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Date:   Sat, 29 Aug 2020 12:12:13 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     Alex Shi <alex.shi@...ux.alibaba.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/2] mm: use
 add_page_to_lru_list()/page_lru()/page_off_lru()

On Thu, Aug 27, 2020 at 05:42:01PM -0600, Yu Zhao wrote:
> This is a trivial but worth having clean-up patch. There should be
> no side effects except page->lru is temporarily poisoned after it's
> deleted but before it's added to the new list in move_pages_to_lru()
> (which is not a problem).
> 
> Signed-off-by: Yu Zhao <yuzhao@...gle.com>

Hi Alex, I just realized your
  [v18,08/32] mm/vmscan: remove unnecessary lruvec adding
at
  https://patchwork.kernel.org/patch/11733123/
also touches move_pages_to_lru(). I agree it's better not to add
a page we are going to free to the list in the first place. The
rest in this patch would be too trivial to be a separate one (on
top of yours).

So would you mind taking of the clean-up too in your series? I'll
drop this one then. Thanks.

> ---
>  mm/swap.c   |  4 +---
>  mm/vmscan.c | 14 ++++----------
>  2 files changed, 5 insertions(+), 13 deletions(-)
> 
> diff --git a/mm/swap.c b/mm/swap.c
> index 40bf20a75278..2735ecf0f566 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -597,11 +597,9 @@ static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
>  {
>  	if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) &&
>  	    !PageSwapCache(page) && !PageUnevictable(page)) {
> -		bool active = PageActive(page);
>  		int nr_pages = thp_nr_pages(page);
>  
> -		del_page_from_lru_list(page, lruvec,
> -				       LRU_INACTIVE_ANON + active);
> +		del_page_from_lru_list(page, lruvec, page_lru(page));
>  		ClearPageActive(page);
>  		ClearPageReferenced(page);
>  		/*
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 99e1796eb833..b479ced26cd3 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1845,13 +1845,12 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
>  	int nr_pages, nr_moved = 0;
>  	LIST_HEAD(pages_to_free);
>  	struct page *page;
> -	enum lru_list lru;
>  
>  	while (!list_empty(list)) {
>  		page = lru_to_page(list);
>  		VM_BUG_ON_PAGE(PageLRU(page), page);
> +		list_del(&page->lru);
>  		if (unlikely(!page_evictable(page))) {
> -			list_del(&page->lru);
>  			spin_unlock_irq(&pgdat->lru_lock);
>  			putback_lru_page(page);
>  			spin_lock_irq(&pgdat->lru_lock);
> @@ -1860,16 +1859,10 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
>  		lruvec = mem_cgroup_page_lruvec(page, pgdat);
>  
>  		SetPageLRU(page);
> -		lru = page_lru(page);
> -
> -		nr_pages = thp_nr_pages(page);
> -		update_lru_size(lruvec, lru, page_zonenum(page), nr_pages);
> -		list_move(&page->lru, &lruvec->lists[lru]);
> +		add_page_to_lru_list(page, lruvec, page_lru(page));
>  
>  		if (put_page_testzero(page)) {
> -			__ClearPageLRU(page);
> -			__ClearPageActive(page);
> -			del_page_from_lru_list(page, lruvec, lru);
> +			del_page_from_lru_list(page, lruvec, page_off_lru(page));
>  
>  			if (unlikely(PageCompound(page))) {
>  				spin_unlock_irq(&pgdat->lru_lock);
> @@ -1878,6 +1871,7 @@ static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
>  			} else
>  				list_add(&page->lru, &pages_to_free);
>  		} else {
> +			nr_pages = thp_nr_pages(page);
>  			nr_moved += nr_pages;
>  			if (PageActive(page))
>  				workingset_age_nonresident(lruvec, nr_pages);
> -- 
> 2.28.0.402.g5ffc5be6b7-goog
> 

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