slub: Do not hold slub_lock when calling sysfs_slab_add()

slub: Do not hold slub_lock when calling sysfs_slab_add()

sysfs_slab_add() calls various sysfs functions that actually may
end up in userspace doing all sorts of things.

Release the slub_lock after adding the kmem_cache structure to the list.
At that point the address of the kmem_cache is not known so we are
guaranteed exlusive access to the following modifications to the
kmem_cache structure.

If the sysfs_slab_add fails then reacquire the slub_lock to
remove the kmem_cache structure from the list.

Cc: <[email protected]>	# 3.3+
Reported-by: Sasha Levin <[email protected]>
Acked-by: Eric Dumazet <[email protected]>
Signed-off-by: Christoph Lameter <[email protected]>
Signed-off-by: Pekka Enberg <[email protected]>