--- 2.3.18ac2-kupdate/fs/buffer.c.~1~	Mon Sep 13 03:38:46 1999
+++ 2.3.18ac2-kupdate/fs/buffer.c	Tue Sep 14 00:33:14 1999
@@ -114,18 +114,18 @@
 				each time we call refill */
 		int nref_dirt; /* Dirty buffer threshold for activating bdflush
 				  when trying to refill buffers. */
-		int dummy1;    /* unused */
+		int interval; /* jiffies delay between kupdate flushes */
 		int age_buffer;  /* Time for normal buffer to age before we flush it */
 		int age_super;  /* Time for superblock to age before we flush it */
 		int dummy2;    /* unused */
 		int dummy3;    /* unused */
 	} b_un;
 	unsigned int data[N_PARAM];
-} bdf_prm = {{40, 500, 64, 256, 15, 30*HZ, 5*HZ, 1884, 2}};
+} bdf_prm = {{40, 500, 64, 256, 5*HZ, 30*HZ, 5*HZ, 1884, 2}};
 
 /* These are the min and max parameter values that we will allow to be assigned */
 int bdflush_min[N_PARAM] = {  0,  10,    5,   25,  0,   1*HZ,   1*HZ, 1, 1};
-int bdflush_max[N_PARAM] = {100,50000, 20000, 20000,1000, 6000*HZ, 6000*HZ, 2047, 5};
+int bdflush_max[N_PARAM] = {100,50000, 20000, 20000,600*HZ, 6000*HZ, 6000*HZ, 2047, 5};
 
 void wakeup_bdflush(int);
 
@@ -2313,6 +2313,10 @@
 		return -EPERM;
 
 	if (func == 1) {
+		/* do_exit directly and let kupdate to do its work alone. */
+		do_exit(0);
+#if 0 /* left here as it's the only example of lazy-mm-stuff used from
+	 a syscall that doesn't care about the current mm context. */
 		int error;
 		struct mm_struct *user_mm;
 
@@ -2326,6 +2330,7 @@
 		error = sync_old_buffers();
 		end_lazy_tlb(user_mm);
 		return error;
+#endif
 	}
 
 	/* Basically func 1 means read param 1, 2 means write param 1, etc */
@@ -2444,9 +2449,68 @@
 	}
 }
 
+/*
+ * This is the kernel update daemon. It was used to live in userspace
+ * but since it's need to run safely we want it unkillable by mistake.
+ * You don't need to change your userspace configuration since
+ * the userspace `update` will do_exit(0) at the first sys_bdflush().
+ */
+int kupdate(void * unused) 
+{
+	struct task_struct * tsk = current;
+	int interval;
+
+	tsk->session = 1;
+	tsk->pgrp = 1;
+	strcpy(tsk->comm, "kupdate");
+
+	/* sigstop and sigcont will stop and wakeup kupdate */
+	spin_lock_irq(&tsk->sigmask_lock);
+	sigfillset(&tsk->blocked);
+	siginitsetinv(&current->blocked, sigmask(SIGCONT) | sigmask(SIGSTOP));
+	recalc_sigpending(tsk);
+	spin_unlock_irq(&tsk->sigmask_lock);
+
+	for (;;) {
+		/* update interval */
+		interval = bdf_prm.b_un.interval;
+		if (interval)
+		{
+			tsk->state = TASK_INTERRUPTIBLE;
+			schedule_timeout(interval);
+		}
+		else
+		{
+		stop_kupdate:
+			tsk->state = TASK_STOPPED;
+			schedule(); /* wait for SIGCONT */
+		}
+		/* check for sigstop */
+		if (signal_pending(tsk))
+		{
+			int stopped = 0;
+			spin_lock_irq(&tsk->sigmask_lock);
+			if (sigismember(&tsk->signal, SIGSTOP))
+			{
+				sigdelset(&tsk->signal, SIGSTOP);
+				stopped = 1;
+			}
+			recalc_sigpending(tsk);
+			spin_unlock_irq(&tsk->sigmask_lock);
+			if (stopped)
+				goto stop_kupdate;
+		}
+#ifdef DEBUG
+		printk("kupdate() activated...\n");
+#endif
+		sync_old_buffers();
+	}
+}
+
 static int __init bdflush_init(void)
 {
 	kernel_thread(bdflush, NULL, CLONE_FS | CLONE_FILES | CLONE_SIGHAND);
+	kernel_thread(kupdate, NULL, CLONE_FS | CLONE_FILES | CLONE_SIGHAND);
 	return 0;
 }