Re: [PATCH 7/8] xfs: Support for transparent PUD pages

From: Matthew Wilcox <willy@linux.intel.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>,
	linux-mm@kvack.org, linux-nvdimm@lists.01.org,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	x86@kernel.org
Subject: Re: [PATCH 7/8] xfs: Support for transparent PUD pages
Date: Sat, 2 Jan 2016 11:43:09 -0500	[thread overview]
Message-ID: <20160102164309.GK2457@linux.intel.com> (raw)
In-Reply-To: <20151230233007.GA6682@dastard>

On Thu, Dec 31, 2015 at 10:30:27AM +1100, Dave Chinner wrote:
> > @@ -1637,6 +1669,7 @@ xfs_filemap_pfn_mkwrite(
> >  static const struct vm_operations_struct xfs_file_vm_ops = {
> >  	.fault		= xfs_filemap_fault,
> >  	.pmd_fault	= xfs_filemap_pmd_fault,
> > +	.pud_fault	= xfs_filemap_pud_fault,
> 
> This is getting silly - we now have 3 different page fault handlers
> that all do exactly the same thing. Please abstract this so that the
> page/pmd/pud is transparent and gets passed through to the generic
> handler code that then handles the differences between page/pmd/pud
> internally.
> 
> This, after all, is the original reason that the ->fault handler was
> introduced....

I agree that it's silly, but this is the direction I was asked to go in by
the MM people at the last MM summit.  There was agreement that this needs
to be abstracted, but that should be left for a separate cleanup round.
I did prototype something I called a vpte (virtual pte), but that's very
much on the back burner for now.

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