200 lines
5.4 KiB
Go
200 lines
5.4 KiB
Go
// Copyright 2019 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 gofer
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import (
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"sync"
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"sync/atomic"
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/context"
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"gvisor.dev/gvisor/pkg/p9"
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"gvisor.dev/gvisor/pkg/sentry/vfs"
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"gvisor.dev/gvisor/pkg/syserror"
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)
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func (d *dentry) isDir() bool {
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return d.fileType() == linux.S_IFDIR
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}
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// Preconditions: d.dirMu must be locked. d.isDir(). fs.opts.interop !=
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// InteropModeShared.
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func (d *dentry) cacheNegativeChildLocked(name string) {
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if d.negativeChildren == nil {
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d.negativeChildren = make(map[string]struct{})
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}
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d.negativeChildren[name] = struct{}{}
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}
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type directoryFD struct {
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fileDescription
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vfs.DirectoryFileDescriptionDefaultImpl
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mu sync.Mutex
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off int64
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dirents []vfs.Dirent
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}
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// Release implements vfs.FileDescriptionImpl.Release.
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func (fd *directoryFD) Release() {
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}
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// IterDirents implements vfs.FileDescriptionImpl.IterDirents.
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func (fd *directoryFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback) error {
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fd.mu.Lock()
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defer fd.mu.Unlock()
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d := fd.dentry()
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if fd.dirents == nil {
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ds, err := d.getDirents(ctx)
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if err != nil {
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return err
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}
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fd.dirents = ds
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}
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if d.fs.opts.interop != InteropModeShared {
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d.touchAtime(fd.vfsfd.Mount())
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}
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for fd.off < int64(len(fd.dirents)) {
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if err := cb.Handle(fd.dirents[fd.off]); err != nil {
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return err
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}
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fd.off++
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}
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return nil
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}
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// Preconditions: d.isDir(). There exists at least one directoryFD representing d.
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func (d *dentry) getDirents(ctx context.Context) ([]vfs.Dirent, error) {
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// 9P2000.L's readdir does not specify behavior in the presence of
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// concurrent mutation of an iterated directory, so implementations may
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// duplicate or omit entries in this case, which violates POSIX semantics.
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// Thus we read all directory entries while holding d.dirMu to exclude
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// directory mutations. (Note that it is impossible for the client to
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// exclude concurrent mutation from other remote filesystem users. Since
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// there is no way to detect if the server has incorrectly omitted
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// directory entries, we simply assume that the server is well-behaved
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// under InteropModeShared.) This is inconsistent with Linux (which appears
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// to assume that directory fids have the correct semantics, and translates
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// struct file_operations::readdir calls directly to readdir RPCs), but is
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// consistent with VFS1.
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//
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// NOTE(b/135560623): In particular, some gofer implementations may not
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// retain state between calls to Readdir, so may not provide a coherent
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// directory stream across in the presence of mutation.
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d.fs.renameMu.RLock()
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defer d.fs.renameMu.RUnlock()
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d.dirMu.Lock()
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defer d.dirMu.Unlock()
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if d.dirents != nil {
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return d.dirents, nil
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}
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// It's not clear if 9P2000.L's readdir is expected to return "." and "..",
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// so we generate them here.
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parent := d.vfsd.ParentOrSelf().Impl().(*dentry)
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dirents := []vfs.Dirent{
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{
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Name: ".",
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Type: linux.DT_DIR,
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Ino: d.ino,
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NextOff: 1,
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},
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{
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Name: "..",
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Type: uint8(atomic.LoadUint32(&parent.mode) >> 12),
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Ino: parent.ino,
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NextOff: 2,
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},
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}
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off := uint64(0)
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const count = 64 * 1024 // for consistency with the vfs1 client
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d.handleMu.RLock()
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defer d.handleMu.RUnlock()
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if !d.handleReadable {
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// This should not be possible because a readable handle should have
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// been opened when the calling directoryFD was opened.
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panic("gofer.dentry.getDirents called without a readable handle")
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}
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for {
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p9ds, err := d.handle.file.readdir(ctx, off, count)
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if err != nil {
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return nil, err
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}
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if len(p9ds) == 0 {
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// Cache dirents for future directoryFDs if permitted.
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if d.fs.opts.interop != InteropModeShared {
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d.dirents = dirents
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}
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return dirents, nil
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}
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for _, p9d := range p9ds {
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if p9d.Name == "." || p9d.Name == ".." {
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continue
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}
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dirent := vfs.Dirent{
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Name: p9d.Name,
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Ino: p9d.QID.Path,
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NextOff: int64(len(dirents) + 1),
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}
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// p9 does not expose 9P2000.U's DMDEVICE, DMNAMEDPIPE, or
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// DMSOCKET.
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switch p9d.Type {
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case p9.TypeSymlink:
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dirent.Type = linux.DT_LNK
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case p9.TypeDir:
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dirent.Type = linux.DT_DIR
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default:
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dirent.Type = linux.DT_REG
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}
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dirents = append(dirents, dirent)
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}
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off = p9ds[len(p9ds)-1].Offset
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}
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}
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// Seek implements vfs.FileDescriptionImpl.Seek.
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func (fd *directoryFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
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fd.mu.Lock()
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defer fd.mu.Unlock()
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switch whence {
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case linux.SEEK_SET:
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if offset < 0 {
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return 0, syserror.EINVAL
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}
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if offset == 0 {
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// Ensure that the next call to fd.IterDirents() calls
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// fd.dentry().getDirents().
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fd.dirents = nil
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}
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fd.off = offset
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return fd.off, nil
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case linux.SEEK_CUR:
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offset += fd.off
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if offset < 0 {
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return 0, syserror.EINVAL
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}
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// Don't clear fd.dirents in this case, even if offset == 0.
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fd.off = offset
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return fd.off, nil
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default:
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return 0, syserror.EINVAL
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}
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}
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