Re: [Qemu-devel] [PATCH v4 02/38] blockdev: Allow creation of BDS trees without BB

[Kevin Wolf <kwolf@redhat.com>]

Am 20.07.2015 um 19:45 hat Max Reitz geschrieben:
> If the "id" field is missing from the options given to blockdev-add,
> just omit the BlockBackend and create the BlockDriverState tree alone.
> 
> However, if "id" is missing, "node-name" must be specified; otherwise,
> the BDS tree would no longer be accessible.

We can probably lift this restriction once Jeff's auto-generated ID
patches are in. However, allowing additional things is easy, so no
objection here.

> Many BDS options which are not parsed by bdrv_open() (like caching)
> cannot be specified for these BB-less BDS trees yet. A future patch will
> remove this limitation.

This makes the command mostly useless, but that's okay. We'll be working
on converting flags to QDict options one by one and then it will start
working.

There is, however, one flag that doesn't correspond to an option or
enable an additional feature that is simply missing until then. That one
worries me a bit: BDRV_O_INCOMING. We should probably include it in this
patch; or maybe better add another patch before this one which moves the
setting of BDRV_O_INCOMING from blockdev_init() to bdrv_open_common().

> Signed-off-by: Max Reitz <mreitz@redhat.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> Reviewed-by: Alberto Garcia <berto@igalia.com>
> ---
>  blockdev.c                 | 44 +++++++++++++++++++++++++++++++-------------
>  qapi/block-core.json       | 13 +++++++++----
>  tests/qemu-iotests/087     |  2 +-
>  tests/qemu-iotests/087.out |  4 ++--
>  4 files changed, 43 insertions(+), 20 deletions(-)

Kevin