bcachefs: BKEY_PADDED_ONSTACK()

Rust bindgen doesn't do anonymous structs very nicely: BKEY_PADDED()
only needs the anonymous struct when it's used on the stack, to
guarantee layout, not when it's embedded in another struct.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs.h

@@ -1123,4 +1123,7 @@ static inline bool bch2_dev_exists2(const struct bch_fs *c, unsigned dev)
 	return dev < c->sb.nr_devices && c->devs[dev];
 }
 
+#define BKEY_PADDED_ONSTACK(key, pad)				\
+	struct { struct bkey_i key; __u64 key ## _pad[pad]; }
+
 #endif /* _BCACHEFS_H */

fs/bcachefs/bcachefs_format.h

@@ -322,7 +322,7 @@ static inline void bkey_init(struct bkey *k)
 #define bkey_bytes(_k)		((_k)->u64s * sizeof(__u64))
 
 #define __BKEY_PADDED(key, pad)					\
-	struct { struct bkey_i key; __u64 key ## _pad[pad]; }
+	struct bkey_i key; __u64 key ## _pad[pad]
 
 /*
  * - DELETED keys are used internally to mark keys that should be ignored but

fs/bcachefs/btree_io.c

@@ -1847,7 +1847,7 @@ static void btree_write_submit(struct work_struct *work)
 {
 	struct btree_write_bio *wbio = container_of(work, struct btree_write_bio, work);
 	struct bch_extent_ptr *ptr;
-	__BKEY_PADDED(k, BKEY_BTREE_PTR_VAL_U64s_MAX) tmp;
+	BKEY_PADDED_ONSTACK(k, BKEY_BTREE_PTR_VAL_U64s_MAX) tmp;
 
 	bkey_copy(&tmp.k, &wbio->key);
 

fs/bcachefs/btree_update_interior.c

@@ -242,7 +242,7 @@ static struct btree *__bch2_btree_node_alloc(struct btree_trans *trans,
 	struct bch_fs *c = trans->c;
 	struct write_point *wp;
 	struct btree *b;
-	__BKEY_PADDED(k, BKEY_BTREE_PTR_VAL_U64s_MAX) tmp;
+	BKEY_PADDED_ONSTACK(k, BKEY_BTREE_PTR_VAL_U64s_MAX) tmp;
 	struct open_buckets ob = { .nr = 0 };
 	struct bch_devs_list devs_have = (struct bch_devs_list) { 0 };
 	unsigned nr_reserve;