Re: [Qemu-block] [PATCH 6/8] block/backup: teach backup_cow_with_bounce_buffer to copy more at once

[Max Reitz]

On 07.08.19 10:07, Vladimir Sementsov-Ogievskiy wrote:
> backup_cow_with_offload can transfer more than on cluster. Let
> backup_cow_with_bounce_buffer behave similarly. It reduces number
> of IO and there are no needs to copy cluster by cluster.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
>  block/backup.c | 30 +++++++++++++++---------------
>  1 file changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/block/backup.c b/block/backup.c
> index eb41e4af4f..c765c073ad 100644
> --- a/block/backup.c
> +++ b/block/backup.c
> @@ -104,22 +104,24 @@ static int coroutine_fn 
> backup_cow_with_bounce_buffer(BackupBlockJob *job,
>                                                        int64_t start,
>                                                        int64_t end,
>                                                        bool is_write_notifier,
> -                                                      bool *error_is_read,
> -                                                      void **bounce_buffer)
> +                                                      bool *error_is_read)
>  {
>      int ret;
>      BlockBackend *blk = job->common.blk;
>      int nbytes;
>      int read_flags = is_write_notifier ? BDRV_REQ_NO_SERIALISING : 0;
> +    void *bounce_buffer = blk_try_blockalign(blk, end);

s/end/end - start/ (or probably rather s/end/nbytes/ after that has been
set).

Rest looks good.

Max

>  
> -    assert(QEMU_IS_ALIGNED(start, job->cluster_size));
> -    bdrv_reset_dirty_bitmap(job->copy_bitmap, start, job->cluster_size);
> -    nbytes = MIN(job->cluster_size, job->len - start);
> -    if (!*bounce_buffer) {
> -        *bounce_buffer = blk_blockalign(blk, job->cluster_size);
> +    if (!bounce_buffer) {
> +        return -ENOMEM;
>      }

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