From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1994346E017; Tue, 21 Jul 2026 17:47:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784656040; cv=none; b=Takbn4ZJ/1SJrL37e6qMPj7BgXFcBrWe1H/4Ed3s1q8t+IRoBvkPKKC+eZtE3MI5Q/pfsfR0plK0SpmwaCyHY6w6vjgP2EL8KROfxMXSjgGdpnDjUTNBbhIShbR6Q6jsIOoV9qbXp51h6vMPGa3p6qpnOqJTqXgSgpU2ZN9yhso= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784656040; c=relaxed/simple; bh=RmfC1URVH7wN0fRNSQR8nUo31fdgI6x6Pfn50LdfgGU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bsduSEdpVx/GdSRVnIbSL/o8sdHRBkKiRuH9YGUzlxvBxTjln5x6PonKm3GGesTutA3VYoovQRBfyOoEVDhnpIwSpFwmm3MsFl/ZAkgVQbdiowHKPgB5VUm6V9y/o2snkmAglIw28MX7ZjpTbHEHAJzt0U7uY/MPpv6TtH61yvk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=X8dpyZJr; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="X8dpyZJr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 43E8B1F000E9; Tue, 21 Jul 2026 17:47:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784656038; bh=KQISrWgOGdKpdnxx100UufL1wblYaG/5SYniGwfCDPw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=X8dpyZJrSReWvAgmb8+PzF7bAzSJSSfBQPFGCGY5Rn6G4IIKwuyaawRXgVsO0PeXn YjSKyQFcpCsfUhCXxc6Nw51kzOU7MDIQVtPAEGEZX9LY0iHBkN1zuTDn71u7Ja/IpK xj8lXe82EMQmFTE+VaTivyczFZZQAZajoPpHoeEw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jan Kara , Baokun Li , Tejun Heo , "Christian Brauner (Amutable)" , Sasha Levin Subject: [PATCH 6.18 0193/1611] writeback: drop now-unnecessary rcu_barrier() in cgroup_writeback_umount() Date: Tue, 21 Jul 2026 17:05:09 +0200 Message-ID: <20260721152519.284670072@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152514.750365251@linuxfoundation.org> References: <20260721152514.750365251@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Baokun Li [ Upstream commit e90a6d668e26e00a72df2d09c173b563468f09c9 ] Commit e1b849cfa6b6 ("writeback: Avoid contention on wb->list_lock when switching inodes") replaced the queue_rcu_work() based scheduling of inode wb switches with a plain queue_work(). Since then no switcher goes through call_rcu(), so rcu_barrier() in cgroup_writeback_umount() has no callbacks of its own to wait for. It still drains unrelated call_rcu() callbacks from other subsystems on busy systems, which incidentally slows umount down; drop it. Fixes: e1b849cfa6b6 ("writeback: Avoid contention on wb->list_lock when switching inodes") Reviewed-by: Jan Kara Signed-off-by: Baokun Li Link: https://patch.msgid.link/20260521095016.2791354-3-libaokun@linux.alibaba.com Acked-by: Tejun Heo Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Sasha Levin --- fs/fs-writeback.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 99d0658b49a220..d2510c818da9aa 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1237,11 +1237,6 @@ void cgroup_writeback_umount(struct super_block *sb) * will then drain it. */ synchronize_rcu(); - /* - * Use rcu_barrier() to wait for all pending callbacks to - * ensure that all in-flight wb switches are in the workqueue. - */ - rcu_barrier(); flush_workqueue(isw_wq); } } -- 2.53.0