Re: [PATCH 4/6] libmultipath: fix suspended devs from failed reloads

["Benjamin Marzinski" <bmarzins@redhat.com>]

On Tue, May 16, 2017 at 08:56:40PM +0200, Martin Wilck wrote:
> On Tue, 2017-05-16 at 12:33 -0500, Benjamin Marzinski wrote:
> > On Thu, May 11, 2017 at 10:26:52PM +0200, Martin Wilck wrote:
> > > On Tue, 2017-05-09 at 11:57 -0500, Benjamin Marzinski wrote:
> > > > When multipath reloads a device, it can either fail while loading
> > > > the
> > > > new table or while resuming the device. If it fails while
> > > > resuming
> > > > the
> > > > device, the device can get stuck in the suspended state.  To fix
> > > > this,
> > > > multipath needs to resume the device again so that it can
> > > > continue
> > > > using
> > > > the old table.
> > > > 
> > > > Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
> > > > ---
> > > >  libmultipath/devmapper.c | 19 ++++++++++++++++++-
> > > >  libmultipath/devmapper.h |  1 +
> > > >  2 files changed, 19 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/libmultipath/devmapper.c b/libmultipath/devmapper.c
> > > > index 2c4a13a..69b634b 100644
> > > > --- a/libmultipath/devmapper.c
> > > > +++ b/libmultipath/devmapper.c
> > > > @@ -396,7 +396,13 @@ int dm_addmap_reload(struct multipath *mpp,
> > > > char
> > > > *params, int flush)
> > > >  	if (r)
> > > >  		r = dm_simplecmd(DM_DEVICE_RESUME, mpp->alias,
> > > > !flush,
> > > >  				 1, udev_flags, 0);
> > > > -	return r;
> > > > +	if (r)
> > > > +		return r;
> > > > +
> > > > +	if (dm_is_suspended(mpp->alias))
> > > > +		dm_simplecmd(DM_DEVICE_RESUME, mpp->alias,
> > > > !flush,
> > > > 1,
> > > > +			     udev_flags, 0);
> > > > +	return 0;
> > > >  }
> > > 
> > > Why would the second DM_DEVICE_RESUME call succeed if the first one
> > > failed?
> > 
> > Because if the first resume fails, device-mapper rolls back to the
> > original table.
> 
> Ah. I didn't know that, and I'm likely to forget it again. Would you
> mind adding a short comment at that point in the code? 

Sure.

-Ben

> 
> Otherwise, ACK.
> 
> Martin
> 
> -- 
> Dr. Martin Wilck <mwilck@suse.com>, Tel. +49 (0)911 74053 2107
> SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
> HRB 21284 (AG Nürnberg)