lib/sg_pool.c

   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
  10 struct 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
  21 static 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
  40 static 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
  54 static 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
  62 static 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  **/
  80 void 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 }
  86 EXPORT_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  **/
  99 int 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 }
 120 EXPORT_SYMBOL_GPL(sg_alloc_table_chained);
 121
 122 static __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
 149 cleanup_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
 160 static __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
 171 module_init(sg_pool_init);
 172 module_exit(sg_pool_exit);