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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 278F8C4CED1 for ; Thu, 3 Oct 2019 16:00:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EA55F222BE for ; Thu, 3 Oct 2019 16:00:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570118404; bh=UBCdzCG37r0flkITDq3m10cAnvvif7pzX4cphOzD3yw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=t8QEu8ArgwUvFPhMcKsciOGafVrfAT5PUIACpMa24CW0rErMp5ClWauqWLGtZUxZC dwW8t5tR4UFwxG3eta5QakQ6PzdJkLKM4VPQJPKML7iy8ooPURWH8Ic9Skgs8VcsBc VZ/FiuIGjhlaRvh3HJv6IyOMLYkP4rOnt9a+Wh2I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729690AbfJCQAD (ORCPT ); Thu, 3 Oct 2019 12:00:03 -0400 Received: from mail.kernel.org ([198.145.29.99]:43466 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731473AbfJCQAA (ORCPT ); Thu, 3 Oct 2019 12:00:00 -0400 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 4D28321848; Thu, 3 Oct 2019 15:59:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570118399; bh=UBCdzCG37r0flkITDq3m10cAnvvif7pzX4cphOzD3yw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Clx3ng8ZY68RlSz+gn7khC8BMzR/MkZxtEf9Q4glpUDpTVb3qhVuKBrJbHZMeYWVb CqT5HM+582IfOmvhN3enZcDzlLVqXcUom6m5C6vMUwvup74v8ym0tMD17FgI3HBwL8 cKcA7dVUIFHI9AiZbMy/SgTO5PBU/jUMsqRZQ58I= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Johannes Thumshirn , Nikolay Borisov , David Sterba Subject: [PATCH 4.4 98/99] btrfs: Relinquish CPUs in btrfs_compare_trees Date: Thu, 3 Oct 2019 17:54:01 +0200 Message-Id: <20191003154344.957569945@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191003154252.297991283@linuxfoundation.org> References: <20191003154252.297991283@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: Nikolay Borisov commit 6af112b11a4bc1b560f60a618ac9c1dcefe9836e upstream. When doing any form of incremental send the parent and the child trees need to be compared via btrfs_compare_trees. This can result in long loop chains without ever relinquishing the CPU. This causes softlockup detector to trigger when comparing trees with a lot of items. Example report: watchdog: BUG: soft lockup - CPU#0 stuck for 24s! [snapperd:16153] CPU: 0 PID: 16153 Comm: snapperd Not tainted 5.2.9-1-default #1 openSUSE Tumbleweed (unreleased) Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 pstate: 40000005 (nZcv daif -PAN -UAO) pc : __ll_sc_arch_atomic_sub_return+0x14/0x20 lr : btrfs_release_extent_buffer_pages+0xe0/0x1e8 [btrfs] sp : ffff00001273b7e0 Call trace: __ll_sc_arch_atomic_sub_return+0x14/0x20 release_extent_buffer+0xdc/0x120 [btrfs] free_extent_buffer.part.0+0xb0/0x118 [btrfs] free_extent_buffer+0x24/0x30 [btrfs] btrfs_release_path+0x4c/0xa0 [btrfs] btrfs_free_path.part.0+0x20/0x40 [btrfs] btrfs_free_path+0x24/0x30 [btrfs] get_inode_info+0xa8/0xf8 [btrfs] finish_inode_if_needed+0xe0/0x6d8 [btrfs] changed_cb+0x9c/0x410 [btrfs] btrfs_compare_trees+0x284/0x648 [btrfs] send_subvol+0x33c/0x520 [btrfs] btrfs_ioctl_send+0x8a0/0xaf0 [btrfs] btrfs_ioctl+0x199c/0x2288 [btrfs] do_vfs_ioctl+0x4b0/0x820 ksys_ioctl+0x84/0xb8 __arm64_sys_ioctl+0x28/0x38 el0_svc_common.constprop.0+0x7c/0x188 el0_svc_handler+0x34/0x90 el0_svc+0x8/0xc Fix this by adding a call to cond_resched at the beginning of the main loop in btrfs_compare_trees. Fixes: 7069830a9e38 ("Btrfs: add btrfs_compare_trees function") CC: stable@vger.kernel.org # 4.4+ Reviewed-by: Johannes Thumshirn Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/ctree.c | 1 + 1 file changed, 1 insertion(+) --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -5435,6 +5435,7 @@ int btrfs_compare_trees(struct btrfs_roo advance_left = advance_right = 0; while (1) { + cond_resched(); if (advance_left && !left_end_reached) { ret = tree_advance(left_root, left_path, &left_level, left_root_level,