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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 C0162C3276F for ; Thu, 2 Jan 2020 22:46:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9794A22314 for ; Thu, 2 Jan 2020 22:46:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578005186; bh=obYcbybQK0iRzuQodJ35Y2/yu1p1+C2bxabYBA70L0c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=AIHFGldHKv0jk6qnOq7pHeiDrxpJm52IBVJATxQ1eVQc15/6jpUsU9AOSMB+FyMN4 1ibKLwePxH53aKQEozHYSgZ31HC9zNH2vQLOe8uZcN5Pa6DeWfv8HVCSaLzbV5YkW4 HvmB44np+sC0kXG/hZMb3gtNeIi/PfXPsQX/vrrY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730210AbgABWay (ORCPT ); Thu, 2 Jan 2020 17:30:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:35244 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730019AbgABWav (ORCPT ); Thu, 2 Jan 2020 17:30:51 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7C02820863; Thu, 2 Jan 2020 22:30:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578004251; bh=obYcbybQK0iRzuQodJ35Y2/yu1p1+C2bxabYBA70L0c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MfwnlQQOvgNIh0qLMZiGXcxFfLSZQloPPa9ljjmIri81y5sZqGmJrhQfl9yQ/E2go gY1TeVDl0fcNsu27R1a3NJ+Zj/F1wPXipZxVhRAuRnGNtH4l63Uuur2o8x0jxUnaA1 dYvXc+MRHUOyT7WqFdYUA0pqZRAOgbQ9bNsV9axw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Johannes Thumshirn , Omar Sandoval , David Sterba , Sasha Levin Subject: [PATCH 4.9 075/171] btrfs: dont prematurely free work in end_workqueue_fn() Date: Thu, 2 Jan 2020 23:06:46 +0100 Message-Id: <20200102220557.382989729@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200102220546.960200039@linuxfoundation.org> References: <20200102220546.960200039@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 9d3352fe8dc9..b37519241eb1 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