nfsd_read_splice_ok(9)

📦 version 7.3.1, in nixpkgs unstable

✨ nfsd_read_splice_ok(9) ✨

okay so bestie, this is a page from the Kernel API Manual (section 9, kernel-functions territory 🧚) and it's literally just one tiny little vibe-check function. don't let the tiny synopsis fool you though — there's lore here 💅

💖 NAME 💖

nfsd_read_splice_ok — the little function that checks if spliced reading is even allowed rn

🦋 SYNOPSIS 🦋

bool nfsd_read_splice_ok (struct svc_rqst *rqstp );

🌸 ARGUMENTS 🌸

  • rqstp — the RPC transaction context 🫶 like, the whole situation for this one request, wrapped up in a struct

🎀 DESCRIPTION 🎀

okay so it returns a bool, and here's the tea on what the two possible answers mean:

  • true — nfsd_splice_read may be used ✅ slay
  • false — nfsd_splice_read must not be used 🙅‍♀️ absolutely not, do not

now for the why, because this is the interesting part, no cap 👑

NFS READ normally uses splice to send data in-place. iconic, efficient, main character energy. However — and this is the plot twist 😭 — the data in cache can change after the reply's MIC is computed but before the RPC reply is actually sent.

so to prevent the client from rejecting the server-computed MIC in this somewhat rare case, do not use splice with the GSS integrity and privacy services 💀

like... it's a rare case, but rare isn't never, and a rejected MIC is a bad time. so the function says no. vibe check failed. respectfully. 🙈

🌈 SEE ALSO 🌈

kernel file ./fs/nfsd/vfs.c — that's where the actual code lives, go say hi 🫶

and the whole friend group:

aaand that's the whole page 🎉 short, sweet, and highkey important. mwah 💋

source: ./fs/nfsd · dated October 2026 · part of the Kernel API Manual, section 9 🦋✨ bye bestie, go read some NFS code 💜

📦 where this page comes from