Fixed CreateFile concurrency issues in memfs.

errors.go

@@ -23,6 +23,7 @@ import (
 const (
 	// Errors corresponding to kernel error numbers. These may be treated
 	// specially by fuseops.Op.Respond methods.
+	EEXIST    = bazilfuse.EEXIST
 	EINVAL    = bazilfuse.Errno(syscall.EINVAL)
 	EIO       = bazilfuse.EIO
 	ENOENT    = bazilfuse.ENOENT

samples/memfs/memfs.go

@@ -341,6 +341,14 @@ func (fs *memFS) CreateFile(
 	parent := fs.getInodeForModifyingOrDie(op.Parent)
 	defer parent.mu.Unlock()
 
+	// Ensure that the name doesn't alread exist, so we don't wind up with a
+	// duplicate.
+	_, exists := parent.LookUpChild(op.Name)
+	if exists {
+		err = fuse.EEXIST
+		return
+	}
+
 	// Set up attributes from the child, using the credentials of the calling
 	// process as owner (matching inode_init_owner, cf. http://goo.gl/5qavg8).
 	now := fs.clock.Now()

samples/memfs/memfs_test.go

@@ -1251,3 +1251,15 @@ func (t *MemFSTest) DeleteSymlink() {
 	AssertEq(nil, err)
 	ExpectThat(entries, ElementsAre())
 }
+
+func (t *MemFSTest) CreateInParallel_NoTruncate() {
+	runCreateInParallelTest_NoTruncate(t.Ctx, t.Dir)
+}
+
+func (t *MemFSTest) CreateInParallel_Truncate() {
+	runCreateInParallelTest_Truncate(t.Ctx, t.Dir)
+}
+
+func (t *MemFSTest) CreateInParallel_Exclusive() {
+	runCreateInParallelTest_Exclusive(t.Ctx, t.Dir)
+}