[PATCH 2/2] mm: fix mm_struct reference counting bugs in mm/oom_kill.c

[Dave Peterson <dsp@llnl.gov>]

The patch below fixes some mm_struct reference counting bugs in
badness().

Signed-Off-By: David S. Peterson <dsp@llnl.gov>
---

Index: linux-2.6.17-rc1-oom/mm/oom_kill.c
===================================================================
--- linux-2.6.17-rc1-oom.orig/mm/oom_kill.c	2006-04-13 14:25:16.000000000 -0700
+++ linux-2.6.17-rc1-oom/mm/oom_kill.c	2006-04-13 14:31:47.000000000 -0700
@@ -47,14 +47,17 @@ unsigned long badness(struct task_struct
 {
 	unsigned long points, cpu_time, run_time, s;
 	struct list_head *tsk;
+	struct mm_struct *mm, *child_mm;
 
-	if (!p->mm)
+	mm = get_task_mm(p);
+
+	if (mm == NULL)
 		return 0;
 
 	/*
 	 * The memory size of the process is the basis for the badness.
 	 */
-	points = p->mm->total_vm;
+	points = mm->total_vm;
 
 	/*
 	 * Processes which fork a lot of child processes are likely
@@ -67,10 +70,21 @@ unsigned long badness(struct task_struct
 	list_for_each(tsk, &p->children) {
 		struct task_struct *chld;
 		chld = list_entry(tsk, struct task_struct, sibling);
-		if (chld->mm != p->mm && chld->mm)
-			points += chld->mm->total_vm/2 + 1;
+
+		if (chld->mm == mm)
+			continue;
+
+		child_mm = get_task_mm(chld);
+
+		if (child_mm == NULL)
+			continue;
+
+		points += child_mm->total_vm/2 + 1;
+		mmput(child_mm);
 	}
 
+	mmput(mm);
+
 	/*
 	 * CPU time is in tens of seconds and run time is in thousands
          * of seconds. There is no particular reason for this other than