From 019807a111d3daf1f9c27b895fd1d0fded8da545 Mon Sep 17 00:00:00 2001
From: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Date: Thu, 31 Mar 2022 10:38:25 +0200
Subject: [PATCH] config: add a switch to control truncate before update

To avoid extra truncate on non WORM file systems, add a new config
option `localstorage.unlink_on_truncate`, which defaults to false.

The OC\Files\Storage\Local is update to respect that option.
---
 config/config.sample.php            |  8 ++++++++
 lib/private/Files/Storage/Local.php | 18 ++++++++++++------
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/config/config.sample.php b/config/config.sample.php
index 357321f6d29c2..cc1e0ea36fdbf 100644
--- a/config/config.sample.php
+++ b/config/config.sample.php
@@ -1796,6 +1796,14 @@
  */
 'localstorage.allowsymlinks' => false,
 
+/**
+ * This options allows storage systems that don't allow to modify existing files
+ * to overcome this limitation by removing the files before overwriting.
+ *
+ * Defaults to ``false``
+ */
+'localstorage.unlink_on_truncate' => false,
+
 /**
  * EXPERIMENTAL: option whether to include external storage in quota
  * calculation, defaults to false.
diff --git a/lib/private/Files/Storage/Local.php b/lib/private/Files/Storage/Local.php
index a5767d5b9a028..10e2726f7e2a7 100644
--- a/lib/private/Files/Storage/Local.php
+++ b/lib/private/Files/Storage/Local.php
@@ -66,6 +66,8 @@ class Local extends \OC\Files\Storage\Common {
 
 	private IMimeTypeDetector $mimeTypeDetector;
 
+	protected $unlinkOnTruncate;
+
 	public function __construct($arguments) {
 		if (!isset($arguments['datadir']) || !is_string($arguments['datadir'])) {
 			throw new \InvalidArgumentException('No data directory set for local storage');
@@ -84,6 +86,9 @@ public function __construct($arguments) {
 		$this->dataDirLength = strlen($this->realDataDir);
 		$this->config = \OC::$server->get(IConfig::class);
 		$this->mimeTypeDetector = \OC::$server->get(IMimeTypeDetector::class);
+
+		// support Write-Once-Read-Many file systems
+		$this->unlinkOnTruncate = $this->config->getSystemValue('localstorage.unlink_on_truncate', false);
 	}
 
 	public function __destruct() {
@@ -289,8 +294,9 @@ public function file_get_contents($path) {
 
 	public function file_put_contents($path, $data) {
 		$oldMask = umask(022);
-		// support Write-Once-Read-Many filesystems
-		$this->unlink($path);
+		if ($this->unlinkOnTruncate) {
+			$this->unlink($path);
+		}
 		$result = file_put_contents($this->getSourcePath($path), $data);
 		umask($oldMask);
 		return $result;
@@ -364,8 +370,9 @@ public function copy($path1, $path2) {
 			return parent::copy($path1, $path2);
 		} else {
 			$oldMask = umask(022);
-			// support Write-Once-Read-Many filesystems
-			$this->unlink($path2);
+			if ($this->unlinkOnTruncate) {
+				$this->unlink($path2);
+			}
 			$result = copy($this->getSourcePath($path1), $this->getSourcePath($path2));
 			umask($oldMask);
 			return $result;
@@ -374,8 +381,7 @@ public function copy($path1, $path2) {
 
 	public function fopen($path, $mode) {
 		$oldMask = umask(022);
-		if ($mode === 'w') {
-			// support Write-Once-Read-Many filesystems
+		if ($mode === 'w' && $this->unlinkOnTruncate) {
 			$this->unlink($path);
 		}
 		$result = fopen($this->getSourcePath($path), $mode);