Re: [PATCH v2 0/2] mm: stop calling pmd_folio() on special PMDs

[Gregory Price]

On Sat, Sep 12, 2026 at 06:35:08AM -0400, Gregory Price wrote:
> On Fri, Sep 11, 2026 at 09:25:03PM -0700, Andrew Morton wrote:
> > On Fri, 11 Sep 2026 23:48:31 -0400 Gregory Price <gourry@xxxxxxxxxx> wrote:
> > 
> > > Reproducer
> > > ==========
> > > 
> > > No hardware needed.  An out of tree module stands in for the drivers above:
> > > three misc devices, each with a ->huge_fault calling vmf_insert_pfn_pmd(),
> > > plus VM_HUGEPAGE so the fault path takes the PMD branch.
> > 
> > I take it there's no known way of triggering this in current mainline?
> 
> As far as I can tell there are no in-tree modules that reach this state,
> at least not obviously.  
> 

Ah - sashiko did report a similar issue in fs/proc/task_mmu.c though, so
I'm going to take a run at doing a larger detection run for this
problem.  These patches are good to go though.

~Gregory