On Tue, May 28, 2019 at 09:22:57PM -0700, Andrew Morton wrote: > On Sun, 26 May 2019 14:23:53 +0800 Hillf Danton <hdanton@xxxxxxxx> wrote: > > > In the function isolate_lru_pages(), we check scan_control::may_unmap and set > > isolation mode accordingly in order to not isolate from the lru list any page > > that does not match the isolation mode. For example, we should skip all sill > > mapped pages if isolation mode is set to be ISOLATE_UNMAPPED. > > > > So complain, while scanning the isolated pages, about the very unlikely event > > that we hit a mapped page that we should never have isolated. Note no change > > is added in the current scanning behavior without VM debug configured. > > The patch is inoffensive enough, but one wonders what inspired it. Do > you have reason to believe that this will trigger? I don't think this patch makes sense. There isn't anything preventing someone from mapping the page between the LRU isolation and shrink_page_list(). The isolation filter is only an optimization to reduce unnecessary LRU churn, not a guarantee.
