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Date: Wed, 24 Nov 2021 07:36:05 +0100
From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Subject: Re: [PATCH 06/29] dax: move the partition alignment check into
 fs_dax_get_by_bdev
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On Tue, Nov 23, 2021 at 02:25:55PM -0800, Darrick J. Wong wrote:
> > +	if ((get_start_sect(bdev) * SECTOR_SIZE) % PAGE_SIZE ||
> > +	    (bdev_nr_sectors(bdev) * SECTOR_SIZE) % PAGE_SIZE) {
> 
> Do we have to be careful about 64-bit division here, or do we not
> support DAX on 32-bit?

I can't find anything in the Kconfig limiting DAX to 32-bit.  But
then again the existing code has divisions like this, so the compiler
is probably smart enough to turn them into shifts.

> > +		pr_info("%pg: error: unaligned partition for dax\n", bdev);
> 
> I also wonder if this should be ratelimited...?

This happens once (or maybe three times for XFS with rt and log devices)
at mount time, so I see no need for a ratelimit.