Add functions syncer_suspend() and syncer_resume(), which are supposed

to be called before suspension and after resume, correspondingly.  The
syncer_suspend() ensures that all filesystems dirty data and metadata
are saved to the permanent storage, and stops kernel threads which
might modify filesystems.  The syncer_resume() restores stopped
threads.

For now, only syncer is stopped.  This is needed, because each sync
loop causes superblock updates for UFS.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week

1 files changed, 21 insertions, 1 deletions

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 345aad6..b4dde06 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -1773,6 +1773,8 @@ sync_vnode(struct synclist *slp, struct bufobj **bo, struct thread *td)
 	return (0);
 }
 
+static int first_printf = 1;
+
 /*
  * System filesystem synchronizer daemon.
  */
@@ -1791,7 +1793,6 @@ sched_sync(void)
 
 	last_work_seen = 0;
 	syncer_final_iter = 0;
-	first_printf = 1;
 	syncer_state = SYNCER_RUNNING;
 	starttime = time_uptime;
 	td->td_pflags |= TDP_NORUNNINGBUF;
@@ -1955,6 +1956,25 @@ syncer_shutdown(void *arg, int howto)
 	kproc_shutdown(arg, howto);
 }
 
+void
+syncer_suspend(void)
+{
+
+	syncer_shutdown(updateproc, 0);
+}
+
+void
+syncer_resume(void)
+{
+
+	mtx_lock(&sync_mtx);
+	first_printf = 1;
+	syncer_state = SYNCER_RUNNING;
+	mtx_unlock(&sync_mtx);
+	cv_broadcast(&sync_wakeup);
+	kproc_resume(updateproc);
+}
+
 /*
  * Reassign a buffer from one vnode to another.
  * Used to assign file specific control information