The Btrfs “enospc-rework” that’s been in development for several months by Facebook’s Josef Bacik is landing with the Linux 4.8 kernel.
The ENOSPC rework is about reworking the handling for no-space checking/handling by the file-system. The existing code would encounter issues with huge latency spikes, too much being flushed, and not all of the file-system’s flushing being asynchronous. The code by Josef Bacik is making use of tickets for reservations of space on the file-system. The new ticket-based reservation approach is explained further by this patch.