Message ID | 20161130011851.24696-23-mreitz@redhat.com |
---|---|
State | New |
Headers | show |
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 <mreitz@redhat.com> > --- > 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); > } > } >
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 <mreitz@redhat.com> >> --- >> 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
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) && + !generate_json_filename) + { strcpy(bs->exact_filename, bs->file->bs->exact_filename); } }
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 <mreitz@redhat.com> --- block.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-)