linux-kernel - Re: [PATCH v5 4/5] fs, xfs: introduce MAP_DIRECT for creating block-map-atomic file ranges

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Message-ID: <CAPcyv4ioikcZvVqZQZmy9kU6tSX5zRgOqJTKHZLxes2TtT9UkA@mail.gmail.com>
Date:   Wed, 16 Aug 2017 09:32:48 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, Jan Kara <jack@...e.cz>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        Linux API <linux-api@...r.kernel.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        Dave Chinner <david@...morbit.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-xfs@...r.kernel.org, Linux MM <linux-mm@...ck.org>,
        Jeff Moyer <jmoyer@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v5 4/5] fs, xfs: introduce MAP_DIRECT for creating
 block-map-atomic file ranges

On Wed, Aug 16, 2017 at 9:29 AM, Dan Williams <dan.j.williams@...el.com> wrote:
> On Wed, Aug 16, 2017 at 4:12 AM, Kirill A. Shutemov
> <kirill@...temov.name> wrote:
>> On Wed, Aug 16, 2017 at 12:44:28AM -0700, Dan Williams wrote:
>>> @@ -1411,6 +1422,9 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
>>>
>>>                       /* fall through */
>>>               case MAP_PRIVATE:
>>> +                     if ((flags & (MAP_PRIVATE|MAP_DIRECT))
>>> +                                     == (MAP_PRIVATE|MAP_DIRECT))
>>> +                             return -EINVAL;
>>
>> We've already checked for MAP_PRIVATE in this codepath. Simple (flags &
>> MAP_DIRECT) would be enough.
>
> True, willl fix.

Actually, no, because of the fallthrough we need to check MAP_SHARED
or MAP_PRIVATE along with MAP_DIRECT.