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1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * mm/percpu.c - percpu memory allocator
4  *
5  * Copyright (C) 2009		SUSE Linux Products GmbH
6  * Copyright (C) 2009		Tejun Heo <tj@kernel.org>
7  *
8  * Copyright (C) 2017		Facebook Inc.
9  * Copyright (C) 2017		Dennis Zhou <dennis@kernel.org>
10  *
11  * The percpu allocator handles both static and dynamic areas.  Percpu
12  * areas are allocated in chunks which are divided into units.  There is
13  * a 1-to-1 mapping for units to possible cpus.  These units are grouped
14  * based on NUMA properties of the machine.
15  *
16  *  c0                           c1                         c2
17  *  -------------------          -------------------        ------------
18  * | u0 | u1 | u2 | u3 |        | u0 | u1 | u2 | u3 |      | u0 | u1 | u
19  *  -------------------  ......  -------------------  ....  ------------
20  *
21  * Allocation is done by offsets into a unit's address space.  Ie., an
22  * area of 512 bytes at 6k in c1 occupies 512 bytes at 6k in c1:u0,
23  * c1:u1, c1:u2, etc.  On NUMA machines, the mapping may be non-linear
24  * and even sparse.  Access is handled by configuring percpu base
25  * registers according to the cpu to unit mappings and offsetting the
26  * base address using pcpu_unit_size.
27  *
28  * There is special consideration for the first chunk which must handle
29  * the static percpu variables in the kernel image as allocation services
30  * are not online yet.  In short, the first chunk is structured like so:
31  *
32  *                  <Static | [Reserved] | Dynamic>
33  *
34  * The static data is copied from the original section managed by the
35  * linker.  The reserved section, if non-zero, primarily manages static
36  * percpu variables from kernel modules.  Finally, the dynamic section
37  * takes care of normal allocations.
38  *
39  * The allocator organizes chunks into lists according to free size and
40  * memcg-awareness.  To make a percpu allocation memcg-aware the __GFP_ACCOUNT
41  * flag should be passed.  All memcg-aware allocations are sharing one set
42  * of chunks and all unaccounted allocations and allocations performed
43  * by processes belonging to the root memory cgroup are using the second set.
44  *
45  * The allocator tries to allocate from the fullest chunk first. Each chunk
46  * is managed by a bitmap with metadata blocks.  The allocation map is updated
47  * on every allocation and free to reflect the current state while the boundary
48  * map is only updated on allocation.  Each metadata block contains
49  * information to help mitigate the need to iterate over large portions
50  * of the bitmap.  The reverse mapping from page to chunk is stored in
51  * the page's index.  Lastly, units are lazily backed and grow in unison.
52  *
53  * There is a unique conversion that goes on here between bytes and bits.
54  * Each bit represents a fragment of size PCPU_MIN_ALLOC_SIZE.  The chunk
55  * tracks the number of pages it is responsible for in nr_pages.  Helper
56  * functions are used to convert from between the bytes, bits, and blocks.
57  * All hints are managed in bits unless explicitly stated.
58  *
59  * To use this allocator, arch code should do the following:
60  *
61  * - define __addr_to_pcpu_ptr() and __pcpu_ptr_to_addr() to translate
62  *   regular address to percpu pointer and back if they need to be
63  *   different from the default
64  *
65  * - use pcpu_setup_first_chunk() during percpu area initialization to
66  *   setup the first chunk containing the kernel static percpu area
67  */
68 
69 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
70 
71 #include <linux/bitmap.h>
72 #include <linux/cpumask.h>
73 #include <linux/memblock.h>
74 #include <linux/err.h>
75 #include <linux/lcm.h>
76 #include <linux/list.h>
77 #include <linux/log2.h>
78 #include <linux/mm.h>
79 #include <linux/module.h>
80 #include <linux/mutex.h>
81 #include <linux/percpu.h>
82 #include <linux/pfn.h>
83 #include <linux/slab.h>
84 #include <linux/spinlock.h>
85 #include <linux/vmalloc.h>
86 #include <linux/workqueue.h>
87 #include <linux/kmemleak.h>
88 #include <linux/sched.h>
89 #include <linux/sched/mm.h>
90 #include <linux/memcontrol.h>
91 
92 #include <asm/cacheflush.h>
93 #include <asm/sections.h>
94 #include <asm/tlbflush.h>
95 #include <asm/io.h>
96 
97 #define CREATE_TRACE_POINTS
98 #include <trace/events/percpu.h>
99 
100 #include "percpu-internal.h"
101 
102 /*
103  * The slots are sorted by the size of the biggest continuous free area.
104  * 1-31 bytes share the same slot.
105  */
106 #define PCPU_SLOT_BASE_SHIFT		5
107 /* chunks in slots below this are subject to being sidelined on failed alloc */
108 #define PCPU_SLOT_FAIL_THRESHOLD	3
109 
110 #define PCPU_EMPTY_POP_PAGES_LOW	2
111 #define PCPU_EMPTY_POP_PAGES_HIGH	4
112 
113 #ifdef CONFIG_SMP
114 /* default addr <-> pcpu_ptr mapping, override in asm/percpu.h if necessary */
115 #ifndef __addr_to_pcpu_ptr
116 #define __addr_to_pcpu_ptr(addr)					\
117 	(void __percpu *)((unsigned long)(addr) -			\
118 			  (unsigned long)pcpu_base_addr	+		\
119 			  (unsigned long)__per_cpu_start)
120 #endif
121 #ifndef __pcpu_ptr_to_addr
122 #define __pcpu_ptr_to_addr(ptr)						\
123 	(void __force *)((unsigned long)(ptr) +				\
124 			 (unsigned long)pcpu_base_addr -		\
125 			 (unsigned long)__per_cpu_start)
126 #endif
127 #else	/* CONFIG_SMP */
128 /* on UP, it's always identity mapped */
129 #define __addr_to_pcpu_ptr(addr)	(void __percpu *)(addr)
130 #define __pcpu_ptr_to_addr(ptr)		(void __force *)(ptr)
131 #endif	/* CONFIG_SMP */
132 
133 static int pcpu_unit_pages __ro_after_init;
134 static int pcpu_unit_size __ro_after_init;
135 static int pcpu_nr_units __ro_after_init;
136 static int pcpu_atom_size __ro_after_init;
137 int pcpu_nr_slots __ro_after_init;
138 static int pcpu_free_slot __ro_after_init;
139 int pcpu_sidelined_slot __ro_after_init;
140 int pcpu_to_depopulate_slot __ro_after_init;
141 static size_t pcpu_chunk_struct_size __ro_after_init;
142 
143 /* cpus with the lowest and highest unit addresses */
144 static unsigned int pcpu_low_unit_cpu __ro_after_init;
145 static unsigned int pcpu_high_unit_cpu __ro_after_init;
146 
147 /* the address of the first chunk which starts with the kernel static area */
148 void *pcpu_base_addr __ro_after_init;
149 
150 static const int *pcpu_unit_map __ro_after_init;		/* cpu -> unit */
151 const unsigned long *pcpu_unit_offsets __ro_after_init;	/* cpu -> unit offset */
152 
153 /* group information, used for vm allocation */
154 static int pcpu_nr_groups __ro_after_init;
155 static const unsigned long *pcpu_group_offsets __ro_after_init;
156 static const size_t *pcpu_group_sizes __ro_after_init;
157 
158 /*
159  * The first chunk which always exists.  Note that unlike other
160  * chunks, this one can be allocated and mapped in several different
161  * ways and thus often doesn't live in the vmalloc area.
162  */
163 struct pcpu_chunk *pcpu_first_chunk __ro_after_init;
164 
165 /*
166  * Optional reserved chunk.  This chunk reserves part of the first
167  * chunk and serves it for reserved allocations.  When the reserved
168  * region doesn't exist, the following variable is NULL.
169  */
170 struct pcpu_chunk *pcpu_reserved_chunk __ro_after_init;
171 
172 DEFINE_SPINLOCK(pcpu_lock);	/* all internal data structures */
173 static DEFINE_MUTEX(pcpu_alloc_mutex);	/* chunk create/destroy, [de]pop, map ext */
174 
175 struct list_head *pcpu_chunk_lists __ro_after_init; /* chunk list slots */
176 
177 /* chunks which need their map areas extended, protected by pcpu_lock */
178 static LIST_HEAD(pcpu_map_extend_chunks);
179 
180 /*
181  * The number of empty populated pages, protected by pcpu_lock.
182  * The reserved chunk doesn't contribute to the count.
183  */
184 int pcpu_nr_empty_pop_pages;
185 
186 /*
187  * The number of populated pages in use by the allocator, protected by
188  * pcpu_lock.  This number is kept per a unit per chunk (i.e. when a page gets
189  * allocated/deallocated, it is allocated/deallocated in all units of a chunk
190  * and increments/decrements this count by 1).
191  */
192 static unsigned long pcpu_nr_populated;
193 
194 /*
195  * Balance work is used to populate or destroy chunks asynchronously.  We
196  * try to keep the number of populated free pages between
197  * PCPU_EMPTY_POP_PAGES_LOW and HIGH for atomic allocations and at most one
198  * empty chunk.
199  */
200 static void pcpu_balance_workfn(struct work_struct *work);
201 static DECLARE_WORK(pcpu_balance_work, pcpu_balance_workfn);
202 static bool pcpu_async_enabled __read_mostly;
203 static bool pcpu_atomic_alloc_failed;
204 
pcpu_schedule_balance_work(void)205 static void pcpu_schedule_balance_work(void)
206 {
207 	if (pcpu_async_enabled)
208 		schedule_work(&pcpu_balance_work);
209 }
210 
211 /**
212  * pcpu_addr_in_chunk - check if the address is served from this chunk
213  * @chunk: chunk of interest
214  * @addr: percpu address
215  *
216  * RETURNS:
217  * True if the address is served from this chunk.
218  */
pcpu_addr_in_chunk(struct pcpu_chunk * chunk,void * addr)219 static bool pcpu_addr_in_chunk(struct pcpu_chunk *chunk, void *addr)
220 {
221 	void *start_addr, *end_addr;
222 
223 	if (!chunk)
224 		return false;
225 
226 	start_addr = chunk->base_addr + chunk->start_offset;
227 	end_addr = chunk->base_addr + chunk->nr_pages * PAGE_SIZE -
228 		   chunk->end_offset;
229 
230 	return addr >= start_addr && addr < end_addr;
231 }
232 
__pcpu_size_to_slot(int size)233 static int __pcpu_size_to_slot(int size)
234 {
235 	int highbit = fls(size);	/* size is in bytes */
236 	return max(highbit - PCPU_SLOT_BASE_SHIFT + 2, 1);
237 }
238 
pcpu_size_to_slot(int size)239 static int pcpu_size_to_slot(int size)
240 {
241 	if (size == pcpu_unit_size)
242 		return pcpu_free_slot;
243 	return __pcpu_size_to_slot(size);
244 }
245 
pcpu_chunk_slot(const struct pcpu_chunk * chunk)246 static int pcpu_chunk_slot(const struct pcpu_chunk *chunk)
247 {
248 	const struct pcpu_block_md *chunk_md = &chunk->chunk_md;
249 
250 	if (chunk->free_bytes < PCPU_MIN_ALLOC_SIZE ||
251 	    chunk_md->contig_hint == 0)
252 		return 0;
253 
254 	return pcpu_size_to_slot(chunk_md->contig_hint * PCPU_MIN_ALLOC_SIZE);
255 }
256 
257 /* set the pointer to a chunk in a page struct */
pcpu_set_page_chunk(struct page * page,struct pcpu_chunk * pcpu)258 static void pcpu_set_page_chunk(struct page *page, struct pcpu_chunk *pcpu)
259 {
260 	page->index = (unsigned long)pcpu;
261 }
262 
263 /* obtain pointer to a chunk from a page struct */
pcpu_get_page_chunk(struct page * page)264 static struct pcpu_chunk *pcpu_get_page_chunk(struct page *page)
265 {
266 	return (struct pcpu_chunk *)page->index;
267 }
268 
pcpu_page_idx(unsigned int cpu,int page_idx)269 static int __maybe_unused pcpu_page_idx(unsigned int cpu, int page_idx)
270 {
271 	return pcpu_unit_map[cpu] * pcpu_unit_pages + page_idx;
272 }
273 
pcpu_unit_page_offset(unsigned int cpu,int page_idx)274 static unsigned long pcpu_unit_page_offset(unsigned int cpu, int page_idx)
275 {
276 	return pcpu_unit_offsets[cpu] + (page_idx << PAGE_SHIFT);
277 }
278 
pcpu_chunk_addr(struct pcpu_chunk * chunk,unsigned int cpu,int page_idx)279 static unsigned long pcpu_chunk_addr(struct pcpu_chunk *chunk,
280 				     unsigned int cpu, int page_idx)
281 {
282 	return (unsigned long)chunk->base_addr +
283 	       pcpu_unit_page_offset(cpu, page_idx);
284 }
285 
286 /*
287  * The following are helper functions to help access bitmaps and convert
288  * between bitmap offsets to address offsets.
289  */
pcpu_index_alloc_map(struct pcpu_chunk * chunk,int index)290 static unsigned long *pcpu_index_alloc_map(struct pcpu_chunk *chunk, int index)
291 {
292 	return chunk->alloc_map +
293 	       (index * PCPU_BITMAP_BLOCK_BITS / BITS_PER_LONG);
294 }
295 
pcpu_off_to_block_index(int off)296 static unsigned long pcpu_off_to_block_index(int off)
297 {
298 	return off / PCPU_BITMAP_BLOCK_BITS;
299 }
300 
pcpu_off_to_block_off(int off)301 static unsigned long pcpu_off_to_block_off(int off)
302 {
303 	return off & (PCPU_BITMAP_BLOCK_BITS - 1);
304 }
305 
pcpu_block_off_to_off(int index,int off)306 static unsigned long pcpu_block_off_to_off(int index, int off)
307 {
308 	return index * PCPU_BITMAP_BLOCK_BITS + off;
309 }
310 
311 /**
312  * pcpu_check_block_hint - check against the contig hint
313  * @block: block of interest
314  * @bits: size of allocation
315  * @align: alignment of area (max PAGE_SIZE)
316  *
317  * Check to see if the allocation can fit in the block's contig hint.
318  * Note, a chunk uses the same hints as a block so this can also check against
319  * the chunk's contig hint.
320  */
pcpu_check_block_hint(struct pcpu_block_md * block,int bits,size_t align)321 static bool pcpu_check_block_hint(struct pcpu_block_md *block, int bits,
322 				  size_t align)
323 {
324 	int bit_off = ALIGN(block->contig_hint_start, align) -
325 		block->contig_hint_start;
326 
327 	return bit_off + bits <= block->contig_hint;
328 }
329 
330 /*
331  * pcpu_next_hint - determine which hint to use
332  * @block: block of interest
333  * @alloc_bits: size of allocation
334  *
335  * This determines if we should scan based on the scan_hint or first_free.
336  * In general, we want to scan from first_free to fulfill allocations by
337  * first fit.  However, if we know a scan_hint at position scan_hint_start
338  * cannot fulfill an allocation, we can begin scanning from there knowing
339  * the contig_hint will be our fallback.
340  */
pcpu_next_hint(struct pcpu_block_md * block,int alloc_bits)341 static int pcpu_next_hint(struct pcpu_block_md *block, int alloc_bits)
342 {
343 	/*
344 	 * The three conditions below determine if we can skip past the
345 	 * scan_hint.  First, does the scan hint exist.  Second, is the
346 	 * contig_hint after the scan_hint (possibly not true iff
347 	 * contig_hint == scan_hint).  Third, is the allocation request
348 	 * larger than the scan_hint.
349 	 */
350 	if (block->scan_hint &&
351 	    block->contig_hint_start > block->scan_hint_start &&
352 	    alloc_bits > block->scan_hint)
353 		return block->scan_hint_start + block->scan_hint;
354 
355 	return block->first_free;
356 }
357 
358 /**
359  * pcpu_next_md_free_region - finds the next hint free area
360  * @chunk: chunk of interest
361  * @bit_off: chunk offset
362  * @bits: size of free area
363  *
364  * Helper function for pcpu_for_each_md_free_region.  It checks
365  * block->contig_hint and performs aggregation across blocks to find the
366  * next hint.  It modifies bit_off and bits in-place to be consumed in the
367  * loop.
368  */
pcpu_next_md_free_region(struct pcpu_chunk * chunk,int * bit_off,int * bits)369 static void pcpu_next_md_free_region(struct pcpu_chunk *chunk, int *bit_off,
370 				     int *bits)
371 {
372 	int i = pcpu_off_to_block_index(*bit_off);
373 	int block_off = pcpu_off_to_block_off(*bit_off);
374 	struct pcpu_block_md *block;
375 
376 	*bits = 0;
377 	for (block = chunk->md_blocks + i; i < pcpu_chunk_nr_blocks(chunk);
378 	     block++, i++) {
379 		/* handles contig area across blocks */
380 		if (*bits) {
381 			*bits += block->left_free;
382 			if (block->left_free == PCPU_BITMAP_BLOCK_BITS)
383 				continue;
384 			return;
385 		}
386 
387 		/*
388 		 * This checks three things.  First is there a contig_hint to
389 		 * check.  Second, have we checked this hint before by
390 		 * comparing the block_off.  Third, is this the same as the
391 		 * right contig hint.  In the last case, it spills over into
392 		 * the next block and should be handled by the contig area
393 		 * across blocks code.
394 		 */
395 		*bits = block->contig_hint;
396 		if (*bits && block->contig_hint_start >= block_off &&
397 		    *bits + block->contig_hint_start < PCPU_BITMAP_BLOCK_BITS) {
398 			*bit_off = pcpu_block_off_to_off(i,
399 					block->contig_hint_start);
400 			return;
401 		}
402 		/* reset to satisfy the second predicate above */
403 		block_off = 0;
404 
405 		*bits = block->right_free;
406 		*bit_off = (i + 1) * PCPU_BITMAP_BLOCK_BITS - block->right_free;
407 	}
408 }
409 
410 /**
411  * pcpu_next_fit_region - finds fit areas for a given allocation request
412  * @chunk: chunk of interest
413  * @alloc_bits: size of allocation
414  * @align: alignment of area (max PAGE_SIZE)
415  * @bit_off: chunk offset
416  * @bits: size of free area
417  *
418  * Finds the next free region that is viable for use with a given size and
419  * alignment.  This only returns if there is a valid area to be used for this
420  * allocation.  block->first_free is returned if the allocation request fits
421  * within the block to see if the request can be fulfilled prior to the contig
422  * hint.
423  */
pcpu_next_fit_region(struct pcpu_chunk * chunk,int alloc_bits,int align,int * bit_off,int * bits)424 static void pcpu_next_fit_region(struct pcpu_chunk *chunk, int alloc_bits,
425 				 int align, int *bit_off, int *bits)
426 {
427 	int i = pcpu_off_to_block_index(*bit_off);
428 	int block_off = pcpu_off_to_block_off(*bit_off);
429 	struct pcpu_block_md *block;
430 
431 	*bits = 0;
432 	for (block = chunk->md_blocks + i; i < pcpu_chunk_nr_blocks(chunk);
433 	     block++, i++) {
434 		/* handles contig area across blocks */
435 		if (*bits) {
436 			*bits += block->left_free;
437 			if (*bits >= alloc_bits)
438 				return;
439 			if (block->left_free == PCPU_BITMAP_BLOCK_BITS)
440 				continue;
441 		}
442 
443 		/* check block->contig_hint */
444 		*bits = ALIGN(block->contig_hint_start, align) -
445 			block->contig_hint_start;
446 		/*
447 		 * This uses the block offset to determine if this has been
448 		 * checked in the prior iteration.
449 		 */
450 		if (block->contig_hint &&
451 		    block->contig_hint_start >= block_off &&
452 		    block->contig_hint >= *bits + alloc_bits) {
453 			int start = pcpu_next_hint(block, alloc_bits);
454 
455 			*bits += alloc_bits + block->contig_hint_start -
456 				 start;
457 			*bit_off = pcpu_block_off_to_off(i, start);
458 			return;
459 		}
460 		/* reset to satisfy the second predicate above */
461 		block_off = 0;
462 
463 		*bit_off = ALIGN(PCPU_BITMAP_BLOCK_BITS - block->right_free,
464 				 align);
465 		*bits = PCPU_BITMAP_BLOCK_BITS - *bit_off;
466 		*bit_off = pcpu_block_off_to_off(i, *bit_off);
467 		if (*bits >= alloc_bits)
468 			return;
469 	}
470 
471 	/* no valid offsets were found - fail condition */
472 	*bit_off = pcpu_chunk_map_bits(chunk);
473 }
474 
475 /*
476  * Metadata free area iterators.  These perform aggregation of free areas
477  * based on the metadata blocks and return the offset @bit_off and size in
478  * bits of the free area @bits.  pcpu_for_each_fit_region only returns when
479  * a fit is found for the allocation request.
480  */
481 #define pcpu_for_each_md_free_region(chunk, bit_off, bits)		\
482 	for (pcpu_next_md_free_region((chunk), &(bit_off), &(bits));	\
483 	     (bit_off) < pcpu_chunk_map_bits((chunk));			\
484 	     (bit_off) += (bits) + 1,					\
485 	     pcpu_next_md_free_region((chunk), &(bit_off), &(bits)))
486 
487 #define pcpu_for_each_fit_region(chunk, alloc_bits, align, bit_off, bits)     \
488 	for (pcpu_next_fit_region((chunk), (alloc_bits), (align), &(bit_off), \
489 				  &(bits));				      \
490 	     (bit_off) < pcpu_chunk_map_bits((chunk));			      \
491 	     (bit_off) += (bits),					      \
492 	     pcpu_next_fit_region((chunk), (alloc_bits), (align), &(bit_off), \
493 				  &(bits)))
494 
495 /**
496  * pcpu_mem_zalloc - allocate memory
497  * @size: bytes to allocate
498  * @gfp: allocation flags
499  *
500  * Allocate @size bytes.  If @size is smaller than PAGE_SIZE,
501  * kzalloc() is used; otherwise, the equivalent of vzalloc() is used.
502  * This is to facilitate passing through whitelisted flags.  The
503  * returned memory is always zeroed.
504  *
505  * RETURNS:
506  * Pointer to the allocated area on success, NULL on failure.
507  */
pcpu_mem_zalloc(size_t size,gfp_t gfp)508 static void *pcpu_mem_zalloc(size_t size, gfp_t gfp)
509 {
510 	if (WARN_ON_ONCE(!slab_is_available()))
511 		return NULL;
512 
513 	if (size <= PAGE_SIZE)
514 		return kzalloc(size, gfp);
515 	else
516 		return __vmalloc(size, gfp | __GFP_ZERO);
517 }
518 
519 /**
520  * pcpu_mem_free - free memory
521  * @ptr: memory to free
522  *
523  * Free @ptr.  @ptr should have been allocated using pcpu_mem_zalloc().
524  */
pcpu_mem_free(void * ptr)525 static void pcpu_mem_free(void *ptr)
526 {
527 	kvfree(ptr);
528 }
529 
__pcpu_chunk_move(struct pcpu_chunk * chunk,int slot,bool move_front)530 static void __pcpu_chunk_move(struct pcpu_chunk *chunk, int slot,
531 			      bool move_front)
532 {
533 	if (chunk != pcpu_reserved_chunk) {
534 		if (move_front)
535 			list_move(&chunk->list, &pcpu_chunk_lists[slot]);
536 		else
537 			list_move_tail(&chunk->list, &pcpu_chunk_lists[slot]);
538 	}
539 }
540 
pcpu_chunk_move(struct pcpu_chunk * chunk,int slot)541 static void pcpu_chunk_move(struct pcpu_chunk *chunk, int slot)
542 {
543 	__pcpu_chunk_move(chunk, slot, true);
544 }
545 
546 /**
547  * pcpu_chunk_relocate - put chunk in the appropriate chunk slot
548  * @chunk: chunk of interest
549  * @oslot: the previous slot it was on
550  *
551  * This function is called after an allocation or free changed @chunk.
552  * New slot according to the changed state is determined and @chunk is
553  * moved to the slot.  Note that the reserved chunk is never put on
554  * chunk slots.
555  *
556  * CONTEXT:
557  * pcpu_lock.
558  */
pcpu_chunk_relocate(struct pcpu_chunk * chunk,int oslot)559 static void pcpu_chunk_relocate(struct pcpu_chunk *chunk, int oslot)
560 {
561 	int nslot = pcpu_chunk_slot(chunk);
562 
563 	/* leave isolated chunks in-place */
564 	if (chunk->isolated)
565 		return;
566 
567 	if (oslot != nslot)
568 		__pcpu_chunk_move(chunk, nslot, oslot < nslot);
569 }
570 
pcpu_isolate_chunk(struct pcpu_chunk * chunk)571 static void pcpu_isolate_chunk(struct pcpu_chunk *chunk)
572 {
573 	lockdep_assert_held(&pcpu_lock);
574 
575 	if (!chunk->isolated) {
576 		chunk->isolated = true;
577 		pcpu_nr_empty_pop_pages -= chunk->nr_empty_pop_pages;
578 	}
579 	list_move(&chunk->list, &pcpu_chunk_lists[pcpu_to_depopulate_slot]);
580 }
581 
pcpu_reintegrate_chunk(struct pcpu_chunk * chunk)582 static void pcpu_reintegrate_chunk(struct pcpu_chunk *chunk)
583 {
584 	lockdep_assert_held(&pcpu_lock);
585 
586 	if (chunk->isolated) {
587 		chunk->isolated = false;
588 		pcpu_nr_empty_pop_pages += chunk->nr_empty_pop_pages;
589 		pcpu_chunk_relocate(chunk, -1);
590 	}
591 }
592 
593 /*
594  * pcpu_update_empty_pages - update empty page counters
595  * @chunk: chunk of interest
596  * @nr: nr of empty pages
597  *
598  * This is used to keep track of the empty pages now based on the premise
599  * a md_block covers a page.  The hint update functions recognize if a block
600  * is made full or broken to calculate deltas for keeping track of free pages.
601  */
pcpu_update_empty_pages(struct pcpu_chunk * chunk,int nr)602 static inline void pcpu_update_empty_pages(struct pcpu_chunk *chunk, int nr)
603 {
604 	chunk->nr_empty_pop_pages += nr;
605 	if (chunk != pcpu_reserved_chunk && !chunk->isolated)
606 		pcpu_nr_empty_pop_pages += nr;
607 }
608 
609 /*
610  * pcpu_region_overlap - determines if two regions overlap
611  * @a: start of first region, inclusive
612  * @b: end of first region, exclusive
613  * @x: start of second region, inclusive
614  * @y: end of second region, exclusive
615  *
616  * This is used to determine if the hint region [a, b) overlaps with the
617  * allocated region [x, y).
618  */
pcpu_region_overlap(int a,int b,int x,int y)619 static inline bool pcpu_region_overlap(int a, int b, int x, int y)
620 {
621 	return (a < y) && (x < b);
622 }
623 
624 /**
625  * pcpu_block_update - updates a block given a free area
626  * @block: block of interest
627  * @start: start offset in block
628  * @end: end offset in block
629  *
630  * Updates a block given a known free area.  The region [start, end) is
631  * expected to be the entirety of the free area within a block.  Chooses
632  * the best starting offset if the contig hints are equal.
633  */
pcpu_block_update(struct pcpu_block_md * block,int start,int end)634 static void pcpu_block_update(struct pcpu_block_md *block, int start, int end)
635 {
636 	int contig = end - start;
637 
638 	block->first_free = min(block->first_free, start);
639 	if (start == 0)
640 		block->left_free = contig;
641 
642 	if (end == block->nr_bits)
643 		block->right_free = contig;
644 
645 	if (contig > block->contig_hint) {
646 		/* promote the old contig_hint to be the new scan_hint */
647 		if (start > block->contig_hint_start) {
648 			if (block->contig_hint > block->scan_hint) {
649 				block->scan_hint_start =
650 					block->contig_hint_start;
651 				block->scan_hint = block->contig_hint;
652 			} else if (start < block->scan_hint_start) {
653 				/*
654 				 * The old contig_hint == scan_hint.  But, the
655 				 * new contig is larger so hold the invariant
656 				 * scan_hint_start < contig_hint_start.
657 				 */
658 				block->scan_hint = 0;
659 			}
660 		} else {
661 			block->scan_hint = 0;
662 		}
663 		block->contig_hint_start = start;
664 		block->contig_hint = contig;
665 	} else if (contig == block->contig_hint) {
666 		if (block->contig_hint_start &&
667 		    (!start ||
668 		     __ffs(start) > __ffs(block->contig_hint_start))) {
669 			/* start has a better alignment so use it */
670 			block->contig_hint_start = start;
671 			if (start < block->scan_hint_start &&
672 			    block->contig_hint > block->scan_hint)
673 				block->scan_hint = 0;
674 		} else if (start > block->scan_hint_start ||
675 			   block->contig_hint > block->scan_hint) {
676 			/*
677 			 * Knowing contig == contig_hint, update the scan_hint
678 			 * if it is farther than or larger than the current
679 			 * scan_hint.
680 			 */
681 			block->scan_hint_start = start;
682 			block->scan_hint = contig;
683 		}
684 	} else {
685 		/*
686 		 * The region is smaller than the contig_hint.  So only update
687 		 * the scan_hint if it is larger than or equal and farther than
688 		 * the current scan_hint.
689 		 */
690 		if ((start < block->contig_hint_start &&
691 		     (contig > block->scan_hint ||
692 		      (contig == block->scan_hint &&
693 		       start > block->scan_hint_start)))) {
694 			block->scan_hint_start = start;
695 			block->scan_hint = contig;
696 		}
697 	}
698 }
699 
700 /*
701  * pcpu_block_update_scan - update a block given a free area from a scan
702  * @chunk: chunk of interest
703  * @bit_off: chunk offset
704  * @bits: size of free area
705  *
706  * Finding the final allocation spot first goes through pcpu_find_block_fit()
707  * to find a block that can hold the allocation and then pcpu_alloc_area()
708  * where a scan is used.  When allocations require specific alignments,
709  * we can inadvertently create holes which will not be seen in the alloc
710  * or free paths.
711  *
712  * This takes a given free area hole and updates a block as it may change the
713  * scan_hint.  We need to scan backwards to ensure we don't miss free bits
714  * from alignment.
715  */
pcpu_block_update_scan(struct pcpu_chunk * chunk,int bit_off,int bits)716 static void pcpu_block_update_scan(struct pcpu_chunk *chunk, int bit_off,
717 				   int bits)
718 {
719 	int s_off = pcpu_off_to_block_off(bit_off);
720 	int e_off = s_off + bits;
721 	int s_index, l_bit;
722 	struct pcpu_block_md *block;
723 
724 	if (e_off > PCPU_BITMAP_BLOCK_BITS)
725 		return;
726 
727 	s_index = pcpu_off_to_block_index(bit_off);
728 	block = chunk->md_blocks + s_index;
729 
730 	/* scan backwards in case of alignment skipping free bits */
731 	l_bit = find_last_bit(pcpu_index_alloc_map(chunk, s_index), s_off);
732 	s_off = (s_off == l_bit) ? 0 : l_bit + 1;
733 
734 	pcpu_block_update(block, s_off, e_off);
735 }
736 
737 /**
738  * pcpu_chunk_refresh_hint - updates metadata about a chunk
739  * @chunk: chunk of interest
740  * @full_scan: if we should scan from the beginning
741  *
742  * Iterates over the metadata blocks to find the largest contig area.
743  * A full scan can be avoided on the allocation path as this is triggered
744  * if we broke the contig_hint.  In doing so, the scan_hint will be before
745  * the contig_hint or after if the scan_hint == contig_hint.  This cannot
746  * be prevented on freeing as we want to find the largest area possibly
747  * spanning blocks.
748  */
pcpu_chunk_refresh_hint(struct pcpu_chunk * chunk,bool full_scan)749 static void pcpu_chunk_refresh_hint(struct pcpu_chunk *chunk, bool full_scan)
750 {
751 	struct pcpu_block_md *chunk_md = &chunk->chunk_md;
752 	int bit_off, bits;
753 
754 	/* promote scan_hint to contig_hint */
755 	if (!full_scan && chunk_md->scan_hint) {
756 		bit_off = chunk_md->scan_hint_start + chunk_md->scan_hint;
757 		chunk_md->contig_hint_start = chunk_md->scan_hint_start;
758 		chunk_md->contig_hint = chunk_md->scan_hint;
759 		chunk_md->scan_hint = 0;
760 	} else {
761 		bit_off = chunk_md->first_free;
762 		chunk_md->contig_hint = 0;
763 	}
764 
765 	bits = 0;
766 	pcpu_for_each_md_free_region(chunk, bit_off, bits)
767 		pcpu_block_update(chunk_md, bit_off, bit_off + bits);
768 }
769 
770 /**
771  * pcpu_block_refresh_hint
772  * @chunk: chunk of interest
773  * @index: index of the metadata block
774  *
775  * Scans over the block beginning at first_free and updates the block
776  * metadata accordingly.
777  */
pcpu_block_refresh_hint(struct pcpu_chunk * chunk,int index)778 static void pcpu_block_refresh_hint(struct pcpu_chunk *chunk, int index)
779 {
780 	struct pcpu_block_md *block = chunk->md_blocks + index;
781 	unsigned long *alloc_map = pcpu_index_alloc_map(chunk, index);
782 	unsigned int rs, re, start;	/* region start, region end */
783 
784 	/* promote scan_hint to contig_hint */
785 	if (block->scan_hint) {
786 		start = block->scan_hint_start + block->scan_hint;
787 		block->contig_hint_start = block->scan_hint_start;
788 		block->contig_hint = block->scan_hint;
789 		block->scan_hint = 0;
790 	} else {
791 		start = block->first_free;
792 		block->contig_hint = 0;
793 	}
794 
795 	block->right_free = 0;
796 
797 	/* iterate over free areas and update the contig hints */
798 	bitmap_for_each_clear_region(alloc_map, rs, re, start,
799 				     PCPU_BITMAP_BLOCK_BITS)
800 		pcpu_block_update(block, rs, re);
801 }
802 
803 /**
804  * pcpu_block_update_hint_alloc - update hint on allocation path
805  * @chunk: chunk of interest
806  * @bit_off: chunk offset
807  * @bits: size of request
808  *
809  * Updates metadata for the allocation path.  The metadata only has to be
810  * refreshed by a full scan iff the chunk's contig hint is broken.  Block level
811  * scans are required if the block's contig hint is broken.
812  */
pcpu_block_update_hint_alloc(struct pcpu_chunk * chunk,int bit_off,int bits)813 static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off,
814 					 int bits)
815 {
816 	struct pcpu_block_md *chunk_md = &chunk->chunk_md;
817 	int nr_empty_pages = 0;
818 	struct pcpu_block_md *s_block, *e_block, *block;
819 	int s_index, e_index;	/* block indexes of the freed allocation */
820 	int s_off, e_off;	/* block offsets of the freed allocation */
821 
822 	/*
823 	 * Calculate per block offsets.
824 	 * The calculation uses an inclusive range, but the resulting offsets
825 	 * are [start, end).  e_index always points to the last block in the
826 	 * range.
827 	 */
828 	s_index = pcpu_off_to_block_index(bit_off);
829 	e_index = pcpu_off_to_block_index(bit_off + bits - 1);
830 	s_off = pcpu_off_to_block_off(bit_off);
831 	e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;
832 
833 	s_block = chunk->md_blocks + s_index;
834 	e_block = chunk->md_blocks + e_index;
835 
836 	/*
837 	 * Update s_block.
838 	 * block->first_free must be updated if the allocation takes its place.
839 	 * If the allocation breaks the contig_hint, a scan is required to
840 	 * restore this hint.
841 	 */
842 	if (s_block->contig_hint == PCPU_BITMAP_BLOCK_BITS)
843 		nr_empty_pages++;
844 
845 	if (s_off == s_block->first_free)
846 		s_block->first_free = find_next_zero_bit(
847 					pcpu_index_alloc_map(chunk, s_index),
848 					PCPU_BITMAP_BLOCK_BITS,
849 					s_off + bits);
850 
851 	if (pcpu_region_overlap(s_block->scan_hint_start,
852 				s_block->scan_hint_start + s_block->scan_hint,
853 				s_off,
854 				s_off + bits))
855 		s_block->scan_hint = 0;
856 
857 	if (pcpu_region_overlap(s_block->contig_hint_start,
858 				s_block->contig_hint_start +
859 				s_block->contig_hint,
860 				s_off,
861 				s_off + bits)) {
862 		/* block contig hint is broken - scan to fix it */
863 		if (!s_off)
864 			s_block->left_free = 0;
865 		pcpu_block_refresh_hint(chunk, s_index);
866 	} else {
867 		/* update left and right contig manually */
868 		s_block->left_free = min(s_block->left_free, s_off);
869 		if (s_index == e_index)
870 			s_block->right_free = min_t(int, s_block->right_free,
871 					PCPU_BITMAP_BLOCK_BITS - e_off);
872 		else
873 			s_block->right_free = 0;
874 	}
875 
876 	/*
877 	 * Update e_block.
878 	 */
879 	if (s_index != e_index) {
880 		if (e_block->contig_hint == PCPU_BITMAP_BLOCK_BITS)
881 			nr_empty_pages++;
882 
883 		/*
884 		 * When the allocation is across blocks, the end is along
885 		 * the left part of the e_block.
886 		 */
887 		e_block->first_free = find_next_zero_bit(
888 				pcpu_index_alloc_map(chunk, e_index),
889 				PCPU_BITMAP_BLOCK_BITS, e_off);
890 
891 		if (e_off == PCPU_BITMAP_BLOCK_BITS) {
892 			/* reset the block */
893 			e_block++;
894 		} else {
895 			if (e_off > e_block->scan_hint_start)
896 				e_block->scan_hint = 0;
897 
898 			e_block->left_free = 0;
899 			if (e_off > e_block->contig_hint_start) {
900 				/* contig hint is broken - scan to fix it */
901 				pcpu_block_refresh_hint(chunk, e_index);
902 			} else {
903 				e_block->right_free =
904 					min_t(int, e_block->right_free,
905 					      PCPU_BITMAP_BLOCK_BITS - e_off);
906 			}
907 		}
908 
909 		/* update in-between md_blocks */
910 		nr_empty_pages += (e_index - s_index - 1);
911 		for (block = s_block + 1; block < e_block; block++) {
912 			block->scan_hint = 0;
913 			block->contig_hint = 0;
914 			block->left_free = 0;
915 			block->right_free = 0;
916 		}
917 	}
918 
919 	if (nr_empty_pages)
920 		pcpu_update_empty_pages(chunk, -nr_empty_pages);
921 
922 	if (pcpu_region_overlap(chunk_md->scan_hint_start,
923 				chunk_md->scan_hint_start +
924 				chunk_md->scan_hint,
925 				bit_off,
926 				bit_off + bits))
927 		chunk_md->scan_hint = 0;
928 
929 	/*
930 	 * The only time a full chunk scan is required is if the chunk
931 	 * contig hint is broken.  Otherwise, it means a smaller space
932 	 * was used and therefore the chunk contig hint is still correct.
933 	 */
934 	if (pcpu_region_overlap(chunk_md->contig_hint_start,
935 				chunk_md->contig_hint_start +
936 				chunk_md->contig_hint,
937 				bit_off,
938 				bit_off + bits))
939 		pcpu_chunk_refresh_hint(chunk, false);
940 }
941 
942 /**
943  * pcpu_block_update_hint_free - updates the block hints on the free path
944  * @chunk: chunk of interest
945  * @bit_off: chunk offset
946  * @bits: size of request
947  *
948  * Updates metadata for the allocation path.  This avoids a blind block
949  * refresh by making use of the block contig hints.  If this fails, it scans
950  * forward and backward to determine the extent of the free area.  This is
951  * capped at the boundary of blocks.
952  *
953  * A chunk update is triggered if a page becomes free, a block becomes free,
954  * or the free spans across blocks.  This tradeoff is to minimize iterating
955  * over the block metadata to update chunk_md->contig_hint.
956  * chunk_md->contig_hint may be off by up to a page, but it will never be more
957  * than the available space.  If the contig hint is contained in one block, it
958  * will be accurate.
959  */
pcpu_block_update_hint_free(struct pcpu_chunk * chunk,int bit_off,int bits)960 static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off,
961 					int bits)
962 {
963 	int nr_empty_pages = 0;
964 	struct pcpu_block_md *s_block, *e_block, *block;
965 	int s_index, e_index;	/* block indexes of the freed allocation */
966 	int s_off, e_off;	/* block offsets of the freed allocation */
967 	int start, end;		/* start and end of the whole free area */
968 
969 	/*
970 	 * Calculate per block offsets.
971 	 * The calculation uses an inclusive range, but the resulting offsets
972 	 * are [start, end).  e_index always points to the last block in the
973 	 * range.
974 	 */
975 	s_index = pcpu_off_to_block_index(bit_off);
976 	e_index = pcpu_off_to_block_index(bit_off + bits - 1);
977 	s_off = pcpu_off_to_block_off(bit_off);
978 	e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;
979 
980 	s_block = chunk->md_blocks + s_index;
981 	e_block = chunk->md_blocks + e_index;
982 
983 	/*
984 	 * Check if the freed area aligns with the block->contig_hint.
985 	 * If it does, then the scan to find the beginning/end of the
986 	 * larger free area can be avoided.
987 	 *
988 	 * start and end refer to beginning and end of the free area
989 	 * within each their respective blocks.  This is not necessarily
990 	 * the entire free area as it may span blocks past the beginning
991 	 * or end of the block.
992 	 */
993 	start = s_off;
994 	if (s_off == s_block->contig_hint + s_block->contig_hint_start) {
995 		start = s_block->contig_hint_start;
996 	} else {
997 		/*
998 		 * Scan backwards to find the extent of the free area.
999 		 * find_last_bit returns the starting bit, so if the start bit
1000 		 * is returned, that means there was no last bit and the
1001 		 * remainder of the chunk is free.
1002 		 */
1003 		int l_bit = find_last_bit(pcpu_index_alloc_map(chunk, s_index),
1004 					  start);
1005 		start = (start == l_bit) ? 0 : l_bit + 1;
1006 	}
1007 
1008 	end = e_off;
1009 	if (e_off == e_block->contig_hint_start)
1010 		end = e_block->contig_hint_start + e_block->contig_hint;
1011 	else
1012 		end = find_next_bit(pcpu_index_alloc_map(chunk, e_index),
1013 				    PCPU_BITMAP_BLOCK_BITS, end);
1014 
1015 	/* update s_block */
1016 	e_off = (s_index == e_index) ? end : PCPU_BITMAP_BLOCK_BITS;
1017 	if (!start && e_off == PCPU_BITMAP_BLOCK_BITS)
1018 		nr_empty_pages++;
1019 	pcpu_block_update(s_block, start, e_off);
1020 
1021 	/* freeing in the same block */
1022 	if (s_index != e_index) {
1023 		/* update e_block */
1024 		if (end == PCPU_BITMAP_BLOCK_BITS)
1025 			nr_empty_pages++;
1026 		pcpu_block_update(e_block, 0, end);
1027 
1028 		/* reset md_blocks in the middle */
1029 		nr_empty_pages += (e_index - s_index - 1);
1030 		for (block = s_block + 1; block < e_block; block++) {
1031 			block->first_free = 0;
1032 			block->scan_hint = 0;
1033 			block->contig_hint_start = 0;
1034 			block->contig_hint = PCPU_BITMAP_BLOCK_BITS;
1035 			block->left_free = PCPU_BITMAP_BLOCK_BITS;
1036 			block->right_free = PCPU_BITMAP_BLOCK_BITS;
1037 		}
1038 	}
1039 
1040 	if (nr_empty_pages)
1041 		pcpu_update_empty_pages(chunk, nr_empty_pages);
1042 
1043 	/*
1044 	 * Refresh chunk metadata when the free makes a block free or spans
1045 	 * across blocks.  The contig_hint may be off by up to a page, but if
1046 	 * the contig_hint is contained in a block, it will be accurate with
1047 	 * the else condition below.
1048 	 */
1049 	if (((end - start) >= PCPU_BITMAP_BLOCK_BITS) || s_index != e_index)
1050 		pcpu_chunk_refresh_hint(chunk, true);
1051 	else
1052 		pcpu_block_update(&chunk->chunk_md,
1053 				  pcpu_block_off_to_off(s_index, start),
1054 				  end);
1055 }
1056 
1057 /**
1058  * pcpu_is_populated - determines if the region is populated
1059  * @chunk: chunk of interest
1060  * @bit_off: chunk offset
1061  * @bits: size of area
1062  * @next_off: return value for the next offset to start searching
1063  *
1064  * For atomic allocations, check if the backing pages are populated.
1065  *
1066  * RETURNS:
1067  * Bool if the backing pages are populated.
1068  * next_index is to skip over unpopulated blocks in pcpu_find_block_fit.
1069  */
pcpu_is_populated(struct pcpu_chunk * chunk,int bit_off,int bits,int * next_off)1070 static bool pcpu_is_populated(struct pcpu_chunk *chunk, int bit_off, int bits,
1071 			      int *next_off)
1072 {
1073 	unsigned int page_start, page_end, rs, re;
1074 
1075 	page_start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE);
1076 	page_end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE);
1077 
1078 	rs = page_start;
1079 	bitmap_next_clear_region(chunk->populated, &rs, &re, page_end);
1080 	if (rs >= page_end)
1081 		return true;
1082 
1083 	*next_off = re * PAGE_SIZE / PCPU_MIN_ALLOC_SIZE;
1084 	return false;
1085 }
1086 
1087 /**
1088  * pcpu_find_block_fit - finds the block index to start searching
1089  * @chunk: chunk of interest
1090  * @alloc_bits: size of request in allocation units
1091  * @align: alignment of area (max PAGE_SIZE bytes)
1092  * @pop_only: use populated regions only
1093  *
1094  * Given a chunk and an allocation spec, find the offset to begin searching
1095  * for a free region.  This iterates over the bitmap metadata blocks to
1096  * find an offset that will be guaranteed to fit the requirements.  It is
1097  * not quite first fit as if the allocation does not fit in the contig hint
1098  * of a block or chunk, it is skipped.  This errs on the side of caution
1099  * to prevent excess iteration.  Poor alignment can cause the allocator to
1100  * skip over blocks and chunks that have valid free areas.
1101  *
1102  * RETURNS:
1103  * The offset in the bitmap to begin searching.
1104  * -1 if no offset is found.
1105  */
pcpu_find_block_fit(struct pcpu_chunk * chunk,int alloc_bits,size_t align,bool pop_only)1106 static int pcpu_find_block_fit(struct pcpu_chunk *chunk, int alloc_bits,
1107 			       size_t align, bool pop_only)
1108 {
1109 	struct pcpu_block_md *chunk_md = &chunk->chunk_md;
1110 	int bit_off, bits, next_off;
1111 
1112 	/*
1113 	 * This is an optimization to prevent scanning by assuming if the
1114 	 * allocation cannot fit in the global hint, there is memory pressure
1115 	 * and creating a new chunk would happen soon.
1116 	 */
1117 	if (!pcpu_check_block_hint(chunk_md, alloc_bits, align))
1118 		return -1;
1119 
1120 	bit_off = pcpu_next_hint(chunk_md, alloc_bits);
1121 	bits = 0;
1122 	pcpu_for_each_fit_region(chunk, alloc_bits, align, bit_off, bits) {
1123 		if (!pop_only || pcpu_is_populated(chunk, bit_off, bits,
1124 						   &next_off))
1125 			break;
1126 
1127 		bit_off = next_off;
1128 		bits = 0;
1129 	}
1130 
1131 	if (bit_off == pcpu_chunk_map_bits(chunk))
1132 		return -1;
1133 
1134 	return bit_off;
1135 }
1136 
1137 /*
1138  * pcpu_find_zero_area - modified from bitmap_find_next_zero_area_off()
1139  * @map: the address to base the search on
1140  * @size: the bitmap size in bits
1141  * @start: the bitnumber to start searching at
1142  * @nr: the number of zeroed bits we're looking for
1143  * @align_mask: alignment mask for zero area
1144  * @largest_off: offset of the largest area skipped
1145  * @largest_bits: size of the largest area skipped
1146  *
1147  * The @align_mask should be one less than a power of 2.
1148  *
1149  * This is a modified version of bitmap_find_next_zero_area_off() to remember
1150  * the largest area that was skipped.  This is imperfect, but in general is
1151  * good enough.  The largest remembered region is the largest failed region
1152  * seen.  This does not include anything we possibly skipped due to alignment.
1153  * pcpu_block_update_scan() does scan backwards to try and recover what was
1154  * lost to alignment.  While this can cause scanning to miss earlier possible
1155  * free areas, smaller allocations will eventually fill those holes.
1156  */
pcpu_find_zero_area(unsigned long * map,unsigned long size,unsigned long start,unsigned long nr,unsigned long align_mask,unsigned long * largest_off,unsigned long * largest_bits)1157 static unsigned long pcpu_find_zero_area(unsigned long *map,
1158 					 unsigned long size,
1159 					 unsigned long start,
1160 					 unsigned long nr,
1161 					 unsigned long align_mask,
1162 					 unsigned long *largest_off,
1163 					 unsigned long *largest_bits)
1164 {
1165 	unsigned long index, end, i, area_off, area_bits;
1166 again:
1167 	index = find_next_zero_bit(map, size, start);
1168 
1169 	/* Align allocation */
1170 	index = __ALIGN_MASK(index, align_mask);
1171 	area_off = index;
1172 
1173 	end = index + nr;
1174 	if (end > size)
1175 		return end;
1176 	i = find_next_bit(map, end, index);
1177 	if (i < end) {
1178 		area_bits = i - area_off;
1179 		/* remember largest unused area with best alignment */
1180 		if (area_bits > *largest_bits ||
1181 		    (area_bits == *largest_bits && *largest_off &&
1182 		     (!area_off || __ffs(area_off) > __ffs(*largest_off)))) {
1183 			*largest_off = area_off;
1184 			*largest_bits = area_bits;
1185 		}
1186 
1187 		start = i + 1;
1188 		goto again;
1189 	}
1190 	return index;
1191 }
1192 
1193 /**
1194  * pcpu_alloc_area - allocates an area from a pcpu_chunk
1195  * @chunk: chunk of interest
1196  * @alloc_bits: size of request in allocation units
1197  * @align: alignment of area (max PAGE_SIZE)
1198  * @start: bit_off to start searching
1199  *
1200  * This function takes in a @start offset to begin searching to fit an
1201  * allocation of @alloc_bits with alignment @align.  It needs to scan
1202  * the allocation map because if it fits within the block's contig hint,
1203  * @start will be block->first_free. This is an attempt to fill the
1204  * allocation prior to breaking the contig hint.  The allocation and
1205  * boundary maps are updated accordingly if it confirms a valid
1206  * free area.
1207  *
1208  * RETURNS:
1209  * Allocated addr offset in @chunk on success.
1210  * -1 if no matching area is found.
1211  */
pcpu_alloc_area(struct pcpu_chunk * chunk,int alloc_bits,size_t align,int start)1212 static int pcpu_alloc_area(struct pcpu_chunk *chunk, int alloc_bits,
1213 			   size_t align, int start)
1214 {
1215 	struct pcpu_block_md *chunk_md = &chunk->chunk_md;
1216 	size_t align_mask = (align) ? (align - 1) : 0;
1217 	unsigned long area_off = 0, area_bits = 0;
1218 	int bit_off, end, oslot;
1219 
1220 	lockdep_assert_held(&pcpu_lock);
1221 
1222 	oslot = pcpu_chunk_slot(chunk);
1223 
1224 	/*
1225 	 * Search to find a fit.
1226 	 */
1227 	end = min_t(int, start + alloc_bits + PCPU_BITMAP_BLOCK_BITS,
1228 		    pcpu_chunk_map_bits(chunk));
1229 	bit_off = pcpu_find_zero_area(chunk->alloc_map, end, start, alloc_bits,
1230 				      align_mask, &area_off, &area_bits);
1231 	if (bit_off >= end)
1232 		return -1;
1233 
1234 	if (area_bits)
1235 		pcpu_block_update_scan(chunk, area_off, area_bits);
1236 
1237 	/* update alloc map */
1238 	bitmap_set(chunk->alloc_map, bit_off, alloc_bits);
1239 
1240 	/* update boundary map */
1241 	set_bit(bit_off, chunk->bound_map);
1242 	bitmap_clear(chunk->bound_map, bit_off + 1, alloc_bits - 1);
1243 	set_bit(bit_off + alloc_bits, chunk->bound_map);
1244 
1245 	chunk->free_bytes -= alloc_bits * PCPU_MIN_ALLOC_SIZE;
1246 
1247 	/* update first free bit */
1248 	if (bit_off == chunk_md->first_free)
1249 		chunk_md->first_free = find_next_zero_bit(
1250 					chunk->alloc_map,
1251 					pcpu_chunk_map_bits(chunk),
1252 					bit_off + alloc_bits);
1253 
1254 	pcpu_block_update_hint_alloc(chunk, bit_off, alloc_bits);
1255 
1256 	pcpu_chunk_relocate(chunk, oslot);
1257 
1258 	return bit_off * PCPU_MIN_ALLOC_SIZE;
1259 }
1260 
1261 /**
1262  * pcpu_free_area - frees the corresponding offset
1263  * @chunk: chunk of interest
1264  * @off: addr offset into chunk
1265  *
1266  * This function determines the size of an allocation to free using
1267  * the boundary bitmap and clears the allocation map.
1268  *
1269  * RETURNS:
1270  * Number of freed bytes.
1271  */
pcpu_free_area(struct pcpu_chunk * chunk,int off)1272 static int pcpu_free_area(struct pcpu_chunk *chunk, int off)
1273 {
1274 	struct pcpu_block_md *chunk_md = &chunk->chunk_md;
1275 	int bit_off, bits, end, oslot, freed;
1276 
1277 	lockdep_assert_held(&pcpu_lock);
1278 	pcpu_stats_area_dealloc(chunk);
1279 
1280 	oslot = pcpu_chunk_slot(chunk);
1281 
1282 	bit_off = off / PCPU_MIN_ALLOC_SIZE;
1283 
1284 	/* find end index */
1285 	end = find_next_bit(chunk->bound_map, pcpu_chunk_map_bits(chunk),
1286 			    bit_off + 1);
1287 	bits = end - bit_off;
1288 	bitmap_clear(chunk->alloc_map, bit_off, bits);
1289 
1290 	freed = bits * PCPU_MIN_ALLOC_SIZE;
1291 
1292 	/* update metadata */
1293 	chunk->free_bytes += freed;
1294 
1295 	/* update first free bit */
1296 	chunk_md->first_free = min(chunk_md->first_free, bit_off);
1297 
1298 	pcpu_block_update_hint_free(chunk, bit_off, bits);
1299 
1300 	pcpu_chunk_relocate(chunk, oslot);
1301 
1302 	return freed;
1303 }
1304 
pcpu_init_md_block(struct pcpu_block_md * block,int nr_bits)1305 static void pcpu_init_md_block(struct pcpu_block_md *block, int nr_bits)
1306 {
1307 	block->scan_hint = 0;
1308 	block->contig_hint = nr_bits;
1309 	block->left_free = nr_bits;
1310 	block->right_free = nr_bits;
1311 	block->first_free = 0;
1312 	block->nr_bits = nr_bits;
1313 }
1314 
pcpu_init_md_blocks(struct pcpu_chunk * chunk)1315 static void pcpu_init_md_blocks(struct pcpu_chunk *chunk)
1316 {
1317 	struct pcpu_block_md *md_block;
1318 
1319 	/* init the chunk's block */
1320 	pcpu_init_md_block(&chunk->chunk_md, pcpu_chunk_map_bits(chunk));
1321 
1322 	for (md_block = chunk->md_blocks;
1323 	     md_block != chunk->md_blocks + pcpu_chunk_nr_blocks(chunk);
1324 	     md_block++)
1325 		pcpu_init_md_block(md_block, PCPU_BITMAP_BLOCK_BITS);
1326 }
1327 
1328 /**
1329  * pcpu_alloc_first_chunk - creates chunks that serve the first chunk
1330  * @tmp_addr: the start of the region served
1331  * @map_size: size of the region served
1332  *
1333  * This is responsible for creating the chunks that serve the first chunk.  The
1334  * base_addr is page aligned down of @tmp_addr while the region end is page
1335  * aligned up.  Offsets are kept track of to determine the region served. All
1336  * this is done to appease the bitmap allocator in avoiding partial blocks.
1337  *
1338  * RETURNS:
1339  * Chunk serving the region at @tmp_addr of @map_size.
1340  */
pcpu_alloc_first_chunk(unsigned long tmp_addr,int map_size)1341 static struct pcpu_chunk * __init pcpu_alloc_first_chunk(unsigned long tmp_addr,
1342 							 int map_size)
1343 {
1344 	struct pcpu_chunk *chunk;
1345 	unsigned long aligned_addr, lcm_align;
1346 	int start_offset, offset_bits, region_size, region_bits;
1347 	size_t alloc_size;
1348 
1349 	/* region calculations */
1350 	aligned_addr = tmp_addr & PAGE_MASK;
1351 
1352 	start_offset = tmp_addr - aligned_addr;
1353 
1354 	/*
1355 	 * Align the end of the region with the LCM of PAGE_SIZE and
1356 	 * PCPU_BITMAP_BLOCK_SIZE.  One of these constants is a multiple of
1357 	 * the other.
1358 	 */
1359 	lcm_align = lcm(PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE);
1360 	region_size = ALIGN(start_offset + map_size, lcm_align);
1361 
1362 	/* allocate chunk */
1363 	alloc_size = struct_size(chunk, populated,
1364 				 BITS_TO_LONGS(region_size >> PAGE_SHIFT));
1365 	chunk = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
1366 	if (!chunk)
1367 		panic("%s: Failed to allocate %zu bytes\n", __func__,
1368 		      alloc_size);
1369 
1370 	INIT_LIST_HEAD(&chunk->list);
1371 
1372 	chunk->base_addr = (void *)aligned_addr;
1373 	chunk->start_offset = start_offset;
1374 	chunk->end_offset = region_size - chunk->start_offset - map_size;
1375 
1376 	chunk->nr_pages = region_size >> PAGE_SHIFT;
1377 	region_bits = pcpu_chunk_map_bits(chunk);
1378 
1379 	alloc_size = BITS_TO_LONGS(region_bits) * sizeof(chunk->alloc_map[0]);
1380 	chunk->alloc_map = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
1381 	if (!chunk->alloc_map)
1382 		panic("%s: Failed to allocate %zu bytes\n", __func__,
1383 		      alloc_size);
1384 
1385 	alloc_size =
1386 		BITS_TO_LONGS(region_bits + 1) * sizeof(chunk->bound_map[0]);
1387 	chunk->bound_map = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
1388 	if (!chunk->bound_map)
1389 		panic("%s: Failed to allocate %zu bytes\n", __func__,
1390 		      alloc_size);
1391 
1392 	alloc_size = pcpu_chunk_nr_blocks(chunk) * sizeof(chunk->md_blocks[0]);
1393 	chunk->md_blocks = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
1394 	if (!chunk->md_blocks)
1395 		panic("%s: Failed to allocate %zu bytes\n", __func__,
1396 		      alloc_size);
1397 
1398 #ifdef CONFIG_MEMCG_KMEM
1399 	/* first chunk is free to use */
1400 	chunk->obj_cgroups = NULL;
1401 #endif
1402 	pcpu_init_md_blocks(chunk);
1403 
1404 	/* manage populated page bitmap */
1405 	chunk->immutable = true;
1406 	bitmap_fill(chunk->populated, chunk->nr_pages);
1407 	chunk->nr_populated = chunk->nr_pages;
1408 	chunk->nr_empty_pop_pages = chunk->nr_pages;
1409 
1410 	chunk->free_bytes = map_size;
1411 
1412 	if (chunk->start_offset) {
1413 		/* hide the beginning of the bitmap */
1414 		offset_bits = chunk->start_offset / PCPU_MIN_ALLOC_SIZE;
1415 		bitmap_set(chunk->alloc_map, 0, offset_bits);
1416 		set_bit(0, chunk->bound_map);
1417 		set_bit(offset_bits, chunk->bound_map);
1418 
1419 		chunk->chunk_md.first_free = offset_bits;
1420 
1421 		pcpu_block_update_hint_alloc(chunk, 0, offset_bits);
1422 	}
1423 
1424 	if (chunk->end_offset) {
1425 		/* hide the end of the bitmap */
1426 		offset_bits = chunk->end_offset / PCPU_MIN_ALLOC_SIZE;
1427 		bitmap_set(chunk->alloc_map,
1428 			   pcpu_chunk_map_bits(chunk) - offset_bits,
1429 			   offset_bits);
1430 		set_bit((start_offset + map_size) / PCPU_MIN_ALLOC_SIZE,
1431 			chunk->bound_map);
1432 		set_bit(region_bits, chunk->bound_map);
1433 
1434 		pcpu_block_update_hint_alloc(chunk, pcpu_chunk_map_bits(chunk)
1435 					     - offset_bits, offset_bits);
1436 	}
1437 
1438 	return chunk;
1439 }
1440 
pcpu_alloc_chunk(gfp_t gfp)1441 static struct pcpu_chunk *pcpu_alloc_chunk(gfp_t gfp)
1442 {
1443 	struct pcpu_chunk *chunk;
1444 	int region_bits;
1445 
1446 	chunk = pcpu_mem_zalloc(pcpu_chunk_struct_size, gfp);
1447 	if (!chunk)
1448 		return NULL;
1449 
1450 	INIT_LIST_HEAD(&chunk->list);
1451 	chunk->nr_pages = pcpu_unit_pages;
1452 	region_bits = pcpu_chunk_map_bits(chunk);
1453 
1454 	chunk->alloc_map = pcpu_mem_zalloc(BITS_TO_LONGS(region_bits) *
1455 					   sizeof(chunk->alloc_map[0]), gfp);
1456 	if (!chunk->alloc_map)
1457 		goto alloc_map_fail;
1458 
1459 	chunk->bound_map = pcpu_mem_zalloc(BITS_TO_LONGS(region_bits + 1) *
1460 					   sizeof(chunk->bound_map[0]), gfp);
1461 	if (!chunk->bound_map)
1462 		goto bound_map_fail;
1463 
1464 	chunk->md_blocks = pcpu_mem_zalloc(pcpu_chunk_nr_blocks(chunk) *
1465 					   sizeof(chunk->md_blocks[0]), gfp);
1466 	if (!chunk->md_blocks)
1467 		goto md_blocks_fail;
1468 
1469 #ifdef CONFIG_MEMCG_KMEM
1470 	if (!mem_cgroup_kmem_disabled()) {
1471 		chunk->obj_cgroups =
1472 			pcpu_mem_zalloc(pcpu_chunk_map_bits(chunk) *
1473 					sizeof(struct obj_cgroup *), gfp);
1474 		if (!chunk->obj_cgroups)
1475 			goto objcg_fail;
1476 	}
1477 #endif
1478 
1479 	pcpu_init_md_blocks(chunk);
1480 
1481 	/* init metadata */
1482 	chunk->free_bytes = chunk->nr_pages * PAGE_SIZE;
1483 
1484 	return chunk;
1485 
1486 #ifdef CONFIG_MEMCG_KMEM
1487 objcg_fail:
1488 	pcpu_mem_free(chunk->md_blocks);
1489 #endif
1490 md_blocks_fail:
1491 	pcpu_mem_free(chunk->bound_map);
1492 bound_map_fail:
1493 	pcpu_mem_free(chunk->alloc_map);
1494 alloc_map_fail:
1495 	pcpu_mem_free(chunk);
1496 
1497 	return NULL;
1498 }
1499 
pcpu_free_chunk(struct pcpu_chunk * chunk)1500 static void pcpu_free_chunk(struct pcpu_chunk *chunk)
1501 {
1502 	if (!chunk)
1503 		return;
1504 #ifdef CONFIG_MEMCG_KMEM
1505 	pcpu_mem_free(chunk->obj_cgroups);
1506 #endif
1507 	pcpu_mem_free(chunk->md_blocks);
1508 	pcpu_mem_free(chunk->bound_map);
1509 	pcpu_mem_free(chunk->alloc_map);
1510 	pcpu_mem_free(chunk);
1511 }
1512 
1513 /**
1514  * pcpu_chunk_populated - post-population bookkeeping
1515  * @chunk: pcpu_chunk which got populated
1516  * @page_start: the start page
1517  * @page_end: the end page
1518  *
1519  * Pages in [@page_start,@page_end) have been populated to @chunk.  Update
1520  * the bookkeeping information accordingly.  Must be called after each
1521  * successful population.
1522  */
pcpu_chunk_populated(struct pcpu_chunk * chunk,int page_start,int page_end)1523 static void pcpu_chunk_populated(struct pcpu_chunk *chunk, int page_start,
1524 				 int page_end)
1525 {
1526 	int nr = page_end - page_start;
1527 
1528 	lockdep_assert_held(&pcpu_lock);
1529 
1530 	bitmap_set(chunk->populated, page_start, nr);
1531 	chunk->nr_populated += nr;
1532 	pcpu_nr_populated += nr;
1533 
1534 	pcpu_update_empty_pages(chunk, nr);
1535 }
1536 
1537 /**
1538  * pcpu_chunk_depopulated - post-depopulation bookkeeping
1539  * @chunk: pcpu_chunk which got depopulated
1540  * @page_start: the start page
1541  * @page_end: the end page
1542  *
1543  * Pages in [@page_start,@page_end) have been depopulated from @chunk.
1544  * Update the bookkeeping information accordingly.  Must be called after
1545  * each successful depopulation.
1546  */
pcpu_chunk_depopulated(struct pcpu_chunk * chunk,int page_start,int page_end)1547 static void pcpu_chunk_depopulated(struct pcpu_chunk *chunk,
1548 				   int page_start, int page_end)
1549 {
1550 	int nr = page_end - page_start;
1551 
1552 	lockdep_assert_held(&pcpu_lock);
1553 
1554 	bitmap_clear(chunk->populated, page_start, nr);
1555 	chunk->nr_populated -= nr;
1556 	pcpu_nr_populated -= nr;
1557 
1558 	pcpu_update_empty_pages(chunk, -nr);
1559 }
1560 
1561 /*
1562  * Chunk management implementation.
1563  *
1564  * To allow different implementations, chunk alloc/free and
1565  * [de]population are implemented in a separate file which is pulled
1566  * into this file and compiled together.  The following functions
1567  * should be implemented.
1568  *
1569  * pcpu_populate_chunk		- populate the specified range of a chunk
1570  * pcpu_depopulate_chunk	- depopulate the specified range of a chunk
1571  * pcpu_post_unmap_tlb_flush	- flush tlb for the specified range of a chunk
1572  * pcpu_create_chunk		- create a new chunk
1573  * pcpu_destroy_chunk		- destroy a chunk, always preceded by full depop
1574  * pcpu_addr_to_page		- translate address to physical address
1575  * pcpu_verify_alloc_info	- check alloc_info is acceptable during init
1576  */
1577 static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
1578 			       int page_start, int page_end, gfp_t gfp);
1579 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
1580 				  int page_start, int page_end);
1581 static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,
1582 				      int page_start, int page_end);
1583 static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp);
1584 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk);
1585 static struct page *pcpu_addr_to_page(void *addr);
1586 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai);
1587 
1588 #ifdef CONFIG_NEED_PER_CPU_KM
1589 #include "percpu-km.c"
1590 #else
1591 #include "percpu-vm.c"
1592 #endif
1593 
1594 /**
1595  * pcpu_chunk_addr_search - determine chunk containing specified address
1596  * @addr: address for which the chunk needs to be determined.
1597  *
1598  * This is an internal function that handles all but static allocations.
1599  * Static percpu address values should never be passed into the allocator.
1600  *
1601  * RETURNS:
1602  * The address of the found chunk.
1603  */
pcpu_chunk_addr_search(void * addr)1604 static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
1605 {
1606 	/* is it in the dynamic region (first chunk)? */
1607 	if (pcpu_addr_in_chunk(pcpu_first_chunk, addr))
1608 		return pcpu_first_chunk;
1609 
1610 	/* is it in the reserved region? */
1611 	if (pcpu_addr_in_chunk(pcpu_reserved_chunk, addr))
1612 		return pcpu_reserved_chunk;
1613 
1614 	/*
1615 	 * The address is relative to unit0 which might be unused and
1616 	 * thus unmapped.  Offset the address to the unit space of the
1617 	 * current processor before looking it up in the vmalloc
1618 	 * space.  Note that any possible cpu id can be used here, so
1619 	 * there's no need to worry about preemption or cpu hotplug.
1620 	 */
1621 	addr += pcpu_unit_offsets[raw_smp_processor_id()];
1622 	return pcpu_get_page_chunk(pcpu_addr_to_page(addr));
1623 }
1624 
1625 #ifdef CONFIG_MEMCG_KMEM
pcpu_memcg_pre_alloc_hook(size_t size,gfp_t gfp,struct obj_cgroup ** objcgp)1626 static bool pcpu_memcg_pre_alloc_hook(size_t size, gfp_t gfp,
1627 				      struct obj_cgroup **objcgp)
1628 {
1629 	struct obj_cgroup *objcg;
1630 
1631 	if (!memcg_kmem_enabled() || !(gfp & __GFP_ACCOUNT))
1632 		return true;
1633 
1634 	objcg = get_obj_cgroup_from_current();
1635 	if (!objcg)
1636 		return true;
1637 
1638 	if (obj_cgroup_charge(objcg, gfp, size * num_possible_cpus())) {
1639 		obj_cgroup_put(objcg);
1640 		return false;
1641 	}
1642 
1643 	*objcgp = objcg;
1644 	return true;
1645 }
1646 
pcpu_memcg_post_alloc_hook(struct obj_cgroup * objcg,struct pcpu_chunk * chunk,int off,size_t size)1647 static void pcpu_memcg_post_alloc_hook(struct obj_cgroup *objcg,
1648 				       struct pcpu_chunk *chunk, int off,
1649 				       size_t size)
1650 {
1651 	if (!objcg)
1652 		return;
1653 
1654 	if (likely(chunk && chunk->obj_cgroups)) {
1655 		chunk->obj_cgroups[off >> PCPU_MIN_ALLOC_SHIFT] = objcg;
1656 
1657 		rcu_read_lock();
1658 		mod_memcg_state(obj_cgroup_memcg(objcg), MEMCG_PERCPU_B,
1659 				size * num_possible_cpus());
1660 		rcu_read_unlock();
1661 	} else {
1662 		obj_cgroup_uncharge(objcg, size * num_possible_cpus());
1663 		obj_cgroup_put(objcg);
1664 	}
1665 }
1666 
pcpu_memcg_free_hook(struct pcpu_chunk * chunk,int off,size_t size)1667 static void pcpu_memcg_free_hook(struct pcpu_chunk *chunk, int off, size_t size)
1668 {
1669 	struct obj_cgroup *objcg;
1670 
1671 	if (unlikely(!chunk->obj_cgroups))
1672 		return;
1673 
1674 	objcg = chunk->obj_cgroups[off >> PCPU_MIN_ALLOC_SHIFT];
1675 	if (!objcg)
1676 		return;
1677 	chunk->obj_cgroups[off >> PCPU_MIN_ALLOC_SHIFT] = NULL;
1678 
1679 	obj_cgroup_uncharge(objcg, size * num_possible_cpus());
1680 
1681 	rcu_read_lock();
1682 	mod_memcg_state(obj_cgroup_memcg(objcg), MEMCG_PERCPU_B,
1683 			-(size * num_possible_cpus()));
1684 	rcu_read_unlock();
1685 
1686 	obj_cgroup_put(objcg);
1687 }
1688 
1689 #else /* CONFIG_MEMCG_KMEM */
1690 static bool
pcpu_memcg_pre_alloc_hook(size_t size,gfp_t gfp,struct obj_cgroup ** objcgp)1691 pcpu_memcg_pre_alloc_hook(size_t size, gfp_t gfp, struct obj_cgroup **objcgp)
1692 {
1693 	return true;
1694 }
1695 
pcpu_memcg_post_alloc_hook(struct obj_cgroup * objcg,struct pcpu_chunk * chunk,int off,size_t size)1696 static void pcpu_memcg_post_alloc_hook(struct obj_cgroup *objcg,
1697 				       struct pcpu_chunk *chunk, int off,
1698 				       size_t size)
1699 {
1700 }
1701 
pcpu_memcg_free_hook(struct pcpu_chunk * chunk,int off,size_t size)1702 static void pcpu_memcg_free_hook(struct pcpu_chunk *chunk, int off, size_t size)
1703 {
1704 }
1705 #endif /* CONFIG_MEMCG_KMEM */
1706 
1707 /**
1708  * pcpu_alloc - the percpu allocator
1709  * @size: size of area to allocate in bytes
1710  * @align: alignment of area (max PAGE_SIZE)
1711  * @reserved: allocate from the reserved chunk if available
1712  * @gfp: allocation flags
1713  *
1714  * Allocate percpu area of @size bytes aligned at @align.  If @gfp doesn't
1715  * contain %GFP_KERNEL, the allocation is atomic. If @gfp has __GFP_NOWARN
1716  * then no warning will be triggered on invalid or failed allocation
1717  * requests.
1718  *
1719  * RETURNS:
1720  * Percpu pointer to the allocated area on success, NULL on failure.
1721  */
pcpu_alloc(size_t size,size_t align,bool reserved,gfp_t gfp)1722 static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
1723 				 gfp_t gfp)
1724 {
1725 	gfp_t pcpu_gfp;
1726 	bool is_atomic;
1727 	bool do_warn;
1728 	struct obj_cgroup *objcg = NULL;
1729 	static int warn_limit = 10;
1730 	struct pcpu_chunk *chunk, *next;
1731 	const char *err;
1732 	int slot, off, cpu, ret;
1733 	unsigned long flags;
1734 	void __percpu *ptr;
1735 	size_t bits, bit_align;
1736 
1737 	gfp = current_gfp_context(gfp);
1738 	/* whitelisted flags that can be passed to the backing allocators */
1739 	pcpu_gfp = gfp & (GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
1740 	is_atomic = (gfp & GFP_KERNEL) != GFP_KERNEL;
1741 	do_warn = !(gfp & __GFP_NOWARN);
1742 
1743 	/*
1744 	 * There is now a minimum allocation size of PCPU_MIN_ALLOC_SIZE,
1745 	 * therefore alignment must be a minimum of that many bytes.
1746 	 * An allocation may have internal fragmentation from rounding up
1747 	 * of up to PCPU_MIN_ALLOC_SIZE - 1 bytes.
1748 	 */
1749 	if (unlikely(align < PCPU_MIN_ALLOC_SIZE))
1750 		align = PCPU_MIN_ALLOC_SIZE;
1751 
1752 	size = ALIGN(size, PCPU_MIN_ALLOC_SIZE);
1753 	bits = size >> PCPU_MIN_ALLOC_SHIFT;
1754 	bit_align = align >> PCPU_MIN_ALLOC_SHIFT;
1755 
1756 	if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE ||
1757 		     !is_power_of_2(align))) {
1758 		WARN(do_warn, "illegal size (%zu) or align (%zu) for percpu allocation\n",
1759 		     size, align);
1760 		return NULL;
1761 	}
1762 
1763 	if (unlikely(!pcpu_memcg_pre_alloc_hook(size, gfp, &objcg)))
1764 		return NULL;
1765 
1766 	if (!is_atomic) {
1767 		/*
1768 		 * pcpu_balance_workfn() allocates memory under this mutex,
1769 		 * and it may wait for memory reclaim. Allow current task
1770 		 * to become OOM victim, in case of memory pressure.
1771 		 */
1772 		if (gfp & __GFP_NOFAIL) {
1773 			mutex_lock(&pcpu_alloc_mutex);
1774 		} else if (mutex_lock_killable(&pcpu_alloc_mutex)) {
1775 			pcpu_memcg_post_alloc_hook(objcg, NULL, 0, size);
1776 			return NULL;
1777 		}
1778 	}
1779 
1780 	spin_lock_irqsave(&pcpu_lock, flags);
1781 
1782 	/* serve reserved allocations from the reserved chunk if available */
1783 	if (reserved && pcpu_reserved_chunk) {
1784 		chunk = pcpu_reserved_chunk;
1785 
1786 		off = pcpu_find_block_fit(chunk, bits, bit_align, is_atomic);
1787 		if (off < 0) {
1788 			err = "alloc from reserved chunk failed";
1789 			goto fail_unlock;
1790 		}
1791 
1792 		off = pcpu_alloc_area(chunk, bits, bit_align, off);
1793 		if (off >= 0)
1794 			goto area_found;
1795 
1796 		err = "alloc from reserved chunk failed";
1797 		goto fail_unlock;
1798 	}
1799 
1800 restart:
1801 	/* search through normal chunks */
1802 	for (slot = pcpu_size_to_slot(size); slot <= pcpu_free_slot; slot++) {
1803 		list_for_each_entry_safe(chunk, next, &pcpu_chunk_lists[slot],
1804 					 list) {
1805 			off = pcpu_find_block_fit(chunk, bits, bit_align,
1806 						  is_atomic);
1807 			if (off < 0) {
1808 				if (slot < PCPU_SLOT_FAIL_THRESHOLD)
1809 					pcpu_chunk_move(chunk, 0);
1810 				continue;
1811 			}
1812 
1813 			off = pcpu_alloc_area(chunk, bits, bit_align, off);
1814 			if (off >= 0) {
1815 				pcpu_reintegrate_chunk(chunk);
1816 				goto area_found;
1817 			}
1818 		}
1819 	}
1820 
1821 	spin_unlock_irqrestore(&pcpu_lock, flags);
1822 
1823 	/*
1824 	 * No space left.  Create a new chunk.  We don't want multiple
1825 	 * tasks to create chunks simultaneously.  Serialize and create iff
1826 	 * there's still no empty chunk after grabbing the mutex.
1827 	 */
1828 	if (is_atomic) {
1829 		err = "atomic alloc failed, no space left";
1830 		goto fail;
1831 	}
1832 
1833 	if (list_empty(&pcpu_chunk_lists[pcpu_free_slot])) {
1834 		chunk = pcpu_create_chunk(pcpu_gfp);
1835 		if (!chunk) {
1836 			err = "failed to allocate new chunk";
1837 			goto fail;
1838 		}
1839 
1840 		spin_lock_irqsave(&pcpu_lock, flags);
1841 		pcpu_chunk_relocate(chunk, -1);
1842 	} else {
1843 		spin_lock_irqsave(&pcpu_lock, flags);
1844 	}
1845 
1846 	goto restart;
1847 
1848 area_found:
1849 	pcpu_stats_area_alloc(chunk, size);
1850 	spin_unlock_irqrestore(&pcpu_lock, flags);
1851 
1852 	/* populate if not all pages are already there */
1853 	if (!is_atomic) {
1854 		unsigned int page_start, page_end, rs, re;
1855 
1856 		page_start = PFN_DOWN(off);
1857 		page_end = PFN_UP(off + size);
1858 
1859 		bitmap_for_each_clear_region(chunk->populated, rs, re,
1860 					     page_start, page_end) {
1861 			WARN_ON(chunk->immutable);
1862 
1863 			ret = pcpu_populate_chunk(chunk, rs, re, pcpu_gfp);
1864 
1865 			spin_lock_irqsave(&pcpu_lock, flags);
1866 			if (ret) {
1867 				pcpu_free_area(chunk, off);
1868 				err = "failed to populate";
1869 				goto fail_unlock;
1870 			}
1871 			pcpu_chunk_populated(chunk, rs, re);
1872 			spin_unlock_irqrestore(&pcpu_lock, flags);
1873 		}
1874 
1875 		mutex_unlock(&pcpu_alloc_mutex);
1876 	}
1877 
1878 	if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
1879 		pcpu_schedule_balance_work();
1880 
1881 	/* clear the areas and return address relative to base address */
1882 	for_each_possible_cpu(cpu)
1883 		memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
1884 
1885 	ptr = __addr_to_pcpu_ptr(chunk->base_addr + off);
1886 	kmemleak_alloc_percpu(ptr, size, gfp);
1887 
1888 	trace_percpu_alloc_percpu(reserved, is_atomic, size, align,
1889 			chunk->base_addr, off, ptr);
1890 
1891 	pcpu_memcg_post_alloc_hook(objcg, chunk, off, size);
1892 
1893 	return ptr;
1894 
1895 fail_unlock:
1896 	spin_unlock_irqrestore(&pcpu_lock, flags);
1897 fail:
1898 	trace_percpu_alloc_percpu_fail(reserved, is_atomic, size, align);
1899 
1900 	if (!is_atomic && do_warn && warn_limit) {
1901 		pr_warn("allocation failed, size=%zu align=%zu atomic=%d, %s\n",
1902 			size, align, is_atomic, err);
1903 		dump_stack();
1904 		if (!--warn_limit)
1905 			pr_info("limit reached, disable warning\n");
1906 	}
1907 	if (is_atomic) {
1908 		/* see the flag handling in pcpu_balance_workfn() */
1909 		pcpu_atomic_alloc_failed = true;
1910 		pcpu_schedule_balance_work();
1911 	} else {
1912 		mutex_unlock(&pcpu_alloc_mutex);
1913 	}
1914 
1915 	pcpu_memcg_post_alloc_hook(objcg, NULL, 0, size);
1916 
1917 	return NULL;
1918 }
1919 
1920 /**
1921  * __alloc_percpu_gfp - allocate dynamic percpu area
1922  * @size: size of area to allocate in bytes
1923  * @align: alignment of area (max PAGE_SIZE)
1924  * @gfp: allocation flags
1925  *
1926  * Allocate zero-filled percpu area of @size bytes aligned at @align.  If
1927  * @gfp doesn't contain %GFP_KERNEL, the allocation doesn't block and can
1928  * be called from any context but is a lot more likely to fail. If @gfp
1929  * has __GFP_NOWARN then no warning will be triggered on invalid or failed
1930  * allocation requests.
1931  *
1932  * RETURNS:
1933  * Percpu pointer to the allocated area on success, NULL on failure.
1934  */
__alloc_percpu_gfp(size_t size,size_t align,gfp_t gfp)1935 void __percpu *__alloc_percpu_gfp(size_t size, size_t align, gfp_t gfp)
1936 {
1937 	return pcpu_alloc(size, align, false, gfp);
1938 }
1939 EXPORT_SYMBOL_GPL(__alloc_percpu_gfp);
1940 
1941 /**
1942  * __alloc_percpu - allocate dynamic percpu area
1943  * @size: size of area to allocate in bytes
1944  * @align: alignment of area (max PAGE_SIZE)
1945  *
1946  * Equivalent to __alloc_percpu_gfp(size, align, %GFP_KERNEL).
1947  */
__alloc_percpu(size_t size,size_t align)1948 void __percpu *__alloc_percpu(size_t size, size_t align)
1949 {
1950 	return pcpu_alloc(size, align, false, GFP_KERNEL);
1951 }
1952 EXPORT_SYMBOL_GPL(__alloc_percpu);
1953 
1954 /**
1955  * __alloc_reserved_percpu - allocate reserved percpu area
1956  * @size: size of area to allocate in bytes
1957  * @align: alignment of area (max PAGE_SIZE)
1958  *
1959  * Allocate zero-filled percpu area of @size bytes aligned at @align
1960  * from reserved percpu area if arch has set it up; otherwise,
1961  * allocation is served from the same dynamic area.  Might sleep.
1962  * Might trigger writeouts.
1963  *
1964  * CONTEXT:
1965  * Does GFP_KERNEL allocation.
1966  *
1967  * RETURNS:
1968  * Percpu pointer to the allocated area on success, NULL on failure.
1969  */
__alloc_reserved_percpu(size_t size,size_t align)1970 void __percpu *__alloc_reserved_percpu(size_t size, size_t align)
1971 {
1972 	return pcpu_alloc(size, align, true, GFP_KERNEL);
1973 }
1974 
1975 /**
1976  * pcpu_balance_free - manage the amount of free chunks
1977  * @empty_only: free chunks only if there are no populated pages
1978  *
1979  * If empty_only is %false, reclaim all fully free chunks regardless of the
1980  * number of populated pages.  Otherwise, only reclaim chunks that have no
1981  * populated pages.
1982  *
1983  * CONTEXT:
1984  * pcpu_lock (can be dropped temporarily)
1985  */
pcpu_balance_free(bool empty_only)1986 static void pcpu_balance_free(bool empty_only)
1987 {
1988 	LIST_HEAD(to_free);
1989 	struct list_head *free_head = &pcpu_chunk_lists[pcpu_free_slot];
1990 	struct pcpu_chunk *chunk, *next;
1991 
1992 	lockdep_assert_held(&pcpu_lock);
1993 
1994 	/*
1995 	 * There's no reason to keep around multiple unused chunks and VM
1996 	 * areas can be scarce.  Destroy all free chunks except for one.
1997 	 */
1998 	list_for_each_entry_safe(chunk, next, free_head, list) {
1999 		WARN_ON(chunk->immutable);
2000 
2001 		/* spare the first one */
2002 		if (chunk == list_first_entry(free_head, struct pcpu_chunk, list))
2003 			continue;
2004 
2005 		if (!empty_only || chunk->nr_empty_pop_pages == 0)
2006 			list_move(&chunk->list, &to_free);
2007 	}
2008 
2009 	if (list_empty(&to_free))
2010 		return;
2011 
2012 	spin_unlock_irq(&pcpu_lock);
2013 	list_for_each_entry_safe(chunk, next, &to_free, list) {
2014 		unsigned int rs, re;
2015 
2016 		bitmap_for_each_set_region(chunk->populated, rs, re, 0,
2017 					   chunk->nr_pages) {
2018 			pcpu_depopulate_chunk(chunk, rs, re);
2019 			spin_lock_irq(&pcpu_lock);
2020 			pcpu_chunk_depopulated(chunk, rs, re);
2021 			spin_unlock_irq(&pcpu_lock);
2022 		}
2023 		pcpu_destroy_chunk(chunk);
2024 		cond_resched();
2025 	}
2026 	spin_lock_irq(&pcpu_lock);
2027 }
2028 
2029 /**
2030  * pcpu_balance_populated - manage the amount of populated pages
2031  *
2032  * Maintain a certain amount of populated pages to satisfy atomic allocations.
2033  * It is possible that this is called when physical memory is scarce causing
2034  * OOM killer to be triggered.  We should avoid doing so until an actual
2035  * allocation causes the failure as it is possible that requests can be
2036  * serviced from already backed regions.
2037  *
2038  * CONTEXT:
2039  * pcpu_lock (can be dropped temporarily)
2040  */
pcpu_balance_populated(void)2041 static void pcpu_balance_populated(void)
2042 {
2043 	/* gfp flags passed to underlying allocators */
2044 	const gfp_t gfp = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
2045 	struct pcpu_chunk *chunk;
2046 	int slot, nr_to_pop, ret;
2047 
2048 	lockdep_assert_held(&pcpu_lock);
2049 
2050 	/*
2051 	 * Ensure there are certain number of free populated pages for
2052 	 * atomic allocs.  Fill up from the most packed so that atomic
2053 	 * allocs don't increase fragmentation.  If atomic allocation
2054 	 * failed previously, always populate the maximum amount.  This
2055 	 * should prevent atomic allocs larger than PAGE_SIZE from keeping
2056 	 * failing indefinitely; however, large atomic allocs are not
2057 	 * something we support properly and can be highly unreliable and
2058 	 * inefficient.
2059 	 */
2060 retry_pop:
2061 	if (pcpu_atomic_alloc_failed) {
2062 		nr_to_pop = PCPU_EMPTY_POP_PAGES_HIGH;
2063 		/* best effort anyway, don't worry about synchronization */
2064 		pcpu_atomic_alloc_failed = false;
2065 	} else {
2066 		nr_to_pop = clamp(PCPU_EMPTY_POP_PAGES_HIGH -
2067 				  pcpu_nr_empty_pop_pages,
2068 				  0, PCPU_EMPTY_POP_PAGES_HIGH);
2069 	}
2070 
2071 	for (slot = pcpu_size_to_slot(PAGE_SIZE); slot <= pcpu_free_slot; slot++) {
2072 		unsigned int nr_unpop = 0, rs, re;
2073 
2074 		if (!nr_to_pop)
2075 			break;
2076 
2077 		list_for_each_entry(chunk, &pcpu_chunk_lists[slot], list) {
2078 			nr_unpop = chunk->nr_pages - chunk->nr_populated;
2079 			if (nr_unpop)
2080 				break;
2081 		}
2082 
2083 		if (!nr_unpop)
2084 			continue;
2085 
2086 		/* @chunk can't go away while pcpu_alloc_mutex is held */
2087 		bitmap_for_each_clear_region(chunk->populated, rs, re, 0,
2088 					     chunk->nr_pages) {
2089 			int nr = min_t(int, re - rs, nr_to_pop);
2090 
2091 			spin_unlock_irq(&pcpu_lock);
2092 			ret = pcpu_populate_chunk(chunk, rs, rs + nr, gfp);
2093 			cond_resched();
2094 			spin_lock_irq(&pcpu_lock);
2095 			if (!ret) {
2096 				nr_to_pop -= nr;
2097 				pcpu_chunk_populated(chunk, rs, rs + nr);
2098 			} else {
2099 				nr_to_pop = 0;
2100 			}
2101 
2102 			if (!nr_to_pop)
2103 				break;
2104 		}
2105 	}
2106 
2107 	if (nr_to_pop) {
2108 		/* ran out of chunks to populate, create a new one and retry */
2109 		spin_unlock_irq(&pcpu_lock);
2110 		chunk = pcpu_create_chunk(gfp);
2111 		cond_resched();
2112 		spin_lock_irq(&pcpu_lock);
2113 		if (chunk) {
2114 			pcpu_chunk_relocate(chunk, -1);
2115 			goto retry_pop;
2116 		}
2117 	}
2118 }
2119 
2120 /**
2121  * pcpu_reclaim_populated - scan over to_depopulate chunks and free empty pages
2122  *
2123  * Scan over chunks in the depopulate list and try to release unused populated
2124  * pages back to the system.  Depopulated chunks are sidelined to prevent
2125  * repopulating these pages unless required.  Fully free chunks are reintegrated
2126  * and freed accordingly (1 is kept around).  If we drop below the empty
2127  * populated pages threshold, reintegrate the chunk if it has empty free pages.
2128  * Each chunk is scanned in the reverse order to keep populated pages close to
2129  * the beginning of the chunk.
2130  *
2131  * CONTEXT:
2132  * pcpu_lock (can be dropped temporarily)
2133  *
2134  */
pcpu_reclaim_populated(void)2135 static void pcpu_reclaim_populated(void)
2136 {
2137 	struct pcpu_chunk *chunk;
2138 	struct pcpu_block_md *block;
2139 	int freed_page_start, freed_page_end;
2140 	int i, end;
2141 	bool reintegrate;
2142 
2143 	lockdep_assert_held(&pcpu_lock);
2144 
2145 	/*
2146 	 * Once a chunk is isolated to the to_depopulate list, the chunk is no
2147 	 * longer discoverable to allocations whom may populate pages.  The only
2148 	 * other accessor is the free path which only returns area back to the
2149 	 * allocator not touching the populated bitmap.
2150 	 */
2151 	while (!list_empty(&pcpu_chunk_lists[pcpu_to_depopulate_slot])) {
2152 		chunk = list_first_entry(&pcpu_chunk_lists[pcpu_to_depopulate_slot],
2153 					 struct pcpu_chunk, list);
2154 		WARN_ON(chunk->immutable);
2155 
2156 		/*
2157 		 * Scan chunk's pages in the reverse order to keep populated
2158 		 * pages close to the beginning of the chunk.
2159 		 */
2160 		freed_page_start = chunk->nr_pages;
2161 		freed_page_end = 0;
2162 		reintegrate = false;
2163 		for (i = chunk->nr_pages - 1, end = -1; i >= 0; i--) {
2164 			/* no more work to do */
2165 			if (chunk->nr_empty_pop_pages == 0)
2166 				break;
2167 
2168 			/* reintegrate chunk to prevent atomic alloc failures */
2169 			if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_HIGH) {
2170 				reintegrate = true;
2171 				goto end_chunk;
2172 			}
2173 
2174 			/*
2175 			 * If the page is empty and populated, start or
2176 			 * extend the (i, end) range.  If i == 0, decrease
2177 			 * i and perform the depopulation to cover the last
2178 			 * (first) page in the chunk.
2179 			 */
2180 			block = chunk->md_blocks + i;
2181 			if (block->contig_hint == PCPU_BITMAP_BLOCK_BITS &&
2182 			    test_bit(i, chunk->populated)) {
2183 				if (end == -1)
2184 					end = i;
2185 				if (i > 0)
2186 					continue;
2187 				i--;
2188 			}
2189 
2190 			/* depopulate if there is an active range */
2191 			if (end == -1)
2192 				continue;
2193 
2194 			spin_unlock_irq(&pcpu_lock);
2195 			pcpu_depopulate_chunk(chunk, i + 1, end + 1);
2196 			cond_resched();
2197 			spin_lock_irq(&pcpu_lock);
2198 
2199 			pcpu_chunk_depopulated(chunk, i + 1, end + 1);
2200 			freed_page_start = min(freed_page_start, i + 1);
2201 			freed_page_end = max(freed_page_end, end + 1);
2202 
2203 			/* reset the range and continue */
2204 			end = -1;
2205 		}
2206 
2207 end_chunk:
2208 		/* batch tlb flush per chunk to amortize cost */
2209 		if (freed_page_start < freed_page_end) {
2210 			spin_unlock_irq(&pcpu_lock);
2211 			pcpu_post_unmap_tlb_flush(chunk,
2212 						  freed_page_start,
2213 						  freed_page_end);
2214 			cond_resched();
2215 			spin_lock_irq(&pcpu_lock);
2216 		}
2217 
2218 		if (reintegrate || chunk->free_bytes == pcpu_unit_size)
2219 			pcpu_reintegrate_chunk(chunk);
2220 		else
2221 			list_move_tail(&chunk->list,
2222 				       &pcpu_chunk_lists[pcpu_sidelined_slot]);
2223 	}
2224 }
2225 
2226 /**
2227  * pcpu_balance_workfn - manage the amount of free chunks and populated pages
2228  * @work: unused
2229  *
2230  * For each chunk type, manage the number of fully free chunks and the number of
2231  * populated pages.  An important thing to consider is when pages are freed and
2232  * how they contribute to the global counts.
2233  */
pcpu_balance_workfn(struct work_struct * work)2234 static void pcpu_balance_workfn(struct work_struct *work)
2235 {
2236 	/*
2237 	 * pcpu_balance_free() is called twice because the first time we may
2238 	 * trim pages in the active pcpu_nr_empty_pop_pages which may cause us
2239 	 * to grow other chunks.  This then gives pcpu_reclaim_populated() time
2240 	 * to move fully free chunks to the active list to be freed if
2241 	 * appropriate.
2242 	 */
2243 	mutex_lock(&pcpu_alloc_mutex);
2244 	spin_lock_irq(&pcpu_lock);
2245 
2246 	pcpu_balance_free(false);
2247 	pcpu_reclaim_populated();
2248 	pcpu_balance_populated();
2249 	pcpu_balance_free(true);
2250 
2251 	spin_unlock_irq(&pcpu_lock);
2252 	mutex_unlock(&pcpu_alloc_mutex);
2253 }
2254 
2255 /**
2256  * free_percpu - free percpu area
2257  * @ptr: pointer to area to free
2258  *
2259  * Free percpu area @ptr.
2260  *
2261  * CONTEXT:
2262  * Can be called from atomic context.
2263  */
free_percpu(void __percpu * ptr)2264 void free_percpu(void __percpu *ptr)
2265 {
2266 	void *addr;
2267 	struct pcpu_chunk *chunk;
2268 	unsigned long flags;
2269 	int size, off;
2270 	bool need_balance = false;
2271 
2272 	if (!ptr)
2273 		return;
2274 
2275 	kmemleak_free_percpu(ptr);
2276 
2277 	addr = __pcpu_ptr_to_addr(ptr);
2278 
2279 	spin_lock_irqsave(&pcpu_lock, flags);
2280 
2281 	chunk = pcpu_chunk_addr_search(addr);
2282 	off = addr - chunk->base_addr;
2283 
2284 	size = pcpu_free_area(chunk, off);
2285 
2286 	pcpu_memcg_free_hook(chunk, off, size);
2287 
2288 	/*
2289 	 * If there are more than one fully free chunks, wake up grim reaper.
2290 	 * If the chunk is isolated, it may be in the process of being
2291 	 * reclaimed.  Let reclaim manage cleaning up of that chunk.
2292 	 */
2293 	if (!chunk->isolated && chunk->free_bytes == pcpu_unit_size) {
2294 		struct pcpu_chunk *pos;
2295 
2296 		list_for_each_entry(pos, &pcpu_chunk_lists[pcpu_free_slot], list)
2297 			if (pos != chunk) {
2298 				need_balance = true;
2299 				break;
2300 			}
2301 	} else if (pcpu_should_reclaim_chunk(chunk)) {
2302 		pcpu_isolate_chunk(chunk);
2303 		need_balance = true;
2304 	}
2305 
2306 	trace_percpu_free_percpu(chunk->base_addr, off, ptr);
2307 
2308 	spin_unlock_irqrestore(&pcpu_lock, flags);
2309 
2310 	if (need_balance)
2311 		pcpu_schedule_balance_work();
2312 }
2313 EXPORT_SYMBOL_GPL(free_percpu);
2314 
__is_kernel_percpu_address(unsigned long addr,unsigned long * can_addr)2315 bool __is_kernel_percpu_address(unsigned long addr, unsigned long *can_addr)
2316 {
2317 #ifdef CONFIG_SMP
2318 	const size_t static_size = __per_cpu_end - __per_cpu_start;
2319 	void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
2320 	unsigned int cpu;
2321 
2322 	for_each_possible_cpu(cpu) {
2323 		void *start = per_cpu_ptr(base, cpu);
2324 		void *va = (void *)addr;
2325 
2326 		if (va >= start && va < start + static_size) {
2327 			if (can_addr) {
2328 				*can_addr = (unsigned long) (va - start);
2329 				*can_addr += (unsigned long)
2330 					per_cpu_ptr(base, get_boot_cpu_id());
2331 			}
2332 			return true;
2333 		}
2334 	}
2335 #endif
2336 	/* on UP, can't distinguish from other static vars, always false */
2337 	return false;
2338 }
2339 
2340 /**
2341  * is_kernel_percpu_address - test whether address is from static percpu area
2342  * @addr: address to test
2343  *
2344  * Test whether @addr belongs to in-kernel static percpu area.  Module
2345  * static percpu areas are not considered.  For those, use
2346  * is_module_percpu_address().
2347  *
2348  * RETURNS:
2349  * %true if @addr is from in-kernel static percpu area, %false otherwise.
2350  */
is_kernel_percpu_address(unsigned long addr)2351 bool is_kernel_percpu_address(unsigned long addr)
2352 {
2353 	return __is_kernel_percpu_address(addr, NULL);
2354 }
2355 
2356 /**
2357  * per_cpu_ptr_to_phys - convert translated percpu address to physical address
2358  * @addr: the address to be converted to physical address
2359  *
2360  * Given @addr which is dereferenceable address obtained via one of
2361  * percpu access macros, this function translates it into its physical
2362  * address.  The caller is responsible for ensuring @addr stays valid
2363  * until this function finishes.
2364  *
2365  * percpu allocator has special setup for the first chunk, which currently
2366  * supports either embedding in linear address space or vmalloc mapping,
2367  * and, from the second one, the backing allocator (currently either vm or
2368  * km) provides translation.
2369  *
2370  * The addr can be translated simply without checking if it falls into the
2371  * first chunk. But the current code reflects better how percpu allocator
2372  * actually works, and the verification can discover both bugs in percpu
2373  * allocator itself and per_cpu_ptr_to_phys() callers. So we keep current
2374  * code.
2375  *
2376  * RETURNS:
2377  * The physical address for @addr.
2378  */
per_cpu_ptr_to_phys(void * addr)2379 phys_addr_t per_cpu_ptr_to_phys(void *addr)
2380 {
2381 	void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
2382 	bool in_first_chunk = false;
2383 	unsigned long first_low, first_high;
2384 	unsigned int cpu;
2385 
2386 	/*
2387 	 * The following test on unit_low/high isn't strictly
2388 	 * necessary but will speed up lookups of addresses which
2389 	 * aren't in the first chunk.
2390 	 *
2391 	 * The address check is against full chunk sizes.  pcpu_base_addr
2392 	 * points to the beginning of the first chunk including the
2393 	 * static region.  Assumes good intent as the first chunk may
2394 	 * not be full (ie. < pcpu_unit_pages in size).
2395 	 */
2396 	first_low = (unsigned long)pcpu_base_addr +
2397 		    pcpu_unit_page_offset(pcpu_low_unit_cpu, 0);
2398 	first_high = (unsigned long)pcpu_base_addr +
2399 		     pcpu_unit_page_offset(pcpu_high_unit_cpu, pcpu_unit_pages);
2400 	if ((unsigned long)addr >= first_low &&
2401 	    (unsigned long)addr < first_high) {
2402 		for_each_possible_cpu(cpu) {
2403 			void *start = per_cpu_ptr(base, cpu);
2404 
2405 			if (addr >= start && addr < start + pcpu_unit_size) {
2406 				in_first_chunk = true;
2407 				break;
2408 			}
2409 		}
2410 	}
2411 
2412 	if (in_first_chunk) {
2413 		if (!is_vmalloc_addr(addr))
2414 			return __pa(addr);
2415 		else
2416 			return page_to_phys(vmalloc_to_page(addr)) +
2417 			       offset_in_page(addr);
2418 	} else
2419 		return page_to_phys(pcpu_addr_to_page(addr)) +
2420 		       offset_in_page(addr);
2421 }
2422 EXPORT_SYMBOL_GPL(per_cpu_ptr_to_phys);
2423 
2424 /**
2425  * pcpu_alloc_alloc_info - allocate percpu allocation info
2426  * @nr_groups: the number of groups
2427  * @nr_units: the number of units
2428  *
2429  * Allocate ai which is large enough for @nr_groups groups containing
2430  * @nr_units units.  The returned ai's groups[0].cpu_map points to the
2431  * cpu_map array which is long enough for @nr_units and filled with
2432  * NR_CPUS.  It's the caller's responsibility to initialize cpu_map
2433  * pointer of other groups.
2434  *
2435  * RETURNS:
2436  * Pointer to the allocated pcpu_alloc_info on success, NULL on
2437  * failure.
2438  */
pcpu_alloc_alloc_info(int nr_groups,int nr_units)2439 struct pcpu_alloc_info * __init pcpu_alloc_alloc_info(int nr_groups,
2440 						      int nr_units)
2441 {
2442 	struct pcpu_alloc_info *ai;
2443 	size_t base_size, ai_size;
2444 	void *ptr;
2445 	int unit;
2446 
2447 	base_size = ALIGN(struct_size(ai, groups, nr_groups),
2448 			  __alignof__(ai->groups[0].cpu_map[0]));
2449 	ai_size = base_size + nr_units * sizeof(ai->groups[0].cpu_map[0]);
2450 
2451 	ptr = memblock_alloc(PFN_ALIGN(ai_size), PAGE_SIZE);
2452 	if (!ptr)
2453 		return NULL;
2454 	ai = ptr;
2455 	ptr += base_size;
2456 
2457 	ai->groups[0].cpu_map = ptr;
2458 
2459 	for (unit = 0; unit < nr_units; unit++)
2460 		ai->groups[0].cpu_map[unit] = NR_CPUS;
2461 
2462 	ai->nr_groups = nr_groups;
2463 	ai->__ai_size = PFN_ALIGN(ai_size);
2464 
2465 	return ai;
2466 }
2467 
2468 /**
2469  * pcpu_free_alloc_info - free percpu allocation info
2470  * @ai: pcpu_alloc_info to free
2471  *
2472  * Free @ai which was allocated by pcpu_alloc_alloc_info().
2473  */
pcpu_free_alloc_info(struct pcpu_alloc_info * ai)2474 void __init pcpu_free_alloc_info(struct pcpu_alloc_info *ai)
2475 {
2476 	memblock_free_early(__pa(ai), ai->__ai_size);
2477 }
2478 
2479 /**
2480  * pcpu_dump_alloc_info - print out information about pcpu_alloc_info
2481  * @lvl: loglevel
2482  * @ai: allocation info to dump
2483  *
2484  * Print out information about @ai using loglevel @lvl.
2485  */
pcpu_dump_alloc_info(const char * lvl,const struct pcpu_alloc_info * ai)2486 static void pcpu_dump_alloc_info(const char *lvl,
2487 				 const struct pcpu_alloc_info *ai)
2488 {
2489 	int group_width = 1, cpu_width = 1, width;
2490 	char empty_str[] = "--------";
2491 	int alloc = 0, alloc_end = 0;
2492 	int group, v;
2493 	int upa, apl;	/* units per alloc, allocs per line */
2494 
2495 	v = ai->nr_groups;
2496 	while (v /= 10)
2497 		group_width++;
2498 
2499 	v = num_possible_cpus();
2500 	while (v /= 10)
2501 		cpu_width++;
2502 	empty_str[min_t(int, cpu_width, sizeof(empty_str) - 1)] = '\0';
2503 
2504 	upa = ai->alloc_size / ai->unit_size;
2505 	width = upa * (cpu_width + 1) + group_width + 3;
2506 	apl = rounddown_pow_of_two(max(60 / width, 1));
2507 
2508 	printk("%spcpu-alloc: s%zu r%zu d%zu u%zu alloc=%zu*%zu",
2509 	       lvl, ai->static_size, ai->reserved_size, ai->dyn_size,
2510 	       ai->unit_size, ai->alloc_size / ai->atom_size, ai->atom_size);
2511 
2512 	for (group = 0; group < ai->nr_groups; group++) {
2513 		const struct pcpu_group_info *gi = &ai->groups[group];
2514 		int unit = 0, unit_end = 0;
2515 
2516 		BUG_ON(gi->nr_units % upa);
2517 		for (alloc_end += gi->nr_units / upa;
2518 		     alloc < alloc_end; alloc++) {
2519 			if (!(alloc % apl)) {
2520 				pr_cont("\n");
2521 				printk("%spcpu-alloc: ", lvl);
2522 			}
2523 			pr_cont("[%0*d] ", group_width, group);
2524 
2525 			for (unit_end += upa; unit < unit_end; unit++)
2526 				if (gi->cpu_map[unit] != NR_CPUS)
2527 					pr_cont("%0*d ",
2528 						cpu_width, gi->cpu_map[unit]);
2529 				else
2530 					pr_cont("%s ", empty_str);
2531 		}
2532 	}
2533 	pr_cont("\n");
2534 }
2535 
2536 /**
2537  * pcpu_setup_first_chunk - initialize the first percpu chunk
2538  * @ai: pcpu_alloc_info describing how to percpu area is shaped
2539  * @base_addr: mapped address
2540  *
2541  * Initialize the first percpu chunk which contains the kernel static
2542  * percpu area.  This function is to be called from arch percpu area
2543  * setup path.
2544  *
2545  * @ai contains all information necessary to initialize the first
2546  * chunk and prime the dynamic percpu allocator.
2547  *
2548  * @ai->static_size is the size of static percpu area.
2549  *
2550  * @ai->reserved_size, if non-zero, specifies the amount of bytes to
2551  * reserve after the static area in the first chunk.  This reserves
2552  * the first chunk such that it's available only through reserved
2553  * percpu allocation.  This is primarily used to serve module percpu
2554  * static areas on architectures where the addressing model has
2555  * limited offset range for symbol relocations to guarantee module
2556  * percpu symbols fall inside the relocatable range.
2557  *
2558  * @ai->dyn_size determines the number of bytes available for dynamic
2559  * allocation in the first chunk.  The area between @ai->static_size +
2560  * @ai->reserved_size + @ai->dyn_size and @ai->unit_size is unused.
2561  *
2562  * @ai->unit_size specifies unit size and must be aligned to PAGE_SIZE
2563  * and equal to or larger than @ai->static_size + @ai->reserved_size +
2564  * @ai->dyn_size.
2565  *
2566  * @ai->atom_size is the allocation atom size and used as alignment
2567  * for vm areas.
2568  *
2569  * @ai->alloc_size is the allocation size and always multiple of
2570  * @ai->atom_size.  This is larger than @ai->atom_size if
2571  * @ai->unit_size is larger than @ai->atom_size.
2572  *
2573  * @ai->nr_groups and @ai->groups describe virtual memory layout of
2574  * percpu areas.  Units which should be colocated are put into the
2575  * same group.  Dynamic VM areas will be allocated according to these
2576  * groupings.  If @ai->nr_groups is zero, a single group containing
2577  * all units is assumed.
2578  *
2579  * The caller should have mapped the first chunk at @base_addr and
2580  * copied static data to each unit.
2581  *
2582  * The first chunk will always contain a static and a dynamic region.
2583  * However, the static region is not managed by any chunk.  If the first
2584  * chunk also contains a reserved region, it is served by two chunks -
2585  * one for the reserved region and one for the dynamic region.  They
2586  * share the same vm, but use offset regions in the area allocation map.
2587  * The chunk serving the dynamic region is circulated in the chunk slots
2588  * and available for dynamic allocation like any other chunk.
2589  */
pcpu_setup_first_chunk(const struct pcpu_alloc_info * ai,void * base_addr)2590 void __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
2591 				   void *base_addr)
2592 {
2593 	size_t size_sum = ai->static_size + ai->reserved_size + ai->dyn_size;
2594 	size_t static_size, dyn_size;
2595 	struct pcpu_chunk *chunk;
2596 	unsigned long *group_offsets;
2597 	size_t *group_sizes;
2598 	unsigned long *unit_off;
2599 	unsigned int cpu;
2600 	int *unit_map;
2601 	int group, unit, i;
2602 	int map_size;
2603 	unsigned long tmp_addr;
2604 	size_t alloc_size;
2605 
2606 #define PCPU_SETUP_BUG_ON(cond)	do {					\
2607 	if (unlikely(cond)) {						\
2608 		pr_emerg("failed to initialize, %s\n", #cond);		\
2609 		pr_emerg("cpu_possible_mask=%*pb\n",			\
2610 			 cpumask_pr_args(cpu_possible_mask));		\
2611 		pcpu_dump_alloc_info(KERN_EMERG, ai);			\
2612 		BUG();							\
2613 	}								\
2614 } while (0)
2615 
2616 	/* sanity checks */
2617 	PCPU_SETUP_BUG_ON(ai->nr_groups <= 0);
2618 #ifdef CONFIG_SMP
2619 	PCPU_SETUP_BUG_ON(!ai->static_size);
2620 	PCPU_SETUP_BUG_ON(offset_in_page(__per_cpu_start));
2621 #endif
2622 	PCPU_SETUP_BUG_ON(!base_addr);
2623 	PCPU_SETUP_BUG_ON(offset_in_page(base_addr));
2624 	PCPU_SETUP_BUG_ON(ai->unit_size < size_sum);
2625 	PCPU_SETUP_BUG_ON(offset_in_page(ai->unit_size));
2626 	PCPU_SETUP_BUG_ON(ai->unit_size < PCPU_MIN_UNIT_SIZE);
2627 	PCPU_SETUP_BUG_ON(!IS_ALIGNED(ai->unit_size, PCPU_BITMAP_BLOCK_SIZE));
2628 	PCPU_SETUP_BUG_ON(ai->dyn_size < PERCPU_DYNAMIC_EARLY_SIZE);
2629 	PCPU_SETUP_BUG_ON(!ai->dyn_size);
2630 	PCPU_SETUP_BUG_ON(!IS_ALIGNED(ai->reserved_size, PCPU_MIN_ALLOC_SIZE));
2631 	PCPU_SETUP_BUG_ON(!(IS_ALIGNED(PCPU_BITMAP_BLOCK_SIZE, PAGE_SIZE) ||
2632 			    IS_ALIGNED(PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE)));
2633 	PCPU_SETUP_BUG_ON(pcpu_verify_alloc_info(ai) < 0);
2634 
2635 	/* process group information and build config tables accordingly */
2636 	alloc_size = ai->nr_groups * sizeof(group_offsets[0]);
2637 	group_offsets = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2638 	if (!group_offsets)
2639 		panic("%s: Failed to allocate %zu bytes\n", __func__,
2640 		      alloc_size);
2641 
2642 	alloc_size = ai->nr_groups * sizeof(group_sizes[0]);
2643 	group_sizes = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2644 	if (!group_sizes)
2645 		panic("%s: Failed to allocate %zu bytes\n", __func__,
2646 		      alloc_size);
2647 
2648 	alloc_size = nr_cpu_ids * sizeof(unit_map[0]);
2649 	unit_map = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2650 	if (!unit_map)
2651 		panic("%s: Failed to allocate %zu bytes\n", __func__,
2652 		      alloc_size);
2653 
2654 	alloc_size = nr_cpu_ids * sizeof(unit_off[0]);
2655 	unit_off = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2656 	if (!unit_off)
2657 		panic("%s: Failed to allocate %zu bytes\n", __func__,
2658 		      alloc_size);
2659 
2660 	for (cpu = 0; cpu < nr_cpu_ids; cpu++)
2661 		unit_map[cpu] = UINT_MAX;
2662 
2663 	pcpu_low_unit_cpu = NR_CPUS;
2664 	pcpu_high_unit_cpu = NR_CPUS;
2665 
2666 	for (group = 0, unit = 0; group < ai->nr_groups; group++, unit += i) {
2667 		const struct pcpu_group_info *gi = &ai->groups[group];
2668 
2669 		group_offsets[group] = gi->base_offset;
2670 		group_sizes[group] = gi->nr_units * ai->unit_size;
2671 
2672 		for (i = 0; i < gi->nr_units; i++) {
2673 			cpu = gi->cpu_map[i];
2674 			if (cpu == NR_CPUS)
2675 				continue;
2676 
2677 			PCPU_SETUP_BUG_ON(cpu >= nr_cpu_ids);
2678 			PCPU_SETUP_BUG_ON(!cpu_possible(cpu));
2679 			PCPU_SETUP_BUG_ON(unit_map[cpu] != UINT_MAX);
2680 
2681 			unit_map[cpu] = unit + i;
2682 			unit_off[cpu] = gi->base_offset + i * ai->unit_size;
2683 
2684 			/* determine low/high unit_cpu */
2685 			if (pcpu_low_unit_cpu == NR_CPUS ||
2686 			    unit_off[cpu] < unit_off[pcpu_low_unit_cpu])
2687 				pcpu_low_unit_cpu = cpu;
2688 			if (pcpu_high_unit_cpu == NR_CPUS ||
2689 			    unit_off[cpu] > unit_off[pcpu_high_unit_cpu])
2690 				pcpu_high_unit_cpu = cpu;
2691 		}
2692 	}
2693 	pcpu_nr_units = unit;
2694 
2695 	for_each_possible_cpu(cpu)
2696 		PCPU_SETUP_BUG_ON(unit_map[cpu] == UINT_MAX);
2697 
2698 	/* we're done parsing the input, undefine BUG macro and dump config */
2699 #undef PCPU_SETUP_BUG_ON
2700 	pcpu_dump_alloc_info(KERN_DEBUG, ai);
2701 
2702 	pcpu_nr_groups = ai->nr_groups;
2703 	pcpu_group_offsets = group_offsets;
2704 	pcpu_group_sizes = group_sizes;
2705 	pcpu_unit_map = unit_map;
2706 	pcpu_unit_offsets = unit_off;
2707 
2708 	/* determine basic parameters */
2709 	pcpu_unit_pages = ai->unit_size >> PAGE_SHIFT;
2710 	pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
2711 	pcpu_atom_size = ai->atom_size;
2712 	pcpu_chunk_struct_size = struct_size(chunk, populated,
2713 					     BITS_TO_LONGS(pcpu_unit_pages));
2714 
2715 	pcpu_stats_save_ai(ai);
2716 
2717 	/*
2718 	 * Allocate chunk slots.  The slots after the active slots are:
2719 	 *   sidelined_slot - isolated, depopulated chunks
2720 	 *   free_slot - fully free chunks
2721 	 *   to_depopulate_slot - isolated, chunks to depopulate
2722 	 */
2723 	pcpu_sidelined_slot = __pcpu_size_to_slot(pcpu_unit_size) + 1;
2724 	pcpu_free_slot = pcpu_sidelined_slot + 1;
2725 	pcpu_to_depopulate_slot = pcpu_free_slot + 1;
2726 	pcpu_nr_slots = pcpu_to_depopulate_slot + 1;
2727 	pcpu_chunk_lists = memblock_alloc(pcpu_nr_slots *
2728 					  sizeof(pcpu_chunk_lists[0]),
2729 					  SMP_CACHE_BYTES);
2730 	if (!pcpu_chunk_lists)
2731 		panic("%s: Failed to allocate %zu bytes\n", __func__,
2732 		      pcpu_nr_slots * sizeof(pcpu_chunk_lists[0]));
2733 
2734 	for (i = 0; i < pcpu_nr_slots; i++)
2735 		INIT_LIST_HEAD(&pcpu_chunk_lists[i]);
2736 
2737 	/*
2738 	 * The end of the static region needs to be aligned with the
2739 	 * minimum allocation size as this offsets the reserved and
2740 	 * dynamic region.  The first chunk ends page aligned by
2741 	 * expanding the dynamic region, therefore the dynamic region
2742 	 * can be shrunk to compensate while still staying above the
2743 	 * configured sizes.
2744 	 */
2745 	static_size = ALIGN(ai->static_size, PCPU_MIN_ALLOC_SIZE);
2746 	dyn_size = ai->dyn_size - (static_size - ai->static_size);
2747 
2748 	/*
2749 	 * Initialize first chunk.
2750 	 * If the reserved_size is non-zero, this initializes the reserved
2751 	 * chunk.  If the reserved_size is zero, the reserved chunk is NULL
2752 	 * and the dynamic region is initialized here.  The first chunk,
2753 	 * pcpu_first_chunk, will always point to the chunk that serves
2754 	 * the dynamic region.
2755 	 */
2756 	tmp_addr = (unsigned long)base_addr + static_size;
2757 	map_size = ai->reserved_size ?: dyn_size;
2758 	chunk = pcpu_alloc_first_chunk(tmp_addr, map_size);
2759 
2760 	/* init dynamic chunk if necessary */
2761 	if (ai->reserved_size) {
2762 		pcpu_reserved_chunk = chunk;
2763 
2764 		tmp_addr = (unsigned long)base_addr + static_size +
2765 			   ai->reserved_size;
2766 		map_size = dyn_size;
2767 		chunk = pcpu_alloc_first_chunk(tmp_addr, map_size);
2768 	}
2769 
2770 	/* link the first chunk in */
2771 	pcpu_first_chunk = chunk;
2772 	pcpu_nr_empty_pop_pages = pcpu_first_chunk->nr_empty_pop_pages;
2773 	pcpu_chunk_relocate(pcpu_first_chunk, -1);
2774 
2775 	/* include all regions of the first chunk */
2776 	pcpu_nr_populated += PFN_DOWN(size_sum);
2777 
2778 	pcpu_stats_chunk_alloc();
2779 	trace_percpu_create_chunk(base_addr);
2780 
2781 	/* we're done */
2782 	pcpu_base_addr = base_addr;
2783 }
2784 
2785 #ifdef CONFIG_SMP
2786 
2787 const char * const pcpu_fc_names[PCPU_FC_NR] __initconst = {
2788 	[PCPU_FC_AUTO]	= "auto",
2789 	[PCPU_FC_EMBED]	= "embed",
2790 	[PCPU_FC_PAGE]	= "page",
2791 };
2792 
2793 enum pcpu_fc pcpu_chosen_fc __initdata = PCPU_FC_AUTO;
2794 
percpu_alloc_setup(char * str)2795 static int __init percpu_alloc_setup(char *str)
2796 {
2797 	if (!str)
2798 		return -EINVAL;
2799 
2800 	if (0)
2801 		/* nada */;
2802 #ifdef CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK
2803 	else if (!strcmp(str, "embed"))
2804 		pcpu_chosen_fc = PCPU_FC_EMBED;
2805 #endif
2806 #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
2807 	else if (!strcmp(str, "page"))
2808 		pcpu_chosen_fc = PCPU_FC_PAGE;
2809 #endif
2810 	else
2811 		pr_warn("unknown allocator %s specified\n", str);
2812 
2813 	return 0;
2814 }
2815 early_param("percpu_alloc", percpu_alloc_setup);
2816 
2817 /*
2818  * pcpu_embed_first_chunk() is used by the generic percpu setup.
2819  * Build it if needed by the arch config or the generic setup is going
2820  * to be used.
2821  */
2822 #if defined(CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK) || \
2823 	!defined(CONFIG_HAVE_SETUP_PER_CPU_AREA)
2824 #define BUILD_EMBED_FIRST_CHUNK
2825 #endif
2826 
2827 /* build pcpu_page_first_chunk() iff needed by the arch config */
2828 #if defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
2829 #define BUILD_PAGE_FIRST_CHUNK
2830 #endif
2831 
2832 /* pcpu_build_alloc_info() is used by both embed and page first chunk */
2833 #if defined(BUILD_EMBED_FIRST_CHUNK) || defined(BUILD_PAGE_FIRST_CHUNK)
2834 /**
2835  * pcpu_build_alloc_info - build alloc_info considering distances between CPUs
2836  * @reserved_size: the size of reserved percpu area in bytes
2837  * @dyn_size: minimum free size for dynamic allocation in bytes
2838  * @atom_size: allocation atom size
2839  * @cpu_distance_fn: callback to determine distance between cpus, optional
2840  *
2841  * This function determines grouping of units, their mappings to cpus
2842  * and other parameters considering needed percpu size, allocation
2843  * atom size and distances between CPUs.
2844  *
2845  * Groups are always multiples of atom size and CPUs which are of
2846  * LOCAL_DISTANCE both ways are grouped together and share space for
2847  * units in the same group.  The returned configuration is guaranteed
2848  * to have CPUs on different nodes on different groups and >=75% usage
2849  * of allocated virtual address space.
2850  *
2851  * RETURNS:
2852  * On success, pointer to the new allocation_info is returned.  On
2853  * failure, ERR_PTR value is returned.
2854  */
pcpu_build_alloc_info(size_t reserved_size,size_t dyn_size,size_t atom_size,pcpu_fc_cpu_distance_fn_t cpu_distance_fn)2855 static struct pcpu_alloc_info * __init __flatten pcpu_build_alloc_info(
2856 				size_t reserved_size, size_t dyn_size,
2857 				size_t atom_size,
2858 				pcpu_fc_cpu_distance_fn_t cpu_distance_fn)
2859 {
2860 	static int group_map[NR_CPUS] __initdata;
2861 	static int group_cnt[NR_CPUS] __initdata;
2862 	static struct cpumask mask __initdata;
2863 	const size_t static_size = __per_cpu_end - __per_cpu_start;
2864 	int nr_groups = 1, nr_units = 0;
2865 	size_t size_sum, min_unit_size, alloc_size;
2866 	int upa, max_upa, best_upa;	/* units_per_alloc */
2867 	int last_allocs, group, unit;
2868 	unsigned int cpu, tcpu;
2869 	struct pcpu_alloc_info *ai;
2870 	unsigned int *cpu_map;
2871 
2872 	/* this function may be called multiple times */
2873 	memset(group_map, 0, sizeof(group_map));
2874 	memset(group_cnt, 0, sizeof(group_cnt));
2875 	cpumask_clear(&mask);
2876 
2877 	/* calculate size_sum and ensure dyn_size is enough for early alloc */
2878 	size_sum = PFN_ALIGN(static_size + reserved_size +
2879 			    max_t(size_t, dyn_size, PERCPU_DYNAMIC_EARLY_SIZE));
2880 	dyn_size = size_sum - static_size - reserved_size;
2881 
2882 	/*
2883 	 * Determine min_unit_size, alloc_size and max_upa such that
2884 	 * alloc_size is multiple of atom_size and is the smallest
2885 	 * which can accommodate 4k aligned segments which are equal to
2886 	 * or larger than min_unit_size.
2887 	 */
2888 	min_unit_size = max_t(size_t, size_sum, PCPU_MIN_UNIT_SIZE);
2889 
2890 	/* determine the maximum # of units that can fit in an allocation */
2891 	alloc_size = roundup(min_unit_size, atom_size);
2892 	upa = alloc_size / min_unit_size;
2893 	while (alloc_size % upa || (offset_in_page(alloc_size / upa)))
2894 		upa--;
2895 	max_upa = upa;
2896 
2897 	cpumask_copy(&mask, cpu_possible_mask);
2898 
2899 	/* group cpus according to their proximity */
2900 	for (group = 0; !cpumask_empty(&mask); group++) {
2901 		/* pop the group's first cpu */
2902 		cpu = cpumask_first(&mask);
2903 		group_map[cpu] = group;
2904 		group_cnt[group]++;
2905 		cpumask_clear_cpu(cpu, &mask);
2906 
2907 		for_each_cpu(tcpu, &mask) {
2908 			if (!cpu_distance_fn ||
2909 			    (cpu_distance_fn(cpu, tcpu) == LOCAL_DISTANCE &&
2910 			     cpu_distance_fn(tcpu, cpu) == LOCAL_DISTANCE)) {
2911 				group_map[tcpu] = group;
2912 				group_cnt[group]++;
2913 				cpumask_clear_cpu(tcpu, &mask);
2914 			}
2915 		}
2916 	}
2917 	nr_groups = group;
2918 
2919 	/*
2920 	 * Wasted space is caused by a ratio imbalance of upa to group_cnt.
2921 	 * Expand the unit_size until we use >= 75% of the units allocated.
2922 	 * Related to atom_size, which could be much larger than the unit_size.
2923 	 */
2924 	last_allocs = INT_MAX;
2925 	best_upa = 0;
2926 	for (upa = max_upa; upa; upa--) {
2927 		int allocs = 0, wasted = 0;
2928 
2929 		if (alloc_size % upa || (offset_in_page(alloc_size / upa)))
2930 			continue;
2931 
2932 		for (group = 0; group < nr_groups; group++) {
2933 			int this_allocs = DIV_ROUND_UP(group_cnt[group], upa);
2934 			allocs += this_allocs;
2935 			wasted += this_allocs * upa - group_cnt[group];
2936 		}
2937 
2938 		/*
2939 		 * Don't accept if wastage is over 1/3.  The
2940 		 * greater-than comparison ensures upa==1 always
2941 		 * passes the following check.
2942 		 */
2943 		if (wasted > num_possible_cpus() / 3)
2944 			continue;
2945 
2946 		/* and then don't consume more memory */
2947 		if (allocs > last_allocs)
2948 			break;
2949 		last_allocs = allocs;
2950 		best_upa = upa;
2951 	}
2952 	BUG_ON(!best_upa);
2953 	upa = best_upa;
2954 
2955 	/* allocate and fill alloc_info */
2956 	for (group = 0; group < nr_groups; group++)
2957 		nr_units += roundup(group_cnt[group], upa);
2958 
2959 	ai = pcpu_alloc_alloc_info(nr_groups, nr_units);
2960 	if (!ai)
2961 		return ERR_PTR(-ENOMEM);
2962 	cpu_map = ai->groups[0].cpu_map;
2963 
2964 	for (group = 0; group < nr_groups; group++) {
2965 		ai->groups[group].cpu_map = cpu_map;
2966 		cpu_map += roundup(group_cnt[group], upa);
2967 	}
2968 
2969 	ai->static_size = static_size;
2970 	ai->reserved_size = reserved_size;
2971 	ai->dyn_size = dyn_size;
2972 	ai->unit_size = alloc_size / upa;
2973 	ai->atom_size = atom_size;
2974 	ai->alloc_size = alloc_size;
2975 
2976 	for (group = 0, unit = 0; group < nr_groups; group++) {
2977 		struct pcpu_group_info *gi = &ai->groups[group];
2978 
2979 		/*
2980 		 * Initialize base_offset as if all groups are located
2981 		 * back-to-back.  The caller should update this to
2982 		 * reflect actual allocation.
2983 		 */
2984 		gi->base_offset = unit * ai->unit_size;
2985 
2986 		for_each_possible_cpu(cpu)
2987 			if (group_map[cpu] == group)
2988 				gi->cpu_map[gi->nr_units++] = cpu;
2989 		gi->nr_units = roundup(gi->nr_units, upa);
2990 		unit += gi->nr_units;
2991 	}
2992 	BUG_ON(unit != nr_units);
2993 
2994 	return ai;
2995 }
2996 #endif /* BUILD_EMBED_FIRST_CHUNK || BUILD_PAGE_FIRST_CHUNK */
2997 
2998 #if defined(BUILD_EMBED_FIRST_CHUNK)
2999 /**
3000  * pcpu_embed_first_chunk - embed the first percpu chunk into bootmem
3001  * @reserved_size: the size of reserved percpu area in bytes
3002  * @dyn_size: minimum free size for dynamic allocation in bytes
3003  * @atom_size: allocation atom size
3004  * @cpu_distance_fn: callback to determine distance between cpus, optional
3005  * @alloc_fn: function to allocate percpu page
3006  * @free_fn: function to free percpu page
3007  *
3008  * This is a helper to ease setting up embedded first percpu chunk and
3009  * can be called where pcpu_setup_first_chunk() is expected.
3010  *
3011  * If this function is used to setup the first chunk, it is allocated
3012  * by calling @alloc_fn and used as-is without being mapped into
3013  * vmalloc area.  Allocations are always whole multiples of @atom_size
3014  * aligned to @atom_size.
3015  *
3016  * This enables the first chunk to piggy back on the linear physical
3017  * mapping which often uses larger page size.  Please note that this
3018  * can result in very sparse cpu->unit mapping on NUMA machines thus
3019  * requiring large vmalloc address space.  Don't use this allocator if
3020  * vmalloc space is not orders of magnitude larger than distances
3021  * between node memory addresses (ie. 32bit NUMA machines).
3022  *
3023  * @dyn_size specifies the minimum dynamic area size.
3024  *
3025  * If the needed size is smaller than the minimum or specified unit
3026  * size, the leftover is returned using @free_fn.
3027  *
3028  * RETURNS:
3029  * 0 on success, -errno on failure.
3030  */
pcpu_embed_first_chunk(size_t reserved_size,size_t dyn_size,size_t atom_size,pcpu_fc_cpu_distance_fn_t cpu_distance_fn,pcpu_fc_alloc_fn_t alloc_fn,pcpu_fc_free_fn_t free_fn)3031 int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
3032 				  size_t atom_size,
3033 				  pcpu_fc_cpu_distance_fn_t cpu_distance_fn,
3034 				  pcpu_fc_alloc_fn_t alloc_fn,
3035 				  pcpu_fc_free_fn_t free_fn)
3036 {
3037 	void *base = (void *)ULONG_MAX;
3038 	void **areas = NULL;
3039 	struct pcpu_alloc_info *ai;
3040 	size_t size_sum, areas_size;
3041 	unsigned long max_distance;
3042 	int group, i, highest_group, rc = 0;
3043 
3044 	ai = pcpu_build_alloc_info(reserved_size, dyn_size, atom_size,
3045 				   cpu_distance_fn);
3046 	if (IS_ERR(ai))
3047 		return PTR_ERR(ai);
3048 
3049 	size_sum = ai->static_size + ai->reserved_size + ai->dyn_size;
3050 	areas_size = PFN_ALIGN(ai->nr_groups * sizeof(void *));
3051 
3052 	areas = memblock_alloc(areas_size, SMP_CACHE_BYTES);
3053 	if (!areas) {
3054 		rc = -ENOMEM;
3055 		goto out_free;
3056 	}
3057 
3058 	/* allocate, copy and determine base address & max_distance */
3059 	highest_group = 0;
3060 	for (group = 0; group < ai->nr_groups; group++) {
3061 		struct pcpu_group_info *gi = &ai->groups[group];
3062 		unsigned int cpu = NR_CPUS;
3063 		void *ptr;
3064 
3065 		for (i = 0; i < gi->nr_units && cpu == NR_CPUS; i++)
3066 			cpu = gi->cpu_map[i];
3067 		BUG_ON(cpu == NR_CPUS);
3068 
3069 		/* allocate space for the whole group */
3070 		ptr = alloc_fn(cpu, gi->nr_units * ai->unit_size, atom_size);
3071 		if (!ptr) {
3072 			rc = -ENOMEM;
3073 			goto out_free_areas;
3074 		}
3075 		/* kmemleak tracks the percpu allocations separately */
3076 		kmemleak_free(ptr);
3077 		areas[group] = ptr;
3078 
3079 		base = min(ptr, base);
3080 		if (ptr > areas[highest_group])
3081 			highest_group = group;
3082 	}
3083 	max_distance = areas[highest_group] - base;
3084 	max_distance += ai->unit_size * ai->groups[highest_group].nr_units;
3085 
3086 	/* warn if maximum distance is further than 75% of vmalloc space */
3087 	if (max_distance > VMALLOC_TOTAL * 3 / 4) {
3088 		pr_warn("max_distance=0x%lx too large for vmalloc space 0x%lx\n",
3089 				max_distance, VMALLOC_TOTAL);
3090 #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
3091 		/* and fail if we have fallback */
3092 		rc = -EINVAL;
3093 		goto out_free_areas;
3094 #endif
3095 	}
3096 
3097 	/*
3098 	 * Copy data and free unused parts.  This should happen after all
3099 	 * allocations are complete; otherwise, we may end up with
3100 	 * overlapping groups.
3101 	 */
3102 	for (group = 0; group < ai->nr_groups; group++) {
3103 		struct pcpu_group_info *gi = &ai->groups[group];
3104 		void *ptr = areas[group];
3105 
3106 		for (i = 0; i < gi->nr_units; i++, ptr += ai->unit_size) {
3107 			if (gi->cpu_map[i] == NR_CPUS) {
3108 				/* unused unit, free whole */
3109 				free_fn(ptr, ai->unit_size);
3110 				continue;
3111 			}
3112 			/* copy and return the unused part */
3113 			memcpy(ptr, __per_cpu_load, ai->static_size);
3114 			free_fn(ptr + size_sum, ai->unit_size - size_sum);
3115 		}
3116 	}
3117 
3118 	/* base address is now known, determine group base offsets */
3119 	for (group = 0; group < ai->nr_groups; group++) {
3120 		ai->groups[group].base_offset = areas[group] - base;
3121 	}
3122 
3123 	pr_info("Embedded %zu pages/cpu s%zu r%zu d%zu u%zu\n",
3124 		PFN_DOWN(size_sum), ai->static_size, ai->reserved_size,
3125 		ai->dyn_size, ai->unit_size);
3126 
3127 	pcpu_setup_first_chunk(ai, base);
3128 	goto out_free;
3129 
3130 out_free_areas:
3131 	for (group = 0; group < ai->nr_groups; group++)
3132 		if (areas[group])
3133 			free_fn(areas[group],
3134 				ai->groups[group].nr_units * ai->unit_size);
3135 out_free:
3136 	pcpu_free_alloc_info(ai);
3137 	if (areas)
3138 		memblock_free_early(__pa(areas), areas_size);
3139 	return rc;
3140 }
3141 #endif /* BUILD_EMBED_FIRST_CHUNK */
3142 
3143 #ifdef BUILD_PAGE_FIRST_CHUNK
3144 /**
3145  * pcpu_page_first_chunk - map the first chunk using PAGE_SIZE pages
3146  * @reserved_size: the size of reserved percpu area in bytes
3147  * @alloc_fn: function to allocate percpu page, always called with PAGE_SIZE
3148  * @free_fn: function to free percpu page, always called with PAGE_SIZE
3149  * @populate_pte_fn: function to populate pte
3150  *
3151  * This is a helper to ease setting up page-remapped first percpu
3152  * chunk and can be called where pcpu_setup_first_chunk() is expected.
3153  *
3154  * This is the basic allocator.  Static percpu area is allocated
3155  * page-by-page into vmalloc area.
3156  *
3157  * RETURNS:
3158  * 0 on success, -errno on failure.
3159  */
pcpu_page_first_chunk(size_t reserved_size,pcpu_fc_alloc_fn_t alloc_fn,pcpu_fc_free_fn_t free_fn,pcpu_fc_populate_pte_fn_t populate_pte_fn)3160 int __init pcpu_page_first_chunk(size_t reserved_size,
3161 				 pcpu_fc_alloc_fn_t alloc_fn,
3162 				 pcpu_fc_free_fn_t free_fn,
3163 				 pcpu_fc_populate_pte_fn_t populate_pte_fn)
3164 {
3165 	static struct vm_struct vm;
3166 	struct pcpu_alloc_info *ai;
3167 	char psize_str[16];
3168 	int unit_pages;
3169 	size_t pages_size;
3170 	struct page **pages;
3171 	int unit, i, j, rc = 0;
3172 	int upa;
3173 	int nr_g0_units;
3174 
3175 	snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);
3176 
3177 	ai = pcpu_build_alloc_info(reserved_size, 0, PAGE_SIZE, NULL);
3178 	if (IS_ERR(ai))
3179 		return PTR_ERR(ai);
3180 	BUG_ON(ai->nr_groups != 1);
3181 	upa = ai->alloc_size/ai->unit_size;
3182 	nr_g0_units = roundup(num_possible_cpus(), upa);
3183 	if (WARN_ON(ai->groups[0].nr_units != nr_g0_units)) {
3184 		pcpu_free_alloc_info(ai);
3185 		return -EINVAL;
3186 	}
3187 
3188 	unit_pages = ai->unit_size >> PAGE_SHIFT;
3189 
3190 	/* unaligned allocations can't be freed, round up to page size */
3191 	pages_size = PFN_ALIGN(unit_pages * num_possible_cpus() *
3192 			       sizeof(pages[0]));
3193 	pages = memblock_alloc(pages_size, SMP_CACHE_BYTES);
3194 	if (!pages)
3195 		panic("%s: Failed to allocate %zu bytes\n", __func__,
3196 		      pages_size);
3197 
3198 	/* allocate pages */
3199 	j = 0;
3200 	for (unit = 0; unit < num_possible_cpus(); unit++) {
3201 		unsigned int cpu = ai->groups[0].cpu_map[unit];
3202 		for (i = 0; i < unit_pages; i++) {
3203 			void *ptr;
3204 
3205 			ptr = alloc_fn(cpu, PAGE_SIZE, PAGE_SIZE);
3206 			if (!ptr) {
3207 				pr_warn("failed to allocate %s page for cpu%u\n",
3208 						psize_str, cpu);
3209 				goto enomem;
3210 			}
3211 			/* kmemleak tracks the percpu allocations separately */
3212 			kmemleak_free(ptr);
3213 			pages[j++] = virt_to_page(ptr);
3214 		}
3215 	}
3216 
3217 	/* allocate vm area, map the pages and copy static data */
3218 	vm.flags = VM_ALLOC;
3219 	vm.size = num_possible_cpus() * ai->unit_size;
3220 	vm_area_register_early(&vm, PAGE_SIZE);
3221 
3222 	for (unit = 0; unit < num_possible_cpus(); unit++) {
3223 		unsigned long unit_addr =
3224 			(unsigned long)vm.addr + unit * ai->unit_size;
3225 
3226 		for (i = 0; i < unit_pages; i++)
3227 			populate_pte_fn(unit_addr + (i << PAGE_SHIFT));
3228 
3229 		/* pte already populated, the following shouldn't fail */
3230 		rc = __pcpu_map_pages(unit_addr, &pages[unit * unit_pages],
3231 				      unit_pages);
3232 		if (rc < 0)
3233 			panic("failed to map percpu area, err=%d\n", rc);
3234 
3235 		/*
3236 		 * FIXME: Archs with virtual cache should flush local
3237 		 * cache for the linear mapping here - something
3238 		 * equivalent to flush_cache_vmap() on the local cpu.
3239 		 * flush_cache_vmap() can't be used as most supporting
3240 		 * data structures are not set up yet.
3241 		 */
3242 
3243 		/* copy static data */
3244 		memcpy((void *)unit_addr, __per_cpu_load, ai->static_size);
3245 	}
3246 
3247 	/* we're ready, commit */
3248 	pr_info("%d %s pages/cpu s%zu r%zu d%zu\n",
3249 		unit_pages, psize_str, ai->static_size,
3250 		ai->reserved_size, ai->dyn_size);
3251 
3252 	pcpu_setup_first_chunk(ai, vm.addr);
3253 	goto out_free_ar;
3254 
3255 enomem:
3256 	while (--j >= 0)
3257 		free_fn(page_address(pages[j]), PAGE_SIZE);
3258 	rc = -ENOMEM;
3259 out_free_ar:
3260 	memblock_free_early(__pa(pages), pages_size);
3261 	pcpu_free_alloc_info(ai);
3262 	return rc;
3263 }
3264 #endif /* BUILD_PAGE_FIRST_CHUNK */
3265 
3266 #ifndef	CONFIG_HAVE_SETUP_PER_CPU_AREA
3267 /*
3268  * Generic SMP percpu area setup.
3269  *
3270  * The embedding helper is used because its behavior closely resembles
3271  * the original non-dynamic generic percpu area setup.  This is
3272  * important because many archs have addressing restrictions and might
3273  * fail if the percpu area is located far away from the previous
3274  * location.  As an added bonus, in non-NUMA cases, embedding is
3275  * generally a good idea TLB-wise because percpu area can piggy back
3276  * on the physical linear memory mapping which uses large page
3277  * mappings on applicable archs.
3278  */
3279 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
3280 EXPORT_SYMBOL(__per_cpu_offset);
3281 
pcpu_dfl_fc_alloc(unsigned int cpu,size_t size,size_t align)3282 static void * __init pcpu_dfl_fc_alloc(unsigned int cpu, size_t size,
3283 				       size_t align)
3284 {
3285 	return  memblock_alloc_from(size, align, __pa(MAX_DMA_ADDRESS));
3286 }
3287 
pcpu_dfl_fc_free(void * ptr,size_t size)3288 static void __init pcpu_dfl_fc_free(void *ptr, size_t size)
3289 {
3290 	memblock_free_early(__pa(ptr), size);
3291 }
3292 
setup_per_cpu_areas(void)3293 void __init setup_per_cpu_areas(void)
3294 {
3295 	unsigned long delta;
3296 	unsigned int cpu;
3297 	int rc;
3298 
3299 	/*
3300 	 * Always reserve area for module percpu variables.  That's
3301 	 * what the legacy allocator did.
3302 	 */
3303 	rc = pcpu_embed_first_chunk(PERCPU_MODULE_RESERVE,
3304 				    PERCPU_DYNAMIC_RESERVE, PAGE_SIZE, NULL,
3305 				    pcpu_dfl_fc_alloc, pcpu_dfl_fc_free);
3306 	if (rc < 0)
3307 		panic("Failed to initialize percpu areas.");
3308 
3309 	delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
3310 	for_each_possible_cpu(cpu)
3311 		__per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];
3312 }
3313 #endif	/* CONFIG_HAVE_SETUP_PER_CPU_AREA */
3314 
3315 #else	/* CONFIG_SMP */
3316 
3317 /*
3318  * UP percpu area setup.
3319  *
3320  * UP always uses km-based percpu allocator with identity mapping.
3321  * Static percpu variables are indistinguishable from the usual static
3322  * variables and don't require any special preparation.
3323  */
setup_per_cpu_areas(void)3324 void __init setup_per_cpu_areas(void)
3325 {
3326 	const size_t unit_size =
3327 		roundup_pow_of_two(max_t(size_t, PCPU_MIN_UNIT_SIZE,
3328 					 PERCPU_DYNAMIC_RESERVE));
3329 	struct pcpu_alloc_info *ai;
3330 	void *fc;
3331 
3332 	ai = pcpu_alloc_alloc_info(1, 1);
3333 	fc = memblock_alloc_from(unit_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
3334 	if (!ai || !fc)
3335 		panic("Failed to allocate memory for percpu areas.");
3336 	/* kmemleak tracks the percpu allocations separately */
3337 	kmemleak_free(fc);
3338 
3339 	ai->dyn_size = unit_size;
3340 	ai->unit_size = unit_size;
3341 	ai->atom_size = unit_size;
3342 	ai->alloc_size = unit_size;
3343 	ai->groups[0].nr_units = 1;
3344 	ai->groups[0].cpu_map[0] = 0;
3345 
3346 	pcpu_setup_first_chunk(ai, fc);
3347 	pcpu_free_alloc_info(ai);
3348 }
3349 
3350 #endif	/* CONFIG_SMP */
3351 
3352 /*
3353  * pcpu_nr_pages - calculate total number of populated backing pages
3354  *
3355  * This reflects the number of pages populated to back chunks.  Metadata is
3356  * excluded in the number exposed in meminfo as the number of backing pages
3357  * scales with the number of cpus and can quickly outweigh the memory used for
3358  * metadata.  It also keeps this calculation nice and simple.
3359  *
3360  * RETURNS:
3361  * Total number of populated backing pages in use by the allocator.
3362  */
pcpu_nr_pages(void)3363 unsigned long pcpu_nr_pages(void)
3364 {
3365 	return pcpu_nr_populated * pcpu_nr_units;
3366 }
3367 EXPORT_SYMBOL_GPL(pcpu_nr_pages);
3368 
3369 /*
3370  * Percpu allocator is initialized early during boot when neither slab or
3371  * workqueue is available.  Plug async management until everything is up
3372  * and running.
3373  */
percpu_enable_async(void)3374 static int __init percpu_enable_async(void)
3375 {
3376 	pcpu_async_enabled = true;
3377 	return 0;
3378 }
3379 subsys_initcall(percpu_enable_async);
3380