/
os_unix.go
359 lines (318 loc) · 9.27 KB
/
os_unix.go
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//go:build (linux && !appengine) || darwin || freebsd || netbsd || openbsd
// +build linux,!appengine darwin freebsd netbsd openbsd
// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package cmd
import (
"bytes"
"fmt"
"os"
"strings"
"sync"
"syscall"
"unsafe"
"golang.org/x/sys/unix"
)
func access(name string) error {
if err := unix.Access(name, unix.F_OK); err != nil {
return &os.PathError{Op: "lstat", Path: name, Err: err}
}
return nil
}
// openFileWithFD return 'fd' based file descriptor
func openFileWithFD(name string, flag int, perm os.FileMode) (fd int, err error) {
switch flag & writeMode {
case writeMode:
defer updateOSMetrics(osMetricOpenFileWFd, name)(err)
default:
defer updateOSMetrics(osMetricOpenFileRFd, name)(err)
}
var e error
fd, e = syscall.Open(name, flag|syscall.O_CLOEXEC, uint32(perm))
if e != nil {
return -1, &os.PathError{Op: "open", Path: name, Err: e}
}
return fd, nil
}
// Forked from Golang but chooses to avoid performing lookup
//
// osMkdirAll creates a directory named path,
// along with any necessary parents, and returns nil,
// or else returns an error.
// The permission bits perm (before umask) are used for all
// directories that MkdirAll creates.
// If path is already a directory, MkdirAll does nothing
// and returns nil.
func osMkdirAll(dirPath string, perm os.FileMode, baseDir string) error {
if baseDir != "" {
if strings.HasPrefix(baseDir, dirPath) {
return nil
}
}
// Slow path: make sure parent exists and then call Mkdir for path.
i := len(dirPath)
for i > 0 && os.IsPathSeparator(dirPath[i-1]) { // Skip trailing path separator.
i--
}
j := i
for j > 0 && !os.IsPathSeparator(dirPath[j-1]) { // Scan backward over element.
j--
}
if j > 1 {
// Create parent.
if err := osMkdirAll(dirPath[:j-1], perm, baseDir); err != nil {
return err
}
}
// Parent now exists; invoke Mkdir and use its result.
if err := Mkdir(dirPath, perm); err != nil {
if osIsExist(err) {
return nil
}
return 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 at least 128 entries in single getdents call (1MiB buffer)
var (
direntPool = sync.Pool{
New: func() interface{} {
buf := make([]byte, blockSize*128)
return &buf
},
}
direntNamePool = sync.Pool{
New: func() interface{} {
buf := make([]byte, blockSize)
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
}
// 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 {
fd, err := openFileWithFD(dirPath, readMode, 0o666)
if err != nil {
if osErrToFileErr(err) == errFileNotFound {
return nil
}
if !osIsPermission(err) {
return osErrToFileErr(err)
}
// There may be permission error when dirPath
// is at the root of the disk mount that may
// not have the permissions to avoid 'noatime'
fd, err = openFileWithFD(dirPath, os.O_RDONLY, 0o666)
if err != nil {
if osErrToFileErr(err) == errFileNotFound {
return nil
}
return osErrToFileErr(err)
}
}
defer syscall.Close(fd)
bufp := direntPool.Get().(*[]byte)
defer direntPool.Put(bufp)
buf := *bufp
boff := 0 // starting read position in buf
nbuf := 0 // end valid data in buf
for {
if boff >= nbuf {
boff = 0
stop := globalOSMetrics.time(osMetricReadDirent)
nbuf, err = syscall.ReadDirent(fd, buf)
stop()
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 := 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 readDirWithOpts(dirPath string, opts readDirOpts) (entries []string, err error) {
fd, err := openFileWithFD(dirPath, readMode, 0o666)
if err != nil {
if !osIsPermission(err) {
return nil, osErrToFileErr(err)
}
// There may be permission error when dirPath
// is at the root of the disk mount that may
// not have the permissions to avoid 'noatime'
fd, err = openFileWithFD(dirPath, os.O_RDONLY, 0o666)
if err != nil {
return nil, osErrToFileErr(err)
}
}
defer syscall.Close(fd)
bufp := direntPool.Get().(*[]byte)
defer direntPool.Put(bufp)
buf := *bufp
nameTmp := direntNamePool.Get().(*[]byte)
defer direntNamePool.Put(nameTmp)
tmp := *nameTmp
boff := 0 // starting read position in buf
nbuf := 0 // end valid data in buf
count := opts.count
for count != 0 {
if boff >= nbuf {
boff = 0
stop := globalOSMetrics.time(osMetricReadDirent)
nbuf, err = syscall.ReadDirent(fd, buf)
stop()
if err != nil {
if isSysErrNotDir(err) {
return nil, errFileNotFound
}
return nil, osErrToFileErr(err)
}
if nbuf <= 0 {
break
}
}
consumed, name, typ, err := parseDirEnt(buf[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 := 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 !opts.followDirSymlink && 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() {
defer globalOSMetrics.time(osMetricSync)()
syscall.Sync()
}