[libmultipath] blacklist exceptions issues

the current situation is fishy. Ben pointed a true braino in the
code I introduced when restructuring the blacklist lib :

in _filter_path(), I test each _filter_*() for r!=0 , where I intented
to check for r>0.

r==0 implements  : "exit on first blacklist or exception match".
 r>0 implements  : "exit on first blacklist match".

With this later behaviour I can set things like that for max safety and
efficiency :

blacklist {
        devnode .*
        device {
                vendor .*
                product .*
        }
        wwid .*
}
blacklist_exceptions {
        devnode sd.*
        device {
                vendor IET.*
                product .*
        }
        wwid "1646561646265.*"
}

or pragmatically :

blacklist {
        devnode .*
        wwid .*
}
blacklist_exceptions {
        devnode sd.*
        wwid "1646561646265.*"
}

Working that out, I also realized there may be another small
misbehaviour :

First, a little background on path discovery operations :

1) /sys/block parsing shows devnode names
2) devnode names examination shows device identification strings
3) these strings help us choose a getuid helper, which finally shows
wwids

Meaning we want the devnode blacklisting to prevail over device and
wwid, in case we know we don't have device strings available (loop, dm-,
raw, ...)

Similarily, we want the device blacklist to prevail over wwid, in case
we know we don't have getuid callout available. I have no example for
this case though, so it shouldn't be as important as the previous one.

Problem is we challenge _filter_device() after _filter_wwid().
This can be easily shufled around.

1 files changed, 4 insertions, 6 deletions

diff --git a/libmultipath/blacklist.c b/libmultipath/blacklist.c
index 9a058f7..6297516 100644
--- a/libmultipath/blacklist.c
+++ b/libmultipath/blacklist.c
@@ -297,16 +297,14 @@ _filter_path (struct config * conf, struct path * pp)
 	int r;
 
 	r = _filter_devnode(conf->blist_devnode, conf->elist_devnode,pp->dev);
-	if (r)
-		return r;
-	r = _filter_wwid(conf->blist_wwid, conf->elist_wwid, pp->wwid);
-	if (r)
+	if (r > 0)
 		return r;
 	r = _filter_device(conf->blist_device, conf->elist_device,
 		 	   pp->vendor_id, pp->product_id);
-	if (r)
+	if (r > 0)
 		return r;
-	return 0;
+	r = _filter_wwid(conf->blist_wwid, conf->elist_wwid, pp->wwid);
+	return r;
 }
 
 int