Re: [Qemu-devel] [PATCH 5/5] block: Always enable discard on the protocol level

[Paolo Bonzini <pbonzini@redhat.com>]

Il 13/06/2013 07:47, Kevin Wolf ha scritto:
> Turning on discard options in qcow2 doesn't help a lot when the discard
> requests that it issues are thrown away by the raw-posix layer. This
> patch always enables discard functionality on the protocol level so that
> it's the image format's responsibility to send (or not) discard
> requests. Requests sent by the guest will be allowed or ignored by the
> top level BlockDriverState, which depends on the discard=... option like
> before.
> 
> In particular, this means that even without specifying options, the
> qcow2 default of discarding deleted snapshots actually takes effect now,
> both for qemu and qemu-img.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block.c b/block.c
> index 79ad33d..0a7cf2f 100644
> --- a/block.c
> +++ b/block.c
> @@ -1045,7 +1045,7 @@ int bdrv_open(BlockDriverState *bs, const char *filename, QDict *options,
>      extract_subqdict(options, &file_options, "file.");
>  
>      ret = bdrv_file_open(&file, filename, file_options,
> -                         bdrv_open_flags(bs, flags));
> +                         bdrv_open_flags(bs, flags | BDRV_O_UNMAP));
>      if (ret < 0) {
>          goto fail;
>      }
> 

Can you still disable it with -drive file.discard=ignore?

Paolo