xref: /openbmc/linux/lib/sg_pool.c (revision a10c9ede)
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