linux-kernel - Re: [RFC] IB/srp: export reset-host via sysfs

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Date:   Tue, 4 Oct 2016 17:22:18 +0200
From:   Gioh Kim <gi-oh.kim@...fitbricks.com>
To:     Bart Van Assche <bart.vanassche@...disk.com>,
        "dledford@...hat.com" <dledford@...hat.com>,
        "sean.hefty@...el.com" <sean.hefty@...el.com>,
        "hal.rosenstock@...il.com" <hal.rosenstock@...il.com>
Cc:     "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] IB/srp: export reset-host via sysfs



On 04.10.2016 16:24, Bart Van Assche wrote:
> On 10/04/16 07:00, Gioh Kim wrote:
>> Standard SCSI device has host_reset sysfs interface.
>> This patch exports the host_reset interface for upper layer.
>>
>> Signed-off-by: Gioh Kim <gi-oh.kim@...fitbricks.com>
>> ---
>>  drivers/infiniband/ulp/srp/ib_srp.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/infiniband/ulp/srp/ib_srp.c 
>> b/drivers/infiniband/ulp/srp/ib_srp.c
>> index 3322ed7..92e6c3f 100644
>> --- a/drivers/infiniband/ulp/srp/ib_srp.c
>> +++ b/drivers/infiniband/ulp/srp/ib_srp.c
>> @@ -2628,6 +2628,15 @@ static int srp_reset_device(struct scsi_cmnd 
>> *scmnd)
>>      return SUCCESS;
>>  }
>>
>> +static int srp_scsi_host_reset(struct Scsi_Host *shost, int reset_type)
>> +{
>> +    struct srp_target_port *target = host_to_target(shost);
>> +
>> +    shost_printk(KERN_EMERG, target->scsi_host, PFX "SRP reset_host 
>> called\n");
>> +
>> +    return srp_reconnect_rport(target->rport);
>> +}
>> +
>>  static int srp_reset_host(struct scsi_cmnd *scmnd)
>>  {
>>      struct srp_target_port *target = 
>> host_to_target(scmnd->device->host);
>> @@ -2858,6 +2867,7 @@ static struct scsi_host_template srp_template = {
>>      .use_clustering            = ENABLE_CLUSTERING,
>>      .shost_attrs            = srp_host_attrs,
>>      .track_queue_depth        = 1,
>> +    .host_reset            = srp_scsi_host_reset,
>>  };
>
> Hello Gioh,
>
> A patch description should not only explain what is changed but also 
> why a change is considered useful. Why do you think it would be useful 
> to allow users to trigger a call of srp_reconnect_rport() through 
> sysfs instead of using the functionality that is already available 
> through sysfs, namely removing a SCSI host and reconnecting?
Hello Bart,

It's my mistake to miss 0000-cover-letter.patch file including description.

I'm testing SCSI devices which are exported by the remote servers via IB 
network. I know that SCSI error handling mechanism calls reset-host when 
something wrong happens. But the SCSI error handling tries sending ABORT 
commands and other actions before resetting host. I found that those 
ABORT commands could generate more stress on the remove server. So I 
need to reset SCSI host (which mean reconnecting) when the remote server 
starts to become slow or have some problem to handle IO.

And I think I can use some utilities for SCSI device, such like sg3 
utils, to handle srp connection.

Thank you for your reply.

Best regards,
Gioh Kim

>
> Bart.
>