__alloc_flex(9)

📦 version 7.3.1, in nixpkgs unstable

🌸 __alloc_flex — Kernel API Manual ✨

Hiii bestie, welcome to the page for __alloc_flex from the Linux Kernel API Manual 💖 This one's a macro (iykyk) and it's lowkey iconic — it's gonna hand you a struct with a little extra room at the end for your flexible array member. Let's get into it 🫶

✨ NAME ✨

__alloc_flex — allocate an object that has a trailing flexible array 💅

🎀 SYNOPSIS 🎀

__alloc_flex (KMALLOC , GFP , TYPE , FAM , COUNT );

That's the whole vibe. Five things go in, one pointer comes out 👑

🦋 ARGUMENTS 🦋

  • KMALLOC — the kmalloc wrapper function you wanna use for the allocation, bestie. Pick your fave 💫
  • GFP — the GFP flags for the allocation 🌱 (yes they matter, no you can't skip them)
  • TYPE — the type of structure you're allocating space for, like the actual struct name 🏗️
  • FAM — the name of the flexible array member inside the TYPE struct 🌈 (the trailing bit, the main character of the tail end)
  • COUNT — how many FAM elements you want space for 🔢 like, how many lil guys are riding along at the end

⭐ RETURN ⭐

You get back a newly allocated pointer to TYPE with COUNT-many trailing FAM elements 💖

OR you get NULL 😭 — and that happens in two cases, no cap:

  • the allocation failed, or
  • COUNT cannot be represented by the member of TYPE that counts the FAM elements (the one annotated via __counted_by) 🙈
So fr fr, always check for NULL. It's giving "trust me bro" if you don't 🚨

🔥 SEE ALSO 🔥

Kernel file ./include/linux/slab.h — and honestly the whole slab/allocator friend group 🫶:

Okay that's the whole page, you ate that 💅✨ This lil masterpiece lives over in ./include/linux and it's dated October 2026, filed under __alloc_flex(9). Go forth and allocate responsibly, bestie 🧚💜

📦 where this page comes from