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
 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}
 95EXPORT_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 **/
111int 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}
139EXPORT_SYMBOL_GPL(sg_alloc_table_chained);
140
141static __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
168cleanup_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
179static __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
190module_init(sg_pool_init);
191module_exit(sg_pool_exit);