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 start, end;	/* 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 	for_each_clear_bitrange_from(start, end, alloc_map, PCPU_BITMAP_BLOCK_BITS)
799 		pcpu_block_update(block, start, end);
800 }
801 
802 /**
803  * pcpu_block_update_hint_alloc - update hint on allocation path
804  * @chunk: chunk of interest
805  * @bit_off: chunk offset
806  * @bits: size of request
807  *
808  * Updates metadata for the allocation path.  The metadata only has to be
809  * refreshed by a full scan iff the chunk's contig hint is broken.  Block level
810  * scans are required if the block's contig hint is broken.
811  */
pcpu_block_update_hint_alloc(struct pcpu_chunk * chunk,int bit_off,int bits)812 static void pcpu_block_update_hint_alloc(struct pcpu_chunk *chunk, int bit_off,
813 					 int bits)
814 {
815 	struct pcpu_block_md *chunk_md = &chunk->chunk_md;
816 	int nr_empty_pages = 0;
817 	struct pcpu_block_md *s_block, *e_block, *block;
818 	int s_index, e_index;	/* block indexes of the freed allocation */
819 	int s_off, e_off;	/* block offsets of the freed allocation */
820 
821 	/*
822 	 * Calculate per block offsets.
823 	 * The calculation uses an inclusive range, but the resulting offsets
824 	 * are [start, end).  e_index always points to the last block in the
825 	 * range.
826 	 */
827 	s_index = pcpu_off_to_block_index(bit_off);
828 	e_index = pcpu_off_to_block_index(bit_off + bits - 1);
829 	s_off = pcpu_off_to_block_off(bit_off);
830 	e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;
831 
832 	s_block = chunk->md_blocks + s_index;
833 	e_block = chunk->md_blocks + e_index;
834 
835 	/*
836 	 * Update s_block.
837 	 * block->first_free must be updated if the allocation takes its place.
838 	 * If the allocation breaks the contig_hint, a scan is required to
839 	 * restore this hint.
840 	 */
841 	if (s_block->contig_hint == PCPU_BITMAP_BLOCK_BITS)
842 		nr_empty_pages++;
843 
844 	if (s_off == s_block->first_free)
845 		s_block->first_free = find_next_zero_bit(
846 					pcpu_index_alloc_map(chunk, s_index),
847 					PCPU_BITMAP_BLOCK_BITS,
848 					s_off + bits);
849 
850 	if (pcpu_region_overlap(s_block->scan_hint_start,
851 				s_block->scan_hint_start + s_block->scan_hint,
852 				s_off,
853 				s_off + bits))
854 		s_block->scan_hint = 0;
855 
856 	if (pcpu_region_overlap(s_block->contig_hint_start,
857 				s_block->contig_hint_start +
858 				s_block->contig_hint,
859 				s_off,
860 				s_off + bits)) {
861 		/* block contig hint is broken - scan to fix it */
862 		if (!s_off)
863 			s_block->left_free = 0;
864 		pcpu_block_refresh_hint(chunk, s_index);
865 	} else {
866 		/* update left and right contig manually */
867 		s_block->left_free = min(s_block->left_free, s_off);
868 		if (s_index == e_index)
869 			s_block->right_free = min_t(int, s_block->right_free,
870 					PCPU_BITMAP_BLOCK_BITS - e_off);
871 		else
872 			s_block->right_free = 0;
873 	}
874 
875 	/*
876 	 * Update e_block.
877 	 */
878 	if (s_index != e_index) {
879 		if (e_block->contig_hint == PCPU_BITMAP_BLOCK_BITS)
880 			nr_empty_pages++;
881 
882 		/*
883 		 * When the allocation is across blocks, the end is along
884 		 * the left part of the e_block.
885 		 */
886 		e_block->first_free = find_next_zero_bit(
887 				pcpu_index_alloc_map(chunk, e_index),
888 				PCPU_BITMAP_BLOCK_BITS, e_off);
889 
890 		if (e_off == PCPU_BITMAP_BLOCK_BITS) {
891 			/* reset the block */
892 			e_block++;
893 		} else {
894 			if (e_off > e_block->scan_hint_start)
895 				e_block->scan_hint = 0;
896 
897 			e_block->left_free = 0;
898 			if (e_off > e_block->contig_hint_start) {
899 				/* contig hint is broken - scan to fix it */
900 				pcpu_block_refresh_hint(chunk, e_index);
901 			} else {
902 				e_block->right_free =
903 					min_t(int, e_block->right_free,
904 					      PCPU_BITMAP_BLOCK_BITS - e_off);
905 			}
906 		}
907 
908 		/* update in-between md_blocks */
909 		nr_empty_pages += (e_index - s_index - 1);
910 		for (block = s_block + 1; block < e_block; block++) {
911 			block->scan_hint = 0;
912 			block->contig_hint = 0;
913 			block->left_free = 0;
914 			block->right_free = 0;
915 		}
916 	}
917 
918 	if (nr_empty_pages)
919 		pcpu_update_empty_pages(chunk, -nr_empty_pages);
920 
921 	if (pcpu_region_overlap(chunk_md->scan_hint_start,
922 				chunk_md->scan_hint_start +
923 				chunk_md->scan_hint,
924 				bit_off,
925 				bit_off + bits))
926 		chunk_md->scan_hint = 0;
927 
928 	/*
929 	 * The only time a full chunk scan is required is if the chunk
930 	 * contig hint is broken.  Otherwise, it means a smaller space
931 	 * was used and therefore the chunk contig hint is still correct.
932 	 */
933 	if (pcpu_region_overlap(chunk_md->contig_hint_start,
934 				chunk_md->contig_hint_start +
935 				chunk_md->contig_hint,
936 				bit_off,
937 				bit_off + bits))
938 		pcpu_chunk_refresh_hint(chunk, false);
939 }
940 
941 /**
942  * pcpu_block_update_hint_free - updates the block hints on the free path
943  * @chunk: chunk of interest
944  * @bit_off: chunk offset
945  * @bits: size of request
946  *
947  * Updates metadata for the allocation path.  This avoids a blind block
948  * refresh by making use of the block contig hints.  If this fails, it scans
949  * forward and backward to determine the extent of the free area.  This is
950  * capped at the boundary of blocks.
951  *
952  * A chunk update is triggered if a page becomes free, a block becomes free,
953  * or the free spans across blocks.  This tradeoff is to minimize iterating
954  * over the block metadata to update chunk_md->contig_hint.
955  * chunk_md->contig_hint may be off by up to a page, but it will never be more
956  * than the available space.  If the contig hint is contained in one block, it
957  * will be accurate.
958  */
pcpu_block_update_hint_free(struct pcpu_chunk * chunk,int bit_off,int bits)959 static void pcpu_block_update_hint_free(struct pcpu_chunk *chunk, int bit_off,
960 					int bits)
961 {
962 	int nr_empty_pages = 0;
963 	struct pcpu_block_md *s_block, *e_block, *block;
964 	int s_index, e_index;	/* block indexes of the freed allocation */
965 	int s_off, e_off;	/* block offsets of the freed allocation */
966 	int start, end;		/* start and end of the whole free area */
967 
968 	/*
969 	 * Calculate per block offsets.
970 	 * The calculation uses an inclusive range, but the resulting offsets
971 	 * are [start, end).  e_index always points to the last block in the
972 	 * range.
973 	 */
974 	s_index = pcpu_off_to_block_index(bit_off);
975 	e_index = pcpu_off_to_block_index(bit_off + bits - 1);
976 	s_off = pcpu_off_to_block_off(bit_off);
977 	e_off = pcpu_off_to_block_off(bit_off + bits - 1) + 1;
978 
979 	s_block = chunk->md_blocks + s_index;
980 	e_block = chunk->md_blocks + e_index;
981 
982 	/*
983 	 * Check if the freed area aligns with the block->contig_hint.
984 	 * If it does, then the scan to find the beginning/end of the
985 	 * larger free area can be avoided.
986 	 *
987 	 * start and end refer to beginning and end of the free area
988 	 * within each their respective blocks.  This is not necessarily
989 	 * the entire free area as it may span blocks past the beginning
990 	 * or end of the block.
991 	 */
992 	start = s_off;
993 	if (s_off == s_block->contig_hint + s_block->contig_hint_start) {
994 		start = s_block->contig_hint_start;
995 	} else {
996 		/*
997 		 * Scan backwards to find the extent of the free area.
998 		 * find_last_bit returns the starting bit, so if the start bit
999 		 * is returned, that means there was no last bit and the
1000 		 * remainder of the chunk is free.
1001 		 */
1002 		int l_bit = find_last_bit(pcpu_index_alloc_map(chunk, s_index),
1003 					  start);
1004 		start = (start == l_bit) ? 0 : l_bit + 1;
1005 	}
1006 
1007 	end = e_off;
1008 	if (e_off == e_block->contig_hint_start)
1009 		end = e_block->contig_hint_start + e_block->contig_hint;
1010 	else
1011 		end = find_next_bit(pcpu_index_alloc_map(chunk, e_index),
1012 				    PCPU_BITMAP_BLOCK_BITS, end);
1013 
1014 	/* update s_block */
1015 	e_off = (s_index == e_index) ? end : PCPU_BITMAP_BLOCK_BITS;
1016 	if (!start && e_off == PCPU_BITMAP_BLOCK_BITS)
1017 		nr_empty_pages++;
1018 	pcpu_block_update(s_block, start, e_off);
1019 
1020 	/* freeing in the same block */
1021 	if (s_index != e_index) {
1022 		/* update e_block */
1023 		if (end == PCPU_BITMAP_BLOCK_BITS)
1024 			nr_empty_pages++;
1025 		pcpu_block_update(e_block, 0, end);
1026 
1027 		/* reset md_blocks in the middle */
1028 		nr_empty_pages += (e_index - s_index - 1);
1029 		for (block = s_block + 1; block < e_block; block++) {
1030 			block->first_free = 0;
1031 			block->scan_hint = 0;
1032 			block->contig_hint_start = 0;
1033 			block->contig_hint = PCPU_BITMAP_BLOCK_BITS;
1034 			block->left_free = PCPU_BITMAP_BLOCK_BITS;
1035 			block->right_free = PCPU_BITMAP_BLOCK_BITS;
1036 		}
1037 	}
1038 
1039 	if (nr_empty_pages)
1040 		pcpu_update_empty_pages(chunk, nr_empty_pages);
1041 
1042 	/*
1043 	 * Refresh chunk metadata when the free makes a block free or spans
1044 	 * across blocks.  The contig_hint may be off by up to a page, but if
1045 	 * the contig_hint is contained in a block, it will be accurate with
1046 	 * the else condition below.
1047 	 */
1048 	if (((end - start) >= PCPU_BITMAP_BLOCK_BITS) || s_index != e_index)
1049 		pcpu_chunk_refresh_hint(chunk, true);
1050 	else
1051 		pcpu_block_update(&chunk->chunk_md,
1052 				  pcpu_block_off_to_off(s_index, start),
1053 				  end);
1054 }
1055 
1056 /**
1057  * pcpu_is_populated - determines if the region is populated
1058  * @chunk: chunk of interest
1059  * @bit_off: chunk offset
1060  * @bits: size of area
1061  * @next_off: return value for the next offset to start searching
1062  *
1063  * For atomic allocations, check if the backing pages are populated.
1064  *
1065  * RETURNS:
1066  * Bool if the backing pages are populated.
1067  * next_index is to skip over unpopulated blocks in pcpu_find_block_fit.
1068  */
pcpu_is_populated(struct pcpu_chunk * chunk,int bit_off,int bits,int * next_off)1069 static bool pcpu_is_populated(struct pcpu_chunk *chunk, int bit_off, int bits,
1070 			      int *next_off)
1071 {
1072 	unsigned int start, end;
1073 
1074 	start = PFN_DOWN(bit_off * PCPU_MIN_ALLOC_SIZE);
1075 	end = PFN_UP((bit_off + bits) * PCPU_MIN_ALLOC_SIZE);
1076 
1077 	start = find_next_zero_bit(chunk->populated, end, start);
1078 	if (start >= end)
1079 		return true;
1080 
1081 	end = find_next_bit(chunk->populated, end, start + 1);
1082 
1083 	*next_off = end * 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, pcpu_obj_full_size(size))) {
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 				pcpu_obj_full_size(size));
1660 		rcu_read_unlock();
1661 	} else {
1662 		obj_cgroup_uncharge(objcg, pcpu_obj_full_size(size));
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, pcpu_obj_full_size(size));
1680 
1681 	rcu_read_lock();
1682 	mod_memcg_state(obj_cgroup_memcg(objcg), MEMCG_PERCPU_B,
1683 			-pcpu_obj_full_size(size));
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_end, rs, re;
1855 
1856 		rs = PFN_DOWN(off);
1857 		page_end = PFN_UP(off + size);
1858 
1859 		for_each_clear_bitrange_from(rs, re, chunk->populated, page_end) {
1860 			WARN_ON(chunk->immutable);
1861 
1862 			ret = pcpu_populate_chunk(chunk, rs, re, pcpu_gfp);
1863 
1864 			spin_lock_irqsave(&pcpu_lock, flags);
1865 			if (ret) {
1866 				pcpu_free_area(chunk, off);
1867 				err = "failed to populate";
1868 				goto fail_unlock;
1869 			}
1870 			pcpu_chunk_populated(chunk, rs, re);
1871 			spin_unlock_irqrestore(&pcpu_lock, flags);
1872 		}
1873 
1874 		mutex_unlock(&pcpu_alloc_mutex);
1875 	}
1876 
1877 	if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
1878 		pcpu_schedule_balance_work();
1879 
1880 	/* clear the areas and return address relative to base address */
1881 	for_each_possible_cpu(cpu)
1882 		memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
1883 
1884 	ptr = __addr_to_pcpu_ptr(chunk->base_addr + off);
1885 	kmemleak_alloc_percpu(ptr, size, gfp);
1886 
1887 	trace_percpu_alloc_percpu(_RET_IP_, reserved, is_atomic, size, align,
1888 				  chunk->base_addr, off, ptr,
1889 				  pcpu_obj_full_size(size), gfp);
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 		for_each_set_bitrange(rs, re, chunk->populated, chunk->nr_pages) {
2017 			pcpu_depopulate_chunk(chunk, rs, re);
2018 			spin_lock_irq(&pcpu_lock);
2019 			pcpu_chunk_depopulated(chunk, rs, re);
2020 			spin_unlock_irq(&pcpu_lock);
2021 		}
2022 		pcpu_destroy_chunk(chunk);
2023 		cond_resched();
2024 	}
2025 	spin_lock_irq(&pcpu_lock);
2026 }
2027 
2028 /**
2029  * pcpu_balance_populated - manage the amount of populated pages
2030  *
2031  * Maintain a certain amount of populated pages to satisfy atomic allocations.
2032  * It is possible that this is called when physical memory is scarce causing
2033  * OOM killer to be triggered.  We should avoid doing so until an actual
2034  * allocation causes the failure as it is possible that requests can be
2035  * serviced from already backed regions.
2036  *
2037  * CONTEXT:
2038  * pcpu_lock (can be dropped temporarily)
2039  */
pcpu_balance_populated(void)2040 static void pcpu_balance_populated(void)
2041 {
2042 	/* gfp flags passed to underlying allocators */
2043 	const gfp_t gfp = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
2044 	struct pcpu_chunk *chunk;
2045 	int slot, nr_to_pop, ret;
2046 
2047 	lockdep_assert_held(&pcpu_lock);
2048 
2049 	/*
2050 	 * Ensure there are certain number of free populated pages for
2051 	 * atomic allocs.  Fill up from the most packed so that atomic
2052 	 * allocs don't increase fragmentation.  If atomic allocation
2053 	 * failed previously, always populate the maximum amount.  This
2054 	 * should prevent atomic allocs larger than PAGE_SIZE from keeping
2055 	 * failing indefinitely; however, large atomic allocs are not
2056 	 * something we support properly and can be highly unreliable and
2057 	 * inefficient.
2058 	 */
2059 retry_pop:
2060 	if (pcpu_atomic_alloc_failed) {
2061 		nr_to_pop = PCPU_EMPTY_POP_PAGES_HIGH;
2062 		/* best effort anyway, don't worry about synchronization */
2063 		pcpu_atomic_alloc_failed = false;
2064 	} else {
2065 		nr_to_pop = clamp(PCPU_EMPTY_POP_PAGES_HIGH -
2066 				  pcpu_nr_empty_pop_pages,
2067 				  0, PCPU_EMPTY_POP_PAGES_HIGH);
2068 	}
2069 
2070 	for (slot = pcpu_size_to_slot(PAGE_SIZE); slot <= pcpu_free_slot; slot++) {
2071 		unsigned int nr_unpop = 0, rs, re;
2072 
2073 		if (!nr_to_pop)
2074 			break;
2075 
2076 		list_for_each_entry(chunk, &pcpu_chunk_lists[slot], list) {
2077 			nr_unpop = chunk->nr_pages - chunk->nr_populated;
2078 			if (nr_unpop)
2079 				break;
2080 		}
2081 
2082 		if (!nr_unpop)
2083 			continue;
2084 
2085 		/* @chunk can't go away while pcpu_alloc_mutex is held */
2086 		for_each_clear_bitrange(rs, re, chunk->populated, chunk->nr_pages) {
2087 			int nr = min_t(int, re - rs, nr_to_pop);
2088 
2089 			spin_unlock_irq(&pcpu_lock);
2090 			ret = pcpu_populate_chunk(chunk, rs, rs + nr, gfp);
2091 			cond_resched();
2092 			spin_lock_irq(&pcpu_lock);
2093 			if (!ret) {
2094 				nr_to_pop -= nr;
2095 				pcpu_chunk_populated(chunk, rs, rs + nr);
2096 			} else {
2097 				nr_to_pop = 0;
2098 			}
2099 
2100 			if (!nr_to_pop)
2101 				break;
2102 		}
2103 	}
2104 
2105 	if (nr_to_pop) {
2106 		/* ran out of chunks to populate, create a new one and retry */
2107 		spin_unlock_irq(&pcpu_lock);
2108 		chunk = pcpu_create_chunk(gfp);
2109 		cond_resched();
2110 		spin_lock_irq(&pcpu_lock);
2111 		if (chunk) {
2112 			pcpu_chunk_relocate(chunk, -1);
2113 			goto retry_pop;
2114 		}
2115 	}
2116 }
2117 
2118 /**
2119  * pcpu_reclaim_populated - scan over to_depopulate chunks and free empty pages
2120  *
2121  * Scan over chunks in the depopulate list and try to release unused populated
2122  * pages back to the system.  Depopulated chunks are sidelined to prevent
2123  * repopulating these pages unless required.  Fully free chunks are reintegrated
2124  * and freed accordingly (1 is kept around).  If we drop below the empty
2125  * populated pages threshold, reintegrate the chunk if it has empty free pages.
2126  * Each chunk is scanned in the reverse order to keep populated pages close to
2127  * the beginning of the chunk.
2128  *
2129  * CONTEXT:
2130  * pcpu_lock (can be dropped temporarily)
2131  *
2132  */
pcpu_reclaim_populated(void)2133 static void pcpu_reclaim_populated(void)
2134 {
2135 	struct pcpu_chunk *chunk;
2136 	struct pcpu_block_md *block;
2137 	int freed_page_start, freed_page_end;
2138 	int i, end;
2139 	bool reintegrate;
2140 
2141 	lockdep_assert_held(&pcpu_lock);
2142 
2143 	/*
2144 	 * Once a chunk is isolated to the to_depopulate list, the chunk is no
2145 	 * longer discoverable to allocations whom may populate pages.  The only
2146 	 * other accessor is the free path which only returns area back to the
2147 	 * allocator not touching the populated bitmap.
2148 	 */
2149 	while (!list_empty(&pcpu_chunk_lists[pcpu_to_depopulate_slot])) {
2150 		chunk = list_first_entry(&pcpu_chunk_lists[pcpu_to_depopulate_slot],
2151 					 struct pcpu_chunk, list);
2152 		WARN_ON(chunk->immutable);
2153 
2154 		/*
2155 		 * Scan chunk's pages in the reverse order to keep populated
2156 		 * pages close to the beginning of the chunk.
2157 		 */
2158 		freed_page_start = chunk->nr_pages;
2159 		freed_page_end = 0;
2160 		reintegrate = false;
2161 		for (i = chunk->nr_pages - 1, end = -1; i >= 0; i--) {
2162 			/* no more work to do */
2163 			if (chunk->nr_empty_pop_pages == 0)
2164 				break;
2165 
2166 			/* reintegrate chunk to prevent atomic alloc failures */
2167 			if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_HIGH) {
2168 				reintegrate = true;
2169 				goto end_chunk;
2170 			}
2171 
2172 			/*
2173 			 * If the page is empty and populated, start or
2174 			 * extend the (i, end) range.  If i == 0, decrease
2175 			 * i and perform the depopulation to cover the last
2176 			 * (first) page in the chunk.
2177 			 */
2178 			block = chunk->md_blocks + i;
2179 			if (block->contig_hint == PCPU_BITMAP_BLOCK_BITS &&
2180 			    test_bit(i, chunk->populated)) {
2181 				if (end == -1)
2182 					end = i;
2183 				if (i > 0)
2184 					continue;
2185 				i--;
2186 			}
2187 
2188 			/* depopulate if there is an active range */
2189 			if (end == -1)
2190 				continue;
2191 
2192 			spin_unlock_irq(&pcpu_lock);
2193 			pcpu_depopulate_chunk(chunk, i + 1, end + 1);
2194 			cond_resched();
2195 			spin_lock_irq(&pcpu_lock);
2196 
2197 			pcpu_chunk_depopulated(chunk, i + 1, end + 1);
2198 			freed_page_start = min(freed_page_start, i + 1);
2199 			freed_page_end = max(freed_page_end, end + 1);
2200 
2201 			/* reset the range and continue */
2202 			end = -1;
2203 		}
2204 
2205 end_chunk:
2206 		/* batch tlb flush per chunk to amortize cost */
2207 		if (freed_page_start < freed_page_end) {
2208 			spin_unlock_irq(&pcpu_lock);
2209 			pcpu_post_unmap_tlb_flush(chunk,
2210 						  freed_page_start,
2211 						  freed_page_end);
2212 			cond_resched();
2213 			spin_lock_irq(&pcpu_lock);
2214 		}
2215 
2216 		if (reintegrate || chunk->free_bytes == pcpu_unit_size)
2217 			pcpu_reintegrate_chunk(chunk);
2218 		else
2219 			list_move_tail(&chunk->list,
2220 				       &pcpu_chunk_lists[pcpu_sidelined_slot]);
2221 	}
2222 }
2223 
2224 /**
2225  * pcpu_balance_workfn - manage the amount of free chunks and populated pages
2226  * @work: unused
2227  *
2228  * For each chunk type, manage the number of fully free chunks and the number of
2229  * populated pages.  An important thing to consider is when pages are freed and
2230  * how they contribute to the global counts.
2231  */
pcpu_balance_workfn(struct work_struct * work)2232 static void pcpu_balance_workfn(struct work_struct *work)
2233 {
2234 	/*
2235 	 * pcpu_balance_free() is called twice because the first time we may
2236 	 * trim pages in the active pcpu_nr_empty_pop_pages which may cause us
2237 	 * to grow other chunks.  This then gives pcpu_reclaim_populated() time
2238 	 * to move fully free chunks to the active list to be freed if
2239 	 * appropriate.
2240 	 */
2241 	mutex_lock(&pcpu_alloc_mutex);
2242 	spin_lock_irq(&pcpu_lock);
2243 
2244 	pcpu_balance_free(false);
2245 	pcpu_reclaim_populated();
2246 	pcpu_balance_populated();
2247 	pcpu_balance_free(true);
2248 
2249 	spin_unlock_irq(&pcpu_lock);
2250 	mutex_unlock(&pcpu_alloc_mutex);
2251 }
2252 
2253 /**
2254  * free_percpu - free percpu area
2255  * @ptr: pointer to area to free
2256  *
2257  * Free percpu area @ptr.
2258  *
2259  * CONTEXT:
2260  * Can be called from atomic context.
2261  */
free_percpu(void __percpu * ptr)2262 void free_percpu(void __percpu *ptr)
2263 {
2264 	void *addr;
2265 	struct pcpu_chunk *chunk;
2266 	unsigned long flags;
2267 	int size, off;
2268 	bool need_balance = false;
2269 
2270 	if (!ptr)
2271 		return;
2272 
2273 	kmemleak_free_percpu(ptr);
2274 
2275 	addr = __pcpu_ptr_to_addr(ptr);
2276 
2277 	spin_lock_irqsave(&pcpu_lock, flags);
2278 
2279 	chunk = pcpu_chunk_addr_search(addr);
2280 	off = addr - chunk->base_addr;
2281 
2282 	size = pcpu_free_area(chunk, off);
2283 
2284 	pcpu_memcg_free_hook(chunk, off, size);
2285 
2286 	/*
2287 	 * If there are more than one fully free chunks, wake up grim reaper.
2288 	 * If the chunk is isolated, it may be in the process of being
2289 	 * reclaimed.  Let reclaim manage cleaning up of that chunk.
2290 	 */
2291 	if (!chunk->isolated && chunk->free_bytes == pcpu_unit_size) {
2292 		struct pcpu_chunk *pos;
2293 
2294 		list_for_each_entry(pos, &pcpu_chunk_lists[pcpu_free_slot], list)
2295 			if (pos != chunk) {
2296 				need_balance = true;
2297 				break;
2298 			}
2299 	} else if (pcpu_should_reclaim_chunk(chunk)) {
2300 		pcpu_isolate_chunk(chunk);
2301 		need_balance = true;
2302 	}
2303 
2304 	trace_percpu_free_percpu(chunk->base_addr, off, ptr);
2305 
2306 	spin_unlock_irqrestore(&pcpu_lock, flags);
2307 
2308 	if (need_balance)
2309 		pcpu_schedule_balance_work();
2310 }
2311 EXPORT_SYMBOL_GPL(free_percpu);
2312 
__is_kernel_percpu_address(unsigned long addr,unsigned long * can_addr)2313 bool __is_kernel_percpu_address(unsigned long addr, unsigned long *can_addr)
2314 {
2315 #ifdef CONFIG_SMP
2316 	const size_t static_size = __per_cpu_end - __per_cpu_start;
2317 	void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
2318 	unsigned int cpu;
2319 
2320 	for_each_possible_cpu(cpu) {
2321 		void *start = per_cpu_ptr(base, cpu);
2322 		void *va = (void *)addr;
2323 
2324 		if (va >= start && va < start + static_size) {
2325 			if (can_addr) {
2326 				*can_addr = (unsigned long) (va - start);
2327 				*can_addr += (unsigned long)
2328 					per_cpu_ptr(base, get_boot_cpu_id());
2329 			}
2330 			return true;
2331 		}
2332 	}
2333 #endif
2334 	/* on UP, can't distinguish from other static vars, always false */
2335 	return false;
2336 }
2337 
2338 /**
2339  * is_kernel_percpu_address - test whether address is from static percpu area
2340  * @addr: address to test
2341  *
2342  * Test whether @addr belongs to in-kernel static percpu area.  Module
2343  * static percpu areas are not considered.  For those, use
2344  * is_module_percpu_address().
2345  *
2346  * RETURNS:
2347  * %true if @addr is from in-kernel static percpu area, %false otherwise.
2348  */
is_kernel_percpu_address(unsigned long addr)2349 bool is_kernel_percpu_address(unsigned long addr)
2350 {
2351 	return __is_kernel_percpu_address(addr, NULL);
2352 }
2353 
2354 /**
2355  * per_cpu_ptr_to_phys - convert translated percpu address to physical address
2356  * @addr: the address to be converted to physical address
2357  *
2358  * Given @addr which is dereferenceable address obtained via one of
2359  * percpu access macros, this function translates it into its physical
2360  * address.  The caller is responsible for ensuring @addr stays valid
2361  * until this function finishes.
2362  *
2363  * percpu allocator has special setup for the first chunk, which currently
2364  * supports either embedding in linear address space or vmalloc mapping,
2365  * and, from the second one, the backing allocator (currently either vm or
2366  * km) provides translation.
2367  *
2368  * The addr can be translated simply without checking if it falls into the
2369  * first chunk. But the current code reflects better how percpu allocator
2370  * actually works, and the verification can discover both bugs in percpu
2371  * allocator itself and per_cpu_ptr_to_phys() callers. So we keep current
2372  * code.
2373  *
2374  * RETURNS:
2375  * The physical address for @addr.
2376  */
per_cpu_ptr_to_phys(void * addr)2377 phys_addr_t per_cpu_ptr_to_phys(void *addr)
2378 {
2379 	void __percpu *base = __addr_to_pcpu_ptr(pcpu_base_addr);
2380 	bool in_first_chunk = false;
2381 	unsigned long first_low, first_high;
2382 	unsigned int cpu;
2383 
2384 	/*
2385 	 * The following test on unit_low/high isn't strictly
2386 	 * necessary but will speed up lookups of addresses which
2387 	 * aren't in the first chunk.
2388 	 *
2389 	 * The address check is against full chunk sizes.  pcpu_base_addr
2390 	 * points to the beginning of the first chunk including the
2391 	 * static region.  Assumes good intent as the first chunk may
2392 	 * not be full (ie. < pcpu_unit_pages in size).
2393 	 */
2394 	first_low = (unsigned long)pcpu_base_addr +
2395 		    pcpu_unit_page_offset(pcpu_low_unit_cpu, 0);
2396 	first_high = (unsigned long)pcpu_base_addr +
2397 		     pcpu_unit_page_offset(pcpu_high_unit_cpu, pcpu_unit_pages);
2398 	if ((unsigned long)addr >= first_low &&
2399 	    (unsigned long)addr < first_high) {
2400 		for_each_possible_cpu(cpu) {
2401 			void *start = per_cpu_ptr(base, cpu);
2402 
2403 			if (addr >= start && addr < start + pcpu_unit_size) {
2404 				in_first_chunk = true;
2405 				break;
2406 			}
2407 		}
2408 	}
2409 
2410 	if (in_first_chunk) {
2411 		if (!is_vmalloc_addr(addr))
2412 			return __pa(addr);
2413 		else
2414 			return page_to_phys(vmalloc_to_page(addr)) +
2415 			       offset_in_page(addr);
2416 	} else
2417 		return page_to_phys(pcpu_addr_to_page(addr)) +
2418 		       offset_in_page(addr);
2419 }
2420 
2421 /**
2422  * pcpu_alloc_alloc_info - allocate percpu allocation info
2423  * @nr_groups: the number of groups
2424  * @nr_units: the number of units
2425  *
2426  * Allocate ai which is large enough for @nr_groups groups containing
2427  * @nr_units units.  The returned ai's groups[0].cpu_map points to the
2428  * cpu_map array which is long enough for @nr_units and filled with
2429  * NR_CPUS.  It's the caller's responsibility to initialize cpu_map
2430  * pointer of other groups.
2431  *
2432  * RETURNS:
2433  * Pointer to the allocated pcpu_alloc_info on success, NULL on
2434  * failure.
2435  */
pcpu_alloc_alloc_info(int nr_groups,int nr_units)2436 struct pcpu_alloc_info * __init pcpu_alloc_alloc_info(int nr_groups,
2437 						      int nr_units)
2438 {
2439 	struct pcpu_alloc_info *ai;
2440 	size_t base_size, ai_size;
2441 	void *ptr;
2442 	int unit;
2443 
2444 	base_size = ALIGN(struct_size(ai, groups, nr_groups),
2445 			  __alignof__(ai->groups[0].cpu_map[0]));
2446 	ai_size = base_size + nr_units * sizeof(ai->groups[0].cpu_map[0]);
2447 
2448 	ptr = memblock_alloc(PFN_ALIGN(ai_size), PAGE_SIZE);
2449 	if (!ptr)
2450 		return NULL;
2451 	ai = ptr;
2452 	ptr += base_size;
2453 
2454 	ai->groups[0].cpu_map = ptr;
2455 
2456 	for (unit = 0; unit < nr_units; unit++)
2457 		ai->groups[0].cpu_map[unit] = NR_CPUS;
2458 
2459 	ai->nr_groups = nr_groups;
2460 	ai->__ai_size = PFN_ALIGN(ai_size);
2461 
2462 	return ai;
2463 }
2464 
2465 /**
2466  * pcpu_free_alloc_info - free percpu allocation info
2467  * @ai: pcpu_alloc_info to free
2468  *
2469  * Free @ai which was allocated by pcpu_alloc_alloc_info().
2470  */
pcpu_free_alloc_info(struct pcpu_alloc_info * ai)2471 void __init pcpu_free_alloc_info(struct pcpu_alloc_info *ai)
2472 {
2473 	memblock_free(ai, ai->__ai_size);
2474 }
2475 
2476 /**
2477  * pcpu_dump_alloc_info - print out information about pcpu_alloc_info
2478  * @lvl: loglevel
2479  * @ai: allocation info to dump
2480  *
2481  * Print out information about @ai using loglevel @lvl.
2482  */
pcpu_dump_alloc_info(const char * lvl,const struct pcpu_alloc_info * ai)2483 static void pcpu_dump_alloc_info(const char *lvl,
2484 				 const struct pcpu_alloc_info *ai)
2485 {
2486 	int group_width = 1, cpu_width = 1, width;
2487 	char empty_str[] = "--------";
2488 	int alloc = 0, alloc_end = 0;
2489 	int group, v;
2490 	int upa, apl;	/* units per alloc, allocs per line */
2491 
2492 	v = ai->nr_groups;
2493 	while (v /= 10)
2494 		group_width++;
2495 
2496 	v = num_possible_cpus();
2497 	while (v /= 10)
2498 		cpu_width++;
2499 	empty_str[min_t(int, cpu_width, sizeof(empty_str) - 1)] = '\0';
2500 
2501 	upa = ai->alloc_size / ai->unit_size;
2502 	width = upa * (cpu_width + 1) + group_width + 3;
2503 	apl = rounddown_pow_of_two(max(60 / width, 1));
2504 
2505 	printk("%spcpu-alloc: s%zu r%zu d%zu u%zu alloc=%zu*%zu",
2506 	       lvl, ai->static_size, ai->reserved_size, ai->dyn_size,
2507 	       ai->unit_size, ai->alloc_size / ai->atom_size, ai->atom_size);
2508 
2509 	for (group = 0; group < ai->nr_groups; group++) {
2510 		const struct pcpu_group_info *gi = &ai->groups[group];
2511 		int unit = 0, unit_end = 0;
2512 
2513 		BUG_ON(gi->nr_units % upa);
2514 		for (alloc_end += gi->nr_units / upa;
2515 		     alloc < alloc_end; alloc++) {
2516 			if (!(alloc % apl)) {
2517 				pr_cont("\n");
2518 				printk("%spcpu-alloc: ", lvl);
2519 			}
2520 			pr_cont("[%0*d] ", group_width, group);
2521 
2522 			for (unit_end += upa; unit < unit_end; unit++)
2523 				if (gi->cpu_map[unit] != NR_CPUS)
2524 					pr_cont("%0*d ",
2525 						cpu_width, gi->cpu_map[unit]);
2526 				else
2527 					pr_cont("%s ", empty_str);
2528 		}
2529 	}
2530 	pr_cont("\n");
2531 }
2532 
2533 /**
2534  * pcpu_setup_first_chunk - initialize the first percpu chunk
2535  * @ai: pcpu_alloc_info describing how to percpu area is shaped
2536  * @base_addr: mapped address
2537  *
2538  * Initialize the first percpu chunk which contains the kernel static
2539  * percpu area.  This function is to be called from arch percpu area
2540  * setup path.
2541  *
2542  * @ai contains all information necessary to initialize the first
2543  * chunk and prime the dynamic percpu allocator.
2544  *
2545  * @ai->static_size is the size of static percpu area.
2546  *
2547  * @ai->reserved_size, if non-zero, specifies the amount of bytes to
2548  * reserve after the static area in the first chunk.  This reserves
2549  * the first chunk such that it's available only through reserved
2550  * percpu allocation.  This is primarily used to serve module percpu
2551  * static areas on architectures where the addressing model has
2552  * limited offset range for symbol relocations to guarantee module
2553  * percpu symbols fall inside the relocatable range.
2554  *
2555  * @ai->dyn_size determines the number of bytes available for dynamic
2556  * allocation in the first chunk.  The area between @ai->static_size +
2557  * @ai->reserved_size + @ai->dyn_size and @ai->unit_size is unused.
2558  *
2559  * @ai->unit_size specifies unit size and must be aligned to PAGE_SIZE
2560  * and equal to or larger than @ai->static_size + @ai->reserved_size +
2561  * @ai->dyn_size.
2562  *
2563  * @ai->atom_size is the allocation atom size and used as alignment
2564  * for vm areas.
2565  *
2566  * @ai->alloc_size is the allocation size and always multiple of
2567  * @ai->atom_size.  This is larger than @ai->atom_size if
2568  * @ai->unit_size is larger than @ai->atom_size.
2569  *
2570  * @ai->nr_groups and @ai->groups describe virtual memory layout of
2571  * percpu areas.  Units which should be colocated are put into the
2572  * same group.  Dynamic VM areas will be allocated according to these
2573  * groupings.  If @ai->nr_groups is zero, a single group containing
2574  * all units is assumed.
2575  *
2576  * The caller should have mapped the first chunk at @base_addr and
2577  * copied static data to each unit.
2578  *
2579  * The first chunk will always contain a static and a dynamic region.
2580  * However, the static region is not managed by any chunk.  If the first
2581  * chunk also contains a reserved region, it is served by two chunks -
2582  * one for the reserved region and one for the dynamic region.  They
2583  * share the same vm, but use offset regions in the area allocation map.
2584  * The chunk serving the dynamic region is circulated in the chunk slots
2585  * and available for dynamic allocation like any other chunk.
2586  */
pcpu_setup_first_chunk(const struct pcpu_alloc_info * ai,void * base_addr)2587 void __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai,
2588 				   void *base_addr)
2589 {
2590 	size_t size_sum = ai->static_size + ai->reserved_size + ai->dyn_size;
2591 	size_t static_size, dyn_size;
2592 	struct pcpu_chunk *chunk;
2593 	unsigned long *group_offsets;
2594 	size_t *group_sizes;
2595 	unsigned long *unit_off;
2596 	unsigned int cpu;
2597 	int *unit_map;
2598 	int group, unit, i;
2599 	int map_size;
2600 	unsigned long tmp_addr;
2601 	size_t alloc_size;
2602 
2603 #define PCPU_SETUP_BUG_ON(cond)	do {					\
2604 	if (unlikely(cond)) {						\
2605 		pr_emerg("failed to initialize, %s\n", #cond);		\
2606 		pr_emerg("cpu_possible_mask=%*pb\n",			\
2607 			 cpumask_pr_args(cpu_possible_mask));		\
2608 		pcpu_dump_alloc_info(KERN_EMERG, ai);			\
2609 		BUG();							\
2610 	}								\
2611 } while (0)
2612 
2613 	/* sanity checks */
2614 	PCPU_SETUP_BUG_ON(ai->nr_groups <= 0);
2615 #ifdef CONFIG_SMP
2616 	PCPU_SETUP_BUG_ON(!ai->static_size);
2617 	PCPU_SETUP_BUG_ON(offset_in_page(__per_cpu_start));
2618 #endif
2619 	PCPU_SETUP_BUG_ON(!base_addr);
2620 	PCPU_SETUP_BUG_ON(offset_in_page(base_addr));
2621 	PCPU_SETUP_BUG_ON(ai->unit_size < size_sum);
2622 	PCPU_SETUP_BUG_ON(offset_in_page(ai->unit_size));
2623 	PCPU_SETUP_BUG_ON(ai->unit_size < PCPU_MIN_UNIT_SIZE);
2624 	PCPU_SETUP_BUG_ON(!IS_ALIGNED(ai->unit_size, PCPU_BITMAP_BLOCK_SIZE));
2625 	PCPU_SETUP_BUG_ON(ai->dyn_size < PERCPU_DYNAMIC_EARLY_SIZE);
2626 	PCPU_SETUP_BUG_ON(!ai->dyn_size);
2627 	PCPU_SETUP_BUG_ON(!IS_ALIGNED(ai->reserved_size, PCPU_MIN_ALLOC_SIZE));
2628 	PCPU_SETUP_BUG_ON(!(IS_ALIGNED(PCPU_BITMAP_BLOCK_SIZE, PAGE_SIZE) ||
2629 			    IS_ALIGNED(PAGE_SIZE, PCPU_BITMAP_BLOCK_SIZE)));
2630 	PCPU_SETUP_BUG_ON(pcpu_verify_alloc_info(ai) < 0);
2631 
2632 	/* process group information and build config tables accordingly */
2633 	alloc_size = ai->nr_groups * sizeof(group_offsets[0]);
2634 	group_offsets = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2635 	if (!group_offsets)
2636 		panic("%s: Failed to allocate %zu bytes\n", __func__,
2637 		      alloc_size);
2638 
2639 	alloc_size = ai->nr_groups * sizeof(group_sizes[0]);
2640 	group_sizes = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2641 	if (!group_sizes)
2642 		panic("%s: Failed to allocate %zu bytes\n", __func__,
2643 		      alloc_size);
2644 
2645 	alloc_size = nr_cpu_ids * sizeof(unit_map[0]);
2646 	unit_map = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2647 	if (!unit_map)
2648 		panic("%s: Failed to allocate %zu bytes\n", __func__,
2649 		      alloc_size);
2650 
2651 	alloc_size = nr_cpu_ids * sizeof(unit_off[0]);
2652 	unit_off = memblock_alloc(alloc_size, SMP_CACHE_BYTES);
2653 	if (!unit_off)
2654 		panic("%s: Failed to allocate %zu bytes\n", __func__,
2655 		      alloc_size);
2656 
2657 	for (cpu = 0; cpu < nr_cpu_ids; cpu++)
2658 		unit_map[cpu] = UINT_MAX;
2659 
2660 	pcpu_low_unit_cpu = NR_CPUS;
2661 	pcpu_high_unit_cpu = NR_CPUS;
2662 
2663 	for (group = 0, unit = 0; group < ai->nr_groups; group++, unit += i) {
2664 		const struct pcpu_group_info *gi = &ai->groups[group];
2665 
2666 		group_offsets[group] = gi->base_offset;
2667 		group_sizes[group] = gi->nr_units * ai->unit_size;
2668 
2669 		for (i = 0; i < gi->nr_units; i++) {
2670 			cpu = gi->cpu_map[i];
2671 			if (cpu == NR_CPUS)
2672 				continue;
2673 
2674 			PCPU_SETUP_BUG_ON(cpu >= nr_cpu_ids);
2675 			PCPU_SETUP_BUG_ON(!cpu_possible(cpu));
2676 			PCPU_SETUP_BUG_ON(unit_map[cpu] != UINT_MAX);
2677 
2678 			unit_map[cpu] = unit + i;
2679 			unit_off[cpu] = gi->base_offset + i * ai->unit_size;
2680 
2681 			/* determine low/high unit_cpu */
2682 			if (pcpu_low_unit_cpu == NR_CPUS ||
2683 			    unit_off[cpu] < unit_off[pcpu_low_unit_cpu])
2684 				pcpu_low_unit_cpu = cpu;
2685 			if (pcpu_high_unit_cpu == NR_CPUS ||
2686 			    unit_off[cpu] > unit_off[pcpu_high_unit_cpu])
2687 				pcpu_high_unit_cpu = cpu;
2688 		}
2689 	}
2690 	pcpu_nr_units = unit;
2691 
2692 	for_each_possible_cpu(cpu)
2693 		PCPU_SETUP_BUG_ON(unit_map[cpu] == UINT_MAX);
2694 
2695 	/* we're done parsing the input, undefine BUG macro and dump config */
2696 #undef PCPU_SETUP_BUG_ON
2697 	pcpu_dump_alloc_info(KERN_DEBUG, ai);
2698 
2699 	pcpu_nr_groups = ai->nr_groups;
2700 	pcpu_group_offsets = group_offsets;
2701 	pcpu_group_sizes = group_sizes;
2702 	pcpu_unit_map = unit_map;
2703 	pcpu_unit_offsets = unit_off;
2704 
2705 	/* determine basic parameters */
2706 	pcpu_unit_pages = ai->unit_size >> PAGE_SHIFT;
2707 	pcpu_unit_size = pcpu_unit_pages << PAGE_SHIFT;
2708 	pcpu_atom_size = ai->atom_size;
2709 	pcpu_chunk_struct_size = struct_size(chunk, populated,
2710 					     BITS_TO_LONGS(pcpu_unit_pages));
2711 
2712 	pcpu_stats_save_ai(ai);
2713 
2714 	/*
2715 	 * Allocate chunk slots.  The slots after the active slots are:
2716 	 *   sidelined_slot - isolated, depopulated chunks
2717 	 *   free_slot - fully free chunks
2718 	 *   to_depopulate_slot - isolated, chunks to depopulate
2719 	 */
2720 	pcpu_sidelined_slot = __pcpu_size_to_slot(pcpu_unit_size) + 1;
2721 	pcpu_free_slot = pcpu_sidelined_slot + 1;
2722 	pcpu_to_depopulate_slot = pcpu_free_slot + 1;
2723 	pcpu_nr_slots = pcpu_to_depopulate_slot + 1;
2724 	pcpu_chunk_lists = memblock_alloc(pcpu_nr_slots *
2725 					  sizeof(pcpu_chunk_lists[0]),
2726 					  SMP_CACHE_BYTES);
2727 	if (!pcpu_chunk_lists)
2728 		panic("%s: Failed to allocate %zu bytes\n", __func__,
2729 		      pcpu_nr_slots * sizeof(pcpu_chunk_lists[0]));
2730 
2731 	for (i = 0; i < pcpu_nr_slots; i++)
2732 		INIT_LIST_HEAD(&pcpu_chunk_lists[i]);
2733 
2734 	/*
2735 	 * The end of the static region needs to be aligned with the
2736 	 * minimum allocation size as this offsets the reserved and
2737 	 * dynamic region.  The first chunk ends page aligned by
2738 	 * expanding the dynamic region, therefore the dynamic region
2739 	 * can be shrunk to compensate while still staying above the
2740 	 * configured sizes.
2741 	 */
2742 	static_size = ALIGN(ai->static_size, PCPU_MIN_ALLOC_SIZE);
2743 	dyn_size = ai->dyn_size - (static_size - ai->static_size);
2744 
2745 	/*
2746 	 * Initialize first chunk.
2747 	 * If the reserved_size is non-zero, this initializes the reserved
2748 	 * chunk.  If the reserved_size is zero, the reserved chunk is NULL
2749 	 * and the dynamic region is initialized here.  The first chunk,
2750 	 * pcpu_first_chunk, will always point to the chunk that serves
2751 	 * the dynamic region.
2752 	 */
2753 	tmp_addr = (unsigned long)base_addr + static_size;
2754 	map_size = ai->reserved_size ?: dyn_size;
2755 	chunk = pcpu_alloc_first_chunk(tmp_addr, map_size);
2756 
2757 	/* init dynamic chunk if necessary */
2758 	if (ai->reserved_size) {
2759 		pcpu_reserved_chunk = chunk;
2760 
2761 		tmp_addr = (unsigned long)base_addr + static_size +
2762 			   ai->reserved_size;
2763 		map_size = dyn_size;
2764 		chunk = pcpu_alloc_first_chunk(tmp_addr, map_size);
2765 	}
2766 
2767 	/* link the first chunk in */
2768 	pcpu_first_chunk = chunk;
2769 	pcpu_nr_empty_pop_pages = pcpu_first_chunk->nr_empty_pop_pages;
2770 	pcpu_chunk_relocate(pcpu_first_chunk, -1);
2771 
2772 	/* include all regions of the first chunk */
2773 	pcpu_nr_populated += PFN_DOWN(size_sum);
2774 
2775 	pcpu_stats_chunk_alloc();
2776 	trace_percpu_create_chunk(base_addr);
2777 
2778 	/* we're done */
2779 	pcpu_base_addr = base_addr;
2780 }
2781 
2782 #ifdef CONFIG_SMP
2783 
2784 const char * const pcpu_fc_names[PCPU_FC_NR] __initconst = {
2785 	[PCPU_FC_AUTO]	= "auto",
2786 	[PCPU_FC_EMBED]	= "embed",
2787 	[PCPU_FC_PAGE]	= "page",
2788 };
2789 
2790 enum pcpu_fc pcpu_chosen_fc __initdata = PCPU_FC_AUTO;
2791 
percpu_alloc_setup(char * str)2792 static int __init percpu_alloc_setup(char *str)
2793 {
2794 	if (!str)
2795 		return -EINVAL;
2796 
2797 	if (0)
2798 		/* nada */;
2799 #ifdef CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK
2800 	else if (!strcmp(str, "embed"))
2801 		pcpu_chosen_fc = PCPU_FC_EMBED;
2802 #endif
2803 #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
2804 	else if (!strcmp(str, "page"))
2805 		pcpu_chosen_fc = PCPU_FC_PAGE;
2806 #endif
2807 	else
2808 		pr_warn("unknown allocator %s specified\n", str);
2809 
2810 	return 0;
2811 }
2812 early_param("percpu_alloc", percpu_alloc_setup);
2813 
2814 /*
2815  * pcpu_embed_first_chunk() is used by the generic percpu setup.
2816  * Build it if needed by the arch config or the generic setup is going
2817  * to be used.
2818  */
2819 #if defined(CONFIG_NEED_PER_CPU_EMBED_FIRST_CHUNK) || \
2820 	!defined(CONFIG_HAVE_SETUP_PER_CPU_AREA)
2821 #define BUILD_EMBED_FIRST_CHUNK
2822 #endif
2823 
2824 /* build pcpu_page_first_chunk() iff needed by the arch config */
2825 #if defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
2826 #define BUILD_PAGE_FIRST_CHUNK
2827 #endif
2828 
2829 /* pcpu_build_alloc_info() is used by both embed and page first chunk */
2830 #if defined(BUILD_EMBED_FIRST_CHUNK) || defined(BUILD_PAGE_FIRST_CHUNK)
2831 /**
2832  * pcpu_build_alloc_info - build alloc_info considering distances between CPUs
2833  * @reserved_size: the size of reserved percpu area in bytes
2834  * @dyn_size: minimum free size for dynamic allocation in bytes
2835  * @atom_size: allocation atom size
2836  * @cpu_distance_fn: callback to determine distance between cpus, optional
2837  *
2838  * This function determines grouping of units, their mappings to cpus
2839  * and other parameters considering needed percpu size, allocation
2840  * atom size and distances between CPUs.
2841  *
2842  * Groups are always multiples of atom size and CPUs which are of
2843  * LOCAL_DISTANCE both ways are grouped together and share space for
2844  * units in the same group.  The returned configuration is guaranteed
2845  * to have CPUs on different nodes on different groups and >=75% usage
2846  * of allocated virtual address space.
2847  *
2848  * RETURNS:
2849  * On success, pointer to the new allocation_info is returned.  On
2850  * failure, ERR_PTR value is returned.
2851  */
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)2852 static struct pcpu_alloc_info * __init __flatten pcpu_build_alloc_info(
2853 				size_t reserved_size, size_t dyn_size,
2854 				size_t atom_size,
2855 				pcpu_fc_cpu_distance_fn_t cpu_distance_fn)
2856 {
2857 	static int group_map[NR_CPUS] __initdata;
2858 	static int group_cnt[NR_CPUS] __initdata;
2859 	static struct cpumask mask __initdata;
2860 	const size_t static_size = __per_cpu_end - __per_cpu_start;
2861 	int nr_groups = 1, nr_units = 0;
2862 	size_t size_sum, min_unit_size, alloc_size;
2863 	int upa, max_upa, best_upa;	/* units_per_alloc */
2864 	int last_allocs, group, unit;
2865 	unsigned int cpu, tcpu;
2866 	struct pcpu_alloc_info *ai;
2867 	unsigned int *cpu_map;
2868 
2869 	/* this function may be called multiple times */
2870 	memset(group_map, 0, sizeof(group_map));
2871 	memset(group_cnt, 0, sizeof(group_cnt));
2872 	cpumask_clear(&mask);
2873 
2874 	/* calculate size_sum and ensure dyn_size is enough for early alloc */
2875 	size_sum = PFN_ALIGN(static_size + reserved_size +
2876 			    max_t(size_t, dyn_size, PERCPU_DYNAMIC_EARLY_SIZE));
2877 	dyn_size = size_sum - static_size - reserved_size;
2878 
2879 	/*
2880 	 * Determine min_unit_size, alloc_size and max_upa such that
2881 	 * alloc_size is multiple of atom_size and is the smallest
2882 	 * which can accommodate 4k aligned segments which are equal to
2883 	 * or larger than min_unit_size.
2884 	 */
2885 	min_unit_size = max_t(size_t, size_sum, PCPU_MIN_UNIT_SIZE);
2886 
2887 	/* determine the maximum # of units that can fit in an allocation */
2888 	alloc_size = roundup(min_unit_size, atom_size);
2889 	upa = alloc_size / min_unit_size;
2890 	while (alloc_size % upa || (offset_in_page(alloc_size / upa)))
2891 		upa--;
2892 	max_upa = upa;
2893 
2894 	cpumask_copy(&mask, cpu_possible_mask);
2895 
2896 	/* group cpus according to their proximity */
2897 	for (group = 0; !cpumask_empty(&mask); group++) {
2898 		/* pop the group's first cpu */
2899 		cpu = cpumask_first(&mask);
2900 		group_map[cpu] = group;
2901 		group_cnt[group]++;
2902 		cpumask_clear_cpu(cpu, &mask);
2903 
2904 		for_each_cpu(tcpu, &mask) {
2905 			if (!cpu_distance_fn ||
2906 			    (cpu_distance_fn(cpu, tcpu) == LOCAL_DISTANCE &&
2907 			     cpu_distance_fn(tcpu, cpu) == LOCAL_DISTANCE)) {
2908 				group_map[tcpu] = group;
2909 				group_cnt[group]++;
2910 				cpumask_clear_cpu(tcpu, &mask);
2911 			}
2912 		}
2913 	}
2914 	nr_groups = group;
2915 
2916 	/*
2917 	 * Wasted space is caused by a ratio imbalance of upa to group_cnt.
2918 	 * Expand the unit_size until we use >= 75% of the units allocated.
2919 	 * Related to atom_size, which could be much larger than the unit_size.
2920 	 */
2921 	last_allocs = INT_MAX;
2922 	best_upa = 0;
2923 	for (upa = max_upa; upa; upa--) {
2924 		int allocs = 0, wasted = 0;
2925 
2926 		if (alloc_size % upa || (offset_in_page(alloc_size / upa)))
2927 			continue;
2928 
2929 		for (group = 0; group < nr_groups; group++) {
2930 			int this_allocs = DIV_ROUND_UP(group_cnt[group], upa);
2931 			allocs += this_allocs;
2932 			wasted += this_allocs * upa - group_cnt[group];
2933 		}
2934 
2935 		/*
2936 		 * Don't accept if wastage is over 1/3.  The
2937 		 * greater-than comparison ensures upa==1 always
2938 		 * passes the following check.
2939 		 */
2940 		if (wasted > num_possible_cpus() / 3)
2941 			continue;
2942 
2943 		/* and then don't consume more memory */
2944 		if (allocs > last_allocs)
2945 			break;
2946 		last_allocs = allocs;
2947 		best_upa = upa;
2948 	}
2949 	BUG_ON(!best_upa);
2950 	upa = best_upa;
2951 
2952 	/* allocate and fill alloc_info */
2953 	for (group = 0; group < nr_groups; group++)
2954 		nr_units += roundup(group_cnt[group], upa);
2955 
2956 	ai = pcpu_alloc_alloc_info(nr_groups, nr_units);
2957 	if (!ai)
2958 		return ERR_PTR(-ENOMEM);
2959 	cpu_map = ai->groups[0].cpu_map;
2960 
2961 	for (group = 0; group < nr_groups; group++) {
2962 		ai->groups[group].cpu_map = cpu_map;
2963 		cpu_map += roundup(group_cnt[group], upa);
2964 	}
2965 
2966 	ai->static_size = static_size;
2967 	ai->reserved_size = reserved_size;
2968 	ai->dyn_size = dyn_size;
2969 	ai->unit_size = alloc_size / upa;
2970 	ai->atom_size = atom_size;
2971 	ai->alloc_size = alloc_size;
2972 
2973 	for (group = 0, unit = 0; group < nr_groups; group++) {
2974 		struct pcpu_group_info *gi = &ai->groups[group];
2975 
2976 		/*
2977 		 * Initialize base_offset as if all groups are located
2978 		 * back-to-back.  The caller should update this to
2979 		 * reflect actual allocation.
2980 		 */
2981 		gi->base_offset = unit * ai->unit_size;
2982 
2983 		for_each_possible_cpu(cpu)
2984 			if (group_map[cpu] == group)
2985 				gi->cpu_map[gi->nr_units++] = cpu;
2986 		gi->nr_units = roundup(gi->nr_units, upa);
2987 		unit += gi->nr_units;
2988 	}
2989 	BUG_ON(unit != nr_units);
2990 
2991 	return ai;
2992 }
2993 
pcpu_fc_alloc(unsigned int cpu,size_t size,size_t align,pcpu_fc_cpu_to_node_fn_t cpu_to_nd_fn)2994 static void * __init pcpu_fc_alloc(unsigned int cpu, size_t size, size_t align,
2995 				   pcpu_fc_cpu_to_node_fn_t cpu_to_nd_fn)
2996 {
2997 	const unsigned long goal = __pa(MAX_DMA_ADDRESS);
2998 #ifdef CONFIG_NUMA
2999 	int node = NUMA_NO_NODE;
3000 	void *ptr;
3001 
3002 	if (cpu_to_nd_fn)
3003 		node = cpu_to_nd_fn(cpu);
3004 
3005 	if (node == NUMA_NO_NODE || !node_online(node) || !NODE_DATA(node)) {
3006 		ptr = memblock_alloc_from(size, align, goal);
3007 		pr_info("cpu %d has no node %d or node-local memory\n",
3008 			cpu, node);
3009 		pr_debug("per cpu data for cpu%d %zu bytes at 0x%llx\n",
3010 			 cpu, size, (u64)__pa(ptr));
3011 	} else {
3012 		ptr = memblock_alloc_try_nid(size, align, goal,
3013 					     MEMBLOCK_ALLOC_ACCESSIBLE,
3014 					     node);
3015 
3016 		pr_debug("per cpu data for cpu%d %zu bytes on node%d at 0x%llx\n",
3017 			 cpu, size, node, (u64)__pa(ptr));
3018 	}
3019 	return ptr;
3020 #else
3021 	return memblock_alloc_from(size, align, goal);
3022 #endif
3023 }
3024 
pcpu_fc_free(void * ptr,size_t size)3025 static void __init pcpu_fc_free(void *ptr, size_t size)
3026 {
3027 	memblock_free(ptr, size);
3028 }
3029 #endif /* BUILD_EMBED_FIRST_CHUNK || BUILD_PAGE_FIRST_CHUNK */
3030 
3031 #if defined(BUILD_EMBED_FIRST_CHUNK)
3032 /**
3033  * pcpu_embed_first_chunk - embed the first percpu chunk into bootmem
3034  * @reserved_size: the size of reserved percpu area in bytes
3035  * @dyn_size: minimum free size for dynamic allocation in bytes
3036  * @atom_size: allocation atom size
3037  * @cpu_distance_fn: callback to determine distance between cpus, optional
3038  * @cpu_to_nd_fn: callback to convert cpu to it's node, optional
3039  *
3040  * This is a helper to ease setting up embedded first percpu chunk and
3041  * can be called where pcpu_setup_first_chunk() is expected.
3042  *
3043  * If this function is used to setup the first chunk, it is allocated
3044  * by calling pcpu_fc_alloc and used as-is without being mapped into
3045  * vmalloc area.  Allocations are always whole multiples of @atom_size
3046  * aligned to @atom_size.
3047  *
3048  * This enables the first chunk to piggy back on the linear physical
3049  * mapping which often uses larger page size.  Please note that this
3050  * can result in very sparse cpu->unit mapping on NUMA machines thus
3051  * requiring large vmalloc address space.  Don't use this allocator if
3052  * vmalloc space is not orders of magnitude larger than distances
3053  * between node memory addresses (ie. 32bit NUMA machines).
3054  *
3055  * @dyn_size specifies the minimum dynamic area size.
3056  *
3057  * If the needed size is smaller than the minimum or specified unit
3058  * size, the leftover is returned using pcpu_fc_free.
3059  *
3060  * RETURNS:
3061  * 0 on success, -errno on failure.
3062  */
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_cpu_to_node_fn_t cpu_to_nd_fn)3063 int __init pcpu_embed_first_chunk(size_t reserved_size, size_t dyn_size,
3064 				  size_t atom_size,
3065 				  pcpu_fc_cpu_distance_fn_t cpu_distance_fn,
3066 				  pcpu_fc_cpu_to_node_fn_t cpu_to_nd_fn)
3067 {
3068 	void *base = (void *)ULONG_MAX;
3069 	void **areas = NULL;
3070 	struct pcpu_alloc_info *ai;
3071 	size_t size_sum, areas_size;
3072 	unsigned long max_distance;
3073 	int group, i, highest_group, rc = 0;
3074 
3075 	ai = pcpu_build_alloc_info(reserved_size, dyn_size, atom_size,
3076 				   cpu_distance_fn);
3077 	if (IS_ERR(ai))
3078 		return PTR_ERR(ai);
3079 
3080 	size_sum = ai->static_size + ai->reserved_size + ai->dyn_size;
3081 	areas_size = PFN_ALIGN(ai->nr_groups * sizeof(void *));
3082 
3083 	areas = memblock_alloc(areas_size, SMP_CACHE_BYTES);
3084 	if (!areas) {
3085 		rc = -ENOMEM;
3086 		goto out_free;
3087 	}
3088 
3089 	/* allocate, copy and determine base address & max_distance */
3090 	highest_group = 0;
3091 	for (group = 0; group < ai->nr_groups; group++) {
3092 		struct pcpu_group_info *gi = &ai->groups[group];
3093 		unsigned int cpu = NR_CPUS;
3094 		void *ptr;
3095 
3096 		for (i = 0; i < gi->nr_units && cpu == NR_CPUS; i++)
3097 			cpu = gi->cpu_map[i];
3098 		BUG_ON(cpu == NR_CPUS);
3099 
3100 		/* allocate space for the whole group */
3101 		ptr = pcpu_fc_alloc(cpu, gi->nr_units * ai->unit_size, atom_size, cpu_to_nd_fn);
3102 		if (!ptr) {
3103 			rc = -ENOMEM;
3104 			goto out_free_areas;
3105 		}
3106 		/* kmemleak tracks the percpu allocations separately */
3107 		kmemleak_ignore_phys(__pa(ptr));
3108 		areas[group] = ptr;
3109 
3110 		base = min(ptr, base);
3111 		if (ptr > areas[highest_group])
3112 			highest_group = group;
3113 	}
3114 	max_distance = areas[highest_group] - base;
3115 	max_distance += ai->unit_size * ai->groups[highest_group].nr_units;
3116 
3117 	/* warn if maximum distance is further than 75% of vmalloc space */
3118 	if (max_distance > VMALLOC_TOTAL * 3 / 4) {
3119 		pr_warn("max_distance=0x%lx too large for vmalloc space 0x%lx\n",
3120 				max_distance, VMALLOC_TOTAL);
3121 #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
3122 		/* and fail if we have fallback */
3123 		rc = -EINVAL;
3124 		goto out_free_areas;
3125 #endif
3126 	}
3127 
3128 	/*
3129 	 * Copy data and free unused parts.  This should happen after all
3130 	 * allocations are complete; otherwise, we may end up with
3131 	 * overlapping groups.
3132 	 */
3133 	for (group = 0; group < ai->nr_groups; group++) {
3134 		struct pcpu_group_info *gi = &ai->groups[group];
3135 		void *ptr = areas[group];
3136 
3137 		for (i = 0; i < gi->nr_units; i++, ptr += ai->unit_size) {
3138 			if (gi->cpu_map[i] == NR_CPUS) {
3139 				/* unused unit, free whole */
3140 				pcpu_fc_free(ptr, ai->unit_size);
3141 				continue;
3142 			}
3143 			/* copy and return the unused part */
3144 			memcpy(ptr, __per_cpu_load, ai->static_size);
3145 			pcpu_fc_free(ptr + size_sum, ai->unit_size - size_sum);
3146 		}
3147 	}
3148 
3149 	/* base address is now known, determine group base offsets */
3150 	for (group = 0; group < ai->nr_groups; group++) {
3151 		ai->groups[group].base_offset = areas[group] - base;
3152 	}
3153 
3154 	pr_info("Embedded %zu pages/cpu s%zu r%zu d%zu u%zu\n",
3155 		PFN_DOWN(size_sum), ai->static_size, ai->reserved_size,
3156 		ai->dyn_size, ai->unit_size);
3157 
3158 	pcpu_setup_first_chunk(ai, base);
3159 	goto out_free;
3160 
3161 out_free_areas:
3162 	for (group = 0; group < ai->nr_groups; group++)
3163 		if (areas[group])
3164 			pcpu_fc_free(areas[group],
3165 				ai->groups[group].nr_units * ai->unit_size);
3166 out_free:
3167 	pcpu_free_alloc_info(ai);
3168 	if (areas)
3169 		memblock_free(areas, areas_size);
3170 	return rc;
3171 }
3172 #endif /* BUILD_EMBED_FIRST_CHUNK */
3173 
3174 #ifdef BUILD_PAGE_FIRST_CHUNK
3175 #include <asm/pgalloc.h>
3176 
3177 #ifndef P4D_TABLE_SIZE
3178 #define P4D_TABLE_SIZE PAGE_SIZE
3179 #endif
3180 
3181 #ifndef PUD_TABLE_SIZE
3182 #define PUD_TABLE_SIZE PAGE_SIZE
3183 #endif
3184 
3185 #ifndef PMD_TABLE_SIZE
3186 #define PMD_TABLE_SIZE PAGE_SIZE
3187 #endif
3188 
3189 #ifndef PTE_TABLE_SIZE
3190 #define PTE_TABLE_SIZE PAGE_SIZE
3191 #endif
pcpu_populate_pte(unsigned long addr)3192 void __init __weak pcpu_populate_pte(unsigned long addr)
3193 {
3194 	pgd_t *pgd = pgd_offset_k(addr);
3195 	p4d_t *p4d;
3196 	pud_t *pud;
3197 	pmd_t *pmd;
3198 
3199 	if (pgd_none(*pgd)) {
3200 		p4d_t *new;
3201 
3202 		new = memblock_alloc(P4D_TABLE_SIZE, P4D_TABLE_SIZE);
3203 		if (!new)
3204 			goto err_alloc;
3205 		pgd_populate(&init_mm, pgd, new);
3206 	}
3207 
3208 	p4d = p4d_offset(pgd, addr);
3209 	if (p4d_none(*p4d)) {
3210 		pud_t *new;
3211 
3212 		new = memblock_alloc(PUD_TABLE_SIZE, PUD_TABLE_SIZE);
3213 		if (!new)
3214 			goto err_alloc;
3215 		p4d_populate(&init_mm, p4d, new);
3216 	}
3217 
3218 	pud = pud_offset(p4d, addr);
3219 	if (pud_none(*pud)) {
3220 		pmd_t *new;
3221 
3222 		new = memblock_alloc(PMD_TABLE_SIZE, PMD_TABLE_SIZE);
3223 		if (!new)
3224 			goto err_alloc;
3225 		pud_populate(&init_mm, pud, new);
3226 	}
3227 
3228 	pmd = pmd_offset(pud, addr);
3229 	if (!pmd_present(*pmd)) {
3230 		pte_t *new;
3231 
3232 		new = memblock_alloc(PTE_TABLE_SIZE, PTE_TABLE_SIZE);
3233 		if (!new)
3234 			goto err_alloc;
3235 		pmd_populate_kernel(&init_mm, pmd, new);
3236 	}
3237 
3238 	return;
3239 
3240 err_alloc:
3241 	panic("%s: Failed to allocate memory\n", __func__);
3242 }
3243 
3244 /**
3245  * pcpu_page_first_chunk - map the first chunk using PAGE_SIZE pages
3246  * @reserved_size: the size of reserved percpu area in bytes
3247  * @cpu_to_nd_fn: callback to convert cpu to it's node, optional
3248  *
3249  * This is a helper to ease setting up page-remapped first percpu
3250  * chunk and can be called where pcpu_setup_first_chunk() is expected.
3251  *
3252  * This is the basic allocator.  Static percpu area is allocated
3253  * page-by-page into vmalloc area.
3254  *
3255  * RETURNS:
3256  * 0 on success, -errno on failure.
3257  */
pcpu_page_first_chunk(size_t reserved_size,pcpu_fc_cpu_to_node_fn_t cpu_to_nd_fn)3258 int __init pcpu_page_first_chunk(size_t reserved_size, pcpu_fc_cpu_to_node_fn_t cpu_to_nd_fn)
3259 {
3260 	static struct vm_struct vm;
3261 	struct pcpu_alloc_info *ai;
3262 	char psize_str[16];
3263 	int unit_pages;
3264 	size_t pages_size;
3265 	struct page **pages;
3266 	int unit, i, j, rc = 0;
3267 	int upa;
3268 	int nr_g0_units;
3269 
3270 	snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);
3271 
3272 	ai = pcpu_build_alloc_info(reserved_size, 0, PAGE_SIZE, NULL);
3273 	if (IS_ERR(ai))
3274 		return PTR_ERR(ai);
3275 	BUG_ON(ai->nr_groups != 1);
3276 	upa = ai->alloc_size/ai->unit_size;
3277 	nr_g0_units = roundup(num_possible_cpus(), upa);
3278 	if (WARN_ON(ai->groups[0].nr_units != nr_g0_units)) {
3279 		pcpu_free_alloc_info(ai);
3280 		return -EINVAL;
3281 	}
3282 
3283 	unit_pages = ai->unit_size >> PAGE_SHIFT;
3284 
3285 	/* unaligned allocations can't be freed, round up to page size */
3286 	pages_size = PFN_ALIGN(unit_pages * num_possible_cpus() *
3287 			       sizeof(pages[0]));
3288 	pages = memblock_alloc(pages_size, SMP_CACHE_BYTES);
3289 	if (!pages)
3290 		panic("%s: Failed to allocate %zu bytes\n", __func__,
3291 		      pages_size);
3292 
3293 	/* allocate pages */
3294 	j = 0;
3295 	for (unit = 0; unit < num_possible_cpus(); unit++) {
3296 		unsigned int cpu = ai->groups[0].cpu_map[unit];
3297 		for (i = 0; i < unit_pages; i++) {
3298 			void *ptr;
3299 
3300 			ptr = pcpu_fc_alloc(cpu, PAGE_SIZE, PAGE_SIZE, cpu_to_nd_fn);
3301 			if (!ptr) {
3302 				pr_warn("failed to allocate %s page for cpu%u\n",
3303 						psize_str, cpu);
3304 				goto enomem;
3305 			}
3306 			/* kmemleak tracks the percpu allocations separately */
3307 			kmemleak_ignore_phys(__pa(ptr));
3308 			pages[j++] = virt_to_page(ptr);
3309 		}
3310 	}
3311 
3312 	/* allocate vm area, map the pages and copy static data */
3313 	vm.flags = VM_ALLOC;
3314 	vm.size = num_possible_cpus() * ai->unit_size;
3315 	vm_area_register_early(&vm, PAGE_SIZE);
3316 
3317 	for (unit = 0; unit < num_possible_cpus(); unit++) {
3318 		unsigned long unit_addr =
3319 			(unsigned long)vm.addr + unit * ai->unit_size;
3320 
3321 		for (i = 0; i < unit_pages; i++)
3322 			pcpu_populate_pte(unit_addr + (i << PAGE_SHIFT));
3323 
3324 		/* pte already populated, the following shouldn't fail */
3325 		rc = __pcpu_map_pages(unit_addr, &pages[unit * unit_pages],
3326 				      unit_pages);
3327 		if (rc < 0)
3328 			panic("failed to map percpu area, err=%d\n", rc);
3329 
3330 		/*
3331 		 * FIXME: Archs with virtual cache should flush local
3332 		 * cache for the linear mapping here - something
3333 		 * equivalent to flush_cache_vmap() on the local cpu.
3334 		 * flush_cache_vmap() can't be used as most supporting
3335 		 * data structures are not set up yet.
3336 		 */
3337 
3338 		/* copy static data */
3339 		memcpy((void *)unit_addr, __per_cpu_load, ai->static_size);
3340 	}
3341 
3342 	/* we're ready, commit */
3343 	pr_info("%d %s pages/cpu s%zu r%zu d%zu\n",
3344 		unit_pages, psize_str, ai->static_size,
3345 		ai->reserved_size, ai->dyn_size);
3346 
3347 	pcpu_setup_first_chunk(ai, vm.addr);
3348 	goto out_free_ar;
3349 
3350 enomem:
3351 	while (--j >= 0)
3352 		pcpu_fc_free(page_address(pages[j]), PAGE_SIZE);
3353 	rc = -ENOMEM;
3354 out_free_ar:
3355 	memblock_free(pages, pages_size);
3356 	pcpu_free_alloc_info(ai);
3357 	return rc;
3358 }
3359 #endif /* BUILD_PAGE_FIRST_CHUNK */
3360 
3361 #ifndef	CONFIG_HAVE_SETUP_PER_CPU_AREA
3362 /*
3363  * Generic SMP percpu area setup.
3364  *
3365  * The embedding helper is used because its behavior closely resembles
3366  * the original non-dynamic generic percpu area setup.  This is
3367  * important because many archs have addressing restrictions and might
3368  * fail if the percpu area is located far away from the previous
3369  * location.  As an added bonus, in non-NUMA cases, embedding is
3370  * generally a good idea TLB-wise because percpu area can piggy back
3371  * on the physical linear memory mapping which uses large page
3372  * mappings on applicable archs.
3373  */
3374 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
3375 EXPORT_SYMBOL(__per_cpu_offset);
3376 
setup_per_cpu_areas(void)3377 void __init setup_per_cpu_areas(void)
3378 {
3379 	unsigned long delta;
3380 	unsigned int cpu;
3381 	int rc;
3382 
3383 	/*
3384 	 * Always reserve area for module percpu variables.  That's
3385 	 * what the legacy allocator did.
3386 	 */
3387 	rc = pcpu_embed_first_chunk(PERCPU_MODULE_RESERVE, PERCPU_DYNAMIC_RESERVE,
3388 				    PAGE_SIZE, NULL, NULL);
3389 	if (rc < 0)
3390 		panic("Failed to initialize percpu areas.");
3391 
3392 	delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
3393 	for_each_possible_cpu(cpu)
3394 		__per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];
3395 }
3396 #endif	/* CONFIG_HAVE_SETUP_PER_CPU_AREA */
3397 
3398 #else	/* CONFIG_SMP */
3399 
3400 /*
3401  * UP percpu area setup.
3402  *
3403  * UP always uses km-based percpu allocator with identity mapping.
3404  * Static percpu variables are indistinguishable from the usual static
3405  * variables and don't require any special preparation.
3406  */
setup_per_cpu_areas(void)3407 void __init setup_per_cpu_areas(void)
3408 {
3409 	const size_t unit_size =
3410 		roundup_pow_of_two(max_t(size_t, PCPU_MIN_UNIT_SIZE,
3411 					 PERCPU_DYNAMIC_RESERVE));
3412 	struct pcpu_alloc_info *ai;
3413 	void *fc;
3414 
3415 	ai = pcpu_alloc_alloc_info(1, 1);
3416 	fc = memblock_alloc_from(unit_size, PAGE_SIZE, __pa(MAX_DMA_ADDRESS));
3417 	if (!ai || !fc)
3418 		panic("Failed to allocate memory for percpu areas.");
3419 	/* kmemleak tracks the percpu allocations separately */
3420 	kmemleak_ignore_phys(__pa(fc));
3421 
3422 	ai->dyn_size = unit_size;
3423 	ai->unit_size = unit_size;
3424 	ai->atom_size = unit_size;
3425 	ai->alloc_size = unit_size;
3426 	ai->groups[0].nr_units = 1;
3427 	ai->groups[0].cpu_map[0] = 0;
3428 
3429 	pcpu_setup_first_chunk(ai, fc);
3430 	pcpu_free_alloc_info(ai);
3431 }
3432 
3433 #endif	/* CONFIG_SMP */
3434 
3435 /*
3436  * pcpu_nr_pages - calculate total number of populated backing pages
3437  *
3438  * This reflects the number of pages populated to back chunks.  Metadata is
3439  * excluded in the number exposed in meminfo as the number of backing pages
3440  * scales with the number of cpus and can quickly outweigh the memory used for
3441  * metadata.  It also keeps this calculation nice and simple.
3442  *
3443  * RETURNS:
3444  * Total number of populated backing pages in use by the allocator.
3445  */
pcpu_nr_pages(void)3446 unsigned long pcpu_nr_pages(void)
3447 {
3448 	return pcpu_nr_populated * pcpu_nr_units;
3449 }
3450 
3451 /*
3452  * Percpu allocator is initialized early during boot when neither slab or
3453  * workqueue is available.  Plug async management until everything is up
3454  * and running.
3455  */
percpu_enable_async(void)3456 static int __init percpu_enable_async(void)
3457 {
3458 	pcpu_async_enabled = true;
3459 	return 0;
3460 }
3461 subsys_initcall(percpu_enable_async);
3462