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
sg_pool_index(unsigned short nents)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
sg_pool_free(struct scatterlist * sgl,unsigned int nents)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
sg_pool_alloc(unsigned int nents,gfp_t gfp_mask)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 **/
sg_free_table_chained(struct sg_table * table,unsigned nents_first_chunk)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 **/
sg_alloc_table_chained(struct sg_table * table,int nents,struct scatterlist * first_chunk,unsigned nents_first_chunk)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
sg_pool_init(void)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
sg_pool_exit(void)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);
192