SLUB: kmem_cache_destroy doesn't

From: Neil Brown
Date: Thu Apr 12 2007 - 03:27:53 EST



I tried out SLOB in latest mm.
raid5 uses kmem_cache_create to create a cache, a deletes it with
kmem_cache_destroy.

After I change the name for the slab to not include a '/' the create
worked fine, but the destroy seems incomplete.
If I stop an array and restart it, the second kmem_cache_create fails
because it thinks the name is already in use.

If I look in sysfs, I can see it there.
And

# cat /sys/slab/raid5-md1/aliases
-1

is a bit suspicious.

And

void kmem_cache_destroy(struct kmem_cache *s)
{
down_write(&slub_lock);
if (s->refcount)
s->refcount--;
else {
list_del(&s->list);
WARN_ON(kmem_cache_close(s));
sysfs_slab_remove(s);
kfree(s);
}
up_write(&slub_lock);
}

looks a bit odd.
I would have thought the test should be:

if (s->refcount > 1)

??

(2.6.21-rc6-mm1 to be precise)

NeilBrown
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