Re: [PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB & OBJFREELIST_SLAB

From	Thomas Garnier <thgarnie@google.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB & OBJFREELIST_SLAB
Date	2016-11-07 21:00 +0100
Message-ID	<sAYff-7Eq-3@gated-at.bofh.it> (permalink)
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On Mon, Nov 7, 2016 at 11:28 AM, Christoph Lameter <cl@linux.com> wrote:
> On Mon, 7 Nov 2016, Thomas Garnier wrote:
>
>> 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.
>
> What does aliasing have to do with this? The aliases must have the same
> flags otherwise the caches would not have been merged.
>

I assume there might be cases where the parent cache and the new memcg
cache are compatible for merge (same flags and size). We can bypass
that by adding SLAB_NEVER_MERGE but I am not sure what is the
consequence of that.

>> 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?
>
> Sure.
>

Great, I will send both patches.

>> > 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.
>
> These surprises can be caught later ... Just make sure that the core works
> fine with this. You cannot audit all drivers.
>

Okay, I will.



-- 
Thomas

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[PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB & OBJFREELIST_SLAB Thomas Garnier <thgarnie@google.com> - 2016-10-31 19:40 +0100
  Re: [PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB &  OBJFREELIST_SLAB David Rientjes <rientjes@google.com> - 2016-11-01 00:40 +0100
    Re: [PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB & OBJFREELIST_SLAB Thomas Garnier <thgarnie@google.com> - 2016-11-02 17:10 +0100
      Re: [PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB &  OBJFREELIST_SLAB David Rientjes <rientjes@google.com> - 2016-11-03 01:50 +0100
        Re: [PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB &  OBJFREELIST_SLAB Christoph Lameter <cl@linux.com> - 2016-11-03 21:40 +0100
          Re: [PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB & OBJFREELIST_SLAB Thomas Garnier <thgarnie@google.com> - 2016-11-07 20:00 +0100
            Re: [PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB &  OBJFREELIST_SLAB Christoph Lameter <cl@linux.com> - 2016-11-07 20:30 +0100
              Re: [PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB & OBJFREELIST_SLAB Thomas Garnier <thgarnie@google.com> - 2016-11-07 21:00 +0100

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