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// Copyright 2018 Google Inc.
//
// 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 fs
import "gvisor.googlesource.com/gvisor/pkg/sentry/context"
// overlayMountSourceOperations implements MountSourceOperations for an overlay
// mount point.
type overlayMountSourceOperations struct {
upper *MountSource
lower *MountSource
}
func newOverlayMountSource(upper, lower *MountSource, flags MountSourceFlags) *MountSource {
upper.IncRef()
lower.IncRef()
return NewMountSource(&overlayMountSourceOperations{
upper: upper,
lower: lower,
}, &overlayFilesystem{}, flags)
}
// Revalidate panics if the upper or lower MountSource require that dirent be
// revalidated. Otherwise always returns false.
func (o *overlayMountSourceOperations) Revalidate(ctx context.Context, dirent *Dirent) bool {
if o.upper.Revalidate(ctx, dirent) || o.lower.Revalidate(ctx, dirent) {
panic("an overlay cannot revalidate file objects")
}
return false
}
// Keep returns true if either upper or lower MountSource require that the
// dirent be kept in memory.
func (o *overlayMountSourceOperations) Keep(dirent *Dirent) bool {
return o.upper.Keep(dirent) || o.lower.Keep(dirent)
}
// ResetInodeMappings propagates the call to both upper and lower MountSource.
func (o *overlayMountSourceOperations) ResetInodeMappings() {
o.upper.ResetInodeMappings()
o.lower.ResetInodeMappings()
}
// SaveInodeMapping propagates the call to both upper and lower MountSource.
func (o *overlayMountSourceOperations) SaveInodeMapping(inode *Inode, path string) {
inode.overlay.copyMu.RLock()
defer inode.overlay.copyMu.RUnlock()
if inode.overlay.upper != nil {
o.upper.SaveInodeMapping(inode.overlay.upper, path)
}
if inode.overlay.lower != nil {
o.lower.SaveInodeMapping(inode.overlay.lower, path)
}
}
// Destroy drops references on the upper and lower MountSource.
func (o *overlayMountSourceOperations) Destroy() {
o.upper.DecRef()
o.lower.DecRef()
}
// type overlayFilesystem is the filesystem for overlay mounts.
type overlayFilesystem struct{}
// Name implements Filesystem.Name.
func (ofs *overlayFilesystem) Name() string {
return "overlayfs"
}
// Flags implements Filesystem.Flags.
func (ofs *overlayFilesystem) Flags() FilesystemFlags {
return 0
}
// AllowUserMount implements Filesystem.AllowUserMount.
func (ofs *overlayFilesystem) AllowUserMount() bool {
return false
}
// AllowUserList implements Filesystem.AllowUserList.
func (*overlayFilesystem) AllowUserList() bool {
return true
}
// Mount implements Filesystem.Mount.
func (ofs *overlayFilesystem) Mount(ctx context.Context, device string, flags MountSourceFlags, data string) (*Inode, error) {
panic("overlayFilesystem.Mount should not be called!")
}
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