Add 'bytes available' to fs info.

The current capacity and usage numbers are insufficient to figure out
actual bytes available for a non-root user for the fs. Available is the
value used by df and the one we need to track to detect low diskspace
condition.

container/raw/handler.go

@@ -264,6 +264,7 @@ func (self *rawContainerHandler) getFsStats(stats *info.ContainerStats) error {
 					Device:          fs.Device,
 					Limit:           fs.Capacity,
 					Usage:           fs.Capacity - fs.Free,
+					Available:       fs.Available,
 					ReadsCompleted:  fs.DiskStats.ReadsCompleted,
 					ReadsMerged:     fs.DiskStats.ReadsMerged,
 					SectorsRead:     fs.DiskStats.SectorsRead,

fs/fs.go

@@ -20,6 +20,7 @@ package fs
 /*
  extern int getBytesFree(const char *path, unsigned long long *bytes);
  extern int getBytesTotal(const char *path, unsigned long long *bytes);
+ extern int getBytesAvail(const char *path, unsigned long long *bytes);
 */
 import "C"
 
@@ -176,7 +177,7 @@ func (self *RealFsInfo) GetFsInfoForPath(mountSet map[string]struct{}) ([]Fs, er
 		_, hasMount := mountSet[partition.mountpoint]
 		_, hasDevice := deviceSet[device]
 		if mountSet == nil || (hasMount && !hasDevice) {
-			total, free, err := getVfsStats(partition.mountpoint)
+			total, free, avail, err := getVfsStats(partition.mountpoint)
 			if err != nil {
 				glog.Errorf("Statvfs failed. Error: %v", err)
 			} else {
@@ -186,7 +187,7 @@ func (self *RealFsInfo) GetFsInfoForPath(mountSet map[string]struct{}) ([]Fs, er
 					Major:  uint(partition.major),
 					Minor:  uint(partition.minor),
 				}
-				fs := Fs{deviceInfo, total, free, diskStatsMap[device]}
+				fs := Fs{deviceInfo, total, free, avail, diskStatsMap[device]}
 				filesystems = append(filesystems, fs)
 			}
 		}
@@ -287,18 +288,22 @@ func (self *RealFsInfo) GetDirUsage(dir string) (uint64, error) {
 	return usageInKb * 1024, nil
 }
 
-func getVfsStats(path string) (total uint64, free uint64, err error) {
+func getVfsStats(path string) (total uint64, free uint64, avail uint64, err error) {
 	_p0, err := syscall.BytePtrFromString(path)
 	if err != nil {
-		return 0, 0, err
+		return 0, 0, 0, err
 	}
 	res, err := C.getBytesFree((*C.char)(unsafe.Pointer(_p0)), (*_Ctype_ulonglong)(unsafe.Pointer(&free)))
 	if res != 0 {
-		return 0, 0, err
+		return 0, 0, 0, err
 	}
 	res, err = C.getBytesTotal((*C.char)(unsafe.Pointer(_p0)), (*_Ctype_ulonglong)(unsafe.Pointer(&total)))
 	if res != 0 {
-		return 0, 0, err
+		return 0, 0, 0, err
 	}
-	return total, free, nil
+	res, err = C.getBytesAvail((*C.char)(unsafe.Pointer(_p0)), (*_Ctype_ulonglong)(unsafe.Pointer(&avail)))
+	if res != 0 {
+		return 0, 0, 0, err
+	}
+	return total, free, avail, nil
 }

fs/statvfs.c

@@ -21,3 +21,14 @@ int getBytesTotal(const char *path, unsigned long long *bytes) {
 	*bytes = buf.f_frsize * buf.f_blocks;
 	return 0;
 }
+
+// Bytes available to non-root.
+int getBytesAvail(const char *path, unsigned long long *bytes) {
+	struct statvfs buf;
+	int res;
+	if ((res = statvfs(path, &buf)) && res != 0) {
+		return -1;
+	}
+	*bytes = buf.f_frsize * buf.f_bavail;
+	return 0;
+}

fs/types.go

@@ -24,6 +24,7 @@ type Fs struct {
 	DeviceInfo
 	Capacity  uint64
 	Free      uint64
+	Available uint64
 	DiskStats DiskStats
 }
 

info/v1/container.go

@@ -341,6 +341,9 @@ type FsStats struct {
 	// Number of bytes that is consumed by the container on this filesystem.
 	Usage uint64 `json:"usage"`
 
+	// Number of bytes available for non-root user.
+	Available uint64 `json:"available"`
+
 	// Number of reads completed
 	// This is the total number of reads completed successfully.
 	ReadsCompleted uint64 `json:"reads_completed"`