Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756760AbaGNRay (ORCPT ); Mon, 14 Jul 2014 13:30:54 -0400 Received: from mail-wg0-f44.google.com ([74.125.82.44]:57344 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756050AbaGNRaq (ORCPT ); Mon, 14 Jul 2014 13:30:46 -0400 Message-ID: <53C413C3.7050308@kernel.dk> Date: Mon, 14 Jul 2014 19:30:43 +0200 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Benjamin LaHaise , Linus Torvalds , Robert Elliot CC: linux-aio@kvack.org, linux-kernel@vger.kernel.org, Christoph Hellwig , stable@vger.kernel.org Subject: Re: [PATCH] aio: protect reqs_available updates from changes in interrupt handlers References: <20140714171227.GC11326@kvack.org> In-Reply-To: <20140714171227.GC11326@kvack.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014-07-14 19:12, Benjamin LaHaise wrote: > Hello everyone, > > Please pull the following commit (263782c1c95bbddbb022dc092fd89a36bb8d5577) > from git://git.kvack.org/aio-fixes.git to fix an aio bug reported by Robert > Elliot. > --- > As of commit f8567a3845ac05bb28f3c1b478ef752762bd39ef it is now possible to > have put_reqs_available() called from irq context. While put_reqs_available() > is per cpu, it did not protect itself from interrupts on the same CPU. This > lead to aio_complete() corrupting the available io requests count when run > under a heavy O_DIRECT workloads as reported by Robert Elliott. Fix this by > disabling irq updates around the per cpu batch updates of reqs_available. > > Many thanks to Robert and folks for testing and tracking this down. > > Reported-by: Robert Elliot > Tested-by: Robert Elliot > Signed-off-by: Benjamin LaHaise > Cc: Jens Axboe , Christoph Hellwig > Cc: stable@vger.kenel.org > --- > fs/aio.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/fs/aio.c b/fs/aio.c > index 955947e..1c9c5f0 100644 > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -830,16 +830,20 @@ void exit_aio(struct mm_struct *mm) > static void put_reqs_available(struct kioctx *ctx, unsigned nr) > { > struct kioctx_cpu *kcpu; > + unsigned long flags; > > preempt_disable(); > kcpu = this_cpu_ptr(ctx->cpu); > > + local_irq_save(flags); > kcpu->reqs_available += nr; Why not just makes this: local_irq_save(flags); kcpu = this_put_ptr(...); ... and get rid of the preemption bits, it's a bit redundant now you need to kill local interrupts anyway. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/