On 4/15/20 2:11 PM, Alberto Garcia wrote:
On Fri 10 Apr 2020 11:29:59 AM CEST, Vladimir Sementsov-Ogievskiy wrote:
Should we also document that extended L2 entries are incompatible
with raw external files? [...] After all, when raw external file is
enabled, the entire image is allocated, at which point subclusters
don't make much sense.
It still may cache information about zeroed subclusters: gives more
detailed block-status.
That's a good point about one reason why it might be useful.
So shall I forbid extended_l2 + data_file_raw then?
I wonder, if the only problem is that it's just not very useful, does it
make sense to add additional complexity and restrictions to the code
simply to prevent the user from making a sub-optimal choice?
At this point, I'm not seeing a technical reason why we have to forbid
subclusters with data-file-raw. Mixing may be inefficient compared to
using raw-data-file without subclusters, but inefficiencies are not
worth the code bloat to forbid the combination. If we come up with a
scenario where the mix would cause data corruption, that's a different
story, but I'm not seeing such a reason at the moment.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
