bcachefs

Posted Feb 24, 2025 21:37 UTC (Mon) by Cyberax (✭ supporter ✭, #52523)
In reply to: bcachefs by tim-day-387
Parent article: Filesystem support for block sizes larger than the page size

How does Lustre currently handle transactions? Especially rollbacks?

It looks like transactions in Lustre are more like an atomic group of operations, rather than something long-lived? I.e. you can't start a transaction, spend 2 hours doing something with it, and then commit it?

bcachefs

Posted Feb 25, 2025 16:49 UTC (Tue) by tim-day-387 (subscriber, #171751) [Link]

Currently, Lustre hooks into ext4 transactions in osd_trans_start() and osd_trans_stop() [1]. So the transactions aren't long-lived and are usually scoped to a single function. Lustre patches ext4 (to create ldiskfs) and interfaces with it directly. But it'd probably be better to have a generic way for filesystems to (optionally) expose these primitives. Infiniband has a concept of kverbs - drivers can optionally expose an interface to in-kernel users. We'd could do something similar for transaction handling.

[1] https://git.whamcloud.com/?p=fs/lustre-release.git;a=blob;...