/*
    FUSE: Filesystem in Userspace

    Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>

  
    This program can be distributed under the terms of the GNU GPL.
    See the file COPYING.
  */

  #ifndef _FS_FUSE_I_H
  #define _FS_FUSE_I_H

  #include <linux/fuse.h>
  #include <linux/fs.h>

  #include <linux/mount.h>

  #include <linux/wait.h>
  #include <linux/list.h>
  #include <linux/spinlock.h>
  #include <linux/mm.h>
  #include <linux/backing-dev.h>

  #include <linux/mutex.h>

  #include <linux/rwsem.h>

  #include <linux/rbtree.h>
  #include <linux/poll.h>

  #include <linux/workqueue.h>

  #include <linux/kref.h>

  /** Max number of pages that can be used in a single read request */
  #define FUSE_MAX_PAGES_PER_REQ 32

  /** Bias for fi->writectr, meaning new writepages must not be sent */
  #define FUSE_NOWRITE INT_MIN

  /** It could be as large as PATH_MAX, but would that have any uses? */
  #define FUSE_NAME_MAX 1024

  /** Number of dentries for each connection in the control filesystem */

  #define FUSE_CTL_NUM_DENTRIES 5

  /** If the FUSE_DEFAULT_PERMISSIONS flag is given, the filesystem
      module will check permissions based on the file mode.  Otherwise no
      permission checking is done in the kernel */
  #define FUSE_DEFAULT_PERMISSIONS (1 << 0)
  
  /** If the FUSE_ALLOW_OTHER flag is given, then not only the user
      doing the mount will be allowed to access the filesystem */
  #define FUSE_ALLOW_OTHER         (1 << 1)

  /** Number of page pointers embedded in fuse_req */
  #define FUSE_REQ_INLINE_PAGES 1

  /** List of active connections */
  extern struct list_head fuse_conn_list;
  
  /** Global mutex protecting fuse_conn_list and the control filesystem */
  extern struct mutex fuse_mutex;

  /** Module parameters */
  extern unsigned max_user_bgreq;
  extern unsigned max_user_congthresh;

  /* One forget request */
  struct fuse_forget_link {

  	struct fuse_forget_one forget_one;

  	struct fuse_forget_link *next;
  };

  /** FUSE inode */
  struct fuse_inode {
  	/** Inode data */
  	struct inode inode;
  
  	/** Unique ID, which identifies the inode between userspace
  	 * and kernel */
  	u64 nodeid;

  	/** Number of lookups on this inode */
  	u64 nlookup;

  	/** The request used for sending the FORGET message */

  	struct fuse_forget_link *forget;

  	/** Time in jiffies until the file attributes are valid */

  	u64 i_time;

  
  	/** The sticky bit in inode->i_mode may have been removed, so
  	    preserve the original mode */

  	umode_t orig_i_mode;

  	/** 64 bit inode number */
  	u64 orig_ino;

  	/** Version of last attribute change */
  	u64 attr_version;

  
  	/** Files usable in writepage.  Protected by fc->lock */
  	struct list_head write_files;

  
  	/** Writepages pending on truncate or fsync */
  	struct list_head queued_writes;
  
  	/** Number of sent writes, a negative bias (FUSE_NOWRITE)
  	 * means more writes are blocked */
  	int writectr;
  
  	/** Waitq for writepage completion */
  	wait_queue_head_t page_waitq;
  
  	/** List of writepage requestst (pending or sent) */
  	struct list_head writepages;

  
  	/** Miscellaneous bits describing inode state */
  	unsigned long state;
  };
  
  /** FUSE inode state bits */
  enum {
  	/** Advise readdirplus  */
  	FUSE_I_ADVISE_RDPLUS,

  	/** Initialized with readdirplus */
  	FUSE_I_INIT_RDPLUS,

  	/** An operation changing file size is in progress  */
  	FUSE_I_SIZE_UNSTABLE,

  };

  struct fuse_conn;

  /** FUSE specific file data */
  struct fuse_file {

  	/** Fuse connection for this file */
  	struct fuse_conn *fc;

  	/** Request reserved for flush and release */

  	struct fuse_req *reserved_req;

  	/** Kernel file handle guaranteed to be unique */
  	u64 kh;

  	/** File handle used by userspace */
  	u64 fh;

  	/** Node id of this file */
  	u64 nodeid;

  	/** Refcount */
  	atomic_t count;

  	/** FOPEN_* flags returned by open */
  	u32 open_flags;

  	/** Entry on inode's write_files list */
  	struct list_head write_entry;

  
  	/** RB node to be linked on fuse_conn->polled_files */
  	struct rb_node polled_node;
  
  	/** Wait queue head for poll */
  	wait_queue_head_t poll_wait;

  
  	/** Has flock been performed on this file? */
  	bool flock:1;

  };

  /** One input argument of a request */
  struct fuse_in_arg {
  	unsigned size;
  	const void *value;
  };
  
  /** The request input */
  struct fuse_in {
  	/** The request header */
  	struct fuse_in_header h;
  
  	/** True if the data for the last argument is in req->pages */
  	unsigned argpages:1;
  
  	/** Number of arguments */
  	unsigned numargs;
  
  	/** Array of arguments */
  	struct fuse_in_arg args[3];
  };
  
  /** One output argument of a request */
  struct fuse_arg {
  	unsigned size;
  	void *value;
  };
  
  /** The request output */
  struct fuse_out {
  	/** Header returned from userspace */
  	struct fuse_out_header h;

  	/*
  	 * The following bitfields are not changed during the request
  	 * processing
  	 */

  	/** Last argument is variable length (can be shorter than
  	    arg->size) */
  	unsigned argvar:1;
  
  	/** Last argument is a list of pages to copy data to */
  	unsigned argpages:1;
  
  	/** Zero partially or not copied pages */
  	unsigned page_zeroing:1;

  	/** Pages may be replaced with new ones */
  	unsigned page_replace:1;

  	/** Number or arguments */
  	unsigned numargs;
  
  	/** Array of arguments */

  	struct fuse_arg args[2];

  };

  /** FUSE page descriptor */
  struct fuse_page_desc {
  	unsigned int length;
  	unsigned int offset;
  };

  struct fuse_args {
  	struct {
  		struct {
  			uint32_t opcode;
  			uint64_t nodeid;
  		} h;
  		unsigned numargs;
  		struct fuse_in_arg args[3];
  
  	} in;
  	struct {
  		unsigned argvar:1;
  		unsigned numargs;
  		struct fuse_arg args[2];
  	} out;
  };
  
  #define FUSE_ARGS(args) struct fuse_args args = {}

  /** The request IO state (for asynchronous processing) */
  struct fuse_io_priv {

  	struct kref refcnt;

  	int async;
  	spinlock_t lock;
  	unsigned reqs;
  	ssize_t bytes;
  	size_t size;
  	__u64 offset;
  	bool write;
  	int err;
  	struct kiocb *iocb;
  	struct file *file;

  	struct completion *done;

  };

  #define FUSE_IO_PRIV_SYNC(f) \
  {					\
  	.refcnt = { ATOMIC_INIT(1) },	\
  	.async = 0,			\
  	.file = f,			\
  }

  /**

   * Request flags
   *
   * FR_ISREPLY:		set if the request has reply
   * FR_FORCE:		force sending of the request even if interrupted
   * FR_BACKGROUND:	request is sent in the background
   * FR_WAITING:		request is counted as "waiting"
   * FR_ABORTED:		the request was aborted
   * FR_INTERRUPTED:	the request has been interrupted
   * FR_LOCKED:		data is being copied to/from the request

   * FR_PENDING:		request is not yet in userspace
   * FR_SENT:		request is in userspace, waiting for an answer
   * FR_FINISHED:		request is finished

   * FR_PRIVATE:		request is on private list

   */
  enum fuse_req_flag {
  	FR_ISREPLY,
  	FR_FORCE,
  	FR_BACKGROUND,
  	FR_WAITING,
  	FR_ABORTED,
  	FR_INTERRUPTED,
  	FR_LOCKED,

  	FR_PENDING,
  	FR_SENT,
  	FR_FINISHED,

  	FR_PRIVATE,

  };
  
  /**

   * A request to the client

   *
   * .waitq.lock protects the following fields:
   *   - FR_ABORTED
   *   - FR_LOCKED (may also be modified under fc->lock, tested under both)

   */
  struct fuse_req {

  	/** This can be on either pending processing or io lists in
  	    fuse_conn */

  	struct list_head list;

  	/** Entry on the interrupts list  */
  	struct list_head intr_entry;

  	/** refcount */
  	atomic_t count;

  	/** Unique ID for the interrupt request */
  	u64 intr_unique;

  	/* Request flags, updated with test/set/clear_bit() */
  	unsigned long flags;

  	/** The request input */
  	struct fuse_in in;
  
  	/** The request output */
  	struct fuse_out out;
  
  	/** Used to wake up the task waiting for completion of request*/
  	wait_queue_head_t waitq;
  
  	/** Data for asynchronous requests */
  	union {

  		struct {

  			struct fuse_release_in in;
  			struct inode *inode;

  		} release;

  		struct fuse_init_in init_in;
  		struct fuse_init_out init_out;

  		struct cuse_init_in cuse_init_in;

  		struct {
  			struct fuse_read_in in;
  			u64 attr_ver;
  		} read;

  		struct {
  			struct fuse_write_in in;
  			struct fuse_write_out out;

  			struct fuse_req *next;

  		} write;

  		struct fuse_notify_retrieve_in retrieve_in;

  	} misc;
  
  	/** page vector */

  	struct page **pages;

  	/** page-descriptor vector */
  	struct fuse_page_desc *page_descs;

  	/** size of the 'pages' array */
  	unsigned max_pages;
  
  	/** inline page vector */
  	struct page *inline_pages[FUSE_REQ_INLINE_PAGES];

  	/** inline page-descriptor vector */
  	struct fuse_page_desc inline_page_descs[FUSE_REQ_INLINE_PAGES];

  	/** number of pages in vector */
  	unsigned num_pages;

  	/** File used in the request (or NULL) */

  	struct fuse_file *ff;

  	/** Inode used in the request or NULL */
  	struct inode *inode;

  	/** AIO control block */
  	struct fuse_io_priv *io;

  	/** Link on fi->writepages */
  	struct list_head writepages_entry;

  	/** Request completion callback */
  	void (*end)(struct fuse_conn *, struct fuse_req *);

  
  	/** Request is stolen from fuse_file->reserved_req */
  	struct file *stolen_file;

  };

  struct fuse_iqueue {

  	/** Connection established */
  	unsigned connected;

  	/** Readers of the connection are waiting on this */
  	wait_queue_head_t waitq;
  
  	/** The next unique request id */
  	u64 reqctr;
  
  	/** The list of pending requests */
  	struct list_head pending;
  
  	/** Pending interrupts */
  	struct list_head interrupts;
  
  	/** Queue of pending forgets */
  	struct fuse_forget_link forget_list_head;
  	struct fuse_forget_link *forget_list_tail;
  
  	/** Batching of FORGET requests (positive indicates FORGET batch) */
  	int forget_batch;
  
  	/** O_ASYNC requests */
  	struct fasync_struct *fasync;
  };

  struct fuse_pqueue {

  	/** Connection established */
  	unsigned connected;

  	/** Lock protecting accessess to  members of this structure */
  	spinlock_t lock;

  	/** The list of requests being processed */
  	struct list_head processing;
  
  	/** The list of requests under I/O */
  	struct list_head io;
  };

  /**

   * Fuse device instance
   */
  struct fuse_dev {
  	/** Fuse connection for this device */
  	struct fuse_conn *fc;

  	/** Processing queue */
  	struct fuse_pqueue pq;

  	/** list entry on fc->devices */
  	struct list_head entry;
  };
  
  /**

   * A Fuse connection.
   *
   * This structure is created, when the filesystem is mounted, and is
   * destroyed, when the client device is closed and the filesystem is
   * unmounted.
   */
  struct fuse_conn {

  	/** Lock protecting accessess to  members of this structure */
  	spinlock_t lock;

  	/** Refcount */
  	atomic_t count;

  	/** Number of fuse_dev's */
  	atomic_t dev_count;

  	struct rcu_head rcu;

  	/** The user id for this mount */

  	kuid_t user_id;

  	/** The group id for this mount */

  	kgid_t group_id;

  	/** The fuse mount flags for this mount */
  	unsigned flags;

  	/** Maximum read size */
  	unsigned max_read;

  	/** Maximum write size */
  	unsigned max_write;

  	/** Input queue */
  	struct fuse_iqueue iq;

  	/** The next unique kernel file handle */
  	u64 khctr;

  	/** rbtree of fuse_files waiting for poll events indexed by ph */
  	struct rb_root polled_files;

  	/** Maximum number of outstanding background requests */
  	unsigned max_background;
  
  	/** Number of background requests at which congestion starts */
  	unsigned congestion_threshold;

  	/** Number of requests currently in the background */
  	unsigned num_background;

  	/** Number of background requests currently queued for userspace */
  	unsigned active_background;
  
  	/** The list of background requests set aside for later queuing */
  	struct list_head bg_queue;

  	/** Flag indicating that INIT reply has been received. Allocating
  	 * any fuse request will be suspended until the flag is set */
  	int initialized;

  	/** Flag indicating if connection is blocked.  This will be
  	    the case before the INIT reply is received, and if there
  	    are too many outstading backgrounds requests */
  	int blocked;
  
  	/** waitq for blocked connection */
  	wait_queue_head_t blocked_waitq;

  
  	/** waitq for reserved requests */
  	wait_queue_head_t reserved_req_waitq;

  	/** Connection established, cleared on umount, connection
  	    abort and device release */

  	unsigned connected;

  	/** Connection failed (version mismatch).  Cannot race with
  	    setting other bitfields since it is only set once in INIT
  	    reply, before any other request, and never cleared */

  	unsigned conn_error:1;

  	/** Connection successful.  Only set in INIT */

  	unsigned conn_init:1;

  	/** Do readpages asynchronously?  Only set in INIT */

  	unsigned async_read:1;

  	/** Do not send separate SETATTR request before open(O_TRUNC)  */

  	unsigned atomic_o_trunc:1;

  	/** Filesystem supports NFS exporting.  Only set in INIT */

  	unsigned export_support:1;

  	/** Set if bdi is valid */
  	unsigned bdi_initialized:1;

  	/** write-back cache policy (default is write-through) */
  	unsigned writeback_cache:1;

  	/*
  	 * The following bitfields are only for optimization purposes
  	 * and hence races in setting them will not cause malfunction
  	 */

  	/** Is open/release not implemented by fs? */
  	unsigned no_open:1;

  	/** Is fsync not implemented by fs? */

  	unsigned no_fsync:1;

  	/** Is fsyncdir not implemented by fs? */

  	unsigned no_fsyncdir:1;

  	/** Is flush not implemented by fs? */

  	unsigned no_flush:1;

  	/** Is setxattr not implemented by fs? */

  	unsigned no_setxattr:1;

  
  	/** Is getxattr not implemented by fs? */

  	unsigned no_getxattr:1;

  
  	/** Is listxattr not implemented by fs? */

  	unsigned no_listxattr:1;

  
  	/** Is removexattr not implemented by fs? */

  	unsigned no_removexattr:1;

  	/** Are posix file locking primitives not implemented by fs? */

  	unsigned no_lock:1;

  	/** Is access not implemented by fs? */

  	unsigned no_access:1;

  	/** Is create not implemented by fs? */

  	unsigned no_create:1;

  	/** Is interrupt not implemented by fs? */

  	unsigned no_interrupt:1;

  	/** Is bmap not implemented by fs? */

  	unsigned no_bmap:1;

  	/** Is poll not implemented by fs? */
  	unsigned no_poll:1;

  	/** Do multi-page cached writes */

  	unsigned big_writes:1;

  	/** Don't apply umask to creation modes */
  	unsigned dont_mask:1;

  	/** Are BSD file locking primitives not implemented by fs? */
  	unsigned no_flock:1;

  	/** Is fallocate not implemented by fs? */
  	unsigned no_fallocate:1;

  	/** Is rename with flags implemented by fs? */
  	unsigned no_rename2:1;

  	/** Use enhanced/automatic page cache invalidation. */
  	unsigned auto_inval_data:1;

  	/** Does the filesystem support readdirplus? */

  	unsigned do_readdirplus:1;

  	/** Does the filesystem want adaptive readdirplus? */
  	unsigned readdirplus_auto:1;

  	/** Does the filesystem support asynchronous direct-IO submission? */
  	unsigned async_dio:1;

  	/** Is lseek not implemented by fs? */
  	unsigned no_lseek:1;

  	/** The number of requests waiting for completion */
  	atomic_t num_waiting;

  	/** Negotiated minor version */
  	unsigned minor;

  	/** Backing dev info */
  	struct backing_dev_info bdi;

  	/** Entry on the fuse_conn_list */
  	struct list_head entry;

  	/** Device ID from super block */
  	dev_t dev;

  
  	/** Dentries in the control filesystem */
  	struct dentry *ctl_dentry[FUSE_CTL_NUM_DENTRIES];
  
  	/** number of dentries used in the above array */
  	int ctl_ndents;

  	/** Key for lock owner ID scrambling */
  	u32 scramble_key[4];

  
  	/** Reserved request for the DESTROY message */
  	struct fuse_req *destroy_req;

  
  	/** Version counter for attribute changes */
  	u64 attr_version;

  
  	/** Called on final put */
  	void (*release)(struct fuse_conn *);

  
  	/** Super block for this connection. */
  	struct super_block *sb;
  
  	/** Read/write semaphore to hold when accessing sb. */
  	struct rw_semaphore killsb;

  
  	/** List of device instances belonging to this connection */
  	struct list_head devices;

  };

  static inline struct fuse_conn *get_fuse_conn_super(struct super_block *sb)
  {

  	return sb->s_fs_info;

  }
  
  static inline struct fuse_conn *get_fuse_conn(struct inode *inode)
  {
  	return get_fuse_conn_super(inode->i_sb);
  }
  
  static inline struct fuse_inode *get_fuse_inode(struct inode *inode)
  {
  	return container_of(inode, struct fuse_inode, inode);
  }
  
  static inline u64 get_node_id(struct inode *inode)
  {
  	return get_fuse_inode(inode)->nodeid;
  }

  /** Device operations */

  extern const struct file_operations fuse_dev_operations;

  extern const struct dentry_operations fuse_dentry_operations;

  /**

   * Inode to nodeid comparison.
   */
  int fuse_inode_eq(struct inode *inode, void *_nodeidp);
  
  /**

   * Get a filled in inode
   */

  struct inode *fuse_iget(struct super_block *sb, u64 nodeid,

  			int generation, struct fuse_attr *attr,
  			u64 attr_valid, u64 attr_version);

  int fuse_lookup_name(struct super_block *sb, u64 nodeid, struct qstr *name,
  		     struct fuse_entry_out *outarg, struct inode **inode);

  /**
   * Send FORGET command
   */

  void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget,
  		       u64 nodeid, u64 nlookup);
  
  struct fuse_forget_link *fuse_alloc_forget(void);

  /* Used by READDIRPLUS */
  void fuse_force_forget(struct file *file, u64 nodeid);

  /**

   * Initialize READ or READDIR request

   */

  void fuse_read_fill(struct fuse_req *req, struct file *file,

  		    loff_t pos, size_t count, int opcode);

  
  /**
   * Send OPEN or OPENDIR request
   */

  int fuse_open_common(struct inode *inode, struct file *file, bool isdir);

  struct fuse_file *fuse_file_alloc(struct fuse_conn *fc);

  struct fuse_file *fuse_file_get(struct fuse_file *ff);

  void fuse_file_free(struct fuse_file *ff);

  void fuse_finish_open(struct inode *inode, struct file *file);

  void fuse_sync_release(struct fuse_file *ff, int flags);

  /**
   * Send RELEASE or RELEASEDIR request
   */

  void fuse_release_common(struct file *file, int opcode);

  
  /**

   * Send FSYNC or FSYNCDIR request
   */

  int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
  		      int datasync, int isdir);

  
  /**

   * Notify poll wakeup
   */
  int fuse_notify_poll_wakeup(struct fuse_conn *fc,
  			    struct fuse_notify_poll_wakeup_out *outarg);
  
  /**

   * Initialize file operations on a regular file

   */
  void fuse_init_file_inode(struct inode *inode);
  
  /**

   * Initialize inode operations on regular files and special files

   */
  void fuse_init_common(struct inode *inode);
  
  /**

   * Initialize inode and file operations on a directory

   */
  void fuse_init_dir(struct inode *inode);
  
  /**

   * Initialize inode operations on a symlink

   */
  void fuse_init_symlink(struct inode *inode);
  
  /**
   * Change attributes of an inode
   */

  void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
  			    u64 attr_valid, u64 attr_version);

  void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
  				   u64 attr_valid);

  /**

   * Initialize the client device
   */
  int fuse_dev_init(void);
  
  /**
   * Cleanup the client device
   */
  void fuse_dev_cleanup(void);

  int fuse_ctl_init(void);

  void __exit fuse_ctl_cleanup(void);

  /**
   * Allocate a request
   */

  struct fuse_req *fuse_request_alloc(unsigned npages);

  struct fuse_req *fuse_request_alloc_nofs(unsigned npages);

  /**
   * Free a request
   */
  void fuse_request_free(struct fuse_req *req);
  
  /**

   * Get a request, may fail with -ENOMEM,
   * caller should specify # elements in req->pages[] explicitly

   */

  struct fuse_req *fuse_get_req(struct fuse_conn *fc, unsigned npages);

  struct fuse_req *fuse_get_req_for_background(struct fuse_conn *fc,
  					     unsigned npages);

  /*
   * Increment reference count on request
   */
  void __fuse_get_request(struct fuse_req *req);

  /**

   * Gets a requests for a file operation, always succeeds
   */

  struct fuse_req *fuse_get_req_nofail_nopages(struct fuse_conn *fc,
  					     struct file *file);

  
  /**

   * Decrement reference count of a request.  If count goes to zero free
   * the request.

   */
  void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req);
  
  /**

   * Send a request (synchronous)

   */

  void fuse_request_send(struct fuse_conn *fc, struct fuse_req *req);

  
  /**

   * Simple request sending that does request allocation and freeing
   */
  ssize_t fuse_simple_request(struct fuse_conn *fc, struct fuse_args *args);
  
  /**

   * Send a request in the background
   */

  void fuse_request_send_background(struct fuse_conn *fc, struct fuse_req *req);

  void fuse_request_send_background_locked(struct fuse_conn *fc,
  					 struct fuse_req *req);

  /* Abort all requests */

  void fuse_abort_conn(struct fuse_conn *fc);

  /**

   * Invalidate inode attributes
   */
  void fuse_invalidate_attr(struct inode *inode);

  void fuse_invalidate_entry_cache(struct dentry *entry);

  void fuse_invalidate_atime(struct inode *inode);

  /**
   * Acquire reference to fuse_conn
   */
  struct fuse_conn *fuse_conn_get(struct fuse_conn *fc);
  
  /**

   * Initialize fuse_conn
   */

  void fuse_conn_init(struct fuse_conn *fc);

  
  /**

   * Release reference to fuse_conn
   */
  void fuse_conn_put(struct fuse_conn *fc);

  struct fuse_dev *fuse_dev_alloc(struct fuse_conn *fc);
  void fuse_dev_free(struct fuse_dev *fud);

  /**
   * Add connection to control filesystem
   */
  int fuse_ctl_add_conn(struct fuse_conn *fc);
  
  /**
   * Remove connection from control filesystem
   */
  void fuse_ctl_remove_conn(struct fuse_conn *fc);

  
  /**
   * Is file type valid?
   */
  int fuse_valid_type(int m);

  
  /**

   * Is current process allowed to perform filesystem operation?

   */

  int fuse_allow_current_process(struct fuse_conn *fc);

  
  u64 fuse_lock_owner_id(struct fuse_conn *fc, fl_owner_t id);

  
  int fuse_update_attributes(struct inode *inode, struct kstat *stat,
  			   struct file *file, bool *refreshed);

  
  void fuse_flush_writepages(struct inode *inode);
  
  void fuse_set_nowrite(struct inode *inode);
  void fuse_release_nowrite(struct inode *inode);

  
  u64 fuse_get_attr_version(struct fuse_conn *fc);

  /**
   * File-system tells the kernel to invalidate cache for the given node id.
   */
  int fuse_reverse_inval_inode(struct super_block *sb, u64 nodeid,
  			     loff_t offset, loff_t len);
  
  /**
   * File-system tells the kernel to invalidate parent attributes and
   * the dentry matching parent/name.

   *
   * If the child_nodeid is non-zero and:
   *    - matches the inode number for the dentry matching parent/name,
   *    - is not a mount point
   *    - is a file or oan empty directory
   * then the dentry is unhashed (d_delete()).

   */
  int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid,

  			     u64 child_nodeid, struct qstr *name);

  int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
  		 bool isdir);

  
  /**
   * fuse_direct_io() flags
   */
  
  /** If set, it is WRITE; otherwise - READ */
  #define FUSE_DIO_WRITE (1 << 0)
  
  /** CUSE pass fuse_direct_io() a file which f_mapping->host is not from FUSE */
  #define FUSE_DIO_CUSE  (1 << 1)

  ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
  		       loff_t *ppos, int flags);

  long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
  		   unsigned int flags);

  long fuse_ioctl_common(struct file *file, unsigned int cmd,
  		       unsigned long arg, unsigned int flags);

  unsigned fuse_file_poll(struct file *file, poll_table *wait);
  int fuse_dev_release(struct inode *inode, struct file *file);

  bool fuse_write_update_size(struct inode *inode, loff_t pos);

  int fuse_flush_times(struct inode *inode, struct fuse_file *ff);

  int fuse_write_inode(struct inode *inode, struct writeback_control *wbc);

  int fuse_do_setattr(struct inode *inode, struct iattr *attr,
  		    struct file *file);

  void fuse_set_initialized(struct fuse_conn *fc);

  #endif /* _FS_FUSE_I_H */