1/*
2 * mm/percpu-km.c - kernel memory based chunk allocation
3 *
4 * Copyright (C) 2010		SUSE Linux Products GmbH
5 * Copyright (C) 2010		Tejun Heo <tj@kernel.org>
6 *
7 * This file is released under the GPLv2.
8 *
9 * Chunks are allocated as a contiguous kernel memory using gfp
10 * allocation.  This is to be used on nommu architectures.
11 *
12 * To use percpu-km,
13 *
14 * - define CONFIG_NEED_PER_CPU_KM from the arch Kconfig.
15 *
16 * - CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK must not be defined.  It's
17 *   not compatible with PER_CPU_KM.  EMBED_FIRST_CHUNK should work
18 *   fine.
19 *
20 * - NUMA is not supported.  When setting up the first chunk,
21 *   @cpu_distance_fn should be NULL or report all CPUs to be nearer
22 *   than or at LOCAL_DISTANCE.
23 *
24 * - It's best if the chunk size is power of two multiple of
25 *   PAGE_SIZE.  Because each chunk is allocated as a contiguous
26 *   kernel memory block using alloc_pages(), memory will be wasted if
27 *   chunk size is not aligned.  percpu-km code will whine about it.
28 */
29
30#if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
31#error "contiguous percpu allocation is incompatible with paged first chunk"
32#endif
33
34#include <linux/log2.h>
35
36static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
37			       int page_start, int page_end)
38{
39	return 0;
40}
41
42static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
43				  int page_start, int page_end)
44{
45	/* nada */
46}
47
48static struct pcpu_chunk *pcpu_create_chunk(void)
49{
50	const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
51	struct pcpu_chunk *chunk;
52	struct page *pages;
53	int i;
54
55	chunk = pcpu_alloc_chunk();
56	if (!chunk)
57		return NULL;
58
59	pages = alloc_pages(GFP_KERNEL, order_base_2(nr_pages));
60	if (!pages) {
61		pcpu_free_chunk(chunk);
62		return NULL;
63	}
64
65	for (i = 0; i < nr_pages; i++)
66		pcpu_set_page_chunk(nth_page(pages, i), chunk);
67
68	chunk->data = pages;
69	chunk->base_addr = page_address(pages) - pcpu_group_offsets[0];
70
71	spin_lock_irq(&pcpu_lock);
72	pcpu_chunk_populated(chunk, 0, nr_pages);
73	spin_unlock_irq(&pcpu_lock);
74
75	return chunk;
76}
77
78static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
79{
80	const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
81
82	if (chunk && chunk->data)
83		__free_pages(chunk->data, order_base_2(nr_pages));
84	pcpu_free_chunk(chunk);
85}
86
87static struct page *pcpu_addr_to_page(void *addr)
88{
89	return virt_to_page(addr);
90}
91
92static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
93{
94	size_t nr_pages, alloc_pages;
95
96	/* all units must be in a single group */
97	if (ai->nr_groups != 1) {
98		printk(KERN_CRIT "percpu: can't handle more than one groups\n");
99		return -EINVAL;
100	}
101
102	nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT;
103	alloc_pages = roundup_pow_of_two(nr_pages);
104
105	if (alloc_pages > nr_pages)
106		printk(KERN_WARNING "percpu: wasting %zu pages per chunk\n",
107		       alloc_pages - nr_pages);
108
109	return 0;
110}
111