block: Drop unused .bdrv_has_zero_init_truncate

Now that there are no clients of bdrv_has_zero_init_truncate, none of
the drivers need to worry about providing it.

What's more, this eliminates a source of some confusion: a literal
reading of the documentation as written in ceaca56f and implemented in
commit 1dcaf527 claims that a driver which returns 0 for
bdrv_has_zero_init_truncate() must not return 1 for
bdrv_has_zero_init(); this condition was violated for parallels, qcow,
and sometimes for vdi, although in practice it did not matter since
those drivers also lacked .bdrv_co_truncate.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200428202905.770727-10-eblake@redhat.com>
Acked-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 0 insertions, 21 deletions

diff --git a/block.c b/block.c
index cf5c19b..0653ccb 100644
--- a/block.c
+++ b/block.c
@@ -5284,27 +5284,6 @@ int bdrv_has_zero_init(BlockDriverState *bs)
     return 0;
 }
 
-int bdrv_has_zero_init_truncate(BlockDriverState *bs)
-{
-    if (!bs->drv) {
-        return 0;
-    }
-
-    if (bs->backing) {
-        /* Depends on the backing image length, but better safe than sorry */
-        return 0;
-    }
-    if (bs->drv->bdrv_has_zero_init_truncate) {
-        return bs->drv->bdrv_has_zero_init_truncate(bs);
-    }
-    if (bs->file && bs->drv->is_filter) {
-        return bdrv_has_zero_init_truncate(bs->file->bs);
-    }
-
-    /* safe default */
-    return 0;
-}
-
 bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs)
 {
     BlockDriverInfo bdi;