On 11/21/2016 06:20 PM, Jerome Glisse wrote: > On Mon, Nov 21, 2016 at 01:48:26PM +0530, Anshuman Khandual wrote: >> On 11/18/2016 11:48 PM, 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 to catch refcounting issues in a sane way for 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 0fbfead..09b2630 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -2435,6 +2435,16 @@ 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); >>> + page_ref_inc(page); >>> + return; >>> + } >> >> This fixes an issue in the existing ZONE_DEVICE code, should not this >> patch be sent separately not in this series ? >> > > Well this is more like a safetynet feature, i can send it separately from the > series. It is not an issue per say as a trap to catch bugs. I had refcounting > bugs while working on this patchset and having this safetynet was helpful to > quickly pin-point issues.
Sure at the least move them up in the series as ZONE_DEVICE preparatory fixes before expanding ZONE_DEVICE framework to accommodate the new un-addressable memory representation.
