Re: [PATCH 01/16] mm/migration: remove unneeded local variable mapping_locked

[Miaohe Lin]

On 2022/3/7 10:00, Huang, Ying wrote:
> Miaohe Lin <linmiaohe@xxxxxxxxxx> writes:
> 
>> When mapping_locked is true, TTU_RMAP_LOCKED is always set to ttu. We can
>> check ttu instead so mapping_locked can be removed. And ttu is either 0
>> or TTU_RMAP_LOCKED now. Change '|=' to '=' to reflect this.
>>
>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>> ---
>>  mm/migrate.c | 6 ++----
>>  1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index 42e3a944f35c..50bc62d85eaf 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1230,7 +1230,6 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>>  		goto put_anon;
>>  
>>  	if (page_mapped(hpage)) {
>> -		bool mapping_locked = false;
>>  		enum ttu_flags ttu = 0;
>>  
>>  		if (!PageAnon(hpage)) {
>> @@ -1244,14 +1243,13 @@ static int unmap_and_move_huge_page(new_page_t get_new_page,
>>  			if (unlikely(!mapping))
>>  				goto unlock_put_anon;
>>  
>> -			mapping_locked = true;
>> -			ttu |= TTU_RMAP_LOCKED;
>> +			ttu = TTU_RMAP_LOCKED;
>>  		}
>>  
>>  		try_to_migrate(src, ttu);
>>  		page_was_mapped = 1;
>>  
>> -		if (mapping_locked)
>> +		if (ttu & TTU_RMAP_LOCKED)
>>  			i_mmap_unlock_write(mapping);
>>  	}
> 
> I think this is a code style issue.  The original code looks more
> readable for me.
> 

I think "ttu |= TTU_RMAP_LOCKED;" is the product of the code changing.
And (ttu & TTU_RMAP_LOCKED) can do the right thing as mapping_locked
while removing the page_was_mapped. But if you insist on this, I will
drop this patch.

Thanks.

> Best Regards,
> Huang, Ying
> 
> .
>