829f0bcb5f
To quote from a comment above vput_final: <quote> * XXX Some filesystems pass in an exclusively locked vnode and strongly depend * on the lock being held all the way until VOP_INACTIVE. This in particular * happens with UFS which adds half-constructed vnodes to the hash, where they * can be found by other code. </quote> As is there is no mechanism which allows filesystems to denote that a vnode is fully initialized, consequently problems like the above are only found the hard way(tm). Add rudimentary support for state transitions, which in particular allow to assert the vnode is not legally unlocked until its fate is decided (either construction finishes or vgone is called to abort it). The new field lands in a 1-byte hole, thus it does not grow the struct. Bump __FreeBSD_version to 1400077 Reviewed by: kib (previous version) Tested by: pho Differential Revision: https://reviews.freebsd.org/D37759
99 lines
3.0 KiB
C
99 lines
3.0 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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VOP_UNLOCK(ovp);
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vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
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vn_set_state(vp, VSTATE_CONSTRUCTED);
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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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ASSERT_VOP_ELOCKED(vp, "mntfs_freevp");
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vgone(vp);
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vput(vp);
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}
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