[#970] fstree: Move file locking to the generic writer

It is not a part of FSTree itself, but rather a way to solve concurrent
counter update on non-linux implementations. New linux implementations
is pretty simple: link fails when the file exists, unlink fails when the
file doesn't exist.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/local_object_storage/blobstor/fstree/counter.go

@@ -18,6 +18,11 @@ func (c *noopCounter) Set(uint64) {}
 func (c *noopCounter) Inc()       {}
 func (c *noopCounter) Dec()       {}
 
+func counterEnabled(c FileCounter) bool {
+	_, noop := c.(*noopCounter)
+	return !noop
+}
+
 type SimpleCounter struct {
 	v atomic.Uint64
 }

pkg/local_object_storage/blobstor/fstree/fstree.go

@@ -53,9 +53,7 @@ type FSTree struct {
 	readOnly bool
 	metrics  Metrics
 
-	fileGuard          keyLock
 	fileCounter FileCounter
-	fileCounterEnabled bool
 
 	writer writer
 }
@@ -88,14 +86,13 @@ func New(opts ...Option) *FSTree {
 		Depth:       4,
 		DirNameLen:  DirNameLen,
 		metrics:     &noopMetrics{},
-		fileGuard:   &noopKeyLock{},
 		fileCounter: &noopCounter{},
 		log:         &logger.Logger{Logger: zap.L()},
 	}
 	for i := range opts {
 		opts[i](f)
 	}
-	f.writer = newGenericWriteData(f)
+	f.writer = newGenericWriteData(f.fileCounter, f.Permissions, f.noSync)
 
 	return f
 }
@@ -444,7 +441,7 @@ func (t *FSTree) GetRange(ctx context.Context, prm common.GetRangePrm) (common.G
 // initFileCounter walks the file tree rooted at FSTree's root,
 // counts total items count, inits counter and returns number of stored objects.
 func (t *FSTree) initFileCounter() error {
-	if !t.fileCounterEnabled {
+	if !counterEnabled(t.fileCounter) {
 		return nil
 	}
 

pkg/local_object_storage/blobstor/fstree/fstree_write_generic.go

@@ -10,6 +10,7 @@ import (
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/blobstor/common"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/util/logicerr"
+	utilSync "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/sync"
 	apistatus "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/client/status"
 )
 
@@ -22,19 +23,31 @@ type genericWriter struct {
 	perm  fs.FileMode
 	flags int
 
-	t      *FSTree
+	fileGuard          keyLock
+	fileCounter        FileCounter
+	fileCounterEnabled bool
 	suffix             atomic.Uint64
 }
 
-func newGenericWriteData(t *FSTree) writer {
+func newGenericWriteData(c FileCounter, perm fs.FileMode, noSync bool) writer {
 	flags := os.O_WRONLY | os.O_CREATE | os.O_TRUNC | os.O_EXCL
-	if !t.noSync {
+	if !noSync {
 		flags |= os.O_SYNC
 	}
+
+	var fileGuard keyLock = &noopKeyLock{}
+	fileCounterEnabled := counterEnabled(c)
+	if fileCounterEnabled {
+		fileGuard = utilSync.NewKeyLocker[string]()
+	}
+
 	var w = &genericWriter{
-		perm:  t.Permissions,
+		perm:  perm,
 		flags: flags,
-		t:     t,
+
+		fileCounterEnabled: fileCounterEnabled,
+		fileGuard:          fileGuard,
+		fileCounter:        c,
 	}
 	return w
 }
@@ -46,9 +59,9 @@ func (w *genericWriter) writeData(p string, data []byte) error {
 
 // writeAndRename opens tmpPath exclusively, writes data to it and renames it to p.
 func (w *genericWriter) writeAndRename(tmpPath, p string, data []byte) error {
-	if w.t.fileCounterEnabled {
+	if w.fileCounterEnabled {
-		w.t.fileGuard.Lock(p)
+		w.fileGuard.Lock(p)
-		defer w.t.fileGuard.Unlock(p)
+		defer w.fileGuard.Unlock(p)
 	}
 
 	err := w.writeFile(tmpPath, data)
@@ -64,15 +77,15 @@ func (w *genericWriter) writeAndRename(tmpPath, p string, data []byte) error {
 		return err
 	}
 
-	if w.t.fileCounterEnabled {
+	if w.fileCounterEnabled {
-		w.t.fileCounter.Inc()
+		w.fileCounter.Inc()
 		var targetFileExists bool
 		if _, e := os.Stat(p); e == nil {
 			targetFileExists = true
 		}
 		err = os.Rename(tmpPath, p)
 		if err == nil && targetFileExists {
-			w.t.fileCounter.Dec()
+			w.fileCounter.Dec()
 		}
 	} else {
 		err = os.Rename(tmpPath, p)
@@ -96,12 +109,12 @@ func (w *genericWriter) writeFile(p string, data []byte) error {
 
 func (w *genericWriter) removeFile(p string) error {
 	var err error
-	if w.t.fileCounterEnabled {
+	if w.fileCounterEnabled {
-		w.t.fileGuard.Lock(p)
+		w.fileGuard.Lock(p)
 		err = os.Remove(p)
-		w.t.fileGuard.Unlock(p)
+		w.fileGuard.Unlock(p)
 		if err == nil {
-			w.t.fileCounter.Dec()
+			w.fileCounter.Dec()
 		}
 	} else {
 		err = os.Remove(p)

pkg/local_object_storage/blobstor/fstree/option.go

@@ -4,7 +4,6 @@ import (
 	"io/fs"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/logger"
-	utilSync "git.frostfs.info/TrueCloudLab/frostfs-node/pkg/util/sync"
 	"go.uber.org/zap"
 )
 
@@ -48,9 +47,7 @@ func WithMetrics(m Metrics) Option {
 
 func WithFileCounter(c FileCounter) Option {
 	return func(f *FSTree) {
-		f.fileCounterEnabled = true
 		f.fileCounter = c
-		f.fileGuard = utilSync.NewKeyLocker[string]()
 	}
 }