Messages in this thread | | | From | Thomas Garnier <> | Date | Mon, 7 Nov 2016 10:52:08 -0800 | Subject | Re: [PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB & OBJFREELIST_SLAB |
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On Thu, Nov 3, 2016 at 1:33 PM, Christoph Lameter <cl@linux.com> wrote: > On Wed, 2 Nov 2016, David Rientjes wrote: > >> > Christoph on the first version advised removing invalid flags on the >> > caller and checking they are correct in kmem_cache_create. The memcg >> > path putting the wrong flags is through create_cache but I still used >> > this approach. >> > >> >> I think this is a rather trivial point since it doesn't matter if we clear >> invalid flags on the caller or in the callee and obviously >> kmem_cache_create() does it in the callee. > > In order to be correct we need to do the following: > > kmem_cache_create should check for invalid flags (and that includes > internal alloocator flgs) being set and refuse to create the slab cache. > > memcg needs to call kmem_cache_create without any internal flags. >
I am not sure that is possible. kmem_cache_create currently check for possible alias, I assume that it goes against what memcg tries to do.
Separate the changes in two patches might make sense:
1) Fix the original bug by masking the flags passed to create_cache 2) Add flags check in kmem_cache_create.
Does it make sense?
> I also want to make sure that there are no other callers that specify > extraneou flags while we are at it. >
I will review as many as I can but we might run into surprises (quick boot on defconfig didn't show anything). That's why having two different patches might be useful.
-- Thomas
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