2021-02-01 09:35:33

by Miaohe Lin

Subject: [PATCH] mm/huge_memory.c: use helper range_in_vma() in __split_huge_p[u|m]d_locked()

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 <[email protected]>
---
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

2021-02-01 10:58:07

by David Hildenbrand

Subject: Re: [PATCH] mm/huge_memory.c: use helper range_in_vma() in __split_huge_p[u|m]d_locked()

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 <[email protected]>
> ---
> 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 <[email protected]>

--
Thanks,

David / dhildenb

2021-02-01 21:29:30

by David Rientjes

Subject: Re: [PATCH] mm/huge_memory.c: use helper range_in_vma() in __split_huge_p[u|m]d_locked()

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 <[email protected]>
> ---
> 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 :)

2021-02-02 01:35:59

by Miaohe Lin

Subject: Re: [PATCH] mm/huge_memory.c: use helper range_in_vma() in __split_huge_p[u|m]d_locked()

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 <[email protected]>
>> ---
>> 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 :)
> .
>