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Linux/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                 if (sgp->pool)
152                         mempool_destroy(sgp->pool);
153                 if (sgp->slab)
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);
173 

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