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 * @nents_first_chunk: size of the first_chunk SGL passed to
  74 *              sg_alloc_table_chained
  75 *
  76 *  Description:
  77 *    Free an sg table previously allocated and setup with
  78 *    sg_alloc_table_chained().
  79 *
  80 *    @nents_first_chunk has to be same with that same parameter passed
  81 *    to sg_alloc_table_chained().
  82 *
  83 **/
  84void sg_free_table_chained(struct sg_table *table,
  85                unsigned nents_first_chunk)
  86{
  87        if (table->orig_nents <= nents_first_chunk)
  88                return;
  89
  90        if (nents_first_chunk == 1)
  91                nents_first_chunk = 0;
  92
  93        __sg_free_table(table, SG_CHUNK_SIZE, nents_first_chunk, sg_pool_free);
  94}
  95EXPORT_SYMBOL_GPL(sg_free_table_chained);
  96
  97/**
  98 * sg_alloc_table_chained - Allocate and chain SGLs in an sg table
  99 * @table:      The sg table header to use
 100 * @nents:      Number of entries in sg list
 101 * @first_chunk: first SGL
 102 * @nents_first_chunk: number of the SGL of @first_chunk
 103 *
 104 *  Description:
 105 *    Allocate and chain SGLs in an sg table. If @nents@ is larger than
 106 *    @nents_first_chunk a chained sg table will be setup. @first_chunk is
 107 *    ignored if nents_first_chunk <= 1 because user expects the SGL points
 108 *    non-chain SGL.
 109 *
 110 **/
 111int sg_alloc_table_chained(struct sg_table *table, int nents,
 112                struct scatterlist *first_chunk, unsigned nents_first_chunk)
 113{
 114        int ret;
 115
 116        BUG_ON(!nents);
 117
 118        if (first_chunk && nents_first_chunk) {
 119                if (nents <= nents_first_chunk) {
 120                        table->nents = table->orig_nents = nents;
 121                        sg_init_table(table->sgl, nents);
 122                        return 0;
 123                }
 124        }
 125
 126        /* User supposes that the 1st SGL includes real entry */
 127        if (nents_first_chunk <= 1) {
 128                first_chunk = NULL;
 129                nents_first_chunk = 0;
 130        }
 131
 132        ret = __sg_alloc_table(table, nents, SG_CHUNK_SIZE,
 133                               first_chunk, nents_first_chunk,
 134                               GFP_ATOMIC, sg_pool_alloc);
 135        if (unlikely(ret))
 136                sg_free_table_chained(table, nents_first_chunk);
 137        return ret;
 138}
 139EXPORT_SYMBOL_GPL(sg_alloc_table_chained);
 140
 141static __init int sg_pool_init(void)
 142{
 143        int i;
 144
 145        for (i = 0; i < SG_MEMPOOL_NR; i++) {
 146                struct sg_pool *sgp = sg_pools + i;
 147                int size = sgp->size * sizeof(struct scatterlist);
 148
 149                sgp->slab = kmem_cache_create(sgp->name, size, 0,
 150                                SLAB_HWCACHE_ALIGN, NULL);
 151                if (!sgp->slab) {
 152                        printk(KERN_ERR "SG_POOL: can't init sg slab %s\n",
 153                                        sgp->name);
 154                        goto cleanup_sdb;
 155                }
 156
 157                sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
 158                                                     sgp->slab);
 159                if (!sgp->pool) {
 160                        printk(KERN_ERR "SG_POOL: can't init sg mempool %s\n",
 161                                        sgp->name);
 162                        goto cleanup_sdb;
 163                }
 164        }
 165
 166        return 0;
 167
 168cleanup_sdb:
 169        for (i = 0; i < SG_MEMPOOL_NR; i++) {
 170                struct sg_pool *sgp = sg_pools + i;
 171
 172                mempool_destroy(sgp->pool);
 173                kmem_cache_destroy(sgp->slab);
 174        }
 175
 176        return -ENOMEM;
 177}
 178
 179static __exit void sg_pool_exit(void)
 180{
 181        int i;
 182
 183        for (i = 0; i < SG_MEMPOOL_NR; i++) {
 184                struct sg_pool *sgp = sg_pools + i;
 185                mempool_destroy(sgp->pool);
 186                kmem_cache_destroy(sgp->slab);
 187        }
 188}
 189
 190module_init(sg_pool_init);
 191module_exit(sg_pool_exit);
 192