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

[Vlastimil Babka]

On 3/16/20 7:37 AM, Huang, Ying wrote:
> From: Huang Ying <ying.huang@xxxxxxxxx>
> 
> 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@xxxxxxxxx>
> Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Suggested-and-acked-by: David Rientjes <rientjes@xxxxxxxxxx>
> Acked-by: Michal Hocko <mhocko@xxxxxxxxxx>
> Acked-by: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

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. ...

> + * 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);
>  }