Libguestfs - Jan 2023 - [PATCH nbdkit] New plugin: blkio [incomplete]

This is upstream in nbdkit now:
https://gitlab.com/nbdkit/nbdkit/-/tree/master/plugins/blkio

Another question:

(6) vhost-user + "read-only" property acts a bit strangely.  After
opening virtio-blk-vhost-user it throws an EROFS error if you try to
"blkio_start" it.  However if you set the "read-only"
property to true
then it's OK to start it, and subsequent read operations work too.

I would expect that any device can be started without needing to set
this property, and in general I don't understand why vhost-user is r/o
since everything I read about it seems to indicate it's a general
purpose writable protocol.

Rich.

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On Sat, Jan 07, 2023 at 07:44:37PM +0000, Richard W.M. Jones
wrote:
> 
> This is upstream in nbdkit now:
> https://gitlab.com/nbdkit/nbdkit/-/tree/master/plugins/blkio
> 
> Another question:
> 
> (6) vhost-user + "read-only" property acts a bit strangely. 
After
> opening virtio-blk-vhost-user it throws an EROFS error if you try to
> "blkio_start" it.  However if you set the "read-only"
property to true
> then it's OK to start it, and subsequent read operations work too.
> 
> I would expect that any device can be started without needing to set
> this property, and in general I don't understand why vhost-user is r/o
> since everything I read about it seems to indicate it's a general
> purpose writable protocol.
I guess the vhost-user-blk server is read-only and that's why it's
refusing to blkio_start() unless readonly was set to true.

If you're using qemu-storage-daemon, set the writable=on parameter on
the export.

Stefan
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