f15ccf8836
file systems to safely access their disk devices, and adapt FFS to use it. Also add a new BO_NOBUFS flag to allow enforcing that file systems using mntfs vnodes do not accidentally use the original devfs vnode to create buffers. Reviewed by: kib, mckusick Approved by: imp (mentor) Sponsored by: Netflix Differential Revision: https://reviews.freebsd.org/D23787
96 lines
2.9 KiB
C
96 lines
2.9 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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*
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* Copyright (c) 2020 Netflix, Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
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* TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
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* USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/conf.h>
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#include <sys/mount.h>
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#include <sys/vnode.h>
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/*
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* The "mntfs" VCHR vnodes implemented here provide a safe way for file systems
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* to access their disk devices. Using the normal devfs vnode has the problem
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* that if the device disappears, the devfs vnode is vgone'd as part of
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* removing it from the application-visible namespace, and some file systems
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* (notably FFS with softdep) get very unhappy if their dirty buffers are
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* invalidated out from under them. By using a separate, private vnode,
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* file systems are able to clean up their buffer state in a controlled fashion
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* when the underlying device disappears.
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*/
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static int
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mntfs_reclaim(struct vop_reclaim_args *ap)
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{
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struct vnode *vp = ap->a_vp;
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dev_rel(vp->v_rdev);
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return (0);
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}
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struct vop_vector mntfs_vnodeops = {
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.vop_default = &default_vnodeops,
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.vop_fsync = vop_stdfsync,
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.vop_strategy = VOP_PANIC,
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.vop_reclaim = mntfs_reclaim,
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};
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VFS_VOP_VECTOR_REGISTER(mntfs_vnodeops);
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/*
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* Allocate a private VCHR vnode for use by a mounted fs.
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* The underlying device will be the same as for the given vnode.
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* This mntfs vnode must be freed with mntfs_freevp() rather than just
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* releasing the reference.
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*/
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struct vnode *
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mntfs_allocvp(struct mount *mp, struct vnode *ovp)
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{
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struct vnode *vp;
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struct cdev *dev;
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ASSERT_VOP_ELOCKED(ovp, __func__);
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dev = ovp->v_rdev;
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getnewvnode("mntfs", mp, &mntfs_vnodeops, &vp);
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vp->v_type = VCHR;
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vp->v_data = NULL;
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dev_ref(dev);
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vp->v_rdev = dev;
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return (vp);
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}
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void
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mntfs_freevp(struct vnode *vp)
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{
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vgone(vp);
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vrele(vp);
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}
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