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

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