Address critical and high-priority review comments

- Add per-session locking to prevent race conditions in updateTusSessionOffset
- Stream data directly to volume server instead of buffering entire chunk
- Only buffer 512 bytes for MIME type detection, then stream remaining data
- Clean up session locks when session is deleted

weed/server/filer_server_tus_handlers.go

@@ -292,15 +292,6 @@ func (fs *FilerServer) tusWriteData(ctx context.Context, session *TusSession, of
 	}
 
 	// Read data into buffer
-	buf := new(bytes.Buffer)
-	n, err := io.CopyN(buf, reader, contentLength)
-	if err != nil && err != io.EOF {
-		return 0, fmt.Errorf("read data: %w", err)
-	}
-	if n == 0 {
-		return 0, nil
-	}
-
 	// Determine storage options based on target path
 	so, err := fs.detectStorageOption0(ctx, session.TargetPath, "", "", "", "", "", "", "", "", "")
 	if err != nil {
@@ -319,10 +310,31 @@ func (fs *FilerServer) tusWriteData(ctx context.Context, session *TusSession, of
 		return 0, fmt.Errorf("create uploader: %w", uploaderErr)
 	}
 
-	// Detect MIME type from data
-	mimeType := http.DetectContentType(buf.Bytes())
+	// Read first 512 bytes for MIME type detection, then stream the rest
+	sniffBuf := make([]byte, 512)
+	sniffN, sniffErr := io.ReadFull(reader, sniffBuf)
+	if sniffErr != nil && sniffErr != io.EOF && sniffErr != io.ErrUnexpectedEOF {
+		return 0, fmt.Errorf("read data for mime detection: %w", sniffErr)
+	}
+	if sniffN == 0 {
+		return 0, nil
+	}
+	sniffBuf = sniffBuf[:sniffN]
+
+	// Detect MIME type from sniffed bytes
+	mimeType := http.DetectContentType(sniffBuf)
+
+	// Create a reader that combines sniffed bytes with remaining data
+	var dataReader io.Reader
+	if int64(sniffN) >= contentLength {
+		// All data fits in sniff buffer
+		dataReader = bytes.NewReader(sniffBuf)
+	} else {
+		// Combine sniffed bytes with remaining stream
+		dataReader = io.MultiReader(bytes.NewReader(sniffBuf), io.LimitReader(reader, contentLength-int64(sniffN)))
+	}
 
-	uploadResult, uploadErr, _ := uploader.Upload(ctx, bytes.NewReader(buf.Bytes()), &operation.UploadOption{
+	uploadResult, uploadErr, _ := uploader.Upload(ctx, dataReader, &operation.UploadOption{
 		UploadUrl:         urlLocation,
 		Filename:          "",
 		Cipher:            fs.option.Cipher,

weed/server/filer_server_tus_session.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"os"
 	"sort"
+	"sync"
 	"time"
 
 	"github.com/seaweedfs/seaweedfs/weed/filer"
@@ -14,6 +15,39 @@ import (
 	"github.com/seaweedfs/seaweedfs/weed/util"
 )
 
+// tusSessionLocks provides per-session locking to prevent race conditions
+var tusSessionLocks = struct {
+	sync.RWMutex
+	locks map[string]*sync.Mutex
+}{locks: make(map[string]*sync.Mutex)}
+
+// getTusSessionLock returns a lock for the given upload ID
+func getTusSessionLock(uploadID string) *sync.Mutex {
+	tusSessionLocks.RLock()
+	lock, exists := tusSessionLocks.locks[uploadID]
+	tusSessionLocks.RUnlock()
+	if exists {
+		return lock
+	}
+
+	tusSessionLocks.Lock()
+	defer tusSessionLocks.Unlock()
+	// Double-check after acquiring write lock
+	if lock, exists = tusSessionLocks.locks[uploadID]; exists {
+		return lock
+	}
+	lock = &sync.Mutex{}
+	tusSessionLocks.locks[uploadID] = lock
+	return lock
+}
+
+// removeTusSessionLock removes the lock for the given upload ID
+func removeTusSessionLock(uploadID string) {
+	tusSessionLocks.Lock()
+	defer tusSessionLocks.Unlock()
+	delete(tusSessionLocks.locks, uploadID)
+}
+
 const (
 	TusVersion       = "1.0.0"
 	TusMaxSize       = int64(5 * 1024 * 1024 * 1024) // 5GB default max size
@@ -145,6 +179,11 @@ func (fs *FilerServer) getTusSession(ctx context.Context, uploadID string) (*Tus
 
 // updateTusSessionOffset updates the session offset after a successful chunk upload
 func (fs *FilerServer) updateTusSessionOffset(ctx context.Context, uploadID string, newOffset int64, chunk *TusChunkInfo) error {
+	// Lock the session to prevent concurrent modifications
+	lock := getTusSessionLock(uploadID)
+	lock.Lock()
+	defer lock.Unlock()
+
 	session, err := fs.getTusSession(ctx, uploadID)
 	if err != nil {
 		return err
@@ -160,6 +199,9 @@ func (fs *FilerServer) updateTusSessionOffset(ctx context.Context, uploadID stri
 
 // deleteTusSession removes a TUS upload session and all its data
 func (fs *FilerServer) deleteTusSession(ctx context.Context, uploadID string) error {
+	// Clean up the session lock
+	defer removeTusSessionLock(uploadID)
+
 	session, err := fs.getTusSession(ctx, uploadID)
 	if err != nil {
 		// Session might already be deleted or never existed