Re: [PATCH 3/3] xfs: convert buffer cache to use high order folios

From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-xfs@vger.kernel.org, willy@infradead.org, linux-mm@kvack.org
Subject: Re: [PATCH 3/3] xfs: convert buffer cache to use high order folios
Date: Mon, 22 Jan 2024 22:57:44 +1100	[thread overview]
Message-ID: <Za5YOCbA2rJTjdqp@dread.disaster.area> (raw)
In-Reply-To: <Za4PI5h2BQ8DoPrN@infradead.org>

On Sun, Jan 21, 2024 at 10:45:55PM -0800, Christoph Hellwig wrote:
> > +	int		length = BBTOB(bp->b_length);
> > +	int		order;
> > +
> > +	order = ilog2(length);
> > +	if ((1 << order) < length)
> > +		order = ilog2(length - 1) + 1;
> > +
> > +	if (order <= PAGE_SHIFT)
> > +		order = 0;
> > +	else
> > +		order -= PAGE_SHIFT;
> 
> Shouldn't this simply use get_order()?

Huh. Yes, it should.

I went looking for a helper and didn't find one in the mm or folio
code. Now you point it out, I find that it is in it's own asm header
(include/asm-generic/getorder.h) so it's no wonder I didn't find
it.

Why is it in include/asm-generic? There's nothing asm related
to that function or it's implementation....

-Dave.
-- 
Dave Chinner
david@fromorbit.com