On Thu 06-12-18 05:21:38, Naoya Horiguchi wrote: > On Wed, Dec 05, 2018 at 05:57:16PM +0100, Michal Hocko wrote: > > On Wed 05-12-18 13:29:18, Michal Hocko wrote: > > [...] > > > After some more thinking I am not really sure the above reasoning is > > > still true with the current upstream kernel. Maybe I just managed to > > > confuse myself so please hold off on this patch for now. Testing by > > > Oscar has shown this patch is helping but the changelog might need to be > > > updated. > > > > OK, so Oscar has nailed it down and it seems that 4.4 kernel we have > > been debugging on behaves slightly different. The underlying problem is > > the same though. So I have reworded the changelog and added "just in > > case" PageLRU handling. Naoya, maybe you have an argument that would > > make this void for current upstream kernels. > > The following commit (not in 4.4.x stable tree) might explain the > difference you experienced: > > commit 286c469a988fbaf68e3a97ddf1e6c245c1446968 > Author: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Date: Wed May 3 14:56:22 2017 -0700 > > mm: hwpoison: call shake_page() after try_to_unmap() for mlocked page > > This commit adds shake_page() for mlocked pages to make sure that the target > page is flushed out from LRU cache. Without this shake_page(), subsequent > delete_from_lru_cache() (from me_pagecache_clean()) fails to isolate it and > the page will finally return back to LRU list. So this scenario leads to > "hwpoisoned by still linked to LRU list" page. OK, I see. So does that mean that the LRU handling is no longer needed and there is a guanratee that all kernels with the above commit cannot ever get an LRU page? -- Michal Hocko SUSE Labs
