Re: [PATCH 1/3] Revert "dax: fix NULL pointer in __dax_pmd_fault()"

[Ross Zwisler <ross.zwisler@linux.intel.com>]

On Fri, Oct 02, 2015 at 02:11:03PM -0700, Dan Williams wrote:
> On Fri, Oct 2, 2015 at 2:02 PM, Ross Zwisler
> <ross.zwisler@linux.intel.com> wrote:
> > This reverts commit 8346c416d17bf5b4ea1508662959bb62e73fd6a5.
> >
> > This commit did fix the issue it intended to fix, but it turns out that
> > the locking changes introduced by these two commits:
> >
> > commit 843172978bb9 ("dax: fix race between simultaneous faults")
> > commit 46c043ede471 ("mm: take i_mmap_lock in unmap_mapping_range() for DAX")
> >
> > had other issues as well, so they need to just be reverted.
> 
> Wait, why introduce two points in the kernel history where we have a
> known uninitialized variable?  I'd say fix up the revert of "mm: take
> i_mmap_lock in unmap_mapping_range() for DAX" to address the conflict
> with the fix, one less patch and keeps the stability rolling forward.

Essentially because I wasn't sure about the rules regarding reverts, if there
are any.  I assumed (perhaps incorrectly) that you'd want a 1:1 relationship
between original commits and reverts.  If it's better to not have intermediate
breakage, sure, let's squash them.