Re: [PATCH -V2] mm: Code cleanup for MADV_FREE

["Huang\, Ying" <ying.huang@intel.com>]

Vlastimil Babka <vbabka@suse.cz> writes:

> On 3/16/20 7:37 AM, Huang, Ying wrote:
>> From: Huang Ying <ying.huang@intel.com>
>> 
>> Some comments for MADV_FREE is revised and added to help people understand the
>> MADV_FREE code, especially the page flag, PG_swapbacked.  This makes
>> page_is_file_cache() isn't consistent with its comments.  So the function is
>> renamed to page_is_file_lru() to make them consistent again.  All these are put
>> in one patch as one logical change.
>> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>> Suggested-by: David Hildenbrand <david@redhat.com>
>> Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
>> Suggested-and-acked-by: David Rientjes <rientjes@google.com>
>> Acked-by: Michal Hocko <mhocko@kernel.org>
>> Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
>> Cc: Dave Hansen <dave.hansen@linux.intel.com>
>> Cc: Mel Gorman <mgorman@suse.de>
>> Cc: Vlastimil Babka <vbabka@suse.cz>
>> Cc: Minchan Kim <minchan@kernel.org>
>> Cc: Hugh Dickins <hughd@google.com>
>> Cc: Rik van Riel <riel@surriel.com>
>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
>
> Thanks! A grammar nit below:
>
>> --- a/include/linux/mm_inline.h
>> +++ b/include/linux/mm_inline.h
>> @@ -6,19 +6,20 @@
>>  #include <linux/swap.h>
>>  
>>  /**
>> - * page_is_file_cache - should the page be on a file LRU or anon LRU?
>> + * page_is_file_lru - should the page be on a file LRU or anon LRU?
>>   * @page: the page to test
>>   *
>> - * Returns 1 if @page is page cache page backed by a regular filesystem,
>> - * or 0 if @page is anonymous, tmpfs or otherwise ram or swap backed.
>> - * Used by functions that manipulate the LRU lists, to sort a page
>> - * onto the right LRU list.
>> + * Returns 1 if @page is page cache page backed by a regular filesystem or
>> + * anonymous page lazily freed (e.g. via MADV_FREE).  Returns 0 if @page is
>
>       a lazily freed anonymous page (e.g. ...

Thought again.  Should we make the 2 sub-clauses consistent?  That is,
either

if @page is page cache page backed by a regular filesystem or anonymous
page freed lazily

or

if @page is a regular filesystem backed page cache page or a lazily
freed anonymous page

But I know that my English grammar isn't good enough :-(

Best Regards,
Huang, Ying

>> + * normal anonymous page, tmpfs or otherwise ram or swap backed.  Used by
>> + * functions that manipulate the LRU lists, to sort a page onto the right LRU
>> + * list.
>>   *
>>   * We would like to get this info without a page flag, but the state
>>   * needs to survive until the page is last deleted from the LRU, which
>>   * could be as far down as __page_cache_release.
>>   */
>> -static inline int page_is_file_cache(struct page *page)
>> +static inline int page_is_file_lru(struct page *page)
>>  {
>>  	return !PageSwapBacked(page);
>>  }