Re: [Qemu-block] [PATCH v2 06/10] block: Forbid trying to change unsupported options during reopen

[Max Reitz]

On 2018-09-03 16:34, Alberto Garcia wrote:
> The bdrv_reopen_prepare() function checks all options passed to each
> BlockDriverState (in the reopen_state->options QDict) and makes all
> necessary preparations to apply the option changes requested by the
> user.
> 
> Options are removed from the QDict as they are processed, so at the
> end of bdrv_reopen_prepare() only the options that can't be changed
> are left. Then a loop goes over all remaining options and verifies
> that the old and new values are identical, returning an error if
> they're not.
> 
> The problem is that at the moment there are options that are removed
> from the QDict although they can't be changed. The consequence of this
> is any modification to any of those options is silently ignored:
> 
>    (qemu) qemu-io virtio0 "reopen -o discard=on"
> 
> This happens when all options from bdrv_runtime_opts are removed
> from the QDict but then only a few of them are processed. Since
> it's especially important that "node-name" and "driver" are not
> changed, the code puts them back into the QDict so they are checked
> at the end of the function. Instead of putting only those two options
> back into the QDict, this patch puts all unprocessed options using
> qemu_opts_to_qdict().
> 
> update_flags_from_options() also needs to be modified to prevent
> BDRV_OPT_CACHE_NO_FLUSH, BDRV_OPT_CACHE_DIRECT and BDRV_OPT_READ_ONLY
> from going back to the QDict.
> 
> Signed-off-by: Alberto Garcia <address@hidden>
> ---
>  block.c | 22 +++++++---------------
>  1 file changed, 7 insertions(+), 15 deletions(-)

Reviewed-by: Max Reitz <address@hidden>

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