On Wed, 9 Jul 2014 00:54:48 +0400 Cyrill Gorcunov <gorcunov@xxxxxxxxx> wrote: > On Tue, Jul 08, 2014 at 01:45:11PM -0700, Andrew Morton wrote: > > > > The user doesn't know or care about pte bits. > > > > What actually *happens*? Does criu migration hang? Does it lose data? > > Does it take longer? > > Ah, I see. Yes, the softdirty bit might be lost that usespace program > won't see that a page was modified. So data lose is possible. > > > IOW, what would an end-user's bug report look like? > > > > It's important to think this way because a year from now some person > > we've never heard of may be looking at a user's bug report and > > wondering whether backporting this patch will fix it. Amongst other > > reasons. > > Here is updated changelog, sounds better? > --- > > In case if page fault happend on dirty filemapping the newly created pte > may loose softdirty bit thus if a userspace program is tracking memory > changes with help of a memory tracker (CONFIG_MEM_SOFT_DIRTY) it might > miss modification of a memory page (which in worts case may lead to > data inconsistency). Much better, thanks. It's a rather gross-looking bug and data inconsistency sounds serious. Do you think a -stable backport is needed? -- 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>