// SPDX-License-Identifier: GPL-2.0-only#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)#endifstatic 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 * @nents_first_chunk: size of the first_chunk SGL passed to *		sg_alloc_table_chained * *  Description: *    Free an sg table previously allocated and setup with *    sg_alloc_table_chained(). * *    @nents_first_chunk has to be same with that same parameter passed *    to sg_alloc_table_chained(). * **/void sg_free_table_chained(struct sg_table *table,		unsigned nents_first_chunk){	if (table->orig_nents <= nents_first_chunk)		return; 	if (nents_first_chunk == 1)		nents_first_chunk = 0; 	__sg_free_table(table, SG_CHUNK_SIZE, nents_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 * @nents_first_chunk: number of the SGL of @first_chunk * *  Description: *    Allocate and chain SGLs in an sg table. If @nents@ is larger than *    @nents_first_chunk a chained sg table will be setup. @first_chunk is *    ignored if nents_first_chunk <= 1 because user expects the SGL points *    non-chain SGL. * **/int sg_alloc_table_chained(struct sg_table *table, int nents,		struct scatterlist *first_chunk, unsigned nents_first_chunk){	int ret; 	BUG_ON(!nents); 	if (first_chunk && nents_first_chunk) {		if (nents <= nents_first_chunk) {			table->nents = table->orig_nents = nents;			sg_init_table(table->sgl, nents);			return 0;		}	} 	/* User supposes that the 1st SGL includes real entry */	if (nents_first_chunk <= 1) {		first_chunk = NULL;		nents_first_chunk = 0;	} 	ret = __sg_alloc_table(table, nents, SG_CHUNK_SIZE,			       first_chunk, nents_first_chunk,			       GFP_ATOMIC, sg_pool_alloc);	if (unlikely(ret))		sg_free_table_chained(table, nents_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; 		mempool_destroy(sgp->pool);		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);