all: follow-up after 34634ec357

- Use windows.FlushFileBuffers() instead of windows.Fsync() at streamTracker.adviseDontNeed()
  for consistency with implementations for other architectures.
- Use filepath.Base() instead of filepath.Split(), since the dir part isn't used.
  This simplifies the code a bit.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/70

lib/filestream/filestream_windows.go

@@ -8,7 +8,7 @@ import (
 
 func (st *streamTracker) adviseDontNeed(n int, fdatasync bool) error {
 	if fdatasync && st.fd > 0 {
-		if err := windows.Fsync(windows.Handle(st.fd)); err != nil {
+		if err := windows.FlushFileBuffers(windows.Handle(st.fd)); err != nil {
 			return fmt.Errorf("windows.Fsync error: %w", err)
 		}
 	}

lib/fs/fs_windows.go

@@ -58,8 +58,8 @@ func createFlockFile(flockFile string) (*os.File, error) {
 }
 
 var (
-	fileMappingMU     sync.Mutex
-	fileMappingByAddr = map[uintptr]windows.Handle{}
+	mmapByAddrLock sync.Mutex
+	mmapByAddr     = map[uintptr]windows.Handle{}
 )
 
 func mmap(fd int, length int) ([]byte, error) {
@@ -77,15 +77,16 @@ func mmap(fd int, length int) ([]byte, error) {
 		windows.CloseHandle(h)
 		return nil, os.NewSyscallError("MapViewOfFile", errno)
 	}
-	fileMappingMU.Lock()
-	fileMappingByAddr[addr] = h
-	fileMappingMU.Unlock()
 	data := make([]byte, 0)
 	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&data))
 	hdr.Data = addr
 	hdr.Len = length
 	hdr.Cap = hdr.Len
 
+	mmapByAddrLock.Lock()
+	mmapByAddr[addr] = h
+	mmapByAddrLock.Unlock()
+
 	return data, nil
 }
 
@@ -94,20 +95,20 @@ func mUnmap(data []byte) error {
 	// In case of write, additional call FlushViewOfFile must be performed.
 	header := (*reflect.SliceHeader)(unsafe.Pointer(&data))
 	addr := header.Data
-	fileMappingMU.Lock()
-	defer fileMappingMU.Unlock()
-	if err := windows.UnmapViewOfFile(addr); err != nil {
-		return err
-	}
 
-	handle, ok := fileMappingByAddr[addr]
+	mmapByAddrLock.Lock()
+	h, ok := mmapByAddr[addr]
 	if !ok {
 		logger.Fatalf("BUG: unmapping for non exist addr: %d", addr)
 	}
-	delete(fileMappingByAddr, addr)
+	delete(mmapByAddr, addr)
+	mmapByAddrLock.Unlock()
 
-	e := windows.CloseHandle(handle)
-	return os.NewSyscallError("CloseHandle", e)
+	if err := windows.UnmapViewOfFile(addr); err != nil {
+		return fmt.Errorf("cannot unmap memory mapped file: %w", err)
+	}
+	errno := windows.CloseHandle(h)
+	return os.NewSyscallError("CloseHandle", errno)
 }
 
 func mustGetFreeSpace(path string) uint64 {
@@ -115,8 +116,7 @@ func mustGetFreeSpace(path string) uint64 {
 	r, _, err := procDisk.Call(uintptr(unsafe.Pointer(windows.StringToUTF16Ptr(path))),
 		uintptr(unsafe.Pointer(&freeBytes)))
 	if r == 0 {
-		logger.Errorf("cannot get free space for path: %q : %s", path, err)
-		return 0
+		logger.Panicf("FATAL: cannot get free space for %q : %s", path, err)
 	}
 	return uint64(freeBytes)
 }

lib/storage/part_header.go

@@ -83,10 +83,7 @@ func (ph *partHeader) ParseFromPath(path string) error {
 	path = filepath.Clean(path)
 
 	// Extract encoded part name.
-	dir, partName := filepath.Split(path)
-	if len(dir) == 0 {
-		return fmt.Errorf("cannot find encoded part name in the path %q", path)
-	}
+	partName := filepath.Base(path)
 
 	// PartName must have the following form:
 	// RowsCount_BlocksCount_MinTimestamp_MaxTimestamp_Garbage

lib/storage/partition.go

@@ -259,11 +259,7 @@ func openPartition(smallPartsPath, bigPartsPath string, s *Storage) (*partition,
 	smallPartsPath = filepath.Clean(smallPartsPath)
 	bigPartsPath = filepath.Clean(bigPartsPath)
 
-	dir, name := filepath.Split(smallPartsPath)
-	if len(dir) == 0 {
-		return nil, fmt.Errorf("cannot find partition name from smallPartsPath %q; must be in the form /path/to/smallparts/YYYY_MM", smallPartsPath)
-	}
-
+	name := filepath.Base(smallPartsPath)
 	if !strings.HasSuffix(bigPartsPath, name) {
 		return nil, fmt.Errorf("patititon name in bigPartsPath %q doesn't match smallPartsPath %q; want %q", bigPartsPath, smallPartsPath, name)
 	}