_address_space(vma->vm_mm);
623 if (ret)
624 goto unlock_release;
625
626 /* Deliver the page fault to userland */
627 if (userfaultfd_missing(vma)) {
628 spin_unlock(vmf->ptl);
629 put_page(page);
630 pte_free(vma->vm_mm, pgtable);
631 ret = handle_userfault(vmf, VM_UFFD_MISSING);
632 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
633 return ret;
634 }
635
636 entry = mk_huge_pmd(page, vma->vm_page_prot);
637 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
638 page_add_new_anon_rmap(page, vma, haddr, true);
639 lru_cache_add_inactive_or_unevictable(page, vma);
640 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
641 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
642 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
643 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
644 mm_inc_nr_ptes(vma->vm_mm);
645 spin_unlock(vmf->ptl);
646 count_vm_event(THP_FAULT_ALLOC);
647 count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
648 }
649
650 return 0;
651 unlock_release:
652 spin_unlock(vmf->ptl);
653 release:
654 if (pgtable)
655 pte_free(vma->vm_mm, pgtable);
656 put_page(page);
657 return ret;
658
659 }
660
661 /*
662 * always: directly stall for all thp allocations
663 * defer: wake kswapd and fail if not immediately available
664 * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
665 * fail if not immediately available
666 * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
667 * available
668 * never: never stall for any thp allocation
669 */
vma_thp_gfp_mask(struct vm_area_struct * vma)670 gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma)
671 {
672 const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE);
673
674 /* Always do synchronous compaction */
675 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
676 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
677
678 /* Kick kcompactd and fail quickly */
679 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
680 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
681
682 /* Synchronous compaction if madvised, otherwise kick kcompactd */
683 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
684 return GFP_TRANSHUGE_LIGHT |
685 (vma_madvised ? __GFP_DIRECT_RECLAIM :
686 __GFP_KSWAPD_RECLAIM);
687
688 /* Only do synchronous compaction if madvised */
689 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
690 return GFP_TRANSHUGE_LIGHT |
691 (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
692
693 return GFP_TRANSHUGE_LIGHT;
694 }
695
696 /* Caller must hold page table lock. */
set_huge_zero_page(pgtable_t pgtable,struct mm_struct * mm,struct vm_area_struct * vma,unsigned long haddr,pmd_t * pmd,struct page * zero_page)697 static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
698 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
699 struct page *zero_page)
700 {
701 pmd_t entry;
702 if (!pmd_none(*pmd))
703 return;
704 entry = mk_pmd(zero_page, vma->vm_page_prot);
705 entry = pmd_mkhuge(entry);
706 if (pgtable)
707 pgtable_trans_huge_deposit(mm, pmd, pgtable);
708 set_pmd_at(mm, haddr, pmd, entry);
709 mm_inc_nr_ptes(mm);
710 }
711
do_huge_pmd_anonymous_page(struct vm_fault * vmf)712 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
713 {
714 struct vm_area_struct *vma = vmf->vma;
715 gfp_t gfp;
716 struct page *page;
717 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
718
719 if (!transhuge_vma_suitable(vma, haddr))
720 return VM_FAULT_FALLBACK;
721 if (unlikely(anon_vma_prepare(vma)))
722 return VM_FAULT_OOM;
723 if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
724 return VM_FAULT_OOM;
725 if (!(vmf->flags & FAULT_FLAG_WRITE) &&
726 !mm_forbids_zeropage(vma->vm_mm) &&
727 transparent_hugepage_use_zero_page()) {
728 pgtable_t pgtable;
729 struct page *zero_page;
730 vm_fault_t ret;
731 pgtable = pte_alloc_one(vma->vm_mm);
732 if (unlikely(!pgtable))
733 return VM_FAULT_OOM;
734 zero_page = mm_get_huge_zero_page(vma->vm_mm);
735 if (unlikely(!zero_page)) {
736 pte_free(vma->vm_mm, pgtable);
737 count_vm_event(THP_FAULT_FALLBACK);
738 return VM_FAULT_FALLBACK;
739 }
740 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
741 ret = 0;
742 if (pmd_none(*vmf->pmd)) {
743 ret = check_stable_address_space(vma->vm_mm);
744 if (ret) {
745 spin_unlock(vmf->ptl);
746 pte_free(vma->vm_mm, pgtable);
747 } else if (userfaultfd_missing(vma)) {
748 spin_unlock(vmf->ptl);
749 pte_free(vma->vm_mm, pgtable);
750 ret = handle_userfault(vmf, VM_UFFD_MISSING);
751 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
752 } else {
753 set_huge_zero_page(pgtable, vma->vm_mm, vma,
754 haddr, vmf->pmd, zero_page);
755 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
756 spin_unlock(vmf->ptl);
757 }
758 } else {
759 spin_unlock(vmf->ptl);
760 pte_free(vma->vm_mm, pgtable);
761 }
762 return ret;
763 }
764 gfp = vma_thp_gfp_mask(vma);
765 page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
766 if (unlikely(!page)) {
767 count_vm_event(THP_FAULT_FALLBACK);
768 return VM_FAULT_FALLBACK;
769 }
770 prep_transhuge_page(page);
771 return __do_huge_pmd_anonymous_page(vmf, page, gfp);
772 }
773
insert_pfn_pmd(struct vm_area_struct * vma,unsigned long addr,pmd_t * pmd,pfn_t pfn,pgprot_t prot,bool write,pgtable_t pgtable)774 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
775 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
776 pgtable_t pgtable)
777 {
778 struct mm_struct *mm = vma->vm_mm;
779 pmd_t entry;
780 spinlock_t *ptl;
781
782 ptl = pmd_lock(mm, pmd);
783 if (!pmd_none(*pmd)) {
784 if (write) {
785 if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
786 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
787 goto out_unlock;
788 }
789 entry = pmd_mkyoung(*pmd);
790 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
791 if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
792 update_mmu_cache_pmd(vma, addr, pmd);
793 }
794
795 goto out_unlock;
796 }
797
798 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
799 if (pfn_t_devmap(pfn))
800 entry = pmd_mkdevmap(entry);
801 if (write) {
802 entry = pmd_mkyoung(pmd_mkdirty(entry));
803 entry = maybe_pmd_mkwrite(entry, vma);
804 }
805
806 if (pgtable) {
807 pgtable_trans_huge_deposit(mm, pmd, pgtable);
808 mm_inc_nr_ptes(mm);
809 pgtable = NULL;
810 }
811
812 set_pmd_at(mm, addr, pmd, entry);
813 update_mmu_cache_pmd(vma, addr, pmd);
814
815 out_unlock:
816 spin_unlock(ptl);
817 if (pgtable)
818 pte_free(mm, pgtable);
819 }
820
821 /**
822 * vmf_insert_pfn_pmd_prot - insert a pmd size pfn
823 * @vmf: Structure describing the fault
824 * @pfn: pfn to insert
825 * @pgprot: page protection to use
826 * @write: whether it's a write fault
827 *
828 * Insert a pmd size pfn. See vmf_insert_pfn() for additional info and
829 * also consult the vmf_insert_mixed_prot() documentation when
830 * @pgprot != @vmf->vma->vm_page_prot.
831 *
832 * Return: vm_fault_t value.
833 */
vmf_insert_pfn_pmd_prot(struct vm_fault * vmf,pfn_t pfn,pgprot_t pgprot,bool write)834 vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, pfn_t pfn,
835 pgprot_t pgprot, bool write)
836 {
837 unsigned long addr = vmf->address & PMD_MASK;
838 struct vm_area_struct *vma = vmf->vma;
839 pgtable_t pgtable = NULL;
840
841 /*
842 * If we had pmd_special, we could avoid all these restrictions,
843 * but we need to be consistent with PTEs and architectures that
844 * can't support a 'special' bit.
845 */
846 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
847 !pfn_t_devmap(pfn));
848 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
849 (VM_PFNMAP|VM_MIXEDMAP));
850 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
851
852 if (addr < vma->vm_start || addr >= vma->vm_end)
853 return VM_FAULT_SIGBUS;
854
855 if (arch_needs_pgtable_deposit()) {
856 pgtable = pte_alloc_one(vma->vm_mm);
857 if (!pgtable)
858 return VM_FAULT_OOM;
859 }
860
861 track_pfn_insert(vma, &pgprot, pfn);
862
863 insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
864 return VM_FAULT_NOPAGE;
865 }
866 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd_prot);
867
868 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
maybe_pud_mkwrite(pud_t pud,struct vm_area_struct * vma)869 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
870 {
871 if (likely(vma->vm_flags & VM_WRITE))
872 pud = pud_mkwrite(pud);
873 return pud;
874 }
875
insert_pfn_pud(struct vm_area_struct * vma,unsigned long addr,pud_t * pud,pfn_t pfn,pgprot_t prot,bool write)876 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
877 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
878 {
879 struct mm_struct *mm = vma->vm_mm;
880 pud_t entry;
881 spinlock_t *ptl;
882
883 ptl = pud_lock(mm, pud);
884 if (!pud_none(*pud)) {
885 if (write) {
886 if (pud_pfn(*pud) != pfn_t_to_pfn(pfn)) {
887 WARN_ON_ONCE(!is_huge_zero_pud(*pud));
888 goto out_unlock;
889 }
890 entry = pud_mkyoung(*pud);
891 entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
892 if (pudp_set_access_flags(vma, addr, pud, entry, 1))
893 update_mmu_cache_pud(vma, addr, pud);
894 }
895 goto out_unlock;
896 }
897
898 entry = pud_mkhuge(pfn_t_pud(pfn, prot));
899 if (pfn_t_devmap(pfn))
900 entry = pud_mkdevmap(entry);
901 if (write) {
902 entry = pud_mkyoung(pud_mkdirty(entry));
903 entry = maybe_pud_mkwrite(entry, vma);
904 }
905 set_pud_at(mm, addr, pud, entry);
906 update_mmu_cache_pud(vma, addr, pud);
907
908 out_unlock:
909 spin_unlock(ptl);
910 }
911
912 /**
913 * vmf_insert_pfn_pud_prot - insert a pud size pfn
914 * @vmf: Structure describing the fault
915 * @pfn: pfn to insert
916 * @pgprot: page protection to use
917 * @write: whether it's a write fault
918 *
919 * Insert a pud size pfn. See vmf_insert_pfn() for additional info and
920 * also consult the vmf_insert_mixed_prot() documentation when
921 * @pgprot != @vmf->vma->vm_page_prot.
922 *
923 * Return: vm_fault_t value.
924 */
vmf_insert_pfn_pud_prot(struct vm_fault * vmf,pfn_t pfn,pgprot_t pgprot,bool write)925 vm_fault_t vmf_insert_pfn_pud_prot(struct vm_fault *vmf, pfn_t pfn,
926 pgprot_t pgprot, bool write)
927 {
928 unsigned long addr = vmf->address & PUD_MASK;
929 struct vm_area_struct *vma = vmf->vma;
930
931 /*
932 * If we had pud_special, we could avoid all these restrictions,
933 * but we need to be consistent with PTEs and architectures that
934 * can't support a 'special' bit.
935 */
936 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
937 !pfn_t_devmap(pfn));
938 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
939 (VM_PFNMAP|VM_MIXEDMAP));
940 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
941
942 if (addr < vma->vm_start || addr >= vma->vm_end)
943 return VM_FAULT_SIGBUS;
944
945 track_pfn_insert(vma, &pgprot, pfn);
946
947 insert_pfn_pud(vma, addr, vmf->pud, pfn, pgprot, write);
948 return VM_FAULT_NOPAGE;
949 }
950 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud_prot);
951 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
952
touch_pmd(struct vm_area_struct * vma,unsigned long addr,pmd_t * pmd,int flags)953 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
954 pmd_t *pmd, int flags)
955 {
956 pmd_t _pmd;
957
958 _pmd = pmd_mkyoung(*pmd);
959 if (flags & FOLL_WRITE)
960 _pmd = pmd_mkdirty(_pmd);
961 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
962 pmd, _pmd, flags & FOLL_WRITE))
963 update_mmu_cache_pmd(vma, addr, pmd);
964 }
965
follow_devmap_pmd(struct vm_area_struct * vma,unsigned long addr,pmd_t * pmd,int flags,struct dev_pagemap ** pgmap)966 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
967 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
968 {
969 unsigned long pfn = pmd_pfn(*pmd);
970 struct mm_struct *mm = vma->vm_mm;
971 struct page *page;
972
973 assert_spin_locked(pmd_lockptr(mm, pmd));
974
975 /*
976 * When we COW a devmap PMD entry, we split it into PTEs, so we should
977 * not be in this function with `flags & FOLL_COW` set.
978 */
979 WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
980
981 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
982 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
983 (FOLL_PIN | FOLL_GET)))
984 return NULL;
985
986 if (flags & FOLL_WRITE && !pmd_write(*pmd))
987 return NULL;
988
989 if (pmd_present(*pmd) && pmd_devmap(*pmd))
990 /* pass */;
991 else
992 return NULL;
993
994 if (flags & FOLL_TOUCH)
995 touch_pmd(vma, addr, pmd, flags);
996
997 /*
998 * device mapped pages can only be returned if the
999 * caller will manage the page reference count.
1000 */
1001 if (!(flags & (FOLL_GET | FOLL_PIN)))
1002 return ERR_PTR(-EEXIST);
1003
1004 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1005 *pgmap = get_dev_pagemap(pfn, *pgmap);
1006 if (!*pgmap)
1007 return ERR_PTR(-EFAULT);
1008 page = pfn_to_page(pfn);
1009 if (!try_grab_page(page, flags))
1010 page = ERR_PTR(-ENOMEM);
1011
1012 return page;
1013 }
1014
copy_huge_pmd(struct mm_struct * dst_mm,struct mm_struct * src_mm,pmd_t * dst_pmd,pmd_t * src_pmd,unsigned long addr,struct vm_area_struct * vma)1015 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1016 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1017 struct vm_area_struct *vma)
1018 {
1019 spinlock_t *dst_ptl, *src_ptl;
1020 struct page *src_page;
1021 pmd_t pmd;
1022 pgtable_t pgtable = NULL;
1023 int ret = -ENOMEM;
1024
1025 /* Skip if can be re-fill on fault */
1026 if (!vma_is_anonymous(vma))
1027 return 0;
1028
1029 pgtable = pte_alloc_one(dst_mm);
1030 if (unlikely(!pgtable))
1031 goto out;
1032
1033 dst_ptl = pmd_lock(dst_mm, dst_pmd);
1034 src_ptl = pmd_lockptr(src_mm, src_pmd);
1035 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1036
1037 ret = -EAGAIN;
1038 pmd = *src_pmd;
1039
1040 /*
1041 * Make sure the _PAGE_UFFD_WP bit is cleared if the new VMA
1042 * does not have the VM_UFFD_WP, which means that the uffd
1043 * fork event is not enabled.
1044 */
1045 if (!(vma->vm_flags & VM_UFFD_WP))
1046 pmd = pmd_clear_uffd_wp(pmd);
1047
1048 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1049 if (unlikely(is_swap_pmd(pmd))) {
1050 swp_entry_t entry = pmd_to_swp_entry(pmd);
1051
1052 VM_BUG_ON(!is_pmd_migration_entry(pmd));
1053 if (is_write_migration_entry(entry)) {
1054 make_migration_entry_read(&entry);
1055 pmd = swp_entry_to_pmd(entry);
1056 if (pmd_swp_soft_dirty(*src_pmd))
1057 pmd = pmd_swp_mksoft_dirty(pmd);
1058 set_pmd_at(src_mm, addr, src_pmd, pmd);
1059 }
1060 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1061 mm_inc_nr_ptes(dst_mm);
1062 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1063 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1064 ret = 0;
1065 goto out_unlock;
1066 }
1067 #endif
1068
1069 if (unlikely(!pmd_trans_huge(pmd))) {
1070 pte_free(dst_mm, pgtable);
1071 goto out_unlock;
1072 }
1073 /*
1074 * When page table lock is held, the huge zero pmd should not be
1075 * under splitting since we don't split the page itself, only pmd to
1076 * a page table.
1077 */
1078 if (is_huge_zero_pmd(pmd)) {
1079 struct page *zero_page;
1080 /*
1081 * get_huge_zero_page() will never allocate a new page here,
1082 * since we already have a zero page to copy. It just takes a
1083 * reference.
1084 */
1085 zero_page = mm_get_huge_zero_page(dst_mm);
1086 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
1087 zero_page);
1088 ret = 0;
1089 goto out_unlock;
1090 }
1091
1092 src_page = pmd_page(pmd);
1093 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1094
1095 /*
1096 * If this page is a potentially pinned page, split and retry the fault
1097 * with smaller page size. Normally this should not happen because the
1098 * userspace should use MADV_DONTFORK upon pinned regions. This is a
1099 * best effort that the pinned pages won't be replaced by another
1100 * random page during the coming copy-on-write.
1101 */
1102 if (unlikely(page_needs_cow_for_dma(vma, src_page))) {
1103 pte_free(dst_mm, pgtable);
1104 spin_unlock(src_ptl);
1105 spin_unlock(dst_ptl);
1106 __split_huge_pmd(vma, src_pmd, addr, false, NULL);
1107 return -EAGAIN;
1108 }
1109
1110 get_page(src_page);
1111 page_dup_rmap(src_page, true);
1112 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1113 mm_inc_nr_ptes(dst_mm);
1114 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1115
1116 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1117 pmd = pmd_mkold(pmd_wrprotect(pmd));
1118 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1119
1120 ret = 0;
1121 out_unlock:
1122 spin_unlock(src_ptl);
1123 spin_unlock(dst_ptl);
1124 out:
1125 return ret;
1126 }
1127
1128 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
touch_pud(struct vm_area_struct * vma,unsigned long addr,pud_t * pud,int flags)1129 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1130 pud_t *pud, int flags)
1131 {
1132 pud_t _pud;
1133
1134 _pud = pud_mkyoung(*pud);
1135 if (flags & FOLL_WRITE)
1136 _pud = pud_mkdirty(_pud);
1137 if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1138 pud, _pud, flags & FOLL_WRITE))
1139 update_mmu_cache_pud(vma, addr, pud);
1140 }
1141
follow_devmap_pud(struct vm_area_struct * vma,unsigned long addr,pud_t * pud,int flags,struct dev_pagemap ** pgmap)1142 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1143 pud_t *pud, int flags, struct dev_pagemap **pgmap)
1144 {
1145 unsigned long pfn = pud_pfn(*pud);
1146 struct mm_struct *mm = vma->vm_mm;
1147 struct page *page;
1148
1149 assert_spin_locked(pud_lockptr(mm, pud));
1150
1151 if (flags & FOLL_WRITE && !pud_write(*pud))
1152 return NULL;
1153
1154 /* FOLL_GET and FOLL_PIN are mutually exclusive. */
1155 if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) ==
1156 (FOLL_PIN | FOLL_GET)))
1157 return NULL;
1158
1159 if (pud_present(*pud) && pud_devmap(*pud))
1160 /* pass */;
1161 else
1162 return NULL;
1163
1164 if (flags & FOLL_TOUCH)
1165 touch_pud(vma, addr, pud, flags);
1166
1167 /*
1168 * device mapped pages can only be returned if the
1169 * caller will manage the page reference count.
1170 *
1171 * At least one of FOLL_GET | FOLL_PIN must be set, so assert that here:
1172 */
1173 if (!(flags & (FOLL_GET | FOLL_PIN)))
1174 return ERR_PTR(-EEXIST);
1175
1176 pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1177 *pgmap = get_dev_pagemap(pfn, *pgmap);
1178 if (!*pgmap)
1179 return ERR_PTR(-EFAULT);
1180 page = pfn_to_page(pfn);
1181 if (!try_grab_page(page, flags))
1182 page = ERR_PTR(-ENOMEM);
1183
1184 return page;
1185 }
1186
copy_huge_pud(struct mm_struct * dst_mm,struct mm_struct * src_mm,pud_t * dst_pud,pud_t * src_pud,unsigned long addr,struct vm_area_struct * vma)1187 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1188 pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1189 struct vm_area_struct *vma)
1190 {
1191 spinlock_t *dst_ptl, *src_ptl;
1192 pud_t pud;
1193 int ret;
1194
1195 dst_ptl = pud_lock(dst_mm, dst_pud);
1196 src_ptl = pud_lockptr(src_mm, src_pud);
1197 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1198
1199 ret = -EAGAIN;
1200 pud = *src_pud;
1201 if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1202 goto out_unlock;
1203
1204 /*
1205 * When page table lock is held, the huge zero pud should not be
1206 * under splitting since we don't split the page itself, only pud to
1207 * a page table.
1208 */
1209 if (is_huge_zero_pud(pud)) {
1210 /* No huge zero pud yet */
1211 }
1212
1213 /* Please refer to comments in copy_huge_pmd() */
1214 if (unlikely(page_needs_cow_for_dma(vma, pud_page(pud)))) {
1215 spin_unlock(src_ptl);
1216 spin_unlock(dst_ptl);
1217 __split_huge_pud(vma, src_pud, addr);
1218 return -EAGAIN;
1219 }
1220
1221 pudp_set_wrprotect(src_mm, addr, src_pud);
1222 pud = pud_mkold(pud_wrprotect(pud));
1223 set_pud_at(dst_mm, addr, dst_pud, pud);
1224
1225 ret = 0;
1226 out_unlock:
1227 spin_unlock(src_ptl);
1228 spin_unlock(dst_ptl);
1229 return ret;
1230 }
1231
huge_pud_set_accessed(struct vm_fault * vmf,pud_t orig_pud)1232 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1233 {
1234 pud_t entry;
1235 unsigned long haddr;
1236 bool write = vmf->flags & FAULT_FLAG_WRITE;
1237
1238 vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1239 if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1240 goto unlock;
1241
1242 entry = pud_mkyoung(orig_pud);
1243 if (write)
1244 entry = pud_mkdirty(entry);
1245 haddr = vmf->address & HPAGE_PUD_MASK;
1246 if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1247 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1248
1249 unlock:
1250 spin_unlock(vmf->ptl);
1251 }
1252 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1253
huge_pmd_set_accessed(struct vm_fault * vmf,pmd_t orig_pmd)1254 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1255 {
1256 pmd_t entry;
1257 unsigned long haddr;
1258 bool write = vmf->flags & FAULT_FLAG_WRITE;
1259
1260 vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1261 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1262 goto unlock;
1263
1264 entry = pmd_mkyoung(orig_pmd);
1265 if (write)
1266 entry = pmd_mkdirty(entry);
1267 haddr = vmf->address & HPAGE_PMD_MASK;
1268 if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1269 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1270
1271 unlock:
1272 spin_unlock(vmf->ptl);
1273 }
1274
do_huge_pmd_wp_page(struct vm_fault * vmf,pmd_t orig_pmd)1275 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1276 {
1277 struct vm_area_struct *vma = vmf->vma;
1278 struct page *page;
1279 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1280
1281 vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1282 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1283
1284 if (is_huge_zero_pmd(orig_pmd))
1285 goto fallback;
1286
1287 spin_lock(vmf->ptl);
1288
1289 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1290 spin_unlock(vmf->ptl);
1291 return 0;
1292 }
1293
1294 page = pmd_page(orig_pmd);
1295 VM_BUG_ON_PAGE(!PageHead(page), page);
1296
1297 /* Lock page for reuse_swap_page() */
1298 if (!trylock_page(page)) {
1299 get_page(page);
1300 spin_unlock(vmf->ptl);
1301 lock_page(page);
1302 spin_lock(vmf->ptl);
1303 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1304 spin_unlock(vmf->ptl);
1305 unlock_page(page);
1306 put_page(page);
1307 return 0;
1308 }
1309 put_page(page);
1310 }
1311
1312 /*
1313 * We can only reuse the page if nobody else maps the huge page or it's
1314 * part.
1315 */
1316 if (reuse_swap_page(page, NULL)) {
1317 pmd_t entry;
1318 entry = pmd_mkyoung(orig_pmd);
1319 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1320 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
1321 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1322 unlock_page(page);
1323 spin_unlock(vmf->ptl);
1324 return VM_FAULT_WRITE;
1325 }
1326
1327 unlock_page(page);
1328 spin_unlock(vmf->ptl);
1329 fallback:
1330 __split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL);
1331 return VM_FAULT_FALLBACK;
1332 }
1333
1334 /*
1335 * FOLL_FORCE can write to even unwritable pmd's, but only
1336 * after we've gone through a COW cycle and they are dirty.
1337 */
can_follow_write_pmd(pmd_t pmd,unsigned int flags)1338 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1339 {
1340 return pmd_write(pmd) ||
1341 ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1342 }
1343
follow_trans_huge_pmd(struct vm_area_struct * vma,unsigned long addr,pmd_t * pmd,unsigned int flags)1344 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1345 unsigned long addr,
1346 pmd_t *pmd,
1347 unsigned int flags)
1348 {
1349 struct mm_struct *mm = vma->vm_mm;
1350 struct page *page = NULL;
1351
1352 assert_spin_locked(pmd_lockptr(mm, pmd));
1353
1354 if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1355 goto out;
1356
1357 /* Avoid dumping huge zero page */
1358 if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1359 return ERR_PTR(-EFAULT);
1360
1361 /* Full NUMA hinting faults to serialise migration in fault paths */
1362 if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1363 goto out;
1364
1365 page = pmd_page(*pmd);
1366 VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1367
1368 if (!try_grab_page(page, flags))
1369 return ERR_PTR(-ENOMEM);
1370
1371 if (flags & FOLL_TOUCH)
1372 touch_pmd(vma, addr, pmd, flags);
1373
1374 if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1375 /*
1376 * We don't mlock() pte-mapped THPs. This way we can avoid
1377 * leaking mlocked pages into non-VM_LOCKED VMAs.
1378 *
1379 * For anon THP:
1380 *
1381 * In most cases the pmd is the only mapping of the page as we
1382 * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1383 * writable private mappings in populate_vma_page_range().
1384 *
1385 * The only scenario when we have the page shared here is if we
1386 * mlocking read-only mapping shared over fork(). We skip
1387 * mlocking such pages.
1388 *
1389 * For file THP:
1390 *
1391 * We can expect PageDoubleMap() to be stable under page lock:
1392 * for file pages we set it in page_add_file_rmap(), which
1393 * requires page to be locked.
1394 */
1395
1396 if (PageAnon(page) && compound_mapcount(page) != 1)
1397 goto skip_mlock;
1398 if (PageDoubleMap(page) || !page->mapping)
1399 goto skip_mlock;
1400 if (!trylock_page(page))
1401 goto skip_mlock;
1402 if (page->mapping && !PageDoubleMap(page))
1403 mlock_vma_page(page);
1404 unlock_page(page);
1405 }
1406 skip_mlock:
1407 page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1408 VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1409
1410 out:
1411 return page;
1412 }
1413
1414 /* NUMA hinting page fault entry point for trans huge pmds */
do_huge_pmd_numa_page(struct vm_fault * vmf,pmd_t pmd)1415 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1416 {
1417 struct vm_area_struct *vma = vmf->vma;
1418 struct anon_vma *anon_vma = NULL;
1419 struct page *page;
1420 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1421 int page_nid = NUMA_NO_NODE, this_nid = numa_node_id();
1422 int target_nid, last_cpupid = -1;
1423 bool page_locked;
1424 bool migrated = false;
1425 bool was_writable;
1426 int flags = 0;
1427
1428 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1429 if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1430 goto out_unlock;
1431
1432 /*
1433 * If there are potential migrations, wait for completion and retry
1434 * without disrupting NUMA hinting information. Do not relock and
1435 * check_same as the page may no longer be mapped.
1436 */
1437 if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1438 page = pmd_page(*vmf->pmd);
1439 if (!get_page_unless_zero(page))
1440 goto out_unlock;
1441 spin_unlock(vmf->ptl);
1442 put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE);
1443 goto out;
1444 }
1445
1446 page = pmd_page(pmd);
1447 BUG_ON(is_huge_zero_page(page));
1448 page_nid = page_to_nid(page);
1449 last_cpupid = page_cpupid_last(page);
1450 count_vm_numa_event(NUMA_HINT_FAULTS);
1451 if (page_nid == this_nid) {
1452 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1453 flags |= TNF_FAULT_LOCAL;
1454 }
1455
1456 /* See similar comment in do_numa_page for explanation */
1457 if (!pmd_savedwrite(pmd))
1458 flags |= TNF_NO_GROUP;
1459
1460 /*
1461 * Acquire the page lock to serialise THP migrations but avoid dropping
1462 * page_table_lock if at all possible
1463 */
1464 page_locked = trylock_page(page);
1465 target_nid = mpol_misplaced(page, vma, haddr);
1466 /* Migration could have started since the pmd_trans_migrating check */
1467 if (!page_locked) {
1468 page_nid = NUMA_NO_NODE;
1469 if (!get_page_unless_zero(page))
1470 goto out_unlock;
1471 spin_unlock(vmf->ptl);
1472 put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE);
1473 goto out;
1474 } else if (target_nid == NUMA_NO_NODE) {
1475 /* There are no parallel migrations and page is in the right
1476 * node. Clear the numa hinting info in this pmd.
1477 */
1478 goto clear_pmdnuma;
1479 }
1480
1481 /*
1482 * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1483 * to serialises splits
1484 */
1485 get_page(page);
1486 spin_unlock(vmf->ptl);
1487 anon_vma = page_lock_anon_vma_read(page);
1488
1489 /* Confirm the PMD did not change while page_table_lock was released */
1490 spin_lock(vmf->ptl);
1491 if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1492 unlock_page(page);
1493 put_page(page);
1494 page_nid = NUMA_NO_NODE;
1495 goto out_unlock;
1496 }
1497
1498 /* Bail if we fail to protect against THP splits for any reason */
1499 if (unlikely(!anon_vma)) {
1500 put_page(page);
1501 page_nid = NUMA_NO_NODE;
1502 goto clear_pmdnuma;
1503 }
1504
1505 /*
1506 * Since we took the NUMA fault, we must have observed the !accessible
1507 * bit. Make sure all other CPUs agree with that, to avoid them
1508 * modifying the page we're about to migrate.
1509 *
1510 * Must be done under PTL such that we'll observe the relevant
1511 * inc_tlb_flush_pending().
1512 *
1513 * We are not sure a pending tlb flush here is for a huge page
1514 * mapping or not. Hence use the tlb range variant
1515 */
1516 if (mm_tlb_flush_pending(vma->vm_mm)) {
1517 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1518 /*
1519 * change_huge_pmd() released the pmd lock before
1520 * invalidating the secondary MMUs sharing the primary
1521 * MMU pagetables (with ->invalidate_range()). The
1522 * mmu_notifier_invalidate_range_end() (which
1523 * internally calls ->invalidate_range()) in
1524 * change_pmd_range() will run after us, so we can't
1525 * rely on it here and we need an explicit invalidate.
1526 */
1527 mmu_notifier_invalidate_range(vma->vm_mm, haddr,
1528 haddr + HPAGE_PMD_SIZE);
1529 }
1530
1531 /*
1532 * Migrate the THP to the requested node, returns with page unlocked
1533 * and access rights restored.
1534 */
1535 spin_unlock(vmf->ptl);
1536
1537 migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1538 vmf->pmd, pmd, vmf->address, page, target_nid);
1539 if (migrated) {
1540 flags |= TNF_MIGRATED;
1541 page_nid = target_nid;
1542 } else
1543 flags |= TNF_MIGRATE_FAIL;
1544
1545 goto out;
1546 clear_pmdnuma:
1547 BUG_ON(!PageLocked(page));
1548 was_writable = pmd_savedwrite(pmd);
1549 pmd = pmd_modify(pmd, vma->vm_page_prot);
1550 pmd = pmd_mkyoung(pmd);
1551 if (was_writable)
1552 pmd = pmd_mkwrite(pmd);
1553 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1554 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1555 unlock_page(page);
1556 out_unlock:
1557 spin_unlock(vmf->ptl);
1558
1559 out:
1560 if (anon_vma)
1561 page_unlock_anon_vma_read(anon_vma);
1562
1563 if (page_nid != NUMA_NO_NODE)
1564 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1565 flags);
1566
1567 return 0;
1568 }
1569
1570 /*
1571 * Return true if we do MADV_FREE successfully on entire pmd page.
1572 * Otherwise, return false.
1573 */
madvise_free_huge_pmd(struct mmu_gather * tlb,struct vm_area_struct * vma,pmd_t * pmd,unsigned long addr,unsigned long next)1574 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1575 pmd_t *pmd, unsigned long addr, unsigned long next)
1576 {
1577 spinlock_t *ptl;
1578 pmd_t orig_pmd;
1579 struct page *page;
1580 struct mm_struct *mm = tlb->mm;
1581 bool ret = false;
1582
1583 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1584
1585 ptl = pmd_trans_huge_lock(pmd, vma);
1586 if (!ptl)
1587 goto out_unlocked;
1588
1589 orig_pmd = *pmd;
1590 if (is_huge_zero_pmd(orig_pmd))
1591 goto out;
1592
1593 if (unlikely(!pmd_present(orig_pmd))) {
1594 VM_BUG_ON(thp_migration_supported() &&
1595 !is_pmd_migration_entry(orig_pmd));
1596 goto out;
1597 }
1598
1599 page = pmd_page(orig_pmd);
1600 /*
1601 * If other processes are mapping this page, we couldn't discard
1602 * the page unless they all do MADV_FREE so let's skip the page.
1603 */
1604 if (page_mapcount(page) != 1)
1605 goto out;
1606
1607 if (!trylock_page(page))
1608 goto out;
1609
1610 /*
1611 * If user want to discard part-pages of THP, split it so MADV_FREE
1612 * will deactivate only them.
1613 */
1614 if (next - addr != HPAGE_PMD_SIZE) {
1615 get_page(page);
1616 spin_unlock(ptl);
1617 split_huge_page(page);
1618 unlock_page(page);
1619 put_page(page);
1620 goto out_unlocked;
1621 }
1622
1623 if (PageDirty(page))
1624 ClearPageDirty(page);
1625 unlock_page(page);
1626
1627 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1628 pmdp_invalidate(vma, addr, pmd);
1629 orig_pmd = pmd_mkold(orig_pmd);
1630 orig_pmd = pmd_mkclean(orig_pmd);
1631
1632 set_pmd_at(mm, addr, pmd, orig_pmd);
1633 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1634 }
1635
1636 mark_page_lazyfree(page);
1637 ret = true;
1638 out:
1639 spin_unlock(ptl);
1640 out_unlocked:
1641 return ret;
1642 }
1643
zap_deposited_table(struct mm_struct * mm,pmd_t * pmd)1644 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1645 {
1646 pgtable_t pgtable;
1647
1648 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1649 pte_free(mm, pgtable);
1650 mm_dec_nr_ptes(mm);
1651 }
1652
zap_huge_pmd(struct mmu_gather * tlb,struct vm_area_struct * vma,pmd_t * pmd,unsigned long addr)1653 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1654 pmd_t *pmd, unsigned long addr)
1655 {
1656 pmd_t orig_pmd;
1657 spinlock_t *ptl;
1658
1659 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
1660
1661 ptl = __pmd_trans_huge_lock(pmd, vma);
1662 if (!ptl)
1663 return 0;
1664 /*
1665 * For architectures like ppc64 we look at deposited pgtable
1666 * when calling pmdp_huge_get_and_clear. So do the
1667 * pgtable_trans_huge_withdraw after finishing pmdp related
1668 * operations.
1669 */
1670 orig_pmd = pmdp_huge_get_and_clear_full(vma, addr, pmd,
1671 tlb->fullmm);
1672 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1673 if (vma_is_special_huge(vma)) {
1674 if (arch_needs_pgtable_deposit())
1675 zap_deposited_table(tlb->mm, pmd);
1676 spin_unlock(ptl);
1677 if (is_huge_zero_pmd(orig_pmd))
1678 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1679 } else if (is_huge_zero_pmd(orig_pmd)) {
1680 zap_deposited_table(tlb->mm, pmd);
1681 spin_unlock(ptl);
1682 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1683 } else {
1684 struct page *page = NULL;
1685 int flush_needed = 1;
1686
1687 if (pmd_present(orig_pmd)) {
1688 page = pmd_page(orig_pmd);
1689 page_remove_rmap(page, true);
1690 VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1691 VM_BUG_ON_PAGE(!PageHead(page), page);
1692 } else if (thp_migration_supported()) {
1693 swp_entry_t entry;
1694
1695 VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1696 entry = pmd_to_swp_entry(orig_pmd);
1697 page = migration_entry_to_page(entry);
1698 flush_needed = 0;
1699 } else
1700 WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1701
1702 if (PageAnon(page)) {
1703 zap_deposited_table(tlb->mm, pmd);
1704 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1705 } else {
1706 if (arch_needs_pgtable_deposit())
1707 zap_deposited_table(tlb->mm, pmd);
1708 add_mm_counter(tlb->mm, mm_counter_file(page), -HPAGE_PMD_NR);
1709 }
1710
1711 spin_unlock(ptl);
1712 if (flush_needed)
1713 tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1714 }
1715 return 1;
1716 }
1717
1718 #ifndef pmd_move_must_withdraw
pmd_move_must_withdraw(spinlock_t * new_pmd_ptl,spinlock_t * old_pmd_ptl,struct vm_area_struct * vma)1719 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1720 spinlock_t *old_pmd_ptl,
1721 struct vm_area_struct *vma)
1722 {
1723 /*
1724 * With split pmd lock we also need to move preallocated
1725 * PTE page table if new_pmd is on different PMD page table.
1726 *
1727 * We also don't deposit and withdraw tables for file pages.
1728 */
1729 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1730 }
1731 #endif
1732
move_soft_dirty_pmd(pmd_t pmd)1733 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1734 {
1735 #ifdef CONFIG_MEM_SOFT_DIRTY
1736 if (unlikely(is_pmd_migration_entry(pmd)))
1737 pmd = pmd_swp_mksoft_dirty(pmd);
1738 else if (pmd_present(pmd))
1739 pmd = pmd_mksoft_dirty(pmd);
1740 #endif
1741 return pmd;
1742 }
1743
move_huge_pmd(struct vm_area_struct * vma,unsigned long old_addr,unsigned long new_addr,pmd_t * old_pmd,pmd_t * new_pmd)1744 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1745 unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
1746 {
1747 spinlock_t *old_ptl, *new_ptl;
1748 pmd_t pmd;
1749 struct mm_struct *mm = vma->vm_mm;
1750 bool force_flush = false;
1751
1752 /*
1753 * The destination pmd shouldn't be established, free_pgtables()
1754 * should have release it.
1755 */
1756 if (WARN_ON(!pmd_none(*new_pmd))) {
1757 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1758 return false;
1759 }
1760
1761 /*
1762 * We don't have to worry about the ordering of src and dst
1763 * ptlocks because exclusive mmap_lock prevents deadlock.
1764 */
1765 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1766 if (old_ptl) {
1767 new_ptl = pmd_lockptr(mm, new_pmd);
1768 if (new_ptl != old_ptl)
1769 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1770 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1771 if (pmd_present(pmd))
1772 force_flush = true;
1773 VM_BUG_ON(!pmd_none(*new_pmd));
1774
1775 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1776 pgtable_t pgtable;
1777 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1778 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1779 }
1780 pmd = move_soft_dirty_pmd(pmd);
1781 set_pmd_at(mm, new_addr, new_pmd, pmd);
1782 if (force_flush)
1783 flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1784 if (new_ptl != old_ptl)
1785 spin_unlock(new_ptl);
1786 spin_unlock(old_ptl);
1787 return true;
1788 }
1789 return false;
1790 }
1791
1792 /*
1793 * Returns
1794 * - 0 if PMD could not be locked
1795 * - 1 if PMD was locked but protections unchanged and TLB flush unnecessary
1796 * - HPAGE_PMD_NR if protections changed and TLB flush necessary
1797 */
change_huge_pmd(struct vm_area_struct * vma,pmd_t * pmd,unsigned long addr,pgprot_t newprot,unsigned long cp_flags)1798 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1799 unsigned long addr, pgprot_t newprot, unsigned long cp_flags)
1800 {
1801 struct mm_struct *mm = vma->vm_mm;
1802 spinlock_t *ptl;
1803 pmd_t entry;
1804 bool preserve_write;
1805 int ret;
1806 bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
1807 bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
1808 bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
1809
1810 ptl = __pmd_trans_huge_lock(pmd, vma);
1811 if (!ptl)
1812 return 0;
1813
1814 preserve_write = prot_numa && pmd_write(*pmd);
1815 ret = 1;
1816
1817 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1818 if (is_swap_pmd(*pmd)) {
1819 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1820
1821 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1822 if (is_write_migration_entry(entry)) {
1823 pmd_t newpmd;
1824 /*
1825 * A protection check is difficult so
1826 * just be safe and disable write
1827 */
1828 make_migration_entry_read(&entry);
1829 newpmd = swp_entry_to_pmd(entry);
1830 if (pmd_swp_soft_dirty(*pmd))
1831 newpmd = pmd_swp_mksoft_dirty(newpmd);
1832 set_pmd_at(mm, addr, pmd, newpmd);
1833 }
1834 goto unlock;
1835 }
1836 #endif
1837
1838 /*
1839 * Avoid trapping faults against the zero page. The read-only
1840 * data is likely to be read-cached on the local CPU and
1841 * local/remote hits to the zero page are not interesting.
1842 */
1843 if (prot_numa && is_huge_zero_pmd(*pmd))
1844 goto unlock;
1845
1846 if (prot_numa && pmd_protnone(*pmd))
1847 goto unlock;
1848
1849 /*
1850 * In case prot_numa, we are under mmap_read_lock(mm). It's critical
1851 * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1852 * which is also under mmap_read_lock(mm):
1853 *
1854 * CPU0: CPU1:
1855 * change_huge_pmd(prot_numa=1)
1856 * pmdp_huge_get_and_clear_notify()
1857 * madvise_dontneed()
1858 * zap_pmd_range()
1859 * pmd_trans_huge(*pmd) == 0 (without ptl)
1860 * // skip the pmd
1861 * set_pmd_at();
1862 * // pmd is re-established
1863 *
1864 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1865 * which may break userspace.
1866 *
1867 * pmdp_invalidate() is required to make sure we don't miss
1868 * dirty/young flags set by hardware.
1869 */
1870 entry = pmdp_invalidate(vma, addr, pmd);
1871
1872 entry = pmd_modify(entry, newprot);
1873 if (preserve_write)
1874 entry = pmd_mk_savedwrite(entry);
1875 if (uffd_wp) {
1876 entry = pmd_wrprotect(entry);
1877 entry = pmd_mkuffd_wp(entry);
1878 } else if (uffd_wp_resolve) {
1879 /*
1880 * Leave the write bit to be handled by PF interrupt
1881 * handler, then things like COW could be properly
1882 * handled.
1883 */
1884 entry = pmd_clear_uffd_wp(entry);
1885 }
1886 ret = HPAGE_PMD_NR;
1887 set_pmd_at(mm, addr, pmd, entry);
1888 BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1889 unlock:
1890 spin_unlock(ptl);
1891 return ret;
1892 }
1893
1894 /*
1895 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1896 *
1897 * Note that if it returns page table lock pointer, this routine returns without
1898 * unlocking page table lock. So callers must unlock it.
1899 */
__pmd_trans_huge_lock(pmd_t * pmd,struct vm_area_struct * vma)1900 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1901 {
1902 spinlock_t *ptl;
1903 ptl = pmd_lock(vma->vm_mm, pmd);
1904 if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1905 pmd_devmap(*pmd)))
1906 return ptl;
1907 spin_unlock(ptl);
1908 return NULL;
1909 }
1910
1911 /*
1912 * Returns true if a given pud maps a thp, false otherwise.
1913 *
1914 * Note that if it returns true, this routine returns without unlocking page
1915 * table lock. So callers must unlock it.
1916 */
__pud_trans_huge_lock(pud_t * pud,struct vm_area_struct * vma)1917 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1918 {
1919 spinlock_t *ptl;
1920
1921 ptl = pud_lock(vma->vm_mm, pud);
1922 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1923 return ptl;
1924 spin_unlock(ptl);
1925 return NULL;
1926 }
1927
1928 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
zap_huge_pud(struct mmu_gather * tlb,struct vm_area_struct * vma,pud_t * pud,unsigned long addr)1929 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1930 pud_t *pud, unsigned long addr)
1931 {
1932 spinlock_t *ptl;
1933
1934 ptl = __pud_trans_huge_lock(pud, vma);
1935 if (!ptl)
1936 return 0;
1937 /*
1938 * For architectures like ppc64 we look at deposited pgtable
1939 * when calling pudp_huge_get_and_clear. So do the
1940 * pgtable_trans_huge_withdraw after finishing pudp related
1941 * operations.
1942 */
1943 pudp_huge_get_and_clear_full(tlb->mm, addr, pud, tlb->fullmm);
1944 tlb_remove_pud_tlb_entry(tlb, pud, addr);
1945 if (vma_is_special_huge(vma)) {
1946 spin_unlock(ptl);
1947 /* No zero page support yet */
1948 } else {
1949 /* No support for anonymous PUD pages yet */
1950 BUG();
1951 }
1952 return 1;
1953 }
1954
__split_huge_pud_locked(struct vm_area_struct * vma,pud_t * pud,unsigned long haddr)1955 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
1956 unsigned long haddr)
1957 {
1958 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
1959 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1960 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
1961 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
1962
1963 count_vm_event(THP_SPLIT_PUD);
1964
1965 pudp_huge_clear_flush_notify(vma, haddr, pud);
1966 }
1967
__split_huge_pud(struct vm_area_struct * vma,pud_t * pud,unsigned long address)1968 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
1969 unsigned long address)
1970 {
1971 spinlock_t *ptl;
1972 struct mmu_notifier_range range;
1973
1974 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
1975 address & HPAGE_PUD_MASK,
1976 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
1977 mmu_notifier_invalidate_range_start(&range);
1978 ptl = pud_lock(vma->vm_mm, pud);
1979 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
1980 goto out;
1981 __split_huge_pud_locked(vma, pud, range.start);
1982
1983 out:
1984 spin_unlock(ptl);
1985 /*
1986 * No need to double call mmu_notifier->invalidate_range() callback as
1987 * the above pudp_huge_clear_flush_notify() did already call it.
1988 */
1989 mmu_notifier_invalidate_range_only_end(&range);
1990 }
1991 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1992
__split_huge_zero_page_pmd(struct vm_area_struct * vma,unsigned long haddr,pmd_t * pmd)1993 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
1994 unsigned long haddr, pmd_t *pmd)
1995 {
1996 struct mm_struct *mm = vma->vm_mm;
1997 pgtable_t pgtable;
1998 pmd_t _pmd;
1999 int i;
2000
2001 /*
2002 * Leave pmd empty until pte is filled note that it is fine to delay
2003 * notification until mmu_notifier_invalidate_range_end() as we are
2004 * replacing a zero pmd write protected page with a zero pte write
2005 * protected page.
2006 *
2007 * See Documentation/vm/mmu_notifier.rst
2008 */
2009 pmdp_huge_clear_flush(vma, haddr, pmd);
2010
2011 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2012 pmd_populate(mm, &_pmd, pgtable);
2013
2014 for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2015 pte_t *pte, entry;
2016 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2017 entry = pte_mkspecial(entry);
2018 pte = pte_offset_map(&_pmd, haddr);
2019 VM_BUG_ON(!pte_none(*pte));
2020 set_pte_at(mm, haddr, pte, entry);
2021 pte_unmap(pte);
2022 }
2023 smp_wmb(); /* make pte visible before pmd */
2024 pmd_populate(mm, pmd, pgtable);
2025 }
2026
__split_huge_pmd_locked(struct vm_area_struct * vma,pmd_t * pmd,unsigned long haddr,bool freeze)2027 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2028 unsigned long haddr, bool freeze)
2029 {
2030 struct mm_struct *mm = vma->vm_mm;
2031 struct page *page;
2032 pgtable_t pgtable;
2033 pmd_t old_pmd, _pmd;
2034 bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false;
2035 unsigned long addr;
2036 int i;
2037
2038 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2039 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2040 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2041 VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2042 && !pmd_devmap(*pmd));
2043
2044 count_vm_event(THP_SPLIT_PMD);
2045
2046 if (!vma_is_anonymous(vma)) {
2047 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2048 /*
2049 * We are going to unmap this huge page. So
2050 * just go ahead and zap it
2051 */
2052 if (arch_needs_pgtable_deposit())
2053 zap_deposited_table(mm, pmd);
2054 if (vma_is_special_huge(vma))
2055 return;
2056 page = pmd_page(_pmd);
2057 if (!PageDirty(page) && pmd_dirty(_pmd))
2058 set_page_dirty(page);
2059 if (!PageReferenced(page) && pmd_young(_pmd))
2060 SetPageReferenced(page);
2061 page_remove_rmap(page, true);
2062 put_page(page);
2063 add_mm_counter(mm, mm_counter_file(page), -HPAGE_PMD_NR);
2064 return;
2065 } else if (pmd_trans_huge(*pmd) && is_huge_zero_pmd(*pmd)) {
2066 /*
2067 * FIXME: Do we want to invalidate secondary mmu by calling
2068 * mmu_notifier_invalidate_range() see comments below inside
2069 * __split_huge_pmd() ?
2070 *
2071 * We are going from a zero huge page write protected to zero
2072 * small page also write protected so it does not seems useful
2073 * to invalidate secondary mmu at this time.
2074 */
2075 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2076 }
2077
2078 /*
2079 * Up to this point the pmd is present and huge and userland has the
2080 * whole access to the hugepage during the split (which happens in
2081 * place). If we overwrite the pmd with the not-huge version pointing
2082 * to the pte here (which of course we could if all CPUs were bug
2083 * free), userland could trigger a small page size TLB miss on the
2084 * small sized TLB while the hugepage TLB entry is still established in
2085 * the huge TLB. Some CPU doesn't like that.
2086 * See http://support.amd.com/TechDocs/41322_10h_Rev_Gd.pdf, Erratum
2087 * 383 on page 105. Intel should be safe but is also warns that it's
2088 * only safe if the permission and cache attributes of the two entries
2089 * loaded in the two TLB is identical (which should be the case here).
2090 * But it is generally safer to never allow small and huge TLB entries
2091 * for the same virtual address to be loaded simultaneously. So instead
2092 * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2093 * current pmd notpresent (atomically because here the pmd_trans_huge
2094 * must remain set at all times on the pmd until the split is complete
2095 * for this pmd), then we flush the SMP TLB and finally we write the
2096 * non-huge version of the pmd entry with pmd_populate.
2097 */
2098 old_pmd = pmdp_invalidate(vma, haddr, pmd);
2099
2100 pmd_migration = is_pmd_migration_entry(old_pmd);
2101 if (unlikely(pmd_migration)) {
2102 swp_entry_t entry;
2103
2104 entry = pmd_to_swp_entry(old_pmd);
2105 page = migration_entry_to_page(entry);
2106 write = is_write_migration_entry(entry);
2107 young = false;
2108 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2109 uffd_wp = pmd_swp_uffd_wp(old_pmd);
2110 } else {
2111 page = pmd_page(old_pmd);
2112 if (pmd_dirty(old_pmd))
2113 SetPageDirty(page);
2114 write = pmd_write(old_pmd);
2115 young = pmd_young(old_pmd);
2116 soft_dirty = pmd_soft_dirty(old_pmd);
2117 uffd_wp = pmd_uffd_wp(old_pmd);
2118 }
2119 VM_BUG_ON_PAGE(!page_count(page), page);
2120 page_ref_add(page, HPAGE_PMD_NR - 1);
2121
2122 /*
2123 * Withdraw the table only after we mark the pmd entry invalid.
2124 * This's critical for some architectures (Power).
2125 */
2126 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2127 pmd_populate(mm, &_pmd, pgtable);
2128
2129 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2130 pte_t entry, *pte;
2131 /*
2132 * Note that NUMA hinting access restrictions are not
2133 * transferred to avoid any possibility of altering
2134 * permissions across VMAs.
2135 */
2136 if (freeze || pmd_migration) {
2137 swp_entry_t swp_entry;
2138 swp_entry = make_migration_entry(page + i, write);
2139 entry = swp_entry_to_pte(swp_entry);
2140 if (soft_dirty)
2141 entry = pte_swp_mksoft_dirty(entry);
2142 if (uffd_wp)
2143 entry = pte_swp_mkuffd_wp(entry);
2144 } else {
2145 entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2146 entry = maybe_mkwrite(entry, vma);
2147 if (!write)
2148 entry = pte_wrprotect(entry);
2149 if (!young)
2150 entry = pte_mkold(entry);
2151 if (soft_dirty)
2152 entry = pte_mksoft_dirty(entry);
2153 if (uffd_wp)
2154 entry = pte_mkuffd_wp(entry);
2155 }
2156 pte = pte_offset_map(&_pmd, addr);
2157 BUG_ON(!pte_none(*pte));
2158 set_pte_at(mm, addr, pte, entry);
2159 if (!pmd_migration)
2160 atomic_inc(&page[i]._mapcount);
2161 pte_unmap(pte);
2162 }
2163
2164 if (!pmd_migration) {
2165 /*
2166 * Set PG_double_map before dropping compound_mapcount to avoid
2167 * false-negative page_mapped().
2168 */
2169 if (compound_mapcount(page) > 1 &&
2170 !TestSetPageDoubleMap(page)) {
2171 for (i = 0; i < HPAGE_PMD_NR; i++)
2172 atomic_inc(&page[i]._mapcount);
2173 }
2174
2175 lock_page_memcg(page);
2176 if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2177 /* Last compound_mapcount is gone. */
2178 __mod_lruvec_page_state(page, NR_ANON_THPS,
2179 -HPAGE_PMD_NR);
2180 if (TestClearPageDoubleMap(page)) {
2181 /* No need in mapcount reference anymore */
2182 for (i = 0; i < HPAGE_PMD_NR; i++)
2183 atomic_dec(&page[i]._mapcount);
2184 }
2185 }
2186 unlock_page_memcg(page);
2187 }
2188
2189 smp_wmb(); /* make pte visible before pmd */
2190 pmd_populate(mm, pmd, pgtable);
2191
2192 if (freeze) {
2193 for (i = 0; i < HPAGE_PMD_NR; i++) {
2194 page_remove_rmap(page + i, false);
2195 put_page(page + i);
2196 }
2197 }
2198 }
2199
__split_huge_pmd(struct vm_area_struct * vma,pmd_t * pmd,unsigned long address,bool freeze,struct page * page)2200 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2201 unsigned long address, bool freeze, struct page *page)
2202 {
2203 spinlock_t *ptl;
2204 struct mmu_notifier_range range;
2205 bool do_unlock_page = false;
2206 pmd_t _pmd;
2207
2208 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
2209 address & HPAGE_PMD_MASK,
2210 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2211 mmu_notifier_invalidate_range_start(&range);
2212 ptl = pmd_lock(vma->vm_mm, pmd);
2213
2214 /*
2215 * If caller asks to setup a migration entries, we need a page to check
2216 * pmd against. Otherwise we can end up replacing wrong page.
2217 */
2218 VM_BUG_ON(freeze && !page);
2219 if (page) {
2220 VM_WARN_ON_ONCE(!PageLocked(page));
2221 if (page != pmd_page(*pmd))
2222 goto out;
2223 }
2224
2225 repeat:
2226 if (pmd_trans_huge(*pmd)) {
2227 if (!page) {
2228 page = pmd_page(*pmd);
2229 /*
2230 * An anonymous page must be locked, to ensure that a
2231 * concurrent reuse_swap_page() sees stable mapcount;
2232 * but reuse_swap_page() is not used on shmem or file,
2233 * and page lock must not be taken when zap_pmd_range()
2234 * calls __split_huge_pmd() while i_mmap_lock is held.
2235 */
2236 if (PageAnon(page)) {
2237 if (unlikely(!trylock_page(page))) {
2238 get_page(page);
2239 _pmd = *pmd;
2240 spin_unlock(ptl);
2241 lock_page(page);
2242 spin_lock(ptl);
2243 if (unlikely(!pmd_same(*pmd, _pmd))) {
2244 unlock_page(page);
2245 put_page(page);
2246 page = NULL;
2247 goto repeat;
2248 }
2249 put_page(page);
2250 }
2251 do_unlock_page = true;
2252 }
2253 }
2254 if (PageMlocked(page))
2255 clear_page_mlock(page);
2256 } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2257 goto out;
2258 __split_huge_pmd_locked(vma, pmd, range.start, freeze);
2259 out:
2260 spin_unlock(ptl);
2261 if (do_unlock_page)
2262 unlock_page(page);
2263 /*
2264 * No need to double call mmu_notifier->invalidate_range() callback.
2265 * They are 3 cases to consider inside __split_huge_pmd_locked():
2266 * 1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2267 * 2) __split_huge_zero_page_pmd() read only zero page and any write
2268 * fault will trigger a flush_notify before pointing to a new page
2269 * (it is fine if the secondary mmu keeps pointing to the old zero
2270 * page in the meantime)
2271 * 3) Split a huge pmd into pte pointing to the same page. No need
2272 * to invalidate secondary tlb entry they are all still valid.
2273 * any further changes to individual pte will notify. So no need
2274 * to call mmu_notifier->invalidate_range()
2275 */
2276 mmu_notifier_invalidate_range_only_end(&range);
2277 }
2278
split_huge_pmd_address(struct vm_area_struct * vma,unsigned long address,bool freeze,struct page * page)2279 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2280 bool freeze, struct page *page)
2281 {
2282 pgd_t *pgd;
2283 p4d_t *p4d;
2284 pud_t *pud;
2285 pmd_t *pmd;
2286
2287 pgd = pgd_offset(vma->vm_mm, address);
2288 if (!pgd_present(*pgd))
2289 return;
2290
2291 p4d = p4d_offset(pgd, address);
2292 if (!p4d_present(*p4d))
2293 return;
2294
2295 pud = pud_offset(p4d, address);
2296 if (!pud_present(*pud))
2297 return;
2298
2299 pmd = pmd_offset(pud, address);
2300
2301 __split_huge_pmd(vma, pmd, address, freeze, page);
2302 }
2303
split_huge_pmd_if_needed(struct vm_area_struct * vma,unsigned long address)2304 static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address)
2305 {
2306 /*
2307 * If the new address isn't hpage aligned and it could previously
2308 * contain an hugepage: check if we need to split an huge pmd.
2309 */
2310 if (!IS_ALIGNED(address, HPAGE_PMD_SIZE) &&
2311 range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE),
2312 ALIGN(address, HPAGE_PMD_SIZE)))
2313 split_huge_pmd_address(vma, address, false, NULL);
2314 }
2315
vma_adjust_trans_huge(struct vm_area_struct * vma,unsigned long start,unsigned long end,long adjust_next)2316 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2317 unsigned long start,
2318 unsigned long end,
2319 long adjust_next)
2320 {
2321 /* Check if we need to split start first. */
2322 split_huge_pmd_if_needed(vma, start);
2323
2324 /* Check if we need to split end next. */
2325 split_huge_pmd_if_needed(vma, end);
2326
2327 /*
2328 * If we're also updating the vma->vm_next->vm_start,
2329 * check if we need to split it.
2330 */
2331 if (adjust_next > 0) {
2332 struct vm_area_struct *next = vma->vm_next;
2333 unsigned long nstart = next->vm_start;
2334 nstart += adjust_next;
2335 split_huge_pmd_if_needed(next, nstart);
2336 }
2337 }
2338
unmap_page(struct page * page)2339 static void unmap_page(struct page *page)
2340 {
2341 enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK |
2342 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2343 bool unmap_success;
2344
2345 VM_BUG_ON_PAGE(!PageHead(page), page);
2346
2347 if (PageAnon(page))
2348 ttu_flags |= TTU_SPLIT_FREEZE;
2349
2350 unmap_success = try_to_unmap(page, ttu_flags);
2351 VM_BUG_ON_PAGE(!unmap_success, page);
2352 }
2353
remap_page(struct page * page,unsigned int nr)2354 static void remap_page(struct page *page, unsigned int nr)
2355 {
2356 int i;
2357 if (PageTransHuge(page)) {
2358 remove_migration_ptes(page, page, true);
2359 } else {
2360 for (i = 0; i < nr; i++)
2361 remove_migration_ptes(page + i, page + i, true);
2362 }
2363 }
2364
lru_add_page_tail(struct page * head,struct page * tail,struct lruvec * lruvec,struct list_head * list)2365 static void lru_add_page_tail(struct page *head, struct page *tail,
2366 struct lruvec *lruvec, struct list_head *list)
2367 {
2368 VM_BUG_ON_PAGE(!PageHead(head), head);
2369 VM_BUG_ON_PAGE(PageCompound(tail), head);
2370 VM_BUG_ON_PAGE(PageLRU(tail), head);
2371 lockdep_assert_held(&lruvec->lru_lock);
2372
2373 if (list) {
2374 /* page reclaim is reclaiming a huge page */
2375 VM_WARN_ON(PageLRU(head));
2376 get_page(tail);
2377 list_add_tail(&tail->lru, list);
2378 } else {
2379 /* head is still on lru (and we have it frozen) */
2380 VM_WARN_ON(!PageLRU(head));
2381 SetPageLRU(tail);
2382 list_add_tail(&tail->lru, &head->lru);
2383 }
2384 }
2385
__split_huge_page_tail(struct page * head,int tail,struct lruvec * lruvec,struct list_head * list)2386 static void __split_huge_page_tail(struct page *head, int tail,
2387 struct lruvec *lruvec, struct list_head *list)
2388 {
2389 struct page *page_tail = head + tail;
2390
2391 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2392
2393 /*
2394 * Clone page flags before unfreezing refcount.
2395 *
2396 * After successful get_page_unless_zero() might follow flags change,
2397 * for example lock_page() which set PG_waiters.
2398 */
2399 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2400 page_tail->flags |= (head->flags &
2401 ((1L << PG_referenced) |
2402 (1L << PG_swapbacked) |
2403 (1L << PG_swapcache) |
2404 (1L << PG_mlocked) |
2405 (1L << PG_uptodate) |
2406 (1L << PG_active) |
2407 (1L << PG_workingset) |
2408 (1L << PG_locked) |
2409 (1L << PG_unevictable) |
2410 #ifdef CONFIG_64BIT
2411 (1L << PG_arch_2) |
2412 #endif
2413 (1L << PG_dirty)));
2414
2415 /* ->mapping in first tail page is compound_mapcount */
2416 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2417 page_tail);
2418 page_tail->mapping = head->mapping;
2419 page_tail->index = head->index + tail;
2420
2421 /* Page flags must be visible before we make the page non-compound. */
2422 smp_wmb();
2423
2424 /*
2425 * Clear PageTail before unfreezing page refcount.
2426 *
2427 * After successful get_page_unless_zero() might follow put_page()
2428 * which needs correct compound_head().
2429 */
2430 clear_compound_head(page_tail);
2431
2432 /* Finally unfreeze refcount. Additional reference from page cache. */
2433 page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) ||
2434 PageSwapCache(head)));
2435
2436 if (page_is_young(head))
2437 set_page_young(page_tail);
2438 if (page_is_idle(head))
2439 set_page_idle(page_tail);
2440
2441 page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2442
2443 /*
2444 * always add to the tail because some iterators expect new
2445 * pages to show after the currently processed elements - e.g.
2446 * migrate_pages
2447 */
2448 lru_add_page_tail(head, page_tail, lruvec, list);
2449 }
2450
__split_huge_page(struct page * page,struct list_head * list,pgoff_t end)2451 static void __split_huge_page(struct page *page, struct list_head *list,
2452 pgoff_t end)
2453 {
2454 struct page *head = compound_head(page);
2455 struct lruvec *lruvec;
2456 struct address_space *swap_cache = NULL;
2457 unsigned long offset = 0;
2458 unsigned int nr = thp_nr_pages(head);
2459 int i;
2460
2461 /* complete memcg works before add pages to LRU */
2462 split_page_memcg(head, nr);
2463
2464 if (PageAnon(head) && PageSwapCache(head)) {
2465 swp_entry_t entry = { .val = page_private(head) };
2466
2467 offset = swp_offset(entry);
2468 swap_cache = swap_address_space(entry);
2469 xa_lock(&swap_cache->i_pages);
2470 }
2471
2472 /* lock lru list/PageCompound, ref frozen by page_ref_freeze */
2473 lruvec = lock_page_lruvec(head);
2474
2475 for (i = nr - 1; i >= 1; i--) {
2476 __split_huge_page_tail(head, i, lruvec, list);
2477 /* Some pages can be beyond i_size: drop them from page cache */
2478 if (head[i].index >= end) {
2479 ClearPageDirty(head + i);
2480 __delete_from_page_cache(head + i, NULL);
2481 if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2482 shmem_uncharge(head->mapping->host, 1);
2483 put_page(head + i);
2484 } else if (!PageAnon(page)) {
2485 __xa_store(&head->mapping->i_pages, head[i].index,
2486 head + i, 0);
2487 } else if (swap_cache) {
2488 __xa_store(&swap_cache->i_pages, offset + i,
2489 head + i, 0);
2490 }
2491 }
2492
2493 ClearPageCompound(head);
2494 unlock_page_lruvec(lruvec);
2495 /* Caller disabled irqs, so they are still disabled here */
2496
2497 split_page_owner(head, nr);
2498
2499 /* See comment in __split_huge_page_tail() */
2500 if (PageAnon(head)) {
2501 /* Additional pin to swap cache */
2502 if (PageSwapCache(head)) {
2503 page_ref_add(head, 2);
2504 xa_unlock(&swap_cache->i_pages);
2505 } else {
2506 page_ref_inc(head);
2507 }
2508 } else {
2509 /* Additional pin to page cache */
2510 page_ref_add(head, 2);
2511 xa_unlock(&head->mapping->i_pages);
2512 }
2513 local_irq_enable();
2514
2515 remap_page(head, nr);
2516
2517 if (PageSwapCache(head)) {
2518 swp_entry_t entry = { .val = page_private(head) };
2519
2520 split_swap_cluster(entry);
2521 }
2522
2523 for (i = 0; i < nr; i++) {
2524 struct page *subpage = head + i;
2525 if (subpage == page)
2526 continue;
2527 unlock_page(subpage);
2528
2529 /*
2530 * Subpages may be freed if there wasn't any mapping
2531 * like if add_to_swap() is running on a lru page that
2532 * had its mapping zapped. And freeing these pages
2533 * requires taking the lru_lock so we do the put_page
2534 * of the tail pages after the split is complete.
2535 */
2536 put_page(subpage);
2537 }
2538 }
2539
total_mapcount(struct page * page)2540 int total_mapcount(struct page *page)
2541 {
2542 int i, compound, nr, ret;
2543
2544 VM_BUG_ON_PAGE(PageTail(page), page);
2545
2546 if (likely(!PageCompound(page)))
2547 return atomic_read(&page->_mapcount) + 1;
2548
2549 compound = compound_mapcount(page);
2550 nr = compound_nr(page);
2551 if (PageHuge(page))
2552 return compound;
2553 ret = compound;
2554 for (i = 0; i < nr; i++)
2555 ret += atomic_read(&page[i]._mapcount) + 1;
2556 /* File pages has compound_mapcount included in _mapcount */
2557 if (!PageAnon(page))
2558 return ret - compound * nr;
2559 if (PageDoubleMap(page))
2560 ret -= nr;
2561 return ret;
2562 }
2563
2564 /*
2565 * This calculates accurately how many mappings a transparent hugepage
2566 * has (unlike page_mapcount() which isn't fully accurate). This full
2567 * accuracy is primarily needed to know if copy-on-write faults can
2568 * reuse the page and change the mapping to read-write instead of
2569 * copying them. At the same time this returns the total_mapcount too.
2570 *
2571 * The function returns the highest mapcount any one of the subpages
2572 * has. If the return value is one, even if different processes are
2573 * mapping different subpages of the transparent hugepage, they can
2574 * all reuse it, because each process is reusing a different subpage.
2575 *
2576 * The total_mapcount is instead counting all virtual mappings of the
2577 * subpages. If the total_mapcount is equal to "one", it tells the
2578 * caller all mappings belong to the same "mm" and in turn the
2579 * anon_vma of the transparent hugepage can become the vma->anon_vma
2580 * local one as no other process may be mapping any of the subpages.
2581 *
2582 * It would be more accurate to replace page_mapcount() with
2583 * page_trans_huge_mapcount(), however we only use
2584 * page_trans_huge_mapcount() in the copy-on-write faults where we
2585 * need full accuracy to avoid breaking page pinning, because
2586 * page_trans_huge_mapcount() is slower than page_mapcount().
2587 */
page_trans_huge_mapcount(struct page * page,int * total_mapcount)2588 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2589 {
2590 int i, ret, _total_mapcount, mapcount;
2591
2592 /* hugetlbfs shouldn't call it */
2593 VM_BUG_ON_PAGE(PageHuge(page), page);
2594
2595 if (likely(!PageTransCompound(page))) {
2596 mapcount = atomic_read(&page->_mapcount) + 1;
2597 if (total_mapcount)
2598 *total_mapcount = mapcount;
2599 return mapcount;
2600 }
2601
2602 page = compound_head(page);
2603
2604 _total_mapcount = ret = 0;
2605 for (i = 0; i < thp_nr_pages(page); i++) {
2606 mapcount = atomic_read(&page[i]._mapcount) + 1;
2607 ret = max(ret, mapcount);
2608 _total_mapcount += mapcount;
2609 }
2610 if (PageDoubleMap(page)) {
2611 ret -= 1;
2612 _total_mapcount -= thp_nr_pages(page);
2613 }
2614 mapcount = compound_mapcount(page);
2615 ret += mapcount;
2616 _total_mapcount += mapcount;
2617 if (total_mapcount)
2618 *total_mapcount = _total_mapcount;
2619 return ret;
2620 }
2621
2622 /* Racy check whether the huge page can be split */
can_split_huge_page(struct page * page,int * pextra_pins)2623 bool can_split_huge_page(struct page *page, int *pextra_pins)
2624 {
2625 int extra_pins;
2626
2627 /* Additional pins from page cache */
2628 if (PageAnon(page))
2629 extra_pins = PageSwapCache(page) ? thp_nr_pages(page) : 0;
2630 else
2631 extra_pins = thp_nr_pages(page);
2632 if (pextra_pins)
2633 *pextra_pins = extra_pins;
2634 return total_mapcount(page) == page_count(page) - extra_pins - 1;
2635 }
2636
2637 /*
2638 * This function splits huge page into normal pages. @page can point to any
2639 * subpage of huge page to split. Split doesn't change the position of @page.
2640 *
2641 * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2642 * The huge page must be locked.
2643 *
2644 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2645 *
2646 * Both head page and tail pages will inherit mapping, flags, and so on from
2647 * the hugepage.
2648 *
2649 * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2650 * they are not mapped.
2651 *
2652 * Returns 0 if the hugepage is split successfully.
2653 * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2654 * us.
2655 */
split_huge_page_to_list(struct page * page,struct list_head * list)2656 int split_huge_page_to_list(struct page *page, struct list_head *list)
2657 {
2658 struct page *head = compound_head(page);
2659 struct deferred_split *ds_queue = get_deferred_split_queue(head);
2660 struct anon_vma *anon_vma = NULL;
2661 struct address_space *mapping = NULL;
2662 int count, mapcount, extra_pins, ret;
2663 pgoff_t end;
2664
2665 VM_BUG_ON_PAGE(is_huge_zero_page(head), head);
2666 VM_BUG_ON_PAGE(!PageLocked(head), head);
2667 VM_BUG_ON_PAGE(!PageCompound(head), head);
2668
2669 if (PageWriteback(head))
2670 return -EBUSY;
2671
2672 if (PageAnon(head)) {
2673 /*
2674 * The caller does not necessarily hold an mmap_lock that would
2675 * prevent the anon_vma disappearing so we first we take a
2676 * reference to it and then lock the anon_vma for write. This
2677 * is similar to page_lock_anon_vma_read except the write lock
2678 * is taken to serialise against parallel split or collapse
2679 * operations.
2680 */
2681 anon_vma = page_get_anon_vma(head);
2682 if (!anon_vma) {
2683 ret = -EBUSY;
2684 goto out;
2685 }
2686 end = -1;
2687 mapping = NULL;
2688 anon_vma_lock_write(anon_vma);
2689 } else {
2690 mapping = head->mapping;
2691
2692 /* Truncated ? */
2693 if (!mapping) {
2694 ret = -EBUSY;
2695 goto out;
2696 }
2697
2698 anon_vma = NULL;
2699 i_mmap_lock_read(mapping);
2700
2701 /*
2702 *__split_huge_page() may need to trim off pages beyond EOF:
2703 * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
2704 * which cannot be nested inside the page tree lock. So note
2705 * end now: i_size itself may be changed at any moment, but
2706 * head page lock is good enough to serialize the trimming.
2707 */
2708 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2709 }
2710
2711 /*
2712 * Racy check if we can split the page, before unmap_page() will
2713 * split PMDs
2714 */
2715 if (!can_split_huge_page(head, &extra_pins)) {
2716 ret = -EBUSY;
2717 goto out_unlock;
2718 }
2719
2720 unmap_page(head);
2721 VM_BUG_ON_PAGE(compound_mapcount(head), head);
2722
2723 /* block interrupt reentry in xa_lock and spinlock */
2724 local_irq_disable();
2725 if (mapping) {
2726 XA_STATE(xas, &mapping->i_pages, page_index(head));
2727
2728 /*
2729 * Check if the head page is present in page cache.
2730 * We assume all tail are present too, if head is there.
2731 */
2732 xa_lock(&mapping->i_pages);
2733 if (xas_load(&xas) != head)
2734 goto fail;
2735 }
2736
2737 /* Prevent deferred_split_scan() touching ->_refcount */
2738 spin_lock(&ds_queue->split_queue_lock);
2739 count = page_count(head);
2740 mapcount = total_mapcount(head);
2741 if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2742 if (!list_empty(page_deferred_list(head))) {
2743 ds_queue->split_queue_len--;
2744 list_del(page_deferred_list(head));
2745 }
2746 spin_unlock(&ds_queue->split_queue_lock);
2747 if (mapping) {
2748 int nr = thp_nr_pages(head);
2749
2750 if (PageSwapBacked(head))
2751 __mod_lruvec_page_state(head, NR_SHMEM_THPS,
2752 -nr);
2753 else
2754 __mod_lruvec_page_state(head, NR_FILE_THPS,
2755 -nr);
2756 }
2757
2758 __split_huge_page(page, list, end);
2759 ret = 0;
2760 } else {
2761 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2762 pr_alert("total_mapcount: %u, page_count(): %u\n",
2763 mapcount, count);
2764 if (PageTail(page))
2765 dump_page(head, NULL);
2766 dump_page(page, "total_mapcount(head) > 0");
2767 BUG();
2768 }
2769 spin_unlock(&ds_queue->split_queue_lock);
2770 fail: if (mapping)
2771 xa_unlock(&mapping->i_pages);
2772 local_irq_enable();
2773 remap_page(head, thp_nr_pages(head));
2774 ret = -EBUSY;
2775 }
2776
2777 out_unlock:
2778 if (anon_vma) {
2779 anon_vma_unlock_write(anon_vma);
2780 put_anon_vma(anon_vma);
2781 }
2782 if (mapping)
2783 i_mmap_unlock_read(mapping);
2784 out:
2785 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2786 return ret;
2787 }
2788
free_transhuge_page(struct page * page)2789 void free_transhuge_page(struct page *page)
2790 {
2791 struct deferred_split *ds_queue = get_deferred_split_queue(page);
2792 unsigned long flags;
2793
2794 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2795 if (!list_empty(page_deferred_list(page))) {
2796 ds_queue->split_queue_len--;
2797 list_del(page_deferred_list(page));
2798 }
2799 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2800 free_compound_page(page);
2801 }
2802
deferred_split_huge_page(struct page * page)2803 void deferred_split_huge_page(struct page *page)
2804 {
2805 struct deferred_split *ds_queue = get_deferred_split_queue(page);
2806 #ifdef CONFIG_MEMCG
2807 struct mem_cgroup *memcg = page_memcg(compound_head(page));
2808 #endif
2809 unsigned long flags;
2810
2811 VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2812
2813 /*
2814 * The try_to_unmap() in page reclaim path might reach here too,
2815 * this may cause a race condition to corrupt deferred split queue.
2816 * And, if page reclaim is already handling the same page, it is
2817 * unnecessary to handle it again in shrinker.
2818 *
2819 * Check PageSwapCache to determine if the page is being
2820 * handled by page reclaim since THP swap would add the page into
2821 * swap cache before calling try_to_unmap().
2822 */
2823 if (PageSwapCache(page))
2824 return;
2825
2826 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2827 if (list_empty(page_deferred_list(page))) {
2828 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2829 list_add_tail(page_deferred_list(page), &ds_queue->split_queue);
2830 ds_queue->split_queue_len++;
2831 #ifdef CONFIG_MEMCG
2832 if (memcg)
2833 set_shrinker_bit(memcg, page_to_nid(page),
2834 deferred_split_shrinker.id);
2835 #endif
2836 }
2837 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2838 }
2839
deferred_split_count(struct shrinker * shrink,struct shrink_control * sc)2840 static unsigned long deferred_split_count(struct shrinker *shrink,
2841 struct shrink_control *sc)
2842 {
2843 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2844 struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2845
2846 #ifdef CONFIG_MEMCG
2847 if (sc->memcg)
2848 ds_queue = &sc->memcg->deferred_split_queue;
2849 #endif
2850 return READ_ONCE(ds_queue->split_queue_len);
2851 }
2852
deferred_split_scan(struct shrinker * shrink,struct shrink_control * sc)2853 static unsigned long deferred_split_scan(struct shrinker *shrink,
2854 struct shrink_control *sc)
2855 {
2856 struct pglist_data *pgdata = NODE_DATA(sc->nid);
2857 struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
2858 unsigned long flags;
2859 LIST_HEAD(list), *pos, *next;
2860 struct page *page;
2861 int split = 0;
2862
2863 #ifdef CONFIG_MEMCG
2864 if (sc->memcg)
2865 ds_queue = &sc->memcg->deferred_split_queue;
2866 #endif
2867
2868 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2869 /* Take pin on all head pages to avoid freeing them under us */
2870 list_for_each_safe(pos, next, &ds_queue->split_queue) {
2871 page = list_entry((void *)pos, struct page, mapping);
2872 page = compound_head(page);
2873 if (get_page_unless_zero(page)) {
2874 list_move(page_deferred_list(page), &list);
2875 } else {
2876 /* We lost race with put_compound_page() */
2877 list_del_init(page_deferred_list(page));
2878 ds_queue->split_queue_len--;
2879 }
2880 if (!--sc->nr_to_scan)
2881 break;
2882 }
2883 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2884
2885 list_for_each_safe(pos, next, &list) {
2886 page = list_entry((void *)pos, struct page, mapping);
2887 if (!trylock_page(page))
2888 goto next;
2889 /* split_huge_page() removes page from list on success */
2890 if (!split_huge_page(page))
2891 split++;
2892 unlock_page(page);
2893 next:
2894 put_page(page);
2895 }
2896
2897 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
2898 list_splice_tail(&list, &ds_queue->split_queue);
2899 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
2900
2901 /*
2902 * Stop shrinker if we didn't split any page, but the queue is empty.
2903 * This can happen if pages were freed under us.
2904 */
2905 if (!split && list_empty(&ds_queue->split_queue))
2906 return SHRINK_STOP;
2907 return split;
2908 }
2909
2910 static struct shrinker deferred_split_shrinker = {
2911 .count_objects = deferred_split_count,
2912 .scan_objects = deferred_split_scan,
2913 .seeks = DEFAULT_SEEKS,
2914 .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
2915 SHRINKER_NONSLAB,
2916 };
2917
2918 #ifdef CONFIG_DEBUG_FS
split_huge_pages_all(void)2919 static void split_huge_pages_all(void)
2920 {
2921 struct zone *zone;
2922 struct page *page;
2923 unsigned long pfn, max_zone_pfn;
2924 unsigned long total = 0, split = 0;
2925
2926 pr_debug("Split all THPs\n");
2927 for_each_populated_zone(zone) {
2928 max_zone_pfn = zone_end_pfn(zone);
2929 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2930 if (!pfn_valid(pfn))
2931 continue;
2932
2933 page = pfn_to_page(pfn);
2934 if (!get_page_unless_zero(page))
2935 continue;
2936
2937 if (zone != page_zone(page))
2938 goto next;
2939
2940 if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2941 goto next;
2942
2943 total++;
2944 lock_page(page);
2945 if (!split_huge_page(page))
2946 split++;
2947 unlock_page(page);
2948 next:
2949 put_page(page);
2950 cond_resched();
2951 }
2952 }
2953
2954 pr_debug("%lu of %lu THP split\n", split, total);
2955 }
2956
vma_not_suitable_for_thp_split(struct vm_area_struct * vma)2957 static inline bool vma_not_suitable_for_thp_split(struct vm_area_struct *vma)
2958 {
2959 return vma_is_special_huge(vma) || (vma->vm_flags & VM_IO) ||
2960 is_vm_hugetlb_page(vma);
2961 }
2962
split_huge_pages_pid(int pid,unsigned long vaddr_start,unsigned long vaddr_end)2963 static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
2964 unsigned long vaddr_end)
2965 {
2966 int ret = 0;
2967 struct task_struct *task;
2968 struct mm_struct *mm;
2969 unsigned long total = 0, split = 0;
2970 unsigned long addr;
2971
2972 vaddr_start &= PAGE_MASK;
2973 vaddr_end &= PAGE_MASK;
2974
2975 /* Find the task_struct from pid */
2976 rcu_read_lock();
2977 task = find_task_by_vpid(pid);
2978 if (!task) {
2979 rcu_read_unlock();
2980 ret = -ESRCH;
2981 goto out;
2982 }
2983 get_task_struct(task);
2984 rcu_read_unlock();
2985
2986 /* Find the mm_struct */
2987 mm = get_task_mm(task);
2988 put_task_struct(task);
2989
2990 if (!mm) {
2991 ret = -EINVAL;
2992 goto out;
2993 }
2994
2995 pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx]\n",
2996 pid, vaddr_start, vaddr_end);
2997
2998 mmap_read_lock(mm);
2999 /*
3000 * always increase addr by PAGE_SIZE, since we could have a PTE page
3001 * table filled with PTE-mapped THPs, each of which is distinct.
3002 */
3003 for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) {
3004 struct vm_area_struct *vma = find_vma(mm, addr);
3005 unsigned int follflags;
3006 struct page *page;
3007
3008 if (!vma || addr < vma->vm_start)
3009 break;
3010
3011 /* skip special VMA and hugetlb VMA */
3012 if (vma_not_suitable_for_thp_split(vma)) {
3013 addr = vma->vm_end;
3014 continue;
3015 }
3016
3017 /* FOLL_DUMP to ignore special (like zero) pages */
3018 follflags = FOLL_GET | FOLL_DUMP;
3019 page = follow_page(vma, addr, follflags);
3020
3021 if (IS_ERR(page))
3022 continue;
3023 if (!page)
3024 continue;
3025
3026 if (!is_transparent_hugepage(page))
3027 goto next;
3028
3029 total++;
3030 if (!can_split_huge_page(compound_head(page), NULL))
3031 goto next;
3032
3033 if (!trylock_page(page))
3034 goto next;
3035
3036 if (!split_huge_page(page))
3037 split++;
3038
3039 unlock_page(page);
3040 next:
3041 put_page(page);
3042 cond_resched();
3043 }
3044 mmap_read_unlock(mm);
3045 mmput(mm);
3046
3047 pr_debug("%lu of %lu THP split\n", split, total);
3048
3049 out:
3050 return ret;
3051 }
3052
split_huge_pages_in_file(const char * file_path,pgoff_t off_start,pgoff_t off_end)3053 static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
3054 pgoff_t off_end)
3055 {
3056 struct filename *file;
3057 struct file *candidate;
3058 struct address_space *mapping;
3059 int ret = -EINVAL;
3060 pgoff_t index;
3061 int nr_pages = 1;
3062 unsigned long total = 0, split = 0;
3063
3064 file = getname_kernel(file_path);
3065 if (IS_ERR(file))
3066 return ret;
3067
3068 candidate = file_open_name(file, O_RDONLY, 0);
3069 if (IS_ERR(candidate))
3070 goto out;
3071
3072 pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n",
3073 file_path, off_start, off_end);
3074
3075 mapping = candidate->f_mapping;
3076
3077 for (index = off_start; index < off_end; index += nr_pages) {
3078 struct page *fpage = pagecache_get_page(mapping, index,
3079 FGP_ENTRY | FGP_HEAD, 0);
3080
3081 nr_pages = 1;
3082 if (xa_is_value(fpage) || !fpage)
3083 continue;
3084
3085 if (!is_transparent_hugepage(fpage))
3086 goto next;
3087
3088 total++;
3089 nr_pages = thp_nr_pages(fpage);
3090
3091 if (!trylock_page(fpage))
3092 goto next;
3093
3094 if (!split_huge_page(fpage))
3095 split++;
3096
3097 unlock_page(fpage);
3098 next:
3099 put_page(fpage);
3100 cond_resched();
3101 }
3102
3103 filp_close(candidate, NULL);
3104 ret = 0;
3105
3106 pr_debug("%lu of %lu file-backed THP split\n", split, total);
3107 out:
3108 putname(file);
3109 return ret;
3110 }
3111
3112 #define MAX_INPUT_BUF_SZ 255
3113
split_huge_pages_write(struct file * file,const char __user * buf,size_t count,loff_t * ppops)3114 static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
3115 size_t count, loff_t *ppops)
3116 {
3117 static DEFINE_MUTEX(split_debug_mutex);
3118 ssize_t ret;
3119 /* hold pid, start_vaddr, end_vaddr or file_path, off_start, off_end */
3120 char input_buf[MAX_INPUT_BUF_SZ];
3121 int pid;
3122 unsigned long vaddr_start, vaddr_end;
3123
3124 ret = mutex_lock_interruptible(&split_debug_mutex);
3125 if (ret)
3126 return ret;
3127
3128 ret = -EFAULT;
3129
3130 memset(input_buf, 0, MAX_INPUT_BUF_SZ);
3131 if (copy_from_user(input_buf, buf, min_t(size_t, count, MAX_INPUT_BUF_SZ)))
3132 goto out;
3133
3134 input_buf[MAX_INPUT_BUF_SZ - 1] = '\0';
3135
3136 if (input_buf[0] == '/') {
3137 char *tok;
3138 char *buf = input_buf;
3139 char file_path[MAX_INPUT_BUF_SZ];
3140 pgoff_t off_start = 0, off_end = 0;
3141 size_t input_len = strlen(input_buf);
3142
3143 tok = strsep(&buf, ",");
3144 if (tok) {
3145 strncpy(file_path, tok, MAX_INPUT_BUF_SZ);
3146 } else {
3147 ret = -EINVAL;
3148 goto out;
3149 }
3150
3151 ret = sscanf(buf, "0x%lx,0x%lx", &off_start, &off_end);
3152 if (ret != 2) {
3153 ret = -EINVAL;
3154 goto out;
3155 }
3156 ret = split_huge_pages_in_file(file_path, off_start, off_end);
3157 if (!ret)
3158 ret = input_len;
3159
3160 goto out;
3161 }
3162
3163 ret = sscanf(input_buf, "%d,0x%lx,0x%lx", &pid, &vaddr_start, &vaddr_end);
3164 if (ret == 1 && pid == 1) {
3165 split_huge_pages_all();
3166 ret = strlen(input_buf);
3167 goto out;
3168 } else if (ret != 3) {
3169 ret = -EINVAL;
3170 goto out;
3171 }
3172
3173 ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end);
3174 if (!ret)
3175 ret = strlen(input_buf);
3176 out:
3177 mutex_unlock(&split_debug_mutex);
3178 return ret;
3179
3180 }
3181
3182 static const struct file_operations split_huge_pages_fops = {
3183 .owner = THIS_MODULE,
3184 .write = split_huge_pages_write,
3185 .llseek = no_llseek,
3186 };
3187
split_huge_pages_debugfs(void)3188 static int __init split_huge_pages_debugfs(void)
3189 {
3190 debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
3191 &split_huge_pages_fops);
3192 return 0;
3193 }
3194 late_initcall(split_huge_pages_debugfs);
3195 #endif
3196
3197 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
set_pmd_migration_entry(struct page_vma_mapped_walk * pvmw,struct page * page)3198 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
3199 struct page *page)
3200 {
3201 struct vm_area_struct *vma = pvmw->vma;
3202 struct mm_struct *mm = vma->vm_mm;
3203 unsigned long address = pvmw->address;
3204 pmd_t pmdval;
3205 swp_entry_t entry;
3206 pmd_t pmdswp;
3207
3208 if (!(pvmw->pmd && !pvmw->pte))
3209 return;
3210
3211 flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
3212 pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
3213 if (pmd_dirty(pmdval))
3214 set_page_dirty(page);
3215 entry = make_migration_entry(page, pmd_write(pmdval));
3216 pmdswp = swp_entry_to_pmd(entry);
3217 if (pmd_soft_dirty(pmdval))
3218 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
3219 set_pmd_at(mm, address, pvmw->pmd, pmdswp);
3220 page_remove_rmap(page, true);
3221 put_page(page);
3222 }
3223
remove_migration_pmd(struct page_vma_mapped_walk * pvmw,struct page * new)3224 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
3225 {
3226 struct vm_area_struct *vma = pvmw->vma;
3227 struct mm_struct *mm = vma->vm_mm;
3228 unsigned long address = pvmw->address;
3229 unsigned long mmun_start = address & HPAGE_PMD_MASK;
3230 pmd_t pmde;
3231 swp_entry_t entry;
3232
3233 if (!(pvmw->pmd && !pvmw->pte))
3234 return;
3235
3236 entry = pmd_to_swp_entry(*pvmw->pmd);
3237 get_page(new);
3238 pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
3239 if (pmd_swp_soft_dirty(*pvmw->pmd))
3240 pmde = pmd_mksoft_dirty(pmde);
3241 if (is_write_migration_entry(entry))
3242 pmde = maybe_pmd_mkwrite(pmde, vma);
3243
3244 flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
3245 if (PageAnon(new))
3246 page_add_anon_rmap(new, vma, mmun_start, true);
3247 else
3248 page_add_file_rmap(new, true);
3249 set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
3250 if ((vma->vm_flags & VM_LOCKED) && !PageDoubleMap(new))
3251 mlock_vma_page(new);
3252 update_mmu_cache_pmd(vma, address, pvmw->pmd);
3253 }
3254 #endif
3255