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SubjectRe: [PATCH] slab, slub: skip unnecessary kasan_cache_shutdown()
On Tue, Mar 27, 2018 at 5:16 PM, David Rientjes <rientjes@google.com> wrote:
> On Tue, 27 Mar 2018, Shakeel Butt wrote:
>
>> diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
>> index 49fffb0ca83b..135ce2838c89 100644
>> --- a/mm/kasan/kasan.c
>> +++ b/mm/kasan/kasan.c
>> @@ -382,7 +382,8 @@ void kasan_cache_shrink(struct kmem_cache *cache)
>>
>> void kasan_cache_shutdown(struct kmem_cache *cache)
>> {
>> - quarantine_remove_cache(cache);
>> + if (!__kmem_cache_empty(cache))
>> + quarantine_remove_cache(cache);
>> }
>>
>> size_t kasan_metadata_size(struct kmem_cache *cache)
>> diff --git a/mm/slab.c b/mm/slab.c
>> index 9212c64bb705..b59f2cdf28d1 100644
>> --- a/mm/slab.c
>> +++ b/mm/slab.c
>> @@ -2291,6 +2291,18 @@ static int drain_freelist(struct kmem_cache *cache,
>> return nr_freed;
>> }
>>
>> +bool __kmem_cache_empty(struct kmem_cache *s)
>> +{
>> + int node;
>> + struct kmem_cache_node *n;
>> +
>> + for_each_kmem_cache_node(s, node, n)
>> + if (!list_empty(&n->slabs_full) ||
>> + !list_empty(&n->slabs_partial))
>> + return false;
>> + return true;
>> +}
>> +
>> int __kmem_cache_shrink(struct kmem_cache *cachep)
>> {
>> int ret = 0;
>> diff --git a/mm/slab.h b/mm/slab.h
>> index e8981e811c45..68bdf498da3b 100644
>> --- a/mm/slab.h
>> +++ b/mm/slab.h
>> @@ -166,6 +166,7 @@ static inline slab_flags_t kmem_cache_flags(unsigned int object_size,
>> SLAB_TEMPORARY | \
>> SLAB_ACCOUNT)
>>
>> +bool __kmem_cache_empty(struct kmem_cache *);
>> int __kmem_cache_shutdown(struct kmem_cache *);
>> void __kmem_cache_release(struct kmem_cache *);
>> int __kmem_cache_shrink(struct kmem_cache *);
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 1edc8d97c862..44aa7847324a 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -3707,6 +3707,17 @@ static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
>> discard_slab(s, page);
>> }
>>
>> +bool __kmem_cache_empty(struct kmem_cache *s)
>> +{
>> + int node;
>> + struct kmem_cache_node *n;
>> +
>> + for_each_kmem_cache_node(s, node, n)
>> + if (n->nr_partial || slabs_node(s, node))
>> + return false;
>> + return true;
>> +}
>> +
>> /*
>> * Release all resources used by a slab cache.
>> */
>
> Any reason not to just make quarantine_remove_cache() part of
> __kmem_cache_shutdown() instead of duplicating its logic?

Can you please explain what you mean by making
quarantine_remove_cache() part of __kmem_cache_shutdown()? Do you mean
calling quarantine_remove_cache() inside __kmem_cache_shutdown()? The
__kmem_cache_shutdown() of both SLAB & SLUB does per-cpu
draining/flushing and we want the free the quarantined objects before
that. So, I am not sure how to incorporate quarantine_remove_cache()
into __kmem_cache_shutdown() without duplicating the for-loop &
if-condition.

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