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=unavailable 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 B05B2C43603 for ; Tue, 10 Dec 2019 22:35:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7BB7E207FF for ; Tue, 10 Dec 2019 22:35:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576017342; bh=g+6Q1nqTZIyboOk9ybA2T2qqr2ssXMoBmdNKNjbQx3g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=1hYQkKH6DBgQ26SpFxRSLr3pVJo+RddL4cqVwTMO4QvJUEO1Ps8IGNsKRBKCNbp5E kF4EoZb7TMQvvG9Dd39jAg6tw/Ssxk7CJCoohz0xITqjCd6WKKTEEn4R/yA1rgauzN u2FAgf1KG770TwD6a95jB4kLClyjXpE50ar9hqOI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729900AbfLJWfh (ORCPT ); Tue, 10 Dec 2019 17:35:37 -0500 Received: from mail.kernel.org ([198.145.29.99]:56016 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730370AbfLJWec (ORCPT ); Tue, 10 Dec 2019 17:34:32 -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 F1A732077B; Tue, 10 Dec 2019 22:34:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576017271; bh=g+6Q1nqTZIyboOk9ybA2T2qqr2ssXMoBmdNKNjbQx3g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IA7rio29VRkQ+fU5Cl7H0ZZObvU9DJerVsbDOZD5UKfNZGLG2FOp9P757r5q/+GrD lAQvZPQvEQ6huRGfHdJvLCARAjO/CnxUjA+ev2Zej5PB2j4K986y5TXa9sL4PrwTPB IP712Zvq7SwlscivWxdf5HBeOjD0jeVzofHJ19VI= 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 4.4 63/71] btrfs: don't prematurely free work in end_workqueue_fn() Date: Tue, 10 Dec 2019 17:33:08 -0500 Message-Id: <20191210223316.14988-63-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191210223316.14988-1-sashal@kernel.org> References: <20191210223316.14988-1-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 78722aaffecd3..d50fc503f73b8 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1698,8 +1698,8 @@ 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