Re: [PATCH 02/18] fuse: Allow exporting BDSs via FUSE

[Eric Blake]

On 12/19/19 8:38 AM, Max Reitz wrote:
> fuse-export-add allows mounting block graph nodes via FUSE on some
> existing regular file.  That file should then appears like a raw disk
> image, and accesses to it result in accesses to the exported BDS.
>
> Right now, we only set up the mount point and tear all mount points down
> in bdrv_close_all().  We do not implement any access functions, so
> accessing the mount point only results in errors.  This will be
> addressed by a followup patch.
>
> The set of exported nodes is kept in a hash table so we can later add a
> fuse-export-remove that allows unmounting.

Before I review this, a quick question:

How does this compare to the recently added nbdfuse?
https://www.redhat.com/archives/libguestfs/2019-October/msg00080.html

Or put another way, maybe we get the same effect by combining qemu-nbd 
with nbdfuse, but this new utility would cut out a middleman for more 
efficiency, right?


> +++ b/block/fuse.c
> @@ -0,0 +1,260 @@
> +/*
> + * Present a block device as a raw image through FUSE
> + *
> + * Copyright (c) 2019 Max Reitz <address@hidden>


--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org