linux-kernel - Re: [PATCH -V2] mm: Code cleanup for MADV

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Date:   Tue, 17 Mar 2020 09:51:04 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, David Hildenbrand <david@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        David Rientjes <rientjes@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Mel Gorman <mgorman@...e.de>, Minchan Kim <minchan@...nel.org>,
        Hugh Dickins <hughd@...gle.com>,
        Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH -V2] mm: Code cleanup for MADV_FREE

On 3/17/20 9:10 AM, Huang, Ying wrote:
> Vlastimil Babka <vbabka@...e.cz> writes:
> 
>> On 3/16/20 7:37 AM, Huang, Ying wrote:
>>> From: Huang Ying <ying.huang@...el.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@...el.com>
>>> Suggested-by: David Hildenbrand <david@...hat.com>
>>> Suggested-by: Johannes Weiner <hannes@...xchg.org>
>>> Suggested-and-acked-by: David Rientjes <rientjes@...gle.com>
>>> Acked-by: Michal Hocko <mhocko@...nel.org>
>>> Acked-by: Pankaj Gupta <pankaj.gupta.linux@...il.com>
>>> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
>>> Cc: Mel Gorman <mgorman@...e.de>
>>> Cc: Vlastimil Babka <vbabka@...e.cz>
>>> Cc: Minchan Kim <minchan@...nel.org>
>>> Cc: Hugh Dickins <hughd@...gle.com>
>>> Cc: Rik van Riel <riel@...riel.com>
>>
>> Acked-by: Vlastimil Babka <vbabka@...e.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

Yeah this one looks fine :)

> 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);
>>>  }
>