diff options
Diffstat (limited to 'vendor/github.com/containerd/continuity/fs/dtype_linux.go')
-rw-r--r-- | vendor/github.com/containerd/continuity/fs/dtype_linux.go | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/vendor/github.com/containerd/continuity/fs/dtype_linux.go b/vendor/github.com/containerd/continuity/fs/dtype_linux.go new file mode 100644 index 000000000..10510d8de --- /dev/null +++ b/vendor/github.com/containerd/continuity/fs/dtype_linux.go @@ -0,0 +1,103 @@ +// +build linux + +/* + Copyright The containerd 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 fs + +import ( + "fmt" + "io/ioutil" + "os" + "syscall" + "unsafe" +) + +func locateDummyIfEmpty(path string) (string, error) { + children, err := ioutil.ReadDir(path) + if err != nil { + return "", err + } + if len(children) != 0 { + return "", nil + } + dummyFile, err := ioutil.TempFile(path, "fsutils-dummy") + if err != nil { + return "", err + } + name := dummyFile.Name() + err = dummyFile.Close() + return name, err +} + +// SupportsDType returns whether the filesystem mounted on path supports d_type +func SupportsDType(path string) (bool, error) { + // locate dummy so that we have at least one dirent + dummy, err := locateDummyIfEmpty(path) + if err != nil { + return false, err + } + if dummy != "" { + defer os.Remove(dummy) + } + + visited := 0 + supportsDType := true + fn := func(ent *syscall.Dirent) bool { + visited++ + if ent.Type == syscall.DT_UNKNOWN { + supportsDType = false + // stop iteration + return true + } + // continue iteration + return false + } + if err = iterateReadDir(path, fn); err != nil { + return false, err + } + if visited == 0 { + return false, fmt.Errorf("did not hit any dirent during iteration %s", path) + } + return supportsDType, nil +} + +func iterateReadDir(path string, fn func(*syscall.Dirent) bool) error { + d, err := os.Open(path) + if err != nil { + return err + } + defer d.Close() + fd := int(d.Fd()) + buf := make([]byte, 4096) + for { + nbytes, err := syscall.ReadDirent(fd, buf) + if err != nil { + return err + } + if nbytes == 0 { + break + } + for off := 0; off < nbytes; { + ent := (*syscall.Dirent)(unsafe.Pointer(&buf[off])) + if stop := fn(ent); stop { + return nil + } + off += int(ent.Reclen) + } + } + return nil +} |