block: Add bdrv_refresh_filename()

Some block devices may not have a filename in their BDS; and for some,
there may not even be a normal filename at all. To work around this, add
a function which tries to construct a valid filename for the
BDS.filename field.

If a filename exists or a block driver is able to reconstruct a valid
filename (which is placed in BDS.exact_filename), this can directly be
used.

If no filename can be constructed, we can still construct an options
QDict which is then converted to a JSON object and prefixed with the
"json:" pseudo protocol prefix. The QDict is placed in
BDS.full_open_options.

For most block drivers, this process can be done automatically; those
that need special handling may define a .bdrv_refresh_filename() method
to fill BDS.exact_filename and BDS.full_open_options themselves.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/block/block.h b/include/block/block.h
index e94b701667..8f4ad16d8f 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -274,6 +274,7 @@ int coroutine_fn bdrv_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
 BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
     const char *backing_file);
 int bdrv_get_backing_file_depth(BlockDriverState *bs);
+void bdrv_refresh_filename(BlockDriverState *bs);
 int bdrv_truncate(BlockDriverState *bs, int64_t offset);
 int64_t bdrv_nb_sectors(BlockDriverState *bs);
 int64_t bdrv_getlength(BlockDriverState *bs);