disable disk-usage when export is root mount path (#6091)

disk usage crawling is not needed when a tenant
is not sharing the same disk for multiple other
tenants. This PR adds an optimization when we
see a setup uses entire disk, we simply rely on
statvfs() to give us total usage.

This PR also additionally adds low priority
scheduling for usage check routine, such that
other go-routines blocked will be automatically
unblocked and prioritized before usage.

cmd/fs-v1.go

@@ -34,6 +34,7 @@ import (
 	"github.com/minio/minio/pkg/lock"
 	"github.com/minio/minio/pkg/madmin"
 	"github.com/minio/minio/pkg/mimedb"
+	"github.com/minio/minio/pkg/mountinfo"
 	"github.com/minio/minio/pkg/policy"
 )
 
@@ -64,6 +65,8 @@ type FSObjects struct {
 	// ListObjects pool management.
 	listPool *treeWalkPool
 
+	diskMount bool
+
 	appendFileMap   map[string]*fsAppendFile
 	appendFileMapMu sync.Mutex
 
@@ -138,6 +141,7 @@ func NewFSObjectLayer(fsPath string) (ObjectLayer, error) {
 		nsMutex:       newNSLock(false),
 		listPool:      newTreeWalkPool(globalLookupTimeout),
 		appendFileMap: make(map[string]*fsAppendFile),
+		diskMount:     mountinfo.IsLikelyMountPoint(fsPath),
 	}
 
 	// Once the filesystem has initialized hold the read lock for
@@ -156,7 +160,10 @@ func NewFSObjectLayer(fsPath string) (ObjectLayer, error) {
 		return nil, uiErrUnableToReadFromBackend(err).Msg("Unable to initialize policy system")
 	}
 
-	go fs.diskUsage(globalServiceDoneCh)
+	if !fs.diskMount {
+		go fs.diskUsage(globalServiceDoneCh)
+	}
+
 	go fs.cleanupStaleMultipartUploads(ctx, globalMultipartCleanupInterval, globalMultipartExpiry, globalServiceDoneCh)
 
 	// Return successfully initialized object layer.
@@ -177,17 +184,29 @@ func (fs *FSObjects) diskUsage(doneCh chan struct{}) {
 	defer ticker.Stop()
 
 	usageFn := func(ctx context.Context, entry string) error {
-		var fi os.FileInfo
-		var err error
-		if hasSuffix(entry, slashSeparator) {
-			fi, err = fsStatDir(ctx, entry)
-		} else {
-			fi, err = fsStatFile(ctx, entry)
+		if globalHTTPServer != nil {
+			// Any requests in progress, delay the usage.
+			for globalHTTPServer.GetRequestCount() > 0 {
+				time.Sleep(1 * time.Second)
+			}
 		}
-		if err != nil {
-			return err
+
+		select {
+		case <-doneCh:
+			return errWalkAbort
+		default:
+			var fi os.FileInfo
+			var err error
+			if hasSuffix(entry, slashSeparator) {
+				fi, err = fsStatDir(ctx, entry)
+			} else {
+				fi, err = fsStatFile(ctx, entry)
+			}
+			if err != nil {
+				return err
+			}
+			atomic.AddUint64(&fs.totalUsed, uint64(fi.Size()))
 		}
-		atomic.AddUint64(&fs.totalUsed, uint64(fi.Size()))
 		return nil
 	}
 
@@ -216,6 +235,13 @@ func (fs *FSObjects) diskUsage(doneCh chan struct{}) {
 
 			var usage uint64
 			usageFn = func(ctx context.Context, entry string) error {
+				if globalHTTPServer != nil {
+					// Any requests in progress, delay the usage.
+					for globalHTTPServer.GetRequestCount() > 0 {
+						time.Sleep(1 * time.Second)
+					}
+				}
+
 				var fi os.FileInfo
 				var err error
 				if hasSuffix(entry, slashSeparator) {
@@ -243,8 +269,16 @@ func (fs *FSObjects) diskUsage(doneCh chan struct{}) {
 
 // StorageInfo - returns underlying storage statistics.
 func (fs *FSObjects) StorageInfo(ctx context.Context) StorageInfo {
+	di, err := getDiskInfo(fs.fsPath)
+	if err != nil {
+		return StorageInfo{}
+	}
+	used := di.Total - di.Free
+	if !fs.diskMount {
+		used = atomic.LoadUint64(&fs.totalUsed)
+	}
 	storageInfo := StorageInfo{
-		Used: atomic.LoadUint64(&fs.totalUsed),
+		Used: used,
 	}
 	storageInfo.Backend.Type = FS
 	return storageInfo

cmd/http/server.go

@@ -59,7 +59,12 @@ type Server struct {
 	listenerMutex          *sync.Mutex   // to guard 'listener' field.
 	listener               *httpListener // HTTP listener for all 'Addrs' field.
 	inShutdown             uint32        // indicates whether the server is in shutdown or not
-	requestCount           int32         // counter holds no. of request in process.
+	requestCount           int32         // counter holds no. of request in progress.
+}
+
+// GetRequestCount - returns number of request in progress.
+func (srv *Server) GetRequestCount() int32 {
+	return atomic.LoadInt32(&srv.requestCount)
 }
 
 // Start - start HTTP server

cmd/posix.go

@@ -34,6 +34,7 @@ import (
 	humanize "github.com/dustin/go-humanize"
 	"github.com/minio/minio/cmd/logger"
 	"github.com/minio/minio/pkg/disk"
+	"github.com/minio/minio/pkg/mountinfo"
 )
 
 const (
@@ -69,6 +70,8 @@ type posix struct {
 	pool      sync.Pool
 	connected bool
 
+	diskMount bool // indicates if the path is an actual mount.
+
 	// Disk usage metrics
 	stopUsageCh chan struct{}
 }
@@ -183,9 +186,12 @@ func newPosix(path string) (*posix, error) {
 			},
 		},
 		stopUsageCh: make(chan struct{}),
+		diskMount:   mountinfo.IsLikelyMountPoint(path),
 	}
 
-	go p.diskUsage(globalServiceDoneCh)
+	if !p.diskMount {
+		go p.diskUsage(globalServiceDoneCh)
+	}
 
 	// Success.
 	return p, nil
@@ -293,10 +299,14 @@ func (s *posix) DiskInfo() (info DiskInfo, err error) {
 	if err != nil {
 		return info, err
 	}
+	used := di.Total - di.Free
+	if !s.diskMount {
+		used = atomic.LoadUint64(&s.totalUsed)
+	}
 	return DiskInfo{
 		Total: di.Total,
 		Free:  di.Free,
-		Used:  atomic.LoadUint64(&s.totalUsed),
+		Used:  used,
 	}, nil
 
 }
@@ -336,7 +346,16 @@ func (s *posix) diskUsage(doneCh chan struct{}) {
 	defer ticker.Stop()
 
 	usageFn := func(ctx context.Context, entry string) error {
+		if globalHTTPServer != nil {
+			// Any requests in progress, delay the usage.
+			for globalHTTPServer.GetRequestCount() > 0 {
+				time.Sleep(1 * time.Second)
+			}
+		}
+
 		select {
+		case <-doneCh:
+			return errWalkAbort
 		case <-s.stopUsageCh:
 			return errWalkAbort
 		default:
@@ -377,6 +396,13 @@ func (s *posix) diskUsage(doneCh chan struct{}) {
 
 			var usage uint64
 			usageFn = func(ctx context.Context, entry string) error {
+				if globalHTTPServer != nil {
+					// Any requests in progress, delay the usage.
+					for globalHTTPServer.GetRequestCount() > 0 {
+						time.Sleep(1 * time.Second)
+					}
+				}
+
 				select {
 				case <-s.stopUsageCh:
 					return errWalkAbort

pkg/mountinfo/mountinfo_linux.go

@@ -1,7 +1,7 @@
 // +build linux
 
 /*
- * Minio Cloud Storage, (C) 2017 Minio, Inc.
+ * Minio Cloud Storage, (C) 2017, 2018 Minio, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,6 +26,7 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"syscall"
 )
 
 const (
@@ -35,6 +36,27 @@ const (
 	procMountsPath = "/proc/mounts"
 )
 
+// IsLikelyMountPoint determines if a directory is a mountpoint.
+// It is fast but not necessarily ALWAYS correct. If the path is in fact
+// a bind mount from one part of a mount to another it will not be detected.
+// mkdir /tmp/a /tmp/b; mount --bin /tmp/a /tmp/b; IsLikelyMountPoint("/tmp/b")
+// will return false. When in fact /tmp/b is a mount point. If this situation
+// if of interest to you, don't use this function...
+func IsLikelyMountPoint(file string) bool {
+	stat, err := os.Stat(file)
+	if err != nil {
+		return false
+	}
+
+	rootStat, err := os.Lstat(filepath.Dir(strings.TrimSuffix(file, "/")))
+	if err != nil {
+		return false
+	}
+
+	// If the directory has a different device as parent, then it is a mountpoint.
+	return stat.Sys().(*syscall.Stat_t).Dev != rootStat.Sys().(*syscall.Stat_t).Dev
+}
+
 // CheckCrossDevice - check if any list of paths has any sub-mounts at /proc/mounts.
 func CheckCrossDevice(absPaths []string) error {
 	return checkCrossDevice(absPaths, procMountsPath)

pkg/mountinfo/mountinfo_others.go

@@ -1,7 +1,7 @@
-// +build !linux
+// +build !linux,!windows
 
 /*
- * Minio Cloud Storage, (C) 2017 Minio, Inc.
+ * Minio Cloud Storage, (C) 2017, 2018 Minio, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,3 +23,8 @@ package mountinfo
 func CheckCrossDevice(paths []string) error {
 	return nil
 }
+
+// IsLikelyMountPoint determines if a directory is a mountpoint.
+func IsLikelyMountPoint(file string) bool {
+	return false
+}

pkg/mountinfo/mountinfo_windows.go

@@ -0,0 +1,59 @@
+// +build windows
+
+/*
+ * Minio Cloud Storage, (C) 2018 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package mountinfo
+
+import (
+	"os"
+)
+
+// CheckCrossDevice - check if any input path has multiple sub-mounts.
+// this is a dummy function and returns nil for now.
+func CheckCrossDevice(paths []string) error {
+	return nil
+}
+
+// fileExists checks if specified file exists.
+func fileExists(filename string) (bool, error) {
+	if _, err := os.Stat(filename); os.IsNotExist(err) {
+		return false, nil
+	} else if err != nil {
+		return false, err
+	}
+	return true, nil
+}
+
+// IsLikelyMountPoint determines if a directory is a mountpoint.
+func IsLikelyMountPoint(file string) bool {
+	stat, err := os.Lstat(file)
+	if err != nil {
+		return false
+	}
+
+	// If current file is a symlink, then it is a mountpoint.
+	if stat.Mode()&os.ModeSymlink != 0 {
+		target, err := os.Readlink(file)
+		if err != nil {
+			return false
+		}
+		exists, _ := fileExists(target)
+		return exists
+	}
+
+	return false
+}