linux-kernel - Re: [PATCH 4/4] mm: Generalize putback scan functions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 13 Feb 2019 14:20:11 -0500
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     akpm@...ux-foundation.org, mhocko@...e.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] mm: Generalize putback scan functions

On Tue, Feb 12, 2019 at 06:14:16PM +0300, Kirill Tkhai wrote:
> +static unsigned noinline_for_stack move_pages_to_lru(struct lruvec *lruvec,
> +						     struct list_head *list)
>  {
>  	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
> +	int nr_pages, nr_moved = 0;
>  	LIST_HEAD(pages_to_free);
> +	struct page *page;
> +	enum lru_list lru;
>  
> -	/*
> -	 * Put back any unfreeable pages.
> -	 */
> -	while (!list_empty(page_list)) {
> -		struct page *page = lru_to_page(page_list);
> -		int lru;
> -
> -		VM_BUG_ON_PAGE(PageLRU(page), page);
> -		list_del(&page->lru);
> +	while (!list_empty(list)) {
> +		page = lru_to_page(list);
>  		if (unlikely(!page_evictable(page))) {
> +			list_del_init(&page->lru);
>  			spin_unlock_irq(&pgdat->lru_lock);
>  			putback_lru_page(page);
>  			spin_lock_irq(&pgdat->lru_lock);
>  			continue;
>  		}
> -
>  		lruvec = mem_cgroup_page_lruvec(page, pgdat);
>  
> +		VM_BUG_ON_PAGE(PageLRU(page), page);

Nit, but moving the BUG down here weakens it a little bit since we miss
checking it if the page is unevictable.


Maybe worth pointing out in the changelog that the main difference from
combining these two functions is that we're now checking for !page_evictable
coming from shrink_active_list, which shouldn't change any behavior since that
path works with evictable pages only.