81 lines
2.4 KiB
Go
81 lines
2.4 KiB
Go
// Copyright 2020 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package genericfstree provides tools for implementing vfs.FilesystemImpls
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// where a single statically-determined lock or set of locks is sufficient to
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// ensure that a Dentry's name and parent are contextually immutable.
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//
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// Clients using this package must use the go_template_instance rule in
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// tools/go_generics/defs.bzl to create an instantiation of this template
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// package, providing types to use in place of Dentry.
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package genericfstree
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import (
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"gvisor.dev/gvisor/pkg/fspath"
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"gvisor.dev/gvisor/pkg/sentry/vfs"
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)
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// Dentry is a required type parameter that is a struct with the given fields.
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type Dentry struct {
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// vfsd is the embedded vfs.Dentry corresponding to this vfs.DentryImpl.
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vfsd vfs.Dentry
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// parent is the parent of this Dentry in the filesystem's tree. If this
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// Dentry is a filesystem root, parent is nil.
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parent *Dentry
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// name is the name of this Dentry in its parent. If this Dentry is a
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// filesystem root, name is unspecified.
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name string
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}
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// IsAncestorDentry returns true if d is an ancestor of d2; that is, d is
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// either d2's parent or an ancestor of d2's parent.
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func IsAncestorDentry(d, d2 *Dentry) bool {
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for {
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if d2.parent == d {
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return true
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}
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if d2.parent == d2 {
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return false
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}
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d2 = d2.parent
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}
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}
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// ParentOrSelf returns d.parent. If d.parent is nil, ParentOrSelf returns d.
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func ParentOrSelf(d *Dentry) *Dentry {
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if d.parent != nil {
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return d.parent
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}
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return d
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}
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// PrependPath is a generic implementation of FilesystemImpl.PrependPath().
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func PrependPath(vfsroot vfs.VirtualDentry, mnt *vfs.Mount, d *Dentry, b *fspath.Builder) error {
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for {
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if mnt == vfsroot.Mount() && &d.vfsd == vfsroot.Dentry() {
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return vfs.PrependPathAtVFSRootError{}
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}
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if &d.vfsd == mnt.Root() {
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return nil
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}
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if d.parent == nil {
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return vfs.PrependPathAtNonMountRootError{}
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}
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b.PrependComponent(d.name)
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d = d.parent
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}
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}
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