1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2020 Netflix, Inc. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR 17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 23 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR 24 * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE 25 * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26 * 27 * $FreeBSD$ 28 */ 29 30 #include <sys/param.h> 31 #include <sys/conf.h> 32 #include <sys/mount.h> 33 #include <sys/vnode.h> 34 35 /* 36 * The "mntfs" VCHR vnodes implemented here provide a safe way for file systems 37 * to access their disk devices. Using the normal devfs vnode has the problem 38 * that if the device disappears, the devfs vnode is vgone'd as part of 39 * removing it from the application-visible namespace, and some file systems 40 * (notably FFS with softdep) get very unhappy if their dirty buffers are 41 * invalidated out from under them. By using a separate, private vnode, 42 * file systems are able to clean up their buffer state in a controlled fashion 43 * when the underlying device disappears. 44 */ 45 46 static int 47 mntfs_reclaim(struct vop_reclaim_args *ap) 48 { 49 struct vnode *vp = ap->a_vp; 50 51 dev_rel(vp->v_rdev); 52 return (0); 53 } 54 55 struct vop_vector mntfs_vnodeops = { 56 .vop_default = &default_vnodeops, 57 58 .vop_fsync = vop_stdfsync, 59 .vop_strategy = VOP_PANIC, 60 .vop_reclaim = mntfs_reclaim, 61 }; 62 VFS_VOP_VECTOR_REGISTER(mntfs_vnodeops); 63 64 /* 65 * Allocate a private VCHR vnode for use by a mounted fs. 66 * The underlying device will be the same as for the given vnode. 67 * This mntfs vnode must be freed with mntfs_freevp() rather than just 68 * releasing the reference. 69 */ 70 struct vnode * 71 mntfs_allocvp(struct mount *mp, struct vnode *ovp) 72 { 73 struct vnode *vp; 74 struct cdev *dev; 75 76 ASSERT_VOP_ELOCKED(ovp, __func__); 77 78 dev = ovp->v_rdev; 79 80 getnewvnode("mntfs", mp, &mntfs_vnodeops, &vp); 81 vp->v_type = VCHR; 82 vp->v_data = NULL; 83 dev_ref(dev); 84 vp->v_rdev = dev; 85 86 return (vp); 87 } 88 89 void 90 mntfs_freevp(struct vnode *vp) 91 { 92 93 vgone(vp); 94 vrele(vp); 95 } 96