driver core: debug for bad dev_attr_show() return value.

Try to find the culprit who caused
http://bugzilla.kernel.org/show_bug.cgi?id=10150

Cc: <balajirrao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/base/core.c

@@ -19,6 +19,7 @@
 #include <linux/kdev_t.h>
 #include <linux/notifier.h>
 #include <linux/genhd.h>
+#include <linux/kallsyms.h>
 #include <asm/semaphore.h>
 
 #include "base.h"
@@ -68,6 +69,10 @@ static ssize_t dev_attr_show(struct kobject *kobj, struct attribute *attr,
 
 	if (dev_attr->show)
 		ret = dev_attr->show(dev, dev_attr, buf);
+	if (ret >= (ssize_t)PAGE_SIZE) {
+		print_symbol("dev_attr_show: %s returned bad count\n",
+				(unsigned long)dev_attr->show);
+	}
 	return ret;
 }