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* [PATCH] mm/huge_memory.c: use helper range_in_vma() in __split_huge_p[u|m]d_locked()
@ 2021-02-01  9:32 Miaohe Lin
  2021-02-01 10:54 ` David Hildenbrand
  2021-02-01 21:27 ` David Rientjes
  0 siblings, 2 replies; 4+ messages in thread
From: Miaohe Lin @ 2021-02-01  9:32 UTC (permalink / raw)
  To: akpm; +Cc: linux-mm, linux-kernel, linmiaohe

The helper range_in_vma() is introduced via commit 017b1660df89 ("mm:
migration: fix migration of huge PMD shared pages"). But we forgot to
use it in __split_huge_pud_locked() and __split_huge_pmd_locked().

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 mm/huge_memory.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 987cf5e4cf90..33353a4f95fb 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1959,8 +1959,7 @@ static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
 		unsigned long haddr)
 {
 	VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
-	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
-	VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
+	VM_BUG_ON_VMA(!range_in_vma(vma, haddr, haddr + HPAGE_PUD_SIZE), vma);
 	VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
 
 	count_vm_event(THP_SPLIT_PUD);
@@ -2039,8 +2038,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 	int i;
 
 	VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
-	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
-	VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
+	VM_BUG_ON_VMA(!range_in_vma(vma, haddr, haddr + HPAGE_PMD_SIZE), vma);
 	VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
 				&& !pmd_devmap(*pmd));
 
-- 
2.19.1



^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] mm/huge_memory.c: use helper range_in_vma() in __split_huge_p[u|m]d_locked()
  2021-02-01  9:32 [PATCH] mm/huge_memory.c: use helper range_in_vma() in __split_huge_p[u|m]d_locked() Miaohe Lin
@ 2021-02-01 10:54 ` David Hildenbrand
  2021-02-01 21:27 ` David Rientjes
  1 sibling, 0 replies; 4+ messages in thread
From: David Hildenbrand @ 2021-02-01 10:54 UTC (permalink / raw)
  To: Miaohe Lin, akpm; +Cc: linux-mm, linux-kernel

On 01.02.21 10:32, Miaohe Lin wrote:
> The helper range_in_vma() is introduced via commit 017b1660df89 ("mm:
> migration: fix migration of huge PMD shared pages"). But we forgot to
> use it in __split_huge_pud_locked() and __split_huge_pmd_locked().
> 
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
>   mm/huge_memory.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 987cf5e4cf90..33353a4f95fb 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1959,8 +1959,7 @@ static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
>   		unsigned long haddr)
>   {
>   	VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
> -	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
> -	VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
> +	VM_BUG_ON_VMA(!range_in_vma(vma, haddr, haddr + HPAGE_PUD_SIZE), vma);
>   	VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
>   
>   	count_vm_event(THP_SPLIT_PUD);
> @@ -2039,8 +2038,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
>   	int i;
>   
>   	VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
> -	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
> -	VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
> +	VM_BUG_ON_VMA(!range_in_vma(vma, haddr, haddr + HPAGE_PMD_SIZE), vma);
>   	VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
>   				&& !pmd_devmap(*pmd));
>   
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb



^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] mm/huge_memory.c: use helper range_in_vma() in __split_huge_p[u|m]d_locked()
  2021-02-01  9:32 [PATCH] mm/huge_memory.c: use helper range_in_vma() in __split_huge_p[u|m]d_locked() Miaohe Lin
  2021-02-01 10:54 ` David Hildenbrand
@ 2021-02-01 21:27 ` David Rientjes
  2021-02-02  1:33   ` Miaohe Lin
  1 sibling, 1 reply; 4+ messages in thread
From: David Rientjes @ 2021-02-01 21:27 UTC (permalink / raw)
  To: Miaohe Lin; +Cc: akpm, linux-mm, linux-kernel

On Mon, 1 Feb 2021, Miaohe Lin wrote:

> The helper range_in_vma() is introduced via commit 017b1660df89 ("mm:
> migration: fix migration of huge PMD shared pages"). But we forgot to
> use it in __split_huge_pud_locked() and __split_huge_pmd_locked().
> 
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
>  mm/huge_memory.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 987cf5e4cf90..33353a4f95fb 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1959,8 +1959,7 @@ static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
>  		unsigned long haddr)
>  {
>  	VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
> -	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
> -	VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
> +	VM_BUG_ON_VMA(!range_in_vma(vma, haddr, haddr + HPAGE_PUD_SIZE), vma);
>  	VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
>  
>  	count_vm_event(THP_SPLIT_PUD);
> @@ -2039,8 +2038,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
>  	int i;
>  
>  	VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
> -	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
> -	VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
> +	VM_BUG_ON_VMA(!range_in_vma(vma, haddr, haddr + HPAGE_PMD_SIZE), vma);
>  	VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
>  				&& !pmd_devmap(*pmd));
>  

This actually loses information, right?  Before the patch, we can 
determine which conditional is failing because we know the line number 
that the VM_BUG_ON() is happening on.  After the patch, we don't know 
this.

I don't think that's crucial, but I'm not sure it makes sense to do this 
if the only upside is that we removed one total line of code :)


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] mm/huge_memory.c: use helper range_in_vma() in __split_huge_p[u|m]d_locked()
  2021-02-01 21:27 ` David Rientjes
@ 2021-02-02  1:33   ` Miaohe Lin
  0 siblings, 0 replies; 4+ messages in thread
From: Miaohe Lin @ 2021-02-02  1:33 UTC (permalink / raw)
  To: David Rientjes; +Cc: akpm, linux-mm, linux-kernel

On 2021/2/2 5:27, David Rientjes wrote:
> On Mon, 1 Feb 2021, Miaohe Lin wrote:
> 
>> The helper range_in_vma() is introduced via commit 017b1660df89 ("mm:
>> migration: fix migration of huge PMD shared pages"). But we forgot to
>> use it in __split_huge_pud_locked() and __split_huge_pmd_locked().
>>
>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>> ---
>>  mm/huge_memory.c | 6 ++----
>>  1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 987cf5e4cf90..33353a4f95fb 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -1959,8 +1959,7 @@ static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud,
>>  		unsigned long haddr)
>>  {
>>  	VM_BUG_ON(haddr & ~HPAGE_PUD_MASK);
>> -	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
>> -	VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma);
>> +	VM_BUG_ON_VMA(!range_in_vma(vma, haddr, haddr + HPAGE_PUD_SIZE), vma);
>>  	VM_BUG_ON(!pud_trans_huge(*pud) && !pud_devmap(*pud));
>>  
>>  	count_vm_event(THP_SPLIT_PUD);
>> @@ -2039,8 +2038,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
>>  	int i;
>>  
>>  	VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
>> -	VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
>> -	VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
>> +	VM_BUG_ON_VMA(!range_in_vma(vma, haddr, haddr + HPAGE_PMD_SIZE), vma);
>>  	VM_BUG_ON(!is_pmd_migration_entry(*pmd) && !pmd_trans_huge(*pmd)
>>  				&& !pmd_devmap(*pmd));
>>  
> 
> This actually loses information, right?  Before the patch, we can 
> determine which conditional is failing because we know the line number 
> that the VM_BUG_ON() is happening on.  After the patch, we don't know 
> this.
> 

You are right. We can determine which conditional is failing only through line number
via VM_BUG_ON_VMA. So this will loses the information. My careless. :(
Many thanks for kindly explanation.

> I don't think that's crucial, but I'm not sure it makes sense to do this 
> if the only upside is that we removed one total line of code :)
> .
> 



^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2021-02-02  1:33 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-02-01  9:32 [PATCH] mm/huge_memory.c: use helper range_in_vma() in __split_huge_p[u|m]d_locked() Miaohe Lin
2021-02-01 10:54 ` David Hildenbrand
2021-02-01 21:27 ` David Rientjes
2021-02-02  1:33   ` Miaohe Lin

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