From ac62ef430d826902cf3279a28f24f1ea07ee9da5 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Fri, 17 Feb 2017 08:37:53 +0000
Subject: [PATCH] Prevent double closes on async buffer

---
 fs/buffer.go | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/fs/buffer.go b/fs/buffer.go
index 9ba3fb3cf..436b42383 100644
--- a/fs/buffer.go
+++ b/fs/buffer.go
@@ -30,6 +30,7 @@ type asyncReader struct {
 	cur     *buffer       // Current buffer being served
 	exited  chan struct{} // Channel is closed been the async reader shuts down
 	size    int           // size of buffer to use
+	closed  bool          // whether we have closed the underlying stream
 }
 
 // newAsyncReader returns a reader that will asynchronously read from
@@ -162,13 +163,12 @@ func (a *asyncReader) WriteTo(w io.Writer) (n int64, err error) {
 	}
 }
 
-// close will ensure that the underlying async reader is shut down.
-// If closeIn is set it will also close the input supplied on
-// newAsyncReader.
-func (a *asyncReader) close(closeIn bool) (err error) {
-	// Return if already closed
+// Abandon will ensure that the underlying async reader is shut down.
+// It will NOT close the input supplied on newAsyncReader.
+func (a *asyncReader) Abandon() {
 	select {
 	case <-a.exit:
+		// Do nothing if reader routine already exited
 		return
 	default:
 	}
@@ -178,26 +178,22 @@ func (a *asyncReader) close(closeIn bool) (err error) {
 	// Return any outstanding buffers to the Pool
 	if a.cur != nil {
 		a.putBuffer(a.cur)
+		a.cur = nil
 	}
 	for b := range a.ready {
 		a.putBuffer(b)
 	}
-	if closeIn {
-		return a.in.Close()
-	}
-	return nil
 }
 
 // Close will ensure that the underlying async reader is shut down.
 // It will also close the input supplied on newAsyncReader.
 func (a *asyncReader) Close() (err error) {
-	return a.close(true)
-}
-
-// Abandon will ensure that the underlying async reader is shut down.
-// It will NOT close the input supplied on newAsyncReader.
-func (a *asyncReader) Abandon() {
-	_ = a.close(false)
+	a.Abandon()
+	if a.closed {
+		return nil
+	}
+	a.closed = true
+	return a.in.Close()
 }
 
 // Internal buffer