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
10struct 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
21static 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
40static 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
54static 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
62static 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 **/
84void 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}
96EXPORT_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 **/
112int 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}
140EXPORT_SYMBOL_GPL(sg_alloc_table_chained);
141
142static __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
169cleanup_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
180subsys_initcall(sg_pool_init);
181