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Re: [PATCH v5 11/12] nbd: Expose actual depth in qemu:allocation-depth
From: |
Eric Blake |
Subject: |
Re: [PATCH v5 11/12] nbd: Expose actual depth in qemu:allocation-depth |
Date: |
Mon, 26 Oct 2020 07:31:24 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 |
On 10/24/20 4:59 AM, Vladimir Sementsov-Ogievskiy wrote:
> 23.10.2020 21:36, Eric Blake wrote:
>> Preserve the tri-state encoding in the low bits, as that still remains
>> a valuable way to utilize qemu-img map with x-dirty-bitmap for
>> accessing quick information without needing a third-party NBD client.
>
> Hmm.. that doesn't sound as a good reason for redundant information in
> the protocol. Previously good reason was additional effort needed to
> implement sever part, but you've implemented it. And if we export depth
> anyway, it seems better to hack a bit nbd_client_co_block_status to
> convert extent.flags appropriately if metadata context is
> "qemu:allocation-depth" (to keep x-dirty-bitmap working), than have a
> workaround at the protocol layer.
I'm happy to respin this to expose JUST a depth rather than redundant
information, but time is short if we want it in 5.2 (as soft freeze is
this week). I'll see what I can get to today; I'll rearrange the series
to put multiple bitmap exports first (as that appears ready), while
saving 'qemu-nbd -A' until we're happy with the qemu:allocation-depth
semantics. After all, once we release something, we've committed to
that user interface.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
- Re: [PATCH v5 06/12] nbd: Update qapi to support exporting multiple bitmaps, (continued)
- [PATCH v5 08/12] nbd: Refactor counting of metadata contexts, Eric Blake, 2020/10/23
- [PATCH v5 07/12] nbd: Simplify qemu bitmap context name, Eric Blake, 2020/10/23
- [PATCH v5 09/12] nbd: Allow export of multiple bitmaps for one device, Eric Blake, 2020/10/23
- [PATCH v5 10/12] block: Return depth level during bdrv_is_allocated_above, Eric Blake, 2020/10/23
- [PATCH v5 11/12] nbd: Expose actual depth in qemu:allocation-depth, Eric Blake, 2020/10/23
- [PATCH v5 12/12] qapi: Use QAPI_LIST_ADD() where possible, Eric Blake, 2020/10/23
- Re: [PATCH v5 00/12] Exposing backing-chain allocation over NBD, Eric Blake, 2020/10/23