Re: [Qemu-devel] [PATCH v3 1/2] block: Do not prematurely remove "filename"

[Kevin Wolf <kwolf@redhat.com>]

Am 26.06.2014 um 23:38 hat Max Reitz geschrieben:
> If "filename" is removed from the options QDict before entering
> bdrv_open_common(), it cannot be stored in the BDS.  Therefore, wait
> until it has been copied there and remove it from the options only
> afterwards.
> 
> This fixes "filename" in the BDS being empty for block drivers which do
> not need the filename because they have parsed it already (e.g. NBD).
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>

I can't say I like this approach. It looks a bit odd to pass a boolean
variable to bdrv_open(), and in some other function called from there
the cleanup is done that logically really belong to bdrv_fill_options().

More importantly, the goal was to get rid of the filename and handle
everything through the options so that we get a uniform state again.
This would involve replacing bs->filename by a new callback function in
BlockDriver that constructs a filename that describes the BDS. This way
we would get useful output not only for "nbd:localhost:10809", but also
for "driver=nbd,host=localhost".

In hard cases, the callback might just use "json:{...}" syntax. This
suggests that maybe in the end we'll want to have two different
callbacks, one giving a short human-readable description
('localhost:10809') and another one giving something that can be used on
the command line ('json:{"driver": "nbd", "host": "localhost", "ipv6":
true}').

Kevin