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 # define is_migrate_cma_page(_page) (get_pageblock_migratetype(_page) == MIGRATE_CMA)
69 #else
70 # define is_migrate_cma(migratetype) false
71 # define is_migrate_cma_page(_page) false
72 #endif
73
74 #define for_each_migratetype_order(order, type) \
75 for (order = 0; order < MAX_ORDER; order++) \
76 for (type = 0; type < MIGRATE_TYPES; type++)
77
78 extern int page_group_by_mobility_disabled;
79
80 #define NR_MIGRATETYPE_BITS (PB_migrate_end - PB_migrate + 1)
81 #define MIGRATETYPE_MASK ((1UL << NR_MIGRATETYPE_BITS) - 1)
82
83 #define get_pageblock_migratetype(page) \
84 get_pfnblock_flags_mask(page, page_to_pfn(page), \
85 PB_migrate_end, MIGRATETYPE_MASK)
86
get_pfnblock_migratetype(struct page * page,unsigned long pfn)87 static inline int get_pfnblock_migratetype(struct page *page, unsigned long pfn)
88 {
89 BUILD_BUG_ON(PB_migrate_end - PB_migrate != 2);
90 return get_pfnblock_flags_mask(page, pfn, PB_migrate_end,
91 MIGRATETYPE_MASK);
92 }
93
94 struct free_area {
95 struct list_head free_list[MIGRATE_TYPES];
96 unsigned long nr_free;
97 };
98
99 struct pglist_data;
100
101 /*
102 * zone->lock and zone->lru_lock are two of the hottest locks in the kernel.
103 * So add a wild amount of padding here to ensure that they fall into separate
104 * cachelines. There are very few zone structures in the machine, so space
105 * consumption is not a concern here.
106 */
107 #if defined(CONFIG_SMP)
108 struct zone_padding {
109 char x[0];
110 } ____cacheline_internodealigned_in_smp;
111 #define ZONE_PADDING(name) struct zone_padding name;
112 #else
113 #define ZONE_PADDING(name)
114 #endif
115
116 enum zone_stat_item {
117 /* First 128 byte cacheline (assuming 64 bit words) */
118 NR_FREE_PAGES,
119 NR_ALLOC_BATCH,
120 NR_LRU_BASE,
121 NR_INACTIVE_ANON = NR_LRU_BASE, /* must match order of LRU_[IN]ACTIVE */
122 NR_ACTIVE_ANON, /* " " " " " */
123 NR_INACTIVE_FILE, /* " " " " " */
124 NR_ACTIVE_FILE, /* " " " " " */
125 NR_UNEVICTABLE, /* " " " " " */
126 NR_MLOCK, /* mlock()ed pages found and moved off LRU */
127 NR_ANON_PAGES, /* Mapped anonymous pages */
128 NR_FILE_MAPPED, /* pagecache pages mapped into pagetables.
129 only modified from process context */
130 NR_FILE_PAGES,
131 NR_FILE_DIRTY,
132 NR_WRITEBACK,
133 NR_SLAB_RECLAIMABLE,
134 NR_SLAB_UNRECLAIMABLE,
135 NR_PAGETABLE, /* used for pagetables */
136 /* Second 128 byte cacheline */
137 NR_KERNEL_STACK,
138 NR_KAISERTABLE,
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
is_file_lru(enum lru_list lru)191 static inline int is_file_lru(enum lru_list lru)
192 {
193 return (lru == LRU_INACTIVE_FILE || lru == LRU_ACTIVE_FILE);
194 }
195
is_active_lru(enum lru_list lru)196 static inline int is_active_lru(enum lru_list lru)
197 {
198 return (lru == LRU_ACTIVE_ANON || lru == LRU_ACTIVE_FILE);
199 }
200
is_unevictable_lru(enum lru_list lru)201 static inline int is_unevictable_lru(enum lru_list lru)
202 {
203 return (lru == LRU_UNEVICTABLE);
204 }
205
206 struct zone_reclaim_stat {
207 /*
208 * The pageout code in vmscan.c keeps track of how many of the
209 * mem/swap backed and file backed pages are referenced.
210 * The higher the rotated/scanned ratio, the more valuable
211 * that cache is.
212 *
213 * The anon LRU stats live in [0], file LRU stats in [1]
214 */
215 unsigned long recent_rotated[2];
216 unsigned long recent_scanned[2];
217 };
218
219 struct lruvec {
220 struct list_head lists[NR_LRU_LISTS];
221 struct zone_reclaim_stat reclaim_stat;
222 #ifdef CONFIG_MEMCG
223 struct zone *zone;
224 #endif
225 };
226
227 /* Mask used at gathering information at once (see memcontrol.c) */
228 #define LRU_ALL_FILE (BIT(LRU_INACTIVE_FILE) | BIT(LRU_ACTIVE_FILE))
229 #define LRU_ALL_ANON (BIT(LRU_INACTIVE_ANON) | BIT(LRU_ACTIVE_ANON))
230 #define LRU_ALL ((1 << NR_LRU_LISTS) - 1)
231
232 /* Isolate clean file */
233 #define ISOLATE_CLEAN ((__force isolate_mode_t)0x1)
234 /* Isolate unmapped file */
235 #define ISOLATE_UNMAPPED ((__force isolate_mode_t)0x2)
236 /* Isolate for asynchronous migration */
237 #define ISOLATE_ASYNC_MIGRATE ((__force isolate_mode_t)0x4)
238 /* Isolate unevictable pages */
239 #define ISOLATE_UNEVICTABLE ((__force isolate_mode_t)0x8)
240
241 /* LRU Isolation modes. */
242 typedef unsigned __bitwise__ isolate_mode_t;
243
244 enum zone_watermarks {
245 WMARK_MIN,
246 WMARK_LOW,
247 WMARK_HIGH,
248 NR_WMARK
249 };
250
251 #define min_wmark_pages(z) (z->watermark[WMARK_MIN])
252 #define low_wmark_pages(z) (z->watermark[WMARK_LOW])
253 #define high_wmark_pages(z) (z->watermark[WMARK_HIGH])
254
255 struct per_cpu_pages {
256 int count; /* number of pages in the list */
257 int high; /* high watermark, emptying needed */
258 int batch; /* chunk size for buddy add/remove */
259
260 /* Lists of pages, one per migrate type stored on the pcp-lists */
261 struct list_head lists[MIGRATE_PCPTYPES];
262 };
263
264 struct per_cpu_pageset {
265 struct per_cpu_pages pcp;
266 #ifdef CONFIG_NUMA
267 s8 expire;
268 #endif
269 #ifdef CONFIG_SMP
270 s8 stat_threshold;
271 s8 vm_stat_diff[NR_VM_ZONE_STAT_ITEMS];
272 #endif
273 };
274
275 #endif /* !__GENERATING_BOUNDS.H */
276
277 enum zone_type {
278 #ifdef CONFIG_ZONE_DMA
279 /*
280 * ZONE_DMA is used when there are devices that are not able
281 * to do DMA to all of addressable memory (ZONE_NORMAL). Then we
282 * carve out the portion of memory that is needed for these devices.
283 * The range is arch specific.
284 *
285 * Some examples
286 *
287 * Architecture Limit
288 * ---------------------------
289 * parisc, ia64, sparc <4G
290 * s390 <2G
291 * arm Various
292 * alpha Unlimited or 0-16MB.
293 *
294 * i386, x86_64 and multiple other arches
295 * <16M.
296 */
297 ZONE_DMA,
298 #endif
299 #ifdef CONFIG_ZONE_DMA32
300 /*
301 * x86_64 needs two ZONE_DMAs because it supports devices that are
302 * only able to do DMA to the lower 16M but also 32 bit devices that
303 * can only do DMA areas below 4G.
304 */
305 ZONE_DMA32,
306 #endif
307 /*
308 * Normal addressable memory is in ZONE_NORMAL. DMA operations can be
309 * performed on pages in ZONE_NORMAL if the DMA devices support
310 * transfers to all addressable memory.
311 */
312 ZONE_NORMAL,
313 #ifdef CONFIG_HIGHMEM
314 /*
315 * A memory area that is only addressable by the kernel through
316 * mapping portions into its own address space. This is for example
317 * used by i386 to allow the kernel to address the memory beyond
318 * 900MB. The kernel will set up special mappings (page
319 * table entries on i386) for each page that the kernel needs to
320 * access.
321 */
322 ZONE_HIGHMEM,
323 #endif
324 ZONE_MOVABLE,
325 #ifdef CONFIG_ZONE_DEVICE
326 ZONE_DEVICE,
327 #endif
328 __MAX_NR_ZONES
329
330 };
331
332 #ifndef __GENERATING_BOUNDS_H
333
334 struct zone {
335 /* Read-mostly fields */
336
337 /* zone watermarks, access with *_wmark_pages(zone) macros */
338 unsigned long watermark[NR_WMARK];
339
340 unsigned long nr_reserved_highatomic;
341
342 /*
343 * We don't know if the memory that we're going to allocate will be
344 * freeable or/and it will be released eventually, so to avoid totally
345 * wasting several GB of ram we must reserve some of the lower zone
346 * memory (otherwise we risk to run OOM on the lower zones despite
347 * there being tons of freeable ram on the higher zones). This array is
348 * recalculated at runtime if the sysctl_lowmem_reserve_ratio sysctl
349 * changes.
350 */
351 long lowmem_reserve[MAX_NR_ZONES];
352
353 #ifdef CONFIG_NUMA
354 int node;
355 #endif
356
357 /*
358 * The target ratio of ACTIVE_ANON to INACTIVE_ANON pages on
359 * this zone's LRU. Maintained by the pageout code.
360 */
361 unsigned int inactive_ratio;
362
363 struct pglist_data *zone_pgdat;
364 struct per_cpu_pageset __percpu *pageset;
365
366 /*
367 * This is a per-zone reserve of pages that should not be
368 * considered dirtyable memory.
369 */
370 unsigned long dirty_balance_reserve;
371
372 #ifndef CONFIG_SPARSEMEM
373 /*
374 * Flags for a pageblock_nr_pages block. See pageblock-flags.h.
375 * In SPARSEMEM, this map is stored in struct mem_section
376 */
377 unsigned long *pageblock_flags;
378 #endif /* CONFIG_SPARSEMEM */
379
380 #ifdef CONFIG_NUMA
381 /*
382 * zone reclaim becomes active if more unmapped pages exist.
383 */
384 unsigned long min_unmapped_pages;
385 unsigned long min_slab_pages;
386 #endif /* CONFIG_NUMA */
387
388 /* zone_start_pfn == zone_start_paddr >> PAGE_SHIFT */
389 unsigned long zone_start_pfn;
390
391 /*
392 * spanned_pages is the total pages spanned by the zone, including
393 * holes, which is calculated as:
394 * spanned_pages = zone_end_pfn - zone_start_pfn;
395 *
396 * present_pages is physical pages existing within the zone, which
397 * is calculated as:
398 * present_pages = spanned_pages - absent_pages(pages in holes);
399 *
400 * managed_pages is present pages managed by the buddy system, which
401 * is calculated as (reserved_pages includes pages allocated by the
402 * bootmem allocator):
403 * managed_pages = present_pages - reserved_pages;
404 *
405 * So present_pages may be used by memory hotplug or memory power
406 * management logic to figure out unmanaged pages by checking
407 * (present_pages - managed_pages). And managed_pages should be used
408 * by page allocator and vm scanner to calculate all kinds of watermarks
409 * and thresholds.
410 *
411 * Locking rules:
412 *
413 * zone_start_pfn and spanned_pages are protected by span_seqlock.
414 * It is a seqlock because it has to be read outside of zone->lock,
415 * and it is done in the main allocator path. But, it is written
416 * quite infrequently.
417 *
418 * The span_seq lock is declared along with zone->lock because it is
419 * frequently read in proximity to zone->lock. It's good to
420 * give them a chance of being in the same cacheline.
421 *
422 * Write access to present_pages at runtime should be protected by
423 * mem_hotplug_begin/end(). Any reader who can't tolerant drift of
424 * present_pages should get_online_mems() to get a stable value.
425 *
426 * Read access to managed_pages should be safe because it's unsigned
427 * long. Write access to zone->managed_pages and totalram_pages are
428 * protected by managed_page_count_lock at runtime. Idealy only
429 * adjust_managed_page_count() should be used instead of directly
430 * touching zone->managed_pages and totalram_pages.
431 */
432 unsigned long managed_pages;
433 unsigned long spanned_pages;
434 unsigned long present_pages;
435
436 const char *name;
437
438 #ifdef CONFIG_MEMORY_ISOLATION
439 /*
440 * Number of isolated pageblock. It is used to solve incorrect
441 * freepage counting problem due to racy retrieving migratetype
442 * of pageblock. Protected by zone->lock.
443 */
444 unsigned long nr_isolate_pageblock;
445 #endif
446
447 #ifdef CONFIG_MEMORY_HOTPLUG
448 /* see spanned/present_pages for more description */
449 seqlock_t span_seqlock;
450 #endif
451
452 /*
453 * wait_table -- the array holding the hash table
454 * wait_table_hash_nr_entries -- the size of the hash table array
455 * wait_table_bits -- wait_table_size == (1 << wait_table_bits)
456 *
457 * The purpose of all these is to keep track of the people
458 * waiting for a page to become available and make them
459 * runnable again when possible. The trouble is that this
460 * consumes a lot of space, especially when so few things
461 * wait on pages at a given time. So instead of using
462 * per-page waitqueues, we use a waitqueue hash table.
463 *
464 * The bucket discipline is to sleep on the same queue when
465 * colliding and wake all in that wait queue when removing.
466 * When something wakes, it must check to be sure its page is
467 * truly available, a la thundering herd. The cost of a
468 * collision is great, but given the expected load of the
469 * table, they should be so rare as to be outweighed by the
470 * benefits from the saved space.
471 *
472 * __wait_on_page_locked() and unlock_page() in mm/filemap.c, are the
473 * primary users of these fields, and in mm/page_alloc.c
474 * free_area_init_core() performs the initialization of them.
475 */
476 wait_queue_head_t *wait_table;
477 unsigned long wait_table_hash_nr_entries;
478 unsigned long wait_table_bits;
479
480 ZONE_PADDING(_pad1_)
481 /* free areas of different sizes */
482 struct free_area free_area[MAX_ORDER];
483
484 /* zone flags, see below */
485 unsigned long flags;
486
487 /* Write-intensive fields used from the page allocator */
488 spinlock_t lock;
489
490 ZONE_PADDING(_pad2_)
491
492 /* Write-intensive fields used by page reclaim */
493
494 /* Fields commonly accessed by the page reclaim scanner */
495 spinlock_t lru_lock;
496 struct lruvec lruvec;
497
498 /* Evictions & activations on the inactive file list */
499 atomic_long_t inactive_age;
500
501 /*
502 * When free pages are below this point, additional steps are taken
503 * when reading the number of free pages to avoid per-cpu counter
504 * drift allowing watermarks to be breached
505 */
506 unsigned long percpu_drift_mark;
507
508 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
509 /* pfn where compaction free scanner should start */
510 unsigned long compact_cached_free_pfn;
511 /* pfn where async and sync compaction migration scanner should start */
512 unsigned long compact_cached_migrate_pfn[2];
513 #endif
514
515 #ifdef CONFIG_COMPACTION
516 /*
517 * On compaction failure, 1<<compact_defer_shift compactions
518 * are skipped before trying again. The number attempted since
519 * last failure is tracked with compact_considered.
520 */
521 unsigned int compact_considered;
522 unsigned int compact_defer_shift;
523 int compact_order_failed;
524 #endif
525
526 #if defined CONFIG_COMPACTION || defined CONFIG_CMA
527 /* Set to true when the PG_migrate_skip bits should be cleared */
528 bool compact_blockskip_flush;
529 #endif
530
531 ZONE_PADDING(_pad3_)
532 /* Zone statistics */
533 atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
534 } ____cacheline_internodealigned_in_smp;
535
536 enum zone_flags {
537 ZONE_RECLAIM_LOCKED, /* prevents concurrent reclaim */
538 ZONE_OOM_LOCKED, /* zone is in OOM killer zonelist */
539 ZONE_CONGESTED, /* zone has many dirty pages backed by
540 * a congested BDI
541 */
542 ZONE_DIRTY, /* reclaim scanning has recently found
543 * many dirty file pages at the tail
544 * of the LRU.
545 */
546 ZONE_WRITEBACK, /* reclaim scanning has recently found
547 * many pages under writeback
548 */
549 ZONE_FAIR_DEPLETED, /* fair zone policy batch depleted */
550 };
551
zone_end_pfn(const struct zone * zone)552 static inline unsigned long zone_end_pfn(const struct zone *zone)
553 {
554 return zone->zone_start_pfn + zone->spanned_pages;
555 }
556
zone_spans_pfn(const struct zone * zone,unsigned long pfn)557 static inline bool zone_spans_pfn(const struct zone *zone, unsigned long pfn)
558 {
559 return zone->zone_start_pfn <= pfn && pfn < zone_end_pfn(zone);
560 }
561
zone_is_initialized(struct zone * zone)562 static inline bool zone_is_initialized(struct zone *zone)
563 {
564 return !!zone->wait_table;
565 }
566
zone_is_empty(struct zone * zone)567 static inline bool zone_is_empty(struct zone *zone)
568 {
569 return zone->spanned_pages == 0;
570 }
571
572 /*
573 * The "priority" of VM scanning is how much of the queues we will scan in one
574 * go. A value of 12 for DEF_PRIORITY implies that we will scan 1/4096th of the
575 * queues ("queue_length >> 12") during an aging round.
576 */
577 #define DEF_PRIORITY 12
578
579 /* Maximum number of zones on a zonelist */
580 #define MAX_ZONES_PER_ZONELIST (MAX_NUMNODES * MAX_NR_ZONES)
581
582 #ifdef CONFIG_NUMA
583
584 /*
585 * The NUMA zonelists are doubled because we need zonelists that restrict the
586 * allocations to a single node for __GFP_THISNODE.
587 *
588 * [0] : Zonelist with fallback
589 * [1] : No fallback (__GFP_THISNODE)
590 */
591 #define MAX_ZONELISTS 2
592 #else
593 #define MAX_ZONELISTS 1
594 #endif
595
596 /*
597 * This struct contains information about a zone in a zonelist. It is stored
598 * here to avoid dereferences into large structures and lookups of tables
599 */
600 struct zoneref {
601 struct zone *zone; /* Pointer to actual zone */
602 int zone_idx; /* zone_idx(zoneref->zone) */
603 };
604
605 /*
606 * One allocation request operates on a zonelist. A zonelist
607 * is a list of zones, the first one is the 'goal' of the
608 * allocation, the other zones are fallback zones, in decreasing
609 * priority.
610 *
611 * To speed the reading of the zonelist, the zonerefs contain the zone index
612 * of the entry being read. Helper functions to access information given
613 * a struct zoneref are
614 *
615 * zonelist_zone() - Return the struct zone * for an entry in _zonerefs
616 * zonelist_zone_idx() - Return the index of the zone for an entry
617 * zonelist_node_idx() - Return the index of the node for an entry
618 */
619 struct zonelist {
620 struct zoneref _zonerefs[MAX_ZONES_PER_ZONELIST + 1];
621 };
622
623 #ifndef CONFIG_DISCONTIGMEM
624 /* The array of struct pages - for discontigmem use pgdat->lmem_map */
625 extern struct page *mem_map;
626 #endif
627
628 /*
629 * The pg_data_t structure is used in machines with CONFIG_DISCONTIGMEM
630 * (mostly NUMA machines?) to denote a higher-level memory zone than the
631 * zone denotes.
632 *
633 * On NUMA machines, each NUMA node would have a pg_data_t to describe
634 * it's memory layout.
635 *
636 * Memory statistics and page replacement data structures are maintained on a
637 * per-zone basis.
638 */
639 struct bootmem_data;
640 typedef struct pglist_data {
641 struct zone node_zones[MAX_NR_ZONES];
642 struct zonelist node_zonelists[MAX_ZONELISTS];
643 int nr_zones;
644 #ifdef CONFIG_FLAT_NODE_MEM_MAP /* means !SPARSEMEM */
645 struct page *node_mem_map;
646 #ifdef CONFIG_PAGE_EXTENSION
647 struct page_ext *node_page_ext;
648 #endif
649 #endif
650 #ifndef CONFIG_NO_BOOTMEM
651 struct bootmem_data *bdata;
652 #endif
653 #ifdef CONFIG_MEMORY_HOTPLUG
654 /*
655 * Must be held any time you expect node_start_pfn, node_present_pages
656 * or node_spanned_pages stay constant. Holding this will also
657 * guarantee that any pfn_valid() stays that way.
658 *
659 * pgdat_resize_lock() and pgdat_resize_unlock() are provided to
660 * manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG.
661 *
662 * Nests above zone->lock and zone->span_seqlock
663 */
664 spinlock_t node_size_lock;
665 #endif
666 unsigned long node_start_pfn;
667 unsigned long node_present_pages; /* total number of physical pages */
668 unsigned long node_spanned_pages; /* total size of physical page
669 range, including holes */
670 int node_id;
671 wait_queue_head_t kswapd_wait;
672 wait_queue_head_t pfmemalloc_wait;
673 struct task_struct *kswapd; /* Protected by
674 mem_hotplug_begin/end() */
675 int kswapd_max_order;
676 enum zone_type classzone_idx;
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 /* Number of non-deferred pages */
695 unsigned long static_init_pgcnt;
696 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
697 } pg_data_t;
698
699 #define node_present_pages(nid) (NODE_DATA(nid)->node_present_pages)
700 #define node_spanned_pages(nid) (NODE_DATA(nid)->node_spanned_pages)
701 #ifdef CONFIG_FLAT_NODE_MEM_MAP
702 #define pgdat_page_nr(pgdat, pagenr) ((pgdat)->node_mem_map + (pagenr))
703 #else
704 #define pgdat_page_nr(pgdat, pagenr) pfn_to_page((pgdat)->node_start_pfn + (pagenr))
705 #endif
706 #define nid_page_nr(nid, pagenr) pgdat_page_nr(NODE_DATA(nid),(pagenr))
707
708 #define node_start_pfn(nid) (NODE_DATA(nid)->node_start_pfn)
709 #define node_end_pfn(nid) pgdat_end_pfn(NODE_DATA(nid))
710
pgdat_end_pfn(pg_data_t * pgdat)711 static inline unsigned long pgdat_end_pfn(pg_data_t *pgdat)
712 {
713 return pgdat->node_start_pfn + pgdat->node_spanned_pages;
714 }
715
pgdat_is_empty(pg_data_t * pgdat)716 static inline bool pgdat_is_empty(pg_data_t *pgdat)
717 {
718 return !pgdat->node_start_pfn && !pgdat->node_spanned_pages;
719 }
720
zone_id(const struct zone * zone)721 static inline int zone_id(const struct zone *zone)
722 {
723 struct pglist_data *pgdat = zone->zone_pgdat;
724
725 return zone - pgdat->node_zones;
726 }
727
728 #ifdef CONFIG_ZONE_DEVICE
is_dev_zone(const struct zone * zone)729 static inline bool is_dev_zone(const struct zone *zone)
730 {
731 return zone_id(zone) == ZONE_DEVICE;
732 }
733 #else
is_dev_zone(const struct zone * zone)734 static inline bool is_dev_zone(const struct zone *zone)
735 {
736 return false;
737 }
738 #endif
739
740 #include <linux/memory_hotplug.h>
741
742 extern struct mutex zonelists_mutex;
743 void build_all_zonelists(pg_data_t *pgdat, struct zone *zone);
744 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx);
745 bool zone_watermark_ok(struct zone *z, unsigned int order,
746 unsigned long mark, int classzone_idx, int alloc_flags);
747 bool zone_watermark_ok_safe(struct zone *z, unsigned int order,
748 unsigned long mark, int classzone_idx);
749 enum memmap_context {
750 MEMMAP_EARLY,
751 MEMMAP_HOTPLUG,
752 };
753 extern int init_currently_empty_zone(struct zone *zone, unsigned long start_pfn,
754 unsigned long size);
755
756 extern void lruvec_init(struct lruvec *lruvec);
757
lruvec_zone(struct lruvec * lruvec)758 static inline struct zone *lruvec_zone(struct lruvec *lruvec)
759 {
760 #ifdef CONFIG_MEMCG
761 return lruvec->zone;
762 #else
763 return container_of(lruvec, struct zone, lruvec);
764 #endif
765 }
766
767 #ifdef CONFIG_HAVE_MEMORY_PRESENT
768 void memory_present(int nid, unsigned long start, unsigned long end);
769 #else
memory_present(int nid,unsigned long start,unsigned long end)770 static inline void memory_present(int nid, unsigned long start, unsigned long end) {}
771 #endif
772
773 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
774 int local_memory_node(int node_id);
775 #else
local_memory_node(int node_id)776 static inline int local_memory_node(int node_id) { return node_id; };
777 #endif
778
779 #ifdef CONFIG_NEED_NODE_MEMMAP_SIZE
780 unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
781 #endif
782
783 /*
784 * zone_idx() returns 0 for the ZONE_DMA zone, 1 for the ZONE_NORMAL zone, etc.
785 */
786 #define zone_idx(zone) ((zone) - (zone)->zone_pgdat->node_zones)
787
populated_zone(struct zone * zone)788 static inline int populated_zone(struct zone *zone)
789 {
790 return (!!zone->present_pages);
791 }
792
793 extern int movable_zone;
794
795 #ifdef CONFIG_HIGHMEM
zone_movable_is_highmem(void)796 static inline int zone_movable_is_highmem(void)
797 {
798 #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
799 return movable_zone == ZONE_HIGHMEM;
800 #else
801 return (ZONE_MOVABLE - 1) == ZONE_HIGHMEM;
802 #endif
803 }
804 #endif
805
is_highmem_idx(enum zone_type idx)806 static inline int is_highmem_idx(enum zone_type idx)
807 {
808 #ifdef CONFIG_HIGHMEM
809 return (idx == ZONE_HIGHMEM ||
810 (idx == ZONE_MOVABLE && zone_movable_is_highmem()));
811 #else
812 return 0;
813 #endif
814 }
815
816 /**
817 * is_highmem - helper function to quickly check if a struct zone is a
818 * highmem zone or not. This is an attempt to keep references
819 * to ZONE_{DMA/NORMAL/HIGHMEM/etc} in general code to a minimum.
820 * @zone - pointer to struct zone variable
821 */
is_highmem(struct zone * zone)822 static inline int is_highmem(struct zone *zone)
823 {
824 #ifdef CONFIG_HIGHMEM
825 int zone_off = (char *)zone - (char *)zone->zone_pgdat->node_zones;
826 return zone_off == ZONE_HIGHMEM * sizeof(*zone) ||
827 (zone_off == ZONE_MOVABLE * sizeof(*zone) &&
828 zone_movable_is_highmem());
829 #else
830 return 0;
831 #endif
832 }
833
834 /* These two functions are used to setup the per zone pages min values */
835 struct ctl_table;
836 int min_free_kbytes_sysctl_handler(struct ctl_table *, int,
837 void __user *, size_t *, loff_t *);
838 extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1];
839 int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int,
840 void __user *, size_t *, loff_t *);
841 int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *, int,
842 void __user *, size_t *, loff_t *);
843 int sysctl_min_unmapped_ratio_sysctl_handler(struct ctl_table *, int,
844 void __user *, size_t *, loff_t *);
845 int sysctl_min_slab_ratio_sysctl_handler(struct ctl_table *, int,
846 void __user *, size_t *, loff_t *);
847
848 extern int numa_zonelist_order_handler(struct ctl_table *, int,
849 void __user *, size_t *, loff_t *);
850 extern char numa_zonelist_order[];
851 #define NUMA_ZONELIST_ORDER_LEN 16 /* string buffer size */
852
853 #ifndef CONFIG_NEED_MULTIPLE_NODES
854
855 extern struct pglist_data contig_page_data;
856 #define NODE_DATA(nid) (&contig_page_data)
857 #define NODE_MEM_MAP(nid) mem_map
858
859 #else /* CONFIG_NEED_MULTIPLE_NODES */
860
861 #include <asm/mmzone.h>
862
863 #endif /* !CONFIG_NEED_MULTIPLE_NODES */
864
865 extern struct pglist_data *first_online_pgdat(void);
866 extern struct pglist_data *next_online_pgdat(struct pglist_data *pgdat);
867 extern struct zone *next_zone(struct zone *zone);
868
869 /**
870 * for_each_online_pgdat - helper macro to iterate over all online nodes
871 * @pgdat - pointer to a pg_data_t variable
872 */
873 #define for_each_online_pgdat(pgdat) \
874 for (pgdat = first_online_pgdat(); \
875 pgdat; \
876 pgdat = next_online_pgdat(pgdat))
877 /**
878 * for_each_zone - helper macro to iterate over all memory zones
879 * @zone - pointer to struct zone variable
880 *
881 * The user only needs to declare the zone variable, for_each_zone
882 * fills it in.
883 */
884 #define for_each_zone(zone) \
885 for (zone = (first_online_pgdat())->node_zones; \
886 zone; \
887 zone = next_zone(zone))
888
889 #define for_each_populated_zone(zone) \
890 for (zone = (first_online_pgdat())->node_zones; \
891 zone; \
892 zone = next_zone(zone)) \
893 if (!populated_zone(zone)) \
894 ; /* do nothing */ \
895 else
896
zonelist_zone(struct zoneref * zoneref)897 static inline struct zone *zonelist_zone(struct zoneref *zoneref)
898 {
899 return zoneref->zone;
900 }
901
zonelist_zone_idx(struct zoneref * zoneref)902 static inline int zonelist_zone_idx(struct zoneref *zoneref)
903 {
904 return zoneref->zone_idx;
905 }
906
zonelist_node_idx(struct zoneref * zoneref)907 static inline int zonelist_node_idx(struct zoneref *zoneref)
908 {
909 #ifdef CONFIG_NUMA
910 /* zone_to_nid not available in this context */
911 return zoneref->zone->node;
912 #else
913 return 0;
914 #endif /* CONFIG_NUMA */
915 }
916
917 /**
918 * 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
919 * @z - The cursor used as a starting point for the search
920 * @highest_zoneidx - The zone index of the highest zone to return
921 * @nodes - An optional nodemask to filter the zonelist with
922 *
923 * This function returns the next zone at or below a given zone index that is
924 * within the allowed nodemask using a cursor as the starting point for the
925 * search. The zoneref returned is a cursor that represents the current zone
926 * being examined. It should be advanced by one before calling
927 * next_zones_zonelist again.
928 */
929 struct zoneref *next_zones_zonelist(struct zoneref *z,
930 enum zone_type highest_zoneidx,
931 nodemask_t *nodes);
932
933 /**
934 * first_zones_zonelist - Returns the first zone at or below highest_zoneidx within the allowed nodemask in a zonelist
935 * @zonelist - The zonelist to search for a suitable zone
936 * @highest_zoneidx - The zone index of the highest zone to return
937 * @nodes - An optional nodemask to filter the zonelist with
938 * @zone - The first suitable zone found is returned via this parameter
939 *
940 * This function returns the first zone at or below a given zone index that is
941 * within the allowed nodemask. The zoneref returned is a cursor that can be
942 * used to iterate the zonelist with next_zones_zonelist by advancing it by
943 * one before calling.
944 */
first_zones_zonelist(struct zonelist * zonelist,enum zone_type highest_zoneidx,nodemask_t * nodes,struct zone ** zone)945 static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,
946 enum zone_type highest_zoneidx,
947 nodemask_t *nodes,
948 struct zone **zone)
949 {
950 struct zoneref *z = next_zones_zonelist(zonelist->_zonerefs,
951 highest_zoneidx, nodes);
952 *zone = zonelist_zone(z);
953 return z;
954 }
955
956 /**
957 * 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
958 * @zone - The current zone in the iterator
959 * @z - The current pointer within zonelist->zones being iterated
960 * @zlist - The zonelist being iterated
961 * @highidx - The zone index of the highest zone to return
962 * @nodemask - Nodemask allowed by the allocator
963 *
964 * This iterator iterates though all zones at or below a given zone index and
965 * within a given nodemask
966 */
967 #define for_each_zone_zonelist_nodemask(zone, z, zlist, highidx, nodemask) \
968 for (z = first_zones_zonelist(zlist, highidx, nodemask, &zone); \
969 zone; \
970 z = next_zones_zonelist(++z, highidx, nodemask), \
971 zone = zonelist_zone(z)) \
972
973 /**
974 * for_each_zone_zonelist - helper macro to iterate over valid zones in a zonelist at or below a given zone index
975 * @zone - The current zone in the iterator
976 * @z - The current pointer within zonelist->zones being iterated
977 * @zlist - The zonelist being iterated
978 * @highidx - The zone index of the highest zone to return
979 *
980 * This iterator iterates though all zones at or below a given zone index.
981 */
982 #define for_each_zone_zonelist(zone, z, zlist, highidx) \
983 for_each_zone_zonelist_nodemask(zone, z, zlist, highidx, NULL)
984
985 #ifdef CONFIG_SPARSEMEM
986 #include <asm/sparsemem.h>
987 #endif
988
989 #if !defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) && \
990 !defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP)
early_pfn_to_nid(unsigned long pfn)991 static inline unsigned long early_pfn_to_nid(unsigned long pfn)
992 {
993 return 0;
994 }
995 #endif
996
997 #ifdef CONFIG_FLATMEM
998 #define pfn_to_nid(pfn) (0)
999 #endif
1000
1001 #ifdef CONFIG_SPARSEMEM
1002
1003 /*
1004 * SECTION_SHIFT #bits space required to store a section #
1005 *
1006 * PA_SECTION_SHIFT physical address to/from section number
1007 * PFN_SECTION_SHIFT pfn to/from section number
1008 */
1009 #define PA_SECTION_SHIFT (SECTION_SIZE_BITS)
1010 #define PFN_SECTION_SHIFT (SECTION_SIZE_BITS - PAGE_SHIFT)
1011
1012 #define NR_MEM_SECTIONS (1UL << SECTIONS_SHIFT)
1013
1014 #define PAGES_PER_SECTION (1UL << PFN_SECTION_SHIFT)
1015 #define PAGE_SECTION_MASK (~(PAGES_PER_SECTION-1))
1016
1017 #define SECTION_BLOCKFLAGS_BITS \
1018 ((1UL << (PFN_SECTION_SHIFT - pageblock_order)) * NR_PAGEBLOCK_BITS)
1019
1020 #if (MAX_ORDER - 1 + PAGE_SHIFT) > SECTION_SIZE_BITS
1021 #error Allocator MAX_ORDER exceeds SECTION_SIZE
1022 #endif
1023
1024 #define pfn_to_section_nr(pfn) ((pfn) >> PFN_SECTION_SHIFT)
1025 #define section_nr_to_pfn(sec) ((sec) << PFN_SECTION_SHIFT)
1026
1027 #define SECTION_ALIGN_UP(pfn) (((pfn) + PAGES_PER_SECTION - 1) & PAGE_SECTION_MASK)
1028 #define SECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SECTION_MASK)
1029
1030 struct page;
1031 struct page_ext;
1032 struct mem_section {
1033 /*
1034 * This is, logically, a pointer to an array of struct
1035 * pages. However, it is stored with some other magic.
1036 * (see sparse.c::sparse_init_one_section())
1037 *
1038 * Additionally during early boot we encode node id of
1039 * the location of the section here to guide allocation.
1040 * (see sparse.c::memory_present())
1041 *
1042 * Making it a UL at least makes someone do a cast
1043 * before using it wrong.
1044 */
1045 unsigned long section_mem_map;
1046
1047 /* See declaration of similar field in struct zone */
1048 unsigned long *pageblock_flags;
1049 #ifdef CONFIG_PAGE_EXTENSION
1050 /*
1051 * If !SPARSEMEM, pgdat doesn't have page_ext pointer. We use
1052 * section. (see page_ext.h about this.)
1053 */
1054 struct page_ext *page_ext;
1055 unsigned long pad;
1056 #endif
1057 /*
1058 * WARNING: mem_section must be a power-of-2 in size for the
1059 * calculation and use of SECTION_ROOT_MASK to make sense.
1060 */
1061 };
1062
1063 #ifdef CONFIG_SPARSEMEM_EXTREME
1064 #define SECTIONS_PER_ROOT (PAGE_SIZE / sizeof (struct mem_section))
1065 #else
1066 #define SECTIONS_PER_ROOT 1
1067 #endif
1068
1069 #define SECTION_NR_TO_ROOT(sec) ((sec) / SECTIONS_PER_ROOT)
1070 #define NR_SECTION_ROOTS DIV_ROUND_UP(NR_MEM_SECTIONS, SECTIONS_PER_ROOT)
1071 #define SECTION_ROOT_MASK (SECTIONS_PER_ROOT - 1)
1072
1073 #ifdef CONFIG_SPARSEMEM_EXTREME
1074 extern struct mem_section *mem_section[NR_SECTION_ROOTS];
1075 #else
1076 extern struct mem_section mem_section[NR_SECTION_ROOTS][SECTIONS_PER_ROOT];
1077 #endif
1078
__nr_to_section(unsigned long nr)1079 static inline struct mem_section *__nr_to_section(unsigned long nr)
1080 {
1081 if (!mem_section[SECTION_NR_TO_ROOT(nr)])
1082 return NULL;
1083 return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
1084 }
1085 extern int __section_nr(struct mem_section* ms);
1086 extern unsigned long usemap_size(void);
1087
1088 /*
1089 * We use the lower bits of the mem_map pointer to store
1090 * a little bit of information. There should be at least
1091 * 3 bits here due to 32-bit alignment.
1092 */
1093 #define SECTION_MARKED_PRESENT (1UL<<0)
1094 #define SECTION_HAS_MEM_MAP (1UL<<1)
1095 #define SECTION_MAP_LAST_BIT (1UL<<2)
1096 #define SECTION_MAP_MASK (~(SECTION_MAP_LAST_BIT-1))
1097 #define SECTION_NID_SHIFT 2
1098
__section_mem_map_addr(struct mem_section * section)1099 static inline struct page *__section_mem_map_addr(struct mem_section *section)
1100 {
1101 unsigned long map = section->section_mem_map;
1102 map &= SECTION_MAP_MASK;
1103 return (struct page *)map;
1104 }
1105
present_section(struct mem_section * section)1106 static inline int present_section(struct mem_section *section)
1107 {
1108 return (section && (section->section_mem_map & SECTION_MARKED_PRESENT));
1109 }
1110
present_section_nr(unsigned long nr)1111 static inline int present_section_nr(unsigned long nr)
1112 {
1113 return present_section(__nr_to_section(nr));
1114 }
1115
valid_section(struct mem_section * section)1116 static inline int valid_section(struct mem_section *section)
1117 {
1118 return (section && (section->section_mem_map & SECTION_HAS_MEM_MAP));
1119 }
1120
valid_section_nr(unsigned long nr)1121 static inline int valid_section_nr(unsigned long nr)
1122 {
1123 return valid_section(__nr_to_section(nr));
1124 }
1125
__pfn_to_section(unsigned long pfn)1126 static inline struct mem_section *__pfn_to_section(unsigned long pfn)
1127 {
1128 return __nr_to_section(pfn_to_section_nr(pfn));
1129 }
1130
1131 #ifndef CONFIG_HAVE_ARCH_PFN_VALID
pfn_valid(unsigned long pfn)1132 static inline int pfn_valid(unsigned long pfn)
1133 {
1134 if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
1135 return 0;
1136 return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
1137 }
1138 #endif
1139
pfn_present(unsigned long pfn)1140 static inline int pfn_present(unsigned long pfn)
1141 {
1142 if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
1143 return 0;
1144 return present_section(__nr_to_section(pfn_to_section_nr(pfn)));
1145 }
1146
1147 /*
1148 * These are _only_ used during initialisation, therefore they
1149 * can use __initdata ... They could have names to indicate
1150 * this restriction.
1151 */
1152 #ifdef CONFIG_NUMA
1153 #define pfn_to_nid(pfn) \
1154 ({ \
1155 unsigned long __pfn_to_nid_pfn = (pfn); \
1156 page_to_nid(pfn_to_page(__pfn_to_nid_pfn)); \
1157 })
1158 #else
1159 #define pfn_to_nid(pfn) (0)
1160 #endif
1161
1162 #define early_pfn_valid(pfn) pfn_valid(pfn)
1163 void sparse_init(void);
1164 #else
1165 #define sparse_init() do {} while (0)
1166 #define sparse_index_init(_sec, _nid) do {} while (0)
1167 #endif /* CONFIG_SPARSEMEM */
1168
1169 /*
1170 * During memory init memblocks map pfns to nids. The search is expensive and
1171 * this caches recent lookups. The implementation of __early_pfn_to_nid
1172 * may treat start/end as pfns or sections.
1173 */
1174 struct mminit_pfnnid_cache {
1175 unsigned long last_start;
1176 unsigned long last_end;
1177 int last_nid;
1178 };
1179
1180 #ifndef early_pfn_valid
1181 #define early_pfn_valid(pfn) (1)
1182 #endif
1183
1184 void memory_present(int nid, unsigned long start, unsigned long end);
1185 unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);
1186
1187 /*
1188 * If it is possible to have holes within a MAX_ORDER_NR_PAGES, then we
1189 * need to check pfn validility within that MAX_ORDER_NR_PAGES block.
1190 * pfn_valid_within() should be used in this case; we optimise this away
1191 * when we have no holes within a MAX_ORDER_NR_PAGES block.
1192 */
1193 #ifdef CONFIG_HOLES_IN_ZONE
1194 #define pfn_valid_within(pfn) pfn_valid(pfn)
1195 #else
1196 #define pfn_valid_within(pfn) (1)
1197 #endif
1198
1199 #ifdef CONFIG_ARCH_HAS_HOLES_MEMORYMODEL
1200 /*
1201 * pfn_valid() is meant to be able to tell if a given PFN has valid memmap
1202 * associated with it or not. In FLATMEM, it is expected that holes always
1203 * have valid memmap as long as there is valid PFNs either side of the hole.
1204 * In SPARSEMEM, it is assumed that a valid section has a memmap for the
1205 * entire section.
1206 *
1207 * However, an ARM, and maybe other embedded architectures in the future
1208 * free memmap backing holes to save memory on the assumption the memmap is
1209 * never used. The page_zone linkages are then broken even though pfn_valid()
1210 * returns true. A walker of the full memmap must then do this additional
1211 * check to ensure the memmap they are looking at is sane by making sure
1212 * the zone and PFN linkages are still valid. This is expensive, but walkers
1213 * of the full memmap are extremely rare.
1214 */
1215 int memmap_valid_within(unsigned long pfn,
1216 struct page *page, struct zone *zone);
1217 #else
memmap_valid_within(unsigned long pfn,struct page * page,struct zone * zone)1218 static inline int memmap_valid_within(unsigned long pfn,
1219 struct page *page, struct zone *zone)
1220 {
1221 return 1;
1222 }
1223 #endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */
1224
1225 #endif /* !__GENERATING_BOUNDS.H */
1226 #endif /* !__ASSEMBLY__ */
1227 #endif /* _LINUX_MMZONE_H */
1228