Re: [Qemu-devel] [PATCH v6] migration/block: use blk_pwrite_zeroes for each zero cluster

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Thu, Apr 13, 2017 at 10:34:28AM +0800, jemmy858585@gmail.com wrote:
> From: Lidong Chen <lidongchen@tencent.com>
> 
> BLOCK_SIZE is (1 << 20), qcow2 cluster size is 65536 by default,
> this may cause the qcow2 file size to be bigger after migration.
> This patch checks each cluster, using blk_pwrite_zeroes for each
> zero cluster.
> 
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Lidong Chen <lidongchen@tencent.com>
> ---
> v6 changelog:
> Fix up some grammar in the comment.
> ---
>  migration/block.c | 35 +++++++++++++++++++++++++++++++++--
>  1 file changed, 33 insertions(+), 2 deletions(-)

I fixed the following gcc warning when merging the patch:

  migration/block.c:958:25: error: ‘cluster_size’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
                            buffer_is_zero(cur_buf, cluster_size)) {

Thanks, applied to my block-next tree:
https://github.com/stefanha/qemu/commits/block-next

Stefan

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