LXR linux/lib/sg

   1// SPDX-License-Identifier: GPL-2.0-only
   2#include <linux/module.h>
   3#include <linux/scatterlist.h>
   4#include <linux/mempool.h>
   5#include <linux/slab.h>
   6
   7#define SG_MEMPOOL_NR           ARRAY_SIZE(sg_pools)
   8#define SG_MEMPOOL_SIZE         2
   9
  10struct sg_pool {
  11        size_t          size;
  12        char            *name;
  13        struct kmem_cache       *slab;
  14        mempool_t       *pool;
  15};
  16
  17#define SP(x) { .size = x, "sgpool-" __stringify(x) }
  18#if (SG_CHUNK_SIZE < 32)
  19#error SG_CHUNK_SIZE is too small (must be 32 or greater)
  20#endif
  21static struct sg_pool sg_pools[] = {
  22        SP(8),
  23        SP(16),
  24#if (SG_CHUNK_SIZE > 32)
  25        SP(32),
  26#if (SG_CHUNK_SIZE > 64)
  27        SP(64),
  28#if (SG_CHUNK_SIZE > 128)
  29        SP(128),
  30#if (SG_CHUNK_SIZE > 256)
  31#error SG_CHUNK_SIZE is too large (256 MAX)
  32#endif
  33#endif
  34#endif
  35#endif
  36        SP(SG_CHUNK_SIZE)
  37};
  38#undef SP
  39
  40static inline unsigned int sg_pool_index(unsigned short nents)
  41{
  42        unsigned int index;
  43
  44        BUG_ON(nents > SG_CHUNK_SIZE);
  45
  46        if (nents <= 8)
  47                index = 0;
  48        else
  49                index = get_count_order(nents) - 3;
  50
  51        return index;
  52}
  53
  54static void sg_pool_free(struct scatterlist *sgl, unsigned int nents)
  55{
  56        struct sg_pool *sgp;
  57
  58        sgp = sg_pools + sg_pool_index(nents);
  59        mempool_free(sgl, sgp->pool);
  60}
  61
  62static struct scatterlist *sg_pool_alloc(unsigned int nents, gfp_t gfp_mask)
  63{
  64        struct sg_pool *sgp;
  65
  66        sgp = sg_pools + sg_pool_index(nents);
  67        return mempool_alloc(sgp->pool, gfp_mask);
  68}
  69
  70/**
  71 * sg_free_table_chained - Free a previously mapped sg table
  72 * @table:      The sg table header to use
  73 * @first_chunk: was first_chunk not NULL in sg_alloc_table_chained?
  74 *
  75 *  Description:
  76 *    Free an sg table previously allocated and setup with
  77 *    sg_alloc_table_chained().
  78 *
  79 **/
  80void sg_free_table_chained(struct sg_table *table, bool first_chunk)
  81{
  82        if (first_chunk && table->orig_nents <= SG_CHUNK_SIZE)
  83                return;
  84        __sg_free_table(table, SG_CHUNK_SIZE, first_chunk, sg_pool_free);
  85}
  86EXPORT_SYMBOL_GPL(sg_free_table_chained);
  87
  88/**
  89 * sg_alloc_table_chained - Allocate and chain SGLs in an sg table
  90 * @table:      The sg table header to use
  91 * @nents:      Number of entries in sg list
  92 * @first_chunk: first SGL
  93 *
  94 *  Description:
  95 *    Allocate and chain SGLs in an sg table. If @nents@ is larger than
  96 *    SG_CHUNK_SIZE a chained sg table will be setup.
  97 *
  98 **/
  99int sg_alloc_table_chained(struct sg_table *table, int nents,
 100                struct scatterlist *first_chunk)
 101{
 102        int ret;
 103
 104        BUG_ON(!nents);
 105
 106        if (first_chunk) {
 107                if (nents <= SG_CHUNK_SIZE) {
 108                        table->nents = table->orig_nents = nents;
 109                        sg_init_table(table->sgl, nents);
 110                        return 0;
 111                }
 112        }
 113
 114        ret = __sg_alloc_table(table, nents, SG_CHUNK_SIZE,
 115                               first_chunk, GFP_ATOMIC, sg_pool_alloc);
 116        if (unlikely(ret))
 117                sg_free_table_chained(table, (bool)first_chunk);
 118        return ret;
 119}
 120EXPORT_SYMBOL_GPL(sg_alloc_table_chained);
 121
 122static __init int sg_pool_init(void)
 123{
 124        int i;
 125
 126        for (i = 0; i < SG_MEMPOOL_NR; i++) {
 127                struct sg_pool *sgp = sg_pools + i;
 128                int size = sgp->size * sizeof(struct scatterlist);
 129
 130                sgp->slab = kmem_cache_create(sgp->name, size, 0,
 131                                SLAB_HWCACHE_ALIGN, NULL);
 132                if (!sgp->slab) {
 133                        printk(KERN_ERR "SG_POOL: can't init sg slab %s\n",
 134                                        sgp->name);
 135                        goto cleanup_sdb;
 136                }
 137
 138                sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
 139                                                     sgp->slab);
 140                if (!sgp->pool) {
 141                        printk(KERN_ERR "SG_POOL: can't init sg mempool %s\n",
 142                                        sgp->name);
 143                        goto cleanup_sdb;
 144                }
 145        }
 146
 147        return 0;
 148
 149cleanup_sdb:
 150        for (i = 0; i < SG_MEMPOOL_NR; i++) {
 151                struct sg_pool *sgp = sg_pools + i;
 152
 153                mempool_destroy(sgp->pool);
 154                kmem_cache_destroy(sgp->slab);
 155        }
 156
 157        return -ENOMEM;
 158}
 159
 160static __exit void sg_pool_exit(void)
 161{
 162        int i;
 163
 164        for (i = 0; i < SG_MEMPOOL_NR; i++) {
 165                struct sg_pool *sgp = sg_pools + i;
 166                mempool_destroy(sgp->pool);
 167                kmem_cache_destroy(sgp->slab);
 168        }
 169}
 170
 171module_init(sg_pool_init);
 172module_exit(sg_pool_exit);
 173