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Date:   Tue, 18 Apr 2023 14:41:07 -0700 (PDT)
From:   Hugh Dickins <hughd@google.com>
To:     Luis Chamberlain <mcgrof@kernel.org>
cc:     Hugh Dickins <hughd@google.com>, akpm@linux-foundation.org,
        willy@infradead.org, brauner@kernel.org, linux-mm@kvack.org,
        p.raghav@samsung.com, da.gomez@samsung.com,
        a.manzanares@samsung.com, dave@stgolabs.net, yosryahmed@google.com,
        keescook@chromium.org, patches@lists.linux.dev,
        linux-kernel@vger.kernel.org, David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v2 5/6] shmem: update documentation
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References: <20230309230545.2930737-1-mcgrof@kernel.org> <20230309230545.2930737-6-mcgrof@kernel.org> <a4afef5c-27e4-5e67-9771-374132db61f8@google.com> <ZD8JgfphE+HWCGve@bombadil.infradead.org>
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On Tue, 18 Apr 2023, Luis Chamberlain wrote:
> On Mon, Apr 17, 2023 at 10:29:59PM -0700, Hugh Dickins wrote:
> > On Thu, 9 Mar 2023, Luis Chamberlain wrote:
> > 
> > > Update the docs to reflect a bit better why some folks prefer tmpfs
> > > over ramfs and clarify a bit more about the difference between brd
> > > ramdisks.
> > > 
> > > While at it, add THP docs for tmpfs, both the mount options and the
> > > sysfs file.
> > 
> > Okay: the original canonical reference for THP options on tmpfs has
> > been Documentation/admin-guide/mm/transhuge.rst.  You're right that
> > they would be helpful here too: IIRC (but I might well be confusing
> > with our Google tree) we used to have them documented in both places,
> > but grew tired of keeping the two in synch.  You're volunteering to
> > do so! so please check now that they tell the same story.
> 
> Hehe. Sure, we should just make one point to the other. Which one should
> be the authoritive source?

Documentation/admin-guide/mm/transhuge.rst has been the authoritative
source up until this patch, so I suggest it remain so; but good if you
point to it from this Doc - unless in reading it you find that actually
its account is wrong.  (Haha, it refers to fadvise too, never mind that.)

But the man page is more important than either, so it would be good to
point to that too.  Mention the "huge=" option in this document, but
point to elsewhere for the detail of its values.

> 
> > But nowadays, "man 5 tmpfs" is much more important (and that might
> > give you a hint for what needs to be done after this series goes into
> > 6.4-rc - and I wonder if there are tmpfs manpage updates needed from
> > Christian for idmapped too? or already taken care of?).
> 
> Sure, what's the man page git tree to use? I can do that once these
> documents are settled as well. I'll send fixes.

Thanks. I'll look up a mail to lkml from Alejandro and forward that
to you, it has the details.

Hugh