[PATCH v3 0/5] mempool based chained scatterlist alloc/free api

[PATCH v3 0/5] mempool based chained scatterlist alloc/free api

[Ming Lin]

From: Ming Lin <ming.l@ssi.samsung.com>

The fist 4 patches make the SG related definitions/structs/functions
in SCSI code generic and the last patch move it to lib/sg_pool.c.

v3:
  - Resend for Tejun to review. No code change since v2.
  - Add review/ack tags

v2:
  - do modification in scsi code first then move to lib/sg_pool.c
  - address Christoph's comments


Ming Lin (5):
  scsi: replace "scsi_data_buffer" with "sg_table" in SG functions
  scsi: replace "mq" with "first_chunk" in SG functions
  scsi: rename SG related struct and functions
  scsi: rename SCSI_MAX_{SG, SG_CHAIN}_SEGMENTS
  lib: scatterlist: move SG pool code from SCSI driver to lib/sg_pool.c

 drivers/ata/pata_icside.c           |   2 +-
 drivers/infiniband/ulp/srp/ib_srp.c |   4 +-
 drivers/scsi/Kconfig                |   1 +
 drivers/scsi/arm/cumana_2.c         |   2 +-
 drivers/scsi/arm/eesox.c            |   2 +-
 drivers/scsi/arm/powertec.c         |   2 +-
 drivers/scsi/esas2r/esas2r_main.c   |   4 +-
 drivers/scsi/hisi_sas/hisi_sas.h    |   2 +-
 drivers/scsi/mpt3sas/mpt3sas_base.c |   4 +-
 drivers/scsi/mpt3sas/mpt3sas_base.h |   2 +-
 drivers/scsi/scsi_debug.c           |   2 +-
 drivers/scsi/scsi_lib.c             | 172 +++++-------------------------------
 drivers/usb/storage/scsiglue.c      |   2 +-
 include/linux/scatterlist.h         |  25 ++++++
 include/scsi/scsi.h                 |  19 ----
 include/scsi/scsi_host.h            |   2 +-
 lib/Kconfig                         |   7 ++
 lib/Makefile                        |   1 +
 lib/sg_pool.c                       | 172 ++++++++++++++++++++++++++++++++++++
 19 files changed, 241 insertions(+), 186 deletions(-)
 create mode 100644 lib/sg_pool.c

-- 
1.9.1

[PATCH v3 1/5] scsi: replace "scsi_data_buffer" with "sg_table" in SG functions

[Ming Lin]

From: Ming Lin <ming.l@ssi.samsung.com>

Replace parameter "struct scsi_data_buffer" with "struct sg_table" in
SG alloc/free functions to make them generic.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
---
 drivers/scsi/scsi_lib.c | 41 +++++++++++++++++++++++------------------
 1 file changed, 23 insertions(+), 18 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 8106515..4229c18 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -583,14 +583,14 @@ static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
 	return mempool_alloc(sgp->pool, gfp_mask);
 }
 
-static void scsi_free_sgtable(struct scsi_data_buffer *sdb, bool mq)
+static void scsi_free_sgtable(struct sg_table *table, bool mq)
 {
-	if (mq && sdb->table.orig_nents <= SCSI_MAX_SG_SEGMENTS)
+	if (mq && table->orig_nents <= SCSI_MAX_SG_SEGMENTS)
 		return;
-	__sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, mq, scsi_sg_free);
+	__sg_free_table(table, SCSI_MAX_SG_SEGMENTS, mq, scsi_sg_free);
 }
 
-static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents, bool mq)
+static int scsi_alloc_sgtable(struct sg_table *table, int nents, bool mq)
 {
 	struct scatterlist *first_chunk = NULL;
 	int ret;
@@ -599,17 +599,17 @@ static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nents, bool mq)
 
 	if (mq) {
 		if (nents <= SCSI_MAX_SG_SEGMENTS) {
-			sdb->table.nents = sdb->table.orig_nents = nents;
-			sg_init_table(sdb->table.sgl, nents);
+			table->nents = table->orig_nents = nents;
+			sg_init_table(table->sgl, nents);
 			return 0;
 		}
-		first_chunk = sdb->table.sgl;
+		first_chunk = table->sgl;
 	}
 
-	ret = __sg_alloc_table(&sdb->table, nents, SCSI_MAX_SG_SEGMENTS,
+	ret = __sg_alloc_table(table, nents, SCSI_MAX_SG_SEGMENTS,
 			       first_chunk, GFP_ATOMIC, scsi_sg_alloc);
 	if (unlikely(ret))
-		scsi_free_sgtable(sdb, mq);
+		scsi_free_sgtable(table, mq);
 	return ret;
 }
 
@@ -625,12 +625,17 @@ static void scsi_uninit_cmd(struct scsi_cmnd *cmd)
 
 static void scsi_mq_free_sgtables(struct scsi_cmnd *cmd)
 {
+	struct scsi_data_buffer *sdb;
+
 	if (cmd->sdb.table.nents)
-		scsi_free_sgtable(&cmd->sdb, true);
-	if (cmd->request->next_rq && cmd->request->next_rq->special)
-		scsi_free_sgtable(cmd->request->next_rq->special, true);
+		scsi_free_sgtable(&cmd->sdb.table, true);
+	if (cmd->request->next_rq) {
+		sdb = cmd->request->next_rq->special;
+		if (sdb)
+			scsi_free_sgtable(&sdb->table, true);
+	}
 	if (scsi_prot_sg_count(cmd))
-		scsi_free_sgtable(cmd->prot_sdb, true);
+		scsi_free_sgtable(&cmd->prot_sdb->table, true);
 }
 
 static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
@@ -669,19 +674,19 @@ static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
 static void scsi_release_buffers(struct scsi_cmnd *cmd)
 {
 	if (cmd->sdb.table.nents)
-		scsi_free_sgtable(&cmd->sdb, false);
+		scsi_free_sgtable(&cmd->sdb.table, false);
 
 	memset(&cmd->sdb, 0, sizeof(cmd->sdb));
 
 	if (scsi_prot_sg_count(cmd))
-		scsi_free_sgtable(cmd->prot_sdb, false);
+		scsi_free_sgtable(&cmd->prot_sdb->table, false);
 }
 
 static void scsi_release_bidi_buffers(struct scsi_cmnd *cmd)
 {
 	struct scsi_data_buffer *bidi_sdb = cmd->request->next_rq->special;
 
-	scsi_free_sgtable(bidi_sdb, false);
+	scsi_free_sgtable(&bidi_sdb->table, false);
 	kmem_cache_free(scsi_sdb_cache, bidi_sdb);
 	cmd->request->next_rq->special = NULL;
 }
@@ -1085,7 +1090,7 @@ static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb)
 	/*
 	 * If sg table allocation fails, requeue request later.
 	 */
-	if (unlikely(scsi_alloc_sgtable(sdb, req->nr_phys_segments,
+	if (unlikely(scsi_alloc_sgtable(&sdb->table, req->nr_phys_segments,
 					req->mq_ctx != NULL)))
 		return BLKPREP_DEFER;
 
@@ -1158,7 +1163,7 @@ int scsi_init_io(struct scsi_cmnd *cmd)
 
 		ivecs = blk_rq_count_integrity_sg(rq->q, rq->bio);
 
-		if (scsi_alloc_sgtable(prot_sdb, ivecs, is_mq)) {
+		if (scsi_alloc_sgtable(&prot_sdb->table, ivecs, is_mq)) {
 			error = BLKPREP_DEFER;
 			goto err_exit;
 		}
-- 
1.9.1

[PATCH v3 2/5] scsi: replace "mq" with "first_chunk" in SG functions

[Ming Lin]

From: Ming Lin <ming.l@ssi.samsung.com>

Parameter "bool mq" is block driver specific.
Change it to "first_chunk" to make it more generic.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
---
 drivers/scsi/scsi_lib.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 4229c18..9675353 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -583,33 +583,32 @@ static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
 	return mempool_alloc(sgp->pool, gfp_mask);
 }
 
-static void scsi_free_sgtable(struct sg_table *table, bool mq)
+static void scsi_free_sgtable(struct sg_table *table, bool first_chunk)
 {
-	if (mq && table->orig_nents <= SCSI_MAX_SG_SEGMENTS)
+	if (first_chunk && table->orig_nents <= SCSI_MAX_SG_SEGMENTS)
 		return;
-	__sg_free_table(table, SCSI_MAX_SG_SEGMENTS, mq, scsi_sg_free);
+	__sg_free_table(table, SCSI_MAX_SG_SEGMENTS, first_chunk, scsi_sg_free);
 }
 
-static int scsi_alloc_sgtable(struct sg_table *table, int nents, bool mq)
+static int scsi_alloc_sgtable(struct sg_table *table, int nents,
+		struct scatterlist *first_chunk)
 {
-	struct scatterlist *first_chunk = NULL;
 	int ret;
 
 	BUG_ON(!nents);
 
-	if (mq) {
+	if (first_chunk) {
 		if (nents <= SCSI_MAX_SG_SEGMENTS) {
 			table->nents = table->orig_nents = nents;
 			sg_init_table(table->sgl, nents);
 			return 0;
 		}
-		first_chunk = table->sgl;
 	}
 
 	ret = __sg_alloc_table(table, nents, SCSI_MAX_SG_SEGMENTS,
 			       first_chunk, GFP_ATOMIC, scsi_sg_alloc);
 	if (unlikely(ret))
-		scsi_free_sgtable(table, mq);
+		scsi_free_sgtable(table, (bool)first_chunk);
 	return ret;
 }
 
@@ -1091,7 +1090,7 @@ static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb)
 	 * If sg table allocation fails, requeue request later.
 	 */
 	if (unlikely(scsi_alloc_sgtable(&sdb->table, req->nr_phys_segments,
-					req->mq_ctx != NULL)))
+					sdb->table.sgl)))
 		return BLKPREP_DEFER;
 
 	/* 
@@ -1163,7 +1162,8 @@ int scsi_init_io(struct scsi_cmnd *cmd)
 
 		ivecs = blk_rq_count_integrity_sg(rq->q, rq->bio);
 
-		if (scsi_alloc_sgtable(&prot_sdb->table, ivecs, is_mq)) {
+		if (scsi_alloc_sgtable(&prot_sdb->table, ivecs,
+				prot_sdb->table.sgl)) {
 			error = BLKPREP_DEFER;
 			goto err_exit;
 		}
-- 
1.9.1

[PATCH v3 3/5] scsi: rename SG related struct and functions

[Ming Lin]

From: Ming Lin <ming.l@ssi.samsung.com>

Rename SCSI specific struct and functions to more genenic names.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
---
 drivers/scsi/scsi_lib.c | 52 ++++++++++++++++++++++++-------------------------
 1 file changed, 26 insertions(+), 26 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 9675353..08134f6 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -40,10 +40,10 @@
 #include "scsi_logging.h"
 
 
-#define SG_MEMPOOL_NR		ARRAY_SIZE(scsi_sg_pools)
+#define SG_MEMPOOL_NR		ARRAY_SIZE(sg_pools)
 #define SG_MEMPOOL_SIZE		2
 
-struct scsi_host_sg_pool {
+struct sg_pool {
 	size_t		size;
 	char		*name;
 	struct kmem_cache	*slab;
@@ -54,7 +54,7 @@ struct scsi_host_sg_pool {
 #if (SCSI_MAX_SG_SEGMENTS < 32)
 #error SCSI_MAX_SG_SEGMENTS is too small (must be 32 or greater)
 #endif
-static struct scsi_host_sg_pool scsi_sg_pools[] = {
+static struct sg_pool sg_pools[] = {
 	SP(8),
 	SP(16),
 #if (SCSI_MAX_SG_SEGMENTS > 32)
@@ -553,7 +553,7 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-static inline unsigned int scsi_sgtable_index(unsigned short nents)
+static inline unsigned int sg_pool_index(unsigned short nents)
 {
 	unsigned int index;
 
@@ -567,30 +567,30 @@ static inline unsigned int scsi_sgtable_index(unsigned short nents)
 	return index;
 }
 
-static void scsi_sg_free(struct scatterlist *sgl, unsigned int nents)
+static void sg_pool_free(struct scatterlist *sgl, unsigned int nents)
 {
-	struct scsi_host_sg_pool *sgp;
+	struct sg_pool *sgp;
 
-	sgp = scsi_sg_pools + scsi_sgtable_index(nents);
+	sgp = sg_pools + sg_pool_index(nents);
 	mempool_free(sgl, sgp->pool);
 }
 
-static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
+static struct scatterlist *sg_pool_alloc(unsigned int nents, gfp_t gfp_mask)
 {
-	struct scsi_host_sg_pool *sgp;
+	struct sg_pool *sgp;
 
-	sgp = scsi_sg_pools + scsi_sgtable_index(nents);
+	sgp = sg_pools + sg_pool_index(nents);
 	return mempool_alloc(sgp->pool, gfp_mask);
 }
 
-static void scsi_free_sgtable(struct sg_table *table, bool first_chunk)
+static void sg_free_table_chained(struct sg_table *table, bool first_chunk)
 {
 	if (first_chunk && table->orig_nents <= SCSI_MAX_SG_SEGMENTS)
 		return;
-	__sg_free_table(table, SCSI_MAX_SG_SEGMENTS, first_chunk, scsi_sg_free);
+	__sg_free_table(table, SCSI_MAX_SG_SEGMENTS, first_chunk, sg_pool_free);
 }
 
-static int scsi_alloc_sgtable(struct sg_table *table, int nents,
+static int sg_alloc_table_chained(struct sg_table *table, int nents,
 		struct scatterlist *first_chunk)
 {
 	int ret;
@@ -606,9 +606,9 @@ static int scsi_alloc_sgtable(struct sg_table *table, int nents,
 	}
 
 	ret = __sg_alloc_table(table, nents, SCSI_MAX_SG_SEGMENTS,
-			       first_chunk, GFP_ATOMIC, scsi_sg_alloc);
+			       first_chunk, GFP_ATOMIC, sg_pool_alloc);
 	if (unlikely(ret))
-		scsi_free_sgtable(table, (bool)first_chunk);
+		sg_free_table_chained(table, (bool)first_chunk);
 	return ret;
 }
 
@@ -627,14 +627,14 @@ static void scsi_mq_free_sgtables(struct scsi_cmnd *cmd)
 	struct scsi_data_buffer *sdb;
 
 	if (cmd->sdb.table.nents)
-		scsi_free_sgtable(&cmd->sdb.table, true);
+		sg_free_table_chained(&cmd->sdb.table, true);
 	if (cmd->request->next_rq) {
 		sdb = cmd->request->next_rq->special;
 		if (sdb)
-			scsi_free_sgtable(&sdb->table, true);
+			sg_free_table_chained(&sdb->table, true);
 	}
 	if (scsi_prot_sg_count(cmd))
-		scsi_free_sgtable(&cmd->prot_sdb->table, true);
+		sg_free_table_chained(&cmd->prot_sdb->table, true);
 }
 
 static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
@@ -673,19 +673,19 @@ static void scsi_mq_uninit_cmd(struct scsi_cmnd *cmd)
 static void scsi_release_buffers(struct scsi_cmnd *cmd)
 {
 	if (cmd->sdb.table.nents)
-		scsi_free_sgtable(&cmd->sdb.table, false);
+		sg_free_table_chained(&cmd->sdb.table, false);
 
 	memset(&cmd->sdb, 0, sizeof(cmd->sdb));
 
 	if (scsi_prot_sg_count(cmd))
-		scsi_free_sgtable(&cmd->prot_sdb->table, false);
+		sg_free_table_chained(&cmd->prot_sdb->table, false);
 }
 
 static void scsi_release_bidi_buffers(struct scsi_cmnd *cmd)
 {
 	struct scsi_data_buffer *bidi_sdb = cmd->request->next_rq->special;
 
-	scsi_free_sgtable(&bidi_sdb->table, false);
+	sg_free_table_chained(&bidi_sdb->table, false);
 	kmem_cache_free(scsi_sdb_cache, bidi_sdb);
 	cmd->request->next_rq->special = NULL;
 }
@@ -1089,7 +1089,7 @@ static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb)
 	/*
 	 * If sg table allocation fails, requeue request later.
 	 */
-	if (unlikely(scsi_alloc_sgtable(&sdb->table, req->nr_phys_segments,
+	if (unlikely(sg_alloc_table_chained(&sdb->table, req->nr_phys_segments,
 					sdb->table.sgl)))
 		return BLKPREP_DEFER;
 
@@ -1162,7 +1162,7 @@ int scsi_init_io(struct scsi_cmnd *cmd)
 
 		ivecs = blk_rq_count_integrity_sg(rq->q, rq->bio);
 
-		if (scsi_alloc_sgtable(&prot_sdb->table, ivecs,
+		if (sg_alloc_table_chained(&prot_sdb->table, ivecs,
 				prot_sdb->table.sgl)) {
 			error = BLKPREP_DEFER;
 			goto err_exit;
@@ -2280,7 +2280,7 @@ int __init scsi_init_queue(void)
 	}
 
 	for (i = 0; i < SG_MEMPOOL_NR; i++) {
-		struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
+		struct sg_pool *sgp = sg_pools + i;
 		int size = sgp->size * sizeof(struct scatterlist);
 
 		sgp->slab = kmem_cache_create(sgp->name, size, 0,
@@ -2304,7 +2304,7 @@ int __init scsi_init_queue(void)
 
 cleanup_sdb:
 	for (i = 0; i < SG_MEMPOOL_NR; i++) {
-		struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
+		struct sg_pool *sgp = sg_pools + i;
 		if (sgp->pool)
 			mempool_destroy(sgp->pool);
 		if (sgp->slab)
@@ -2322,7 +2322,7 @@ void scsi_exit_queue(void)
 	kmem_cache_destroy(scsi_sdb_cache);
 
 	for (i = 0; i < SG_MEMPOOL_NR; i++) {
-		struct scsi_host_sg_pool *sgp = scsi_sg_pools + i;
+		struct sg_pool *sgp = sg_pools + i;
 		mempool_destroy(sgp->pool);
 		kmem_cache_destroy(sgp->slab);
 	}
-- 
1.9.1

[PATCH v3 4/5] scsi: rename SCSI_MAX_{SG, SG_CHAIN}_SEGMENTS

[Ming Lin]

From: Ming Lin <ming.l@ssi.samsung.com>

Rename SCSI_MAX_SG_SEGMENTS to SG_CHUNK_SIZE, which means the amount
we fit into a single scatterlist chunk.

Rename SCSI_MAX_SG_CHAIN_SEGMENTS to SG_MAX_SEGMENTS.

Will move these 2 generic definitions to scatterlist.h later.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Bart Van Assche <bart.vanassche@sandisk.com> (for ib_srp changes)
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
---
 drivers/ata/pata_icside.c           |  2 +-
 drivers/infiniband/ulp/srp/ib_srp.c |  4 ++--
 drivers/scsi/arm/cumana_2.c         |  2 +-
 drivers/scsi/arm/eesox.c            |  2 +-
 drivers/scsi/arm/powertec.c         |  2 +-
 drivers/scsi/esas2r/esas2r_main.c   |  4 ++--
 drivers/scsi/hisi_sas/hisi_sas.h    |  2 +-
 drivers/scsi/mpt3sas/mpt3sas_base.c |  4 ++--
 drivers/scsi/mpt3sas/mpt3sas_base.h |  2 +-
 drivers/scsi/scsi_debug.c           |  2 +-
 drivers/scsi/scsi_lib.c             | 34 +++++++++++++++++-----------------
 drivers/usb/storage/scsiglue.c      |  2 +-
 include/scsi/scsi.h                 |  8 ++++----
 include/scsi/scsi_host.h            |  2 +-
 14 files changed, 36 insertions(+), 36 deletions(-)

diff --git a/drivers/ata/pata_icside.c b/drivers/ata/pata_icside.c
index d7c7320..188f2f2 100644
--- a/drivers/ata/pata_icside.c
+++ b/drivers/ata/pata_icside.c
@@ -294,7 +294,7 @@ static int icside_dma_init(struct pata_icside_info *info)
 
 static struct scsi_host_template pata_icside_sht = {
 	ATA_BASE_SHT(DRV_NAME),
-	.sg_tablesize		= SCSI_MAX_SG_CHAIN_SEGMENTS,
+	.sg_tablesize		= SG_MAX_SEGMENTS,
 	.dma_boundary		= IOMD_DMA_BOUNDARY,
 };
 
diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
index ff21597..369a75e 100644
--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -81,7 +81,7 @@ MODULE_PARM_DESC(cmd_sg_entries,
 
 module_param(indirect_sg_entries, uint, 0444);
 MODULE_PARM_DESC(indirect_sg_entries,
-		 "Default max number of gather/scatter entries (default is 12, max is " __stringify(SCSI_MAX_SG_CHAIN_SEGMENTS) ")");
+		 "Default max number of gather/scatter entries (default is 12, max is " __stringify(SG_MAX_SEGMENTS) ")");
 
 module_param(allow_ext_sg, bool, 0444);
 MODULE_PARM_DESC(allow_ext_sg,
@@ -3097,7 +3097,7 @@ static int srp_parse_options(const char *buf, struct srp_target_port *target)
 
 		case SRP_OPT_SG_TABLESIZE:
 			if (match_int(args, &token) || token < 1 ||
-					token > SCSI_MAX_SG_CHAIN_SEGMENTS) {
+					token > SG_MAX_SEGMENTS) {
 				pr_warn("bad max sg_tablesize parameter '%s'\n",
 					p);
 				goto out;
diff --git a/drivers/scsi/arm/cumana_2.c b/drivers/scsi/arm/cumana_2.c
index faa1bee..edce5f3 100644
--- a/drivers/scsi/arm/cumana_2.c
+++ b/drivers/scsi/arm/cumana_2.c
@@ -365,7 +365,7 @@ static struct scsi_host_template cumanascsi2_template = {
 	.eh_abort_handler		= fas216_eh_abort,
 	.can_queue			= 1,
 	.this_id			= 7,
-	.sg_tablesize			= SCSI_MAX_SG_CHAIN_SEGMENTS,
+	.sg_tablesize			= SG_MAX_SEGMENTS,
 	.dma_boundary			= IOMD_DMA_BOUNDARY,
 	.use_clustering			= DISABLE_CLUSTERING,
 	.proc_name			= "cumanascsi2",
diff --git a/drivers/scsi/arm/eesox.c b/drivers/scsi/arm/eesox.c
index a8ad688..e93e047 100644
--- a/drivers/scsi/arm/eesox.c
+++ b/drivers/scsi/arm/eesox.c
@@ -484,7 +484,7 @@ static struct scsi_host_template eesox_template = {
 	.eh_abort_handler		= fas216_eh_abort,
 	.can_queue			= 1,
 	.this_id			= 7,
-	.sg_tablesize			= SCSI_MAX_SG_CHAIN_SEGMENTS,
+	.sg_tablesize			= SG_MAX_SEGMENTS,
 	.dma_boundary			= IOMD_DMA_BOUNDARY,
 	.use_clustering			= DISABLE_CLUSTERING,
 	.proc_name			= "eesox",
diff --git a/drivers/scsi/arm/powertec.c b/drivers/scsi/arm/powertec.c
index 5e1b73e..79aa889 100644
--- a/drivers/scsi/arm/powertec.c
+++ b/drivers/scsi/arm/powertec.c
@@ -291,7 +291,7 @@ static struct scsi_host_template powertecscsi_template = {
 
 	.can_queue			= 8,
 	.this_id			= 7,
-	.sg_tablesize			= SCSI_MAX_SG_CHAIN_SEGMENTS,
+	.sg_tablesize			= SG_MAX_SEGMENTS,
 	.dma_boundary			= IOMD_DMA_BOUNDARY,
 	.cmd_per_lun			= 2,
 	.use_clustering			= ENABLE_CLUSTERING,
diff --git a/drivers/scsi/esas2r/esas2r_main.c b/drivers/scsi/esas2r/esas2r_main.c
index 33581ba..2aca4d1 100644
--- a/drivers/scsi/esas2r/esas2r_main.c
+++ b/drivers/scsi/esas2r/esas2r_main.c
@@ -246,7 +246,7 @@ static struct scsi_host_template driver_template = {
 	.eh_target_reset_handler	= esas2r_target_reset,
 	.can_queue			= 128,
 	.this_id			= -1,
-	.sg_tablesize			= SCSI_MAX_SG_SEGMENTS,
+	.sg_tablesize			= SG_CHUNK_SIZE,
 	.cmd_per_lun			=
 		ESAS2R_DEFAULT_CMD_PER_LUN,
 	.present			= 0,
@@ -271,7 +271,7 @@ module_param(num_sg_lists, int, 0);
 MODULE_PARM_DESC(num_sg_lists,
 		 "Number of scatter/gather lists.  Default 1024.");
 
-int sg_tablesize = SCSI_MAX_SG_SEGMENTS;
+int sg_tablesize = SG_CHUNK_SIZE;
 module_param(sg_tablesize, int, 0);
 MODULE_PARM_DESC(sg_tablesize,
 		 "Maximum number of entries in a scatter/gather table.");
diff --git a/drivers/scsi/hisi_sas/hisi_sas.h b/drivers/scsi/hisi_sas/hisi_sas.h
index 29e89f3..fa12eea 100644
--- a/drivers/scsi/hisi_sas/hisi_sas.h
+++ b/drivers/scsi/hisi_sas/hisi_sas.h
@@ -298,7 +298,7 @@ struct hisi_sas_command_table_stp {
 	u8	atapi_cdb[ATAPI_CDB_LEN];
 };
 
-#define HISI_SAS_SGE_PAGE_CNT SCSI_MAX_SG_SEGMENTS
+#define HISI_SAS_SGE_PAGE_CNT SG_CHUNK_SIZE
 struct hisi_sas_sge_page {
 	struct hisi_sas_sge sge[HISI_SAS_SGE_PAGE_CNT];
 };
diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
index 8c44b9c..28d8531 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
@@ -3207,10 +3207,10 @@ _base_allocate_memory_pools(struct MPT3SAS_ADAPTER *ioc,  int sleep_flag)
 		sg_tablesize = MPT_MIN_PHYS_SEGMENTS;
 	else if (sg_tablesize > MPT_MAX_PHYS_SEGMENTS) {
 		sg_tablesize = min_t(unsigned short, sg_tablesize,
-				      SCSI_MAX_SG_CHAIN_SEGMENTS);
+				      SG_MAX_SEGMENTS);
 		pr_warn(MPT3SAS_FMT
 		 "sg_tablesize(%u) is bigger than kernel"
-		 " defined SCSI_MAX_SG_SEGMENTS(%u)\n", ioc->name,
+		 " defined SG_CHUNK_SIZE(%u)\n", ioc->name,
 		 sg_tablesize, MPT_MAX_PHYS_SEGMENTS);
 	}
 	ioc->shost->sg_tablesize = sg_tablesize;
diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.h b/drivers/scsi/mpt3sas/mpt3sas_base.h
index 32580b5..6940c57 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.h
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.h
@@ -90,7 +90,7 @@
 /*
  * Set MPT3SAS_SG_DEPTH value based on user input.
  */
-#define MPT_MAX_PHYS_SEGMENTS	SCSI_MAX_SG_SEGMENTS
+#define MPT_MAX_PHYS_SEGMENTS	SG_CHUNK_SIZE
 #define MPT_MIN_PHYS_SEGMENTS	16
 
 #ifdef CONFIG_SCSI_MPT3SAS_MAX_SGE
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index f3d69a98..06b1517 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -5305,7 +5305,7 @@ static struct scsi_host_template sdebug_driver_template = {
 	.eh_host_reset_handler = scsi_debug_host_reset,
 	.can_queue =		SCSI_DEBUG_CANQUEUE,
 	.this_id =		7,
-	.sg_tablesize =		SCSI_MAX_SG_CHAIN_SEGMENTS,
+	.sg_tablesize =		SG_MAX_SEGMENTS,
 	.cmd_per_lun =		DEF_CMD_PER_LUN,
 	.max_sectors =		-1U,
 	.use_clustering = 	DISABLE_CLUSTERING,
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 08134f6..8f776f1 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -51,25 +51,25 @@ struct sg_pool {
 };
 
 #define SP(x) { .size = x, "sgpool-" __stringify(x) }
-#if (SCSI_MAX_SG_SEGMENTS < 32)
-#error SCSI_MAX_SG_SEGMENTS is too small (must be 32 or greater)
+#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 (SCSI_MAX_SG_SEGMENTS > 32)
+#if (SG_CHUNK_SIZE > 32)
 	SP(32),
-#if (SCSI_MAX_SG_SEGMENTS > 64)
+#if (SG_CHUNK_SIZE > 64)
 	SP(64),
-#if (SCSI_MAX_SG_SEGMENTS > 128)
+#if (SG_CHUNK_SIZE > 128)
 	SP(128),
-#if (SCSI_MAX_SG_SEGMENTS > 256)
-#error SCSI_MAX_SG_SEGMENTS is too large (256 MAX)
+#if (SG_CHUNK_SIZE > 256)
+#error SG_CHUNK_SIZE is too large (256 MAX)
 #endif
 #endif
 #endif
 #endif
-	SP(SCSI_MAX_SG_SEGMENTS)
+	SP(SG_CHUNK_SIZE)
 };
 #undef SP
 
@@ -557,7 +557,7 @@ static inline unsigned int sg_pool_index(unsigned short nents)
 {
 	unsigned int index;
 
-	BUG_ON(nents > SCSI_MAX_SG_SEGMENTS);
+	BUG_ON(nents > SG_CHUNK_SIZE);
 
 	if (nents <= 8)
 		index = 0;
@@ -585,9 +585,9 @@ static struct scatterlist *sg_pool_alloc(unsigned int nents, gfp_t gfp_mask)
 
 static void sg_free_table_chained(struct sg_table *table, bool first_chunk)
 {
-	if (first_chunk && table->orig_nents <= SCSI_MAX_SG_SEGMENTS)
+	if (first_chunk && table->orig_nents <= SG_CHUNK_SIZE)
 		return;
-	__sg_free_table(table, SCSI_MAX_SG_SEGMENTS, first_chunk, sg_pool_free);
+	__sg_free_table(table, SG_CHUNK_SIZE, first_chunk, sg_pool_free);
 }
 
 static int sg_alloc_table_chained(struct sg_table *table, int nents,
@@ -598,14 +598,14 @@ static int sg_alloc_table_chained(struct sg_table *table, int nents,
 	BUG_ON(!nents);
 
 	if (first_chunk) {
-		if (nents <= SCSI_MAX_SG_SEGMENTS) {
+		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, SCSI_MAX_SG_SEGMENTS,
+	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);
@@ -1937,7 +1937,7 @@ static int scsi_mq_prep_fn(struct request *req)
 	if (scsi_host_get_prot(shost)) {
 		cmd->prot_sdb = (void *)sg +
 			min_t(unsigned int,
-			      shost->sg_tablesize, SCSI_MAX_SG_SEGMENTS) *
+			      shost->sg_tablesize, SG_CHUNK_SIZE) *
 			sizeof(struct scatterlist);
 		memset(cmd->prot_sdb, 0, sizeof(struct scsi_data_buffer));
 
@@ -2110,7 +2110,7 @@ static void __scsi_init_queue(struct Scsi_Host *shost, struct request_queue *q)
 	 * this limit is imposed by hardware restrictions
 	 */
 	blk_queue_max_segments(q, min_t(unsigned short, shost->sg_tablesize,
-					SCSI_MAX_SG_CHAIN_SEGMENTS));
+					SG_MAX_SEGMENTS));
 
 	if (scsi_host_prot_dma(shost)) {
 		shost->sg_prot_tablesize =
@@ -2192,8 +2192,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
 	unsigned int cmd_size, sgl_size, tbl_size;
 
 	tbl_size = shost->sg_tablesize;
-	if (tbl_size > SCSI_MAX_SG_SEGMENTS)
-		tbl_size = SCSI_MAX_SG_SEGMENTS;
+	if (tbl_size > SG_CHUNK_SIZE)
+		tbl_size = SG_CHUNK_SIZE;
 	sgl_size = tbl_size * sizeof(struct scatterlist);
 	cmd_size = sizeof(struct scsi_cmnd) + shost->hostt->cmd_size + sgl_size;
 	if (scsi_host_get_prot(shost))
diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index dba5136..82e5eddc 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -563,7 +563,7 @@ static const struct scsi_host_template usb_stor_host_template = {
 	.target_alloc =			target_alloc,
 
 	/* lots of sg segments can be handled */
-	.sg_tablesize =			SCSI_MAX_SG_CHAIN_SEGMENTS,
+	.sg_tablesize =			SG_MAX_SEGMENTS,
 
 	/* limit the total size of a transfer to 120 KB */
 	.max_sectors =                  240,
diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
index e0a3398..74dafa7 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -24,16 +24,16 @@ enum scsi_timeouts {
  * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
  * minimum value is 32
  */
-#define SCSI_MAX_SG_SEGMENTS	128
+#define SG_CHUNK_SIZE	128
 
 /*
- * Like SCSI_MAX_SG_SEGMENTS, but for archs that have sg chaining. This limit
+ * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
  * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
  */
 #ifdef CONFIG_ARCH_HAS_SG_CHAIN
-#define SCSI_MAX_SG_CHAIN_SEGMENTS	2048
+#define SG_MAX_SEGMENTS	2048
 #else
-#define SCSI_MAX_SG_CHAIN_SEGMENTS	SCSI_MAX_SG_SEGMENTS
+#define SG_MAX_SEGMENTS	SG_CHUNK_SIZE
 #endif
 
 /*
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index fcfa3d7..76e9d27 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -37,7 +37,7 @@ struct blk_queue_tags;
  *	 used in one scatter-gather request.
  */
 #define SG_NONE 0
-#define SG_ALL	SCSI_MAX_SG_SEGMENTS
+#define SG_ALL	SG_CHUNK_SIZE
 
 #define MODE_UNKNOWN 0x00
 #define MODE_INITIATOR 0x01
-- 
1.9.1

[PATCH v3 5/5] lib: scatterlist: move SG pool code from SCSI driver to lib/sg_pool.c

[Ming Lin]

From: Ming Lin <ming.l@ssi.samsung.com>

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>
---
 drivers/scsi/Kconfig        |   1 +
 drivers/scsi/scsi_lib.c     | 137 -----------------------------------
 include/linux/scatterlist.h |  25 +++++++
 include/scsi/scsi.h         |  19 -----
 lib/Kconfig                 |   7 ++
 lib/Makefile                |   1 +
 lib/sg_pool.c               | 172 ++++++++++++++++++++++++++++++++++++++++++++
 7 files changed, 206 insertions(+), 156 deletions(-)
 create mode 100644 lib/sg_pool.c

diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index 0950567..98e5d51 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -17,6 +17,7 @@ config SCSI
 	tristate "SCSI device support"
 	depends on BLOCK
 	select SCSI_DMA if HAS_DMA
+	select SG_POOL
 	---help---
 	  If you want to use a SCSI hard disk, SCSI tape drive, SCSI CD-ROM or
 	  any other SCSI device under Linux, say Y and make sure that you know
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 8f776f1..b920c5d 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -14,8 +14,6 @@
 #include <linux/completion.h>
 #include <linux/kernel.h>
 #include <linux/export.h>
-#include <linux/mempool.h>
-#include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/pci.h>
 #include <linux/delay.h>
@@ -40,39 +38,6 @@
 #include "scsi_logging.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
-
 struct kmem_cache *scsi_sdb_cache;
 
 /*
@@ -553,65 +518,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-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);
-}
-
-static 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);
-}
-
-static 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;
-}
-
 static void scsi_uninit_cmd(struct scsi_cmnd *cmd)
 {
 	if (cmd->request->cmd_type == REQ_TYPE_FS) {
@@ -2269,8 +2175,6 @@ EXPORT_SYMBOL(scsi_unblock_requests);
 
 int __init scsi_init_queue(void)
 {
-	int i;
-
 	scsi_sdb_cache = kmem_cache_create("scsi_data_buffer",
 					   sizeof(struct scsi_data_buffer),
 					   0, 0, NULL);
@@ -2279,53 +2183,12 @@ int __init scsi_init_queue(void)
 		return -ENOMEM;
 	}
 
-	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 "SCSI: 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 "SCSI: 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);
-	}
-	kmem_cache_destroy(scsi_sdb_cache);
-
-	return -ENOMEM;
 }
 
 void scsi_exit_queue(void)
 {
-	int i;
-
 	kmem_cache_destroy(scsi_sdb_cache);
-
-	for (i = 0; i < SG_MEMPOOL_NR; i++) {
-		struct sg_pool *sgp = sg_pools + i;
-		mempool_destroy(sgp->pool);
-		kmem_cache_destroy(sgp->slab);
-	}
 }
 
 /**
diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 556ec1e..cb3c8fe 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -286,6 +286,31 @@ size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents,
 #define SG_MAX_SINGLE_ALLOC		(PAGE_SIZE / sizeof(struct scatterlist))
 
 /*
+ * The maximum number of SG segments that we will put inside a
+ * scatterlist (unless chaining is used). Should ideally fit inside a
+ * single page, to avoid a higher order allocation.  We could define this
+ * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
+ * minimum value is 32
+ */
+#define SG_CHUNK_SIZE	128
+
+/*
+ * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
+ * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
+ */
+#ifdef CONFIG_ARCH_HAS_SG_CHAIN
+#define SG_MAX_SEGMENTS	2048
+#else
+#define SG_MAX_SEGMENTS	SG_CHUNK_SIZE
+#endif
+
+#ifdef CONFIG_SG_POOL
+void sg_free_table_chained(struct sg_table *table, bool first_chunk);
+int sg_alloc_table_chained(struct sg_table *table, int nents,
+			   struct scatterlist *first_chunk);
+#endif
+
+/*
  * sg page iterator
  *
  * Iterates over sg entries page-by-page.  On each successful iteration,
diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
index 74dafa7..8ec7c30 100644
--- a/include/scsi/scsi.h
+++ b/include/scsi/scsi.h
@@ -18,25 +18,6 @@ enum scsi_timeouts {
 };
 
 /*
- * The maximum number of SG segments that we will put inside a
- * scatterlist (unless chaining is used). Should ideally fit inside a
- * single page, to avoid a higher order allocation.  We could define this
- * to SG_MAX_SINGLE_ALLOC to pack correctly at the highest order.  The
- * minimum value is 32
- */
-#define SG_CHUNK_SIZE	128
-
-/*
- * Like SG_CHUNK_SIZE, but for archs that have sg chaining. This limit
- * is totally arbitrary, a setting of 2048 will get you at least 8mb ios.
- */
-#ifdef CONFIG_ARCH_HAS_SG_CHAIN
-#define SG_MAX_SEGMENTS	2048
-#else
-#define SG_MAX_SEGMENTS	SG_CHUNK_SIZE
-#endif
-
-/*
  * DIX-capable adapters effectively support infinite chaining for the
  * protection information scatterlist
  */
diff --git a/lib/Kconfig b/lib/Kconfig
index 3cca122..61d55bd 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -523,6 +523,13 @@ config SG_SPLIT
 	 a scatterlist. This should be selected by a driver or an API which
 	 whishes to split a scatterlist amongst multiple DMA channels.
 
+config SG_POOL
+	def_bool n
+	help
+	 Provides a helper to allocate chained scatterlists. This should be
+	 selected by a driver or an API which whishes to allocate chained
+	 scatterlist.
+
 #
 # sg chaining option
 #
diff --git a/lib/Makefile b/lib/Makefile
index 7bd6fd4..bf01c26 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -178,6 +178,7 @@ obj-$(CONFIG_GENERIC_STRNLEN_USER) += strnlen_user.o
 obj-$(CONFIG_GENERIC_NET_UTILS) += net_utils.o
 
 obj-$(CONFIG_SG_SPLIT) += sg_split.o
+obj-$(CONFIG_SG_POOL) += sg_pool.o
 obj-$(CONFIG_STMP_DEVICE) += stmp_device.o
 obj-$(CONFIG_IRQ_POLL) += irq_poll.o
 
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);
-- 
1.9.1

Re: [PATCH v3 4/5] scsi: rename SCSI_MAX_{SG, SG_CHAIN}_SEGMENTS

[Tejun Heo]

On Mon, Apr 04, 2016 at 02:48:10PM -0700, Ming Lin wrote:
> From: Ming Lin <ming.l@ssi.samsung.com>
> 
> Rename SCSI_MAX_SG_SEGMENTS to SG_CHUNK_SIZE, which means the amount
> we fit into a single scatterlist chunk.
> 
> Rename SCSI_MAX_SG_CHAIN_SEGMENTS to SG_MAX_SEGMENTS.
> 
> Will move these 2 generic definitions to scatterlist.h later.
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Acked-by: Bart Van Assche <bart.vanassche@sandisk.com> (for ib_srp changes)
> Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>

For libata,

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

Re: [PATCH v3 4/5] scsi: rename SCSI_MAX_{SG, SG_CHAIN}_SEGMENTS

[Ming Lin]

On Tue, Apr 5, 2016 at 7:55 AM, Tejun Heo <tj@kernel.org> wrote:
> On Mon, Apr 04, 2016 at 02:48:10PM -0700, Ming Lin wrote:
>> From: Ming Lin <ming.l@ssi.samsung.com>
>>
>> Rename SCSI_MAX_SG_SEGMENTS to SG_CHUNK_SIZE, which means the amount
>> we fit into a single scatterlist chunk.
>>
>> Rename SCSI_MAX_SG_CHAIN_SEGMENTS to SG_MAX_SEGMENTS.
>>
>> Will move these 2 generic definitions to scatterlist.h later.
>>
>> Reviewed-by: Christoph Hellwig <hch@lst.de>
>> Acked-by: Bart Van Assche <bart.vanassche@sandisk.com> (for ib_srp changes)
>> Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
>
> For libata,
>
> Acked-by: Tejun Heo <tj@kernel.org>

Hi James,

Are we ready to merge it?

Thanks,
Ming

Re: [PATCH v3 4/5] scsi: rename SCSI_MAX_{SG, SG_CHAIN}_SEGMENTS

[Martin K. Petersen]

>>>>> "Ming" == Ming Lin <mlin@kernel.org> writes:

Ming> Are we ready to merge it?

We're still missing an ack from Sagi.

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: [PATCH v3 4/5] scsi: rename SCSI_MAX_{SG, SG_CHAIN}_SEGMENTS

[Ming Lin]

On Mon, Apr 11, 2016 at 2:34 PM, Martin K. Petersen
<martin.petersen@oracle.com> wrote:
>>>>>> "Ming" == Ming Lin <mlin@kernel.org> writes:
>
> Ming> Are we ready to merge it?
>
> We're still missing an ack from Sagi.

Thought we already had a ack from Bart.
OK, let's get one more from Sagi.

Re: [PATCH v3 4/5] scsi: rename SCSI_MAX_{SG, SG_CHAIN}_SEGMENTS

[Bart Van Assche]

On 04/11/16 15:04, Ming Lin wrote:
> On Mon, Apr 11, 2016 at 2:34 PM, Martin K. Petersen
> <martin.petersen@oracle.com> wrote:
>>>>>>> "Ming" == Ming Lin <mlin@kernel.org> writes:
>>
>> Ming> Are we ready to merge it?
>>
>> We're still missing an ack from Sagi.
>
> Thought we already had a ack from Bart.
> OK, let's get one more from Sagi.

Hmm ... this patch doesn't touch any code for which Sagi is the 
maintainer so I think my ack for the ib_srp changes is sufficient.

Bart.

Re: [PATCH v3 4/5] scsi: rename SCSI_MAX_{SG, SG_CHAIN}_SEGMENTS

[Sagi Grimberg]

> We're still missing an ack from Sagi.

Oops, wasn't aware that mine was needed.
I reviewed these on the nvme-fabrics project.

I'll add my review tags too.

Re: [PATCH v3 1/5] scsi: replace "scsi_data_buffer" with "sg_table" in SG functions

[Sagi Grimberg]

> From: Ming Lin <ming.l@ssi.samsung.com>
>
> Replace parameter "struct scsi_data_buffer" with "struct sg_table" in
> SG alloc/free functions to make them generic.
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>

Re: [PATCH v3 2/5] scsi: replace "mq" with "first_chunk" in SG functions

[Sagi Grimberg]

> From: Ming Lin <ming.l@ssi.samsung.com>
>
> Parameter "bool mq" is block driver specific.
> Change it to "first_chunk" to make it more generic.
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>

Re: [PATCH v3 3/5] scsi: rename SG related struct and functions

[Sagi Grimberg]

> From: Ming Lin <ming.l@ssi.samsung.com>
>
> Rename SCSI specific struct and functions to more genenic names.
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>

Reviewed-by: Sagi Grimberg <sgi@grimberg.me>

Re: [PATCH v3 4/5] scsi: rename SCSI_MAX_{SG, SG_CHAIN}_SEGMENTS

[Sagi Grimberg]

>> <martin.petersen@oracle.com> wrote:
>>>>>>>> "Ming" == Ming Lin <mlin@kernel.org> writes:
>>>
>>> Ming> Are we ready to merge it?
>>>
>>> We're still missing an ack from Sagi.
>>
>> Thought we already had a ack from Bart.
>> OK, let's get one more from Sagi.
>
> Hmm ... this patch doesn't touch any code for which Sagi is the
> maintainer so I think my ack for the ib_srp changes is sufficient.

Indeed no need for my ack, but a review tag can't hurt ;)

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>

Re: [PATCH v3 5/5] lib: scatterlist: move SG pool code from SCSI driver to lib/sg_pool.c

[Sagi Grimberg]

> From: Ming Lin <ming.l@ssi.samsung.com>
>
> 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>

Re: [PATCH v3 4/5] scsi: rename SCSI_MAX_{SG, SG_CHAIN}_SEGMENTS

[Martin K. Petersen]

>>>>> "Ming" == Ming Lin <mlin@kernel.org> writes:

Ming> Are we ready to merge it?

I have queued your patches in my for-next branch. Will let them simmer
there for a bit so they can get tested in linux-next. Barring any
problems I will shuffle them over to 4.7/scsi-queue at the end of the
week.

-- 
Martin K. Petersen	Oracle Linux Engineering