From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933291AbeBVQEg (ORCPT ); Thu, 22 Feb 2018 11:04:36 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:39004 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933029AbeBVQEe (ORCPT ); Thu, 22 Feb 2018 11:04:34 -0500 Date: Thu, 22 Feb 2018 11:04:32 -0500 From: Mike Snitzer To: Arnd Bergmann Cc: Alasdair Kergon , dm-devel@redhat.com, Mikulas Patocka , Ingo Molnar , Aliaksei Karaliou , Jens Axboe , Jan Kara , Dan Carpenter , Mark Rutland , Eric Biggers , linux-kernel@vger.kernel.org Subject: Re: dm-bufio: avoid false-positive Wmaybe-uninitialized warning Message-ID: <20180222160432.GA16971@redhat.com> References: <20180222155627.1800948-1-arnd@arndb.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180222155627.1800948-1-arnd@arndb.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 22 2018 at 10:56am -0500, Arnd Bergmann wrote: > gcc-6.3 and earlier show a new warning after a seemingly unrelated change > to the arm64 PAGE_KERNEL definition: > > In file included from drivers/md/dm-bufio.c:14:0: > drivers/md/dm-bufio.c: In function 'alloc_buffer': > include/linux/sched/mm.h:182:56: warning: 'noio_flag' may be used uninitialized in this function [-Wmaybe-uninitialized] > current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags; > ^ > > The same warning happened earlier on linux-3.18 for MIPS and I did a > workaround for that, but now it's come back. > > gcc-7 and newer are apparently smart enough to figure this out, and > other architectures don't show it, so the best I could come up with is > to rework the caller slightly in a way that makes it obvious enough to > all arm64 compilers what is happening here. > > Fixes: 41acec624087 ("arm64: kpti: Make use of nG dependent on arm64_kernel_unmapped_at_el0()") > Link: https://patchwork.kernel.org/patch/9692829/ > Signed-off-by: Arnd Bergmann > --- > drivers/md/dm-bufio.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c > index 414c9af54ded..e7ad6fc6a5ea 100644 > --- a/drivers/md/dm-bufio.c > +++ b/drivers/md/dm-bufio.c > @@ -413,13 +413,13 @@ static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask, > * as if GFP_NOIO was specified. > */ > > - if (gfp_mask & __GFP_NORETRY) > + if (gfp_mask & __GFP_NORETRY) { > noio_flag = memalloc_noio_save(); > - > - ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); > - > - if (gfp_mask & __GFP_NORETRY) > + ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); > memalloc_noio_restore(noio_flag); > + } else { > + ptr = __vmalloc(c->block_size, gfp_mask, PAGE_KERNEL); > + } > > return ptr; > } Mikulas already sent a fix for this: https://patchwork.kernel.org/patch/10211631/ But I like yours a bit better, though I'll likely move the declaration of 'noio_flag' temporary inside the conditional. Anyway, I'll get this fixed up shortly, thanks. Mike