From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Snitzer <snitzer@redhat.com>
Subject: Re: IBM request to allow unprivledged ioctls [Was: Revert "dm mpath:
 fix stalls when handling invalid ioctls"]
Date: Mon, 2 Nov 2015 10:49:43 -0500
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>, hch@lst.de, Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>, dm-devel@redhat.com, linux-scsi@vger.kernel.org, Peter Rajnoha <prajnoha@redhat.com>

On Mon, Nov 02 2015 at 10:45am -0500,
Paolo Bonzini <pbonzini@redhat.com> wrote:

> 
> 
> On 02/11/2015 16:05, Mike Snitzer wrote:
> > > In any case, if we don't start path activation we should return
> > > ENOTCONN, not ENOTTY.
> > 
> > Currently, if we don't start path activation we're returning EIO.
> > ENOTCONN is used for when we do start path activation (and ENOTCONN is
> > the means for DM core to retry)
> > 
> > We _could_ change the ENOTCONN to be EAGAIN and EIO to ENOTCONN...
> 
> This makes sense... though of course testing the impact of this on
> userspace is going to be hard. :(  Chances are that userspace is not
> expecting EAGAIN either.
> 
> Even if they did, how would someone know that they can now retry the
> ioctl after getting EAGAIN?  Should they just do it in a loop?

Turns out multipath (userspace) has a udev rule for this now (prajnoha
pointed this out):
http://git.opensvc.com/gitweb.cgi?p=multipath-tools/.git;a=blob;f=multipath/11-dm-mpath.rules

So now I'm wondering if we _need_ to do any retries in kernel (aside
from while activation is active)?