1 files changed, 28 insertions, 4 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 3b8ae1a8f02d..e3adb714c04b 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -28,15 +28,18 @@ static const unsigned int btrfs_blocked_trans_types[TRANS_STATE_MAX] = {
 	[TRANS_STATE_COMMIT_START]	= (__TRANS_START | __TRANS_ATTACH),
 	[TRANS_STATE_COMMIT_DOING]	= (__TRANS_START |
 					   __TRANS_ATTACH |
-					   __TRANS_JOIN),
+					   __TRANS_JOIN |
+					   __TRANS_JOIN_NOSTART),
 	[TRANS_STATE_UNBLOCKED]		= (__TRANS_START |
 					   __TRANS_ATTACH |
 					   __TRANS_JOIN |
-					   __TRANS_JOIN_NOLOCK),
+					   __TRANS_JOIN_NOLOCK |
+					   __TRANS_JOIN_NOSTART),
 	[TRANS_STATE_COMPLETED]		= (__TRANS_START |
 					   __TRANS_ATTACH |
 					   __TRANS_JOIN |
-					   __TRANS_JOIN_NOLOCK),
+					   __TRANS_JOIN_NOLOCK |
+					   __TRANS_JOIN_NOSTART),
 };
 
 void btrfs_put_transaction(struct btrfs_transaction *transaction)
@@ -543,7 +546,8 @@ again:
 		ret = join_transaction(fs_info, type);
 		if (ret == -EBUSY) {
 			wait_current_trans(fs_info);
-			if (unlikely(type == TRANS_ATTACH))
+			if (unlikely(type == TRANS_ATTACH ||
+				     type == TRANS_JOIN_NOSTART))
 				ret = -ENOENT;
 		}
 	} while (ret == -EBUSY);
@@ -660,6 +664,16 @@ struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root
 }
 
 /*
+ * Similar to regular join but it never starts a transaction when none is
+ * running or after waiting for the current one to finish.
+ */
+struct btrfs_trans_handle *btrfs_join_transaction_nostart(struct btrfs_root *root)
+{
+	return start_transaction(root, 0, TRANS_JOIN_NOSTART,
+				 BTRFS_RESERVE_NO_FLUSH, true);
+}
+
+/*
  * btrfs_attach_transaction() - catch the running transaction
  *
  * It is used when we want to commit the current the transaction, but
@@ -2037,6 +2051,16 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 		}
 	} else {
 		spin_unlock(&fs_info->trans_lock);
+		/*
+		 * The previous transaction was aborted and was already removed
+		 * from the list of transactions at fs_info->trans_list. So we
+		 * abort to prevent writing a new superblock that reflects a
+		 * corrupt state (pointing to trees with unwritten nodes/leafs).
+		 */
+		if (test_bit(BTRFS_FS_STATE_TRANS_ABORTED, &fs_info->fs_state)) {
+			ret = -EROFS;
+			goto cleanup_transaction;
+		}
 	}
 
 	extwriter_counter_dec(cur_trans, trans->type);