luo_retrieve_file(9)

💅 luo_retrieve_file(9) — Kernel API Manual ✨

okay so bestie, gather round, because this one is literally the glow-up function of the whole live update situation. We're talking luo_retrieve_file — the icon, the main character, the one that brings your preserved file back from the void 🫶

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🌸 NAME 🌸

luo_retrieve_file — restores a preserved file out of a file_set by its token. that's it. that's the vibe check. 🎀

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✨ SYNOPSIS ✨

int luo_retrieve_file (struct luo_file_set *file_set , u64 token ,
struct file **filep );

like yes, three args, she's not complicated, she's just effective 💅

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🦋 ARGUMENTS 🦋

• file_set — the file_set you're pulling the file out of. your source of truth, your origin story, your whole personality for this call ngl.
• token — the unique token that IDs exactly which file is getting restored. it's giving VIP wristband. no token, no entry 💀
• filep — an output parameter!! on success this gets populated with a pointer to the newly retrieved struct file. so like, it starts empty and leaves iconic. that's growth 🌱✨

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💖 DESCRIPTION 💖

so this function is the primary mechanism for recreating a file in the new kernel after a live update. the whole point. the assignment. and she understands it 🫡

here's what she does: she searches the file_set's list of deserialized files for an entry matching the token you handed her. little detective moment. magnifying glass out. 🔍

and the best part? the operation is idempotent. say it with me — idempotent. if a file has already been successfully retrieved, this function will simply return a pointer to the existing operation. no drama, no double-restoring, no chaos. she's not doing the work twice, she's smarter than that 😌

this is handled by checking the 'retrieved' flag under a lock. yes bestie, there's a lock. there's always a lock. safety first, slay second 🔒✨

also!! file retrieval can happen in any order — it is not bound by the order of preservation. so you don't have to retrieve things in the same sequence they were preserved in. freedom. flexibility. she contains multitudes 🌈

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🎀 CONTEXT 🎀

can be called from an ioctl or other in-kernel code in the new kernel. so like, in-kernel besties only. she's not taking calls from userspace randos 💅

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🔥 RETURN 🔥

• 0 on success — the good ending 🥳
• a negative errno on failure, specifically:
  • -ENOENT if no file with the matching token is found. tragic. the token led nowhere. we've all been there 😭
• and also, any error code returned by the handler's .retrieve op — because sometimes the handler has opinions and we respect them 🙈

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👑 SEE ALSO 👑

• Kernel file ./kernel/liveupdate/luo_file.c
• LUO File Descriptors(9)
• struct luo_file(9)
• luo_preserve_file(9)
• luo_file_unpreserve_files(9)
• luo_file_freeze(9)
• luo_file_unfreeze(9)
• luo_file_finish(9)
• luo_file_deserialize(9)
• liveupdate_register_file_handler(9)
• liveupdate_unregister_file_handler(9)

the whole friend group fr fr, go read them all, iykyk 🧚💜

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lowkey a reminder bestie: idempotency here depends on that 'retrieved' flag being checked under the lock — that's the mechanism the page describes, so don't go reinventing it, mwah 🍓

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and that's the page!! brought to you by ./kernel/liveupdate, dated October 2026 — she's serving version-and-date realness and honestly? iconic. bye bestie, go retrieve some files 💖✨🎀💅🌟