On Thu, Sep 01, 2022 at 10:50:48AM -0700, Yang Shi wrote: > Yeah, because THP collapse does copy the data before clearing pte. If > we want to remove pmdp_collapse_flush() by just clearing pmd, we > should clear *AND* flush pte before copying the data IIRC. Yes tlb flush is still needed. IIUC the generic pmdp_collapse_flush() will still be working (with the pte level flushing there) but it should just start to work for all archs, so potentially we could drop the arch-specific pmdp_collapse_flush()s, mostly the ppc impl. This also reminded me that the s390 version of pmdp_collapse_flush() is a bit weird, since it doesn't even have the tlb flush there. I feel like it's broken but I can't really tell whether something I've overlooked. Worth an eye on. -- Peter Xu
