diff options
Diffstat (limited to 'pkg/sentry/vfs/vfs.go')
| -rw-r--r-- | pkg/sentry/vfs/vfs.go | 135 |
1 files changed, 0 insertions, 135 deletions
diff --git a/pkg/sentry/vfs/vfs.go b/pkg/sentry/vfs/vfs.go deleted file mode 100644 index 4a8a69540..000000000 --- a/pkg/sentry/vfs/vfs.go +++ /dev/null @@ -1,135 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -// Package vfs implements a virtual filesystem layer. -// -// Lock order: -// -// Filesystem implementation locks -// VirtualFilesystem.mountMu -// VirtualFilesystem.fsTypesMu -package vfs - -import ( - "sync" -) - -// A VirtualFilesystem (VFS for short) combines Filesystems in trees of Mounts. -// -// There is no analogue to the VirtualFilesystem type in Linux, as the -// equivalent state in Linux is global. -type VirtualFilesystem struct { - // mountMu serializes mount mutations. - // - // mountMu is analogous to Linux's namespace_sem. - mountMu sync.RWMutex - - // mounts maps (mount parent, mount point) pairs to mounts. (Since mounts - // are uniquely namespaced, including mount parent in the key correctly - // handles both bind mounts and mount namespaces; Linux does the same.) - // Synchronization between mutators and readers is provided by mounts.seq; - // synchronization between mutators is provided by mountMu. - // - // mounts is used to follow mount points during path traversal. We use a - // single table rather than per-Dentry tables to reduce size (and therefore - // cache footprint) for the vast majority of Dentries that are not mount - // points. - // - // mounts is analogous to Linux's mount_hashtable. - mounts mountTable - - // mountpoints maps mount points to mounts at those points in all - // namespaces. mountpoints is protected by mountMu. - // - // mountpoints is used to find mounts that must be unmounted due to - // removal of a mount point Dentry from another mount namespace. ("A file - // or directory that is a mount point in one namespace that is not a mount - // point in another namespace, may be renamed, unlinked, or removed - // (rmdir(2)) in the mount namespace in which it is not a mount point - // (subject to the usual permission checks)." - mount_namespaces(7)) - // - // mountpoints is analogous to Linux's mountpoint_hashtable. - mountpoints map[*Dentry]map[*Mount]struct{} - - // fsTypes contains all FilesystemTypes that are usable in the - // VirtualFilesystem. fsTypes is protected by fsTypesMu. - fsTypesMu sync.RWMutex - fsTypes map[string]FilesystemType -} - -// New returns a new VirtualFilesystem with no mounts or FilesystemTypes. -func New() *VirtualFilesystem { - vfs := &VirtualFilesystem{ - mountpoints: make(map[*Dentry]map[*Mount]struct{}), - fsTypes: make(map[string]FilesystemType), - } - vfs.mounts.Init() - return vfs -} - -// A VirtualDentry represents a node in a VFS tree, by combining a Dentry -// (which represents a node in a Filesystem's tree) and a Mount (which -// represents the Filesystem's position in a VFS mount tree). -// -// VirtualDentry's semantics are similar to that of a Go interface object -// representing a pointer: it is a copyable value type that represents -// references to another entity. The zero value of VirtualDentry is an "empty -// VirtualDentry", directly analogous to a nil interface object. -// VirtualDentry.Ok() checks that a VirtualDentry is not zero-valued; unless -// otherwise specified, all other VirtualDentry methods require -// VirtualDentry.Ok() == true. -// -// Mounts and Dentries are reference-counted, requiring that users call -// VirtualDentry.{Inc,Dec}Ref() as appropriate. We often colloquially refer to -// references on the Mount and Dentry referred to by a VirtualDentry as -// references on the VirtualDentry itself. Unless otherwise specified, all -// VirtualDentry methods require that a reference is held on the VirtualDentry. -// -// VirtualDentry is analogous to Linux's struct path. -type VirtualDentry struct { - mount *Mount - dentry *Dentry -} - -// Ok returns true if vd is not empty. It does not require that a reference is -// held. -func (vd VirtualDentry) Ok() bool { - return vd.mount != nil -} - -// IncRef increments the reference counts on the Mount and Dentry represented -// by vd. -func (vd VirtualDentry) IncRef() { - vd.mount.incRef() - vd.dentry.incRef(vd.mount.fs) -} - -// DecRef decrements the reference counts on the Mount and Dentry represented -// by vd. -func (vd VirtualDentry) DecRef() { - vd.dentry.decRef(vd.mount.fs) - vd.mount.decRef() -} - -// Mount returns the Mount associated with vd. It does not take a reference on -// the returned Mount. -func (vd VirtualDentry) Mount() *Mount { - return vd.mount -} - -// Dentry returns the Dentry associated with vd. It does not take a reference -// on the returned Dentry. -func (vd VirtualDentry) Dentry() *Dentry { - return vd.dentry -} |