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/numa_balancing.h>
12 #include <linux/highmem.h>
13 #include <linux/hugetlb.h>
14 #include <linux/mmu_notifier.h>
15 #include <linux/rmap.h>
16 #include <linux/swap.h>
17 #include <linux/shrinker.h>
18 #include <linux/mm_inline.h>
19 #include <linux/swapops.h>
20 #include <linux/backing-dev.h>
21 #include <linux/dax.h>
22 #include <linux/mm_types.h>
23 #include <linux/khugepaged.h>
24 #include <linux/freezer.h>
25 #include <linux/pfn_t.h>
26 #include <linux/mman.h>
27 #include <linux/memremap.h>
28 #include <linux/pagemap.h>
29 #include <linux/debugfs.h>
30 #include <linux/migrate.h>
31 #include <linux/hashtable.h>
32 #include <linux/userfaultfd_k.h>
33 #include <linux/page_idle.h>
34 #include <linux/shmem_fs.h>
35 #include <linux/oom.h>
36 #include <linux/numa.h>
37 #include <linux/page_owner.h>
38 #include <linux/sched/sysctl.h>
39 #include <linux/memory-tiers.h>
40 #include <linux/compat.h>
41 #include <linux/pgalloc_tag.h>
42 #include <linux/pagewalk.h>
43
44 #include <asm/tlb.h>
45 #include <asm/pgalloc.h>
46 #include "internal.h"
47 #include "swap.h"
48
49 #define CREATE_TRACE_POINTS
50 #include <trace/events/thp.h>
51
52 /*
53 * By default, transparent hugepage support is disabled in order to avoid
54 * risking an increased memory footprint for applications that are not
55 * guaranteed to benefit from it. When transparent hugepage support is
56 * enabled, it is for all mappings, and khugepaged scans all mappings.
57 * Defrag is invoked by khugepaged hugepage allocations and by page faults
58 * for all hugepage allocations.
59 */
60 unsigned long transparent_hugepage_flags __read_mostly =
61 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
62 (1<<TRANSPARENT_HUGEPAGE_FLAG)|
63 #endif
64 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
65 (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
66 #endif
67 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
68 (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
69 (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
70
71 static struct shrinker *deferred_split_shrinker;
72 static unsigned long deferred_split_count(struct shrinker *shrink,
73 struct shrink_control *sc);
74 static unsigned long deferred_split_scan(struct shrinker *shrink,
75 struct shrink_control *sc);
76 static bool split_underused_thp = true;
77
78 static atomic_t huge_zero_refcount;
79 struct folio *huge_zero_folio __read_mostly;
80 unsigned long huge_zero_pfn __read_mostly = ~0UL;
81 unsigned long huge_anon_orders_always __read_mostly;
82 unsigned long huge_anon_orders_madvise __read_mostly;
83 unsigned long huge_anon_orders_inherit __read_mostly;
84 static bool anon_orders_configured __initdata;
85
file_thp_enabled(struct vm_area_struct * vma)86 static inline bool file_thp_enabled(struct vm_area_struct *vma)
87 {
88 struct inode *inode;
89
90 if (!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS))
91 return false;
92
93 if (!vma->vm_file)
94 return false;
95
96 inode = file_inode(vma->vm_file);
97
98 return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode);
99 }
100
__thp_vma_allowable_orders(struct vm_area_struct * vma,unsigned long vm_flags,unsigned long tva_flags,unsigned long orders)101 unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma,
102 unsigned long vm_flags,
103 unsigned long tva_flags,
104 unsigned long orders)
105 {
106 bool smaps = tva_flags & TVA_SMAPS;
107 bool in_pf = tva_flags & TVA_IN_PF;
108 bool enforce_sysfs = tva_flags & TVA_ENFORCE_SYSFS;
109 unsigned long supported_orders;
110
111 /* Check the intersection of requested and supported orders. */
112 if (vma_is_anonymous(vma))
113 supported_orders = THP_ORDERS_ALL_ANON;
114 else if (vma_is_special_huge(vma))
115 supported_orders = THP_ORDERS_ALL_SPECIAL;
116 else
117 supported_orders = THP_ORDERS_ALL_FILE_DEFAULT;
118
119 orders &= supported_orders;
120 if (!orders)
121 return 0;
122
123 if (!vma->vm_mm) /* vdso */
124 return 0;
125
126 if (thp_disabled_by_hw() || vma_thp_disabled(vma, vm_flags))
127 return 0;
128
129 /* khugepaged doesn't collapse DAX vma, but page fault is fine. */
130 if (vma_is_dax(vma))
131 return in_pf ? orders : 0;
132
133 /*
134 * khugepaged special VMA and hugetlb VMA.
135 * Must be checked after dax since some dax mappings may have
136 * VM_MIXEDMAP set.
137 */
138 if (!in_pf && !smaps && (vm_flags & VM_NO_KHUGEPAGED))
139 return 0;
140
141 /*
142 * Check alignment for file vma and size for both file and anon vma by
143 * filtering out the unsuitable orders.
144 *
145 * Skip the check for page fault. Huge fault does the check in fault
146 * handlers.
147 */
148 if (!in_pf) {
149 int order = highest_order(orders);
150 unsigned long addr;
151
152 while (orders) {
153 addr = vma->vm_end - (PAGE_SIZE << order);
154 if (thp_vma_suitable_order(vma, addr, order))
155 break;
156 order = next_order(&orders, order);
157 }
158
159 if (!orders)
160 return 0;
161 }
162
163 /*
164 * Enabled via shmem mount options or sysfs settings.
165 * Must be done before hugepage flags check since shmem has its
166 * own flags.
167 */
168 if (!in_pf && shmem_file(vma->vm_file))
169 return shmem_allowable_huge_orders(file_inode(vma->vm_file),
170 vma, vma->vm_pgoff, 0,
171 !enforce_sysfs);
172
173 if (!vma_is_anonymous(vma)) {
174 /*
175 * Enforce sysfs THP requirements as necessary. Anonymous vmas
176 * were already handled in thp_vma_allowable_orders().
177 */
178 if (enforce_sysfs &&
179 (!hugepage_global_enabled() || (!(vm_flags & VM_HUGEPAGE) &&
180 !hugepage_global_always())))
181 return 0;
182
183 /*
184 * Trust that ->huge_fault() handlers know what they are doing
185 * in fault path.
186 */
187 if (((in_pf || smaps)) && vma->vm_ops->huge_fault)
188 return orders;
189 /* Only regular file is valid in collapse path */
190 if (((!in_pf || smaps)) && file_thp_enabled(vma))
191 return orders;
192 return 0;
193 }
194
195 if (vma_is_temporary_stack(vma))
196 return 0;
197
198 /*
199 * THPeligible bit of smaps should show 1 for proper VMAs even
200 * though anon_vma is not initialized yet.
201 *
202 * Allow page fault since anon_vma may be not initialized until
203 * the first page fault.
204 */
205 if (!vma->anon_vma)
206 return (smaps || in_pf) ? orders : 0;
207
208 return orders;
209 }
210
get_huge_zero_page(void)211 static bool get_huge_zero_page(void)
212 {
213 struct folio *zero_folio;
214 retry:
215 if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
216 return true;
217
218 zero_folio = folio_alloc((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
219 HPAGE_PMD_ORDER);
220 if (!zero_folio) {
221 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
222 return false;
223 }
224 /* Ensure zero folio won't have large_rmappable flag set. */
225 folio_clear_large_rmappable(zero_folio);
226 preempt_disable();
227 if (cmpxchg(&huge_zero_folio, NULL, zero_folio)) {
228 preempt_enable();
229 folio_put(zero_folio);
230 goto retry;
231 }
232 WRITE_ONCE(huge_zero_pfn, folio_pfn(zero_folio));
233
234 /* We take additional reference here. It will be put back by shrinker */
235 atomic_set(&huge_zero_refcount, 2);
236 preempt_enable();
237 count_vm_event(THP_ZERO_PAGE_ALLOC);
238 return true;
239 }
240
put_huge_zero_page(void)241 static void put_huge_zero_page(void)
242 {
243 /*
244 * Counter should never go to zero here. Only shrinker can put
245 * last reference.
246 */
247 BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
248 }
249
mm_get_huge_zero_folio(struct mm_struct * mm)250 struct folio *mm_get_huge_zero_folio(struct mm_struct *mm)
251 {
252 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
253 return READ_ONCE(huge_zero_folio);
254
255 if (!get_huge_zero_page())
256 return NULL;
257
258 if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
259 put_huge_zero_page();
260
261 return READ_ONCE(huge_zero_folio);
262 }
263
mm_put_huge_zero_folio(struct mm_struct * mm)264 void mm_put_huge_zero_folio(struct mm_struct *mm)
265 {
266 if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
267 put_huge_zero_page();
268 }
269
shrink_huge_zero_page_count(struct shrinker * shrink,struct shrink_control * sc)270 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
271 struct shrink_control *sc)
272 {
273 /* we can free zero page only if last reference remains */
274 return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
275 }
276
shrink_huge_zero_page_scan(struct shrinker * shrink,struct shrink_control * sc)277 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
278 struct shrink_control *sc)
279 {
280 if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
281 struct folio *zero_folio = xchg(&huge_zero_folio, NULL);
282 BUG_ON(zero_folio == NULL);
283 WRITE_ONCE(huge_zero_pfn, ~0UL);
284 folio_put(zero_folio);
285 return HPAGE_PMD_NR;
286 }
287
288 return 0;
289 }
290
291 static struct shrinker *huge_zero_page_shrinker;
292
293 #ifdef CONFIG_SYSFS
enabled_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)294 static ssize_t enabled_show(struct kobject *kobj,
295 struct kobj_attribute *attr, char *buf)
296 {
297 const char *output;
298
299 if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
300 output = "[always] madvise never";
301 else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
302 &transparent_hugepage_flags))
303 output = "always [madvise] never";
304 else
305 output = "always madvise [never]";
306
307 return sysfs_emit(buf, "%s\n", output);
308 }
309
enabled_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)310 static ssize_t enabled_store(struct kobject *kobj,
311 struct kobj_attribute *attr,
312 const char *buf, size_t count)
313 {
314 ssize_t ret = count;
315
316 if (sysfs_streq(buf, "always")) {
317 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
318 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
319 } else if (sysfs_streq(buf, "madvise")) {
320 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
321 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
322 } else if (sysfs_streq(buf, "never")) {
323 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
324 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
325 } else
326 ret = -EINVAL;
327
328 if (ret > 0) {
329 int err = start_stop_khugepaged();
330 if (err)
331 ret = err;
332 }
333 return ret;
334 }
335
336 static struct kobj_attribute enabled_attr = __ATTR_RW(enabled);
337
single_hugepage_flag_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf,enum transparent_hugepage_flag flag)338 ssize_t single_hugepage_flag_show(struct kobject *kobj,
339 struct kobj_attribute *attr, char *buf,
340 enum transparent_hugepage_flag flag)
341 {
342 return sysfs_emit(buf, "%d\n",
343 !!test_bit(flag, &transparent_hugepage_flags));
344 }
345
single_hugepage_flag_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count,enum transparent_hugepage_flag flag)346 ssize_t single_hugepage_flag_store(struct kobject *kobj,
347 struct kobj_attribute *attr,
348 const char *buf, size_t count,
349 enum transparent_hugepage_flag flag)
350 {
351 unsigned long value;
352 int ret;
353
354 ret = kstrtoul(buf, 10, &value);
355 if (ret < 0)
356 return ret;
357 if (value > 1)
358 return -EINVAL;
359
360 if (value)
361 set_bit(flag, &transparent_hugepage_flags);
362 else
363 clear_bit(flag, &transparent_hugepage_flags);
364
365 return count;
366 }
367
defrag_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)368 static ssize_t defrag_show(struct kobject *kobj,
369 struct kobj_attribute *attr, char *buf)
370 {
371 const char *output;
372
373 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
374 &transparent_hugepage_flags))
375 output = "[always] defer defer+madvise madvise never";
376 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG,
377 &transparent_hugepage_flags))
378 output = "always [defer] defer+madvise madvise never";
379 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG,
380 &transparent_hugepage_flags))
381 output = "always defer [defer+madvise] madvise never";
382 else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
383 &transparent_hugepage_flags))
384 output = "always defer defer+madvise [madvise] never";
385 else
386 output = "always defer defer+madvise madvise [never]";
387
388 return sysfs_emit(buf, "%s\n", output);
389 }
390
defrag_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)391 static ssize_t defrag_store(struct kobject *kobj,
392 struct kobj_attribute *attr,
393 const char *buf, size_t count)
394 {
395 if (sysfs_streq(buf, "always")) {
396 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
397 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
398 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
399 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
400 } else if (sysfs_streq(buf, "defer+madvise")) {
401 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
402 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
403 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
404 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
405 } else if (sysfs_streq(buf, "defer")) {
406 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
407 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
408 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
409 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
410 } else if (sysfs_streq(buf, "madvise")) {
411 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
412 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
413 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
414 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
415 } else if (sysfs_streq(buf, "never")) {
416 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
417 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
418 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
419 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
420 } else
421 return -EINVAL;
422
423 return count;
424 }
425 static struct kobj_attribute defrag_attr = __ATTR_RW(defrag);
426
use_zero_page_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)427 static ssize_t use_zero_page_show(struct kobject *kobj,
428 struct kobj_attribute *attr, char *buf)
429 {
430 return single_hugepage_flag_show(kobj, attr, buf,
431 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
432 }
use_zero_page_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)433 static ssize_t use_zero_page_store(struct kobject *kobj,
434 struct kobj_attribute *attr, const char *buf, size_t count)
435 {
436 return single_hugepage_flag_store(kobj, attr, buf, count,
437 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
438 }
439 static struct kobj_attribute use_zero_page_attr = __ATTR_RW(use_zero_page);
440
hpage_pmd_size_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)441 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
442 struct kobj_attribute *attr, char *buf)
443 {
444 return sysfs_emit(buf, "%lu\n", HPAGE_PMD_SIZE);
445 }
446 static struct kobj_attribute hpage_pmd_size_attr =
447 __ATTR_RO(hpage_pmd_size);
448
split_underused_thp_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)449 static ssize_t split_underused_thp_show(struct kobject *kobj,
450 struct kobj_attribute *attr, char *buf)
451 {
452 return sysfs_emit(buf, "%d\n", split_underused_thp);
453 }
454
split_underused_thp_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)455 static ssize_t split_underused_thp_store(struct kobject *kobj,
456 struct kobj_attribute *attr,
457 const char *buf, size_t count)
458 {
459 int err = kstrtobool(buf, &split_underused_thp);
460
461 if (err < 0)
462 return err;
463
464 return count;
465 }
466
467 static struct kobj_attribute split_underused_thp_attr = __ATTR(
468 shrink_underused, 0644, split_underused_thp_show, split_underused_thp_store);
469
470 static struct attribute *hugepage_attr[] = {
471 &enabled_attr.attr,
472 &defrag_attr.attr,
473 &use_zero_page_attr.attr,
474 &hpage_pmd_size_attr.attr,
475 #ifdef CONFIG_SHMEM
476 &shmem_enabled_attr.attr,
477 #endif
478 &split_underused_thp_attr.attr,
479 NULL,
480 };
481
482 static const struct attribute_group hugepage_attr_group = {
483 .attrs = hugepage_attr,
484 };
485
486 static void hugepage_exit_sysfs(struct kobject *hugepage_kobj);
487 static void thpsize_release(struct kobject *kobj);
488 static DEFINE_SPINLOCK(huge_anon_orders_lock);
489 static LIST_HEAD(thpsize_list);
490
anon_enabled_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)491 static ssize_t anon_enabled_show(struct kobject *kobj,
492 struct kobj_attribute *attr, char *buf)
493 {
494 int order = to_thpsize(kobj)->order;
495 const char *output;
496
497 if (test_bit(order, &huge_anon_orders_always))
498 output = "[always] inherit madvise never";
499 else if (test_bit(order, &huge_anon_orders_inherit))
500 output = "always [inherit] madvise never";
501 else if (test_bit(order, &huge_anon_orders_madvise))
502 output = "always inherit [madvise] never";
503 else
504 output = "always inherit madvise [never]";
505
506 return sysfs_emit(buf, "%s\n", output);
507 }
508
anon_enabled_store(struct kobject * kobj,struct kobj_attribute * attr,const char * buf,size_t count)509 static ssize_t anon_enabled_store(struct kobject *kobj,
510 struct kobj_attribute *attr,
511 const char *buf, size_t count)
512 {
513 int order = to_thpsize(kobj)->order;
514 ssize_t ret = count;
515
516 if (sysfs_streq(buf, "always")) {
517 spin_lock(&huge_anon_orders_lock);
518 clear_bit(order, &huge_anon_orders_inherit);
519 clear_bit(order, &huge_anon_orders_madvise);
520 set_bit(order, &huge_anon_orders_always);
521 spin_unlock(&huge_anon_orders_lock);
522 } else if (sysfs_streq(buf, "inherit")) {
523 spin_lock(&huge_anon_orders_lock);
524 clear_bit(order, &huge_anon_orders_always);
525 clear_bit(order, &huge_anon_orders_madvise);
526 set_bit(order, &huge_anon_orders_inherit);
527 spin_unlock(&huge_anon_orders_lock);
528 } else if (sysfs_streq(buf, "madvise")) {
529 spin_lock(&huge_anon_orders_lock);
530 clear_bit(order, &huge_anon_orders_always);
531 clear_bit(order, &huge_anon_orders_inherit);
532 set_bit(order, &huge_anon_orders_madvise);
533 spin_unlock(&huge_anon_orders_lock);
534 } else if (sysfs_streq(buf, "never")) {
535 spin_lock(&huge_anon_orders_lock);
536 clear_bit(order, &huge_anon_orders_always);
537 clear_bit(order, &huge_anon_orders_inherit);
538 clear_bit(order, &huge_anon_orders_madvise);
539 spin_unlock(&huge_anon_orders_lock);
540 } else
541 ret = -EINVAL;
542
543 if (ret > 0) {
544 int err;
545
546 err = start_stop_khugepaged();
547 if (err)
548 ret = err;
549 }
550 return ret;
551 }
552
553 static struct kobj_attribute anon_enabled_attr =
554 __ATTR(enabled, 0644, anon_enabled_show, anon_enabled_store);
555
556 static struct attribute *anon_ctrl_attrs[] = {
557 &anon_enabled_attr.attr,
558 NULL,
559 };
560
561 static const struct attribute_group anon_ctrl_attr_grp = {
562 .attrs = anon_ctrl_attrs,
563 };
564
565 static struct attribute *file_ctrl_attrs[] = {
566 #ifdef CONFIG_SHMEM
567 &thpsize_shmem_enabled_attr.attr,
568 #endif
569 NULL,
570 };
571
572 static const struct attribute_group file_ctrl_attr_grp = {
573 .attrs = file_ctrl_attrs,
574 };
575
576 static struct attribute *any_ctrl_attrs[] = {
577 NULL,
578 };
579
580 static const struct attribute_group any_ctrl_attr_grp = {
581 .attrs = any_ctrl_attrs,
582 };
583
584 static const struct kobj_type thpsize_ktype = {
585 .release = &thpsize_release,
586 .sysfs_ops = &kobj_sysfs_ops,
587 };
588
589 DEFINE_PER_CPU(struct mthp_stat, mthp_stats) = {{{0}}};
590
sum_mthp_stat(int order,enum mthp_stat_item item)591 static unsigned long sum_mthp_stat(int order, enum mthp_stat_item item)
592 {
593 unsigned long sum = 0;
594 int cpu;
595
596 for_each_possible_cpu(cpu) {
597 struct mthp_stat *this = &per_cpu(mthp_stats, cpu);
598
599 sum += this->stats[order][item];
600 }
601
602 return sum;
603 }
604
605 #define DEFINE_MTHP_STAT_ATTR(_name, _index) \
606 static ssize_t _name##_show(struct kobject *kobj, \
607 struct kobj_attribute *attr, char *buf) \
608 { \
609 int order = to_thpsize(kobj)->order; \
610 \
611 return sysfs_emit(buf, "%lu\n", sum_mthp_stat(order, _index)); \
612 } \
613 static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
614
615 DEFINE_MTHP_STAT_ATTR(anon_fault_alloc, MTHP_STAT_ANON_FAULT_ALLOC);
616 DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, MTHP_STAT_ANON_FAULT_FALLBACK);
617 DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
618 DEFINE_MTHP_STAT_ATTR(zswpout, MTHP_STAT_ZSWPOUT);
619 DEFINE_MTHP_STAT_ATTR(swpin, MTHP_STAT_SWPIN);
620 DEFINE_MTHP_STAT_ATTR(swpin_fallback, MTHP_STAT_SWPIN_FALLBACK);
621 DEFINE_MTHP_STAT_ATTR(swpin_fallback_charge, MTHP_STAT_SWPIN_FALLBACK_CHARGE);
622 DEFINE_MTHP_STAT_ATTR(swpout, MTHP_STAT_SWPOUT);
623 DEFINE_MTHP_STAT_ATTR(swpout_fallback, MTHP_STAT_SWPOUT_FALLBACK);
624 #ifdef CONFIG_SHMEM
625 DEFINE_MTHP_STAT_ATTR(shmem_alloc, MTHP_STAT_SHMEM_ALLOC);
626 DEFINE_MTHP_STAT_ATTR(shmem_fallback, MTHP_STAT_SHMEM_FALLBACK);
627 DEFINE_MTHP_STAT_ATTR(shmem_fallback_charge, MTHP_STAT_SHMEM_FALLBACK_CHARGE);
628 #endif
629 DEFINE_MTHP_STAT_ATTR(split, MTHP_STAT_SPLIT);
630 DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED);
631 DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED);
632 DEFINE_MTHP_STAT_ATTR(nr_anon, MTHP_STAT_NR_ANON);
633 DEFINE_MTHP_STAT_ATTR(nr_anon_partially_mapped, MTHP_STAT_NR_ANON_PARTIALLY_MAPPED);
634
635 static struct attribute *anon_stats_attrs[] = {
636 &anon_fault_alloc_attr.attr,
637 &anon_fault_fallback_attr.attr,
638 &anon_fault_fallback_charge_attr.attr,
639 #ifndef CONFIG_SHMEM
640 &zswpout_attr.attr,
641 &swpin_attr.attr,
642 &swpin_fallback_attr.attr,
643 &swpin_fallback_charge_attr.attr,
644 &swpout_attr.attr,
645 &swpout_fallback_attr.attr,
646 #endif
647 &split_deferred_attr.attr,
648 &nr_anon_attr.attr,
649 &nr_anon_partially_mapped_attr.attr,
650 NULL,
651 };
652
653 static struct attribute_group anon_stats_attr_grp = {
654 .name = "stats",
655 .attrs = anon_stats_attrs,
656 };
657
658 static struct attribute *file_stats_attrs[] = {
659 #ifdef CONFIG_SHMEM
660 &shmem_alloc_attr.attr,
661 &shmem_fallback_attr.attr,
662 &shmem_fallback_charge_attr.attr,
663 #endif
664 NULL,
665 };
666
667 static struct attribute_group file_stats_attr_grp = {
668 .name = "stats",
669 .attrs = file_stats_attrs,
670 };
671
672 static struct attribute *any_stats_attrs[] = {
673 #ifdef CONFIG_SHMEM
674 &zswpout_attr.attr,
675 &swpin_attr.attr,
676 &swpin_fallback_attr.attr,
677 &swpin_fallback_charge_attr.attr,
678 &swpout_attr.attr,
679 &swpout_fallback_attr.attr,
680 #endif
681 &split_attr.attr,
682 &split_failed_attr.attr,
683 NULL,
684 };
685
686 static struct attribute_group any_stats_attr_grp = {
687 .name = "stats",
688 .attrs = any_stats_attrs,
689 };
690
sysfs_add_group(struct kobject * kobj,const struct attribute_group * grp)691 static int sysfs_add_group(struct kobject *kobj,
692 const struct attribute_group *grp)
693 {
694 int ret = -ENOENT;
695
696 /*
697 * If the group is named, try to merge first, assuming the subdirectory
698 * was already created. This avoids the warning emitted by
699 * sysfs_create_group() if the directory already exists.
700 */
701 if (grp->name)
702 ret = sysfs_merge_group(kobj, grp);
703 if (ret)
704 ret = sysfs_create_group(kobj, grp);
705
706 return ret;
707 }
708
thpsize_create(int order,struct kobject * parent)709 static struct thpsize *thpsize_create(int order, struct kobject *parent)
710 {
711 unsigned long size = (PAGE_SIZE << order) / SZ_1K;
712 struct thpsize *thpsize;
713 int ret = -ENOMEM;
714
715 thpsize = kzalloc(sizeof(*thpsize), GFP_KERNEL);
716 if (!thpsize)
717 goto err;
718
719 thpsize->order = order;
720
721 ret = kobject_init_and_add(&thpsize->kobj, &thpsize_ktype, parent,
722 "hugepages-%lukB", size);
723 if (ret) {
724 kfree(thpsize);
725 goto err;
726 }
727
728
729 ret = sysfs_add_group(&thpsize->kobj, &any_ctrl_attr_grp);
730 if (ret)
731 goto err_put;
732
733 ret = sysfs_add_group(&thpsize->kobj, &any_stats_attr_grp);
734 if (ret)
735 goto err_put;
736
737 if (BIT(order) & THP_ORDERS_ALL_ANON) {
738 ret = sysfs_add_group(&thpsize->kobj, &anon_ctrl_attr_grp);
739 if (ret)
740 goto err_put;
741
742 ret = sysfs_add_group(&thpsize->kobj, &anon_stats_attr_grp);
743 if (ret)
744 goto err_put;
745 }
746
747 if (BIT(order) & THP_ORDERS_ALL_FILE_DEFAULT) {
748 ret = sysfs_add_group(&thpsize->kobj, &file_ctrl_attr_grp);
749 if (ret)
750 goto err_put;
751
752 ret = sysfs_add_group(&thpsize->kobj, &file_stats_attr_grp);
753 if (ret)
754 goto err_put;
755 }
756
757 return thpsize;
758 err_put:
759 kobject_put(&thpsize->kobj);
760 err:
761 return ERR_PTR(ret);
762 }
763
thpsize_release(struct kobject * kobj)764 static void thpsize_release(struct kobject *kobj)
765 {
766 kfree(to_thpsize(kobj));
767 }
768
hugepage_init_sysfs(struct kobject ** hugepage_kobj)769 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
770 {
771 int err;
772 struct thpsize *thpsize;
773 unsigned long orders;
774 int order;
775
776 /*
777 * Default to setting PMD-sized THP to inherit the global setting and
778 * disable all other sizes. powerpc's PMD_ORDER isn't a compile-time
779 * constant so we have to do this here.
780 */
781 if (!anon_orders_configured)
782 huge_anon_orders_inherit = BIT(PMD_ORDER);
783
784 *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
785 if (unlikely(!*hugepage_kobj)) {
786 pr_err("failed to create transparent hugepage kobject\n");
787 return -ENOMEM;
788 }
789
790 err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
791 if (err) {
792 pr_err("failed to register transparent hugepage group\n");
793 goto delete_obj;
794 }
795
796 err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
797 if (err) {
798 pr_err("failed to register transparent hugepage group\n");
799 goto remove_hp_group;
800 }
801
802 orders = THP_ORDERS_ALL_ANON | THP_ORDERS_ALL_FILE_DEFAULT;
803 order = highest_order(orders);
804 while (orders) {
805 thpsize = thpsize_create(order, *hugepage_kobj);
806 if (IS_ERR(thpsize)) {
807 pr_err("failed to create thpsize for order %d\n", order);
808 err = PTR_ERR(thpsize);
809 goto remove_all;
810 }
811 list_add(&thpsize->node, &thpsize_list);
812 order = next_order(&orders, order);
813 }
814
815 return 0;
816
817 remove_all:
818 hugepage_exit_sysfs(*hugepage_kobj);
819 return err;
820 remove_hp_group:
821 sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
822 delete_obj:
823 kobject_put(*hugepage_kobj);
824 return err;
825 }
826
hugepage_exit_sysfs(struct kobject * hugepage_kobj)827 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
828 {
829 struct thpsize *thpsize, *tmp;
830
831 list_for_each_entry_safe(thpsize, tmp, &thpsize_list, node) {
832 list_del(&thpsize->node);
833 kobject_put(&thpsize->kobj);
834 }
835
836 sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
837 sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
838 kobject_put(hugepage_kobj);
839 }
840 #else
hugepage_init_sysfs(struct kobject ** hugepage_kobj)841 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
842 {
843 return 0;
844 }
845
hugepage_exit_sysfs(struct kobject * hugepage_kobj)846 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
847 {
848 }
849 #endif /* CONFIG_SYSFS */
850
thp_shrinker_init(void)851 static int __init thp_shrinker_init(void)
852 {
853 huge_zero_page_shrinker = shrinker_alloc(0, "thp-zero");
854 if (!huge_zero_page_shrinker)
855 return -ENOMEM;
856
857 deferred_split_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE |
858 SHRINKER_MEMCG_AWARE |
859 SHRINKER_NONSLAB,
860 "thp-deferred_split");
861 if (!deferred_split_shrinker) {
862 shrinker_free(huge_zero_page_shrinker);
863 return -ENOMEM;
864 }
865
866 huge_zero_page_shrinker->count_objects = shrink_huge_zero_page_count;
867 huge_zero_page_shrinker->scan_objects = shrink_huge_zero_page_scan;
868 shrinker_register(huge_zero_page_shrinker);
869
870 deferred_split_shrinker->count_objects = deferred_split_count;
871 deferred_split_shrinker->scan_objects = deferred_split_scan;
872 shrinker_register(deferred_split_shrinker);
873
874 return 0;
875 }
876
thp_shrinker_exit(void)877 static void __init thp_shrinker_exit(void)
878 {
879 shrinker_free(huge_zero_page_shrinker);
880 shrinker_free(deferred_split_shrinker);
881 }
882
hugepage_init(void)883 static int __init hugepage_init(void)
884 {
885 int err;
886 struct kobject *hugepage_kobj;
887
888 if (!has_transparent_hugepage()) {
889 transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_UNSUPPORTED;
890 return -EINVAL;
891 }
892
893 /*
894 * hugepages can't be allocated by the buddy allocator
895 */
896 MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER > MAX_PAGE_ORDER);
897
898 err = hugepage_init_sysfs(&hugepage_kobj);
899 if (err)
900 goto err_sysfs;
901
902 err = khugepaged_init();
903 if (err)
904 goto err_slab;
905
906 err = thp_shrinker_init();
907 if (err)
908 goto err_shrinker;
909
910 /*
911 * By default disable transparent hugepages on smaller systems,
912 * where the extra memory used could hurt more than TLB overhead
913 * is likely to save. The admin can still enable it through /sys.
914 */
915 if (totalram_pages() < (512 << (20 - PAGE_SHIFT))) {
916 transparent_hugepage_flags = 0;
917 return 0;
918 }
919
920 err = start_stop_khugepaged();
921 if (err)
922 goto err_khugepaged;
923
924 return 0;
925 err_khugepaged:
926 thp_shrinker_exit();
927 err_shrinker:
928 khugepaged_destroy();
929 err_slab:
930 hugepage_exit_sysfs(hugepage_kobj);
931 err_sysfs:
932 return err;
933 }
934 subsys_initcall(hugepage_init);
935
setup_transparent_hugepage(char * str)936 static int __init setup_transparent_hugepage(char *str)
937 {
938 int ret = 0;
939 if (!str)
940 goto out;
941 if (!strcmp(str, "always")) {
942 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
943 &transparent_hugepage_flags);
944 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
945 &transparent_hugepage_flags);
946 ret = 1;
947 } else if (!strcmp(str, "madvise")) {
948 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
949 &transparent_hugepage_flags);
950 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
951 &transparent_hugepage_flags);
952 ret = 1;
953 } else if (!strcmp(str, "never")) {
954 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
955 &transparent_hugepage_flags);
956 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
957 &transparent_hugepage_flags);
958 ret = 1;
959 }
960 out:
961 if (!ret)
962 pr_warn("transparent_hugepage= cannot parse, ignored\n");
963 return ret;
964 }
965 __setup("transparent_hugepage=", setup_transparent_hugepage);
966
967 static char str_dup[PAGE_SIZE] __initdata;
setup_thp_anon(char * str)968 static int __init setup_thp_anon(char *str)
969 {
970 char *token, *range, *policy, *subtoken;
971 unsigned long always, inherit, madvise;
972 char *start_size, *end_size;
973 int start, end, nr;
974 char *p;
975
976 if (!str || strlen(str) + 1 > PAGE_SIZE)
977 goto err;
978 strscpy(str_dup, str);
979
980 always = huge_anon_orders_always;
981 madvise = huge_anon_orders_madvise;
982 inherit = huge_anon_orders_inherit;
983 p = str_dup;
984 while ((token = strsep(&p, ";")) != NULL) {
985 range = strsep(&token, ":");
986 policy = token;
987
988 if (!policy)
989 goto err;
990
991 while ((subtoken = strsep(&range, ",")) != NULL) {
992 if (strchr(subtoken, '-')) {
993 start_size = strsep(&subtoken, "-");
994 end_size = subtoken;
995
996 start = get_order_from_str(start_size, THP_ORDERS_ALL_ANON);
997 end = get_order_from_str(end_size, THP_ORDERS_ALL_ANON);
998 } else {
999 start_size = end_size = subtoken;
1000 start = end = get_order_from_str(subtoken,
1001 THP_ORDERS_ALL_ANON);
1002 }
1003
1004 if (start == -EINVAL) {
1005 pr_err("invalid size %s in thp_anon boot parameter\n", start_size);
1006 goto err;
1007 }
1008
1009 if (end == -EINVAL) {
1010 pr_err("invalid size %s in thp_anon boot parameter\n", end_size);
1011 goto err;
1012 }
1013
1014 if (start < 0 || end < 0 || start > end)
1015 goto err;
1016
1017 nr = end - start + 1;
1018 if (!strcmp(policy, "always")) {
1019 bitmap_set(&always, start, nr);
1020 bitmap_clear(&inherit, start, nr);
1021 bitmap_clear(&madvise, start, nr);
1022 } else if (!strcmp(policy, "madvise")) {
1023 bitmap_set(&madvise, start, nr);
1024 bitmap_clear(&inherit, start, nr);
1025 bitmap_clear(&always, start, nr);
1026 } else if (!strcmp(policy, "inherit")) {
1027 bitmap_set(&inherit, start, nr);
1028 bitmap_clear(&madvise, start, nr);
1029 bitmap_clear(&always, start, nr);
1030 } else if (!strcmp(policy, "never")) {
1031 bitmap_clear(&inherit, start, nr);
1032 bitmap_clear(&madvise, start, nr);
1033 bitmap_clear(&always, start, nr);
1034 } else {
1035 pr_err("invalid policy %s in thp_anon boot parameter\n", policy);
1036 goto err;
1037 }
1038 }
1039 }
1040
1041 huge_anon_orders_always = always;
1042 huge_anon_orders_madvise = madvise;
1043 huge_anon_orders_inherit = inherit;
1044 anon_orders_configured = true;
1045 return 1;
1046
1047 err:
1048 pr_warn("thp_anon=%s: error parsing string, ignoring setting\n", str);
1049 return 0;
1050 }
1051 __setup("thp_anon=", setup_thp_anon);
1052
maybe_pmd_mkwrite(pmd_t pmd,struct vm_area_struct * vma)1053 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
1054 {
1055 if (likely(vma->vm_flags & VM_WRITE))
1056 pmd = pmd_mkwrite(pmd, vma);
1057 return pmd;
1058 }
1059
1060 #ifdef CONFIG_MEMCG
1061 static inline
get_deferred_split_queue(struct folio * folio)1062 struct deferred_split *get_deferred_split_queue(struct folio *folio)
1063 {
1064 struct mem_cgroup *memcg = folio_memcg(folio);
1065 struct pglist_data *pgdat = NODE_DATA(folio_nid(folio));
1066
1067 if (memcg)
1068 return &memcg->deferred_split_queue;
1069 else
1070 return &pgdat->deferred_split_queue;
1071 }
1072 #else
1073 static inline
get_deferred_split_queue(struct folio * folio)1074 struct deferred_split *get_deferred_split_queue(struct folio *folio)
1075 {
1076 struct pglist_data *pgdat = NODE_DATA(folio_nid(folio));
1077
1078 return &pgdat->deferred_split_queue;
1079 }
1080 #endif
1081
is_transparent_hugepage(const struct folio * folio)1082 static inline bool is_transparent_hugepage(const struct folio *folio)
1083 {
1084 if (!folio_test_large(folio))
1085 return false;
1086
1087 return is_huge_zero_folio(folio) ||
1088 folio_test_large_rmappable(folio);
1089 }
1090
__thp_get_unmapped_area(struct file * filp,unsigned long addr,unsigned long len,loff_t off,unsigned long flags,unsigned long size,vm_flags_t vm_flags)1091 static unsigned long __thp_get_unmapped_area(struct file *filp,
1092 unsigned long addr, unsigned long len,
1093 loff_t off, unsigned long flags, unsigned long size,
1094 vm_flags_t vm_flags)
1095 {
1096 loff_t off_end = off + len;
1097 loff_t off_align = round_up(off, size);
1098 unsigned long len_pad, ret, off_sub;
1099
1100 if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall())
1101 return 0;
1102
1103 if (off_end <= off_align || (off_end - off_align) < size)
1104 return 0;
1105
1106 len_pad = len + size;
1107 if (len_pad < len || (off + len_pad) < off)
1108 return 0;
1109
1110 ret = mm_get_unmapped_area_vmflags(current->mm, filp, addr, len_pad,
1111 off >> PAGE_SHIFT, flags, vm_flags);
1112
1113 /*
1114 * The failure might be due to length padding. The caller will retry
1115 * without the padding.
1116 */
1117 if (IS_ERR_VALUE(ret))
1118 return 0;
1119
1120 /*
1121 * Do not try to align to THP boundary if allocation at the address
1122 * hint succeeds.
1123 */
1124 if (ret == addr)
1125 return addr;
1126
1127 off_sub = (off - ret) & (size - 1);
1128
1129 if (test_bit(MMF_TOPDOWN, ¤t->mm->flags) && !off_sub)
1130 return ret + size;
1131
1132 ret += off_sub;
1133 return ret;
1134 }
1135
thp_get_unmapped_area_vmflags(struct file * filp,unsigned long addr,unsigned long len,unsigned long pgoff,unsigned long flags,vm_flags_t vm_flags)1136 unsigned long thp_get_unmapped_area_vmflags(struct file *filp, unsigned long addr,
1137 unsigned long len, unsigned long pgoff, unsigned long flags,
1138 vm_flags_t vm_flags)
1139 {
1140 unsigned long ret;
1141 loff_t off = (loff_t)pgoff << PAGE_SHIFT;
1142
1143 ret = __thp_get_unmapped_area(filp, addr, len, off, flags, PMD_SIZE, vm_flags);
1144 if (ret)
1145 return ret;
1146
1147 return mm_get_unmapped_area_vmflags(current->mm, filp, addr, len, pgoff, flags,
1148 vm_flags);
1149 }
1150
thp_get_unmapped_area(struct file * filp,unsigned long addr,unsigned long len,unsigned long pgoff,unsigned long flags)1151 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
1152 unsigned long len, unsigned long pgoff, unsigned long flags)
1153 {
1154 return thp_get_unmapped_area_vmflags(filp, addr, len, pgoff, flags, 0);
1155 }
1156 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
1157
vma_alloc_anon_folio_pmd(struct vm_area_struct * vma,unsigned long addr)1158 static struct folio *vma_alloc_anon_folio_pmd(struct vm_area_struct *vma,
1159 unsigned long addr)
1160 {
1161 gfp_t gfp = vma_thp_gfp_mask(vma);
1162 const int order = HPAGE_PMD_ORDER;
1163 struct folio *folio;
1164
1165 folio = vma_alloc_folio(gfp, order, vma, addr & HPAGE_PMD_MASK);
1166
1167 if (unlikely(!folio)) {
1168 count_vm_event(THP_FAULT_FALLBACK);
1169 count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK);
1170 return NULL;
1171 }
1172
1173 VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
1174 if (mem_cgroup_charge(folio, vma->vm_mm, gfp)) {
1175 folio_put(folio);
1176 count_vm_event(THP_FAULT_FALLBACK);
1177 count_vm_event(THP_FAULT_FALLBACK_CHARGE);
1178 count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK);
1179 count_mthp_stat(order, MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
1180 return NULL;
1181 }
1182 folio_throttle_swaprate(folio, gfp);
1183
1184 /*
1185 * When a folio is not zeroed during allocation (__GFP_ZERO not used)
1186 * or user folios require special handling, folio_zero_user() is used to
1187 * make sure that the page corresponding to the faulting address will be
1188 * hot in the cache after zeroing.
1189 */
1190 if (user_alloc_needs_zeroing())
1191 folio_zero_user(folio, addr);
1192 /*
1193 * The memory barrier inside __folio_mark_uptodate makes sure that
1194 * folio_zero_user writes become visible before the set_pmd_at()
1195 * write.
1196 */
1197 __folio_mark_uptodate(folio);
1198 return folio;
1199 }
1200
map_anon_folio_pmd(struct folio * folio,pmd_t * pmd,struct vm_area_struct * vma,unsigned long haddr)1201 static void map_anon_folio_pmd(struct folio *folio, pmd_t *pmd,
1202 struct vm_area_struct *vma, unsigned long haddr)
1203 {
1204 pmd_t entry;
1205
1206 entry = mk_huge_pmd(&folio->page, vma->vm_page_prot);
1207 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1208 folio_add_new_anon_rmap(folio, vma, haddr, RMAP_EXCLUSIVE);
1209 folio_add_lru_vma(folio, vma);
1210 set_pmd_at(vma->vm_mm, haddr, pmd, entry);
1211 update_mmu_cache_pmd(vma, haddr, pmd);
1212 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1213 count_vm_event(THP_FAULT_ALLOC);
1214 count_mthp_stat(HPAGE_PMD_ORDER, MTHP_STAT_ANON_FAULT_ALLOC);
1215 count_memcg_event_mm(vma->vm_mm, THP_FAULT_ALLOC);
1216 }
1217
__do_huge_pmd_anonymous_page(struct vm_fault * vmf)1218 static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf)
1219 {
1220 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1221 struct vm_area_struct *vma = vmf->vma;
1222 struct folio *folio;
1223 pgtable_t pgtable;
1224 vm_fault_t ret = 0;
1225
1226 folio = vma_alloc_anon_folio_pmd(vma, vmf->address);
1227 if (unlikely(!folio))
1228 return VM_FAULT_FALLBACK;
1229
1230 pgtable = pte_alloc_one(vma->vm_mm);
1231 if (unlikely(!pgtable)) {
1232 ret = VM_FAULT_OOM;
1233 goto release;
1234 }
1235
1236 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1237 if (unlikely(!pmd_none(*vmf->pmd))) {
1238 goto unlock_release;
1239 } else {
1240 ret = check_stable_address_space(vma->vm_mm);
1241 if (ret)
1242 goto unlock_release;
1243
1244 /* Deliver the page fault to userland */
1245 if (userfaultfd_missing(vma)) {
1246 spin_unlock(vmf->ptl);
1247 folio_put(folio);
1248 pte_free(vma->vm_mm, pgtable);
1249 ret = handle_userfault(vmf, VM_UFFD_MISSING);
1250 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
1251 return ret;
1252 }
1253 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
1254 map_anon_folio_pmd(folio, vmf->pmd, vma, haddr);
1255 mm_inc_nr_ptes(vma->vm_mm);
1256 deferred_split_folio(folio, false);
1257 spin_unlock(vmf->ptl);
1258 }
1259
1260 return 0;
1261 unlock_release:
1262 spin_unlock(vmf->ptl);
1263 release:
1264 if (pgtable)
1265 pte_free(vma->vm_mm, pgtable);
1266 folio_put(folio);
1267 return ret;
1268
1269 }
1270
1271 /*
1272 * always: directly stall for all thp allocations
1273 * defer: wake kswapd and fail if not immediately available
1274 * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
1275 * fail if not immediately available
1276 * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
1277 * available
1278 * never: never stall for any thp allocation
1279 */
vma_thp_gfp_mask(struct vm_area_struct * vma)1280 gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma)
1281 {
1282 const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE);
1283
1284 /* Always do synchronous compaction */
1285 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
1286 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
1287
1288 /* Kick kcompactd and fail quickly */
1289 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
1290 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
1291
1292 /* Synchronous compaction if madvised, otherwise kick kcompactd */
1293 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
1294 return GFP_TRANSHUGE_LIGHT |
1295 (vma_madvised ? __GFP_DIRECT_RECLAIM :
1296 __GFP_KSWAPD_RECLAIM);
1297
1298 /* Only do synchronous compaction if madvised */
1299 if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
1300 return GFP_TRANSHUGE_LIGHT |
1301 (vma_madvised ? __GFP_DIRECT_RECLAIM : 0);
1302
1303 return GFP_TRANSHUGE_LIGHT;
1304 }
1305
1306 /* Caller must hold page table lock. */
set_huge_zero_folio(pgtable_t pgtable,struct mm_struct * mm,struct vm_area_struct * vma,unsigned long haddr,pmd_t * pmd,struct folio * zero_folio)1307 static void set_huge_zero_folio(pgtable_t pgtable, struct mm_struct *mm,
1308 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
1309 struct folio *zero_folio)
1310 {
1311 pmd_t entry;
1312 if (!pmd_none(*pmd))
1313 return;
1314 entry = mk_pmd(&zero_folio->page, vma->vm_page_prot);
1315 entry = pmd_mkhuge(entry);
1316 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1317 set_pmd_at(mm, haddr, pmd, entry);
1318 mm_inc_nr_ptes(mm);
1319 }
1320
do_huge_pmd_anonymous_page(struct vm_fault * vmf)1321 vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
1322 {
1323 struct vm_area_struct *vma = vmf->vma;
1324 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1325 vm_fault_t ret;
1326
1327 if (!thp_vma_suitable_order(vma, haddr, PMD_ORDER))
1328 return VM_FAULT_FALLBACK;
1329 ret = vmf_anon_prepare(vmf);
1330 if (ret)
1331 return ret;
1332 khugepaged_enter_vma(vma, vma->vm_flags);
1333
1334 if (!(vmf->flags & FAULT_FLAG_WRITE) &&
1335 !mm_forbids_zeropage(vma->vm_mm) &&
1336 transparent_hugepage_use_zero_page()) {
1337 pgtable_t pgtable;
1338 struct folio *zero_folio;
1339 vm_fault_t ret;
1340
1341 pgtable = pte_alloc_one(vma->vm_mm);
1342 if (unlikely(!pgtable))
1343 return VM_FAULT_OOM;
1344 zero_folio = mm_get_huge_zero_folio(vma->vm_mm);
1345 if (unlikely(!zero_folio)) {
1346 pte_free(vma->vm_mm, pgtable);
1347 count_vm_event(THP_FAULT_FALLBACK);
1348 return VM_FAULT_FALLBACK;
1349 }
1350 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1351 ret = 0;
1352 if (pmd_none(*vmf->pmd)) {
1353 ret = check_stable_address_space(vma->vm_mm);
1354 if (ret) {
1355 spin_unlock(vmf->ptl);
1356 pte_free(vma->vm_mm, pgtable);
1357 } else if (userfaultfd_missing(vma)) {
1358 spin_unlock(vmf->ptl);
1359 pte_free(vma->vm_mm, pgtable);
1360 ret = handle_userfault(vmf, VM_UFFD_MISSING);
1361 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
1362 } else {
1363 set_huge_zero_folio(pgtable, vma->vm_mm, vma,
1364 haddr, vmf->pmd, zero_folio);
1365 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1366 spin_unlock(vmf->ptl);
1367 }
1368 } else {
1369 spin_unlock(vmf->ptl);
1370 pte_free(vma->vm_mm, pgtable);
1371 }
1372 return ret;
1373 }
1374
1375 return __do_huge_pmd_anonymous_page(vmf);
1376 }
1377
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)1378 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
1379 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
1380 pgtable_t pgtable)
1381 {
1382 struct mm_struct *mm = vma->vm_mm;
1383 pmd_t entry;
1384 spinlock_t *ptl;
1385
1386 ptl = pmd_lock(mm, pmd);
1387 if (!pmd_none(*pmd)) {
1388 if (write) {
1389 if (pmd_pfn(*pmd) != pfn_t_to_pfn(pfn)) {
1390 WARN_ON_ONCE(!is_huge_zero_pmd(*pmd));
1391 goto out_unlock;
1392 }
1393 entry = pmd_mkyoung(*pmd);
1394 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1395 if (pmdp_set_access_flags(vma, addr, pmd, entry, 1))
1396 update_mmu_cache_pmd(vma, addr, pmd);
1397 }
1398
1399 goto out_unlock;
1400 }
1401
1402 entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
1403 if (pfn_t_devmap(pfn))
1404 entry = pmd_mkdevmap(entry);
1405 else
1406 entry = pmd_mkspecial(entry);
1407 if (write) {
1408 entry = pmd_mkyoung(pmd_mkdirty(entry));
1409 entry = maybe_pmd_mkwrite(entry, vma);
1410 }
1411
1412 if (pgtable) {
1413 pgtable_trans_huge_deposit(mm, pmd, pgtable);
1414 mm_inc_nr_ptes(mm);
1415 pgtable = NULL;
1416 }
1417
1418 set_pmd_at(mm, addr, pmd, entry);
1419 update_mmu_cache_pmd(vma, addr, pmd);
1420
1421 out_unlock:
1422 spin_unlock(ptl);
1423 if (pgtable)
1424 pte_free(mm, pgtable);
1425 }
1426
1427 /**
1428 * vmf_insert_pfn_pmd - insert a pmd size pfn
1429 * @vmf: Structure describing the fault
1430 * @pfn: pfn to insert
1431 * @write: whether it's a write fault
1432 *
1433 * Insert a pmd size pfn. See vmf_insert_pfn() for additional info.
1434 *
1435 * Return: vm_fault_t value.
1436 */
vmf_insert_pfn_pmd(struct vm_fault * vmf,pfn_t pfn,bool write)1437 vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write)
1438 {
1439 unsigned long addr = vmf->address & PMD_MASK;
1440 struct vm_area_struct *vma = vmf->vma;
1441 pgprot_t pgprot = vma->vm_page_prot;
1442 pgtable_t pgtable = NULL;
1443
1444 /*
1445 * If we had pmd_special, we could avoid all these restrictions,
1446 * but we need to be consistent with PTEs and architectures that
1447 * can't support a 'special' bit.
1448 */
1449 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
1450 !pfn_t_devmap(pfn));
1451 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1452 (VM_PFNMAP|VM_MIXEDMAP));
1453 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1454
1455 if (addr < vma->vm_start || addr >= vma->vm_end)
1456 return VM_FAULT_SIGBUS;
1457
1458 if (arch_needs_pgtable_deposit()) {
1459 pgtable = pte_alloc_one(vma->vm_mm);
1460 if (!pgtable)
1461 return VM_FAULT_OOM;
1462 }
1463
1464 track_pfn_insert(vma, &pgprot, pfn);
1465
1466 insert_pfn_pmd(vma, addr, vmf->pmd, pfn, pgprot, write, pgtable);
1467 return VM_FAULT_NOPAGE;
1468 }
1469 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
1470
1471 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
maybe_pud_mkwrite(pud_t pud,struct vm_area_struct * vma)1472 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
1473 {
1474 if (likely(vma->vm_flags & VM_WRITE))
1475 pud = pud_mkwrite(pud);
1476 return pud;
1477 }
1478
insert_pfn_pud(struct vm_area_struct * vma,unsigned long addr,pud_t * pud,pfn_t pfn,bool write)1479 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
1480 pud_t *pud, pfn_t pfn, bool write)
1481 {
1482 struct mm_struct *mm = vma->vm_mm;
1483 pgprot_t prot = vma->vm_page_prot;
1484 pud_t entry;
1485 spinlock_t *ptl;
1486
1487 ptl = pud_lock(mm, pud);
1488 if (!pud_none(*pud)) {
1489 if (write) {
1490 if (WARN_ON_ONCE(pud_pfn(*pud) != pfn_t_to_pfn(pfn)))
1491 goto out_unlock;
1492 entry = pud_mkyoung(*pud);
1493 entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma);
1494 if (pudp_set_access_flags(vma, addr, pud, entry, 1))
1495 update_mmu_cache_pud(vma, addr, pud);
1496 }
1497 goto out_unlock;
1498 }
1499
1500 entry = pud_mkhuge(pfn_t_pud(pfn, prot));
1501 if (pfn_t_devmap(pfn))
1502 entry = pud_mkdevmap(entry);
1503 else
1504 entry = pud_mkspecial(entry);
1505 if (write) {
1506 entry = pud_mkyoung(pud_mkdirty(entry));
1507 entry = maybe_pud_mkwrite(entry, vma);
1508 }
1509 set_pud_at(mm, addr, pud, entry);
1510 update_mmu_cache_pud(vma, addr, pud);
1511
1512 out_unlock:
1513 spin_unlock(ptl);
1514 }
1515
1516 /**
1517 * vmf_insert_pfn_pud - insert a pud size pfn
1518 * @vmf: Structure describing the fault
1519 * @pfn: pfn to insert
1520 * @write: whether it's a write fault
1521 *
1522 * Insert a pud size pfn. See vmf_insert_pfn() for additional info.
1523 *
1524 * Return: vm_fault_t value.
1525 */
vmf_insert_pfn_pud(struct vm_fault * vmf,pfn_t pfn,bool write)1526 vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write)
1527 {
1528 unsigned long addr = vmf->address & PUD_MASK;
1529 struct vm_area_struct *vma = vmf->vma;
1530 pgprot_t pgprot = vma->vm_page_prot;
1531
1532 /*
1533 * If we had pud_special, we could avoid all these restrictions,
1534 * but we need to be consistent with PTEs and architectures that
1535 * can't support a 'special' bit.
1536 */
1537 BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
1538 !pfn_t_devmap(pfn));
1539 BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
1540 (VM_PFNMAP|VM_MIXEDMAP));
1541 BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
1542
1543 if (addr < vma->vm_start || addr >= vma->vm_end)
1544 return VM_FAULT_SIGBUS;
1545
1546 track_pfn_insert(vma, &pgprot, pfn);
1547
1548 insert_pfn_pud(vma, addr, vmf->pud, pfn, write);
1549 return VM_FAULT_NOPAGE;
1550 }
1551 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
1552 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1553
touch_pmd(struct vm_area_struct * vma,unsigned long addr,pmd_t * pmd,bool write)1554 void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
1555 pmd_t *pmd, bool write)
1556 {
1557 pmd_t _pmd;
1558
1559 _pmd = pmd_mkyoung(*pmd);
1560 if (write)
1561 _pmd = pmd_mkdirty(_pmd);
1562 if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
1563 pmd, _pmd, write))
1564 update_mmu_cache_pmd(vma, addr, pmd);
1565 }
1566
follow_devmap_pmd(struct vm_area_struct * vma,unsigned long addr,pmd_t * pmd,int flags,struct dev_pagemap ** pgmap)1567 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
1568 pmd_t *pmd, int flags, struct dev_pagemap **pgmap)
1569 {
1570 unsigned long pfn = pmd_pfn(*pmd);
1571 struct mm_struct *mm = vma->vm_mm;
1572 struct page *page;
1573 int ret;
1574
1575 assert_spin_locked(pmd_lockptr(mm, pmd));
1576
1577 if (flags & FOLL_WRITE && !pmd_write(*pmd))
1578 return NULL;
1579
1580 if (pmd_present(*pmd) && pmd_devmap(*pmd))
1581 /* pass */;
1582 else
1583 return NULL;
1584
1585 if (flags & FOLL_TOUCH)
1586 touch_pmd(vma, addr, pmd, flags & FOLL_WRITE);
1587
1588 /*
1589 * device mapped pages can only be returned if the
1590 * caller will manage the page reference count.
1591 */
1592 if (!(flags & (FOLL_GET | FOLL_PIN)))
1593 return ERR_PTR(-EEXIST);
1594
1595 pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
1596 *pgmap = get_dev_pagemap(pfn, *pgmap);
1597 if (!*pgmap)
1598 return ERR_PTR(-EFAULT);
1599 page = pfn_to_page(pfn);
1600 ret = try_grab_folio(page_folio(page), 1, flags);
1601 if (ret)
1602 page = ERR_PTR(ret);
1603
1604 return page;
1605 }
1606
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 * dst_vma,struct vm_area_struct * src_vma)1607 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1608 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
1609 struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
1610 {
1611 spinlock_t *dst_ptl, *src_ptl;
1612 struct page *src_page;
1613 struct folio *src_folio;
1614 pmd_t pmd;
1615 pgtable_t pgtable = NULL;
1616 int ret = -ENOMEM;
1617
1618 pmd = pmdp_get_lockless(src_pmd);
1619 if (unlikely(pmd_present(pmd) && pmd_special(pmd))) {
1620 dst_ptl = pmd_lock(dst_mm, dst_pmd);
1621 src_ptl = pmd_lockptr(src_mm, src_pmd);
1622 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1623 /*
1624 * No need to recheck the pmd, it can't change with write
1625 * mmap lock held here.
1626 *
1627 * Meanwhile, making sure it's not a CoW VMA with writable
1628 * mapping, otherwise it means either the anon page wrongly
1629 * applied special bit, or we made the PRIVATE mapping be
1630 * able to wrongly write to the backend MMIO.
1631 */
1632 VM_WARN_ON_ONCE(is_cow_mapping(src_vma->vm_flags) && pmd_write(pmd));
1633 goto set_pmd;
1634 }
1635
1636 /* Skip if can be re-fill on fault */
1637 if (!vma_is_anonymous(dst_vma))
1638 return 0;
1639
1640 pgtable = pte_alloc_one(dst_mm);
1641 if (unlikely(!pgtable))
1642 goto out;
1643
1644 dst_ptl = pmd_lock(dst_mm, dst_pmd);
1645 src_ptl = pmd_lockptr(src_mm, src_pmd);
1646 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1647
1648 ret = -EAGAIN;
1649 pmd = *src_pmd;
1650
1651 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1652 if (unlikely(is_swap_pmd(pmd))) {
1653 swp_entry_t entry = pmd_to_swp_entry(pmd);
1654
1655 VM_BUG_ON(!is_pmd_migration_entry(pmd));
1656 if (!is_readable_migration_entry(entry)) {
1657 entry = make_readable_migration_entry(
1658 swp_offset(entry));
1659 pmd = swp_entry_to_pmd(entry);
1660 if (pmd_swp_soft_dirty(*src_pmd))
1661 pmd = pmd_swp_mksoft_dirty(pmd);
1662 if (pmd_swp_uffd_wp(*src_pmd))
1663 pmd = pmd_swp_mkuffd_wp(pmd);
1664 set_pmd_at(src_mm, addr, src_pmd, pmd);
1665 }
1666 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1667 mm_inc_nr_ptes(dst_mm);
1668 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1669 if (!userfaultfd_wp(dst_vma))
1670 pmd = pmd_swp_clear_uffd_wp(pmd);
1671 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1672 ret = 0;
1673 goto out_unlock;
1674 }
1675 #endif
1676
1677 if (unlikely(!pmd_trans_huge(pmd))) {
1678 pte_free(dst_mm, pgtable);
1679 goto out_unlock;
1680 }
1681 /*
1682 * When page table lock is held, the huge zero pmd should not be
1683 * under splitting since we don't split the page itself, only pmd to
1684 * a page table.
1685 */
1686 if (is_huge_zero_pmd(pmd)) {
1687 /*
1688 * mm_get_huge_zero_folio() will never allocate a new
1689 * folio here, since we already have a zero page to
1690 * copy. It just takes a reference.
1691 */
1692 mm_get_huge_zero_folio(dst_mm);
1693 goto out_zero_page;
1694 }
1695
1696 src_page = pmd_page(pmd);
1697 VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
1698 src_folio = page_folio(src_page);
1699
1700 folio_get(src_folio);
1701 if (unlikely(folio_try_dup_anon_rmap_pmd(src_folio, src_page, src_vma))) {
1702 /* Page maybe pinned: split and retry the fault on PTEs. */
1703 folio_put(src_folio);
1704 pte_free(dst_mm, pgtable);
1705 spin_unlock(src_ptl);
1706 spin_unlock(dst_ptl);
1707 __split_huge_pmd(src_vma, src_pmd, addr, false, NULL);
1708 return -EAGAIN;
1709 }
1710 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1711 out_zero_page:
1712 mm_inc_nr_ptes(dst_mm);
1713 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
1714 pmdp_set_wrprotect(src_mm, addr, src_pmd);
1715 if (!userfaultfd_wp(dst_vma))
1716 pmd = pmd_clear_uffd_wp(pmd);
1717 pmd = pmd_wrprotect(pmd);
1718 set_pmd:
1719 pmd = pmd_mkold(pmd);
1720 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
1721
1722 ret = 0;
1723 out_unlock:
1724 spin_unlock(src_ptl);
1725 spin_unlock(dst_ptl);
1726 out:
1727 return ret;
1728 }
1729
1730 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
touch_pud(struct vm_area_struct * vma,unsigned long addr,pud_t * pud,bool write)1731 void touch_pud(struct vm_area_struct *vma, unsigned long addr,
1732 pud_t *pud, bool write)
1733 {
1734 pud_t _pud;
1735
1736 _pud = pud_mkyoung(*pud);
1737 if (write)
1738 _pud = pud_mkdirty(_pud);
1739 if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1740 pud, _pud, write))
1741 update_mmu_cache_pud(vma, addr, pud);
1742 }
1743
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)1744 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1745 pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1746 struct vm_area_struct *vma)
1747 {
1748 spinlock_t *dst_ptl, *src_ptl;
1749 pud_t pud;
1750 int ret;
1751
1752 dst_ptl = pud_lock(dst_mm, dst_pud);
1753 src_ptl = pud_lockptr(src_mm, src_pud);
1754 spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1755
1756 ret = -EAGAIN;
1757 pud = *src_pud;
1758 if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1759 goto out_unlock;
1760
1761 /*
1762 * TODO: once we support anonymous pages, use
1763 * folio_try_dup_anon_rmap_*() and split if duplicating fails.
1764 */
1765 if (is_cow_mapping(vma->vm_flags) && pud_write(pud)) {
1766 pudp_set_wrprotect(src_mm, addr, src_pud);
1767 pud = pud_wrprotect(pud);
1768 }
1769 pud = pud_mkold(pud);
1770 set_pud_at(dst_mm, addr, dst_pud, pud);
1771
1772 ret = 0;
1773 out_unlock:
1774 spin_unlock(src_ptl);
1775 spin_unlock(dst_ptl);
1776 return ret;
1777 }
1778
huge_pud_set_accessed(struct vm_fault * vmf,pud_t orig_pud)1779 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1780 {
1781 bool write = vmf->flags & FAULT_FLAG_WRITE;
1782
1783 vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1784 if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1785 goto unlock;
1786
1787 touch_pud(vmf->vma, vmf->address, vmf->pud, write);
1788 unlock:
1789 spin_unlock(vmf->ptl);
1790 }
1791 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1792
huge_pmd_set_accessed(struct vm_fault * vmf)1793 void huge_pmd_set_accessed(struct vm_fault *vmf)
1794 {
1795 bool write = vmf->flags & FAULT_FLAG_WRITE;
1796
1797 vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1798 if (unlikely(!pmd_same(*vmf->pmd, vmf->orig_pmd)))
1799 goto unlock;
1800
1801 touch_pmd(vmf->vma, vmf->address, vmf->pmd, write);
1802
1803 unlock:
1804 spin_unlock(vmf->ptl);
1805 }
1806
do_huge_zero_wp_pmd(struct vm_fault * vmf)1807 static vm_fault_t do_huge_zero_wp_pmd(struct vm_fault *vmf)
1808 {
1809 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1810 struct vm_area_struct *vma = vmf->vma;
1811 struct mmu_notifier_range range;
1812 struct folio *folio;
1813 vm_fault_t ret = 0;
1814
1815 folio = vma_alloc_anon_folio_pmd(vma, vmf->address);
1816 if (unlikely(!folio))
1817 return VM_FAULT_FALLBACK;
1818
1819 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, haddr,
1820 haddr + HPAGE_PMD_SIZE);
1821 mmu_notifier_invalidate_range_start(&range);
1822 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1823 if (unlikely(!pmd_same(pmdp_get(vmf->pmd), vmf->orig_pmd)))
1824 goto release;
1825 ret = check_stable_address_space(vma->vm_mm);
1826 if (ret)
1827 goto release;
1828 (void)pmdp_huge_clear_flush(vma, haddr, vmf->pmd);
1829 map_anon_folio_pmd(folio, vmf->pmd, vma, haddr);
1830 goto unlock;
1831 release:
1832 folio_put(folio);
1833 unlock:
1834 spin_unlock(vmf->ptl);
1835 mmu_notifier_invalidate_range_end(&range);
1836 return ret;
1837 }
1838
do_huge_pmd_wp_page(struct vm_fault * vmf)1839 vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
1840 {
1841 const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
1842 struct vm_area_struct *vma = vmf->vma;
1843 struct folio *folio;
1844 struct page *page;
1845 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1846 pmd_t orig_pmd = vmf->orig_pmd;
1847
1848 vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1849 VM_BUG_ON_VMA(!vma->anon_vma, vma);
1850
1851 if (is_huge_zero_pmd(orig_pmd)) {
1852 vm_fault_t ret = do_huge_zero_wp_pmd(vmf);
1853
1854 if (!(ret & VM_FAULT_FALLBACK))
1855 return ret;
1856
1857 /* Fallback to splitting PMD if THP cannot be allocated */
1858 goto fallback;
1859 }
1860
1861 spin_lock(vmf->ptl);
1862
1863 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1864 spin_unlock(vmf->ptl);
1865 return 0;
1866 }
1867
1868 page = pmd_page(orig_pmd);
1869 folio = page_folio(page);
1870 VM_BUG_ON_PAGE(!PageHead(page), page);
1871
1872 /* Early check when only holding the PT lock. */
1873 if (PageAnonExclusive(page))
1874 goto reuse;
1875
1876 if (!folio_trylock(folio)) {
1877 folio_get(folio);
1878 spin_unlock(vmf->ptl);
1879 folio_lock(folio);
1880 spin_lock(vmf->ptl);
1881 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1882 spin_unlock(vmf->ptl);
1883 folio_unlock(folio);
1884 folio_put(folio);
1885 return 0;
1886 }
1887 folio_put(folio);
1888 }
1889
1890 /* Recheck after temporarily dropping the PT lock. */
1891 if (PageAnonExclusive(page)) {
1892 folio_unlock(folio);
1893 goto reuse;
1894 }
1895
1896 /*
1897 * See do_wp_page(): we can only reuse the folio exclusively if
1898 * there are no additional references. Note that we always drain
1899 * the LRU cache immediately after adding a THP.
1900 */
1901 if (folio_ref_count(folio) >
1902 1 + folio_test_swapcache(folio) * folio_nr_pages(folio))
1903 goto unlock_fallback;
1904 if (folio_test_swapcache(folio))
1905 folio_free_swap(folio);
1906 if (folio_ref_count(folio) == 1) {
1907 pmd_t entry;
1908
1909 folio_move_anon_rmap(folio, vma);
1910 SetPageAnonExclusive(page);
1911 folio_unlock(folio);
1912 reuse:
1913 if (unlikely(unshare)) {
1914 spin_unlock(vmf->ptl);
1915 return 0;
1916 }
1917 entry = pmd_mkyoung(orig_pmd);
1918 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1919 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1))
1920 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1921 spin_unlock(vmf->ptl);
1922 return 0;
1923 }
1924
1925 unlock_fallback:
1926 folio_unlock(folio);
1927 spin_unlock(vmf->ptl);
1928 fallback:
1929 __split_huge_pmd(vma, vmf->pmd, vmf->address, false, NULL);
1930 return VM_FAULT_FALLBACK;
1931 }
1932
can_change_pmd_writable(struct vm_area_struct * vma,unsigned long addr,pmd_t pmd)1933 static inline bool can_change_pmd_writable(struct vm_area_struct *vma,
1934 unsigned long addr, pmd_t pmd)
1935 {
1936 struct page *page;
1937
1938 if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
1939 return false;
1940
1941 /* Don't touch entries that are not even readable (NUMA hinting). */
1942 if (pmd_protnone(pmd))
1943 return false;
1944
1945 /* Do we need write faults for softdirty tracking? */
1946 if (pmd_needs_soft_dirty_wp(vma, pmd))
1947 return false;
1948
1949 /* Do we need write faults for uffd-wp tracking? */
1950 if (userfaultfd_huge_pmd_wp(vma, pmd))
1951 return false;
1952
1953 if (!(vma->vm_flags & VM_SHARED)) {
1954 /* See can_change_pte_writable(). */
1955 page = vm_normal_page_pmd(vma, addr, pmd);
1956 return page && PageAnon(page) && PageAnonExclusive(page);
1957 }
1958
1959 /* See can_change_pte_writable(). */
1960 return pmd_dirty(pmd);
1961 }
1962
1963 /* NUMA hinting page fault entry point for trans huge pmds */
do_huge_pmd_numa_page(struct vm_fault * vmf)1964 vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
1965 {
1966 struct vm_area_struct *vma = vmf->vma;
1967 struct folio *folio;
1968 unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1969 int nid = NUMA_NO_NODE;
1970 int target_nid, last_cpupid;
1971 pmd_t pmd, old_pmd;
1972 bool writable = false;
1973 int flags = 0;
1974
1975 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1976 old_pmd = pmdp_get(vmf->pmd);
1977
1978 if (unlikely(!pmd_same(old_pmd, vmf->orig_pmd))) {
1979 spin_unlock(vmf->ptl);
1980 return 0;
1981 }
1982
1983 pmd = pmd_modify(old_pmd, vma->vm_page_prot);
1984
1985 /*
1986 * Detect now whether the PMD could be writable; this information
1987 * is only valid while holding the PT lock.
1988 */
1989 writable = pmd_write(pmd);
1990 if (!writable && vma_wants_manual_pte_write_upgrade(vma) &&
1991 can_change_pmd_writable(vma, vmf->address, pmd))
1992 writable = true;
1993
1994 folio = vm_normal_folio_pmd(vma, haddr, pmd);
1995 if (!folio)
1996 goto out_map;
1997
1998 nid = folio_nid(folio);
1999
2000 target_nid = numa_migrate_check(folio, vmf, haddr, &flags, writable,
2001 &last_cpupid);
2002 if (target_nid == NUMA_NO_NODE)
2003 goto out_map;
2004 if (migrate_misplaced_folio_prepare(folio, vma, target_nid)) {
2005 flags |= TNF_MIGRATE_FAIL;
2006 goto out_map;
2007 }
2008 /* The folio is isolated and isolation code holds a folio reference. */
2009 spin_unlock(vmf->ptl);
2010 writable = false;
2011
2012 if (!migrate_misplaced_folio(folio, target_nid)) {
2013 flags |= TNF_MIGRATED;
2014 nid = target_nid;
2015 task_numa_fault(last_cpupid, nid, HPAGE_PMD_NR, flags);
2016 return 0;
2017 }
2018
2019 flags |= TNF_MIGRATE_FAIL;
2020 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
2021 if (unlikely(!pmd_same(pmdp_get(vmf->pmd), vmf->orig_pmd))) {
2022 spin_unlock(vmf->ptl);
2023 return 0;
2024 }
2025 out_map:
2026 /* Restore the PMD */
2027 pmd = pmd_modify(pmdp_get(vmf->pmd), vma->vm_page_prot);
2028 pmd = pmd_mkyoung(pmd);
2029 if (writable)
2030 pmd = pmd_mkwrite(pmd, vma);
2031 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
2032 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
2033 spin_unlock(vmf->ptl);
2034
2035 if (nid != NUMA_NO_NODE)
2036 task_numa_fault(last_cpupid, nid, HPAGE_PMD_NR, flags);
2037 return 0;
2038 }
2039
2040 /*
2041 * Return true if we do MADV_FREE successfully on entire pmd page.
2042 * Otherwise, return false.
2043 */
madvise_free_huge_pmd(struct mmu_gather * tlb,struct vm_area_struct * vma,pmd_t * pmd,unsigned long addr,unsigned long next)2044 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
2045 pmd_t *pmd, unsigned long addr, unsigned long next)
2046 {
2047 spinlock_t *ptl;
2048 pmd_t orig_pmd;
2049 struct folio *folio;
2050 struct mm_struct *mm = tlb->mm;
2051 bool ret = false;
2052
2053 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
2054
2055 ptl = pmd_trans_huge_lock(pmd, vma);
2056 if (!ptl)
2057 goto out_unlocked;
2058
2059 orig_pmd = *pmd;
2060 if (is_huge_zero_pmd(orig_pmd))
2061 goto out;
2062
2063 if (unlikely(!pmd_present(orig_pmd))) {
2064 VM_BUG_ON(thp_migration_supported() &&
2065 !is_pmd_migration_entry(orig_pmd));
2066 goto out;
2067 }
2068
2069 folio = pmd_folio(orig_pmd);
2070 /*
2071 * If other processes are mapping this folio, we couldn't discard
2072 * the folio unless they all do MADV_FREE so let's skip the folio.
2073 */
2074 if (folio_likely_mapped_shared(folio))
2075 goto out;
2076
2077 if (!folio_trylock(folio))
2078 goto out;
2079
2080 /*
2081 * If user want to discard part-pages of THP, split it so MADV_FREE
2082 * will deactivate only them.
2083 */
2084 if (next - addr != HPAGE_PMD_SIZE) {
2085 folio_get(folio);
2086 spin_unlock(ptl);
2087 split_folio(folio);
2088 folio_unlock(folio);
2089 folio_put(folio);
2090 goto out_unlocked;
2091 }
2092
2093 if (folio_test_dirty(folio))
2094 folio_clear_dirty(folio);
2095 folio_unlock(folio);
2096
2097 if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
2098 pmdp_invalidate(vma, addr, pmd);
2099 orig_pmd = pmd_mkold(orig_pmd);
2100 orig_pmd = pmd_mkclean(orig_pmd);
2101
2102 set_pmd_at(mm, addr, pmd, orig_pmd);
2103 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
2104 }
2105
2106 folio_mark_lazyfree(folio);
2107 ret = true;
2108 out:
2109 spin_unlock(ptl);
2110 out_unlocked:
2111 return ret;
2112 }
2113
zap_deposited_table(struct mm_struct * mm,pmd_t * pmd)2114 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
2115 {
2116 pgtable_t pgtable;
2117
2118 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2119 pte_free(mm, pgtable);
2120 mm_dec_nr_ptes(mm);
2121 }
2122
zap_huge_pmd(struct mmu_gather * tlb,struct vm_area_struct * vma,pmd_t * pmd,unsigned long addr)2123 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
2124 pmd_t *pmd, unsigned long addr)
2125 {
2126 pmd_t orig_pmd;
2127 spinlock_t *ptl;
2128
2129 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
2130
2131 ptl = __pmd_trans_huge_lock(pmd, vma);
2132 if (!ptl)
2133 return 0;
2134 /*
2135 * For architectures like ppc64 we look at deposited pgtable
2136 * when calling pmdp_huge_get_and_clear. So do the
2137 * pgtable_trans_huge_withdraw after finishing pmdp related
2138 * operations.
2139 */
2140 orig_pmd = pmdp_huge_get_and_clear_full(vma, addr, pmd,
2141 tlb->fullmm);
2142 arch_check_zapped_pmd(vma, orig_pmd);
2143 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
2144 if (vma_is_special_huge(vma)) {
2145 if (arch_needs_pgtable_deposit())
2146 zap_deposited_table(tlb->mm, pmd);
2147 spin_unlock(ptl);
2148 } else if (is_huge_zero_pmd(orig_pmd)) {
2149 zap_deposited_table(tlb->mm, pmd);
2150 spin_unlock(ptl);
2151 } else {
2152 struct folio *folio = NULL;
2153 int flush_needed = 1;
2154
2155 if (pmd_present(orig_pmd)) {
2156 struct page *page = pmd_page(orig_pmd);
2157
2158 folio = page_folio(page);
2159 folio_remove_rmap_pmd(folio, page, vma);
2160 WARN_ON_ONCE(folio_mapcount(folio) < 0);
2161 VM_BUG_ON_PAGE(!PageHead(page), page);
2162 } else if (thp_migration_supported()) {
2163 swp_entry_t entry;
2164
2165 VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
2166 entry = pmd_to_swp_entry(orig_pmd);
2167 folio = pfn_swap_entry_folio(entry);
2168 flush_needed = 0;
2169 } else
2170 WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
2171
2172 if (folio_test_anon(folio)) {
2173 zap_deposited_table(tlb->mm, pmd);
2174 add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
2175 } else {
2176 if (arch_needs_pgtable_deposit())
2177 zap_deposited_table(tlb->mm, pmd);
2178 add_mm_counter(tlb->mm, mm_counter_file(folio),
2179 -HPAGE_PMD_NR);
2180 }
2181
2182 spin_unlock(ptl);
2183 if (flush_needed)
2184 tlb_remove_page_size(tlb, &folio->page, HPAGE_PMD_SIZE);
2185 }
2186 return 1;
2187 }
2188
2189 #ifndef pmd_move_must_withdraw
pmd_move_must_withdraw(spinlock_t * new_pmd_ptl,spinlock_t * old_pmd_ptl,struct vm_area_struct * vma)2190 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
2191 spinlock_t *old_pmd_ptl,
2192 struct vm_area_struct *vma)
2193 {
2194 /*
2195 * With split pmd lock we also need to move preallocated
2196 * PTE page table if new_pmd is on different PMD page table.
2197 *
2198 * We also don't deposit and withdraw tables for file pages.
2199 */
2200 return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
2201 }
2202 #endif
2203
move_soft_dirty_pmd(pmd_t pmd)2204 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
2205 {
2206 #ifdef CONFIG_MEM_SOFT_DIRTY
2207 if (unlikely(is_pmd_migration_entry(pmd)))
2208 pmd = pmd_swp_mksoft_dirty(pmd);
2209 else if (pmd_present(pmd))
2210 pmd = pmd_mksoft_dirty(pmd);
2211 #endif
2212 return pmd;
2213 }
2214
clear_uffd_wp_pmd(pmd_t pmd)2215 static pmd_t clear_uffd_wp_pmd(pmd_t pmd)
2216 {
2217 if (pmd_present(pmd))
2218 pmd = pmd_clear_uffd_wp(pmd);
2219 else if (is_swap_pmd(pmd))
2220 pmd = pmd_swp_clear_uffd_wp(pmd);
2221
2222 return pmd;
2223 }
2224
move_huge_pmd(struct vm_area_struct * vma,unsigned long old_addr,unsigned long new_addr,pmd_t * old_pmd,pmd_t * new_pmd)2225 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
2226 unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
2227 {
2228 spinlock_t *old_ptl, *new_ptl;
2229 pmd_t pmd;
2230 struct mm_struct *mm = vma->vm_mm;
2231 bool force_flush = false;
2232
2233 /*
2234 * The destination pmd shouldn't be established, free_pgtables()
2235 * should have released it; but move_page_tables() might have already
2236 * inserted a page table, if racing against shmem/file collapse.
2237 */
2238 if (!pmd_none(*new_pmd)) {
2239 VM_BUG_ON(pmd_trans_huge(*new_pmd));
2240 return false;
2241 }
2242
2243 /*
2244 * We don't have to worry about the ordering of src and dst
2245 * ptlocks because exclusive mmap_lock prevents deadlock.
2246 */
2247 old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
2248 if (old_ptl) {
2249 new_ptl = pmd_lockptr(mm, new_pmd);
2250 if (new_ptl != old_ptl)
2251 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
2252 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
2253 if (pmd_present(pmd))
2254 force_flush = true;
2255 VM_BUG_ON(!pmd_none(*new_pmd));
2256
2257 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
2258 pgtable_t pgtable;
2259 pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
2260 pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
2261 }
2262 pmd = move_soft_dirty_pmd(pmd);
2263 if (vma_has_uffd_without_event_remap(vma))
2264 pmd = clear_uffd_wp_pmd(pmd);
2265 set_pmd_at(mm, new_addr, new_pmd, pmd);
2266 if (force_flush)
2267 flush_pmd_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
2268 if (new_ptl != old_ptl)
2269 spin_unlock(new_ptl);
2270 spin_unlock(old_ptl);
2271 return true;
2272 }
2273 return false;
2274 }
2275
2276 /*
2277 * Returns
2278 * - 0 if PMD could not be locked
2279 * - 1 if PMD was locked but protections unchanged and TLB flush unnecessary
2280 * or if prot_numa but THP migration is not supported
2281 * - HPAGE_PMD_NR if protections changed and TLB flush necessary
2282 */
change_huge_pmd(struct mmu_gather * tlb,struct vm_area_struct * vma,pmd_t * pmd,unsigned long addr,pgprot_t newprot,unsigned long cp_flags)2283 int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
2284 pmd_t *pmd, unsigned long addr, pgprot_t newprot,
2285 unsigned long cp_flags)
2286 {
2287 struct mm_struct *mm = vma->vm_mm;
2288 spinlock_t *ptl;
2289 pmd_t oldpmd, entry;
2290 bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
2291 bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
2292 bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
2293 int ret = 1;
2294
2295 tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
2296
2297 if (prot_numa && !thp_migration_supported())
2298 return 1;
2299
2300 ptl = __pmd_trans_huge_lock(pmd, vma);
2301 if (!ptl)
2302 return 0;
2303
2304 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2305 if (is_swap_pmd(*pmd)) {
2306 swp_entry_t entry = pmd_to_swp_entry(*pmd);
2307 struct folio *folio = pfn_swap_entry_folio(entry);
2308 pmd_t newpmd;
2309
2310 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
2311 if (is_writable_migration_entry(entry)) {
2312 /*
2313 * A protection check is difficult so
2314 * just be safe and disable write
2315 */
2316 if (folio_test_anon(folio))
2317 entry = make_readable_exclusive_migration_entry(swp_offset(entry));
2318 else
2319 entry = make_readable_migration_entry(swp_offset(entry));
2320 newpmd = swp_entry_to_pmd(entry);
2321 if (pmd_swp_soft_dirty(*pmd))
2322 newpmd = pmd_swp_mksoft_dirty(newpmd);
2323 } else {
2324 newpmd = *pmd;
2325 }
2326
2327 if (uffd_wp)
2328 newpmd = pmd_swp_mkuffd_wp(newpmd);
2329 else if (uffd_wp_resolve)
2330 newpmd = pmd_swp_clear_uffd_wp(newpmd);
2331 if (!pmd_same(*pmd, newpmd))
2332 set_pmd_at(mm, addr, pmd, newpmd);
2333 goto unlock;
2334 }
2335 #endif
2336
2337 if (prot_numa) {
2338 struct folio *folio;
2339 bool toptier;
2340 /*
2341 * Avoid trapping faults against the zero page. The read-only
2342 * data is likely to be read-cached on the local CPU and
2343 * local/remote hits to the zero page are not interesting.
2344 */
2345 if (is_huge_zero_pmd(*pmd))
2346 goto unlock;
2347
2348 if (pmd_protnone(*pmd))
2349 goto unlock;
2350
2351 folio = pmd_folio(*pmd);
2352 toptier = node_is_toptier(folio_nid(folio));
2353 /*
2354 * Skip scanning top tier node if normal numa
2355 * balancing is disabled
2356 */
2357 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_NORMAL) &&
2358 toptier)
2359 goto unlock;
2360
2361 if (folio_use_access_time(folio))
2362 folio_xchg_access_time(folio,
2363 jiffies_to_msecs(jiffies));
2364 }
2365 /*
2366 * In case prot_numa, we are under mmap_read_lock(mm). It's critical
2367 * to not clear pmd intermittently to avoid race with MADV_DONTNEED
2368 * which is also under mmap_read_lock(mm):
2369 *
2370 * CPU0: CPU1:
2371 * change_huge_pmd(prot_numa=1)
2372 * pmdp_huge_get_and_clear_notify()
2373 * madvise_dontneed()
2374 * zap_pmd_range()
2375 * pmd_trans_huge(*pmd) == 0 (without ptl)
2376 * // skip the pmd
2377 * set_pmd_at();
2378 * // pmd is re-established
2379 *
2380 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
2381 * which may break userspace.
2382 *
2383 * pmdp_invalidate_ad() is required to make sure we don't miss
2384 * dirty/young flags set by hardware.
2385 */
2386 oldpmd = pmdp_invalidate_ad(vma, addr, pmd);
2387
2388 entry = pmd_modify(oldpmd, newprot);
2389 if (uffd_wp)
2390 entry = pmd_mkuffd_wp(entry);
2391 else if (uffd_wp_resolve)
2392 /*
2393 * Leave the write bit to be handled by PF interrupt
2394 * handler, then things like COW could be properly
2395 * handled.
2396 */
2397 entry = pmd_clear_uffd_wp(entry);
2398
2399 /* See change_pte_range(). */
2400 if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && !pmd_write(entry) &&
2401 can_change_pmd_writable(vma, addr, entry))
2402 entry = pmd_mkwrite(entry, vma);
2403
2404 ret = HPAGE_PMD_NR;
2405 set_pmd_at(mm, addr, pmd, entry);
2406
2407 if (huge_pmd_needs_flush(oldpmd, entry))
2408 tlb_flush_pmd_range(tlb, addr, HPAGE_PMD_SIZE);
2409 unlock:
2410 spin_unlock(ptl);
2411 return ret;
2412 }
2413
2414 /*
2415 * Returns:
2416 *
2417 * - 0: if pud leaf changed from under us
2418 * - 1: if pud can be skipped
2419 * - HPAGE_PUD_NR: if pud was successfully processed
2420 */
2421 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
change_huge_pud(struct mmu_gather * tlb,struct vm_area_struct * vma,pud_t * pudp,unsigned long addr,pgprot_t newprot,unsigned long cp_flags)2422 int change_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
2423 pud_t *pudp, unsigned long addr, pgprot_t newprot,
2424 unsigned long cp_flags)
2425 {
2426 struct mm_struct *mm = vma->vm_mm;
2427 pud_t oldpud, entry;
2428 spinlock_t *ptl;
2429
2430 tlb_change_page_size(tlb, HPAGE_PUD_SIZE);
2431
2432 /* NUMA balancing doesn't apply to dax */
2433 if (cp_flags & MM_CP_PROT_NUMA)
2434 return 1;
2435
2436 /*
2437 * Huge entries on userfault-wp only works with anonymous, while we
2438 * don't have anonymous PUDs yet.
2439 */
2440 if (WARN_ON_ONCE(cp_flags & MM_CP_UFFD_WP_ALL))
2441 return 1;
2442
2443 ptl = __pud_trans_huge_lock(pudp, vma);
2444 if (!ptl)
2445 return 0;
2446
2447 /*
2448 * Can't clear PUD or it can race with concurrent zapping. See
2449 * change_huge_pmd().
2450 */
2451 oldpud = pudp_invalidate(vma, addr, pudp);
2452 entry = pud_modify(oldpud, newprot);
2453 set_pud_at(mm, addr, pudp, entry);
2454 tlb_flush_pud_range(tlb, addr, HPAGE_PUD_SIZE);
2455
2456 spin_unlock(ptl);
2457 return HPAGE_PUD_NR;
2458 }
2459 #endif
2460
2461 #ifdef CONFIG_USERFAULTFD
2462 /*
2463 * The PT lock for src_pmd and dst_vma/src_vma (for reading) are locked by
2464 * the caller, but it must return after releasing the page_table_lock.
2465 * Just move the page from src_pmd to dst_pmd if possible.
2466 * Return zero if succeeded in moving the page, -EAGAIN if it needs to be
2467 * repeated by the caller, or other errors in case of failure.
2468 */
move_pages_huge_pmd(struct mm_struct * mm,pmd_t * dst_pmd,pmd_t * src_pmd,pmd_t dst_pmdval,struct vm_area_struct * dst_vma,struct vm_area_struct * src_vma,unsigned long dst_addr,unsigned long src_addr)2469 int move_pages_huge_pmd(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd, pmd_t dst_pmdval,
2470 struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
2471 unsigned long dst_addr, unsigned long src_addr)
2472 {
2473 pmd_t _dst_pmd, src_pmdval;
2474 struct page *src_page;
2475 struct folio *src_folio;
2476 struct anon_vma *src_anon_vma;
2477 spinlock_t *src_ptl, *dst_ptl;
2478 pgtable_t src_pgtable;
2479 struct mmu_notifier_range range;
2480 int err = 0;
2481
2482 src_pmdval = *src_pmd;
2483 src_ptl = pmd_lockptr(mm, src_pmd);
2484
2485 lockdep_assert_held(src_ptl);
2486 vma_assert_locked(src_vma);
2487 vma_assert_locked(dst_vma);
2488
2489 /* Sanity checks before the operation */
2490 if (WARN_ON_ONCE(!pmd_none(dst_pmdval)) || WARN_ON_ONCE(src_addr & ~HPAGE_PMD_MASK) ||
2491 WARN_ON_ONCE(dst_addr & ~HPAGE_PMD_MASK)) {
2492 spin_unlock(src_ptl);
2493 return -EINVAL;
2494 }
2495
2496 if (!pmd_trans_huge(src_pmdval)) {
2497 spin_unlock(src_ptl);
2498 if (is_pmd_migration_entry(src_pmdval)) {
2499 pmd_migration_entry_wait(mm, &src_pmdval);
2500 return -EAGAIN;
2501 }
2502 return -ENOENT;
2503 }
2504
2505 src_page = pmd_page(src_pmdval);
2506
2507 if (!is_huge_zero_pmd(src_pmdval)) {
2508 if (unlikely(!PageAnonExclusive(src_page))) {
2509 spin_unlock(src_ptl);
2510 return -EBUSY;
2511 }
2512
2513 src_folio = page_folio(src_page);
2514 folio_get(src_folio);
2515 } else
2516 src_folio = NULL;
2517
2518 spin_unlock(src_ptl);
2519
2520 flush_cache_range(src_vma, src_addr, src_addr + HPAGE_PMD_SIZE);
2521 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, src_addr,
2522 src_addr + HPAGE_PMD_SIZE);
2523 mmu_notifier_invalidate_range_start(&range);
2524
2525 if (src_folio) {
2526 folio_lock(src_folio);
2527
2528 /*
2529 * split_huge_page walks the anon_vma chain without the page
2530 * lock. Serialize against it with the anon_vma lock, the page
2531 * lock is not enough.
2532 */
2533 src_anon_vma = folio_get_anon_vma(src_folio);
2534 if (!src_anon_vma) {
2535 err = -EAGAIN;
2536 goto unlock_folio;
2537 }
2538 anon_vma_lock_write(src_anon_vma);
2539 } else
2540 src_anon_vma = NULL;
2541
2542 dst_ptl = pmd_lockptr(mm, dst_pmd);
2543 double_pt_lock(src_ptl, dst_ptl);
2544 if (unlikely(!pmd_same(*src_pmd, src_pmdval) ||
2545 !pmd_same(*dst_pmd, dst_pmdval))) {
2546 err = -EAGAIN;
2547 goto unlock_ptls;
2548 }
2549 if (src_folio) {
2550 if (folio_maybe_dma_pinned(src_folio) ||
2551 !PageAnonExclusive(&src_folio->page)) {
2552 err = -EBUSY;
2553 goto unlock_ptls;
2554 }
2555
2556 if (WARN_ON_ONCE(!folio_test_head(src_folio)) ||
2557 WARN_ON_ONCE(!folio_test_anon(src_folio))) {
2558 err = -EBUSY;
2559 goto unlock_ptls;
2560 }
2561
2562 src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd);
2563 /* Folio got pinned from under us. Put it back and fail the move. */
2564 if (folio_maybe_dma_pinned(src_folio)) {
2565 set_pmd_at(mm, src_addr, src_pmd, src_pmdval);
2566 err = -EBUSY;
2567 goto unlock_ptls;
2568 }
2569
2570 folio_move_anon_rmap(src_folio, dst_vma);
2571 src_folio->index = linear_page_index(dst_vma, dst_addr);
2572
2573 _dst_pmd = mk_huge_pmd(&src_folio->page, dst_vma->vm_page_prot);
2574 /* Follow mremap() behavior and treat the entry dirty after the move */
2575 _dst_pmd = pmd_mkwrite(pmd_mkdirty(_dst_pmd), dst_vma);
2576 } else {
2577 src_pmdval = pmdp_huge_clear_flush(src_vma, src_addr, src_pmd);
2578 _dst_pmd = mk_huge_pmd(src_page, dst_vma->vm_page_prot);
2579 }
2580 set_pmd_at(mm, dst_addr, dst_pmd, _dst_pmd);
2581
2582 src_pgtable = pgtable_trans_huge_withdraw(mm, src_pmd);
2583 pgtable_trans_huge_deposit(mm, dst_pmd, src_pgtable);
2584 unlock_ptls:
2585 double_pt_unlock(src_ptl, dst_ptl);
2586 if (src_anon_vma) {
2587 anon_vma_unlock_write(src_anon_vma);
2588 put_anon_vma(src_anon_vma);
2589 }
2590 unlock_folio:
2591 /* unblock rmap walks */
2592 if (src_folio)
2593 folio_unlock(src_folio);
2594 mmu_notifier_invalidate_range_end(&range);
2595 if (src_folio)
2596 folio_put(src_folio);
2597 return err;
2598 }
2599 #endif /* CONFIG_USERFAULTFD */
2600
2601 /*
2602 * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
2603 *
2604 * Note that if it returns page table lock pointer, this routine returns without
2605 * unlocking page table lock. So callers must unlock it.
2606 */
__pmd_trans_huge_lock(pmd_t * pmd,struct vm_area_struct * vma)2607 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
2608 {
2609 spinlock_t *ptl;
2610 ptl = pmd_lock(vma->vm_mm, pmd);
2611 if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
2612 pmd_devmap(*pmd)))
2613 return ptl;
2614 spin_unlock(ptl);
2615 return NULL;
2616 }
2617
2618 /*
2619 * Returns page table lock pointer if a given pud maps a thp, NULL otherwise.
2620 *
2621 * Note that if it returns page table lock pointer, this routine returns without
2622 * unlocking page table lock. So callers must unlock it.
2623 */
__pud_trans_huge_lock(pud_t * pud,struct vm_area_struct * vma)2624 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
2625 {
2626 spinlock_t *ptl;
2627
2628 ptl = pud_lock(vma->vm_mm, pud);
2629 if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
2630 return ptl;
2631 spin_unlock(ptl);
2632 return NULL;
2633 }
2634
2635 #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)2636 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
2637 pud_t *pud, unsigned long addr)
2638 {
2639 spinlock_t *ptl;
2640 pud_t orig_pud;
2641
2642 ptl = __pud_trans_huge_lock(pud, vma);
2643 if (!ptl)
2644 return 0;
2645
2646 orig_pud = pudp_huge_get_and_clear_full(vma, addr, pud, tlb->fullmm);
2647 arch_check_zapped_pud(vma, orig_pud);
2648 tlb_remove_pud_tlb_entry(tlb, pud, addr);
2649 if (vma_is_special_huge(vma)) {
2650 spin_unlock(ptl);
2651 /* No zero page support yet */
2652 } else {
2653 /* No support for anonymous PUD pages yet */
2654 BUG();
2655 }
2656 return 1;
2657 }
2658
__split_huge_pud_locked(struct vm_area_struct * vma,pud_t * pud,unsigned long haddr)2659 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
2660 unsigned long haddr)
2661 {
2662 VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
2663 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2664 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
2665 VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
2666
2667 count_vm_event(THP_SPLIT_PUD);
2668
2669 pudp_huge_clear_flush(vma, haddr, pud);
2670 }
2671
__split_huge_pud(struct vm_area_struct * vma,pud_t * pud,unsigned long address)2672 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2673 unsigned long address)
2674 {
2675 spinlock_t *ptl;
2676 struct mmu_notifier_range range;
2677
2678 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
2679 address & HPAGE_PUD_MASK,
2680 (address & HPAGE_PUD_MASK) + HPAGE_PUD_SIZE);
2681 mmu_notifier_invalidate_range_start(&range);
2682 ptl = pud_lock(vma->vm_mm, pud);
2683 if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2684 goto out;
2685 __split_huge_pud_locked(vma, pud, range.start);
2686
2687 out:
2688 spin_unlock(ptl);
2689 mmu_notifier_invalidate_range_end(&range);
2690 }
2691 #else
__split_huge_pud(struct vm_area_struct * vma,pud_t * pud,unsigned long address)2692 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2693 unsigned long address)
2694 {
2695 }
2696 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2697
__split_huge_zero_page_pmd(struct vm_area_struct * vma,unsigned long haddr,pmd_t * pmd)2698 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2699 unsigned long haddr, pmd_t *pmd)
2700 {
2701 struct mm_struct *mm = vma->vm_mm;
2702 pgtable_t pgtable;
2703 pmd_t _pmd, old_pmd;
2704 unsigned long addr;
2705 pte_t *pte;
2706 int i;
2707
2708 /*
2709 * Leave pmd empty until pte is filled note that it is fine to delay
2710 * notification until mmu_notifier_invalidate_range_end() as we are
2711 * replacing a zero pmd write protected page with a zero pte write
2712 * protected page.
2713 *
2714 * See Documentation/mm/mmu_notifier.rst
2715 */
2716 old_pmd = pmdp_huge_clear_flush(vma, haddr, pmd);
2717
2718 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2719 pmd_populate(mm, &_pmd, pgtable);
2720
2721 pte = pte_offset_map(&_pmd, haddr);
2722 VM_BUG_ON(!pte);
2723 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2724 pte_t entry;
2725
2726 entry = pfn_pte(my_zero_pfn(addr), vma->vm_page_prot);
2727 entry = pte_mkspecial(entry);
2728 if (pmd_uffd_wp(old_pmd))
2729 entry = pte_mkuffd_wp(entry);
2730 VM_BUG_ON(!pte_none(ptep_get(pte)));
2731 set_pte_at(mm, addr, pte, entry);
2732 pte++;
2733 }
2734 pte_unmap(pte - 1);
2735 smp_wmb(); /* make pte visible before pmd */
2736 pmd_populate(mm, pmd, pgtable);
2737 }
2738
__split_huge_pmd_locked(struct vm_area_struct * vma,pmd_t * pmd,unsigned long haddr,bool freeze)2739 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2740 unsigned long haddr, bool freeze)
2741 {
2742 struct mm_struct *mm = vma->vm_mm;
2743 struct folio *folio;
2744 struct page *page;
2745 pgtable_t pgtable;
2746 pmd_t old_pmd, _pmd;
2747 bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false;
2748 bool anon_exclusive = false, dirty = false;
2749 unsigned long addr;
2750 pte_t *pte;
2751 int i;
2752
2753 VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2754 VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2755 VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2756 VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2757 && !pmd_devmap(*pmd));
2758
2759 count_vm_event(THP_SPLIT_PMD);
2760
2761 if (!vma_is_anonymous(vma)) {
2762 old_pmd = pmdp_huge_clear_flush(vma, haddr, pmd);
2763 /*
2764 * We are going to unmap this huge page. So
2765 * just go ahead and zap it
2766 */
2767 if (arch_needs_pgtable_deposit())
2768 zap_deposited_table(mm, pmd);
2769 if (vma_is_special_huge(vma))
2770 return;
2771 if (unlikely(is_pmd_migration_entry(old_pmd))) {
2772 swp_entry_t entry;
2773
2774 entry = pmd_to_swp_entry(old_pmd);
2775 folio = pfn_swap_entry_folio(entry);
2776 } else {
2777 page = pmd_page(old_pmd);
2778 folio = page_folio(page);
2779 if (!folio_test_dirty(folio) && pmd_dirty(old_pmd))
2780 folio_mark_dirty(folio);
2781 if (!folio_test_referenced(folio) && pmd_young(old_pmd))
2782 folio_set_referenced(folio);
2783 folio_remove_rmap_pmd(folio, page, vma);
2784 folio_put(folio);
2785 }
2786 add_mm_counter(mm, mm_counter_file(folio), -HPAGE_PMD_NR);
2787 return;
2788 }
2789
2790 if (is_huge_zero_pmd(*pmd)) {
2791 /*
2792 * FIXME: Do we want to invalidate secondary mmu by calling
2793 * mmu_notifier_arch_invalidate_secondary_tlbs() see comments below
2794 * inside __split_huge_pmd() ?
2795 *
2796 * We are going from a zero huge page write protected to zero
2797 * small page also write protected so it does not seems useful
2798 * to invalidate secondary mmu at this time.
2799 */
2800 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2801 }
2802
2803 pmd_migration = is_pmd_migration_entry(*pmd);
2804 if (unlikely(pmd_migration)) {
2805 swp_entry_t entry;
2806
2807 old_pmd = *pmd;
2808 entry = pmd_to_swp_entry(old_pmd);
2809 page = pfn_swap_entry_to_page(entry);
2810 write = is_writable_migration_entry(entry);
2811 if (PageAnon(page))
2812 anon_exclusive = is_readable_exclusive_migration_entry(entry);
2813 young = is_migration_entry_young(entry);
2814 dirty = is_migration_entry_dirty(entry);
2815 soft_dirty = pmd_swp_soft_dirty(old_pmd);
2816 uffd_wp = pmd_swp_uffd_wp(old_pmd);
2817 } else {
2818 /*
2819 * Up to this point the pmd is present and huge and userland has
2820 * the whole access to the hugepage during the split (which
2821 * happens in place). If we overwrite the pmd with the not-huge
2822 * version pointing to the pte here (which of course we could if
2823 * all CPUs were bug free), userland could trigger a small page
2824 * size TLB miss on the small sized TLB while the hugepage TLB
2825 * entry is still established in the huge TLB. Some CPU doesn't
2826 * like that. See
2827 * http://support.amd.com/TechDocs/41322_10h_Rev_Gd.pdf, Erratum
2828 * 383 on page 105. Intel should be safe but is also warns that
2829 * it's only safe if the permission and cache attributes of the
2830 * two entries loaded in the two TLB is identical (which should
2831 * be the case here). But it is generally safer to never allow
2832 * small and huge TLB entries for the same virtual address to be
2833 * loaded simultaneously. So instead of doing "pmd_populate();
2834 * flush_pmd_tlb_range();" we first mark the current pmd
2835 * notpresent (atomically because here the pmd_trans_huge must
2836 * remain set at all times on the pmd until the split is
2837 * complete for this pmd), then we flush the SMP TLB and finally
2838 * we write the non-huge version of the pmd entry with
2839 * pmd_populate.
2840 */
2841 old_pmd = pmdp_invalidate(vma, haddr, pmd);
2842 page = pmd_page(old_pmd);
2843 folio = page_folio(page);
2844 if (pmd_dirty(old_pmd)) {
2845 dirty = true;
2846 folio_set_dirty(folio);
2847 }
2848 write = pmd_write(old_pmd);
2849 young = pmd_young(old_pmd);
2850 soft_dirty = pmd_soft_dirty(old_pmd);
2851 uffd_wp = pmd_uffd_wp(old_pmd);
2852
2853 VM_WARN_ON_FOLIO(!folio_ref_count(folio), folio);
2854 VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
2855
2856 /*
2857 * Without "freeze", we'll simply split the PMD, propagating the
2858 * PageAnonExclusive() flag for each PTE by setting it for
2859 * each subpage -- no need to (temporarily) clear.
2860 *
2861 * With "freeze" we want to replace mapped pages by
2862 * migration entries right away. This is only possible if we
2863 * managed to clear PageAnonExclusive() -- see
2864 * set_pmd_migration_entry().
2865 *
2866 * In case we cannot clear PageAnonExclusive(), split the PMD
2867 * only and let try_to_migrate_one() fail later.
2868 *
2869 * See folio_try_share_anon_rmap_pmd(): invalidate PMD first.
2870 */
2871 anon_exclusive = PageAnonExclusive(page);
2872 if (freeze && anon_exclusive &&
2873 folio_try_share_anon_rmap_pmd(folio, page))
2874 freeze = false;
2875 if (!freeze) {
2876 rmap_t rmap_flags = RMAP_NONE;
2877
2878 folio_ref_add(folio, HPAGE_PMD_NR - 1);
2879 if (anon_exclusive)
2880 rmap_flags |= RMAP_EXCLUSIVE;
2881 folio_add_anon_rmap_ptes(folio, page, HPAGE_PMD_NR,
2882 vma, haddr, rmap_flags);
2883 }
2884 }
2885
2886 /*
2887 * Withdraw the table only after we mark the pmd entry invalid.
2888 * This's critical for some architectures (Power).
2889 */
2890 pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2891 pmd_populate(mm, &_pmd, pgtable);
2892
2893 pte = pte_offset_map(&_pmd, haddr);
2894 VM_BUG_ON(!pte);
2895
2896 /*
2897 * Note that NUMA hinting access restrictions are not transferred to
2898 * avoid any possibility of altering permissions across VMAs.
2899 */
2900 if (freeze || pmd_migration) {
2901 for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2902 pte_t entry;
2903 swp_entry_t swp_entry;
2904
2905 if (write)
2906 swp_entry = make_writable_migration_entry(
2907 page_to_pfn(page + i));
2908 else if (anon_exclusive)
2909 swp_entry = make_readable_exclusive_migration_entry(
2910 page_to_pfn(page + i));
2911 else
2912 swp_entry = make_readable_migration_entry(
2913 page_to_pfn(page + i));
2914 if (young)
2915 swp_entry = make_migration_entry_young(swp_entry);
2916 if (dirty)
2917 swp_entry = make_migration_entry_dirty(swp_entry);
2918 entry = swp_entry_to_pte(swp_entry);
2919 if (soft_dirty)
2920 entry = pte_swp_mksoft_dirty(entry);
2921 if (uffd_wp)
2922 entry = pte_swp_mkuffd_wp(entry);
2923
2924 VM_WARN_ON(!pte_none(ptep_get(pte + i)));
2925 set_pte_at(mm, addr, pte + i, entry);
2926 }
2927 } else {
2928 pte_t entry;
2929
2930 entry = mk_pte(page, READ_ONCE(vma->vm_page_prot));
2931 if (write)
2932 entry = pte_mkwrite(entry, vma);
2933 if (!young)
2934 entry = pte_mkold(entry);
2935 /* NOTE: this may set soft-dirty too on some archs */
2936 if (dirty)
2937 entry = pte_mkdirty(entry);
2938 if (soft_dirty)
2939 entry = pte_mksoft_dirty(entry);
2940 if (uffd_wp)
2941 entry = pte_mkuffd_wp(entry);
2942
2943 for (i = 0; i < HPAGE_PMD_NR; i++)
2944 VM_WARN_ON(!pte_none(ptep_get(pte + i)));
2945
2946 set_ptes(mm, haddr, pte, entry, HPAGE_PMD_NR);
2947 }
2948 pte_unmap(pte);
2949
2950 if (!pmd_migration)
2951 folio_remove_rmap_pmd(folio, page, vma);
2952 if (freeze)
2953 put_page(page);
2954
2955 smp_wmb(); /* make pte visible before pmd */
2956 pmd_populate(mm, pmd, pgtable);
2957 }
2958
split_huge_pmd_locked(struct vm_area_struct * vma,unsigned long address,pmd_t * pmd,bool freeze,struct folio * folio)2959 void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
2960 pmd_t *pmd, bool freeze, struct folio *folio)
2961 {
2962 VM_WARN_ON_ONCE(folio && !folio_test_pmd_mappable(folio));
2963 VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE));
2964 VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
2965 VM_BUG_ON(freeze && !folio);
2966
2967 /*
2968 * When the caller requests to set up a migration entry, we
2969 * require a folio to check the PMD against. Otherwise, there
2970 * is a risk of replacing the wrong folio.
2971 */
2972 if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
2973 is_pmd_migration_entry(*pmd)) {
2974 if (folio && folio != pmd_folio(*pmd))
2975 return;
2976 __split_huge_pmd_locked(vma, pmd, address, freeze);
2977 }
2978 }
2979
__split_huge_pmd(struct vm_area_struct * vma,pmd_t * pmd,unsigned long address,bool freeze,struct folio * folio)2980 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2981 unsigned long address, bool freeze, struct folio *folio)
2982 {
2983 spinlock_t *ptl;
2984 struct mmu_notifier_range range;
2985
2986 mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
2987 address & HPAGE_PMD_MASK,
2988 (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
2989 mmu_notifier_invalidate_range_start(&range);
2990 ptl = pmd_lock(vma->vm_mm, pmd);
2991 split_huge_pmd_locked(vma, range.start, pmd, freeze, folio);
2992 spin_unlock(ptl);
2993 mmu_notifier_invalidate_range_end(&range);
2994 }
2995
split_huge_pmd_address(struct vm_area_struct * vma,unsigned long address,bool freeze,struct folio * folio)2996 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2997 bool freeze, struct folio *folio)
2998 {
2999 pmd_t *pmd = mm_find_pmd(vma->vm_mm, address);
3000
3001 if (!pmd)
3002 return;
3003
3004 __split_huge_pmd(vma, pmd, address, freeze, folio);
3005 }
3006
split_huge_pmd_if_needed(struct vm_area_struct * vma,unsigned long address)3007 static inline void split_huge_pmd_if_needed(struct vm_area_struct *vma, unsigned long address)
3008 {
3009 /*
3010 * If the new address isn't hpage aligned and it could previously
3011 * contain an hugepage: check if we need to split an huge pmd.
3012 */
3013 if (!IS_ALIGNED(address, HPAGE_PMD_SIZE) &&
3014 range_in_vma(vma, ALIGN_DOWN(address, HPAGE_PMD_SIZE),
3015 ALIGN(address, HPAGE_PMD_SIZE)))
3016 split_huge_pmd_address(vma, address, false, NULL);
3017 }
3018
vma_adjust_trans_huge(struct vm_area_struct * vma,unsigned long start,unsigned long end,long adjust_next)3019 void vma_adjust_trans_huge(struct vm_area_struct *vma,
3020 unsigned long start,
3021 unsigned long end,
3022 long adjust_next)
3023 {
3024 /* Check if we need to split start first. */
3025 split_huge_pmd_if_needed(vma, start);
3026
3027 /* Check if we need to split end next. */
3028 split_huge_pmd_if_needed(vma, end);
3029
3030 /*
3031 * If we're also updating the next vma vm_start,
3032 * check if we need to split it.
3033 */
3034 if (adjust_next > 0) {
3035 struct vm_area_struct *next = find_vma(vma->vm_mm, vma->vm_end);
3036 unsigned long nstart = next->vm_start;
3037 nstart += adjust_next;
3038 split_huge_pmd_if_needed(next, nstart);
3039 }
3040 }
3041
unmap_folio(struct folio * folio)3042 static void unmap_folio(struct folio *folio)
3043 {
3044 enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SYNC |
3045 TTU_BATCH_FLUSH;
3046
3047 VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
3048
3049 if (folio_test_pmd_mappable(folio))
3050 ttu_flags |= TTU_SPLIT_HUGE_PMD;
3051
3052 /*
3053 * Anon pages need migration entries to preserve them, but file
3054 * pages can simply be left unmapped, then faulted back on demand.
3055 * If that is ever changed (perhaps for mlock), update remap_page().
3056 */
3057 if (folio_test_anon(folio))
3058 try_to_migrate(folio, ttu_flags);
3059 else
3060 try_to_unmap(folio, ttu_flags | TTU_IGNORE_MLOCK);
3061
3062 try_to_unmap_flush();
3063 }
3064
__discard_anon_folio_pmd_locked(struct vm_area_struct * vma,unsigned long addr,pmd_t * pmdp,struct folio * folio)3065 static bool __discard_anon_folio_pmd_locked(struct vm_area_struct *vma,
3066 unsigned long addr, pmd_t *pmdp,
3067 struct folio *folio)
3068 {
3069 struct mm_struct *mm = vma->vm_mm;
3070 int ref_count, map_count;
3071 pmd_t orig_pmd = *pmdp;
3072
3073 if (folio_test_dirty(folio) || pmd_dirty(orig_pmd))
3074 return false;
3075
3076 orig_pmd = pmdp_huge_clear_flush(vma, addr, pmdp);
3077
3078 /*
3079 * Syncing against concurrent GUP-fast:
3080 * - clear PMD; barrier; read refcount
3081 * - inc refcount; barrier; read PMD
3082 */
3083 smp_mb();
3084
3085 ref_count = folio_ref_count(folio);
3086 map_count = folio_mapcount(folio);
3087
3088 /*
3089 * Order reads for folio refcount and dirty flag
3090 * (see comments in __remove_mapping()).
3091 */
3092 smp_rmb();
3093
3094 /*
3095 * If the folio or its PMD is redirtied at this point, or if there
3096 * are unexpected references, we will give up to discard this folio
3097 * and remap it.
3098 *
3099 * The only folio refs must be one from isolation plus the rmap(s).
3100 */
3101 if (folio_test_dirty(folio) || pmd_dirty(orig_pmd) ||
3102 ref_count != map_count + 1) {
3103 set_pmd_at(mm, addr, pmdp, orig_pmd);
3104 return false;
3105 }
3106
3107 folio_remove_rmap_pmd(folio, pmd_page(orig_pmd), vma);
3108 zap_deposited_table(mm, pmdp);
3109 add_mm_counter(mm, MM_ANONPAGES, -HPAGE_PMD_NR);
3110 if (vma->vm_flags & VM_LOCKED)
3111 mlock_drain_local();
3112 folio_put(folio);
3113
3114 return true;
3115 }
3116
unmap_huge_pmd_locked(struct vm_area_struct * vma,unsigned long addr,pmd_t * pmdp,struct folio * folio)3117 bool unmap_huge_pmd_locked(struct vm_area_struct *vma, unsigned long addr,
3118 pmd_t *pmdp, struct folio *folio)
3119 {
3120 VM_WARN_ON_FOLIO(!folio_test_pmd_mappable(folio), folio);
3121 VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio);
3122 VM_WARN_ON_ONCE(!IS_ALIGNED(addr, HPAGE_PMD_SIZE));
3123
3124 if (folio_test_anon(folio) && !folio_test_swapbacked(folio))
3125 return __discard_anon_folio_pmd_locked(vma, addr, pmdp, folio);
3126
3127 return false;
3128 }
3129
remap_page(struct folio * folio,unsigned long nr,int flags)3130 static void remap_page(struct folio *folio, unsigned long nr, int flags)
3131 {
3132 int i = 0;
3133
3134 /* If unmap_folio() uses try_to_migrate() on file, remove this check */
3135 if (!folio_test_anon(folio))
3136 return;
3137 for (;;) {
3138 remove_migration_ptes(folio, folio, RMP_LOCKED | flags);
3139 i += folio_nr_pages(folio);
3140 if (i >= nr)
3141 break;
3142 folio = folio_next(folio);
3143 }
3144 }
3145
lru_add_page_tail(struct folio * folio,struct page * tail,struct lruvec * lruvec,struct list_head * list)3146 static void lru_add_page_tail(struct folio *folio, struct page *tail,
3147 struct lruvec *lruvec, struct list_head *list)
3148 {
3149 VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
3150 VM_BUG_ON_FOLIO(PageLRU(tail), folio);
3151 lockdep_assert_held(&lruvec->lru_lock);
3152
3153 if (list) {
3154 /* page reclaim is reclaiming a huge page */
3155 VM_WARN_ON(folio_test_lru(folio));
3156 get_page(tail);
3157 list_add_tail(&tail->lru, list);
3158 } else {
3159 /* head is still on lru (and we have it frozen) */
3160 VM_WARN_ON(!folio_test_lru(folio));
3161 if (folio_test_unevictable(folio))
3162 tail->mlock_count = 0;
3163 else
3164 list_add_tail(&tail->lru, &folio->lru);
3165 SetPageLRU(tail);
3166 }
3167 }
3168
__split_huge_page_tail(struct folio * folio,int tail,struct lruvec * lruvec,struct list_head * list,unsigned int new_order)3169 static void __split_huge_page_tail(struct folio *folio, int tail,
3170 struct lruvec *lruvec, struct list_head *list,
3171 unsigned int new_order)
3172 {
3173 struct page *head = &folio->page;
3174 struct page *page_tail = head + tail;
3175 /*
3176 * Careful: new_folio is not a "real" folio before we cleared PageTail.
3177 * Don't pass it around before clear_compound_head().
3178 */
3179 struct folio *new_folio = (struct folio *)page_tail;
3180
3181 VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
3182
3183 /*
3184 * Clone page flags before unfreezing refcount.
3185 *
3186 * After successful get_page_unless_zero() might follow flags change,
3187 * for example lock_page() which set PG_waiters.
3188 *
3189 * Note that for mapped sub-pages of an anonymous THP,
3190 * PG_anon_exclusive has been cleared in unmap_folio() and is stored in
3191 * the migration entry instead from where remap_page() will restore it.
3192 * We can still have PG_anon_exclusive set on effectively unmapped and
3193 * unreferenced sub-pages of an anonymous THP: we can simply drop
3194 * PG_anon_exclusive (-> PG_mappedtodisk) for these here.
3195 */
3196 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
3197 page_tail->flags |= (head->flags &
3198 ((1L << PG_referenced) |
3199 (1L << PG_swapbacked) |
3200 (1L << PG_swapcache) |
3201 (1L << PG_mlocked) |
3202 (1L << PG_uptodate) |
3203 (1L << PG_active) |
3204 (1L << PG_workingset) |
3205 (1L << PG_locked) |
3206 (1L << PG_unevictable) |
3207 #ifdef CONFIG_ARCH_USES_PG_ARCH_2
3208 (1L << PG_arch_2) |
3209 #endif
3210 #ifdef CONFIG_ARCH_USES_PG_ARCH_3
3211 (1L << PG_arch_3) |
3212 #endif
3213 (1L << PG_dirty) |
3214 LRU_GEN_MASK | LRU_REFS_MASK));
3215
3216 /* ->mapping in first and second tail page is replaced by other uses */
3217 VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
3218 page_tail);
3219 new_folio->mapping = folio->mapping;
3220 new_folio->index = folio->index + tail;
3221
3222 /*
3223 * page->private should not be set in tail pages. Fix up and warn once
3224 * if private is unexpectedly set.
3225 */
3226 if (unlikely(page_tail->private)) {
3227 VM_WARN_ON_ONCE_PAGE(true, page_tail);
3228 page_tail->private = 0;
3229 }
3230 if (folio_test_swapcache(folio))
3231 new_folio->swap.val = folio->swap.val + tail;
3232
3233 /* Page flags must be visible before we make the page non-compound. */
3234 smp_wmb();
3235
3236 /*
3237 * Clear PageTail before unfreezing page refcount.
3238 *
3239 * After successful get_page_unless_zero() might follow put_page()
3240 * which needs correct compound_head().
3241 */
3242 clear_compound_head(page_tail);
3243 if (new_order) {
3244 prep_compound_page(page_tail, new_order);
3245 folio_set_large_rmappable(new_folio);
3246 }
3247
3248 /* Finally unfreeze refcount. Additional reference from page cache. */
3249 page_ref_unfreeze(page_tail,
3250 1 + ((!folio_test_anon(folio) || folio_test_swapcache(folio)) ?
3251 folio_nr_pages(new_folio) : 0));
3252
3253 if (folio_test_young(folio))
3254 folio_set_young(new_folio);
3255 if (folio_test_idle(folio))
3256 folio_set_idle(new_folio);
3257
3258 folio_xchg_last_cpupid(new_folio, folio_last_cpupid(folio));
3259
3260 /*
3261 * always add to the tail because some iterators expect new
3262 * pages to show after the currently processed elements - e.g.
3263 * migrate_pages
3264 */
3265 lru_add_page_tail(folio, page_tail, lruvec, list);
3266 }
3267
__split_huge_page(struct page * page,struct list_head * list,pgoff_t end,unsigned int new_order)3268 static void __split_huge_page(struct page *page, struct list_head *list,
3269 pgoff_t end, unsigned int new_order)
3270 {
3271 struct folio *folio = page_folio(page);
3272 struct page *head = &folio->page;
3273 struct lruvec *lruvec;
3274 struct address_space *swap_cache = NULL;
3275 unsigned long offset = 0;
3276 int i, nr_dropped = 0;
3277 unsigned int new_nr = 1 << new_order;
3278 int order = folio_order(folio);
3279 unsigned int nr = 1 << order;
3280
3281 /* complete memcg works before add pages to LRU */
3282 split_page_memcg(head, order, new_order);
3283
3284 if (folio_test_anon(folio) && folio_test_swapcache(folio)) {
3285 offset = swap_cache_index(folio->swap);
3286 swap_cache = swap_address_space(folio->swap);
3287 xa_lock(&swap_cache->i_pages);
3288 }
3289
3290 /* lock lru list/PageCompound, ref frozen by page_ref_freeze */
3291 lruvec = folio_lruvec_lock(folio);
3292
3293 folio_clear_has_hwpoisoned(folio);
3294
3295 for (i = nr - new_nr; i >= new_nr; i -= new_nr) {
3296 struct folio *tail;
3297 __split_huge_page_tail(folio, i, lruvec, list, new_order);
3298 tail = page_folio(head + i);
3299 /* Some pages can be beyond EOF: drop them from page cache */
3300 if (tail->index >= end) {
3301 if (shmem_mapping(folio->mapping))
3302 nr_dropped++;
3303 else if (folio_test_clear_dirty(tail))
3304 folio_account_cleaned(tail,
3305 inode_to_wb(folio->mapping->host));
3306 __filemap_remove_folio(tail, NULL);
3307 folio_put(tail);
3308 } else if (!folio_test_anon(folio)) {
3309 __xa_store(&folio->mapping->i_pages, tail->index,
3310 tail, 0);
3311 } else if (swap_cache) {
3312 __xa_store(&swap_cache->i_pages, offset + i,
3313 tail, 0);
3314 }
3315 }
3316
3317 if (!new_order)
3318 ClearPageCompound(head);
3319 else {
3320 struct folio *new_folio = (struct folio *)head;
3321
3322 folio_set_order(new_folio, new_order);
3323 }
3324 unlock_page_lruvec(lruvec);
3325 /* Caller disabled irqs, so they are still disabled here */
3326
3327 split_page_owner(head, order, new_order);
3328 pgalloc_tag_split(folio, order, new_order);
3329
3330 /* See comment in __split_huge_page_tail() */
3331 if (folio_test_anon(folio)) {
3332 /* Additional pin to swap cache */
3333 if (folio_test_swapcache(folio)) {
3334 folio_ref_add(folio, 1 + new_nr);
3335 xa_unlock(&swap_cache->i_pages);
3336 } else {
3337 folio_ref_inc(folio);
3338 }
3339 } else {
3340 /* Additional pin to page cache */
3341 folio_ref_add(folio, 1 + new_nr);
3342 xa_unlock(&folio->mapping->i_pages);
3343 }
3344 local_irq_enable();
3345
3346 if (nr_dropped)
3347 shmem_uncharge(folio->mapping->host, nr_dropped);
3348 remap_page(folio, nr, PageAnon(head) ? RMP_USE_SHARED_ZEROPAGE : 0);
3349
3350 /*
3351 * set page to its compound_head when split to non order-0 pages, so
3352 * we can skip unlocking it below, since PG_locked is transferred to
3353 * the compound_head of the page and the caller will unlock it.
3354 */
3355 if (new_order)
3356 page = compound_head(page);
3357
3358 for (i = 0; i < nr; i += new_nr) {
3359 struct page *subpage = head + i;
3360 struct folio *new_folio = page_folio(subpage);
3361 if (subpage == page)
3362 continue;
3363 folio_unlock(new_folio);
3364
3365 /*
3366 * Subpages may be freed if there wasn't any mapping
3367 * like if add_to_swap() is running on a lru page that
3368 * had its mapping zapped. And freeing these pages
3369 * requires taking the lru_lock so we do the put_page
3370 * of the tail pages after the split is complete.
3371 */
3372 free_page_and_swap_cache(subpage);
3373 }
3374 }
3375
3376 /* Racy check whether the huge page can be split */
can_split_folio(struct folio * folio,int caller_pins,int * pextra_pins)3377 bool can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins)
3378 {
3379 int extra_pins;
3380
3381 /* Additional pins from page cache */
3382 if (folio_test_anon(folio))
3383 extra_pins = folio_test_swapcache(folio) ?
3384 folio_nr_pages(folio) : 0;
3385 else
3386 extra_pins = folio_nr_pages(folio);
3387 if (pextra_pins)
3388 *pextra_pins = extra_pins;
3389 return folio_mapcount(folio) == folio_ref_count(folio) - extra_pins -
3390 caller_pins;
3391 }
3392
3393 /*
3394 * This function splits a large folio into smaller folios of order @new_order.
3395 * @page can point to any page of the large folio to split. The split operation
3396 * does not change the position of @page.
3397 *
3398 * Prerequisites:
3399 *
3400 * 1) The caller must hold a reference on the @page's owning folio, also known
3401 * as the large folio.
3402 *
3403 * 2) The large folio must be locked.
3404 *
3405 * 3) The folio must not be pinned. Any unexpected folio references, including
3406 * GUP pins, will result in the folio not getting split; instead, the caller
3407 * will receive an -EAGAIN.
3408 *
3409 * 4) @new_order > 1, usually. Splitting to order-1 anonymous folios is not
3410 * supported for non-file-backed folios, because folio->_deferred_list, which
3411 * is used by partially mapped folios, is stored in subpage 2, but an order-1
3412 * folio only has subpages 0 and 1. File-backed order-1 folios are supported,
3413 * since they do not use _deferred_list.
3414 *
3415 * After splitting, the caller's folio reference will be transferred to @page,
3416 * resulting in a raised refcount of @page after this call. The other pages may
3417 * be freed if they are not mapped.
3418 *
3419 * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
3420 *
3421 * Pages in @new_order will inherit the mapping, flags, and so on from the
3422 * huge page.
3423 *
3424 * Returns 0 if the huge page was split successfully.
3425 *
3426 * Returns -EAGAIN if the folio has unexpected reference (e.g., GUP) or if
3427 * the folio was concurrently removed from the page cache.
3428 *
3429 * Returns -EBUSY when trying to split the huge zeropage, if the folio is
3430 * under writeback, if fs-specific folio metadata cannot currently be
3431 * released, or if some unexpected race happened (e.g., anon VMA disappeared,
3432 * truncation).
3433 *
3434 * Callers should ensure that the order respects the address space mapping
3435 * min-order if one is set for non-anonymous folios.
3436 *
3437 * Returns -EINVAL when trying to split to an order that is incompatible
3438 * with the folio. Splitting to order 0 is compatible with all folios.
3439 */
split_huge_page_to_list_to_order(struct page * page,struct list_head * list,unsigned int new_order)3440 int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
3441 unsigned int new_order)
3442 {
3443 struct folio *folio = page_folio(page);
3444 struct deferred_split *ds_queue = get_deferred_split_queue(folio);
3445 /* reset xarray order to new order after split */
3446 XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order);
3447 bool is_anon = folio_test_anon(folio);
3448 struct address_space *mapping = NULL;
3449 struct anon_vma *anon_vma = NULL;
3450 int order = folio_order(folio);
3451 int extra_pins, ret;
3452 pgoff_t end;
3453 bool is_hzp;
3454
3455 VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
3456 VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
3457
3458 if (new_order >= folio_order(folio))
3459 return -EINVAL;
3460
3461 if (is_anon) {
3462 /* order-1 is not supported for anonymous THP. */
3463 if (new_order == 1) {
3464 VM_WARN_ONCE(1, "Cannot split to order-1 folio");
3465 return -EINVAL;
3466 }
3467 } else if (new_order) {
3468 /* Split shmem folio to non-zero order not supported */
3469 if (shmem_mapping(folio->mapping)) {
3470 VM_WARN_ONCE(1,
3471 "Cannot split shmem folio to non-0 order");
3472 return -EINVAL;
3473 }
3474 /*
3475 * No split if the file system does not support large folio.
3476 * Note that we might still have THPs in such mappings due to
3477 * CONFIG_READ_ONLY_THP_FOR_FS. But in that case, the mapping
3478 * does not actually support large folios properly.
3479 */
3480 if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) &&
3481 !mapping_large_folio_support(folio->mapping)) {
3482 VM_WARN_ONCE(1,
3483 "Cannot split file folio to non-0 order");
3484 return -EINVAL;
3485 }
3486 }
3487
3488 /* Only swapping a whole PMD-mapped folio is supported */
3489 if (folio_test_swapcache(folio) && new_order)
3490 return -EINVAL;
3491
3492 is_hzp = is_huge_zero_folio(folio);
3493 if (is_hzp) {
3494 pr_warn_ratelimited("Called split_huge_page for huge zero page\n");
3495 return -EBUSY;
3496 }
3497
3498 if (folio_test_writeback(folio))
3499 return -EBUSY;
3500
3501 if (is_anon) {
3502 /*
3503 * The caller does not necessarily hold an mmap_lock that would
3504 * prevent the anon_vma disappearing so we first we take a
3505 * reference to it and then lock the anon_vma for write. This
3506 * is similar to folio_lock_anon_vma_read except the write lock
3507 * is taken to serialise against parallel split or collapse
3508 * operations.
3509 */
3510 anon_vma = folio_get_anon_vma(folio);
3511 if (!anon_vma) {
3512 ret = -EBUSY;
3513 goto out;
3514 }
3515 end = -1;
3516 mapping = NULL;
3517 anon_vma_lock_write(anon_vma);
3518 } else {
3519 unsigned int min_order;
3520 gfp_t gfp;
3521
3522 mapping = folio->mapping;
3523
3524 /* Truncated ? */
3525 if (!mapping) {
3526 ret = -EBUSY;
3527 goto out;
3528 }
3529
3530 min_order = mapping_min_folio_order(folio->mapping);
3531 if (new_order < min_order) {
3532 VM_WARN_ONCE(1, "Cannot split mapped folio below min-order: %u",
3533 min_order);
3534 ret = -EINVAL;
3535 goto out;
3536 }
3537
3538 gfp = current_gfp_context(mapping_gfp_mask(mapping) &
3539 GFP_RECLAIM_MASK);
3540
3541 if (!filemap_release_folio(folio, gfp)) {
3542 ret = -EBUSY;
3543 goto out;
3544 }
3545
3546 xas_split_alloc(&xas, folio, folio_order(folio), gfp);
3547 if (xas_error(&xas)) {
3548 ret = xas_error(&xas);
3549 goto out;
3550 }
3551
3552 anon_vma = NULL;
3553 i_mmap_lock_read(mapping);
3554
3555 /*
3556 *__split_huge_page() may need to trim off pages beyond EOF:
3557 * but on 32-bit, i_size_read() takes an irq-unsafe seqlock,
3558 * which cannot be nested inside the page tree lock. So note
3559 * end now: i_size itself may be changed at any moment, but
3560 * folio lock is good enough to serialize the trimming.
3561 */
3562 end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
3563 if (shmem_mapping(mapping))
3564 end = shmem_fallocend(mapping->host, end);
3565 }
3566
3567 /*
3568 * Racy check if we can split the page, before unmap_folio() will
3569 * split PMDs
3570 */
3571 if (!can_split_folio(folio, 1, &extra_pins)) {
3572 ret = -EAGAIN;
3573 goto out_unlock;
3574 }
3575
3576 unmap_folio(folio);
3577
3578 /* block interrupt reentry in xa_lock and spinlock */
3579 local_irq_disable();
3580 if (mapping) {
3581 /*
3582 * Check if the folio is present in page cache.
3583 * We assume all tail are present too, if folio is there.
3584 */
3585 xas_lock(&xas);
3586 xas_reset(&xas);
3587 if (xas_load(&xas) != folio)
3588 goto fail;
3589 }
3590
3591 /* Prevent deferred_split_scan() touching ->_refcount */
3592 spin_lock(&ds_queue->split_queue_lock);
3593 if (folio_ref_freeze(folio, 1 + extra_pins)) {
3594 if (folio_order(folio) > 1 &&
3595 !list_empty(&folio->_deferred_list)) {
3596 ds_queue->split_queue_len--;
3597 if (folio_test_partially_mapped(folio)) {
3598 folio_clear_partially_mapped(folio);
3599 mod_mthp_stat(folio_order(folio),
3600 MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1);
3601 }
3602 /*
3603 * Reinitialize page_deferred_list after removing the
3604 * page from the split_queue, otherwise a subsequent
3605 * split will see list corruption when checking the
3606 * page_deferred_list.
3607 */
3608 list_del_init(&folio->_deferred_list);
3609 }
3610 spin_unlock(&ds_queue->split_queue_lock);
3611 if (mapping) {
3612 int nr = folio_nr_pages(folio);
3613
3614 xas_split(&xas, folio, folio_order(folio));
3615 if (folio_test_pmd_mappable(folio) &&
3616 new_order < HPAGE_PMD_ORDER) {
3617 if (folio_test_swapbacked(folio)) {
3618 __lruvec_stat_mod_folio(folio,
3619 NR_SHMEM_THPS, -nr);
3620 } else {
3621 __lruvec_stat_mod_folio(folio,
3622 NR_FILE_THPS, -nr);
3623 filemap_nr_thps_dec(mapping);
3624 }
3625 }
3626 }
3627
3628 if (is_anon) {
3629 mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1);
3630 mod_mthp_stat(new_order, MTHP_STAT_NR_ANON, 1 << (order - new_order));
3631 }
3632 __split_huge_page(page, list, end, new_order);
3633 ret = 0;
3634 } else {
3635 spin_unlock(&ds_queue->split_queue_lock);
3636 fail:
3637 if (mapping)
3638 xas_unlock(&xas);
3639 local_irq_enable();
3640 remap_page(folio, folio_nr_pages(folio), 0);
3641 ret = -EAGAIN;
3642 }
3643
3644 out_unlock:
3645 if (anon_vma) {
3646 anon_vma_unlock_write(anon_vma);
3647 put_anon_vma(anon_vma);
3648 }
3649 if (mapping)
3650 i_mmap_unlock_read(mapping);
3651 out:
3652 xas_destroy(&xas);
3653 if (order == HPAGE_PMD_ORDER)
3654 count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
3655 count_mthp_stat(order, !ret ? MTHP_STAT_SPLIT : MTHP_STAT_SPLIT_FAILED);
3656 return ret;
3657 }
3658
min_order_for_split(struct folio * folio)3659 int min_order_for_split(struct folio *folio)
3660 {
3661 if (folio_test_anon(folio))
3662 return 0;
3663
3664 if (!folio->mapping) {
3665 if (folio_test_pmd_mappable(folio))
3666 count_vm_event(THP_SPLIT_PAGE_FAILED);
3667 return -EBUSY;
3668 }
3669
3670 return mapping_min_folio_order(folio->mapping);
3671 }
3672
split_folio_to_list(struct folio * folio,struct list_head * list)3673 int split_folio_to_list(struct folio *folio, struct list_head *list)
3674 {
3675 int ret = min_order_for_split(folio);
3676
3677 if (ret < 0)
3678 return ret;
3679
3680 return split_huge_page_to_list_to_order(&folio->page, list, ret);
3681 }
3682
3683 /*
3684 * __folio_unqueue_deferred_split() is not to be called directly:
3685 * the folio_unqueue_deferred_split() inline wrapper in mm/internal.h
3686 * limits its calls to those folios which may have a _deferred_list for
3687 * queueing THP splits, and that list is (racily observed to be) non-empty.
3688 *
3689 * It is unsafe to call folio_unqueue_deferred_split() until folio refcount is
3690 * zero: because even when split_queue_lock is held, a non-empty _deferred_list
3691 * might be in use on deferred_split_scan()'s unlocked on-stack list.
3692 *
3693 * If memory cgroups are enabled, split_queue_lock is in the mem_cgroup: it is
3694 * therefore important to unqueue deferred split before changing folio memcg.
3695 */
__folio_unqueue_deferred_split(struct folio * folio)3696 bool __folio_unqueue_deferred_split(struct folio *folio)
3697 {
3698 struct deferred_split *ds_queue;
3699 unsigned long flags;
3700 bool unqueued = false;
3701
3702 WARN_ON_ONCE(folio_ref_count(folio));
3703 WARN_ON_ONCE(!mem_cgroup_disabled() && !folio_memcg(folio));
3704
3705 ds_queue = get_deferred_split_queue(folio);
3706 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
3707 if (!list_empty(&folio->_deferred_list)) {
3708 ds_queue->split_queue_len--;
3709 if (folio_test_partially_mapped(folio)) {
3710 folio_clear_partially_mapped(folio);
3711 mod_mthp_stat(folio_order(folio),
3712 MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1);
3713 }
3714 list_del_init(&folio->_deferred_list);
3715 unqueued = true;
3716 }
3717 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
3718
3719 return unqueued; /* useful for debug warnings */
3720 }
3721
3722 /* partially_mapped=false won't clear PG_partially_mapped folio flag */
deferred_split_folio(struct folio * folio,bool partially_mapped)3723 void deferred_split_folio(struct folio *folio, bool partially_mapped)
3724 {
3725 struct deferred_split *ds_queue = get_deferred_split_queue(folio);
3726 #ifdef CONFIG_MEMCG
3727 struct mem_cgroup *memcg = folio_memcg(folio);
3728 #endif
3729 unsigned long flags;
3730
3731 /*
3732 * Order 1 folios have no space for a deferred list, but we also
3733 * won't waste much memory by not adding them to the deferred list.
3734 */
3735 if (folio_order(folio) <= 1)
3736 return;
3737
3738 if (!partially_mapped && !split_underused_thp)
3739 return;
3740
3741 /*
3742 * Exclude swapcache: originally to avoid a corrupt deferred split
3743 * queue. Nowadays that is fully prevented by mem_cgroup_swapout();
3744 * but if page reclaim is already handling the same folio, it is
3745 * unnecessary to handle it again in the shrinker, so excluding
3746 * swapcache here may still be a useful optimization.
3747 */
3748 if (folio_test_swapcache(folio))
3749 return;
3750
3751 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
3752 if (partially_mapped) {
3753 if (!folio_test_partially_mapped(folio)) {
3754 folio_set_partially_mapped(folio);
3755 if (folio_test_pmd_mappable(folio))
3756 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
3757 count_mthp_stat(folio_order(folio), MTHP_STAT_SPLIT_DEFERRED);
3758 mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, 1);
3759
3760 }
3761 } else {
3762 /* partially mapped folios cannot become non-partially mapped */
3763 VM_WARN_ON_FOLIO(folio_test_partially_mapped(folio), folio);
3764 }
3765 if (list_empty(&folio->_deferred_list)) {
3766 list_add_tail(&folio->_deferred_list, &ds_queue->split_queue);
3767 ds_queue->split_queue_len++;
3768 #ifdef CONFIG_MEMCG
3769 if (memcg)
3770 set_shrinker_bit(memcg, folio_nid(folio),
3771 deferred_split_shrinker->id);
3772 #endif
3773 }
3774 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
3775 }
3776
deferred_split_count(struct shrinker * shrink,struct shrink_control * sc)3777 static unsigned long deferred_split_count(struct shrinker *shrink,
3778 struct shrink_control *sc)
3779 {
3780 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3781 struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
3782
3783 #ifdef CONFIG_MEMCG
3784 if (sc->memcg)
3785 ds_queue = &sc->memcg->deferred_split_queue;
3786 #endif
3787 return READ_ONCE(ds_queue->split_queue_len);
3788 }
3789
thp_underused(struct folio * folio)3790 static bool thp_underused(struct folio *folio)
3791 {
3792 int num_zero_pages = 0, num_filled_pages = 0;
3793 void *kaddr;
3794 int i;
3795
3796 if (khugepaged_max_ptes_none == HPAGE_PMD_NR - 1)
3797 return false;
3798
3799 for (i = 0; i < folio_nr_pages(folio); i++) {
3800 kaddr = kmap_local_folio(folio, i * PAGE_SIZE);
3801 if (!memchr_inv(kaddr, 0, PAGE_SIZE)) {
3802 num_zero_pages++;
3803 if (num_zero_pages > khugepaged_max_ptes_none) {
3804 kunmap_local(kaddr);
3805 return true;
3806 }
3807 } else {
3808 /*
3809 * Another path for early exit once the number
3810 * of non-zero filled pages exceeds threshold.
3811 */
3812 num_filled_pages++;
3813 if (num_filled_pages >= HPAGE_PMD_NR - khugepaged_max_ptes_none) {
3814 kunmap_local(kaddr);
3815 return false;
3816 }
3817 }
3818 kunmap_local(kaddr);
3819 }
3820 return false;
3821 }
3822
deferred_split_scan(struct shrinker * shrink,struct shrink_control * sc)3823 static unsigned long deferred_split_scan(struct shrinker *shrink,
3824 struct shrink_control *sc)
3825 {
3826 struct pglist_data *pgdata = NODE_DATA(sc->nid);
3827 struct deferred_split *ds_queue = &pgdata->deferred_split_queue;
3828 unsigned long flags;
3829 LIST_HEAD(list);
3830 struct folio *folio, *next, *prev = NULL;
3831 int split = 0, removed = 0;
3832
3833 #ifdef CONFIG_MEMCG
3834 if (sc->memcg)
3835 ds_queue = &sc->memcg->deferred_split_queue;
3836 #endif
3837
3838 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
3839 /* Take pin on all head pages to avoid freeing them under us */
3840 list_for_each_entry_safe(folio, next, &ds_queue->split_queue,
3841 _deferred_list) {
3842 if (folio_try_get(folio)) {
3843 list_move(&folio->_deferred_list, &list);
3844 } else {
3845 /* We lost race with folio_put() */
3846 if (folio_test_partially_mapped(folio)) {
3847 folio_clear_partially_mapped(folio);
3848 mod_mthp_stat(folio_order(folio),
3849 MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1);
3850 }
3851 list_del_init(&folio->_deferred_list);
3852 ds_queue->split_queue_len--;
3853 }
3854 if (!--sc->nr_to_scan)
3855 break;
3856 }
3857 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
3858
3859 list_for_each_entry_safe(folio, next, &list, _deferred_list) {
3860 bool did_split = false;
3861 bool underused = false;
3862
3863 if (!folio_test_partially_mapped(folio)) {
3864 underused = thp_underused(folio);
3865 if (!underused)
3866 goto next;
3867 }
3868 if (!folio_trylock(folio))
3869 goto next;
3870 if (!split_folio(folio)) {
3871 did_split = true;
3872 if (underused)
3873 count_vm_event(THP_UNDERUSED_SPLIT_PAGE);
3874 split++;
3875 }
3876 folio_unlock(folio);
3877 next:
3878 /*
3879 * split_folio() removes folio from list on success.
3880 * Only add back to the queue if folio is partially mapped.
3881 * If thp_underused returns false, or if split_folio fails
3882 * in the case it was underused, then consider it used and
3883 * don't add it back to split_queue.
3884 */
3885 if (did_split) {
3886 ; /* folio already removed from list */
3887 } else if (!folio_test_partially_mapped(folio)) {
3888 list_del_init(&folio->_deferred_list);
3889 removed++;
3890 } else {
3891 /*
3892 * That unlocked list_del_init() above would be unsafe,
3893 * unless its folio is separated from any earlier folios
3894 * left on the list (which may be concurrently unqueued)
3895 * by one safe folio with refcount still raised.
3896 */
3897 swap(folio, prev);
3898 }
3899 if (folio)
3900 folio_put(folio);
3901 }
3902
3903 spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
3904 list_splice_tail(&list, &ds_queue->split_queue);
3905 ds_queue->split_queue_len -= removed;
3906 spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
3907
3908 if (prev)
3909 folio_put(prev);
3910
3911 /*
3912 * Stop shrinker if we didn't split any page, but the queue is empty.
3913 * This can happen if pages were freed under us.
3914 */
3915 if (!split && list_empty(&ds_queue->split_queue))
3916 return SHRINK_STOP;
3917 return split;
3918 }
3919
3920 #ifdef CONFIG_DEBUG_FS
split_huge_pages_all(void)3921 static void split_huge_pages_all(void)
3922 {
3923 struct zone *zone;
3924 struct page *page;
3925 struct folio *folio;
3926 unsigned long pfn, max_zone_pfn;
3927 unsigned long total = 0, split = 0;
3928
3929 pr_debug("Split all THPs\n");
3930 for_each_zone(zone) {
3931 if (!managed_zone(zone))
3932 continue;
3933 max_zone_pfn = zone_end_pfn(zone);
3934 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
3935 int nr_pages;
3936
3937 page = pfn_to_online_page(pfn);
3938 if (!page || PageTail(page))
3939 continue;
3940 folio = page_folio(page);
3941 if (!folio_try_get(folio))
3942 continue;
3943
3944 if (unlikely(page_folio(page) != folio))
3945 goto next;
3946
3947 if (zone != folio_zone(folio))
3948 goto next;
3949
3950 if (!folio_test_large(folio)
3951 || folio_test_hugetlb(folio)
3952 || !folio_test_lru(folio))
3953 goto next;
3954
3955 total++;
3956 folio_lock(folio);
3957 nr_pages = folio_nr_pages(folio);
3958 if (!split_folio(folio))
3959 split++;
3960 pfn += nr_pages - 1;
3961 folio_unlock(folio);
3962 next:
3963 folio_put(folio);
3964 cond_resched();
3965 }
3966 }
3967
3968 pr_debug("%lu of %lu THP split\n", split, total);
3969 }
3970
vma_not_suitable_for_thp_split(struct vm_area_struct * vma)3971 static inline bool vma_not_suitable_for_thp_split(struct vm_area_struct *vma)
3972 {
3973 return vma_is_special_huge(vma) || (vma->vm_flags & VM_IO) ||
3974 is_vm_hugetlb_page(vma);
3975 }
3976
split_huge_pages_pid(int pid,unsigned long vaddr_start,unsigned long vaddr_end,unsigned int new_order)3977 static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
3978 unsigned long vaddr_end, unsigned int new_order)
3979 {
3980 int ret = 0;
3981 struct task_struct *task;
3982 struct mm_struct *mm;
3983 unsigned long total = 0, split = 0;
3984 unsigned long addr;
3985
3986 vaddr_start &= PAGE_MASK;
3987 vaddr_end &= PAGE_MASK;
3988
3989 task = find_get_task_by_vpid(pid);
3990 if (!task) {
3991 ret = -ESRCH;
3992 goto out;
3993 }
3994
3995 /* Find the mm_struct */
3996 mm = get_task_mm(task);
3997 put_task_struct(task);
3998
3999 if (!mm) {
4000 ret = -EINVAL;
4001 goto out;
4002 }
4003
4004 pr_debug("Split huge pages in pid: %d, vaddr: [0x%lx - 0x%lx]\n",
4005 pid, vaddr_start, vaddr_end);
4006
4007 mmap_read_lock(mm);
4008 /*
4009 * always increase addr by PAGE_SIZE, since we could have a PTE page
4010 * table filled with PTE-mapped THPs, each of which is distinct.
4011 */
4012 for (addr = vaddr_start; addr < vaddr_end; addr += PAGE_SIZE) {
4013 struct vm_area_struct *vma = vma_lookup(mm, addr);
4014 struct folio_walk fw;
4015 struct folio *folio;
4016 struct address_space *mapping;
4017 unsigned int target_order = new_order;
4018
4019 if (!vma)
4020 break;
4021
4022 /* skip special VMA and hugetlb VMA */
4023 if (vma_not_suitable_for_thp_split(vma)) {
4024 addr = vma->vm_end;
4025 continue;
4026 }
4027
4028 folio = folio_walk_start(&fw, vma, addr, 0);
4029 if (!folio)
4030 continue;
4031
4032 if (!is_transparent_hugepage(folio))
4033 goto next;
4034
4035 if (!folio_test_anon(folio)) {
4036 mapping = folio->mapping;
4037 target_order = max(new_order,
4038 mapping_min_folio_order(mapping));
4039 }
4040
4041 if (target_order >= folio_order(folio))
4042 goto next;
4043
4044 total++;
4045 /*
4046 * For folios with private, split_huge_page_to_list_to_order()
4047 * will try to drop it before split and then check if the folio
4048 * can be split or not. So skip the check here.
4049 */
4050 if (!folio_test_private(folio) &&
4051 !can_split_folio(folio, 0, NULL))
4052 goto next;
4053
4054 if (!folio_trylock(folio))
4055 goto next;
4056 folio_get(folio);
4057 folio_walk_end(&fw, vma);
4058
4059 if (!folio_test_anon(folio) && folio->mapping != mapping)
4060 goto unlock;
4061
4062 if (!split_folio_to_order(folio, target_order))
4063 split++;
4064
4065 unlock:
4066
4067 folio_unlock(folio);
4068 folio_put(folio);
4069
4070 cond_resched();
4071 continue;
4072 next:
4073 folio_walk_end(&fw, vma);
4074 cond_resched();
4075 }
4076 mmap_read_unlock(mm);
4077 mmput(mm);
4078
4079 pr_debug("%lu of %lu THP split\n", split, total);
4080
4081 out:
4082 return ret;
4083 }
4084
split_huge_pages_in_file(const char * file_path,pgoff_t off_start,pgoff_t off_end,unsigned int new_order)4085 static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
4086 pgoff_t off_end, unsigned int new_order)
4087 {
4088 struct filename *file;
4089 struct file *candidate;
4090 struct address_space *mapping;
4091 int ret = -EINVAL;
4092 pgoff_t index;
4093 int nr_pages = 1;
4094 unsigned long total = 0, split = 0;
4095 unsigned int min_order;
4096 unsigned int target_order;
4097
4098 file = getname_kernel(file_path);
4099 if (IS_ERR(file))
4100 return ret;
4101
4102 candidate = file_open_name(file, O_RDONLY, 0);
4103 if (IS_ERR(candidate))
4104 goto out;
4105
4106 pr_debug("split file-backed THPs in file: %s, page offset: [0x%lx - 0x%lx]\n",
4107 file_path, off_start, off_end);
4108
4109 mapping = candidate->f_mapping;
4110 min_order = mapping_min_folio_order(mapping);
4111 target_order = max(new_order, min_order);
4112
4113 for (index = off_start; index < off_end; index += nr_pages) {
4114 struct folio *folio = filemap_get_folio(mapping, index);
4115
4116 nr_pages = 1;
4117 if (IS_ERR(folio))
4118 continue;
4119
4120 if (!folio_test_large(folio))
4121 goto next;
4122
4123 total++;
4124 nr_pages = folio_nr_pages(folio);
4125
4126 if (target_order >= folio_order(folio))
4127 goto next;
4128
4129 if (!folio_trylock(folio))
4130 goto next;
4131
4132 if (folio->mapping != mapping)
4133 goto unlock;
4134
4135 if (!split_folio_to_order(folio, target_order))
4136 split++;
4137
4138 unlock:
4139 folio_unlock(folio);
4140 next:
4141 folio_put(folio);
4142 cond_resched();
4143 }
4144
4145 filp_close(candidate, NULL);
4146 ret = 0;
4147
4148 pr_debug("%lu of %lu file-backed THP split\n", split, total);
4149 out:
4150 putname(file);
4151 return ret;
4152 }
4153
4154 #define MAX_INPUT_BUF_SZ 255
4155
split_huge_pages_write(struct file * file,const char __user * buf,size_t count,loff_t * ppops)4156 static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
4157 size_t count, loff_t *ppops)
4158 {
4159 static DEFINE_MUTEX(split_debug_mutex);
4160 ssize_t ret;
4161 /*
4162 * hold pid, start_vaddr, end_vaddr, new_order or
4163 * file_path, off_start, off_end, new_order
4164 */
4165 char input_buf[MAX_INPUT_BUF_SZ];
4166 int pid;
4167 unsigned long vaddr_start, vaddr_end;
4168 unsigned int new_order = 0;
4169
4170 ret = mutex_lock_interruptible(&split_debug_mutex);
4171 if (ret)
4172 return ret;
4173
4174 ret = -EFAULT;
4175
4176 memset(input_buf, 0, MAX_INPUT_BUF_SZ);
4177 if (copy_from_user(input_buf, buf, min_t(size_t, count, MAX_INPUT_BUF_SZ)))
4178 goto out;
4179
4180 input_buf[MAX_INPUT_BUF_SZ - 1] = '\0';
4181
4182 if (input_buf[0] == '/') {
4183 char *tok;
4184 char *tok_buf = input_buf;
4185 char file_path[MAX_INPUT_BUF_SZ];
4186 pgoff_t off_start = 0, off_end = 0;
4187 size_t input_len = strlen(input_buf);
4188
4189 tok = strsep(&tok_buf, ",");
4190 if (tok && tok_buf) {
4191 strscpy(file_path, tok);
4192 } else {
4193 ret = -EINVAL;
4194 goto out;
4195 }
4196
4197 ret = sscanf(tok_buf, "0x%lx,0x%lx,%d", &off_start,
4198 &off_end, &new_order);
4199 if (ret != 2 && ret != 3) {
4200 ret = -EINVAL;
4201 goto out;
4202 }
4203 ret = split_huge_pages_in_file(file_path, off_start, off_end, new_order);
4204 if (!ret)
4205 ret = input_len;
4206
4207 goto out;
4208 }
4209
4210 ret = sscanf(input_buf, "%d,0x%lx,0x%lx,%d", &pid, &vaddr_start, &vaddr_end, &new_order);
4211 if (ret == 1 && pid == 1) {
4212 split_huge_pages_all();
4213 ret = strlen(input_buf);
4214 goto out;
4215 } else if (ret != 3 && ret != 4) {
4216 ret = -EINVAL;
4217 goto out;
4218 }
4219
4220 ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end, new_order);
4221 if (!ret)
4222 ret = strlen(input_buf);
4223 out:
4224 mutex_unlock(&split_debug_mutex);
4225 return ret;
4226
4227 }
4228
4229 static const struct file_operations split_huge_pages_fops = {
4230 .owner = THIS_MODULE,
4231 .write = split_huge_pages_write,
4232 };
4233
split_huge_pages_debugfs(void)4234 static int __init split_huge_pages_debugfs(void)
4235 {
4236 debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
4237 &split_huge_pages_fops);
4238 return 0;
4239 }
4240 late_initcall(split_huge_pages_debugfs);
4241 #endif
4242
4243 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
set_pmd_migration_entry(struct page_vma_mapped_walk * pvmw,struct page * page)4244 int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
4245 struct page *page)
4246 {
4247 struct folio *folio = page_folio(page);
4248 struct vm_area_struct *vma = pvmw->vma;
4249 struct mm_struct *mm = vma->vm_mm;
4250 unsigned long address = pvmw->address;
4251 bool anon_exclusive;
4252 pmd_t pmdval;
4253 swp_entry_t entry;
4254 pmd_t pmdswp;
4255
4256 if (!(pvmw->pmd && !pvmw->pte))
4257 return 0;
4258
4259 flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
4260 pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
4261
4262 /* See folio_try_share_anon_rmap_pmd(): invalidate PMD first. */
4263 anon_exclusive = folio_test_anon(folio) && PageAnonExclusive(page);
4264 if (anon_exclusive && folio_try_share_anon_rmap_pmd(folio, page)) {
4265 set_pmd_at(mm, address, pvmw->pmd, pmdval);
4266 return -EBUSY;
4267 }
4268
4269 if (pmd_dirty(pmdval))
4270 folio_mark_dirty(folio);
4271 if (pmd_write(pmdval))
4272 entry = make_writable_migration_entry(page_to_pfn(page));
4273 else if (anon_exclusive)
4274 entry = make_readable_exclusive_migration_entry(page_to_pfn(page));
4275 else
4276 entry = make_readable_migration_entry(page_to_pfn(page));
4277 if (pmd_young(pmdval))
4278 entry = make_migration_entry_young(entry);
4279 if (pmd_dirty(pmdval))
4280 entry = make_migration_entry_dirty(entry);
4281 pmdswp = swp_entry_to_pmd(entry);
4282 if (pmd_soft_dirty(pmdval))
4283 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
4284 if (pmd_uffd_wp(pmdval))
4285 pmdswp = pmd_swp_mkuffd_wp(pmdswp);
4286 set_pmd_at(mm, address, pvmw->pmd, pmdswp);
4287 folio_remove_rmap_pmd(folio, page, vma);
4288 folio_put(folio);
4289 trace_set_migration_pmd(address, pmd_val(pmdswp));
4290
4291 return 0;
4292 }
4293
remove_migration_pmd(struct page_vma_mapped_walk * pvmw,struct page * new)4294 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
4295 {
4296 struct folio *folio = page_folio(new);
4297 struct vm_area_struct *vma = pvmw->vma;
4298 struct mm_struct *mm = vma->vm_mm;
4299 unsigned long address = pvmw->address;
4300 unsigned long haddr = address & HPAGE_PMD_MASK;
4301 pmd_t pmde;
4302 swp_entry_t entry;
4303
4304 if (!(pvmw->pmd && !pvmw->pte))
4305 return;
4306
4307 entry = pmd_to_swp_entry(*pvmw->pmd);
4308 folio_get(folio);
4309 pmde = mk_huge_pmd(new, READ_ONCE(vma->vm_page_prot));
4310 if (pmd_swp_soft_dirty(*pvmw->pmd))
4311 pmde = pmd_mksoft_dirty(pmde);
4312 if (is_writable_migration_entry(entry))
4313 pmde = pmd_mkwrite(pmde, vma);
4314 if (pmd_swp_uffd_wp(*pvmw->pmd))
4315 pmde = pmd_mkuffd_wp(pmde);
4316 if (!is_migration_entry_young(entry))
4317 pmde = pmd_mkold(pmde);
4318 /* NOTE: this may contain setting soft-dirty on some archs */
4319 if (folio_test_dirty(folio) && is_migration_entry_dirty(entry))
4320 pmde = pmd_mkdirty(pmde);
4321
4322 if (folio_test_anon(folio)) {
4323 rmap_t rmap_flags = RMAP_NONE;
4324
4325 if (!is_readable_migration_entry(entry))
4326 rmap_flags |= RMAP_EXCLUSIVE;
4327
4328 folio_add_anon_rmap_pmd(folio, new, vma, haddr, rmap_flags);
4329 } else {
4330 folio_add_file_rmap_pmd(folio, new, vma);
4331 }
4332 VM_BUG_ON(pmd_write(pmde) && folio_test_anon(folio) && !PageAnonExclusive(new));
4333 set_pmd_at(mm, haddr, pvmw->pmd, pmde);
4334
4335 /* No need to invalidate - it was non-present before */
4336 update_mmu_cache_pmd(vma, address, pvmw->pmd);
4337 trace_remove_migration_pmd(address, pmd_val(pmde));
4338 }
4339 #endif
4340