From 63373660bc2ef10ad6de3d3101cd8a9910692407 Mon Sep 17 00:00:00 2001
From: Ben Johnson <benbjohnson@yahoo.com>
Date: Thu, 5 Jun 2014 09:58:41 -0600
Subject: [PATCH] Add fallback for O_DIRECT in Tx.Copy().

This commit adds the ability for Bolt to fallback to using a regular file open if Tx.Copy()
errors while opening with O_DIRECT. This only affects Linux.
---
 tx.go | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/tx.go b/tx.go
index cc2b13f..a9781f2 100644
--- a/tx.go
+++ b/tx.go
@@ -239,10 +239,15 @@ func (tx *Tx) close() {
 // using the database while a copy is in progress.
 // Copy will write exactly tx.Size() bytes into the writer.
 func (tx *Tx) Copy(w io.Writer) error {
-	// Open reader on the database.
-	f, err := os.OpenFile(tx.db.path, os.O_RDONLY|odirect, 0)
-	if err != nil {
-		return err
+	var f *os.File
+	var err error
+
+	// Attempt to open reader directly.
+	if f, err = os.OpenFile(tx.db.path, os.O_RDONLY|odirect, 0); err != nil {
+		// Fallback to a regular open if that doesn't work.
+		if f, err = os.OpenFile(tx.db.path, os.O_RDONLY, 0); err != nil {
+			return err
+		}
 	}
 
 	// Copy the meta pages.