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

[Gioh Kim]

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@xxxxxxxxxxxxxxxx>
> > ---
> >  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.