unwritten-extent · shipping · also uninitialized extent

Unwritten extent

An allocated filesystem extent whose data is not initialized and is exposed as zeros when read through the filesystem.

Unlike a hole it has allocation; unlike delayed allocation it has assigned storage. Zero reads do not establish device contents or sanitization.

Relations

related

file-extent, file-preallocation, sparse-file, hole-punching

Citations

1. Linux 6.12: FIEMAP extent states and access restrictions (accessed 2026-10-13)
2. Sparse files, preallocation and thin-pool capacity (accessed 2026-10-13)

JSON: /data/terms/unwritten-extent.json