Re: [Qemu-devel] [RFC V6 12/33] qcow2: Makes qcow2_alloc_cluster_link_l2 mark to deduplicate clusters.

[Stefan Hajnoczi]

On Wed, Feb 06, 2013 at 01:31:45PM +0100, Benoît Canet wrote:
> ---
>  block/qcow2-cluster.c |    8 ++++++--
>  block/qcow2-dedup.c   |    7 +++++++
>  block/qcow2.h         |    3 +++
>  3 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index dbcb6d2..ef91216 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -709,6 +709,7 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, 
> QCowL2Meta *m)
>      qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
>  
>      for (i = 0; i < m->nb_clusters; i++) {
> +        uint64_t flags = 0;
>          /* if two concurrent writes happen to the same unallocated cluster
>        * each write allocates separate cluster and writes data concurrently.
>        * The first one to complete updates l2 table with pointer to its
> @@ -718,9 +719,11 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, 
> QCowL2Meta *m)
>          if(l2_table[l2_index + i] != 0)
>              old_cluster[j++] = l2_table[l2_index + i];
>  
> +        flags = m->oflag_copied ? QCOW_OFLAG_COPIED : 0;
> +        flags |= m->to_deduplicate ? QCOW_OFLAG_TO_DEDUP : 0;

It would be easier to have a m->l2_entry_flags field that is ORed in.
Then we don't need separate fields for QCOW_OFLAG_COPIED and
QCOW_OFLAG_TO_DEDUP, or code to check them and build flags.