On 11.01.2017 17:29, Max Reitz wrote: > 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.
And now it turns out that it's again more complicated... blkdebug is a protocol block driver that has a bs->file. So when using blkdebug, bs->file->bs->file is set on the format layer. So I guess I'll have to resort to testing bs->file->bs->drv->bdrv_file_open... Max
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