From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-f70.google.com (mail-vk0-f70.google.com [209.85.213.70]) by kanga.kvack.org (Postfix) with ESMTP id B42D46B000D for ; Wed, 21 Mar 2018 18:54:06 -0400 (EDT) Received: by mail-vk0-f70.google.com with SMTP id z186so4434360vkd.15 for ; Wed, 21 Mar 2018 15:54:06 -0700 (PDT) Received: from aserp2130.oracle.com (aserp2130.oracle.com. [141.146.126.79]) by mx.google.com with ESMTPS id s28si1848832uac.350.2018.03.21.15.54.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 21 Mar 2018 15:54:05 -0700 (PDT) Subject: Re: [PATCH v2] shm: add split function to shm_vm_ops References: <0d24f817-303a-7b4d-4603-b2d14e4b391a@oracle.com> <20180321161314.7711-1-mike.kravetz@oracle.com> <20180321135618.f3d4a0c30d9f413ce4092ddf@linux-foundation.org> From: Mike Kravetz Message-ID: <051fa302-f4c2-cc90-7a12-eaedfa806e73@oracle.com> Date: Wed, 21 Mar 2018 15:53:56 -0700 MIME-Version: 1.0 In-Reply-To: <20180321135618.f3d4a0c30d9f413ce4092ddf@linux-foundation.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Laurent Dufour , Michal Hocko , Dan Williams , Andrea Arcangeli , stable@vger.kernel.org On 03/21/2018 01:56 PM, Andrew Morton wrote: > On Wed, 21 Mar 2018 09:13:14 -0700 Mike Kravetz wrote: >> >> +static int shm_split(struct vm_area_struct *vma, unsigned long addr) >> +{ >> + struct file *file = vma->vm_file; >> + struct shm_file_data *sfd = shm_file_data(file); >> + >> + if (sfd->vm_ops && sfd->vm_ops->split) >> + return sfd->vm_ops->split(vma, addr); > > This will be the only site which tests for NULL shm_file_data.vm_ops. > It's a can't-happen, methinks. You are correct, thanks for catching this. > > I think I'll leave it as it is for now and will queue up a non-urgent > patch: > > > > From: Andrew Morton > Subject: ipc/shm.c: shm_split(): remove unneeded test for NULL shm_file_data.vm_ops > > This was added by the recent "ipc/shm.c: add split function to > shm_vm_ops", but it is not necessary. > > Cc: Laurent Dufour > Cc: Dan Williams > Cc: Michal Hocko > Cc: Davidlohr Bueso > Cc: Manfred Spraul > Signed-off-by: Andrew Morton Looks good, FWIW Reviewed-by: Mike Kravetz -- Mike Kravetz > --- > > ipc/shm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff -puN ipc/shm.c~ipc-shmc-shm_split-remove-unneeded-test-for-null-shm_file_datavm_ops ipc/shm.c > --- a/ipc/shm.c~ipc-shmc-shm_split-remove-unneeded-test-for-null-shm_file_datavm_ops > +++ a/ipc/shm.c > @@ -391,7 +391,7 @@ static int shm_split(struct vm_area_stru > struct file *file = vma->vm_file; > struct shm_file_data *sfd = shm_file_data(file); > > - if (sfd->vm_ops && sfd->vm_ops->split) > + if (sfd->vm_ops->split) > return sfd->vm_ops->split(vma, addr); > > return 0; > _ >