STRUCT NILFS_SUPER_BLOCK(9)

💖 NAME 💖

okay so this is the struct nilfs_super_block(9) page from the Kernel API Manual, bestie — and it’s literally the structure of the super block on disk. no cap, that’s the whole vibe. 🫶

🌸 SYNOPSIS 🌸

here’s the struct in all its on-disk glory, every field kept exactly in order:

       struct nilfs_super_block {
           __le32 s_rev_level;
           __le16 s_minor_rev_level;
           __le16 s_magic;
           __le16 s_bytes;
           __le16 s_flags;
           __le32 s_crc_seed;
           __le32 s_sum;
           __le32 s_log_block_size;
           __le64 s_nsegments;
           __le64 s_dev_size;
           __le64 s_first_data_block;
           __le32 s_blocks_per_segment;
           __le32 s_r_segments_percentage;
           __le64 s_last_cno;
           __le64 s_last_pseg;
           __le64 s_last_seq;
           __le64 s_free_blocks_count;
           __le64 s_ctime;
           __le64 s_mtime;
           __le64 s_wtime;
           __le16 s_mnt_count;
           __le16 s_max_mnt_count;
           __le16 s_state;
           __le16 s_errors;
           __le64 s_lastcheck;
           __le32 s_checkinterval;
           __le32 s_creator_os;
           __le16 s_def_resuid;
           __le16 s_def_resgid;
           __le32 s_first_ino;
           __le16 s_inode_size;
           __le16 s_dat_entry_size;
           __le16 s_checkpoint_size;
           __le16 s_segment_usage_size;
           __u8 s_uuid[16];
           char s_volume_name[80]       __kernel_nonstring;
           __le32 s_c_interval;
           __le32 s_c_block_max;
           __le64 s_feature_compat;
           __le64 s_feature_compat_ro;
           __le64 s_feature_incompat;
           __u32 s_reserved[186];
        };

🎀 Members 🎀

field-by-field vibe check, bestie — same order, all the lore 💅

• s_rev_level — revision level, periodt.
• s_minor_rev_level — minor revision level, the little sibling energy.
• s_magic — magic signature, iconic.
• s_bytes — bytes count of CRC calculation for this structure. s_reserved is excluded. noted, fr fr.
• s_flags — flags. that’s it, flags.
• s_crc_seed — seed value of CRC calculation.
• s_sum — check sum of super block.
• s_log_block_size — block size represented as follows: blocksize = 1 << (s_log_block_size + 10).
• s_nsegments — number of segments in filesystem.
• s_dev_size — block device size in bytes.
• s_first_data_block — 1st seg disk block number.
• s_blocks_per_segment — number of blocks per full segment.
• s_r_segments_percentage — reserved segments percentage.
• s_last_cno — last checkpoint number.
• s_last_pseg — disk block addr pseg written last.
• s_last_seq — seq. number of seg written last.
• s_free_blocks_count — free blocks count.
• s_ctime — creation time (execution time of newfs).
• s_mtime — mount time.
• s_wtime — write time.
• s_mnt_count — mount count.
• s_max_mnt_count — maximal mount count.
• s_state — file system state.
• s_errors — behaviour when detecting errors.
• s_lastcheck — time of last check.
• s_checkinterval — max. time between checks.
• s_creator_os — OS.
• s_def_resuid — default uid for reserved blocks.
• s_def_resgid — default gid for reserved blocks.
• s_first_ino — first non-reserved inode.
• s_inode_size — size of an inode.
• s_dat_entry_size — size of a dat entry.
• s_checkpoint_size — size of a checkpoint.
• s_segment_usage_size — size of a segment usage.
• s_uuid — 128-bit uuid for volume.
• s_volume_name — volume name.
• s_c_interval — commit interval of segment.
• s_c_block_max — threshold of data amount for the segment construction.
• s_feature_compat — compatible feature set.
• s_feature_compat_ro — read-only compatible feature set.
• s_feature_incompat — incompatible feature set.
• s_reserved — padding to the end of the block.

🦋 SEE ALSO 🦋

go read these too, iykyk 👑

• Kernel file ./include/uapi/linux/nilfs2_ondisk.h
• struct nilfs_inode(9)
• struct nilfs_super_root(9)
• struct nilfs_finfo(9)
• struct nilfs_binfo_v(9)
• struct nilfs_binfo_dat(9)
• union nilfs_binfo(9)
• struct nilfs_segment_summary(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)

mwah 💋 — source/version: ./include/uapi/linux, date: October 2026, page: struct nilfs_super_block(9). byeee 🫶✨