fideduperange · shipping · also file range deduplication ioctl

FIDEDUPERANGE

FIDEDUPERANGE is a Linux ioctl that compares file ranges and shares their storage when they match.

Related Observatory article: FIDEDUPERANGE on hesela.com

Unlike cloning, this operation preserves different destination bytes instead of replacing them with source contents. It works within one filesystem and reports status separately for each destination. [1]

A successful outer call can contain failed or mismatched destinations. In the Linux v6.18 VFS path, a nonnegative callback result is reported using the capped request length, even if generic preparation shortened it. That historical counter is not a byte-accurate coverage certificate or a measurement of reclaimed storage. [2]

The Linux v6.12 ioctl wrapper performs work before copying the results back to userspace. Failure of that copy can return EFAULT after work occurred, so an error is not a general rollback guarantee. [3]

Relations

related
Reflink, Data deduplication, Copy-on-write (storage), File extent, Btrfs filesystem du

Citations

  1. Linux man-pages: FIDEDUPERANGE, compare-and-share and per-destination results (accessed 2026-10-20)
  2. Linux v6.18: remap_range.c, length rounding and historical bytes_deduped reporting (accessed 2026-10-20)
  3. Linux v6.12: ioctl.c, FIDEDUPERANGE validation and copying results to userspace (accessed 2026-10-20)

Further reading

  1. Hesela: file cloning and deduplication result accounting (accessed 2026-10-20)
Sources & caveats
  • Implementation details refer to the cited upstream tags, not every downstream kernel or the newest release.
  • The companion worksheet is source-derived arithmetic, not measured filesystem behavior.

JSON: /data/terms/fideduperange.json

Published by Hesela team · Updated

Report a correction · Editorial standards · Reuse guidance

Cite this page
Hesela team. FIDEDUPERANGE. Hesela. 2026-10-20. https://hesela.dev/terms/fideduperange/