Re: [PATCH] dax: Fix last_page check in __bdev_dax_supported()

[Dan Williams]

On Thu, May 16, 2019 at 10:37 PM Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> wrote:
>
> Dan Williams <dan.j.williams@xxxxxxxxx> writes:
>
> > On Wed, May 15, 2019 at 10:55 PM Vaibhav Jain <vaibhav@xxxxxxxxxxxxx> wrote:
> >>
> >> Presently __bdev_dax_supported() checks if first sector of last
> >> page ( last_page ) on the block device is aligned to page
> >> boundary. However the code to compute 'last_page' assumes that there
> >> are 8 sectors/page assuming a 4K page-size.
> >>
> >> This assumption breaks on architectures which use a different page
> >> size specifically PPC64 where page-size == 64K. Hence a warning is
> >> seen while trying to mount a xfs/ext4 file-system with dax enabled:
> >>
> >> $ sudo mount -o dax /dev/pmem0 /mnt/pmem
> >> XFS (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
> >> XFS (pmem0): DAX unsupported by block device. Turning off DAX.
> >>
> >> The patch fixes this issue by updating calculation of 'last_var' to
> >> take into account number-of-sectors/page instead of assuming it to be
> >> '8'.
> >
> > Yes, I noticed this too and fixed it up in a wider change that also
> > allows device-mapper to validate each component device. Does this
> > patch work for you?
> >
> > https://lore.kernel.org/lkml/155789172402.748145.11853718580748830476.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
>
> Thanks Dan, I tested your patch and not seeing the issue anymore.

Thanks, I recorded a "Tested-by" for you.