* Dave Hansen <dave@xxxxxxxx> wrote: > > From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > > The concept here was a suggestion from Ingo. The implementation > horrors are all mine. > > This allows get_user_pages(), get_user_pages_unlocked(), and > get_user_pages_locked() to be called with or without the > leading tsk/mm arguments. We will give a compile-time warning > about the old style being __deprecated and we will also > WARN_ON() if the non-remote version is used for a remote-style > access. So at minimum this should be WARN_ON_ONCE(), to make it easier to recover some meaningful kernel log from such incidents. But: > Doing this, folks will get nice warnings and will not break the > build. This should be nice for -next and will hopefully let > developers fix up their own code instead of maintainers needing > to do it at merge time. > > The way we do this is hideous. It uses the __VA_ARGS__ macro > functionality to call different functions based on the number > of arguments passed to the macro. > > There's an additional hack to ensure that our EXPORT_SYMBOL() > of the deprecated symbols doesn't trigger a warning. > > We should be able to remove this mess as soon as -rc1 hits in > the release after this is merged. So when I suggested this then it looked a _lot_ cleanear to me, in my head! OTOH this, if factored out a bit perhaps, could be the basis for a useful technical model to do 'phased in, -next invariant' prototype migrations in the future, especially when it involves lots of subsystems. Strictly only in cases where -rc1 will truly get rid of the __VA_ARGS__ hackery - which we'd do in this case. Nevertheless I'd love to have a high level buy-in from either Linus or Andrew that we can do it this way, as the hackery looks very hideous... The alternative would be to allow the -next churn and to allow the occasional (fairly trivial but tester-disruptive) build breakage. Thanks, Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>