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@xxxxxxxxxxxxx/ 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
