vfs: Make tests run reliably

On file Remove
- cancel any writebacks in progress
- ignore error message deleting non existent file if file was in the
  process of being uploaded

Writeback
- Don't transfer the file if it has disappeared in the meantime
- Take our own copy of the file name to avoid deadlocks
- Fix delayed retry logic
- Wait for upload to finish when cancelling upload

Fix race condition in item saving

Fix race condition in vfscache test

Make sure we delete the file on the error path - this makes cascading
failures much less likely

vfs/file.go

@@ -527,7 +527,8 @@ func (f *File) Sync() error {
 }
 
 // Remove the file
-func (f *File) Remove() error {
+func (f *File) Remove() (err error) {
+	defer log.Trace(f.Path(), "")("err=%v", &err)
 	f.mu.RLock()
 	d := f.d
 	f.mu.RUnlock()
@@ -535,28 +536,33 @@ func (f *File) Remove() error {
 	if d.vfs.Opt.ReadOnly {
 		return EROFS
 	}
-	f.muRW.Lock() // muRW must be locked before mu to avoid
-	f.mu.Lock()   // deadlock in RWFileHandle.openPending and .close
-	if f.o != nil {
-		err := f.o.Remove(context.TODO())
-		if err != nil {
-			fs.Debugf(f._path(), "File.Remove file error: %v", err)
-			f.mu.Unlock()
-			f.muRW.Unlock()
-			return err
+
+	// Remove the object from the cache
+	wasWriting := false
+	if d.vfs.cache != nil {
+		wasWriting = d.vfs.cache.Remove(f.Path())
 	}
-	}
-	f.mu.Unlock()
-	f.muRW.Unlock()
 
 	// Remove the item from the directory listing
 	// called with File.mu released
 	d.delObject(f.Name())
-	// Remove the object from the cache
-	if d.vfs.cache != nil {
-		d.vfs.cache.Remove(f.Path())
+
+	f.muRW.Lock() // muRW must be locked before mu to avoid
+	f.mu.Lock()   // deadlock in RWFileHandle.openPending and .close
+	if f.o != nil {
+		err = f.o.Remove(context.TODO())
 	}
-	return nil
+	f.mu.Unlock()
+	f.muRW.Unlock()
+	if err != nil {
+		if wasWriting {
+			// Ignore error deleting file if was writing it as it may not be uploaded yet
+			err = nil
+		} else {
+			fs.Debugf(f._path(), "File.Remove file error: %v", err)
+		}
+	}
+	return err
 }
 
 // RemoveAll the file - same as remove for files

vfs/read_write_test.go

@@ -565,6 +565,11 @@ func TestRWFileHandleSizeCreateNew(t *testing.T) {
 func testRWFileHandleOpenTest(t *testing.T, vfs *VFS, test *openTest) {
 	fileName := "open-test-file"
 
+	// Make sure we delete the file on failure too
+	defer func() {
+		_ = vfs.Remove(fileName)
+	}()
+
 	// first try with file not existing
 	_, err := vfs.Stat(fileName)
 	require.True(t, os.IsNotExist(err))

vfs/vfscache/cache.go

@@ -309,14 +309,16 @@ func (c *Cache) Rename(name string, newName string, newObj fs.Object) (err error
 }
 
 // Remove should be called if name is deleted
-func (c *Cache) Remove(name string) {
+//
+// This returns true if the file was in the transfer queue so may not
+// have completedly uploaded yet.
+func (c *Cache) Remove(name string) (wasWriting bool) {
 	name = clean(name)
 	c.mu.Lock()
 	item, _ := c._get(name)
 	delete(c.item, name)
 	c.mu.Unlock()
-	item.remove("file deleted")
-
+	return item.remove("file deleted")
 }
 
 // SetModTime should be called to set the modification time of the cache file

vfs/vfscache/cache_test.go

@@ -76,7 +76,7 @@ func newTestCache(t *testing.T) (r *fstest.Run, c *Cache, cleanup func()) {
 	// Disable the cache cleaner as it interferes with these tests
 	opt.CachePollInterval = 0
 
-	// Enable synchronous write
+	// Disable synchronous write
 	opt.WriteBack = 0
 
 	return newTestCacheOpt(t, opt)
@@ -264,7 +264,7 @@ func TestCachePurgeOld(t *testing.T) {
 	var removed []string
 	removeFile := func(item *Item) {
 		removed = append(removed, item.name)
-		item._remove("TestCachePurgeOld")
+		item.remove("TestCachePurgeOld")
 	}
 
 	removed = nil
@@ -326,7 +326,7 @@ func TestCachePurgeOverQuota(t *testing.T) {
 	var removed []string
 	remove := func(item *Item) {
 		removed = append(removed, item.name)
-		item._remove("TestCachePurgeOverQuota")
+		item.remove("TestCachePurgeOverQuota")
 	}
 
 	removed = nil
@@ -402,7 +402,6 @@ func TestCachePurgeOverQuota(t *testing.T) {
 
 	// make potato definitely after potato2
 	t2 := t1.Add(20 * time.Second)
-	require.NoError(t, potato.Truncate(5))
 	potato.info.ATime = t2
 
 	// Check only potato2 removed to get below quota
@@ -563,13 +562,13 @@ func TestCacheCleaner(t *testing.T) {
 
 	potato := c.Item("potato")
 	potato2, found := c.get("potato")
-	assert.Equal(t, potato, potato2)
+	assert.Equal(t, fmt.Sprintf("%p", potato), fmt.Sprintf("%p", potato2))
 	assert.True(t, found)
 
 	time.Sleep(10 * opt.CachePollInterval)
 
 	potato2, found = c.get("potato")
-	assert.NotEqual(t, potato, potato2)
+	assert.NotEqual(t, fmt.Sprintf("%p", potato), fmt.Sprintf("%p", potato2))
 	assert.False(t, found)
 }
 

vfs/vfscache/item.go

@@ -471,10 +471,12 @@ func (item *Item) _store(ctx context.Context, storeFn StoreFn) (err error) {
 
 	// Transfer the temp file to the remote
 	cacheObj, err := item.c.fcache.NewObject(ctx, item.name)
-	if err != nil {
+	if err != nil && err != fs.ErrorObjectNotFound {
 		return errors.Wrap(err, "vfs cache: failed to find cache file")
 	}
 
+	// Object has disappeared if cacheObj == nil
+	if cacheObj != nil {
 		item.mu.Unlock()
 		o, err := operations.Copy(ctx, item.c.fremote, item.o, item.name, cacheObj)
 		item.mu.Lock()
@@ -483,6 +485,8 @@ func (item *Item) _store(ctx context.Context, storeFn StoreFn) (err error) {
 		}
 		item.o = o
 		item._updateFingerprint()
+	}
+
 	item.info.Dirty = false
 	err = item._save()
 	if err != nil {
@@ -529,10 +533,12 @@ func (item *Item) Close(storeFn StoreFn) (err error) {
 		}
 		// save the metadata once more since it may be dirty
 		// after the downloader
+		item.mu.Lock()
 		saveErr := item._save()
 		if saveErr != nil && err == nil {
 			err = errors.Wrap(saveErr, "close failed to save item")
 		}
+		item.mu.Unlock()
 	}()
 	item.mu.Lock()
 	defer item.mu.Unlock()
@@ -582,7 +588,7 @@ func (item *Item) Close(storeFn StoreFn) (err error) {
 			err = item._store(context.Background(), storeFn)
 		} else {
 			// asynchronous writeback
-			item.c.writeback.add(item, storeFn)
+			item.c.writeback.add(item, item.name, storeFn)
 		}
 	}
 
@@ -666,10 +672,10 @@ func (item *Item) _removeFile(reason string) {
 	err := os.Remove(osPath)
 	if err != nil {
 		if !os.IsNotExist(err) {
-			fs.Errorf(item.name, "Failed to remove cache file as %s: %v", reason, err)
+			fs.Errorf(item.name, "vfs cache: failed to remove cache file as %s: %v", reason, err)
 		}
 	} else {
-		fs.Infof(item.name, "Removed cache file as %s", reason)
+		fs.Infof(item.name, "vfs cache: removed cache file as %s", reason)
 	}
 }
 
@@ -681,28 +687,37 @@ func (item *Item) _removeMeta(reason string) {
 	err := os.Remove(osPathMeta)
 	if err != nil {
 		if !os.IsNotExist(err) {
-			fs.Errorf(item.name, "Failed to remove metadata from cache as %s: %v", reason, err)
+			fs.Errorf(item.name, "vfs cache: failed to remove metadata from cache as %s: %v", reason, err)
 		}
 	} else {
-		fs.Infof(item.name, "Removed metadata from cache as %s", reason)
+		fs.Infof(item.name, "vfs cache: removed metadata from cache as %s", reason)
 	}
 }
 
 // remove the cached file and empty the metadata
 //
+// This returns true if the file was in the transfer queue so may not
+// have completedly uploaded yet.
+//
 // call with lock held
-func (item *Item) _remove(reason string) {
+func (item *Item) _remove(reason string) (wasWriting bool) {
+	// Cancel writeback, if any
+	wasWriting = item.c.writeback.cancel(item)
 	item.info.clean()
 	item.metaDirty = false
 	item._removeFile(reason)
 	item._removeMeta(reason)
+	return wasWriting
 }
 
 // remove the cached file and empty the metadata
-func (item *Item) remove(reason string) {
+//
+// This returns true if the file was in the transfer queue so may not
+// have completedly uploaded yet.
+func (item *Item) remove(reason string) (wasWriting bool) {
 	item.mu.Lock()
-	item._remove(reason)
-	item.mu.Unlock()
+	defer item.mu.Unlock()
+	return item._remove(reason)
 }
 
 // create a downloader for the item

vfs/vfscache/writeback.go

@@ -13,15 +13,14 @@ import (
 )
 
 const (
-	uploadDelay       = 10 * time.Second // delay betwen upload attempts
-	maxUploadAttempts = 10               // max number of times to try to upload
+	maxUploadDelay = 5 * time.Minute // max delay betwen upload attempts
 )
 
 // writeBack keeps track of the items which need to be written back to the disk at some point
 type writeBack struct {
 	mu      sync.Mutex
-	items   writeBackItems           // priority queue of *writeBackItem
-	lookup  map[*Item]*writeBackItem // for getting a *writeBackItem from a *Item
+	items   writeBackItems           // priority queue of *writeBackItem - writeBackItems are in here while awaiting transfer only
+	lookup  map[*Item]*writeBackItem // for getting a *writeBackItem from a *Item - writeBackItems are in here until cancelled
 	opt     *vfscommon.Options       // VFS options
 	timer   *time.Timer              // next scheduled time for the uploader
 	kick    chan struct{}            // send on this channel to wake up the uploader
@@ -47,13 +46,19 @@ func newWriteBack(ctx context.Context, opt *vfscommon.Options) *writeBack {
 
 // writeBackItem stores an Item awaiting writeback
 //
+// These are stored on the items heap when awaiting transfer but
+// removed from the items heap when transferring. They remain in the
+// lookup map until cancelled.
+//
 // writeBack.mu must be held to manipulate this
 type writeBackItem struct {
+	name      string             // name of the item so we don't have to read it from item
 	index     int                // index into the priority queue for update
 	item      *Item              // Item that needs writeback
 	expiry    time.Time          // When this expires we will write it back
 	uploading bool               // If we are uploading the item
 	cancel    context.CancelFunc // To cancel the upload with
+	done      chan struct{}      // closed when the cancellation completes
 	storeFn   StoreFn            // To write the object back with
 	tries     int                // number of times we have tried to upload
 	delay     time.Duration      // delay between upload attempts
@@ -114,11 +119,12 @@ func (wb *writeBack) _newExpiry() time.Time {
 // make a new writeBackItem
 //
 // call with the lock held
-func (wb *writeBack) _newItem(item *Item) *writeBackItem {
+func (wb *writeBack) _newItem(item *Item, name string) *writeBackItem {
 	wbItem := &writeBackItem{
+		name:   name,
 		item:   item,
 		expiry: wb._newExpiry(),
-		delay:  uploadDelay,
+		delay:  wb.opt.WriteBack,
 	}
 	wb._addItem(wbItem)
 	wb._pushItem(wbItem)
@@ -153,6 +159,13 @@ func (wb *writeBack) _pushItem(wbItem *writeBackItem) {
 	heap.Push(&wb.items, wbItem)
 }
 
+// remove a writeBackItem from the items heap
+//
+// call with the lock held
+func (wb *writeBack) _removeItem(wbItem *writeBackItem) {
+	heap.Remove(&wb.items, wbItem.index)
+}
+
 // peek the oldest writeBackItem - may be nil
 //
 // call with the lock held
@@ -179,13 +192,13 @@ func (wb *writeBack) _resetTimer() {
 
 // add adds an item to the writeback queue or resets its timer if it
 // is already there
-func (wb *writeBack) add(item *Item, storeFn StoreFn) {
+func (wb *writeBack) add(item *Item, name string, storeFn StoreFn) {
 	wb.mu.Lock()
 	defer wb.mu.Unlock()
 
 	wbItem, ok := wb.lookup[item]
 	if !ok {
-		wbItem = wb._newItem(item)
+		wbItem = wb._newItem(item, name)
 	} else {
 		if wbItem.uploading {
 			// We are uploading already so cancel the upload
@@ -198,6 +211,28 @@ func (wb *writeBack) add(item *Item, storeFn StoreFn) {
 	wb._resetTimer()
 }
 
+// cancel a writeback if there is one
+func (wb *writeBack) cancel(item *Item) (found bool) {
+	wb.mu.Lock()
+	defer wb.mu.Unlock()
+
+	wbItem, found := wb.lookup[item]
+	if found {
+		fs.Debugf(wbItem.name, "vfs cache: cancelling writeback")
+		if wbItem.uploading {
+			// We are uploading already so cancel the upload
+			wb._cancelUpload(wbItem)
+		} else {
+			// Remove the item from the heap
+			wb._removeItem(wbItem)
+		}
+		// Remove the item from the lookup map
+		wb._delItem(wbItem)
+	}
+	wb._resetTimer()
+	return found
+}
+
 // kick the upload checker
 //
 // This should be called at the end of uploads just in case we had to
@@ -229,20 +264,22 @@ func (wb *writeBack) upload(ctx context.Context, wbItem *writeBackItem) {
 	}
 
 	if err != nil {
-		if wbItem.tries < maxUploadAttempts {
-			fs.Errorf(item.getName(), "vfs cache: failed to upload, will retry in %v: %v", wb.opt.WriteBack, err)
+		// FIXME should this have a max number of transfer attempts?
+		wbItem.delay *= 2
+		if wbItem.delay > maxUploadDelay {
+			wbItem.delay = maxUploadDelay
+		}
+		fs.Errorf(wbItem.name, "vfs cache: failed to upload try #%d, will retry in %v: %v", wbItem.tries, wbItem.delay, err)
 		// push the item back on the queue for retry
 		wb._pushItem(wbItem)
 		wb.items._update(wbItem, time.Now().Add(wbItem.delay))
-			wbItem.delay *= 2
-		} else {
-			fs.Errorf(item.getName(), "vfs cache: failed to upload, will retry in %v: %v", wb.opt.WriteBack, err)
-		}
 	} else {
+		fs.Infof(wbItem.name, "vfs cache: upload succeeded try #%d", wbItem.tries)
 		// show that we are done with the item
 		wb._delItem(wbItem)
 	}
 	wb._kickUploader()
+	close(wbItem.done)
 }
 
 // cancel the upload
@@ -252,11 +289,12 @@ func (wb *writeBack) _cancelUpload(wbItem *writeBackItem) {
 	if !wbItem.uploading {
 		return
 	}
-	fs.Debugf(wbItem.item.getName(), "vfs cache: canceling upload")
+	fs.Debugf(wbItem.name, "vfs cache: cancelling upload")
 	if wbItem.cancel != nil {
 		// Cancel the upload - this may or may not be effective
-		// we don't wait for the completion
 		wbItem.cancel()
+		// wait for the uploader to finish
+		<-wbItem.done
 	}
 	if wbItem.uploading {
 		wbItem.uploading = false
@@ -275,7 +313,7 @@ func (wb *writeBack) processItems(ctx context.Context) {
 	for wbItem := wb._peekItem(); wbItem != nil && time.Until(wbItem.expiry) <= 0; wbItem = wb._peekItem() {
 		// If reached transfer limit don't restart the timer
 		if wb.uploads >= fs.Config.Transfers {
-			fs.Debugf(wbItem.item.getName(), "vfs cache: delaying writeback as --transfers exceeded")
+			fs.Debugf(wbItem.name, "vfs cache: delaying writeback as --transfers exceeded")
 			resetTimer = false
 			break
 		}
@@ -286,6 +324,7 @@ func (wb *writeBack) processItems(ctx context.Context) {
 		wb.uploads++
 		newCtx, cancel := context.WithCancel(ctx)
 		wbItem.cancel = cancel
+		wbItem.done = make(chan struct{})
 		go wb.upload(newCtx, wbItem)
 	}