[RFC PATCH 07/18] libiscsi: add task prealloc/free callouts

[Mike Christie <michael.christie@xxxxxxxxxx>]

Some drivers need to allocate resources that functions
like dma_alloc* that can't be allocated with the iscsi_task struct.
The next patches have the iscsi drivers use the block/scsi mq cmd
allocators for scsi tasks and the drivers can use the init_cmd_priv
callout to allocate these extra resource for scsi tasks there. For
mgmt tasks, drivers can use the callouts added in this patch.

Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
---
 drivers/scsi/libiscsi.c             | 21 +++++++++++++++++++--
 include/scsi/scsi_transport_iscsi.h |  5 +++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index ae8b755..6621a69 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -2885,10 +2885,15 @@ struct iscsi_cls_session *
 		task->itt = cmd_i;
 		task->state = ISCSI_TASK_FREE;
 		INIT_LIST_HEAD(&task->running);
+
+		if (iscsit->alloc_task_priv) {
+			if (iscsit->alloc_task_priv(session, task))
+				goto free_task_priv;
+		}
 	}
 
 	if (!try_module_get(iscsit->owner))
-		goto module_get_fail;
+		goto free_task_priv;
 
 	if (iscsi_add_session(cls_session, id))
 		goto cls_session_fail;
@@ -2897,7 +2902,12 @@ struct iscsi_cls_session *
 
 cls_session_fail:
 	module_put(iscsit->owner);
-module_get_fail:
+free_task_priv:
+	for (cmd_i--; cmd_i >= 0; cmd_i--) {
+		if (iscsit->free_task_priv)
+			iscsit->free_task_priv(session, session->cmds[cmd_i]);
+	}
+
 	iscsi_pool_free(&session->cmdpool);
 cmdpool_alloc_fail:
 	iscsi_free_session(cls_session);
@@ -2916,6 +2926,13 @@ void iscsi_session_teardown(struct iscsi_cls_session *cls_session)
 	struct iscsi_session *session = cls_session->dd_data;
 	struct module *owner = cls_session->transport->owner;
 	struct Scsi_Host *shost = session->host;
+	int cmd_i;
+
+	for (cmd_i = 0; cmd_i < session->cmds_max; cmd_i++) {
+		if (session->tt->free_task_priv)
+			session->tt->free_task_priv(session,
+						    session->cmds[cmd_i]);
+	}
 
 	iscsi_pool_free(&session->cmdpool);
 
diff --git a/include/scsi/scsi_transport_iscsi.h b/include/scsi/scsi_transport_iscsi.h
index 8a26a2f..cdd358e 100644
--- a/include/scsi/scsi_transport_iscsi.h
+++ b/include/scsi/scsi_transport_iscsi.h
@@ -22,6 +22,7 @@
 struct scsi_cmnd;
 struct iscsi_cls_conn;
 struct iscsi_conn;
+struct iscsi_session;
 struct iscsi_task;
 struct sockaddr;
 struct iscsi_iface;
@@ -106,6 +107,10 @@ struct iscsi_transport {
 	void (*get_stats) (struct iscsi_cls_conn *conn,
 			   struct iscsi_stats *stats);
 
+	int (*alloc_task_priv) (struct iscsi_session *session,
+				struct iscsi_task *task);
+	void (*free_task_priv) (struct iscsi_session *session,
+				struct iscsi_task *task);
 	int (*init_task) (struct iscsi_task *task);
 	int (*xmit_task) (struct iscsi_task *task);
 	void (*cleanup_task) (struct iscsi_task *task);
-- 
1.8.3.1