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lib/fs, lib/model: Add error channel to Watch to avoid panics (fixes #5697) (#5734)

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* lib/fs, lib/model: Add error channel to Watch to avoid panics (fixes #5697)

* forgot unsupported watch

* and more non(-standard)-unixy fixes

* and windows test

* review
This commit is contained in:
Simon Frei 2019-05-25 21:08:26 +02:00 committed by Audrius Butkevicius
parent 9e6db72535
commit 486230768e
12 changed files with 158 additions and 105 deletions
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11
lib/fs/basicfs.go
View File

@ -8,6 +8,7 @@ package fs
import (
"errors"
"fmt"
"os"
"path/filepath"
"runtime"
@ -334,3 +335,13 @@ func longFilenameSupport(path string) string {
}
return path
}
type ErrWatchEventOutsideRoot struct{ msg string }
func (e *ErrWatchEventOutsideRoot) Error() string {
return e.msg
}
func (f *BasicFilesystem) newErrWatchEventOutsideRoot(absPath, root string) *ErrWatchEventOutsideRoot {
return &ErrWatchEventOutsideRoot{fmt.Sprintf("Watching for changes encountered an event outside of the filesystem root: f.root==%v, root==%v, path==%v. This should never happen, please report this message to forum.syncthing.net.", f.root, root, absPath)}
}

11
lib/fs/basicfs_unix.go
View File

@ -9,7 +9,6 @@
package fs
import (
"fmt"
"os"
"path/filepath"
"strings"
@ -58,17 +57,17 @@ func (f *BasicFilesystem) Roots() ([]string, error) {
}
// unrootedChecked returns the path relative to the folder root (same as
// unrooted). It panics if the given path is not a subpath and handles the
// unrooted) or an error if the given path is not a subpath and handles the
// special case when the given path is the folder root without a trailing
// pathseparator.
func (f *BasicFilesystem) unrootedChecked(absPath, root string) string {
func (f *BasicFilesystem) unrootedChecked(absPath, root string) (string, *ErrWatchEventOutsideRoot) {
if absPath+string(PathSeparator) == root {
return "."
return ".", nil
}
if !strings.HasPrefix(absPath, root) {
panic(fmt.Sprintf("bug: Notify backend is processing a change outside of the filesystem root: f.root==%v, root==%v, path==%v", f.root, root, absPath))
return "", f.newErrWatchEventOutsideRoot(absPath, root)
}
return rel(absPath, root)
return rel(absPath, root), nil
}
func rel(path, prefix string) string {

32
lib/fs/basicfs_watch.go
View File

@ -20,10 +20,10 @@ import (
// Not meant to be changed, but must be changeable for tests
var backendBuffer = 500
func (f *BasicFilesystem) Watch(name string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, error) {
func (f *BasicFilesystem) Watch(name string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, <-chan error, error) {
watchPath, root, err := f.watchPaths(name)
if err != nil {
return nil, err
return nil, nil, err
}
outChan := make(chan Event)
@ -36,7 +36,11 @@ func (f *BasicFilesystem) Watch(name string, ignore Matcher, ctx context.Context
if ignore.SkipIgnoredDirs() {
absShouldIgnore := func(absPath string) bool {
return ignore.ShouldIgnore(f.unrootedChecked(absPath, root))
rel, err := f.unrootedChecked(absPath, root)
if err != nil {
return true
}
return ignore.ShouldIgnore(rel)
}
err = notify.WatchWithFilter(watchPath, backendChan, absShouldIgnore, eventMask)
} else {
@ -47,15 +51,16 @@ func (f *BasicFilesystem) Watch(name string, ignore Matcher, ctx context.Context
if reachedMaxUserWatches(err) {
err = errors.New("failed to setup inotify handler. Please increase inotify limits, see https://docs.syncthing.net/users/faq.html#inotify-limits")
}
return nil, err
return nil, nil, err
}
go f.watchLoop(name, root, backendChan, outChan, ignore, ctx)
errChan := make(chan error)
go f.watchLoop(name, root, backendChan, outChan, errChan, ignore, ctx)
return outChan, nil
return outChan, errChan, nil
}
func (f *BasicFilesystem) watchLoop(name, evalRoot string, backendChan chan notify.EventInfo, outChan chan<- Event, ignore Matcher, ctx context.Context) {
func (f *BasicFilesystem) watchLoop(name, evalRoot string, backendChan chan notify.EventInfo, outChan chan<- Event, errChan chan<- error, ignore Matcher, ctx context.Context) {
for {
// Detect channel overflow
if len(backendChan) == backendBuffer {
@ -74,7 +79,18 @@ func (f *BasicFilesystem) watchLoop(name, evalRoot string, backendChan chan noti
select {
case ev := <-backendChan:
relPath := f.unrootedChecked(ev.Path(), evalRoot)
relPath, err := f.unrootedChecked(ev.Path(), evalRoot)
if err != nil {
select {
case errChan <- err:
l.Debugln(f.Type(), f.URI(), "Watch: Sending error", err)
case <-ctx.Done():
}
notify.Stop(backendChan)
l.Debugln(f.Type(), f.URI(), "Watch: Stopped due to", err)
return
}
if ignore.ShouldIgnore(relPath) {
l.Debugln(f.Type(), f.URI(), "Watch: Ignoring", relPath)
continue

47
lib/fs/basicfs_watch_test.go
View File

@ -159,6 +159,7 @@ func TestWatchWinRoot(t *testing.T) {
outChan := make(chan Event)
backendChan := make(chan notify.EventInfo, backendBuffer)
errChan := make(chan error)
ctx, cancel := context.WithCancel(context.Background())
@ -177,7 +178,7 @@ func TestWatchWinRoot(t *testing.T) {
}
cancel()
}()
fs.watchLoop(".", root, backendChan, outChan, fakeMatcher{}, ctx)
fs.watchLoop(".", root, backendChan, outChan, errChan, fakeMatcher{}, ctx)
}()
// filepath.Dir as watch has a /... suffix
@ -192,6 +193,8 @@ func TestWatchWinRoot(t *testing.T) {
if ev.Name != name {
t.Errorf("Unexpected event %v, expected %v", ev.Name, name)
}
case err := <-errChan:
t.Error("Received fatal watch error:", err)
case <-ctx.Done():
}
}
@ -200,32 +203,22 @@ func TestWatchWinRoot(t *testing.T) {
func TestWatchOutside(t *testing.T) {
outChan := make(chan Event)
backendChan := make(chan notify.EventInfo, backendBuffer)
errChan := make(chan error)
ctx, cancel := context.WithCancel(context.Background())
// testFs is Filesystem, but we need BasicFilesystem here
fs := newBasicFilesystem(testDirAbs)
go func() {
defer func() {
if recover() == nil {
select {
case <-ctx.Done(): // timed out
default:
t.Fatalf("Watch did not panic on receiving event outside of folder")
}
}
cancel()
}()
fs.watchLoop(".", testDirAbs, backendChan, outChan, fakeMatcher{}, ctx)
}()
go fs.watchLoop(".", testDirAbs, backendChan, outChan, errChan, fakeMatcher{}, ctx)
backendChan <- fakeEventInfo(filepath.Join(filepath.Dir(testDirAbs), "outside"))
select {
case <-time.After(10 * time.Second):
cancel()
t.Errorf("Timed out before panicing")
t.Errorf("Timed out before receiving error")
case <-errChan:
case <-ctx.Done():
}
}
@ -233,6 +226,7 @@ func TestWatchOutside(t *testing.T) {
func TestWatchSubpath(t *testing.T) {
outChan := make(chan Event)
backendChan := make(chan notify.EventInfo, backendBuffer)
errChan := make(chan error)
ctx, cancel := context.WithCancel(context.Background())
@ -240,7 +234,7 @@ func TestWatchSubpath(t *testing.T) {
fs := newBasicFilesystem(testDirAbs)
abs, _ := fs.rooted("sub")
go fs.watchLoop("sub", testDirAbs, backendChan, outChan, fakeMatcher{}, ctx)
go fs.watchLoop("sub", testDirAbs, backendChan, outChan, errChan, fakeMatcher{}, ctx)
backendChan <- fakeEventInfo(filepath.Join(abs, "file"))
@ -253,6 +247,8 @@ func TestWatchSubpath(t *testing.T) {
if ev.Name != filepath.Join("sub", "file") {
t.Errorf("While watching a subfolder, received an event with unexpected path %v", ev.Name)
}
case err := <-errChan:
t.Error("Received fatal watch error:", err)
}
cancel()
@ -337,7 +333,7 @@ func TestWatchSymlinkedRoot(t *testing.T) {
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
if _, err := linkedFs.Watch(".", fakeMatcher{}, ctx, false); err != nil {
if _, _, err := linkedFs.Watch(".", fakeMatcher{}, ctx, false); err != nil {
panic(err)
}
@ -350,14 +346,10 @@ func TestWatchSymlinkedRoot(t *testing.T) {
}
func TestUnrootedChecked(t *testing.T) {
var unrooted string
defer func() {
if recover() == nil {
t.Fatal("unrootedChecked did not panic on outside path, but returned", unrooted)
}
}()
fs := newBasicFilesystem(testDirAbs)
unrooted = fs.unrootedChecked("/random/other/path", testDirAbs)
if unrooted, err := fs.unrootedChecked("/random/other/path", testDirAbs); err == nil {
t.Error("unrootedChecked did not return an error on outside path, but returned", unrooted)
}
}
func TestWatchIssue4877(t *testing.T) {
@ -428,7 +420,7 @@ func testScenario(t *testing.T, name string, testCase func(), expectedEvents, al
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
eventChan, err := testFs.Watch(name, fm, ctx, false)
eventChan, errChan, err := testFs.Watch(name, fm, ctx, false)
if err != nil {
panic(err)
}
@ -439,8 +431,9 @@ func testScenario(t *testing.T, name string, testCase func(), expectedEvents, al
select {
case <-time.After(10 * time.Second):
t.Errorf("Timed out before receiving all expected events")
t.Error("Timed out before receiving all expected events")
case err := <-errChan:
t.Error("Received fatal watch error:", err)
case <-ctx.Done():
}
}

4
lib/fs/basicfs_watch_unsupported.go
View File

@ -10,6 +10,6 @@ package fs
import "context"
func (f *BasicFilesystem) Watch(path string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, error) {
return nil, ErrWatchNotSupported
func (f *BasicFilesystem) Watch(name string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, <-chan error, error) {
return nil, nil, ErrWatchNotSupported
}

10
lib/fs/basicfs_windows.go
View File

@ -153,20 +153,20 @@ func (f *BasicFilesystem) Roots() ([]string, error) {
}
// unrootedChecked returns the path relative to the folder root (same as
// unrooted). It panics if the given path is not a subpath and handles the
// unrooted) or an error if the given path is not a subpath and handles the
// special case when the given path is the folder root without a trailing
// pathseparator.
func (f *BasicFilesystem) unrootedChecked(absPath, root string) string {
func (f *BasicFilesystem) unrootedChecked(absPath, root string) (string, error) {
absPath = f.resolveWin83(absPath)
lowerAbsPath := UnicodeLowercase(absPath)
lowerRoot := UnicodeLowercase(root)
if lowerAbsPath+string(PathSeparator) == lowerRoot {
return "."
return ".", nil
}
if !strings.HasPrefix(lowerAbsPath, lowerRoot) {
panic(fmt.Sprintf("bug: Notify backend is processing a change outside of the filesystem root: f.root==%v, root==%v (lower), path==%v (lower)", f.root, lowerRoot, lowerAbsPath))
return "", f.newErrWatchEventOutsideRoot(lowerAbsPath, lowerRoot)
}
return rel(absPath, root)
return rel(absPath, root), nil
}
func rel(path, prefix string) string {

20
lib/fs/basicfs_windows_test.go
View File

@ -127,19 +127,15 @@ func TestRelUnrootedCheckedWindows(t *testing.T) {
}
// unrootedChecked really just wraps rel, and does not care about
// the actual root of that filesystem, but should not panic on these
// test cases.
fs := BasicFilesystem{root: tc.root}
if res := fs.unrootedChecked(tc.abs, tc.root); res != tc.expectedRel {
t.Errorf(`unrootedChecked("%v", "%v") == "%v", expected "%v"`, tc.abs, tc.root, res, tc.expectedRel)
// the actual root of that filesystem, but should not return an error
// on these test cases.
for _, root := range []string{tc.root, strings.ToLower(tc.root), strings.ToUpper(tc.root)} {
fs := BasicFilesystem{root: root}
if res, err := fs.unrootedChecked(tc.abs, tc.root); err != nil {
t.Errorf(`Unexpected error from unrootedChecked("%v", "%v"): %v (fs.root: %v)`, tc.abs, tc.root, err, root)
} else if res != tc.expectedRel {
t.Errorf(`unrootedChecked("%v", "%v") == "%v", expected "%v" (fs.root: %v)`, tc.abs, tc.root, res, tc.expectedRel, root)
}
fs = BasicFilesystem{root: strings.ToLower(tc.root)}
if res := fs.unrootedChecked(tc.abs, tc.root); res != tc.expectedRel {
t.Errorf(`unrootedChecked("%v", "%v") == "%v", expected "%v"`, tc.abs, tc.root, res, tc.expectedRel)
}
fs = BasicFilesystem{root: strings.ToUpper(tc.root)}
if res := fs.unrootedChecked(tc.abs, tc.root); res != tc.expectedRel {
t.Errorf(`unrootedChecked("%v", "%v") == "%v", expected "%v"`, tc.abs, tc.root, res, tc.expectedRel)
}
}
}

4
lib/fs/errorfs.go
View File

@ -44,6 +44,6 @@ func (fs *errorFilesystem) Usage(name string) (Usage, error)
func (fs *errorFilesystem) Type() FilesystemType { return fs.fsType }
func (fs *errorFilesystem) URI() string { return fs.uri }
func (fs *errorFilesystem) SameFile(fi1, fi2 FileInfo) bool { return false }
func (fs *errorFilesystem) Watch(path string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, error) {
return nil, fs.err
func (fs *errorFilesystem) Watch(path string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, <-chan error, error) {
return nil, nil, fs.err
}

4
lib/fs/fakefs.go
View File

@ -466,8 +466,8 @@ func (fs *fakefs) Walk(name string, walkFn WalkFunc) error {
return errors.New("not implemented")
}
func (fs *fakefs) Watch(path string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, error) {
return nil, ErrWatchNotSupported
func (fs *fakefs) Watch(path string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, <-chan error, error) {
return nil, nil, ErrWatchNotSupported
}
func (fs *fakefs) Hide(name string) error {

5
lib/fs/filesystem.go
View File

@ -36,7 +36,10 @@ type Filesystem interface {
Stat(name string) (FileInfo, error)
SymlinksSupported() bool
Walk(name string, walkFn WalkFunc) error
Watch(path string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, error)
// If setup fails, returns non-nil error, and if afterwards a fatal (!)
// error occurs, sends that error on the channel. Afterwards this watch
// can be considered stopped.
Watch(path string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, <-chan error, error)
Hide(name string) error
Unhide(name string) error
Glob(pattern string) ([]string, error)

6
lib/fs/logfs.go
View File

@ -128,10 +128,10 @@ func (fs *logFilesystem) Walk(root string, walkFn WalkFunc) error {
return err
}
func (fs *logFilesystem) Watch(path string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, error) {
evChan, err := fs.Filesystem.Watch(path, ignore, ctx, ignorePerms)
func (fs *logFilesystem) Watch(path string, ignore Matcher, ctx context.Context, ignorePerms bool) (<-chan Event, <-chan error, error) {
evChan, errChan, err := fs.Filesystem.Watch(path, ignore, ctx, ignorePerms)
l.Debugln(getCaller(), fs.Type(), fs.URI(), "Watch", path, ignore, ignorePerms, err)
return evChan, err
return evChan, errChan, err
}
func (fs *logFilesystem) Unhide(name string) error {

81
lib/model/folder.go
View File

@ -173,9 +173,6 @@ func (f *folder) Serve() {
pullFailTimer.Reset(pause)
}
// The reason for running the scanner from within the puller is that
// this is the easiest way to make sure we are not doing both at the
// same time.
case <-f.scanTimer.C:
l.Debugln(f, "Scanning subdirectories")
f.scanTimerFired()
@ -611,17 +608,56 @@ func (f *folder) startWatch() {
f.watchChan = make(chan []string)
f.watchCancel = cancel
f.watchMut.Unlock()
go f.startWatchAsync(ctx)
go f.monitorWatch(ctx)
}
// startWatchAsync tries to start the filesystem watching and retries every minute on failure.
// It is a convenience function that should not be used except in startWatch.
func (f *folder) startWatchAsync(ctx context.Context) {
timer := time.NewTimer(0)
// monitorWatch starts the filesystem watching and retries every minute on failure.
// It should not be used except in startWatch.
func (f *folder) monitorWatch(ctx context.Context) {
failTimer := time.NewTimer(0)
aggrCtx, aggrCancel := context.WithCancel(ctx)
var err error
var eventChan <-chan fs.Event
var errChan <-chan error
warnedOutside := false
for {
select {
case <-timer.C:
eventChan, err := f.Filesystem().Watch(".", f.ignores, ctx, f.IgnorePerms)
case <-failTimer.C:
eventChan, errChan, err = f.Filesystem().Watch(".", f.ignores, ctx, f.IgnorePerms)
// We do this at most once per minute which is the
// default rescan time without watcher.
f.scanOnWatchErr()
f.setWatchError(err)
if err != nil {
failTimer.Reset(time.Minute)
continue
}
watchaggregator.Aggregate(eventChan, f.watchChan, f.FolderConfiguration, f.model.cfg, aggrCtx)
l.Debugln("Started filesystem watcher for folder", f.Description())
case err = <-errChan:
f.setWatchError(err)
// This error was previously a panic and should never occur, so generate
// a warning, but don't do it repetitively.
if !warnedOutside {
if _, ok := err.(*fs.ErrWatchEventOutsideRoot); ok {
l.Warnln(err)
warnedOutside = true
return
}
}
aggrCancel()
errChan = nil
aggrCtx, aggrCancel = context.WithCancel(ctx)
failTimer.Reset(time.Minute)
case <-ctx.Done():
return
}
}
}
// setWatchError sets the current error state of the watch and should be called
// regardless of whether err is nil or not.
func (f *folder) setWatchError(err error) {
f.watchMut.Lock()
prevErr := f.watchErr
f.watchErr = err
@ -638,24 +674,23 @@ func (f *folder) startWatchAsync(ctx context.Context) {
}
events.Default.Log(events.FolderWatchStateChanged, data)
}
if err != nil {
if err == nil {
return
}
if prevErr == errWatchNotStarted {
l.Infof("Error while trying to start filesystem watcher for folder %s, trying again in 1min: %v", f.Description(), err)
} else {
return
}
l.Debugf("Repeat error while trying to start filesystem watcher for folder %s, trying again in 1min: %v", f.Description(), err)
}
timer.Reset(time.Minute)
continue
}
}
// scanOnWatchErr schedules a full scan immediately if an error occurred while watching.
func (f *folder) scanOnWatchErr() {
f.watchMut.Lock()
defer f.watchMut.Unlock()
watchaggregator.Aggregate(eventChan, f.watchChan, f.FolderConfiguration, f.model.cfg, ctx)
l.Debugln("Started filesystem watcher for folder", f.Description())
return
case <-ctx.Done():
return
}
if f.watchErr != nil && f.watchErr != errWatchNotStarted {
f.Delay(0)
}
f.watchMut.Unlock()
}
func (f *folder) setError(err error) {