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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 | |
36 | static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size) |
37 | { |
38 | unsigned int cpu; |
39 | |
40 | for_each_possible_cpu(cpu) |
41 | memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size); |
42 | |
43 | return 0; |
44 | } |
45 | |
46 | static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size) |
47 | { |
48 | /* nada */ |
49 | } |
50 | |
51 | static struct pcpu_chunk *pcpu_create_chunk(void) |
52 | { |
53 | const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT; |
54 | struct pcpu_chunk *chunk; |
55 | struct page *pages; |
56 | int i; |
57 | |
58 | chunk = pcpu_alloc_chunk(); |
59 | if (!chunk) |
60 | return NULL; |
61 | |
62 | pages = alloc_pages(GFP_KERNEL, order_base_2(nr_pages)); |
63 | if (!pages) { |
64 | pcpu_free_chunk(chunk); |
65 | return NULL; |
66 | } |
67 | |
68 | for (i = 0; i < nr_pages; i++) |
69 | pcpu_set_page_chunk(nth_page(pages, i), chunk); |
70 | |
71 | chunk->data = pages; |
72 | chunk->base_addr = page_address(pages) - pcpu_group_offsets[0]; |
73 | return chunk; |
74 | } |
75 | |
76 | static void pcpu_destroy_chunk(struct pcpu_chunk *chunk) |
77 | { |
78 | const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT; |
79 | |
80 | if (chunk && chunk->data) |
81 | __free_pages(chunk->data, order_base_2(nr_pages)); |
82 | pcpu_free_chunk(chunk); |
83 | } |
84 | |
85 | static struct page *pcpu_addr_to_page(void *addr) |
86 | { |
87 | return virt_to_page(addr); |
88 | } |
89 | |
90 | static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai) |
91 | { |
92 | size_t nr_pages, alloc_pages; |
93 | |
94 | /* all units must be in a single group */ |
95 | if (ai->nr_groups != 1) { |
96 | printk(KERN_CRIT "percpu: can't handle more than one groups\n"); |
97 | return -EINVAL; |
98 | } |
99 | |
100 | nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT; |
101 | alloc_pages = roundup_pow_of_two(nr_pages); |
102 | |
103 | if (alloc_pages > nr_pages) |
104 | printk(KERN_WARNING "percpu: wasting %zu pages per chunk\n", |
105 | alloc_pages - nr_pages); |
106 | |
107 | return 0; |
108 | } |
109 |
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