Re: [RFC PATCH v2 18/26] qcow2: Add subcluster support to expand_zero_clusters_in_l1()

[Max Reitz]

On 26.10.19 23:25, Alberto Garcia wrote:
> Two changes are needed in order to add subcluster support to this
> function: deallocated clusters must have their bitmaps cleared, and
> expanded clusters must have all the "subcluster allocated" bits set.
> 
> Signed-off-by: Alberto Garcia <address@hidden>
> ---
>  block/qcow2-cluster.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index aa3eb727a5..62f2a9fcc0 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -2036,6 +2036,7 @@ static int expand_zero_clusters_in_l1(BlockDriverState 
> *bs, uint64_t *l1_table,
>                          /* not backed; therefore we can simply deallocate the
>                           * cluster */
>                          set_l2_entry(s, l2_slice, j, 0);
> +                        set_l2_bitmap(s, l2_slice, j, 0);
>                          l2_dirty = true;
>                          continue;
>                      }
> @@ -2102,6 +2103,7 @@ static int expand_zero_clusters_in_l1(BlockDriverState 
> *bs, uint64_t *l1_table,
>                  } else {
>                      set_l2_entry(s, l2_slice, j, offset);
>                  }
> +                set_l2_bitmap(s, l2_slice, j, QCOW_L2_BITMAP_ALL_ALLOC);
>                  l2_dirty = true;
>              }

Technically this isn’t needed because this function is only called when
downgrading v3 to v2 images (which can’t have subclusters), but of
course it won’t hurt.

Max

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