simple_lmk: Pass a custom swap function to sort()

When sort() isn't provided with a custom swap function, it falls back
onto its generic implementation of just swapping one byte at a time,
which is quite slow. Since we know the type of the objects being sorted,
we can provide our own swap function which simply uses the swap() macro.

Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>

drivers/android/simple_lmk.c

@@ -62,6 +62,14 @@ static int victim_cmp(const void *lhs_ptr, const void *rhs_ptr)
 	return rhs->size - lhs->size;
 }
 
+static void victim_swap(void *lhs_ptr, void *rhs_ptr, int size)
+{
+	struct victim_info *lhs = (typeof(lhs))lhs_ptr;
+	struct victim_info *rhs = (typeof(rhs))rhs_ptr;
+
+	swap(*lhs, *rhs);
+}
+
 static bool vtsk_is_duplicate(int vlen, struct task_struct *vtsk)
 {
 	int i;
@@ -137,7 +145,7 @@ static unsigned long find_victims(int *vindex, unsigned short target_adj_min,
 	 */
 	if (pages_found)
 		sort(&victims[old_vindex], *vindex - old_vindex,
-		     sizeof(*victims), victim_cmp, NULL);
+		     sizeof(*victims), victim_cmp, victim_swap);
 
 	return pages_found;
 }
@@ -198,7 +206,8 @@ static void scan_and_kill(void)
 		 * victims that have a lower adj can be killed in place of
 		 * smaller victims with a high adj.
 		 */
-		sort(victims, nr_to_kill, sizeof(*victims), victim_cmp, NULL);
+		sort(victims, nr_to_kill, sizeof(*victims), victim_cmp,
+		     victim_swap);
 
 		/* Second round of processing to finally select the victims */
 		nr_to_kill = process_victims(nr_to_kill);