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Message-ID: <20110912093058.GA3207@suse.de>
Date: Mon, 12 Sep 2011 10:34:34 +0100
From: Mel Gorman <mgorman@...e.de>
To: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Christoph Hellwig <hch@...radead.org>,
Linux-MM <linux-mm@...ck.org>,
Linux-Netdev <netdev@...r.kernel.org>,
Linux-NFS <linux-nfs@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
David Miller <davem@...emloft.net>,
Trond Myklebust <Trond.Myklebust@...app.com>,
Neil Brown <neilb@...e.de>
Subject: Re: [PATCH 03/10] mm: Add support for a filesystem to control swap
files
On Mon, Sep 12, 2011 at 11:04:45AM +0200, Peter Zijlstra wrote:
> On Fri, 2011-09-09 at 09:36 -0400, Christoph Hellwig wrote:
> > The equivalent of ->direct_IO should be used for both reads and writes.
>
> So the difference between DIO and swapIO is that swapIO needs the block
> map pinned in memory.. So at the very least you'll need those
> swap_{activate,deactivate} aops. The read/write-page thingies could
> indeed be shared with DIO.
>
I'm travelling at the moment so it'll be later in the week when I investigate
properly but I agree swap_[de|a]ctivate are still necessary. NFS does not
need to pin a block map but it's still necessary for calling xs_set_memalloc.
--
Mel Gorman
SUSE Labs
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