root/lib/sg_pool.c

DEFINITIONS

1. sg_pool_index
2. sg_pool_free
3. sg_pool_alloc
4. sg_free_table_chained
5. sg_alloc_table_chained
6. sg_pool_init
7. sg_pool_exit

   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  * @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  **/
  84 void 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 }
  95 EXPORT_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  **/
 111 int 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 }
 139 EXPORT_SYMBOL_GPL(sg_alloc_table_chained);
 140 
 141 static __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 
 168 cleanup_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 
 179 static __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 
 190 module_init(sg_pool_init);
 191 module_exit(sg_pool_exit);