mm: slub: only warn once when allocating slab obj extensions fails

In memory bound systems, a large number of warnings for failing this
allocation repeatedly may mask any real issues in the system
during memory pressure being reported in dmesg. Change this to
warning only once.

Signed-off-by: Usama Arif <[email protected]>
Reported-by: Vlad Poenaru <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Reviewed-by: Shakeel Butt <[email protected]>
Reviewed-by: SeongJae Park <[email protected]>
Acked-by: Harry Yoo <[email protected]>
Signed-off-by: Vlastimil Babka <[email protected]>

Author: uarif1

mm/slub.c

@@ -2102,10 +2102,11 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp_t flags, void *p)
 
 	slab = virt_to_slab(p);
 	if (!slab_obj_exts(slab) &&
-	    WARN(alloc_slab_obj_exts(slab, s, flags, false),
-		 "%s, %s: Failed to create slab extension vector!\n",
-		 __func__, s->name))
+	    alloc_slab_obj_exts(slab, s, flags, false)) {
+		pr_warn_once("%s, %s: Failed to create slab extension vector!\n",
+			     __func__, s->name);
 		return NULL;
+	}
 
 	return slab_obj_exts(slab) + obj_to_index(s, slab, p);
 }