Re: [PATCH] mm/mempolicy: Move VMA address bound checks inside mpol_misplaced()

[Vlastimil Babka <vbabka@suse.cz>]

On 09/01/2017 09:02 AM, Anshuman Khandual wrote:
> The VMA address bound checks are applicable to all memory policy modes,
> not just MPOL_INTERLEAVE.

But only MPOL_INTERLEAVE actually uses addr and vma->vm_start.

> Hence move it to the front and make it common.
> 
> Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>

I would just remove them instead. Together with the BUG_ON(!vma). Looks
like just leftover from development.

> ---
>  mm/mempolicy.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 618ab12..7ec6694 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2173,6 +2173,8 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long
>  	int ret = -1;
>  
>  	BUG_ON(!vma);
> +	BUG_ON(addr >= vma->vm_end);
> +	BUG_ON(addr < vma->vm_start);
>  
>  	pol = get_vma_policy(vma, addr);
>  	if (!(pol->flags & MPOL_F_MOF))
> @@ -2180,9 +2182,6 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long
>  
>  	switch (pol->mode) {
>  	case MPOL_INTERLEAVE:
> -		BUG_ON(addr >= vma->vm_end);
> -		BUG_ON(addr < vma->vm_start);
> -
>  		pgoff = vma->vm_pgoff;
>  		pgoff += (addr - vma->vm_start) >> PAGE_SHIFT;
>  		polnid = offset_il_node(pol, vma, pgoff);
> 

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