linux-ext4 - Re: [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP

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Message-ID: <20171020214753.GA15733@linux.intel.com>
Date:   Fri, 20 Oct 2017 15:47:53 -0600
From:   Ross Zwisler <ross.zwisler@...ux.intel.com>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-fsdevel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        linux-api@...r.kernel.org
Subject: Re: [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and
 MAP_SYNC

On Thu, Oct 19, 2017 at 02:58:17PM +0200, Jan Kara wrote:
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  man2/mmap.2 | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/man2/mmap.2 b/man2/mmap.2
> index 47c3148653be..598ff0c64f7f 100644
> --- a/man2/mmap.2
> +++ b/man2/mmap.2
> @@ -125,6 +125,21 @@ are carried through to the underlying file.
>  to the underlying file requires the use of
>  .BR msync (2).)
>  .TP
> +.B MAP_SHARED_VALIDATE
> +The same as
> +.B MAP_SHARED
> +except that
> +.B MAP_SHARED
> +mappings ignore unknown flags in
> +.IR flags .
> +In contrast when creating mapping of
> +.B MAP_SHARED_VALIDATE
> +mapping type, the kernel verifies all passed flags are known and fails the
> +mapping with
> +.BR EOPNOTSUPP
> +otherwise. This mapping type is also required to be able to use some mapping
> +flags.
> +.TP

Some small nits:

I think you should maybe include a "(since Linux 4.15)" type note after the
MAP_SHARED_VALIDATE header.  You also need to update the following line:

       Both of these flags are described in POSIX.1-2001 and POSIX.1-2008.

Which used to refer to MAP_SYNC and MAP_PRIVATE.