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From: | Eric Blake |
Subject: | Re: [RFC PATCH 07/22] block/export: Remove magic from block-export-add |
Date: | Thu, 20 Aug 2020 09:41:14 -0500 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 |
On 8/20/20 6:05 AM, Kevin Wolf wrote:
As long as we can keep the compatibility code local to qmp_nbd_*(), I don't think it's too bad. In particular because it's already written. Instead of adjusting libvirt to changes in the nbd-* commands, I'd rather have it change over to block-export-*. I would like to see the nbd-server-add/remove commands deprecated soon after we have the replacements.
Makes sense to me. So deprecate nbd-server-add in 5.2, and require block-export in 6.1.
+ /* + * nbd-server-add doesn't complain when a read-only device should be + * exported as writable, but simply downgrades it. This is an error with + * block-export-add.I'd be happy with either marking this deprecated now (and fixing it in two releases), or declaring it a bug in nbd-server-add now (and fixing it outright).How about deprecating nbd-server-add completely?
Works for me. Keeping the warts backwards-compatible in nbd-server-add is more palatable if we know we are going to drop it wholesale down the road.
+ /* + * nbd-server-add removes the export when the named BlockBackend used for + * @device goes away. + */ + on_eject_blk = blk_by_name(arg->device); + if (on_eject_blk) { + nbd_export_set_on_eject_blk(export, on_eject_blk); + }Wait - is the magic export removal tied only to exporting a drive name, and not a node name? So as long as libvirt is using only node names whwen adding exports, a drive being unplugged won't interfere?Yes, seems so. It's the existing behaviour, I'm only moving the code around.Overall, the change makes sense to me, although I'd love to see if we could go further on the writable vs. read-only issue.If nbd-server-add will be going away relatively soon, it's probably not worth the trouble. But if you have reasons to keep it, maybe we should consider it.
No, I'm fine with the idea of getting rid of nbd-server-add, at which point changing it before removal is pointless.
-- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
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