From: Matthew Wilcox <mawilcox@microsoft.com>
Subject: RE: [PATCH v2 2/9] ext2: tell DAX the size of allocation holes
Date: Sat, 10 Sep 2016 15:55:17 +0000
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Cc: Ross Zwisler <ross.zwisler@linux.intel.com>, Theodore Ts'o
	<tytso@mit.edu>, "linux-kernel@vger.kernel.org"
	<linux-kernel@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>,
	"linux-nvdimm@ml01.01.org" <linux-nvdimm@ml01.01.org>, Dave Chinner
	<david@fromorbit.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>, "Andreas
 Dilger" <adilger.kernel@dilger.ca>, Alexander Viro <viro@zeniv.linux.org.uk>,
	Jan Kara <jack@suse.com>, "linux-fsdevel@vger.kernel.org"
	<linux-fsdevel@vger.kernel.org>, "linux-ext4@vger.kernel.org"
	<linux-ext4@vger.kernel.org>
To: Christoph Hellwig <hch@infradead.org>
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From: Christoph Hellwig [mailto:hch@infradead.org]
> Either way we need to get rid of buffer_heads, and another aop that is en=
tirely
> caller specific is unaceptable.

I finally figured out what you actually meant by this.  You mean that inste=
ad of having an aop->populate_pfn, you want to define a populate_pfn_t call=
back and pass it in.

Something like this:

int ext2_populate_pfn(struct address_space *mapping, pgoff_t pgoff)
{
	struct iomap iomap;
	...
	return dax_populate_pfn(mapping, pgoff, &iomap);
}

int ext2_dax_fault(vma, vmf)
{
	...
	ret =3D dax_fault(vma, vmf, ext2_populate_pfn);
	...
}

I don't have a problem with that.  I'll work up something along those lines=
 next week.

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