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:

quoted

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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