xdr_reserve_space(9)

📦 version 7.3.1, in nixpkgs unstable

✨ xdr_reserve_space ✨

Okay bestie, so this one is a kernel API manual page — section 9, the whole "Kernel API Manual" vibe — and it's literally called xdr_reserve_space. It's giving "I just need a little room to write" energy, and honestly? Same.

🌸 SYNOPSIS 🌸

__be32 * xdr_reserve_space (struct xdr_stream *xdr , size_t nbytes );

That's the whole signature, no cap. It hands you back a __be32 * — a pointer you're gonna want to hold onto for approximately five seconds. 💅

🎀 ARGUMENTS 🎀

  • xdr — pointer to xdr_stream. That's your stream, your main character. Everything revolves around her.
  • nbytes — number of bytes to reserve. How much space you're asking for, in bytes, fr fr.

🦋 DESCRIPTION 🦋

So what it does is: it checks that we have enough buffer space to encode nbytes more bytes of data. That's the vibe check. If it passes — if there's room — then it updates the total xdr_buf length, and adjusts the length of the current kvec. Slay.

⚠️ Important bestie warning: the returned pointer is valid only until the next call to xdr_reserve_space or xdr_commit_encode on xdr. So don't go hoarding it. It expires faster than a Snapchat streak. 😭

And then there's this little detail that is so important I'm putting it in its own paragraph:

The current implementation of this API guarantees that space reserved for a four-byte data item remains valid until xdr is destroyed — but that might not always be true in the future. So it's a "today yes, tomorrow maybe" kind of guarantee. Not a forever promise. Highkey a situationship. 🙈

🔥 SEE ALSO 🔥

So much lore here — the whole XDR family tree. Kernel file ./net/sunrpc/xdr.c and honestly like thirty other functions:

Like I said. The whole family. Every single one. Go read them, iykyk. 👑

💖 Okay that's the page!! It lives in ./net/sunrpc, the version tag says October 2026, and it's all xdr_reserve_space(9) from the Kernel API Manual. Mwah. Go reserve some space bestie, you've earned it. 🫶✨

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