Messages in this thread |  | | Subject | Re: [RFC PATCH v2 0/3] mm/gup: fix gup_fast with dynamic page table folding | From | Christophe Leroy <> | Date | Tue, 8 Sep 2020 06:42:50 +0200 |
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Le 07/09/2020 à 20:00, Gerald Schaefer a écrit : > This is v2 of an RFC previously discussed here: > https://lore.kernel.org/lkml/20200828140314.8556-1-gerald.schaefer@linux.ibm.com/ > > Patch 1 is a fix for a regression in gup_fast on s390, after our conversion > to common gup_fast code. It will introduce special helper functions > pXd_addr_end_folded(), which have to be used in places where pagetable walk > is done w/o lock and with READ_ONCE, so currently only in gup_fast. > > Patch 2 is an attempt to make that more generic, i.e. change pXd_addr_end() > themselves by adding an extra pXd value parameter. That was suggested by > Jason during v1 discussion, because he is already thinking of some other > places where he might want to switch to the READ_ONCE logic for pagetable > walks. In general, that would be the cleanest / safest solution, but there > is some impact on other architectures and common code, hence the new and > greatly enlarged recipient list. > > Patch 3 is a "nice to have" add-on, which makes pXd_addr_end() inline > functions instead of #defines, so that we get some type checking for the > new pXd value parameter. > > Not sure about Fixes/stable tags for the generic solution. Only patch 1 > fixes a real bug on s390, and has Fixes/stable tags. Patches 2 + 3 might > still be nice to have in stable, to ease future backports, but I guess > "nice to have" does not really qualify for stable backports.
If one day you have to backport a fix that requires patch 2 and/or 3, just mark it "depends-on:" and the patches will go in stable at the relevant time.
Christophe
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