Re: [Xen-devel] [PATCH 1/1] tools/hotplug: Scan xenstore once when attaching shared images files

[Mike Latimer <mlatimer@xxxxxxxx>]

Hi George,

On Thursday, October 01, 2015 10:51:08 AM George Dunlap wrote:
> >        then
> > -        echo 'local'
> > +        echo "local $d"
> >          return
> >        fi
> >      fi
> > @@ -90,13 +107,13 @@ check_sharing()
> >      do
> >        d=$(xenstore_read_default "$base_path/$dom/$dev/physical-device" 
"")
> >
> > -      if [ "$d" = "$devmm" ]
> > +      if [ -n "$d" ] && [[ "$devmm" == *"$d,"* ]]
> 
> Is there a risk here of aliasing?  i.e., suppose that a device with
> major-minor '11:1' that's already in use by a guest, and you're
> checking to see if you can share device '1:1' with a different guest.
> Won't this match, and (falsely) reject 1:1, even though it's not being
> used by anyone else?
> 
> Would it make more sense maybe to initialize devmm to ",", and then
> search for *",$d,"*?

Ah, thanks for catching that! I caught the "1:11" case, but somehow missed the 
"11:1" side.

I'll address that, and your other comments and submit a V2 shortly.

-Mike

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