STRUCT THE_NILFS(9)

💅 struct the_nilfs(9) 💅

okay so bestie, welcome to the Kernel API Manual — yes that's the manual name, we're fancy now — and today's main character is struct the_nilfs, the struct that supervises multiple nilfs mount points. like, all of them. she's the momager. 🎀

---

✨ NAME ✨

struct the_nilfs — the struct that supervises multiple nilfs mount points. she runs the whole friend group, no cap. 👑

---

🌸 SYNOPSIS 🌸

struct the_nilfs {
    unsigned long           ns_flags;
    int ns_flushed_device;
    struct super_block     *ns_sb;
    struct block_device    *ns_bdev;
    struct rw_semaphore     ns_sem;
    struct mutex            ns_snapshot_mount_mutex;
    struct buffer_head     *ns_sbh[2];
    struct nilfs_super_block *ns_sbp[2];
    time64_t ns_sbwtime;
    unsigned int            ns_sbwcount;
    unsigned int            ns_sbsize;
    unsigned int            ns_mount_state;
    unsigned int            ns_sb_update_freq;
    u64 ns_seg_seq;
    __u64 ns_segnum;
    __u64 ns_nextnum;
    unsigned long           ns_pseg_offset;
    __u64 ns_cno;
    time64_t ns_ctime;
    time64_t ns_nongc_ctime;
    atomic_t ns_ndirtyblks;
    spinlock_t ns_last_segment_lock;
    sector_t ns_last_pseg;
    u64 ns_last_seq;
    __u64 ns_last_cno;
    u64 ns_prot_seq;
    u64 ns_prev_seq;
    struct nilfs_sc_info   *ns_writer;
    struct rw_semaphore     ns_segctor_sem;
    struct inode           *ns_dat;
    struct inode           *ns_cpfile;
    struct inode           *ns_sufile;
    struct rb_root          ns_cptree;
    spinlock_t ns_cptree_lock;
    struct list_head        ns_dirty_files;
    spinlock_t ns_inode_lock;
    struct list_head        ns_gc_inodes;
    unsigned long           ns_mount_opt;
    uid_t ns_resuid;
    gid_t ns_resgid;
    unsigned long           ns_interval;
    unsigned long           ns_watermark;
    unsigned int            ns_blocksize_bits;
    unsigned int            ns_blocksize;
    unsigned long           ns_nsegments;
    unsigned long           ns_blocks_per_segment;
    unsigned long           ns_r_segments_percentage;
    unsigned long           ns_nrsvsegs;
    unsigned long           ns_first_data_block;
    int ns_inode_size;
    unsigned int            ns_first_ino;
    u32 ns_crc_seed;
    struct kobject ns_dev_kobj;
    struct completion ns_dev_kobj_unregister;
    struct nilfs_sysfs_dev_subgroups *ns_dev_subgroups;
 };

like, look at her. that's a lot of fields and every single one is doing her part. we love a hardworking queen. 🫶

---

🦋 DESCRIPTION 🦋

she's the struct that supervises multiple nilfs mount points. literally her whole job. now let's meet the members one by one, because they all deserve their moment. 💖

---

💜 MEMBERS 💜

• ns_flags — flags. short, sweet, iconic.
• ns_flushed_device — a flag indicating if all volatile data was flushed. basically the "did everyone make it home safe" check. 😭
• ns_sb — back pointer to the super block instance.
• ns_bdev — the block device.
• ns_sem — semaphore for shared states. sharing is caring but lock it first, bestie.
• ns_snapshot_mount_mutex — mutex to protect snapshot mounts. do not skip the mutex, i'm begging. 🙈
• ns_sbh — buffer heads of on-disk super blocks.
• ns_sbp — pointers to super block data.
• ns_sbwtime — previous write time of super block.
• ns_sbwcount — write count of super block.
• ns_sbsize — size of valid data in super block.
• ns_mount_state — file system state.
• ns_sb_update_freq — interval of periodical update of superblocks (in seconds). yes, seconds, keep the units, they matter. ⏰
• ns_seg_seq — segment sequence counter.
• ns_segnum — index number of the latest full segment.
• ns_nextnum — index number of the full segment index to be used next.
• ns_pseg_offset — offset of next partial segment in the current full segment.
• ns_cno — next checkpoint number.
• ns_ctime — write time of the last segment.
• ns_nongc_ctime — write time of the last segment not for cleaner operation. not the cleaner's, okay? different vibe entirely.
• ns_ndirtyblks — Number of dirty data blocks. capital N, that's canon, we don't question the source.
• ns_last_segment_lock — lock protecting fields for the latest segment.
• ns_last_pseg — start block number of the latest segment.
• ns_last_seq — sequence value of the latest segment.
• ns_last_cno — checkpoint number of the latest segment.
• ns_prot_seq — least sequence number of segments which must not be reclaimed. hands off, protected, do not touch. 🚫
• ns_prev_seq — base sequence number used to decide if advance log cursor.
• ns_writer — log writer. the scribe. the note-taker of the group chat. ✍️
• ns_segctor_sem — semaphore protecting log write.
• ns_dat — DAT file inode.
• ns_cpfile — checkpoint file inode.
• ns_sufile — segusage file inode.
• ns_cptree — rb-tree of all mounted checkpoints (nilfs_root).
• ns_cptree_lock — lock protecting ns_cptree.
• ns_dirty_files — list of dirty files.
• ns_inode_lock — lock protecting ns_dirty_files. see how she pairs them up? iconic behavior.
• ns_gc_inodes — dummy inodes to keep live blocks.
• ns_mount_opt — mount options.
• ns_resuid — uid for reserved blocks.
• ns_resgid — gid for reserved blocks.
• ns_interval — checkpoint creation interval.
• ns_watermark — watermark for the number of dirty buffers.
• ns_blocksize_bits — bit length of block size.
• ns_blocksize — block size.
• ns_nsegments — number of segments in filesystem.
• ns_blocks_per_segment — number of blocks per segment.
• ns_r_segments_percentage — reserved segments percentage.
• ns_nrsvsegs — number of reserved segments.
• ns_first_data_block — block number of first data block.
• ns_inode_size — size of on-disk inode.
• ns_first_ino — first not-special inode number.
• ns_crc_seed — seed value of CRC32 calculation.
• ns_dev_kobj — literally /sys/fs/<nilfs>/<device>. she lives there rent free. 🏠
• ns_dev_kobj_unregister — completion state.
• ns_dev_subgroups — <device> subgroups pointer.

---

🔥 SEE ALSO 🔥

• Kernel file ./fs/nilfs2/the_nilfs.h
• struct nilfs_root(9)

---

ok but fr fr, go read ./fs/nilfs2/the_nilfs.h when you're done here. iykyk. 📖✨

---

and that's the whole page, bestie — brought to you by the source ./fs/nilfs2, dated October 2026. periodt. 💅🎀🦋