Re: [PATCH v2] mm: fix the memory leak after collapsing the huge page fails

[Vlastimil Babka <vbabka@suse.cz>]

On 05/09/2017 12:55 PM, 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.
> 
> Signed-off-by: zhong jiang <zhongjiang@huawei.com>

Hmm, scratch that, there's no memory leak. The pointer to new_page is
stored in *hpage, and put_page() is called all the way up in
khugepaged_do_scan().

> ---
>  mm/khugepaged.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 7cb9c88..586b1f1 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -1082,6 +1082,8 @@ static void collapse_huge_page(struct mm_struct *mm,
>  	up_write(&mm->mmap_sem);
>  out_nolock:
>  	trace_mm_collapse_huge_page(mm, isolated, result);
> +	if (page != NULL && result != SCAN_SUCCEED)
> +		put_page(new_page);
>  	return;
>  out:
>  	mem_cgroup_cancel_charge(new_page, memcg, true);
> @@ -1555,6 +1557,8 @@ static void collapse_shmem(struct mm_struct *mm,
>  	}
>  out:
>  	VM_BUG_ON(!list_empty(&pagelist));
> +	if (page != NULL && result != SCAN_SUCCEED)
> +		put_page(new_page);
>  	/* TODO: tracepoints */
>  }
>  
> 

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