On Tue, Feb 07, 2017 at 08:56:56AM -0800, Dan Williams wrote:

On Tue, Feb 7, 2017 at 12:44 AM, Kirill A. Shutemov
[off-list ref] wrote:

quoted

On Mon, Feb 06, 2017 at 09:30:22AM -0800, Dan Williams wrote:

quoted

On Mon, Feb 6, 2017 at 9:27 AM, Christoph Hellwig [off-list ref] wrote:

quoted

On Mon, Feb 06, 2017 at 08:24:48AM -0800, Dan Williams wrote:

quoted

quoted

Also can be use this opportunity
to fold ->huge_fault into ->fault?

BTW, for tmpfs we already use ->fault for both small and huge pages.
If ->fault returned THP, core mm look if it's possible to map the page as
huge in this particular VMA (due to size/alignment). If yes mm maps the
page with PMD, if not fallback to PTE.

I think it would be nice to do the same for DAX: filesystem provides core
mm with largest page this part of file can be mapped with (base aligned
address + lenght for DAX) and core mm sort out the rest.

For DAX we would need plumb pfn_t into the core mm so that we have the
PFN_DEV and PFN_MAP flags beyond the raw pfn.

Sounds good to me.

quoted

quoted

quoted

quoted

Hmm, yes, just need a scheme to not attempt huge_faults on pte-only handlers.

Do we need anything more than checking vma->vm_flags for VM_HUGETLB?

s/VM_HUGETLB/VM_HUGEPAGE/

...but yes as long as we specify that a VM_HUGEPAGE handler must
minimally handle pud and pmd.

VM_HUGEPAGE is result of MADV_HUGEPAGE. It's not required to have THP in
the VMA.

Filesystem-DAX and Device-DAX specify VM_HUGEPAGE by default.

But why? Looks like abuse of the flag.

-- 
 Kirill A. Shutemov

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