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walk.go
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walk.go
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// Copyright (C) 2014 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package scanner
import (
"context"
"errors"
"fmt"
"path/filepath"
"runtime"
"strings"
"sync/atomic"
"time"
"unicode/utf8"
metrics "github.com/rcrowley/go-metrics"
"github.com/syncthing/syncthing/lib/events"
"github.com/syncthing/syncthing/lib/fs"
"github.com/syncthing/syncthing/lib/ignore"
"github.com/syncthing/syncthing/lib/protocol"
"golang.org/x/text/unicode/norm"
)
type Config struct {
// Folder for which the walker has been created
Folder string
// Limit walking to these paths within Dir, or no limit if Sub is empty
Subs []string
// If Matcher is not nil, it is used to identify files to ignore which were specified by the user.
Matcher *ignore.Matcher
// Number of hours to keep temporary files for
TempLifetime time.Duration
// If CurrentFiler is not nil, it is queried for the current file before rescanning.
CurrentFiler CurrentFiler
// The Filesystem provides an abstraction on top of the actual filesystem.
Filesystem fs.Filesystem
// If IgnorePerms is true, changes to permission bits will not be
// detected. Scanned files will get zero permission bits and the
// NoPermissionBits flag set.
IgnorePerms bool
// When AutoNormalize is set, file names that are in UTF8 but incorrect
// normalization form will be corrected.
AutoNormalize bool
// Number of routines to use for hashing
Hashers int
// Our vector clock id
ShortID protocol.ShortID
// Optional progress tick interval which defines how often FolderScanProgress
// events are emitted. Negative number means disabled.
ProgressTickIntervalS int
// Local flags to set on scanned files
LocalFlags uint32
}
type CurrentFiler interface {
// CurrentFile returns the file as seen at last scan.
CurrentFile(name string) (protocol.FileInfo, bool)
}
type ScanResult struct {
File protocol.FileInfo
Err error
Path string // to be set in case Err != nil and File == nil
}
func Walk(ctx context.Context, cfg Config) chan ScanResult {
w := walker{cfg}
if w.CurrentFiler == nil {
w.CurrentFiler = noCurrentFiler{}
}
if w.Filesystem == nil {
panic("no filesystem specified")
}
if w.Matcher == nil {
w.Matcher = ignore.New(w.Filesystem)
}
return w.walk(ctx)
}
var (
errUTF8Invalid = errors.New("item is not in UTF8 encoding")
errUTF8Normalization = errors.New("item is not in the correct UTF8 normalization form")
errUTF8Conflict = errors.New("item has UTF8 encoding conflict with another item")
)
type walker struct {
Config
}
// Walk returns the list of files found in the local folder by scanning the
// file system. Files are blockwise hashed.
func (w *walker) walk(ctx context.Context) chan ScanResult {
l.Debugln("Walk", w.Subs, w.Matcher)
toHashChan := make(chan protocol.FileInfo)
finishedChan := make(chan ScanResult)
// A routine which walks the filesystem tree, and sends files which have
// been modified to the counter routine.
go func() {
hashFiles := w.walkAndHashFiles(ctx, toHashChan, finishedChan)
if len(w.Subs) == 0 {
w.Filesystem.Walk(".", hashFiles)
} else {
for _, sub := range w.Subs {
w.Filesystem.Walk(sub, hashFiles)
}
}
close(toHashChan)
}()
// We're not required to emit scan progress events, just kick off hashers,
// and feed inputs directly from the walker.
if w.ProgressTickIntervalS < 0 {
newParallelHasher(ctx, w.Filesystem, w.Hashers, finishedChan, toHashChan, nil, nil)
return finishedChan
}
// Defaults to every 2 seconds.
if w.ProgressTickIntervalS == 0 {
w.ProgressTickIntervalS = 2
}
ticker := time.NewTicker(time.Duration(w.ProgressTickIntervalS) * time.Second)
// We need to emit progress events, hence we create a routine which buffers
// the list of files to be hashed, counts the total number of
// bytes to hash, and once no more files need to be hashed (chan gets closed),
// start a routine which periodically emits FolderScanProgress events,
// until a stop signal is sent by the parallel hasher.
// Parallel hasher is stopped by this routine when we close the channel over
// which it receives the files we ask it to hash.
go func() {
var filesToHash []protocol.FileInfo
var total int64 = 1
for file := range toHashChan {
filesToHash = append(filesToHash, file)
total += file.Size
}
realToHashChan := make(chan protocol.FileInfo)
done := make(chan struct{})
progress := newByteCounter()
newParallelHasher(ctx, w.Filesystem, w.Hashers, finishedChan, realToHashChan, progress, done)
// A routine which actually emits the FolderScanProgress events
// every w.ProgressTicker ticks, until the hasher routines terminate.
go func() {
defer progress.Close()
for {
select {
case <-done:
l.Debugln("Walk progress done", w.Folder, w.Subs, w.Matcher)
ticker.Stop()
return
case <-ticker.C:
current := progress.Total()
rate := progress.Rate()
l.Debugf("Walk %s %s current progress %d/%d at %.01f MiB/s (%d%%)", w.Folder, w.Subs, current, total, rate/1024/1024, current*100/total)
events.Default.Log(events.FolderScanProgress, map[string]interface{}{
"folder": w.Folder,
"current": current,
"total": total,
"rate": rate, // bytes per second
})
case <-ctx.Done():
ticker.Stop()
return
}
}
}()
loop:
for _, file := range filesToHash {
l.Debugln("real to hash:", file.Name)
select {
case realToHashChan <- file:
case <-ctx.Done():
break loop
}
}
close(realToHashChan)
}()
return finishedChan
}
func (w *walker) walkAndHashFiles(ctx context.Context, toHashChan chan<- protocol.FileInfo, finishedChan chan<- ScanResult) fs.WalkFunc {
now := time.Now()
ignoredParent := ""
return func(path string, info fs.FileInfo, err error) error {
select {
case <-ctx.Done():
return ctx.Err()
default:
}
// Return value used when we are returning early and don't want to
// process the item. For directories, this means do-not-descend.
var skip error // nil
// info nil when error is not nil
if info != nil && info.IsDir() {
skip = fs.SkipDir
}
if !utf8.ValidString(path) {
w.handleError(ctx, "scan", path, errUTF8Invalid, finishedChan)
return skip
}
if fs.IsTemporary(path) {
l.Debugln("temporary:", path, "err:", err)
if err == nil && info.IsRegular() && info.ModTime().Add(w.TempLifetime).Before(now) {
w.Filesystem.Remove(path)
l.Debugln("removing temporary:", path, info.ModTime())
}
return nil
}
if fs.IsInternal(path) {
l.Debugln("ignored (internal):", path)
return skip
}
if w.Matcher.Match(path).IsIgnored() {
l.Debugln("ignored (patterns):", path)
// Only descend if matcher says so and the current file is not a symlink.
if err != nil || w.Matcher.SkipIgnoredDirs() || info.IsSymlink() {
return skip
}
// If the parent wasn't ignored already, set this path as the "highest" ignored parent
if info.IsDir() && (ignoredParent == "" || !fs.IsParent(path, ignoredParent)) {
ignoredParent = path
}
return nil
}
if err != nil {
w.handleError(ctx, "scan", path, err, finishedChan)
return skip
}
if path == "." {
return nil
}
if ignoredParent == "" {
// parent isn't ignored, nothing special
return w.handleItem(ctx, path, toHashChan, finishedChan, skip)
}
// Part of current path below the ignored (potential) parent
rel := strings.TrimPrefix(path, ignoredParent+string(fs.PathSeparator))
// ignored path isn't actually a parent of the current path
if rel == path {
ignoredParent = ""
return w.handleItem(ctx, path, toHashChan, finishedChan, skip)
}
// The previously ignored parent directories of the current, not
// ignored path need to be handled as well.
if err = w.handleItem(ctx, ignoredParent, toHashChan, finishedChan, skip); err != nil {
return err
}
for _, name := range strings.Split(rel, string(fs.PathSeparator)) {
ignoredParent = filepath.Join(ignoredParent, name)
if err = w.handleItem(ctx, ignoredParent, toHashChan, finishedChan, skip); err != nil {
return err
}
}
ignoredParent = ""
return nil
}
}
func (w *walker) handleItem(ctx context.Context, path string, toHashChan chan<- protocol.FileInfo, finishedChan chan<- ScanResult, skip error) error {
info, err := w.Filesystem.Lstat(path)
// An error here would be weird as we've already gotten to this point, but act on it nonetheless
if err != nil {
w.handleError(ctx, "scan", path, err, finishedChan)
return skip
}
oldPath := path
path, err = w.normalizePath(path, info)
if err != nil {
w.handleError(ctx, "normalizing path", oldPath, err, finishedChan)
return skip
}
switch {
case info.IsSymlink():
if err := w.walkSymlink(ctx, path, info, finishedChan); err != nil {
return err
}
if info.IsDir() {
// under no circumstances shall we descend into a symlink
return fs.SkipDir
}
return nil
case info.IsDir():
err = w.walkDir(ctx, path, info, finishedChan)
case info.IsRegular():
err = w.walkRegular(ctx, path, info, toHashChan)
}
return err
}
func (w *walker) walkRegular(ctx context.Context, relPath string, info fs.FileInfo, toHashChan chan<- protocol.FileInfo) error {
curFile, hasCurFile := w.CurrentFiler.CurrentFile(relPath)
blockSize := protocol.BlockSize(info.Size())
if hasCurFile {
// Check if we should retain current block size.
curBlockSize := curFile.BlockSize()
if blockSize > curBlockSize && blockSize/curBlockSize <= 2 {
// New block size is larger, but not more than twice larger.
// Retain.
blockSize = curBlockSize
} else if curBlockSize > blockSize && curBlockSize/blockSize <= 2 {
// Old block size is larger, but not more than twice larger.
// Retain.
blockSize = curBlockSize
}
}
f, _ := CreateFileInfo(info, relPath, nil)
f = w.updateFileInfo(f, curFile)
f.NoPermissions = w.IgnorePerms
f.RawBlockSize = int32(blockSize)
if hasCurFile {
if curFile.IsEquivalentOptional(f, w.IgnorePerms, true, w.LocalFlags) {
return nil
}
if curFile.ShouldConflict() {
// The old file was invalid for whatever reason and probably not
// up to date with what was out there in the cluster. Drop all
// others from the version vector to indicate that we haven't
// taken their version into account, and possibly cause a
// conflict.
f.Version = f.Version.DropOthers(w.ShortID)
}
l.Debugln("rescan:", curFile, info.ModTime().Unix(), info.Mode()&fs.ModePerm)
}
l.Debugln("to hash:", relPath, f)
select {
case toHashChan <- f:
case <-ctx.Done():
return ctx.Err()
}
return nil
}
func (w *walker) walkDir(ctx context.Context, relPath string, info fs.FileInfo, finishedChan chan<- ScanResult) error {
curFile, hasCurFile := w.CurrentFiler.CurrentFile(relPath)
f, _ := CreateFileInfo(info, relPath, nil)
f = w.updateFileInfo(f, curFile)
f.NoPermissions = w.IgnorePerms
if hasCurFile {
if curFile.IsEquivalentOptional(f, w.IgnorePerms, true, w.LocalFlags) {
return nil
}
if curFile.ShouldConflict() {
// The old file was invalid for whatever reason and probably not
// up to date with what was out there in the cluster. Drop all
// others from the version vector to indicate that we haven't
// taken their version into account, and possibly cause a
// conflict.
f.Version = f.Version.DropOthers(w.ShortID)
}
}
l.Debugln("dir:", relPath, f)
select {
case finishedChan <- ScanResult{File: f}:
case <-ctx.Done():
return ctx.Err()
}
return nil
}
// walkSymlink returns nil or an error, if the error is of the nature that
// it should stop the entire walk.
func (w *walker) walkSymlink(ctx context.Context, relPath string, info fs.FileInfo, finishedChan chan<- ScanResult) error {
// Symlinks are not supported on Windows. We ignore instead of returning
// an error.
if runtime.GOOS == "windows" {
return nil
}
f, err := CreateFileInfo(info, relPath, w.Filesystem)
if err != nil {
w.handleError(ctx, "reading link:", relPath, err, finishedChan)
return nil
}
curFile, hasCurFile := w.CurrentFiler.CurrentFile(relPath)
f = w.updateFileInfo(f, curFile)
if hasCurFile {
if curFile.IsEquivalentOptional(f, w.IgnorePerms, true, w.LocalFlags) {
return nil
}
if curFile.ShouldConflict() {
// The old file was invalid for whatever reason and probably not
// up to date with what was out there in the cluster. Drop all
// others from the version vector to indicate that we haven't
// taken their version into account, and possibly cause a
// conflict.
f.Version = f.Version.DropOthers(w.ShortID)
}
}
l.Debugln("symlink changedb:", relPath, f)
select {
case finishedChan <- ScanResult{File: f}:
case <-ctx.Done():
return ctx.Err()
}
return nil
}
// normalizePath returns the normalized relative path (possibly after fixing
// it on disk), or skip is true.
func (w *walker) normalizePath(path string, info fs.FileInfo) (normPath string, err error) {
if runtime.GOOS == "darwin" {
// Mac OS X file names should always be NFD normalized.
normPath = norm.NFD.String(path)
} else {
// Every other OS in the known universe uses NFC or just plain
// doesn't bother to define an encoding. In our case *we* do care,
// so we enforce NFC regardless.
normPath = norm.NFC.String(path)
}
if path == normPath {
// The file name is already normalized: nothing to do
return path, nil
}
if !w.AutoNormalize {
// We're not authorized to do anything about it, so complain and skip.
return "", errUTF8Normalization
}
// We will attempt to normalize it.
normInfo, err := w.Filesystem.Lstat(normPath)
if fs.IsNotExist(err) {
// Nothing exists with the normalized filename. Good.
if err = w.Filesystem.Rename(path, normPath); err != nil {
return "", err
}
l.Infof(`Normalized UTF8 encoding of file name "%s".`, path)
return normPath, nil
}
if w.Filesystem.SameFile(info, normInfo) {
// With some filesystems (ZFS), if there is an un-normalized path and you ask whether the normalized
// version exists, it responds with true. Therefore we need to check fs.SameFile as well.
// In this case, a call to Rename won't do anything, so we have to rename via a temp file.
// We don't want to use the standard syncthing prefix here, as that will result in the file being ignored
// and eventually deleted by Syncthing if the rename back fails.
tempPath := fs.TempNameWithPrefix(normPath, "")
if err = w.Filesystem.Rename(path, tempPath); err != nil {
return "", err
}
if err = w.Filesystem.Rename(tempPath, normPath); err != nil {
// I don't ever expect this to happen, but if it does, we should probably tell our caller that the normalized
// path is the temp path: that way at least the user's data still gets synced.
l.Warnf(`Error renaming "%s" to "%s" while normalizating UTF8 encoding: %v. You will want to rename this file back manually`, tempPath, normPath, err)
return tempPath, nil
}
return normPath, nil
}
// There is something already in the way at the normalized
// file name.
return "", errUTF8Conflict
}
// updateFileInfo updates walker specific members of protocol.FileInfo that do not depend on type
func (w *walker) updateFileInfo(file, curFile protocol.FileInfo) protocol.FileInfo {
if file.Type == protocol.FileInfoTypeFile && runtime.GOOS == "windows" {
// If we have an existing index entry, copy the executable bits
// from there.
file.Permissions |= (curFile.Permissions & 0111)
}
file.Version = curFile.Version.Update(w.ShortID)
file.ModifiedBy = w.ShortID
file.LocalFlags = w.LocalFlags
return file
}
func (w *walker) handleError(ctx context.Context, context, path string, err error, finishedChan chan<- ScanResult) {
// Ignore missing items, as deletions are not handled by the scanner.
if fs.IsNotExist(err) {
return
}
l.Infof("Scanner (folder %s, item %q): %s: %v", w.Folder, path, context, err)
select {
case finishedChan <- ScanResult{
Err: fmt.Errorf("%s: %s", context, err.Error()),
Path: path,
}:
case <-ctx.Done():
}
}
// A byteCounter gets bytes added to it via Update() and then provides the
// Total() and one minute moving average Rate() in bytes per second.
type byteCounter struct {
total int64 // atomic, must remain 64-bit aligned
metrics.EWMA
stop chan struct{}
}
func newByteCounter() *byteCounter {
c := &byteCounter{
EWMA: metrics.NewEWMA1(), // a one minute exponentially weighted moving average
stop: make(chan struct{}),
}
go c.ticker()
return c
}
func (c *byteCounter) ticker() {
// The metrics.EWMA expects clock ticks every five seconds in order to
// decay the average properly.
t := time.NewTicker(5 * time.Second)
for {
select {
case <-t.C:
c.Tick()
case <-c.stop:
t.Stop()
return
}
}
}
func (c *byteCounter) Update(bytes int64) {
atomic.AddInt64(&c.total, bytes)
c.EWMA.Update(bytes)
}
func (c *byteCounter) Total() int64 {
return atomic.LoadInt64(&c.total)
}
func (c *byteCounter) Close() {
close(c.stop)
}
// A no-op CurrentFiler
type noCurrentFiler struct{}
func (noCurrentFiler) CurrentFile(name string) (protocol.FileInfo, bool) {
return protocol.FileInfo{}, false
}
func CreateFileInfo(fi fs.FileInfo, name string, filesystem fs.Filesystem) (protocol.FileInfo, error) {
f := protocol.FileInfo{Name: name}
if fi.IsSymlink() {
f.Type = protocol.FileInfoTypeSymlink
target, err := filesystem.ReadSymlink(name)
if err != nil {
return protocol.FileInfo{}, err
}
f.SymlinkTarget = target
f.NoPermissions = true // Symlinks don't have permissions of their own
return f, nil
}
f.Permissions = uint32(fi.Mode() & fs.ModePerm)
f.ModifiedS = fi.ModTime().Unix()
f.ModifiedNs = int32(fi.ModTime().Nanosecond())
if fi.IsDir() {
f.Type = protocol.FileInfoTypeDirectory
return f, nil
}
f.Size = fi.Size()
f.Type = protocol.FileInfoTypeFile
return f, nil
}