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Date: Thu, 28 Dec 2000 12:44:14 -0500
From: Chris Mason <mason@suse.com>
To: Daniel Phillips <phillips@innominate.de>,
        Rik van Riel <riel@conectiva.com.br>
cc: Linus Torvalds <torvalds@transmeta.com>, linux-kernel@vger.kernel.org
Subject: Re: innd mmap bug in 2.4.0-test12
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On Thursday, December 28, 2000 16:15:48 +0100 Daniel Phillips
<phillips@innominate.de> wrote:

> On Thu, 28 Dec 2000, Rik van Riel wrote:
>> On Thu, 28 Dec 2000, Daniel Phillips wrote:
>> 
>> > It's logical that PageDirty should never be get for ramfs,
>> 
>> No. Not setting PageDirty will cause the system to move the
>> page to the inactive_clean list and happily reclaim your data.
>> 
>> We _have to_ use something like PageDirty for this, and
>> checking for the ->writepage method will even allow us to
>> do stuff like dynamically switching swapping support for
>> ramfs on/off (or other funny things).
> 
> You're suggesting using the absence of a method as a kind of flag, but
> the code is really too full of obscure stuff like that already.
> 
> How about taking an extra user on the ramfs pages instead.  It doesn't
> sound right to set PageDirty when you are not requesting IO.

I think a dirty page without a writepage func seems a bit broken.  How
about we give ramfs a writepage func that just returns 1.  That way nobody
does any special if (ramfs_page(page)) kinds of tests...

-chris

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