Thread by @vj_chidambaram

Folks heading to #atc18 check out our work on TxFS, the Texas Transactional File System!

cs.utexas.edu/~vijay/papers/…

We built TxFS in only 5K LOC by utilizing the file-system journal to get atomic and durable transactions.

Providing isolation for TxFS transactions was a hard problem. We customized isolation to each kernel data structure. For data structures like pages which have a narrow access interface, we provide eager conflict detection.

For inodes and dentries which are modified all over the place, we add a timestamp which captures modifications, and provide timestamp-based conflict detection.

One problem with allowing concurrent transactions is that they all modify global data structures like bitmaps and super blocks. We solve this problem by deferring global updates until commit/abort, while allowing the local updates within the transaction.

TxFS has a simple interface, with only three system calls: tx_begin(), tx_commit(), and tx_abort(). All file-system operations within tx_begin() and tx_commit() become part of the transaction. We ported SQLite, Android Mail, and Git to use TxFS transactions.

The code for TxFS is available at github.com/ut-osa/txfs