mfs: use rwlock for the nodelk

This allows us to, e.g., get the size, etc. in parallel.

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

mfs/fd.go

@@ -154,9 +154,9 @@ func (fi *fileDescriptor) flushUp(fullsync bool) error {
 			return nil
 		}
 		if nd == nil {
-			fi.inode.nodelk.Lock()
+			fi.inode.nodelk.RLock()
 			nd = fi.inode.node
-			fi.inode.nodelk.Unlock()
+			fi.inode.nodelk.RUnlock()
 		}
 
 		if err := fi.inode.parent.closeChild(fi.inode.name, nd, fullsync); err != nil {

mfs/file.go

@@ -22,7 +22,7 @@ type File struct {
 
 	dserv  dag.DAGService
 	node   node.Node
-	nodelk sync.Mutex
+	nodelk sync.RWMutex
 
 	RawLeaves bool
 }
@@ -60,9 +60,10 @@ func (fi *File) Open(flags Flags) (_ FileDescriptor, _retErr error) {
 	} else {
 		return nil, fmt.Errorf("file opened for neither reading nor writing")
 	}
-	fi.nodelk.Lock()
+
+	fi.nodelk.RLock()
 	node := fi.node
-	fi.nodelk.Unlock()
+	fi.nodelk.RUnlock()
 
 	switch node := node.(type) {
 	case *dag.ProtoNode:
@@ -98,8 +99,8 @@ func (fi *File) Open(flags Flags) (_ FileDescriptor, _retErr error) {
 
 // Size returns the size of this file
 func (fi *File) Size() (int64, error) {
-	fi.nodelk.Lock()
-	defer fi.nodelk.Unlock()
+	fi.nodelk.RLock()
+	defer fi.nodelk.RUnlock()
 	switch nd := fi.node.(type) {
 	case *dag.ProtoNode:
 		pbd, err := ft.FromBytes(nd.Data())
@@ -116,8 +117,8 @@ func (fi *File) Size() (int64, error) {
 
 // GetNode returns the dag node associated with this file
 func (fi *File) GetNode() (node.Node, error) {
-	fi.nodelk.Lock()
-	defer fi.nodelk.Unlock()
+	fi.nodelk.RLock()
+	defer fi.nodelk.RUnlock()
 	return fi.node, nil
 }