[dm-devel] multipath - unable to use multiple active paths at once, and deprecated example in docs

[Martin Wilck]

On Fri, 2019-11-22 at 13:27 -0700, Drew Hastings wrote:
> My use case doesn't lend itself well to multipathd, so I'm trying to
> implement multipathing with device mapper directly.
> 
> My only assumption is that the multipath features, in particular
> queue_mode bio, prevent this from behaving properly. If that is the
> case, why can this not be achieved with bios, as this is not a
> limitation of raid1 (which will load balance read IO to device mapper
> targets). I also believe this is the only feature option that is
> viable for me, since this multipath device is on top of device mapper
> targets.

I think you are seeing this FIXME:

https://elixir.bootlin.com/linux/v4.19.79/source/drivers/md/dm-mpath.c#L612

For your testing, perhaps you just remove that if(!pgpath) condition.

Regards,
Martin