check_mapping(9)

📦 version 7.3.1, in nixpkgs unstable

💅 check_mapping(9) — the kernel api manual, but make it make sense 🎀

okay so bestie, welcome to check_mapping(9) from the Kernel API Manual ✨ this one's a lil UBI detective story and honestly it ate. let's get into it 🫶

🌸 NAME 🌸

check_mapping — check and fixup a mapping 💖 (yes, both. it checks and it fixes, she's multifunctional)

✨ SYNOPSIS ✨

int check_mapping (struct ubi_device *ubi , struct ubi_volume *vol , int
lnum , int *pnum );

literally the whole signature, character for character, no cap 🔥

🦋 ARGUMENTS 🦋

  • ubi — the UBI device description object, aka the big boss device 💅
  • vol — the volume description object, her volume bestie 🎀
  • lnum — logical eraseblock number, the LEB in question ✨
  • pnum — physical eraseblock number, the PEB that's supposedly behind it 👑

💜 DESCRIPTION 💜

so here's the vibe check 👀 — this function checks whether a given mapping is actually valid. sounds simple right? it's giving "just look at it" but it's NOT, okay 😭

here's the plot twist: Fastmap cannot track LEB unmap operations. like, it just can't, bless her. so if such an unmapping operation gets interrupted mid-way, the mapping still looks good — totally fine, nothing to see here — but the moment somebody does the first read, an ECC gets reported to the upper layer 💀 rude.

normally this gets patched up during the full-scan at attach time, so it's all chill. but for Fastmap? nope, we've gotta deal with it while reading, live, in the moment, main character energy 🔥

and if the PEB behind a LEB is showing this symptom (the original calls it "symthom" and honestly, we respect the spelling, we're keeping the energy 🙈), then we change the mapping to UBI_LEB_UNMAPPED and schedule that PEB for erasure. bye girl 👋 she's getting wiped.

returns 0 on success, or a negative error code in case of failure 😭 that's the whole mood.

💖 SEE ALSO 💖

the whole group chat, in this exact order, no skipping 🫶

aaaand that's the page!! 🌈 this lil angel lives in ./drivers/mtd/ubi, she was stamped October 2026, and her name is check_mapping(9) — ok bye, love u, go read your eraseblocks 💜🧚‍♀️⭐

📦 where this page comes from