linux-kernel - Re: [PATCH] [1/4] SLAB: Handle node-not-up case in fallback

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.2.00.1002060148300.17897@chino.kir.corp.google.com>
Date:	Sat, 6 Feb 2010 01:53:00 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Andi Kleen <andi@...stfloor.org>
cc:	submit@...stfloor.org, linux-kernel@...r.kernel.org,
	haicheng.li@...el.com, Pekka Enberg <penberg@...helsinki.fi>,
	linux-mm@...ck.org
Subject: Re: [PATCH] [1/4] SLAB: Handle node-not-up case in
 fallback_alloc()

On Sat, 6 Feb 2010, Andi Kleen wrote:

> > That other node must be allowed by current's cpuset, otherwise 
> > kmem_getpages() will fail when get_page_from_freelist() iterates only over 
> > unallowed nodes.
> 
> All theses cases are really only interesting in the memory hotplug path
> itself (afterwards the slab is working anyways and memory is there)
> and if someone sets funny cpusets for those he gets what he deserves ...
> 

If a hot-added node has not been initialized for the cache, your code is 
picking an existing one in zonelist order which may be excluded by 
current's cpuset.  Thus, your code has a very real chance of having 
kmem_getpages() return NULL because get_page_from_freelist() will reject 
non-atomic ALLOC_CPUSET allocations for prohibited nodes.  That isn't a 
scenario that requires a "funny cpuset," it just has to not allow whatever 
initialized node comes first in the zonelist.

My suggested alternative does not pick a single initialized node, rather 
it tries all nodes that actually have a chance of having kmem_getpages() 
succeed which increases the probability that your patch actually has an 
effect for cpuset users.
--
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/