Re: [Qemu-devel] [PATCH v3 06/20] commit: Switch commit_run() to byte-based

[Jeff Cody <jcody@redhat.com>]

On Tue, Jun 27, 2017 at 02:24:44PM -0500, Eric Blake wrote:
> We are gradually converting to byte-based interfaces, as they are
> easier to reason about than sector-based.  Change the internal
> loop iteration of committing to track by bytes instead of sectors
> (although we are still guaranteed that we iterate by steps that
> are sector-aligned).
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> Reviewed-by: John Snow <jsnow@redhat.com>
> 

Reviewed-by: Jeff Cody <jcody@redhat.com>

> ---
> v2: no change
> ---
>  block/commit.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/block/commit.c b/block/commit.c
> index 6f67d78..c3a7bca 100644
> --- a/block/commit.c
> +++ b/block/commit.c
> @@ -143,17 +143,16 @@ static void coroutine_fn commit_run(void *opaque)
>  {
>      CommitBlockJob *s = opaque;
>      CommitCompleteData *data;
> -    int64_t sector_num, end;
> +    int64_t offset;
>      uint64_t delay_ns = 0;
>      int ret = 0;
> -    int n = 0;
> +    int n = 0; /* sectors */
>      void *buf = NULL;
>      int bytes_written = 0;
>      int64_t base_len;
> 
>      ret = s->common.len = blk_getlength(s->top);
> 
> -
>      if (s->common.len < 0) {
>          goto out;
>      }
> @@ -170,10 +169,9 @@ static void coroutine_fn commit_run(void *opaque)
>          }
>      }
> 
> -    end = s->common.len >> BDRV_SECTOR_BITS;
>      buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
> 
> -    for (sector_num = 0; sector_num < end; sector_num += n) {
> +    for (offset = 0; offset < s->common.len; offset += n * BDRV_SECTOR_SIZE) {
>          bool copy;
> 
>          /* Note that even when no rate limit is applied we need to yield
> @@ -185,15 +183,13 @@ static void coroutine_fn commit_run(void *opaque)
>          }
>          /* Copy if allocated above the base */
>          ret = bdrv_is_allocated_above(blk_bs(s->top), blk_bs(s->base),
> -                                      sector_num,
> +                                      offset / BDRV_SECTOR_SIZE,
>                                        COMMIT_BUFFER_SIZE / BDRV_SECTOR_SIZE,
>                                        &n);
>          copy = (ret == 1);
> -        trace_commit_one_iteration(s, sector_num * BDRV_SECTOR_SIZE,
> -                                   n * BDRV_SECTOR_SIZE, ret);
> +        trace_commit_one_iteration(s, offset, n * BDRV_SECTOR_SIZE, ret);
>          if (copy) {
> -            ret = commit_populate(s->top, s->base,
> -                                  sector_num * BDRV_SECTOR_SIZE,
> +            ret = commit_populate(s->top, s->base, offset,
>                                    n * BDRV_SECTOR_SIZE, buf);
>              bytes_written += n * BDRV_SECTOR_SIZE;
>          }
> -- 
> 2.9.4
>