feat(simple reader): Destroy MRDinstance & remove it from cache when inode is destroyed

internal/fs/inode/file.go

@@ -517,6 +517,9 @@ func (f *FileInode) Destroy() (err error) {
 	} else if f.content != nil {
 		f.content.Destroy()
 	}
+	if f.mrdInstance != nil {
+		f.mrdInstance.Destroy()
+	}
 	return
 }
 

internal/fs/inode/file_test.go

@@ -545,6 +545,25 @@ func (t *FileTest) TestTruncateNegative() {
 	assert.False(t.T(), gcsSynced)
 }
 
+func (t *FileTest) TestDestroy_MrdInstanceDestroyed() {
+	// Manually initialize MRD pool since FileInode.Read doesn't use it directly.
+	mi := t.in.GetMRDInstance()
+	require.NotNil(t.T(), mi)
+	// Perform a read on MrdInstance to trigger pool creation.
+	buf := make([]byte, 1)
+	_, err := mi.Read(t.ctx, buf, 0)
+	require.NoError(t.T(), err)
+	// Verify pool is initialized.
+	assert.Greater(t.T(), int(mi.Size()), 0)
+
+	// Destroy the inode.
+	err = t.in.Destroy()
+
+	require.NoError(t.T(), err)
+	// Verify MRD instance is destroyed (pool closed and set to nil).
+	assert.Equal(t.T(), uint64(0), mi.Size())
+}
+
 func (t *FileTest) TestWriteThenSync() {
 	testcases := []struct {
 		name     string

internal/gcsx/mrd_instance.go

@@ -190,8 +190,8 @@ func (mi *MrdInstance) RecreateMRD() error {
 	return nil
 }
 
-// Destroy closes all MRD instances in the pool and releases associated resources.
-func (mi *MrdInstance) Destroy() {
+// closePool closes all MRD instances in the pool and releases associated resources.
+func (mi *MrdInstance) closePool() {
 	mi.poolMu.Lock()
 	defer mi.poolMu.Unlock()
 	if mi.mrdPool != nil {
@@ -201,6 +201,28 @@ func (mi *MrdInstance) Destroy() {
 	}
 }
 
+// Destroy completely destroys the MrdInstance, cleaning up
+// its resources and ensuring it is removed from the cache. This should be
+// called when the owning inode is destroyed.
+func (mi *MrdInstance) Destroy() {
+	mi.refCountMu.Lock()
+	defer mi.refCountMu.Unlock()
+
+	// If it's in use, this indicates a potential lifecycle mismatch between the
+	// inode and its readers.
+	if mi.refCount > 0 {
+		logger.Warnf("MrdInstance::Destroy called on an instance with refCount %d", mi.refCount)
+	}
+
+	// Remove from cache.
+	if mi.mrdCache != nil {
+		mi.mrdCache.Erase(getKey(mi.inodeId))
+	}
+
+	// Destroy the pool.
+	mi.closePool()
+}
+
 // getKey generates a unique key for the MrdInstance based on its inode ID.
 func getKey(id fuseops.InodeID) string {
 	return strconv.FormatUint(uint64(id), 10)
@@ -223,26 +245,23 @@ func (mi *MrdInstance) IncrementRefCount() {
 	}
 }
 
-// destroyEvictedCacheEntries is a helper function to destroy evicted MrdInstance objects.
-// It handles type assertion and ensures that only truly inactive instances are destroyed.
-// This function should not be called when refCountMu is held.
-func destroyEvictedCacheEntries(evictedValues []lru.ValueType) {
-	for _, instance := range evictedValues {
-		mrdInstance, ok := instance.(*MrdInstance)
-		if !ok {
-			logger.Errorf("destroyEvictedCacheEntries: Invalid value type, expected *MrdInstance, got %T", instance)
-		} else {
-			// Check if the instance was resurrected.
-			mrdInstance.refCountMu.Lock()
-			if mrdInstance.refCount > 0 {
-				mrdInstance.refCountMu.Unlock()
-				continue
-			}
-			// Safe to destroy. Hold refCountMu to prevent concurrent resurrection.
-			mrdInstance.Destroy()
-			mrdInstance.refCountMu.Unlock()
-		}
+// handleEviction handles the cleanup of the MrdInstance when it is evicted from the cache.
+// Race protection: MrdInstance could be reopened (refCount>0) or re-added to cache before eviction.
+func (mi *MrdInstance) handleEviction() {
+	mi.refCountMu.Lock()
+	defer mi.refCountMu.Unlock()
+
+	// Check if mrdInstance was reopened (refCount>0) - must skip eviction.
+	if mi.refCount > 0 {
+		return
+	}
+
+	// Check if mrdInstance was re-added to cache (refCount went 0→1→0 in between eviction and closure.)
+	// Lock order: refCountMu -> cache.mu (consistent with Increment/DecrementRefCount)
+	if mi.mrdCache != nil && mi.mrdCache.LookUpWithoutChangingOrder(getKey(mi.inodeId)) == mi {
+		return
 	}
+	mi.closePool()
 }
 
 // DecrementRefCount decreases the reference count. When the count drops to zero, the
@@ -272,7 +291,7 @@ func (mi *MrdInstance) DecrementRefCount() {
 		logger.Errorf("MrdInstance::DecrementRefCount: Failed to insert MrdInstance for object (%s) into cache, destroying immediately: %v", mi.object.Name, err)
 		// The instance could not be inserted into the cache. Since the refCount is 0,
 		// we must destroy it now to prevent it from being leaked.
-		mi.Destroy()
+		mi.closePool()
 		return
 	}
 	logger.Tracef("MrdInstance::DecrementRefCount: MrdInstance for object (%s) added to cache", mi.object.Name)
@@ -284,7 +303,14 @@ func (mi *MrdInstance) DecrementRefCount() {
 
 	// Evict outside all locks.
 	mi.refCountMu.Unlock()
-	destroyEvictedCacheEntries(evictedValues)
+	for _, instance := range evictedValues {
+		mrdInstance, ok := instance.(*MrdInstance)
+		if !ok {
+			logger.Errorf("MrdInstance::DecrementRefCount: Invalid value type, expected *MrdInstance, got %T", instance)
+		} else {
+			mrdInstance.handleEviction()
+		}
+	}
 	// Reacquire the lock ensuring safe defer's Unlock.
 	mi.refCountMu.Lock()
 }

internal/gcsx/mrd_instance_test.go

@@ -15,14 +15,18 @@
 package gcsx
 
 import (
+	"bytes"
 	"context"
 	"fmt"
+	"os"
 	"strconv"
 	"testing"
 	"time"
 
 	"github.com/googlecloudplatform/gcsfuse/v3/cfg"
 	"github.com/googlecloudplatform/gcsfuse/v3/internal/cache/lru"
+	"github.com/googlecloudplatform/gcsfuse/v3/internal/logger"
+
 	"github.com/googlecloudplatform/gcsfuse/v3/internal/storage"
 	"github.com/googlecloudplatform/gcsfuse/v3/internal/storage/fake"
 	"github.com/googlecloudplatform/gcsfuse/v3/internal/storage/gcs"
@@ -326,38 +330,6 @@ func (t *MrdInstanceTest) TestDecrementRefCount_Eviction() {
 	assert.NotNil(t.T(), t.cache.LookUpWithoutChangingOrder("other2"))
 }
 
-func (t *MrdInstanceTest) TestDestroyEvictedCacheEntries() {
-	// 1. Instance to be destroyed
-	mi1 := NewMrdInstance(t.object, t.bucket, t.cache, 1, t.mrdConfig)
-	fakeMRD1 := fake.NewFakeMultiRangeDownloader(t.object, nil)
-	t.bucket.On("NewMultiRangeDownloader", mock.Anything, mock.Anything).Return(fakeMRD1, nil).Once()
-	buf := make([]byte, 1)
-	_, err := mi1.Read(context.Background(), buf, 0)
-	assert.NoError(t.T(), err)
-	assert.NotNil(t.T(), mi1.mrdPool)
-	// 2. Instance that is resurrected (refCount > 0)
-	mi2 := NewMrdInstance(t.object, t.bucket, t.cache, 2, t.mrdConfig)
-	fakeMRD2 := fake.NewFakeMultiRangeDownloader(t.object, nil)
-	t.bucket.On("NewMultiRangeDownloader", mock.Anything, mock.Anything).Return(fakeMRD2, nil).Once()
-	_, err = mi2.Read(context.Background(), buf, 0)
-	assert.NoError(t.T(), err)
-	assert.NotNil(t.T(), mi2.mrdPool)
-	mi2.refCount = 1
-	// Entries to be evicted
-	evicted := []lru.ValueType{mi1, mi2}
-
-	destroyEvictedCacheEntries(evicted)
-
-	// Verify mi1 is destroyed
-	mi1.poolMu.RLock()
-	assert.Nil(t.T(), mi1.mrdPool)
-	mi1.poolMu.RUnlock()
-	// Verify mi2 is NOT destroyed
-	mi2.poolMu.RLock()
-	assert.NotNil(t.T(), mi2.mrdPool)
-	mi2.poolMu.RUnlock()
-}
-
 func (t *MrdInstanceTest) TestGetKey() {
 	testCases := []struct {
 		inodeID  fuseops.InodeID
@@ -409,3 +381,158 @@ func (t *MrdInstanceTest) TestEnsureMRDPool_Failure() {
 	assert.Nil(t.T(), t.mrdInstance.mrdPool)
 	assert.Contains(t.T(), err.Error(), "init error")
 }
+
+func (t *MrdInstanceTest) TestSize() {
+	assert.Equal(t.T(), uint64(0), t.mrdInstance.Size())
+	fakeMRD := fake.NewFakeMultiRangeDownloader(t.object, nil)
+	t.bucket.On("NewMultiRangeDownloader", mock.Anything, mock.Anything).Return(fakeMRD, nil).Once()
+	buf := make([]byte, 1)
+	_, err := t.mrdInstance.Read(context.Background(), buf, 0)
+	assert.NoError(t.T(), err)
+
+	poolSize := t.mrdInstance.Size()
+
+	// Pool size is 1 based on SetupTest config (PoolSize: 1)
+	assert.Equal(t.T(), uint64(1), poolSize)
+	t.mrdInstance.Destroy()
+	assert.Equal(t.T(), uint64(0), t.mrdInstance.Size())
+}
+
+func (t *MrdInstanceTest) TestDestroy_RemovesFromCache() {
+	// Manually insert into cache
+	key := getKey(t.inodeID)
+	_, err := t.cache.Insert(key, t.mrdInstance)
+	assert.NoError(t.T(), err)
+	assert.NotNil(t.T(), t.cache.LookUpWithoutChangingOrder(key))
+
+	t.mrdInstance.Destroy()
+
+	assert.Nil(t.T(), t.cache.LookUpWithoutChangingOrder(key))
+}
+
+func (t *MrdInstanceTest) TestDestroy_WithRefCount() {
+	t.mrdInstance.refCount = 1
+	// Should log warning but proceed to destroy
+	fakeMRD := fake.NewFakeMultiRangeDownloader(t.object, nil)
+	t.bucket.On("NewMultiRangeDownloader", mock.Anything, mock.Anything).Return(fakeMRD, nil).Once()
+	err := t.mrdInstance.ensureMRDPool()
+	assert.NoError(t.T(), err)
+	assert.NotNil(t.T(), t.mrdInstance.mrdPool)
+	// Capture logs to verify error message
+	var buf bytes.Buffer
+	logger.SetOutput(&buf)
+	defer logger.SetOutput(os.Stdout)
+
+	t.mrdInstance.Destroy()
+
+	assert.Nil(t.T(), t.mrdInstance.mrdPool)
+	assert.Contains(t.T(), buf.String(), "MrdInstance::Destroy called on an instance with refCount")
+}
+
+func (t *MrdInstanceTest) TestDecrementRefCount_Negative() {
+	t.mrdInstance.refCount = 0
+
+	// Should log error and return, not panic. RefCount should remain 0.
+	t.mrdInstance.DecrementRefCount()
+
+	assert.Equal(t.T(), int64(0), t.mrdInstance.refCount)
+}
+
+func (t *MrdInstanceTest) TestDecrementRefCount_CacheInsertFailure() {
+	// Create a cache with capacity 1
+	smallCache := lru.NewCache(1)
+	// Create instance with pool size 2 (so Size() returns 2).
+	config := cfg.MrdConfig{PoolSize: 2}
+	mi := NewMrdInstance(t.object, t.bucket, smallCache, t.inodeID, config)
+	fakeMRD := fake.NewFakeMultiRangeDownloader(t.object, nil)
+	t.bucket.On("NewMultiRangeDownloader", mock.Anything, mock.Anything).Return(fakeMRD, nil)
+	// Initialize pool.
+	err := mi.ensureMRDPool()
+	assert.NoError(t.T(), err)
+	mi.refCount = 1
+	// Capture logs to verify error message
+	var buf bytes.Buffer
+	logger.SetOutput(&buf)
+	defer logger.SetOutput(os.Stdout)
+
+	// This should fail to insert into cache (Size 2 > Cap 1) and trigger Destroy
+	mi.DecrementRefCount()
+
+	assert.Equal(t.T(), int64(0), mi.refCount)
+	mi.poolMu.RLock()
+	assert.Nil(t.T(), mi.mrdPool)
+	mi.poolMu.RUnlock()
+	assert.Contains(t.T(), buf.String(), "Failed to insert MrdInstance")
+}
+
+func (t *MrdInstanceTest) TestClosePool() {
+	fakeMRD := fake.NewFakeMultiRangeDownloader(t.object, nil)
+	t.bucket.On("NewMultiRangeDownloader", mock.Anything, mock.Anything).Return(fakeMRD, nil).Once()
+	err := t.mrdInstance.ensureMRDPool()
+	assert.NoError(t.T(), err)
+	assert.NotNil(t.T(), t.mrdInstance.mrdPool)
+
+	t.mrdInstance.closePool()
+
+	t.mrdInstance.poolMu.RLock()
+	assert.Nil(t.T(), t.mrdInstance.mrdPool)
+	t.mrdInstance.poolMu.RUnlock()
+}
+
+func (t *MrdInstanceTest) TestHandleEviction_Resurrected() {
+	fakeMRD := fake.NewFakeMultiRangeDownloader(t.object, nil)
+	t.bucket.On("NewMultiRangeDownloader", mock.Anything, mock.Anything).Return(fakeMRD, nil).Once()
+	// Initialize pool.
+	err := t.mrdInstance.ensureMRDPool()
+	assert.NoError(t.T(), err)
+	// Simulate resurrection (refCount > 0).
+	t.mrdInstance.refCount = 1
+
+	t.mrdInstance.handleEviction()
+
+	// Pool should still exist because refCount > 0.
+	t.mrdInstance.poolMu.RLock()
+	assert.NotNil(t.T(), t.mrdInstance.mrdPool)
+	t.mrdInstance.poolMu.RUnlock()
+}
+
+func (t *MrdInstanceTest) TestHandleEviction_ReAddedToCache() {
+	fakeMRD := fake.NewFakeMultiRangeDownloader(t.object, nil)
+	t.bucket.On("NewMultiRangeDownloader", mock.Anything, mock.Anything).Return(fakeMRD, nil).Once()
+	// Initialize pool.
+	err := t.mrdInstance.ensureMRDPool()
+	assert.NoError(t.T(), err)
+	// Add to cache to simulate it being re-added concurrently.
+	key := getKey(t.inodeID)
+	_, err = t.cache.Insert(key, t.mrdInstance)
+	assert.NoError(t.T(), err)
+	// refCount is 0, but it is in the cache.
+	t.mrdInstance.refCount = 0
+
+	t.mrdInstance.handleEviction()
+
+	// Pool should still exist because it's in the cache.
+	t.mrdInstance.poolMu.RLock()
+	assert.NotNil(t.T(), t.mrdInstance.mrdPool)
+	t.mrdInstance.poolMu.RUnlock()
+}
+
+func (t *MrdInstanceTest) TestHandleEviction_SafeToClose() {
+	fakeMRD := fake.NewFakeMultiRangeDownloader(t.object, nil)
+	t.bucket.On("NewMultiRangeDownloader", mock.Anything, mock.Anything).Return(fakeMRD, nil).Once()
+	// Initialize pool.
+	err := t.mrdInstance.ensureMRDPool()
+	assert.NoError(t.T(), err)
+	// Ensure not in cache.
+	key := getKey(t.inodeID)
+	t.cache.Erase(key)
+	// refCount is 0.
+	t.mrdInstance.refCount = 0
+
+	t.mrdInstance.handleEviction()
+
+	// Pool should be closed (nil).
+	t.mrdInstance.poolMu.RLock()
+	assert.Nil(t.T(), t.mrdInstance.mrdPool)
+	t.mrdInstance.poolMu.RUnlock()
+}

internal/logger/logger.go

@@ -229,6 +229,13 @@ func Fatal(format string, v ...any) {
 	os.Exit(1)
 }
 
+// SetOutput sets the output destination for the default logger.
+// This is primarily used for testing.
+func SetOutput(w io.Writer) {
+	defaultLogger = slog.New(defaultLoggerFactory.createJsonOrTextHandler(w, programLevel, ""))
+	slog.SetDefault(defaultLogger)
+}
+
 type loggerFactory struct {
 	// If nil, log to stdout or stderr. Otherwise, log to this file.
 	file       *os.File