Re: [Qemu-devel] [PATCH v5 11/22] block: Allow block devices without files

[Max Reitz]

On 13.12.2013 21:06, Kevin Wolf wrote:
> Am 13.12.2013 um 18:10 hat Max Reitz geschrieben:
> > blkdebug and blkverify will, in order to retain compatibility, not
> > support the field "file" implicitly through bdrv_open(). In order to be
> > able to use those drivers without giving a filename anyway, it is
> > necessary to be able to have block devices without files implicitly
> > opened by bdrv_open(). This is the case, if there was neither a file
> > name, a reference to an existing block device to use as a file nor
> > options specific to the file.
> >
> > Signed-off-by: Max Reitz <address@hidden>
> > ---
> >   block.c | 15 +++++++++------
> >   1 file changed, 9 insertions(+), 6 deletions(-)
> >
> > diff --git a/block.c b/block.c
> > index bef4f82..9659eb5 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -1145,11 +1145,14 @@ int bdrv_open(BlockDriverState *bs, const char 
> > *filename, QDict *options,
> >       qdict_extract_subqdict(options, &file_options, "file.");
> >       file_reference = qdict_get_try_str(options, "file");
> >   
> > -    ret = bdrv_file_open(&file, filename, file_reference, file_options,
> > -                         bdrv_open_flags(bs, flags | BDRV_O_UNMAP), 
> > &local_err);
> > -    qdict_del(options, "file");
> > -    if (ret < 0) {
> > -        goto fail;
> > +    if (filename || file_reference || qdict_size(file_options)) {
> > +        ret = bdrv_file_open(&file, filename, file_reference, file_options,
> > +                             bdrv_open_flags(bs, flags | BDRV_O_UNMAP),
> > +                             &local_err);
> > +        qdict_del(options, "file");
> > +        if (ret < 0) {
> > +            goto fail;
> > +        }
> >       }
> >   
> >       /* Find the right image format driver */
> > @@ -1178,7 +1181,7 @@ int bdrv_open(BlockDriverState *bs, const char *filename, 
> > QDict *options,
> Manually adding more context before the next hunk:
>
> >      if (!drv) {
> >          ret = find_image_format(file, filename, &drv, &local_err);
> >      }
> We can get file == NULL now, which will cause a segfault in
> find_image_format. (For a reproducer of the segfault, try
> 'x86_64-softmmu/qemu-system-x86_64 -drive foo=bar')

Right, thanks.

Max