[PATCH 4/7] xfs: use ranged writeback and invalidation for direct IO

[Christoph Hellwig]

On Thu, Aug 28, 2014 at 09:49:08PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner at redhat.com>
> 
> Now we are not doing silly things with dirtying buffers beyond EOF
> and using invalidation correctly, we can finally reduce the ranges of
> writeback and invalidation used by direct IO to match that of the IO
> being issued.
> 
> Bring the writeback and invalidation ranges back to match the
> generic direct IO code - this will greatly reduce the perturbation
> of cached data when direct IO and buffered IO are mixed, but still
> provide the same buffered vs direct IO coherency behaviour we
> currently have.
> 
> Signed-off-by: Dave Chinner <dchinner at redhat.com>

Looks correct, although I wonder if it's really worth the risk exposing
us to the crazy details of the page cache invalidation range notations..

Reviewed-by: Christoph Hellwig <hch at lst.de>