bpf: Add is_fd_htab() helper

JIRA: https://issues.redhat.com/browse/RHEL-110274

commit e8a6585
Author: Hou Tao <houtao1@huawei.com>
Date:   Tue Apr 1 14:22:48 2025 +0800

    bpf: Add is_fd_htab() helper
    
    Add is_fd_htab() helper to check whether the map is htab of maps.
    
    Acked-by: Andrii Nakryiko <andrii@kernel.org>
    Signed-off-by: Hou Tao <houtao1@huawei.com>
    Link: https://lore.kernel.org/r/20250401062250.543403-5-houtao@huaweicloud.com
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Signed-off-by: Viktor Malik <vmalik@redhat.com>

Author: viktormalik

kernel/bpf/hashtab.c

@@ -194,6 +194,11 @@ static bool htab_is_percpu(const struct bpf_htab *htab)
 		htab->map.map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH;
 }
 
+static inline bool is_fd_htab(const struct bpf_htab *htab)
+{
+	return htab->map.map_type == BPF_MAP_TYPE_HASH_OF_MAPS;
+}
+
 static inline void *htab_elem_value(struct htab_elem *l, u32 key_size)
 {
 	return l->key + round_up(key_size, 8);
@@ -1005,8 +1010,7 @@ static void pcpu_init_value(struct bpf_htab *htab, void __percpu *pptr,
 
 static bool fd_htab_map_needs_adjust(const struct bpf_htab *htab)
 {
-	return htab->map.map_type == BPF_MAP_TYPE_HASH_OF_MAPS &&
-	       BITS_PER_LONG == 64;
+	return is_fd_htab(htab) && BITS_PER_LONG == 64;
 }
 
 static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
@@ -1845,7 +1849,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 			}
 		} else {
 			value = htab_elem_value(l, key_size);
-			if (map->map_type == BPF_MAP_TYPE_HASH_OF_MAPS) {
+			if (is_fd_htab(htab)) {
 				struct bpf_map **inner_map = value;
 
 				 /* Actual value is the id of the inner map */