Module Name: src
Committed By: hannken
Date: Fri Jul 8 07:43:19 UTC 2022
Modified Files:
src/sys/kern: vfs_mount.c
Log Message:
Suspend file system after VFS_MOUNT() and before taking mnt_updating.
Prevents deadlock against concurrent unmounts of layered file systems.
To generate a diff of this commit:
cvs rdiff -u -r1.93 -r1.94 src/sys/kern/vfs_mount.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/vfs_mount.c
diff -u src/sys/kern/vfs_mount.c:1.93 src/sys/kern/vfs_mount.c:1.94
--- src/sys/kern/vfs_mount.c:1.93 Sat Apr 9 23:38:33 2022
+++ src/sys/kern/vfs_mount.c Fri Jul 8 07:43:19 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: vfs_mount.c,v 1.93 2022/04/09 23:38:33 riastradh Exp $ */
+/* $NetBSD: vfs_mount.c,v 1.94 2022/07/08 07:43:19 hannken Exp $ */
/*-
* Copyright (c) 1997-2020 The NetBSD Foundation, Inc.
@@ -67,7 +67,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.93 2022/04/09 23:38:33 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.94 2022/07/08 07:43:19 hannken Exp $");
#include <sys/param.h>
#include <sys/kernel.h>
@@ -773,12 +773,20 @@ mount_domount(struct lwp *l, vnode_t **v
*/
mp->mnt_flag = flags & (MNT_BASIC_FLAGS | MNT_FORCE | MNT_IGNORE);
- mutex_enter(mp->mnt_updating);
error = VFS_MOUNT(mp, path, data, data_len);
mp->mnt_flag &= ~MNT_OP_FLAGS;
- if (error != 0)
- goto err_unmounted;
+ if (error != 0) {
+ vfs_rele(mp);
+ return error;
+ }
+
+ /* Suspend new file system before taking mnt_updating. */
+ do {
+ error2 = vfs_suspend(mp, 0);
+ } while (error2 == EINTR || error2 == ERESTART);
+ KASSERT(error2 == 0 || error2 == EOPNOTSUPP);
+ mutex_enter(mp->mnt_updating);
/*
* Validate and prepare the mount point.
@@ -823,6 +831,8 @@ mount_domount(struct lwp *l, vnode_t **v
mount_checkdirs(vp);
mutex_exit(mp->mnt_updating);
+ if (error2 == 0)
+ vfs_resume(mp);
/* Hold an additional reference to the mount across VFS_START(). */
vfs_ref(mp);
@@ -840,19 +850,11 @@ mount_domount(struct lwp *l, vnode_t **v
return error;
err_mounted:
- do {
- error2 = vfs_suspend(mp, 0);
- } while (error2 == EINTR || error2 == ERESTART);
- KASSERT(error2 == 0 || error2 == EOPNOTSUPP);
-
if (VFS_UNMOUNT(mp, MNT_FORCE) != 0)
panic("Unmounting fresh file system failed");
-
+ mutex_exit(mp->mnt_updating);
if (error2 == 0)
vfs_resume(mp);
-
-err_unmounted:
- mutex_exit(mp->mnt_updating);
vfs_rele(mp);
return error;
