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Index: sys/conf/files
===================================================================
--- sys/conf/files
+++ sys/conf/files
@@ -3486,6 +3486,7 @@
fs/fuse/fuse_node.c optional fusefs
fs/fuse/fuse_vfsops.c optional fusefs
fs/fuse/fuse_vnops.c optional fusefs
+fs/mntfs/mntfs_vnops.c standard
fs/msdosfs/msdosfs_conv.c optional msdosfs
fs/msdosfs/msdosfs_denode.c optional msdosfs
fs/msdosfs/msdosfs_fat.c optional msdosfs
Index: sys/fs/mntfs/mntfs_vnops.c
===================================================================
--- /dev/null
+++ sys/fs/mntfs/mntfs_vnops.c
@@ -0,0 +1,96 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2020 Chuck Silvers
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+ * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+ * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include <sys/param.h>
+#include <sys/conf.h>
+#include <sys/mount.h>
+#include <sys/vnode.h>
+
+/*
+ * The "mntfs" VCHR vnodes implemented here provide a safe way for file systems
+ * to access their disk devices. Using the normal devfs vnode has the problem
+ * that if the device disappears, the devfs vnode is vgone'd as part of
+ * removing it from the application-visible namespace, and some file systems
+ * (notably FFS with softdep) get very unhappy if their dirty buffers are
+ * invalidated out from under them. By using a separate, private vnode,
+ * file systems are able to clean up their buffer state in a controlled fashion
+ * when the underlying device disappears.
+ */
+
+static int
+mntfs_reclaim(struct vop_reclaim_args *ap)
+{
+ struct vnode *vp = ap->a_vp;
+
+ dev_rel(vp->v_rdev);
+ return (0);
+}
+
+struct vop_vector mntfs_vnodeops = {
+ .vop_default = &default_vnodeops,
+
+ .vop_fsync = vop_stdfsync,
+ .vop_strategy = VOP_PANIC,
+ .vop_reclaim = mntfs_reclaim,
+};
+VFS_VOP_VECTOR_REGISTER(mntfs_vnodeops);
+
+/*
+ * Allocate a private VCHR vnode for use by a mounted fs.
+ * The underlying device will be the same as for the given vnode.
+ * This mntfs vnode must be freed with mntfs_freevp() rather than just
+ * releasing the reference.
+ */
+struct vnode *
+mntfs_allocvp(struct mount *mp, struct vnode *ovp)
+{
+ struct vnode *vp;
+ struct cdev *dev;
+
+ ASSERT_VOP_ELOCKED(ovp, __func__);
+
+ dev = ovp->v_rdev;
+
+ getnewvnode("mntfs", mp, &mntfs_vnodeops, &vp);
+ vp->v_type = VCHR;
+ vp->v_data = NULL;
+ dev_ref(dev);
+ vp->v_rdev = dev;
+
+ return (vp);
+}
+
+void
+mntfs_freevp(struct vnode *vp)
+{
+
+ vgone(vp);
+ vrele(vp);
+}
Index: sys/sys/mount.h
===================================================================
--- sys/sys/mount.h
+++ sys/sys/mount.h
@@ -940,6 +940,8 @@
#define vfsconf_unlock() sx_xunlock(&vfsconf_sx)
#define vfsconf_slock() sx_slock(&vfsconf_sx)
#define vfsconf_sunlock() sx_sunlock(&vfsconf_sx)
+struct vnode *mntfs_allocvp(struct mount *, struct vnode *);
+void mntfs_freevp(struct vnode *);
/*
* Declarations for these vfs default operations are located in
Index: sys/ufs/ffs/ffs_vfsops.c
===================================================================
--- sys/ufs/ffs/ffs_vfsops.c
+++ sys/ufs/ffs/ffs_vfsops.c
@@ -151,7 +151,7 @@
static int
ffs_mount(struct mount *mp)
{
- struct vnode *devvp;
+ struct vnode *devvp, *odevvp;
struct thread *td;
struct ufsmount *ump = NULL;
struct fs *fs;
@@ -246,6 +246,7 @@
if (mp->mnt_flag & MNT_UPDATE) {
ump = VFSTOUFS(mp);
fs = ump->um_fs;
+ odevvp = ump->um_odevvp;
devvp = ump->um_devvp;
if (fsckpid == -1 && ump->um_fsckpid > 0) {
if ((error = ffs_flushfiles(mp, WRITECLOSE, td)) != 0 ||
@@ -337,16 +338,15 @@
* If upgrade to read-write by non-root, then verify
* that user has necessary permissions on the device.
*/
- vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
- error = VOP_ACCESS(devvp, VREAD | VWRITE,
+ vn_lock(odevvp, LK_EXCLUSIVE | LK_RETRY);
+ error = VOP_ACCESS(odevvp, VREAD | VWRITE,
td->td_ucred, td);
if (error)
error = priv_check(td, PRIV_VFS_MOUNT_PERM);
+ VOP_UNLOCK(odevvp);
if (error) {
- VOP_UNLOCK(devvp);
return (error);
}
- VOP_UNLOCK(devvp);
fs->fs_flags &= ~FS_UNCLEAN;
if (fs->fs_clean == 0) {
fs->fs_flags |= FS_UNCLEAN;
@@ -782,8 +782,8 @@
* Common code for mount and mountroot
*/
static int
-ffs_mountfs(devvp, mp, td)
- struct vnode *devvp;
+ffs_mountfs(odevvp, mp, td)
+ struct vnode *odevvp;
struct mount *mp;
struct thread *td;
{
@@ -794,6 +794,7 @@
struct ucred *cred;
struct g_consumer *cp;
struct mount *nmp;
+ struct vnode *devvp;
int candelete, canspeedup;
off_t loc;
@@ -802,11 +803,13 @@
cred = td ? td->td_ucred : NOCRED;
ronly = (mp->mnt_flag & MNT_RDONLY) != 0;
+ devvp = mntfs_allocvp(mp, odevvp);
+ VOP_UNLOCK(odevvp);
KASSERT(devvp->v_type == VCHR, ("reclaimed devvp"));
dev = devvp->v_rdev;
if (atomic_cmpset_acq_ptr((uintptr_t *)&dev->si_mountpt, 0,
(uintptr_t)mp) == 0) {
- VOP_UNLOCK(devvp);
+ mntfs_freevp(devvp);
return (EBUSY);
}
g_topology_lock();
@@ -814,12 +817,11 @@
g_topology_unlock();
if (error != 0) {
atomic_store_rel_ptr((uintptr_t *)&dev->si_mountpt, 0);
- VOP_UNLOCK(devvp);
+ mntfs_freevp(devvp);
return (error);
}
dev_ref(dev);
devvp->v_bufobj.bo_ops = &ffs_ops;
- VOP_UNLOCK(devvp);
if (dev->si_iosize_max != 0)
mp->mnt_iosize_max = dev->si_iosize_max;
if (mp->mnt_iosize_max > MAXPHYS)
@@ -1020,6 +1022,7 @@
ump->um_mountp = mp;
ump->um_dev = dev;
ump->um_devvp = devvp;
+ ump->um_odevvp = odevvp;
ump->um_nindir = fs->fs_nindir;
ump->um_bptrtodb = fs->fs_fsbtodb;
ump->um_seqinc = fs->fs_frag;
@@ -1100,6 +1103,7 @@
mp->mnt_data = NULL;
}
atomic_store_rel_ptr((uintptr_t *)&dev->si_mountpt, 0);
+ mntfs_freevp(devvp);
dev_rel(dev);
return (error);
}
@@ -1305,7 +1309,8 @@
g_vfs_close(ump->um_cp);
g_topology_unlock();
atomic_store_rel_ptr((uintptr_t *)&ump->um_dev->si_mountpt, 0);
- vrele(ump->um_devvp);
+ mntfs_freevp(ump->um_devvp);
+ vrele(ump->um_odevvp);
dev_rel(ump->um_dev);
mtx_destroy(UFS_MTX(ump));
if (mp->mnt_gjprovider != NULL) {
Index: sys/ufs/ufs/ufsmount.h
===================================================================
--- sys/ufs/ufs/ufsmount.h
+++ sys/ufs/ufs/ufsmount.h
@@ -83,7 +83,8 @@
struct cdev *um_dev; /* (r) device mounted */
struct g_consumer *um_cp; /* (r) GEOM access point */
struct bufobj *um_bo; /* (r) Buffer cache object */
- struct vnode *um_devvp; /* (r) blk dev mounted vnode */
+ struct vnode *um_odevvp; /* (r) devfs dev vnode */
+ struct vnode *um_devvp; /* (r) mntfs private vnode */
u_long um_fstype; /* (c) type of filesystem */
struct fs *um_fs; /* (r) pointer to superblock */
struct ufs_extattr_per_mount um_extattr; /* (c) extended attrs */

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