minio/cmd/os-readdir_unix.go
Harshavardhana d93c6cb9c7
use Access() instead of Lstat() for frequent use (#11911)
using Lstat() is causing tiny memory allocations,
that are usually wasted and never used, instead
we can simply uses Access() call that does 0
memory allocations.
2021-03-29 08:07:23 -07:00

259 lines
6.6 KiB
Go

// +build linux,!appengine darwin freebsd netbsd openbsd
/*
* MinIO Cloud Storage, (C) 2016-2020 MinIO, 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 cmd
import (
"bytes"
"fmt"
"os"
"sync"
"syscall"
"unsafe"
"golang.org/x/sys/unix"
)
func access(name string) error {
if err := unix.Access(name, unix.R_OK|unix.W_OK); err != nil {
return &os.PathError{Op: "lstat", Path: name, Err: err}
}
return nil
}
// The buffer must be at least a block long.
// refer https://github.com/golang/go/issues/24015
const blockSize = 8 << 10 // 8192
// By default atleast 128 entries in single getdents call (1MiB buffer)
var direntPool = sync.Pool{
New: func() interface{} {
buf := make([]byte, blockSize*128)
return &buf
},
}
// unexpectedFileMode is a sentinel (and bogus) os.FileMode
// value used to represent a syscall.DT_UNKNOWN Dirent.Type.
const unexpectedFileMode os.FileMode = os.ModeNamedPipe | os.ModeSocket | os.ModeDevice
func parseDirEnt(buf []byte) (consumed int, name []byte, typ os.FileMode, err error) {
// golang.org/issue/15653
dirent := (*syscall.Dirent)(unsafe.Pointer(&buf[0]))
if v := unsafe.Offsetof(dirent.Reclen) + unsafe.Sizeof(dirent.Reclen); uintptr(len(buf)) < v {
return consumed, nil, typ, fmt.Errorf("buf size of %d smaller than dirent header size %d", len(buf), v)
}
if len(buf) < int(dirent.Reclen) {
return consumed, nil, typ, fmt.Errorf("buf size %d < record length %d", len(buf), dirent.Reclen)
}
consumed = int(dirent.Reclen)
if direntInode(dirent) == 0 { // File absent in directory.
return
}
switch dirent.Type {
case syscall.DT_REG:
typ = 0
case syscall.DT_DIR:
typ = os.ModeDir
case syscall.DT_LNK:
typ = os.ModeSymlink
default:
// Skip all other file types. Revisit if/when this code needs
// to handle such files, MinIO is only interested in
// files and directories.
typ = unexpectedFileMode
}
nameBuf := (*[unsafe.Sizeof(dirent.Name)]byte)(unsafe.Pointer(&dirent.Name[0]))
nameLen, err := direntNamlen(dirent)
if err != nil {
return consumed, nil, typ, err
}
return consumed, nameBuf[:nameLen], typ, nil
}
// Return all the entries at the directory dirPath.
func readDir(dirPath string) (entries []string, err error) {
return readDirN(dirPath, -1)
}
// readDirFn applies the fn() function on each entries at dirPath, doesn't recurse into
// the directory itself, if the dirPath doesn't exist this function doesn't return
// an error.
func readDirFn(dirPath string, fn func(name string, typ os.FileMode) error) error {
f, err := os.Open(dirPath)
if err != nil {
if osErrToFileErr(err) == errFileNotFound {
return nil
}
return osErrToFileErr(err)
}
defer f.Close()
buf := make([]byte, blockSize)
boff := 0 // starting read position in buf
nbuf := 0 // end valid data in buf
for {
if boff >= nbuf {
boff = 0
nbuf, err = syscall.ReadDirent(int(f.Fd()), buf)
if err != nil {
if isSysErrNotDir(err) {
return nil
}
err = osErrToFileErr(err)
if err == errFileNotFound {
return nil
}
return err
}
if nbuf <= 0 {
break // EOF
}
}
consumed, name, typ, err := parseDirEnt(buf[boff:nbuf])
if err != nil {
return err
}
boff += consumed
if len(name) == 0 || bytes.Equal(name, []byte{'.'}) || bytes.Equal(name, []byte{'.', '.'}) {
continue
}
// Fallback for filesystems (like old XFS) that don't
// support Dirent.Type and have DT_UNKNOWN (0) there
// instead.
if typ == unexpectedFileMode || typ&os.ModeSymlink == os.ModeSymlink {
fi, err := os.Stat(pathJoin(dirPath, string(name)))
if err != nil {
// It got deleted in the meantime, not found
// or returns too many symlinks ignore this
// file/directory.
if osIsNotExist(err) || isSysErrPathNotFound(err) ||
isSysErrTooManySymlinks(err) {
continue
}
return err
}
// Ignore symlinked directories.
if typ&os.ModeSymlink == os.ModeSymlink && fi.IsDir() {
continue
}
typ = fi.Mode() & os.ModeType
}
if err = fn(string(name), typ); err == errDoneForNow {
// fn() requested to return by caller.
return nil
}
}
return err
}
// Return count entries at the directory dirPath and all entries
// if count is set to -1
func readDirN(dirPath string, count int) (entries []string, err error) {
f, err := os.Open(dirPath)
if err != nil {
return nil, osErrToFileErr(err)
}
defer f.Close()
bufp := direntPool.Get().(*[]byte)
defer direntPool.Put(bufp)
nameTmp := direntPool.Get().(*[]byte)
defer direntPool.Put(nameTmp)
tmp := *nameTmp
boff := 0 // starting read position in buf
nbuf := 0 // end valid data in buf
for count != 0 {
if boff >= nbuf {
boff = 0
nbuf, err = syscall.ReadDirent(int(f.Fd()), *bufp)
if err != nil {
if isSysErrNotDir(err) {
return nil, errFileNotFound
}
return nil, osErrToFileErr(err)
}
if nbuf <= 0 {
break
}
}
consumed, name, typ, err := parseDirEnt((*bufp)[boff:nbuf])
if err != nil {
return nil, err
}
boff += consumed
if len(name) == 0 || bytes.Equal(name, []byte{'.'}) || bytes.Equal(name, []byte{'.', '.'}) {
continue
}
// Fallback for filesystems (like old XFS) that don't
// support Dirent.Type and have DT_UNKNOWN (0) there
// instead.
if typ == unexpectedFileMode || typ&os.ModeSymlink == os.ModeSymlink {
fi, err := os.Stat(pathJoin(dirPath, string(name)))
if err != nil {
// It got deleted in the meantime, not found
// or returns too many symlinks ignore this
// file/directory.
if osIsNotExist(err) || isSysErrPathNotFound(err) ||
isSysErrTooManySymlinks(err) {
continue
}
return nil, err
}
// Ignore symlinked directories.
if typ&os.ModeSymlink == os.ModeSymlink && fi.IsDir() {
continue
}
typ = fi.Mode() & os.ModeType
}
var nameStr string
if typ.IsRegular() {
nameStr = string(name)
} else if typ.IsDir() {
// Use temp buffer to append a slash to avoid string concat.
tmp = tmp[:len(name)+1]
copy(tmp, name)
tmp[len(tmp)-1] = '/' // SlashSeparator
nameStr = string(tmp)
}
count--
entries = append(entries, nameStr)
}
return
}
func globalSync() {
syscall.Sync()
}