[Qemu-devel] [PATCH v2 17/17] block: look for zero blocks in bs->file

[Paolo Bonzini]

Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
 block.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/block.c b/block.c
index 557ce29..2d7d71f 100644
--- a/block.c
+++ b/block.c
@@ -2977,7 +2977,7 @@ static int64_t coroutine_fn 
bdrv_co_get_block_status(BlockDriverState *bs,
                                                      int nb_sectors, int *pnum)
 {
     int64_t n;
-    int64_t ret;
+    int64_t ret, ret2;
 
     if (sector_num >= bs->total_sectors) {
         *pnum = 0;
@@ -3003,6 +3003,14 @@ static int64_t coroutine_fn 
bdrv_co_get_block_status(BlockDriverState *bs,
         ret |= BDRV_BLOCK_ZERO;
     }
 
+    if (bs->file &&
+        (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
+        (ret & BDRV_BLOCK_OFFSET_VALID)) {
+        ret2 = bdrv_co_get_block_status(bs->file, ret >> BDRV_SECTOR_BITS,
+                                        *pnum, pnum);
+        ret |= (ret2 & BDRV_BLOCK_ZERO);
+    }
+
     return ret;
 }
 
-- 
1.8.3.1