Prevent overflow.

vfs/memdb/memdb.go

@@ -78,19 +78,15 @@ type memDB struct {
 
 	// +checklocks:dataMtx
 	data []*[sectorSize]byte
-
 	// +checklocks:dataMtx
 	size int64
 
-	// +checklocks:lockMtx
-	shared int32
-	// +checklocks:lockMtx
-	reserved bool
-	// +checklocks:lockMtx
-	pending bool
-
 	// +checklocks:memoryMtx
-	refs int
+	refs int32
+
+	shared   int32 // +checklocks:lockMtx
+	pending  bool  // +checklocks:lockMtx
+	reserved bool  // +checklocks:lockMtx
 
 	lockMtx sync.Mutex
 	dataMtx sync.RWMutex
@@ -253,12 +249,12 @@ func (m *memFile) Unlock(lock vfs.LockLevel) error {
 	m.lockMtx.Lock()
 	defer m.lockMtx.Unlock()
 
-	if m.pending && m.lock >= vfs.LOCK_PENDING {
-		m.pending = false
-	}
-	if m.reserved && m.lock >= vfs.LOCK_RESERVED {
+	if m.lock >= vfs.LOCK_RESERVED {
 		m.reserved = false
 	}
+	if m.lock >= vfs.LOCK_PENDING {
+		m.pending = false
+	}
 	if lock < vfs.LOCK_SHARED {
 		m.shared--
 	}

vfs/shm.go

@@ -55,7 +55,7 @@ type vfsShm struct {
 	regions  []*util.MappedRegion
 	readOnly bool
 	blocking bool
-	sync.Mutex
+	barrier  sync.Mutex
 }
 
 func (s *vfsShm) shmOpen() _ErrorCode {
@@ -202,9 +202,9 @@ func (s *vfsShm) shmUnmap(delete bool) {
 }
 
 func (s *vfsShm) shmBarrier() {
-	s.Lock()
+	s.barrier.Lock()
 	//lint:ignore SA2001 memory barrier.
-	s.Unlock()
+	s.barrier.Unlock()
 }
 
 func (s *vfsShm) shmEnableBlocking(block bool) {

vfs/shm_bsd.go

@@ -224,7 +224,7 @@ func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
 			if s.lock[i] {
 				panic(util.AssertErr())
 			}
-			if s.vfsShmFile.lock[i] < 0 {
+			if s.vfsShmFile.lock[i]+1 <= 0 {
 				return _BUSY
 			}
 		}