linux-kernel - Re: [PATCH v2] vmscan: fix increasing nr_isolated incurred by putback unevictable pages

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]

Message-ID: <20150804233108.GA662@bgram>
Date:	Wed, 5 Aug 2015 08:31:08 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jaewon Kim <jaewon31.kim@...sung.com>, mgorman@...e.de,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	jaewon31.kim@...il.com
Subject: Re: [PATCH v2] vmscan: fix increasing nr_isolated incurred by
 putback unevictable pages

Hello,

On Tue, Aug 04, 2015 at 03:09:37PM -0700, Andrew Morton wrote:
> On Tue, 04 Aug 2015 19:40:08 +0900 Jaewon Kim <jaewon31.kim@...sung.com> wrote:
> 
> > reclaim_clean_pages_from_list() assumes that shrink_page_list() returns
> > number of pages removed from the candidate list. But shrink_page_list()
> > puts back mlocked pages without passing it to caller and without
> > counting as nr_reclaimed. This incurrs increasing nr_isolated.
> > To fix this, this patch changes shrink_page_list() to pass unevictable
> > pages back to caller. Caller will take care those pages.
> > 
> > ..
> >
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -1157,7 +1157,7 @@ cull_mlocked:
> >  		if (PageSwapCache(page))
> >  			try_to_free_swap(page);
> >  		unlock_page(page);
> > -		putback_lru_page(page);
> > +		list_add(&page->lru, &ret_pages);
> >  		continue;
> >  
> >  activate_locked:
> 
> Is this going to cause a whole bunch of mlocked pages to be migrated
> whereas in current kernels they stay where they are?
> 

It fixes two issues.

1. With unevictable page, cma_alloc will be successful.

Exactly speaking, cma_alloc of current kernel will fail due to unevictable pages.

2. fix leaking of NR_ISOLATED counter of vmstat

With it, too_many_isolated works. Otherwise, it could make hang until
the process get SIGKILL.

So, I think it's stable material.

Acked-by: Minchan Kim <minchan@...nel.org>


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/