diff --git a/drivers/scsi/qla2xxx/Kconfig b/drivers/scsi/qla2xxx/Kconfig
index 10aa18b..5110fab 100644
--- a/drivers/scsi/qla2xxx/Kconfig
+++ b/drivers/scsi/qla2xxx/Kconfig
@@ -36,3 +36,14 @@ config TCM_QLA2XXX
 	default n
 	---help---
 	Say Y here to enable the TCM_QLA2XXX fabric module for QLogic 24xx+ series target mode HBAs
+
+config TCM_QLA2XXX_DEBUG
+	bool "TCM_QLA2XXX fabric module DEBUG mode for QLogic 24xx+ series target mode HBAs"
+	depends on SCSI_QLA_FC && TARGET_CORE
+	depends on LIBFC
+	select BTREE
+	default n
+	---help---
+	Say Y here to enable the TCM_QLA2XXX fabric module DEBUG for QLogic 24xx+ series target mode HBAs
+	This will include code to enable the SCSI command jammer
+
diff --git a/drivers/scsi/qla2xxx/tcm_qla2xxx.c b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
index 1808a01..411a450 100644
--- a/drivers/scsi/qla2xxx/tcm_qla2xxx.c
+++ b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
@@ -457,6 +457,10 @@ static int tcm_qla2xxx_handle_cmd(scsi_qla_host_t *vha, struct qla_tgt_cmd *cmd,
 	struct se_cmd *se_cmd = &cmd->se_cmd;
 	struct se_session *se_sess;
 	struct qla_tgt_sess *sess;
+#ifdef CONFIG_TCM_QLA2XXX_DEBUG
+        struct se_portal_group *se_tpg;
+        struct tcm_qla2xxx_tpg *tpg;
+#endif
 	int flags = TARGET_SCF_ACK_KREF;
 
 	if (bidi)
@@ -476,6 +480,15 @@ static int tcm_qla2xxx_handle_cmd(scsi_qla_host_t *vha, struct qla_tgt_cmd *cmd,
 		pr_err("Unable to locate active struct se_session\n");
 		return -EINVAL;
 	}
+ 
+#ifdef CONFIG_TCM_QLA2XXX_DEBUG
+	se_tpg = se_sess->se_tpg;
+	tpg = container_of(se_tpg,struct tcm_qla2xxx_tpg, se_tpg);
+ 	if (unlikely(tpg->tpg_attrib.jam_host)) {
+ 		/* return, and dont run target_submit_cmd,discarding command */
+                return 0;
+	}
+#endif
 
 	cmd->vha->tgt_counters.qla_core_sbt_cmd++;
 	return target_submit_cmd(se_cmd, se_sess, cdb, &cmd->sense_buffer[0],
@@ -844,6 +857,9 @@ DEF_QLA_TPG_ATTRIB(cache_dynamic_acls);
 DEF_QLA_TPG_ATTRIB(demo_mode_write_protect);
 DEF_QLA_TPG_ATTRIB(prod_mode_write_protect);
 DEF_QLA_TPG_ATTRIB(demo_mode_login_only);
+#ifdef CONFIG_TCM_QLA2XXX_DEBUG
+DEF_QLA_TPG_ATTRIB(jam_host);
+#endif
 
 static struct configfs_attribute *tcm_qla2xxx_tpg_attrib_attrs[] = {
 	&tcm_qla2xxx_tpg_attrib_attr_generate_node_acls,
@@ -851,6 +867,9 @@ static struct configfs_attribute *tcm_qla2xxx_tpg_attrib_attrs[] = {
 	&tcm_qla2xxx_tpg_attrib_attr_demo_mode_write_protect,
 	&tcm_qla2xxx_tpg_attrib_attr_prod_mode_write_protect,
 	&tcm_qla2xxx_tpg_attrib_attr_demo_mode_login_only,
+#ifdef CONFIG_TCM_QLA2XXX_DEBUG
+        &tcm_qla2xxx_tpg_attrib_attr_jam_host,
+#endif
 	NULL,
 };
 
@@ -1023,6 +1042,7 @@ static struct se_portal_group *tcm_qla2xxx_make_tpg(
 	tpg->tpg_attrib.demo_mode_write_protect = 1;
 	tpg->tpg_attrib.cache_dynamic_acls = 1;
 	tpg->tpg_attrib.demo_mode_login_only = 1;
+	tpg->tpg_attrib.jam_host = 0;
 
 	ret = core_tpg_register(wwn, &tpg->se_tpg, SCSI_PROTOCOL_FCP);
 	if (ret < 0) {
diff --git a/drivers/scsi/qla2xxx/tcm_qla2xxx.h b/drivers/scsi/qla2xxx/tcm_qla2xxx.h
index 3bbf4cb..37e026a 100644
--- a/drivers/scsi/qla2xxx/tcm_qla2xxx.h
+++ b/drivers/scsi/qla2xxx/tcm_qla2xxx.h
@@ -34,6 +34,7 @@ struct tcm_qla2xxx_tpg_attrib {
 	int prod_mode_write_protect;
 	int demo_mode_login_only;
 	int fabric_prot_type;
+	int jam_host;
 };
 
 struct tcm_qla2xxx_tpg {
-- 
1.7.1

Tested by: Laurence Oberman <loberman@redhat.com>
Signed-off-by: Laurence Oberman <loberman@redhat.com>
---
 Documentation/scsi/tcm_qla2xxx.txt |   22 ++++++++++++++++++++++
 1 files changed, 22 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/scsi/tcm_qla2xxx.txt

diff --git a/Documentation/scsi/tcm_qla2xxx.txt b/Documentation/scsi/tcm_qla2xxx.txt
new file mode 100644
index 0000000..364c817
--- /dev/null
+++ b/Documentation/scsi/tcm_qla2xxx.txt
@@ -0,0 +1,22 @@
+tcm_qla2xxx jam_host attribute
+------------------------------
+There is now a new module endpoint atribute called jam_host
+attribute: jam_host: boolean=0/1 
+This attribute and accompanying code is only included if the 
+Kconfig parameter TCM_QLA2XXX_DEBUG is set to Y
+By default this jammer code and functionality is disabled
+
+Use this attribute to control the discarding of SCSI commands to a 
+selected host.
+This may be useful for testing error handling and simulating slow drain
+and other fabric issues.
+
+Setting a boolean of 1 for the jam_host attribute for a particular host
+ will discard the commands for that host.
+Reset back to 0 to stop the jamming.
+
+Enable host 4 to be jammed
+echo 1 > /sys/kernel/config/target/qla2xxx/21:00:00:24:ff:27:8f:ae/tpgt_1/attrib/jam_host
+
+Disable jamming on host 4
+echo 0 > /sys/kernel/config/target/qla2xxx/21:00:00:24:ff:27:8f:ae/tpgt_1/attrib/jam_host
-- 
1.7.1

Laurence Oberman
Principal Software Maintenance Engineer
Red Hat Global Support Services

----- Original Message -----
From: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
To: "Laurence Oberman" <loberman@redhat.com>
Cc: "Himanshu Madhani" <himanshu.madhani@qlogic.com>, "Bart Van Assche" <bart.vanassche@sandisk.com>, "linux-scsi" <linux-scsi@vger.kernel.org>, "target-devel" <target-devel@vger.kernel.org>, "Quinn Tran" <quinn.tran@qlogic.com>
Sent: Saturday, April 2, 2016 7:39:35 PM
Subject: Re: tcm_qla2xxx Add SCSI command jammer/discard capabilty to the tcm_qla2xxx module - revision4

Hi Laurence,

On Sat, 2016-04-02 at 13:10 -0400, Laurence Oberman wrote:
> Hello Himanshu
> 
> I noticed a typo in the patch I submitted here is the corrected patch.
> Please ignore the prior patch
> 
> I was missing the full CONFIG name in the #ifdef check 
> 
> Corrected Patch

Two quick process related comments:

Please avoid top-posting responses, as it makes the thread more
difficult for others to follow.

Also, please send out kernel patches for list review using
git-format-patch + git-send-email tools, instead of responding with new
versions in the original email thread.

> 
> [root@localhost home]# linux-4.5/scripts/checkpatch.pl jammer_patch.v4
> total: 0 errors, 0 warnings, 81 lines checked
> 
> jammer_patch.v4 has no obvious style problems and is ready for submission.
> 
> 
> This patch was reworked to only include the jammer code if the parameter TCM_QLA2XXX_DEBUG=Y is set.
> The default is to not provide this functionality at all.
> I looked at using attributes but this code is in the fastpath and the overhead or fetching the attribute
> each time is not a good idea.
> Control of this needs to be dynamic and the module parameter allows a simple compare in the fastpath.
> 

I don't see how a per tcm_qla2xxx (scsi_qla_host) TPG endpoint attribute
has any noticeable performance impact with TCM_QLA2XXX_DEBUG=y vs. a
global module parameter doing scsi_qla_host->host_no comparison.

Eg, have you tried something like the following..?

diff --git a/drivers/scsi/qla2xxx/tcm_qla2xxx.c b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
index c1461d2..3b13a89a 100644
--- a/drivers/scsi/qla2xxx/tcm_qla2xxx.c
+++ b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
@@ -477,6 +477,17 @@ static int tcm_qla2xxx_handle_cmd(scsi_qla_host_t *vha, struct qla_tgt_c
                return -EINVAL;
        }
 
+#ifdef CONFIG_TCM_QLA2XXX_DEBUG
+       {
+       struct se_portal_group *se_tpg = se_sess->se_tpg;
+       struct tcm_qla2xxx_tpg *tpg = container_of(se_tpg,
+                               struct tcm_qla2xxx_tpg, se_tpg);
+
+       if (tpg->tpg_attrib.jam_host)
+               return 0;
+
+       }
+#endif
        cmd->vha->tgt_counters.qla_core_sbt_cmd++;
        return target_submit_cmd(se_cmd, se_sess, cdb, &cmd->sense_buffer[0],
                                cmd->unpacked_lun, data_length, fcp_task_attr,
@@ -845,12 +856,19 @@ DEF_QLA_TPG_ATTRIB(demo_mode_write_protect);
 DEF_QLA_TPG_ATTRIB(prod_mode_write_protect);
 DEF_QLA_TPG_ATTRIB(demo_mode_login_only);
 
+#ifdef CONFIG_TCM_QLA2XXX_DEBUG
+DEF_QLA_TPG_ATTRIB(jam_host);
+#endif
+
 static struct configfs_attribute *tcm_qla2xxx_tpg_attrib_attrs[] = {
        &tcm_qla2xxx_tpg_attrib_attr_generate_node_acls,
        &tcm_qla2xxx_tpg_attrib_attr_cache_dynamic_acls,
        &tcm_qla2xxx_tpg_attrib_attr_demo_mode_write_protect,
        &tcm_qla2xxx_tpg_attrib_attr_prod_mode_write_protect,
        &tcm_qla2xxx_tpg_attrib_attr_demo_mode_login_only,
+#ifdef CONFIG_TCM_QLA2XXX_DEBUG
+       &tcm_qla2xxx_tpg_attrib_attr_jam_host,
+#endif
        NULL,
 };
 
diff --git a/drivers/scsi/qla2xxx/tcm_qla2xxx.h b/drivers/scsi/qla2xxx/tcm_qla2xxx.h
index 3bbf4cb..37e026a 100644
--- a/drivers/scsi/qla2xxx/tcm_qla2xxx.h
+++ b/drivers/scsi/qla2xxx/tcm_qla2xxx.h
@@ -34,6 +34,7 @@ struct tcm_qla2xxx_tpg_attrib {
        int prod_mode_write_protect;
        int demo_mode_login_only;
        int fabric_prot_type;
+       int jam_host;
 };
 
 struct tcm_qla2xxx_tpg {
