ext4 ext4_super_block

ext4 超级块描述：struct ext4_super_block

/* * Structure of the super block */struct ext4_super_block {/*00*/__le32s_inodes_count;/* Inodes count */__le32s_blocks_count_lo;/* Blocks count */__le32s_r_blocks_count_lo;/* Reserved blocks count */__le32s_free_blocks_count_lo;/* Free blocks count *//*10*/__le32s_free_inodes_count;/* Free inodes count */__le32s_first_data_block;/* First Data Block */__le32s_log_block_size;/* Block size */__le32s_log_cluster_size;/* Allocation cluster size *//*20*/__le32s_blocks_per_group;/* # Blocks per group */__le32s_clusters_per_group;/* # Clusters per group */__le32s_inodes_per_group;/* # Inodes per group */__le32s_mtime;/* Mount time *//*30*/__le32s_wtime;/* Write time */__le16s_mnt_count;/* Mount count */__le16s_max_mnt_count;/* Maximal mount count */__le16s_magic;/* Magic signature */__le16s_state;/* File system state */__le16s_errors;/* Behaviour when detecting errors */__le16s_minor_rev_level;/* minor revision level *//*40*/__le32s_lastcheck;/* time of last check */__le32s_checkinterval;/* max. time between checks */__le32s_creator_os;/* OS */__le32s_rev_level;/* Revision level *//*50*/__le16s_def_resuid;/* Default uid for reserved blocks */__le16s_def_resgid;/* Default gid for reserved blocks *//* * These fields are for EXT4_DYNAMIC_REV superblocks only. * * Note: the difference between the compatible feature set and * the incompatible feature set is that if there is a bit set * in the incompatible feature set that the kernel doesn't * know about, it should refuse to mount the filesystem. * * e2fsck's requirements are more strict; if it doesn't know * about a feature in either the compatible or incompatible * feature set, it must abort and not try to meddle with * things it doesn't understand... */__le32s_first_ino;/* First non-reserved inode */__le16  s_inode_size;/* size of inode structure */__le16s_block_group_nr;/* block group # of this superblock */__le32s_feature_compat;/* compatible feature set *//*60*/__le32s_feature_incompat;/* incompatible feature set */__le32s_feature_ro_compat;/* readonly-compatible feature set *//*68*/__u8s_uuid[16];/* 128-bit uuid for volume *//*78*/chars_volume_name[16];/* volume name *//*88*/chars_last_mounted[64];/* directory where last mounted *//*C8*/__le32s_algorithm_usage_bitmap; /* For compression *//* * Performance hints.  Directory preallocation should only * happen if the EXT4_FEATURE_COMPAT_DIR_PREALLOC flag is on. */__u8s_prealloc_blocks;/* Nr of blocks to try to preallocate*/__u8s_prealloc_dir_blocks;/* Nr to preallocate for dirs */__le16s_reserved_gdt_blocks;/* Per group desc for online growth *//* * Journaling support valid if EXT4_FEATURE_COMPAT_HAS_JOURNAL set. *//*D0*/__u8s_journal_uuid[16];/* uuid of journal superblock *//*E0*/__le32s_journal_inum;/* inode number of journal file */__le32s_journal_dev;/* device number of journal file */__le32s_last_orphan;/* start of list of inodes to delete */__le32s_hash_seed[4];/* HTREE hash seed */__u8s_def_hash_version;/* Default hash version to use */__u8s_jnl_backup_type;__le16  s_desc_size;/* size of group descriptor *//*100*/__le32s_default_mount_opts;__le32s_first_meta_bg;/* First metablock block group */__le32s_mkfs_time;/* When the filesystem was created */__le32s_jnl_blocks[17];/* Backup of the journal inode *//* 64bit support valid if EXT4_FEATURE_COMPAT_64BIT *//*150*/__le32s_blocks_count_hi;/* Blocks count */__le32s_r_blocks_count_hi;/* Reserved blocks count */__le32s_free_blocks_count_hi;/* Free blocks count */__le16s_min_extra_isize;/* All inodes have at least # bytes */__le16s_want_extra_isize; /* New inodes should reserve # bytes */__le32s_flags;/* Miscellaneous flags */__le16  s_raid_stride;/* RAID stride */__le16  s_mmp_update_interval;  /* # seconds to wait in MMP checking */__le64  s_mmp_block;            /* Block for multi-mount protection */__le32  s_raid_stripe_width;    /* blocks on all data disks (N*stride)*/__u8s_log_groups_per_flex;  /* FLEX_BG group size */__u8s_checksum_type;/* metadata checksum algorithm used */__u8s_encryption_level;/* versioning level for encryption */__u8s_reserved_pad;/* Padding to next 32bits */__le64s_kbytes_written;/* nr of lifetime kilobytes written */__le32s_snapshot_inum;/* Inode number of active snapshot */__le32s_snapshot_id;/* sequential ID of active snapshot */__le64s_snapshot_r_blocks_count; /* reserved blocks for active      snapshot's future use */__le32s_snapshot_list;/* inode number of the head of the   on-disk snapshot list */#define EXT4_S_ERR_START offsetof(struct ext4_super_block, s_error_count)__le32s_error_count;/* number of fs errors */__le32s_first_error_time;/* first time an error happened */__le32s_first_error_ino;/* inode involved in first error */__le64s_first_error_block;/* block involved of first error */__u8s_first_error_func[32];/* function where the error happened */__le32s_first_error_line;/* line number where error happened */__le32s_last_error_time;/* most recent time of an error */__le32s_last_error_ino;/* inode involved in last error */__le32s_last_error_line;/* line number where error happened */__le64s_last_error_block;/* block involved of last error */__u8s_last_error_func[32];/* function where the error happened */#define EXT4_S_ERR_END offsetof(struct ext4_super_block, s_mount_opts)__u8s_mount_opts[64];__le32s_usr_quota_inum;/* inode for tracking user quota */__le32s_grp_quota_inum;/* inode for tracking group quota */__le32s_overhead_clusters;/* overhead blocks/clusters in fs */__le32s_backup_bgs[2];/* groups with sparse_super2 SBs */__u8s_encrypt_algos[4];/* Encryption algorithms in use  */__u8s_encrypt_pw_salt[16];/* Salt used for string2key algorithm */__le32s_lpf_ino;/* Location of the lost+found inode */__le32s_prj_quota_inum;/* inode for tracking project quota */__le32s_checksum_seed;/* crc32c(uuid) if csum_seed set */__le32s_reserved[98];/* Padding to the end of the block */__le32s_checksum;/* crc32c(superblock) */};