scsi: target/core: Simplify the code for aborting SCSI commands

Instead of allowing the code that aborts a SCSI command to finish before
all iSCSI data frames have been received, make that code wait until all
iSCSI data frames have been received. Introduce a new member variable in
the target driver template to communicate that information from the iSCSI
target driver to the target core. This change allows to leave out the check
whether or not it is already safe to send the TASK_ABORTED reply from
transport_send_task_abort().

Cc: Nicholas Bellinger <[e-mail]>
Cc: Mike Christie <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: David Disseldorp <[e-mail]>
Cc: Hannes Reinecke <[e-mail]>
Signed-off-by: Bart Van Assche <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/target/iscsi/iscsi_target_configfs.c

···
 	.tfc_tpg_nacl_attrib_attrs	= lio_target_nacl_attrib_attrs,
 	.tfc_tpg_nacl_auth_attrs	= lio_target_nacl_auth_attrs,
 	.tfc_tpg_nacl_param_attrs	= lio_target_nacl_param_attrs,
+
+	.write_pending_must_be_called	= true,
 };

drivers/target/target_core_transport.c

···
 	 * Determine if frontend context caller is requesting the stopping of
 	 * this command for frontend exceptions.
 	 */
-	if (cmd->transport_state & CMD_T_STOP) {
+	if (cmd->transport_state & CMD_T_STOP &&
+	    !cmd->se_tfo->write_pending_must_be_called) {
 		pr_debug("%s:%d CMD_T_STOP for ITT: 0x%08llx\n",
 			 __func__, __LINE__, cmd->tag);
 
···
 	}
 	spin_unlock_irqrestore(&cmd->t_state_lock, flags);
 
-	/*
-	 * If there are still expected incoming fabric WRITEs, we wait
-	 * until until they have completed before sending a TASK_ABORTED
-	 * response.  This response with TASK_ABORTED status will be
-	 * queued back to fabric module by transport_check_aborted_status().
-	 */
-	if (cmd->data_direction == DMA_TO_DEVICE) {
-		if (cmd->se_tfo->write_pending_status(cmd) != 0) {
-			spin_lock_irqsave(&cmd->t_state_lock, flags);
-			if (cmd->se_cmd_flags & SCF_SEND_DELAYED_TAS) {
-				spin_unlock_irqrestore(&cmd->t_state_lock, flags);
-				goto send_abort;
-			}
-			cmd->se_cmd_flags |= SCF_SEND_DELAYED_TAS;
-			spin_unlock_irqrestore(&cmd->t_state_lock, flags);
-			return;
-		}
-	}
-send_abort:
 	cmd->scsi_status = SAM_STAT_TASK_ABORTED;
 
 	transport_lun_remove_cmd(cmd);

include/target/target_core_fabric.h

···
 	struct configfs_attribute **tfc_tpg_nacl_attrib_attrs;
 	struct configfs_attribute **tfc_tpg_nacl_auth_attrs;
 	struct configfs_attribute **tfc_tpg_nacl_param_attrs;
+
+	/*
+	 * Set this member variable to true if the SCSI transport protocol
+	 * (e.g. iSCSI) requires that the Data-Out buffer is transferred in
+	 * its entirety before a command is aborted.
+	 */
+	bool write_pending_must_be_called;
 };
 
 int target_register_template(const struct target_core_fabric_ops *fo);