mm, slub: remove slub_memcg_sysfs boot param and CONFIG_SLUB_MEMCG_SYSFS_ON

The boot param and config determine the value of memcg_sysfs_enabled,
which is unused since commit 10befea91b ("mm: memcg/slab: use a single
set of kmem_caches for all allocations") as there are no per-memcg kmem
caches anymore.

Link: https://lkml.kernel.org/r/20210127124745.7928-1-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

init/Kconfig

@@ -1861,20 +1861,6 @@ config SLUB_DEBUG
 	  SLUB sysfs support. /sys/slab will not exist and there will be
 	  no support for cache validation etc.
 
-config SLUB_MEMCG_SYSFS_ON
-	default n
-	bool "Enable memcg SLUB sysfs support by default" if EXPERT
-	depends on SLUB && SYSFS && MEMCG
-	help
-	  SLUB creates a directory under /sys/kernel/slab for each
-	  allocation cache to host info and debug files. If memory
-	  cgroup is enabled, each cache can have per memory cgroup
-	  caches. SLUB can create the same sysfs directories for these
-	  caches under /sys/kernel/slab/CACHE/cgroup but it can lead
-	  to a very high number of debug files being created. This is
-	  controlled by slub_memcg_sysfs boot parameter and this
-	  config option determines the parameter's default value.
-
 config COMPAT_BRK
 	bool "Disable heap randomization"
 	default y