the-tree/mm/percpu-km.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * mm/percpu-km.c - kernel memory based chunk allocation
0004  *
0005  * Copyright (C) 2010       SUSE Linux Products GmbH
0006  * Copyright (C) 2010       Tejun Heo <tj@kernel.org>
0007  *
0008  * Chunks are allocated as a contiguous kernel memory using gfp
0009  * allocation.  This is to be used on nommu architectures.
0010  *
0011  * To use percpu-km,
0012  *
0013  * - define CONFIG_NEED_PER_CPU_KM from the arch Kconfig.
0014  *
0015  * - CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK must not be defined.  It's
0016  *   not compatible with PER_CPU_KM.  EMBED_FIRST_CHUNK should work
0017  *   fine.
0018  *
0019  * - NUMA is not supported.  When setting up the first chunk,
0020  *   @cpu_distance_fn should be NULL or report all CPUs to be nearer
0021  *   than or at LOCAL_DISTANCE.
0022  *
0023  * - It's best if the chunk size is power of two multiple of
0024  *   PAGE_SIZE.  Because each chunk is allocated as a contiguous
0025  *   kernel memory block using alloc_pages(), memory will be wasted if
0026  *   chunk size is not aligned.  percpu-km code will whine about it.
0027  */
0028
0029 #if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK)
0030 #error "contiguous percpu allocation is incompatible with paged first chunk"
0031 #endif
0032
0033 #include <linux/log2.h>
0034
0035 static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,
0036                       int page_start, int page_end)
0037 {
0038     /* nothing */
0039 }
0040
0041 static int pcpu_populate_chunk(struct pcpu_chunk *chunk,
0042                    int page_start, int page_end, gfp_t gfp)
0043 {
0044     return 0;
0045 }
0046
0047 static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
0048                   int page_start, int page_end)
0049 {
0050     /* nada */
0051 }
0052
0053 static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp)
0054 {
0055     const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
0056     struct pcpu_chunk *chunk;
0057     struct page *pages;
0058     unsigned long flags;
0059     int i;
0060
0061     chunk = pcpu_alloc_chunk(gfp);
0062     if (!chunk)
0063         return NULL;
0064
0065     pages = alloc_pages(gfp, order_base_2(nr_pages));
0066     if (!pages) {
0067         pcpu_free_chunk(chunk);
0068         return NULL;
0069     }
0070
0071     for (i = 0; i < nr_pages; i++)
0072         pcpu_set_page_chunk(nth_page(pages, i), chunk);
0073
0074     chunk->data = pages;
0075     chunk->base_addr = page_address(pages);
0076
0077     spin_lock_irqsave(&pcpu_lock, flags);
0078     pcpu_chunk_populated(chunk, 0, nr_pages);
0079     spin_unlock_irqrestore(&pcpu_lock, flags);
0080
0081     pcpu_stats_chunk_alloc();
0082     trace_percpu_create_chunk(chunk->base_addr);
0083
0084     return chunk;
0085 }
0086
0087 static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
0088 {
0089     const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
0090
0091     if (!chunk)
0092         return;
0093
0094     pcpu_stats_chunk_dealloc();
0095     trace_percpu_destroy_chunk(chunk->base_addr);
0096
0097     if (chunk->data)
0098         __free_pages(chunk->data, order_base_2(nr_pages));
0099     pcpu_free_chunk(chunk);
0100 }
0101
0102 static struct page *pcpu_addr_to_page(void *addr)
0103 {
0104     return virt_to_page(addr);
0105 }
0106
0107 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
0108 {
0109     size_t nr_pages, alloc_pages;
0110
0111     /* all units must be in a single group */
0112     if (ai->nr_groups != 1) {
0113         pr_crit("can't handle more than one group\n");
0114         return -EINVAL;
0115     }
0116
0117     nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT;
0118     alloc_pages = roundup_pow_of_two(nr_pages);
0119
0120     if (alloc_pages > nr_pages)
0121         pr_warn("wasting %zu pages per chunk\n",
0122             alloc_pages - nr_pages);
0123
0124     return 0;
0125 }
0126
0127 static bool pcpu_should_reclaim_chunk(struct pcpu_chunk *chunk)
0128 {
0129     return false;
0130 }