STRUCT NILFS_SEGMENT_SUMMARY(9)

💅 struct nilfs_segment_summary(9) — the kernel API manual, bestie edition 🎀

okay so bestie, we're deep in the kernel API docs rn (the Kernel API Manual, no big deal) and today's main character is struct nilfs_segment_summary — literally the segment summary header. it's giving "the receipt at the top of the file, but make it NILFS2" ✨

---

🌸 NAME 🌸

struct nilfs_segment_summary — the segment summary header, periodt 💅

---

✨ SYNOPSIS ✨

here's the whole vibe, character for character, don't touch a single underscore:

struct nilfs_segment_summary {
    __le32 ss_datasum;
    __le32 ss_sumsum;
    __le32 ss_magic;
    __le16 ss_bytes;
    __le16 ss_flags;
    __le64 ss_seq;
    __le64 ss_create;
    __le64 ss_next;
    __le32 ss_nblocks;
    __le32 ss_nfinfo;
    __le32 ss_sumbytes;
    __le32 ss_pad;
    __le64 ss_cno;
 };

look at all those __le32s and __le64s — endianness queen 👑 ngl the __le16 girlies are doing the most with the least and I respect it 🫶

---

🦋 Members 🦋

okay let's go member by member, no skipping, no cap:

• ss_datasum — the checksum of the data 🧾 so like, the data's little fingerprint, iconic
• ss_sumsum — the checksum of the segment summary. yes bestie, a checksum for the summary itself, she contains multitudes 😭
• ss_magic — the magic number ✨ obviously
• ss_bytes — how big this structure is, in bytes. it knows its own size, self-aware king 💀
• ss_flags — the flags 🚩 (the good kind, hopefully)
• ss_seq — the sequence number, keeping everything in order fr fr
• ss_create — the creation timestamp 🕰️ born at a specific moment, we love a timestamped queen
• ss_next — the next segment, pointing the way forward ➡️
• ss_nblocks — the number of blocks 🧱 count them, bestie
• ss_nfinfo — the number of finfo structures — yes that's the literal word from the docs, finfo, and I'm obsessed with how unbothered it is 💅
• ss_sumbytes — the total size of the segment summary in bytes. "total" is doing heavy lifting there, so don't confuse her with ss_bytes — they're different girlies, iykyk 🙈
• ss_pad — padding, the structural equivalent of "this meeting could have been an email" but make it alignment 🌸
• ss_cno — the checkpoint number 🔖

---

👑 SEE ALSO 👑

Kernel file ./include/uapi/linux/nilfs2_ondisk.h, plus the whole entire NILFS2 friend group — like, the full group chat:

• struct nilfs_inode(9)
• struct nilfs_super_root(9)
• struct nilfs_super_block(9)
• struct nilfs_finfo(9)
• struct nilfs_binfo_v(9)
• struct nilfs_binfo_dat(9)
• union nilfs_binfo(9)
• struct nilfs_btree_node(9)
• struct nilfs_direct_node(9)
• struct nilfs_palloc_group_desc(9)
• struct nilfs_dat_entry(9)
• struct nilfs_snapshot_list(9)
• struct nilfs_checkpoint(9)
• struct nilfs_cpfile_header(9)
• struct nilfs_segment_usage(9)
• struct nilfs_sufile_header(9)

---

that's the whole page bestie, you ate it up 💖 this lil' gem lives in ./include/uapi/linux, dated October 2026, and it's formatted as a Kernel API Manual page — go forth and read structs responsibly 🧚‍♀️🌈