XL: Introduce new API StorageInfo. (#1770)

This is necessary for calculating the total storage
capacity from object layer. This value is also needed for
browser UI.

Buckets used to carry this information, this patch
deprecates this feature.

xl-v1.go

@@ -20,8 +20,11 @@ import (
 	"errors"
 	"fmt"
 	"path/filepath"
+	"sort"
 	"strings"
 	"sync"
+
+	"github.com/minio/minio/pkg/disk"
 )
 
 const (
@@ -33,6 +36,7 @@ const (
 // xlObjects - Implements fs object layer.
 type xlObjects struct {
 	storageDisks       []StorageAPI
+	physicalDisks      []string
 	dataBlocks         int
 	parityBlocks       int
 	readQuorum         int
@@ -147,6 +151,7 @@ func newXLObjects(disks []string) (ObjectLayer, error) {
 
 	xl := xlObjects{
 		storageDisks:       newPosixDisks,
+		physicalDisks:      disks,
 		dataBlocks:         dataBlocks,
 		parityBlocks:       parityBlocks,
 		listObjectMap:      make(map[listParams][]*treeWalker),
@@ -168,3 +173,36 @@ func newXLObjects(disks []string) (ObjectLayer, error) {
 	// Return successfully initialized object layer.
 	return xl, nil
 }
+
+// byDiskTotal is a collection satisfying sort.Interface.
+type byDiskTotal []disk.Info
+
+func (d byDiskTotal) Len() int      { return len(d) }
+func (d byDiskTotal) Swap(i, j int) { d[i], d[j] = d[j], d[i] }
+func (d byDiskTotal) Less(i, j int) bool {
+	return d[i].Total < d[j].Total
+}
+
+// StorageInfo - returns underlying storage statistics.
+func (xl xlObjects) StorageInfo() StorageInfo {
+	var disksInfo []disk.Info
+	for _, diskPath := range xl.physicalDisks {
+		info, err := disk.GetInfo(diskPath)
+		if err != nil {
+			errorIf(err, "Unable to fetch disk info for "+diskPath)
+			continue
+		}
+		disksInfo = append(disksInfo, info)
+	}
+
+	// Sort so that the first element is the smallest.
+	sort.Sort(byDiskTotal(disksInfo))
+
+	// Return calculated storage info, choose the lowest Total and
+	// Free as the total aggregated values. Total capacity is always
+	// the multiple of smallest disk among the disk list.
+	return StorageInfo{
+		Total: disksInfo[0].Total * int64(len(xl.storageDisks)),
+		Free:  disksInfo[0].Free * int64(len(xl.storageDisks)),
+	}
+}