mm/slab, kfence, memcg: completely remove obj_ext for kfence objects

We have already disabled memory allocation profiling for objects
allocated for KFENCE to avoid complexity. KFENCE allocations are rare
and there can be only CONFIG_KFENCE_NUM_OBJECTS (default to 255)
outstanding ones at any time, so they are among noise in the profiling
stats.

For the same reasons, we can stop memcg_kmem accounting of kfence
objects as their memory usage will be negligible wrt any practical
memcg limits.

This allows us simplifying the code and getting rid of
is_kfence_address() checks in various places, including slab_obj_ext()'s
usage of obj_to_index(). Instead we rely on the fact that slab_obj_exts()
will now always return 0 for a kfence object's fake slab, which makes
those places unreachable.

All we need to do to keep this assumption valid is not to allocate
obj_exts for kfence objects, so the checks need to guard
alloc_slab_obj_exts() where necessary.

Suggested-by: Harry Yoo <harry@kernel.org>
Link: https://patch.msgid.link/20260727-b4-objext_split-v3-13-c29ef0f1f257@kernel.org
Reviewed-by: Hao Li <hao.li@linux.dev>
Signed-off-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>

0 files changed, 0 insertions, 0 deletions