Re: [Qemu-devel] [PATCH v3 5/6] vmdk: Set maximum bytes allocated in one cycle

[Fam Zheng <famz@redhat.com>]

On Sat, 04/01 20:14, Ashijeet Acharya wrote:
> Set the maximum bytes allowed to get allocated at once to be not more
> than the extent size boundary to handle writes at two separate extents
> appropriately.
> 
> Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
> ---
>  block/vmdk.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/block/vmdk.c b/block/vmdk.c
> index a8babd7..9456ddd 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -1767,6 +1767,7 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t offset,
>      int64_t offset_in_cluster, n_bytes;
>      uint64_t cluster_offset;
>      uint64_t bytes_done = 0;
> +    uint64_t extent_size;
>      VmdkMetaData m_data;
>      uint32_t total_alloc_clusters = 0;
>  
> @@ -1782,9 +1783,17 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t offset,
>          if (!extent) {
>              return -EIO;
>          }
> +        extent_size = extent->end_sector * BDRV_SECTOR_SIZE;

Maybe extent_end to be more accurate?

> +
>          offset_in_cluster = vmdk_find_offset_in_cluster(extent, offset);
> -        n_bytes = MIN(bytes, extent->cluster_sectors * BDRV_SECTOR_SIZE
> -                             - offset_in_cluster);
> +
> +        /* truncate n_bytes to first cluster because we need to perform COW */

Makes sense, but shouldn't this be squashed into patch patch 3? Because it looks
like it is fixing an intermediate bug.

> +        if (offset_in_cluster > 0) {
> +            n_bytes = MIN(bytes, extent->cluster_sectors * BDRV_SECTOR_SIZE
> +                                 - offset_in_cluster);
> +        } else {
> +            n_bytes = MIN(bytes, extent_size - offset);
> +        }
>  
>          ret = vmdk_alloc_cluster_offset(bs, extent, &m_data, offset,
>                                          !(extent->compressed || zeroed),
> -- 
> 2.6.2
> 

Fam