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 2F83A44607D; Tue, 21 Jul 2026 15:45:57 +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=1784648758; cv=none; b=T7/kK0RBx8/o0UfqXRo2xMamzvmcLldYO9qo2TcvzxLkF2we3ebj3HHXcbISK1zNTCmYlB92Y1MiZLmvFQ+gBVE5iII34/fm1XOEMqmB/Iiao9pEaLxv+/bsTjtVbT23HAxFHakZuBsZ5AG0UzBlquclURsISMlBSeNAmpq84oM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784648758; c=relaxed/simple; bh=fO5L0ZTq8j+/RaoDdcB7xgpeo/xg3W9O4v/+/mnA27I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ND7259ufyFtxHaEMqx6H+DHMP6PEDN4soUOe2F+H5NGs911XQsjOaS5WWGAfBZfQynaIqy3HH/qwNIxKZq/KWMpq520SaFmj9C5mfyQgylmOS/3dirQDfFD7b6wgi1uF3HF5AcvGsdFB3aQeg6tz8HfnDAbpQgOIkixUzkLA/dc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Mf1F+IqZ; 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="Mf1F+IqZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C41D1F000E9; Tue, 21 Jul 2026 15:45:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784648757; bh=DsFHB7/5lvjJU5sZHU1UDtvkIEczuO9XH7aoGO9+/T4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Mf1F+IqZSFYOxiwmKetEIEi5+Xu3jjXRkhvEt4bRMTnfuhzxDsIHi9rTDoha1dqeh 75yJzLh6K2nKMwx0HAFFrjVBF/XkbUyvTMIQsxMskENe+HGNb5TyjbDJ3NGk9hfjaf +nN/7DE1h2Nb2AyIUDGQC0huSGzgAPzPwN9kbQ4w= 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 7.1 0277/2077] writeback: drop now-unnecessary rcu_barrier() in cgroup_writeback_umount() Date: Tue, 21 Jul 2026 16:59:10 +0200 Message-ID: <20260721152559.216863453@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152552.646164743@linuxfoundation.org> References: <20260721152552.646164743@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 7.1-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 6766de9f9d75b3..325a30cc35bfb8 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -1248,11 +1248,6 @@ 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