commit c3d8688470a33feb0ea78c006b4399d50c13185e
author Peter Lieven <pl@kamp.de> Thu Oct 24 12:07:04 2013 +0200
committer Kevin Wolf <kwolf@redhat.com> Thu Nov 28 10:30:52 2013 +0100
tree b9fcb57cd372cbdaec924fb19ea266f0fde0a87e
parent d75cbb5e68f5a7d64248ba89399a7f2073231de5

block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks

this patch does 2 things:
a) only do additional call outs if BDRV_BLOCK_ZERO is not already set.
b) use the newly introduced bdrv_unallocated_blocks_are_zero()
   to return the zero state of an unallocated block. the used callout
   to bdrv_has_zero_init() is only valid right after bdrv_create.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block.c

diff --git a/block.c b/block.c
index c390f20..e22b55f 100644
--- a/block.c
+++ b/block.c
@@ -3272,8 +3272,8 @@
                                      *pnum, pnum);
     }
 
-    if (!(ret & BDRV_BLOCK_DATA)) {
-        if (bdrv_has_zero_init(bs)) {
+    if (!(ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO)) {
+        if (bdrv_unallocated_blocks_are_zero(bs)) {
             ret |= BDRV_BLOCK_ZERO;
         } else if (bs->backing_hd) {
             BlockDriverState *bs2 = bs->backing_hd;