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

[zhong jiang <zhongjiang@huawei.com>]

On 2017/5/9 16:42, Vlastimil Babka wrote:
> 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?
 my God, I forget this.
> - the out_nolock: case should be also handled
 khugepage_alloc_page fails . it also will reach out_nolock.
 The out_nolock is very mess, need to reconsider.
> - collapse_shmem() seems to have the same problem
 yes. I will add the path to fix.
>>  out_nolock:
>>  	trace_mm_collapse_huge_page(mm, isolated, result);
>>  	return;
>>
>
> .
>


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