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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DAA5C32771 for ; Mon, 26 Sep 2022 11:35:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238059AbiIZLf0 (ORCPT ); Mon, 26 Sep 2022 07:35:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48438 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238146AbiIZLeM (ORCPT ); Mon, 26 Sep 2022 07:34:12 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B14866E2DE; Mon, 26 Sep 2022 03:43:22 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 415D060A52; Mon, 26 Sep 2022 10:43:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 56196C433C1; Mon, 26 Sep 2022 10:43:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1664188998; bh=jLm3OD3DQ5HM9meF13VdBawooU2t/bfBfnoqYP3gKJA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Z/zDM+9hdd+EwBtJQKXIOzT2aE0lyhtbKU6gJ6yrkgsL0FeZ2GCUxOon/w/ShJxZj SwJeDwwa7gr43EnKExB0fGGLYBAMtBho4ACJE2z2bDF/s+nlh+H8Ek5GYI5mveocLl c4G7Lequoi6xKzEcOBBPHliRvMpDuBtYvN4kHo1c= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Josef Bacik , Filipe Manana , David Sterba Subject: [PATCH 5.19 041/207] btrfs: fix hang during unmount when stopping block group reclaim worker Date: Mon, 26 Sep 2022 12:10:30 +0200 Message-Id: <20220926100808.459198084@linuxfoundation.org> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20220926100806.522017616@linuxfoundation.org> References: <20220926100806.522017616@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Filipe Manana commit 8a1f1e3d1eecf9d2359a2709e276743a67e145db upstream. During early unmount, at close_ctree(), we try to stop the block group reclaim task with cancel_work_sync(), but that may hang if the block group reclaim task is currently at btrfs_relocate_block_group() waiting for the flag BTRFS_FS_UNFINISHED_DROPS to be cleared from fs_info->flags. During unmount we only clear that flag later, after trying to stop the block group reclaim task. Fix that by clearing BTRFS_FS_UNFINISHED_DROPS before trying to stop the block group reclaim task and after setting BTRFS_FS_CLOSING_START, so that if the reclaim task is waiting on that bit, it will stop immediately after being woken, because it sees the filesystem is closing (with a call to btrfs_fs_closing()), and then returns immediately with -EINTR. Fixes: 31e70e527806c5 ("btrfs: fix hang during unmount when block group reclaim task is running") CC: stable@vger.kernel.org # 5.15+ Reviewed-by: Josef Bacik Signed-off-by: Filipe Manana Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/disk-io.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -4587,6 +4587,17 @@ void __cold close_ctree(struct btrfs_fs_ set_bit(BTRFS_FS_CLOSING_START, &fs_info->flags); /* + * If we had UNFINISHED_DROPS we could still be processing them, so + * clear that bit and wake up relocation so it can stop. + * We must do this before stopping the block group reclaim task, because + * at btrfs_relocate_block_group() we wait for this bit, and after the + * wait we stop with -EINTR if btrfs_fs_closing() returns non-zero - we + * have just set BTRFS_FS_CLOSING_START, so btrfs_fs_closing() will + * return 1. + */ + btrfs_wake_unfinished_drop(fs_info); + + /* * We may have the reclaim task running and relocating a data block group, * in which case it may create delayed iputs. So stop it before we park * the cleaner kthread otherwise we can get new delayed iputs after @@ -4604,12 +4615,6 @@ void __cold close_ctree(struct btrfs_fs_ */ kthread_park(fs_info->cleaner_kthread); - /* - * If we had UNFINISHED_DROPS we could still be processing them, so - * clear that bit and wake up relocation so it can stop. - */ - btrfs_wake_unfinished_drop(fs_info); - /* wait for the qgroup rescan worker to stop */ btrfs_qgroup_wait_for_completion(fs_info, false);