iscsi-target: Fix iscsit_add_reject* usage for iser

This patch changes iscsit_add_reject() + iscsit_add_reject_from_cmd()
usage to not sleep on iscsi_cmd->reject_comp to address a free-after-use
usage bug in v3.10 with iser-target code.

It saves ->reject_reason for use within iscsit_build_reject() so the
correct value for both transport cases.  It also drops the legacy
fail_conn parameter usage throughput iscsi-target code and adds
two iscsit_add_reject_cmd() and iscsit_reject_cmd helper functions,
along with various small cleanups.

(v2: Re-enable target_put_sess_cmd() to be called from
     iscsit_add_reject_from_cmd() for rejects invoked after
     target_get_sess_cmd() has been called)

Cc: Or Gerlitz <ogerlitz@mellanox.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: stable@vger.kernel.org  # 3.10+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/iscsi/iscsi_target_erl1.c b/drivers/target/iscsi/iscsi_target_erl1.c
index 40d9dbc..d00f132 100644
--- a/drivers/target/iscsi/iscsi_target_erl1.c
+++ b/drivers/target/iscsi/iscsi_target_erl1.c
@@ -162,9 +162,8 @@
 			" protocol error.\n", cmd->init_task_tag, begrun,
 			(begrun + runlength), cmd->acked_data_sn);
 
-			return iscsit_add_reject_from_cmd(
-					ISCSI_REASON_PROTOCOL_ERROR,
-					1, 0, buf, cmd);
+			return iscsit_reject_cmd(cmd,
+					ISCSI_REASON_PROTOCOL_ERROR, buf);
 	}
 
 	if (runlength) {
@@ -173,8 +172,8 @@
 			" with BegRun: 0x%08x, RunLength: 0x%08x, exceeds"
 			" current R2TSN: 0x%08x, protocol error.\n",
 			cmd->init_task_tag, begrun, runlength, cmd->r2t_sn);
-			return iscsit_add_reject_from_cmd(
-				ISCSI_REASON_BOOKMARK_INVALID, 1, 0, buf, cmd);
+			return iscsit_reject_cmd(cmd,
+					ISCSI_REASON_BOOKMARK_INVALID, buf);
 		}
 		last_r2tsn = (begrun + runlength);
 	} else
@@ -433,8 +432,7 @@
 			" protocol error.\n", cmd->init_task_tag, begrun,
 			(begrun + runlength), cmd->acked_data_sn);
 
-		return iscsit_add_reject_from_cmd(ISCSI_REASON_PROTOCOL_ERROR,
-				1, 0, buf, cmd);
+		return iscsit_reject_cmd(cmd, ISCSI_REASON_PROTOCOL_ERROR, buf);
 	}
 
 	/*
@@ -445,14 +443,14 @@
 		pr_err("Initiator requesting BegRun: 0x%08x, RunLength"
 			": 0x%08x greater than maximum DataSN: 0x%08x.\n",
 				begrun, runlength, (cmd->data_sn - 1));
-		return iscsit_add_reject_from_cmd(ISCSI_REASON_BOOKMARK_INVALID,
-				1, 0, buf, cmd);
+		return iscsit_reject_cmd(cmd, ISCSI_REASON_BOOKMARK_INVALID,
+					 buf);
 	}
 
 	dr = iscsit_allocate_datain_req();
 	if (!dr)
-		return iscsit_add_reject_from_cmd(ISCSI_REASON_BOOKMARK_NO_RESOURCES,
-				1, 0, buf, cmd);
+		return iscsit_reject_cmd(cmd, ISCSI_REASON_BOOKMARK_NO_RESOURCES,
+					 buf);
 
 	dr->data_sn = dr->begrun = begrun;
 	dr->runlength = runlength;