From 9fa8c959ee331938a8a05fbe318ce61af1296972 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Mon, 20 Aug 2018 20:14:19 +0100
Subject: [PATCH] local: preallocate files on linux with fallocate(2)

---
 backend/local/preallocate_other.go |  2 +-
 backend/local/preallocate_unix.go  | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 backend/local/preallocate_unix.go

diff --git a/backend/local/preallocate_other.go b/backend/local/preallocate_other.go
index 7afff5e29..fb71cad59 100644
--- a/backend/local/preallocate_other.go
+++ b/backend/local/preallocate_other.go
@@ -1,4 +1,4 @@
-//+build !windows
+//+build !windows,!linux
 
 package local
 
diff --git a/backend/local/preallocate_unix.go b/backend/local/preallocate_unix.go
new file mode 100644
index 000000000..f7208ab0b
--- /dev/null
+++ b/backend/local/preallocate_unix.go
@@ -0,0 +1,22 @@
+//+build linux
+
+package local
+
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+// preAllocate the file for performance reasons
+func preAllocate(size int64, out *os.File) error {
+	if size <= 0 {
+		return nil
+	}
+	err := unix.Fallocate(int(out.Fd()), unix.FALLOC_FL_KEEP_SIZE, 0, size)
+	// FIXME could be doing something here
+	// if err == unix.ENOSPC {
+	// 	log.Printf("No space")
+	// }
+	return err
+}