[08/13] mm: remove the mask variable in hmm_vma_walk_hugetlb_entry

Submitted by Christoph Hellwig on July 30, 2019, 5:51 a.m.

Details

Message ID 20190730055203.28467-9-hch@lst.de
State New
Headers show
Series "Series without cover letter" ( rev: 1 ) in AMD X.Org drivers

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Commit Message

Christoph Hellwig July 30, 2019, 5:51 a.m.
The pagewalk code already passes the value as the hmask parameter.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 mm/hmm.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

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diff --git a/mm/hmm.c b/mm/hmm.c
index f26d6abc4ed2..88b77a4a6a1e 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -771,19 +771,16 @@  static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 				      struct mm_walk *walk)
 {
 #ifdef CONFIG_HUGETLB_PAGE
-	unsigned long addr = start, i, pfn, mask;
+	unsigned long addr = start, i, pfn;
 	struct hmm_vma_walk *hmm_vma_walk = walk->private;
 	struct hmm_range *range = hmm_vma_walk->range;
 	struct vm_area_struct *vma = walk->vma;
-	struct hstate *h = hstate_vma(vma);
 	uint64_t orig_pfn, cpu_flags;
 	bool fault, write_fault;
 	spinlock_t *ptl;
 	pte_t entry;
 	int ret = 0;
 
-	mask = huge_page_size(h) - 1;
-
 	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
 	entry = huge_ptep_get(pte);
 
@@ -799,7 +796,7 @@  static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
 		goto unlock;
 	}
 
-	pfn = pte_pfn(entry) + ((start & mask) >> PAGE_SHIFT);
+	pfn = pte_pfn(entry) + ((start & hmask) >> PAGE_SHIFT);
 	for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
 		range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
 				 cpu_flags;

Comments

On Tue, Jul 30, 2019 at 08:51:58AM +0300, Christoph Hellwig wrote:
> The pagewalk code already passes the value as the hmask parameter.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
>  mm/hmm.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index f26d6abc4ed2..88b77a4a6a1e 100644
> +++ b/mm/hmm.c
> @@ -771,19 +771,16 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>  				      struct mm_walk *walk)
>  {
>  #ifdef CONFIG_HUGETLB_PAGE
> -	unsigned long addr = start, i, pfn, mask;
> +	unsigned long addr = start, i, pfn;
>  	struct hmm_vma_walk *hmm_vma_walk = walk->private;
>  	struct hmm_range *range = hmm_vma_walk->range;
>  	struct vm_area_struct *vma = walk->vma;
> -	struct hstate *h = hstate_vma(vma);
>  	uint64_t orig_pfn, cpu_flags;
>  	bool fault, write_fault;
>  	spinlock_t *ptl;
>  	pte_t entry;
>  	int ret = 0;
>  
> -	mask = huge_page_size(h) - 1;
> -
>  	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
>  	entry = huge_ptep_get(pte);
>  
> @@ -799,7 +796,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>  		goto unlock;
>  	}
>  
> -	pfn = pte_pfn(entry) + ((start & mask) >> PAGE_SHIFT);
> +	pfn = pte_pfn(entry) + ((start & hmask) >> PAGE_SHIFT);

I don't know this hstate stuff, but this doesn't look the same?

static int walk_hugetlb_range(unsigned long addr, unsigned long end, {
        struct hstate *h = hstate_vma(vma);
        unsigned long hmask = huge_page_mask(h); // aka h->mask

                        err = walk->hugetlb_entry(pte, hmask, addr, next, walk);

And the first place I found setting h->mask is:

void __init hugetlb_add_hstate(unsigned int order) {
	h->mask = ~((1ULL << (order + PAGE_SHIFT)) - 1);

Compared with
    mask = huge_page_size(h) - 1;
         = ((unsigned long)PAGE_SIZE << h->order) - 1

Looks like hmask == ~mask

?

Jason
On 7/29/19 10:51 PM, Christoph Hellwig wrote:
> The pagewalk code already passes the value as the hmask parameter.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   mm/hmm.c | 7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/hmm.c b/mm/hmm.c
> index f26d6abc4ed2..88b77a4a6a1e 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -771,19 +771,16 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>   				      struct mm_walk *walk)
>   {
>   #ifdef CONFIG_HUGETLB_PAGE
> -	unsigned long addr = start, i, pfn, mask;
> +	unsigned long addr = start, i, pfn;
>   	struct hmm_vma_walk *hmm_vma_walk = walk->private;
>   	struct hmm_range *range = hmm_vma_walk->range;
>   	struct vm_area_struct *vma = walk->vma;
> -	struct hstate *h = hstate_vma(vma);
>   	uint64_t orig_pfn, cpu_flags;
>   	bool fault, write_fault;
>   	spinlock_t *ptl;
>   	pte_t entry;
>   	int ret = 0;
>   
> -	mask = huge_page_size(h) - 1;
> -
>   	ptl = huge_pte_lock(hstate_vma(vma), walk->mm, pte);
>   	entry = huge_ptep_get(pte);
>   
> @@ -799,7 +796,7 @@ static int hmm_vma_walk_hugetlb_entry(pte_t *pte, unsigned long hmask,
>   		goto unlock;
>   	}
>   
> -	pfn = pte_pfn(entry) + ((start & mask) >> PAGE_SHIFT);
> +	pfn = pte_pfn(entry) + ((start & hmask) >> PAGE_SHIFT);

This needs to be "~hmask" so that the upper bits of the start address
are not added to the pfn. It's the middle bits of the address that
offset into the huge page that are needed.

>   	for (; addr < end; addr += PAGE_SIZE, i++, pfn++)
>   		range->pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
>   				 cpu_flags;
>