Re: [PATCH 06/29] dax: move the partition alignment check into fs_dax_get_by_bdev

Christoph Hellwig
2021-11-24T06:36:14Z

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.