linux-kernel - Re: [PATCH 3/4] mm/migrate: remove putback_lru_pages, fix comment on putback_movable

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Date:	Fri, 06 Dec 2013 16:58:59 +0800
From:	Zhang Yanfei <zhangyanfei@...fujitsu.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Rafael Aquini <aquini@...hat.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Christoph Lameter <cl@...ux.com>,
	Joonsoo Kim <js1304@...il.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 3/4] mm/migrate: remove putback_lru_pages, fix comment
 on putback_movable_pages

Hello

On 12/06/2013 04:41 PM, Joonsoo Kim wrote:
> Some part of putback_lru_pages() and putback_movable_pages() is
> duplicated, so it could confuse us what we should use.
> We can remove putback_lru_pages() since it is not really needed now.
> This makes us undestand and maintain the code more easily.
> 
> And comment on putback_movable_pages() is stale now, so fix it.
> 
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
> 
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index f5096b5..7782b74 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -35,7 +35,6 @@ enum migrate_reason {
>  
>  #ifdef CONFIG_MIGRATION
>  
> -extern void putback_lru_pages(struct list_head *l);
>  extern void putback_movable_pages(struct list_head *l);
>  extern int migrate_page(struct address_space *,
>  			struct page *, struct page *, enum migrate_mode);
> @@ -59,7 +58,6 @@ extern int migrate_page_move_mapping(struct address_space *mapping,
>  #else
>  
>  static inline void putback_lru_pages(struct list_head *l) {}

If you want to remove the function, this should be removed, right?

> -static inline void putback_movable_pages(struct list_head *l) {}
>  static inline int migrate_pages(struct list_head *l, new_page_t x,
>  		unsigned long private, enum migrate_mode mode, int reason)
>  	{ return -ENOSYS; }
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index b7c1716..1debdea 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1569,7 +1569,13 @@ static int __soft_offline_page(struct page *page, int flags)
>  		ret = migrate_pages(&pagelist, new_page, MPOL_MF_MOVE_ALL,
>  					MIGRATE_SYNC, MR_MEMORY_FAILURE);
>  		if (ret) {
> -			putback_lru_pages(&pagelist);
> +			if (!list_empty(&pagelist)) {
> +				list_del(&page->lru);
> +				dec_zone_page_state(page, NR_ISOLATED_ANON +
> +						page_is_file_cache(page));
> +				putback_lru_page(page);
> +			}
> +
>  			pr_info("soft offline: %#lx: migration failed %d, type %lx\n",
>  				pfn, ret, page->flags);
>  			if (ret > 0)
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 1f59ccc..8392de4 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -71,28 +71,12 @@ int migrate_prep_local(void)
>  }
>  
>  /*
> - * Add isolated pages on the list back to the LRU under page lock
> - * to avoid leaking evictable pages back onto unevictable list.
> - */
> -void putback_lru_pages(struct list_head *l)
> -{
> -	struct page *page;
> -	struct page *page2;
> -
> -	list_for_each_entry_safe(page, page2, l, lru) {
> -		list_del(&page->lru);
> -		dec_zone_page_state(page, NR_ISOLATED_ANON +
> -				page_is_file_cache(page));
> -			putback_lru_page(page);
> -	}
> -}
> -
> -/*
>   * Put previously isolated pages back onto the appropriate lists
>   * from where they were once taken off for compaction/migration.
>   *
> - * This function shall be used instead of putback_lru_pages(),
> - * whenever the isolated pageset has been built by isolate_migratepages_range()
> + * This function shall be used whenever the isolated pageset has been
> + * built from lru, balloon, hugetlbfs page. See isolate_migratepages_range()
> + * and isolate_huge_page().
>   */
>  void putback_movable_pages(struct list_head *l)
>  {
> @@ -1697,6 +1681,12 @@ int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
>  	nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page,
>  				     node, MIGRATE_ASYNC, MR_NUMA_MISPLACED);
>  	if (nr_remaining) {
> +		if (!list_empty(&migratepages)) {
> +			list_del(&page->lru);
> +			dec_zone_page_state(page, NR_ISOLATED_ANON +
> +					page_is_file_cache(page));
> +			putback_lru_page(page);
> +		}
>  		putback_lru_pages(&migratepages);
>  		isolated = 0;
>  	} else
> 


-- 
Thanks.
Zhang Yanfei
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