Hello, John, On Fri, Jul 28, 2023 at 02:32:12PM -0700, John Hubbard wrote: > On 7/28/23 14:20, Peter Xu wrote: > > On Fri, Jul 28, 2023 at 11:02:46PM +0200, David Hildenbrand wrote: > > > Can we get a simple revert in first (without that FOLL_FORCE special casing > > > and ideally with a better name) to handle stable backports, and I'll > > > follow-up with more documentation and letting GUP callers pass in that flag > > > instead? > > > > > > That would help a lot. Then we also have more time to let that "move it to > > > GUP callers" mature a bit in -next, to see if we find any surprises? > > > > As I raised my concern over the other thread, I still worry numa users can > > be affected by this change. After all, numa isn't so uncommon to me, at > > least fedora / rhel as CONFIG_NUMA_BALANCING_DEFAULT_ENABLED=y. I highly > > suspect that's also true to major distros. Meanwhile all kernel modules > > use gup.. > > > > I'd say we can go ahead and try if we want, but I really don't know why > > that helps in any form to move it to the callers.. with the risk of > > breaking someone. > > It's worth the trouble, in order to clear up this historical mess. It's > helping *future* callers of the API, and future maintenance efforts. Yes > there is some risk, but it seems very manageable. > > The story of how FOLL_NUMA and FOLL_FORCE became entangled was enlightening, > by the way, and now that I've read it I don't want to go back. :) Yeah I fully agree we should hopefully remove the NUMA / FORCE tangling.. even if we want to revert back to the FOLL_NUMA flag we may want to not revive that specific part. I had a feeling that we're all on the same page there. It's more about the further step to make FOLL_NUMA opt-in for GUP. Thanks, -- Peter Xu
