xref: /openbmc/linux/lib/sg_pool.c (revision 2010776f)
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 			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 static __exit void sg_pool_exit(void)
181 {
182 	int i;
183 
184 	for (i = 0; i < SG_MEMPOOL_NR; i++) {
185 		struct sg_pool *sgp = sg_pools + i;
186 		mempool_destroy(sgp->pool);
187 		kmem_cache_destroy(sgp->slab);
188 	}
189 }
190 
191 module_init(sg_pool_init);
192 module_exit(sg_pool_exit);
193