From f0ad5712d5d15ff272b9e107910be4aae468fb3d Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Wed, 4 Sep 2013 19:00:32 +0200
Subject: [PATCH] block: return BDRV_BLOCK_ZERO past end of backing file
If the sectors are unallocated and we are past the end of the
backing file, they will read as zero.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
block.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/block.c b/block.c
index aa9ec835a7..82bbd6c933 100644
--- a/block.c
+++ b/block.c
@@ -3102,8 +3102,16 @@ static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
return ret;
}
- if (!(ret & BDRV_BLOCK_DATA) && bdrv_has_zero_init(bs)) {
- ret |= BDRV_BLOCK_ZERO;
+ if (!(ret & BDRV_BLOCK_DATA)) {
+ if (bdrv_has_zero_init(bs)) {
+ ret |= BDRV_BLOCK_ZERO;
+ } else {
+ BlockDriverState *bs2 = bs->backing_hd;
+ int64_t length2 = bdrv_getlength(bs2);
+ if (length2 >= 0 && sector_num >= (length2 >> BDRV_SECTOR_BITS)) {
+ ret |= BDRV_BLOCK_ZERO;
+ }
+ }
}
return ret;
}