Re: [Qemu-devel] [PATCH v2 1/1] mirror: do not increase offset during initial zero_or_discard phase

[Jeff Cody]

On Thu, Feb 02, 2017 at 05:25:15PM +0300, Denis V. Lunev wrote:
> From: Anton Nefedov <address@hidden>
> 
> If explicit zeroing out before mirroring is required for the target image,
> it moves the block job offset counter to EOF, then offset and len counters
> count the image size twice. There is no harm but stats are confusing,
> specifically the progress of the operation is always reported as 99% by
> management tools.
> 
> The patch skips offset increase for the first "technical" pass over the
> image. This should not cause any further harm.
> 
> Signed-off-by: Anton Nefedov <address@hidden>
> Signed-off-by: Denis V. Lunev <address@hidden>
> CC: Jeff Cody <address@hidden>
> CC: Kevin Wolf <address@hidden>
> CC: Max Reitz <address@hidden>
> CC: Eric Blake <address@hidden>
> ---
> Changes from v1:
> - changed the approach - we do not allow to increase the offset rather then
>   to move it back
> - description rewritten
> - kludges to tests are removed as not actually needed with this approach
> 
>  block/mirror.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/block/mirror.c b/block/mirror.c
> index 301ba92..f100f5d 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -69,6 +69,7 @@ typedef struct MirrorBlockJob {
>      bool waiting_for_io;
>      int target_cluster_sectors;
>      int max_iov;
> +    bool initial_zeroing_ongoing;
>  } MirrorBlockJob;
>  
>  typedef struct MirrorOp {
> @@ -117,9 +118,10 @@ static void mirror_iteration_done(MirrorOp *op, int ret)
>          if (s->cow_bitmap) {
>              bitmap_set(s->cow_bitmap, chunk_num, nb_chunks);
>          }
> -        s->common.offset += (uint64_t)op->nb_sectors * BDRV_SECTOR_SIZE;
> +        if (!s->initial_zeroing_ongoing) {
> +            s->common.offset += (uint64_t)op->nb_sectors * BDRV_SECTOR_SIZE;
> +        }
>      }
> -
>      qemu_iovec_destroy(&op->qiov);
>      g_free(op);
>  
> @@ -566,6 +568,7 @@ static int coroutine_fn mirror_dirty_init(MirrorBlockJob 
> *s)
>              return 0;
>          }
>  
> +        s->initial_zeroing_ongoing = true;
>          for (sector_num = 0; sector_num < end; ) {
>              int nb_sectors = MIN(end - sector_num,
>                  QEMU_ALIGN_DOWN(INT_MAX, s->granularity) >> 
> BDRV_SECTOR_BITS);
> @@ -573,6 +576,7 @@ static int coroutine_fn mirror_dirty_init(MirrorBlockJob 
> *s)
>              mirror_throttle(s);
>  
>              if (block_job_is_cancelled(&s->common)) {
> +                s->initial_zeroing_ongoing = false;
>                  return 0;
>              }
>  
> @@ -587,6 +591,7 @@ static int coroutine_fn mirror_dirty_init(MirrorBlockJob 
> *s)
>          }
>  
>          mirror_wait_for_all_io(s);
> +        s->initial_zeroing_ongoing = false;
>      }
>  
>      /* First part, loop on the sectors and initialize the dirty bitmap.  */
> -- 
> 2.7.4
> 

Thanks,

Applied to my block branch:

git://github.com/codyprime/qemu-kvm-jtc.git block

-Jeff