gfs2_bitfit(9)

💖 gfs2_bitfit(9) 💖

okay so this is a page from the Kernel API Manual, and bestie, it's literally about gfs2_bitfit — the function whose whole vibe is searching an rgrp's bitmap buffer to find a bit-pair that represents a block in a given allocation state. slay. 🎀

---

✨ NAME ✨

gfs2_bitfit — Search an rgrp's bitmap buffer to find a bit-pair representing a block in a given allocation state. that's it, that's the whole job, and honestly? iconic. 💅

---

🦋 SYNOPSIS 🦋

u32 gfs2_bitfit (const u8 *buf , const unsigned int len , u32 goal , u8
state );

like, copy it exactly, no edits, I'm watching 👀

---

🌸 ARGUMENTS 🌸

• buf — the buffer that holds the bitmaps. the main character, fr fr 🫶
• len — the length (in bytes) of the buffer. yes bestie, bytes, remember that, it matters later 😭
• goal — start the search at this block's bit-pair (within the buffer). it's giving "we begin here and we do not ask questions" ✨
• state — GFS2_BLKST_XXX, the state of the block we're looking for. you tell it what you want, it goes and finds it. king behavior 👑

---

💀 DESCRIPTION 💀

Okay so scope check, because this is the part people get wrong: the goal and the returned block number only mean something within this bitmap buffer — not the entire rgrp, and definitely not the entire filesystem. keep that straight, iykyk. 🧚

The buffer will be offset from the actual beginning of a bitmap block buffer, skipping any header structures — but lowkey it's fine, because headers are always a multiple of 64 bits long, so the buffer is always aligned to a 64 bit boundary. the universe simply kind of works out 🌈

Here's the slightly unhinged part: the size of the buffer is in bytes, but it is assumed that it's always ok to read a complete multiple of 64 bits at the end of the block, in case the end is no aligned to a natural boundary. 🔥 so yeah, that's a thing that's assumed. noted. don't be weird about it.

---

👑 RETURN 👑

the block number (bitmap buffer scope) that was found. that's the answer, that's the gift, go off 💖

reminder bestie: bitmap buffer scope. not rgrp scope, not filesystem scope. the scope thing is real and it will bite you 🙈

---

⭐ SEE ALSO ⭐

Kernel file ./fs/gfs2/rgrp.c, plus the whole extended friend group — every single one of these, no skips:

gfs2_setbit(9), gfs2_testbit(9), gfs2_bit_search(9), rs_cmp(9), gfs2_rbm_from_block(9), gfs2_rbm_add(9), gfs2_unaligned_extlen(9), gfs2_free_extlen(9), gfs2_bitcount(9), gfs2_rgrp_verify(9), gfs2_blk2rgrpd(9), gfs2_rgrpd_get_first(9), gfs2_rgrpd_get_next(9), __rs_deltree(9), gfs2_rs_deltree(9), gfs2_rs_delete(9), return_all_reservations(9), compute_bitstructs(9), gfs2_ri_total(9), read_rindex_entry(9), set_rgrp_preferences(9), gfs2_ri_update(9), gfs2_rindex_update(9), gfs2_rgrp_go_instantiate(9), gfs2_rgrp_brelse(9), gfs2_fitrim(9), rs_insert(9), rgd_free(9), rg_mblk_search(9), gfs2_next_unreserved_block(9), gfs2_reservation_check_and_update(9), gfs2_rbm_find(9), try_rgrp_unlink(9), gfs2_rgrp_congested(9), gfs2_rgrp_used_recently(9), fast_to_acquire(9), gfs2_inplace_reserve(9), gfs2_inplace_release(9), gfs2_alloc_extent(9), rgblk_free(9), gfs2_rgrp_dump(9), gfs2_adjust_reservation(9), gfs2_set_alloc_start(9), gfs2_alloc_blocks(9), __gfs2_free_blocks(9), gfs2_free_meta(9), gfs2_check_blk_type(9), gfs2_rlist_add(9), gfs2_rlist_alloc(9), gfs2_rlist_free(9)

like, that's a whole party 🎉

---

and that's the page!! mwah 💋 this all came from the ./fs/gfs2 source, dated October 2026 — so, you know, shoutout to the future and to whoever wrote this. stan. bye bestie, go read gfs2_setbit(9) next, I believe in you 🌸🫶