Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751192AbdCQMKA (ORCPT ); Fri, 17 Mar 2017 08:10:00 -0400 Received: from merlin.infradead.org ([205.233.59.134]:43684 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750926AbdCQMJy (ORCPT ); Fri, 17 Mar 2017 08:09:54 -0400 Date: Fri, 17 Mar 2017 13:08:37 +0100 From: Peter Zijlstra To: Michael Davidson Cc: Michal Marek , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Herbert Xu , "David S. Miller" , Shaohua Li , Alexander Potapenko , Dmitry Vyukov , Matthias Kaehlcke , x86@kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, linux-raid@vger.kernel.org Subject: Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Message-ID: <20170317120837.pr74cv3xuj7qpoin@hirez.programming.kicks-ass.net> References: <20170317001520.85223-1-md@google.com> <20170317001520.85223-7-md@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170317001520.85223-7-md@google.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1224 Lines: 32 On Thu, Mar 16, 2017 at 05:15:19PM -0700, Michael Davidson wrote: > Replace a variable length array in a struct by allocating > the memory for the entire struct in a char array on the stack. > > Signed-off-by: Michael Davidson > --- > drivers/md/raid10.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c > index 063c43d83b72..158ebdff782c 100644 > --- a/drivers/md/raid10.c > +++ b/drivers/md/raid10.c > @@ -4654,11 +4654,10 @@ static int handle_reshape_read_error(struct mddev *mddev, > /* Use sync reads to get the blocks from somewhere else */ > int sectors = r10_bio->sectors; > struct r10conf *conf = mddev->private; > - struct { > - struct r10bio r10_bio; > - struct r10dev devs[conf->copies]; > - } on_stack; > - struct r10bio *r10b = &on_stack.r10_bio; > + char on_stack_r10_bio[sizeof(struct r10bio) + > + conf->copies * sizeof(struct r10dev)] > + __aligned(__alignof__(struct r10bio)); > + struct r10bio *r10b = (struct r10bio *)on_stack_r10_bio; > int slot = 0; > int idx = 0; > struct bio_vec *bvec = r10_bio->master_bio->bi_io_vec; That's disgusting. Why not fix LLVM to support this?