[PATCH 0/3] target: Fixes for v4.12-rc1

[PATCH 0/3] target: Fixes for v4.12-rc1

[Nicholas A. Bellinger]

From: Nicholas Bellinger <nab@linux-iscsi.org>

Hi all,

Here are a couple of fixes from the last weeks testing while
continuing longevity and scale out workloads on v4.x target code.

This series contains three patches.  The first is to address
a COMPARE_AND_WRITE se_cmd reference leak where the READ phase
hits a non GOOD status, observed with ESX VAAI hosts when
outstanding READ I/O reaches a point where non SAM_STAT_GOOD
status completions start to happen.

The second addresses a hung task bug observed with iscsi-target
ports while explicitly changing the active per se_node_acl
queue_depth via the existing configfs attribute, if a new iscsi
login was already forcing session reinstatement.

And the third to is avoid forcing an session reinstatement if
queue_depth is changed via configfs, but the value itself has
not changed.

The series has been verified on v4.1.y by DATERA Q/A and
automation teams.

Thank you,

--nab

Nicholas Bellinger (3):
  target: Fix compare_and_write_callback handling for non GOOD status
  iscsi-target: Set session_fall_back_to_erl0 when forcing reinstatement
  target: Don't force session reset if queue_depth does not change

 drivers/target/iscsi/iscsi_target.c          | 1 +
 drivers/target/iscsi/iscsi_target_configfs.c | 1 +
 drivers/target/iscsi/iscsi_target_login.c    | 1 +
 drivers/target/target_core_sbc.c             | 5 ++++-
 drivers/target/target_core_tpg.c             | 7 +++++++
 5 files changed, 14 insertions(+), 1 deletion(-)

-- 
1.9.1

[PATCH 1/3] target: Fix compare_and_write_callback handling for non GOOD status

[Nicholas A. Bellinger]

From: Nicholas Bellinger <nab@linux-iscsi.org>

Following the bugfix for handling non SAM_STAT_GOOD COMPARE_AND_WRITE
status during COMMIT phase in commit 9b2792c3da1, the same bug exists
for the READ phase as well.

This would manifest first as a lost SCSI response, and eventual
hung task during fabric driver logout or re-login, as existing
shutdown logic waited for the COMPARE_AND_WRITE se_cmd->cmd_kref
to reach zero.

To address this bug, compare_and_write_callback() has been changed
to set post_ret = 1 and return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE
as necessary to signal failure status.

Reported-by: Bill Borsari <wgb@datera.io>
Cc: Bill Borsari <wgb@datera.io>
Tested-by: Gary Guo <ghg@datera.io>
Cc: Gary Guo <ghg@datera.io>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---
 drivers/target/target_core_sbc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/target/target_core_sbc.c b/drivers/target/target_core_sbc.c
index f9250b3..a0ad618 100644
--- a/drivers/target/target_core_sbc.c
+++ b/drivers/target/target_core_sbc.c
@@ -507,8 +507,11 @@ static sense_reason_t compare_and_write_callback(struct se_cmd *cmd, bool succes
 	 * been failed with a non-zero SCSI status.
 	 */
 	if (cmd->scsi_status) {
-		pr_err("compare_and_write_callback: non zero scsi_status:"
+		pr_debug("compare_and_write_callback: non zero scsi_status:"
 			" 0x%02x\n", cmd->scsi_status);
+		*post_ret = 1;
+		if (cmd->scsi_status == SAM_STAT_CHECK_CONDITION)
+			ret = TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
 		goto out;
 	}
 
-- 
1.9.1

[PATCH 2/3] iscsi-target: Set session_fall_back_to_erl0 when forcing reinstatement

[Nicholas A. Bellinger]

From: Nicholas Bellinger <nab@linux-iscsi.org>

While testing modification of per se_node_acl queue_depth forcing
session reinstatement via lio_target_nacl_cmdsn_depth_store() ->
core_tpg_set_initiator_node_queue_depth(), a hung task bug triggered
when changing cmdsn_depth invoked session reinstatement while an iscsi
login was already waiting for session reinstatement to complete.

This can happen when an outstanding se_cmd descriptor is taking a
long time to complete, and session reinstatement from iscsi login
or cmdsn_depth change occurs concurrently.

To address this bug, explicitly set session_fall_back_to_erl0 = 1
when forcing session reinstatement, so session reinstatement is
not attempted if an active session is already being shutdown.

This patch has been tested with two scenarios.  The first when
iscsi login is blocked waiting for iscsi session reinstatement
to complete followed by queue_depth change via configfs, and
second when queue_depth change via configfs us blocked followed
by a iscsi login driven session reinstatement.

Note this patch depends on commit d36ad77f702 to handle multiple
sessions per se_node_acl when changing cmdsn_depth, and for
pre v4.5 kernels will need to be included for stable as well.

Reported-by: Gary Guo <ghg@datera.io>
Tested-by: Gary Guo <ghg@datera.io>
Cc: Gary Guo <ghg@datera.io>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---
 drivers/target/iscsi/iscsi_target.c          | 1 +
 drivers/target/iscsi/iscsi_target_configfs.c | 1 +
 drivers/target/iscsi/iscsi_target_login.c    | 1 +
 3 files changed, 3 insertions(+)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 0f7ade0..26a9bcd 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -4663,6 +4663,7 @@ int iscsit_release_sessions_for_tpg(struct iscsi_portal_group *tpg, int force)
 			continue;
 		}
 		atomic_set(&sess->session_reinstatement, 1);
+		atomic_set(&sess->session_fall_back_to_erl0, 1);
 		spin_unlock(&sess->conn_lock);
 
 		list_move_tail(&se_sess->sess_list, &free_list);
diff --git a/drivers/target/iscsi/iscsi_target_configfs.c b/drivers/target/iscsi/iscsi_target_configfs.c
index 344e844..96d9c73 100644
--- a/drivers/target/iscsi/iscsi_target_configfs.c
+++ b/drivers/target/iscsi/iscsi_target_configfs.c
@@ -1528,6 +1528,7 @@ static void lio_tpg_close_session(struct se_session *se_sess)
 		return;
 	}
 	atomic_set(&sess->session_reinstatement, 1);
+	atomic_set(&sess->session_fall_back_to_erl0, 1);
 	spin_unlock(&sess->conn_lock);
 
 	iscsit_stop_time2retain_timer(sess);
diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
index ad8f301..6623847 100644
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -208,6 +208,7 @@ int iscsi_check_for_session_reinstatement(struct iscsi_conn *conn)
 			    initiatorname_param->value) &&
 		   (sess_p->sess_ops->SessionType == sessiontype))) {
 			atomic_set(&sess_p->session_reinstatement, 1);
+			atomic_set(&sess_p->session_fall_back_to_erl0, 1);
 			spin_unlock(&sess_p->conn_lock);
 			iscsit_inc_session_usage_count(sess_p);
 			iscsit_stop_time2retain_timer(sess_p);
-- 
1.9.1

[PATCH 3/3] target: Don't force session reset if queue_depth does not change

[Nicholas A. Bellinger]

From: Nicholas Bellinger <nab@linux-iscsi.org>

Keeping in the idempotent nature of target_core_fabric_configfs.c,
if a queue_depth value is set and it's the same as the existing
value, don't attempt to force session reinstatement.

Reported-by: Raghu Krishnamurthy <rk@datera.io>
Cc: Raghu Krishnamurthy <rk@datera.io>
Tested-by: Gary Guo <ghg@datera.io>
Cc: Gary Guo <ghg@datera.io>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---
 drivers/target/target_core_tpg.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
index dfaef4d..310d9e5 100644
--- a/drivers/target/target_core_tpg.c
+++ b/drivers/target/target_core_tpg.c
@@ -398,6 +398,13 @@ int core_tpg_set_initiator_node_queue_depth(
 	struct se_portal_group *tpg = acl->se_tpg;
 
 	/*
+	 * Allow the setting of se_node_acl queue_depth to be idempotent,
+	 * and not force a session shutdown event if the value is not
+	 * changing.
+	 */
+	if (acl->queue_depth == queue_depth)
+		return 0;
+	/*
 	 * User has requested to change the queue depth for a Initiator Node.
 	 * Change the value in the Node's struct se_node_acl, and call
 	 * target_set_nacl_queue_depth() to set the new queue depth.
-- 
1.9.1