On Mon, 17 Feb 2014, Joonsoo Kim wrote:

quoted

Why change the BAD_ALIEN_MAGIC?

Hello, Christoph.

BAD_ALIEN_MAGIC is only checked by slab_set_lock_classes(). We remove this
function in this patch, so returning BAD_ALIEN_MAGIC is useless.

Its not useless. The point is if there is a pointer deref then we will see
this as a pointer value and know that it is realted to alien cache
processing.

And, in fact, BAD_ALIEN_MAGIC is already useless, because alloc_alien_cache()
can't be called on !CONFIG_NUMA. This function is called if use_alien_caches
is positive, but on !CONFIG_NUMA, use_alien_caches is always 0. So we don't
have any chance to meet this BAD_ALIEN_MAGIC in runtime.

Maybe it no longer serves a point. But note that caches may not be
populated because processors/nodes are not up yet.

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