From 497524bf7280284244d1206da3aabb105ee3b926 Mon Sep 17 00:00:00 2001
From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Tue, 5 Apr 2011 21:36:12 -0700
Subject: [PATCH] kernel - Add shutdown method for vm.swapcache

* Add shutdown methods for the swapcache to stop operations during a
  shutdown.  If not stopped swapcache operations can extend beyond the
  device shutdown and cause a crash.
---
 sys/sys/eventhandler.h |  2 ++
 sys/vm/vm_swapcache.c  | 24 +++++++++++++++++++++++-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/sys/sys/eventhandler.h b/sys/sys/eventhandler.h
index c334310f74..147c6fcaba 100644
--- a/sys/sys/eventhandler.h
+++ b/sys/sys/eventhandler.h
@@ -171,6 +171,8 @@ struct proc;
 typedef void (*shutdown_fn) (void *, int);
 
 #define	SHUTDOWN_PRI_FIRST	EVENTHANDLER_PRI_FIRST
+#define	SHUTDOWN_PRI_SECOND	(EVENTHANDLER_PRI_FIRST + 1)
+#define	SHUTDOWN_PRI_THIRD	(EVENTHANDLER_PRI_FIRST + 2)
 #define	SHUTDOWN_PRI_DEFAULT	EVENTHANDLER_PRI_ANY
 #define	SHUTDOWN_PRI_DRIVER	(EVENTHANDLER_PRI_ANY + 5000)
 #define	SHUTDOWN_PRI_LAST	EVENTHANDLER_PRI_LAST
diff --git a/sys/vm/vm_swapcache.c b/sys/vm/vm_swapcache.c
index e0e8a8afc4..f29164571a 100644
--- a/sys/vm/vm_swapcache.c
+++ b/sys/vm/vm_swapcache.c
@@ -62,6 +62,7 @@
 #include <sys/vnode.h>
 #include <sys/vmmeter.h>
 #include <sys/sysctl.h>
+#include <sys/eventhandler.h>
 
 #include <vm/vm.h>
 #include <vm/vm_param.h>
@@ -136,6 +137,19 @@ SYSCTL_QUAD(_vm_swapcache, OID_AUTO, write_count,
 #define SWAPMAX(adj)	\
 	((int64_t)vm_swap_max * (vm_swapcache_maxswappct + (adj)) / 100)
 
+/*
+ * When shutting down the machine we want to stop swapcache operation
+ * immediately so swap is not accessed after devices have been shuttered.
+ */
+static void
+shutdown_swapcache(void *arg __unused)
+{
+	vm_swapcache_read_enable = 0;
+	vm_swapcache_data_enable = 0;
+	vm_swapcache_meta_enable = 0;
+	wakeup(&vm_swapcache_sleep);	/* shortcut 5-second wait */
+}
+
 /*
  * vm_swapcached is the high level pageout daemon.
  *
@@ -153,7 +167,10 @@ vm_swapcached_thread(void)
 	 * Thread setup
 	 */
 	curthread->td_flags |= TDF_SYSTHREAD;
-
+	EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc,
+			      swapcached_thread, SHUTDOWN_PRI_FIRST);
+	EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_swapcache,
+			      NULL, SHUTDOWN_PRI_SECOND);
 	lwkt_gettoken(&vm_token);
 	crit_enter();
 
@@ -178,6 +195,11 @@ vm_swapcached_thread(void)
 	lwkt_reltoken(&vmobj_token);
 
 	for (;;) {
+		/*
+		 * Handle shutdown
+		 */
+		kproc_suspend_loop();
+
 		/*
 		 * Check every 5 seconds when not enabled or if no swap
 		 * is present.
-- 
2.41.0