[PATCH 2/3] target: Add TARGET_SCF_LOOKUP_LUN_FROM_TAG support for ABORT_TASK

[Nicholas A. Bellinger]

From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>

This patch introduces support in target_submit_tmr() for locating a
unpacked_lun from an existing se_cmd->tag during ABORT_TASK.

When TARGET_SCF_LOOKUP_LUN_FROM_TAG is set, target_submit_tmr()
will do the extra lookup via target_lookup_lun_from_tag() and
subsequently invoke transport_lookup_tmr_lun() so a proper
percpu se_lun->lun_ref is taken before workqueue dispatch into
se_device->tmr_wq happens.

Aside from the extra target_lookup_lun_from_tag(), the existing
code-path remains unchanged.

Cc: Himanshu Madhani <himanshu.madhani@xxxxxxxxxx>
Cc: Quinn Tran <quinn.tran@xxxxxxxxxx>
Cc: Mike Christie <mchristi@xxxxxxxxxx>
Cc: Hannes Reinecke <hare@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
 drivers/target/target_core_transport.c | 53 ++++++++++++++++++++++++++++------
 include/target/target_core_base.h      |  3 +-
 2 files changed, 46 insertions(+), 10 deletions(-)

diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 83bfc97..dbb8101 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1592,6 +1592,29 @@ static void target_complete_tmr_failure(struct work_struct *work)
 	transport_cmd_check_stop_to_fabric(se_cmd);
 }
 
+static bool target_lookup_lun_from_tag(struct se_session *se_sess, u64 tag,
+				       u64 *unpacked_lun)
+{
+	struct se_cmd *se_cmd;
+	unsigned long flags;
+	bool ret = false;
+
+	spin_lock_irqsave(&se_sess->sess_cmd_lock, flags);
+	list_for_each_entry(se_cmd, &se_sess->sess_cmd_list, se_cmd_list) {
+		if (se_cmd->se_cmd_flags & SCF_SCSI_TMR_CDB)
+			continue;
+
+		if (se_cmd->tag == tag) {
+			*unpacked_lun = se_cmd->orig_fe_lun;
+			ret = true;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&se_sess->sess_cmd_lock, flags);
+
+	return ret;
+}
+
 /**
  * target_submit_tmr - lookup unpacked lun and submit uninitialized se_cmd
  *                     for TMR CDBs
@@ -1639,19 +1662,31 @@ int target_submit_tmr(struct se_cmd *se_cmd, struct se_session *se_sess,
 		core_tmr_release_req(se_cmd->se_tmr_req);
 		return ret;
 	}
+	/*
+	 * If this is ABORT_TASK with no explicit fabric provided LUN,
+	 * go ahead and search active session tags for a match to figure
+	 * out unpacked_lun for the original se_cmd.
+	 */
+	if (tm_type == TMR_ABORT_TASK && (flags & TARGET_SCF_LOOKUP_LUN_FROM_TAG)) {
+		if (!target_lookup_lun_from_tag(se_sess, tag, &unpacked_lun))
+			goto failure;
+	}
 
 	ret = transport_lookup_tmr_lun(se_cmd, unpacked_lun);
-	if (ret) {
-		/*
-		 * For callback during failure handling, push this work off
-		 * to process context with TMR_LUN_DOES_NOT_EXIST status.
-		 */
-		INIT_WORK(&se_cmd->work, target_complete_tmr_failure);
-		schedule_work(&se_cmd->work);
-		return 0;
-	}
+	if (ret)
+		goto failure;
+
 	transport_generic_handle_tmr(se_cmd);
 	return 0;
+
+	/*
+	 * For callback during failure handling, push this work off
+	 * to process context with TMR_LUN_DOES_NOT_EXIST status.
+	 */
+failure:
+	INIT_WORK(&se_cmd->work, target_complete_tmr_failure);
+	schedule_work(&se_cmd->work);
+	return 0;
 }
 EXPORT_SYMBOL(target_submit_tmr);
 
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index db2c7b3..a3af69f 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -188,7 +188,8 @@ enum target_sc_flags_table {
 	TARGET_SCF_BIDI_OP		= 0x01,
 	TARGET_SCF_ACK_KREF		= 0x02,
 	TARGET_SCF_UNKNOWN_SIZE		= 0x04,
-	TARGET_SCF_USE_CPUID	= 0x08,
+	TARGET_SCF_USE_CPUID		= 0x08,
+	TARGET_SCF_LOOKUP_LUN_FROM_TAG	= 0x10,
 };
 
 /* fabric independent task management function values */
-- 
1.9.1