mm/slab: stop allocating objcg pointers when unnecessary

Start using the slab_needs_objcg() helper to calculate slabobj_ext size.
Caches that we know to never need objcg pointers (currently
KMALLOC_NORMAL caches) will thus stop wasting memory on them when memory
allocation profiling is enabled.

For things to work properly, we need to also add slab_needs_objcg()
checks to mem_cgroup_from_obj_slab() and memcg_slab_free_hook(), because
when obj_exts array exists for a slab only due to mem_alloc profiling,
we would otherwise attempt to access a non-existing objcg pointer in
that slab.

In slab_obj_ext_[set_]objcg() add debug warnings if called on a slab
where slab_needs_objcg() is false.

Reviewed-by: Hao Li <hao.li@linux.dev>
Link: https://patch.msgid.link/20260727-b4-objext_split-v3-12-c29ef0f1f257@kernel.org
Reviewed-by: Harry Yoo <harry@kernel.org>
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>

0 files changed, 0 insertions, 0 deletions