Quelle percpu-km.c Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
/*
* mm/percpu-km.c - kernel memory based chunk allocation
*
* Copyright (C) 2010 SUSE Linux Products GmbH
* Copyright (C) 2010 Tejun Heo <tj@kernel.org>
*
* Chunks are allocated as a contiguous kernel memory using gfp
* allocation.  This is to be used on nommu architectures.
*
* To use percpu-km,
*
* - define CONFIG_NEED_PER_CPU_KM from the arch Kconfig.
*
* - CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK must not be defined.  It's
*   not compatible with PER_CPU_KM.  EMBED_FIRST_CHUNK should work
*   fine.
*
* - NUMA is not supported.  When setting up the first chunk,
*   @cpu_distance_fn should be NULL or report all CPUs to be nearer
*   than or at LOCAL_DISTANCE.
*
* - It's best if the chunk size is power of two multiple of
*   PAGE_SIZE.  Because each chunk is allocated as a contiguous
*   kernel memory block using alloc_pages(), memory will be wasted if
*   chunk size is not aligned.  percpu-km code will whine about it.
*/

#if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
#error "contiguous percpu allocation is incompatible with paged first chunk"
#endif

#include <linux/log2.h>

static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,
          int page_start, int page_end)
{
/* nothing */
}

static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
          int page_start, int page_end, gfp_t gfp)
{
return 0;
}

static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
      int page_start, int page_end)
{
/* nada */
}

static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp)
{
const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
struct pcpu_chunk *chunk;
struct page *pages;
unsigned long flags;
int i;

chunk = pcpu_alloc_chunk(gfp);
if (!chunk)
  return NULL;

pages = alloc_pages(gfp, order_base_2(nr_pages));
if (!pages) {
  pcpu_free_chunk(chunk);
  return NULL;
}

for (i = 0; i < nr_pages; i++)
  pcpu_set_page_chunk(nth_page(pages, i), chunk);

chunk->data = pages;
chunk->base_addr = page_address(pages);

spin_lock_irqsave(&pcpu_lock, flags);
pcpu_chunk_populated(chunk, 0, nr_pages);
spin_unlock_irqrestore(&pcpu_lock, flags);

pcpu_stats_chunk_alloc();
trace_percpu_create_chunk(chunk->base_addr);

return chunk;
}

static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
{
const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;

if (!chunk)
  return;

pcpu_stats_chunk_dealloc();
trace_percpu_destroy_chunk(chunk->base_addr);

if (chunk->data)
  __free_pages(chunk->data, order_base_2(nr_pages));
pcpu_free_chunk(chunk);
}

static struct page *pcpu_addr_to_page(void *addr)
{
return virt_to_page(addr);
}

static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
{
size_t nr_pages, alloc_pages;

/* all units must be in a single group */
if (ai->nr_groups != 1) {
  pr_crit("can't handle more than one group\n");
  return -EINVAL;
}

nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT;
alloc_pages = roundup_pow_of_two(nr_pages);

if (alloc_pages > nr_pages)
  pr_warn("wasting %zu pages per chunk\n",
   alloc_pages - nr_pages);

return 0;
}

static bool pcpu_should_reclaim_chunk(struct pcpu_chunk *chunk)
{
return false;
}

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