1/* SPDX-License-Identifier: GPL-2.0-or-later */
2/* internal.h: mm/ internal definitions
3 *
4 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7#ifndef __MM_INTERNAL_H
8#define __MM_INTERNAL_H
9
10#include <linux/fs.h>
11#include <linux/mm.h>
12#include <linux/pagemap.h>
13#include <linux/rmap.h>
14#include <linux/tracepoint-defs.h>
15
16struct folio_batch;
17
18/*
19 * The set of flags that only affect watermark checking and reclaim
20 * behaviour. This is used by the MM to obey the caller constraints
21 * about IO, FS and watermark checking while ignoring placement
22 * hints such as HIGHMEM usage.
23 */
24#define GFP_RECLAIM_MASK (__GFP_RECLAIM|__GFP_HIGH|__GFP_IO|__GFP_FS|\
25 __GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_NOFAIL|\
26 __GFP_NORETRY|__GFP_MEMALLOC|__GFP_NOMEMALLOC|\
27 __GFP_NOLOCKDEP)
28
29/* The GFP flags allowed during early boot */
30#define GFP_BOOT_MASK (__GFP_BITS_MASK & ~(__GFP_RECLAIM|__GFP_IO|__GFP_FS))
31
32/* Control allocation cpuset and node placement constraints */
33#define GFP_CONSTRAINT_MASK (__GFP_HARDWALL|__GFP_THISNODE)
34
35/* Do not use these with a slab allocator */
36#define GFP_SLAB_BUG_MASK (__GFP_DMA32|__GFP_HIGHMEM|~__GFP_BITS_MASK)
37
38/*
39 * Different from WARN_ON_ONCE(), no warning will be issued
40 * when we specify __GFP_NOWARN.
41 */
42#define WARN_ON_ONCE_GFP(cond, gfp) ({ \
43 static bool __section(".data.once") __warned; \
44 int __ret_warn_once = !!(cond); \
45 \
46 if (unlikely(!(gfp & __GFP_NOWARN) && __ret_warn_once && !__warned)) { \
47 __warned = true; \
48 WARN_ON(1); \
49 } \
50 unlikely(__ret_warn_once); \
51})
52
53void page_writeback_init(void);
54
55/*
56 * If a 16GB hugetlb folio were mapped by PTEs of all of its 4kB pages,
57 * its nr_pages_mapped would be 0x400000: choose the COMPOUND_MAPPED bit
58 * above that range, instead of 2*(PMD_SIZE/PAGE_SIZE). Hugetlb currently
59 * leaves nr_pages_mapped at 0, but avoid surprise if it participates later.
60 */
61#define COMPOUND_MAPPED 0x800000
62#define FOLIO_PAGES_MAPPED (COMPOUND_MAPPED - 1)
63
64/*
65 * Flags passed to __show_mem() and show_free_areas() to suppress output in
66 * various contexts.
67 */
68#define SHOW_MEM_FILTER_NODES (0x0001u) /* disallowed nodes */
69
70/*
71 * How many individual pages have an elevated _mapcount. Excludes
72 * the folio's entire_mapcount.
73 */
74static inline int folio_nr_pages_mapped(struct folio *folio)
75{
76 return atomic_read(v: &folio->_nr_pages_mapped) & FOLIO_PAGES_MAPPED;
77}
78
79static inline void *folio_raw_mapping(struct folio *folio)
80{
81 unsigned long mapping = (unsigned long)folio->mapping;
82
83 return (void *)(mapping & ~PAGE_MAPPING_FLAGS);
84}
85
86void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
87 int nr_throttled);
88static inline void acct_reclaim_writeback(struct folio *folio)
89{
90 pg_data_t *pgdat = folio_pgdat(folio);
91 int nr_throttled = atomic_read(v: &pgdat->nr_writeback_throttled);
92
93 if (nr_throttled)
94 __acct_reclaim_writeback(pgdat, folio, nr_throttled);
95}
96
97static inline void wake_throttle_isolated(pg_data_t *pgdat)
98{
99 wait_queue_head_t *wqh;
100
101 wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_ISOLATED];
102 if (waitqueue_active(wq_head: wqh))
103 wake_up(wqh);
104}
105
106vm_fault_t do_swap_page(struct vm_fault *vmf);
107void folio_rotate_reclaimable(struct folio *folio);
108bool __folio_end_writeback(struct folio *folio);
109void deactivate_file_folio(struct folio *folio);
110void folio_activate(struct folio *folio);
111
112void free_pgtables(struct mmu_gather *tlb, struct ma_state *mas,
113 struct vm_area_struct *start_vma, unsigned long floor,
114 unsigned long ceiling, bool mm_wr_locked);
115void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte);
116
117struct zap_details;
118void unmap_page_range(struct mmu_gather *tlb,
119 struct vm_area_struct *vma,
120 unsigned long addr, unsigned long end,
121 struct zap_details *details);
122
123void page_cache_ra_order(struct readahead_control *, struct file_ra_state *,
124 unsigned int order);
125void force_page_cache_ra(struct readahead_control *, unsigned long nr);
126static inline void force_page_cache_readahead(struct address_space *mapping,
127 struct file *file, pgoff_t index, unsigned long nr_to_read)
128{
129 DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, index);
130 force_page_cache_ra(&ractl, nr: nr_to_read);
131}
132
133unsigned find_lock_entries(struct address_space *mapping, pgoff_t *start,
134 pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices);
135unsigned find_get_entries(struct address_space *mapping, pgoff_t *start,
136 pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices);
137void filemap_free_folio(struct address_space *mapping, struct folio *folio);
138int truncate_inode_folio(struct address_space *mapping, struct folio *folio);
139bool truncate_inode_partial_folio(struct folio *folio, loff_t start,
140 loff_t end);
141long invalidate_inode_page(struct page *page);
142unsigned long mapping_try_invalidate(struct address_space *mapping,
143 pgoff_t start, pgoff_t end, unsigned long *nr_failed);
144
145/**
146 * folio_evictable - Test whether a folio is evictable.
147 * @folio: The folio to test.
148 *
149 * Test whether @folio is evictable -- i.e., should be placed on
150 * active/inactive lists vs unevictable list.
151 *
152 * Reasons folio might not be evictable:
153 * 1. folio's mapping marked unevictable
154 * 2. One of the pages in the folio is part of an mlocked VMA
155 */
156static inline bool folio_evictable(struct folio *folio)
157{
158 bool ret;
159
160 /* Prevent address_space of inode and swap cache from being freed */
161 rcu_read_lock();
162 ret = !mapping_unevictable(mapping: folio_mapping(folio)) &&
163 !folio_test_mlocked(folio);
164 rcu_read_unlock();
165 return ret;
166}
167
168/*
169 * Turn a non-refcounted page (->_refcount == 0) into refcounted with
170 * a count of one.
171 */
172static inline void set_page_refcounted(struct page *page)
173{
174 VM_BUG_ON_PAGE(PageTail(page), page);
175 VM_BUG_ON_PAGE(page_ref_count(page), page);
176 set_page_count(page, v: 1);
177}
178
179/*
180 * Return true if a folio needs ->release_folio() calling upon it.
181 */
182static inline bool folio_needs_release(struct folio *folio)
183{
184 struct address_space *mapping = folio_mapping(folio);
185
186 return folio_has_private(folio) ||
187 (mapping && mapping_release_always(mapping));
188}
189
190extern unsigned long highest_memmap_pfn;
191
192/*
193 * Maximum number of reclaim retries without progress before the OOM
194 * killer is consider the only way forward.
195 */
196#define MAX_RECLAIM_RETRIES 16
197
198/*
199 * in mm/vmscan.c:
200 */
201bool isolate_lru_page(struct page *page);
202bool folio_isolate_lru(struct folio *folio);
203void putback_lru_page(struct page *page);
204void folio_putback_lru(struct folio *folio);
205extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason);
206
207/*
208 * in mm/rmap.c:
209 */
210pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address);
211
212/*
213 * in mm/page_alloc.c
214 */
215#define K(x) ((x) << (PAGE_SHIFT-10))
216
217extern char * const zone_names[MAX_NR_ZONES];
218
219/* perform sanity checks on struct pages being allocated or freed */
220DECLARE_STATIC_KEY_MAYBE(CONFIG_DEBUG_VM, check_pages_enabled);
221
222extern int min_free_kbytes;
223
224void setup_per_zone_wmarks(void);
225void calculate_min_free_kbytes(void);
226int __meminit init_per_zone_wmark_min(void);
227void page_alloc_sysctl_init(void);
228
229/*
230 * Structure for holding the mostly immutable allocation parameters passed
231 * between functions involved in allocations, including the alloc_pages*
232 * family of functions.
233 *
234 * nodemask, migratetype and highest_zoneidx are initialized only once in
235 * __alloc_pages() and then never change.
236 *
237 * zonelist, preferred_zone and highest_zoneidx are set first in
238 * __alloc_pages() for the fast path, and might be later changed
239 * in __alloc_pages_slowpath(). All other functions pass the whole structure
240 * by a const pointer.
241 */
242struct alloc_context {
243 struct zonelist *zonelist;
244 nodemask_t *nodemask;
245 struct zoneref *preferred_zoneref;
246 int migratetype;
247
248 /*
249 * highest_zoneidx represents highest usable zone index of
250 * the allocation request. Due to the nature of the zone,
251 * memory on lower zone than the highest_zoneidx will be
252 * protected by lowmem_reserve[highest_zoneidx].
253 *
254 * highest_zoneidx is also used by reclaim/compaction to limit
255 * the target zone since higher zone than this index cannot be
256 * usable for this allocation request.
257 */
258 enum zone_type highest_zoneidx;
259 bool spread_dirty_pages;
260};
261
262/*
263 * This function returns the order of a free page in the buddy system. In
264 * general, page_zone(page)->lock must be held by the caller to prevent the
265 * page from being allocated in parallel and returning garbage as the order.
266 * If a caller does not hold page_zone(page)->lock, it must guarantee that the
267 * page cannot be allocated or merged in parallel. Alternatively, it must
268 * handle invalid values gracefully, and use buddy_order_unsafe() below.
269 */
270static inline unsigned int buddy_order(struct page *page)
271{
272 /* PageBuddy() must be checked by the caller */
273 return page_private(page);
274}
275
276/*
277 * Like buddy_order(), but for callers who cannot afford to hold the zone lock.
278 * PageBuddy() should be checked first by the caller to minimize race window,
279 * and invalid values must be handled gracefully.
280 *
281 * READ_ONCE is used so that if the caller assigns the result into a local
282 * variable and e.g. tests it for valid range before using, the compiler cannot
283 * decide to remove the variable and inline the page_private(page) multiple
284 * times, potentially observing different values in the tests and the actual
285 * use of the result.
286 */
287#define buddy_order_unsafe(page) READ_ONCE(page_private(page))
288
289/*
290 * This function checks whether a page is free && is the buddy
291 * we can coalesce a page and its buddy if
292 * (a) the buddy is not in a hole (check before calling!) &&
293 * (b) the buddy is in the buddy system &&
294 * (c) a page and its buddy have the same order &&
295 * (d) a page and its buddy are in the same zone.
296 *
297 * For recording whether a page is in the buddy system, we set PageBuddy.
298 * Setting, clearing, and testing PageBuddy is serialized by zone->lock.
299 *
300 * For recording page's order, we use page_private(page).
301 */
302static inline bool page_is_buddy(struct page *page, struct page *buddy,
303 unsigned int order)
304{
305 if (!page_is_guard(page: buddy) && !PageBuddy(page: buddy))
306 return false;
307
308 if (buddy_order(page: buddy) != order)
309 return false;
310
311 /*
312 * zone check is done late to avoid uselessly calculating
313 * zone/node ids for pages that could never merge.
314 */
315 if (page_zone_id(page) != page_zone_id(page: buddy))
316 return false;
317
318 VM_BUG_ON_PAGE(page_count(buddy) != 0, buddy);
319
320 return true;
321}
322
323/*
324 * Locate the struct page for both the matching buddy in our
325 * pair (buddy1) and the combined O(n+1) page they form (page).
326 *
327 * 1) Any buddy B1 will have an order O twin B2 which satisfies
328 * the following equation:
329 * B2 = B1 ^ (1 << O)
330 * For example, if the starting buddy (buddy2) is #8 its order
331 * 1 buddy is #10:
332 * B2 = 8 ^ (1 << 1) = 8 ^ 2 = 10
333 *
334 * 2) Any buddy B will have an order O+1 parent P which
335 * satisfies the following equation:
336 * P = B & ~(1 << O)
337 *
338 * Assumption: *_mem_map is contiguous at least up to MAX_ORDER
339 */
340static inline unsigned long
341__find_buddy_pfn(unsigned long page_pfn, unsigned int order)
342{
343 return page_pfn ^ (1 << order);
344}
345
346/*
347 * Find the buddy of @page and validate it.
348 * @page: The input page
349 * @pfn: The pfn of the page, it saves a call to page_to_pfn() when the
350 * function is used in the performance-critical __free_one_page().
351 * @order: The order of the page
352 * @buddy_pfn: The output pointer to the buddy pfn, it also saves a call to
353 * page_to_pfn().
354 *
355 * The found buddy can be a non PageBuddy, out of @page's zone, or its order is
356 * not the same as @page. The validation is necessary before use it.
357 *
358 * Return: the found buddy page or NULL if not found.
359 */
360static inline struct page *find_buddy_page_pfn(struct page *page,
361 unsigned long pfn, unsigned int order, unsigned long *buddy_pfn)
362{
363 unsigned long __buddy_pfn = __find_buddy_pfn(page_pfn: pfn, order);
364 struct page *buddy;
365
366 buddy = page + (__buddy_pfn - pfn);
367 if (buddy_pfn)
368 *buddy_pfn = __buddy_pfn;
369
370 if (page_is_buddy(page, buddy, order))
371 return buddy;
372 return NULL;
373}
374
375extern struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
376 unsigned long end_pfn, struct zone *zone);
377
378static inline struct page *pageblock_pfn_to_page(unsigned long start_pfn,
379 unsigned long end_pfn, struct zone *zone)
380{
381 if (zone->contiguous)
382 return pfn_to_page(start_pfn);
383
384 return __pageblock_pfn_to_page(start_pfn, end_pfn, zone);
385}
386
387void set_zone_contiguous(struct zone *zone);
388
389static inline void clear_zone_contiguous(struct zone *zone)
390{
391 zone->contiguous = false;
392}
393
394extern int __isolate_free_page(struct page *page, unsigned int order);
395extern void __putback_isolated_page(struct page *page, unsigned int order,
396 int mt);
397extern void memblock_free_pages(struct page *page, unsigned long pfn,
398 unsigned int order);
399extern void __free_pages_core(struct page *page, unsigned int order);
400
401/*
402 * This will have no effect, other than possibly generating a warning, if the
403 * caller passes in a non-large folio.
404 */
405static inline void folio_set_order(struct folio *folio, unsigned int order)
406{
407 if (WARN_ON_ONCE(!order || !folio_test_large(folio)))
408 return;
409
410 folio->_flags_1 = (folio->_flags_1 & ~0xffUL) | order;
411#ifdef CONFIG_64BIT
412 folio->_folio_nr_pages = 1U << order;
413#endif
414}
415
416void folio_undo_large_rmappable(struct folio *folio);
417
418static inline struct folio *page_rmappable_folio(struct page *page)
419{
420 struct folio *folio = (struct folio *)page;
421
422 if (folio && folio_order(folio) > 1)
423 folio_prep_large_rmappable(folio);
424 return folio;
425}
426
427static inline void prep_compound_head(struct page *page, unsigned int order)
428{
429 struct folio *folio = (struct folio *)page;
430
431 folio_set_order(folio, order);
432 atomic_set(v: &folio->_entire_mapcount, i: -1);
433 atomic_set(v: &folio->_nr_pages_mapped, i: 0);
434 atomic_set(v: &folio->_pincount, i: 0);
435}
436
437static inline void prep_compound_tail(struct page *head, int tail_idx)
438{
439 struct page *p = head + tail_idx;
440
441 p->mapping = TAIL_MAPPING;
442 set_compound_head(page: p, head);
443 set_page_private(page: p, private: 0);
444}
445
446extern void prep_compound_page(struct page *page, unsigned int order);
447
448extern void post_alloc_hook(struct page *page, unsigned int order,
449 gfp_t gfp_flags);
450extern int user_min_free_kbytes;
451
452extern void free_unref_page(struct page *page, unsigned int order);
453extern void free_unref_page_list(struct list_head *list);
454
455extern void zone_pcp_reset(struct zone *zone);
456extern void zone_pcp_disable(struct zone *zone);
457extern void zone_pcp_enable(struct zone *zone);
458extern void zone_pcp_init(struct zone *zone);
459
460extern void *memmap_alloc(phys_addr_t size, phys_addr_t align,
461 phys_addr_t min_addr,
462 int nid, bool exact_nid);
463
464void memmap_init_range(unsigned long, int, unsigned long, unsigned long,
465 unsigned long, enum meminit_context, struct vmem_altmap *, int);
466
467
468int split_free_page(struct page *free_page,
469 unsigned int order, unsigned long split_pfn_offset);
470
471#if defined CONFIG_COMPACTION || defined CONFIG_CMA
472
473/*
474 * in mm/compaction.c
475 */
476/*
477 * compact_control is used to track pages being migrated and the free pages
478 * they are being migrated to during memory compaction. The free_pfn starts
479 * at the end of a zone and migrate_pfn begins at the start. Movable pages
480 * are moved to the end of a zone during a compaction run and the run
481 * completes when free_pfn <= migrate_pfn
482 */
483struct compact_control {
484 struct list_head freepages; /* List of free pages to migrate to */
485 struct list_head migratepages; /* List of pages being migrated */
486 unsigned int nr_freepages; /* Number of isolated free pages */
487 unsigned int nr_migratepages; /* Number of pages to migrate */
488 unsigned long free_pfn; /* isolate_freepages search base */
489 /*
490 * Acts as an in/out parameter to page isolation for migration.
491 * isolate_migratepages uses it as a search base.
492 * isolate_migratepages_block will update the value to the next pfn
493 * after the last isolated one.
494 */
495 unsigned long migrate_pfn;
496 unsigned long fast_start_pfn; /* a pfn to start linear scan from */
497 struct zone *zone;
498 unsigned long total_migrate_scanned;
499 unsigned long total_free_scanned;
500 unsigned short fast_search_fail;/* failures to use free list searches */
501 short search_order; /* order to start a fast search at */
502 const gfp_t gfp_mask; /* gfp mask of a direct compactor */
503 int order; /* order a direct compactor needs */
504 int migratetype; /* migratetype of direct compactor */
505 const unsigned int alloc_flags; /* alloc flags of a direct compactor */
506 const int highest_zoneidx; /* zone index of a direct compactor */
507 enum migrate_mode mode; /* Async or sync migration mode */
508 bool ignore_skip_hint; /* Scan blocks even if marked skip */
509 bool no_set_skip_hint; /* Don't mark blocks for skipping */
510 bool ignore_block_suitable; /* Scan blocks considered unsuitable */
511 bool direct_compaction; /* False from kcompactd or /proc/... */
512 bool proactive_compaction; /* kcompactd proactive compaction */
513 bool whole_zone; /* Whole zone should/has been scanned */
514 bool contended; /* Signal lock contention */
515 bool finish_pageblock; /* Scan the remainder of a pageblock. Used
516 * when there are potentially transient
517 * isolation or migration failures to
518 * ensure forward progress.
519 */
520 bool alloc_contig; /* alloc_contig_range allocation */
521};
522
523/*
524 * Used in direct compaction when a page should be taken from the freelists
525 * immediately when one is created during the free path.
526 */
527struct capture_control {
528 struct compact_control *cc;
529 struct page *page;
530};
531
532unsigned long
533isolate_freepages_range(struct compact_control *cc,
534 unsigned long start_pfn, unsigned long end_pfn);
535int
536isolate_migratepages_range(struct compact_control *cc,
537 unsigned long low_pfn, unsigned long end_pfn);
538
539int __alloc_contig_migrate_range(struct compact_control *cc,
540 unsigned long start, unsigned long end);
541
542/* Free whole pageblock and set its migration type to MIGRATE_CMA. */
543void init_cma_reserved_pageblock(struct page *page);
544
545#endif /* CONFIG_COMPACTION || CONFIG_CMA */
546
547int find_suitable_fallback(struct free_area *area, unsigned int order,
548 int migratetype, bool only_stealable, bool *can_steal);
549
550static inline bool free_area_empty(struct free_area *area, int migratetype)
551{
552 return list_empty(head: &area->free_list[migratetype]);
553}
554
555/*
556 * These three helpers classifies VMAs for virtual memory accounting.
557 */
558
559/*
560 * Executable code area - executable, not writable, not stack
561 */
562static inline bool is_exec_mapping(vm_flags_t flags)
563{
564 return (flags & (VM_EXEC | VM_WRITE | VM_STACK)) == VM_EXEC;
565}
566
567/*
568 * Stack area (including shadow stacks)
569 *
570 * VM_GROWSUP / VM_GROWSDOWN VMAs are always private anonymous:
571 * do_mmap() forbids all other combinations.
572 */
573static inline bool is_stack_mapping(vm_flags_t flags)
574{
575 return ((flags & VM_STACK) == VM_STACK) || (flags & VM_SHADOW_STACK);
576}
577
578/*
579 * Data area - private, writable, not stack
580 */
581static inline bool is_data_mapping(vm_flags_t flags)
582{
583 return (flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE;
584}
585
586/* mm/util.c */
587struct anon_vma *folio_anon_vma(struct folio *folio);
588
589#ifdef CONFIG_MMU
590void unmap_mapping_folio(struct folio *folio);
591extern long populate_vma_page_range(struct vm_area_struct *vma,
592 unsigned long start, unsigned long end, int *locked);
593extern long faultin_vma_page_range(struct vm_area_struct *vma,
594 unsigned long start, unsigned long end,
595 bool write, int *locked);
596extern bool mlock_future_ok(struct mm_struct *mm, unsigned long flags,
597 unsigned long bytes);
598
599/*
600 * NOTE: This function can't tell whether the folio is "fully mapped" in the
601 * range.
602 * "fully mapped" means all the pages of folio is associated with the page
603 * table of range while this function just check whether the folio range is
604 * within the range [start, end). Function caller needs to do page table
605 * check if it cares about the page table association.
606 *
607 * Typical usage (like mlock or madvise) is:
608 * Caller knows at least 1 page of folio is associated with page table of VMA
609 * and the range [start, end) is intersect with the VMA range. Caller wants
610 * to know whether the folio is fully associated with the range. It calls
611 * this function to check whether the folio is in the range first. Then checks
612 * the page table to know whether the folio is fully mapped to the range.
613 */
614static inline bool
615folio_within_range(struct folio *folio, struct vm_area_struct *vma,
616 unsigned long start, unsigned long end)
617{
618 pgoff_t pgoff, addr;
619 unsigned long vma_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
620
621 VM_WARN_ON_FOLIO(folio_test_ksm(folio), folio);
622 if (start > end)
623 return false;
624
625 if (start < vma->vm_start)
626 start = vma->vm_start;
627
628 if (end > vma->vm_end)
629 end = vma->vm_end;
630
631 pgoff = folio_pgoff(folio);
632
633 /* if folio start address is not in vma range */
634 if (!in_range(pgoff, vma->vm_pgoff, vma_pglen))
635 return false;
636
637 addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
638
639 return !(addr < start || end - addr < folio_size(folio));
640}
641
642static inline bool
643folio_within_vma(struct folio *folio, struct vm_area_struct *vma)
644{
645 return folio_within_range(folio, vma, start: vma->vm_start, end: vma->vm_end);
646}
647
648/*
649 * mlock_vma_folio() and munlock_vma_folio():
650 * should be called with vma's mmap_lock held for read or write,
651 * under page table lock for the pte/pmd being added or removed.
652 *
653 * mlock is usually called at the end of page_add_*_rmap(), munlock at
654 * the end of page_remove_rmap(); but new anon folios are managed by
655 * folio_add_lru_vma() calling mlock_new_folio().
656 */
657void mlock_folio(struct folio *folio);
658static inline void mlock_vma_folio(struct folio *folio,
659 struct vm_area_struct *vma)
660{
661 /*
662 * The VM_SPECIAL check here serves two purposes.
663 * 1) VM_IO check prevents migration from double-counting during mlock.
664 * 2) Although mmap_region() and mlock_fixup() take care that VM_LOCKED
665 * is never left set on a VM_SPECIAL vma, there is an interval while
666 * file->f_op->mmap() is using vm_insert_page(s), when VM_LOCKED may
667 * still be set while VM_SPECIAL bits are added: so ignore it then.
668 */
669 if (unlikely((vma->vm_flags & (VM_LOCKED|VM_SPECIAL)) == VM_LOCKED))
670 mlock_folio(folio);
671}
672
673void munlock_folio(struct folio *folio);
674static inline void munlock_vma_folio(struct folio *folio,
675 struct vm_area_struct *vma)
676{
677 /*
678 * munlock if the function is called. Ideally, we should only
679 * do munlock if any page of folio is unmapped from VMA and
680 * cause folio not fully mapped to VMA.
681 *
682 * But it's not easy to confirm that's the situation. So we
683 * always munlock the folio and page reclaim will correct it
684 * if it's wrong.
685 */
686 if (unlikely(vma->vm_flags & VM_LOCKED))
687 munlock_folio(folio);
688}
689
690void mlock_new_folio(struct folio *folio);
691bool need_mlock_drain(int cpu);
692void mlock_drain_local(void);
693void mlock_drain_remote(int cpu);
694
695extern pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma);
696
697/*
698 * Return the start of user virtual address at the specific offset within
699 * a vma.
700 */
701static inline unsigned long
702vma_pgoff_address(pgoff_t pgoff, unsigned long nr_pages,
703 struct vm_area_struct *vma)
704{
705 unsigned long address;
706
707 if (pgoff >= vma->vm_pgoff) {
708 address = vma->vm_start +
709 ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
710 /* Check for address beyond vma (or wrapped through 0?) */
711 if (address < vma->vm_start || address >= vma->vm_end)
712 address = -EFAULT;
713 } else if (pgoff + nr_pages - 1 >= vma->vm_pgoff) {
714 /* Test above avoids possibility of wrap to 0 on 32-bit */
715 address = vma->vm_start;
716 } else {
717 address = -EFAULT;
718 }
719 return address;
720}
721
722/*
723 * Return the start of user virtual address of a page within a vma.
724 * Returns -EFAULT if all of the page is outside the range of vma.
725 * If page is a compound head, the entire compound page is considered.
726 */
727static inline unsigned long
728vma_address(struct page *page, struct vm_area_struct *vma)
729{
730 VM_BUG_ON_PAGE(PageKsm(page), page); /* KSM page->index unusable */
731 return vma_pgoff_address(pgoff: page_to_pgoff(page), nr_pages: compound_nr(page), vma);
732}
733
734/*
735 * Then at what user virtual address will none of the range be found in vma?
736 * Assumes that vma_address() already returned a good starting address.
737 */
738static inline unsigned long vma_address_end(struct page_vma_mapped_walk *pvmw)
739{
740 struct vm_area_struct *vma = pvmw->vma;
741 pgoff_t pgoff;
742 unsigned long address;
743
744 /* Common case, plus ->pgoff is invalid for KSM */
745 if (pvmw->nr_pages == 1)
746 return pvmw->address + PAGE_SIZE;
747
748 pgoff = pvmw->pgoff + pvmw->nr_pages;
749 address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
750 /* Check for address beyond vma (or wrapped through 0?) */
751 if (address < vma->vm_start || address > vma->vm_end)
752 address = vma->vm_end;
753 return address;
754}
755
756static inline struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf,
757 struct file *fpin)
758{
759 int flags = vmf->flags;
760
761 if (fpin)
762 return fpin;
763
764 /*
765 * FAULT_FLAG_RETRY_NOWAIT means we don't want to wait on page locks or
766 * anything, so we only pin the file and drop the mmap_lock if only
767 * FAULT_FLAG_ALLOW_RETRY is set, while this is the first attempt.
768 */
769 if (fault_flag_allow_retry_first(flags) &&
770 !(flags & FAULT_FLAG_RETRY_NOWAIT)) {
771 fpin = get_file(f: vmf->vma->vm_file);
772 release_fault_lock(vmf);
773 }
774 return fpin;
775}
776#else /* !CONFIG_MMU */
777static inline void unmap_mapping_folio(struct folio *folio) { }
778static inline void mlock_new_folio(struct folio *folio) { }
779static inline bool need_mlock_drain(int cpu) { return false; }
780static inline void mlock_drain_local(void) { }
781static inline void mlock_drain_remote(int cpu) { }
782static inline void vunmap_range_noflush(unsigned long start, unsigned long end)
783{
784}
785#endif /* !CONFIG_MMU */
786
787/* Memory initialisation debug and verification */
788#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
789DECLARE_STATIC_KEY_TRUE(deferred_pages);
790
791bool __init deferred_grow_zone(struct zone *zone, unsigned int order);
792#endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
793
794enum mminit_level {
795 MMINIT_WARNING,
796 MMINIT_VERIFY,
797 MMINIT_TRACE
798};
799
800#ifdef CONFIG_DEBUG_MEMORY_INIT
801
802extern int mminit_loglevel;
803
804#define mminit_dprintk(level, prefix, fmt, arg...) \
805do { \
806 if (level < mminit_loglevel) { \
807 if (level <= MMINIT_WARNING) \
808 pr_warn("mminit::" prefix " " fmt, ##arg); \
809 else \
810 printk(KERN_DEBUG "mminit::" prefix " " fmt, ##arg); \
811 } \
812} while (0)
813
814extern void mminit_verify_pageflags_layout(void);
815extern void mminit_verify_zonelist(void);
816#else
817
818static inline void mminit_dprintk(enum mminit_level level,
819 const char *prefix, const char *fmt, ...)
820{
821}
822
823static inline void mminit_verify_pageflags_layout(void)
824{
825}
826
827static inline void mminit_verify_zonelist(void)
828{
829}
830#endif /* CONFIG_DEBUG_MEMORY_INIT */
831
832#define NODE_RECLAIM_NOSCAN -2
833#define NODE_RECLAIM_FULL -1
834#define NODE_RECLAIM_SOME 0
835#define NODE_RECLAIM_SUCCESS 1
836
837#ifdef CONFIG_NUMA
838extern int node_reclaim(struct pglist_data *, gfp_t, unsigned int);
839extern int find_next_best_node(int node, nodemask_t *used_node_mask);
840#else
841static inline int node_reclaim(struct pglist_data *pgdat, gfp_t mask,
842 unsigned int order)
843{
844 return NODE_RECLAIM_NOSCAN;
845}
846static inline int find_next_best_node(int node, nodemask_t *used_node_mask)
847{
848 return NUMA_NO_NODE;
849}
850#endif
851
852/*
853 * mm/memory-failure.c
854 */
855extern int hwpoison_filter(struct page *p);
856
857extern u32 hwpoison_filter_dev_major;
858extern u32 hwpoison_filter_dev_minor;
859extern u64 hwpoison_filter_flags_mask;
860extern u64 hwpoison_filter_flags_value;
861extern u64 hwpoison_filter_memcg;
862extern u32 hwpoison_filter_enable;
863
864extern unsigned long __must_check vm_mmap_pgoff(struct file *, unsigned long,
865 unsigned long, unsigned long,
866 unsigned long, unsigned long);
867
868extern void set_pageblock_order(void);
869unsigned long reclaim_pages(struct list_head *folio_list);
870unsigned int reclaim_clean_pages_from_list(struct zone *zone,
871 struct list_head *folio_list);
872/* The ALLOC_WMARK bits are used as an index to zone->watermark */
873#define ALLOC_WMARK_MIN WMARK_MIN
874#define ALLOC_WMARK_LOW WMARK_LOW
875#define ALLOC_WMARK_HIGH WMARK_HIGH
876#define ALLOC_NO_WATERMARKS 0x04 /* don't check watermarks at all */
877
878/* Mask to get the watermark bits */
879#define ALLOC_WMARK_MASK (ALLOC_NO_WATERMARKS-1)
880
881/*
882 * Only MMU archs have async oom victim reclaim - aka oom_reaper so we
883 * cannot assume a reduced access to memory reserves is sufficient for
884 * !MMU
885 */
886#ifdef CONFIG_MMU
887#define ALLOC_OOM 0x08
888#else
889#define ALLOC_OOM ALLOC_NO_WATERMARKS
890#endif
891
892#define ALLOC_NON_BLOCK 0x10 /* Caller cannot block. Allow access
893 * to 25% of the min watermark or
894 * 62.5% if __GFP_HIGH is set.
895 */
896#define ALLOC_MIN_RESERVE 0x20 /* __GFP_HIGH set. Allow access to 50%
897 * of the min watermark.
898 */
899#define ALLOC_CPUSET 0x40 /* check for correct cpuset */
900#define ALLOC_CMA 0x80 /* allow allocations from CMA areas */
901#ifdef CONFIG_ZONE_DMA32
902#define ALLOC_NOFRAGMENT 0x100 /* avoid mixing pageblock types */
903#else
904#define ALLOC_NOFRAGMENT 0x0
905#endif
906#define ALLOC_HIGHATOMIC 0x200 /* Allows access to MIGRATE_HIGHATOMIC */
907#define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */
908
909/* Flags that allow allocations below the min watermark. */
910#define ALLOC_RESERVES (ALLOC_NON_BLOCK|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM)
911
912enum ttu_flags;
913struct tlbflush_unmap_batch;
914
915
916/*
917 * only for MM internal work items which do not depend on
918 * any allocations or locks which might depend on allocations
919 */
920extern struct workqueue_struct *mm_percpu_wq;
921
922#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
923void try_to_unmap_flush(void);
924void try_to_unmap_flush_dirty(void);
925void flush_tlb_batched_pending(struct mm_struct *mm);
926#else
927static inline void try_to_unmap_flush(void)
928{
929}
930static inline void try_to_unmap_flush_dirty(void)
931{
932}
933static inline void flush_tlb_batched_pending(struct mm_struct *mm)
934{
935}
936#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
937
938extern const struct trace_print_flags pageflag_names[];
939extern const struct trace_print_flags pagetype_names[];
940extern const struct trace_print_flags vmaflag_names[];
941extern const struct trace_print_flags gfpflag_names[];
942
943static inline bool is_migrate_highatomic(enum migratetype migratetype)
944{
945 return migratetype == MIGRATE_HIGHATOMIC;
946}
947
948static inline bool is_migrate_highatomic_page(struct page *page)
949{
950 return get_pageblock_migratetype(page) == MIGRATE_HIGHATOMIC;
951}
952
953void setup_zone_pageset(struct zone *zone);
954
955struct migration_target_control {
956 int nid; /* preferred node id */
957 nodemask_t *nmask;
958 gfp_t gfp_mask;
959};
960
961/*
962 * mm/filemap.c
963 */
964size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
965 struct folio *folio, loff_t fpos, size_t size);
966
967/*
968 * mm/vmalloc.c
969 */
970#ifdef CONFIG_MMU
971void __init vmalloc_init(void);
972int __must_check vmap_pages_range_noflush(unsigned long addr, unsigned long end,
973 pgprot_t prot, struct page **pages, unsigned int page_shift);
974#else
975static inline void vmalloc_init(void)
976{
977}
978
979static inline
980int __must_check vmap_pages_range_noflush(unsigned long addr, unsigned long end,
981 pgprot_t prot, struct page **pages, unsigned int page_shift)
982{
983 return -EINVAL;
984}
985#endif
986
987int __must_check __vmap_pages_range_noflush(unsigned long addr,
988 unsigned long end, pgprot_t prot,
989 struct page **pages, unsigned int page_shift);
990
991void vunmap_range_noflush(unsigned long start, unsigned long end);
992
993void __vunmap_range_noflush(unsigned long start, unsigned long end);
994
995int numa_migrate_prep(struct folio *folio, struct vm_area_struct *vma,
996 unsigned long addr, int page_nid, int *flags);
997
998void free_zone_device_page(struct page *page);
999int migrate_device_coherent_page(struct page *page);
1000
1001/*
1002 * mm/gup.c
1003 */
1004struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags);
1005int __must_check try_grab_page(struct page *page, unsigned int flags);
1006
1007/*
1008 * mm/huge_memory.c
1009 */
1010struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
1011 unsigned long addr, pmd_t *pmd,
1012 unsigned int flags);
1013
1014/*
1015 * mm/mmap.c
1016 */
1017struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi,
1018 struct vm_area_struct *vma,
1019 unsigned long delta);
1020
1021enum {
1022 /* mark page accessed */
1023 FOLL_TOUCH = 1 << 16,
1024 /* a retry, previous pass started an IO */
1025 FOLL_TRIED = 1 << 17,
1026 /* we are working on non-current tsk/mm */
1027 FOLL_REMOTE = 1 << 18,
1028 /* pages must be released via unpin_user_page */
1029 FOLL_PIN = 1 << 19,
1030 /* gup_fast: prevent fall-back to slow gup */
1031 FOLL_FAST_ONLY = 1 << 20,
1032 /* allow unlocking the mmap lock */
1033 FOLL_UNLOCKABLE = 1 << 21,
1034};
1035
1036#define INTERNAL_GUP_FLAGS (FOLL_TOUCH | FOLL_TRIED | FOLL_REMOTE | FOLL_PIN | \
1037 FOLL_FAST_ONLY | FOLL_UNLOCKABLE)
1038
1039/*
1040 * Indicates for which pages that are write-protected in the page table,
1041 * whether GUP has to trigger unsharing via FAULT_FLAG_UNSHARE such that the
1042 * GUP pin will remain consistent with the pages mapped into the page tables
1043 * of the MM.
1044 *
1045 * Temporary unmapping of PageAnonExclusive() pages or clearing of
1046 * PageAnonExclusive() has to protect against concurrent GUP:
1047 * * Ordinary GUP: Using the PT lock
1048 * * GUP-fast and fork(): mm->write_protect_seq
1049 * * GUP-fast and KSM or temporary unmapping (swap, migration): see
1050 * page_try_share_anon_rmap()
1051 *
1052 * Must be called with the (sub)page that's actually referenced via the
1053 * page table entry, which might not necessarily be the head page for a
1054 * PTE-mapped THP.
1055 *
1056 * If the vma is NULL, we're coming from the GUP-fast path and might have
1057 * to fallback to the slow path just to lookup the vma.
1058 */
1059static inline bool gup_must_unshare(struct vm_area_struct *vma,
1060 unsigned int flags, struct page *page)
1061{
1062 /*
1063 * FOLL_WRITE is implicitly handled correctly as the page table entry
1064 * has to be writable -- and if it references (part of) an anonymous
1065 * folio, that part is required to be marked exclusive.
1066 */
1067 if ((flags & (FOLL_WRITE | FOLL_PIN)) != FOLL_PIN)
1068 return false;
1069 /*
1070 * Note: PageAnon(page) is stable until the page is actually getting
1071 * freed.
1072 */
1073 if (!PageAnon(page)) {
1074 /*
1075 * We only care about R/O long-term pining: R/O short-term
1076 * pinning does not have the semantics to observe successive
1077 * changes through the process page tables.
1078 */
1079 if (!(flags & FOLL_LONGTERM))
1080 return false;
1081
1082 /* We really need the vma ... */
1083 if (!vma)
1084 return true;
1085
1086 /*
1087 * ... because we only care about writable private ("COW")
1088 * mappings where we have to break COW early.
1089 */
1090 return is_cow_mapping(flags: vma->vm_flags);
1091 }
1092
1093 /* Paired with a memory barrier in page_try_share_anon_rmap(). */
1094 if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
1095 smp_rmb();
1096
1097 /*
1098 * During GUP-fast we might not get called on the head page for a
1099 * hugetlb page that is mapped using cont-PTE, because GUP-fast does
1100 * not work with the abstracted hugetlb PTEs that always point at the
1101 * head page. For hugetlb, PageAnonExclusive only applies on the head
1102 * page (as it cannot be partially COW-shared), so lookup the head page.
1103 */
1104 if (unlikely(!PageHead(page) && PageHuge(page)))
1105 page = compound_head(page);
1106
1107 /*
1108 * Note that PageKsm() pages cannot be exclusive, and consequently,
1109 * cannot get pinned.
1110 */
1111 return !PageAnonExclusive(page);
1112}
1113
1114extern bool mirrored_kernelcore;
1115extern bool memblock_has_mirror(void);
1116
1117static inline bool vma_soft_dirty_enabled(struct vm_area_struct *vma)
1118{
1119 /*
1120 * NOTE: we must check this before VM_SOFTDIRTY on soft-dirty
1121 * enablements, because when without soft-dirty being compiled in,
1122 * VM_SOFTDIRTY is defined as 0x0, then !(vm_flags & VM_SOFTDIRTY)
1123 * will be constantly true.
1124 */
1125 if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY))
1126 return false;
1127
1128 /*
1129 * Soft-dirty is kind of special: its tracking is enabled when the
1130 * vma flags not set.
1131 */
1132 return !(vma->vm_flags & VM_SOFTDIRTY);
1133}
1134
1135static inline void vma_iter_config(struct vma_iterator *vmi,
1136 unsigned long index, unsigned long last)
1137{
1138 MAS_BUG_ON(&vmi->mas, vmi->mas.node != MAS_START &&
1139 (vmi->mas.index > index || vmi->mas.last < index));
1140 __mas_set_range(mas: &vmi->mas, start: index, last: last - 1);
1141}
1142
1143/*
1144 * VMA Iterator functions shared between nommu and mmap
1145 */
1146static inline int vma_iter_prealloc(struct vma_iterator *vmi,
1147 struct vm_area_struct *vma)
1148{
1149 return mas_preallocate(mas: &vmi->mas, entry: vma, GFP_KERNEL);
1150}
1151
1152static inline void vma_iter_clear(struct vma_iterator *vmi)
1153{
1154 mas_store_prealloc(mas: &vmi->mas, NULL);
1155}
1156
1157static inline int vma_iter_clear_gfp(struct vma_iterator *vmi,
1158 unsigned long start, unsigned long end, gfp_t gfp)
1159{
1160 __mas_set_range(mas: &vmi->mas, start, last: end - 1);
1161 mas_store_gfp(mas: &vmi->mas, NULL, gfp);
1162 if (unlikely(mas_is_err(&vmi->mas)))
1163 return -ENOMEM;
1164
1165 return 0;
1166}
1167
1168static inline struct vm_area_struct *vma_iter_load(struct vma_iterator *vmi)
1169{
1170 return mas_walk(mas: &vmi->mas);
1171}
1172
1173/* Store a VMA with preallocated memory */
1174static inline void vma_iter_store(struct vma_iterator *vmi,
1175 struct vm_area_struct *vma)
1176{
1177
1178#if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
1179 if (MAS_WARN_ON(&vmi->mas, vmi->mas.node != MAS_START &&
1180 vmi->mas.index > vma->vm_start)) {
1181 pr_warn("%lx > %lx\n store vma %lx-%lx\n into slot %lx-%lx\n",
1182 vmi->mas.index, vma->vm_start, vma->vm_start,
1183 vma->vm_end, vmi->mas.index, vmi->mas.last);
1184 }
1185 if (MAS_WARN_ON(&vmi->mas, vmi->mas.node != MAS_START &&
1186 vmi->mas.last < vma->vm_start)) {
1187 pr_warn("%lx < %lx\nstore vma %lx-%lx\ninto slot %lx-%lx\n",
1188 vmi->mas.last, vma->vm_start, vma->vm_start, vma->vm_end,
1189 vmi->mas.index, vmi->mas.last);
1190 }
1191#endif
1192
1193 if (vmi->mas.node != MAS_START &&
1194 ((vmi->mas.index > vma->vm_start) || (vmi->mas.last < vma->vm_start)))
1195 vma_iter_invalidate(vmi);
1196
1197 __mas_set_range(mas: &vmi->mas, start: vma->vm_start, last: vma->vm_end - 1);
1198 mas_store_prealloc(mas: &vmi->mas, entry: vma);
1199}
1200
1201static inline int vma_iter_store_gfp(struct vma_iterator *vmi,
1202 struct vm_area_struct *vma, gfp_t gfp)
1203{
1204 if (vmi->mas.node != MAS_START &&
1205 ((vmi->mas.index > vma->vm_start) || (vmi->mas.last < vma->vm_start)))
1206 vma_iter_invalidate(vmi);
1207
1208 __mas_set_range(mas: &vmi->mas, start: vma->vm_start, last: vma->vm_end - 1);
1209 mas_store_gfp(mas: &vmi->mas, entry: vma, gfp);
1210 if (unlikely(mas_is_err(&vmi->mas)))
1211 return -ENOMEM;
1212
1213 return 0;
1214}
1215
1216/*
1217 * VMA lock generalization
1218 */
1219struct vma_prepare {
1220 struct vm_area_struct *vma;
1221 struct vm_area_struct *adj_next;
1222 struct file *file;
1223 struct address_space *mapping;
1224 struct anon_vma *anon_vma;
1225 struct vm_area_struct *insert;
1226 struct vm_area_struct *remove;
1227 struct vm_area_struct *remove2;
1228};
1229
1230void __meminit __init_single_page(struct page *page, unsigned long pfn,
1231 unsigned long zone, int nid);
1232
1233/* shrinker related functions */
1234unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct mem_cgroup *memcg,
1235 int priority);
1236
1237#ifdef CONFIG_SHRINKER_DEBUG
1238static inline __printf(2, 0) int shrinker_debugfs_name_alloc(
1239 struct shrinker *shrinker, const char *fmt, va_list ap)
1240{
1241 shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, args: ap);
1242
1243 return shrinker->name ? 0 : -ENOMEM;
1244}
1245
1246static inline void shrinker_debugfs_name_free(struct shrinker *shrinker)
1247{
1248 kfree_const(x: shrinker->name);
1249 shrinker->name = NULL;
1250}
1251
1252extern int shrinker_debugfs_add(struct shrinker *shrinker);
1253extern struct dentry *shrinker_debugfs_detach(struct shrinker *shrinker,
1254 int *debugfs_id);
1255extern void shrinker_debugfs_remove(struct dentry *debugfs_entry,
1256 int debugfs_id);
1257#else /* CONFIG_SHRINKER_DEBUG */
1258static inline int shrinker_debugfs_add(struct shrinker *shrinker)
1259{
1260 return 0;
1261}
1262static inline int shrinker_debugfs_name_alloc(struct shrinker *shrinker,
1263 const char *fmt, va_list ap)
1264{
1265 return 0;
1266}
1267static inline void shrinker_debugfs_name_free(struct shrinker *shrinker)
1268{
1269}
1270static inline struct dentry *shrinker_debugfs_detach(struct shrinker *shrinker,
1271 int *debugfs_id)
1272{
1273 *debugfs_id = -1;
1274 return NULL;
1275}
1276static inline void shrinker_debugfs_remove(struct dentry *debugfs_entry,
1277 int debugfs_id)
1278{
1279}
1280#endif /* CONFIG_SHRINKER_DEBUG */
1281
1282#endif /* __MM_INTERNAL_H */
1283

source code of linux/mm/internal.h