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

[zhong jiang <zhongjiang@huawei.com>]

On 2017/5/9 19:34, Vlastimil Babka wrote:
> 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().
 I see. I miss it. but why the new_page need to be release all the way.
 I do not see the count increment when scan success. it save the memory,
 only when page fault happen.

 Thanks
 zhongjiang
>> ---
>>  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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