Re: [PATCH] mm: fix the memory leak after collapsing the huge page fails

[Vlastimil Babka <vbabka@suse.cz>]

On 05/09/2017 10:12 AM, zhongjiang wrote:
> From: zhong jiang <zhongjiang@huawei.com>
> 
> Current, when we prepare a huge page to collapse, due to some
> reasons, it can fail to collapse. At the moment, we should
> release the preallocate huge page.

Yeah, looks like the leak is there...

> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
> ---
>  mm/khugepaged.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 7cb9c88..3f5749e 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -1080,6 +1080,7 @@ static void collapse_huge_page(struct mm_struct *mm,
>  	result = SCAN_SUCCEED;
>  out_up_write:
>  	up_write(&mm->mmap_sem);
> +	put_page(new_page);

This doesn't seem correct.
- the put_page() will be called also on success, so a premature free?
- the out_nolock: case should be also handled
- collapse_shmem() seems to have the same problem

>  out_nolock:
>  	trace_mm_collapse_huge_page(mm, isolated, result);
>  	return;
> 

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