mm, memory hotplug: print debug message in the proper way for online_pages

online_pages() simply returns an error value if
memory_notify(MEM_GOING_ONLINE, &arg) return a value that is not what we
want for successfully onlining target pages.  This patch arms to print
more failure information like offline_pages() in online_pages.

This patch also converts printk(KERN_<LEVEL>) to pr_<level>(), and moves
__offline_pages() to not print failure information with KERN_INFO
according to David Rientjes's suggestion[1].

[1] https://lkml.org/lkml/2016/2/24/1094Signed-off-by: Chen Yucong <slaoub@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memory_hotplug.c

@@ -1059,10 +1059,9 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 
 	ret = memory_notify(MEM_GOING_ONLINE, &arg);
 	ret = notifier_to_errno(ret);
-	if (ret) {
-		memory_notify(MEM_CANCEL_ONLINE, &arg);
-		return ret;
-	}
+	if (ret)
+		goto failed_addition;
+
 	/*
 	 * If this zone is not populated, then it is not in zonelist.
 	 * This means the page allocator ignores this zone.
@@ -1080,12 +1079,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 		if (need_zonelists_rebuild)
 			zone_pcp_reset(zone);
 		mutex_unlock(&zonelists_mutex);
-		printk(KERN_DEBUG "online_pages [mem %#010llx-%#010llx] failed\n",
-		       (unsigned long long) pfn << PAGE_SHIFT,
-		       (((unsigned long long) pfn + nr_pages)
-			    << PAGE_SHIFT) - 1);
-		memory_notify(MEM_CANCEL_ONLINE, &arg);
-		return ret;
+		goto failed_addition;
 	}
 
 	zone->present_pages += onlined_pages;
@@ -1118,6 +1112,13 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 	if (onlined_pages)
 		memory_notify(MEM_ONLINE, &arg);
 	return 0;
+
+failed_addition:
+	pr_debug("online_pages [mem %#010llx-%#010llx] failed\n",
+		 (unsigned long long) pfn << PAGE_SHIFT,
+		 (((unsigned long long) pfn + nr_pages) << PAGE_SHIFT) - 1);
+	memory_notify(MEM_CANCEL_ONLINE, &arg);
+	return ret;
 }
 #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
 
@@ -1529,8 +1530,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 
 		} else {
 #ifdef CONFIG_DEBUG_VM
-			printk(KERN_ALERT "removing pfn %lx from LRU failed\n",
-			       pfn);
+			pr_alert("removing pfn %lx from LRU failed\n", pfn);
 			dump_page(page, "failed to remove from LRU");
 #endif
 			put_page(page);
@@ -1858,7 +1858,7 @@ static int __ref __offline_pages(unsigned long start_pfn,
 		ret = -EBUSY;
 		goto failed_removal;
 	}
-	printk(KERN_INFO "Offlined Pages %ld\n", offlined_pages);
+	pr_info("Offlined Pages %ld\n", offlined_pages);
 	/* Ok, all of our target is isolated.
 	   We cannot do rollback at this point. */
 	offline_isolated_pages(start_pfn, end_pfn);
@@ -1895,7 +1895,7 @@ static int __ref __offline_pages(unsigned long start_pfn,
 	return 0;
 
 failed_removal:
-	printk(KERN_INFO "memory offlining [mem %#010llx-%#010llx] failed\n",
+	pr_debug("memory offlining [mem %#010llx-%#010llx] failed\n",
 		 (unsigned long long) start_pfn << PAGE_SHIFT,
 		 ((unsigned long long) end_pfn << PAGE_SHIFT) - 1);
 	memory_notify(MEM_CANCEL_OFFLINE, &arg);