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Linux/include/linux/mmzone.h

  1 #ifndef _LINUX_MMZONE_H
  2 #define _LINUX_MMZONE_H
  3 
  4 #ifndef __ASSEMBLY__
  5 #ifndef __GENERATING_BOUNDS_H
  6 
  7 #include <linux/spinlock.h>
  8 #include <linux/list.h>
  9 #include <linux/wait.h>
 10 #include <linux/bitops.h>
 11 #include <linux/cache.h>
 12 #include <linux/threads.h>
 13 #include <linux/numa.h>
 14 #include <linux/init.h>
 15 #include <linux/seqlock.h>
 16 #include <linux/nodemask.h>
 17 #include <linux/pageblock-flags.h>
 18 #include <linux/page-flags-layout.h>
 19 #include <linux/atomic.h>
 20 #include <asm/page.h>
 21 
 22 /* Free memory management - zoned buddy allocator.  */
 23 #ifndef CONFIG_FORCE_MAX_ZONEORDER
 24 #define MAX_ORDER 11
 25 #else
 26 #define MAX_ORDER CONFIG_FORCE_MAX_ZONEORDER
 27 #endif
 28 #define MAX_ORDER_NR_PAGES (1 << (MAX_ORDER - 1))
 29 
 30 /*
 31  * PAGE_ALLOC_COSTLY_ORDER is the order at which allocations are deemed
 32  * costly to service.  That is between allocation orders which should
 33  * coalesce naturally under reasonable reclaim pressure and those which
 34  * will not.
 35  */
 36 #define PAGE_ALLOC_COSTLY_ORDER 3
 37 
 38 enum {
 39         MIGRATE_UNMOVABLE,
 40         MIGRATE_MOVABLE,
 41         MIGRATE_RECLAIMABLE,
 42         MIGRATE_PCPTYPES,       /* the number of types on the pcp lists */
 43         MIGRATE_HIGHATOMIC = MIGRATE_PCPTYPES,
 44 #ifdef CONFIG_CMA
 45         /*
 46          * MIGRATE_CMA migration type is designed to mimic the way
 47          * ZONE_MOVABLE works.  Only movable pages can be allocated
 48          * from MIGRATE_CMA pageblocks and page allocator never
 49          * implicitly change migration type of MIGRATE_CMA pageblock.
 50          *
 51          * The way to use it is to change migratetype of a range of
 52          * pageblocks to MIGRATE_CMA which can be done by
 53          * __free_pageblock_cma() function.  What is important though
 54          * is that a range of pageblocks must be aligned to
 55          * MAX_ORDER_NR_PAGES should biggest page be bigger then
 56          * a single pageblock.
 57          */
 58         MIGRATE_CMA,
 59 #endif
 60 #ifdef CONFIG_MEMORY_ISOLATION
 61         MIGRATE_ISOLATE,        /* can't allocate from here */
 62 #endif
 63         MIGRATE_TYPES
 64 };
 65 
 66 #ifdef CONFIG_CMA
 67 #  define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)
 68 #else
 69 #  define is_migrate_cma(migratetype) false
 70 #endif
 71 
 72 #define for_each_migratetype_order(order, type) \
 73         for (order = 0; order < MAX_ORDER; order++) \
 74                 for (type = 0; type < MIGRATE_TYPES; type++)
 75 
 76 extern int page_group_by_mobility_disabled;
 77 
 78 #define NR_MIGRATETYPE_BITS (PB_migrate_end - PB_migrate + 1)
 79 #define MIGRATETYPE_MASK ((1UL << NR_MIGRATETYPE_BITS) - 1)
 80 
 81 #define get_pageblock_migratetype(page)                                 \
 82         get_pfnblock_flags_mask(page, page_to_pfn(page),                \
 83                         PB_migrate_end, MIGRATETYPE_MASK)
 84 
 85 static inline int get_pfnblock_migratetype(struct page *page, unsigned long pfn)
 86 {
 87         BUILD_BUG_ON(PB_migrate_end - PB_migrate != 2);
 88         return get_pfnblock_flags_mask(page, pfn, PB_migrate_end,
 89                                         MIGRATETYPE_MASK);
 90 }
 91 
 92 struct free_area {
 93         struct list_head        free_list[MIGRATE_TYPES];
 94         unsigned long           nr_free;
 95 };
 96 
 97 struct pglist_data;
 98 
 99 /*
100  * zone->lock and zone->lru_lock are two of the hottest locks in the kernel.
101  * So add a wild amount of padding here to ensure that they fall into separate
102  * cachelines.  There are very few zone structures in the machine, so space
103  * consumption is not a concern here.
104  */
105 #if defined(CONFIG_SMP)
106 struct zone_padding {
107         char x[0];
108 } ____cacheline_internodealigned_in_smp;
109 #define ZONE_PADDING(name)      struct zone_padding name;
110 #else
111 #define ZONE_PADDING(name)
112 #endif
113 
114 enum zone_stat_item {
115         /* First 128 byte cacheline (assuming 64 bit words) */
116         NR_FREE_PAGES,
117         NR_ALLOC_BATCH,
118         NR_LRU_BASE,
119         NR_INACTIVE_ANON = NR_LRU_BASE, /* must match order of LRU_[IN]ACTIVE */
120         NR_ACTIVE_ANON,         /*  "     "     "   "       "         */
121         NR_INACTIVE_FILE,       /*  "     "     "   "       "         */
122         NR_ACTIVE_FILE,         /*  "     "     "   "       "         */
123         NR_UNEVICTABLE,         /*  "     "     "   "       "         */
124         NR_MLOCK,               /* mlock()ed pages found and moved off LRU */
125         NR_ANON_PAGES,  /* Mapped anonymous pages */
126         NR_FILE_MAPPED, /* pagecache pages mapped into pagetables.
127                            only modified from process context */
128         NR_FILE_PAGES,
129         NR_FILE_DIRTY,
130         NR_WRITEBACK,
131         NR_SLAB_RECLAIMABLE,
132         NR_SLAB_UNRECLAIMABLE,
133         NR_PAGETABLE,           /* used for pagetables */
134         NR_KERNEL_STACK,
135         /* Second 128 byte cacheline */
136         NR_UNSTABLE_NFS,        /* NFS unstable pages */
137         NR_BOUNCE,
138         NR_VMSCAN_WRITE,
139         NR_VMSCAN_IMMEDIATE,    /* Prioritise for reclaim when writeback ends */
140         NR_WRITEBACK_TEMP,      /* Writeback using temporary buffers */
141         NR_ISOLATED_ANON,       /* Temporary isolated pages from anon lru */
142         NR_ISOLATED_FILE,       /* Temporary isolated pages from file lru */
143         NR_SHMEM,               /* shmem pages (included tmpfs/GEM pages) */
144         NR_DIRTIED,             /* page dirtyings since bootup */
145         NR_WRITTEN,             /* page writings since bootup */
146         NR_PAGES_SCANNED,       /* pages scanned since last reclaim */
147 #ifdef CONFIG_NUMA
148         NUMA_HIT,               /* allocated in intended node */
149         NUMA_MISS,              /* allocated in non intended node */
150         NUMA_FOREIGN,           /* was intended here, hit elsewhere */
151         NUMA_INTERLEAVE_HIT,    /* interleaver preferred this zone */
152         NUMA_LOCAL,             /* allocation from local node */
153         NUMA_OTHER,             /* allocation from other node */
154 #endif
155         WORKINGSET_REFAULT,
156         WORKINGSET_ACTIVATE,
157         WORKINGSET_NODERECLAIM,
158         NR_ANON_TRANSPARENT_HUGEPAGES,
159         NR_FREE_CMA_PAGES,
160         NR_VM_ZONE_STAT_ITEMS };
161 
162 /*
163  * We do arithmetic on the LRU lists in various places in the code,
164  * so it is important to keep the active lists LRU_ACTIVE higher in
165  * the array than the corresponding inactive lists, and to keep
166  * the *_FILE lists LRU_FILE higher than the corresponding _ANON lists.
167  *
168  * This has to be kept in sync with the statistics in zone_stat_item
169  * above and the descriptions in vmstat_text in mm/vmstat.c
170  */
171 #define LRU_BASE 0
172 #define LRU_ACTIVE 1
173 #define LRU_FILE 2
174 
175 enum lru_list {
176         LRU_INACTIVE_ANON = LRU_BASE,
177         LRU_ACTIVE_ANON = LRU_BASE + LRU_ACTIVE,
178         LRU_INACTIVE_FILE = LRU_BASE + LRU_FILE,
179         LRU_ACTIVE_FILE = LRU_BASE + LRU_FILE + LRU_ACTIVE,
180         LRU_UNEVICTABLE,
181         NR_LRU_LISTS
182 };
183 
184 #define for_each_lru(lru) for (lru = 0; lru < NR_LRU_LISTS; lru++)
185 
186 #define for_each_evictable_lru(lru) for (lru = 0; lru <= LRU_ACTIVE_FILE; lru++)
187 
188 static inline int is_file_lru(enum lru_list lru)
189 {
190         return (lru == LRU_INACTIVE_FILE || lru == LRU_ACTIVE_FILE);
191 }
192 
193 static inline int is_active_lru(enum lru_list lru)
194 {
195         return (lru == LRU_ACTIVE_ANON || lru == LRU_ACTIVE_FILE);
196 }
197 
198 static inline int is_unevictable_lru(enum lru_list lru)
199 {
200         return (lru == LRU_UNEVICTABLE);
201 }
202 
203 struct zone_reclaim_stat {
204         /*
205          * The pageout code in vmscan.c keeps track of how many of the
206          * mem/swap backed and file backed pages are referenced.
207          * The higher the rotated/scanned ratio, the more valuable
208          * that cache is.
209          *
210          * The anon LRU stats live in [0], file LRU stats in [1]
211          */
212         unsigned long           recent_rotated[2];
213         unsigned long           recent_scanned[2];
214 };
215 
216 struct lruvec {
217         struct list_head lists[NR_LRU_LISTS];
218         struct zone_reclaim_stat reclaim_stat;
219 #ifdef CONFIG_MEMCG
220         struct zone *zone;
221 #endif
222 };
223 
224 /* Mask used at gathering information at once (see memcontrol.c) */
225 #define LRU_ALL_FILE (BIT(LRU_INACTIVE_FILE) | BIT(LRU_ACTIVE_FILE))
226 #define LRU_ALL_ANON (BIT(LRU_INACTIVE_ANON) | BIT(LRU_ACTIVE_ANON))
227 #define LRU_ALL      ((1 << NR_LRU_LISTS) - 1)
228 
229 /* Isolate clean file */
230 #define ISOLATE_CLEAN           ((__force isolate_mode_t)0x1)
231 /* Isolate unmapped file */
232 #define ISOLATE_UNMAPPED        ((__force isolate_mode_t)0x2)
233 /* Isolate for asynchronous migration */
234 #define ISOLATE_ASYNC_MIGRATE   ((__force isolate_mode_t)0x4)
235 /* Isolate unevictable pages */
236 #define ISOLATE_UNEVICTABLE     ((__force isolate_mode_t)0x8)
237 
238 /* LRU Isolation modes. */
239 typedef unsigned __bitwise__ isolate_mode_t;
240 
241 enum zone_watermarks {
242         WMARK_MIN,
243         WMARK_LOW,
244         WMARK_HIGH,
245         NR_WMARK
246 };
247 
248 #define min_wmark_pages(z) (z->watermark[WMARK_MIN])
249 #define low_wmark_pages(z) (z->watermark[WMARK_LOW])
250 #define high_wmark_pages(z) (z->watermark[WMARK_HIGH])
251 
252 struct per_cpu_pages {
253         int count;              /* number of pages in the list */
254         int high;               /* high watermark, emptying needed */
255         int batch;              /* chunk size for buddy add/remove */
256 
257         /* Lists of pages, one per migrate type stored on the pcp-lists */
258         struct list_head lists[MIGRATE_PCPTYPES];
259 };
260 
261 struct per_cpu_pageset {
262         struct per_cpu_pages pcp;
263 #ifdef CONFIG_NUMA
264         s8 expire;
265 #endif
266 #ifdef CONFIG_SMP
267         s8 stat_threshold;
268         s8 vm_stat_diff[NR_VM_ZONE_STAT_ITEMS];
269 #endif
270 };
271 
272 #endif /* !__GENERATING_BOUNDS.H */
273 
274 enum zone_type {
275 #ifdef CONFIG_ZONE_DMA
276         /*
277          * ZONE_DMA is used when there are devices that are not able
278          * to do DMA to all of addressable memory (ZONE_NORMAL). Then we
279          * carve out the portion of memory that is needed for these devices.
280          * The range is arch specific.
281          *
282          * Some examples
283          *
284          * Architecture         Limit
285          * ---------------------------
286          * parisc, ia64, sparc  <4G
287          * s390                 <2G
288          * arm                  Various
289          * alpha                Unlimited or 0-16MB.
290          *
291          * i386, x86_64 and multiple other arches
292          *                      <16M.
293          */
294         ZONE_DMA,
295 #endif
296 #ifdef CONFIG_ZONE_DMA32
297         /*
298          * x86_64 needs two ZONE_DMAs because it supports devices that are
299          * only able to do DMA to the lower 16M but also 32 bit devices that
300          * can only do DMA areas below 4G.
301          */
302         ZONE_DMA32,
303 #endif
304         /*
305          * Normal addressable memory is in ZONE_NORMAL. DMA operations can be
306          * performed on pages in ZONE_NORMAL if the DMA devices support
307          * transfers to all addressable memory.
308          */
309         ZONE_NORMAL,
310 #ifdef CONFIG_HIGHMEM
311         /*
312          * A memory area that is only addressable by the kernel through
313          * mapping portions into its own address space. This is for example
314          * used by i386 to allow the kernel to address the memory beyond
315          * 900MB. The kernel will set up special mappings (page
316          * table entries on i386) for each page that the kernel needs to
317          * access.
318          */
319         ZONE_HIGHMEM,
320 #endif
321         ZONE_MOVABLE,
322 #ifdef CONFIG_ZONE_DEVICE
323         ZONE_DEVICE,
324 #endif
325         __MAX_NR_ZONES
326 
327 };
328 
329 #ifndef __GENERATING_BOUNDS_H
330 
331 struct zone {
332         /* Read-mostly fields */
333 
334         /* zone watermarks, access with *_wmark_pages(zone) macros */
335         unsigned long watermark[NR_WMARK];
336 
337         unsigned long nr_reserved_highatomic;
338 
339         /*
340          * We don't know if the memory that we're going to allocate will be
341          * freeable or/and it will be released eventually, so to avoid totally
342          * wasting several GB of ram we must reserve some of the lower zone
343          * memory (otherwise we risk to run OOM on the lower zones despite
344          * there being tons of freeable ram on the higher zones).  This array is
345          * recalculated at runtime if the sysctl_lowmem_reserve_ratio sysctl
346          * changes.
347          */
348         long lowmem_reserve[MAX_NR_ZONES];
349 
350 #ifdef CONFIG_NUMA
351         int node;
352 #endif
353 
354         /*
355          * The target ratio of ACTIVE_ANON to INACTIVE_ANON pages on
356          * this zone's LRU.  Maintained by the pageout code.
357          */
358         unsigned int inactive_ratio;
359 
360         struct pglist_data      *zone_pgdat;
361         struct per_cpu_pageset __percpu *pageset;
362 
363         /*
364          * This is a per-zone reserve of pages that should not be
365          * considered dirtyable memory.
366          */
367         unsigned long           dirty_balance_reserve;
368 
369 #ifndef CONFIG_SPARSEMEM
370         /*
371          * Flags for a pageblock_nr_pages block. See pageblock-flags.h.
372          * In SPARSEMEM, this map is stored in struct mem_section
373          */
374         unsigned long           *pageblock_flags;
375 #endif /* CONFIG_SPARSEMEM */
376 
377 #ifdef CONFIG_NUMA
378         /*
379          * zone reclaim becomes active if more unmapped pages exist.
380          */
381         unsigned long           min_unmapped_pages;
382         unsigned long           min_slab_pages;
383 #endif /* CONFIG_NUMA */
384 
385         /* zone_start_pfn == zone_start_paddr >> PAGE_SHIFT */
386         unsigned long           zone_start_pfn;
387 
388         /*
389          * spanned_pages is the total pages spanned by the zone, including
390          * holes, which is calculated as:
391          *      spanned_pages = zone_end_pfn - zone_start_pfn;
392          *
393          * present_pages is physical pages existing within the zone, which
394          * is calculated as:
395          *      present_pages = spanned_pages - absent_pages(pages in holes);
396          *
397          * managed_pages is present pages managed by the buddy system, which
398          * is calculated as (reserved_pages includes pages allocated by the
399          * bootmem allocator):
400          *      managed_pages = present_pages - reserved_pages;
401          *
402          * So present_pages may be used by memory hotplug or memory power
403          * management logic to figure out unmanaged pages by checking
404          * (present_pages - managed_pages). And managed_pages should be used
405          * by page allocator and vm scanner to calculate all kinds of watermarks
406          * and thresholds.
407          *
408          * Locking rules:
409          *
410          * zone_start_pfn and spanned_pages are protected by span_seqlock.
411          * It is a seqlock because it has to be read outside of zone->lock,
412          * and it is done in the main allocator path.  But, it is written
413          * quite infrequently.
414          *
415          * The span_seq lock is declared along with zone->lock because it is
416          * frequently read in proximity to zone->lock.  It's good to
417          * give them a chance of being in the same cacheline.
418          *
419          * Write access to present_pages at runtime should be protected by
420          * mem_hotplug_begin/end(). Any reader who can't tolerant drift of
421          * present_pages should get_online_mems() to get a stable value.
422          *
423          * Read access to managed_pages should be safe because it's unsigned
424          * long. Write access to zone->managed_pages and totalram_pages are
425          * protected by managed_page_count_lock at runtime. Idealy only
426          * adjust_managed_page_count() should be used instead of directly
427          * touching zone->managed_pages and totalram_pages.
428          */
429         unsigned long           managed_pages;
430         unsigned long           spanned_pages;
431         unsigned long           present_pages;
432 
433         const char              *name;
434 
435 #ifdef CONFIG_MEMORY_ISOLATION
436         /*
437          * Number of isolated pageblock. It is used to solve incorrect
438          * freepage counting problem due to racy retrieving migratetype
439          * of pageblock. Protected by zone->lock.
440          */
441         unsigned long           nr_isolate_pageblock;
442 #endif
443 
444 #ifdef CONFIG_MEMORY_HOTPLUG
445         /* see spanned/present_pages for more description */
446         seqlock_t               span_seqlock;
447 #endif
448 
449         /*
450          * wait_table           -- the array holding the hash table
451          * wait_table_hash_nr_entries   -- the size of the hash table array
452          * wait_table_bits      -- wait_table_size == (1 << wait_table_bits)
453          *
454          * The purpose of all these is to keep track of the people
455          * waiting for a page to become available and make them
456          * runnable again when possible. The trouble is that this
457          * consumes a lot of space, especially when so few things
458          * wait on pages at a given time. So instead of using
459          * per-page waitqueues, we use a waitqueue hash table.
460          *
461          * The bucket discipline is to sleep on the same queue when
462          * colliding and wake all in that wait queue when removing.
463          * When something wakes, it must check to be sure its page is
464          * truly available, a la thundering herd. The cost of a
465          * collision is great, but given the expected load of the
466          * table, they should be so rare as to be outweighed by the
467          * benefits from the saved space.
468          *
469          * __wait_on_page_locked() and unlock_page() in mm/filemap.c, are the
470          * primary users of these fields, and in mm/page_alloc.c
471          * free_area_init_core() performs the initialization of them.
472          */
473         wait_queue_head_t       *wait_table;
474         unsigned long           wait_table_hash_nr_entries;
475         unsigned long           wait_table_bits;
476 
477         ZONE_PADDING(_pad1_)
478         /* free areas of different sizes */
479         struct free_area        free_area[MAX_ORDER];
480 
481         /* zone flags, see below */
482         unsigned long           flags;
483 
484         /* Write-intensive fields used from the page allocator */
485         spinlock_t              lock;
486 
487         ZONE_PADDING(_pad2_)
488 
489         /* Write-intensive fields used by page reclaim */
490 
491         /* Fields commonly accessed by the page reclaim scanner */
492         spinlock_t              lru_lock;
493         struct lruvec           lruvec;
494 
495         /* Evictions & activations on the inactive file list */
496         atomic_long_t           inactive_age;
497 
498         /*
499          * When free pages are below this point, additional steps are taken
500          * when reading the number of free pages to avoid per-cpu counter
501          * drift allowing watermarks to be breached
502          */
503         unsigned long percpu_drift_mark;
504 
505 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
506         /* pfn where compaction free scanner should start */
507         unsigned long           compact_cached_free_pfn;
508         /* pfn where async and sync compaction migration scanner should start */
509         unsigned long           compact_cached_migrate_pfn[2];
510 #endif
511 
512 #ifdef CONFIG_COMPACTION
513         /*
514          * On compaction failure, 1<<compact_defer_shift compactions
515          * are skipped before trying again. The number attempted since
516          * last failure is tracked with compact_considered.
517          */
518         unsigned int            compact_considered;
519         unsigned int            compact_defer_shift;
520         int                     compact_order_failed;
521 #endif
522 
523 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
524         /* Set to true when the PG_migrate_skip bits should be cleared */
525         bool                    compact_blockskip_flush;
526 #endif
527 
528         ZONE_PADDING(_pad3_)
529         /* Zone statistics */
530         atomic_long_t           vm_stat[NR_VM_ZONE_STAT_ITEMS];
531 } ____cacheline_internodealigned_in_smp;
532 
533 enum zone_flags {
534         ZONE_RECLAIM_LOCKED,            /* prevents concurrent reclaim */
535         ZONE_OOM_LOCKED,                /* zone is in OOM killer zonelist */
536         ZONE_CONGESTED,                 /* zone has many dirty pages backed by
537                                          * a congested BDI
538                                          */
539         ZONE_DIRTY,                     /* reclaim scanning has recently found
540                                          * many dirty file pages at the tail
541                                          * of the LRU.
542                                          */
543         ZONE_WRITEBACK,                 /* reclaim scanning has recently found
544                                          * many pages under writeback
545                                          */
546         ZONE_FAIR_DEPLETED,             /* fair zone policy batch depleted */
547 };
548 
549 static inline unsigned long zone_end_pfn(const struct zone *zone)
550 {
551         return zone->zone_start_pfn + zone->spanned_pages;
552 }
553 
554 static inline bool zone_spans_pfn(const struct zone *zone, unsigned long pfn)
555 {
556         return zone->zone_start_pfn <= pfn && pfn < zone_end_pfn(zone);
557 }
558 
559 static inline bool zone_is_initialized(struct zone *zone)
560 {
561         return !!zone->wait_table;
562 }
563 
564 static inline bool zone_is_empty(struct zone *zone)
565 {
566         return zone->spanned_pages == 0;
567 }
568 
569 /*
570  * The "priority" of VM scanning is how much of the queues we will scan in one
571  * go. A value of 12 for DEF_PRIORITY implies that we will scan 1/4096th of the
572  * queues ("queue_length >> 12") during an aging round.
573  */
574 #define DEF_PRIORITY 12
575 
576 /* Maximum number of zones on a zonelist */
577 #define MAX_ZONES_PER_ZONELIST (MAX_NUMNODES * MAX_NR_ZONES)
578 
579 #ifdef CONFIG_NUMA
580 
581 /*
582  * The NUMA zonelists are doubled because we need zonelists that restrict the
583  * allocations to a single node for __GFP_THISNODE.
584  *
585  * [0]  : Zonelist with fallback
586  * [1]  : No fallback (__GFP_THISNODE)
587  */
588 #define MAX_ZONELISTS 2
589 #else
590 #define MAX_ZONELISTS 1
591 #endif
592 
593 /*
594  * This struct contains information about a zone in a zonelist. It is stored
595  * here to avoid dereferences into large structures and lookups of tables
596  */
597 struct zoneref {
598         struct zone *zone;      /* Pointer to actual zone */
599         int zone_idx;           /* zone_idx(zoneref->zone) */
600 };
601 
602 /*
603  * One allocation request operates on a zonelist. A zonelist
604  * is a list of zones, the first one is the 'goal' of the
605  * allocation, the other zones are fallback zones, in decreasing
606  * priority.
607  *
608  * To speed the reading of the zonelist, the zonerefs contain the zone index
609  * of the entry being read. Helper functions to access information given
610  * a struct zoneref are
611  *
612  * zonelist_zone()      - Return the struct zone * for an entry in _zonerefs
613  * zonelist_zone_idx()  - Return the index of the zone for an entry
614  * zonelist_node_idx()  - Return the index of the node for an entry
615  */
616 struct zonelist {
617         struct zoneref _zonerefs[MAX_ZONES_PER_ZONELIST + 1];
618 };
619 
620 #ifndef CONFIG_DISCONTIGMEM
621 /* The array of struct pages - for discontigmem use pgdat->lmem_map */
622 extern struct page *mem_map;
623 #endif
624 
625 /*
626  * The pg_data_t structure is used in machines with CONFIG_DISCONTIGMEM
627  * (mostly NUMA machines?) to denote a higher-level memory zone than the
628  * zone denotes.
629  *
630  * On NUMA machines, each NUMA node would have a pg_data_t to describe
631  * it's memory layout.
632  *
633  * Memory statistics and page replacement data structures are maintained on a
634  * per-zone basis.
635  */
636 struct bootmem_data;
637 typedef struct pglist_data {
638         struct zone node_zones[MAX_NR_ZONES];
639         struct zonelist node_zonelists[MAX_ZONELISTS];
640         int nr_zones;
641 #ifdef CONFIG_FLAT_NODE_MEM_MAP /* means !SPARSEMEM */
642         struct page *node_mem_map;
643 #ifdef CONFIG_PAGE_EXTENSION
644         struct page_ext *node_page_ext;
645 #endif
646 #endif
647 #ifndef CONFIG_NO_BOOTMEM
648         struct bootmem_data *bdata;
649 #endif
650 #ifdef CONFIG_MEMORY_HOTPLUG
651         /*
652          * Must be held any time you expect node_start_pfn, node_present_pages
653          * or node_spanned_pages stay constant.  Holding this will also
654          * guarantee that any pfn_valid() stays that way.
655          *
656          * pgdat_resize_lock() and pgdat_resize_unlock() are provided to
657          * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG.
658          *
659          * Nests above zone->lock and zone->span_seqlock
660          */
661         spinlock_t node_size_lock;
662 #endif
663         unsigned long node_start_pfn;
664         unsigned long node_present_pages; /* total number of physical pages */
665         unsigned long node_spanned_pages; /* total size of physical page
666                                              range, including holes */
667         int node_id;
668         wait_queue_head_t kswapd_wait;
669         wait_queue_head_t pfmemalloc_wait;
670         struct task_struct *kswapd;     /* Protected by
671                                            mem_hotplug_begin/end() */
672         int kswapd_max_order;
673         enum zone_type classzone_idx;
674 #ifdef CONFIG_NUMA_BALANCING
675         /* Lock serializing the migrate rate limiting window */
676         spinlock_t numabalancing_migrate_lock;
677 
678         /* Rate limiting time interval */
679         unsigned long numabalancing_migrate_next_window;
680 
681         /* Number of pages migrated during the rate limiting time interval */
682         unsigned long numabalancing_migrate_nr_pages;
683 #endif
684 
685 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
686         /*
687          * If memory initialisation on large machines is deferred then this
688          * is the first PFN that needs to be initialised.
689          */
690         unsigned long first_deferred_pfn;
691 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
692 } pg_data_t;
693 
694 #define node_present_pages(nid) (NODE_DATA(nid)->node_present_pages)
695 #define node_spanned_pages(nid) (NODE_DATA(nid)->node_spanned_pages)
696 #ifdef CONFIG_FLAT_NODE_MEM_MAP
697 #define pgdat_page_nr(pgdat, pagenr)    ((pgdat)->node_mem_map + (pagenr))
698 #else
699 #define pgdat_page_nr(pgdat, pagenr)    pfn_to_page((pgdat)->node_start_pfn + (pagenr))
700 #endif
701 #define nid_page_nr(nid, pagenr)        pgdat_page_nr(NODE_DATA(nid),(pagenr))
702 
703 #define node_start_pfn(nid)     (NODE_DATA(nid)->node_start_pfn)
704 #define node_end_pfn(nid) pgdat_end_pfn(NODE_DATA(nid))
705 
706 static inline unsigned long pgdat_end_pfn(pg_data_t *pgdat)
707 {
708         return pgdat->node_start_pfn + pgdat->node_spanned_pages;
709 }
710 
711 static inline bool pgdat_is_empty(pg_data_t *pgdat)
712 {
713         return !pgdat->node_start_pfn && !pgdat->node_spanned_pages;
714 }
715 
716 static inline int zone_id(const struct zone *zone)
717 {
718         struct pglist_data *pgdat = zone->zone_pgdat;
719 
720         return zone - pgdat->node_zones;
721 }
722 
723 #ifdef CONFIG_ZONE_DEVICE
724 static inline bool is_dev_zone(const struct zone *zone)
725 {
726         return zone_id(zone) == ZONE_DEVICE;
727 }
728 #else
729 static inline bool is_dev_zone(const struct zone *zone)
730 {
731         return false;
732 }
733 #endif
734 
735 #include <linux/memory_hotplug.h>
736 
737 extern struct mutex zonelists_mutex;
738 void build_all_zonelists(pg_data_t *pgdat, struct zone *zone);
739 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx);
740 bool zone_watermark_ok(struct zone *z, unsigned int order,
741                 unsigned long mark, int classzone_idx, int alloc_flags);
742 bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
743                 unsigned long mark, int classzone_idx);
744 enum memmap_context {
745         MEMMAP_EARLY,
746         MEMMAP_HOTPLUG,
747 };
748 extern int init_currently_empty_zone(struct zone *zone, unsigned long start_pfn,
749                                      unsigned long size);
750 
751 extern void lruvec_init(struct lruvec *lruvec);
752 
753 static inline struct zone *lruvec_zone(struct lruvec *lruvec)
754 {
755 #ifdef CONFIG_MEMCG
756         return lruvec->zone;
757 #else
758         return container_of(lruvec, struct zone, lruvec);
759 #endif
760 }
761 
762 #ifdef CONFIG_HAVE_MEMORY_PRESENT
763 void memory_present(int nid, unsigned long start, unsigned long end);
764 #else
765 static inline void memory_present(int nid, unsigned long start, unsigned long end) {}
766 #endif
767 
768 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
769 int local_memory_node(int node_id);
770 #else
771 static inline int local_memory_node(int node_id) { return node_id; };
772 #endif
773 
774 #ifdef CONFIG_NEED_NODE_MEMMAP_SIZE
775 unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
776 #endif
777 
778 /*
779  * zone_idx() returns 0 for the ZONE_DMA zone, 1 for the ZONE_NORMAL zone, etc.
780  */
781 #define zone_idx(zone)          ((zone) - (zone)->zone_pgdat->node_zones)
782 
783 static inline int populated_zone(struct zone *zone)
784 {
785         return (!!zone->present_pages);
786 }
787 
788 extern int movable_zone;
789 
790 #ifdef CONFIG_HIGHMEM
791 static inline int zone_movable_is_highmem(void)
792 {
793 #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
794         return movable_zone == ZONE_HIGHMEM;
795 #else
796         return (ZONE_MOVABLE - 1) == ZONE_HIGHMEM;
797 #endif
798 }
799 #endif
800 
801 static inline int is_highmem_idx(enum zone_type idx)
802 {
803 #ifdef CONFIG_HIGHMEM
804         return (idx == ZONE_HIGHMEM ||
805                 (idx == ZONE_MOVABLE && zone_movable_is_highmem()));
806 #else
807         return 0;
808 #endif
809 }
810 
811 /**
812  * is_highmem - helper function to quickly check if a struct zone is a 
813  *              highmem zone or not.  This is an attempt to keep references
814  *              to ZONE_{DMA/NORMAL/HIGHMEM/etc} in general code to a minimum.
815  * @zone - pointer to struct zone variable
816  */
817 static inline int is_highmem(struct zone *zone)
818 {
819 #ifdef CONFIG_HIGHMEM
820         int zone_off = (char *)zone - (char *)zone->zone_pgdat->node_zones;
821         return zone_off == ZONE_HIGHMEM * sizeof(*zone) ||
822                (zone_off == ZONE_MOVABLE * sizeof(*zone) &&
823                 zone_movable_is_highmem());
824 #else
825         return 0;
826 #endif
827 }
828 
829 /* These two functions are used to setup the per zone pages min values */
830 struct ctl_table;
831 int min_free_kbytes_sysctl_handler(struct ctl_table *, int,
832                                         void __user *, size_t *, loff_t *);
833 extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1];
834 int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int,
835                                         void __user *, size_t *, loff_t *);
836 int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *, int,
837                                         void __user *, size_t *, loff_t *);
838 int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *, int,
839                         void __user *, size_t *, loff_t *);
840 int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *, int,
841                         void __user *, size_t *, loff_t *);
842 
843 extern int numa_zonelist_order_handler(struct ctl_table *, int,
844                         void __user *, size_t *, loff_t *);
845 extern char numa_zonelist_order[];
846 #define NUMA_ZONELIST_ORDER_LEN 16      /* string buffer size */
847 
848 #ifndef CONFIG_NEED_MULTIPLE_NODES
849 
850 extern struct pglist_data contig_page_data;
851 #define NODE_DATA(nid)          (&contig_page_data)
852 #define NODE_MEM_MAP(nid)       mem_map
853 
854 #else /* CONFIG_NEED_MULTIPLE_NODES */
855 
856 #include <asm/mmzone.h>
857 
858 #endif /* !CONFIG_NEED_MULTIPLE_NODES */
859 
860 extern struct pglist_data *first_online_pgdat(void);
861 extern struct pglist_data *next_online_pgdat(struct pglist_data *pgdat);
862 extern struct zone *next_zone(struct zone *zone);
863 
864 /**
865  * for_each_online_pgdat - helper macro to iterate over all online nodes
866  * @pgdat - pointer to a pg_data_t variable
867  */
868 #define for_each_online_pgdat(pgdat)                    \
869         for (pgdat = first_online_pgdat();              \
870              pgdat;                                     \
871              pgdat = next_online_pgdat(pgdat))
872 /**
873  * for_each_zone - helper macro to iterate over all memory zones
874  * @zone - pointer to struct zone variable
875  *
876  * The user only needs to declare the zone variable, for_each_zone
877  * fills it in.
878  */
879 #define for_each_zone(zone)                             \
880         for (zone = (first_online_pgdat())->node_zones; \
881              zone;                                      \
882              zone = next_zone(zone))
883 
884 #define for_each_populated_zone(zone)                   \
885         for (zone = (first_online_pgdat())->node_zones; \
886              zone;                                      \
887              zone = next_zone(zone))                    \
888                 if (!populated_zone(zone))              \
889                         ; /* do nothing */              \
890                 else
891 
892 static inline struct zone *zonelist_zone(struct zoneref *zoneref)
893 {
894         return zoneref->zone;
895 }
896 
897 static inline int zonelist_zone_idx(struct zoneref *zoneref)
898 {
899         return zoneref->zone_idx;
900 }
901 
902 static inline int zonelist_node_idx(struct zoneref *zoneref)
903 {
904 #ifdef CONFIG_NUMA
905         /* zone_to_nid not available in this context */
906         return zoneref->zone->node;
907 #else
908         return 0;
909 #endif /* CONFIG_NUMA */
910 }
911 
912 /**
913  * next_zones_zonelist - Returns the next zone at or below highest_zoneidx within the allowed nodemask using a cursor within a zonelist as a starting point
914  * @z - The cursor used as a starting point for the search
915  * @highest_zoneidx - The zone index of the highest zone to return
916  * @nodes - An optional nodemask to filter the zonelist with
917  *
918  * This function returns the next zone at or below a given zone index that is
919  * within the allowed nodemask using a cursor as the starting point for the
920  * search. The zoneref returned is a cursor that represents the current zone
921  * being examined. It should be advanced by one before calling
922  * next_zones_zonelist again.
923  */
924 struct zoneref *next_zones_zonelist(struct zoneref *z,
925                                         enum zone_type highest_zoneidx,
926                                         nodemask_t *nodes);
927 
928 /**
929  * first_zones_zonelist - Returns the first zone at or below highest_zoneidx within the allowed nodemask in a zonelist
930  * @zonelist - The zonelist to search for a suitable zone
931  * @highest_zoneidx - The zone index of the highest zone to return
932  * @nodes - An optional nodemask to filter the zonelist with
933  * @zone - The first suitable zone found is returned via this parameter
934  *
935  * This function returns the first zone at or below a given zone index that is
936  * within the allowed nodemask. The zoneref returned is a cursor that can be
937  * used to iterate the zonelist with next_zones_zonelist by advancing it by
938  * one before calling.
939  */
940 static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,
941                                         enum zone_type highest_zoneidx,
942                                         nodemask_t *nodes,
943                                         struct zone **zone)
944 {
945         struct zoneref *z = next_zones_zonelist(zonelist->_zonerefs,
946                                                         highest_zoneidx, nodes);
947         *zone = zonelist_zone(z);
948         return z;
949 }
950 
951 /**
952  * for_each_zone_zonelist_nodemask - helper macro to iterate over valid zones in a zonelist at or below a given zone index and within a nodemask
953  * @zone - The current zone in the iterator
954  * @z - The current pointer within zonelist->zones being iterated
955  * @zlist - The zonelist being iterated
956  * @highidx - The zone index of the highest zone to return
957  * @nodemask - Nodemask allowed by the allocator
958  *
959  * This iterator iterates though all zones at or below a given zone index and
960  * within a given nodemask
961  */
962 #define for_each_zone_zonelist_nodemask(zone, z, zlist, highidx, nodemask) \
963         for (z = first_zones_zonelist(zlist, highidx, nodemask, &zone); \
964                 zone;                                                   \
965                 z = next_zones_zonelist(++z, highidx, nodemask),        \
966                         zone = zonelist_zone(z))                        \
967 
968 /**
969  * for_each_zone_zonelist - helper macro to iterate over valid zones in a zonelist at or below a given zone index
970  * @zone - The current zone in the iterator
971  * @z - The current pointer within zonelist->zones being iterated
972  * @zlist - The zonelist being iterated
973  * @highidx - The zone index of the highest zone to return
974  *
975  * This iterator iterates though all zones at or below a given zone index.
976  */
977 #define for_each_zone_zonelist(zone, z, zlist, highidx) \
978         for_each_zone_zonelist_nodemask(zone, z, zlist, highidx, NULL)
979 
980 #ifdef CONFIG_SPARSEMEM
981 #include <asm/sparsemem.h>
982 #endif
983 
984 #if !defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) && \
985         !defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP)
986 static inline unsigned long early_pfn_to_nid(unsigned long pfn)
987 {
988         return 0;
989 }
990 #endif
991 
992 #ifdef CONFIG_FLATMEM
993 #define pfn_to_nid(pfn)         (0)
994 #endif
995 
996 #ifdef CONFIG_SPARSEMEM
997 
998 /*
999  * SECTION_SHIFT                #bits space required to store a section #
1000  *
1001  * PA_SECTION_SHIFT             physical address to/from section number
1002  * PFN_SECTION_SHIFT            pfn to/from section number
1003  */
1004 #define PA_SECTION_SHIFT        (SECTION_SIZE_BITS)
1005 #define PFN_SECTION_SHIFT       (SECTION_SIZE_BITS - PAGE_SHIFT)
1006 
1007 #define NR_MEM_SECTIONS         (1UL << SECTIONS_SHIFT)
1008 
1009 #define PAGES_PER_SECTION       (1UL << PFN_SECTION_SHIFT)
1010 #define PAGE_SECTION_MASK       (~(PAGES_PER_SECTION-1))
1011 
1012 #define SECTION_BLOCKFLAGS_BITS \
1013         ((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)
1014 
1015 #if (MAX_ORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS
1016 #error Allocator MAX_ORDER exceeds SECTION_SIZE
1017 #endif
1018 
1019 #define pfn_to_section_nr(pfn) ((pfn) >> PFN_SECTION_SHIFT)
1020 #define section_nr_to_pfn(sec) ((sec) << PFN_SECTION_SHIFT)
1021 
1022 #define SECTION_ALIGN_UP(pfn)   (((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK)
1023 #define SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SECTION_MASK)
1024 
1025 struct page;
1026 struct page_ext;
1027 struct mem_section {
1028         /*
1029          * This is, logically, a pointer to an array of struct
1030          * pages.  However, it is stored with some other magic.
1031          * (see sparse.c::sparse_init_one_section())
1032          *
1033          * Additionally during early boot we encode node id of
1034          * the location of the section here to guide allocation.
1035          * (see sparse.c::memory_present())
1036          *
1037          * Making it a UL at least makes someone do a cast
1038          * before using it wrong.
1039          */
1040         unsigned long section_mem_map;
1041 
1042         /* See declaration of similar field in struct zone */
1043         unsigned long *pageblock_flags;
1044 #ifdef CONFIG_PAGE_EXTENSION
1045         /*
1046          * If !SPARSEMEM, pgdat doesn't have page_ext pointer. We use
1047          * section. (see page_ext.h about this.)
1048          */
1049         struct page_ext *page_ext;
1050         unsigned long pad;
1051 #endif
1052         /*
1053          * WARNING: mem_section must be a power-of-2 in size for the
1054          * calculation and use of SECTION_ROOT_MASK to make sense.
1055          */
1056 };
1057 
1058 #ifdef CONFIG_SPARSEMEM_EXTREME
1059 #define SECTIONS_PER_ROOT       (PAGE_SIZE / sizeof (struct mem_section))
1060 #else
1061 #define SECTIONS_PER_ROOT       1
1062 #endif
1063 
1064 #define SECTION_NR_TO_ROOT(sec) ((sec) / SECTIONS_PER_ROOT)
1065 #define NR_SECTION_ROOTS        DIV_ROUND_UP(NR_MEM_SECTIONS, SECTIONS_PER_ROOT)
1066 #define SECTION_ROOT_MASK       (SECTIONS_PER_ROOT - 1)
1067 
1068 #ifdef CONFIG_SPARSEMEM_EXTREME
1069 extern struct mem_section *mem_section[NR_SECTION_ROOTS];
1070 #else
1071 extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
1072 #endif
1073 
1074 static inline struct mem_section *__nr_to_section(unsigned long nr)
1075 {
1076         if (!mem_section[SECTION_NR_TO_ROOT(nr)])
1077                 return NULL;
1078         return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
1079 }
1080 extern int __section_nr(struct mem_section* ms);
1081 extern unsigned long usemap_size(void);
1082 
1083 /*
1084  * We use the lower bits of the mem_map pointer to store
1085  * a little bit of information.  There should be at least
1086  * 3 bits here due to 32-bit alignment.
1087  */
1088 #define SECTION_MARKED_PRESENT  (1UL<<0)
1089 #define SECTION_HAS_MEM_MAP     (1UL<<1)
1090 #define SECTION_MAP_LAST_BIT    (1UL<<2)
1091 #define SECTION_MAP_MASK        (~(SECTION_MAP_LAST_BIT-1))
1092 #define SECTION_NID_SHIFT       2
1093 
1094 static inline struct page *__section_mem_map_addr(struct mem_section *section)
1095 {
1096         unsigned long map = section->section_mem_map;
1097         map &= SECTION_MAP_MASK;
1098         return (struct page *)map;
1099 }
1100 
1101 static inline int present_section(struct mem_section *section)
1102 {
1103         return (section && (section->section_mem_map & SECTION_MARKED_PRESENT));
1104 }
1105 
1106 static inline int present_section_nr(unsigned long nr)
1107 {
1108         return present_section(__nr_to_section(nr));
1109 }
1110 
1111 static inline int valid_section(struct mem_section *section)
1112 {
1113         return (section && (section->section_mem_map & SECTION_HAS_MEM_MAP));
1114 }
1115 
1116 static inline int valid_section_nr(unsigned long nr)
1117 {
1118         return valid_section(__nr_to_section(nr));
1119 }
1120 
1121 static inline struct mem_section *__pfn_to_section(unsigned long pfn)
1122 {
1123         return __nr_to_section(pfn_to_section_nr(pfn));
1124 }
1125 
1126 #ifndef CONFIG_HAVE_ARCH_PFN_VALID
1127 static inline int pfn_valid(unsigned long pfn)
1128 {
1129         if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
1130                 return 0;
1131         return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
1132 }
1133 #endif
1134 
1135 static inline int pfn_present(unsigned long pfn)
1136 {
1137         if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
1138                 return 0;
1139         return present_section(__nr_to_section(pfn_to_section_nr(pfn)));
1140 }
1141 
1142 /*
1143  * These are _only_ used during initialisation, therefore they
1144  * can use __initdata ...  They could have names to indicate
1145  * this restriction.
1146  */
1147 #ifdef CONFIG_NUMA
1148 #define pfn_to_nid(pfn)                                                 \
1149 ({                                                                      \
1150         unsigned long __pfn_to_nid_pfn = (pfn);                         \
1151         page_to_nid(pfn_to_page(__pfn_to_nid_pfn));                     \
1152 })
1153 #else
1154 #define pfn_to_nid(pfn)         (0)
1155 #endif
1156 
1157 #define early_pfn_valid(pfn)    pfn_valid(pfn)
1158 void sparse_init(void);
1159 #else
1160 #define sparse_init()   do {} while (0)
1161 #define sparse_index_init(_sec, _nid)  do {} while (0)
1162 #endif /* CONFIG_SPARSEMEM */
1163 
1164 /*
1165  * During memory init memblocks map pfns to nids. The search is expensive and
1166  * this caches recent lookups. The implementation of __early_pfn_to_nid
1167  * may treat start/end as pfns or sections.
1168  */
1169 struct mminit_pfnnid_cache {
1170         unsigned long last_start;
1171         unsigned long last_end;
1172         int last_nid;
1173 };
1174 
1175 #ifndef early_pfn_valid
1176 #define early_pfn_valid(pfn)    (1)
1177 #endif
1178 
1179 void memory_present(int nid, unsigned long start, unsigned long end);
1180 unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
1181 
1182 /*
1183  * If it is possible to have holes within a MAX_ORDER_NR_PAGES, then we
1184  * need to check pfn validility within that MAX_ORDER_NR_PAGES block.
1185  * pfn_valid_within() should be used in this case; we optimise this away
1186  * when we have no holes within a MAX_ORDER_NR_PAGES block.
1187  */
1188 #ifdef CONFIG_HOLES_IN_ZONE
1189 #define pfn_valid_within(pfn) pfn_valid(pfn)
1190 #else
1191 #define pfn_valid_within(pfn) (1)
1192 #endif
1193 
1194 #ifdef CONFIG_ARCH_HAS_HOLES_MEMORYMODEL
1195 /*
1196  * pfn_valid() is meant to be able to tell if a given PFN has valid memmap
1197  * associated with it or not. In FLATMEM, it is expected that holes always
1198  * have valid memmap as long as there is valid PFNs either side of the hole.
1199  * In SPARSEMEM, it is assumed that a valid section has a memmap for the
1200  * entire section.
1201  *
1202  * However, an ARM, and maybe other embedded architectures in the future
1203  * free memmap backing holes to save memory on the assumption the memmap is
1204  * never used. The page_zone linkages are then broken even though pfn_valid()
1205  * returns true. A walker of the full memmap must then do this additional
1206  * check to ensure the memmap they are looking at is sane by making sure
1207  * the zone and PFN linkages are still valid. This is expensive, but walkers
1208  * of the full memmap are extremely rare.
1209  */
1210 int memmap_valid_within(unsigned long pfn,
1211                                         struct page *page, struct zone *zone);
1212 #else
1213 static inline int memmap_valid_within(unsigned long pfn,
1214                                         struct page *page, struct zone *zone)
1215 {
1216         return 1;
1217 }
1218 #endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */
1219 
1220 #endif /* !__GENERATING_BOUNDS.H */
1221 #endif /* !__ASSEMBLY__ */
1222 #endif /* _LINUX_MMZONE_H */
1223 

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