[SCSI] iscsi_tcp: don't fire conn error if pdu init fails

If a command's scsi cmd pdu setup fails then we can just fail
the IO to the scsi layer. If a DATA_OUT for a R2T fails then
we will want to drop the session, because it means we got a
bad request from the target (iscsi protocol error).

This patch has us propogate the error upwards so libiscsi_tcp
or libiscsi can decide what the best action is to take. It
also fixes a bug where we could try to grab the session lock
while holding it, because if iscsi_tcp drops the session in the
pdu setup callout the session lock is held when setting up the
scsi cmd pdu.
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/iscsi_tcp.c

@@ -463,7 +463,7 @@ static int iscsi_sw_tcp_pdu_init(struct iscsi_task *task,
 	}
 
 	if (err) {
-		iscsi_conn_failure(conn, err);
+		/* got invalid offset/len */
 		return -EIO;
 	}
 	return 0;

drivers/scsi/libiscsi_tcp.c

@@ -1036,8 +1036,11 @@ int iscsi_tcp_task_xmit(struct iscsi_task *task)
 
 	rc = conn->session->tt->init_pdu(task, r2t->data_offset + r2t->sent,
 					 r2t->data_count);
-	if (rc)
+	if (rc) {
+		iscsi_conn_failure(conn, ISCSI_ERR_XMIT_FAILED);
 		return rc;
+	}
+
 	r2t->sent += r2t->data_count;
 	goto flush;
 }