On Wed, 07/17 13:04, Ian Main wrote: > This patch adds the original source drive as a backing drive to our target > image so that the target image will appear complete during backup. This > is especially useful for SYNC_MODE_NONE as it allows export via NBD to > have a complete point-in-time snapshot available for export. > > Signed-off-by: Ian Main <im...@redhat.com> > --- > block/backup.c | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/block/backup.c b/block/backup.c > index 68abd23..e086e76 100644 > --- a/block/backup.c > +++ b/block/backup.c > @@ -323,6 +323,10 @@ static void coroutine_fn backup_run(void *opaque) > > hbitmap_free(job->bitmap); > > + /* Set the target backing drive back to NULL before calling delete or > + * it will also delete the underlying drive. */ > + target->backing_hd = NULL; > + > bdrv_iostatus_disable(target); > bdrv_delete(target); > > @@ -362,6 +366,15 @@ void backup_start(BlockDriverState *bs, BlockDriverState > *target, > return; > } > > + /* Manually set the backing hd to be the backup source drive so > + * that all reads done while we are backing up will be passed > + * on to the original source drive. This allows reading from the > + * image while the backup is in progress, or in the case of > + * SYNC_MODE_NONE allows a complete image to be present for export. > + * Note that we do this for all modes including SYNC_MODE_TOP as > + * even then it allows on-the-fly reading. */ > + target->backing_hd = bs; > +
Also set target->backing_file and target->backing_format here? Paolo? Thanks. Fam
