gfs2_free_extlen(9)

📦 version 7.3.1, in nixpkgs unstable

💫 gfs2_free_extlen — a Kernel API Manual moment (section 9, bestie) 💫

okay so real talk, we're in the Kernel API Manual, section 9, and today's main character is gfs2_free_extlen(9). she's a tiny function with one job and she does it immaculately. let's get into it 🎀

✨ NAME ✨

gfs2_free_extlen — Return extent length of free blocks

like... that's the whole vibe. she counts how long a run of free blocks is. no cap. 🦋

🌸 SYNOPSIS 🌸

u32 gfs2_free_extlen (const struct gfs2_rbm *rrbm , u32 len );

yes she takes a const struct gfs2_rbm * pointer and a u32 and she returns a u32. signature stays exactly like that, don't @ me 💅

💖 ARGUMENTS 💖

  • rrbm — Starting position. like, where we begin the little block-stroll, bestie. 🚶‍♀️
  • len — Max length to check. this is your hard ceiling, she will not read past it.

👑 DESCRIPTION 👑

so here's the tea ☕ — starting at the block specified by the rbm, she sees how many free blocks there are, and she does not read more than len blocks ahead. boundaries, queen. respect them. 🙈

now, the fun part: this can be done using memchr_inv when the blocks are byte aligned, but it has to be done on a block by block basis in case of unaligned blocks. no shortcuts for the messy ones, unfortunately. 😭

also, this function can cope with bitmap boundaries — iconique — although it must stop on a resource group boundary. that one's non-negotiable, fr fr. so she's flexible, but not that flexible. 🫶

🔥 RETURN 🔥

Number of free blocks in the extent. that's it, that's the payoff. count 'em and hand 'em over. ✨

🌈 SEE ALSO 🌈

Kernel file ./fs/gfs2/rgrp.c — and honestly the whole group chat showed up for this one:

like I said. the whole group chat. 💀👑

and that's the page, bestie 🎀 — brought to you by the source directory ./fs/gfs2, dated October 2026, filed under gfs2_free_extlen(9). go forth and count your free blocks. slay. 💅✨

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