Linux文件系统学习（二）之重要数据结构（1）

struct file_system_type {
  const char *name;
  int fs_flags;
#define FS_REQUIRES_DEV   1 
#define FS_BINARY_MOUNTDATA 2
#define FS_HAS_SUBTYPE    4
#define FS_USERNS_MOUNT   8 /* Can be mounted by userns root */
#define FS_USERNS_DEV_MOUNT 16 /* A userns mount does not imply MNT_NODEV */
#define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */
  struct dentry *(*mount) (struct file_system_type *, int, 
           const char *, void *);
  void (*kill_sb) (struct super_block *);
  struct module *owner;
  struct file_system_type * next;
  struct hlist_head fs_supers;

  struct lock_class_key s_lock_key;
  struct lock_class_key s_umount_key;
  struct lock_class_key s_vfs_rename_key;
  struct lock_class_key s_writers_key[SB_FREEZE_LEVELS];

  struct lock_class_key i_lock_key;
  struct lock_class_key i_mutex_key;
  struct lock_class_key i_mutex_dir_key;
};

struct super_block {
  struct list_head  s_list;   /* Keep this first */
  dev_t     s_dev;    /* search index; _not_ kdev_t */
  unsigned char   s_blocksize_bits;
  unsigned long   s_blocksize;
  loff_t      s_maxbytes; /* Max file size */
  struct file_system_type *s_type;
  const struct super_operations *s_op;
  const struct dquot_operations *dq_op;
  const struct quotactl_ops *s_qcop;
  const struct export_operations *s_export_op;
  unsigned long   s_flags;
  unsigned long   s_magic;
  struct dentry   *s_root;
  struct rw_semaphore s_umount;
  int     s_count;
  atomic_t    s_active;
#ifdef CONFIG_SECURITY
  void                    *s_security;
#endif
  const struct xattr_handler **s_xattr;

  struct list_head  s_inodes; /* all inodes */
  struct hlist_bl_head  s_anon;   /* anonymous dentries for (nfs) exporting */
#ifdef CONFIG_SMP
  struct list_head __percpu *s_files;
#else
  struct list_head  s_files;
#endif
  struct list_head  s_mounts; /* list of mounts; _not_ for fs use */
  /* s_dentry_lru, s_nr_dentry_unused protected by dcache.c lru locks */
  struct list_head  s_dentry_lru; /* unused dentry lru */
  int     s_nr_dentry_unused; /* # of dentry on lru */

  /* s_inode_lru_lock protects s_inode_lru and s_nr_inodes_unused */
  spinlock_t    s_inode_lru_lock ____cacheline_aligned_in_smp;
  struct list_head  s_inode_lru;    /* unused inode lru */
  int     s_nr_inodes_unused; /* # of inodes on lru */

  struct block_device *s_bdev;
  struct backing_dev_info *s_bdi;
  struct mtd_info   *s_mtd;
  struct hlist_node s_instances;
  struct quota_info s_dquot;  /* Diskquota specific options */

  struct sb_writers s_writers;

  char s_id[32];        /* Informational name */
  u8 s_uuid[16];        /* UUID */

  void      *s_fs_info; /* Filesystem private info */
  unsigned int    s_max_links;
  fmode_t     s_mode;
  /* Granularity of c/m/atime in ns.
     Cannot be worse than a second */
  u32      s_time_gran;

  /*
   * The next field is for VFS *only*. No filesystems have any business
   * even looking at it. You had been warned.
   */
  struct mutex s_vfs_rename_mutex;  /* Kludge */

  /*
   * Filesystem subtype.  If non-empty the filesystem type field
   * in /proc/mounts will be "type.subtype"
   */
  char *s_subtype;

  /*
   * Saved mount options for lazy filesystems using
   * generic_show_options()
   */
  char __rcu *s_options;
  const struct dentry_operations *s_d_op; /* default d_op for dentries */

  /*
   * Saved pool identifier for cleancache (-1 means none)
   */
  int cleancache_poolid;

  struct shrinker s_shrink; /* per-sb shrinker handle */

  /* Number of inodes with nlink == 0 but still referenced */
  atomic_long_t s_remove_count;

  /* Being remounted read-only */
  int s_readonly_remount;
};