lib/fs: Add total disk space retrieval (#9523)

Extends the disk space monitoring functionality by adding support for
retrieving total disk capacity in addition to free space.

Related: https://github.com/VictoriaMetrics/VictoriaLogs/issues/513

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

lib/fs/fs.go

@@ -286,31 +286,56 @@ const FlockFilename = "flock.lock"
 // MustGetFreeSpace returns free space for the given directory path.
 func MustGetFreeSpace(path string) uint64 {
 	// Try obtaining cached value at first.
-	freeSpaceMapLock.Lock()
-	defer freeSpaceMapLock.Unlock()
+	diskSpaceMapLock.Lock()
+	defer diskSpaceMapLock.Unlock()
 
-	e, ok := freeSpaceMap[path]
+	e, ok := diskSpaceMap[path]
 	if ok && fasttime.UnixTimestamp()-e.updateTime < 2 {
 		// Fast path - the entry is fresh.
-		return e.freeSpace
+		return e.free
 	}
 
 	// Slow path.
 	// Determine the amount of free space at path.
-	e.freeSpace = mustGetFreeSpace(path)
+	e = updateDiskSpaceLocked(path)
+	return e.free
+}
+
+// MustGetTotalSpace returns the total disk space for the given directory path.
+func MustGetTotalSpace(path string) uint64 {
+	// Try obtaining cached value at first.
+	defer diskSpaceMapLock.Unlock()
+
+	e, ok := diskSpaceMap[path]
+	if ok && fasttime.UnixTimestamp()-e.updateTime < 2 {
+		// Fast path - the entry is fresh.
+		return e.total
+	}
+
+	// Slow path.
+	// Determine the amount of total space at path.
+	e = updateDiskSpaceLocked(path)
+	return e.total
+}
+
+func updateDiskSpaceLocked(path string) diskSpaceEntry {
+	var e diskSpaceEntry
+	e.total, e.free = mustGetDiskSpace(path)
 	e.updateTime = fasttime.UnixTimestamp()
-	freeSpaceMap[path] = e
-	return e.freeSpace
+	diskSpaceMap[path] = e
+
+	return e
 }
 
 var (
-	freeSpaceMap     = make(map[string]freeSpaceEntry)
-	freeSpaceMapLock sync.Mutex
+	diskSpaceMap     = make(map[string]diskSpaceEntry)
+	diskSpaceMapLock sync.Mutex
 )
 
-type freeSpaceEntry struct {
+type diskSpaceEntry struct {
 	updateTime uint64
-	freeSpace  uint64
+	free       uint64
+	total      uint64
 }
 
 // IsDirOrSymlink returns true if de is directory or symlink.

lib/fs/fs_netbsd.go

@@ -10,6 +10,11 @@ func freeSpace(stat statfs_t) uint64 {
 	return uint64(stat.Bavail) * uint64(stat.Bsize)
 }
 
+// totalSpace returns the total capacity of the filesystem in bytes.
+func totalSpace(stat statfs_t) uint64 {
+	return uint64(stat.Blocks) * uint64(stat.Bsize)
+}
+
 func statfs(path string, buf *statfs_t) (err error) {
 	return unix.Statvfs(path, buf)
 }

lib/fs/fs_nix.go

@@ -12,6 +12,11 @@ func freeSpace(stat statfs_t) uint64 {
 	return uint64(stat.Bavail) * uint64(stat.Bsize)
 }
 
+// totalSpace returns the total capacity of the filesystem described by stat in bytes.
+func totalSpace(stat statfs_t) uint64 {
+	return uint64(stat.Blocks) * uint64(stat.Bsize)
+}
+
 func statfs(path string, stat *statfs_t) (err error) {
 	return unix.Statfs(path, stat)
 }

lib/fs/fs_openbsd.go

@@ -10,6 +10,11 @@ func freeSpace(stat statfs_t) uint64 {
 	return uint64(stat.F_bavail) * uint64(stat.F_bsize)
 }
 
+// totalSpace returns the total capacity of the filesystem in bytes.
+func totalSpace(stat statfs_t) uint64 {
+	return uint64(stat.F_blocks) * uint64(stat.F_bsize)
+}
+
 func statfs(path string, stat *statfs_t) (err error) {
 	return unix.Statfs(path, stat)
 }

lib/fs/fs_solaris.go

@@ -48,12 +48,19 @@ func createFlockFile(flockFile string) (*os.File, error) {
 	return flockF, nil
 }
 
-func mustGetFreeSpace(path string) uint64 {
+func mustGetDiskSpace(path string) (total, free uint64) {
 	var stat unix.Statvfs_t
 	if err := unix.Statvfs(path, &stat); err != nil {
 		logger.Panicf("FATAL: cannot determine free disk space on %q: %s", path, err)
 	}
-	return freeSpace(stat)
+	total = totalSpace(stat)
+	free = freeSpace(stat)
+	return
+}
+
+// totalSpace returns the total capacity of the filesystem in bytes.
+func totalSpace(stat unix.Statvfs_t) uint64 {
+	return uint64(stat.Blocks) * uint64(stat.Bsize)
 }
 
 func freeSpace(stat unix.Statvfs_t) uint64 {

lib/fs/fs_unix.go

@@ -43,10 +43,13 @@ func createFlockFile(flockFile string) (*os.File, error) {
 	return flockF, nil
 }
 
-func mustGetFreeSpace(path string) uint64 {
+func mustGetDiskSpace(path string) (total, free uint64) {
 	var stat statfs_t
 	if err := statfs(path, &stat); err != nil {
 		logger.Panicf("FATAL: cannot determine free disk space on %q: %s", path, err)
 	}
-	return freeSpace(stat)
+
+	total = totalSpace(stat)
+	free = freeSpace(stat)
+	return
 }

lib/fs/fs_windows.go

@@ -102,14 +102,13 @@ func mUnmap(data []byte) error {
 	return os.NewSyscallError("CloseHandle", errno)
 }
 
-func mustGetFreeSpace(path string) uint64 {
-	var freeBytes uint64
+func mustGetDiskSpace(path string) (total, free uint64) {
 	// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getdiskfreespaceexw
-	err := windows.GetDiskFreeSpaceEx(windows.StringToUTF16Ptr(path), &freeBytes, nil, nil)
+	err := windows.GetDiskFreeSpaceEx(windows.StringToUTF16Ptr(path), &free, &total, nil)
 	if err != nil {
 		logger.Panicf("FATAL: cannot get free space for %q : %s", path, err)
 	}
-	return freeBytes
+	return total, free
 }
 
 // stub