linux-kernel - Re: [BUG REPORT] [mm-hotplug, aio] aio ring

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: <50B82B0D.8010206@cn.fujitsu.com>
Date:	Fri, 30 Nov 2012 11:42:05 +0800
From:	Lin Feng <linfeng@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	viro@...iv.linux.org.uk, bcrl@...ck.org,
	kamezawa.hiroyu@...fujitsu.com, mhocko@...e.cz, hughd@...gle.com,
	cl@...ux.com, mgorman@...e.de, minchan@...nel.org,
	isimatu.yasuaki@...fujitsu.com, laijs@...fujitsu.com,
	wency@...fujitsu.com, tangchen@...fujitsu.com,
	linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [BUG REPORT] [mm-hotplug, aio] aio ring_pages can't be offlined

hi Andrew,

On 11/30/2012 07:39 AM, Andrew Morton wrote:
> Tricky.
> 
> I expect the same problem would occur with pages which are under
> O_DIRECT I/O.  Obviously O_DIRECT pages won't be pinned for such long
> periods, but the durations could still be lengthy (seconds).
the offline retry timeout duration is 2 minutes, so to O_DIRECT pages 
seem maybe not a problem for the moment.
> 
> Worse is a futex page, which could easily remain pinned indefinitely.
> 
> The best I can think of is to make changes in or around
> get_user_pages(), to steal the pages from userspace and replace them
> with non-movable ones before pinning them.  The performance cost of
> something like this would surely be unacceptable for direct-io, but
> maybe OK for the aio ring and futexes.
thanks for your advice.
I want to limit the impact as little as possible, as mentioned above,
direct-io seems not a problem, we needn't touch them. Maybe we can 
just change the use of get_user_pages()(in or around) such as aio 
ring pages. I will try to find a way to do this.

Thanks,
linfeng
--
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/