[libvirt PATCH 0/4] storage: support controlling COW attribute for pool

Peter Krempa pkrempa at redhat.com
Thu Jul 23 13:07:03 UTC 2020

On Mon, Jul 20, 2020 at 18:33:18 +0100, Daniel Berrange wrote:
> We already support a "nocow" flag for storage volumes, but this requires
> extra work by the mgmt app or user when creating images on btrfs. We
> want to "do the right thing" out of the box for btrfs.
> We achieve this by changint the storage pool code so that when creating
> a storage pool we always try to disable COW on btrfs filesystems. We
> then add an <cow state="yes|no"/> feature in the pool XML to let apps
> override the default logic.
> The COW setting on the pool is inherited by any volumes.
> The main thing not solved here is that the default directory at
> /var/lib/libvirt/images is created by the RPM itself, not by a
> normal "pool-build" command.
> Fortunately it appears that virt-install  will explicitly invoke a
> storage pool build even if the directory already exists.
> Daniel P. Berrangé (4):
>   util: add a helper method for controlling the COW flag on btrfs
>   storage: convert to use virFileSetCOW
>   storage: attempt to disable COW by default
>   conf: add control over COW for storage pool directories

Once you add the comment to patch 1 and fix the two nits in patch 4:


Reviewed-by: Peter Krempa <pkrempa at redhat.com>

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