iser-target: Kill the ->isert_cmd back pointer in struct iser_tx_desc

We only use the pointer when processing regular iSER commands, and it then
always points to the struct iser_cmd that contains the TX descriptor.

Remove it and rely on container_of to save a little space and avoid a
pointer that is updated multiple times per processed command.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/infiniband/ulp/isert/ib_isert.h b/drivers/infiniband/ulp/isert/ib_isert.h
index f552797..192788a 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.h
+++ b/drivers/infiniband/ulp/isert/ib_isert.h
@@ -110,7 +110,6 @@
 	struct ib_sge	tx_sg[2];
 	struct ib_cqe	tx_cqe;
 	int		num_sge;
-	struct isert_cmd *isert_cmd;
 	struct ib_send_wr send_wr;
 } __packed;
 
@@ -181,6 +180,11 @@
 	struct scatterlist	sg;
 };
 
+static inline struct isert_cmd *tx_desc_to_cmd(struct iser_tx_desc *desc)
+{
+	return container_of(desc, struct isert_cmd, tx_desc);
+}
+
 struct isert_device;
 
 struct isert_conn {