calc_max_reserv(9)

📦 version 7.3.1, in nixpkgs unstable

💅 calc_max_reserv(9)

okay so first things first, bestie — this page lives in the Kernel API Manual, section 9, and the function is called calc_max_reserv. say it with me: calc-max-reserv. iconic name honestly.

✨ NAME ✨

calc_max_reserv — the literal reverse of write_calc_reserv. you give it a number of blocks, and it figures out how many bytes can be written. that's it, that's the whole vibe. 💖

🦋 SYNOPSIS 🦋

void calc_max_reserv (struct gfs2_inode *ip , loff_t *len , unsigned int *data_blocks , unsigned int *ind_blocks , unsigned int max_blocks );

like, look at that signature. five arguments. no cap, she's got a lot going on but she handles it. 👑

🎀 ARGUMENTS 🎀

  • ip — the inode in question. the main character of this whole situation, fr fr.
  • len — the max cap of bytes. and here's the rule, listen up: whatever we hand back in *len must be <= this. no exceptions, bestie, that's a hard boundary. 🚧
  • data_blocks — this one gets computed and returned: the number of data blocks needed. bless her, she's doing double duty. ✨
  • ind_blocks — same situation — computed and returned, but this time it's the number of indirect blocks needed. indirect queen. 💅
  • max_blocks — the total blocks available to work with. the budget. the allowance. do not exceed. 💸

🔥 RETURN 🔥

it's void, so nothing comes back the normal way — but len, data_blocks and ind_blocks all get filled in. so like, technically no return value, but emotionally there's a lot going on. 😭

👑 SEE ALSO 👑

go check out the kernel file ./fs/gfs2/file.c (iykyk) plus all of these:

a whole friend group, honestly. 🫶

aaaand that's the page! this one's comin' at you from ./fs/gfs2, dated October 2026, and the function is calc_max_reserv(9) — love her, read her, cite her. 🍓💜✨

📦 where this page comes from