From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 51839C00454 for ; Tue, 10 Dec 2019 22:40:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1FCBA2053B for ; Tue, 10 Dec 2019 22:40:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576017616; bh=Y+Bla786PDR3c0m1VaYc1CWVHerhCW0OXJGxhWB+QXw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=zRKkGLUxEgdha+w2bVJcCPq3WROEnDJ0BQ6dWnnCewdUYsok9k5Zm5nn+REQ4tKpg dsP7DqJko0wA/N4p92RbeNhR1wyT9gv4l6r1DfDIMY8/nhh7pPQGRUtu+MayfLXCVQ 7P/uW+rI8E/45VjPDeWV3I2TsuxOaiaFQdGeSAHo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727077AbfLJWkO (ORCPT ); Tue, 10 Dec 2019 17:40:14 -0500 Received: from mail.kernel.org ([198.145.29.99]:52556 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727669AbfLJWcK (ORCPT ); Tue, 10 Dec 2019 17:32:10 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5D39C22464; Tue, 10 Dec 2019 22:32:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576017130; bh=Y+Bla786PDR3c0m1VaYc1CWVHerhCW0OXJGxhWB+QXw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TqpfnzHfs3j88F2kWok28a8lyGWmCie/NU3OZBpHDboOHAt3U4+qHyBIm7u82EFBB GtHyeqgFJfjwv3A+FY7QM/iVfwDtn3H+ZHQeh89eEqw5QvXBh6NfRihKA9hqgl8k8/ b5BTxIQHfzgY2259JaGyeYy6vrEFJaMicq9l+6h4= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Omar Sandoval , Johannes Thumshirn , David Sterba , Sasha Levin , linux-btrfs@vger.kernel.org Subject: [PATCH AUTOSEL 4.9 79/91] btrfs: don't prematurely free work in end_workqueue_fn() Date: Tue, 10 Dec 2019 17:30:23 -0500 Message-Id: <20191210223035.14270-79-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191210223035.14270-1-sashal@kernel.org> References: <20191210223035.14270-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Omar Sandoval [ Upstream commit 9be490f1e15c34193b1aae17da58e14dd9f55a95 ] Currently, end_workqueue_fn() frees the end_io_wq entry (which embeds the work item) and then calls bio_endio(). This is another potential instance of the bug in "btrfs: don't prematurely free work in run_ordered_work()". In particular, the endio call may depend on other work items. For example, btrfs_end_dio_bio() can call btrfs_subio_endio_read() -> __btrfs_correct_data_nocsum() -> dio_read_error() -> submit_dio_repair_bio(), which submits a bio that is also completed through a end_workqueue_fn() work item. However, __btrfs_correct_data_nocsum() waits for the newly submitted bio to complete, thus it depends on another work item. This example currently usually works because we use different workqueue helper functions for BTRFS_WQ_ENDIO_DATA and BTRFS_WQ_ENDIO_DIO_REPAIR. However, it may deadlock with stacked filesystems and is fragile overall. The proper fix is to free the work item at the very end of the work function, so let's do that. Reviewed-by: Johannes Thumshirn Signed-off-by: Omar Sandoval Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/disk-io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 9d3352fe8dc92..b37519241eb1c 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1712,8 +1712,8 @@ static void end_workqueue_fn(struct btrfs_work *work) bio->bi_error = end_io_wq->error; bio->bi_private = end_io_wq->private; bio->bi_end_io = end_io_wq->end_io; - kmem_cache_free(btrfs_end_io_wq_cache, end_io_wq); bio_endio(bio); + kmem_cache_free(btrfs_end_io_wq_cache, end_io_wq); } static int cleaner_kthread(void *arg) -- 2.20.1