On Thu, Dec 13, 2018 at 01:15:10PM +0800, Peter Xu wrote: > When splitting a huge migrating PMD, we'll transfer all the existing > PMD bits and apply them again onto the small PTEs. However we are > fetching the bits unconditionally via pmd_soft_dirty(), pmd_write() > or pmd_yound() while actually they don't make sense at all when it's > a migration entry. Fix them up. Since at it, drop the ifdef together > as not needed. > > Note that if my understanding is correct about the problem then if > without the patch there is chance to lose some of the dirty bits in > the migrating pmd pages (on x86_64 we're fetching bit 11 which is part > of swap offset instead of bit 2) and it could potentially corrupt the > memory of an userspace program which depends on the dirty bit. > > CC: Andrea Arcangeli <aarca...@redhat.com> > CC: Andrew Morton <a...@linux-foundation.org> > CC: "Kirill A. Shutemov" <kirill.shute...@linux.intel.com> > CC: Matthew Wilcox <wi...@infradead.org> > CC: Michal Hocko <mho...@suse.com> > CC: Dave Jiang <dave.ji...@intel.com> > CC: "Aneesh Kumar K.V" <aneesh.ku...@linux.vnet.ibm.com> > CC: Souptick Joarder <jrdr.li...@gmail.com> > CC: Konstantin Khlebnikov <khlebni...@yandex-team.ru> > CC: Zi Yan <zi....@cs.rutgers.edu> > CC: linux...@kvack.org > CC: linux-kernel@vger.kernel.org > Signed-off-by: Peter Xu <pet...@redhat.com>
Acked-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com> Stable? -- Kirill A. Shutemov
