linux-kernel - Re: [PATCH] mm: fix a regression with HIGHMEM introduced by changeset 7f1290f2f2a4d

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: <alpine.DEB.2.00.1211151328430.27188@chino.kir.corp.google.com>
Date:	Thu, 15 Nov 2012 13:41:24 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Jiang Liu <liuj97@...il.com>
cc:	Wen Congyang <wency@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	Jianguo Wu <wujianguo@...wei.com>,
	Chris Clayton <chris2553@...glemail.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Mel Gorman <mgorman@...e.de>,
	Minchan Kim <minchan@...nel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Daniel Vetter <daniel.vetter@...ll.ch>
Subject: Re: [PATCH] mm: fix a regression with HIGHMEM introduced by changeset
 7f1290f2f2a4d

On Thu, 15 Nov 2012, Jiang Liu wrote:

> I feel that zone->present_pages has been abused. I guess it means "physical pages 
> present in this zone" originally, but now sometimes zone->present_pages is used as
> "pages in this zone managed by the buddy system".

It's definition is all pages spanned by the zone that are not reserved and 
unavailable to the kernel to allocate from, and the implementation of 
bootmem requires that its memory be considered as "reserved" until freed.  
It's used throughout the kernel to determine the amount of memory that is 
allocatable in that zone from the page allocator since its reclaim 
heuristics and watermarks depend on this memory being allocatable.

> So I'm trying to add a new
> field "managed_pages" into zone, which accounts for pages managed by buddy system.
> That's why I thought the clean solution is a little complex:(
> 

You need to update the pgdat's node_present_pages to be consistent with 
all of its zones' present_pages.
--
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/