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

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Date:   Thu, 12 Apr 2018 16:22:14 +0200
From:   Jan Kara <jack@...e.cz>
To:     "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
Cc:     Jan Kara <jack@...e.cz>, 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

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.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR