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=-1.2 required=3.0 tests=BIGNUM_EMAILS, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,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 1785AC10F11 for ; Wed, 24 Apr 2019 13:40:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DAED221773 for ; Wed, 24 Apr 2019 13:40:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730516AbfDXNkx (ORCPT ); Wed, 24 Apr 2019 09:40:53 -0400 Received: from mx2.suse.de ([195.135.220.15]:36056 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727755AbfDXNkx (ORCPT ); Wed, 24 Apr 2019 09:40:53 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 6E24DAE03; Wed, 24 Apr 2019 13:40:52 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id C2447DA85E; Wed, 24 Apr 2019 15:41:55 +0200 (CEST) Date: Wed, 24 Apr 2019 15:41:53 +0200 From: David Sterba To: Dan Carpenter Cc: dsterba@suse.com, linux-btrfs@vger.kernel.org Subject: Re: [bug report] btrfs: get fs_info from block group in write_pinned_extent_entries Message-ID: <20190424134153.GW20156@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Dan Carpenter , dsterba@suse.com, linux-btrfs@vger.kernel.org References: <20190423141426.GA9375@mwanda> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190423141426.GA9375@mwanda> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Wed, Apr 24, 2019 at 12:52:54PM +0300, Dan Carpenter wrote: > Hello David Sterba, > > This is a semi-automatic email about new static checker warnings. > > The patch b4c7c5d50791: "btrfs: get fs_info from block group in > write_pinned_extent_entries" from Mar 20, 2019, leads to the > following Smatch complaint: > > fs/btrfs/free-space-cache.c:1052 write_pinned_extent_entries() > warn: variable dereferenced before check 'block_group' (see line 1047) > > fs/btrfs/free-space-cache.c > 1046 { > 1047 struct btrfs_fs_info *fs_info = block_group->fs_info; > ^^^^^^^^^^^^^^^^^^^^ > The patch adds a dereference > > 1048 u64 start, extent_start, extent_end, len; > 1049 struct extent_io_tree *unpin = NULL; > 1050 int ret; > 1051 > 1052 if (!block_group) > ^^^^^^^^^^^ > But the old code assumed it could be NULL. Thanks for the report. The pointer will never be null as the caller will pass a valid pointer, so the dereference is ok. This extra check is redundant so I'll remove it.