On Mon, 2018-05-28 at 12:00 +0200, Greg Kroah-Hartman wrote: > 4.4-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> > > [ Upstream commit c58f0bb77ed8bf93dfdde762b01cb67eebbdfc29 ] > > Patch series "Do not lose dirty bit on THP pages", v4. > > Vlastimil noted that pmdp_invalidate() is not atomic and we can lose > dirty and access bits if CPU sets them after pmdp dereference, but > before set_pmd_at(). > > The bug can lead to data loss, but the race window is tiny and I haven't > seen any reports that suggested that it happens in reality. So I don't > think it worth sending it to stable. [...] > This patch (of 12): > > This is an implementation of pmdp_establish() that is only suitable for > an architecture that doesn't have hardware dirty/accessed bits. In this > case we can't race with CPU which sets these bits and non-atomic > approach is fine. [...] There's no point in applying just this patch, since it adds a new function that nothing will call. I tend to think that since this is fixing a potential data loss, the whole series should be backported. But the commit message here says it shouldn't. Ben. -- Ben Hutchings, Software Developer Codethink Ltd https://www.codethink.co.uk/ Dale House, 35 Dale Street Manchester, M1 2HF, United Kingdom
