2019-08-06 16:07:30

by Christoph Hellwig

Subject: [PATCH 09/15] mm: don't abuse pte_index() in hmm_vma_handle_pmd

pte_index is an internal arch helper in various architectures,
without consistent semantics. Open code that calculation of a PMD
index based on the virtual address instead.

Signed-off-by: Christoph Hellwig <[email protected]>
---
mm/hmm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index 03d37e102e3b..2083e4db46f5 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -486,7 +486,7 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk,
if (pmd_protnone(pmd) || fault || write_fault)
return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);

- pfn = pmd_pfn(pmd) + pte_index(addr);
+ pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) {
if (pmd_devmap(pmd)) {
pgmap = get_dev_pagemap(pfn, pgmap);
--
2.20.1

2019-08-07 17:43:45

by Jason Gunthorpe

Subject: Re: [PATCH 09/15] mm: don't abuse pte_index() in hmm_vma_handle_pmd

On Tue, Aug 06, 2019 at 07:05:47PM +0300, Christoph Hellwig wrote:
> pte_index is an internal arch helper in various architectures,
> without consistent semantics. Open code that calculation of a PMD
> index based on the virtual address instead.
>
> Signed-off-by: Christoph Hellwig <[email protected]>
> ---
> mm/hmm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

There sure are a lot of different ways to express this, but this one
looks OK to me, at least the switch from the PTRS_PER_PTE expression
in the x86 imlpementation to PMD_MASK looks equivalent

Reviewed-by: Jason Gunthorpe <[email protected]>

Jason