[src/trunk]: src Move fstrans_unmount() to vfs_rele(), just before it would f...

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

details:   https://anonhg.NetBSD.org/src/rev/15946f582b8b
branches:  trunk
changeset: 449062:15946f582b8b
user:      hannken <hannken%NetBSD.org@localhost>
date:      Wed Feb 20 10:08:37 2019 +0000

description:
Move fstrans_unmount() to vfs_rele(), just before it would free the mount.
Don't take a mount reference for fstrans as it gets notified about the release.

Defer the final free of the mount to fstrans_mount_dtor() when fstrans
has released all references to this mount.  Prevents the mount's memory
to be reused as a new mount before fstrans released all references.

Address PR kern/53928 modules/t_builtin:disable test case randomly fails.

diffstat:

 external/cddl/osnet/dist/uts/common/fs/zfs/zfs_ctldir.c |   2 --
 sys/kern/vfs_mount.c                                    |  14 +++++++++-----
 sys/kern/vfs_trans.c                                    |  13 ++++++++-----
 3 files changed, 17 insertions(+), 12 deletions(-)

diffs (126 lines):

diff -r 3c16a5b1c282 -r 15946f582b8b external/cddl/osnet/dist/uts/common/fs/zfs/zfs_ctldir.c
--- a/external/cddl/osnet/dist/uts/common/fs/zfs/zfs_ctldir.c   Wed Feb 20 10:07:27 2019 +0000
+++ b/external/cddl/osnet/dist/uts/common/fs/zfs/zfs_ctldir.c   Wed Feb 20 10:08:37 2019 +0000
@@ -1261,7 +1261,6 @@
 
 #ifdef __NetBSD__
 
-#include <sys/fstrans.h>
 #include <sys/malloc.h>
 #include <sys/pathname.h>
 #include <miscfs/genfs/genfs.h>
@@ -1354,7 +1353,6 @@
 out:;
        if (error && vfsp) {
                mutex_exit(&vfsp->mnt_updating);
-               fstrans_unmount(vfsp);
                vfs_rele(vfsp);
        }
        PNBUF_PUT(osname);
diff -r 3c16a5b1c282 -r 15946f582b8b sys/kern/vfs_mount.c
--- a/sys/kern/vfs_mount.c      Wed Feb 20 10:07:27 2019 +0000
+++ b/sys/kern/vfs_mount.c      Wed Feb 20 10:08:37 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_mount.c,v 1.69 2019/02/20 10:07:27 hannken Exp $   */
+/*     $NetBSD: vfs_mount.c,v 1.70 2019/02/20 10:08:37 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 1.69 2019/02/20 10:07:27 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.70 2019/02/20 10:08:37 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
@@ -297,7 +297,13 @@
        if (mp->mnt_op != NULL) {
                vfs_delref(mp->mnt_op);
        }
-       kmem_free(mp, sizeof(*mp));
+       fstrans_unmount(mp);
+       /*
+        * Final free of mp gets done from fstrans_mount_dtor().
+        *
+        * Prevents this memory to be reused as a mount before
+        * fstrans releases all references to it.
+        */
 }
 
 /*
@@ -818,7 +824,6 @@
 err_unmounted:
        vp->v_mountedhere = NULL;
        mutex_exit(&mp->mnt_updating);
-       fstrans_unmount(mp);
        vfs_rele(mp);
 
        return error;
@@ -906,7 +911,6 @@
                panic("unmount: dangling vnode");
        vfs_hooks_unmount(mp);
 
-       fstrans_unmount(mp);
        vfs_rele(mp);   /* reference from mount() */
        if (coveredvp != NULLVP) {
                vrele(coveredvp);
diff -r 3c16a5b1c282 -r 15946f582b8b sys/kern/vfs_trans.c
--- a/sys/kern/vfs_trans.c      Wed Feb 20 10:07:27 2019 +0000
+++ b/sys/kern/vfs_trans.c      Wed Feb 20 10:08:37 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_trans.c,v 1.52 2019/02/20 10:07:27 hannken Exp $   */
+/*     $NetBSD: vfs_trans.c,v 1.53 2019/02/20 10:08:37 hannken Exp $   */
 
 /*-
  * Copyright (c) 2007 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_trans.c,v 1.52 2019/02/20 10:07:27 hannken Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_trans.c,v 1.53 2019/02/20 10:08:37 hannken Exp $");
 
 /*
  * File system transaction operations.
@@ -186,8 +186,8 @@
 
        mutex_exit(&fstrans_mount_lock);
 
+       kmem_free(mp, sizeof(*mp));
        kmem_free(fmi, sizeof(*fmi));
-       vfs_rele(mp);
 }
 
 /*
@@ -208,8 +208,6 @@
        mp->mnt_transinfo = newfmi;
        mutex_exit(&fstrans_mount_lock);
 
-       vfs_ref(mp);
-
        return 0;
 }
 
@@ -719,8 +717,11 @@
 
        KASSERT(mp != dead_rootmount);
 
+       mutex_enter(&fstrans_mount_lock);
        fmi = mp->mnt_transinfo;
        KASSERT(fmi != NULL);
+       fmi->fmi_ref_cnt += 1;
+       mutex_exit(&fstrans_mount_lock);
 
        newch = kmem_alloc(sizeof(*newch), KM_SLEEP);
        newch->ch_func = func;
@@ -758,6 +759,8 @@
        }
        cow_change_done(mp);
 
+       fstrans_mount_dtor(mp);
+
        return hp ? 0 : EINVAL;
 }