Re: [PATCH] common/rc: Fix _check_s_dax()

On Wed, Dec 02, 2020 at 01:41:45PM -0800, ira.weiny@intel.com wrote:

From: Ira Weiny <redacted>

There is a conflict with the user visible statx bits 'mount root' and
'dax'.  The kernel is changing the dax bit to correct this conflict.[1]

Adjust _check_s_dax() to use the new bit.  Because DAX tests do not run
on root mounts, STATX_ATTR_MOUNT_ROOT should always be 0, therefore we
can allow either bit to indicate DAX and cover any kernel which may be
running.

[1] https://lore.kernel.org/lkml/3e28d2c7-fbe5-298a-13ba-dcd8fd504666@redhat.com/ (local)

Signed-off-by: Ira Weiny <redacted>
---

I went ahead and used Christoph's suggestion regarding using both bits.

That wasn't my suggestion.  I think we should always error out when
the bit value shared with STATX_ATTR_MOUNT_ROOT is seen.  Because that
means the kernel is not using or fixed ABI we agreed to use going
forward.