1 files changed, 55 insertions, 0 deletions
diff --git a/pkg/sentry/fs/dirent_cache_limiter.go b/pkg/sentry/fs/dirent_cache_limiter.go
new file mode 100644
index 000000000..024c7b2d5
--- /dev/null
+++ b/pkg/sentry/fs/dirent_cache_limiter.go
@@ -0,0 +1,55 @@
+// Copyright 2018 Google LLC
+//
+// 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 fs
+
+import (
+	"fmt"
+	"sync"
+)
+
+// DirentCacheLimiter acts as a global limit for all dirent caches in the
+// process.
+//
+// +stateify savable
+type DirentCacheLimiter struct {
+	mu    sync.Mutex `state:"nosave"`
+	max   uint64
+	count uint64 `state:"zerovalue"`
+}
+
+// NewDirentCacheLimiter creates a new DirentCacheLimiter.
+func NewDirentCacheLimiter(max uint64) *DirentCacheLimiter {
+	return &DirentCacheLimiter{max: max}
+}
+
+func (d *DirentCacheLimiter) tryInc() bool {
+	d.mu.Lock()
+	if d.count >= d.max {
+		d.mu.Unlock()
+		return false
+	}
+	d.count++
+	d.mu.Unlock()
+	return true
+}
+
+func (d *DirentCacheLimiter) dec() {
+	d.mu.Lock()
+	if d.count == 0 {
+		panic(fmt.Sprintf("underflowing DirentCacheLimiter count: %+v", d))
+	}
+	d.count--
+	d.mu.Unlock()
+}