Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932304AbdC1Lmx (ORCPT ); Tue, 28 Mar 2017 07:42:53 -0400 Received: from mail-vk0-f48.google.com ([209.85.213.48]:33619 "EHLO mail-vk0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932115AbdC1Lmv (ORCPT ); Tue, 28 Mar 2017 07:42:51 -0400 MIME-Version: 1.0 In-Reply-To: References: <20170328095029.3500369-1-arnd@arndb.de> From: Ming Lei Date: Tue, 28 Mar 2017 19:42:44 +0800 Message-ID: Subject: Re: [PATCH] Revert "md: raid1: use bio helper in process_checks()" To: Arnd Bergmann Cc: Shaohua Li , NeilBrown , Jens Axboe , "colyli@suse.de" , Guoqing Jiang , Mike Christie , "open list:SOFTWARE RAID (Multiple Disks) SUPPORT" , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1657 Lines: 44 On Tue, Mar 28, 2017 at 7:35 PM, Arnd Bergmann wrote: > On Tue, Mar 28, 2017 at 12:44 PM, Ming Lei wrote: >> On Tue, Mar 28, 2017 at 5:49 PM, Arnd Bergmann wrote: >>> Commit 60928a91b0b3 ("md: raid1: use bio helper in process_checks()") >>> is probably correct, but I get a new compile-time warning after >>> it, and have trouble understanding what it fixes: >>> >>> drivers/md/raid1.c: In function 'sync_request_write': >>> drivers/md/raid1.c:2172:9: error: 'page_len$' may be used uninitialized in this function [-Werror=maybe-uninitialized] >>> if (memcmp(page_address(ppages[j]), >>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>> page_address(spages[j]), >>> ~~~~~~~~~~~~~~~~~~~~~~~~ >>> page_len[j])) >>> ~~~~~~~~~~~~ >>> drivers/md/raid1.c:2160:7: note: 'page_len$' was declared here >>> int page_len[RESYNC_PAGES]; >>> ^~~~~~~~ >>> >>> This reverts it to resolve the warning. >> >> Please try the following patch: >> >> https://lkml.org/lkml/2017/3/28/126 > > > That patch will certainly shut up the warning, but will also prevent > the compiler from warning when the function gets changed in some > way that actually leads to an uninitialized use of the page_len array, Why do you think that it leads to an uninitialized use of the page_len array? The following code does initialize the array well enough for future use: bio_for_each_segment_all(bi, sbio, j) page_len[j] = bi->bv_len; That is why we don't need to initialize the array explicitly, but just for killing the warning. Thanks, Ming Lei