Re: [Qemu-devel] [PATCH 4/4] block/dirty-bitmap: refactor bdrv_dirty_bitmap_next

[John Snow <jsnow@redhat.com>]

On 9/16/19 10:19 AM, Vladimir Sementsov-Ogievskiy wrote:
> bdrv_dirty_bitmap_next is always used in same pattern. So, split it
> into _next and _first, instead of combining two functions into one and
> add FOR_EACH_DIRTY_BITMAP macro.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  include/block/dirty-bitmap.h   |  9 +++++++--
>  block.c                        |  4 +---
>  block/dirty-bitmap.c           | 11 +++++++----
>  block/qcow2-bitmap.c           |  8 ++------
>  migration/block-dirty-bitmap.c |  4 +---
>  5 files changed, 18 insertions(+), 18 deletions(-)

I'm not as sure that this is an improvement.

> 
> diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
> index 4c58d922e4..89e52db7ec 100644
> --- a/include/block/dirty-bitmap.h
> +++ b/include/block/dirty-bitmap.h
> @@ -97,8 +97,13 @@ bool bdrv_dirty_bitmap_get_autoload(const BdrvDirtyBitmap *bitmap);
>  bool bdrv_dirty_bitmap_get_persistence(BdrvDirtyBitmap *bitmap);
>  bool bdrv_dirty_bitmap_inconsistent(const BdrvDirtyBitmap *bitmap);
>  bool bdrv_has_changed_persistent_bitmaps(BlockDriverState *bs);
> -BdrvDirtyBitmap *bdrv_dirty_bitmap_next(BlockDriverState *bs,
> -                                        BdrvDirtyBitmap *bitmap);
> +
> +BdrvDirtyBitmap *bdrv_dirty_bitmap_first(BlockDriverState *bs);
> +BdrvDirtyBitmap *bdrv_dirty_bitmap_next(BdrvDirtyBitmap *bitmap);
> +#define FOR_EACH_DIRTY_BITMAP(bs, bitmap) \
> +for (bitmap = bdrv_dirty_bitmap_first(bs); bitmap; \
> +     bitmap = bdrv_dirty_bitmap_next(bitmap))
> +
>  char *bdrv_dirty_bitmap_sha256(const BdrvDirtyBitmap *bitmap, Error **errp);
>  int64_t bdrv_dirty_bitmap_next_zero(BdrvDirtyBitmap *bitmap, uint64_t offset,
>                                      uint64_t bytes);
> diff --git a/block.c b/block.c
> index 5944124845..96c2c5ae2d 100644
> --- a/block.c
> +++ b/block.c
> @@ -5363,9 +5363,7 @@ static void coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs,
>          }
>      }
>  
> -    for (bm = bdrv_dirty_bitmap_next(bs, NULL); bm;
> -         bm = bdrv_dirty_bitmap_next(bs, bm))
> -    {
> +    FOR_EACH_DIRTY_BITMAP(bs, bm) {
>          bdrv_dirty_bitmap_skip_store(bm, false);
>      }

... and I kind of prefer loops with explicit function calls more than I
like macro-loops.

>  
> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
> index 76a8e59e61..e2df82af01 100644
> --- a/block/dirty-bitmap.c
> +++ b/block/dirty-bitmap.c
> @@ -742,11 +742,14 @@ bool bdrv_has_changed_persistent_bitmaps(BlockDriverState *bs)
>      return false;
>  }
>  
> -BdrvDirtyBitmap *bdrv_dirty_bitmap_next(BlockDriverState *bs,
> -                                        BdrvDirtyBitmap *bitmap)
> +BdrvDirtyBitmap *bdrv_dirty_bitmap_first(BlockDriverState *bs)
>  {
> -    return bitmap == NULL ? QLIST_FIRST(&bs->dirty_bitmaps) :
> -                            QLIST_NEXT(bitmap, list);
> +    return QLIST_FIRST(&bs->dirty_bitmaps);
> +}
> +
> +BdrvDirtyBitmap *bdrv_dirty_bitmap_next(BdrvDirtyBitmap *bitmap)
> +{
> +    return QLIST_NEXT(bitmap, list);
>  }
>  
>  char *bdrv_dirty_bitmap_sha256(const BdrvDirtyBitmap *bitmap, Error **errp)
> diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
> index 6d795a2255..73ebd2ff6a 100644
> --- a/block/qcow2-bitmap.c
> +++ b/block/qcow2-bitmap.c
> @@ -1480,9 +1480,7 @@ void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp)
>      }
>  
>      /* check constraints and names */
> -    for (bitmap = bdrv_dirty_bitmap_next(bs, NULL); bitmap != NULL;
> -         bitmap = bdrv_dirty_bitmap_next(bs, bitmap))
> -    {
> +    FOR_EACH_DIRTY_BITMAP(bs, bitmap) {
>          const char *name = bdrv_dirty_bitmap_name(bitmap);
>          uint32_t granularity = bdrv_dirty_bitmap_granularity(bitmap);
>          Qcow2Bitmap *bm;
> @@ -1602,9 +1600,7 @@ int qcow2_reopen_bitmaps_ro(BlockDriverState *bs, Error **errp)
>          return -EINVAL;
>      }
>  
> -    for (bitmap = bdrv_dirty_bitmap_next(bs, NULL); bitmap != NULL;
> -         bitmap = bdrv_dirty_bitmap_next(bs, bitmap))
> -    {
> +    FOR_EACH_DIRTY_BITMAP(bs, bitmap) {
>          if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
>              bdrv_dirty_bitmap_set_readonly(bitmap, true);
>          }
> diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
> index 793f249aa5..7eafface61 100644
> --- a/migration/block-dirty-bitmap.c
> +++ b/migration/block-dirty-bitmap.c
> @@ -283,9 +283,7 @@ static int init_dirty_bitmap_migration(void)
>      for (bs = bdrv_next_all_states(NULL); bs; bs = bdrv_next_all_states(bs)) {
>          const char *name = bdrv_get_device_or_node_name(bs);
>  
> -        for (bitmap = bdrv_dirty_bitmap_next(bs, NULL); bitmap;
> -             bitmap = bdrv_dirty_bitmap_next(bs, bitmap))
> -        {
> +        FOR_EACH_DIRTY_BITMAP(bs, bitmap) {
>              if (!bdrv_dirty_bitmap_name(bitmap)) {
>                  continue;
>              }
> 

Well, I guess explicit first and next functions is harder to mess up,
anyway.

Reviewed-by: John Snow <jsnow@redhat.com>

(Any other thoughts?)