Search notes:
/include/linux/fs.h
Among others, this file defines the structs
inode
Definition of the
inode struct, one of the central objects in the
VFS (See also
Inode ) as of release 5.18:
struct inode {
umode_t i_mode;
unsigned short i_opflags;
kuid_t i_uid;
kgid_t i_gid;
unsigned int i_flags;
#ifdef CONFIG_FS_POSIX_ACL
struct posix_acl *i_acl;
struct posix_acl *i_default_acl;
#endif
const struct inode_operations *i_op;
struct super_block *i_sb;
struct address_space *i_mapping;
#ifdef CONFIG_SECURITY
void *i_security;
#endif
/* Stat data, not accessed from path walking */
unsigned long i_ino;
/*
* Filesystems may only read i_nlink directly. They shall use the
* following functions for modification:
*
* (set|clear|inc|drop)_nlink
* inode_(inc|dec)_link_count
*/
union {
const unsigned int i_nlink;
unsigned int __i_nlink;
};
dev_t i_rdev;
loff_t i_size;
struct timespec64 i_atime;
struct timespec64 i_mtime;
struct timespec64 i_ctime;
spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */
unsigned short i_bytes;
u8 i_blkbits;
u8 i_write_hint;
blkcnt_t i_blocks;
#ifdef __NEED_I_SIZE_ORDERED
seqcount_t i_size_seqcount;
#endif
/* Misc */
unsigned long i_state;
struct rw_semaphore i_rwsem;
unsigned long dirtied_when; /* jiffies of first dirtying */
unsigned long dirtied_time_when;
struct hlist_node i_hash;
struct list_head i_io_list; /* backing dev IO list */
#ifdef CONFIG_CGROUP_WRITEBACK
struct bdi_writeback *i_wb; /* the associated cgroup wb */
/* foreign inode detection, see wbc_detach_inode() */
int i_wb_frn_winner;
u16 i_wb_frn_avg_time;
u16 i_wb_frn_history;
#endif
struct list_head i_lru; /* inode LRU list */
struct list_head i_sb_list;
struct list_head i_wb_list; /* backing dev writeback list */
union {
struct hlist_head i_dentry;
struct rcu_head i_rcu;
};
atomic64_t i_version;
atomic64_t i_sequence; /* see futex */
atomic_t i_count;
atomic_t i_dio_count;
atomic_t i_writecount;
#if defined(CONFIG_IMA) || defined(CONFIG_FILE_LOCKING)
atomic_t i_readcount; /* struct files open RO */
#endif
union {
const struct file_operations *i_fop; /* former ->i_op->default_file_ops */
void (*free_inode)(struct inode *);
};
struct file_lock_context *i_flctx;
struct address_space i_data;
struct list_head i_devices;
union {
struct pipe_inode_info *i_pipe;
struct cdev *i_cdev;
char *i_link;
unsigned i_dir_seq;
};
__u32 i_generation;
#ifdef CONFIG_FSNOTIFY
__u32 i_fsnotify_mask; /* all events this inode cares about */
struct fsnotify_mark_connector __rcu *i_fsnotify_marks;
#endif
#ifdef CONFIG_FS_ENCRYPTION
struct fscrypt_info *i_crypt_info;
#endif
#ifdef CONFIG_FS_VERITY
struct fsverity_info *i_verity_info;
#endif
void *i_private; /* fs or device private pointer */
} __randomize_layout;
file_system_type
As of Linux 5.18, file_system_type looks like:
struct file_system_type {
const char *name;
int fs_flags;
int (*init_fs_context)(struct fs_context *);
const struct fs_parameter_spec *parameters;
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 invalidate_lock_key;
struct lock_class_key i_mutex_dir_key;
};
Note espacially the
mount function pointer which is called when the respective file system is mounted (for example when using the Shell command
mount ).
mount() returns returns the root
dentry of the tree requested by caller.
file_operations struct file_operations {
struct module *owner;
loff_t (*llseek ) (struct file *, loff_t, int);
ssize_t (*read ) (struct file *, char __user *, size_t, loff_t *);
ssize_t (*write ) (struct file *, const char __user *, size_t, loff_t *);
ssize_t (*read_iter ) (struct kiocb *, struct iov_iter *);
ssize_t (*write_iter ) (struct kiocb *, struct iov_iter *);
int (*iopoll ) (struct kiocb *kiocb, struct io_comp_batch *, unsigned int flags);
int (*iterate ) (struct file *, struct dir_context *);
int (*iterate_shared ) (struct file *, struct dir_context *);
__poll_t (*poll ) (struct file *, struct poll_table_struct *);
long (*unlocked_ioctl ) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl ) (struct file *, unsigned int, unsigned long);
int (*mmap ) (struct file *, struct vm_area_struct *);
unsigned long mmap_supported_flags;
int (*open ) (struct inode *, struct file *);
int (*flush ) (struct file *, fl_owner_t id);
int (*release ) (struct inode *, struct file *);
int (*fsync ) (struct file *, loff_t, loff_t, int datasync);
int (*fasync ) (int, struct file *, int);
int (*lock ) (struct file *, int, struct file_lock *);
ssize_t (*sendpage ) (struct file *, struct page *, int, size_t, loff_t *, int);
unsigned long (*get_unmapped_area) (struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
int (*check_flags ) (int);
int (*flock ) (struct file *, int, struct file_lock *);
ssize_t (*splice_write ) (struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
ssize_t (*splice_read ) (struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
int (*setlease ) (struct file *, long, struct file_lock **, void **);
long (*fallocate ) (struct file *file, int mode, loff_t offset, loff_t len);
void (*show_fdinfo ) (struct seq_file *m, struct file *f);
#ifndef CONFIG_MMU
unsigned (*mmap_capabilities)(struct file *);
#endif
ssize_t (*copy_file_range )( struct file *, loff_t, struct file *, loff_t, size_t, unsigned int);
loff_t (*remap_file_range )( struct file *file_in, loff_t pos_in, struct file *file_out, loff_t pos_out, loff_t len, unsigned int remap_flags);
int (*fadvise )( struct file *, loff_t, loff_t, int);
int (*uring_cmd )( struct io_uring_cmd *ioucmd, unsigned int issue_flags);
} __randomize_layout;
inode_operations
The
inode_operations struct defines the operations that an
inode provides.
struct inode_operations {
struct dentry * (*lookup ) (struct inode *,struct dentry *, unsigned int);
const char * (*get_link ) (struct dentry *, struct inode *, struct delayed_call *);
int (*permission ) (struct user_namespace *, struct inode *, int);
struct posix_acl * (*get_acl ) (struct inode *, int, bool);
int (*readlink ) (struct dentry *, char __user *,int);
int (*create ) (struct user_namespace *, struct inode *,struct dentry *, umode_t, bool);
int (*link ) (struct dentry *,struct inode *,struct dentry *);
int (*unlink ) (struct inode *,struct dentry *);
int (*symlink ) (struct user_namespace *, struct inode *,struct dentry *, const char *);
int (*mkdir ) (struct user_namespace *, struct inode *,struct dentry *, umode_t);
int (*rmdir ) (struct inode *,struct dentry *);
int (*mknod ) (struct user_namespace *, struct inode *,struct dentry *, umode_t,dev_t);
int (*rename ) (struct user_namespace *, struct inode *, struct dentry *, struct inode *, struct dentry *, unsigned int);
int (*setattr ) (struct user_namespace *, struct dentry *, struct iattr *);
int (*getattr ) (struct user_namespace *, const struct path *, struct kstat *, u32, unsigned int);
ssize_t (*listxattr ) (struct dentry *, char *, size_t);
int (*fiemap ) (struct inode *, struct fiemap_extent_info *, u64 start, u64 len);
int (*update_time ) (struct inode *, struct timespec64 *, int);
int (*atomic_open ) (struct inode *, struct dentry *, struct file *, unsigned open_flag, umode_t create_mode);
int (*tmpfile ) (struct user_namespace *, struct inode *, struct dentry *, umode_t);
int (*set_acl ) (struct user_namespace *, struct inode *, struct posix_acl *, int);
int (*fileattr_set ) (struct user_namespace *mnt_userns, struct dentry *dentry, struct fileattr *fa);
int (*fileattr_get ) (struct dentry *dentry, struct fileattr *fa);
} ____cacheline_aligned;
iattr
The
Inode Attributes structure, used for
notify_change()
struct iattr {
unsigned int ia_valid;
umode_t ia_mode;
kuid_t ia_uid;
kgid_t ia_gid;
loff_t ia_size;
struct timespec64 ia_atime;
struct timespec64 ia_mtime;
struct timespec64 ia_ctime;
/*
* Not an attribute, but an auxiliary info for filesystems wanting to
* implement an ftruncate() like method. NOTE: filesystem should
* check for (ia_valid & ATTR_FILE), and not for (ia_file != NULL).
*/
struct file *ia_file;
};