[dm-devel] [PATCH v1 0/5] dm: dm-user: New target that proxies BIOs to userspace

[Christoph Hellwig]

FYI, a few years ago I spent some time helping a customer to prepare
their block device in userspace using fuse code for upstreaming, but
at some point they abandoned the project.  But if for some reason we
don't want to use nbd I think a driver using the fuse infrastructure
would be the next logical choice.