On 3/28/19 11:04 AM, Michal Privoznik wrote:
Here is the problem: If all disks had XATTRs (i.e. domains using them were started with owner remembering turned on) then refcounting implemented in XATTRs would work nicely and we could set the whole backing chain and restore it later. But world is not that simple. As soon as there is one domain that was started with the feature turned off (or simply by older libvirt), the XATTR refounting does not reflect the actual number of uses by running domains and therefore any attempt to restore might cut off the old domain.
There is no simple way around this. Except artificially turning the feature off for the rest of the backing chain.
Is there a thread discussing the issues that led to disabling this code? I looked but couldn't find one. I could use some more context on what case this patch fixes, and the upcoming patches. I'm having trouble groking these comments Thanks, Cole