mm/page_reporting: Add checks for page_reporting_order param

[linux-block.git] / mm / page_reporting.c

diff --git a/mm/page_reporting.c b/mm/page_reporting.c
index 382958eef8a928527026a8b88cfb1bcf1105c33a..79a8554f024c27afb71916817073e5fc34d977d1 100644 (file)
--- a/mm/page_reporting.c
+++ b/mm/page_reporting.c
@@ -11,10 +11,42 @@
 #include "page_reporting.h"
 #include "internal.h"
 
-unsigned int page_reporting_order = MAX_ORDER;
-module_param(page_reporting_order, uint, 0644);
+/* Initialize to an unsupported value */
+unsigned int page_reporting_order = -1;
+
+static int page_order_update_notify(const char *val, const struct kernel_param *kp)
+{
+       /*
+        * If param is set beyond this limit, order is set to default
+        * pageblock_order value
+        */
+       return  param_set_uint_minmax(val, kp, 0, MAX_ORDER-1);
+}
+
+static const struct kernel_param_ops page_reporting_param_ops = {
+       .set = &page_order_update_notify,
+       /*
+        * For the get op, use param_get_int instead of param_get_uint.
+        * This is to make sure that when unset the initialized value of
+        * -1 is shown correctly
+        */
+       .get = &param_get_int,
+};
+
+module_param_cb(page_reporting_order, &page_reporting_param_ops,
+                       &page_reporting_order, 0644);
 MODULE_PARM_DESC(page_reporting_order, "Set page reporting order");
 
+/*
+ * This symbol is also a kernel parameter. Export the page_reporting_order
+ * symbol so that other drivers can access it to control order values without
+ * having to introduce another configurable parameter. Only one driver can
+ * register with the page_reporting driver for the service, so we have just
+ * one control parameter for the use case(which can be accessed in both
+ * drivers)
+ */
+EXPORT_SYMBOL_GPL(page_reporting_order);
+
 #define PAGE_REPORTING_DELAY   (2 * HZ)
 static struct page_reporting_dev_info __rcu *pr_dev_info __read_mostly;
 
@@ -330,10 +362,18 @@ int page_reporting_register(struct page_reporting_dev_info *prdev)
        }
 
        /*
-        * Update the page reporting order if it's specified by driver.
-        * Otherwise, it falls back to @pageblock_order.
+        * If the page_reporting_order value is not set, we check if
+        * an order is provided from the driver that is performing the
+        * registration. If that is not provided either, we default to
+        * pageblock_order.
         */
-       page_reporting_order = prdev->order ? : pageblock_order;
+
+       if (page_reporting_order == -1) {
+               if (prdev->order > 0 && prdev->order <= MAX_ORDER)
+                       page_reporting_order = prdev->order;
+               else
+                       page_reporting_order = pageblock_order;
+       }
 
        /* initialize state and work structures */
        atomic_set(&prdev->state, PAGE_REPORTING_IDLE);