Re: [PATCH 0/3] resource: find_next_iomem_res() improvements

[Dan Williams]

On Tue, Jul 16, 2019 at 3:01 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Tue, 18 Jun 2019 21:56:43 +0000 Nadav Amit <namit@xxxxxxxxxx> wrote:
>
> > > ...and is constant for the life of the device and all subsequent mappings.
> > >
> > >> Perhaps you want to cache the cachability-mode in vma->vm_page_prot (which I
> > >> see being done in quite a few cases), but I donât know the code well enough
> > >> to be certain that every vma should have a single protection and that it
> > >> should not change afterwards.
> > >
> > > No, I'm thinking this would naturally fit as a property hanging off a
> > > 'struct dax_device', and then create a version of vmf_insert_mixed()
> > > and vmf_insert_pfn_pmd() that bypass track_pfn_insert() to insert that
> > > saved value.
> >
> > Thanks for the detailed explanation. Iâll give it a try (the moment I find
> > some free time). I still think that patch 2/3 is beneficial, but based on
> > your feedback, patch 3/3 should be dropped.
>
> It has been a while.  What should we do with
>
> resource-fix-locking-in-find_next_iomem_res.patch

This one looks obviously correct to me, you can add:

Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>

> resource-avoid-unnecessary-lookups-in-find_next_iomem_res.patch

This one is a good bug report that we need to go fix pgprot lookups
for dax, but I don't think we need to increase the trickiness of the
core resource lookup code in the meantime.