linux-kernel - Re: [PATCH v2] mm: remove MIGRATE

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 for Android: free password hash cracker in your pocket

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

Message-Id: <20130115153625.96265439.akpm@linux-foundation.org>
Date:	Tue, 15 Jan 2013 15:36:25 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Minchan Kim <minchan@...nel.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Michal Nazarewicz <mina86@...a86.com>
Subject: Re: [PATCH v2] mm: remove MIGRATE_ISOLATE check in hotpath

On Tue, 15 Jan 2013 09:16:46 +0900
Minchan Kim <minchan@...nel.org> wrote:

> Now mm several functions test MIGRATE_ISOLATE and some of those
> are hotpath but MIGRATE_ISOLATE is used only if we enable
> CONFIG_MEMORY_ISOLATION(ie, CMA, memory-hotplug and memory-failure)
> which are not common config option. So let's not add unnecessary
> overhead and code when we don't enable CONFIG_MEMORY_ISOLATION.

ugh.  Better than nothing, I guess.

There remain call sites which do open-coded

	get_pageblock_migratetype(page) != MIGRATE_ISOLATE

(undo_isolate_page_range() is one).  Wanna clean these up as well?

>
> ...
>
> @@ -683,7 +683,7 @@ static void free_one_page(struct zone *zone, struct page *page, int order,
>  	zone->pages_scanned = 0;
>  
>  	__free_one_page(page, zone, order, migratetype);
> -	if (unlikely(migratetype != MIGRATE_ISOLATE))
> +	if (unlikely(!is_migrate_isolate(migratetype)))
>  		__mod_zone_freepage_state(zone, 1 << order, migratetype);
>  	spin_unlock(&zone->lock);
>  }

The code both before and after this patch is assuming that the
migratetype in free_one_page is likely to be MIGRATE_ISOLATE.  Seems
wrong.  If CONFIG_MEMORY_ISOLATION=n this ends up doing
if(unlikely(true)) which is harmless-but-amusing.

--
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/