On 3/6/19 11:12 AM, Vladimir Sementsov-Ogievskiy wrote: > 06.03.2019 18:59, John Snow wrote: >> >> >> On 3/6/19 7:58 AM, Eric Blake wrote: >>> On 3/5/19 5:43 PM, John Snow wrote: >>>> Usually, we only write out bitmaps when we're about to close out the file, >>>> so we always remove the bitmaps after to make it easier to determine the >>>> source of truth for migration purposes. >>>> >>>> However, there may be times we want to flush bitmap data more aggressively, >>>> like after a truncate event where we need to make the metadata consistent >>>> again. >>> >>> Or, as I've mentioned in other threads, after every >>> bitmap-add/bitmap-delete operation, so that 'qemu-img info -U' can see >>> which persistent bitmaps exist. But that's one step further than this >>> series, so I won't insist on it today. >>> >> >> Yes, I was keeping that in mind as I wrote this. I think it extends to >> those cases trivially, so long as Vladimir is OK with what I'm trying to do. >> > > I still don't see the point of flushing bitmaps, the only thing is optimizing > qemu-img info --force-share, which should never used except for debugging. > > So, at least, if we'll have it, I'd prefer bitmap flushing to be optional, > and other code should not rely on it. > I don't have plans to add more uses of it personally, but I do think that resize represents a genuine case of wanting the feature.
