posix: checkDiskFree() also checks free inodes. (#2086)

Previously checkDiskFree() checks for free available space.  This
patch enables checkDiskFree() also checks for free inodes in linux and
free clusters in windows.

Fixes #2075

pkg/disk/disk.go

@@ -23,5 +23,7 @@ package disk
 type Info struct {
 	Total  int64
 	Free   int64
+	Files  int64
+	Ffree  int64
 	FSType string
 }

pkg/disk/disk_test.go

@@ -41,5 +41,7 @@ func (s *MySuite) TestFree(c *C) {
 	c.Assert(err, IsNil)
 	c.Assert(di.Total, Not(Equals), 0)
 	c.Assert(di.Free, Not(Equals), 0)
+	c.Assert(di.Files, Not(Equals), 0)
+	c.Assert(di.Ffree, Not(Equals), 0)
 	c.Assert(di.FSType, Not(Equals), "UNKNOWN")
 }

pkg/disk/stat_nix.go

@@ -32,6 +32,8 @@ func GetInfo(path string) (info Info, err error) {
 	info = Info{}
 	info.Total = int64(s.Bsize) * int64(s.Blocks)
 	info.Free = int64(s.Bsize) * int64(s.Bfree)
+	info.Files = int64(s.Files)
+	info.Ffree = int64(s.Ffree)
 	info.FSType, err = getFSType(path)
 	if err != nil {
 		return Info{}, err

pkg/disk/stat_windows.go

@@ -60,5 +60,33 @@ func GetInfo(path string) (info Info, err error) {
 	info.Total = int64(lpTotalNumberOfBytes)
 	info.Free = int64(lpFreeBytesAvailable)
 	info.FSType = getFSType(path)
+
+	// https://msdn.microsoft.com/en-us/library/windows/desktop/aa364935(v=vs.85).aspx
+	// Retrieves information about the specified disk, including the amount of free space on the disk.
+	GetDiskFreeSpace := dll.MustFindProc("GetDiskFreeSpaceW")
+
+	// Return values of GetDiskFreeSpace()
+	lpSectorsPerCluster := uint32(0)
+	lpBytesPerSector := uint32(0)
+	lpNumberOfFreeClusters := uint32(0)
+	lpTotalNumberOfClusters := uint32(0)
+
+	// Extract values safely
+	// BOOL WINAPI GetDiskFreeSpace(
+	//   _In_  LPCTSTR lpRootPathName,
+	//   _Out_ LPDWORD lpSectorsPerCluster,
+	//   _Out_ LPDWORD lpBytesPerSector,
+	//   _Out_ LPDWORD lpNumberOfFreeClusters,
+	//   _Out_ LPDWORD lpTotalNumberOfClusters
+	// );
+	_, _, _ = GetDiskFreeSpace.Call(uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(path))),
+		uintptr(unsafe.Pointer(&lpSectorsPerCluster)),
+		uintptr(unsafe.Pointer(&lpBytesPerSector)),
+		uintptr(unsafe.Pointer(&lpNumberOfFreeClusters)),
+		uintptr(unsafe.Pointer(&lpTotalNumberOfClusters)))
+
+	info.Files = int64(lpTotalNumberOfClusters)
+	info.Ffree = int64(lpNumberOfFreeClusters)
+
 	return info, nil
 }

posix.go

@@ -133,7 +133,7 @@ func getDiskInfo(diskPath string) (di disk.Info, err error) {
 	return di, err
 }
 
-// checkDiskFree verifies if disk path has sufficient minimum free disk space.
+// checkDiskFree verifies if disk path has sufficient minimum free disk space and files.
 func checkDiskFree(diskPath string, minFreeDisk int64) (err error) {
 	di, err := getDiskInfo(diskPath)
 	if err != nil {
@@ -143,7 +143,8 @@ func checkDiskFree(diskPath string, minFreeDisk int64) (err error) {
 	// Remove 5% from total space for cumulative disk
 	// space used for journalling, inodes etc.
 	availableDiskSpace := (float64(di.Free) / (float64(di.Total) - (0.05 * float64(di.Total)))) * 100
-	if int64(availableDiskSpace) <= minFreeDisk {
+	availableFiles := (float64(di.Ffree) / (float64(di.Files) - (0.05 * float64(di.Files)))) * 100
+	if int64(availableDiskSpace) <= minFreeDisk || int64(availableFiles) <= minFreeDisk {
 		return errDiskFull
 	}