pkg/fs: for locks, prefer defer and read-only ops

This commit prefers the use of 'defer' for fs.Unlock (and fs.RUnlock)
because it is more idiomatic Go and reduces repetition in the code,
lending to a cleaner code base.

It also switches a few uses of the lock to read-only locks, which should
improve performance of those functions dramatically in certain contexts.

pkg/fs/fs-bucket-acl.go

@@ -18,8 +18,8 @@ package fs
 
 // IsPrivateBucket - is private bucket
 func (fs Filesystem) IsPrivateBucket(bucket string) bool {
-	fs.rwLock.Lock()
+	fs.rwLock.RLock()
-	defer fs.rwLock.Unlock()
+	defer fs.rwLock.RUnlock()
 	bucketMetadata, ok := fs.buckets.Metadata[bucket]
 	if !ok {
 		return true
@@ -29,8 +29,8 @@ func (fs Filesystem) IsPrivateBucket(bucket string) bool {
 
 // IsPublicBucket - is public bucket
 func (fs Filesystem) IsPublicBucket(bucket string) bool {
-	fs.rwLock.Lock()
+	fs.rwLock.RLock()
-	defer fs.rwLock.Unlock()
+	defer fs.rwLock.RUnlock()
 	bucketMetadata, ok := fs.buckets.Metadata[bucket]
 	if !ok {
 		return true
@@ -40,8 +40,8 @@ func (fs Filesystem) IsPublicBucket(bucket string) bool {
 
 // IsReadOnlyBucket - is read only bucket
 func (fs Filesystem) IsReadOnlyBucket(bucket string) bool {
-	fs.rwLock.Lock()
+	fs.rwLock.RLock()
-	defer fs.rwLock.Unlock()
+	defer fs.rwLock.RUnlock()
 	bucketMetadata, ok := fs.buckets.Metadata[bucket]
 	if !ok {
 		return true

pkg/fs/fs-bucket.go

@@ -58,12 +58,12 @@ func (fs Filesystem) DeleteBucket(bucket string) *probe.Error {
 
 	// Critical region hold write lock.
 	fs.rwLock.Lock()
+	defer fs.rwLock.Unlock()
+
 	delete(fs.buckets.Metadata, bucket)
 	if err := saveBucketsMetadata(*fs.buckets); err != nil {
-		fs.rwLock.Unlock()
 		return err.Trace(bucket)
 	}
-	fs.rwLock.Unlock()
 	return nil
 }
 
@@ -171,12 +171,12 @@ func (fs Filesystem) MakeBucket(bucket, acl string) *probe.Error {
 
 	// Critical region hold a write lock.
 	fs.rwLock.Lock()
+	defer fs.rwLock.Unlock()
+
 	fs.buckets.Metadata[bucket] = bucketMetadata
 	if err := saveBucketsMetadata(*fs.buckets); err != nil {
-		fs.rwLock.Unlock()
 		return err.Trace(bucket)
 	}
-	fs.rwLock.Unlock()
 	return nil
 }
 
@@ -266,11 +266,11 @@ func (fs Filesystem) SetBucketMetadata(bucket string, metadata map[string]string
 
 	// Critical region handle write lock.
 	fs.rwLock.Lock()
+	defer fs.rwLock.Unlock()
+
 	fs.buckets.Metadata[bucket] = bucketMetadata
 	if err := saveBucketsMetadata(*fs.buckets); err != nil {
-		fs.rwLock.Unlock()
 		return err.Trace(bucket)
 	}
-	fs.rwLock.Unlock()
 	return nil
 }

pkg/fs/fs-multipart.go

@@ -276,6 +276,7 @@ func (fs Filesystem) NewMultipartUpload(bucket, object string) (string, *probe.E
 
 	// Critical region requiring write lock.
 	fs.rwLock.Lock()
+	defer fs.rwLock.Unlock()
 	// Initialize multipart session.
 	mpartSession := &MultipartSession{}
 	mpartSession.TotalParts = 0
@@ -288,10 +289,8 @@ func (fs Filesystem) NewMultipartUpload(bucket, object string) (string, *probe.E
 
 	fs.multiparts.ActiveSession[uploadID] = mpartSession
 	if err := saveMultipartsSession(*fs.multiparts); err != nil {
-		fs.rwLock.Unlock()
 		return "", err.Trace(objectPath)
 	}
-	fs.rwLock.Unlock()
 	return uploadID, nil
 }
 
@@ -445,12 +444,12 @@ func (fs Filesystem) CreateObjectPart(bucket, object, uploadID, expectedMD5Sum s
 
 	// Critical region requiring write lock.
 	fs.rwLock.Lock()
+	defer fs.rwLock.Unlock()
+
 	fs.multiparts.ActiveSession[uploadID] = deserializedMultipartSession
 	if err := saveMultipartsSession(*fs.multiparts); err != nil {
-		fs.rwLock.Unlock()
 		return "", err.Trace(partPathPrefix)
 	}
-	fs.rwLock.Unlock()
 
 	// Return etag.
 	return partMetadata.ETag, nil
@@ -693,11 +692,11 @@ func (fs Filesystem) AbortMultipartUpload(bucket, object, uploadID string) *prob
 
 	// Critical region requiring write lock.
 	fs.rwLock.Lock()
+	defer fs.rwLock.Unlock()
+
 	delete(fs.multiparts.ActiveSession, uploadID)
 	if err := saveMultipartsSession(*fs.multiparts); err != nil {
-		fs.rwLock.Unlock()
 		return err.Trace(partPathPrefix)
 	}
-	fs.rwLock.Unlock()
 	return nil
 }