1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/init.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 table->orig_nents);
95 }
96 EXPORT_SYMBOL_GPL(sg_free_table_chained);
97
98 /**
99 * sg_alloc_table_chained - Allocate and chain SGLs in an sg table
100 * @table: The sg table header to use
101 * @nents: Number of entries in sg list
102 * @first_chunk: first SGL
103 * @nents_first_chunk: number of the SGL of @first_chunk
104 *
105 * Description:
106 * Allocate and chain SGLs in an sg table. If @nents@ is larger than
107 * @nents_first_chunk a chained sg table will be setup. @first_chunk is
108 * ignored if nents_first_chunk <= 1 because user expects the SGL points
109 * non-chain SGL.
110 *
111 **/
112 int sg_alloc_table_chained(struct sg_table *table, int nents,
113 struct scatterlist *first_chunk, unsigned nents_first_chunk)
114 {
115 int ret;
116
117 BUG_ON(!nents);
118
119 if (first_chunk && nents_first_chunk) {
120 if (nents <= nents_first_chunk) {
121 table->nents = table->orig_nents = nents;
122 sg_init_table(table->sgl, nents);
123 return 0;
124 }
125 }
126
127 /* User supposes that the 1st SGL includes real entry */
128 if (nents_first_chunk <= 1) {
129 first_chunk = NULL;
130 nents_first_chunk = 0;
131 }
132
133 ret = __sg_alloc_table(table, nents, SG_CHUNK_SIZE,
134 first_chunk, nents_first_chunk,
135 GFP_ATOMIC, sg_pool_alloc);
136 if (unlikely(ret))
137 sg_free_table_chained(table, nents_first_chunk);
138 return ret;
139 }
140 EXPORT_SYMBOL_GPL(sg_alloc_table_chained);
141
142 static __init int sg_pool_init(void)
143 {
144 int i;
145
146 for (i = 0; i < SG_MEMPOOL_NR; i++) {
147 struct sg_pool *sgp = sg_pools + i;
148 int size = sgp->size * sizeof(struct scatterlist);
149
150 sgp->slab = kmem_cache_create(sgp->name, size, 0,
151 SLAB_HWCACHE_ALIGN, NULL);
152 if (!sgp->slab) {
153 printk(KERN_ERR "SG_POOL: can't init sg slab %s\n",
154 sgp->name);
155 goto cleanup_sdb;
156 }
157
158 sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
159 sgp->slab);
160 if (!sgp->pool) {
161 printk(KERN_ERR "SG_POOL: can't init sg mempool %s\n",
162 sgp->name);
163 goto cleanup_sdb;
164 }
165 }
166
167 return 0;
168
169 cleanup_sdb:
170 for (i = 0; i < SG_MEMPOOL_NR; i++) {
171 struct sg_pool *sgp = sg_pools + i;
172
173 mempool_destroy(sgp->pool);
174 kmem_cache_destroy(sgp->slab);
175 }
176
177 return -ENOMEM;
178 }
179
180 subsys_initcall(sg_pool_init);
181
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