4 files changed, 107 insertions, 109 deletions

diff --git a/lib/private/Lock/AbstractLockingProvider.php b/lib/private/Lock/AbstractLockingProvider.php
index 6e8289db12e..d7e5976079c 100644
--- a/lib/private/Lock/AbstractLockingProvider.php
+++ b/lib/private/Lock/AbstractLockingProvider.php
@@ -1,28 +1,10 @@
 <?php
 
 declare(strict_types=1);
-
 /**
- * @copyright Copyright (c) 2016, ownCloud, Inc.
- *
- * @author Christoph Wurst <christoph@winzerhof-wurst.at>
- * @author Robin Appelman <robin@icewind.nl>
- * @author Roeland Jago Douma <roeland@famdouma.nl>
- *
- * @license AGPL-3.0
- *
- * This code is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License, version 3,
- * as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License, version 3,
- * along with this program. If not, see <http://www.gnu.org/licenses/>
- *
+ * SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
+ * SPDX-License-Identifier: AGPL-3.0-only
  */
 namespace OC\Lock;
 
@@ -33,14 +15,20 @@ use OCP\Lock\ILockingProvider;
  * to release any leftover locks at the end of the request
  */
 abstract class AbstractLockingProvider implements ILockingProvider {
-	/** how long until we clear stray locks in seconds */
-	protected int $ttl;
-
-	protected $acquiredLocks = [
+	protected array $acquiredLocks = [
 		'shared' => [],
 		'exclusive' => []
 	];
 
+	/**
+	 *
+	 * @param int $ttl how long until we clear stray locks in seconds
+	 */
+	public function __construct(
+		protected int $ttl,
+	) {
+	}
+
 	/** @inheritDoc */
 	protected function hasAcquiredLock(string $path, int $type): bool {
 		if ($type === self::LOCK_SHARED) {
diff --git a/lib/private/Lock/DBLockingProvider.php b/lib/private/Lock/DBLockingProvider.php
index fb8af8ac55b..cb7f5cff350 100644
--- a/lib/private/Lock/DBLockingProvider.php
+++ b/lib/private/Lock/DBLockingProvider.php
@@ -1,30 +1,9 @@
 <?php
+
 /**
- * @copyright Copyright (c) 2016, ownCloud, Inc.
- *
- * @author Christoph Wurst <christoph@winzerhof-wurst.at>
- * @author Individual IT Services <info@individual-it.net>
- * @author Joas Schilling <coding@schilljs.com>
- * @author Morris Jobke <hey@morrisjobke.de>
- * @author Ole Ostergaard <ole.c.ostergaard@gmail.com>
- * @author Robin Appelman <robin@icewind.nl>
- * @author Roeland Jago Douma <roeland@famdouma.nl>
- * @author Carl Schwan <carl@carlschwan.eu>
- *
- * @license AGPL-3.0
- *
- * This code is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License, version 3,
- * as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License, version 3,
- * along with this program. If not, see <http://www.gnu.org/licenses/>
- *
+ * SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
+ * SPDX-License-Identifier: AGPL-3.0-only
  */
 namespace OC\Lock;
 
@@ -39,21 +18,15 @@ use OCP\Lock\LockedException;
  * Locking provider that stores the locks in the database
  */
 class DBLockingProvider extends AbstractLockingProvider {
-	private IDBConnection $connection;
-	private ITimeFactory $timeFactory;
 	private array $sharedLocks = [];
-	private bool $cacheSharedLocks;
 
 	public function __construct(
-		IDBConnection $connection,
-		ITimeFactory $timeFactory,
+		private IDBConnection $connection,
+		private ITimeFactory $timeFactory,
 		int $ttl = 3600,
-		bool $cacheSharedLocks = true
+		private bool $cacheSharedLocks = true,
 	) {
-		$this->connection = $connection;
-		$this->timeFactory = $timeFactory;
-		$this->ttl = $ttl;
-		$this->cacheSharedLocks = $cacheSharedLocks;
+		parent::__construct($ttl);
 	}
 
 	/**
diff --git a/lib/private/Lock/MemcacheLockingProvider.php b/lib/private/Lock/MemcacheLockingProvider.php
index d4eebd7c302..8cc0c27bbf9 100644
--- a/lib/private/Lock/MemcacheLockingProvider.php
+++ b/lib/private/Lock/MemcacheLockingProvider.php
@@ -1,47 +1,49 @@
 <?php
 
 declare(strict_types=1);
-
 /**
- * @copyright Copyright (c) 2016, ownCloud, Inc.
- *
- * @author Christoph Wurst <christoph@winzerhof-wurst.at>
- * @author Jaakko Salo <jaakkos@gmail.com>
- * @author Robin Appelman <robin@icewind.nl>
- * @author Roeland Jago Douma <roeland@famdouma.nl>
- *
- * @license AGPL-3.0
- *
- * This code is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License, version 3,
- * as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License, version 3,
- * along with this program. If not, see <http://www.gnu.org/licenses/>
- *
+ * SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
+ * SPDX-License-Identifier: AGPL-3.0-only
  */
 namespace OC\Lock;
 
+use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\IMemcache;
 use OCP\IMemcacheTTL;
 use OCP\Lock\LockedException;
 
 class MemcacheLockingProvider extends AbstractLockingProvider {
-	private IMemcache $memcache;
+	/** @var array<string, array{time: int, ttl: int}> */
+	private array $oldTTLs = [];
+
+	public function __construct(
+		private IMemcache $memcache,
+		private ITimeFactory $timeFactory,
+		int $ttl = 3600,
+	) {
+		parent::__construct($ttl);
+	}
 
-	public function __construct(IMemcache $memcache, int $ttl = 3600) {
-		$this->memcache = $memcache;
-		$this->ttl = $ttl;
+	private function setTTL(string $path, ?int $ttl = null, mixed $compare = null): void {
+		if (is_null($ttl)) {
+			$ttl = $this->ttl;
+		}
+		if ($this->memcache instanceof IMemcacheTTL) {
+			if ($compare !== null) {
+				$this->memcache->compareSetTTL($path, $compare, $ttl);
+			} else {
+				$this->memcache->setTTL($path, $ttl);
+			}
+		}
 	}
 
-	private function setTTL(string $path): void {
+	private function getTTL(string $path): int {
 		if ($this->memcache instanceof IMemcacheTTL) {
-			$this->memcache->setTTL($path, $this->ttl);
+			$ttl = $this->memcache->getTTL($path);
+			return $ttl === false ? -1 : $ttl;
+		} else {
+			return -1;
 		}
 	}
 
@@ -58,14 +60,22 @@ class MemcacheLockingProvider extends AbstractLockingProvider {
 
 	public function acquireLock(string $path, int $type, ?string $readablePath = null): void {
 		if ($type === self::LOCK_SHARED) {
+			// save the old TTL to for `restoreTTL`
+			$this->oldTTLs[$path] = [
+				'ttl' => $this->getTTL($path),
+				'time' => $this->timeFactory->getTime()
+			];
 			if (!$this->memcache->inc($path)) {
 				throw new LockedException($path, null, $this->getExistingLockForException($path), $readablePath);
 			}
 		} else {
+			// when getting exclusive locks, we know there are no old TTLs to restore
 			$this->memcache->add($path, 0);
+			// ttl is updated automatically when the `set` succeeds
 			if (!$this->memcache->cas($path, 0, 'exclusive')) {
 				throw new LockedException($path, null, $this->getExistingLockForException($path), $readablePath);
 			}
+			unset($this->oldTTLs[$path]);
 		}
 		$this->setTTL($path);
 		$this->markAcquire($path, $type);
@@ -88,6 +98,12 @@ class MemcacheLockingProvider extends AbstractLockingProvider {
 				$newValue = $this->memcache->dec($path);
 			}
 
+			if ($newValue > 0) {
+				$this->restoreTTL($path);
+			} else {
+				unset($this->oldTTLs[$path]);
+			}
+
 			// if we somehow release more locks then exists, reset the lock
 			if ($newValue < 0) {
 				$this->memcache->cad($path, $newValue);
@@ -106,13 +122,52 @@ class MemcacheLockingProvider extends AbstractLockingProvider {
 		} elseif ($targetType === self::LOCK_EXCLUSIVE) {
 			// we can only change a shared lock to an exclusive if there's only a single owner of the shared lock
 			if (!$this->memcache->cas($path, 1, 'exclusive')) {
+				$this->restoreTTL($path);
 				throw new LockedException($path, null, $this->getExistingLockForException($path));
 			}
+			unset($this->oldTTLs[$path]);
 		}
 		$this->setTTL($path);
 		$this->markChange($path, $targetType);
 	}
 
+	/**
+	 * With shared locks, each time the lock is acquired, the ttl for the path is reset.
+	 *
+	 * Due to this "ttl extension" when a shared lock isn't freed correctly for any reason
+	 * the lock won't expire until no shared locks are required for the path for 1h.
+	 * This can lead to a client repeatedly trying to upload a file, and failing forever
+	 * because the lock never gets the opportunity to expire.
+	 *
+	 * To help the lock expire in this case, we lower the TTL back to what it was before we
+	 * took the shared lock *only* if nobody else got a shared lock after we did.
+	 *
+	 * This doesn't handle all cases where multiple requests are acquiring shared locks
+	 * but it should handle some of the more common ones and not hurt things further
+	 */
+	private function restoreTTL(string $path): void {
+		if (isset($this->oldTTLs[$path])) {
+			$saved = $this->oldTTLs[$path];
+			$elapsed = $this->timeFactory->getTime() - $saved['time'];
+
+			// old value to compare to when setting ttl in case someone else changes the lock in the middle of this function
+			$value = $this->memcache->get($path);
+
+			$currentTtl = $this->getTTL($path);
+
+			// what the old ttl would be given the time elapsed since we acquired the lock
+			// note that if this gets negative the key will be expired directly when we set the ttl
+			$remainingOldTtl = $saved['ttl'] - $elapsed;
+			// what the currently ttl would be if nobody else acquired a lock since we did (+1 to cover rounding errors)
+			$expectedTtl = $this->ttl - $elapsed + 1;
+
+			// check if another request has acquired a lock (and didn't release it yet)
+			if ($currentTtl <= $expectedTtl) {
+				$this->setTTL($path, $remainingOldTtl, $value);
+			}
+		}
+	}
+
 	private function getExistingLockForException(string $path): string {
 		$existing = $this->memcache->get($path);
 		if (!$existing) {
diff --git a/lib/private/Lock/NoopLockingProvider.php b/lib/private/Lock/NoopLockingProvider.php
index 542cb5c028e..42f1f9ae5ec 100644
--- a/lib/private/Lock/NoopLockingProvider.php
+++ b/lib/private/Lock/NoopLockingProvider.php
@@ -1,28 +1,10 @@
 <?php
 
 declare(strict_types=1);
-
 /**
- * @copyright Copyright (c) 2016, ownCloud, Inc.
- *
- * @author Robin Appelman <robin@icewind.nl>
- * @author Roeland Jago Douma <roeland@famdouma.nl>
- * @author Vincent Petry <vincent@nextcloud.com>
- *
- * @license AGPL-3.0
- *
- * This code is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License, version 3,
- * as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License, version 3,
- * along with this program. If not, see <http://www.gnu.org/licenses/>
- *
+ * SPDX-FileCopyrightText: 2016-2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-FileCopyrightText: 2016 ownCloud, Inc.
+ * SPDX-License-Identifier: AGPL-3.0-only
  */
 namespace OC\Lock;