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

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Message-ID: <CAKgNAkgtVryFb81QgzwPq8SD241yKDN1xNxOWUUQH9QBYV13SA@mail.gmail.com>
Date:   Thu, 12 Apr 2018 20:20:12 +0200
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Christoph Hellwig <hch@...radead.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        linux-nvdimm@...ts.01.org, Linux-MM <linux-mm@...ck.org>,
        Linux API <linux-api@...r.kernel.org>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        xfs <linux-xfs@...r.kernel.org>,
        "Darrick J . Wong" <darrick.wong@...cle.com>
Subject: Re: [PATCH] mmap.2: Add description of MAP_SHARED_VALIDATE and MAP_SYNC

Jan, Ross.

On 12 April 2018 at 16:22, Jan Kara <jack@...e.cz> wrote:
> Hello Michael!
>
> On Thu 12-04-18 15:00:49, Michael Kerrisk (man-pages) wrote:
>> Hello Jan,
>>
>> I have applied your patch, and tweaked the text a little, and pushed
>> the result to the git repo.
>
> Thanks!
>
>> > +.B MAP_SHARED
>> > +type will silently ignore this flag.
>> > +This flag is supported only for files supporting DAX (direct mapping of persistent
>> > +memory). For other files, creating mapping with this flag results in
>> > +.B EOPNOTSUPP
>> > +error. Shared file mappings with this flag provide the guarantee that while
>> > +some memory is writeably mapped in the address space of the process, it will
>> > +be visible in the same file at the same offset even after the system crashes or
>> > +is rebooted. This allows users of such mappings to make data modifications
>> > +persistent in a more efficient way using appropriate CPU instructions.
>>
>> It feels like there's a word missing/unclear wording in the previous
>> line, before "using". Without that word, the sentence feels a bit
>> ambiguous.
>>
>> Should it be:
>>
>> persistent in a more efficient way *through the use of* appropriate
>> CPU instructions.
>>
>> or:
>>
>> persistent in a more efficient way *than using* appropriate CPU instructions.
>>
>> ?
>>
>> Is suspect the first is correct, but need to check.
>
> Yes, the first is correct.

Thanks for both checking that phrasing. In the end I decided to reword
the sentence a bot more substantially:

              In  conjunction  with  the  use of appropriate CPU
              instructions, this provides users of such mappings
              with a more efficient way of making data modifica‐
              tions persistent.

Thanks,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/