[src/trunk]: src/sys/kern Allow dounmount() with file system already suspended.

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

details:   https://anonhg.NetBSD.org/src/rev/5ad1eb233f13
branches:  trunk
changeset: 448571:5ad1eb233f13
user:      hannken <hannken%NetBSD.org@localhost>
date:      Tue Feb 05 09:49:44 2019 +0000

description:
Allow dounmount() with file system already suspended.

Remove no longer valid test for layered mounts,
ZFS will unmount snapshots bottom up.

diffstat:

 sys/kern/vfs_mount.c |  31 +++++++++++--------------------
 1 files changed, 11 insertions(+), 20 deletions(-)

diffs (77 lines):

diff -r eeff65ddfc9c -r 5ad1eb233f13 sys/kern/vfs_mount.c
--- a/sys/kern/vfs_mount.c      Tue Feb 05 09:45:38 2019 +0000
+++ b/sys/kern/vfs_mount.c      Tue Feb 05 09:49:44 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_mount.c,v 1.67 2017/08/21 09:00:21 hannken Exp $   */
+/*     $NetBSD: vfs_mount.c,v 1.68 2019/02/05 09:49:44 hannken 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 1.67 2017/08/21 09:00:21 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.68 2019/02/05 09:49:44 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
@@ -835,10 +835,9 @@
 int
 dounmount(struct mount *mp, int flags, struct lwp *l)
 {
-       mount_iterator_t *iter;
-       struct mount *cmp;
        vnode_t *coveredvp;
        int error, async, used_syncer, used_extattr;
+       const bool was_suspended = fstrans_is_owner(mp);
 
 #if NVERIEXEC > 0
        error = veriexec_unmountchk(mp);
@@ -846,22 +845,12 @@
                return (error);
 #endif /* NVERIEXEC > 0 */
 
-       /*
-        * No unmount below layered mounts.
-        */
-       mountlist_iterator_init(&iter);
-       while ((cmp = mountlist_iterator_next(iter)) != NULL) {
-               if (cmp->mnt_lower == mp) {
-                       mountlist_iterator_destroy(iter);
-                       return EBUSY;
+       if (!was_suspended) {
+               error = vfs_suspend(mp, 0);
+               if (error) {
+                       return error;
                }
        }
-       mountlist_iterator_destroy(iter);
-
-       error = vfs_suspend(mp, 0);
-       if (error) {
-               return error;
-       }
 
        KASSERT((mp->mnt_iflag & IMNT_GONE) == 0);
 
@@ -888,7 +877,8 @@
                        vfs_syncer_add_to_worklist(mp);
                mp->mnt_flag |= async;
                mutex_exit(&mp->mnt_updating);
-               vfs_resume(mp);
+               if (!was_suspended)
+                       vfs_resume(mp);
                if (used_extattr) {
                        if (start_extattr(mp) != 0)
                                mp->mnt_flag &= ~MNT_EXTATTR;
@@ -905,7 +895,8 @@
         * vfs_busy() from succeeding.
         */
        mp->mnt_iflag |= IMNT_GONE;
-       vfs_resume(mp);
+       if (!was_suspended)
+               vfs_resume(mp);
 
        if ((coveredvp = mp->mnt_vnodecovered) != NULLVP) {
                vn_lock(coveredvp, LK_EXCLUSIVE | LK_RETRY);