Improves storagedriver concurrency testing

Creates trees instead of flat files for TestConcurrentFileStreams

Adds TestConcurrentStreamReads, which writes a large file (smaller in
Short mode), and then ensures that several concurrent readers properly
read their portions of the file with random offsets

storagedriver/testsuites/testsuites.go

@@ -651,9 +651,46 @@ func (suite *DriverSuite) TestStatCall(c *check.C) {
 	}
 }
 
+// TestConcurrentStreamReads checks that multiple clients can safely read from
+// the same file simultaneously with various offsets.
+func (suite *DriverSuite) TestConcurrentStreamReads(c *check.C) {
+	var filesize int64 = 128 * 1024 * 1024
+
+	if testing.Short() {
+		filesize = 10 * 1024 * 1024
+		c.Log("Reducing file size to 10MB for short mode")
+	}
+
+	filename := randomPath(32)
+	contents := randomContents(filesize)
+
+	defer suite.StorageDriver.Delete(firstPart(filename))
+
+	err := suite.StorageDriver.PutContent(filename, contents)
+	c.Assert(err, check.IsNil)
+
+	var wg sync.WaitGroup
+
+	readContents := func() {
+		defer wg.Done()
+		offset := rand.Int63n(int64(len(contents)))
+		reader, err := suite.StorageDriver.ReadStream(filename, offset)
+		c.Assert(err, check.IsNil)
+
+		readContents, err := ioutil.ReadAll(reader)
+		c.Assert(err, check.IsNil)
+		c.Assert(readContents, check.DeepEquals, contents[offset:])
+	}
+
+	wg.Add(10)
+	for i := 0; i < 10; i++ {
+		go readContents()
+	}
+	wg.Wait()
+}
+
 // TestConcurrentFileStreams checks that multiple *os.File objects can be passed
 // in to WriteStream concurrently without hanging.
-// TODO(bbland): fix this test...
 func (suite *DriverSuite) TestConcurrentFileStreams(c *check.C) {
 	// if _, isIPC := suite.StorageDriver.(*ipc.StorageDriverClient); isIPC {
 	// 	c.Skip("Need to fix out-of-process concurrency")
@@ -682,8 +719,8 @@ func (suite *DriverSuite) testFileStreams(c *check.C, size int64) {
 	c.Assert(err, check.IsNil)
 	defer os.Remove(tf.Name())
 
-	tfName := path.Base(tf.Name())
-	defer suite.StorageDriver.Delete(tfName)
+	filename := randomPath(32)
+	defer suite.StorageDriver.Delete(firstPart(filename))
 
 	contents := randomContents(size)
 
@@ -693,11 +730,11 @@ func (suite *DriverSuite) testFileStreams(c *check.C, size int64) {
 	tf.Sync()
 	tf.Seek(0, os.SEEK_SET)
 
-	nn, err := suite.StorageDriver.WriteStream(tfName, 0, tf)
+	nn, err := suite.StorageDriver.WriteStream(filename, 0, tf)
 	c.Assert(err, check.IsNil)
 	c.Assert(nn, check.Equals, size)
 
-	reader, err := suite.StorageDriver.ReadStream(tfName, 0)
+	reader, err := suite.StorageDriver.ReadStream(filename, 0)
 	c.Assert(err, check.IsNil)
 	defer reader.Close()