syncthing/lib/scanner/walk.go
Nicholas Rishel a505231774 lib/scanner: Support walking a symlink root (ref #4353)
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4666
LGTM: AudriusButkevicius, imsodin
2018-01-24 00:05:47 +00:00

542 lines
16 KiB
Go

// 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"
"runtime"
"sync/atomic"
"time"
"unicode/utf8"
"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/osutil"
"github.com/syncthing/syncthing/lib/protocol"
"golang.org/x/text/unicode/norm"
)
var maskModePerm fs.FileMode
func init() {
if runtime.GOOS == "windows" {
// There is no user/group/others in Windows' read-only
// attribute, and all "w" bits are set in fs.FileMode
// if the file is not read-only. Do not send these
// group/others-writable bits to other devices in order to
// avoid unexpected world-writable files on other platforms.
maskModePerm = fs.ModePerm & 0755
} else {
maskModePerm = fs.ModePerm
}
}
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
// BlockSize controls the size of the block used when hashing.
BlockSize int
// 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
// Whether or not we should also compute weak hashes
UseWeakHashes bool
}
type CurrentFiler interface {
// CurrentFile returns the file as seen at last scan.
CurrentFile(name string) (protocol.FileInfo, bool)
}
func Walk(ctx context.Context, cfg Config) chan protocol.FileInfo {
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)
}
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 protocol.FileInfo {
l.Debugln("Walk", w.Subs, w.BlockSize, w.Matcher)
toHashChan := make(chan protocol.FileInfo)
finishedChan := make(chan protocol.FileInfo)
// 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.BlockSize, w.Hashers, finishedChan, toHashChan, nil, nil, w.UseWeakHashes)
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.BlockSize, w.Hashers, finishedChan, realToHashChan, progress, done, w.UseWeakHashes)
// 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.BlockSize, 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, fchan, dchan chan protocol.FileInfo) fs.WalkFunc {
now := time.Now()
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 err != nil {
l.Debugln("error:", path, info, err)
return skip
}
if path == "." {
return nil
}
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 {
return skip
}
if fs.IsTemporary(path) {
l.Debugln("temporary:", path)
if 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)
return skip
}
if !utf8.ValidString(path) {
l.Warnf("File name %q is not in UTF8 encoding; skipping.", path)
return skip
}
path, shouldSkip := w.normalizePath(path, info)
if shouldSkip {
return skip
}
switch {
case info.IsSymlink():
if err := w.walkSymlink(ctx, path, dchan); 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, dchan)
case info.IsRegular():
err = w.walkRegular(ctx, path, info, fchan)
}
return err
}
}
func (w *walker) walkRegular(ctx context.Context, relPath string, info fs.FileInfo, fchan chan protocol.FileInfo) error {
curMode := uint32(info.Mode())
if runtime.GOOS == "windows" && osutil.IsWindowsExecutable(relPath) {
curMode |= 0111
}
// A file is "unchanged", if it
// - exists
// - has the same permissions as previously, unless we are ignoring permissions
// - was not marked deleted (since it apparently exists now)
// - had the same modification time as it has now
// - was not a directory previously (since it's a file now)
// - was not a symlink (since it's a file now)
// - was not invalid (since it looks valid now)
// - has the same size as previously
cf, ok := w.CurrentFiler.CurrentFile(relPath)
permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Permissions, curMode)
if ok && permUnchanged && !cf.IsDeleted() && cf.ModTime().Equal(info.ModTime()) && !cf.IsDirectory() &&
!cf.IsSymlink() && !cf.IsInvalid() && cf.Size == info.Size() {
return nil
}
if ok {
l.Debugln("rescan:", cf, info.ModTime().Unix(), info.Mode()&fs.ModePerm)
}
f := protocol.FileInfo{
Name: relPath,
Type: protocol.FileInfoTypeFile,
Version: cf.Version.Update(w.ShortID),
Permissions: curMode & uint32(maskModePerm),
NoPermissions: w.IgnorePerms,
ModifiedS: info.ModTime().Unix(),
ModifiedNs: int32(info.ModTime().Nanosecond()),
ModifiedBy: w.ShortID,
Size: info.Size(),
}
l.Debugln("to hash:", relPath, f)
select {
case fchan <- f:
case <-ctx.Done():
return ctx.Err()
}
return nil
}
func (w *walker) walkDir(ctx context.Context, relPath string, info fs.FileInfo, dchan chan protocol.FileInfo) error {
// A directory is "unchanged", if it
// - exists
// - has the same permissions as previously, unless we are ignoring permissions
// - was not marked deleted (since it apparently exists now)
// - was a directory previously (not a file or something else)
// - was not a symlink (since it's a directory now)
// - was not invalid (since it looks valid now)
cf, ok := w.CurrentFiler.CurrentFile(relPath)
permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Permissions, uint32(info.Mode()))
if ok && permUnchanged && !cf.IsDeleted() && cf.IsDirectory() && !cf.IsSymlink() && !cf.IsInvalid() {
return nil
}
f := protocol.FileInfo{
Name: relPath,
Type: protocol.FileInfoTypeDirectory,
Version: cf.Version.Update(w.ShortID),
Permissions: uint32(info.Mode() & maskModePerm),
NoPermissions: w.IgnorePerms,
ModifiedS: info.ModTime().Unix(),
ModifiedNs: int32(info.ModTime().Nanosecond()),
ModifiedBy: w.ShortID,
}
l.Debugln("dir:", relPath, f)
select {
case dchan <- 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, dchan chan protocol.FileInfo) error {
// Symlinks are not supported on Windows. We ignore instead of returning
// an error.
if runtime.GOOS == "windows" {
return nil
}
// We always rehash symlinks as they have no modtime or
// permissions. We check if they point to the old target by
// checking that their existing blocks match with the blocks in
// the index.
target, err := w.Filesystem.ReadSymlink(relPath)
if err != nil {
l.Debugln("readlink error:", relPath, err)
return nil
}
// A symlink is "unchanged", if
// - it exists
// - it wasn't deleted (because it isn't now)
// - it was a symlink
// - it wasn't invalid
// - the target was the same
cf, ok := w.CurrentFiler.CurrentFile(relPath)
if ok && !cf.IsDeleted() && cf.IsSymlink() && !cf.IsInvalid() && cf.SymlinkTarget == target {
return nil
}
f := protocol.FileInfo{
Name: relPath,
Type: protocol.FileInfoTypeSymlink,
Version: cf.Version.Update(w.ShortID),
NoPermissions: true, // Symlinks don't have permissions of their own
SymlinkTarget: target,
}
l.Debugln("symlink changedb:", relPath, f)
select {
case dchan <- 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, skip bool) {
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, false
}
if !w.AutoNormalize {
// We're not authorized to do anything about it, so complain and skip.
l.Warnf("File name %q is not in the correct UTF8 normalization form; skipping.", path)
return "", true
}
// 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 {
l.Infof(`Error normalizing UTF8 encoding of file "%s": %v`, path, err)
return "", true
}
l.Infof(`Normalized UTF8 encoding of file name "%s".`, path)
} else 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 {
l.Infof(`Error during normalizing UTF8 encoding of file "%s" (renamed to "%s"): %v`, path, tempPath, err)
return "", true
}
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, false
}
} else {
// There is something already in the way at the normalized
// file name.
l.Infof(`File "%s" path has UTF8 encoding conflict with another file; ignoring.`, path)
return "", true
}
return normPath, false
}
func PermsEqual(a, b uint32) bool {
switch runtime.GOOS {
case "windows":
// There is only writeable and read only, represented for user, group
// and other equally. We only compare against user.
return a&0600 == b&0600
default:
// All bits count
return a&0777 == b&0777
}
}
// 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
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
}