From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f197.google.com (mail-qk0-f197.google.com [209.85.220.197]) by kanga.kvack.org (Postfix) with ESMTP id 70C2D6B02C3 for ; Fri, 21 Jul 2017 17:18:46 -0400 (EDT) Received: by mail-qk0-f197.google.com with SMTP id s18so27956528qks.4 for ; Fri, 21 Jul 2017 14:18:46 -0700 (PDT) Received: from aserp1040.oracle.com (aserp1040.oracle.com. [141.146.126.69]) by mx.google.com with ESMTPS id q27si4295769qtq.519.2017.07.21.14.18.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 21 Jul 2017 14:18:45 -0700 (PDT) Subject: Re: [PATCH v2] mm/mremap: Fail map duplication attempts for private mappings References: <20170720082058.GF9058@dhcp22.suse.cz> <1500583079-26504-1-git-send-email-mike.kravetz@oracle.com> <20170721143644.GC5944@dhcp22.suse.cz> From: Mike Kravetz Message-ID: Date: Fri, 21 Jul 2017 14:18:31 -0700 MIME-Version: 1.0 In-Reply-To: <20170721143644.GC5944@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, Linux API , linux-kernel@vger.kernel.org, Andrew Morton , Andrea Arcangeli , Aaron Lu , "Kirill A . Shutemov" , Vlastimil Babka , Anshuman Khandual On 07/21/2017 07:36 AM, Michal Hocko wrote: > On Thu 20-07-17 13:37:59, Mike Kravetz wrote: >> mremap will create a 'duplicate' mapping if old_size == 0 is >> specified. Such duplicate mappings make no sense for private >> mappings. > > sorry for the nit picking but this is not true strictly speaking. > It makes some sense, arguably (e.g. take an atomic snapshot of the > mapping). It doesn't make any sense with the _current_ implementation. > >> If duplication is attempted for a private mapping, >> mremap creates a separate private mapping unrelated to the >> original mapping and makes no modifications to the original. >> This is contrary to the purpose of mremap which should return >> a mapping which is in some way related to the original. >> >> Therefore, return EINVAL in the case where if an attempt is >> made to duplicate a private mapping. Also, print a warning >> message (once) if such an attempt is made. >> >> Signed-off-by: Mike Kravetz > > I do not insist on the comment update suggested > http://lkml.kernel.org/r/20170720082058.GF9058@dhcp22.suse.cz > but I would appreciate it... > > Other than that looks reasonably to me > > Acked-by: Michal Hocko My apologies. I overlooked your comment about the comment when creating the patch. Below is the patch with commit message and comment updated.