Re: [PATCH next] mm/vmscan: __isolate_lru_page_prepare clean up

[Alex Shi]

在 2020/11/22 下午8:35, Matthew Wilcox 写道:
> On Sun, Nov 22, 2020 at 08:00:19PM +0800, Alex Shi wrote:
>>  mm/compaction.c |  2 +-
>>  mm/vmscan.c     | 69 +++++++++++++++++++++++--------------------------
>>  2 files changed, 34 insertions(+), 37 deletions(-)
> 
> How is it possible you're changing the signature of a function without
> touching a header file?  Surely __isolate_lru_page_prepare() must be declared
> in mm/internal.h ?
> 
>> +++ b/mm/vmscan.c
>> @@ -1536,19 +1536,17 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
>>   * page:	page to consider
>>   * mode:	one of the LRU isolation modes defined above
>>   *
>> - * returns 0 on success, -ve errno on failure.
>> + * returns ture on success, false on failure.
> 
> "true".
> 
>> @@ -1674,35 +1672,34 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>>  		 * only when the page is being freed somewhere else.
>>  		 */
>>  		scan += nr_pages;
>> -		switch (__isolate_lru_page_prepare(page, mode)) {
>> -		case 0:
>> +		if (!__isolate_lru_page_prepare(page, mode)) {
>> +			/* else it is being freed elsewhere */
> 
> I don't think the word "else" helps here.  Just
> 			/* It is being freed elsewhere */
> 
>> +		if (!TestClearPageLRU(page)) {
>>  			/*
>> +			 * This page may in other isolation path,
>> +			 * but we still hold lru_lock.
>>  			 */
> 
> I don't think this comment helps me understand what's going on here.
> Maybe:
> 
> 			/* Another thread is already isolating this page */
> 
>> +			put_page(page);
>>  			list_move(&page->lru, src);
>> +			continue;
>>  		}

Hi Matthew,

Thanks a lot for all comments, I picked all up and here is the v3: