mm, madvise_inject_error: Disable MADV_SOFT_OFFLINE for ZONE_DEVICE pages

Given that dax / device-mapped pages are never subject to page
allocations remove them from consideration by the soft-offline
mechanism.
Reported-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

mm/memory-failure.c

@@ -1751,6 +1751,14 @@ int soft_offline_page(struct page *page, int flags)
 	int ret;
 	unsigned long pfn = page_to_pfn(page);
 
+	if (is_zone_device_page(page)) {
+		pr_debug_ratelimited("soft_offline: %#lx page is device page\n",
+				pfn);
+		if (flags & MF_COUNT_INCREASED)
+			put_page(page);
+		return -EIO;
+	}
+
 	if (PageHWPoison(page)) {
 		pr_info("soft offline: %#lx page already poisoned\n", pfn);
 		if (flags & MF_COUNT_INCREASED)