[dm-devel] [PATCH 44/54] libmultipath: adopt_paths(): don't bail out on single path failure

[Benjamin Marzinski]

On Wed, Aug 05, 2020 at 02:05:00PM +0200, Martin Wilck wrote:
> On Fri, 2020-07-17 at 16:25 -0500, Benjamin Marzinski wrote:
> > On Thu, Jul 09, 2020 at 12:36:13PM +0200, mwilck at suse.com wrote:
> > > From: Martin Wilck <mwilck at suse.com>
> > > 
> > > If pathinfo fails for one path to be adopted, we currently
> > > fail the entire function. This may cause ev_add_path() for a valid
> > > path to fail because some other path is broken. Fix it by just
> > > skipping paths that don't look healthy.
> > 
> > This looks problematic to me.  While I agree that we shouldn't make
> > ev_add_path fail because some other path failed, but what about if
> > the
> > path we are trying to add fails in pathinfo().  In this case
> > multipathd
> > won't orphan the path and it will report "path added to devmap", even
> > though it wasn't. Also what is the correct response for when you try
> > to create a multipath device but none of the paths can be added.
> > Should multipathd create a device with no paths? 
> 
> There are 3 callers of adopt_path():
> 
>  1 add_map_with_path()
>  2 ev_add_path()
>  3 update_map()
> 
> adopt_paths() only ever adds new paths to a map, so in case 3), the map
> would not come out without paths unless it had been empty before
> already. For this caller, my patch is definitely an improvement.
> 
> For 1) and 2), we are adding a specific path, so we should test in the
> caller whether that specific path was successfully added, and fail
> otherwise. Would that address your concern?

That sounds reasonable

-Ben

> 
> Regards,
> Martin
> 
>