From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@lst.de>
Date: Tue, 21 Jul 2020 18:01:43 +0200
Subject: [Cluster-devel] RFC: iomap write invalidation
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	<20200721151616.GA11074@lst.de> <20200721152754.GD7597@magnolia>
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On Tue, Jul 21, 2020 at 08:59:25AM -0700, Darrick J. Wong wrote:
> In the comment that precedes iomap_dio_rw() for the iomap version,

maybe let's just do that..

> ``direct_IO``
> 	called by the generic read/write routines to perform direct_IO -
> 	that is IO requests which bypass the page cache and transfer
> 	data directly between the storage and the application's address
> 	space.  This function can return -ENOTBLK to signal that it is
> 	necessary to fallback to buffered IO.  Note that
> 	blockdev_direct_IO and variants can also return -ENOTBLK.

->direct_IO is not used for iomap and various other implementations.
In fact it is a horrible hack that I've been trying to get rid of
for a while.