Il 28/08/2012 16:26, Stefan Hajnoczi ha scritto:
> It is possible to create an image that is larger than its backing file.
> Reading beyond the end of the backing file produces zeroes if no writes
> have been made to those sectors in the image file.
>
> This patch finishes streaming early when the end of the backing file is
> reached. Without this patch the block job hangs and continually tries
> to stream the first sectors beyond the end of the backing file.
>
> To reproduce the hung block job bug:
>
> $ qemu-img create -f qcow2 backing.qcow2 128M
> $ qemu-img create -f qcow2 -o backing_file=backing.qcow2 image.qcow2 6G
> $ qemu -drive if=virtio,cache=none,file=image.qcow2
> (qemu) block_stream virtio0
> (qemu) info block-jobs
>
> The qemu-iotests 030 streaming test still passes.
>
> Signed-off-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
> ---
> block/stream.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/block/stream.c b/block/stream.c
> index 37c4652..c4f87dd 100644
> --- a/block/stream.c
> +++ b/block/stream.c
> @@ -122,6 +122,12 @@ wait:
> * known-unallocated area [sector_num, sector_num+n). */
> ret = bdrv_co_is_allocated_above(bs->backing_hd, base,
> sector_num, n, &n);
> +
> + /* Finish early if end of backing file has been reached */
> + if (ret == 0 && n == 0) {
> + n = end - sector_num;
> + }
Reviewed-by: Paolo Bonzini <pbonz...@gnu.org>
> copy = (ret == 1);
> }
> trace_stream_one_iteration(s, sector_num, n, ret);
>
