1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 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 28 #include <sys/param.h> 29 #include <sys/conf.h> 30 #include <sys/mount.h> 31 #include <sys/vnode.h> 32 33 /* 34 * The "mntfs" VCHR vnodes implemented here provide a safe way for file systems 35 * to access their disk devices. Using the normal devfs vnode has the problem 36 * that if the device disappears, the devfs vnode is vgone'd as part of 37 * removing it from the application-visible namespace, and some file systems 38 * (notably FFS with softdep) get very unhappy if their dirty buffers are 39 * invalidated out from under them. By using a separate, private vnode, 40 * file systems are able to clean up their buffer state in a controlled fashion 41 * when the underlying device disappears. 42 */ 43 44 static int 45 mntfs_reclaim(struct vop_reclaim_args *ap) 46 { 47 struct vnode *vp = ap->a_vp; 48 49 dev_rel(vp->v_rdev); 50 return (0); 51 } 52 53 struct vop_vector mntfs_vnodeops = { 54 .vop_default = &default_vnodeops, 55 56 .vop_fsync = vop_stdfsync, 57 .vop_strategy = VOP_PANIC, 58 .vop_reclaim = mntfs_reclaim, 59 }; 60 VFS_VOP_VECTOR_REGISTER(mntfs_vnodeops); 61 62 /* 63 * Allocate a private VCHR vnode for use by a mounted fs. 64 * The underlying device will be the same as for the given vnode. 65 * This mntfs vnode must be freed with mntfs_freevp() rather than just 66 * releasing the reference. 67 */ 68 struct vnode * 69 mntfs_allocvp(struct mount *mp, struct vnode *ovp) 70 { 71 struct vnode *vp; 72 struct cdev *dev; 73 74 ASSERT_VOP_ELOCKED(ovp, __func__); 75 76 dev = ovp->v_rdev; 77 78 getnewvnode("mntfs", mp, &mntfs_vnodeops, &vp); 79 vp->v_type = VCHR; 80 vp->v_data = NULL; 81 dev_ref(dev); 82 vp->v_rdev = dev; 83 84 VOP_UNLOCK(ovp); 85 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY); 86 vn_set_state(vp, VSTATE_CONSTRUCTED); 87 return (vp); 88 } 89 90 void 91 mntfs_freevp(struct vnode *vp) 92 { 93 ASSERT_VOP_ELOCKED(vp, "mntfs_freevp"); 94 vgone(vp); 95 vput(vp); 96 } 97