On Tue, 27 Aug 2013 07:26:04 +0800 Wanpeng Li <liw...@linux.vnet.ibm.com> wrote:
> Hi Naoya, > On Mon, Aug 26, 2013 at 11:45:37AM -0400, Naoya Horiguchi wrote: > >On Mon, Aug 26, 2013 at 04:46:12PM +0800, Wanpeng Li wrote: > >> madvise hwpoison inject will poison the read-only empty zero page if there > >> is > >> no write access before poison. Empty zero page reference count will be > >> increased > >> for hwpoison, subsequent poison zero page will return directly since page > >> has > >> already been set PG_hwpoison, however, page reference count is still > >> increased > >> by get_user_pages_fast. The unpoison process will unpoison the empty zero > >> page > >> and decrease the reference count successfully for the fist time, however, > >> subsequent unpoison empty zero page will return directly since page has > >> already > >> been unpoisoned and without decrease the page reference count of empty > >> zero page. > >> This patch fix it by decrease page reference count for empty zero page > >> which has > >> already been unpoisoned and page count > 1. > > > >I guess that fixing on the madvise side looks reasonable to me, because this > >refcount mismatch happens only when we poison with madvise(). The root cause > >is that we can get refcount multiple times on a page, even if > >memory_failure() > >or soft_offline_page() can do its work only once. > > > > I think this just happen in read-only before poison case against empty > zero page. > > Hi Andrew, > > I see you have already merged the patch, which method you prefer? > Addressing it within the madvise code does sound more appropriate. The change which mm-hwpoison-fix-memory-failure-still-holding-reference-count-after-unpoisoning-empty-zero-page.patch makes is pretty darn strange-looking at at least needs a comment telling people what it's doing, and why. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
