Re: [Qemu-devel] [PATCH 02/16] introduce a new API to check if blk is attached

[Eric Blake <eblake@redhat.com>]

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On 09/02/2015 02:51 AM, Wen Congyang wrote:
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> ---
>  block.c                        | 4 ++--
>  block/block-backend.c          | 9 +++++++++
>  include/sysemu/block-backend.h | 1 +
>  3 files changed, 12 insertions(+), 2 deletions(-)
> 

>  /*
> + * Return true if a device model is attached to @blk already,
> + * otherwise, return false.
> + */
> +bool blk_is_attached(BlockBackend *blk)
> +{
> +    return blk != NULL && blk->dev != NULL && blk->dev != (void *)-1;

Again, I don't like the raw magic constant, even if we go with this
patch.  And it is shorter to write:

   return blk && blk->dev && blk->dev != MAGIC;

But I think it is better to just allow for a NULL BDS to represent an
unattached media (in which case Max's patches may already cover what you
are trying to do here), rather than trying to overload a special value
different from NULL.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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