/*
    FUSE: Filesystem in Userspace

    Copyright (C) 2001-2006  Miklos Szeredi <miklos@szeredi.hu>

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

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

  /** Maximum number of outstanding background requests */
  #define FUSE_MAX_BACKGROUND 10

  /** 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 3

  /** 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)

  /** 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;

  /** 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_req *forget_req;

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

  	u64 i_time;

  };

  /** FUSE specific file data */
  struct fuse_file {
  	/** Request reserved for flush and release */

  	struct fuse_req *reserved_req;

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

  /** 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;
  
  	/** Number or arguments */
  	unsigned numargs;
  
  	/** Array of arguments */
  	struct fuse_arg args[3];
  };

  /** The request state */
  enum fuse_req_state {
  	FUSE_REQ_INIT = 0,
  	FUSE_REQ_PENDING,
  	FUSE_REQ_READING,
  	FUSE_REQ_SENT,

  	FUSE_REQ_WRITING,

  	FUSE_REQ_FINISHED
  };

  struct fuse_conn;

  /**
   * A request to the client
   */
  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;

  	/*
  	 * The following bitfields are either set once before the
  	 * request is queued or setting/clearing them is protected by

  	 * fuse_conn->lock

  	 */

  	/** True if the request has reply */
  	unsigned isreply:1;

  	/** Force sending of the request even if interrupted */
  	unsigned force:1;

  	/** The request was aborted */
  	unsigned aborted:1;

  
  	/** Request is sent in the background */
  	unsigned background:1;

  	/** The request has been interrupted */
  	unsigned interrupted:1;

  	/** Data is being copied to/from the request */
  	unsigned locked:1;

  	/** Request is counted as "waiting" */
  	unsigned waiting:1;

  	/** State of the request */
  	enum fuse_req_state state;

  
  	/** 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 fuse_forget_in forget_in;

  		struct fuse_release_in release_in;

  		struct fuse_init_in init_in;
  		struct fuse_init_out init_out;

  		struct fuse_read_in read_in;

  		struct fuse_lk_in lk_in;

  	} misc;
  
  	/** page vector */
  	struct page *pages[FUSE_MAX_PAGES_PER_REQ];
  
  	/** number of pages in vector */
  	unsigned num_pages;
  
  	/** offset of data on first page */
  	unsigned page_offset;

  	/** File used in the request (or NULL) */
  	struct file *file;

  	/** vfsmount used in release */
  	struct vfsmount *vfsmount;
  
  	/** dentry used in release */
  	struct dentry *dentry;

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

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

  };

  /**
   * 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;

  	/** Mutex protecting against directory alias creation */
  	struct mutex inst_mutex;

  	/** Refcount */
  	atomic_t count;

  	/** The user id for this mount */
  	uid_t user_id;

  	/** The group id for this mount */
  	gid_t group_id;

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

  	/** Maximum read size */
  	unsigned max_read;

  	/** Maximum write size */
  	unsigned max_write;

  	/** Readers of the connection are waiting on this */
  	wait_queue_head_t waitq;
  
  	/** The list of pending requests */
  	struct list_head pending;
  
  	/** The list of requests being processed */
  	struct list_head processing;

  	/** The list of requests under I/O */
  	struct list_head io;

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

  	/** Pending interrupts */
  	struct list_head interrupts;

  	/** 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;

  	/** The next unique request id */
  	u64 reqctr;

  	/** 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;

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

  	/** 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 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;

  	/** 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;
  
  	/** Unique ID */
  	u64 id;
  
  	/** Dentries in the control filesystem */
  	struct dentry *ctl_dentry[FUSE_CTL_NUM_DENTRIES];
  
  	/** number of dentries used in the above array */
  	int ctl_ndents;

  
  	/** O_ASYNC requests */
  	struct fasync_struct *fasync;

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

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

  };

  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;

  /**

   * Get a filled in inode
   */
  struct inode *fuse_iget(struct super_block *sb, unsigned long nodeid,

  			int generation, struct fuse_attr *attr);

  
  /**
   * Send FORGET command
   */
  void fuse_send_forget(struct fuse_conn *fc, struct fuse_req *req,

  		      unsigned long nodeid, u64 nlookup);

  
  /**

   * Initialize READ or READDIR request

   */

  void fuse_read_fill(struct fuse_req *req, struct file *file,
  		    struct inode *inode, loff_t pos, size_t count, int opcode);

  
  /**
   * Send OPEN or OPENDIR request
   */
  int fuse_open_common(struct inode *inode, struct file *file, int isdir);

  struct fuse_file *fuse_file_alloc(void);
  void fuse_file_free(struct fuse_file *ff);
  void fuse_finish_open(struct inode *inode, struct file *file,
  		      struct fuse_file *ff, struct fuse_open_out *outarg);

  /** */
  struct fuse_req *fuse_release_fill(struct fuse_file *ff, u64 nodeid, int flags,
  				   int opcode);

  /**
   * Send RELEASE or RELEASEDIR request
   */
  int fuse_release_common(struct inode *inode, struct file *file, int isdir);
  
  /**

   * Send FSYNC or FSYNCDIR request
   */
  int fuse_fsync_common(struct file *file, struct dentry *de, int datasync,
  		      int isdir);
  
  /**

   * 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);
  
  /**

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

  int fuse_ctl_init(void);
  void fuse_ctl_cleanup(void);

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

   * Get a request, may fail with -ENOMEM

   */

  struct fuse_req *fuse_get_req(struct fuse_conn *fc);

  
  /**

   * Gets a requests for a file operation, always succeeds
   */
  struct fuse_req *fuse_get_req_nofail(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 request_send(struct fuse_conn *fc, struct fuse_req *req);
  
  /**

   * Send a request with no reply
   */
  void request_send_noreply(struct fuse_conn *fc, struct fuse_req *req);
  
  /**
   * Send a request in the background
   */
  void request_send_background(struct fuse_conn *fc, struct fuse_req *req);

  /* Abort all requests */

  void fuse_abort_conn(struct fuse_conn *fc);

  /**

   * Get the attributes of a file
   */
  int fuse_do_getattr(struct inode *inode);
  
  /**
   * Invalidate inode attributes
   */
  void fuse_invalidate_attr(struct inode *inode);

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