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// 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 tmpfs
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
)
type directory struct {
inode inode
// childList is a list containing (1) child Dentries and (2) fake Dentries
// (with inode == nil) that represent the iteration position of
// directoryFDs. childList is used to support directoryFD.IterDirents()
// efficiently. childList is protected by filesystem.mu.
childList dentryList
}
func (fs *filesystem) newDirectory(creds *auth.Credentials, mode linux.FileMode) *inode {
dir := &directory{}
dir.inode.init(dir, fs, creds, linux.S_IFDIR|mode)
dir.inode.nlink = 2 // from "." and parent directory or ".." for root
return &dir.inode
}
type directoryFD struct {
fileDescription
vfs.DirectoryFileDescriptionDefaultImpl
// Protected by filesystem.mu.
iter *dentry
off int64
}
// Release implements vfs.FileDescriptionImpl.Release.
func (fd *directoryFD) Release() {
if fd.iter != nil {
fs := fd.filesystem()
dir := fd.inode().impl.(*directory)
fs.mu.Lock()
dir.childList.Remove(fd.iter)
fs.mu.Unlock()
fd.iter = nil
}
}
// IterDirents implements vfs.FileDescriptionImpl.IterDirents.
func (fd *directoryFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback) error {
fs := fd.filesystem()
vfsd := fd.vfsfd.VirtualDentry().Dentry()
fs.mu.Lock()
defer fs.mu.Unlock()
if fd.off == 0 {
if err := cb.Handle(vfs.Dirent{
Name: ".",
Type: linux.DT_DIR,
Ino: vfsd.Impl().(*dentry).inode.ino,
NextOff: 1,
}); err != nil {
return err
}
fd.off++
}
if fd.off == 1 {
parentInode := vfsd.ParentOrSelf().Impl().(*dentry).inode
if err := cb.Handle(vfs.Dirent{
Name: "..",
Type: parentInode.direntType(),
Ino: parentInode.ino,
NextOff: 2,
}); err != nil {
return err
}
fd.off++
}
dir := vfsd.Impl().(*dentry).inode.impl.(*directory)
var child *dentry
if fd.iter == nil {
// Start iteration at the beginning of dir.
child = dir.childList.Front()
fd.iter = &dentry{}
} else {
// Continue iteration from where we left off.
child = fd.iter.Next()
dir.childList.Remove(fd.iter)
}
for child != nil {
// Skip other directoryFD iterators.
if child.inode != nil {
if err := cb.Handle(vfs.Dirent{
Name: child.vfsd.Name(),
Type: child.inode.direntType(),
Ino: child.inode.ino,
NextOff: fd.off + 1,
}); err != nil {
dir.childList.InsertBefore(child, fd.iter)
return err
}
fd.off++
}
child = child.Next()
}
dir.childList.PushBack(fd.iter)
return nil
}
// Seek implements vfs.FileDescriptionImpl.Seek.
func (fd *directoryFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
fs := fd.filesystem()
fs.mu.Lock()
defer fs.mu.Unlock()
switch whence {
case linux.SEEK_SET:
// Use offset as given.
case linux.SEEK_CUR:
offset += fd.off
default:
return 0, syserror.EINVAL
}
if offset < 0 {
return 0, syserror.EINVAL
}
// If the offset isn't changing (e.g. due to lseek(0, SEEK_CUR)), don't
// seek even if doing so might reposition the iterator due to concurrent
// mutation of the directory. Compare fs/libfs.c:dcache_dir_lseek().
if fd.off == offset {
return offset, nil
}
fd.off = offset
// Compensate for "." and "..".
remChildren := int64(0)
if offset >= 2 {
remChildren = offset - 2
}
dir := fd.inode().impl.(*directory)
// Ensure that fd.iter exists and is not linked into dir.childList.
if fd.iter == nil {
fd.iter = &dentry{}
} else {
dir.childList.Remove(fd.iter)
}
// Insert fd.iter before the remChildren'th child, or at the end of the
// list if remChildren >= number of children.
child := dir.childList.Front()
for child != nil {
// Skip other directoryFD iterators.
if child.inode != nil {
if remChildren == 0 {
dir.childList.InsertBefore(child, fd.iter)
return offset, nil
}
remChildren--
}
child = child.Next()
}
dir.childList.PushBack(fd.iter)
return offset, nil
}
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