STRUCT BTT(9)

💅 struct btt(9) 💅

okay so bestie, welcome to the Kernel API Manual, and today's main character is struct btt — literally the handle for a BTT instance. that's it, that's the vibe. it's the little struct that holds the whole BTT situation together 🫶

✨ SYNOPSIS ✨

struct btt {
    struct gendisk *btt_disk;
    struct list_head arena_list;
    struct dentry *debugfs_dir;
    struct nd_btt *nd_btt;
    u64 nlba;
    unsigned long long rawsize;
    u32 lbasize;
    u32 sector_size;
    struct nd_region *nd_region;
    struct mutex init_lock;
    int init_state;
    int num_arenas;
    struct badblocks *phys_bb;
 };

🌸 MEMBERS 🌸

so. let's meet the cast. every single field, no skipping, i promise 🎀

• btt_disk — pointer to the gendisk for the BTT device. the whole disk situation, basically 👑
• arena_list — head of the list of arenas. yes we're talking linked-list head energy, it's giving list_head and we love that for us
• debugfs_dir — the debugfs dentry. your little doorway into debugfs land 🚪
• nd_btt — parent nd_btt struct. it's got a whole parent, very family-oriented of it
• nlba — number of logical blocks exposed to the upper layers, after you subtract all the space that metadata ate. metadata really said "i'm taking some of that" 😭
• rawsize — total size in bytes of the available backing device. the full snack, unfiltered
• lbasize — LBA size as requested and presented to the upper layers. lowkey important: this is sector_size plus the size of any metadata. yes, the metadata is baked in 💅
• sector_size — the Linux sector size — 512 or 4096. those are the only two options, no in-between, no cap 🧚
• nd_region — struct nd_region pointer. that's it, that's the field
• init_lock — mutex used for the BTT initialization. please respect the lock, bestie, or it gets ugly 🔒
• init_state — flag describing the initialization state for the BTT. is it initialized? is it not? the flag knows 🌈
• num_arenas — number of arenas in the BTT instance. count 'em 🔥
• phys_bb — pointer to the namespace's badblocks structure. everybody's got a lil list of bad blocks, no judgement 💀

⭐ SEE ALSO ⭐

• Kernel file ./drivers/nvdimm/btt.h
• struct arena_info(9)

not me documenting a kernel struct like it's a group chat 💀 but honestly? it ate. go read the source, bestie, iykyk 🦋

and that's a wrap! this page came straight out of ./drivers/nvdimm, dated October 2026 — iconic, timeless, periodt 💖✨🎀