[libvirt] [PATCH 1/2] Storage: Suppress metadata refresh for volumes being built.

[Ján Tomko]

On Tue, May 05, 2015 at 08:43:21AM +0530, Prerna Saxena wrote:
> Libvirt periodically calls 'stat' on all volumes in a storage pool,
> to update fields such as 'target.allocation'.
> 
> The operation doesnt make sense for a volume which is curently being allocated.

From the comments in the storage driver, the point of allowing refresh
for a volume that is currently being allocated is to track the progress
of the allocation.

> Also, the 'target.allocation' sub-field is taken into account while copying a raw image.
> To suppress any (potential) corruption, libvirt must not attempt to refresh a volume currently being built.

What would be the corruption?

We do not allow using a volume that is currently building as a
source for cloning the volume - storageVolCreateXMLFrom checks for
origvol->building:

    if (origvol->building) {
        virReportError(VIR_ERR_OPERATION_INVALID,
                       _("volume '%s' is still being allocated."),
                       origvol->name);
        goto cleanup;
    }

Jan
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