[PATCH v2] mm: Fix modifying of page protection by insert_pfn_pmd()

[Dan Williams]

On Wed, Apr 24, 2019 at 10:38 AM Matthew Wilcox <willy at infradead.org> wrote:
>
> On Wed, Apr 24, 2019 at 10:13:15AM -0700, Dan Williams wrote:
> > I think unaligned addresses have always been passed to
> > vmf_insert_pfn_pmd(), but nothing cared until this patch. I *think*
> > the only change needed is the following, thoughts?
> >
> > diff --git a/fs/dax.c b/fs/dax.c
> > index ca0671d55aa6..82aee9a87efa 100644
> > --- a/fs/dax.c
> > +++ b/fs/dax.c
> > @@ -1560,7 +1560,7 @@ static vm_fault_t dax_iomap_pmd_fault(struct
> > vm_fault *vmf, pfn_t *pfnp,
> >                 }
> >
> >                 trace_dax_pmd_insert_mapping(inode, vmf, PMD_SIZE, pfn, entry);
> > -               result = vmf_insert_pfn_pmd(vma, vmf->address, vmf->pmd, pfn,
> > +               result = vmf_insert_pfn_pmd(vma, pmd_addr, vmf->pmd, pfn,
> >                                             write);
>
> We also call vmf_insert_pfn_pmd() in dax_insert_pfn_mkwrite() -- does
> that need to change too?

It wasn't clear to me that it was a problem. I think that one already
happens to be pmd-aligned.