bpf: Re-enable unit_size checking for global per-cpu allocator

With pcpu_alloc_size() in place, check whether or not the size of
the dynamic per-cpu area is matched with unit_size.
Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20231020133202.4043247-4-houtao@huaweicloud.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/memalloc.c

@@ -491,21 +491,17 @@ static int check_obj_size(struct bpf_mem_cache *c, unsigned int idx)
 	struct llist_node *first;
 	unsigned int obj_size;
 
-	/* For per-cpu allocator, the size of free objects in free list doesn't
-	 * match with unit_size and now there is no way to get the size of
-	 * per-cpu pointer saved in free object, so just skip the checking.
-	 */
-	if (c->percpu_size)
-		return 0;
-
 	first = c->free_llist.first;
 	if (!first)
 		return 0;
 
-	obj_size = ksize(first);
+	if (c->percpu_size)
+		obj_size = pcpu_alloc_size(((void **)first)[1]);
+	else
+		obj_size = ksize(first);
 	if (obj_size != c->unit_size) {
-		WARN_ONCE(1, "bpf_mem_cache[%u]: unexpected object size %u, expect %u\n",
-			  idx, obj_size, c->unit_size);
+		WARN_ONCE(1, "bpf_mem_cache[%u]: percpu %d, unexpected object size %u, expect %u\n",
+			  idx, c->percpu_size, obj_size, c->unit_size);
 		return -EINVAL;
 	}
 	return 0;
@@ -973,6 +969,12 @@ void notrace *bpf_mem_cache_alloc_flags(struct bpf_mem_alloc *ma, gfp_t flags)
 	return !ret ? NULL : ret + LLIST_NODE_SZ;
 }
 
+/* The alignment of dynamic per-cpu area is 8, so c->unit_size and the
+ * actual size of dynamic per-cpu area will always be matched and there is
+ * no need to adjust size_index for per-cpu allocation. However for the
+ * simplicity of the implementation, use an unified size_index for both
+ * kmalloc and per-cpu allocation.
+ */
 static __init int bpf_mem_cache_adjust_size(void)
 {
 	unsigned int size;