multipathd currently marks paths as down if they don't have a sysfs
"state" attribute.

Unfortunately, this makes multipathd unusable with Linux virtio_blk
devices, since they don't have this attribute. I need to use multipath
with virtio for consistency with a real configuration when testing a
clustered NAS system - yeah, I'm that guy again... :-)

One way of working around this might be to have path_offline() return
PATH_UP for all devices that don't have a sysfs "state" attribute,
instead of PATH_WILD. However, I'm guessing the current behaviour might
exist for a reason.

The following patch makes path_offline() always return PATH_UP instead
of PATH_WILD for virtio_blk devices. I've implemented the nested if
statements as below to change the code flow as little as possible
when sysfs_get_state() actually succeeds, which I assume is usually the
case. If nobody is feeling paranoid then the check for virtio_blk
could obviously be done before the call to sysfs_get_state().

If people think this patch is too specific then at least it can be
used to start a discussion... ;-)


commit fc2eb79ba3bca70702568cce73be9daffaf3f149
Author: Martin Schwenke <martin@meltin.net>
Date: Thu May 5 14:39:29 2011 +1000

Don't mark a virtio_blk path offline if it has no sysfs "state" attribute.

Signed-off-by: Martin Schwenke <martin@meltin.net>

diff --git a/libmultipath/discovery.c b/libmultipath/discovery.c
index aa25cc4..1155f68 100644
--- a/libmultipath/discovery.c
+++ b/libmultipath/discovery.c
@@ -722,8 +722,15 @@ path_offline (struct path * pp)
return PATH_WILD;
}

- if (sysfs_get_state(parent, buff, SCSI_STATE_SIZE))
- return PATH_WILD;
+ if (sysfs_get_state(parent, buff, SCSI_STATE_SIZE)) {
+ if (!strncmp(parent->driver, "virtio_blk", 10)) {
+ condlog(3, "%s: virtio_blk is always up", pp->dev);
+ return PATH_UP;
+ } else {
+ condlog(3, "%s: failed to get "state"", pp->dev);
+ return PATH_WILD;
+ }
+ }

condlog(3, "%s: state = %s", pp->dev, buff);


peace & happiness,
martin
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