Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <1582889550-9101-1-git-send-email-kernelfans@gmail.com>
 <1582889550-9101-3-git-send-email-kernelfans@gmail.com> <20200228223446.GA4658@iweiny-DESK2.sc.intel.com>
In-Reply-To: <20200228223446.GA4658@iweiny-DESK2.sc.intel.com>
From:   Pingfan Liu <kernelfans@gmail.com>
Date:   Mon, 2 Mar 2020 10:28:45 +0800
Message-ID: <CAFgQCTuK5nTrm_ijohhCJyvUmiVXueGrxbqqM381ViZyx0_MxA@mail.gmail.com>
Subject: Re: [PATCHv5 2/3] mm/gup: fix omission of check on FOLL_LONGTERM in
 gup fast path
To:     Ira Weiny <ira.weiny@intel.com>
Cc:     Linux-MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Matthew Wilcox <willy@infradead.org>,
        John Hubbard <jhubbard@nvidia.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Christoph Hellwig <hch@infradead.org>,
        Shuah Khan <shuah@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Sat, Feb 29, 2020 at 6:34 AM Ira Weiny <ira.weiny@intel.com> wrote:
>
> On Fri, Feb 28, 2020 at 07:32:29PM +0800, Pingfan Liu wrote:
> > FOLL_LONGTERM suggests a pin which is going to be given to hardware and
> > can't move. It would truncate CMA permanently and should be excluded.
>
> I don't understand what is 'truncated' here?
a pinned page will truncate a continuous area, and prevent CMA to
reclaim the continuous area.
>
> I generally agree with Jason that this is going to be confusing to the user.
Please see the reply in anothe mail.

Thanks,
Pingfan
[...]