STRUCT ND_NAMESPACE_INDEX(9)

💖 struct nd_namespace_index(9) 💖

okay bestie so this is a page straight out of the Kernel API Manual, and we're talking about a struct — a label set superblock, no cap. yes it's giving very specific-and-niche but honestly? iconic. let's get into it 🫶

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🌸 NAME 🌸

struct nd_namespace_index — the label set superblock, literally the main character of your label area ✨

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🦋 SYNOPSIS 🦋

struct nd_namespace_index {
    u8 sig[NSINDEX_SIG_LEN];
    u8 flags[3];
    u8 labelsize;
    __le32 seq;
    __le64 myoff;
    __le64 mysize;
    __le64 otheroff;
    __le64 labeloff;
    __le32 nslot;
    __le16 major;
    __le16 minor;
    __le64 checksum;
    u8 free[];
};

like… look at her. she's structured. she's aligned. she's everything 💅

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🎀 Members 🎀

• sig — NAMESPACE_INDEX 🏷️ that's the signature, periodt.
• flags — placeholder. yeah that's it. that's the whole vibe. a placeholder 🙈
• labelsize — log2 size, and note the deets: v1 labels are 128 bytes, v2 labels are 256 bytes. lowkey important 📏
• seq — the sequence number for this index 🔢
• myoff — offset of this index in the label area 📍
• mysize — size of this index struct, so she knows her own size 💖
• otheroff — offset of the other index 👀 there's always another one
• labeloff — offset of the first label slot 🎯
• nslot — total number of label slots 🗂️
• major — label area major version 🔥
• minor — label area minor version ✨
• checksum — fletcher64 of all fields 🧮 every single field, she's thorough
• free — a bitmap, nlabel bits long 🧚

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💜 Description 💜

so here's the tea ☕ — the size of free[] gets rounded up so that the total struct size is a multiple of NSINDEX_ALIGN bytes. that's just how it has to be, bestie 📐

and listen: any bits this allocates beyond the nlabel bits must be zero. not "should", not "ideally" — must. zero. no cap, that's the rule 💀

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/nvdimm/label.h
• struct cxl_region_label(9)
• struct nvdimm_efi_label(9)
• struct nvdimm_cxl_label(9)
• struct nd_label_id(9)

go read those too, they're all linked in the lore 🫶

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okay that's the whole page!! mwah 💋 this one lives in ./drivers/nvdimm, dated October 2026, and it's struct nd_namespace_index(9) all the way down. slay, stay aligned, and remember: the extra bits are zero 🎀✨