On 03/08/2015 04:26 AM, Laurence Oberman wrote:
Hello
I use target LIO for all my storage array test targets and customer problem
resolution here at Red Hat.
This patch resulted from a requirement to mimic behaviour of an expensive
hardware jammer for a customer.
I have used this for some time with good success to simulate and reproduce
latency and slow drain fabric issues and
for testing and validating error handling behaviour in the Emulex, Qlogic and
other F/C drivers.
Works by checking jammer_flag==1 and host # and discards SCSI command,
controlled using echo to sys parameter.
I decided to share the patch, in the hope it may be useful for others but I do
understand this is a special use case.
If this is useful and Nab wants to include it I will create a proper
documentation patch as well.
filename:
/lib/modules/3.17.7-200.jammer.fc20.x86_64/kernel/drivers/scsi/qla2xxx/tcm_qla2xxx.ko
license: GPL
description: TCM QLA2XXX series NPIV enabled fabric driver
depends: target_core_mod,qla2xxx,scsi_transport_fc
intree: Y
vermagic: 3.17.7-200.jammer.fc20.x86_64 SMP mod_unload
parm: jammer_flag:Set to 1: Enable jammer (int)
parm: host_flag:host number to match on (int)
Enable host 6 to be jammed
echo 6 > /sys/module/tcm_qla2xxx/parameters/host_flag
Usage example script:
#!/bin/bash
host=`cat /sys/module/tcm_qla2xxx/parameters/host_flag`
sleep_time=120 ### Time to jam for
echo "We start to discard commands on SCSI host $host"
logger "Jammer started"
echo 1 > /sys/module/tcm_qla2xxx/parameters/jammer_flag
sleep $sleep_time
echo 0 > /sys/module/tcm_qla2xxx/parameters/jammer_flag
echo "We stopped the jammer"
logger "Jammer stopped"
This Patch diff against 3.19.1
Tested by: Laurence Oberman <[email protected]>
Signed-off-by: Laurence Oberman <[email protected]>
diff -Nurp a/drivers/scsi/qla2xxx/tcm_qla2xxx.c
b/drivers/scsi/qla2xxx/tcm_qla2xxx.c
--- a/drivers/scsi/qla2xxx/tcm_qla2xxx.c 2015-03-07 18:35:15.246737589
-0500
+++ b/drivers/scsi/qla2xxx/tcm_qla2xxx.c 2015-03-07 18:35:40.168599630
-0500
@@ -50,6 +50,14 @@
#include "qla_target.h"
#include "tcm_qla2xxx.h"
+int message_flag=0;
+int jammer_flag = 0;
+module_param(jammer_flag, int,0644);
+MODULE_PARM_DESC(jammer_flag, "If set to 1: Enable jammer");
+int host_flag=0;
+module_param(host_flag, int,0644);
+MODULE_PARM_DESC(host_flag, "host number to match on");
+
static struct workqueue_struct *tcm_qla2xxx_free_wq;
static struct workqueue_struct *tcm_qla2xxx_cmd_wq;
@@ -570,6 +578,22 @@ static int tcm_qla2xxx_handle_cmd(scsi_q
pr_err("Unable to locate active struct se_session\n");
return -EINVAL;
}
+
+ // Control messaging here
+ message_flag += jammer_flag;
+ if(message_flag == 1)
+ printk("tcm_qla2xx:SCSI Jammer enabled on host %d\n",host_flag);
+ if((jammer_flag == 0) && (message_flag >=0)) {
+ printk("tcm_qla2xx:SCSI Jammer stopped, %d SCSI commands discarded
for host %d\n",message_flag,host_flag);
+ message_flag=-1;
+ }
+
+ if ((vha->host_no == host_flag) && (jammer_flag == 1))
+ {
+ // return, and don't run target_submit_cmd, effectively
discarding command
+ return 0;
+ }
+
return target_submit_cmd(se_cmd, se_sess, cdb, &cmd->sense_buffer[0],
cmd->unpacked_lun, data_length, fcp_task_attr,
@@ -2165,6 +2189,7 @@ static void tcm_qla2xxx_deregister_confi
static int __init tcm_qla2xxx_init(void)
{
int ret;
+ jammer_flag = 0;
ret = tcm_qla2xxx_register_configfs();
if (ret < 0)
The above code is added in the hot path so it's worth to optimize that
code. Had you already considered to combine the jammer_flag and
host_flag kernel module parameters into a single parameter, e.g.
"jam_host" ? The value "-1" could be used to represent "jamming
disabled" and values >= 0 to represent a host number.
Additionally, please add unlikely() around the test that verifies
whether jamming is enabled. Please also verify your patches with
checkpatch before submission. The above patch does not follow the Linux
kernel coding style completely.
Bart.
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