On Fri, Jan 06, 2017 at 11:46:28AM -0500, Jérôme Glisse wrote: > Catch page from ZONE_DEVICE in free_hot_cold_page(). This should never > happen as ZONE_DEVICE page must always have an elevated refcount. > > This is safety-net to catch any refcounting issues in a sane way for any > ZONE_DEVICE pages. > > Signed-off-by: Jérôme Glisse <[email protected]> > Cc: Dan Williams <[email protected]> > Cc: Ross Zwisler <[email protected]> > --- > mm/page_alloc.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 1c24112..355beb4 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2445,6 +2445,16 @@ void free_hot_cold_page(struct page *page, bool cold) > unsigned long pfn = page_to_pfn(page); > int migratetype; > > + /* > + * This should never happen ! Page from ZONE_DEVICE always must have an > + * active refcount. Complain about it and try to restore the refcount. > + */ > + if (is_zone_device_page(page)) { > + VM_BUG_ON_PAGE(is_zone_device_page(page), page);
This can be VM_BUG_ON_PAGE(1, page), hopefully the compiler does the right thing here. I suspect this should be a BUG_ON, independent of CONFIG_DEBUG_VM > + page_ref_inc(page); > + return; > + } > + Balbir Singh.
