Index: head/sys/dev/acpica/acpi.c
===================================================================
--- head/sys/dev/acpica/acpi.c
+++ head/sys/dev/acpica/acpi.c
@@ -46,6 +46,7 @@
 #include <sys/sysctl.h>
 #include <sys/ctype.h>
 #include <sys/linker.h>
+#include <sys/mount.h>
 #include <sys/power.h>
 #include <sys/sbuf.h>
 #include <sys/sched.h>
@@ -3081,6 +3082,7 @@
 
     EVENTHANDLER_INVOKE(power_suspend_early);
     stop_all_proc();
+    suspend_all_fs();
     EVENTHANDLER_INVOKE(power_suspend);
 
 #ifdef EARLY_AP_STARTUP
@@ -3240,6 +3242,7 @@
     }
 #endif
 
+    resume_all_fs();
     resume_all_proc();
 
     EVENTHANDLER_INVOKE(power_resume);
Index: head/sys/dev/xen/control/control.c
===================================================================
--- head/sys/dev/xen/control/control.c
+++ head/sys/dev/xen/control/control.c
@@ -113,6 +113,7 @@
 #include <sys/filedesc.h>
 #include <sys/kdb.h>
 #include <sys/module.h>
+#include <sys/mount.h>
 #include <sys/namei.h>
 #include <sys/proc.h>
 #include <sys/reboot.h>
@@ -204,6 +205,7 @@
 	xs_lock();
 	stop_all_proc();
 	xs_unlock();
+	suspend_all_fs();
 	EVENTHANDLER_INVOKE(power_suspend);
 
 #ifdef EARLY_AP_STARTUP
@@ -317,6 +319,7 @@
 	}
 #endif
 
+	resume_all_fs();
 	resume_all_proc();
 
 	EVENTHANDLER_INVOKE(power_resume);
Index: head/sys/kern/vfs_mount.c
===================================================================
--- head/sys/kern/vfs_mount.c
+++ head/sys/kern/vfs_mount.c
@@ -2507,3 +2507,67 @@
 	sbuf_delete(&sb);
 	free(buf, M_MOUNT);
 }
+
+/*
+ * Suspend write operations on all local writeable filesystems.  Does
+ * full sync of them in the process.
+ *
+ * Iterate over the mount points in reverse order, suspending most
+ * recently mounted filesystems first.  It handles a case where a
+ * filesystem mounted from a md(4) vnode-backed device should be
+ * suspended before the filesystem that owns the vnode.
+ */
+void
+suspend_all_fs(void)
+{
+	struct mount *mp;
+	int error;
+
+	mtx_lock(&mountlist_mtx);
+	TAILQ_FOREACH_REVERSE(mp, &mountlist, mntlist, mnt_list) {
+		error = vfs_busy(mp, MBF_MNTLSTLOCK | MBF_NOWAIT);
+		if (error != 0)
+			continue;
+		if ((mp->mnt_flag & (MNT_RDONLY | MNT_LOCAL)) != MNT_LOCAL ||
+		    (mp->mnt_kern_flag & MNTK_SUSPEND) != 0) {
+			mtx_lock(&mountlist_mtx);
+			vfs_unbusy(mp);
+			continue;
+		}
+		error = vfs_write_suspend(mp, 0);
+		if (error == 0) {
+			MNT_ILOCK(mp);
+			MPASS((mp->mnt_kern_flag & MNTK_SUSPEND_ALL) == 0);
+			mp->mnt_kern_flag |= MNTK_SUSPEND_ALL;
+			MNT_IUNLOCK(mp);
+			mtx_lock(&mountlist_mtx);
+		} else {
+			printf("suspend of %s failed, error %d\n",
+			    mp->mnt_stat.f_mntonname, error);
+			mtx_lock(&mountlist_mtx);
+			vfs_unbusy(mp);
+		}
+	}
+	mtx_unlock(&mountlist_mtx);
+}
+
+void
+resume_all_fs(void)
+{
+	struct mount *mp;
+
+	mtx_lock(&mountlist_mtx);
+	TAILQ_FOREACH(mp, &mountlist, mnt_list) {
+		if ((mp->mnt_kern_flag & MNTK_SUSPEND_ALL) == 0)
+			continue;
+		mtx_unlock(&mountlist_mtx);
+		MNT_ILOCK(mp);
+		MPASS((mp->mnt_kern_flag & MNTK_SUSPEND) != 0);
+		mp->mnt_kern_flag &= ~MNTK_SUSPEND_ALL;
+		MNT_IUNLOCK(mp);
+		vfs_write_resume(mp, 0);
+		mtx_lock(&mountlist_mtx);
+		vfs_unbusy(mp);
+	}
+	mtx_unlock(&mountlist_mtx);
+}
Index: head/sys/sys/mount.h
===================================================================
--- head/sys/sys/mount.h
+++ head/sys/sys/mount.h
@@ -463,6 +463,7 @@
 #define	MNTK_VMSETSIZE_BUG	0x00010000
 #define	MNTK_UNIONFS	0x00020000	/* A hack for F_ISUNIONSTACK */
 #define	MNTK_FPLOOKUP	0x00040000	/* fast path lookup is supported */
+#define	MNTK_SUSPEND_ALL	0x00080000 /* Suspended by all-fs suspension */
 #define MNTK_NOASYNC	0x00800000	/* disable async */
 #define MNTK_UNMOUNT	0x01000000	/* unmount in progress */
 #define	MNTK_MWAIT	0x02000000	/* waiting for unmount to finish */
@@ -1047,6 +1048,9 @@
 
 enum mount_counter { MNT_COUNT_REF, MNT_COUNT_LOCKREF, MNT_COUNT_WRITEOPCOUNT };
 int	vfs_mount_fetch_counter(struct mount *, enum mount_counter);
+
+void suspend_all_fs(void);
+void resume_all_fs(void);
 
 /*
  * Code transitioning mnt_vfs_ops to > 0 issues IPIs until it observes