On 30.11.2016 02:18, Max Reitz wrote: > If the a format BDS's file BDS is in turn a format BDS, we cannot simply > use the same filename, because when opening a BDS tree based on a > filename alone, qemu will create only one format node on top of one > protocol node (disregarding a potential backing file). > > Signed-off-by: Max Reitz <[email protected]> > --- > block.c | 17 ++++++++++++++--- > 1 file changed, 14 insertions(+), 3 deletions(-) > > diff --git a/block.c b/block.c > index ec25cbf..71c14f4 100644 > --- a/block.c > +++ b/block.c > @@ -4095,9 +4095,20 @@ void bdrv_refresh_filename(BlockDriverState *bs) > > bs->exact_filename[0] = '\0'; > > - /* If no specific options have been given for this BDS, the filename > of > - * the underlying file should suffice for this one as well */ > - if (bs->file->bs->exact_filename[0] && !generate_json_filename) { > + /* We can use the underlying file's filename if: > + * - it has a filename, > + * - the file is a protocol BDS, and > + * - opening that file (as this BDS's format) will automatically > create > + * the BDS tree we have right now, that is: > + * - the user did not significantly change this BDS's behavior with > + * some explicit options > + * - no non-file child of this BDS has been overridden by the user > + * Both of these conditions are represented by > generate_json_filename. > + */ > + if (bs->file->bs->exact_filename[0] && > + (bs->file->bs->open_flags & BDRV_O_PROTOCOL) &&
This was a nice try, but as it turns out, this flag does not have to
always set for protocol BDSs. A more reliable test is:
!bs->file->bs->file
This test may also be a bit more intuitive: We can copy exact_filename
in one layer from bs->file, but not through two layers.
Max
> + !generate_json_filename)
> + {
> strcpy(bs->exact_filename, bs->file->bs->exact_filename);
> }
> }
>
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