STRUCT NILFS_SC_INFO(9)

🌸 STRUCT NILFS_SC_INFO(9) 🌸

okay bestie, welcome to the Kernel API Manual — today's main character is struct nilfs_sc_info, aka the Segment constructor information. no cap, this is the whole vibe of the NILFS2 segment constructor in one struct 💅

✨ SYNOPSIS ✨

struct nilfs_sc_info {
    struct super_block     *sc_super;
    struct nilfs_root      *sc_root;
    unsigned long           sc_nblk_inc;
    struct list_head        sc_dirty_files;
    struct list_head        sc_gc_inodes;
    struct list_head        sc_iput_queue;
    struct work_struct      sc_iput_work;
    __u64 *sc_freesegs;
    size_t sc_nfreesegs;
    struct nilfs_inode_info *sc_dsync_inode;
    loff_t sc_dsync_start;
    loff_t sc_dsync_end;
    struct list_head        sc_segbufs;
    struct list_head        sc_write_logs;
    unsigned long           sc_segbuf_nblocks;
    struct nilfs_segment_buffer *sc_curseg;
    struct nilfs_cstage     sc_stage;
    struct nilfs_segsum_pointer sc_finfo_ptr;
    struct nilfs_segsum_pointer sc_binfo_ptr;
    unsigned long           sc_blk_cnt;
    unsigned long           sc_datablk_cnt;
    unsigned long           sc_nblk_this_inc;
    time64_t sc_seg_ctime;
    __u64 sc_cno;
    unsigned long           sc_flags;
    spinlock_t sc_state_lock;
    unsigned long           sc_state;
    unsigned long           sc_flush_request;
    wait_queue_head_t sc_wait_request;
    wait_queue_head_t sc_wait_daemon;
    __u32 sc_seq_request;
    __u32 sc_seq_accepted;
    __u32 sc_seq_done;
    int sc_sync;
    unsigned long           sc_interval;
    unsigned long           sc_mjcp_freq;
    unsigned long           sc_lseg_stime;
    unsigned long           sc_watermark;
    struct timer_list       sc_timer;
    struct task_struct     *sc_task;
 };

like, look at her. forty fields. she's thriving 💖

🎀 MEMBERS 🎀

okay so here's the field-by-field tour, bestie — every single one, no skips, fr fr:

• sc_super — back pointer to the super_block struct. the classic "who's your parent" situation 🙈
• sc_root — root object of the current filesystem tree 🌳
• sc_nblk_inc — block count of the current generation ✨
• sc_dirty_files — list of files that are gonna get written 💅
• sc_gc_inodes — list of GC inodes that have blocks waiting to be written 🔥
• sc_iput_queue — list of inodes where iput still needs to happen
• sc_iput_work — work struct that defers the iput call (she's patient, she waits 🫶)
• sc_freesegs — array of segment numbers to be freed
• sc_nfreesegs — how many segments are chillin' on sc_freesegs
• sc_dsync_inode — the inode whose data pages get written for a sync operation
• sc_dsync_start — start byte offset of those data pages
• sc_dsync_end — end byte offset of those data pages (inclusive, bestie, don't forget 💀)
• sc_segbufs — list of segment buffers
• sc_write_logs — list of segment buffers holding logs that are currently under writing
• sc_segbuf_nblocks — number of available blocks in the segment buffers
• sc_curseg — the current segment buffer, main character of the moment 👑
• sc_stage — the collection stage
• sc_finfo_ptr — pointer to the current finfo struct in the segment summary
• sc_binfo_ptr — pointer to the current binfo struct in the segment summary
• sc_blk_cnt — block count of a file
• sc_datablk_cnt — data block count of a file
• sc_nblk_this_inc — number of blocks included in the current logical segment
• sc_seg_ctime — creation time ⏰
• sc_cno — checkpoint number of the current log 🧚
• sc_flags — internal flags
• sc_state_lock — spinlock for sc_state and so on, iykyk
• sc_state — segctord state flags
• sc_flush_request — inode bitmap of metadata files that need flushing
• sc_wait_request — client request queue
• sc_wait_daemon — daemon wait queue 😴
• sc_seq_request — request counter
• sc_seq_accepted — accepted request count
• sc_seq_done — completion counter ✅
• sc_sync — request of an explicit sync operation
• sc_interval — timeout value of background construction
• sc_mjcp_freq — frequency of creating checkpoints
• sc_lseg_stime — start time of the latest logical segment
• sc_watermark — watermark for the number of dirty buffers
• sc_timer — timer for segctord ⏱️
• sc_task — current thread of segctord

🔥 SEE ALSO 🔥

kernel file ./fs/nilfs2/segment.h, plus the besties struct nilfs_recovery_info(9) and struct nilfs_cstage(9) — go say hi 🦋

okay that's the whole page, you ate that 💅 lowkey iconic of you to read all forty fields. this one lives under ./fs/nilfs2 and it's dated October 2026, so like… future vibes only 🌈 periodt, go read the header file bestie 💜🎀