Re: [Qemu-devel] [PATCH v4 06/15] block: Hide HBitmap in block dirty bitmap interface

[Max Reitz <mreitz@redhat.com>]

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On 08.03.2016 05:44, Fam Zheng wrote:
> HBitmap is an implementation detail of block dirty bitmap that should be hidden
> from users. Introduce a BdrvDirtyBitmapIter to encapsulate the underlying
> HBitmapIter.
> 
> A small difference in the interface is, before, an HBitmapIter is initialized
> in place, now the new BdrvDirtyBitmapIter must be dynamically allocated because
> the structure definition is in block.c.

It's block/dirty-bitmap.c now. :-)

> Two current users are converted too.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  block/backup.c               | 14 ++++++++------
>  block/dirty-bitmap.c         | 39 +++++++++++++++++++++++++++++++++------
>  block/mirror.c               | 15 +++++++++------
>  include/block/dirty-bitmap.h |  7 +++++--
>  include/qemu/typedefs.h      |  1 +
>  5 files changed, 56 insertions(+), 20 deletions(-)
> 

[...]

> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
> index 556e1d1..16f73b2 100644
> --- a/block/dirty-bitmap.c
> +++ b/block/dirty-bitmap.c

[...]

> @@ -373,12 +401,11 @@ void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector,
>  }
>  
>  /**
> - * Advance an HBitmapIter to an arbitrary offset.
> + * Advance an BdrvDirtyBitmapIter to an arbitrary offset.

This should be "a BdrvDirtyBitmapIter".

>   */
> -void bdrv_set_dirty_iter(HBitmapIter *hbi, int64_t offset)
> +void bdrv_set_dirty_iter(BdrvDirtyBitmapIter *iter, int64_t sector_num)
>  {
> -    assert(hbi->hb);
> -    hbitmap_iter_init(hbi, hbi->hb, offset);
> +    hbitmap_iter_init(&iter->hbi, iter->hbi.hb, sector_num);
>  }
>  
>  int64_t bdrv_get_dirty_count(BdrvDirtyBitmap *bitmap)
> diff --git a/block/mirror.c b/block/mirror.c
> index 9635fa8..87a5a86 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c

[...]

> @@ -304,10 +304,11 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
>      int64_t end = s->bdev_length / BDRV_SECTOR_SIZE;
>      int sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
>  
> -    sector_num = hbitmap_iter_next(&s->hbi);
> +    sector_num = bdrv_dirty_iter_next(s->dbi);
>      if (sector_num < 0) {
> -        bdrv_dirty_iter_init(s->dirty_bitmap, &s->hbi);
> -        sector_num = hbitmap_iter_next(&s->hbi);
> +        bdrv_dirty_iter_free(s->dbi);
> +        s->dbi = bdrv_dirty_iter_new(s->dirty_bitmap, 0);

Works, but wouldn't bdrv_set_dirty_iter(s->dbi, 0); suffice?

> +        sector_num = bdrv_dirty_iter_next(s->dbi);
>          trace_mirror_restart_iter(s, bdrv_get_dirty_count(s->dirty_bitmap));
>          assert(sector_num >= 0);
>      }
> @@ -330,7 +331,7 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
>              mirror_wait_for_io(s);
>              /* Now retry.  */
>          } else {
> -            hbitmap_next = hbitmap_iter_next(&s->hbi);
> +            hbitmap_next = bdrv_dirty_iter_next(s->dbi);

It would make sense to change this variable's name from hbitmap_next to
e.g. bdrv_dirty_next or bs_next_dirty.

>              assert(hbitmap_next == next_sector);
>              nb_chunks++;
>          }
> @@ -577,7 +578,8 @@ static void coroutine_fn mirror_run(void *opaque)
>          }
>      }
>  
> -    bdrv_dirty_iter_init(s->dirty_bitmap, &s->hbi);
> +    bdrv_dirty_iter_free(s->dbi);
> +    s->dbi = bdrv_dirty_iter_new(s->dirty_bitmap, 0);

Again, bdrv_set_dirty_iter(s->dbi, 0); should work just fine.

Since this patch is technically correct, I could still imagine giving an
R-b, but I'm really reluctant to do so because of the
bdrv_dirty_iter_free()/bdrv_dirty_iter_new() pairs.

Max

>      for (;;) {
>          uint64_t delay_ns = 0;
>          int64_t cnt;
> @@ -688,6 +690,7 @@ immediate_exit:
>      qemu_vfree(s->buf);
>      g_free(s->cow_bitmap);
>      g_free(s->in_flight_bitmap);
> +    bdrv_dirty_iter_free(s->dbi);
>      bdrv_release_dirty_bitmap(bs, s->dirty_bitmap);
>      if (s->target->blk) {
>          blk_iostatus_disable(s->target->blk);
> diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
> index 80afe60..2ea601b 100644
> --- a/include/block/dirty-bitmap.h
> +++ b/include/block/dirty-bitmap.h
> @@ -36,8 +36,11 @@ void bdrv_set_dirty_bitmap(BdrvDirtyBitmap *bitmap,
>                             int64_t cur_sector, int nr_sectors);
>  void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
>                               int64_t cur_sector, int nr_sectors);
> -void bdrv_dirty_iter_init(BdrvDirtyBitmap *bitmap, struct HBitmapIter *hbi);
> -void bdrv_set_dirty_iter(struct HBitmapIter *hbi, int64_t offset);
> +BdrvDirtyBitmapIter *bdrv_dirty_iter_new(BdrvDirtyBitmap *bitmap,
> +                                         uint64_t first_sector);
> +void bdrv_dirty_iter_free(BdrvDirtyBitmapIter *iter);
> +int64_t bdrv_dirty_iter_next(BdrvDirtyBitmapIter *iter);
> +void bdrv_set_dirty_iter(BdrvDirtyBitmapIter *hbi, int64_t sector_num);
>  int64_t bdrv_get_dirty_count(BdrvDirtyBitmap *bitmap);
>  void bdrv_dirty_bitmap_truncate(BlockDriverState *bs);
>  
> diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
> index fd039e0..7c39f0f 100644
> --- a/include/qemu/typedefs.h
> +++ b/include/qemu/typedefs.h
> @@ -11,6 +11,7 @@ typedef struct AioContext AioContext;
>  typedef struct AllwinnerAHCIState AllwinnerAHCIState;
>  typedef struct AudioState AudioState;
>  typedef struct BdrvDirtyBitmap BdrvDirtyBitmap;
> +typedef struct BdrvDirtyBitmapIter BdrvDirtyBitmapIter;
>  typedef struct BlockBackend BlockBackend;
>  typedef struct BlockBackendRootState BlockBackendRootState;
>  typedef struct BlockDriverState BlockDriverState;
> 



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