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 <[email protected]> --- block.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/block.c b/block.c index ecae287..cf52489 100644 --- a/block.c +++ b/block.c @@ -3028,8 +3028,16 @@ 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; } -- 1.8.3.1
