lib: scatterlist: move SG pool code from SCSI driver to lib/sg_pool.c
Now it's ready to move the mempool based SG chained allocator code from
SCSI driver to lib/sg_pool.c, which will be compiled only based on a Kconfig
symbol CONFIG_SG_POOL.
SCSI selects CONFIG_SG_POOL.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
diff --git a/lib/sg_pool.c b/lib/sg_pool.c
new file mode 100644
index 0000000..6dd3061
--- /dev/null
+++ b/lib/sg_pool.c
@@ -0,0 +1,172 @@
+#include <linux/module.h>
+#include <linux/scatterlist.h>
+#include <linux/mempool.h>
+#include <linux/slab.h>
+
+#define SG_MEMPOOL_NR ARRAY_SIZE(sg_pools)
+#define SG_MEMPOOL_SIZE 2
+
+struct sg_pool {
+ size_t size;
+ char *name;
+ struct kmem_cache *slab;
+ mempool_t *pool;
+};
+
+#define SP(x) { .size = x, "sgpool-" __stringify(x) }
+#if (SG_CHUNK_SIZE < 32)
+#error SG_CHUNK_SIZE is too small (must be 32 or greater)
+#endif
+static struct sg_pool sg_pools[] = {
+ SP(8),
+ SP(16),
+#if (SG_CHUNK_SIZE > 32)
+ SP(32),
+#if (SG_CHUNK_SIZE > 64)
+ SP(64),
+#if (SG_CHUNK_SIZE > 128)
+ SP(128),
+#if (SG_CHUNK_SIZE > 256)
+#error SG_CHUNK_SIZE is too large (256 MAX)
+#endif
+#endif
+#endif
+#endif
+ SP(SG_CHUNK_SIZE)
+};
+#undef SP
+
+static inline unsigned int sg_pool_index(unsigned short nents)
+{
+ unsigned int index;
+
+ BUG_ON(nents > SG_CHUNK_SIZE);
+
+ if (nents <= 8)
+ index = 0;
+ else
+ index = get_count_order(nents) - 3;
+
+ return index;
+}
+
+static void sg_pool_free(struct scatterlist *sgl, unsigned int nents)
+{
+ struct sg_pool *sgp;
+
+ sgp = sg_pools + sg_pool_index(nents);
+ mempool_free(sgl, sgp->pool);
+}
+
+static struct scatterlist *sg_pool_alloc(unsigned int nents, gfp_t gfp_mask)
+{
+ struct sg_pool *sgp;
+
+ sgp = sg_pools + sg_pool_index(nents);
+ return mempool_alloc(sgp->pool, gfp_mask);
+}
+
+/**
+ * sg_free_table_chained - Free a previously mapped sg table
+ * @table: The sg table header to use
+ * @first_chunk: was first_chunk not NULL in sg_alloc_table_chained?
+ *
+ * Description:
+ * Free an sg table previously allocated and setup with
+ * sg_alloc_table_chained().
+ *
+ **/
+void sg_free_table_chained(struct sg_table *table, bool first_chunk)
+{
+ if (first_chunk && table->orig_nents <= SG_CHUNK_SIZE)
+ return;
+ __sg_free_table(table, SG_CHUNK_SIZE, first_chunk, sg_pool_free);
+}
+EXPORT_SYMBOL_GPL(sg_free_table_chained);
+
+/**
+ * sg_alloc_table_chained - Allocate and chain SGLs in an sg table
+ * @table: The sg table header to use
+ * @nents: Number of entries in sg list
+ * @first_chunk: first SGL
+ *
+ * Description:
+ * Allocate and chain SGLs in an sg table. If @nents@ is larger than
+ * SG_CHUNK_SIZE a chained sg table will be setup.
+ *
+ **/
+int sg_alloc_table_chained(struct sg_table *table, int nents,
+ struct scatterlist *first_chunk)
+{
+ int ret;
+
+ BUG_ON(!nents);
+
+ if (first_chunk) {
+ if (nents <= SG_CHUNK_SIZE) {
+ table->nents = table->orig_nents = nents;
+ sg_init_table(table->sgl, nents);
+ return 0;
+ }
+ }
+
+ ret = __sg_alloc_table(table, nents, SG_CHUNK_SIZE,
+ first_chunk, GFP_ATOMIC, sg_pool_alloc);
+ if (unlikely(ret))
+ sg_free_table_chained(table, (bool)first_chunk);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(sg_alloc_table_chained);
+
+static __init int sg_pool_init(void)
+{
+ int i;
+
+ for (i = 0; i < SG_MEMPOOL_NR; i++) {
+ struct sg_pool *sgp = sg_pools + i;
+ int size = sgp->size * sizeof(struct scatterlist);
+
+ sgp->slab = kmem_cache_create(sgp->name, size, 0,
+ SLAB_HWCACHE_ALIGN, NULL);
+ if (!sgp->slab) {
+ printk(KERN_ERR "SG_POOL: can't init sg slab %s\n",
+ sgp->name);
+ goto cleanup_sdb;
+ }
+
+ sgp->pool = mempool_create_slab_pool(SG_MEMPOOL_SIZE,
+ sgp->slab);
+ if (!sgp->pool) {
+ printk(KERN_ERR "SG_POOL: can't init sg mempool %s\n",
+ sgp->name);
+ goto cleanup_sdb;
+ }
+ }
+
+ return 0;
+
+cleanup_sdb:
+ for (i = 0; i < SG_MEMPOOL_NR; i++) {
+ struct sg_pool *sgp = sg_pools + i;
+ if (sgp->pool)
+ mempool_destroy(sgp->pool);
+ if (sgp->slab)
+ kmem_cache_destroy(sgp->slab);
+ }
+
+ return -ENOMEM;
+}
+
+static __exit void sg_pool_exit(void)
+{
+ int i;
+
+ for (i = 0; i < SG_MEMPOOL_NR; i++) {
+ struct sg_pool *sgp = sg_pools + i;
+ mempool_destroy(sgp->pool);
+ kmem_cache_destroy(sgp->slab);
+ }
+}
+
+module_init(sg_pool_init);
+module_exit(sg_pool_exit);