On 04/29/2014 04:24 PM, Eric Blake wrote: > On 04/29/2014 09:07 AM, Max Reitz wrote: >> bdrv_make_empty() is currently only called if the current image >> represents an external snapshot that has been committed to its base >> image; it is therefore unlikely to have internal snapshots. In this >> case, bdrv_make_empty() can be greatly sped up by creating an empty L1 >> table and dropping all data clusters at once by recreating the refcount >> structure accordingly instead of normally discarding all clusters. >>
>> + /* Only 0 and 1 are possible as refcounts here */ >> + refblock[i] = cpu_to_be16(!cluster_offset || >> + (cluster_offset >= blob_start && >> + cluster_offset < blob_end)); > > Caller passed in refblocks, but you are correct that each refblock entry > is 2 bytes long. > > The image header and all clusters within the blob will have a refcount > of 1, all other clusters will have a refcount of 2. Of course, at this Pardon my review typo; obviously, all other clusters will have a refcount of 0 (they are not in use by any snapshots, since the image already has no snapshots; and they are not in use by our blob or the overall image header). -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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