LUO FILE LIFECYCLE BOUND GLOBAL DATA(9)

💅 LUO File Lifecycle Bound Global Data 💅

okay so this is from the Kernel API Manual, section 9 — buckle up bestie, we're talking FLB objects 💖

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🌸 THE VIBE (aka what it actually is) 🌸

so File-Lifecycle-Bound (FLB) objects are literally the mechanism for managing global state that's shared across multiple live-updatable files. the lifecycle of that shared state is tied to the preservation of the files that depend on it. it's giving ✨reference counting but make it a whole lifecycle✨

an FLB represents a global resource — think like the IOMMU core state — that multiple file descriptors need (e.g. all VFIO fds). yes, all of them. no cap 🫶

the preservation of the FLB's state gets triggered when the first file depending on it is preserved. and the cleanup of that state (unpreserve or finish) gets triggered when the last file depending on it is unpreserved or finished. first one in, last one out. main character bookends 💅

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🦋 Handler Dependency 🦋

a file handler declares its dependency on one or more FLBs by registering them via liveupdate_register_flb. that's how it says "hey, I need this" 🌈

🎀 Callback Model 🎀

each FLB is defined by a set of operations (struct liveupdate_flb_ops) that LUO invokes at key points:

• (empty in the source bestie 😭)
• (yeah, also empty)
• (still empty — check the original doc for the actual callbacks, iykyk)
• (that's four empty bullets, I'm not making stuff up for you 💀)

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👑 why this slays 👑

this reference-counted approach ensures that shared state is saved exactly once and restored exactly once, regardless of how many files depend on it, and that its lifecycle is correctly managed across the kexec transition. exactly once. no double-saving, no accidentally dropping it. periodt 🔥

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✨ SEE ALSO ✨

Kernel file ./kernel/liveupdate/luo_flb.c 🍓

• luo_flb_file_preserve(9)
• luo_flb_file_unpreserve(9)
• luo_flb_file_finish(9)
• luo_flb_unregister_all(9)
• liveupdate_register_flb(9)
• liveupdate_unregister_flb(9)
• liveupdate_flb_get_incoming(9)
• liveupdate_flb_get_outgoing(9)
• luo_flb_serialize(9)

go read those next, bestie, they're literally all right there 💖

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💜 this whole thing lives out of ./kernel/liveupdate, dated October 2026 — that's the source path and the version/date situation, signed, sealed, slayed. mwah 🧚✨