On Tue, Nov 28, 2023 at 08:56:37AM +0000, John Garry wrote: > Are you suggesting some sort of hybrid between the atomic write series you > had a few years ago and this solution? Very roughly, yes. > To me that would be continuing with the following: > - per-IO RWF_ATOMIC (and not O_ATOMIC semantics of nothing is written until > some data sync) Yes. > - writes must be a power-of-two and at a naturally-aligned offset Where offset is offset in the file? It would not require it. You probably want to do it for optimal performance, but requiring it feeels rather limited. > - relying on atomic write HW support always And I think that's where we have different opinions. I think the hw offload is a nice optimization and we should use it wherever we can. But building the entire userspace API around it feels like a mistake. > BTW, we also have rtvol support which does not use forcealign as it already > can guarantee alignment, but still does rely on the same principle of > requiring alignment - would you want CoW support there also? Upstream doesn't have out of place write support for the RT subvolume yet. But Darrick has a series for it and we're actively working on upstreaming it.
