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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 /* In mm/page_alloc.c; keep in sync also with show_migration_types() there */
 67 extern char * const migratetype_names[MIGRATE_TYPES];
 68 
 69 #ifdef CONFIG_CMA
 70 #  define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)
 71 #else
 72 #  define is_migrate_cma(migratetype) false
 73 #endif
 74 
 75 #define for_each_migratetype_order(order, type) \
 76         for (order = 0; order < MAX_ORDER; order++) \
 77                 for (type = 0; type < MIGRATE_TYPES; type++)
 78 
 79 extern int page_group_by_mobility_disabled;
 80 
 81 #define NR_MIGRATETYPE_BITS (PB_migrate_end - PB_migrate + 1)
 82 #define MIGRATETYPE_MASK ((1UL << NR_MIGRATETYPE_BITS) - 1)
 83 
 84 #define get_pageblock_migratetype(page)                                 \
 85         get_pfnblock_flags_mask(page, page_to_pfn(page),                \
 86                         PB_migrate_end, MIGRATETYPE_MASK)
 87 
 88 static inline int get_pfnblock_migratetype(struct page *page, unsigned long pfn)
 89 {
 90         BUILD_BUG_ON(PB_migrate_end - PB_migrate != 2);
 91         return get_pfnblock_flags_mask(page, pfn, PB_migrate_end,
 92                                         MIGRATETYPE_MASK);
 93 }
 94 
 95 struct free_area {
 96         struct list_head        free_list[MIGRATE_TYPES];
 97         unsigned long           nr_free;
 98 };
 99 
100 struct pglist_data;
101 
102 /*
103  * zone->lock and zone->lru_lock are two of the hottest locks in the kernel.
104  * So add a wild amount of padding here to ensure that they fall into separate
105  * cachelines.  There are very few zone structures in the machine, so space
106  * consumption is not a concern here.
107  */
108 #if defined(CONFIG_SMP)
109 struct zone_padding {
110         char x[0];
111 } ____cacheline_internodealigned_in_smp;
112 #define ZONE_PADDING(name)      struct zone_padding name;
113 #else
114 #define ZONE_PADDING(name)
115 #endif
116 
117 enum zone_stat_item {
118         /* First 128 byte cacheline (assuming 64 bit words) */
119         NR_FREE_PAGES,
120         NR_ALLOC_BATCH,
121         NR_LRU_BASE,
122         NR_INACTIVE_ANON = NR_LRU_BASE, /* must match order of LRU_[IN]ACTIVE */
123         NR_ACTIVE_ANON,         /*  "     "     "   "       "         */
124         NR_INACTIVE_FILE,       /*  "     "     "   "       "         */
125         NR_ACTIVE_FILE,         /*  "     "     "   "       "         */
126         NR_UNEVICTABLE,         /*  "     "     "   "       "         */
127         NR_MLOCK,               /* mlock()ed pages found and moved off LRU */
128         NR_ANON_PAGES,  /* Mapped anonymous pages */
129         NR_FILE_MAPPED, /* pagecache pages mapped into pagetables.
130                            only modified from process context */
131         NR_FILE_PAGES,
132         NR_FILE_DIRTY,
133         NR_WRITEBACK,
134         NR_SLAB_RECLAIMABLE,
135         NR_SLAB_UNRECLAIMABLE,
136         NR_PAGETABLE,           /* used for pagetables */
137         NR_KERNEL_STACK,
138         /* Second 128 byte cacheline */
139         NR_UNSTABLE_NFS,        /* NFS unstable pages */
140         NR_BOUNCE,
141         NR_VMSCAN_WRITE,
142         NR_VMSCAN_IMMEDIATE,    /* Prioritise for reclaim when writeback ends */
143         NR_WRITEBACK_TEMP,      /* Writeback using temporary buffers */
144         NR_ISOLATED_ANON,       /* Temporary isolated pages from anon lru */
145         NR_ISOLATED_FILE,       /* Temporary isolated pages from file lru */
146         NR_SHMEM,               /* shmem pages (included tmpfs/GEM pages) */
147         NR_DIRTIED,             /* page dirtyings since bootup */
148         NR_WRITTEN,             /* page writings since bootup */
149         NR_PAGES_SCANNED,       /* pages scanned since last reclaim */
150 #ifdef CONFIG_NUMA
151         NUMA_HIT,               /* allocated in intended node */
152         NUMA_MISS,              /* allocated in non intended node */
153         NUMA_FOREIGN,           /* was intended here, hit elsewhere */
154         NUMA_INTERLEAVE_HIT,    /* interleaver preferred this zone */
155         NUMA_LOCAL,             /* allocation from local node */
156         NUMA_OTHER,             /* allocation from other node */
157 #endif
158         WORKINGSET_REFAULT,
159         WORKINGSET_ACTIVATE,
160         WORKINGSET_NODERECLAIM,
161         NR_ANON_TRANSPARENT_HUGEPAGES,
162         NR_FREE_CMA_PAGES,
163         NR_VM_ZONE_STAT_ITEMS };
164 
165 /*
166  * We do arithmetic on the LRU lists in various places in the code,
167  * so it is important to keep the active lists LRU_ACTIVE higher in
168  * the array than the corresponding inactive lists, and to keep
169  * the *_FILE lists LRU_FILE higher than the corresponding _ANON lists.
170  *
171  * This has to be kept in sync with the statistics in zone_stat_item
172  * above and the descriptions in vmstat_text in mm/vmstat.c
173  */
174 #define LRU_BASE 0
175 #define LRU_ACTIVE 1
176 #define LRU_FILE 2
177 
178 enum lru_list {
179         LRU_INACTIVE_ANON = LRU_BASE,
180         LRU_ACTIVE_ANON = LRU_BASE + LRU_ACTIVE,
181         LRU_INACTIVE_FILE = LRU_BASE + LRU_FILE,
182         LRU_ACTIVE_FILE = LRU_BASE + LRU_FILE + LRU_ACTIVE,
183         LRU_UNEVICTABLE,
184         NR_LRU_LISTS
185 };
186 
187 #define for_each_lru(lru) for (lru = 0; lru < NR_LRU_LISTS; lru++)
188 
189 #define for_each_evictable_lru(lru) for (lru = 0; lru <= LRU_ACTIVE_FILE; lru++)
190 
191 static inline int is_file_lru(enum lru_list lru)
192 {
193         return (lru == LRU_INACTIVE_FILE || lru == LRU_ACTIVE_FILE);
194 }
195 
196 static inline int is_active_lru(enum lru_list lru)
197 {
198         return (lru == LRU_ACTIVE_ANON || lru == LRU_ACTIVE_FILE);
199 }
200 
201 struct zone_reclaim_stat {
202         /*
203          * The pageout code in vmscan.c keeps track of how many of the
204          * mem/swap backed and file backed pages are referenced.
205          * The higher the rotated/scanned ratio, the more valuable
206          * that cache is.
207          *
208          * The anon LRU stats live in [0], file LRU stats in [1]
209          */
210         unsigned long           recent_rotated[2];
211         unsigned long           recent_scanned[2];
212 };
213 
214 struct lruvec {
215         struct list_head                lists[NR_LRU_LISTS];
216         struct zone_reclaim_stat        reclaim_stat;
217         /* Evictions & activations on the inactive file list */
218         atomic_long_t                   inactive_age;
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 are not available
365          * to userspace allocations.
366          */
367         unsigned long           totalreserve_pages;
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         /*
496          * When free pages are below this point, additional steps are taken
497          * when reading the number of free pages to avoid per-cpu counter
498          * drift allowing watermarks to be breached
499          */
500         unsigned long percpu_drift_mark;
501 
502 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
503         /* pfn where compaction free scanner should start */
504         unsigned long           compact_cached_free_pfn;
505         /* pfn where async and sync compaction migration scanner should start */
506         unsigned long           compact_cached_migrate_pfn[2];
507 #endif
508 
509 #ifdef CONFIG_COMPACTION
510         /*
511          * On compaction failure, 1<<compact_defer_shift compactions
512          * are skipped before trying again. The number attempted since
513          * last failure is tracked with compact_considered.
514          */
515         unsigned int            compact_considered;
516         unsigned int            compact_defer_shift;
517         int                     compact_order_failed;
518 #endif
519 
520 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
521         /* Set to true when the PG_migrate_skip bits should be cleared */
522         bool                    compact_blockskip_flush;
523 #endif
524 
525         bool                    contiguous;
526 
527         ZONE_PADDING(_pad3_)
528         /* Zone statistics */
529         atomic_long_t           vm_stat[NR_VM_ZONE_STAT_ITEMS];
530 } ____cacheline_internodealigned_in_smp;
531 
532 enum zone_flags {
533         ZONE_RECLAIM_LOCKED,            /* prevents concurrent reclaim */
534         ZONE_OOM_LOCKED,                /* zone is in OOM killer zonelist */
535         ZONE_CONGESTED,                 /* zone has many dirty pages backed by
536                                          * a congested BDI
537                                          */
538         ZONE_DIRTY,                     /* reclaim scanning has recently found
539                                          * many dirty file pages at the tail
540                                          * of the LRU.
541                                          */
542         ZONE_WRITEBACK,                 /* reclaim scanning has recently found
543                                          * many pages under writeback
544                                          */
545         ZONE_FAIR_DEPLETED,             /* fair zone policy batch depleted */
546 };
547 
548 static inline unsigned long zone_end_pfn(const struct zone *zone)
549 {
550         return zone->zone_start_pfn + zone->spanned_pages;
551 }
552 
553 static inline bool zone_spans_pfn(const struct zone *zone, unsigned long pfn)
554 {
555         return zone->zone_start_pfn <= pfn && pfn < zone_end_pfn(zone);
556 }
557 
558 static inline bool zone_is_initialized(struct zone *zone)
559 {
560         return !!zone->wait_table;
561 }
562 
563 static inline bool zone_is_empty(struct zone *zone)
564 {
565         return zone->spanned_pages == 0;
566 }
567 
568 /*
569  * The "priority" of VM scanning is how much of the queues we will scan in one
570  * go. A value of 12 for DEF_PRIORITY implies that we will scan 1/4096th of the
571  * queues ("queue_length >> 12") during an aging round.
572  */
573 #define DEF_PRIORITY 12
574 
575 /* Maximum number of zones on a zonelist */
576 #define MAX_ZONES_PER_ZONELIST (MAX_NUMNODES * MAX_NR_ZONES)
577 
578 enum {
579         ZONELIST_FALLBACK,      /* zonelist with fallback */
580 #ifdef CONFIG_NUMA
581         /*
582          * The NUMA zonelists are doubled because we need zonelists that
583          * restrict the allocations to a single node for __GFP_THISNODE.
584          */
585         ZONELIST_NOFALLBACK,    /* zonelist without fallback (__GFP_THISNODE) */
586 #endif
587         MAX_ZONELISTS
588 };
589 
590 /*
591  * This struct contains information about a zone in a zonelist. It is stored
592  * here to avoid dereferences into large structures and lookups of tables
593  */
594 struct zoneref {
595         struct zone *zone;      /* Pointer to actual zone */
596         int zone_idx;           /* zone_idx(zoneref->zone) */
597 };
598 
599 /*
600  * One allocation request operates on a zonelist. A zonelist
601  * is a list of zones, the first one is the 'goal' of the
602  * allocation, the other zones are fallback zones, in decreasing
603  * priority.
604  *
605  * To speed the reading of the zonelist, the zonerefs contain the zone index
606  * of the entry being read. Helper functions to access information given
607  * a struct zoneref are
608  *
609  * zonelist_zone()      - Return the struct zone * for an entry in _zonerefs
610  * zonelist_zone_idx()  - Return the index of the zone for an entry
611  * zonelist_node_idx()  - Return the index of the node for an entry
612  */
613 struct zonelist {
614         struct zoneref _zonerefs[MAX_ZONES_PER_ZONELIST + 1];
615 };
616 
617 #ifndef CONFIG_DISCONTIGMEM
618 /* The array of struct pages - for discontigmem use pgdat->lmem_map */
619 extern struct page *mem_map;
620 #endif
621 
622 /*
623  * The pg_data_t structure is used in machines with CONFIG_DISCONTIGMEM
624  * (mostly NUMA machines?) to denote a higher-level memory zone than the
625  * zone denotes.
626  *
627  * On NUMA machines, each NUMA node would have a pg_data_t to describe
628  * it's memory layout.
629  *
630  * Memory statistics and page replacement data structures are maintained on a
631  * per-zone basis.
632  */
633 struct bootmem_data;
634 typedef struct pglist_data {
635         struct zone node_zones[MAX_NR_ZONES];
636         struct zonelist node_zonelists[MAX_ZONELISTS];
637         int nr_zones;
638 #ifdef CONFIG_FLAT_NODE_MEM_MAP /* means !SPARSEMEM */
639         struct page *node_mem_map;
640 #ifdef CONFIG_PAGE_EXTENSION
641         struct page_ext *node_page_ext;
642 #endif
643 #endif
644 #ifndef CONFIG_NO_BOOTMEM
645         struct bootmem_data *bdata;
646 #endif
647 #ifdef CONFIG_MEMORY_HOTPLUG
648         /*
649          * Must be held any time you expect node_start_pfn, node_present_pages
650          * or node_spanned_pages stay constant.  Holding this will also
651          * guarantee that any pfn_valid() stays that way.
652          *
653          * pgdat_resize_lock() and pgdat_resize_unlock() are provided to
654          * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG.
655          *
656          * Nests above zone->lock and zone->span_seqlock
657          */
658         spinlock_t node_size_lock;
659 #endif
660         unsigned long node_start_pfn;
661         unsigned long node_present_pages; /* total number of physical pages */
662         unsigned long node_spanned_pages; /* total size of physical page
663                                              range, including holes */
664         int node_id;
665         wait_queue_head_t kswapd_wait;
666         wait_queue_head_t pfmemalloc_wait;
667         struct task_struct *kswapd;     /* Protected by
668                                            mem_hotplug_begin/end() */
669         int kswapd_max_order;
670         enum zone_type classzone_idx;
671 #ifdef CONFIG_COMPACTION
672         int kcompactd_max_order;
673         enum zone_type kcompactd_classzone_idx;
674         wait_queue_head_t kcompactd_wait;
675         struct task_struct *kcompactd;
676 #endif
677 #ifdef CONFIG_NUMA_BALANCING
678         /* Lock serializing the migrate rate limiting window */
679         spinlock_t numabalancing_migrate_lock;
680 
681         /* Rate limiting time interval */
682         unsigned long numabalancing_migrate_next_window;
683 
684         /* Number of pages migrated during the rate limiting time interval */
685         unsigned long numabalancing_migrate_nr_pages;
686 #endif
687 
688 #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
689         /*
690          * If memory initialisation on large machines is deferred then this
691          * is the first PFN that needs to be initialised.
692          */
693         unsigned long first_deferred_pfn;
694 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
695 
696 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
697         spinlock_t split_queue_lock;
698         struct list_head split_queue;
699         unsigned long split_queue_len;
700 #endif
701 } pg_data_t;
702 
703 #define node_present_pages(nid) (NODE_DATA(nid)->node_present_pages)
704 #define node_spanned_pages(nid) (NODE_DATA(nid)->node_spanned_pages)
705 #ifdef CONFIG_FLAT_NODE_MEM_MAP
706 #define pgdat_page_nr(pgdat, pagenr)    ((pgdat)->node_mem_map + (pagenr))
707 #else
708 #define pgdat_page_nr(pgdat, pagenr)    pfn_to_page((pgdat)->node_start_pfn + (pagenr))
709 #endif
710 #define nid_page_nr(nid, pagenr)        pgdat_page_nr(NODE_DATA(nid),(pagenr))
711 
712 #define node_start_pfn(nid)     (NODE_DATA(nid)->node_start_pfn)
713 #define node_end_pfn(nid) pgdat_end_pfn(NODE_DATA(nid))
714 
715 static inline unsigned long pgdat_end_pfn(pg_data_t *pgdat)
716 {
717         return pgdat->node_start_pfn + pgdat->node_spanned_pages;
718 }
719 
720 static inline bool pgdat_is_empty(pg_data_t *pgdat)
721 {
722         return !pgdat->node_start_pfn && !pgdat->node_spanned_pages;
723 }
724 
725 static inline int zone_id(const struct zone *zone)
726 {
727         struct pglist_data *pgdat = zone->zone_pgdat;
728 
729         return zone - pgdat->node_zones;
730 }
731 
732 #ifdef CONFIG_ZONE_DEVICE
733 static inline bool is_dev_zone(const struct zone *zone)
734 {
735         return zone_id(zone) == ZONE_DEVICE;
736 }
737 #else
738 static inline bool is_dev_zone(const struct zone *zone)
739 {
740         return false;
741 }
742 #endif
743 
744 #include <linux/memory_hotplug.h>
745 
746 extern struct mutex zonelists_mutex;
747 void build_all_zonelists(pg_data_t *pgdat, struct zone *zone);
748 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx);
749 bool zone_watermark_ok(struct zone *z, unsigned int order,
750                 unsigned long mark, int classzone_idx, int alloc_flags);
751 bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
752                 unsigned long mark, int classzone_idx);
753 enum memmap_context {
754         MEMMAP_EARLY,
755         MEMMAP_HOTPLUG,
756 };
757 extern int init_currently_empty_zone(struct zone *zone, unsigned long start_pfn,
758                                      unsigned long size);
759 
760 extern void lruvec_init(struct lruvec *lruvec);
761 
762 static inline struct zone *lruvec_zone(struct lruvec *lruvec)
763 {
764 #ifdef CONFIG_MEMCG
765         return lruvec->zone;
766 #else
767         return container_of(lruvec, struct zone, lruvec);
768 #endif
769 }
770 
771 extern unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru);
772 
773 #ifdef CONFIG_HAVE_MEMORY_PRESENT
774 void memory_present(int nid, unsigned long start, unsigned long end);
775 #else
776 static inline void memory_present(int nid, unsigned long start, unsigned long end) {}
777 #endif
778 
779 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
780 int local_memory_node(int node_id);
781 #else
782 static inline int local_memory_node(int node_id) { return node_id; };
783 #endif
784 
785 #ifdef CONFIG_NEED_NODE_MEMMAP_SIZE
786 unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
787 #endif
788 
789 /*
790  * zone_idx() returns 0 for the ZONE_DMA zone, 1 for the ZONE_NORMAL zone, etc.
791  */
792 #define zone_idx(zone)          ((zone) - (zone)->zone_pgdat->node_zones)
793 
794 static inline int populated_zone(struct zone *zone)
795 {
796         return (!!zone->present_pages);
797 }
798 
799 extern int movable_zone;
800 
801 #ifdef CONFIG_HIGHMEM
802 static inline int zone_movable_is_highmem(void)
803 {
804 #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
805         return movable_zone == ZONE_HIGHMEM;
806 #else
807         return (ZONE_MOVABLE - 1) == ZONE_HIGHMEM;
808 #endif
809 }
810 #endif
811 
812 static inline int is_highmem_idx(enum zone_type idx)
813 {
814 #ifdef CONFIG_HIGHMEM
815         return (idx == ZONE_HIGHMEM ||
816                 (idx == ZONE_MOVABLE && zone_movable_is_highmem()));
817 #else
818         return 0;
819 #endif
820 }
821 
822 /**
823  * is_highmem - helper function to quickly check if a struct zone is a 
824  *              highmem zone or not.  This is an attempt to keep references
825  *              to ZONE_{DMA/NORMAL/HIGHMEM/etc} in general code to a minimum.
826  * @zone - pointer to struct zone variable
827  */
828 static inline int is_highmem(struct zone *zone)
829 {
830 #ifdef CONFIG_HIGHMEM
831         int zone_off = (char *)zone - (char *)zone->zone_pgdat->node_zones;
832         return zone_off == ZONE_HIGHMEM * sizeof(*zone) ||
833                (zone_off == ZONE_MOVABLE * sizeof(*zone) &&
834                 zone_movable_is_highmem());
835 #else
836         return 0;
837 #endif
838 }
839 
840 /* These two functions are used to setup the per zone pages min values */
841 struct ctl_table;
842 int min_free_kbytes_sysctl_handler(struct ctl_table *, int,
843                                         void __user *, size_t *, loff_t *);
844 int watermark_scale_factor_sysctl_handler(struct ctl_table *, int,
845                                         void __user *, size_t *, loff_t *);
846 extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1];
847 int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int,
848                                         void __user *, size_t *, loff_t *);
849 int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *, int,
850                                         void __user *, size_t *, loff_t *);
851 int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *, int,
852                         void __user *, size_t *, loff_t *);
853 int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *, int,
854                         void __user *, size_t *, loff_t *);
855 
856 extern int numa_zonelist_order_handler(struct ctl_table *, int,
857                         void __user *, size_t *, loff_t *);
858 extern char numa_zonelist_order[];
859 #define NUMA_ZONELIST_ORDER_LEN 16      /* string buffer size */
860 
861 #ifndef CONFIG_NEED_MULTIPLE_NODES
862 
863 extern struct pglist_data contig_page_data;
864 #define NODE_DATA(nid)          (&contig_page_data)
865 #define NODE_MEM_MAP(nid)       mem_map
866 
867 #else /* CONFIG_NEED_MULTIPLE_NODES */
868 
869 #include <asm/mmzone.h>
870 
871 #endif /* !CONFIG_NEED_MULTIPLE_NODES */
872 
873 extern struct pglist_data *first_online_pgdat(void);
874 extern struct pglist_data *next_online_pgdat(struct pglist_data *pgdat);
875 extern struct zone *next_zone(struct zone *zone);
876 
877 /**
878  * for_each_online_pgdat - helper macro to iterate over all online nodes
879  * @pgdat - pointer to a pg_data_t variable
880  */
881 #define for_each_online_pgdat(pgdat)                    \
882         for (pgdat = first_online_pgdat();              \
883              pgdat;                                     \
884              pgdat = next_online_pgdat(pgdat))
885 /**
886  * for_each_zone - helper macro to iterate over all memory zones
887  * @zone - pointer to struct zone variable
888  *
889  * The user only needs to declare the zone variable, for_each_zone
890  * fills it in.
891  */
892 #define for_each_zone(zone)                             \
893         for (zone = (first_online_pgdat())->node_zones; \
894              zone;                                      \
895              zone = next_zone(zone))
896 
897 #define for_each_populated_zone(zone)                   \
898         for (zone = (first_online_pgdat())->node_zones; \
899              zone;                                      \
900              zone = next_zone(zone))                    \
901                 if (!populated_zone(zone))              \
902                         ; /* do nothing */              \
903                 else
904 
905 static inline struct zone *zonelist_zone(struct zoneref *zoneref)
906 {
907         return zoneref->zone;
908 }
909 
910 static inline int zonelist_zone_idx(struct zoneref *zoneref)
911 {
912         return zoneref->zone_idx;
913 }
914 
915 static inline int zonelist_node_idx(struct zoneref *zoneref)
916 {
917 #ifdef CONFIG_NUMA
918         /* zone_to_nid not available in this context */
919         return zoneref->zone->node;
920 #else
921         return 0;
922 #endif /* CONFIG_NUMA */
923 }
924 
925 /**
926  * 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
927  * @z - The cursor used as a starting point for the search
928  * @highest_zoneidx - The zone index of the highest zone to return
929  * @nodes - An optional nodemask to filter the zonelist with
930  *
931  * This function returns the next zone at or below a given zone index that is
932  * within the allowed nodemask using a cursor as the starting point for the
933  * search. The zoneref returned is a cursor that represents the current zone
934  * being examined. It should be advanced by one before calling
935  * next_zones_zonelist again.
936  */
937 struct zoneref *next_zones_zonelist(struct zoneref *z,
938                                         enum zone_type highest_zoneidx,
939                                         nodemask_t *nodes);
940 
941 /**
942  * first_zones_zonelist - Returns the first zone at or below highest_zoneidx within the allowed nodemask in a zonelist
943  * @zonelist - The zonelist to search for a suitable zone
944  * @highest_zoneidx - The zone index of the highest zone to return
945  * @nodes - An optional nodemask to filter the zonelist with
946  * @zone - The first suitable zone found is returned via this parameter
947  *
948  * This function returns the first zone at or below a given zone index that is
949  * within the allowed nodemask. The zoneref returned is a cursor that can be
950  * used to iterate the zonelist with next_zones_zonelist by advancing it by
951  * one before calling.
952  */
953 static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,
954                                         enum zone_type highest_zoneidx,
955                                         nodemask_t *nodes,
956                                         struct zone **zone)
957 {
958         struct zoneref *z = next_zones_zonelist(zonelist->_zonerefs,
959                                                         highest_zoneidx, nodes);
960         *zone = zonelist_zone(z);
961         return z;
962 }
963 
964 /**
965  * 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
966  * @zone - The current zone in the iterator
967  * @z - The current pointer within zonelist->zones being iterated
968  * @zlist - The zonelist being iterated
969  * @highidx - The zone index of the highest zone to return
970  * @nodemask - Nodemask allowed by the allocator
971  *
972  * This iterator iterates though all zones at or below a given zone index and
973  * within a given nodemask
974  */
975 #define for_each_zone_zonelist_nodemask(zone, z, zlist, highidx, nodemask) \
976         for (z = first_zones_zonelist(zlist, highidx, nodemask, &zone); \
977                 zone;                                                   \
978                 z = next_zones_zonelist(++z, highidx, nodemask),        \
979                         zone = zonelist_zone(z))                        \
980 
981 /**
982  * for_each_zone_zonelist - helper macro to iterate over valid zones in a zonelist at or below a given zone index
983  * @zone - The current zone in the iterator
984  * @z - The current pointer within zonelist->zones being iterated
985  * @zlist - The zonelist being iterated
986  * @highidx - The zone index of the highest zone to return
987  *
988  * This iterator iterates though all zones at or below a given zone index.
989  */
990 #define for_each_zone_zonelist(zone, z, zlist, highidx) \
991         for_each_zone_zonelist_nodemask(zone, z, zlist, highidx, NULL)
992 
993 #ifdef CONFIG_SPARSEMEM
994 #include <asm/sparsemem.h>
995 #endif
996 
997 #if !defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) && \
998         !defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP)
999 static inline unsigned long early_pfn_to_nid(unsigned long pfn)
1000 {
1001         return 0;
1002 }
1003 #endif
1004 
1005 #ifdef CONFIG_FLATMEM
1006 #define pfn_to_nid(pfn)         (0)
1007 #endif
1008 
1009 #ifdef CONFIG_SPARSEMEM
1010 
1011 /*
1012  * SECTION_SHIFT                #bits space required to store a section #
1013  *
1014  * PA_SECTION_SHIFT             physical address to/from section number
1015  * PFN_SECTION_SHIFT            pfn to/from section number
1016  */
1017 #define PA_SECTION_SHIFT        (SECTION_SIZE_BITS)
1018 #define PFN_SECTION_SHIFT       (SECTION_SIZE_BITS - PAGE_SHIFT)
1019 
1020 #define NR_MEM_SECTIONS         (1UL << SECTIONS_SHIFT)
1021 
1022 #define PAGES_PER_SECTION       (1UL << PFN_SECTION_SHIFT)
1023 #define PAGE_SECTION_MASK       (~(PAGES_PER_SECTION-1))
1024 
1025 #define SECTION_BLOCKFLAGS_BITS \
1026         ((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)
1027 
1028 #if (MAX_ORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS
1029 #error Allocator MAX_ORDER exceeds SECTION_SIZE
1030 #endif
1031 
1032 #define pfn_to_section_nr(pfn) ((pfn) >> PFN_SECTION_SHIFT)
1033 #define section_nr_to_pfn(sec) ((sec) << PFN_SECTION_SHIFT)
1034 
1035 #define SECTION_ALIGN_UP(pfn)   (((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK)
1036 #define SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SECTION_MASK)
1037 
1038 struct page;
1039 struct page_ext;
1040 struct mem_section {
1041         /*
1042          * This is, logically, a pointer to an array of struct
1043          * pages.  However, it is stored with some other magic.
1044          * (see sparse.c::sparse_init_one_section())
1045          *
1046          * Additionally during early boot we encode node id of
1047          * the location of the section here to guide allocation.
1048          * (see sparse.c::memory_present())
1049          *
1050          * Making it a UL at least makes someone do a cast
1051          * before using it wrong.
1052          */
1053         unsigned long section_mem_map;
1054 
1055         /* See declaration of similar field in struct zone */
1056         unsigned long *pageblock_flags;
1057 #ifdef CONFIG_PAGE_EXTENSION
1058         /*
1059          * If !SPARSEMEM, pgdat doesn't have page_ext pointer. We use
1060          * section. (see page_ext.h about this.)
1061          */
1062         struct page_ext *page_ext;
1063         unsigned long pad;
1064 #endif
1065         /*
1066          * WARNING: mem_section must be a power-of-2 in size for the
1067          * calculation and use of SECTION_ROOT_MASK to make sense.
1068          */
1069 };
1070 
1071 #ifdef CONFIG_SPARSEMEM_EXTREME
1072 #define SECTIONS_PER_ROOT       (PAGE_SIZE / sizeof (struct mem_section))
1073 #else
1074 #define SECTIONS_PER_ROOT       1
1075 #endif
1076 
1077 #define SECTION_NR_TO_ROOT(sec) ((sec) / SECTIONS_PER_ROOT)
1078 #define NR_SECTION_ROOTS        DIV_ROUND_UP(NR_MEM_SECTIONS, SECTIONS_PER_ROOT)
1079 #define SECTION_ROOT_MASK       (SECTIONS_PER_ROOT - 1)
1080 
1081 #ifdef CONFIG_SPARSEMEM_EXTREME
1082 extern struct mem_section *mem_section[NR_SECTION_ROOTS];
1083 #else
1084 extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
1085 #endif
1086 
1087 static inline struct mem_section *__nr_to_section(unsigned long nr)
1088 {
1089         if (!mem_section[SECTION_NR_TO_ROOT(nr)])
1090                 return NULL;
1091         return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
1092 }
1093 extern int __section_nr(struct mem_section* ms);
1094 extern unsigned long usemap_size(void);
1095 
1096 /*
1097  * We use the lower bits of the mem_map pointer to store
1098  * a little bit of information.  There should be at least
1099  * 3 bits here due to 32-bit alignment.
1100  */
1101 #define SECTION_MARKED_PRESENT  (1UL<<0)
1102 #define SECTION_HAS_MEM_MAP     (1UL<<1)
1103 #define SECTION_MAP_LAST_BIT    (1UL<<2)
1104 #define SECTION_MAP_MASK        (~(SECTION_MAP_LAST_BIT-1))
1105 #define SECTION_NID_SHIFT       2
1106 
1107 static inline struct page *__section_mem_map_addr(struct mem_section *section)
1108 {
1109         unsigned long map = section->section_mem_map;
1110         map &= SECTION_MAP_MASK;
1111         return (struct page *)map;
1112 }
1113 
1114 static inline int present_section(struct mem_section *section)
1115 {
1116         return (section && (section->section_mem_map & SECTION_MARKED_PRESENT));
1117 }
1118 
1119 static inline int present_section_nr(unsigned long nr)
1120 {
1121         return present_section(__nr_to_section(nr));
1122 }
1123 
1124 static inline int valid_section(struct mem_section *section)
1125 {
1126         return (section && (section->section_mem_map & SECTION_HAS_MEM_MAP));
1127 }
1128 
1129 static inline int valid_section_nr(unsigned long nr)
1130 {
1131         return valid_section(__nr_to_section(nr));
1132 }
1133 
1134 static inline struct mem_section *__pfn_to_section(unsigned long pfn)
1135 {
1136         return __nr_to_section(pfn_to_section_nr(pfn));
1137 }
1138 
1139 #ifndef CONFIG_HAVE_ARCH_PFN_VALID
1140 static inline int pfn_valid(unsigned long pfn)
1141 {
1142         if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
1143                 return 0;
1144         return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
1145 }
1146 #endif
1147 
1148 static inline int pfn_present(unsigned long pfn)
1149 {
1150         if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
1151                 return 0;
1152         return present_section(__nr_to_section(pfn_to_section_nr(pfn)));
1153 }
1154 
1155 /*
1156  * These are _only_ used during initialisation, therefore they
1157  * can use __initdata ...  They could have names to indicate
1158  * this restriction.
1159  */
1160 #ifdef CONFIG_NUMA
1161 #define pfn_to_nid(pfn)                                                 \
1162 ({                                                                      \
1163         unsigned long __pfn_to_nid_pfn = (pfn);                         \
1164         page_to_nid(pfn_to_page(__pfn_to_nid_pfn));                     \
1165 })
1166 #else
1167 #define pfn_to_nid(pfn)         (0)
1168 #endif
1169 
1170 #define early_pfn_valid(pfn)    pfn_valid(pfn)
1171 void sparse_init(void);
1172 #else
1173 #define sparse_init()   do {} while (0)
1174 #define sparse_index_init(_sec, _nid)  do {} while (0)
1175 #endif /* CONFIG_SPARSEMEM */
1176 
1177 /*
1178  * During memory init memblocks map pfns to nids. The search is expensive and
1179  * this caches recent lookups. The implementation of __early_pfn_to_nid
1180  * may treat start/end as pfns or sections.
1181  */
1182 struct mminit_pfnnid_cache {
1183         unsigned long last_start;
1184         unsigned long last_end;
1185         int last_nid;
1186 };
1187 
1188 #ifndef early_pfn_valid
1189 #define early_pfn_valid(pfn)    (1)
1190 #endif
1191 
1192 void memory_present(int nid, unsigned long start, unsigned long end);
1193 unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
1194 
1195 /*
1196  * If it is possible to have holes within a MAX_ORDER_NR_PAGES, then we
1197  * need to check pfn validility within that MAX_ORDER_NR_PAGES block.
1198  * pfn_valid_within() should be used in this case; we optimise this away
1199  * when we have no holes within a MAX_ORDER_NR_PAGES block.
1200  */
1201 #ifdef CONFIG_HOLES_IN_ZONE
1202 #define pfn_valid_within(pfn) pfn_valid(pfn)
1203 #else
1204 #define pfn_valid_within(pfn) (1)
1205 #endif
1206 
1207 #ifdef CONFIG_ARCH_HAS_HOLES_MEMORYMODEL
1208 /*
1209  * pfn_valid() is meant to be able to tell if a given PFN has valid memmap
1210  * associated with it or not. In FLATMEM, it is expected that holes always
1211  * have valid memmap as long as there is valid PFNs either side of the hole.
1212  * In SPARSEMEM, it is assumed that a valid section has a memmap for the
1213  * entire section.
1214  *
1215  * However, an ARM, and maybe other embedded architectures in the future
1216  * free memmap backing holes to save memory on the assumption the memmap is
1217  * never used. The page_zone linkages are then broken even though pfn_valid()
1218  * returns true. A walker of the full memmap must then do this additional
1219  * check to ensure the memmap they are looking at is sane by making sure
1220  * the zone and PFN linkages are still valid. This is expensive, but walkers
1221  * of the full memmap are extremely rare.
1222  */
1223 bool memmap_valid_within(unsigned long pfn,
1224                                         struct page *page, struct zone *zone);
1225 #else
1226 static inline bool memmap_valid_within(unsigned long pfn,
1227                                         struct page *page, struct zone *zone)
1228 {
1229         return true;
1230 }
1231 #endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */
1232 
1233 #endif /* !__GENERATING_BOUNDS.H */
1234 #endif /* !__ASSEMBLY__ */
1235 #endif /* _LINUX_MMZONE_H */
1236 

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