[RFC PATCH 4/4] mm: madvise allow remove operation for hugetlbfs

[RFC PATCH 4/4] mm: madvise allow remove operation for hugetlbfs

[Mike Kravetz]

Now that we have hole punching support for hugetlbfs, we can
also support the MADV_REMOVE interface to it.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 mm/madvise.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index d551475..c4a1027 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -299,7 +299,7 @@ static long madvise_remove(struct vm_area_struct *vma,
 
 	*prev = NULL;	/* tell sys_madvise we drop mmap_sem */
 
-	if (vma->vm_flags & (VM_LOCKED | VM_HUGETLB))
+	if (vma->vm_flags & VM_LOCKED)
 		return -EINVAL;
 
 	f = vma->vm_file;
-- 
2.1.0

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Re: [RFC PATCH 4/4] mm: madvise allow remove operation for hugetlbfs

[Christoph Hellwig]

On Thu, Apr 16, 2015 at 04:02:58PM -0700, Mike Kravetz wrote:
> Now that we have hole punching support for hugetlbfs, we can
> also support the MADV_REMOVE interface to it.

Meh.  Just use fallocate for any new code..

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Re: [RFC PATCH 4/4] mm: madvise allow remove operation for hugetlbfs

[Hillf Danton]

> 
> Now that we have hole punching support for hugetlbfs, we can
> also support the MADV_REMOVE interface to it.
> 
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> ---
>  mm/madvise.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/madvise.c b/mm/madvise.c
> index d551475..c4a1027 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -299,7 +299,7 @@ static long madvise_remove(struct vm_area_struct *vma,
> 
>  	*prev = NULL;	/* tell sys_madvise we drop mmap_sem */
> 
> -	if (vma->vm_flags & (VM_LOCKED | VM_HUGETLB))
> +	if (vma->vm_flags & VM_LOCKED)
>  		return -EINVAL;
> 
>  	f = vma->vm_file;
> --
> 2.1.0

After the above change offset is computed,

	offset = (loff_t)(start - vma->vm_start)
		+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);

and I wonder if it is correct for huge page mapping.

Hillf

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Re: [RFC PATCH 4/4] mm: madvise allow remove operation for hugetlbfs

[Mike Kravetz]

On 04/16/2015 11:44 PM, Christoph Hellwig wrote:
> On Thu, Apr 16, 2015 at 04:02:58PM -0700, Mike Kravetz wrote:
>> Now that we have hole punching support for hugetlbfs, we can
>> also support the MADV_REMOVE interface to it.
>
> Meh.  Just use fallocate for any new code..
>

I don't have the complete context for your comment.  Is there
a general consensus or effort underway to deprecate the use
of MADV_REMOVE?

-- 
Mike Kravetz

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Re: [RFC PATCH 4/4] mm: madvise allow remove operation for hugetlbfs

[Mike Kravetz]

On 04/17/2015 12:10 AM, Hillf Danton wrote:
>>
>> Now that we have hole punching support for hugetlbfs, we can
>> also support the MADV_REMOVE interface to it.
>>
>> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
>> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
>> ---
>>   mm/madvise.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/madvise.c b/mm/madvise.c
>> index d551475..c4a1027 100644
>> --- a/mm/madvise.c
>> +++ b/mm/madvise.c
>> @@ -299,7 +299,7 @@ static long madvise_remove(struct vm_area_struct *vma,
>>
>>   	*prev = NULL;	/* tell sys_madvise we drop mmap_sem */
>>
>> -	if (vma->vm_flags & (VM_LOCKED | VM_HUGETLB))
>> +	if (vma->vm_flags & VM_LOCKED)
>>   		return -EINVAL;
>>
>>   	f = vma->vm_file;
>> --
>> 2.1.0
>
> After the above change offset is computed,
>
> 	offset = (loff_t)(start - vma->vm_start)
> 		+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
>
> and I wonder if it is correct for huge page mapping.

I think it will be correct.

The above will be a (base) page size aligned offset into the file.
This offset will be huge page aligned in the fallocate hole punch
code.

	/*
	 * For hole punch round up the beginning offset of the hole and
	 * round down the end.
	 */
	hole_start = (offset + hpage_size - 1) & ~huge_page_mask(h);
	hole_end = (offset + len - (hpage_size - 1)) * ~huge_page_mask(h);

Was the alignment your concern, or something else?
-- 
Mike Kravetz

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Re: [RFC PATCH 4/4] mm: madvise allow remove operation for hugetlbfs

[Mike Kravetz]

On 04/17/2015 10:11 AM, Mike Kravetz wrote:
> On 04/17/2015 12:10 AM, Hillf Danton wrote:
>>>
>>> Now that we have hole punching support for hugetlbfs, we can
>>> also support the MADV_REMOVE interface to it.
>>>
>>> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
>>> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
>>> ---
>>>   mm/madvise.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/mm/madvise.c b/mm/madvise.c
>>> index d551475..c4a1027 100644
>>> --- a/mm/madvise.c
>>> +++ b/mm/madvise.c
>>> @@ -299,7 +299,7 @@ static long madvise_remove(struct vm_area_struct
>>> *vma,
>>>
>>>       *prev = NULL;    /* tell sys_madvise we drop mmap_sem */
>>>
>>> -    if (vma->vm_flags & (VM_LOCKED | VM_HUGETLB))
>>> +    if (vma->vm_flags & VM_LOCKED)
>>>           return -EINVAL;
>>>
>>>       f = vma->vm_file;
>>> --
>>> 2.1.0
>>
>> After the above change offset is computed,
>>
>>     offset = (loff_t)(start - vma->vm_start)
>>         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
>>
>> and I wonder if it is correct for huge page mapping.
>
> I think it will be correct.
>
> The above will be a (base) page size aligned offset into the file.
> This offset will be huge page aligned in the fallocate hole punch
> code.
>
>      /*
>       * For hole punch round up the beginning offset of the hole and
>       * round down the end.
>       */
>      hole_start = (offset + hpage_size - 1) & ~huge_page_mask(h);
>      hole_end = (offset + len - (hpage_size - 1)) * ~huge_page_mask(h);
>
> Was the alignment your concern, or something else?

Well, that alignment code in fallocate hole punch obviously wrong. :(
Sorry about that.  I'll send out an updated RFC with working hole punch.

-- 
Mike Kravetz

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