block: Introduce bs->zero_beyond_eof

In 4146b46c42e0989cb5842e04d88ab6ccb1713a48 (block: Produce zeros when
protocols reading beyond end of file), we break qemu-iotests ./check
-qcow2 022. This happens because qcow2 temporarily sets ->growable = 1
for vmstate accesses (which are stored beyond the end of regular image
data).

We introduce the bs->zero_beyond_eof to allow qcow2_load_vmstate() to
disable ->zero_beyond_eof temporarily in addition to enable ->growable.

[Since the broken patch "block: Produce zeros when protocols reading
beyond end of file" has not been merged yet, I have applied this fix
*first* and will then apply the next patch to keep the tree bisectable.
-- Stefan]

Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/block.c b/block.c
index 45a545b..e655052 100644
--- a/block.c
+++ b/block.c
@@ -706,6 +706,7 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
 
     bs->open_flags = flags;
     bs->buffer_alignment = 512;
+    bs->zero_beyond_eof = true;
     open_flags = bdrv_open_flags(bs, flags);
     bs->read_only = !(open_flags & BDRV_O_RDWR);
 
@@ -1402,6 +1403,7 @@ void bdrv_close(BlockDriverState *bs)
         bs->valid_key = 0;
         bs->sg = 0;
         bs->growable = 0;
+        bs->zero_beyond_eof = false;
         QDECREF(bs->options);
         bs->options = NULL;