Re: [PATCH v2 04/29] slub: always get the cache from its page inkfree

From: Glauber Costa
Date: Fri May 11 2012 - 14:01:02 EST

On 05/11/2012 02:53 PM, Christoph Lameter wrote:
On Fri, 11 May 2012, Glauber Costa wrote:

struct page already have this information. If we start chaining
caches, this information will always be more trustworthy than
whatever is passed into the function

Other allocators may not have that information and this patch may
cause bugs to go unnoticed if the caller specifies the wrong slab cache.

Adding a VM_BUG_ON may be useful to make sure that kmem_cache_free is
always passed the correct slab cache.

Well, problem is , it isn't always passed the "correct" slab cache.
At least not after this series, since we'll have child caches associated with the main cache.

So we'll pass, for instance, kmem_cache_free(dentry_cache...), but will in fact free from the memcg copy of the dentry cache.

We can, of course, verify if the cache at least belongs to the same "family". But that's quite expensive.
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