lib/sg_pool.c

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