avoid race conditions access to growRequestCount (#3537)

https://github.com/seaweedfs/seaweedfs/issues/3511

weed/topology/volume_layout.go

@@ -6,6 +6,7 @@ import (
 	"github.com/seaweedfs/seaweedfs/weed/storage/types"
 	"math/rand"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/seaweedfs/seaweedfs/weed/glog"
@@ -114,7 +115,7 @@ type VolumeLayout struct {
 	volumeSizeLimit  uint64
 	replicationAsMin bool
 	accessLock       sync.RWMutex
-	growRequestCount int
+	growRequestCount int32
 	growRequestTime  time.Time
 }
 
@@ -319,18 +320,19 @@ func (vl *VolumeLayout) PickForWrite(count uint64, option *VolumeGrowOption) (*n
 }
 
 func (vl *VolumeLayout) HasGrowRequest() bool {
-	if vl.growRequestCount > 0 && vl.growRequestTime.Add(time.Minute).After(time.Now()) {
+	if atomic.LoadInt32(&vl.growRequestCount) > 0 &&
+		vl.growRequestTime.Add(time.Minute).After(time.Now()) {
 		return true
 	}
 	return false
 }
 func (vl *VolumeLayout) AddGrowRequest() {
 	vl.growRequestTime = time.Now()
-	vl.growRequestCount++
+	atomic.AddInt32(&vl.growRequestCount, 1)
 }
 func (vl *VolumeLayout) DoneGrowRequest() {
 	vl.growRequestTime = time.Unix(0, 0)
-	vl.growRequestCount = 0
+	atomic.StoreInt32(&vl.growRequestCount, 0)
 }
 
 func (vl *VolumeLayout) ShouldGrowVolumes(option *VolumeGrowOption) bool {