scsi: target/core: Make ABORT and LUN RESET handling synchronous

Instead of invoking target driver callback functions from the context that
handles an abort or LUN RESET task management function, only set the abort
flag from that context and perform the actual abort handling from the
context of the regular command processing flow. This approach has the
advantage that the task management code becomes much easier to read and to
verify since the number of potential race conditions against the command
processing flow is strongly reduced.

This patch has been tested by running the following two shell commands
concurrently for about ten minutes for both the iSCSI and the SRP target
drivers ($dev is an initiator device node connected with storage provided
by the target driver under test):

 * fio with data verification enabled on a filesystem mounted on top of
   $dev.

 * while true; do sg_reset -d $dev; echo -n .; sleep .1; done

Cc: Nicholas Bellinger <nab@linux-iscsi.org>
Cc: Mike Christie <mchristi@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Disseldorp <ddiss@suse.de>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 28 insertions, 21 deletions

diff --git a/drivers/target/target_core_tmr.c b/drivers/target/target_core_tmr.c
index 71950355074e..ad0061e09d4c 100644
--- a/drivers/target/target_core_tmr.c
+++ b/drivers/target/target_core_tmr.c
@@ -171,11 +171,15 @@ void core_tmr_abort_task(
 
 		spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
 
-		cancel_work_sync(&se_cmd->work);
-		transport_wait_for_tasks(se_cmd);
+		/*
+		 * Ensure that this ABORT request is visible to the LU RESET
+		 * code.
+		 */
+		if (!tmr->tmr_dev)
+			WARN_ON_ONCE(transport_lookup_tmr_lun(tmr->task_cmd,
+						se_cmd->orig_fe_lun) < 0);
 
-		if (!transport_cmd_finish_abort(se_cmd))
-			target_put_sess_cmd(se_cmd);
+		target_put_cmd_and_wait(se_cmd);
 
 		printk("ABORT_TASK: Sending TMR_FUNCTION_COMPLETE for"
 				" ref_tag: %llu\n", ref_tag);
@@ -269,14 +273,28 @@ static void core_tmr_drain_tmr_list(
 			(preempt_and_abort_list) ? "Preempt" : "", tmr_p,
 			tmr_p->function, tmr_p->response, cmd->t_state);
 
-		cancel_work_sync(&cmd->work);
-		transport_wait_for_tasks(cmd);
-
-		if (!transport_cmd_finish_abort(cmd))
-			target_put_sess_cmd(cmd);
+		target_put_cmd_and_wait(cmd);
 	}
 }
 
+/**
+ * core_tmr_drain_state_list() - abort SCSI commands associated with a device
+ *
+ * @dev:       Device for which to abort outstanding SCSI commands.
+ * @prout_cmd: Pointer to the SCSI PREEMPT AND ABORT if this function is called
+ *             to realize the PREEMPT AND ABORT functionality.
+ * @tmr_sess:  Session through which the LUN RESET has been received.
+ * @tas:       Task Aborted Status (TAS) bit from the SCSI control mode page.
+ *             A quote from SPC-4, paragraph "7.5.10 Control mode page":
+ *             "A task aborted status (TAS) bit set to zero specifies that
+ *             aborted commands shall be terminated by the device server
+ *             without any response to the application client. A TAS bit set
+ *             to one specifies that commands aborted by the actions of an I_T
+ *             nexus other than the I_T nexus on which the command was
+ *             received shall be completed with TASK ABORTED status."
+ * @preempt_and_abort_list: For the PREEMPT AND ABORT functionality, a list
+ *             with registrations that will be preempted.
+ */
 static void core_tmr_drain_state_list(
 	struct se_device *dev,
 	struct se_cmd *prout_cmd,
@@ -351,18 +369,7 @@ static void core_tmr_drain_state_list(
 			 cmd->tag, (preempt_and_abort_list) ? "preempt" : "",
 			 cmd->pr_res_key);
 
-		/*
-		 * If the command may be queued onto a workqueue cancel it now.
-		 *
-		 * This is equivalent to removal from the execute queue in the
-		 * loop above, but we do it down here given that
-		 * cancel_work_sync may block.
-		 */
-		cancel_work_sync(&cmd->work);
-		transport_wait_for_tasks(cmd);
-
-		if (!transport_cmd_finish_abort(cmd))
-			target_put_sess_cmd(cmd);
+		target_put_cmd_and_wait(cmd);
 	}
 }