From 5e038a5e1e4efb602b14af652cab1d2df5c77d21 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Wed, 17 Feb 2021 18:11:27 +0000
Subject: [PATCH] lib/file: retry preallocate on EINTR

Before this change, sometimes preallocate failed with EINTR which
rclone ignored.

Retrying the syscall is the correct thing to do and seems to make
preallocate 100% reliable.
---
 lib/file/preallocate_unix.go | 45 +++++++++++++++++++++---------------
 1 file changed, 27 insertions(+), 18 deletions(-)

diff --git a/lib/file/preallocate_unix.go b/lib/file/preallocate_unix.go
index d610b46b1..6f666410f 100644
--- a/lib/file/preallocate_unix.go
+++ b/lib/file/preallocate_unix.go
@@ -6,6 +6,7 @@ import (
 	"os"
 	"sync"
 	"sync/atomic"
+	"syscall"
 
 	"github.com/rclone/rclone/fs"
 	"golang.org/x/sys/unix"
@@ -25,30 +26,38 @@ var (
 const PreallocateImplemented = true
 
 // PreAllocate the file for performance reasons
-func PreAllocate(size int64, out *os.File) error {
+func PreAllocate(size int64, out *os.File) (err error) {
 	if size <= 0 {
 		return nil
 	}
+
 	preAllocateMu.Lock()
 	defer preAllocateMu.Unlock()
-	index := atomic.LoadInt32(&fallocFlagsIndex)
-again:
-	if index >= int32(len(fallocFlags)) {
-		return nil // Fallocate is disabled
-	}
-	flags := fallocFlags[index]
-	err := unix.Fallocate(int(out.Fd()), flags, 0, size)
-	if err == unix.ENOTSUP {
-		// Try the next flags combination
-		index++
-		atomic.StoreInt32(&fallocFlagsIndex, index)
-		fs.Debugf(nil, "preAllocate: got error on fallocate, trying combination %d/%d: %v", index, len(fallocFlags), err)
-		goto again
 
-	}
-	// Wrap important errors
-	if err == unix.ENOSPC {
-		return ErrDiskFull
+	for {
+
+		index := atomic.LoadInt32(&fallocFlagsIndex)
+	again:
+		if index >= int32(len(fallocFlags)) {
+			return nil // Fallocate is disabled
+		}
+		flags := fallocFlags[index]
+		err = unix.Fallocate(int(out.Fd()), flags, 0, size)
+		if err == unix.ENOTSUP {
+			// Try the next flags combination
+			index++
+			atomic.StoreInt32(&fallocFlagsIndex, index)
+			fs.Debugf(nil, "preAllocate: got error on fallocate, trying combination %d/%d: %v", index, len(fallocFlags), err)
+			goto again
+
+		}
+		// Wrap important errors
+		if err == unix.ENOSPC {
+			return ErrDiskFull
+		}
+		if err != syscall.EINTR {
+			break
+		}
 	}
 	return err
 }