linux-kernel - Re: [PATCH] NOMMU: Pages allocated to a ramfs inode's pagecache may get wrongly discarded

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Message-Id: <20090313105618.43DF.A69D9226@jp.fujitsu.com>
Date:	Fri, 13 Mar 2009 11:03:02 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	kosaki.motohiro@...fujitsu.com,
	David Howells <dhowells@...hat.com>,
	torvalds@...ux-foundation.org, peterz@...radead.org,
	Enrik.Berkhan@...com, uclinux-dev@...inux.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] NOMMU: Pages allocated to a ramfs inode's pagecache may get wrongly discarded

Hi

> > Which as Peter points out:
> > 
> > 	The ramfs stuff is rather icky in that it adds the pages to the aging
> > 	list, marks them dirty, but does not provide a writeout method. 
> > 
> > 	This will make the paging code scan over them (continuously) trying to
> > 	clean them, failing that (lack of writeout method) and putting them back
> > 	on the list.
> > 
> > Not requiring the pages to be added to the LRU would be a really good idea.
> > They are not discardable, be it in MMU or NOMMU mode, except when the inode
> > itself is discarded.
> 
> Yep, these pages shouldn't be on the LRU at all.  I guess that will
> require some tweaks to core filemap.c code.

IMHO, UNEVICTABLE_LRU already does lru isolation.
only rest prblem is, getting rid of "depends on MMU" line in mm/Kconfig.

Am I missing anything?




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