2019-04-19 23:37:10

by Ralph Campbell

Subject: [RESEND PATCH] mm/hmm: Fix initial PFN for hugetlbfs pages

From: Ralph Campbell <[email protected]>

The mmotm patch [1] adds hugetlbfs support for HMM but the initial
PFN used to fill the HMM range->pfns[] array doesn't properly
compute the starting PFN offset.
This can be tested by running test-hugetlbfs-read from [2].

Fix the PFN offset by adjusting the page offset by the device's
page size.

Andrew, this should probably be squashed into Jerome's patch.

[1] https://marc.info/?l=linux-mm&m=155432003506068&w=2
("mm/hmm: mirror hugetlbfs (snapshoting, faulting and DMA mapping)")
[2] https://gitlab.freedesktop.org/glisse/svm-cl-tests

Signed-off-by: Ralph Campbell <[email protected]>
Cc: Jérôme Glisse <[email protected]>
Cc: Ira Weiny <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Dan Carpenter <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Souptick Joarder <[email protected]>
Cc: Andrew Morton <[email protected]>
---
mm/hmm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index def451a56c3e..fcf8e4fb5770 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -868,7 +868,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
goto unlock;
}

- pfn = pte_pfn(entry) + (start & mask);
+ pfn = pte_pfn(entry) + ((start & mask) >> range->page_shift);
for (; addr < end; addr += size, i++, pfn += pfn_inc)
range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
cpu_flags;
--
2.20.1

2019-04-22 16:19:09

by Jerome Glisse

Subject: Re: [RESEND PATCH] mm/hmm: Fix initial PFN for hugetlbfs pages

On Fri, Apr 19, 2019 at 04:35:36PM -0700, [email protected] wrote:
> From: Ralph Campbell <[email protected]>
>
> The mmotm patch [1] adds hugetlbfs support for HMM but the initial
> PFN used to fill the HMM range->pfns[] array doesn't properly
> compute the starting PFN offset.
> This can be tested by running test-hugetlbfs-read from [2].
>
> Fix the PFN offset by adjusting the page offset by the device's
> page size.
>
> Andrew, this should probably be squashed into Jerome's patch.
>
> [1] https://marc.info/?l=linux-mm&m=155432003506068&w=2
> ("mm/hmm: mirror hugetlbfs (snapshoting, faulting and DMA mapping)")
> [2] https://gitlab.freedesktop.org/glisse/svm-cl-tests
>
> Signed-off-by: Ralph Campbell <[email protected]>

Good catch.

Reviewed-by: J?r?me Glisse <[email protected]>

> Cc: J?r?me Glisse <[email protected]>
> Cc: Ira Weiny <[email protected]>
> Cc: John Hubbard <[email protected]>
> Cc: Dan Williams <[email protected]>
> Cc: Arnd Bergmann <[email protected]>
> Cc: Balbir Singh <[email protected]>
> Cc: Dan Carpenter <[email protected]>
> Cc: Matthew Wilcox <[email protected]>
> Cc: Souptick Joarder <[email protected]>
> Cc: Andrew Morton <[email protected]>
> ---
> mm/hmm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/hmm.c b/mm/hmm.c
> index def451a56c3e..fcf8e4fb5770 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -868,7 +868,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
> goto unlock;
> }
>
> - pfn = pte_pfn(entry) + (start & mask);
> + pfn = pte_pfn(entry) + ((start & mask) >> range->page_shift);
> for (; addr < end; addr += size, i++, pfn += pfn_inc)
> range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
> cpu_flags;
> --
> 2.20.1
>