From: Thomas Lamprecht <t.lamprecht@proxmox.com>
To: Proxmox VE development discussion <pve-devel@lists.proxmox.com>,
Fabian Ebner <f.ebner@proxmox.com>
Subject: Re: [pve-devel] [PATCH v2 qemu-server 1/2] tests: mock storage locking for migration tests
Date: Tue, 12 Jan 2021 12:07:34 +0100 [thread overview]
Message-ID: <85d4649e-faaa-3cbb-3b72-f5cb3caa006b@proxmox.com> (raw)
In-Reply-To: <c573add7-5db1-d3f5-2deb-d2da3e99768d@proxmox.com>
first, I overlooked your v2 due to lack of reply to Stefans comment there I did
not actually thought there would come one, but my followup seems mostly in line
with your patch here, so no real harm done..
On 12.01.21 09:03, Fabian Ebner wrote:
> I didn't notice yesterday, but it's actually strange that volume_is_base_and_used uses a storage lock. Its callers that plan to change volumes on the storage based on the check need to hold the lock instead. Otherwise it can happen that:
> 1. volume_is_base_and_used is called and the result is used to decide how to branch
> 2. situation on the storage changes in the meantime
> 3. the branch we are taking might not be the one we should be taking anymore
>
> vdisk_free already uses its own lock around both the __no_lock-variant of the check and the modification on the storage it does, so it's fine.
>
> The only two callers for the normal variant are in qemu-server and they both serve as preliminary checks, while the real modification for both of them happens with vdisk_free. One of the callers makes the mocking below necessary, but it wouldn't if we were to remove the storage locking from volume_is_base_and_used.
Sounds sensible without looking into it in depth yet, can you come up with a patch
to do so and look at the specifics?
next prev parent reply other threads:[~2021-01-12 11:07 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 14:00 Fabian Ebner
2021-01-11 14:00 ` [pve-devel] [PATCH v2 qemu-server 2/2] tests: remove migration test run dir with make clean Fabian Ebner
2021-01-12 8:03 ` [pve-devel] [PATCH v2 qemu-server 1/2] tests: mock storage locking for migration tests Fabian Ebner
2021-01-12 11:07 ` Thomas Lamprecht [this message]
2021-01-15 7:47 ` Fabian Ebner
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