Re: [PATCH 2/2] dm-mpath: Remove useless retain_attached_hw_handler parameter

[Mike Snitzer <snitzer@redhat.com>]

On Mon, Nov 28 2016 at  4:39pm -0500,
Mike Snitzer <snitzer@redhat.com> wrote:

> On Thu, Nov 24 2016 at  2:11am -0500,
> tang.junhui@zte.com.cn <tang.junhui@zte.com.cn> wrote:
> 
> > From: "tang.junhui" <tang.junhui@zte.com.cn>
> > 
> > Hardware handle would be retained no matter parameter
> > retain_attached_hw_handler is set or not in the logic
> > of current code. So remove this useless parameter.
> 
> Right, that wasn't always the case.  Previously (before commit )
> dm-mpath would first detach the attached handler.
> 
> I'm not completely opposed to removing the code that checks
> MPATHF_RETAIN_ATTACHED_HW_HANDLER in parse_path() but your proposed
> patch is broken in 2 ways:
> 1) in parse_path() you need to always initialize q
> 2) setting m->hw_handler_name to attached_handler_name needs to still
>    happen regardless of whether m->hw_handler_name was previously set
> 3) the "retain_attached_hw_handler" feature should still be allowed on
>    the command line, no sense to break multipath-tools
> 
> But honestly, I'm not seeing any reason to not just leave the existing
> code.

In addition, your patch actually breaks the ability to cope with -EBUSY
from the call to scsi_dh_attach().  Meaning we wouldn't properly fall
back to retaining the attached hw handler.

So NACK on this patch.