target: ->map_task_SG conversion to ->map_control_SG and ->map_data_SG

This patch breaks up the ->map_task_SG() backend call into two seperate
->map_control_SG() and ->map_data_SG() in order to better address
IBLOCK and pSCSI.  IBLOCK only allocates bios for ->map_data_SG(), and
pSCSI will allocate a struct request for both cases.

This patch fixes incorrect usage of ->map_task_SG() for all se_cmd descriptors
in transport_generic_new_cmd() by moving the call into it's proper location
directly inside of transport_allocate_data_tasks()
Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/target/target_core_iblock.c

@@ -591,7 +591,7 @@ static struct bio *iblock_get_bio(
 	return bio;
 }
 
-static int iblock_map_task_SG(struct se_task *task)
+static int iblock_map_data_SG(struct se_task *task)
 {
 	struct se_cmd *cmd = task->task_se_cmd;
 	struct se_device *dev = cmd->se_dev;
@@ -755,7 +755,7 @@ static struct se_subsystem_api iblock_template = {
 	.name			= "iblock",
 	.owner			= THIS_MODULE,
 	.transport_type		= TRANSPORT_PLUGIN_VHBA_PDEV,
-	.map_task_SG		= iblock_map_task_SG,
+	.map_data_SG		= iblock_map_data_SG,
 	.attach_hba		= iblock_attach_hba,
 	.detach_hba		= iblock_detach_hba,
 	.allocate_virtdevice	= iblock_allocate_virtdevice,

drivers/target/target_core_pscsi.c

@@ -1049,7 +1049,7 @@ static inline struct bio *pscsi_get_bio(int sg_num)
 	return bio;
 }
 
-static int __pscsi_map_task_SG(
+static int __pscsi_map_SG(
 	struct se_task *task,
 	struct scatterlist *task_sg,
 	u32 task_sg_num,
@@ -1198,7 +1198,10 @@ static int __pscsi_map_task_SG(
 	return ret;
 }
 
-static int pscsi_map_task_SG(struct se_task *task)
+/*
+ * pSCSI maps both ->map_control_SG() and ->map_data_SG() to a single call.
+ */
+static int pscsi_map_SG(struct se_task *task)
 {
 	int ret;
 
@@ -1206,13 +1209,13 @@ static int pscsi_map_task_SG(struct se_task *task)
 	 * Setup the main struct request for the task->task_sg[] payload
 	 */
 
-	ret = __pscsi_map_task_SG(task, task->task_sg, task->task_sg_nents, 0);
+	ret = __pscsi_map_SG(task, task->task_sg, task->task_sg_nents, 0);
 	if (ret >= 0 && task->task_sg_bidi) {
 		/*
 		 * If present, set up the extra BIDI-COMMAND SCSI READ
 		 * struct request and payload.
 		 */
-		ret = __pscsi_map_task_SG(task, task->task_sg_bidi,
+		ret = __pscsi_map_SG(task, task->task_sg_bidi,
 					task->task_sg_nents, 1);
 	}
 
@@ -1340,7 +1343,8 @@ static struct se_subsystem_api pscsi_template = {
 	.owner			= THIS_MODULE,
 	.transport_type		= TRANSPORT_PLUGIN_PHBA_PDEV,
 	.cdb_none		= pscsi_CDB_none,
-	.map_task_SG		= pscsi_map_task_SG,
+	.map_control_SG		= pscsi_map_SG,
+	.map_data_SG		= pscsi_map_SG,
 	.attach_hba		= pscsi_attach_hba,
 	.detach_hba		= pscsi_detach_hba,
 	.pmode_enable_hba	= pscsi_pmode_enable_hba,

drivers/target/target_core_transport.c

@@ -4081,8 +4081,7 @@ static int transport_allocate_data_tasks(
 	struct se_device *dev = cmd->se_dev;
 	unsigned long flags;
 	sector_t sectors;
-	int task_count;
-	int i;
+	int task_count, i, ret;
 	sector_t dev_max_sectors = dev->se_sub_dev->se_dev_attrib.max_sectors;
 	u32 sector_size = dev->se_sub_dev->se_dev_attrib.block_size;
 	struct scatterlist *sg;
@@ -4129,7 +4128,7 @@ static int transport_allocate_data_tasks(
 			task->task_padded_sg = 1;
 		}
 
-		task->task_sg = kmalloc(sizeof(struct scatterlist) * \
+		task->task_sg = kmalloc(sizeof(struct scatterlist) *
 					task->task_sg_nents, GFP_KERNEL);
 		if (!task->task_sg) {
 			cmd->se_dev->transport->free_task(task);
@@ -4157,6 +4156,20 @@ static int transport_allocate_data_tasks(
 		list_add_tail(&task->t_list, &cmd->t_task_list);
 		spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 	}
+	/*
+	 * Now perform the memory map of task->task_sg[] into backend
+	 * subsystem memory..
+	 */
+	list_for_each_entry(task, &cmd->t_task_list, t_list) {
+		if (atomic_read(&task->task_sent))
+			continue;
+		if (!dev->transport->map_data_SG)
+			continue;
+
+		ret = dev->transport->map_data_SG(task);
+		if (ret < 0)
+			return 0;
+	}
 
 	return task_count;
 }
@@ -4196,8 +4209,8 @@ transport_allocate_control_task(struct se_cmd *cmd)
 	spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 
 	if (cmd->se_cmd_flags & SCF_SCSI_CONTROL_SG_IO_CDB) {
-		if (dev->transport->map_task_SG)
-			ret = dev->transport->map_task_SG(task);
+		if (dev->transport->map_control_SG)
+			ret = dev->transport->map_control_SG(task);
 	} else if (cmd->se_cmd_flags & SCF_SCSI_NON_DATA_CDB) {
 		if (dev->transport->cdb_none)
 			ret = dev->transport->cdb_none(task);
@@ -4239,8 +4252,6 @@ static u32 transport_allocate_tasks(
 	 */
 int transport_generic_new_cmd(struct se_cmd *cmd)
 {
-	struct se_task *task;
-	struct se_device *dev = cmd->se_dev;
 	int ret = 0;
 
 	/*
@@ -4254,22 +4265,16 @@ int transport_generic_new_cmd(struct se_cmd *cmd)
 		if (ret < 0)
 			return ret;
 	}
-
+	/*
+	 * Call transport_new_cmd_obj() to invoke transport_allocate_tasks() for
+	 * control or data CDB types, and perform the map to backend subsystem
+	 * code from SGL memory allocated here by transport_generic_get_mem(), or
+	 * via pre-existing SGL memory setup explictly by fabric module code with
+	 * transport_generic_map_mem_to_cmd().
+	 */
 	ret = transport_new_cmd_obj(cmd);
 	if (ret < 0)
 		return ret;
-
-	list_for_each_entry(task, &cmd->t_task_list, t_list) {
-		if (atomic_read(&task->task_sent))
-			continue;
-		if (!dev->transport->map_task_SG)
-			continue;
-
-		ret = dev->transport->map_task_SG(task);
-		if (ret < 0)
-			return ret;
-	}
-
 	/*
 	 * For WRITEs, let the fabric know its buffer is ready..
 	 * This WRITE struct se_cmd (and all of its associated struct se_task's)

include/target/target_core_transport.h

@@ -239,9 +239,13 @@ struct se_subsystem_api {
 	 */
 	int (*cdb_none)(struct se_task *);
 	/*
-	 * For SCF_SCSI_DATA_SG_IO_CDB and SCF_SCSI_CONTROL_SG_IO_CDB
+	 * For SCF_SCSI_DATA_SG_IO_CDB
 	 */
-	int (*map_task_SG)(struct se_task *);
+	int (*map_data_SG)(struct se_task *);
+	/*
+	 * For SCF_SCSI_CONTROL_SG_IO_CDB
+	 */
+	int (*map_control_SG)(struct se_task *);
 	/*
 	 * attach_hba():
 	 */