[src/trunk]: src/sys/ufs/ffs need to turn off async during ffs_sync(), otherw...

[jdolecek <jdolecek%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/092ec696f61d
branches:  trunk
changeset: 822365:092ec696f61d
user:      jdolecek <jdolecek%NetBSD.org@localhost>
date:      Thu Mar 16 22:09:19 2017 +0000

description:
need to turn off async during ffs_sync(), otherwise its bwrite() calls are
themselves turned to bdwrite(), creating dirty delayed writes

fixes panic for 'mount -o log,async ...' reported by Masanobu SAITOH
on current-users; fix help by hannken@, thank you

diffstat:

 sys/ufs/ffs/ffs_wapbl.c |  14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

diffs (37 lines):

diff -r c7843fc2026c -r 092ec696f61d sys/ufs/ffs/ffs_wapbl.c
--- a/sys/ufs/ffs/ffs_wapbl.c   Thu Mar 16 16:32:12 2017 +0000
+++ b/sys/ufs/ffs/ffs_wapbl.c   Thu Mar 16 22:09:19 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ffs_wapbl.c,v 1.38 2017/03/10 22:43:03 jdolecek Exp $  */
+/*     $NetBSD: ffs_wapbl.c,v 1.39 2017/03/16 22:09:19 jdolecek Exp $  */
 
 /*-
  * Copyright (c) 2003,2006,2008 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ffs_wapbl.c,v 1.38 2017/03/10 22:43:03 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ffs_wapbl.c,v 1.39 2017/03/16 22:09:19 jdolecek Exp $");
 
 #define WAPBL_INTERNAL
 
@@ -340,10 +340,16 @@
 
                        /*
                         * Make sure we don't carry over any delayed write
-                        * buffers when updating to log.
+                        * buffers when updating to log. Need to turn off
+                        * async termporarily, to prevent ffs_sync() writes
+                        * themselves being turned into delayed writes.
                         */
-                       if (mp->mnt_flag & MNT_UPDATE)
+                       if (mp->mnt_flag & MNT_UPDATE) {
+                               int saveflag = mp->mnt_flag & MNT_ASYNC;
+                               mp->mnt_flag &= ~MNT_ASYNC;
                                ffs_sync(mp, MNT_WAIT, FSCRED);
+                               mp->mnt_flag |= saveflag;
+                       }
 
                        error = wapbl_log_position(mp, fs, devvp, &off,
                            &count, &blksize, &extradata);