[src/netbsd-7]: src/sys/kern Pull up following revision(s) (requested by manu...

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

details:   https://anonhg.NetBSD.org/src/rev/36c57e51faff
branches:  netbsd-7
changeset: 799622:36c57e51faff
user:      riz <riz%NetBSD.org@localhost>
date:      Wed Nov 04 17:55:23 2015 +0000

description:
Pull up following revision(s) (requested by manu in ticket #962):
        sys/kern/vfs_mount.c: revision 1.36
Do not VFS_SYNC before VFS_UNMOUNT on force unmount
VFS_SYNC does not consider whether we are performing a force unmount or not,
and therefore it can wait for a while if the filesytstem is misbehaving.
Removing VFS_SYNC before VFS_UNMOUNT on forced unmount fixes the problem.
This should not cause harm as the VFS_SYNC seems just useless.
As noted by Chuck Silvers in
http://mail-index.netbsd.org/tech-kern/2015/07/13/msg019156.html
- Nothing seems to prevent vnodes from getting dirty again after VFS_SYNC call.
- Filesystems do flush data through vflush() in VFS_UNMOUNT anyway.
As a consequence, the VFS_SYNC call in do_unmount() could probably be
completely removed. But since such a change is quite dangerous, we just
remove it in the case of forced unmounts, which are situations where
the risk of data loss is known to the operator.

diffstat:

 sys/kern/vfs_mount.c |  6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diffs (27 lines):

diff -r 39bef209e278 -r 36c57e51faff sys/kern/vfs_mount.c
--- a/sys/kern/vfs_mount.c      Wed Nov 04 17:50:37 2015 +0000
+++ b/sys/kern/vfs_mount.c      Wed Nov 04 17:55:23 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_mount.c,v 1.30.2.2 2015/01/09 14:50:35 martin Exp $        */
+/*     $NetBSD: vfs_mount.c,v 1.30.2.3 2015/11/04 17:55:23 riz Exp $   */
 
 /*-
  * Copyright (c) 1997-2011 The NetBSD Foundation, Inc.
@@ -67,7 +67,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.30.2.2 2015/01/09 14:50:35 martin Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.30.2.3 2015/11/04 17:55:23 riz Exp $");
 
 #define _VFS_VNODE_PRIVATE
 
@@ -835,7 +835,7 @@
        if (mp->mnt_syncer != NULL)
                vfs_deallocate_syncvnode(mp);
        error = 0;
-       if ((mp->mnt_flag & MNT_RDONLY) == 0) {
+       if (((mp->mnt_flag & MNT_RDONLY) == 0) && ((flags & MNT_FORCE) == 0)) {
                error = VFS_SYNC(mp, MNT_WAIT, l->l_cred);
        }
        if (error == 0 || (flags & MNT_FORCE)) {