From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757088AbbFQSoC (ORCPT ); Wed, 17 Jun 2015 14:44:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46780 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755154AbbFQSnz (ORCPT ); Wed, 17 Jun 2015 14:43:55 -0400 Date: Wed, 17 Jun 2015 20:42:45 +0200 From: Oleg Nesterov To: Jeff Moyer Cc: Al Viro , Andrew Morton , Benjamin LaHaise , linux-aio@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] aio_ring_remap: turn the ctx->dead check into WARN_ON() Message-ID: <20150617184245.GA9295@redhat.com> References: <20150616230426.GA15790@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/17, Jeff Moyer wrote: > > Oleg Nesterov writes: > > > atomic_read(&ctx->dead) in aio_ring_remap() looks confusing. > > kill_ioctx() sets ctx->dead and removes ctx from ->ioctx_table > > "atomically" under mm->ioctx_lock, so aio_ring_remap() can never > > see a dead ctx. > > > > If we really want this check, we should put it under WARN_ON() > > and it should not depend on aio_ring_file == file. > > Just get rid of the check, it doesn't make any sense. Yes, agreed, will redo/resend tomorrow. Thanks! > -Jeff > > > > > Signed-off-by: Oleg Nesterov > > --- > > fs/aio.c | 16 ++++++++-------- > > 1 files changed, 8 insertions(+), 8 deletions(-) > > > > diff --git a/fs/aio.c b/fs/aio.c > > index 480440f..0693333 100644 > > --- a/fs/aio.c > > +++ b/fs/aio.c > > @@ -325,14 +325,14 @@ static int aio_ring_remap(struct file *file, struct vm_area_struct *vma) > > rcu_read_lock(); > > table = rcu_dereference(mm->ioctx_table); > > for (i = 0; i < table->nr; i++) { > > - struct kioctx *ctx; > > - > > - ctx = table->table[i]; > > - if (ctx && ctx->aio_ring_file == file) { > > - if (!atomic_read(&ctx->dead)) { > > - ctx->user_id = ctx->mmap_base = vma->vm_start; > > - res = 0; > > - } > > + struct kioctx *ctx = table->table[i]; > > + > > + if (!ctx || WARN_ON(atomic_read(&ctx->dead))) > > + continue; > > + > > + if (ctx->aio_ring_file == file) { > > + ctx->user_id = ctx->mmap_base = vma->vm_start; > > + res = 0; > > break; > > } > > }