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// Copyright 2023 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 erofs
import (
"sort"
"sync"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/errors/linuxerr"
"gvisor.dev/gvisor/pkg/sentry/vfs"
)
func (i *inode) getDirents() ([]vfs.Dirent, error) {
// Fast path.
i.dirMu.RLock()
dirents := i.dirents
i.dirMu.RUnlock()
if dirents != nil {
return dirents, nil
}
// Slow path.
i.dirMu.Lock()
defer i.dirMu.Unlock()
off := int64(1)
if err := i.IterDirents(func(name string, typ uint8, nid uint64) error {
dirents = append(dirents, vfs.Dirent{
Name: name,
Type: linux.FileTypeToDirentType(typ),
Ino: nid,
NextOff: off,
})
off++
return nil
}); err != nil {
return nil, err
}
// "." and ".." should always be present.
if len(dirents) < 2 {
return nil, linuxerr.EUCLEAN
}
i.dirents = dirents
return dirents, nil
}
func (i *inode) lookup(name string) (uint64, error) {
var dirents []vfs.Dirent
// Lazily fetch dirents.
if i.dirMu.TryRLock() {
dirents = i.dirents // +checklocksforce: TryRLock.
i.dirMu.RUnlock() // +checklocksforce: TryRLock.
}
if dirents == nil {
// The dirents cache is not available immediately, let's do
// binary search on disk data directly.
return i.Lookup(name)
}
// The dirents are sorted in alphabetical order. We do binary search
// to find the target.
idx := sort.Search(len(dirents), func(i int) bool {
return dirents[i].Name >= name
})
if idx >= len(dirents) || dirents[idx].Name != name {
return 0, linuxerr.ENOENT
}
return dirents[idx].Ino, nil
}
func (d *dentry) lookup(ctx context.Context, name string) (*dentry, error) {
// Fast path, dentry already exists.
d.dirMu.RLock()
child, ok := d.childMap[name]
d.dirMu.RUnlock()
if ok {
return child, nil
}
// Slow path, create a new dentry.
d.dirMu.Lock()
defer d.dirMu.Unlock()
if child, ok := d.childMap[name]; ok {
return child, nil
}
nid, err := d.inode.lookup(name)
if err != nil {
return nil, err
}
if d.childMap == nil {
d.childMap = make(map[string]*dentry)
}
child, err = d.inode.fs.newDentry(nid)
if err != nil {
return nil, err
}
child.parent.Store(d)
child.name = name
d.childMap[name] = child
return child, nil
}
// +stateify savable
type directoryFD struct {
fileDescription
vfs.DirectoryFileDescriptionDefaultImpl
// mu protects off.
mu sync.Mutex `state:"nosave"`
// +checklocks:mu
off int64
}
// IterDirents implements vfs.FileDescriptionImpl.IterDirents.
func (fd *directoryFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback) error {
d := fd.dentry()
dirents, err := d.inode.getDirents()
if err != nil {
return err
}
d.InotifyWithParent(ctx, linux.IN_ACCESS, 0, vfs.PathEvent)
fd.mu.Lock()
defer fd.mu.Unlock()
for fd.off < int64(len(dirents)) {
if err := cb.Handle(dirents[fd.off]); err != nil {
return err
}
fd.off++
}
return nil
}
// Seek implements vfs.FileDescriptionImpl.Seek.
func (fd *directoryFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
fd.mu.Lock()
defer fd.mu.Unlock()
switch whence {
case linux.SEEK_SET:
// use offset as specified
case linux.SEEK_CUR:
offset += fd.off
default:
return 0, linuxerr.EINVAL
}
if offset < 0 {
return 0, linuxerr.EINVAL
}
fd.off = offset
return offset, nil
}
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