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TOMOYO Linux Cross Reference
Linux/mm/percpu.c

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  1 /*
  2  * mm/percpu.c - percpu memory allocator
  3  *
  4  * Copyright (C) 2009           SUSE Linux Products GmbH
  5  * Copyright (C) 2009           Tejun Heo <tj@kernel.org>
  6  *
  7  * Copyright (C) 2017           Facebook Inc.
  8  * Copyright (C) 2017           Dennis Zhou <dennisszhou@gmail.com>
  9  *
 10  * This file is released under the GPLv2 license.
 11  *
 12  * The percpu allocator handles both static and dynamic areas.  Percpu
 13  * areas are allocated in chunks which are divided into units.  There is
 14  * a 1-to-1 mapping for units to possible cpus.  These units are grouped
 15  * based on NUMA properties of the machine.
 16  *
 17  *  c0                           c1                         c2
 18  *  -------------------          -------------------        ------------
 19  * | u0 | u1 | u2 | u3 |        | u0 | u1 | u2 | u3 |      | u0 | u1 | u
 20  *  -------------------  ......  -------------------  ....  ------------
 21  *
 22  * Allocation is done by offsets into a unit's address space.  Ie., an
 23  * area of 512 bytes at 6k in c1 occupies 512 bytes at 6k in c1:u0,
 24  * c1:u1, c1:u2, etc.  On NUMA machines, the mapping may be non-linear
 25  * and even sparse.  Access is handled by configuring percpu base
 26  * registers according to the cpu to unit mappings and offsetting the
 27  * base address using pcpu_unit_size.
 28  *
 29  * There is special consideration for the first chunk which must handle
 30  * the static percpu variables in the kernel image as allocation services
 31  * are not online yet.  In short, the first chunk is structured like so:
 32  *
 33  *                  <Static | [Reserved] | Dynamic>
 34  *
 35  * The static data is copied from the original section managed by the
 36  * linker.  The reserved section, if non-zero, primarily manages static
 37  * percpu variables from kernel modules.  Finally, the dynamic section
 38  * takes care of normal allocations.
 39  *
 40  * The allocator organizes chunks into lists according to free size and
 41  * tries to allocate from the fullest chunk first.  Each chunk is managed
 42  * by a bitmap with metadata blocks.  The allocation map is updated on
 43  * every allocation and free to reflect the current state while the boundary
 44  * map is only updated on allocation.  Each metadata block contains
 45  * information to help mitigate the need to iterate over large portions
 46  * of the bitmap.  The reverse mapping from page to chunk is stored in
 47  * the page's index.  Lastly, units are lazily backed and grow in unison.
 48  *
 49  * There is a unique conversion that goes on here between bytes and bits.
 50  * Each bit represents a fragment of size PCPU_MIN_ALLOC_SIZE.  The chunk
 51  * tracks the number of pages it is responsible for in nr_pages.  Helper
 52  * functions are used to convert from between the bytes, bits, and blocks.
 53  * All hints are managed in bits unless explicitly stated.
 54  *
 55  * To use this allocator, arch code should do the following:
 56  *
 57  * - define __addr_to_pcpu_ptr() and __pcpu_ptr_to_addr() to translate
 58  *   regular address to percpu pointer and back if they need to be
 59  *   different from the default
 60  *
 61  * - use pcpu_setup_first_chunk() during percpu area initialization to
 62  *   setup the first chunk containing the kernel static percpu area
 63  */
 64 
 65 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 66 
 67 #include <linux/bitmap.h>
 68 #include <linux/memblock.h>
 69 #include <linux/err.h>
 70 #include <linux/lcm.h>
 71 #include <linux/list.h>
 72 #include <linux/log2.h>
 73 #include <linux/mm.h>
 74 #include <linux/module.h>
 75 #include <linux/mutex.h>
 76 #include <linux/percpu.h>
 77 #include <linux/pfn.h>
 78 #include <linux/slab.h>
 79 #include <linux/spinlock.h>
 80 #include <linux/vmalloc.h>
 81 #include <linux/workqueue.h>
 82 #include <linux/kmemleak.h>
 83 #include <linux/sched.h>
 84 
 85 #include <asm/cacheflush.h>
 86 #include <asm/sections.h>
 87 #include <asm/tlbflush.h>
 88 #include <asm/io.h>
 89 
 90 #define CREATE_TRACE_POINTS
 91 #include <trace/events/percpu.h>
 92 
 93 #include "percpu-internal.h"
 94 
 95 /* the slots are sorted by free bytes left, 1-31 bytes share the same slot */
 96 #define PCPU_SLOT_BASE_SHIFT            5
 97 
 98 #define PCPU_EMPTY_POP_PAGES_LOW        2
 99 #define PCPU_EMPTY_POP_PAGES_HIGH       4
100 
101 #ifdef CONFIG_SMP
102 /* default addr <-> pcpu_ptr mapping, override in asm/percpu.h if necessary */
103 #ifndef __addr_to_pcpu_ptr
104 #define __addr_to_pcpu_ptr(addr)                                        \
105         (void __percpu *)((unsigned long)(addr) -                       \
106                           (unsigned long)pcpu_base_addr +               \
107                           (unsigned long)__per_cpu_start)
108 #endif
109 #ifndef __pcpu_ptr_to_addr
110 #define __pcpu_ptr_to_addr(ptr)                                         \
111         (void __force *)((unsigned long)(ptr) +                         \
112                          (unsigned long)pcpu_base_addr -                \
113                          (unsigned long)__per_cpu_start)
114 #endif
115 #else   /* CONFIG_SMP */
116 /* on UP, it's always identity mapped */
117 #define __addr_to_pcpu_ptr(addr)        (void __percpu *)(addr)
118 #define __pcpu_ptr_to_addr(ptr)         (void __force *)(ptr)
119 #endif  /* CONFIG_SMP */
120 
121 static int pcpu_unit_pages __ro_after_init;
122 static int pcpu_unit_size __ro_after_init;
123 static int pcpu_nr_units __ro_after_init;
124 static int pcpu_atom_size __ro_after_init;
125 int pcpu_nr_slots __ro_after_init;
126 static size_t pcpu_chunk_struct_size __ro_after_init;
127 
128 /* cpus with the lowest and highest unit addresses */
129 static unsigned int pcpu_low_unit_cpu __ro_after_init;
130 static unsigned int pcpu_high_unit_cpu __ro_after_init;
131 
132 /* the address of the first chunk which starts with the kernel static area */
133 void *pcpu_base_addr __ro_after_init;
134 EXPORT_SYMBOL_GPL(pcpu_base_addr);
135 
136 static const int *pcpu_unit_map __ro_after_init;                /* cpu -> unit */
137 const unsigned long *pcpu_unit_offsets __ro_after_init; /* cpu -> unit offset */
138 
139 /* group information, used for vm allocation */
140 static int pcpu_nr_groups __ro_after_init;
141 static const unsigned long *pcpu_group_offsets __ro_after_init;
142 static const size_t *pcpu_group_sizes __ro_after_init;
143 
144 /*
145  * The first chunk which always exists.  Note that unlike other
146  * chunks, this one can be allocated and mapped in several different
147  * ways and thus often doesn't live in the vmalloc area.
148  */
149 struct pcpu_chunk *pcpu_first_chunk __ro_after_init;
150 
151 /*
152  * Optional reserved chunk.  This chunk reserves part of the first
153  * chunk and serves it for reserved allocations.  When the reserved
154  * region doesn't exist, the following variable is NULL.
155  */
156 struct pcpu_chunk *pcpu_reserved_chunk __ro_after_init;
157 
158 DEFINE_SPINLOCK(pcpu_lock);     /* all internal data structures */
159 static DEFINE_MUTEX(pcpu_alloc_mutex);  /* chunk create/destroy, [de]pop, map ext */
160 
161 struct list_head *pcpu_slot __ro_after_init; /* chunk list slots */
162 
163 /* chunks which need their map areas extended, protected by pcpu_lock */
164 static LIST_HEAD(pcpu_map_extend_chunks);
165 
166 /*
167  * The number of empty populated pages, protected by pcpu_lock.  The
168  * reserved chunk doesn't contribute to the count.
169  */
170 int pcpu_nr_empty_pop_pages;
171 
172 /*
173  * The number of populated pages in use by the allocator, protected by
174  * pcpu_lock.  This number is kept per a unit per chunk (i.e. when a page gets
175  * allocated/deallocated, it is allocated/deallocated in all units of a chunk
176  * and increments/decrements this count by 1).
177  */
178 static unsigned long pcpu_nr_populated;
179 
180 /*
181  * Balance work is used to populate or destroy chunks asynchronously.  We
182  * try to keep the number of populated free pages between
183  * PCPU_EMPTY_POP_PAGES_LOW and HIGH for atomic allocations and at most one
184  * empty chunk.
185  */
186 static void pcpu_balance_workfn(struct work_struct *work);
187 static DECLARE_WORK(pcpu_balance_work, pcpu_balance_workfn);
188 static bool pcpu_async_enabled __read_mostly;
189 static bool pcpu_atomic_alloc_failed;
190 
191 static void pcpu_schedule_balance_work(void)
192 {
193         if (pcpu_async_enabled)
194                 schedule_work(&pcpu_balance_work);
195 }
196 
197 /**
198  * pcpu_addr_in_chunk - check if the address is served from this chunk
199  * @chunk: chunk of interest
200  * @addr: percpu address
201  *
202  * RETURNS:
203  * True if the address is served from this chunk.
204  */
205 static bool pcpu_addr_in_chunk(struct pcpu_chunk *chunk, void *addr)
206 {
207         void *start_addr, *end_addr;
208 
209         if (!chunk)
210                 return false;
211 
212         start_addr = chunk->base_addr + chunk->start_offset;
213         end_addr = chunk->base_addr + chunk->nr_pages * PAGE_SIZE -
214                    chunk->end_offset;
215 
216         return addr >= start_addr && addr < end_addr;
217 }
218 
219 static int __pcpu_size_to_slot(int size)
220 {
221         int highbit = fls(size);        /* size is in bytes */
222         return max(highbit - PCPU_SLOT_BASE_SHIFT + 2, 1);
223 }
224 
225 static int pcpu_size_to_slot(int size)
226 {
227         if (size == pcpu_unit_size)
228                 return pcpu_nr_slots - 1;
229         return __pcpu_size_to_slot(size);
230 }
231 
232 static int pcpu_chunk_slot(const struct pcpu_chunk *chunk)
233 {
234         if (chunk->free_bytes < PCPU_MIN_ALLOC_SIZE || chunk->contig_bits == 0)
235                 return 0;
236 
237         return pcpu_size_to_slot(chunk->free_bytes);
238 }
239 
240 /* set the pointer to a chunk in a page struct */
241 static void pcpu_set_page_chunk(struct page *page, struct pcpu_chunk *pcpu)
242 {
243         page->index = (unsigned long)pcpu;
244 }
245 
246 /* obtain pointer to a chunk from a page struct */
247 static struct pcpu_chunk *pcpu_get_page_chunk(struct page *page)
248 {
249         return (struct pcpu_chunk *)page->index;
250 }
251 
252 static int __maybe_unused pcpu_page_idx(unsigned int cpu, int page_idx)
253 {
254         return pcpu_unit_map[cpu] * pcpu_unit_pages + page_idx;
255 }
256 
257 static unsigned long pcpu_unit_page_offset(unsigned int cpu, int page_idx)
258 {
259         return pcpu_unit_offsets[cpu] + (page_idx << PAGE_SHIFT);
260 }
261 
262 static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
263                                      unsigned int cpu, int page_idx)
264 {
265         return (unsigned long)chunk->base_addr +
266                pcpu_unit_page_offset(cpu, page_idx);
267 }
268 
269 static void pcpu_next_unpop(unsigned long *bitmap, int *rs, int *re, int end)
270 {
271         *rs = find_next_zero_bit(bitmap, end, *rs);
272         *re = find_next_bit(bitmap, end, *rs + 1);
273 }
274 
275 static void pcpu_next_pop(unsigned long *bitmap, int *rs, int *re, int end)
276 {
277         *rs = find_next_bit(bitmap, end, *rs);
278         *re = find_next_zero_bit(bitmap, end, *rs + 1);
279 }
280 
281 /*
282  * Bitmap region iterators.  Iterates over the bitmap between
283  * [@start, @end) in @chunk.  @rs and @re should be integer variables
284  * and will be set to start and end index of the current free region.
285  */
286 #define pcpu_for_each_unpop_region(bitmap, rs, re, start, end)               \
287         for ((rs) = (start), pcpu_next_unpop((bitmap), &(rs), &(re), (end)); \
288              (rs) < (re);                                                    \
289              (rs) = (re) + 1, pcpu_next_unpop((bitmap), &(rs), &(re), (end)))
290 
291 #define pcpu_for_each_pop_region(bitmap, rs, re, start, end)                 \
292         for ((rs) = (start), pcpu_next_pop((bitmap), &(rs), &(re), (end));   \
293              (rs) < (re);                                                    \
294              (rs) = (re) + 1, pcpu_next_pop((bitmap), &(rs), &(re), (end)))
295 
296 /*
297  * The following are helper functions to help access bitmaps and convert
298  * between bitmap offsets to address offsets.
299  */
300 static unsigned long *pcpu_index_alloc_map(struct pcpu_chunk *chunk, int index)
301 {
302         return chunk->alloc_map +
303                (index * PCPU_BITMAP_BLOCK_BITS / BITS_PER_LONG);
304 }
305 
306 static unsigned long pcpu_off_to_block_index(int off)
307 {
308         return off / PCPU_BITMAP_BLOCK_BITS;
309 }
310 
311 static unsigned long pcpu_off_to_block_off(int off)
312 {
313         return off & (PCPU_BITMAP_BLOCK_BITS - 1);
314 }
315 
316 static unsigned long pcpu_block_off_to_off(int index, int off)
317 {
318         return index * PCPU_BITMAP_BLOCK_BITS + off;
319 }
320 
321 /**
322  * pcpu_next_md_free_region - finds the next hint free area
323  * @chunk: chunk of interest
324  * @bit_off: chunk offset
325  * @bits: size of free area
326  *
327  * Helper function for pcpu_for_each_md_free_region.  It checks
328  * block->contig_hint and performs aggregation across blocks to find the
329  * next hint.  It modifies bit_off and bits in-place to be consumed in the
330  * loop.
331  */
332 static void pcpu_next_md_free_region(struct pcpu_chunk *chunk, int *bit_off,
333                                      int *bits)
334 {
335         int i = pcpu_off_to_block_index(*bit_off);
336         int block_off = pcpu_off_to_block_off(*bit_off);
337         struct pcpu_block_md *block;
338 
339         *bits = 0;
340         for (block = chunk->md_blocks + i; i < pcpu_chunk_nr_blocks(chunk);
341              block++, i++) {
342                 /* handles contig area across blocks */
343                 if (*bits) {
344                         *bits += block->left_free;
345                         if (block->left_free == PCPU_BITMAP_BLOCK_BITS)
346                                 continue;
347                         return;
348                 }
349 
350                 /*
351                  * This checks three things.  First is there a contig_hint to
352                  * check.  Second, have we checked this hint before by
353                  * comparing the block_off.  Third, is this the same as the
354                  * right contig hint.  In the last case, it spills over into
355                  * the next block and should be handled by the contig area
356                  * across blocks code.
357                  */
358                 *bits = block->contig_hint;
359                 if (*bits && block->contig_hint_start >= block_off &&
360                     *bits + block->contig_hint_start < PCPU_BITMAP_BLOCK_BITS) {
361                         *bit_off = pcpu_block_off_to_off(i,
362                                         block->contig_hint_start);
363                         return;
364                 }
365                 /* reset to satisfy the second predicate above */
366                 block_off = 0;
367 
368                 *bits = block->right_free;
369                 *bit_off = (i + 1) * PCPU_BITMAP_BLOCK_BITS - block->right_free;
370         }
371 }
372 
373 /**
374  * pcpu_next_fit_region - finds fit areas for a given allocation request
375  * @chunk: chunk of interest
376  * @alloc_bits: size of allocation
377  * @align: alignment of area (max PAGE_SIZE)
378  * @bit_off: chunk offset
379  * @bits: size of free area
380  *
381  * Finds the next free region that is viable for use with a given size and
382  * alignment.  This only returns if there is a valid area to be used for this
383  * allocation.  block->first_free is returned if the allocation request fits
384  * within the block to see if the request can be fulfilled prior to the contig
385  * hint.
386  */
387 static void pcpu_next_fit_region(struct pcpu_chunk *chunk, int alloc_bits,
388                                  int align, int *bit_off, int *bits)
389 {
390         int i = pcpu_off_to_block_index(*bit_off);
391         int block_off = pcpu_off_to_block_off(*bit_off);
392         struct pcpu_block_md *block;
393 
394         *bits = 0;
395         for (block = chunk->md_blocks + i; i < pcpu_chunk_nr_blocks(chunk);
396              block++, i++) {
397                 /* handles contig area across blocks */
398                 if (*bits) {
399                         *bits += block->left_free;
400                         if (*bits >= alloc_bits)
401                                 return;
402                         if (block->left_free == PCPU_BITMAP_BLOCK_BITS)
403                                 continue;
404                 }
405 
406                 /* check block->contig_hint */
407                 *bits = ALIGN(block->contig_hint_start, align) -
408                         block->contig_hint_start;
409                 /*
410                  * This uses the block offset to determine if this has been
411                  * checked in the prior iteration.
412                  */
413                 if (block->contig_hint &&
414                     block->contig_hint_start >= block_off &&
415                     block->contig_hint >= *bits + alloc_bits) {
416                         *bits += alloc_bits + block->contig_hint_start -
417                                  block->first_free;
418                         *bit_off = pcpu_block_off_to_off(i, block->first_free);
419                         return;
420                 }
421                 /* reset to satisfy the second predicate above */
422                 block_off = 0;
423 
424                 *bit_off = ALIGN(PCPU_BITMAP_BLOCK_BITS - block->right_free,
425                                  align);
426                 *bits = PCPU_BITMAP_BLOCK_BITS - *bit_off;
427                 *bit_off = pcpu_block_off_to_off(i, *bit_off);
428                 if (*bits >= alloc_bits)
429                         return;
430         }
431 
432         /* no valid offsets were found - fail condition */
433         *bit_off = pcpu_chunk_map_bits(chunk);
434 }
435 
436 /*
437  * Metadata free area iterators.  These perform aggregation of free areas
438  * based on the metadata blocks and return the offset @bit_off and size in
439  * bits of the free area @bits.  pcpu_for_each_fit_region only returns when
440  * a fit is found for the allocation request.
441  */
442 #define pcpu_for_each_md_free_region(chunk, bit_off, bits)              \
443         for (pcpu_next_md_free_region((chunk), &(bit_off), &(bits));    \
444              (bit_off) < pcpu_chunk_map_bits((chunk));                  \
445              (bit_off) += (bits) + 1,                                   \
446              pcpu_next_md_free_region((chunk), &(bit_off), &(bits)))
447 
448 #define pcpu_for_each_fit_region(chunk, alloc_bits, align, bit_off, bits)     \
449         for (pcpu_next_fit_region((chunk), (alloc_bits), (align), &(bit_off), \
450                                   &(bits));                                   \
451              (bit_off) < pcpu_chunk_map_bits((chunk));                        \
452              (bit_off) += (bits),                                             \
453              pcpu_next_fit_region((chunk), (alloc_bits), (align), &(bit_off), \
454                                   &(bits)))
455 
456 /**
457  * pcpu_mem_zalloc - allocate memory
458  * @size: bytes to allocate
459  * @gfp: allocation flags
460  *
461  * Allocate @size bytes.  If @size is smaller than PAGE_SIZE,
462  * kzalloc() is used; otherwise, the equivalent of vzalloc() is used.
463  * This is to facilitate passing through whitelisted flags.  The
464  * returned memory is always zeroed.
465  *
466  * RETURNS:
467  * Pointer to the allocated area on success, NULL on failure.
468  */
469 static void *pcpu_mem_zalloc(size_t size, gfp_t gfp)
470 {
471         if (WARN_ON_ONCE(!slab_is_available()))
472                 return NULL;
473 
474         if (size <= PAGE_SIZE)
475                 return kzalloc(size, gfp);
476         else
477                 return __vmalloc(size, gfp | __GFP_ZERO, PAGE_KERNEL);
478 }
479 
480 /**
481  * pcpu_mem_free - free memory
482  * @ptr: memory to free
483  *
484  * Free @ptr.  @ptr should have been allocated using pcpu_mem_zalloc().
485  */
486 static void pcpu_mem_free(void *ptr)
487 {
488         kvfree(ptr);
489 }
490 
491 /**
492  * pcpu_chunk_relocate - put chunk in the appropriate chunk slot
493  * @chunk: chunk of interest
494  * @oslot: the previous slot it was on
495  *
496  * This function is called after an allocation or free changed @chunk.
497  * New slot according to the changed state is determined and @chunk is
498  * moved to the slot.  Note that the reserved chunk is never put on
499  * chunk slots.
500  *
501  * CONTEXT:
502  * pcpu_lock.
503  */
504 static void pcpu_chunk_relocate(struct pcpu_chunk *chunk, int oslot)
505 {
506         int nslot = pcpu_chunk_slot(chunk);
507 
508         if (chunk != pcpu_reserved_chunk && oslot != nslot) {
509                 if (oslot < nslot)
510                         list_move(&chunk->list, &pcpu_slot[nslot]);
511                 else
512                         list_move_tail(&chunk->list, &pcpu_slot[nslot]);
513         }
514 }
515 
516 /**
517  * pcpu_cnt_pop_pages- counts populated backing pages in range
518  * @chunk: chunk of interest
519  * @bit_off: start offset
520  * @bits: size of area to check
521  *
522  * Calculates the number of populated pages in the region
523  * [page_start, page_end).  This keeps track of how many empty populated
524  * pages are available and decide if async work should be scheduled.
525  *
526  * RETURNS:
527  * The nr of populated pages.
528  */
529 static inline int pcpu_cnt_pop_pages(struct pcpu_chunk *chunk, int bit_off,
530                                      int bits)
531 {
532         int page_start = PFN_UP(bit_off * PCPU_MIN_ALLOC_SIZE);
533         int page_end = PFN_DOWN((bit_off + bits) * PCPU_MIN_ALLOC_SIZE);
534 
535         if (page_start >= page_end)
536                 return 0;
537 
538         /*
539          * bitmap_weight counts the number of bits set in a bitmap up to
540          * the specified number of bits.  This is counting the populated
541          * pages up to page_end and then subtracting the populated pages
542          * up to page_start to count the populated pages in
543          * [page_start, page_end).
544          */
545         return bitmap_weight(chunk->populated, page_end) -
546                bitmap_weight(chunk->populated, page_start);
547 }
548 
549 /**
550  * pcpu_chunk_update - updates the chunk metadata given a free area
551  * @chunk: chunk of interest
552  * @bit_off: chunk offset
553  * @bits: size of free area
554  *
555  * This updates the chunk's contig hint and starting offset given a free area.
556  * Choose the best starting offset if the contig hint is equal.
557  */
558 static void pcpu_chunk_update(struct pcpu_chunk *chunk, int bit_off, int bits)
559 {
560         if (bits > chunk->contig_bits) {
561                 chunk->contig_bits_start = bit_off;
562                 chunk->contig_bits = bits;
563         } else if (bits == chunk->contig_bits && chunk->contig_bits_start &&
564                    (!bit_off ||
565                     __ffs(bit_off) > __ffs(chunk->contig_bits_start))) {
566                 /* use the start with the best alignment */
567                 chunk->contig_bits_start = bit_off;
568         }
569 }
570 
571 /**
572  * pcpu_chunk_refresh_hint - updates metadata about a chunk
573  * @chunk: chunk of interest
574  *
575  * Iterates over the metadata blocks to find the largest contig area.
576  * It also counts the populated pages and uses the delta to update the
577  * global count.
578  *
579  * Updates:
580  *      chunk->contig_bits
581  *      chunk->contig_bits_start
582  *      nr_empty_pop_pages (chunk and global)
583  */
584 static void pcpu_chunk_refresh_hint(struct pcpu_chunk *chunk)
585 {
586         int bit_off, bits, nr_empty_pop_pages;
587 
588         /* clear metadata */
589         chunk->contig_bits = 0;
590 
591         bit_off = chunk->first_bit;
592         bits = nr_empty_pop_pages = 0;
593         pcpu_for_each_md_free_region(chunk, bit_off, bits) {
594                 pcpu_chunk_update(chunk, bit_off, bits);
595 
596                 nr_empty_pop_pages += pcpu_cnt_pop_pages(chunk, bit_off, bits);
597         }
598 
599         /*
600          * Keep track of nr_empty_pop_pages.
601          *
602          * The chunk maintains the previous number of free pages it held,
603          * so the delta is used to update the global counter.  The reserved
604          * chunk is not part of the free page count as they are populated
605          * at init and are special to serving reserved allocations.
606          */
607         if (chunk != pcpu_reserved_chunk)
608                 pcpu_nr_empty_pop_pages +=
609                         (nr_empty_pop_pages - chunk->nr_empty_pop_pages);
610 
611         chunk->nr_empty_pop_pages = nr_empty_pop_pages;
612 }
613 
614 /**
615  * pcpu_block_update - updates a block given a free area
616  * @block: block of interest
617  * @start: start offset in block
618  * @end: end offset in block
619  *
620  * Updates a block given a known free area.  The region [start, end) is
621  * expected to be the entirety of the free area within a block.  Chooses
622  * the best starting offset if the contig hints are equal.
623  */
624 static void pcpu_block_update(struct pcpu_block_md *block, int start, int end)
625 {
626         int contig = end - start;
627 
628         block->first_free = min(block->first_free, start);
629         if (start == 0)
630                 block->left_free = contig;
631 
632         if (end == PCPU_BITMAP_BLOCK_BITS)
633                 block->right_free = contig;
634 
635         if (contig > block->contig_hint) {
636                 block->contig_hint_start = start;
637                 block->contig_hint = contig;
638         } else if (block->contig_hint_start && contig == block->contig_hint &&
639                    (!start || __ffs(start) > __ffs(block->contig_hint_start))) {
640                 /* use the start with the best alignment */
641                 block->contig_hint_start = start;
642         }
643 }
644 
645 /**
646  * pcpu_block_refresh_hint
647  * @chunk: chunk of interest
648  * @index: index of the metadata block
649  *
650  * Scans over the block beginning at first_free and updates the block
651  * metadata accordingly.
652  */
653 static void pcpu_block_refresh_hint(struct pcpu_chunk *chunk, int index)
654 {
655         struct pcpu_block_md *block = chunk->md_blocks + index;
656         unsigned long *alloc_map = pcpu_index_alloc_map(chunk, index);
657         int rs, re;     /* region start, region end */
658 
659         /* clear hints */
660         block->contig_hint = 0;
661         block->left_free = block->right_free = 0;
662 
663         /* iterate over free areas and update the contig hints */
664         pcpu_for_each_unpop_region(alloc_map, rs, re, block->first_free,
665                                    PCPU_BITMAP_BLOCK_BITS) {
666                 pcpu_block_update(block, rs, re);
667         }
668 }
669 
670 /**
671  * pcpu_block_update_hint_alloc - update hint on allocation path
672  * @chunk: chunk of interest
673  * @bit_off: chunk offset
674  * @bits: size of request
675  *
676  * Updates metadata for the allocation path.  The metadata only has to be
677  * refreshed by a full scan iff the chunk's contig hint is broken.  Block level
678  * scans are required if the block's contig hint is broken.
679  */
680 static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off,
681                                          int bits)
682 {
683         struct pcpu_block_md *s_block, *e_block, *block;
684         int s_index, e_index;   /* block indexes of the freed allocation */
685         int s_off, e_off;       /* block offsets of the freed allocation */
686 
687         /*
688          * Calculate per block offsets.
689          * The calculation uses an inclusive range, but the resulting offsets
690          * are [start, end).  e_index always points to the last block in the
691          * range.
692          */
693         s_index = pcpu_off_to_block_index(bit_off);
694         e_index = pcpu_off_to_block_index(bit_off + bits - 1);
695         s_off = pcpu_off_to_block_off(bit_off);
696         e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;
697 
698         s_block = chunk->md_blocks + s_index;
699         e_block = chunk->md_blocks + e_index;
700 
701         /*
702          * Update s_block.
703          * block->first_free must be updated if the allocation takes its place.
704          * If the allocation breaks the contig_hint, a scan is required to
705          * restore this hint.
706          */
707         if (s_off == s_block->first_free)
708                 s_block->first_free = find_next_zero_bit(
709                                         pcpu_index_alloc_map(chunk, s_index),
710                                         PCPU_BITMAP_BLOCK_BITS,
711                                         s_off + bits);
712 
713         if (s_off >= s_block->contig_hint_start &&
714             s_off < s_block->contig_hint_start + s_block->contig_hint) {
715                 /* block contig hint is broken - scan to fix it */
716                 pcpu_block_refresh_hint(chunk, s_index);
717         } else {
718                 /* update left and right contig manually */
719                 s_block->left_free = min(s_block->left_free, s_off);
720                 if (s_index == e_index)
721                         s_block->right_free = min_t(int, s_block->right_free,
722                                         PCPU_BITMAP_BLOCK_BITS - e_off);
723                 else
724                         s_block->right_free = 0;
725         }
726 
727         /*
728          * Update e_block.
729          */
730         if (s_index != e_index) {
731                 /*
732                  * When the allocation is across blocks, the end is along
733                  * the left part of the e_block.
734                  */
735                 e_block->first_free = find_next_zero_bit(
736                                 pcpu_index_alloc_map(chunk, e_index),
737                                 PCPU_BITMAP_BLOCK_BITS, e_off);
738 
739                 if (e_off == PCPU_BITMAP_BLOCK_BITS) {
740                         /* reset the block */
741                         e_block++;
742                 } else {
743                         if (e_off > e_block->contig_hint_start) {
744                                 /* contig hint is broken - scan to fix it */
745                                 pcpu_block_refresh_hint(chunk, e_index);
746                         } else {
747                                 e_block->left_free = 0;
748                                 e_block->right_free =
749                                         min_t(int, e_block->right_free,
750                                               PCPU_BITMAP_BLOCK_BITS - e_off);
751                         }
752                 }
753 
754                 /* update in-between md_blocks */
755                 for (block = s_block + 1; block < e_block; block++) {
756                         block->contig_hint = 0;
757                         block->left_free = 0;
758                         block->right_free = 0;
759                 }
760         }
761 
762         /*
763          * The only time a full chunk scan is required is if the chunk
764          * contig hint is broken.  Otherwise, it means a smaller space
765          * was used and therefore the chunk contig hint is still correct.
766          */
767         if (bit_off >= chunk->contig_bits_start  &&
768             bit_off < chunk->contig_bits_start + chunk->contig_bits)
769                 pcpu_chunk_refresh_hint(chunk);
770 }
771 
772 /**
773  * pcpu_block_update_hint_free - updates the block hints on the free path
774  * @chunk: chunk of interest
775  * @bit_off: chunk offset
776  * @bits: size of request
777  *
778  * Updates metadata for the allocation path.  This avoids a blind block
779  * refresh by making use of the block contig hints.  If this fails, it scans
780  * forward and backward to determine the extent of the free area.  This is
781  * capped at the boundary of blocks.
782  *
783  * A chunk update is triggered if a page becomes free, a block becomes free,
784  * or the free spans across blocks.  This tradeoff is to minimize iterating
785  * over the block metadata to update chunk->contig_bits.  chunk->contig_bits
786  * may be off by up to a page, but it will never be more than the available
787  * space.  If the contig hint is contained in one block, it will be accurate.
788  */
789 static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off,
790                                         int bits)
791 {
792         struct pcpu_block_md *s_block, *e_block, *block;
793         int s_index, e_index;   /* block indexes of the freed allocation */
794         int s_off, e_off;       /* block offsets of the freed allocation */
795         int start, end;         /* start and end of the whole free area */
796 
797         /*
798          * Calculate per block offsets.
799          * The calculation uses an inclusive range, but the resulting offsets
800          * are [start, end).  e_index always points to the last block in the
801          * range.
802          */
803         s_index = pcpu_off_to_block_index(bit_off);
804         e_index = pcpu_off_to_block_index(bit_off + bits - 1);
805         s_off = pcpu_off_to_block_off(bit_off);
806         e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;
807 
808         s_block = chunk->md_blocks + s_index;
809         e_block = chunk->md_blocks + e_index;
810 
811         /*
812          * Check if the freed area aligns with the block->contig_hint.
813          * If it does, then the scan to find the beginning/end of the
814          * larger free area can be avoided.
815          *
816          * start and end refer to beginning and end of the free area
817          * within each their respective blocks.  This is not necessarily
818          * the entire free area as it may span blocks past the beginning
819          * or end of the block.
820          */
821         start = s_off;
822         if (s_off == s_block->contig_hint + s_block->contig_hint_start) {
823                 start = s_block->contig_hint_start;
824         } else {
825                 /*
826                  * Scan backwards to find the extent of the free area.
827                  * find_last_bit returns the starting bit, so if the start bit
828                  * is returned, that means there was no last bit and the
829                  * remainder of the chunk is free.
830                  */
831                 int l_bit = find_last_bit(pcpu_index_alloc_map(chunk, s_index),
832                                           start);
833                 start = (start == l_bit) ? 0 : l_bit + 1;
834         }
835 
836         end = e_off;
837         if (e_off == e_block->contig_hint_start)
838                 end = e_block->contig_hint_start + e_block->contig_hint;
839         else
840                 end = find_next_bit(pcpu_index_alloc_map(chunk, e_index),
841                                     PCPU_BITMAP_BLOCK_BITS, end);
842 
843         /* update s_block */
844         e_off = (s_index == e_index) ? end : PCPU_BITMAP_BLOCK_BITS;
845         pcpu_block_update(s_block, start, e_off);
846 
847         /* freeing in the same block */
848         if (s_index != e_index) {
849                 /* update e_block */
850                 pcpu_block_update(e_block, 0, end);
851 
852                 /* reset md_blocks in the middle */
853                 for (block = s_block + 1; block < e_block; block++) {
854                         block->first_free = 0;
855                         block->contig_hint_start = 0;
856                         block->contig_hint = PCPU_BITMAP_BLOCK_BITS;
857                         block->left_free = PCPU_BITMAP_BLOCK_BITS;
858                         block->right_free = PCPU_BITMAP_BLOCK_BITS;
859                 }
860         }
861 
862         /*
863          * Refresh chunk metadata when the free makes a page free, a block
864          * free, or spans across blocks.  The contig hint may be off by up to
865          * a page, but if the hint is contained in a block, it will be accurate
866          * with the else condition below.
867          */
868         if ((ALIGN_DOWN(end, min(PCPU_BITS_PER_PAGE, PCPU_BITMAP_BLOCK_BITS)) >
869              ALIGN(start, min(PCPU_BITS_PER_PAGE, PCPU_BITMAP_BLOCK_BITS))) ||
870             s_index != e_index)
871                 pcpu_chunk_refresh_hint(chunk);
872         else
873                 pcpu_chunk_update(chunk, pcpu_block_off_to_off(s_index, start),
874                                   s_block->contig_hint);
875 }
876 
877 /**
878  * pcpu_is_populated - determines if the region is populated
879  * @chunk: chunk of interest
880  * @bit_off: chunk offset
881  * @bits: size of area
882  * @next_off: return value for the next offset to start searching
883  *
884  * For atomic allocations, check if the backing pages are populated.
885  *
886  * RETURNS:
887  * Bool if the backing pages are populated.
888  * next_index is to skip over unpopulated blocks in pcpu_find_block_fit.
889  */
890 static bool pcpu_is_populated(struct pcpu_chunk *chunk, int bit_off, int bits,
891                               int *next_off)
892 {
893         int page_start, page_end, rs, re;
894 
895         page_start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE);
896         page_end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE);
897 
898         rs = page_start;
899         pcpu_next_unpop(chunk->populated, &rs, &re, page_end);
900         if (rs >= page_end)
901                 return true;
902 
903         *next_off = re * PAGE_SIZE / PCPU_MIN_ALLOC_SIZE;
904         return false;
905 }
906 
907 /**
908  * pcpu_find_block_fit - finds the block index to start searching
909  * @chunk: chunk of interest
910  * @alloc_bits: size of request in allocation units
911  * @align: alignment of area (max PAGE_SIZE bytes)
912  * @pop_only: use populated regions only
913  *
914  * Given a chunk and an allocation spec, find the offset to begin searching
915  * for a free region.  This iterates over the bitmap metadata blocks to
916  * find an offset that will be guaranteed to fit the requirements.  It is
917  * not quite first fit as if the allocation does not fit in the contig hint
918  * of a block or chunk, it is skipped.  This errs on the side of caution
919  * to prevent excess iteration.  Poor alignment can cause the allocator to
920  * skip over blocks and chunks that have valid free areas.
921  *
922  * RETURNS:
923  * The offset in the bitmap to begin searching.
924  * -1 if no offset is found.
925  */
926 static int pcpu_find_block_fit(struct pcpu_chunk *chunk, int alloc_bits,
927                                size_t align, bool pop_only)
928 {
929         int bit_off, bits, next_off;
930 
931         /*
932          * Check to see if the allocation can fit in the chunk's contig hint.
933          * This is an optimization to prevent scanning by assuming if it
934          * cannot fit in the global hint, there is memory pressure and creating
935          * a new chunk would happen soon.
936          */
937         bit_off = ALIGN(chunk->contig_bits_start, align) -
938                   chunk->contig_bits_start;
939         if (bit_off + alloc_bits > chunk->contig_bits)
940                 return -1;
941 
942         bit_off = chunk->first_bit;
943         bits = 0;
944         pcpu_for_each_fit_region(chunk, alloc_bits, align, bit_off, bits) {
945                 if (!pop_only || pcpu_is_populated(chunk, bit_off, bits,
946                                                    &next_off))
947                         break;
948 
949                 bit_off = next_off;
950                 bits = 0;
951         }
952 
953         if (bit_off == pcpu_chunk_map_bits(chunk))
954                 return -1;
955 
956         return bit_off;
957 }
958 
959 /**
960  * pcpu_alloc_area - allocates an area from a pcpu_chunk
961  * @chunk: chunk of interest
962  * @alloc_bits: size of request in allocation units
963  * @align: alignment of area (max PAGE_SIZE)
964  * @start: bit_off to start searching
965  *
966  * This function takes in a @start offset to begin searching to fit an
967  * allocation of @alloc_bits with alignment @align.  It needs to scan
968  * the allocation map because if it fits within the block's contig hint,
969  * @start will be block->first_free. This is an attempt to fill the
970  * allocation prior to breaking the contig hint.  The allocation and
971  * boundary maps are updated accordingly if it confirms a valid
972  * free area.
973  *
974  * RETURNS:
975  * Allocated addr offset in @chunk on success.
976  * -1 if no matching area is found.
977  */
978 static int pcpu_alloc_area(struct pcpu_chunk *chunk, int alloc_bits,
979                            size_t align, int start)
980 {
981         size_t align_mask = (align) ? (align - 1) : 0;
982         int bit_off, end, oslot;
983 
984         lockdep_assert_held(&pcpu_lock);
985 
986         oslot = pcpu_chunk_slot(chunk);
987 
988         /*
989          * Search to find a fit.
990          */
991         end = start + alloc_bits + PCPU_BITMAP_BLOCK_BITS;
992         bit_off = bitmap_find_next_zero_area(chunk->alloc_map, end, start,
993                                              alloc_bits, align_mask);
994         if (bit_off >= end)
995                 return -1;
996 
997         /* update alloc map */
998         bitmap_set(chunk->alloc_map, bit_off, alloc_bits);
999 
1000         /* update boundary map */
1001         set_bit(bit_off, chunk->bound_map);
1002         bitmap_clear(chunk->bound_map, bit_off + 1, alloc_bits - 1);
1003         set_bit(bit_off + alloc_bits, chunk->bound_map);
1004 
1005         chunk->free_bytes -= alloc_bits * PCPU_MIN_ALLOC_SIZE;
1006 
1007         /* update first free bit */
1008         if (bit_off == chunk->first_bit)
1009                 chunk->first_bit = find_next_zero_bit(
1010                                         chunk->alloc_map,
1011                                         pcpu_chunk_map_bits(chunk),
1012                                         bit_off + alloc_bits);
1013 
1014         pcpu_block_update_hint_alloc(chunk, bit_off, alloc_bits);
1015 
1016         pcpu_chunk_relocate(chunk, oslot);
1017 
1018         return bit_off * PCPU_MIN_ALLOC_SIZE;
1019 }
1020 
1021 /**
1022  * pcpu_free_area - frees the corresponding offset
1023  * @chunk: chunk of interest
1024  * @off: addr offset into chunk
1025  *
1026  * This function determines the size of an allocation to free using
1027  * the boundary bitmap and clears the allocation map.
1028  */
1029 static void pcpu_free_area(struct pcpu_chunk *chunk, int off)
1030 {
1031         int bit_off, bits, end, oslot;
1032 
1033         lockdep_assert_held(&pcpu_lock);
1034         pcpu_stats_area_dealloc(chunk);
1035 
1036         oslot = pcpu_chunk_slot(chunk);
1037 
1038         bit_off = off / PCPU_MIN_ALLOC_SIZE;
1039 
1040         /* find end index */
1041         end = find_next_bit(chunk->bound_map, pcpu_chunk_map_bits(chunk),
1042                             bit_off + 1);
1043         bits = end - bit_off;
1044         bitmap_clear(chunk->alloc_map, bit_off, bits);
1045 
1046         /* update metadata */
1047         chunk->free_bytes += bits * PCPU_MIN_ALLOC_SIZE;
1048 
1049         /* update first free bit */
1050         chunk->first_bit = min(chunk->first_bit, bit_off);
1051 
1052         pcpu_block_update_hint_free(chunk, bit_off, bits);
1053 
1054         pcpu_chunk_relocate(chunk, oslot);
1055 }
1056 
1057 static void pcpu_init_md_blocks(struct pcpu_chunk *chunk)
1058 {
1059         struct pcpu_block_md *md_block;
1060 
1061         for (md_block = chunk->md_blocks;
1062              md_block != chunk->md_blocks + pcpu_chunk_nr_blocks(chunk);
1063              md_block++) {
1064                 md_block->contig_hint = PCPU_BITMAP_BLOCK_BITS;
1065                 md_block->left_free = PCPU_BITMAP_BLOCK_BITS;
1066                 md_block->right_free = PCPU_BITMAP_BLOCK_BITS;
1067         }
1068 }
1069 
1070 /**
1071  * pcpu_alloc_first_chunk - creates chunks that serve the first chunk
1072  * @tmp_addr: the start of the region served
1073  * @map_size: size of the region served
1074  *
1075  * This is responsible for creating the chunks that serve the first chunk.  The
1076  * base_addr is page aligned down of @tmp_addr while the region end is page
1077  * aligned up.  Offsets are kept track of to determine the region served. All
1078  * this is done to appease the bitmap allocator in avoiding partial blocks.
1079  *
1080  * RETURNS:
1081  * Chunk serving the region at @tmp_addr of @map_size.
1082  */
1083 static struct pcpu_chunk * __init pcpu_alloc_first_chunk(unsigned long tmp_addr,
1084                                                          int map_size)
1085 {
1086         struct pcpu_chunk *chunk;
1087         unsigned long aligned_addr, lcm_align;
1088         int start_offset, offset_bits, region_size, region_bits;
1089         size_t alloc_size;
1090 
1091         /* region calculations */
1092         aligned_addr = tmp_addr & PAGE_MASK;
1093 
1094         start_offset = tmp_addr - aligned_addr;
1095 
1096         /*
1097          * Align the end of the region with the LCM of PAGE_SIZE and
1098          * PCPU_BITMAP_BLOCK_SIZE.  One of these constants is a multiple of
1099          * the other.
1100          */
1101         lcm_align = lcm(PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE);
1102         region_size = ALIGN(start_offset + map_size, lcm_align);
1103 
1104         /* allocate chunk */
1105         alloc_size = sizeof(struct pcpu_chunk) +
1106                 BITS_TO_LONGS(region_size >> PAGE_SHIFT);
1107         chunk = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
1108         if (!chunk)
1109                 panic("%s: Failed to allocate %zu bytes\n", __func__,
1110                       alloc_size);
1111 
1112         INIT_LIST_HEAD(&chunk->list);
1113 
1114         chunk->base_addr = (void *)aligned_addr;
1115         chunk->start_offset = start_offset;
1116         chunk->end_offset = region_size - chunk->start_offset - map_size;
1117 
1118         chunk->nr_pages = region_size >> PAGE_SHIFT;
1119         region_bits = pcpu_chunk_map_bits(chunk);
1120 
1121         alloc_size = BITS_TO_LONGS(region_bits) * sizeof(chunk->alloc_map[0]);
1122         chunk->alloc_map = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
1123         if (!chunk->alloc_map)
1124                 panic("%s: Failed to allocate %zu bytes\n", __func__,
1125                       alloc_size);
1126 
1127         alloc_size =
1128                 BITS_TO_LONGS(region_bits + 1) * sizeof(chunk->bound_map[0]);
1129         chunk->bound_map = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
1130         if (!chunk->bound_map)
1131                 panic("%s: Failed to allocate %zu bytes\n", __func__,
1132                       alloc_size);
1133 
1134         alloc_size = pcpu_chunk_nr_blocks(chunk) * sizeof(chunk->md_blocks[0]);
1135         chunk->md_blocks = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
1136         if (!chunk->md_blocks)
1137                 panic("%s: Failed to allocate %zu bytes\n", __func__,
1138                       alloc_size);
1139 
1140         pcpu_init_md_blocks(chunk);
1141 
1142         /* manage populated page bitmap */
1143         chunk->immutable = true;
1144         bitmap_fill(chunk->populated, chunk->nr_pages);
1145         chunk->nr_populated = chunk->nr_pages;
1146         chunk->nr_empty_pop_pages =
1147                 pcpu_cnt_pop_pages(chunk, start_offset / PCPU_MIN_ALLOC_SIZE,
1148                                    map_size / PCPU_MIN_ALLOC_SIZE);
1149 
1150         chunk->contig_bits = map_size / PCPU_MIN_ALLOC_SIZE;
1151         chunk->free_bytes = map_size;
1152 
1153         if (chunk->start_offset) {
1154                 /* hide the beginning of the bitmap */
1155                 offset_bits = chunk->start_offset / PCPU_MIN_ALLOC_SIZE;
1156                 bitmap_set(chunk->alloc_map, 0, offset_bits);
1157                 set_bit(0, chunk->bound_map);
1158                 set_bit(offset_bits, chunk->bound_map);
1159 
1160                 chunk->first_bit = offset_bits;
1161 
1162                 pcpu_block_update_hint_alloc(chunk, 0, offset_bits);
1163         }
1164 
1165         if (chunk->end_offset) {
1166                 /* hide the end of the bitmap */
1167                 offset_bits = chunk->end_offset / PCPU_MIN_ALLOC_SIZE;
1168                 bitmap_set(chunk->alloc_map,
1169                            pcpu_chunk_map_bits(chunk) - offset_bits,
1170                            offset_bits);
1171                 set_bit((start_offset + map_size) / PCPU_MIN_ALLOC_SIZE,
1172                         chunk->bound_map);
1173                 set_bit(region_bits, chunk->bound_map);
1174 
1175                 pcpu_block_update_hint_alloc(chunk, pcpu_chunk_map_bits(chunk)
1176                                              - offset_bits, offset_bits);
1177         }
1178 
1179         return chunk;
1180 }
1181 
1182 static struct pcpu_chunk *pcpu_alloc_chunk(gfp_t gfp)
1183 {
1184         struct pcpu_chunk *chunk;
1185         int region_bits;
1186 
1187         chunk = pcpu_mem_zalloc(pcpu_chunk_struct_size, gfp);
1188         if (!chunk)
1189                 return NULL;
1190 
1191         INIT_LIST_HEAD(&chunk->list);
1192         chunk->nr_pages = pcpu_unit_pages;
1193         region_bits = pcpu_chunk_map_bits(chunk);
1194 
1195         chunk->alloc_map = pcpu_mem_zalloc(BITS_TO_LONGS(region_bits) *
1196                                            sizeof(chunk->alloc_map[0]), gfp);
1197         if (!chunk->alloc_map)
1198                 goto alloc_map_fail;
1199 
1200         chunk->bound_map = pcpu_mem_zalloc(BITS_TO_LONGS(region_bits + 1) *
1201                                            sizeof(chunk->bound_map[0]), gfp);
1202         if (!chunk->bound_map)
1203                 goto bound_map_fail;
1204 
1205         chunk->md_blocks = pcpu_mem_zalloc(pcpu_chunk_nr_blocks(chunk) *
1206                                            sizeof(chunk->md_blocks[0]), gfp);
1207         if (!chunk->md_blocks)
1208                 goto md_blocks_fail;
1209 
1210         pcpu_init_md_blocks(chunk);
1211 
1212         /* init metadata */
1213         chunk->contig_bits = region_bits;
1214         chunk->free_bytes = chunk->nr_pages * PAGE_SIZE;
1215 
1216         return chunk;
1217 
1218 md_blocks_fail:
1219         pcpu_mem_free(chunk->bound_map);
1220 bound_map_fail:
1221         pcpu_mem_free(chunk->alloc_map);
1222 alloc_map_fail:
1223         pcpu_mem_free(chunk);
1224 
1225         return NULL;
1226 }
1227 
1228 static void pcpu_free_chunk(struct pcpu_chunk *chunk)
1229 {
1230         if (!chunk)
1231                 return;
1232         pcpu_mem_free(chunk->md_blocks);
1233         pcpu_mem_free(chunk->bound_map);
1234         pcpu_mem_free(chunk->alloc_map);
1235         pcpu_mem_free(chunk);
1236 }
1237 
1238 /**
1239  * pcpu_chunk_populated - post-population bookkeeping
1240  * @chunk: pcpu_chunk which got populated
1241  * @page_start: the start page
1242  * @page_end: the end page
1243  * @for_alloc: if this is to populate for allocation
1244  *
1245  * Pages in [@page_start,@page_end) have been populated to @chunk.  Update
1246  * the bookkeeping information accordingly.  Must be called after each
1247  * successful population.
1248  *
1249  * If this is @for_alloc, do not increment pcpu_nr_empty_pop_pages because it
1250  * is to serve an allocation in that area.
1251  */
1252 static void pcpu_chunk_populated(struct pcpu_chunk *chunk, int page_start,
1253                                  int page_end, bool for_alloc)
1254 {
1255         int nr = page_end - page_start;
1256 
1257         lockdep_assert_held(&pcpu_lock);
1258 
1259         bitmap_set(chunk->populated, page_start, nr);
1260         chunk->nr_populated += nr;
1261         pcpu_nr_populated += nr;
1262 
1263         if (!for_alloc) {
1264                 chunk->nr_empty_pop_pages += nr;
1265                 pcpu_nr_empty_pop_pages += nr;
1266         }
1267 }
1268 
1269 /**
1270  * pcpu_chunk_depopulated - post-depopulation bookkeeping
1271  * @chunk: pcpu_chunk which got depopulated
1272  * @page_start: the start page
1273  * @page_end: the end page
1274  *
1275  * Pages in [@page_start,@page_end) have been depopulated from @chunk.
1276  * Update the bookkeeping information accordingly.  Must be called after
1277  * each successful depopulation.
1278  */
1279 static void pcpu_chunk_depopulated(struct pcpu_chunk *chunk,
1280                                    int page_start, int page_end)
1281 {
1282         int nr = page_end - page_start;
1283 
1284         lockdep_assert_held(&pcpu_lock);
1285 
1286         bitmap_clear(chunk->populated, page_start, nr);
1287         chunk->nr_populated -= nr;
1288         chunk->nr_empty_pop_pages -= nr;
1289         pcpu_nr_empty_pop_pages -= nr;
1290         pcpu_nr_populated -= nr;
1291 }
1292 
1293 /*
1294  * Chunk management implementation.
1295  *
1296  * To allow different implementations, chunk alloc/free and
1297  * [de]population are implemented in a separate file which is pulled
1298  * into this file and compiled together.  The following functions
1299  * should be implemented.
1300  *
1301  * pcpu_populate_chunk          - populate the specified range of a chunk
1302  * pcpu_depopulate_chunk        - depopulate the specified range of a chunk
1303  * pcpu_create_chunk            - create a new chunk
1304  * pcpu_destroy_chunk           - destroy a chunk, always preceded by full depop
1305  * pcpu_addr_to_page            - translate address to physical address
1306  * pcpu_verify_alloc_info       - check alloc_info is acceptable during init
1307  */
1308 static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
1309                                int page_start, int page_end, gfp_t gfp);
1310 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
1311                                   int page_start, int page_end);
1312 static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp);
1313 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk);
1314 static struct page *pcpu_addr_to_page(void *addr);
1315 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai);
1316 
1317 #ifdef CONFIG_NEED_PER_CPU_KM
1318 #include "percpu-km.c"
1319 #else
1320 #include "percpu-vm.c"
1321 #endif
1322 
1323 /**
1324  * pcpu_chunk_addr_search - determine chunk containing specified address
1325  * @addr: address for which the chunk needs to be determined.
1326  *
1327  * This is an internal function that handles all but static allocations.
1328  * Static percpu address values should never be passed into the allocator.
1329  *
1330  * RETURNS:
1331  * The address of the found chunk.
1332  */
1333 static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
1334 {
1335         /* is it in the dynamic region (first chunk)? */
1336         if (pcpu_addr_in_chunk(pcpu_first_chunk, addr))
1337                 return pcpu_first_chunk;
1338 
1339         /* is it in the reserved region? */
1340         if (pcpu_addr_in_chunk(pcpu_reserved_chunk, addr))
1341                 return pcpu_reserved_chunk;
1342 
1343         /*
1344          * The address is relative to unit0 which might be unused and
1345          * thus unmapped.  Offset the address to the unit space of the
1346          * current processor before looking it up in the vmalloc
1347          * space.  Note that any possible cpu id can be used here, so
1348          * there's no need to worry about preemption or cpu hotplug.
1349          */
1350         addr += pcpu_unit_offsets[raw_smp_processor_id()];
1351         return pcpu_get_page_chunk(pcpu_addr_to_page(addr));
1352 }
1353 
1354 /**
1355  * pcpu_alloc - the percpu allocator
1356  * @size: size of area to allocate in bytes
1357  * @align: alignment of area (max PAGE_SIZE)
1358  * @reserved: allocate from the reserved chunk if available
1359  * @gfp: allocation flags
1360  *
1361  * Allocate percpu area of @size bytes aligned at @align.  If @gfp doesn't
1362  * contain %GFP_KERNEL, the allocation is atomic. If @gfp has __GFP_NOWARN
1363  * then no warning will be triggered on invalid or failed allocation
1364  * requests.
1365  *
1366  * RETURNS:
1367  * Percpu pointer to the allocated area on success, NULL on failure.
1368  */
1369 static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
1370                                  gfp_t gfp)
1371 {
1372         /* whitelisted flags that can be passed to the backing allocators */
1373         gfp_t pcpu_gfp = gfp & (GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
1374         bool is_atomic = (gfp & GFP_KERNEL) != GFP_KERNEL;
1375         bool do_warn = !(gfp & __GFP_NOWARN);
1376         static int warn_limit = 10;
1377         struct pcpu_chunk *chunk;
1378         const char *err;
1379         int slot, off, cpu, ret;
1380         unsigned long flags;
1381         void __percpu *ptr;
1382         size_t bits, bit_align;
1383 
1384         /*
1385          * There is now a minimum allocation size of PCPU_MIN_ALLOC_SIZE,
1386          * therefore alignment must be a minimum of that many bytes.
1387          * An allocation may have internal fragmentation from rounding up
1388          * of up to PCPU_MIN_ALLOC_SIZE - 1 bytes.
1389          */
1390         if (unlikely(align < PCPU_MIN_ALLOC_SIZE))
1391                 align = PCPU_MIN_ALLOC_SIZE;
1392 
1393         size = ALIGN(size, PCPU_MIN_ALLOC_SIZE);
1394         bits = size >> PCPU_MIN_ALLOC_SHIFT;
1395         bit_align = align >> PCPU_MIN_ALLOC_SHIFT;
1396 
1397         if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE ||
1398                      !is_power_of_2(align))) {
1399                 WARN(do_warn, "illegal size (%zu) or align (%zu) for percpu allocation\n",
1400                      size, align);
1401                 return NULL;
1402         }
1403 
1404         if (!is_atomic) {
1405                 /*
1406                  * pcpu_balance_workfn() allocates memory under this mutex,
1407                  * and it may wait for memory reclaim. Allow current task
1408                  * to become OOM victim, in case of memory pressure.
1409                  */
1410                 if (gfp & __GFP_NOFAIL)
1411                         mutex_lock(&pcpu_alloc_mutex);
1412                 else if (mutex_lock_killable(&pcpu_alloc_mutex))
1413                         return NULL;
1414         }
1415 
1416         spin_lock_irqsave(&pcpu_lock, flags);
1417 
1418         /* serve reserved allocations from the reserved chunk if available */
1419         if (reserved && pcpu_reserved_chunk) {
1420                 chunk = pcpu_reserved_chunk;
1421 
1422                 off = pcpu_find_block_fit(chunk, bits, bit_align, is_atomic);
1423                 if (off < 0) {
1424                         err = "alloc from reserved chunk failed";
1425                         goto fail_unlock;
1426                 }
1427 
1428                 off = pcpu_alloc_area(chunk, bits, bit_align, off);
1429                 if (off >= 0)
1430                         goto area_found;
1431 
1432                 err = "alloc from reserved chunk failed";
1433                 goto fail_unlock;
1434         }
1435 
1436 restart:
1437         /* search through normal chunks */
1438         for (slot = pcpu_size_to_slot(size); slot < pcpu_nr_slots; slot++) {
1439                 list_for_each_entry(chunk, &pcpu_slot[slot], list) {
1440                         off = pcpu_find_block_fit(chunk, bits, bit_align,
1441                                                   is_atomic);
1442                         if (off < 0)
1443                                 continue;
1444 
1445                         off = pcpu_alloc_area(chunk, bits, bit_align, off);
1446                         if (off >= 0)
1447                                 goto area_found;
1448 
1449                 }
1450         }
1451 
1452         spin_unlock_irqrestore(&pcpu_lock, flags);
1453 
1454         /*
1455          * No space left.  Create a new chunk.  We don't want multiple
1456          * tasks to create chunks simultaneously.  Serialize and create iff
1457          * there's still no empty chunk after grabbing the mutex.
1458          */
1459         if (is_atomic) {
1460                 err = "atomic alloc failed, no space left";
1461                 goto fail;
1462         }
1463 
1464         if (list_empty(&pcpu_slot[pcpu_nr_slots - 1])) {
1465                 chunk = pcpu_create_chunk(pcpu_gfp);
1466                 if (!chunk) {
1467                         err = "failed to allocate new chunk";
1468                         goto fail;
1469                 }
1470 
1471                 spin_lock_irqsave(&pcpu_lock, flags);
1472                 pcpu_chunk_relocate(chunk, -1);
1473         } else {
1474                 spin_lock_irqsave(&pcpu_lock, flags);
1475         }
1476 
1477         goto restart;
1478 
1479 area_found:
1480         pcpu_stats_area_alloc(chunk, size);
1481         spin_unlock_irqrestore(&pcpu_lock, flags);
1482 
1483         /* populate if not all pages are already there */
1484         if (!is_atomic) {
1485                 int page_start, page_end, rs, re;
1486 
1487                 page_start = PFN_DOWN(off);
1488                 page_end = PFN_UP(off + size);
1489 
1490                 pcpu_for_each_unpop_region(chunk->populated, rs, re,
1491                                            page_start, page_end) {
1492                         WARN_ON(chunk->immutable);
1493 
1494                         ret = pcpu_populate_chunk(chunk, rs, re, pcpu_gfp);
1495 
1496                         spin_lock_irqsave(&pcpu_lock, flags);
1497                         if (ret) {
1498                                 pcpu_free_area(chunk, off);
1499                                 err = "failed to populate";
1500                                 goto fail_unlock;
1501                         }
1502                         pcpu_chunk_populated(chunk, rs, re, true);
1503                         spin_unlock_irqrestore(&pcpu_lock, flags);
1504                 }
1505 
1506                 mutex_unlock(&pcpu_alloc_mutex);
1507         }
1508 
1509         if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
1510                 pcpu_schedule_balance_work();
1511 
1512         /* clear the areas and return address relative to base address */
1513         for_each_possible_cpu(cpu)
1514                 memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
1515 
1516         ptr = __addr_to_pcpu_ptr(chunk->base_addr + off);
1517         kmemleak_alloc_percpu(ptr, size, gfp);
1518 
1519         trace_percpu_alloc_percpu(reserved, is_atomic, size, align,
1520                         chunk->base_addr, off, ptr);
1521 
1522         return ptr;
1523 
1524 fail_unlock:
1525         spin_unlock_irqrestore(&pcpu_lock, flags);
1526 fail:
1527         trace_percpu_alloc_percpu_fail(reserved, is_atomic, size, align);
1528 
1529         if (!is_atomic && do_warn && warn_limit) {
1530                 pr_warn("allocation failed, size=%zu align=%zu atomic=%d, %s\n",
1531                         size, align, is_atomic, err);
1532                 dump_stack();
1533                 if (!--warn_limit)
1534                         pr_info("limit reached, disable warning\n");
1535         }
1536         if (is_atomic) {
1537                 /* see the flag handling in pcpu_blance_workfn() */
1538                 pcpu_atomic_alloc_failed = true;
1539                 pcpu_schedule_balance_work();
1540         } else {
1541                 mutex_unlock(&pcpu_alloc_mutex);
1542         }
1543         return NULL;
1544 }
1545 
1546 /**
1547  * __alloc_percpu_gfp - allocate dynamic percpu area
1548  * @size: size of area to allocate in bytes
1549  * @align: alignment of area (max PAGE_SIZE)
1550  * @gfp: allocation flags
1551  *
1552  * Allocate zero-filled percpu area of @size bytes aligned at @align.  If
1553  * @gfp doesn't contain %GFP_KERNEL, the allocation doesn't block and can
1554  * be called from any context but is a lot more likely to fail. If @gfp
1555  * has __GFP_NOWARN then no warning will be triggered on invalid or failed
1556  * allocation requests.
1557  *
1558  * RETURNS:
1559  * Percpu pointer to the allocated area on success, NULL on failure.
1560  */
1561 void __percpu *__alloc_percpu_gfp(size_t size, size_t align, gfp_t gfp)
1562 {
1563         return pcpu_alloc(size, align, false, gfp);
1564 }
1565 EXPORT_SYMBOL_GPL(__alloc_percpu_gfp);
1566 
1567 /**
1568  * __alloc_percpu - allocate dynamic percpu area
1569  * @size: size of area to allocate in bytes
1570  * @align: alignment of area (max PAGE_SIZE)
1571  *
1572  * Equivalent to __alloc_percpu_gfp(size, align, %GFP_KERNEL).
1573  */
1574 void __percpu *__alloc_percpu(size_t size, size_t align)
1575 {
1576         return pcpu_alloc(size, align, false, GFP_KERNEL);
1577 }
1578 EXPORT_SYMBOL_GPL(__alloc_percpu);
1579 
1580 /**
1581  * __alloc_reserved_percpu - allocate reserved percpu area
1582  * @size: size of area to allocate in bytes
1583  * @align: alignment of area (max PAGE_SIZE)
1584  *
1585  * Allocate zero-filled percpu area of @size bytes aligned at @align
1586  * from reserved percpu area if arch has set it up; otherwise,
1587  * allocation is served from the same dynamic area.  Might sleep.
1588  * Might trigger writeouts.
1589  *
1590  * CONTEXT:
1591  * Does GFP_KERNEL allocation.
1592  *
1593  * RETURNS:
1594  * Percpu pointer to the allocated area on success, NULL on failure.
1595  */
1596 void __percpu *__alloc_reserved_percpu(size_t size, size_t align)
1597 {
1598         return pcpu_alloc(size, align, true, GFP_KERNEL);
1599 }
1600 
1601 /**
1602  * pcpu_balance_workfn - manage the amount of free chunks and populated pages
1603  * @work: unused
1604  *
1605  * Reclaim all fully free chunks except for the first one.  This is also
1606  * responsible for maintaining the pool of empty populated pages.  However,
1607  * it is possible that this is called when physical memory is scarce causing
1608  * OOM killer to be triggered.  We should avoid doing so until an actual
1609  * allocation causes the failure as it is possible that requests can be
1610  * serviced from already backed regions.
1611  */
1612 static void pcpu_balance_workfn(struct work_struct *work)
1613 {
1614         /* gfp flags passed to underlying allocators */
1615         const gfp_t gfp = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
1616         LIST_HEAD(to_free);
1617         struct list_head *free_head = &pcpu_slot[pcpu_nr_slots - 1];
1618         struct pcpu_chunk *chunk, *next;
1619         int slot, nr_to_pop, ret;
1620 
1621         /*
1622          * There's no reason to keep around multiple unused chunks and VM
1623          * areas can be scarce.  Destroy all free chunks except for one.
1624          */
1625         mutex_lock(&pcpu_alloc_mutex);
1626         spin_lock_irq(&pcpu_lock);
1627 
1628         list_for_each_entry_safe(chunk, next, free_head, list) {
1629                 WARN_ON(chunk->immutable);
1630 
1631                 /* spare the first one */
1632                 if (chunk == list_first_entry(free_head, struct pcpu_chunk, list))
1633                         continue;
1634 
1635                 list_move(&chunk->list, &to_free);
1636         }
1637 
1638         spin_unlock_irq(&pcpu_lock);
1639 
1640         list_for_each_entry_safe(chunk, next, &to_free, list) {
1641                 int rs, re;
1642 
1643                 pcpu_for_each_pop_region(chunk->populated, rs, re, 0,
1644                                          chunk->nr_pages) {
1645                         pcpu_depopulate_chunk(chunk, rs, re);
1646                         spin_lock_irq(&pcpu_lock);
1647                         pcpu_chunk_depopulated(chunk, rs, re);
1648                         spin_unlock_irq(&pcpu_lock);
1649                 }
1650                 pcpu_destroy_chunk(chunk);
1651                 cond_resched();
1652         }
1653 
1654         /*
1655          * Ensure there are certain number of free populated pages for
1656          * atomic allocs.  Fill up from the most packed so that atomic
1657          * allocs don't increase fragmentation.  If atomic allocation
1658          * failed previously, always populate the maximum amount.  This
1659          * should prevent atomic allocs larger than PAGE_SIZE from keeping
1660          * failing indefinitely; however, large atomic allocs are not
1661          * something we support properly and can be highly unreliable and
1662          * inefficient.
1663          */
1664 retry_pop:
1665         if (pcpu_atomic_alloc_failed) {
1666                 nr_to_pop = PCPU_EMPTY_POP_PAGES_HIGH;
1667                 /* best effort anyway, don't worry about synchronization */
1668                 pcpu_atomic_alloc_failed = false;
1669         } else {
1670                 nr_to_pop = clamp(PCPU_EMPTY_POP_PAGES_HIGH -
1671                                   pcpu_nr_empty_pop_pages,
1672                                   0, PCPU_EMPTY_POP_PAGES_HIGH);
1673         }
1674 
1675         for (slot = pcpu_size_to_slot(PAGE_SIZE); slot < pcpu_nr_slots; slot++) {
1676                 int nr_unpop = 0, rs, re;
1677 
1678                 if (!nr_to_pop)
1679                         break;
1680 
1681                 spin_lock_irq(&pcpu_lock);
1682                 list_for_each_entry(chunk, &pcpu_slot[slot], list) {
1683                         nr_unpop = chunk->nr_pages - chunk->nr_populated;
1684                         if (nr_unpop)
1685                                 break;
1686                 }
1687                 spin_unlock_irq(&pcpu_lock);
1688 
1689                 if (!nr_unpop)
1690                         continue;
1691 
1692                 /* @chunk can't go away while pcpu_alloc_mutex is held */
1693                 pcpu_for_each_unpop_region(chunk->populated, rs, re, 0,
1694                                            chunk->nr_pages) {
1695                         int nr = min(re - rs, nr_to_pop);
1696 
1697                         ret = pcpu_populate_chunk(chunk, rs, rs + nr, gfp);
1698                         if (!ret) {
1699                                 nr_to_pop -= nr;
1700                                 spin_lock_irq(&pcpu_lock);
1701                                 pcpu_chunk_populated(chunk, rs, rs + nr, false);
1702                                 spin_unlock_irq(&pcpu_lock);
1703                         } else {
1704                                 nr_to_pop = 0;
1705                         }
1706 
1707                         if (!nr_to_pop)
1708                                 break;
1709                 }
1710         }
1711 
1712         if (nr_to_pop) {
1713                 /* ran out of chunks to populate, create a new one and retry */
1714                 chunk = pcpu_create_chunk(gfp);
1715                 if (chunk) {
1716                         spin_lock_irq(&pcpu_lock);
1717                         pcpu_chunk_relocate(chunk, -1);
1718                         spin_unlock_irq(&pcpu_lock);
1719                         goto retry_pop;
1720                 }
1721         }
1722 
1723         mutex_unlock(&pcpu_alloc_mutex);
1724 }
1725 
1726 /**
1727  * free_percpu - free percpu area
1728  * @ptr: pointer to area to free
1729  *
1730  * Free percpu area @ptr.
1731  *
1732  * CONTEXT:
1733  * Can be called from atomic context.
1734  */
1735 void free_percpu(void __percpu *ptr)
1736 {
1737         void *addr;
1738         struct pcpu_chunk *chunk;
1739         unsigned long flags;
1740         int off;
1741 
1742         if (!ptr)
1743                 return;
1744 
1745         kmemleak_free_percpu(ptr);
1746 
1747         addr = __pcpu_ptr_to_addr(ptr);
1748 
1749         spin_lock_irqsave(&pcpu_lock, flags);
1750 
1751         chunk = pcpu_chunk_addr_search(addr);
1752         off = addr - chunk->base_addr;
1753 
1754         pcpu_free_area(chunk, off);
1755 
1756         /* if there are more than one fully free chunks, wake up grim reaper */
1757         if (chunk->free_bytes == pcpu_unit_size) {
1758                 struct pcpu_chunk *pos;
1759 
1760                 list_for_each_entry(pos, &pcpu_slot[pcpu_nr_slots - 1], list)
1761                         if (pos != chunk) {
1762                                 pcpu_schedule_balance_work();
1763                                 break;
1764                         }
1765         }
1766 
1767         trace_percpu_free_percpu(chunk->base_addr, off, ptr);
1768 
1769         spin_unlock_irqrestore(&pcpu_lock, flags);
1770 }
1771 EXPORT_SYMBOL_GPL(free_percpu);
1772 
1773 bool __is_kernel_percpu_address(unsigned long addr, unsigned long *can_addr)
1774 {
1775 #ifdef CONFIG_SMP
1776         const size_t static_size = __per_cpu_end - __per_cpu_start;
1777         void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
1778         unsigned int cpu;
1779 
1780         for_each_possible_cpu(cpu) {
1781                 void *start = per_cpu_ptr(base, cpu);
1782                 void *va = (void *)addr;
1783 
1784                 if (va >= start && va < start + static_size) {
1785                         if (can_addr) {
1786                                 *can_addr = (unsigned long) (va - start);
1787                                 *can_addr += (unsigned long)
1788                                         per_cpu_ptr(base, get_boot_cpu_id());
1789                         }
1790                         return true;
1791                 }
1792         }
1793 #endif
1794         /* on UP, can't distinguish from other static vars, always false */
1795         return false;
1796 }
1797 
1798 /**
1799  * is_kernel_percpu_address - test whether address is from static percpu area
1800  * @addr: address to test
1801  *
1802  * Test whether @addr belongs to in-kernel static percpu area.  Module
1803  * static percpu areas are not considered.  For those, use
1804  * is_module_percpu_address().
1805  *
1806  * RETURNS:
1807  * %true if @addr is from in-kernel static percpu area, %false otherwise.
1808  */
1809 bool is_kernel_percpu_address(unsigned long addr)
1810 {
1811         return __is_kernel_percpu_address(addr, NULL);
1812 }
1813 
1814 /**
1815  * per_cpu_ptr_to_phys - convert translated percpu address to physical address
1816  * @addr: the address to be converted to physical address
1817  *
1818  * Given @addr which is dereferenceable address obtained via one of
1819  * percpu access macros, this function translates it into its physical
1820  * address.  The caller is responsible for ensuring @addr stays valid
1821  * until this function finishes.
1822  *
1823  * percpu allocator has special setup for the first chunk, which currently
1824  * supports either embedding in linear address space or vmalloc mapping,
1825  * and, from the second one, the backing allocator (currently either vm or
1826  * km) provides translation.
1827  *
1828  * The addr can be translated simply without checking if it falls into the
1829  * first chunk. But the current code reflects better how percpu allocator
1830  * actually works, and the verification can discover both bugs in percpu
1831  * allocator itself and per_cpu_ptr_to_phys() callers. So we keep current
1832  * code.
1833  *
1834  * RETURNS:
1835  * The physical address for @addr.
1836  */
1837 phys_addr_t per_cpu_ptr_to_phys(void *addr)
1838 {
1839         void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
1840         bool in_first_chunk = false;
1841         unsigned long first_low, first_high;
1842         unsigned int cpu;
1843 
1844         /*
1845          * The following test on unit_low/high isn't strictly
1846          * necessary but will speed up lookups of addresses which
1847          * aren't in the first chunk.
1848          *
1849          * The address check is against full chunk sizes.  pcpu_base_addr
1850          * points to the beginning of the first chunk including the
1851          * static region.  Assumes good intent as the first chunk may
1852          * not be full (ie. < pcpu_unit_pages in size).
1853          */
1854         first_low = (unsigned long)pcpu_base_addr +
1855                     pcpu_unit_page_offset(pcpu_low_unit_cpu, 0);
1856         first_high = (unsigned long)pcpu_base_addr +
1857                      pcpu_unit_page_offset(pcpu_high_unit_cpu, pcpu_unit_pages);
1858         if ((unsigned long)addr >= first_low &&
1859             (unsigned long)addr < first_high) {
1860                 for_each_possible_cpu(cpu) {
1861                         void *start = per_cpu_ptr(base, cpu);
1862 
1863                         if (addr >= start && addr < start + pcpu_unit_size) {
1864                                 in_first_chunk = true;
1865                                 break;
1866                         }
1867                 }
1868         }
1869 
1870         if (in_first_chunk) {
1871                 if (!is_vmalloc_addr(addr))
1872                         return __pa(addr);
1873                 else
1874                         return page_to_phys(vmalloc_to_page(addr)) +
1875                                offset_in_page(addr);
1876         } else
1877                 return page_to_phys(pcpu_addr_to_page(addr)) +
1878                        offset_in_page(addr);
1879 }
1880 
1881 /**
1882  * pcpu_alloc_alloc_info - allocate percpu allocation info
1883  * @nr_groups: the number of groups
1884  * @nr_units: the number of units
1885  *
1886  * Allocate ai which is large enough for @nr_groups groups containing
1887  * @nr_units units.  The returned ai's groups[0].cpu_map points to the
1888  * cpu_map array which is long enough for @nr_units and filled with
1889  * NR_CPUS.  It's the caller's responsibility to initialize cpu_map
1890  * pointer of other groups.
1891  *
1892  * RETURNS:
1893  * Pointer to the allocated pcpu_alloc_info on success, NULL on
1894  * failure.
1895  */
1896 struct pcpu_alloc_info * __init pcpu_alloc_alloc_info(int nr_groups,
1897                                                       int nr_units)
1898 {
1899         struct pcpu_alloc_info *ai;
1900         size_t base_size, ai_size;
1901         void *ptr;
1902         int unit;
1903 
1904         base_size = ALIGN(sizeof(*ai) + nr_groups * sizeof(ai->groups[0]),
1905                           __alignof__(ai->groups[0].cpu_map[0]));
1906         ai_size = base_size + nr_units * sizeof(ai->groups[0].cpu_map[0]);
1907 
1908         ptr = memblock_alloc(PFN_ALIGN(ai_size), PAGE_SIZE);
1909         if (!ptr)
1910                 return NULL;
1911         ai = ptr;
1912         ptr += base_size;
1913 
1914         ai->groups[0].cpu_map = ptr;
1915 
1916         for (unit = 0; unit < nr_units; unit++)
1917                 ai->groups[0].cpu_map[unit] = NR_CPUS;
1918 
1919         ai->nr_groups = nr_groups;
1920         ai->__ai_size = PFN_ALIGN(ai_size);
1921 
1922         return ai;
1923 }
1924 
1925 /**
1926  * pcpu_free_alloc_info - free percpu allocation info
1927  * @ai: pcpu_alloc_info to free
1928  *
1929  * Free @ai which was allocated by pcpu_alloc_alloc_info().
1930  */
1931 void __init pcpu_free_alloc_info(struct pcpu_alloc_info *ai)
1932 {
1933         memblock_free_early(__pa(ai), ai->__ai_size);
1934 }
1935 
1936 /**
1937  * pcpu_dump_alloc_info - print out information about pcpu_alloc_info
1938  * @lvl: loglevel
1939  * @ai: allocation info to dump
1940  *
1941  * Print out information about @ai using loglevel @lvl.
1942  */
1943 static void pcpu_dump_alloc_info(const char *lvl,
1944                                  const struct pcpu_alloc_info *ai)
1945 {
1946         int group_width = 1, cpu_width = 1, width;
1947         char empty_str[] = "--------";
1948         int alloc = 0, alloc_end = 0;
1949         int group, v;
1950         int upa, apl;   /* units per alloc, allocs per line */
1951 
1952         v = ai->nr_groups;
1953         while (v /= 10)
1954                 group_width++;
1955 
1956         v = num_possible_cpus();
1957         while (v /= 10)
1958                 cpu_width++;
1959         empty_str[min_t(int, cpu_width, sizeof(empty_str) - 1)] = '\0';
1960 
1961         upa = ai->alloc_size / ai->unit_size;
1962         width = upa * (cpu_width + 1) + group_width + 3;
1963         apl = rounddown_pow_of_two(max(60 / width, 1));
1964 
1965         printk("%spcpu-alloc: s%zu r%zu d%zu u%zu alloc=%zu*%zu",
1966                lvl, ai->static_size, ai->reserved_size, ai->dyn_size,
1967                ai->unit_size, ai->alloc_size / ai->atom_size, ai->atom_size);
1968 
1969         for (group = 0; group < ai->nr_groups; group++) {
1970                 const struct pcpu_group_info *gi = &ai->groups[group];
1971                 int unit = 0, unit_end = 0;
1972 
1973                 BUG_ON(gi->nr_units % upa);
1974                 for (alloc_end += gi->nr_units / upa;
1975                      alloc < alloc_end; alloc++) {
1976                         if (!(alloc % apl)) {
1977                                 pr_cont("\n");
1978                                 printk("%spcpu-alloc: ", lvl);
1979                         }
1980                         pr_cont("[%0*d] ", group_width, group);
1981 
1982                         for (unit_end += upa; unit < unit_end; unit++)
1983                                 if (gi->cpu_map[unit] != NR_CPUS)
1984                                         pr_cont("%0*d ",
1985                                                 cpu_width, gi->cpu_map[unit]);
1986                                 else
1987                                         pr_cont("%s ", empty_str);
1988                 }
1989         }
1990         pr_cont("\n");
1991 }
1992 
1993 /**
1994  * pcpu_setup_first_chunk - initialize the first percpu chunk
1995  * @ai: pcpu_alloc_info describing how to percpu area is shaped
1996  * @base_addr: mapped address
1997  *
1998  * Initialize the first percpu chunk which contains the kernel static
1999  * perpcu area.  This function is to be called from arch percpu area
2000  * setup path.
2001  *
2002  * @ai contains all information necessary to initialize the first
2003  * chunk and prime the dynamic percpu allocator.
2004  *
2005  * @ai->static_size is the size of static percpu area.
2006  *
2007  * @ai->reserved_size, if non-zero, specifies the amount of bytes to
2008  * reserve after the static area in the first chunk.  This reserves
2009  * the first chunk such that it's available only through reserved
2010  * percpu allocation.  This is primarily used to serve module percpu
2011  * static areas on architectures where the addressing model has
2012  * limited offset range for symbol relocations to guarantee module
2013  * percpu symbols fall inside the relocatable range.
2014  *
2015  * @ai->dyn_size determines the number of bytes available for dynamic
2016  * allocation in the first chunk.  The area between @ai->static_size +
2017  * @ai->reserved_size + @ai->dyn_size and @ai->unit_size is unused.
2018  *
2019  * @ai->unit_size specifies unit size and must be aligned to PAGE_SIZE
2020  * and equal to or larger than @ai->static_size + @ai->reserved_size +
2021  * @ai->dyn_size.
2022  *
2023  * @ai->atom_size is the allocation atom size and used as alignment
2024  * for vm areas.
2025  *
2026  * @ai->alloc_size is the allocation size and always multiple of
2027  * @ai->atom_size.  This is larger than @ai->atom_size if
2028  * @ai->unit_size is larger than @ai->atom_size.
2029  *
2030  * @ai->nr_groups and @ai->groups describe virtual memory layout of
2031  * percpu areas.  Units which should be colocated are put into the
2032  * same group.  Dynamic VM areas will be allocated according to these
2033  * groupings.  If @ai->nr_groups is zero, a single group containing
2034  * all units is assumed.
2035  *
2036  * The caller should have mapped the first chunk at @base_addr and
2037  * copied static data to each unit.
2038  *
2039  * The first chunk will always contain a static and a dynamic region.
2040  * However, the static region is not managed by any chunk.  If the first
2041  * chunk also contains a reserved region, it is served by two chunks -
2042  * one for the reserved region and one for the dynamic region.  They
2043  * share the same vm, but use offset regions in the area allocation map.
2044  * The chunk serving the dynamic region is circulated in the chunk slots
2045  * and available for dynamic allocation like any other chunk.
2046  *
2047  * RETURNS:
2048  * 0 on success, -errno on failure.
2049  */
2050 int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
2051                                   void *base_addr)
2052 {
2053         size_t size_sum = ai->static_size + ai->reserved_size + ai->dyn_size;
2054         size_t static_size, dyn_size;
2055         struct pcpu_chunk *chunk;
2056         unsigned long *group_offsets;
2057         size_t *group_sizes;
2058         unsigned long *unit_off;
2059         unsigned int cpu;
2060         int *unit_map;
2061         int group, unit, i;
2062         int map_size;
2063         unsigned long tmp_addr;
2064         size_t alloc_size;
2065 
2066 #define PCPU_SETUP_BUG_ON(cond) do {                                    \
2067         if (unlikely(cond)) {                                           \
2068                 pr_emerg("failed to initialize, %s\n", #cond);          \
2069                 pr_emerg("cpu_possible_mask=%*pb\n",                    \
2070                          cpumask_pr_args(cpu_possible_mask));           \
2071                 pcpu_dump_alloc_info(KERN_EMERG, ai);                   \
2072                 BUG();                                                  \
2073         }                                                               \
2074 } while (0)
2075 
2076         /* sanity checks */
2077         PCPU_SETUP_BUG_ON(ai->nr_groups <= 0);
2078 #ifdef CONFIG_SMP
2079         PCPU_SETUP_BUG_ON(!ai->static_size);
2080         PCPU_SETUP_BUG_ON(offset_in_page(__per_cpu_start));
2081 #endif
2082         PCPU_SETUP_BUG_ON(!base_addr);
2083         PCPU_SETUP_BUG_ON(offset_in_page(base_addr));
2084         PCPU_SETUP_BUG_ON(ai->unit_size < size_sum);
2085         PCPU_SETUP_BUG_ON(offset_in_page(ai->unit_size));
2086         PCPU_SETUP_BUG_ON(ai->unit_size < PCPU_MIN_UNIT_SIZE);
2087         PCPU_SETUP_BUG_ON(!IS_ALIGNED(ai->unit_size, PCPU_BITMAP_BLOCK_SIZE));
2088         PCPU_SETUP_BUG_ON(ai->dyn_size < PERCPU_DYNAMIC_EARLY_SIZE);
2089         PCPU_SETUP_BUG_ON(!ai->dyn_size);
2090         PCPU_SETUP_BUG_ON(!IS_ALIGNED(ai->reserved_size, PCPU_MIN_ALLOC_SIZE));
2091         PCPU_SETUP_BUG_ON(!(IS_ALIGNED(PCPU_BITMAP_BLOCK_SIZE, PAGE_SIZE) ||
2092                             IS_ALIGNED(PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE)));
2093         PCPU_SETUP_BUG_ON(pcpu_verify_alloc_info(ai) < 0);
2094 
2095         /* process group information and build config tables accordingly */
2096         alloc_size = ai->nr_groups * sizeof(group_offsets[0]);
2097         group_offsets = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2098         if (!group_offsets)
2099                 panic("%s: Failed to allocate %zu bytes\n", __func__,
2100                       alloc_size);
2101 
2102         alloc_size = ai->nr_groups * sizeof(group_sizes[0]);
2103         group_sizes = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2104         if (!group_sizes)
2105                 panic("%s: Failed to allocate %zu bytes\n", __func__,
2106                       alloc_size);
2107 
2108         alloc_size = nr_cpu_ids * sizeof(unit_map[0]);
2109         unit_map = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2110         if (!unit_map)
2111                 panic("%s: Failed to allocate %zu bytes\n", __func__,
2112                       alloc_size);
2113 
2114         alloc_size = nr_cpu_ids * sizeof(unit_off[0]);
2115         unit_off = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2116         if (!unit_off)
2117                 panic("%s: Failed to allocate %zu bytes\n", __func__,
2118                       alloc_size);
2119 
2120         for (cpu = 0; cpu < nr_cpu_ids; cpu++)
2121                 unit_map[cpu] = UINT_MAX;
2122 
2123         pcpu_low_unit_cpu = NR_CPUS;
2124         pcpu_high_unit_cpu = NR_CPUS;
2125 
2126         for (group = 0, unit = 0; group < ai->nr_groups; group++, unit += i) {
2127                 const struct pcpu_group_info *gi = &ai->groups[group];
2128 
2129                 group_offsets[group] = gi->base_offset;
2130                 group_sizes[group] = gi->nr_units * ai->unit_size;
2131 
2132                 for (i = 0; i < gi->nr_units; i++) {
2133                         cpu = gi->cpu_map[i];
2134                         if (cpu == NR_CPUS)
2135                                 continue;
2136 
2137                         PCPU_SETUP_BUG_ON(cpu >= nr_cpu_ids);
2138                         PCPU_SETUP_BUG_ON(!cpu_possible(cpu));
2139                         PCPU_SETUP_BUG_ON(unit_map[cpu] != UINT_MAX);
2140 
2141                         unit_map[cpu] = unit + i;
2142                         unit_off[cpu] = gi->base_offset + i * ai->unit_size;
2143 
2144                         /* determine low/high unit_cpu */
2145                         if (pcpu_low_unit_cpu == NR_CPUS ||
2146                             unit_off[cpu] < unit_off[pcpu_low_unit_cpu])
2147                                 pcpu_low_unit_cpu = cpu;
2148                         if (pcpu_high_unit_cpu == NR_CPUS ||
2149                             unit_off[cpu] > unit_off[pcpu_high_unit_cpu])
2150                                 pcpu_high_unit_cpu = cpu;
2151                 }
2152         }
2153         pcpu_nr_units = unit;
2154 
2155         for_each_possible_cpu(cpu)
2156                 PCPU_SETUP_BUG_ON(unit_map[cpu] == UINT_MAX);
2157 
2158         /* we're done parsing the input, undefine BUG macro and dump config */
2159 #undef PCPU_SETUP_BUG_ON
2160         pcpu_dump_alloc_info(KERN_DEBUG, ai);
2161 
2162         pcpu_nr_groups = ai->nr_groups;
2163         pcpu_group_offsets = group_offsets;
2164         pcpu_group_sizes = group_sizes;
2165         pcpu_unit_map = unit_map;
2166         pcpu_unit_offsets = unit_off;
2167 
2168         /* determine basic parameters */
2169         pcpu_unit_pages = ai->unit_size >> PAGE_SHIFT;
2170         pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
2171         pcpu_atom_size = ai->atom_size;
2172         pcpu_chunk_struct_size = sizeof(struct pcpu_chunk) +
2173                 BITS_TO_LONGS(pcpu_unit_pages) * sizeof(unsigned long);
2174 
2175         pcpu_stats_save_ai(ai);
2176 
2177         /*
2178          * Allocate chunk slots.  The additional last slot is for
2179          * empty chunks.
2180          */
2181         pcpu_nr_slots = __pcpu_size_to_slot(pcpu_unit_size) + 2;
2182         pcpu_slot = memblock_alloc(pcpu_nr_slots * sizeof(pcpu_slot[0]),
2183                                    SMP_CACHE_BYTES);
2184         if (!pcpu_slot)
2185                 panic("%s: Failed to allocate %zu bytes\n", __func__,
2186                       pcpu_nr_slots * sizeof(pcpu_slot[0]));
2187         for (i = 0; i < pcpu_nr_slots; i++)
2188                 INIT_LIST_HEAD(&pcpu_slot[i]);
2189 
2190         /*
2191          * The end of the static region needs to be aligned with the
2192          * minimum allocation size as this offsets the reserved and
2193          * dynamic region.  The first chunk ends page aligned by
2194          * expanding the dynamic region, therefore the dynamic region
2195          * can be shrunk to compensate while still staying above the
2196          * configured sizes.
2197          */
2198         static_size = ALIGN(ai->static_size, PCPU_MIN_ALLOC_SIZE);
2199         dyn_size = ai->dyn_size - (static_size - ai->static_size);
2200 
2201         /*
2202          * Initialize first chunk.
2203          * If the reserved_size is non-zero, this initializes the reserved
2204          * chunk.  If the reserved_size is zero, the reserved chunk is NULL
2205          * and the dynamic region is initialized here.  The first chunk,
2206          * pcpu_first_chunk, will always point to the chunk that serves
2207          * the dynamic region.
2208          */
2209         tmp_addr = (unsigned long)base_addr + static_size;
2210         map_size = ai->reserved_size ?: dyn_size;
2211         chunk = pcpu_alloc_first_chunk(tmp_addr, map_size);
2212 
2213         /* init dynamic chunk if necessary */
2214         if (ai->reserved_size) {
2215                 pcpu_reserved_chunk = chunk;
2216 
2217                 tmp_addr = (unsigned long)base_addr + static_size +
2218                            ai->reserved_size;
2219                 map_size = dyn_size;
2220                 chunk = pcpu_alloc_first_chunk(tmp_addr, map_size);
2221         }
2222 
2223         /* link the first chunk in */
2224         pcpu_first_chunk = chunk;
2225         pcpu_nr_empty_pop_pages = pcpu_first_chunk->nr_empty_pop_pages;
2226         pcpu_chunk_relocate(pcpu_first_chunk, -1);
2227 
2228         /* include all regions of the first chunk */
2229         pcpu_nr_populated += PFN_DOWN(size_sum);
2230 
2231         pcpu_stats_chunk_alloc();
2232         trace_percpu_create_chunk(base_addr);
2233 
2234         /* we're done */
2235         pcpu_base_addr = base_addr;
2236         return 0;
2237 }
2238 
2239 #ifdef CONFIG_SMP
2240 
2241 const char * const pcpu_fc_names[PCPU_FC_NR] __initconst = {
2242         [PCPU_FC_AUTO]  = "auto",
2243         [PCPU_FC_EMBED] = "embed",
2244         [PCPU_FC_PAGE]  = "page",
2245 };
2246 
2247 enum pcpu_fc pcpu_chosen_fc __initdata = PCPU_FC_AUTO;
2248 
2249 static int __init percpu_alloc_setup(char *str)
2250 {
2251         if (!str)
2252                 return -EINVAL;
2253 
2254         if (0)
2255                 /* nada */;
2256 #ifdef CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK
2257         else if (!strcmp(str, "embed"))
2258                 pcpu_chosen_fc = PCPU_FC_EMBED;
2259 #endif
2260 #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
2261         else if (!strcmp(str, "page"))
2262                 pcpu_chosen_fc = PCPU_FC_PAGE;
2263 #endif
2264         else
2265                 pr_warn("unknown allocator %s specified\n", str);
2266 
2267         return 0;
2268 }
2269 early_param("percpu_alloc", percpu_alloc_setup);
2270 
2271 /*
2272  * pcpu_embed_first_chunk() is used by the generic percpu setup.
2273  * Build it if needed by the arch config or the generic setup is going
2274  * to be used.
2275  */
2276 #if defined(CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK) || \
2277         !defined(CONFIG_HAVE_SETUP_PER_CPU_AREA)
2278 #define BUILD_EMBED_FIRST_CHUNK
2279 #endif
2280 
2281 /* build pcpu_page_first_chunk() iff needed by the arch config */
2282 #if defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
2283 #define BUILD_PAGE_FIRST_CHUNK
2284 #endif
2285 
2286 /* pcpu_build_alloc_info() is used by both embed and page first chunk */
2287 #if defined(BUILD_EMBED_FIRST_CHUNK) || defined(BUILD_PAGE_FIRST_CHUNK)
2288 /**
2289  * pcpu_build_alloc_info - build alloc_info considering distances between CPUs
2290  * @reserved_size: the size of reserved percpu area in bytes
2291  * @dyn_size: minimum free size for dynamic allocation in bytes
2292  * @atom_size: allocation atom size
2293  * @cpu_distance_fn: callback to determine distance between cpus, optional
2294  *
2295  * This function determines grouping of units, their mappings to cpus
2296  * and other parameters considering needed percpu size, allocation
2297  * atom size and distances between CPUs.
2298  *
2299  * Groups are always multiples of atom size and CPUs which are of
2300  * LOCAL_DISTANCE both ways are grouped together and share space for
2301  * units in the same group.  The returned configuration is guaranteed
2302  * to have CPUs on different nodes on different groups and >=75% usage
2303  * of allocated virtual address space.
2304  *
2305  * RETURNS:
2306  * On success, pointer to the new allocation_info is returned.  On
2307  * failure, ERR_PTR value is returned.
2308  */
2309 static struct pcpu_alloc_info * __init pcpu_build_alloc_info(
2310                                 size_t reserved_size, size_t dyn_size,
2311                                 size_t atom_size,
2312                                 pcpu_fc_cpu_distance_fn_t cpu_distance_fn)
2313 {
2314         static int group_map[NR_CPUS] __initdata;
2315         static int group_cnt[NR_CPUS] __initdata;
2316         const size_t static_size = __per_cpu_end - __per_cpu_start;
2317         int nr_groups = 1, nr_units = 0;
2318         size_t size_sum, min_unit_size, alloc_size;
2319         int upa, max_upa, uninitialized_var(best_upa);  /* units_per_alloc */
2320         int last_allocs, group, unit;
2321         unsigned int cpu, tcpu;
2322         struct pcpu_alloc_info *ai;
2323         unsigned int *cpu_map;
2324 
2325         /* this function may be called multiple times */
2326         memset(group_map, 0, sizeof(group_map));
2327         memset(group_cnt, 0, sizeof(group_cnt));
2328 
2329         /* calculate size_sum and ensure dyn_size is enough for early alloc */
2330         size_sum = PFN_ALIGN(static_size + reserved_size +
2331                             max_t(size_t, dyn_size, PERCPU_DYNAMIC_EARLY_SIZE));
2332         dyn_size = size_sum - static_size - reserved_size;
2333 
2334         /*
2335          * Determine min_unit_size, alloc_size and max_upa such that
2336          * alloc_size is multiple of atom_size and is the smallest
2337          * which can accommodate 4k aligned segments which are equal to
2338          * or larger than min_unit_size.
2339          */
2340         min_unit_size = max_t(size_t, size_sum, PCPU_MIN_UNIT_SIZE);
2341 
2342         /* determine the maximum # of units that can fit in an allocation */
2343         alloc_size = roundup(min_unit_size, atom_size);
2344         upa = alloc_size / min_unit_size;
2345         while (alloc_size % upa || (offset_in_page(alloc_size / upa)))
2346                 upa--;
2347         max_upa = upa;
2348 
2349         /* group cpus according to their proximity */
2350         for_each_possible_cpu(cpu) {
2351                 group = 0;
2352         next_group:
2353                 for_each_possible_cpu(tcpu) {
2354                         if (cpu == tcpu)
2355                                 break;
2356                         if (group_map[tcpu] == group && cpu_distance_fn &&
2357                             (cpu_distance_fn(cpu, tcpu) > LOCAL_DISTANCE ||
2358                              cpu_distance_fn(tcpu, cpu) > LOCAL_DISTANCE)) {
2359                                 group++;
2360                                 nr_groups = max(nr_groups, group + 1);
2361                                 goto next_group;
2362                         }
2363                 }
2364                 group_map[cpu] = group;
2365                 group_cnt[group]++;
2366         }
2367 
2368         /*
2369          * Wasted space is caused by a ratio imbalance of upa to group_cnt.
2370          * Expand the unit_size until we use >= 75% of the units allocated.
2371          * Related to atom_size, which could be much larger than the unit_size.
2372          */
2373         last_allocs = INT_MAX;
2374         for (upa = max_upa; upa; upa--) {
2375                 int allocs = 0, wasted = 0;
2376 
2377                 if (alloc_size % upa || (offset_in_page(alloc_size / upa)))
2378                         continue;
2379 
2380                 for (group = 0; group < nr_groups; group++) {
2381                         int this_allocs = DIV_ROUND_UP(group_cnt[group], upa);
2382                         allocs += this_allocs;
2383                         wasted += this_allocs * upa - group_cnt[group];
2384                 }
2385 
2386                 /*
2387                  * Don't accept if wastage is over 1/3.  The
2388                  * greater-than comparison ensures upa==1 always
2389                  * passes the following check.
2390                  */
2391                 if (wasted > num_possible_cpus() / 3)
2392                         continue;
2393 
2394                 /* and then don't consume more memory */
2395                 if (allocs > last_allocs)
2396                         break;
2397                 last_allocs = allocs;
2398                 best_upa = upa;
2399         }
2400         upa = best_upa;
2401 
2402         /* allocate and fill alloc_info */
2403         for (group = 0; group < nr_groups; group++)
2404                 nr_units += roundup(group_cnt[group], upa);
2405 
2406         ai = pcpu_alloc_alloc_info(nr_groups, nr_units);
2407         if (!ai)
2408                 return ERR_PTR(-ENOMEM);
2409         cpu_map = ai->groups[0].cpu_map;
2410 
2411         for (group = 0; group < nr_groups; group++) {
2412                 ai->groups[group].cpu_map = cpu_map;
2413                 cpu_map += roundup(group_cnt[group], upa);
2414         }
2415 
2416         ai->static_size = static_size;
2417         ai->reserved_size = reserved_size;
2418         ai->dyn_size = dyn_size;
2419         ai->unit_size = alloc_size / upa;
2420         ai->atom_size = atom_size;
2421         ai->alloc_size = alloc_size;
2422 
2423         for (group = 0, unit = 0; group < nr_groups; group++) {
2424                 struct pcpu_group_info *gi = &ai->groups[group];
2425 
2426                 /*
2427                  * Initialize base_offset as if all groups are located
2428                  * back-to-back.  The caller should update this to
2429                  * reflect actual allocation.
2430                  */
2431                 gi->base_offset = unit * ai->unit_size;
2432 
2433                 for_each_possible_cpu(cpu)
2434                         if (group_map[cpu] == group)
2435                                 gi->cpu_map[gi->nr_units++] = cpu;
2436                 gi->nr_units = roundup(gi->nr_units, upa);
2437                 unit += gi->nr_units;
2438         }
2439         BUG_ON(unit != nr_units);
2440 
2441         return ai;
2442 }
2443 #endif /* BUILD_EMBED_FIRST_CHUNK || BUILD_PAGE_FIRST_CHUNK */
2444 
2445 #if defined(BUILD_EMBED_FIRST_CHUNK)
2446 /**
2447  * pcpu_embed_first_chunk - embed the first percpu chunk into bootmem
2448  * @reserved_size: the size of reserved percpu area in bytes
2449  * @dyn_size: minimum free size for dynamic allocation in bytes
2450  * @atom_size: allocation atom size
2451  * @cpu_distance_fn: callback to determine distance between cpus, optional
2452  * @alloc_fn: function to allocate percpu page
2453  * @free_fn: function to free percpu page
2454  *
2455  * This is a helper to ease setting up embedded first percpu chunk and
2456  * can be called where pcpu_setup_first_chunk() is expected.
2457  *
2458  * If this function is used to setup the first chunk, it is allocated
2459  * by calling @alloc_fn and used as-is without being mapped into
2460  * vmalloc area.  Allocations are always whole multiples of @atom_size
2461  * aligned to @atom_size.
2462  *
2463  * This enables the first chunk to piggy back on the linear physical
2464  * mapping which often uses larger page size.  Please note that this
2465  * can result in very sparse cpu->unit mapping on NUMA machines thus
2466  * requiring large vmalloc address space.  Don't use this allocator if
2467  * vmalloc space is not orders of magnitude larger than distances
2468  * between node memory addresses (ie. 32bit NUMA machines).
2469  *
2470  * @dyn_size specifies the minimum dynamic area size.
2471  *
2472  * If the needed size is smaller than the minimum or specified unit
2473  * size, the leftover is returned using @free_fn.
2474  *
2475  * RETURNS:
2476  * 0 on success, -errno on failure.
2477  */
2478 int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
2479                                   size_t atom_size,
2480                                   pcpu_fc_cpu_distance_fn_t cpu_distance_fn,
2481                                   pcpu_fc_alloc_fn_t alloc_fn,
2482                                   pcpu_fc_free_fn_t free_fn)
2483 {
2484         void *base = (void *)ULONG_MAX;
2485         void **areas = NULL;
2486         struct pcpu_alloc_info *ai;
2487         size_t size_sum, areas_size;
2488         unsigned long max_distance;
2489         int group, i, highest_group, rc;
2490 
2491         ai = pcpu_build_alloc_info(reserved_size, dyn_size, atom_size,
2492                                    cpu_distance_fn);
2493         if (IS_ERR(ai))
2494                 return PTR_ERR(ai);
2495 
2496         size_sum = ai->static_size + ai->reserved_size + ai->dyn_size;
2497         areas_size = PFN_ALIGN(ai->nr_groups * sizeof(void *));
2498 
2499         areas = memblock_alloc(areas_size, SMP_CACHE_BYTES);
2500         if (!areas) {
2501                 rc = -ENOMEM;
2502                 goto out_free;
2503         }
2504 
2505         /* allocate, copy and determine base address & max_distance */
2506         highest_group = 0;
2507         for (group = 0; group < ai->nr_groups; group++) {
2508                 struct pcpu_group_info *gi = &ai->groups[group];
2509                 unsigned int cpu = NR_CPUS;
2510                 void *ptr;
2511 
2512                 for (i = 0; i < gi->nr_units && cpu == NR_CPUS; i++)
2513                         cpu = gi->cpu_map[i];
2514                 BUG_ON(cpu == NR_CPUS);
2515 
2516                 /* allocate space for the whole group */
2517                 ptr = alloc_fn(cpu, gi->nr_units * ai->unit_size, atom_size);
2518                 if (!ptr) {
2519                         rc = -ENOMEM;
2520                         goto out_free_areas;
2521                 }
2522                 /* kmemleak tracks the percpu allocations separately */
2523                 kmemleak_free(ptr);
2524                 areas[group] = ptr;
2525 
2526                 base = min(ptr, base);
2527                 if (ptr > areas[highest_group])
2528                         highest_group = group;
2529         }
2530         max_distance = areas[highest_group] - base;
2531         max_distance += ai->unit_size * ai->groups[highest_group].nr_units;
2532 
2533         /* warn if maximum distance is further than 75% of vmalloc space */
2534         if (max_distance > VMALLOC_TOTAL * 3 / 4) {
2535                 pr_warn("max_distance=0x%lx too large for vmalloc space 0x%lx\n",
2536                                 max_distance, VMALLOC_TOTAL);
2537 #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
2538                 /* and fail if we have fallback */
2539                 rc = -EINVAL;
2540                 goto out_free_areas;
2541 #endif
2542         }
2543 
2544         /*
2545          * Copy data and free unused parts.  This should happen after all
2546          * allocations are complete; otherwise, we may end up with
2547          * overlapping groups.
2548          */
2549         for (group = 0; group < ai->nr_groups; group++) {
2550                 struct pcpu_group_info *gi = &ai->groups[group];
2551                 void *ptr = areas[group];
2552 
2553                 for (i = 0; i < gi->nr_units; i++, ptr += ai->unit_size) {
2554                         if (gi->cpu_map[i] == NR_CPUS) {
2555                                 /* unused unit, free whole */
2556                                 free_fn(ptr, ai->unit_size);
2557                                 continue;
2558                         }
2559                         /* copy and return the unused part */
2560                         memcpy(ptr, __per_cpu_load, ai->static_size);
2561                         free_fn(ptr + size_sum, ai->unit_size - size_sum);
2562                 }
2563         }
2564 
2565         /* base address is now known, determine group base offsets */
2566         for (group = 0; group < ai->nr_groups; group++) {
2567                 ai->groups[group].base_offset = areas[group] - base;
2568         }
2569 
2570         pr_info("Embedded %zu pages/cpu @%p s%zu r%zu d%zu u%zu\n",
2571                 PFN_DOWN(size_sum), base, ai->static_size, ai->reserved_size,
2572                 ai->dyn_size, ai->unit_size);
2573 
2574         rc = pcpu_setup_first_chunk(ai, base);
2575         goto out_free;
2576 
2577 out_free_areas:
2578         for (group = 0; group < ai->nr_groups; group++)
2579                 if (areas[group])
2580                         free_fn(areas[group],
2581                                 ai->groups[group].nr_units * ai->unit_size);
2582 out_free:
2583         pcpu_free_alloc_info(ai);
2584         if (areas)
2585                 memblock_free_early(__pa(areas), areas_size);
2586         return rc;
2587 }
2588 #endif /* BUILD_EMBED_FIRST_CHUNK */
2589 
2590 #ifdef BUILD_PAGE_FIRST_CHUNK
2591 /**
2592  * pcpu_page_first_chunk - map the first chunk using PAGE_SIZE pages
2593  * @reserved_size: the size of reserved percpu area in bytes
2594  * @alloc_fn: function to allocate percpu page, always called with PAGE_SIZE
2595  * @free_fn: function to free percpu page, always called with PAGE_SIZE
2596  * @populate_pte_fn: function to populate pte
2597  *
2598  * This is a helper to ease setting up page-remapped first percpu
2599  * chunk and can be called where pcpu_setup_first_chunk() is expected.
2600  *
2601  * This is the basic allocator.  Static percpu area is allocated
2602  * page-by-page into vmalloc area.
2603  *
2604  * RETURNS:
2605  * 0 on success, -errno on failure.
2606  */
2607 int __init pcpu_page_first_chunk(size_t reserved_size,
2608                                  pcpu_fc_alloc_fn_t alloc_fn,
2609                                  pcpu_fc_free_fn_t free_fn,
2610                                  pcpu_fc_populate_pte_fn_t populate_pte_fn)
2611 {
2612         static struct vm_struct vm;
2613         struct pcpu_alloc_info *ai;
2614         char psize_str[16];
2615         int unit_pages;
2616         size_t pages_size;
2617         struct page **pages;
2618         int unit, i, j, rc;
2619         int upa;
2620         int nr_g0_units;
2621 
2622         snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);
2623 
2624         ai = pcpu_build_alloc_info(reserved_size, 0, PAGE_SIZE, NULL);
2625         if (IS_ERR(ai))
2626                 return PTR_ERR(ai);
2627         BUG_ON(ai->nr_groups != 1);
2628         upa = ai->alloc_size/ai->unit_size;
2629         nr_g0_units = roundup(num_possible_cpus(), upa);
2630         if (WARN_ON(ai->groups[0].nr_units != nr_g0_units)) {
2631                 pcpu_free_alloc_info(ai);
2632                 return -EINVAL;
2633         }
2634 
2635         unit_pages = ai->unit_size >> PAGE_SHIFT;
2636 
2637         /* unaligned allocations can't be freed, round up to page size */
2638         pages_size = PFN_ALIGN(unit_pages * num_possible_cpus() *
2639                                sizeof(pages[0]));
2640         pages = memblock_alloc(pages_size, SMP_CACHE_BYTES);
2641         if (!pages)
2642                 panic("%s: Failed to allocate %zu bytes\n", __func__,
2643                       pages_size);
2644 
2645         /* allocate pages */
2646         j = 0;
2647         for (unit = 0; unit < num_possible_cpus(); unit++) {
2648                 unsigned int cpu = ai->groups[0].cpu_map[unit];
2649                 for (i = 0; i < unit_pages; i++) {
2650                         void *ptr;
2651 
2652                         ptr = alloc_fn(cpu, PAGE_SIZE, PAGE_SIZE);
2653                         if (!ptr) {
2654                                 pr_warn("failed to allocate %s page for cpu%u\n",
2655                                                 psize_str, cpu);
2656                                 goto enomem;
2657                         }
2658                         /* kmemleak tracks the percpu allocations separately */
2659                         kmemleak_free(ptr);
2660                         pages[j++] = virt_to_page(ptr);
2661                 }
2662         }
2663 
2664         /* allocate vm area, map the pages and copy static data */
2665         vm.flags = VM_ALLOC;
2666         vm.size = num_possible_cpus() * ai->unit_size;
2667         vm_area_register_early(&vm, PAGE_SIZE);
2668 
2669         for (unit = 0; unit < num_possible_cpus(); unit++) {
2670                 unsigned long unit_addr =
2671                         (unsigned long)vm.addr + unit * ai->unit_size;
2672 
2673                 for (i = 0; i < unit_pages; i++)
2674                         populate_pte_fn(unit_addr + (i << PAGE_SHIFT));
2675 
2676                 /* pte already populated, the following shouldn't fail */
2677                 rc = __pcpu_map_pages(unit_addr, &pages[unit * unit_pages],
2678                                       unit_pages);
2679                 if (rc < 0)
2680                         panic("failed to map percpu area, err=%d\n", rc);
2681 
2682                 /*
2683                  * FIXME: Archs with virtual cache should flush local
2684                  * cache for the linear mapping here - something
2685                  * equivalent to flush_cache_vmap() on the local cpu.
2686                  * flush_cache_vmap() can't be used as most supporting
2687                  * data structures are not set up yet.
2688                  */
2689 
2690                 /* copy static data */
2691                 memcpy((void *)unit_addr, __per_cpu_load, ai->static_size);
2692         }
2693 
2694         /* we're ready, commit */
2695         pr_info("%d %s pages/cpu @%p s%zu r%zu d%zu\n",
2696                 unit_pages, psize_str, vm.addr, ai->static_size,
2697                 ai->reserved_size, ai->dyn_size);
2698 
2699         rc = pcpu_setup_first_chunk(ai, vm.addr);
2700         goto out_free_ar;
2701 
2702 enomem:
2703         while (--j >= 0)
2704                 free_fn(page_address(pages[j]), PAGE_SIZE);
2705         rc = -ENOMEM;
2706 out_free_ar:
2707         memblock_free_early(__pa(pages), pages_size);
2708         pcpu_free_alloc_info(ai);
2709         return rc;
2710 }
2711 #endif /* BUILD_PAGE_FIRST_CHUNK */
2712 
2713 #ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
2714 /*
2715  * Generic SMP percpu area setup.
2716  *
2717  * The embedding helper is used because its behavior closely resembles
2718  * the original non-dynamic generic percpu area setup.  This is
2719  * important because many archs have addressing restrictions and might
2720  * fail if the percpu area is located far away from the previous
2721  * location.  As an added bonus, in non-NUMA cases, embedding is
2722  * generally a good idea TLB-wise because percpu area can piggy back
2723  * on the physical linear memory mapping which uses large page
2724  * mappings on applicable archs.
2725  */
2726 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
2727 EXPORT_SYMBOL(__per_cpu_offset);
2728 
2729 static void * __init pcpu_dfl_fc_alloc(unsigned int cpu, size_t size,
2730                                        size_t align)
2731 {
2732         return  memblock_alloc_from(size, align, __pa(MAX_DMA_ADDRESS));
2733 }
2734 
2735 static void __init pcpu_dfl_fc_free(void *ptr, size_t size)
2736 {
2737         memblock_free_early(__pa(ptr), size);
2738 }
2739 
2740 void __init setup_per_cpu_areas(void)
2741 {
2742         unsigned long delta;
2743         unsigned int cpu;
2744         int rc;
2745 
2746         /*
2747          * Always reserve area for module percpu variables.  That's
2748          * what the legacy allocator did.
2749          */
2750         rc = pcpu_embed_first_chunk(PERCPU_MODULE_RESERVE,
2751                                     PERCPU_DYNAMIC_RESERVE, PAGE_SIZE, NULL,
2752                                     pcpu_dfl_fc_alloc, pcpu_dfl_fc_free);
2753         if (rc < 0)
2754                 panic("Failed to initialize percpu areas.");
2755 
2756         delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
2757         for_each_possible_cpu(cpu)
2758                 __per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];
2759 }
2760 #endif  /* CONFIG_HAVE_SETUP_PER_CPU_AREA */
2761 
2762 #else   /* CONFIG_SMP */
2763 
2764 /*
2765  * UP percpu area setup.
2766  *
2767  * UP always uses km-based percpu allocator with identity mapping.
2768  * Static percpu variables are indistinguishable from the usual static
2769  * variables and don't require any special preparation.
2770  */
2771 void __init setup_per_cpu_areas(void)
2772 {
2773         const size_t unit_size =
2774                 roundup_pow_of_two(max_t(size_t, PCPU_MIN_UNIT_SIZE,
2775                                          PERCPU_DYNAMIC_RESERVE));
2776         struct pcpu_alloc_info *ai;
2777         void *fc;
2778 
2779         ai = pcpu_alloc_alloc_info(1, 1);
2780         fc = memblock_alloc_from(unit_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
2781         if (!ai || !fc)
2782                 panic("Failed to allocate memory for percpu areas.");
2783         /* kmemleak tracks the percpu allocations separately */
2784         kmemleak_free(fc);
2785 
2786         ai->dyn_size = unit_size;
2787         ai->unit_size = unit_size;
2788         ai->atom_size = unit_size;
2789         ai->alloc_size = unit_size;
2790         ai->groups[0].nr_units = 1;
2791         ai->groups[0].cpu_map[0] = 0;
2792 
2793         if (pcpu_setup_first_chunk(ai, fc) < 0)
2794                 panic("Failed to initialize percpu areas.");
2795         pcpu_free_alloc_info(ai);
2796 }
2797 
2798 #endif  /* CONFIG_SMP */
2799 
2800 /*
2801  * pcpu_nr_pages - calculate total number of populated backing pages
2802  *
2803  * This reflects the number of pages populated to back chunks.  Metadata is
2804  * excluded in the number exposed in meminfo as the number of backing pages
2805  * scales with the number of cpus and can quickly outweigh the memory used for
2806  * metadata.  It also keeps this calculation nice and simple.
2807  *
2808  * RETURNS:
2809  * Total number of populated backing pages in use by the allocator.
2810  */
2811 unsigned long pcpu_nr_pages(void)
2812 {
2813         return pcpu_nr_populated * pcpu_nr_units;
2814 }
2815 
2816 /*
2817  * Percpu allocator is initialized early during boot when neither slab or
2818  * workqueue is available.  Plug async management until everything is up
2819  * and running.
2820  */
2821 static int __init percpu_enable_async(void)
2822 {
2823         pcpu_async_enabled = true;
2824         return 0;
2825 }
2826 subsys_initcall(percpu_enable_async);
2827 

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