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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 320F6C28D13 for ; Mon, 22 Aug 2022 20:53:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 687E08D0001; Mon, 22 Aug 2022 16:53:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6370E6B0074; Mon, 22 Aug 2022 16:53:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4FF088D0001; Mon, 22 Aug 2022 16:53:19 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 3E0256B0073 for ; Mon, 22 Aug 2022 16:53:19 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 05FC6AB339 for ; Mon, 22 Aug 2022 20:53:19 +0000 (UTC) X-FDA: 79828428918.26.8B0AAEB Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf02.hostedemail.com (Postfix) with ESMTP id A20FB80004 for ; Mon, 22 Aug 2022 20:53:18 +0000 (UTC) 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 AA729612EE; Mon, 22 Aug 2022 20:53:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EF223C433D6; Mon, 22 Aug 2022 20:53:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1661201597; bh=0XYtpJeYJIHTuAMCFA1D+7TBHuPnWebnHkoxH17FW/o=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=raKsoKUJ3D+YKLX5I0Fp20KUC1w4f8jQqCeSn1QA75zKUowJi/lu3eE0+/SxDaoGw IkfWtk48VuSEG1mMMlPer9zM8rLLF+Y790dYCzMbAV8R2vq7hS5px34QAy9JALT+Z7 9uCYMBdmhghHTXgGrvVEg0HIof+j5onbbYkKZVpA= Date: Mon, 22 Aug 2022 13:53:16 -0700 From: Andrew Morton To: Rolf Eike Beer Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/6] mm: pagewalk: make error checks more obvious Message-Id: <20220822135316.ee37696392ff756b1c810059@linux-foundation.org> In-Reply-To: <2203731.iZASKD2KPV@devpool047> References: <3200642.44csPzL39Z@devpool047> <2203731.iZASKD2KPV@devpool047> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661201598; a=rsa-sha256; cv=none; b=s+qx81dZJ3nY2YEa6pF5rmoIaVg1+TNUvLiVRfpYH1b6YbXgHB+lyB8edLyljBHtABDQjV Kqi7dfYr0Jc0RmIyK/Qod0FVEGTwBybd2OTfnU3ZNzwwugteRLl+qF1jL5ySruTG0DZQEE 7T8EKV347cZWAc8rFmlVH0tZxT8Fs0g= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=raKsoKUJ; spf=pass (imf02.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661201598; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=yBteOSxkvww9KUzjV1iXMiUqKa+qSLWTOh5s76WQQ/M=; b=cdZ4qEjKyMDyCG7Z6ACD6wWBQP/7XDQ2/O2hSuCeZNvtBgSxk43UaLZHA3MwpV+LoALbDa I9354TmeWKGxbVqRsRrUVtISvdGOOX06nvoNnT5BEqkuVG27q8D7RmDZclkPsdkVKLK/Xu oFwoCfn6oaHfm+d9xrIg78n4KvG/5CQ= Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=raKsoKUJ; spf=pass (imf02.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A20FB80004 X-Stat-Signature: puiweo1j46rx1nrdprrjynitdr6cjfc4 X-Rspam-User: X-HE-Tag: 1661201598-154321 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 22 Aug 2022 15:00:05 +0200 Rolf Eike Beer wrote: > The err variable only needs to be checked when it was assigned directly > before, it is not carried on to any later checks. Move the checks into the > same "if" conditions where they are assigned. Also just return the error at > the relevant places. While at it move these err variables to a more local > scope at some places. > > ... > > @@ -593,16 +608,15 @@ int walk_page_mapping(struct address_space *mapping, pgoff_t first_index, > walk.mm = vma->vm_mm; > > err = walk_page_test(vma->vm_start, vma->vm_end, &walk); > - if (err > 0) { > - err = 0; > - break; > - } else if (err < 0) > - break; > + if (err > 0) > + return 0; > + else if (err < 0) > + return err; > > err = __walk_page_range(start_addr, end_addr, &walk); > if (err) > - break; > + return err; > } > > - return err; > + return 0; > } I'm not really a fan of multiple return points - it tends to lead to locking/resource leaks as the code evolves. I don't really think it's worth redoing the patch for this reason though; the rest looks good.