~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/mm/huge_memory.c

Version: ~ [ linux-5.16 ] ~ [ linux-5.15.13 ] ~ [ linux-5.14.21 ] ~ [ linux-5.13.19 ] ~ [ linux-5.12.19 ] ~ [ linux-5.11.22 ] ~ [ linux-5.10.90 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.170 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.224 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.261 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.296 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.298 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /*
  2  *  Copyright (C) 2009  Red Hat, Inc.
  3  *
  4  *  This work is licensed under the terms of the GNU GPL, version 2. See
  5  *  the COPYING file in the top-level directory.
  6  */
  7 
  8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  9 
 10 #include <linux/mm.h>
 11 #include <linux/sched.h>
 12 #include <linux/sched/coredump.h>
 13 #include <linux/sched/numa_balancing.h>
 14 #include <linux/highmem.h>
 15 #include <linux/hugetlb.h>
 16 #include <linux/mmu_notifier.h>
 17 #include <linux/rmap.h>
 18 #include <linux/swap.h>
 19 #include <linux/shrinker.h>
 20 #include <linux/mm_inline.h>
 21 #include <linux/swapops.h>
 22 #include <linux/dax.h>
 23 #include <linux/khugepaged.h>
 24 #include <linux/freezer.h>
 25 #include <linux/pfn_t.h>
 26 #include <linux/mman.h>
 27 #include <linux/memremap.h>
 28 #include <linux/pagemap.h>
 29 #include <linux/debugfs.h>
 30 #include <linux/migrate.h>
 31 #include <linux/hashtable.h>
 32 #include <linux/userfaultfd_k.h>
 33 #include <linux/page_idle.h>
 34 #include <linux/shmem_fs.h>
 35 #include <linux/oom.h>
 36 
 37 #include <asm/tlb.h>
 38 #include <asm/pgalloc.h>
 39 #include "internal.h"
 40 
 41 /*
 42  * By default, transparent hugepage support is disabled in order to avoid
 43  * risking an increased memory footprint for applications that are not
 44  * guaranteed to benefit from it. When transparent hugepage support is
 45  * enabled, it is for all mappings, and khugepaged scans all mappings.
 46  * Defrag is invoked by khugepaged hugepage allocations and by page faults
 47  * for all hugepage allocations.
 48  */
 49 unsigned long transparent_hugepage_flags __read_mostly =
 50 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
 51         (1<<TRANSPARENT_HUGEPAGE_FLAG)|
 52 #endif
 53 #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
 54         (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
 55 #endif
 56         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG)|
 57         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
 58         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
 59 
 60 static struct shrinker deferred_split_shrinker;
 61 
 62 static atomic_t huge_zero_refcount;
 63 struct page *huge_zero_page __read_mostly;
 64 
 65 static struct page *get_huge_zero_page(void)
 66 {
 67         struct page *zero_page;
 68 retry:
 69         if (likely(atomic_inc_not_zero(&huge_zero_refcount)))
 70                 return READ_ONCE(huge_zero_page);
 71 
 72         zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
 73                         HPAGE_PMD_ORDER);
 74         if (!zero_page) {
 75                 count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED);
 76                 return NULL;
 77         }
 78         count_vm_event(THP_ZERO_PAGE_ALLOC);
 79         preempt_disable();
 80         if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
 81                 preempt_enable();
 82                 __free_pages(zero_page, compound_order(zero_page));
 83                 goto retry;
 84         }
 85 
 86         /* We take additional reference here. It will be put back by shrinker */
 87         atomic_set(&huge_zero_refcount, 2);
 88         preempt_enable();
 89         return READ_ONCE(huge_zero_page);
 90 }
 91 
 92 static void put_huge_zero_page(void)
 93 {
 94         /*
 95          * Counter should never go to zero here. Only shrinker can put
 96          * last reference.
 97          */
 98         BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
 99 }
100 
101 struct page *mm_get_huge_zero_page(struct mm_struct *mm)
102 {
103         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
104                 return READ_ONCE(huge_zero_page);
105 
106         if (!get_huge_zero_page())
107                 return NULL;
108 
109         if (test_and_set_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
110                 put_huge_zero_page();
111 
112         return READ_ONCE(huge_zero_page);
113 }
114 
115 void mm_put_huge_zero_page(struct mm_struct *mm)
116 {
117         if (test_bit(MMF_HUGE_ZERO_PAGE, &mm->flags))
118                 put_huge_zero_page();
119 }
120 
121 static unsigned long shrink_huge_zero_page_count(struct shrinker *shrink,
122                                         struct shrink_control *sc)
123 {
124         /* we can free zero page only if last reference remains */
125         return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0;
126 }
127 
128 static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
129                                        struct shrink_control *sc)
130 {
131         if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
132                 struct page *zero_page = xchg(&huge_zero_page, NULL);
133                 BUG_ON(zero_page == NULL);
134                 __free_pages(zero_page, compound_order(zero_page));
135                 return HPAGE_PMD_NR;
136         }
137 
138         return 0;
139 }
140 
141 static struct shrinker huge_zero_page_shrinker = {
142         .count_objects = shrink_huge_zero_page_count,
143         .scan_objects = shrink_huge_zero_page_scan,
144         .seeks = DEFAULT_SEEKS,
145 };
146 
147 #ifdef CONFIG_SYSFS
148 static ssize_t enabled_show(struct kobject *kobj,
149                             struct kobj_attribute *attr, char *buf)
150 {
151         if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags))
152                 return sprintf(buf, "[always] madvise never\n");
153         else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags))
154                 return sprintf(buf, "always [madvise] never\n");
155         else
156                 return sprintf(buf, "always madvise [never]\n");
157 }
158 
159 static ssize_t enabled_store(struct kobject *kobj,
160                              struct kobj_attribute *attr,
161                              const char *buf, size_t count)
162 {
163         ssize_t ret = count;
164 
165         if (!memcmp("always", buf,
166                     min(sizeof("always")-1, count))) {
167                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
168                 set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
169         } else if (!memcmp("madvise", buf,
170                            min(sizeof("madvise")-1, count))) {
171                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
172                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
173         } else if (!memcmp("never", buf,
174                            min(sizeof("never")-1, count))) {
175                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags);
176                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags);
177         } else
178                 ret = -EINVAL;
179 
180         if (ret > 0) {
181                 int err = start_stop_khugepaged();
182                 if (err)
183                         ret = err;
184         }
185         return ret;
186 }
187 static struct kobj_attribute enabled_attr =
188         __ATTR(enabled, 0644, enabled_show, enabled_store);
189 
190 ssize_t single_hugepage_flag_show(struct kobject *kobj,
191                                 struct kobj_attribute *attr, char *buf,
192                                 enum transparent_hugepage_flag flag)
193 {
194         return sprintf(buf, "%d\n",
195                        !!test_bit(flag, &transparent_hugepage_flags));
196 }
197 
198 ssize_t single_hugepage_flag_store(struct kobject *kobj,
199                                  struct kobj_attribute *attr,
200                                  const char *buf, size_t count,
201                                  enum transparent_hugepage_flag flag)
202 {
203         unsigned long value;
204         int ret;
205 
206         ret = kstrtoul(buf, 10, &value);
207         if (ret < 0)
208                 return ret;
209         if (value > 1)
210                 return -EINVAL;
211 
212         if (value)
213                 set_bit(flag, &transparent_hugepage_flags);
214         else
215                 clear_bit(flag, &transparent_hugepage_flags);
216 
217         return count;
218 }
219 
220 static ssize_t defrag_show(struct kobject *kobj,
221                            struct kobj_attribute *attr, char *buf)
222 {
223         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
224                 return sprintf(buf, "[always] defer defer+madvise madvise never\n");
225         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
226                 return sprintf(buf, "always [defer] defer+madvise madvise never\n");
227         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
228                 return sprintf(buf, "always defer [defer+madvise] madvise never\n");
229         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
230                 return sprintf(buf, "always defer defer+madvise [madvise] never\n");
231         return sprintf(buf, "always defer defer+madvise madvise [never]\n");
232 }
233 
234 static ssize_t defrag_store(struct kobject *kobj,
235                             struct kobj_attribute *attr,
236                             const char *buf, size_t count)
237 {
238         if (!memcmp("always", buf,
239                     min(sizeof("always")-1, count))) {
240                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
241                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
242                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
243                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
244         } else if (!memcmp("defer+madvise", buf,
245                     min(sizeof("defer+madvise")-1, count))) {
246                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
247                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
248                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
249                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
250         } else if (!memcmp("defer", buf,
251                     min(sizeof("defer")-1, count))) {
252                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
253                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
254                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
255                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
256         } else if (!memcmp("madvise", buf,
257                            min(sizeof("madvise")-1, count))) {
258                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
259                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
260                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
261                 set_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
262         } else if (!memcmp("never", buf,
263                            min(sizeof("never")-1, count))) {
264                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags);
265                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags);
266                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags);
267                 clear_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags);
268         } else
269                 return -EINVAL;
270 
271         return count;
272 }
273 static struct kobj_attribute defrag_attr =
274         __ATTR(defrag, 0644, defrag_show, defrag_store);
275 
276 static ssize_t use_zero_page_show(struct kobject *kobj,
277                 struct kobj_attribute *attr, char *buf)
278 {
279         return single_hugepage_flag_show(kobj, attr, buf,
280                                 TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
281 }
282 static ssize_t use_zero_page_store(struct kobject *kobj,
283                 struct kobj_attribute *attr, const char *buf, size_t count)
284 {
285         return single_hugepage_flag_store(kobj, attr, buf, count,
286                                  TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
287 }
288 static struct kobj_attribute use_zero_page_attr =
289         __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store);
290 
291 static ssize_t hpage_pmd_size_show(struct kobject *kobj,
292                 struct kobj_attribute *attr, char *buf)
293 {
294         return sprintf(buf, "%lu\n", HPAGE_PMD_SIZE);
295 }
296 static struct kobj_attribute hpage_pmd_size_attr =
297         __ATTR_RO(hpage_pmd_size);
298 
299 #ifdef CONFIG_DEBUG_VM
300 static ssize_t debug_cow_show(struct kobject *kobj,
301                                 struct kobj_attribute *attr, char *buf)
302 {
303         return single_hugepage_flag_show(kobj, attr, buf,
304                                 TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
305 }
306 static ssize_t debug_cow_store(struct kobject *kobj,
307                                struct kobj_attribute *attr,
308                                const char *buf, size_t count)
309 {
310         return single_hugepage_flag_store(kobj, attr, buf, count,
311                                  TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG);
312 }
313 static struct kobj_attribute debug_cow_attr =
314         __ATTR(debug_cow, 0644, debug_cow_show, debug_cow_store);
315 #endif /* CONFIG_DEBUG_VM */
316 
317 static struct attribute *hugepage_attr[] = {
318         &enabled_attr.attr,
319         &defrag_attr.attr,
320         &use_zero_page_attr.attr,
321         &hpage_pmd_size_attr.attr,
322 #if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
323         &shmem_enabled_attr.attr,
324 #endif
325 #ifdef CONFIG_DEBUG_VM
326         &debug_cow_attr.attr,
327 #endif
328         NULL,
329 };
330 
331 static const struct attribute_group hugepage_attr_group = {
332         .attrs = hugepage_attr,
333 };
334 
335 static int __init hugepage_init_sysfs(struct kobject **hugepage_kobj)
336 {
337         int err;
338 
339         *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj);
340         if (unlikely(!*hugepage_kobj)) {
341                 pr_err("failed to create transparent hugepage kobject\n");
342                 return -ENOMEM;
343         }
344 
345         err = sysfs_create_group(*hugepage_kobj, &hugepage_attr_group);
346         if (err) {
347                 pr_err("failed to register transparent hugepage group\n");
348                 goto delete_obj;
349         }
350 
351         err = sysfs_create_group(*hugepage_kobj, &khugepaged_attr_group);
352         if (err) {
353                 pr_err("failed to register transparent hugepage group\n");
354                 goto remove_hp_group;
355         }
356 
357         return 0;
358 
359 remove_hp_group:
360         sysfs_remove_group(*hugepage_kobj, &hugepage_attr_group);
361 delete_obj:
362         kobject_put(*hugepage_kobj);
363         return err;
364 }
365 
366 static void __init hugepage_exit_sysfs(struct kobject *hugepage_kobj)
367 {
368         sysfs_remove_group(hugepage_kobj, &khugepaged_attr_group);
369         sysfs_remove_group(hugepage_kobj, &hugepage_attr_group);
370         kobject_put(hugepage_kobj);
371 }
372 #else
373 static inline int hugepage_init_sysfs(struct kobject **hugepage_kobj)
374 {
375         return 0;
376 }
377 
378 static inline void hugepage_exit_sysfs(struct kobject *hugepage_kobj)
379 {
380 }
381 #endif /* CONFIG_SYSFS */
382 
383 static int __init hugepage_init(void)
384 {
385         int err;
386         struct kobject *hugepage_kobj;
387 
388         if (!has_transparent_hugepage()) {
389                 transparent_hugepage_flags = 0;
390                 return -EINVAL;
391         }
392 
393         /*
394          * hugepages can't be allocated by the buddy allocator
395          */
396         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER);
397         /*
398          * we use page->mapping and page->index in second tail page
399          * as list_head: assuming THP order >= 2
400          */
401         MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2);
402 
403         err = hugepage_init_sysfs(&hugepage_kobj);
404         if (err)
405                 goto err_sysfs;
406 
407         err = khugepaged_init();
408         if (err)
409                 goto err_slab;
410 
411         err = register_shrinker(&huge_zero_page_shrinker);
412         if (err)
413                 goto err_hzp_shrinker;
414         err = register_shrinker(&deferred_split_shrinker);
415         if (err)
416                 goto err_split_shrinker;
417 
418         /*
419          * By default disable transparent hugepages on smaller systems,
420          * where the extra memory used could hurt more than TLB overhead
421          * is likely to save.  The admin can still enable it through /sys.
422          */
423         if (totalram_pages < (512 << (20 - PAGE_SHIFT))) {
424                 transparent_hugepage_flags = 0;
425                 return 0;
426         }
427 
428         err = start_stop_khugepaged();
429         if (err)
430                 goto err_khugepaged;
431 
432         return 0;
433 err_khugepaged:
434         unregister_shrinker(&deferred_split_shrinker);
435 err_split_shrinker:
436         unregister_shrinker(&huge_zero_page_shrinker);
437 err_hzp_shrinker:
438         khugepaged_destroy();
439 err_slab:
440         hugepage_exit_sysfs(hugepage_kobj);
441 err_sysfs:
442         return err;
443 }
444 subsys_initcall(hugepage_init);
445 
446 static int __init setup_transparent_hugepage(char *str)
447 {
448         int ret = 0;
449         if (!str)
450                 goto out;
451         if (!strcmp(str, "always")) {
452                 set_bit(TRANSPARENT_HUGEPAGE_FLAG,
453                         &transparent_hugepage_flags);
454                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
455                           &transparent_hugepage_flags);
456                 ret = 1;
457         } else if (!strcmp(str, "madvise")) {
458                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
459                           &transparent_hugepage_flags);
460                 set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
461                         &transparent_hugepage_flags);
462                 ret = 1;
463         } else if (!strcmp(str, "never")) {
464                 clear_bit(TRANSPARENT_HUGEPAGE_FLAG,
465                           &transparent_hugepage_flags);
466                 clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG,
467                           &transparent_hugepage_flags);
468                 ret = 1;
469         }
470 out:
471         if (!ret)
472                 pr_warn("transparent_hugepage= cannot parse, ignored\n");
473         return ret;
474 }
475 __setup("transparent_hugepage=", setup_transparent_hugepage);
476 
477 pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
478 {
479         if (likely(vma->vm_flags & VM_WRITE))
480                 pmd = pmd_mkwrite(pmd);
481         return pmd;
482 }
483 
484 static inline struct list_head *page_deferred_list(struct page *page)
485 {
486         /*
487          * ->lru in the tail pages is occupied by compound_head.
488          * Let's use ->mapping + ->index in the second tail page as list_head.
489          */
490         return (struct list_head *)&page[2].mapping;
491 }
492 
493 void prep_transhuge_page(struct page *page)
494 {
495         /*
496          * we use page->mapping and page->indexlru in second tail page
497          * as list_head: assuming THP order >= 2
498          */
499 
500         INIT_LIST_HEAD(page_deferred_list(page));
501         set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
502 }
503 
504 unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
505                 loff_t off, unsigned long flags, unsigned long size)
506 {
507         unsigned long addr;
508         loff_t off_end = off + len;
509         loff_t off_align = round_up(off, size);
510         unsigned long len_pad;
511 
512         if (off_end <= off_align || (off_end - off_align) < size)
513                 return 0;
514 
515         len_pad = len + size;
516         if (len_pad < len || (off + len_pad) < off)
517                 return 0;
518 
519         addr = current->mm->get_unmapped_area(filp, 0, len_pad,
520                                               off >> PAGE_SHIFT, flags);
521         if (IS_ERR_VALUE(addr))
522                 return 0;
523 
524         addr += (off - addr) & (size - 1);
525         return addr;
526 }
527 
528 unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
529                 unsigned long len, unsigned long pgoff, unsigned long flags)
530 {
531         loff_t off = (loff_t)pgoff << PAGE_SHIFT;
532 
533         if (addr)
534                 goto out;
535         if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
536                 goto out;
537 
538         addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
539         if (addr)
540                 return addr;
541 
542  out:
543         return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
544 }
545 EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
546 
547 static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,
548                 gfp_t gfp)
549 {
550         struct vm_area_struct *vma = vmf->vma;
551         struct mem_cgroup *memcg;
552         pgtable_t pgtable;
553         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
554         int ret = 0;
555 
556         VM_BUG_ON_PAGE(!PageCompound(page), page);
557 
558         if (mem_cgroup_try_charge(page, vma->vm_mm, gfp | __GFP_NORETRY, &memcg,
559                                   true)) {
560                 put_page(page);
561                 count_vm_event(THP_FAULT_FALLBACK);
562                 return VM_FAULT_FALLBACK;
563         }
564 
565         pgtable = pte_alloc_one(vma->vm_mm, haddr);
566         if (unlikely(!pgtable)) {
567                 ret = VM_FAULT_OOM;
568                 goto release;
569         }
570 
571         clear_huge_page(page, vmf->address, HPAGE_PMD_NR);
572         /*
573          * The memory barrier inside __SetPageUptodate makes sure that
574          * clear_huge_page writes become visible before the set_pmd_at()
575          * write.
576          */
577         __SetPageUptodate(page);
578 
579         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
580         if (unlikely(!pmd_none(*vmf->pmd))) {
581                 goto unlock_release;
582         } else {
583                 pmd_t entry;
584 
585                 ret = check_stable_address_space(vma->vm_mm);
586                 if (ret)
587                         goto unlock_release;
588 
589                 /* Deliver the page fault to userland */
590                 if (userfaultfd_missing(vma)) {
591                         int ret;
592 
593                         spin_unlock(vmf->ptl);
594                         mem_cgroup_cancel_charge(page, memcg, true);
595                         put_page(page);
596                         pte_free(vma->vm_mm, pgtable);
597                         ret = handle_userfault(vmf, VM_UFFD_MISSING);
598                         VM_BUG_ON(ret & VM_FAULT_FALLBACK);
599                         return ret;
600                 }
601 
602                 entry = mk_huge_pmd(page, vma->vm_page_prot);
603                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
604                 page_add_new_anon_rmap(page, vma, haddr, true);
605                 mem_cgroup_commit_charge(page, memcg, false, true);
606                 lru_cache_add_active_or_unevictable(page, vma);
607                 pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
608                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
609                 add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
610                 mm_inc_nr_ptes(vma->vm_mm);
611                 spin_unlock(vmf->ptl);
612                 count_vm_event(THP_FAULT_ALLOC);
613         }
614 
615         return 0;
616 unlock_release:
617         spin_unlock(vmf->ptl);
618 release:
619         if (pgtable)
620                 pte_free(vma->vm_mm, pgtable);
621         mem_cgroup_cancel_charge(page, memcg, true);
622         put_page(page);
623         return ret;
624 
625 }
626 
627 /*
628  * always: directly stall for all thp allocations
629  * defer: wake kswapd and fail if not immediately available
630  * defer+madvise: wake kswapd and directly stall for MADV_HUGEPAGE, otherwise
631  *                fail if not immediately available
632  * madvise: directly stall for MADV_HUGEPAGE, otherwise fail if not immediately
633  *          available
634  * never: never stall for any thp allocation
635  */
636 static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
637 {
638         const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
639 
640         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
641                 return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
642         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
643                 return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
644         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
645                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
646                                                              __GFP_KSWAPD_RECLAIM);
647         if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
648                 return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
649                                                              0);
650         return GFP_TRANSHUGE_LIGHT;
651 }
652 
653 /* Caller must hold page table lock. */
654 static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
655                 struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd,
656                 struct page *zero_page)
657 {
658         pmd_t entry;
659         if (!pmd_none(*pmd))
660                 return false;
661         entry = mk_pmd(zero_page, vma->vm_page_prot);
662         entry = pmd_mkhuge(entry);
663         if (pgtable)
664                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
665         set_pmd_at(mm, haddr, pmd, entry);
666         mm_inc_nr_ptes(mm);
667         return true;
668 }
669 
670 int do_huge_pmd_anonymous_page(struct vm_fault *vmf)
671 {
672         struct vm_area_struct *vma = vmf->vma;
673         gfp_t gfp;
674         struct page *page;
675         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
676 
677         if (haddr < vma->vm_start || haddr + HPAGE_PMD_SIZE > vma->vm_end)
678                 return VM_FAULT_FALLBACK;
679         if (unlikely(anon_vma_prepare(vma)))
680                 return VM_FAULT_OOM;
681         if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
682                 return VM_FAULT_OOM;
683         if (!(vmf->flags & FAULT_FLAG_WRITE) &&
684                         !mm_forbids_zeropage(vma->vm_mm) &&
685                         transparent_hugepage_use_zero_page()) {
686                 pgtable_t pgtable;
687                 struct page *zero_page;
688                 bool set;
689                 int ret;
690                 pgtable = pte_alloc_one(vma->vm_mm, haddr);
691                 if (unlikely(!pgtable))
692                         return VM_FAULT_OOM;
693                 zero_page = mm_get_huge_zero_page(vma->vm_mm);
694                 if (unlikely(!zero_page)) {
695                         pte_free(vma->vm_mm, pgtable);
696                         count_vm_event(THP_FAULT_FALLBACK);
697                         return VM_FAULT_FALLBACK;
698                 }
699                 vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
700                 ret = 0;
701                 set = false;
702                 if (pmd_none(*vmf->pmd)) {
703                         ret = check_stable_address_space(vma->vm_mm);
704                         if (ret) {
705                                 spin_unlock(vmf->ptl);
706                         } else if (userfaultfd_missing(vma)) {
707                                 spin_unlock(vmf->ptl);
708                                 ret = handle_userfault(vmf, VM_UFFD_MISSING);
709                                 VM_BUG_ON(ret & VM_FAULT_FALLBACK);
710                         } else {
711                                 set_huge_zero_page(pgtable, vma->vm_mm, vma,
712                                                    haddr, vmf->pmd, zero_page);
713                                 spin_unlock(vmf->ptl);
714                                 set = true;
715                         }
716                 } else
717                         spin_unlock(vmf->ptl);
718                 if (!set)
719                         pte_free(vma->vm_mm, pgtable);
720                 return ret;
721         }
722         gfp = alloc_hugepage_direct_gfpmask(vma);
723         page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
724         if (unlikely(!page)) {
725                 count_vm_event(THP_FAULT_FALLBACK);
726                 return VM_FAULT_FALLBACK;
727         }
728         prep_transhuge_page(page);
729         return __do_huge_pmd_anonymous_page(vmf, page, gfp);
730 }
731 
732 static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
733                 pmd_t *pmd, pfn_t pfn, pgprot_t prot, bool write,
734                 pgtable_t pgtable)
735 {
736         struct mm_struct *mm = vma->vm_mm;
737         pmd_t entry;
738         spinlock_t *ptl;
739 
740         ptl = pmd_lock(mm, pmd);
741         entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
742         if (pfn_t_devmap(pfn))
743                 entry = pmd_mkdevmap(entry);
744         if (write) {
745                 entry = pmd_mkyoung(pmd_mkdirty(entry));
746                 entry = maybe_pmd_mkwrite(entry, vma);
747         }
748 
749         if (pgtable) {
750                 pgtable_trans_huge_deposit(mm, pmd, pgtable);
751                 mm_inc_nr_ptes(mm);
752         }
753 
754         set_pmd_at(mm, addr, pmd, entry);
755         update_mmu_cache_pmd(vma, addr, pmd);
756         spin_unlock(ptl);
757 }
758 
759 int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
760                         pmd_t *pmd, pfn_t pfn, bool write)
761 {
762         pgprot_t pgprot = vma->vm_page_prot;
763         pgtable_t pgtable = NULL;
764         /*
765          * If we had pmd_special, we could avoid all these restrictions,
766          * but we need to be consistent with PTEs and architectures that
767          * can't support a 'special' bit.
768          */
769         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
770         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
771                                                 (VM_PFNMAP|VM_MIXEDMAP));
772         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
773         BUG_ON(!pfn_t_devmap(pfn));
774 
775         if (addr < vma->vm_start || addr >= vma->vm_end)
776                 return VM_FAULT_SIGBUS;
777 
778         if (arch_needs_pgtable_deposit()) {
779                 pgtable = pte_alloc_one(vma->vm_mm, addr);
780                 if (!pgtable)
781                         return VM_FAULT_OOM;
782         }
783 
784         track_pfn_insert(vma, &pgprot, pfn);
785 
786         insert_pfn_pmd(vma, addr, pmd, pfn, pgprot, write, pgtable);
787         return VM_FAULT_NOPAGE;
788 }
789 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pmd);
790 
791 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
792 static pud_t maybe_pud_mkwrite(pud_t pud, struct vm_area_struct *vma)
793 {
794         if (likely(vma->vm_flags & VM_WRITE))
795                 pud = pud_mkwrite(pud);
796         return pud;
797 }
798 
799 static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
800                 pud_t *pud, pfn_t pfn, pgprot_t prot, bool write)
801 {
802         struct mm_struct *mm = vma->vm_mm;
803         pud_t entry;
804         spinlock_t *ptl;
805 
806         ptl = pud_lock(mm, pud);
807         entry = pud_mkhuge(pfn_t_pud(pfn, prot));
808         if (pfn_t_devmap(pfn))
809                 entry = pud_mkdevmap(entry);
810         if (write) {
811                 entry = pud_mkyoung(pud_mkdirty(entry));
812                 entry = maybe_pud_mkwrite(entry, vma);
813         }
814         set_pud_at(mm, addr, pud, entry);
815         update_mmu_cache_pud(vma, addr, pud);
816         spin_unlock(ptl);
817 }
818 
819 int vmf_insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
820                         pud_t *pud, pfn_t pfn, bool write)
821 {
822         pgprot_t pgprot = vma->vm_page_prot;
823         /*
824          * If we had pud_special, we could avoid all these restrictions,
825          * but we need to be consistent with PTEs and architectures that
826          * can't support a 'special' bit.
827          */
828         BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
829         BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
830                                                 (VM_PFNMAP|VM_MIXEDMAP));
831         BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
832         BUG_ON(!pfn_t_devmap(pfn));
833 
834         if (addr < vma->vm_start || addr >= vma->vm_end)
835                 return VM_FAULT_SIGBUS;
836 
837         track_pfn_insert(vma, &pgprot, pfn);
838 
839         insert_pfn_pud(vma, addr, pud, pfn, pgprot, write);
840         return VM_FAULT_NOPAGE;
841 }
842 EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud);
843 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
844 
845 static void touch_pmd(struct vm_area_struct *vma, unsigned long addr,
846                 pmd_t *pmd, int flags)
847 {
848         pmd_t _pmd;
849 
850         _pmd = pmd_mkyoung(*pmd);
851         if (flags & FOLL_WRITE)
852                 _pmd = pmd_mkdirty(_pmd);
853         if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK,
854                                 pmd, _pmd, flags & FOLL_WRITE))
855                 update_mmu_cache_pmd(vma, addr, pmd);
856 }
857 
858 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
859                 pmd_t *pmd, int flags)
860 {
861         unsigned long pfn = pmd_pfn(*pmd);
862         struct mm_struct *mm = vma->vm_mm;
863         struct dev_pagemap *pgmap;
864         struct page *page;
865 
866         assert_spin_locked(pmd_lockptr(mm, pmd));
867 
868         /*
869          * When we COW a devmap PMD entry, we split it into PTEs, so we should
870          * not be in this function with `flags & FOLL_COW` set.
871          */
872         WARN_ONCE(flags & FOLL_COW, "mm: In follow_devmap_pmd with FOLL_COW set");
873 
874         if (flags & FOLL_WRITE && !pmd_write(*pmd))
875                 return NULL;
876 
877         if (pmd_present(*pmd) && pmd_devmap(*pmd))
878                 /* pass */;
879         else
880                 return NULL;
881 
882         if (flags & FOLL_TOUCH)
883                 touch_pmd(vma, addr, pmd, flags);
884 
885         /*
886          * device mapped pages can only be returned if the
887          * caller will manage the page reference count.
888          */
889         if (!(flags & FOLL_GET))
890                 return ERR_PTR(-EEXIST);
891 
892         pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT;
893         pgmap = get_dev_pagemap(pfn, NULL);
894         if (!pgmap)
895                 return ERR_PTR(-EFAULT);
896         page = pfn_to_page(pfn);
897         get_page(page);
898         put_dev_pagemap(pgmap);
899 
900         return page;
901 }
902 
903 int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
904                   pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
905                   struct vm_area_struct *vma)
906 {
907         spinlock_t *dst_ptl, *src_ptl;
908         struct page *src_page;
909         pmd_t pmd;
910         pgtable_t pgtable = NULL;
911         int ret = -ENOMEM;
912 
913         /* Skip if can be re-fill on fault */
914         if (!vma_is_anonymous(vma))
915                 return 0;
916 
917         pgtable = pte_alloc_one(dst_mm, addr);
918         if (unlikely(!pgtable))
919                 goto out;
920 
921         dst_ptl = pmd_lock(dst_mm, dst_pmd);
922         src_ptl = pmd_lockptr(src_mm, src_pmd);
923         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
924 
925         ret = -EAGAIN;
926         pmd = *src_pmd;
927 
928 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
929         if (unlikely(is_swap_pmd(pmd))) {
930                 swp_entry_t entry = pmd_to_swp_entry(pmd);
931 
932                 VM_BUG_ON(!is_pmd_migration_entry(pmd));
933                 if (is_write_migration_entry(entry)) {
934                         make_migration_entry_read(&entry);
935                         pmd = swp_entry_to_pmd(entry);
936                         if (pmd_swp_soft_dirty(*src_pmd))
937                                 pmd = pmd_swp_mksoft_dirty(pmd);
938                         set_pmd_at(src_mm, addr, src_pmd, pmd);
939                 }
940                 add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
941                 mm_inc_nr_ptes(dst_mm);
942                 pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
943                 set_pmd_at(dst_mm, addr, dst_pmd, pmd);
944                 ret = 0;
945                 goto out_unlock;
946         }
947 #endif
948 
949         if (unlikely(!pmd_trans_huge(pmd))) {
950                 pte_free(dst_mm, pgtable);
951                 goto out_unlock;
952         }
953         /*
954          * When page table lock is held, the huge zero pmd should not be
955          * under splitting since we don't split the page itself, only pmd to
956          * a page table.
957          */
958         if (is_huge_zero_pmd(pmd)) {
959                 struct page *zero_page;
960                 /*
961                  * get_huge_zero_page() will never allocate a new page here,
962                  * since we already have a zero page to copy. It just takes a
963                  * reference.
964                  */
965                 zero_page = mm_get_huge_zero_page(dst_mm);
966                 set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd,
967                                 zero_page);
968                 ret = 0;
969                 goto out_unlock;
970         }
971 
972         src_page = pmd_page(pmd);
973         VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
974         get_page(src_page);
975         page_dup_rmap(src_page, true);
976         add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
977         mm_inc_nr_ptes(dst_mm);
978         pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
979 
980         pmdp_set_wrprotect(src_mm, addr, src_pmd);
981         pmd = pmd_mkold(pmd_wrprotect(pmd));
982         set_pmd_at(dst_mm, addr, dst_pmd, pmd);
983 
984         ret = 0;
985 out_unlock:
986         spin_unlock(src_ptl);
987         spin_unlock(dst_ptl);
988 out:
989         return ret;
990 }
991 
992 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
993 static void touch_pud(struct vm_area_struct *vma, unsigned long addr,
994                 pud_t *pud, int flags)
995 {
996         pud_t _pud;
997 
998         _pud = pud_mkyoung(*pud);
999         if (flags & FOLL_WRITE)
1000                 _pud = pud_mkdirty(_pud);
1001         if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK,
1002                                 pud, _pud, flags & FOLL_WRITE))
1003                 update_mmu_cache_pud(vma, addr, pud);
1004 }
1005 
1006 struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
1007                 pud_t *pud, int flags)
1008 {
1009         unsigned long pfn = pud_pfn(*pud);
1010         struct mm_struct *mm = vma->vm_mm;
1011         struct dev_pagemap *pgmap;
1012         struct page *page;
1013 
1014         assert_spin_locked(pud_lockptr(mm, pud));
1015 
1016         if (flags & FOLL_WRITE && !pud_write(*pud))
1017                 return NULL;
1018 
1019         if (pud_present(*pud) && pud_devmap(*pud))
1020                 /* pass */;
1021         else
1022                 return NULL;
1023 
1024         if (flags & FOLL_TOUCH)
1025                 touch_pud(vma, addr, pud, flags);
1026 
1027         /*
1028          * device mapped pages can only be returned if the
1029          * caller will manage the page reference count.
1030          */
1031         if (!(flags & FOLL_GET))
1032                 return ERR_PTR(-EEXIST);
1033 
1034         pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
1035         pgmap = get_dev_pagemap(pfn, NULL);
1036         if (!pgmap)
1037                 return ERR_PTR(-EFAULT);
1038         page = pfn_to_page(pfn);
1039         get_page(page);
1040         put_dev_pagemap(pgmap);
1041 
1042         return page;
1043 }
1044 
1045 int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm,
1046                   pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
1047                   struct vm_area_struct *vma)
1048 {
1049         spinlock_t *dst_ptl, *src_ptl;
1050         pud_t pud;
1051         int ret;
1052 
1053         dst_ptl = pud_lock(dst_mm, dst_pud);
1054         src_ptl = pud_lockptr(src_mm, src_pud);
1055         spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
1056 
1057         ret = -EAGAIN;
1058         pud = *src_pud;
1059         if (unlikely(!pud_trans_huge(pud) && !pud_devmap(pud)))
1060                 goto out_unlock;
1061 
1062         /*
1063          * When page table lock is held, the huge zero pud should not be
1064          * under splitting since we don't split the page itself, only pud to
1065          * a page table.
1066          */
1067         if (is_huge_zero_pud(pud)) {
1068                 /* No huge zero pud yet */
1069         }
1070 
1071         pudp_set_wrprotect(src_mm, addr, src_pud);
1072         pud = pud_mkold(pud_wrprotect(pud));
1073         set_pud_at(dst_mm, addr, dst_pud, pud);
1074 
1075         ret = 0;
1076 out_unlock:
1077         spin_unlock(src_ptl);
1078         spin_unlock(dst_ptl);
1079         return ret;
1080 }
1081 
1082 void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
1083 {
1084         pud_t entry;
1085         unsigned long haddr;
1086         bool write = vmf->flags & FAULT_FLAG_WRITE;
1087 
1088         vmf->ptl = pud_lock(vmf->vma->vm_mm, vmf->pud);
1089         if (unlikely(!pud_same(*vmf->pud, orig_pud)))
1090                 goto unlock;
1091 
1092         entry = pud_mkyoung(orig_pud);
1093         if (write)
1094                 entry = pud_mkdirty(entry);
1095         haddr = vmf->address & HPAGE_PUD_MASK;
1096         if (pudp_set_access_flags(vmf->vma, haddr, vmf->pud, entry, write))
1097                 update_mmu_cache_pud(vmf->vma, vmf->address, vmf->pud);
1098 
1099 unlock:
1100         spin_unlock(vmf->ptl);
1101 }
1102 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
1103 
1104 void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
1105 {
1106         pmd_t entry;
1107         unsigned long haddr;
1108         bool write = vmf->flags & FAULT_FLAG_WRITE;
1109 
1110         vmf->ptl = pmd_lock(vmf->vma->vm_mm, vmf->pmd);
1111         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1112                 goto unlock;
1113 
1114         entry = pmd_mkyoung(orig_pmd);
1115         if (write)
1116                 entry = pmd_mkdirty(entry);
1117         haddr = vmf->address & HPAGE_PMD_MASK;
1118         if (pmdp_set_access_flags(vmf->vma, haddr, vmf->pmd, entry, write))
1119                 update_mmu_cache_pmd(vmf->vma, vmf->address, vmf->pmd);
1120 
1121 unlock:
1122         spin_unlock(vmf->ptl);
1123 }
1124 
1125 static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,
1126                 struct page *page)
1127 {
1128         struct vm_area_struct *vma = vmf->vma;
1129         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1130         struct mem_cgroup *memcg;
1131         pgtable_t pgtable;
1132         pmd_t _pmd;
1133         int ret = 0, i;
1134         struct page **pages;
1135         unsigned long mmun_start;       /* For mmu_notifiers */
1136         unsigned long mmun_end;         /* For mmu_notifiers */
1137 
1138         pages = kmalloc(sizeof(struct page *) * HPAGE_PMD_NR,
1139                         GFP_KERNEL);
1140         if (unlikely(!pages)) {
1141                 ret |= VM_FAULT_OOM;
1142                 goto out;
1143         }
1144 
1145         for (i = 0; i < HPAGE_PMD_NR; i++) {
1146                 pages[i] = alloc_page_vma_node(GFP_HIGHUSER_MOVABLE, vma,
1147                                                vmf->address, page_to_nid(page));
1148                 if (unlikely(!pages[i] ||
1149                              mem_cgroup_try_charge(pages[i], vma->vm_mm,
1150                                      GFP_KERNEL, &memcg, false))) {
1151                         if (pages[i])
1152                                 put_page(pages[i]);
1153                         while (--i >= 0) {
1154                                 memcg = (void *)page_private(pages[i]);
1155                                 set_page_private(pages[i], 0);
1156                                 mem_cgroup_cancel_charge(pages[i], memcg,
1157                                                 false);
1158                                 put_page(pages[i]);
1159                         }
1160                         kfree(pages);
1161                         ret |= VM_FAULT_OOM;
1162                         goto out;
1163                 }
1164                 set_page_private(pages[i], (unsigned long)memcg);
1165         }
1166 
1167         for (i = 0; i < HPAGE_PMD_NR; i++) {
1168                 copy_user_highpage(pages[i], page + i,
1169                                    haddr + PAGE_SIZE * i, vma);
1170                 __SetPageUptodate(pages[i]);
1171                 cond_resched();
1172         }
1173 
1174         mmun_start = haddr;
1175         mmun_end   = haddr + HPAGE_PMD_SIZE;
1176         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1177 
1178         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1179         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1180                 goto out_free_pages;
1181         VM_BUG_ON_PAGE(!PageHead(page), page);
1182 
1183         /*
1184          * Leave pmd empty until pte is filled note we must notify here as
1185          * concurrent CPU thread might write to new page before the call to
1186          * mmu_notifier_invalidate_range_end() happens which can lead to a
1187          * device seeing memory write in different order than CPU.
1188          *
1189          * See Documentation/vm/mmu_notifier.txt
1190          */
1191         pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1192 
1193         pgtable = pgtable_trans_huge_withdraw(vma->vm_mm, vmf->pmd);
1194         pmd_populate(vma->vm_mm, &_pmd, pgtable);
1195 
1196         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
1197                 pte_t entry;
1198                 entry = mk_pte(pages[i], vma->vm_page_prot);
1199                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
1200                 memcg = (void *)page_private(pages[i]);
1201                 set_page_private(pages[i], 0);
1202                 page_add_new_anon_rmap(pages[i], vmf->vma, haddr, false);
1203                 mem_cgroup_commit_charge(pages[i], memcg, false, false);
1204                 lru_cache_add_active_or_unevictable(pages[i], vma);
1205                 vmf->pte = pte_offset_map(&_pmd, haddr);
1206                 VM_BUG_ON(!pte_none(*vmf->pte));
1207                 set_pte_at(vma->vm_mm, haddr, vmf->pte, entry);
1208                 pte_unmap(vmf->pte);
1209         }
1210         kfree(pages);
1211 
1212         smp_wmb(); /* make pte visible before pmd */
1213         pmd_populate(vma->vm_mm, vmf->pmd, pgtable);
1214         page_remove_rmap(page, true);
1215         spin_unlock(vmf->ptl);
1216 
1217         /*
1218          * No need to double call mmu_notifier->invalidate_range() callback as
1219          * the above pmdp_huge_clear_flush_notify() did already call it.
1220          */
1221         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1222                                                 mmun_end);
1223 
1224         ret |= VM_FAULT_WRITE;
1225         put_page(page);
1226 
1227 out:
1228         return ret;
1229 
1230 out_free_pages:
1231         spin_unlock(vmf->ptl);
1232         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
1233         for (i = 0; i < HPAGE_PMD_NR; i++) {
1234                 memcg = (void *)page_private(pages[i]);
1235                 set_page_private(pages[i], 0);
1236                 mem_cgroup_cancel_charge(pages[i], memcg, false);
1237                 put_page(pages[i]);
1238         }
1239         kfree(pages);
1240         goto out;
1241 }
1242 
1243 int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
1244 {
1245         struct vm_area_struct *vma = vmf->vma;
1246         struct page *page = NULL, *new_page;
1247         struct mem_cgroup *memcg;
1248         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1249         unsigned long mmun_start;       /* For mmu_notifiers */
1250         unsigned long mmun_end;         /* For mmu_notifiers */
1251         gfp_t huge_gfp;                 /* for allocation and charge */
1252         int ret = 0;
1253 
1254         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
1255         VM_BUG_ON_VMA(!vma->anon_vma, vma);
1256         if (is_huge_zero_pmd(orig_pmd))
1257                 goto alloc;
1258         spin_lock(vmf->ptl);
1259         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd)))
1260                 goto out_unlock;
1261 
1262         page = pmd_page(orig_pmd);
1263         VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
1264         /*
1265          * We can only reuse the page if nobody else maps the huge page or it's
1266          * part.
1267          */
1268         if (!trylock_page(page)) {
1269                 get_page(page);
1270                 spin_unlock(vmf->ptl);
1271                 lock_page(page);
1272                 spin_lock(vmf->ptl);
1273                 if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1274                         unlock_page(page);
1275                         put_page(page);
1276                         goto out_unlock;
1277                 }
1278                 put_page(page);
1279         }
1280         if (reuse_swap_page(page, NULL)) {
1281                 pmd_t entry;
1282                 entry = pmd_mkyoung(orig_pmd);
1283                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1284                 if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry,  1))
1285                         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1286                 ret |= VM_FAULT_WRITE;
1287                 unlock_page(page);
1288                 goto out_unlock;
1289         }
1290         unlock_page(page);
1291         get_page(page);
1292         spin_unlock(vmf->ptl);
1293 alloc:
1294         if (transparent_hugepage_enabled(vma) &&
1295             !transparent_hugepage_debug_cow()) {
1296                 huge_gfp = alloc_hugepage_direct_gfpmask(vma);
1297                 new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
1298         } else
1299                 new_page = NULL;
1300 
1301         if (likely(new_page)) {
1302                 prep_transhuge_page(new_page);
1303         } else {
1304                 if (!page) {
1305                         split_huge_pmd(vma, vmf->pmd, vmf->address);
1306                         ret |= VM_FAULT_FALLBACK;
1307                 } else {
1308                         ret = do_huge_pmd_wp_page_fallback(vmf, orig_pmd, page);
1309                         if (ret & VM_FAULT_OOM) {
1310                                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1311                                 ret |= VM_FAULT_FALLBACK;
1312                         }
1313                         put_page(page);
1314                 }
1315                 count_vm_event(THP_FAULT_FALLBACK);
1316                 goto out;
1317         }
1318 
1319         if (unlikely(mem_cgroup_try_charge(new_page, vma->vm_mm,
1320                                 huge_gfp | __GFP_NORETRY, &memcg, true))) {
1321                 put_page(new_page);
1322                 split_huge_pmd(vma, vmf->pmd, vmf->address);
1323                 if (page)
1324                         put_page(page);
1325                 ret |= VM_FAULT_FALLBACK;
1326                 count_vm_event(THP_FAULT_FALLBACK);
1327                 goto out;
1328         }
1329 
1330         count_vm_event(THP_FAULT_ALLOC);
1331 
1332         if (!page)
1333                 clear_huge_page(new_page, vmf->address, HPAGE_PMD_NR);
1334         else
1335                 copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR);
1336         __SetPageUptodate(new_page);
1337 
1338         mmun_start = haddr;
1339         mmun_end   = haddr + HPAGE_PMD_SIZE;
1340         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
1341 
1342         spin_lock(vmf->ptl);
1343         if (page)
1344                 put_page(page);
1345         if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) {
1346                 spin_unlock(vmf->ptl);
1347                 mem_cgroup_cancel_charge(new_page, memcg, true);
1348                 put_page(new_page);
1349                 goto out_mn;
1350         } else {
1351                 pmd_t entry;
1352                 entry = mk_huge_pmd(new_page, vma->vm_page_prot);
1353                 entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
1354                 pmdp_huge_clear_flush_notify(vma, haddr, vmf->pmd);
1355                 page_add_new_anon_rmap(new_page, vma, haddr, true);
1356                 mem_cgroup_commit_charge(new_page, memcg, false, true);
1357                 lru_cache_add_active_or_unevictable(new_page, vma);
1358                 set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
1359                 update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1360                 if (!page) {
1361                         add_mm_counter(vma->vm_mm, MM_ANONPAGES, HPAGE_PMD_NR);
1362                 } else {
1363                         VM_BUG_ON_PAGE(!PageHead(page), page);
1364                         page_remove_rmap(page, true);
1365                         put_page(page);
1366                 }
1367                 ret |= VM_FAULT_WRITE;
1368         }
1369         spin_unlock(vmf->ptl);
1370 out_mn:
1371         /*
1372          * No need to double call mmu_notifier->invalidate_range() callback as
1373          * the above pmdp_huge_clear_flush_notify() did already call it.
1374          */
1375         mmu_notifier_invalidate_range_only_end(vma->vm_mm, mmun_start,
1376                                                mmun_end);
1377 out:
1378         return ret;
1379 out_unlock:
1380         spin_unlock(vmf->ptl);
1381         return ret;
1382 }
1383 
1384 /*
1385  * FOLL_FORCE can write to even unwritable pmd's, but only
1386  * after we've gone through a COW cycle and they are dirty.
1387  */
1388 static inline bool can_follow_write_pmd(pmd_t pmd, unsigned int flags)
1389 {
1390         return pmd_write(pmd) ||
1391                ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pmd_dirty(pmd));
1392 }
1393 
1394 struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1395                                    unsigned long addr,
1396                                    pmd_t *pmd,
1397                                    unsigned int flags)
1398 {
1399         struct mm_struct *mm = vma->vm_mm;
1400         struct page *page = NULL;
1401 
1402         assert_spin_locked(pmd_lockptr(mm, pmd));
1403 
1404         if (flags & FOLL_WRITE && !can_follow_write_pmd(*pmd, flags))
1405                 goto out;
1406 
1407         /* Avoid dumping huge zero page */
1408         if ((flags & FOLL_DUMP) && is_huge_zero_pmd(*pmd))
1409                 return ERR_PTR(-EFAULT);
1410 
1411         /* Full NUMA hinting faults to serialise migration in fault paths */
1412         if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
1413                 goto out;
1414 
1415         page = pmd_page(*pmd);
1416         VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page);
1417         if (flags & FOLL_TOUCH)
1418                 touch_pmd(vma, addr, pmd, flags);
1419         if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
1420                 /*
1421                  * We don't mlock() pte-mapped THPs. This way we can avoid
1422                  * leaking mlocked pages into non-VM_LOCKED VMAs.
1423                  *
1424                  * For anon THP:
1425                  *
1426                  * In most cases the pmd is the only mapping of the page as we
1427                  * break COW for the mlock() -- see gup_flags |= FOLL_WRITE for
1428                  * writable private mappings in populate_vma_page_range().
1429                  *
1430                  * The only scenario when we have the page shared here is if we
1431                  * mlocking read-only mapping shared over fork(). We skip
1432                  * mlocking such pages.
1433                  *
1434                  * For file THP:
1435                  *
1436                  * We can expect PageDoubleMap() to be stable under page lock:
1437                  * for file pages we set it in page_add_file_rmap(), which
1438                  * requires page to be locked.
1439                  */
1440 
1441                 if (PageAnon(page) && compound_mapcount(page) != 1)
1442                         goto skip_mlock;
1443                 if (PageDoubleMap(page) || !page->mapping)
1444                         goto skip_mlock;
1445                 if (!trylock_page(page))
1446                         goto skip_mlock;
1447                 lru_add_drain();
1448                 if (page->mapping && !PageDoubleMap(page))
1449                         mlock_vma_page(page);
1450                 unlock_page(page);
1451         }
1452 skip_mlock:
1453         page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT;
1454         VM_BUG_ON_PAGE(!PageCompound(page) && !is_zone_device_page(page), page);
1455         if (flags & FOLL_GET)
1456                 get_page(page);
1457 
1458 out:
1459         return page;
1460 }
1461 
1462 /* NUMA hinting page fault entry point for trans huge pmds */
1463 int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
1464 {
1465         struct vm_area_struct *vma = vmf->vma;
1466         struct anon_vma *anon_vma = NULL;
1467         struct page *page;
1468         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
1469         int page_nid = -1, this_nid = numa_node_id();
1470         int target_nid, last_cpupid = -1;
1471         bool page_locked;
1472         bool migrated = false;
1473         bool was_writable;
1474         int flags = 0;
1475 
1476         vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
1477         if (unlikely(!pmd_same(pmd, *vmf->pmd)))
1478                 goto out_unlock;
1479 
1480         /*
1481          * If there are potential migrations, wait for completion and retry
1482          * without disrupting NUMA hinting information. Do not relock and
1483          * check_same as the page may no longer be mapped.
1484          */
1485         if (unlikely(pmd_trans_migrating(*vmf->pmd))) {
1486                 page = pmd_page(*vmf->pmd);
1487                 if (!get_page_unless_zero(page))
1488                         goto out_unlock;
1489                 spin_unlock(vmf->ptl);
1490                 wait_on_page_locked(page);
1491                 put_page(page);
1492                 goto out;
1493         }
1494 
1495         page = pmd_page(pmd);
1496         BUG_ON(is_huge_zero_page(page));
1497         page_nid = page_to_nid(page);
1498         last_cpupid = page_cpupid_last(page);
1499         count_vm_numa_event(NUMA_HINT_FAULTS);
1500         if (page_nid == this_nid) {
1501                 count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
1502                 flags |= TNF_FAULT_LOCAL;
1503         }
1504 
1505         /* See similar comment in do_numa_page for explanation */
1506         if (!pmd_savedwrite(pmd))
1507                 flags |= TNF_NO_GROUP;
1508 
1509         /*
1510          * Acquire the page lock to serialise THP migrations but avoid dropping
1511          * page_table_lock if at all possible
1512          */
1513         page_locked = trylock_page(page);
1514         target_nid = mpol_misplaced(page, vma, haddr);
1515         if (target_nid == -1) {
1516                 /* If the page was locked, there are no parallel migrations */
1517                 if (page_locked)
1518                         goto clear_pmdnuma;
1519         }
1520 
1521         /* Migration could have started since the pmd_trans_migrating check */
1522         if (!page_locked) {
1523                 page_nid = -1;
1524                 if (!get_page_unless_zero(page))
1525                         goto out_unlock;
1526                 spin_unlock(vmf->ptl);
1527                 wait_on_page_locked(page);
1528                 put_page(page);
1529                 goto out;
1530         }
1531 
1532         /*
1533          * Page is misplaced. Page lock serialises migrations. Acquire anon_vma
1534          * to serialises splits
1535          */
1536         get_page(page);
1537         spin_unlock(vmf->ptl);
1538         anon_vma = page_lock_anon_vma_read(page);
1539 
1540         /* Confirm the PMD did not change while page_table_lock was released */
1541         spin_lock(vmf->ptl);
1542         if (unlikely(!pmd_same(pmd, *vmf->pmd))) {
1543                 unlock_page(page);
1544                 put_page(page);
1545                 page_nid = -1;
1546                 goto out_unlock;
1547         }
1548 
1549         /* Bail if we fail to protect against THP splits for any reason */
1550         if (unlikely(!anon_vma)) {
1551                 put_page(page);
1552                 page_nid = -1;
1553                 goto clear_pmdnuma;
1554         }
1555 
1556         /*
1557          * Since we took the NUMA fault, we must have observed the !accessible
1558          * bit. Make sure all other CPUs agree with that, to avoid them
1559          * modifying the page we're about to migrate.
1560          *
1561          * Must be done under PTL such that we'll observe the relevant
1562          * inc_tlb_flush_pending().
1563          *
1564          * We are not sure a pending tlb flush here is for a huge page
1565          * mapping or not. Hence use the tlb range variant
1566          */
1567         if (mm_tlb_flush_pending(vma->vm_mm))
1568                 flush_tlb_range(vma, haddr, haddr + HPAGE_PMD_SIZE);
1569 
1570         /*
1571          * Migrate the THP to the requested node, returns with page unlocked
1572          * and access rights restored.
1573          */
1574         spin_unlock(vmf->ptl);
1575 
1576         migrated = migrate_misplaced_transhuge_page(vma->vm_mm, vma,
1577                                 vmf->pmd, pmd, vmf->address, page, target_nid);
1578         if (migrated) {
1579                 flags |= TNF_MIGRATED;
1580                 page_nid = target_nid;
1581         } else
1582                 flags |= TNF_MIGRATE_FAIL;
1583 
1584         goto out;
1585 clear_pmdnuma:
1586         BUG_ON(!PageLocked(page));
1587         was_writable = pmd_savedwrite(pmd);
1588         pmd = pmd_modify(pmd, vma->vm_page_prot);
1589         pmd = pmd_mkyoung(pmd);
1590         if (was_writable)
1591                 pmd = pmd_mkwrite(pmd);
1592         set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
1593         update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
1594         unlock_page(page);
1595 out_unlock:
1596         spin_unlock(vmf->ptl);
1597 
1598 out:
1599         if (anon_vma)
1600                 page_unlock_anon_vma_read(anon_vma);
1601 
1602         if (page_nid != -1)
1603                 task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR,
1604                                 flags);
1605 
1606         return 0;
1607 }
1608 
1609 /*
1610  * Return true if we do MADV_FREE successfully on entire pmd page.
1611  * Otherwise, return false.
1612  */
1613 bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1614                 pmd_t *pmd, unsigned long addr, unsigned long next)
1615 {
1616         spinlock_t *ptl;
1617         pmd_t orig_pmd;
1618         struct page *page;
1619         struct mm_struct *mm = tlb->mm;
1620         bool ret = false;
1621 
1622         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1623 
1624         ptl = pmd_trans_huge_lock(pmd, vma);
1625         if (!ptl)
1626                 goto out_unlocked;
1627 
1628         orig_pmd = *pmd;
1629         if (is_huge_zero_pmd(orig_pmd))
1630                 goto out;
1631 
1632         if (unlikely(!pmd_present(orig_pmd))) {
1633                 VM_BUG_ON(thp_migration_supported() &&
1634                                   !is_pmd_migration_entry(orig_pmd));
1635                 goto out;
1636         }
1637 
1638         page = pmd_page(orig_pmd);
1639         /*
1640          * If other processes are mapping this page, we couldn't discard
1641          * the page unless they all do MADV_FREE so let's skip the page.
1642          */
1643         if (page_mapcount(page) != 1)
1644                 goto out;
1645 
1646         if (!trylock_page(page))
1647                 goto out;
1648 
1649         /*
1650          * If user want to discard part-pages of THP, split it so MADV_FREE
1651          * will deactivate only them.
1652          */
1653         if (next - addr != HPAGE_PMD_SIZE) {
1654                 get_page(page);
1655                 spin_unlock(ptl);
1656                 split_huge_page(page);
1657                 unlock_page(page);
1658                 put_page(page);
1659                 goto out_unlocked;
1660         }
1661 
1662         if (PageDirty(page))
1663                 ClearPageDirty(page);
1664         unlock_page(page);
1665 
1666         if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) {
1667                 pmdp_invalidate(vma, addr, pmd);
1668                 orig_pmd = pmd_mkold(orig_pmd);
1669                 orig_pmd = pmd_mkclean(orig_pmd);
1670 
1671                 set_pmd_at(mm, addr, pmd, orig_pmd);
1672                 tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1673         }
1674 
1675         mark_page_lazyfree(page);
1676         ret = true;
1677 out:
1678         spin_unlock(ptl);
1679 out_unlocked:
1680         return ret;
1681 }
1682 
1683 static inline void zap_deposited_table(struct mm_struct *mm, pmd_t *pmd)
1684 {
1685         pgtable_t pgtable;
1686 
1687         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
1688         pte_free(mm, pgtable);
1689         mm_dec_nr_ptes(mm);
1690 }
1691 
1692 int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
1693                  pmd_t *pmd, unsigned long addr)
1694 {
1695         pmd_t orig_pmd;
1696         spinlock_t *ptl;
1697 
1698         tlb_remove_check_page_size_change(tlb, HPAGE_PMD_SIZE);
1699 
1700         ptl = __pmd_trans_huge_lock(pmd, vma);
1701         if (!ptl)
1702                 return 0;
1703         /*
1704          * For architectures like ppc64 we look at deposited pgtable
1705          * when calling pmdp_huge_get_and_clear. So do the
1706          * pgtable_trans_huge_withdraw after finishing pmdp related
1707          * operations.
1708          */
1709         orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd,
1710                         tlb->fullmm);
1711         tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
1712         if (vma_is_dax(vma)) {
1713                 if (arch_needs_pgtable_deposit())
1714                         zap_deposited_table(tlb->mm, pmd);
1715                 spin_unlock(ptl);
1716                 if (is_huge_zero_pmd(orig_pmd))
1717                         tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1718         } else if (is_huge_zero_pmd(orig_pmd)) {
1719                 zap_deposited_table(tlb->mm, pmd);
1720                 spin_unlock(ptl);
1721                 tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE);
1722         } else {
1723                 struct page *page = NULL;
1724                 int flush_needed = 1;
1725 
1726                 if (pmd_present(orig_pmd)) {
1727                         page = pmd_page(orig_pmd);
1728                         page_remove_rmap(page, true);
1729                         VM_BUG_ON_PAGE(page_mapcount(page) < 0, page);
1730                         VM_BUG_ON_PAGE(!PageHead(page), page);
1731                 } else if (thp_migration_supported()) {
1732                         swp_entry_t entry;
1733 
1734                         VM_BUG_ON(!is_pmd_migration_entry(orig_pmd));
1735                         entry = pmd_to_swp_entry(orig_pmd);
1736                         page = pfn_to_page(swp_offset(entry));
1737                         flush_needed = 0;
1738                 } else
1739                         WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
1740 
1741                 if (PageAnon(page)) {
1742                         zap_deposited_table(tlb->mm, pmd);
1743                         add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR);
1744                 } else {
1745                         if (arch_needs_pgtable_deposit())
1746                                 zap_deposited_table(tlb->mm, pmd);
1747                         add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR);
1748                 }
1749 
1750                 spin_unlock(ptl);
1751                 if (flush_needed)
1752                         tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE);
1753         }
1754         return 1;
1755 }
1756 
1757 #ifndef pmd_move_must_withdraw
1758 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
1759                                          spinlock_t *old_pmd_ptl,
1760                                          struct vm_area_struct *vma)
1761 {
1762         /*
1763          * With split pmd lock we also need to move preallocated
1764          * PTE page table if new_pmd is on different PMD page table.
1765          *
1766          * We also don't deposit and withdraw tables for file pages.
1767          */
1768         return (new_pmd_ptl != old_pmd_ptl) && vma_is_anonymous(vma);
1769 }
1770 #endif
1771 
1772 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
1773 {
1774 #ifdef CONFIG_MEM_SOFT_DIRTY
1775         if (unlikely(is_pmd_migration_entry(pmd)))
1776                 pmd = pmd_swp_mksoft_dirty(pmd);
1777         else if (pmd_present(pmd))
1778                 pmd = pmd_mksoft_dirty(pmd);
1779 #endif
1780         return pmd;
1781 }
1782 
1783 bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
1784                   unsigned long new_addr, unsigned long old_end,
1785                   pmd_t *old_pmd, pmd_t *new_pmd, bool *need_flush)
1786 {
1787         spinlock_t *old_ptl, *new_ptl;
1788         pmd_t pmd;
1789         struct mm_struct *mm = vma->vm_mm;
1790         bool force_flush = false;
1791 
1792         if ((old_addr & ~HPAGE_PMD_MASK) ||
1793             (new_addr & ~HPAGE_PMD_MASK) ||
1794             old_end - old_addr < HPAGE_PMD_SIZE)
1795                 return false;
1796 
1797         /*
1798          * The destination pmd shouldn't be established, free_pgtables()
1799          * should have release it.
1800          */
1801         if (WARN_ON(!pmd_none(*new_pmd))) {
1802                 VM_BUG_ON(pmd_trans_huge(*new_pmd));
1803                 return false;
1804         }
1805 
1806         /*
1807          * We don't have to worry about the ordering of src and dst
1808          * ptlocks because exclusive mmap_sem prevents deadlock.
1809          */
1810         old_ptl = __pmd_trans_huge_lock(old_pmd, vma);
1811         if (old_ptl) {
1812                 new_ptl = pmd_lockptr(mm, new_pmd);
1813                 if (new_ptl != old_ptl)
1814                         spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
1815                 pmd = pmdp_huge_get_and_clear(mm, old_addr, old_pmd);
1816                 if (pmd_present(pmd) && pmd_dirty(pmd))
1817                         force_flush = true;
1818                 VM_BUG_ON(!pmd_none(*new_pmd));
1819 
1820                 if (pmd_move_must_withdraw(new_ptl, old_ptl, vma)) {
1821                         pgtable_t pgtable;
1822                         pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
1823                         pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
1824                 }
1825                 pmd = move_soft_dirty_pmd(pmd);
1826                 set_pmd_at(mm, new_addr, new_pmd, pmd);
1827                 if (new_ptl != old_ptl)
1828                         spin_unlock(new_ptl);
1829                 if (force_flush)
1830                         flush_tlb_range(vma, old_addr, old_addr + PMD_SIZE);
1831                 else
1832                         *need_flush = true;
1833                 spin_unlock(old_ptl);
1834                 return true;
1835         }
1836         return false;
1837 }
1838 
1839 /*
1840  * Returns
1841  *  - 0 if PMD could not be locked
1842  *  - 1 if PMD was locked but protections unchange and TLB flush unnecessary
1843  *  - HPAGE_PMD_NR is protections changed and TLB flush necessary
1844  */
1845 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
1846                 unsigned long addr, pgprot_t newprot, int prot_numa)
1847 {
1848         struct mm_struct *mm = vma->vm_mm;
1849         spinlock_t *ptl;
1850         pmd_t entry;
1851         bool preserve_write;
1852         int ret;
1853 
1854         ptl = __pmd_trans_huge_lock(pmd, vma);
1855         if (!ptl)
1856                 return 0;
1857 
1858         preserve_write = prot_numa && pmd_write(*pmd);
1859         ret = 1;
1860 
1861 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
1862         if (is_swap_pmd(*pmd)) {
1863                 swp_entry_t entry = pmd_to_swp_entry(*pmd);
1864 
1865                 VM_BUG_ON(!is_pmd_migration_entry(*pmd));
1866                 if (is_write_migration_entry(entry)) {
1867                         pmd_t newpmd;
1868                         /*
1869                          * A protection check is difficult so
1870                          * just be safe and disable write
1871                          */
1872                         make_migration_entry_read(&entry);
1873                         newpmd = swp_entry_to_pmd(entry);
1874                         if (pmd_swp_soft_dirty(*pmd))
1875                                 newpmd = pmd_swp_mksoft_dirty(newpmd);
1876                         set_pmd_at(mm, addr, pmd, newpmd);
1877                 }
1878                 goto unlock;
1879         }
1880 #endif
1881 
1882         /*
1883          * Avoid trapping faults against the zero page. The read-only
1884          * data is likely to be read-cached on the local CPU and
1885          * local/remote hits to the zero page are not interesting.
1886          */
1887         if (prot_numa && is_huge_zero_pmd(*pmd))
1888                 goto unlock;
1889 
1890         if (prot_numa && pmd_protnone(*pmd))
1891                 goto unlock;
1892 
1893         /*
1894          * In case prot_numa, we are under down_read(mmap_sem). It's critical
1895          * to not clear pmd intermittently to avoid race with MADV_DONTNEED
1896          * which is also under down_read(mmap_sem):
1897          *
1898          *      CPU0:                           CPU1:
1899          *                              change_huge_pmd(prot_numa=1)
1900          *                               pmdp_huge_get_and_clear_notify()
1901          * madvise_dontneed()
1902          *  zap_pmd_range()
1903          *   pmd_trans_huge(*pmd) == 0 (without ptl)
1904          *   // skip the pmd
1905          *                               set_pmd_at();
1906          *                               // pmd is re-established
1907          *
1908          * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
1909          * which may break userspace.
1910          *
1911          * pmdp_invalidate() is required to make sure we don't miss
1912          * dirty/young flags set by hardware.
1913          */
1914         entry = pmdp_invalidate(vma, addr, pmd);
1915 
1916         entry = pmd_modify(entry, newprot);
1917         if (preserve_write)
1918                 entry = pmd_mk_savedwrite(entry);
1919         ret = HPAGE_PMD_NR;
1920         set_pmd_at(mm, addr, pmd, entry);
1921         BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
1922 unlock:
1923         spin_unlock(ptl);
1924         return ret;
1925 }
1926 
1927 /*
1928  * Returns page table lock pointer if a given pmd maps a thp, NULL otherwise.
1929  *
1930  * Note that if it returns page table lock pointer, this routine returns without
1931  * unlocking page table lock. So callers must unlock it.
1932  */
1933 spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma)
1934 {
1935         spinlock_t *ptl;
1936         ptl = pmd_lock(vma->vm_mm, pmd);
1937         if (likely(is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) ||
1938                         pmd_devmap(*pmd)))
1939                 return ptl;
1940         spin_unlock(ptl);
1941         return NULL;
1942 }
1943 
1944 /*
1945  * Returns true if a given pud maps a thp, false otherwise.
1946  *
1947  * Note that if it returns true, this routine returns without unlocking page
1948  * table lock. So callers must unlock it.
1949  */
1950 spinlock_t *__pud_trans_huge_lock(pud_t *pud, struct vm_area_struct *vma)
1951 {
1952         spinlock_t *ptl;
1953 
1954         ptl = pud_lock(vma->vm_mm, pud);
1955         if (likely(pud_trans_huge(*pud) || pud_devmap(*pud)))
1956                 return ptl;
1957         spin_unlock(ptl);
1958         return NULL;
1959 }
1960 
1961 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
1962 int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma,
1963                  pud_t *pud, unsigned long addr)
1964 {
1965         pud_t orig_pud;
1966         spinlock_t *ptl;
1967 
1968         ptl = __pud_trans_huge_lock(pud, vma);
1969         if (!ptl)
1970                 return 0;
1971         /*
1972          * For architectures like ppc64 we look at deposited pgtable
1973          * when calling pudp_huge_get_and_clear. So do the
1974          * pgtable_trans_huge_withdraw after finishing pudp related
1975          * operations.
1976          */
1977         orig_pud = pudp_huge_get_and_clear_full(tlb->mm, addr, pud,
1978                         tlb->fullmm);
1979         tlb_remove_pud_tlb_entry(tlb, pud, addr);
1980         if (vma_is_dax(vma)) {
1981                 spin_unlock(ptl);
1982                 /* No zero page support yet */
1983         } else {
1984                 /* No support for anonymous PUD pages yet */
1985                 BUG();
1986         }
1987         return 1;
1988 }
1989 
1990 static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
1991                 unsigned long haddr)
1992 {
1993         VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
1994         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
1995         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
1996         VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
1997 
1998         count_vm_event(THP_SPLIT_PUD);
1999 
2000         pudp_huge_clear_flush_notify(vma, haddr, pud);
2001 }
2002 
2003 void __split_huge_pud(struct vm_area_struct *vma, pud_t *pud,
2004                 unsigned long address)
2005 {
2006         spinlock_t *ptl;
2007         struct mm_struct *mm = vma->vm_mm;
2008         unsigned long haddr = address & HPAGE_PUD_MASK;
2009 
2010         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PUD_SIZE);
2011         ptl = pud_lock(mm, pud);
2012         if (unlikely(!pud_trans_huge(*pud) && !pud_devmap(*pud)))
2013                 goto out;
2014         __split_huge_pud_locked(vma, pud, haddr);
2015 
2016 out:
2017         spin_unlock(ptl);
2018         /*
2019          * No need to double call mmu_notifier->invalidate_range() callback as
2020          * the above pudp_huge_clear_flush_notify() did already call it.
2021          */
2022         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2023                                                HPAGE_PUD_SIZE);
2024 }
2025 #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
2026 
2027 static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
2028                 unsigned long haddr, pmd_t *pmd)
2029 {
2030         struct mm_struct *mm = vma->vm_mm;
2031         pgtable_t pgtable;
2032         pmd_t _pmd;
2033         int i;
2034 
2035         /*
2036          * Leave pmd empty until pte is filled note that it is fine to delay
2037          * notification until mmu_notifier_invalidate_range_end() as we are
2038          * replacing a zero pmd write protected page with a zero pte write
2039          * protected page.
2040          *
2041          * See Documentation/vm/mmu_notifier.txt
2042          */
2043         pmdp_huge_clear_flush(vma, haddr, pmd);
2044 
2045         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2046         pmd_populate(mm, &_pmd, pgtable);
2047 
2048         for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) {
2049                 pte_t *pte, entry;
2050                 entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
2051                 entry = pte_mkspecial(entry);
2052                 pte = pte_offset_map(&_pmd, haddr);
2053                 VM_BUG_ON(!pte_none(*pte));
2054                 set_pte_at(mm, haddr, pte, entry);
2055                 pte_unmap(pte);
2056         }
2057         smp_wmb(); /* make pte visible before pmd */
2058         pmd_populate(mm, pmd, pgtable);
2059 }
2060 
2061 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
2062                 unsigned long haddr, bool freeze)
2063 {
2064         struct mm_struct *mm = vma->vm_mm;
2065         struct page *page;
2066         pgtable_t pgtable;
2067         pmd_t old_pmd, _pmd;
2068         bool young, write, soft_dirty, pmd_migration = false;
2069         unsigned long addr;
2070         int i;
2071 
2072         VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
2073         VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
2074         VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
2075         VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
2076                                 && !pmd_devmap(*pmd));
2077 
2078         count_vm_event(THP_SPLIT_PMD);
2079 
2080         if (!vma_is_anonymous(vma)) {
2081                 _pmd = pmdp_huge_clear_flush_notify(vma, haddr, pmd);
2082                 /*
2083                  * We are going to unmap this huge page. So
2084                  * just go ahead and zap it
2085                  */
2086                 if (arch_needs_pgtable_deposit())
2087                         zap_deposited_table(mm, pmd);
2088                 if (vma_is_dax(vma))
2089                         return;
2090                 page = pmd_page(_pmd);
2091                 if (!PageReferenced(page) && pmd_young(_pmd))
2092                         SetPageReferenced(page);
2093                 page_remove_rmap(page, true);
2094                 put_page(page);
2095                 add_mm_counter(mm, MM_FILEPAGES, -HPAGE_PMD_NR);
2096                 return;
2097         } else if (is_huge_zero_pmd(*pmd)) {
2098                 /*
2099                  * FIXME: Do we want to invalidate secondary mmu by calling
2100                  * mmu_notifier_invalidate_range() see comments below inside
2101                  * __split_huge_pmd() ?
2102                  *
2103                  * We are going from a zero huge page write protected to zero
2104                  * small page also write protected so it does not seems useful
2105                  * to invalidate secondary mmu at this time.
2106                  */
2107                 return __split_huge_zero_page_pmd(vma, haddr, pmd);
2108         }
2109 
2110         /*
2111          * Up to this point the pmd is present and huge and userland has the
2112          * whole access to the hugepage during the split (which happens in
2113          * place). If we overwrite the pmd with the not-huge version pointing
2114          * to the pte here (which of course we could if all CPUs were bug
2115          * free), userland could trigger a small page size TLB miss on the
2116          * small sized TLB while the hugepage TLB entry is still established in
2117          * the huge TLB. Some CPU doesn't like that.
2118          * See http://support.amd.com/us/Processor_TechDocs/41322.pdf, Erratum
2119          * 383 on page 93. Intel should be safe but is also warns that it's
2120          * only safe if the permission and cache attributes of the two entries
2121          * loaded in the two TLB is identical (which should be the case here).
2122          * But it is generally safer to never allow small and huge TLB entries
2123          * for the same virtual address to be loaded simultaneously. So instead
2124          * of doing "pmd_populate(); flush_pmd_tlb_range();" we first mark the
2125          * current pmd notpresent (atomically because here the pmd_trans_huge
2126          * must remain set at all times on the pmd until the split is complete
2127          * for this pmd), then we flush the SMP TLB and finally we write the
2128          * non-huge version of the pmd entry with pmd_populate.
2129          */
2130         old_pmd = pmdp_invalidate(vma, haddr, pmd);
2131 
2132 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2133         pmd_migration = is_pmd_migration_entry(old_pmd);
2134         if (pmd_migration) {
2135                 swp_entry_t entry;
2136 
2137                 entry = pmd_to_swp_entry(old_pmd);
2138                 page = pfn_to_page(swp_offset(entry));
2139         } else
2140 #endif
2141                 page = pmd_page(old_pmd);
2142         VM_BUG_ON_PAGE(!page_count(page), page);
2143         page_ref_add(page, HPAGE_PMD_NR - 1);
2144         if (pmd_dirty(old_pmd))
2145                 SetPageDirty(page);
2146         write = pmd_write(old_pmd);
2147         young = pmd_young(old_pmd);
2148         soft_dirty = pmd_soft_dirty(old_pmd);
2149 
2150         /*
2151          * Withdraw the table only after we mark the pmd entry invalid.
2152          * This's critical for some architectures (Power).
2153          */
2154         pgtable = pgtable_trans_huge_withdraw(mm, pmd);
2155         pmd_populate(mm, &_pmd, pgtable);
2156 
2157         for (i = 0, addr = haddr; i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE) {
2158                 pte_t entry, *pte;
2159                 /*
2160                  * Note that NUMA hinting access restrictions are not
2161                  * transferred to avoid any possibility of altering
2162                  * permissions across VMAs.
2163                  */
2164                 if (freeze || pmd_migration) {
2165                         swp_entry_t swp_entry;
2166                         swp_entry = make_migration_entry(page + i, write);
2167                         entry = swp_entry_to_pte(swp_entry);
2168                         if (soft_dirty)
2169                                 entry = pte_swp_mksoft_dirty(entry);
2170                 } else {
2171                         entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot));
2172                         entry = maybe_mkwrite(entry, vma);
2173                         if (!write)
2174                                 entry = pte_wrprotect(entry);
2175                         if (!young)
2176                                 entry = pte_mkold(entry);
2177                         if (soft_dirty)
2178                                 entry = pte_mksoft_dirty(entry);
2179                 }
2180                 pte = pte_offset_map(&_pmd, addr);
2181                 BUG_ON(!pte_none(*pte));
2182                 set_pte_at(mm, addr, pte, entry);
2183                 atomic_inc(&page[i]._mapcount);
2184                 pte_unmap(pte);
2185         }
2186 
2187         /*
2188          * Set PG_double_map before dropping compound_mapcount to avoid
2189          * false-negative page_mapped().
2190          */
2191         if (compound_mapcount(page) > 1 && !TestSetPageDoubleMap(page)) {
2192                 for (i = 0; i < HPAGE_PMD_NR; i++)
2193                         atomic_inc(&page[i]._mapcount);
2194         }
2195 
2196         if (atomic_add_negative(-1, compound_mapcount_ptr(page))) {
2197                 /* Last compound_mapcount is gone. */
2198                 __dec_node_page_state(page, NR_ANON_THPS);
2199                 if (TestClearPageDoubleMap(page)) {
2200                         /* No need in mapcount reference anymore */
2201                         for (i = 0; i < HPAGE_PMD_NR; i++)
2202                                 atomic_dec(&page[i]._mapcount);
2203                 }
2204         }
2205 
2206         smp_wmb(); /* make pte visible before pmd */
2207         pmd_populate(mm, pmd, pgtable);
2208 
2209         if (freeze) {
2210                 for (i = 0; i < HPAGE_PMD_NR; i++) {
2211                         page_remove_rmap(page + i, false);
2212                         put_page(page + i);
2213                 }
2214         }
2215 }
2216 
2217 void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
2218                 unsigned long address, bool freeze, struct page *page)
2219 {
2220         spinlock_t *ptl;
2221         struct mm_struct *mm = vma->vm_mm;
2222         unsigned long haddr = address & HPAGE_PMD_MASK;
2223 
2224         mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
2225         ptl = pmd_lock(mm, pmd);
2226 
2227         /*
2228          * If caller asks to setup a migration entries, we need a page to check
2229          * pmd against. Otherwise we can end up replacing wrong page.
2230          */
2231         VM_BUG_ON(freeze && !page);
2232         if (page && page != pmd_page(*pmd))
2233                 goto out;
2234 
2235         if (pmd_trans_huge(*pmd)) {
2236                 page = pmd_page(*pmd);
2237                 if (PageMlocked(page))
2238                         clear_page_mlock(page);
2239         } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
2240                 goto out;
2241         __split_huge_pmd_locked(vma, pmd, haddr, freeze);
2242 out:
2243         spin_unlock(ptl);
2244         /*
2245          * No need to double call mmu_notifier->invalidate_range() callback.
2246          * They are 3 cases to consider inside __split_huge_pmd_locked():
2247          *  1) pmdp_huge_clear_flush_notify() call invalidate_range() obvious
2248          *  2) __split_huge_zero_page_pmd() read only zero page and any write
2249          *    fault will trigger a flush_notify before pointing to a new page
2250          *    (it is fine if the secondary mmu keeps pointing to the old zero
2251          *    page in the meantime)
2252          *  3) Split a huge pmd into pte pointing to the same page. No need
2253          *     to invalidate secondary tlb entry they are all still valid.
2254          *     any further changes to individual pte will notify. So no need
2255          *     to call mmu_notifier->invalidate_range()
2256          */
2257         mmu_notifier_invalidate_range_only_end(mm, haddr, haddr +
2258                                                HPAGE_PMD_SIZE);
2259 }
2260 
2261 void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
2262                 bool freeze, struct page *page)
2263 {
2264         pgd_t *pgd;
2265         p4d_t *p4d;
2266         pud_t *pud;
2267         pmd_t *pmd;
2268 
2269         pgd = pgd_offset(vma->vm_mm, address);
2270         if (!pgd_present(*pgd))
2271                 return;
2272 
2273         p4d = p4d_offset(pgd, address);
2274         if (!p4d_present(*p4d))
2275                 return;
2276 
2277         pud = pud_offset(p4d, address);
2278         if (!pud_present(*pud))
2279                 return;
2280 
2281         pmd = pmd_offset(pud, address);
2282 
2283         __split_huge_pmd(vma, pmd, address, freeze, page);
2284 }
2285 
2286 void vma_adjust_trans_huge(struct vm_area_struct *vma,
2287                              unsigned long start,
2288                              unsigned long end,
2289                              long adjust_next)
2290 {
2291         /*
2292          * If the new start address isn't hpage aligned and it could
2293          * previously contain an hugepage: check if we need to split
2294          * an huge pmd.
2295          */
2296         if (start & ~HPAGE_PMD_MASK &&
2297             (start & HPAGE_PMD_MASK) >= vma->vm_start &&
2298             (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2299                 split_huge_pmd_address(vma, start, false, NULL);
2300 
2301         /*
2302          * If the new end address isn't hpage aligned and it could
2303          * previously contain an hugepage: check if we need to split
2304          * an huge pmd.
2305          */
2306         if (end & ~HPAGE_PMD_MASK &&
2307             (end & HPAGE_PMD_MASK) >= vma->vm_start &&
2308             (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
2309                 split_huge_pmd_address(vma, end, false, NULL);
2310 
2311         /*
2312          * If we're also updating the vma->vm_next->vm_start, if the new
2313          * vm_next->vm_start isn't page aligned and it could previously
2314          * contain an hugepage: check if we need to split an huge pmd.
2315          */
2316         if (adjust_next > 0) {
2317                 struct vm_area_struct *next = vma->vm_next;
2318                 unsigned long nstart = next->vm_start;
2319                 nstart += adjust_next << PAGE_SHIFT;
2320                 if (nstart & ~HPAGE_PMD_MASK &&
2321                     (nstart & HPAGE_PMD_MASK) >= next->vm_start &&
2322                     (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
2323                         split_huge_pmd_address(next, nstart, false, NULL);
2324         }
2325 }
2326 
2327 static void freeze_page(struct page *page)
2328 {
2329         enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS |
2330                 TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD;
2331         bool unmap_success;
2332 
2333         VM_BUG_ON_PAGE(!PageHead(page), page);
2334 
2335         if (PageAnon(page))
2336                 ttu_flags |= TTU_SPLIT_FREEZE;
2337 
2338         unmap_success = try_to_unmap(page, ttu_flags);
2339         VM_BUG_ON_PAGE(!unmap_success, page);
2340 }
2341 
2342 static void unfreeze_page(struct page *page)
2343 {
2344         int i;
2345         if (PageTransHuge(page)) {
2346                 remove_migration_ptes(page, page, true);
2347         } else {
2348                 for (i = 0; i < HPAGE_PMD_NR; i++)
2349                         remove_migration_ptes(page + i, page + i, true);
2350         }
2351 }
2352 
2353 static void __split_huge_page_tail(struct page *head, int tail,
2354                 struct lruvec *lruvec, struct list_head *list)
2355 {
2356         struct page *page_tail = head + tail;
2357 
2358         VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail);
2359         VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail);
2360 
2361         /*
2362          * tail_page->_refcount is zero and not changing from under us. But
2363          * get_page_unless_zero() may be running from under us on the
2364          * tail_page. If we used atomic_set() below instead of atomic_inc() or
2365          * atomic_add(), we would then run atomic_set() concurrently with
2366          * get_page_unless_zero(), and atomic_set() is implemented in C not
2367          * using locked ops. spin_unlock on x86 sometime uses locked ops
2368          * because of PPro errata 66, 92, so unless somebody can guarantee
2369          * atomic_set() here would be safe on all archs (and not only on x86),
2370          * it's safer to use atomic_inc()/atomic_add().
2371          */
2372         if (PageAnon(head) && !PageSwapCache(head)) {
2373                 page_ref_inc(page_tail);
2374         } else {
2375                 /* Additional pin to radix tree */
2376                 page_ref_add(page_tail, 2);
2377         }
2378 
2379         page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
2380         page_tail->flags |= (head->flags &
2381                         ((1L << PG_referenced) |
2382                          (1L << PG_swapbacked) |
2383                          (1L << PG_swapcache) |
2384                          (1L << PG_mlocked) |
2385                          (1L << PG_uptodate) |
2386                          (1L << PG_active) |
2387                          (1L << PG_locked) |
2388                          (1L << PG_unevictable) |
2389                          (1L << PG_dirty)));
2390 
2391         /*
2392          * After clearing PageTail the gup refcount can be released.
2393          * Page flags also must be visible before we make the page non-compound.
2394          */
2395         smp_wmb();
2396 
2397         clear_compound_head(page_tail);
2398 
2399         if (page_is_young(head))
2400                 set_page_young(page_tail);
2401         if (page_is_idle(head))
2402                 set_page_idle(page_tail);
2403 
2404         /* ->mapping in first tail page is compound_mapcount */
2405         VM_BUG_ON_PAGE(tail > 2 && page_tail->mapping != TAIL_MAPPING,
2406                         page_tail);
2407         page_tail->mapping = head->mapping;
2408 
2409         page_tail->index = head->index + tail;
2410         page_cpupid_xchg_last(page_tail, page_cpupid_last(head));
2411         lru_add_page_tail(head, page_tail, lruvec, list);
2412 }
2413 
2414 static void __split_huge_page(struct page *page, struct list_head *list,
2415                 unsigned long flags)
2416 {
2417         struct page *head = compound_head(page);
2418         struct zone *zone = page_zone(head);
2419         struct lruvec *lruvec;
2420         pgoff_t end = -1;
2421         int i;
2422 
2423         lruvec = mem_cgroup_page_lruvec(head, zone->zone_pgdat);
2424 
2425         /* complete memcg works before add pages to LRU */
2426         mem_cgroup_split_huge_fixup(head);
2427 
2428         if (!PageAnon(page))
2429                 end = DIV_ROUND_UP(i_size_read(head->mapping->host), PAGE_SIZE);
2430 
2431         for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
2432                 __split_huge_page_tail(head, i, lruvec, list);
2433                 /* Some pages can be beyond i_size: drop them from page cache */
2434                 if (head[i].index >= end) {
2435                         ClearPageDirty(head + i);
2436                         __delete_from_page_cache(head + i, NULL);
2437                         if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head))
2438                                 shmem_uncharge(head->mapping->host, 1);
2439                         put_page(head + i);
2440                 }
2441         }
2442 
2443         ClearPageCompound(head);
2444         /* See comment in __split_huge_page_tail() */
2445         if (PageAnon(head)) {
2446                 /* Additional pin to radix tree of swap cache */
2447                 if (PageSwapCache(head))
2448                         page_ref_add(head, 2);
2449                 else
2450                         page_ref_inc(head);
2451         } else {
2452                 /* Additional pin to radix tree */
2453                 page_ref_add(head, 2);
2454                 spin_unlock(&head->mapping->tree_lock);
2455         }
2456 
2457         spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2458 
2459         unfreeze_page(head);
2460 
2461         for (i = 0; i < HPAGE_PMD_NR; i++) {
2462                 struct page *subpage = head + i;
2463                 if (subpage == page)
2464                         continue;
2465                 unlock_page(subpage);
2466 
2467                 /*
2468                  * Subpages may be freed if there wasn't any mapping
2469                  * like if add_to_swap() is running on a lru page that
2470                  * had its mapping zapped. And freeing these pages
2471                  * requires taking the lru_lock so we do the put_page
2472                  * of the tail pages after the split is complete.
2473                  */
2474                 put_page(subpage);
2475         }
2476 }
2477 
2478 int total_mapcount(struct page *page)
2479 {
2480         int i, compound, ret;
2481 
2482         VM_BUG_ON_PAGE(PageTail(page), page);
2483 
2484         if (likely(!PageCompound(page)))
2485                 return atomic_read(&page->_mapcount) + 1;
2486 
2487         compound = compound_mapcount(page);
2488         if (PageHuge(page))
2489                 return compound;
2490         ret = compound;
2491         for (i = 0; i < HPAGE_PMD_NR; i++)
2492                 ret += atomic_read(&page[i]._mapcount) + 1;
2493         /* File pages has compound_mapcount included in _mapcount */
2494         if (!PageAnon(page))
2495                 return ret - compound * HPAGE_PMD_NR;
2496         if (PageDoubleMap(page))
2497                 ret -= HPAGE_PMD_NR;
2498         return ret;
2499 }
2500 
2501 /*
2502  * This calculates accurately how many mappings a transparent hugepage
2503  * has (unlike page_mapcount() which isn't fully accurate). This full
2504  * accuracy is primarily needed to know if copy-on-write faults can
2505  * reuse the page and change the mapping to read-write instead of
2506  * copying them. At the same time this returns the total_mapcount too.
2507  *
2508  * The function returns the highest mapcount any one of the subpages
2509  * has. If the return value is one, even if different processes are
2510  * mapping different subpages of the transparent hugepage, they can
2511  * all reuse it, because each process is reusing a different subpage.
2512  *
2513  * The total_mapcount is instead counting all virtual mappings of the
2514  * subpages. If the total_mapcount is equal to "one", it tells the
2515  * caller all mappings belong to the same "mm" and in turn the
2516  * anon_vma of the transparent hugepage can become the vma->anon_vma
2517  * local one as no other process may be mapping any of the subpages.
2518  *
2519  * It would be more accurate to replace page_mapcount() with
2520  * page_trans_huge_mapcount(), however we only use
2521  * page_trans_huge_mapcount() in the copy-on-write faults where we
2522  * need full accuracy to avoid breaking page pinning, because
2523  * page_trans_huge_mapcount() is slower than page_mapcount().
2524  */
2525 int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
2526 {
2527         int i, ret, _total_mapcount, mapcount;
2528 
2529         /* hugetlbfs shouldn't call it */
2530         VM_BUG_ON_PAGE(PageHuge(page), page);
2531 
2532         if (likely(!PageTransCompound(page))) {
2533                 mapcount = atomic_read(&page->_mapcount) + 1;
2534                 if (total_mapcount)
2535                         *total_mapcount = mapcount;
2536                 return mapcount;
2537         }
2538 
2539         page = compound_head(page);
2540 
2541         _total_mapcount = ret = 0;
2542         for (i = 0; i < HPAGE_PMD_NR; i++) {
2543                 mapcount = atomic_read(&page[i]._mapcount) + 1;
2544                 ret = max(ret, mapcount);
2545                 _total_mapcount += mapcount;
2546         }
2547         if (PageDoubleMap(page)) {
2548                 ret -= 1;
2549                 _total_mapcount -= HPAGE_PMD_NR;
2550         }
2551         mapcount = compound_mapcount(page);
2552         ret += mapcount;
2553         _total_mapcount += mapcount;
2554         if (total_mapcount)
2555                 *total_mapcount = _total_mapcount;
2556         return ret;
2557 }
2558 
2559 /* Racy check whether the huge page can be split */
2560 bool can_split_huge_page(struct page *page, int *pextra_pins)
2561 {
2562         int extra_pins;
2563 
2564         /* Additional pins from radix tree */
2565         if (PageAnon(page))
2566                 extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
2567         else
2568                 extra_pins = HPAGE_PMD_NR;
2569         if (pextra_pins)
2570                 *pextra_pins = extra_pins;
2571         return total_mapcount(page) == page_count(page) - extra_pins - 1;
2572 }
2573 
2574 /*
2575  * This function splits huge page into normal pages. @page can point to any
2576  * subpage of huge page to split. Split doesn't change the position of @page.
2577  *
2578  * Only caller must hold pin on the @page, otherwise split fails with -EBUSY.
2579  * The huge page must be locked.
2580  *
2581  * If @list is null, tail pages will be added to LRU list, otherwise, to @list.
2582  *
2583  * Both head page and tail pages will inherit mapping, flags, and so on from
2584  * the hugepage.
2585  *
2586  * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if
2587  * they are not mapped.
2588  *
2589  * Returns 0 if the hugepage is split successfully.
2590  * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under
2591  * us.
2592  */
2593 int split_huge_page_to_list(struct page *page, struct list_head *list)
2594 {
2595         struct page *head = compound_head(page);
2596         struct pglist_data *pgdata = NODE_DATA(page_to_nid(head));
2597         struct anon_vma *anon_vma = NULL;
2598         struct address_space *mapping = NULL;
2599         int count, mapcount, extra_pins, ret;
2600         bool mlocked;
2601         unsigned long flags;
2602 
2603         VM_BUG_ON_PAGE(is_huge_zero_page(page), page);
2604         VM_BUG_ON_PAGE(!PageLocked(page), page);
2605         VM_BUG_ON_PAGE(!PageCompound(page), page);
2606 
2607         if (PageWriteback(page))
2608                 return -EBUSY;
2609 
2610         if (PageAnon(head)) {
2611                 /*
2612                  * The caller does not necessarily hold an mmap_sem that would
2613                  * prevent the anon_vma disappearing so we first we take a
2614                  * reference to it and then lock the anon_vma for write. This
2615                  * is similar to page_lock_anon_vma_read except the write lock
2616                  * is taken to serialise against parallel split or collapse
2617                  * operations.
2618                  */
2619                 anon_vma = page_get_anon_vma(head);
2620                 if (!anon_vma) {
2621                         ret = -EBUSY;
2622                         goto out;
2623                 }
2624                 mapping = NULL;
2625                 anon_vma_lock_write(anon_vma);
2626         } else {
2627                 mapping = head->mapping;
2628 
2629                 /* Truncated ? */
2630                 if (!mapping) {
2631                         ret = -EBUSY;
2632                         goto out;
2633                 }
2634 
2635                 anon_vma = NULL;
2636                 i_mmap_lock_read(mapping);
2637         }
2638 
2639         /*
2640          * Racy check if we can split the page, before freeze_page() will
2641          * split PMDs
2642          */
2643         if (!can_split_huge_page(head, &extra_pins)) {
2644                 ret = -EBUSY;
2645                 goto out_unlock;
2646         }
2647 
2648         mlocked = PageMlocked(page);
2649         freeze_page(head);
2650         VM_BUG_ON_PAGE(compound_mapcount(head), head);
2651 
2652         /* Make sure the page is not on per-CPU pagevec as it takes pin */
2653         if (mlocked)
2654                 lru_add_drain();
2655 
2656         /* prevent PageLRU to go away from under us, and freeze lru stats */
2657         spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
2658 
2659         if (mapping) {
2660                 void **pslot;
2661 
2662                 spin_lock(&mapping->tree_lock);
2663                 pslot = radix_tree_lookup_slot(&mapping->page_tree,
2664                                 page_index(head));
2665                 /*
2666                  * Check if the head page is present in radix tree.
2667                  * We assume all tail are present too, if head is there.
2668                  */
2669                 if (radix_tree_deref_slot_protected(pslot,
2670                                         &mapping->tree_lock) != head)
2671                         goto fail;
2672         }
2673 
2674         /* Prevent deferred_split_scan() touching ->_refcount */
2675         spin_lock(&pgdata->split_queue_lock);
2676         count = page_count(head);
2677         mapcount = total_mapcount(head);
2678         if (!mapcount && page_ref_freeze(head, 1 + extra_pins)) {
2679                 if (!list_empty(page_deferred_list(head))) {
2680                         pgdata->split_queue_len--;
2681                         list_del(page_deferred_list(head));
2682                 }
2683                 if (mapping)
2684                         __dec_node_page_state(page, NR_SHMEM_THPS);
2685                 spin_unlock(&pgdata->split_queue_lock);
2686                 __split_huge_page(page, list, flags);
2687                 if (PageSwapCache(head)) {
2688                         swp_entry_t entry = { .val = page_private(head) };
2689 
2690                         ret = split_swap_cluster(entry);
2691                 } else
2692                         ret = 0;
2693         } else {
2694                 if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
2695                         pr_alert("total_mapcount: %u, page_count(): %u\n",
2696                                         mapcount, count);
2697                         if (PageTail(page))
2698                                 dump_page(head, NULL);
2699                         dump_page(page, "total_mapcount(head) > 0");
2700                         BUG();
2701                 }
2702                 spin_unlock(&pgdata->split_queue_lock);
2703 fail:           if (mapping)
2704                         spin_unlock(&mapping->tree_lock);
2705                 spin_unlock_irqrestore(zone_lru_lock(page_zone(head)), flags);
2706                 unfreeze_page(head);
2707                 ret = -EBUSY;
2708         }
2709 
2710 out_unlock:
2711         if (anon_vma) {
2712                 anon_vma_unlock_write(anon_vma);
2713                 put_anon_vma(anon_vma);
2714         }
2715         if (mapping)
2716                 i_mmap_unlock_read(mapping);
2717 out:
2718         count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
2719         return ret;
2720 }
2721 
2722 void free_transhuge_page(struct page *page)
2723 {
2724         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2725         unsigned long flags;
2726 
2727         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2728         if (!list_empty(page_deferred_list(page))) {
2729                 pgdata->split_queue_len--;
2730                 list_del(page_deferred_list(page));
2731         }
2732         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2733         free_compound_page(page);
2734 }
2735 
2736 void deferred_split_huge_page(struct page *page)
2737 {
2738         struct pglist_data *pgdata = NODE_DATA(page_to_nid(page));
2739         unsigned long flags;
2740 
2741         VM_BUG_ON_PAGE(!PageTransHuge(page), page);
2742 
2743         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2744         if (list_empty(page_deferred_list(page))) {
2745                 count_vm_event(THP_DEFERRED_SPLIT_PAGE);
2746                 list_add_tail(page_deferred_list(page), &pgdata->split_queue);
2747                 pgdata->split_queue_len++;
2748         }
2749         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2750 }
2751 
2752 static unsigned long deferred_split_count(struct shrinker *shrink,
2753                 struct shrink_control *sc)
2754 {
2755         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2756         return READ_ONCE(pgdata->split_queue_len);
2757 }
2758 
2759 static unsigned long deferred_split_scan(struct shrinker *shrink,
2760                 struct shrink_control *sc)
2761 {
2762         struct pglist_data *pgdata = NODE_DATA(sc->nid);
2763         unsigned long flags;
2764         LIST_HEAD(list), *pos, *next;
2765         struct page *page;
2766         int split = 0;
2767 
2768         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2769         /* Take pin on all head pages to avoid freeing them under us */
2770         list_for_each_safe(pos, next, &pgdata->split_queue) {
2771                 page = list_entry((void *)pos, struct page, mapping);
2772                 page = compound_head(page);
2773                 if (get_page_unless_zero(page)) {
2774                         list_move(page_deferred_list(page), &list);
2775                 } else {
2776                         /* We lost race with put_compound_page() */
2777                         list_del_init(page_deferred_list(page));
2778                         pgdata->split_queue_len--;
2779                 }
2780                 if (!--sc->nr_to_scan)
2781                         break;
2782         }
2783         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2784 
2785         list_for_each_safe(pos, next, &list) {
2786                 page = list_entry((void *)pos, struct page, mapping);
2787                 if (!trylock_page(page))
2788                         goto next;
2789                 /* split_huge_page() removes page from list on success */
2790                 if (!split_huge_page(page))
2791                         split++;
2792                 unlock_page(page);
2793 next:
2794                 put_page(page);
2795         }
2796 
2797         spin_lock_irqsave(&pgdata->split_queue_lock, flags);
2798         list_splice_tail(&list, &pgdata->split_queue);
2799         spin_unlock_irqrestore(&pgdata->split_queue_lock, flags);
2800 
2801         /*
2802          * Stop shrinker if we didn't split any page, but the queue is empty.
2803          * This can happen if pages were freed under us.
2804          */
2805         if (!split && list_empty(&pgdata->split_queue))
2806                 return SHRINK_STOP;
2807         return split;
2808 }
2809 
2810 static struct shrinker deferred_split_shrinker = {
2811         .count_objects = deferred_split_count,
2812         .scan_objects = deferred_split_scan,
2813         .seeks = DEFAULT_SEEKS,
2814         .flags = SHRINKER_NUMA_AWARE,
2815 };
2816 
2817 #ifdef CONFIG_DEBUG_FS
2818 static int split_huge_pages_set(void *data, u64 val)
2819 {
2820         struct zone *zone;
2821         struct page *page;
2822         unsigned long pfn, max_zone_pfn;
2823         unsigned long total = 0, split = 0;
2824 
2825         if (val != 1)
2826                 return -EINVAL;
2827 
2828         for_each_populated_zone(zone) {
2829                 max_zone_pfn = zone_end_pfn(zone);
2830                 for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
2831                         if (!pfn_valid(pfn))
2832                                 continue;
2833 
2834                         page = pfn_to_page(pfn);
2835                         if (!get_page_unless_zero(page))
2836                                 continue;
2837 
2838                         if (zone != page_zone(page))
2839                                 goto next;
2840 
2841                         if (!PageHead(page) || PageHuge(page) || !PageLRU(page))
2842                                 goto next;
2843 
2844                         total++;
2845                         lock_page(page);
2846                         if (!split_huge_page(page))
2847                                 split++;
2848                         unlock_page(page);
2849 next:
2850                         put_page(page);
2851                 }
2852         }
2853 
2854         pr_info("%lu of %lu THP split\n", split, total);
2855 
2856         return 0;
2857 }
2858 DEFINE_SIMPLE_ATTRIBUTE(split_huge_pages_fops, NULL, split_huge_pages_set,
2859                 "%llu\n");
2860 
2861 static int __init split_huge_pages_debugfs(void)
2862 {
2863         void *ret;
2864 
2865         ret = debugfs_create_file("split_huge_pages", 0200, NULL, NULL,
2866                         &split_huge_pages_fops);
2867         if (!ret)
2868                 pr_warn("Failed to create split_huge_pages in debugfs");
2869         return 0;
2870 }
2871 late_initcall(split_huge_pages_debugfs);
2872 #endif
2873 
2874 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2875 void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
2876                 struct page *page)
2877 {
2878         struct vm_area_struct *vma = pvmw->vma;
2879         struct mm_struct *mm = vma->vm_mm;
2880         unsigned long address = pvmw->address;
2881         pmd_t pmdval;
2882         swp_entry_t entry;
2883         pmd_t pmdswp;
2884 
2885         if (!(pvmw->pmd && !pvmw->pte))
2886                 return;
2887 
2888         mmu_notifier_invalidate_range_start(mm, address,
2889                         address + HPAGE_PMD_SIZE);
2890 
2891         flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
2892         pmdval = *pvmw->pmd;
2893         pmdp_invalidate(vma, address, pvmw->pmd);
2894         if (pmd_dirty(pmdval))
2895                 set_page_dirty(page);
2896         entry = make_migration_entry(page, pmd_write(pmdval));
2897         pmdswp = swp_entry_to_pmd(entry);
2898         if (pmd_soft_dirty(pmdval))
2899                 pmdswp = pmd_swp_mksoft_dirty(pmdswp);
2900         set_pmd_at(mm, address, pvmw->pmd, pmdswp);
2901         page_remove_rmap(page, true);
2902         put_page(page);
2903 
2904         mmu_notifier_invalidate_range_end(mm, address,
2905                         address + HPAGE_PMD_SIZE);
2906 }
2907 
2908 void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new)
2909 {
2910         struct vm_area_struct *vma = pvmw->vma;
2911         struct mm_struct *mm = vma->vm_mm;
2912         unsigned long address = pvmw->address;
2913         unsigned long mmun_start = address & HPAGE_PMD_MASK;
2914         pmd_t pmde;
2915         swp_entry_t entry;
2916 
2917         if (!(pvmw->pmd && !pvmw->pte))
2918                 return;
2919 
2920         entry = pmd_to_swp_entry(*pvmw->pmd);
2921         get_page(new);
2922         pmde = pmd_mkold(mk_huge_pmd(new, vma->vm_page_prot));
2923         if (pmd_swp_soft_dirty(*pvmw->pmd))
2924                 pmde = pmd_mksoft_dirty(pmde);
2925         if (is_write_migration_entry(entry))
2926                 pmde = maybe_pmd_mkwrite(pmde, vma);
2927 
2928         flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE);
2929         page_add_anon_rmap(new, vma, mmun_start, true);
2930         set_pmd_at(mm, mmun_start, pvmw->pmd, pmde);
2931         if (vma->vm_flags & VM_LOCKED)
2932                 mlock_vma_page(new);
2933         update_mmu_cache_pmd(vma, address, pvmw->pmd);
2934 }
2935 #endif
2936 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp