[Qemu-devel] [PATCH 12/12] block/get_block_status: fix BDRV_BLOCK_ZERO for unallocated blocks

[Peter Lieven <pl@kamp.de>]

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

Signed-off-by: Peter Lieven <pl@kamp.de>
---
 block.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/block.c b/block.c
index 282943b..6698c10 100644
--- a/block.c
+++ b/block.c
@@ -3153,8 +3153,10 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
         return ret;
     }
 
-    if (!(ret & BDRV_BLOCK_DATA)) {
-        if (bdrv_has_zero_init(bs)) {
+    if (!(ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO)) {
+        BlockDriverInfo bdi;
+        if (bdrv_get_info(bs, &bdi) == 0 &&
+            bdi.discard_zeroes) {
             ret |= BDRV_BLOCK_ZERO;
         } else if (bs->backing_hd) {
             BlockDriverState *bs2 = bs->backing_hd;
-- 
1.7.9.5