On Tue, Oct 17, 2017 at 16:41:00 +0200, Kevin Wolf wrote: > Am 12.10.2017 um 16:14 hat Peter Krempa geschrieben: > > When refering to a backing file of an image via node name > > bdrv_open_backing_file would add the 'driver' option to the option list > > filling it with the backing format driver. This breaks construction of > > the backing chain via -blockdev, as bdrv_open_inherit reports an error > > if both 'reference' and 'options' are provided. > > > > Signed-off-by: Peter Krempa <pkre...@redhat.com> > > If you don't mind, I'd add a specific example to the commit message:
I certainly don't mind. I was frustrated after some attempts to find bugs in my code using it before looking into qemu so I forgot to add the info. (Also it would take me some time to figure out that I have the backing format specified in the overlay image). > > $ qemu-img create -f raw /tmp/backing.raw 64M > $ qemu-img create -f qcow2 -F raw -b /tmp/backing.raw /tmp/test.qcow2 > $ qemu-system-x86_64 \ > -blockdev driver=file,filename=/tmp/backing.raw,node-name=backing \ > -blockdev > driver=qcow2,file.driver=file,file.filename=/tmp/test.qcow2,node-name=root,backing=backing > qemu-system-x86_64: -blockdev > driver=qcow2,file.driver=file,file.filename=/tmp/test.qcow2,node-name=root,backing=backing: > Could not open backing file: Cannot reference an existing block device with > additional options or a new filename > > > diff --git a/block.c b/block.c > > index 46eb1728da..684cb018da 100644 > > --- a/block.c > > +++ b/block.c > > @@ -2245,7 +2245,8 @@ int bdrv_open_backing_file(BlockDriverState *bs, > > QDict *parent_options, > > goto free_exit; > > } > > > > - if (bs->backing_format[0] != '\0' && !qdict_haskey(options, "driver")) > > { > > + if (!reference && > > + bs->backing_format[0] != '\0' && !qdict_haskey(options, "driver")) > > { > > qdict_put_str(options, "driver", bs->backing_format); > > } > > Looks good to me. Thanks.
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