Messages in this thread | | | Date | Thu, 1 Sep 2022 14:07:12 -0400 | From | Peter Xu <> | Subject | Re: [PATCH v1] mm/gup: adjust stale comment for RCU GUP-fast |
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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
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