mm, slab: deprecate SLAB_MEM_SPREAD flag

The SLAB_MEM_SPREAD flag used to be implemented in SLAB, which was
removed.  SLUB instead relies on the page allocator's NUMA policies.
Change the flag's value to 0 to free up the value it had, and mark it
for full removal once all users are gone.

Reported-by: Steven Rostedt <rostedt@goodmis.org>
Closes: https://lore.kernel.org/all/20240131172027.10f64405@gandalf.local.home/
Reviewed-and-tested-by: Xiongwei Song <xiongwei.song@windriver.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

include/linux/slab.h

@@ -96,8 +96,6 @@
  */
 /* Defer freeing slabs to RCU */
 #define SLAB_TYPESAFE_BY_RCU	((slab_flags_t __force)0x00080000U)
-/* Spread some memory over cpuset */
-#define SLAB_MEM_SPREAD		((slab_flags_t __force)0x00100000U)
 /* Trace allocations and frees */
 #define SLAB_TRACE		((slab_flags_t __force)0x00200000U)
 
@@ -164,6 +162,9 @@
 #endif
 #define SLAB_TEMPORARY		SLAB_RECLAIM_ACCOUNT	/* Objects are short-lived */
 
+/* Obsolete unused flag, to be removed */
+#define SLAB_MEM_SPREAD		((slab_flags_t __force)0U)
+
 /*
  * ZERO_SIZE_PTR will be returned for zero sized kmalloc requests.
  *

mm/slab.h

@@ -469,7 +469,6 @@ static inline bool is_kmalloc_cache(struct kmem_cache *s)
 			      SLAB_STORE_USER | \
 			      SLAB_TRACE | \
 			      SLAB_CONSISTENCY_CHECKS | \
-			      SLAB_MEM_SPREAD | \
 			      SLAB_NOLEAKTRACE | \
 			      SLAB_RECLAIM_ACCOUNT | \
 			      SLAB_TEMPORARY | \