target: Eliminate usage of struct se_mem

Both backstores and fabrics use arrays of struct scatterlist to describe
data buffers. However TCM used struct se_mems, basically a linked list
of scatterlist entries. We are able to simplify the code by eliminating
this intermediate data structure and just using struct scatterlist[]
throughout.

Also, moved attachment of task to cmd out of transport_generic_get_task
and into allocate_control_task and allocate_data_tasks. The reasoning
is that it's nonintuitive that get_task should automatically add it to
the cmd's task list -- it should just return an allocated, initialized
task. That's all it should do, based on the function's name, so either the
function shouldn't do it, or the name should change to encapsulate the
entire essence of what it does.

(nab: Fix compile warnings in tcm_fc, and make transport_kmap_first_data_page
 honor sg->offset for SGLs from contigious memory with TCM_Loop, and
 fix control se_cmd descriptor memory leak)

Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index d97618a2ee95..465f266a0205 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -490,8 +490,6 @@ struct se_cmd {
 	int			t_tasks_failed;
 	int			t_tasks_fua;
 	bool			t_tasks_bidi;
-	u32			t_tasks_se_num;
-	u32			t_tasks_se_bidi_num;
 	u32			t_tasks_sg_chained_no;
 	atomic_t		t_fe_count;
 	atomic_t		t_se_count;
@@ -523,9 +521,13 @@ struct se_cmd {
 	 */
 	struct scatterlist	*t_task_pt_sgl;
 	u32			t_task_pt_sgl_num;
-	struct list_head	t_mem_list;
+
+	struct scatterlist	*t_data_sg;
+	unsigned int		t_data_nents;
+	struct scatterlist	*t_bidi_data_sg;
+	unsigned int		t_bidi_data_nents;
+
 	/* Used for BIDI READ */
-	struct list_head	t_mem_bidi_list;
 	struct list_head	t_task_list;
 	u32			t_task_list_num;