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=-2.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_MUTT autolearn=ham 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 D7C27C43381 for ; Thu, 21 Feb 2019 14:14:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A60F42070B for ; Thu, 21 Feb 2019 14:14:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="cEjs0vFh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726191AbfBUON7 (ORCPT ); Thu, 21 Feb 2019 09:13:59 -0500 Received: from aserp2130.oracle.com ([141.146.126.79]:59284 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725870AbfBUON7 (ORCPT ); Thu, 21 Feb 2019 09:13:59 -0500 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x1LE9pL6151184; Thu, 21 Feb 2019 14:13:55 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=date : from : to : cc : subject : message-id : mime-version : content-type; s=corp-2018-07-02; bh=tLI02zzX5bHrmNXHbcbp0heITjnG8zF8FjIwLa+Dakw=; b=cEjs0vFhrgVHJTRBFseBX35EmV9wYeOi/2EmeveY5xB91paeXyDNnfWcpu7fEUmMv3OH btUWMLoEdxkCCsTyUs8ZUQUx4K70sEL8IRVecPV1eR4WEwVhqmr3noMnICBQ/okoKs3n RvOIIPCko6uuxroOkj5vFrNBV5mcD1riXRLlgYbcHsBH689jHNcR6laBwtCFkhFxSsur pb6oci4PAlJKSeJLkZNJ5FYG+Y9iEll/awvHfGLWr1IjB/QyjITp4pnLsXzOeVzmqduu eSF0r2LpwkFTAeRHA801nRaqJ1+9H5OcIQyAeBm7wF5wnpkYaBySCqxJc764JeZ/P+js pA== Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by aserp2130.oracle.com with ESMTP id 2qp81egc8r-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 21 Feb 2019 14:13:55 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id x1LEDs6d031628 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 21 Feb 2019 14:13:55 GMT Received: from abhmp0005.oracle.com (abhmp0005.oracle.com [141.146.116.11]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x1LEDrGg012590; Thu, 21 Feb 2019 14:13:54 GMT Received: from kadam (/197.157.34.176) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 21 Feb 2019 06:13:53 -0800 Date: Thu, 21 Feb 2019 17:13:47 +0300 From: Dan Carpenter To: wqu@suse.com Cc: linux-btrfs@vger.kernel.org Subject: [bug report] btrfs: locking: Add extra check in btrfs_init_new_buffer() to avoid deadlock Message-ID: <20190221141347.GA20330@kadam> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9173 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=3 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=777 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1902210104 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org [ This one is not actually your fault. It's the core code which is confusing. -dan ] Hello Qu Wenruo, The patch b72c3aba09a5: "btrfs: locking: Add extra check in btrfs_init_new_buffer() to avoid deadlock" from Aug 21, 2018, leads to the following static checker warning: fs/btrfs/extent-tree.c:8556 btrfs_init_new_buffer() warn: possible NULL dereference of 'buf' fs/btrfs/extent-tree.c 8540 static struct extent_buffer * 8541 btrfs_init_new_buffer(struct btrfs_trans_handle *trans, struct btrfs_root *root, 8542 u64 bytenr, int level, u64 owner) 8543 { 8544 struct btrfs_fs_info *fs_info = root->fs_info; 8545 struct extent_buffer *buf; 8546 8547 buf = btrfs_find_create_tree_block(fs_info, bytenr); The btrfs_find_create_tree_block() function either returns alloc_test_extent_buffer() which returns NULL on error or alloc_extent_buffer() which returns error pointers on error. It confuses static checkers and me also. 8548 if (IS_ERR(buf)) 8549 return buf; 8550 8551 /* 8552 * Extra safety check in case the extent tree is corrupted and extent 8553 * allocator chooses to use a tree block which is already used and 8554 * locked. 8555 */ --> 8556 if (buf->lock_owner == current->pid) { 8557 btrfs_err_rl(fs_info, 8558 "tree block %llu owner %llu already locked by pid=%d, extent tree corruption detected", 8559 buf->start, btrfs_header_owner(buf), current->pid); 8560 free_extent_buffer(buf); regards, dan carpenter