Re: [Qemu-devel] [PATCH 7/9] block: Allow changing 'discard' on reopen

[Max Reitz <mreitz@redhat.com>]

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On 2018-08-26 16:09, Alberto Garcia wrote:
> 'discard' is one of the basic BlockdevOptions available for all
> drivers, but it's silently ignored by bdrv_reopen_prepare/commit(), so
> the user cannot change it and doesn't get an error explaining that it
> can't be changed.
> 
> This should update the discard setting, but does nothing:
> 
>    (qemu) qemu-io virtio0 "reopen -o discard=on"
> 
> Since there's no reason why we shouldn't allow changing it and the
> implementation is simple let's just do it.
> 
> Signed-off-by: Alberto Garcia <berto@igalia.com>
> ---
>  block.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/block.c b/block.c
> index 804d557608..21f1eb9cd1 100644
> --- a/block.c
> +++ b/block.c
> @@ -3178,6 +3178,15 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue,
>  
>      update_flags_from_options(&reopen_state->flags, opts);
>  
> +    value = qemu_opt_get(opts, "discard");
> +    if (value != NULL) {
> +        if (bdrv_parse_discard_flags(value, &reopen_state->flags) != 0) {
> +            error_setg(errp, "Invalid discard option");
> +            ret = -EINVAL;
> +            goto error;
> +        }
> +    }
> +
>      /* node-name and driver must be unchanged. Put them back into the QDict, so
>       * that they are checked at the end of this function. */
>      value = qemu_opt_get(opts, "node-name");

Hm.  Why not just use the same "trick" here as in your last patch, i.e.
use qemu_opt_get_del() above and then qemu_opts_to_qdict() to return all
unhandled options to the QDict?

(We'd have to use *_del() in update_flags_from_options() as well, but
that would be OK for all callers, I believe.)

Max


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