LXR linux/mm/percpu-km.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * mm/percpu-km.c - kernel memory based chunk allocation
   4 *
   5 * Copyright (C) 2010           SUSE Linux Products GmbH
   6 * Copyright (C) 2010           Tejun Heo <tj@kernel.org>
   7 *
   8 * Chunks are allocated as a contiguous kernel memory using gfp
   9 * allocation.  This is to be used on nommu architectures.
  10 *
  11 * To use percpu-km,
  12 *
  13 * - define CONFIG_NEED_PER_CPU_KM from the arch Kconfig.
  14 *
  15 * - CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK must not be defined.  It's
  16 *   not compatible with PER_CPU_KM.  EMBED_FIRST_CHUNK should work
  17 *   fine.
  18 *
  19 * - NUMA is not supported.  When setting up the first chunk,
  20 *   @cpu_distance_fn should be NULL or report all CPUs to be nearer
  21 *   than or at LOCAL_DISTANCE.
  22 *
  23 * - It's best if the chunk size is power of two multiple of
  24 *   PAGE_SIZE.  Because each chunk is allocated as a contiguous
  25 *   kernel memory block using alloc_pages(), memory will be wasted if
  26 *   chunk size is not aligned.  percpu-km code will whine about it.
  27 */
  28
  29#if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
  30#error "contiguous percpu allocation is incompatible with paged first chunk"
  31#endif
  32
  33#include <linux/log2.h>
  34
  35static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
  36                               int page_start, int page_end, gfp_t gfp)
  37{
  38        return 0;
  39}
  40
  41static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
  42                                  int page_start, int page_end)
  43{
  44        /* nada */
  45}
  46
  47static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp)
  48{
  49        const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
  50        struct pcpu_chunk *chunk;
  51        struct page *pages;
  52        unsigned long flags;
  53        int i;
  54
  55        chunk = pcpu_alloc_chunk(gfp);
  56        if (!chunk)
  57                return NULL;
  58
  59        pages = alloc_pages(gfp, 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);
  70
  71        spin_lock_irqsave(&pcpu_lock, flags);
  72        pcpu_chunk_populated(chunk, 0, nr_pages);
  73        spin_unlock_irqrestore(&pcpu_lock, flags);
  74
  75        pcpu_stats_chunk_alloc();
  76        trace_percpu_create_chunk(chunk->base_addr);
  77
  78        return chunk;
  79}
  80
  81static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
  82{
  83        const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
  84
  85        if (!chunk)
  86                return;
  87
  88        pcpu_stats_chunk_dealloc();
  89        trace_percpu_destroy_chunk(chunk->base_addr);
  90
  91        if (chunk->data)
  92                __free_pages(chunk->data, order_base_2(nr_pages));
  93        pcpu_free_chunk(chunk);
  94}
  95
  96static struct page *pcpu_addr_to_page(void *addr)
  97{
  98        return virt_to_page(addr);
  99}
 100
 101static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
 102{
 103        size_t nr_pages, alloc_pages;
 104
 105        /* all units must be in a single group */
 106        if (ai->nr_groups != 1) {
 107                pr_crit("can't handle more than one group\n");
 108                return -EINVAL;
 109        }
 110
 111        nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT;
 112        alloc_pages = roundup_pow_of_two(nr_pages);
 113
 114        if (alloc_pages > nr_pages)
 115                pr_warn("wasting %zu pages per chunk\n",
 116                        alloc_pages - nr_pages);
 117
 118        return 0;
 119}
 120