Re: [Qemu-devel] [PATCH 1.8 4/6] block/iscsi: set bdi->cluster_size

[Paolo Bonzini <pbonzini@redhat.com>]

Il 25/11/2013 14:57, Peter Lieven ha scritto:
> this patch aims to set bdi->cluster_size to the internal page size
> of the iscsi target so that enabled callers can align requests
> properly.
> 
> Signed-off-by: Peter Lieven <pl@kamp.de>
> ---
>  block/iscsi.c |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/block/iscsi.c b/block/iscsi.c
> index 93fee6d..75d6b87 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -1580,6 +1580,13 @@ static int iscsi_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
>      IscsiLun *iscsilun = bs->opaque;
>      bdi->unallocated_blocks_are_zero = !!iscsilun->lbprz;
>      bdi->can_write_zeroes_with_unmap = iscsilun->lbprz && iscsilun->lbp.lbpws;
> +    /* Guess the internal cluster (page) size of the iscsi target by the means
> +     * of opt_unmap_gran. Transfer the unmap granularity only if it has a
> +     * reasonable size for bdi->cluster_size */
> +    if (iscsilun->bl.opt_unmap_gran * iscsilun->block_size >= 64 * 1024 &&
> +        iscsilun->bl.opt_unmap_gran * iscsilun->block_size <= 16 * 1024 * 1024) {
> +        bdi->cluster_size = iscsilun->bl.opt_unmap_gran * iscsilun->block_size;
> +    }
>      return 0;
>  }
>  
> 

After looking at patch 5, I think this one is correct.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

but I think you should make higher layers (qcow2) use the lower BDS's
granularity, at least as a default.

Paolo