[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-block] [Qemu-devel] [RFC] block: Is name of BlockBackend depre

From: Anton Kuchin
Subject: Re: [Qemu-block] [Qemu-devel] [RFC] block: Is name of BlockBackend deprecated with -blockdev parameter?
Date: Fri, 14 Dec 2018 15:18:40 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1

I want to make it consistent but I'm note sure I understand all aspects of current state and legacy clients we need to support.

The initial idea was to have single function blk_lookup(char* name) and search in all namespaces internally as they are guaranteed to have no intersection. This will work a little slower but I see no hot paths that will be affected. And this way transition will be transparent to users but I'm not sure this can be done in backward compatible way.
Do you have any suggestions how to do it correctly?

On 11/12/2018 12:47, Kevin Wolf wrote:
Anton Kuchin <address@hidden> writes:

As far as I understand all named backends are stored in
monitor_block_backends list, but I can't get what is the point of
having this list, and why parse_drive() function doesn't call
monitor_add_blk() like blockdev_init() does with -drive option. Can
someone give me a hint on this?

And what are monitor_block_backends used for? What does monitor reference mean in this context and how backends in this list differ from all others?

I also noticed that some commands fallback to search by qdev_id or
BDS->node_name,  but at the creation time (both in
bdrv_assing_node_name and monitor_add_blk) it is already checked that
names are unique across these namespaces so may be it would be useful
to introduce generic search function?
Yes, BlockBackend names are not supposed to be used in the external
interfaces any more. If the QMP command is about the backend, it will
take a node name, and if it's about the guest device (which may not even
have a node attached with removable media), it will take a qdev ID.

The implementation of qmp_x_block_latency_histogram_set() is incorrect,
it shouldn't use blk_by_name(). I wonder where it got that pattern from
because it was added long after all other QMP commands had switched to
qmp_get_blk() or bdrv_lookup_bs().

Do we still need blk_by_name() to be public? May be we can replace it by new function like blk_lookup() and hide blk_by_name() for internal use only or fix its behavior to search by qdev_id first and if it fails fallback to old way of searching by device_id?

hmp_commit() should indeed use bdrv_lookup_bs() to also accept node
But it also checks blk state before commit, so I'm not quite sure it can work correctly without blk.
I think we reviewed QMP to make sure we converted everything
and forgot about HMP commands that aren't mapped to QMP.



reply via email to

[Prev in Thread] Current Thread [Next in Thread]