target: add struct spc_ops + initial ->execute_rw pointer usage

Remove the execute_cmd method in struct se_subsystem_api, and always use the
one directly in struct se_cmd.  To make life simpler for SBC virtual backends
a struct spc_ops that is passed to sbc_parse_cmd is added.  For now it
only contains an execute_rw member, but more will follow with the subsequent
commits.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c
index e2df308..720ed59 100644
--- a/drivers/target/target_core_file.c
+++ b/drivers/target/target_core_file.c
@@ -375,9 +375,11 @@
 	}
 }
 
-static int fd_execute_cmd(struct se_cmd *cmd, struct scatterlist *sgl,
-		u32 sgl_nents, enum dma_data_direction data_direction)
+static int fd_execute_rw(struct se_cmd *cmd)
 {
+	struct scatterlist *sgl = cmd->t_data_sg;
+	u32 sgl_nents = cmd->t_data_nents;
+	enum dma_data_direction data_direction = cmd->data_direction;
 	struct se_device *dev = cmd->se_dev;
 	int ret = 0;
 
@@ -550,6 +552,15 @@
 	return div_u64(dev_size, dev->se_sub_dev->se_dev_attrib.block_size);
 }
 
+static struct spc_ops fd_spc_ops = {
+	.execute_rw		= fd_execute_rw,
+};
+
+static int fd_parse_cdb(struct se_cmd *cmd)
+{
+	return sbc_parse_cdb(cmd, &fd_spc_ops);
+}
+
 static struct se_subsystem_api fileio_template = {
 	.name			= "fileio",
 	.owner			= THIS_MODULE,
@@ -561,8 +572,7 @@
 	.allocate_virtdevice	= fd_allocate_virtdevice,
 	.create_virtdevice	= fd_create_virtdevice,
 	.free_device		= fd_free_device,
-	.parse_cdb		= sbc_parse_cdb,
-	.execute_cmd		= fd_execute_cmd,
+	.parse_cdb		= fd_parse_cdb,
 	.do_sync_cache		= fd_emulate_sync_cache,
 	.check_configfs_dev_params = fd_check_configfs_dev_params,
 	.set_configfs_dev_params = fd_set_configfs_dev_params,