bcachefs: bch2_bkey_alloc() now calls bch2_trans_update()

It's safe to call bch2_trans_update with a k/v pair where the value
hasn't been filled out, as long as the key part has been and the value
is filled out by transaction commit time.

This patch folds the bch2_trans_update() call into bch2_bkey_alloc(),
eliminating a bit of boilerplate.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_update.h

@@ -251,22 +251,27 @@ static inline struct bkey_i *bch2_bkey_get_mut(struct btree_trans *trans,
 			KEY_TYPE_##_type, sizeof(struct bkey_i_##_type)))
 
 static inline struct bkey_i *__bch2_bkey_alloc(struct btree_trans *trans, struct btree_iter *iter,
-					       unsigned type, unsigned val_size)
+					       unsigned flags, unsigned type, unsigned val_size)
 {
 	struct bkey_i *k = bch2_trans_kmalloc(trans, sizeof(*k) + val_size);
+	int ret;
 
-	if (!IS_ERR(k)) {
-		bkey_init(&k->k);
-		k->k.p = iter->pos;
-		k->k.type = type;
-		set_bkey_val_bytes(&k->k, val_size);
-	}
+	if (IS_ERR(k))
+		return k;
+
+	bkey_init(&k->k);
+	k->k.p = iter->pos;
+	k->k.type = type;
+	set_bkey_val_bytes(&k->k, val_size);
 
+	ret = bch2_trans_update(trans, iter, k, flags);
+	if (unlikely(ret))
+		return ERR_PTR(ret);
 	return k;
 }
 
-#define bch2_bkey_alloc(_trans, _iter, _type)				\
-	bkey_i_to_##_type(__bch2_bkey_alloc(_trans, _iter,		\
+#define bch2_bkey_alloc(_trans, _iter, _flags, _type)			\
+	bkey_i_to_##_type(__bch2_bkey_alloc(_trans, _iter, _flags,	\
 				KEY_TYPE_##_type, sizeof(struct bch_##_type)))
 
 #endif /* _BCACHEFS_BTREE_UPDATE_H */

fs/bcachefs/subvolume.c

@@ -476,7 +476,7 @@ int bch2_snapshot_node_create(struct btree_trans *trans, u32 parent,
 			goto err;
 		}
 
-		n = bch2_bkey_alloc(trans, &iter, snapshot);
+		n = bch2_bkey_alloc(trans, &iter, 0, snapshot);
 		ret = PTR_ERR_OR_ZERO(n);
 		if (ret)
 			goto err;
@@ -487,9 +487,8 @@ int bch2_snapshot_node_create(struct btree_trans *trans, u32 parent,
 		n->v.pad	= 0;
 		SET_BCH_SNAPSHOT_SUBVOL(&n->v, true);
 
-		ret   = bch2_trans_update(trans, &iter, &n->k_i, 0) ?:
-			bch2_mark_snapshot(trans, BTREE_ID_snapshots, 0,
-					   bkey_s_c_null, bkey_i_to_s_c(&n->k_i), 0);
+		ret = bch2_mark_snapshot(trans, BTREE_ID_snapshots, 0,
+					 bkey_s_c_null, bkey_i_to_s_c(&n->k_i), 0);
 		if (ret)
 			goto err;
 
@@ -981,7 +980,7 @@ int bch2_subvolume_create(struct btree_trans *trans, u64 inode,
 			goto err;
 	}
 
-	new_subvol = bch2_bkey_alloc(trans, &dst_iter, subvolume);
+	new_subvol = bch2_bkey_alloc(trans, &dst_iter, 0, subvolume);
 	ret = PTR_ERR_OR_ZERO(new_subvol);
 	if (ret)
 		goto err;
@@ -991,9 +990,6 @@ int bch2_subvolume_create(struct btree_trans *trans, u64 inode,
 	new_subvol->v.inode	= cpu_to_le64(inode);
 	SET_BCH_SUBVOLUME_RO(&new_subvol->v, ro);
 	SET_BCH_SUBVOLUME_SNAP(&new_subvol->v, src_subvolid != 0);
-	ret = bch2_trans_update(trans, &dst_iter, &new_subvol->k_i, 0);
-	if (ret)
-		goto err;
 
 	*new_subvolid	= new_subvol->k.p.offset;
 	*new_snapshotid	= new_nodes[0];