Re: [Qemu-devel] [PATCH v2 1/3] block: Extrace bdrv_parse_detect_zeroes_flags

[Paolo Bonzini <pbonzini@redhat.com>]

On 08/06/2015 16:17, Eric Blake wrote:
>> > +
>> > +    if (detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
>> > +        !(bdrv_flags & BDRV_O_UNMAP)) {
>> > +        error_setg(errp, "setting detect-zeroes to unmap is not allowed "
>> > +                         "without setting discard operation to unmap");
>> > +    }
> I think it might be better to have a tri-state enum, than to have two
> competing bools where only 3 of the 4 states are valid.

Note that this is not a bool.  We have one bool and one 3-element enum
(off/on/unmap), where only 5 of the 6 states are valid.  Also, at least
detect-zeroes would go away if we had some kind of blockdev-mirror
(where the target is added first with blockdev-add), so I think it's
better to leave it separate.

Paolo