From patchwork Thu Jan 2 22:06:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 234604 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 41EFBC3276E for ; Thu, 2 Jan 2020 22:47:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1738D217F4 for ; Thu, 2 Jan 2020 22:47:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578005222; bh=62y6fMdHxwp4nQAatzWsMLdvOZXd8xkaWKa+8vceoJ8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=PbZpoQiwgGdd9gX7so3GTCKyMDh8bQYg5n27k0G5GJbKMF98u+n3rMbkqjKb+zZXL qR+0J7PSgIY36DinAjpYG9wwKX4UsPi01KTGYmEjVf2i2gR+AHmLZaWzcfG9EQ/eMM OVh6ufC33QIJjXDq8oljNVrArse+QLowoAl9qYnU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727607AbgABWaN (ORCPT ); Thu, 2 Jan 2020 17:30:13 -0500 Received: from mail.kernel.org ([198.145.29.99]:33740 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730142AbgABWaN (ORCPT ); Thu, 2 Jan 2020 17:30:13 -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 0BC7620866; Thu, 2 Jan 2020 22:30:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578004212; bh=62y6fMdHxwp4nQAatzWsMLdvOZXd8xkaWKa+8vceoJ8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zBr/vhwKBIBsOkik7hBSRDku6YgK+OaqCb4A30rVkKootGtDwAYczUawoQC/VDMNO JaDpkTEoPUXaKTsyqDY2Sq3C0CKyzqB/uTWUuWiXGAKDV+EsMhpNB1OKJ7y2085zSp Jpv61HTlRXaPrs7bSUb6lbDk0b9zii997MvS0oKI= 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 4.9 085/171] btrfs: dont prematurely free work in reada_start_machine_worker() Date: Thu, 2 Jan 2020 23:06:56 +0100 Message-Id: <20200102220558.786641120@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 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Omar Sandoval [ Upstream commit e732fe95e4cad35fc1df278c23a32903341b08b3 ] Currently, reada_start_machine_worker() frees the reada_machine_work and then calls __reada_start_machine() to do readahead. This is another potential instance of the bug in "btrfs: don't prematurely free work in run_ordered_work()". There _might_ already be a deadlock here: reada_start_machine_worker() can depend on itself through stacked filesystems (__read_start_machine() -> reada_start_machine_dev() -> reada_tree_block_flagged() -> read_extent_buffer_pages() -> submit_one_bio() -> btree_submit_bio_hook() -> btrfs_map_bio() -> submit_stripe_bio() -> submit_bio() onto a loop device can trigger readahead on the lower filesystem). Either way, let's fix it by freeing the work at the end. 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/reada.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c index 94441fdb1ecf..0d1565d71231 100644 --- a/fs/btrfs/reada.c +++ b/fs/btrfs/reada.c @@ -734,21 +734,19 @@ static int reada_start_machine_dev(struct btrfs_fs_info *fs_info, static void reada_start_machine_worker(struct btrfs_work *work) { struct reada_machine_work *rmw; - struct btrfs_fs_info *fs_info; int old_ioprio; rmw = container_of(work, struct reada_machine_work, work); - fs_info = rmw->fs_info; - - kfree(rmw); old_ioprio = IOPRIO_PRIO_VALUE(task_nice_ioclass(current), task_nice_ioprio(current)); set_task_ioprio(current, BTRFS_IOPRIO_READA); - __reada_start_machine(fs_info); + __reada_start_machine(rmw->fs_info); set_task_ioprio(current, old_ioprio); - atomic_dec(&fs_info->reada_works_cnt); + atomic_dec(&rmw->fs_info->reada_works_cnt); + + kfree(rmw); } static void __reada_start_machine(struct btrfs_fs_info *fs_info)