fuse_lowlevel.h

FUSE文件系统开发工具,将内核层面的文件系统开发过程平移到应用层面上来。

	 * If the filesystem supports file locking operations (setlk,
	 * getlk) it should remove all locks belonging to 'fi->owner'.
	 *
	 * Valid replies:
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param fi file information
	 */
	void (*flush) (fuse_req_t req, fuse_ino_t ino,
		       struct fuse_file_info *fi);

	/**
	 * Release an open file
	 *
	 * Release is called when there are no more references to an open
	 * file: all file descriptors are closed and all memory mappings
	 * are unmapped.
	 *
	 * For every open call there will be exactly one release call.
	 *
	 * The filesystem may reply with an error, but error values are
	 * not returned to close() or munmap() which triggered the
	 * release.
	 *
	 * fi->fh will contain the value set by the open method, or will
	 * be undefined if the open method didn't set any value.
	 * fi->flags will contain the same flags as for open.
	 *
	 * Valid replies:
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param fi file information
	 */
	void (*release) (fuse_req_t req, fuse_ino_t ino,
			 struct fuse_file_info *fi);

	/**
	 * Synchronize file contents
	 *
	 * If the datasync parameter is non-zero, then only the user data
	 * should be flushed, not the meta data.
	 *
	 * Valid replies:
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param datasync flag indicating if only data should be flushed
	 * @param fi file information
	 */
	void (*fsync) (fuse_req_t req, fuse_ino_t ino, int datasync,
		       struct fuse_file_info *fi);

	/**
	 * Open a directory
	 *
	 * Filesystem may store an arbitrary file handle (pointer, index,
	 * etc) in fi->fh, and use this in other all other directory
	 * stream operations (readdir, releasedir, fsyncdir).
	 *
	 * Filesystem may also implement stateless directory I/O and not
	 * store anything in fi->fh, though that makes it impossible to
	 * implement standard conforming directory stream operations in
	 * case the contents of the directory can change between opendir
	 * and releasedir.
	 *
	 * Valid replies:
	 *   fuse_reply_open
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param fi file information
	 */
	void (*opendir) (fuse_req_t req, fuse_ino_t ino,
			 struct fuse_file_info *fi);

	/**
	 * Read directory
	 *
	 * Send a buffer filled using fuse_add_direntry(), with size not
	 * exceeding the requested size.  Send an empty buffer on end of
	 * stream.
	 *
	 * fi->fh will contain the value set by the opendir method, or
	 * will be undefined if the opendir method didn't set any value.
	 *
	 * Valid replies:
	 *   fuse_reply_buf
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param size maximum number of bytes to send
	 * @param off offset to continue reading the directory stream
	 * @param fi file information
	 */
	void (*readdir) (fuse_req_t req, fuse_ino_t ino, size_t size, off_t off,
			 struct fuse_file_info *fi);

	/**
	 * Release an open directory
	 *
	 * For every opendir call there will be exactly one releasedir
	 * call.
	 *
	 * fi->fh will contain the value set by the opendir method, or
	 * will be undefined if the opendir method didn't set any value.
	 *
	 * Valid replies:
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param fi file information
	 */
	void (*releasedir) (fuse_req_t req, fuse_ino_t ino,
			    struct fuse_file_info *fi);

	/**
	 * Synchronize directory contents
	 *
	 * If the datasync parameter is non-zero, then only the directory
	 * contents should be flushed, not the meta data.
	 *
	 * fi->fh will contain the value set by the opendir method, or
	 * will be undefined if the opendir method didn't set any value.
	 *
	 * Valid replies:
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param datasync flag indicating if only data should be flushed
	 * @param fi file information
	 */
	void (*fsyncdir) (fuse_req_t req, fuse_ino_t ino, int datasync,
			  struct fuse_file_info *fi);

	/**
	 * Get file system statistics
	 *
	 * Valid replies:
	 *   fuse_reply_statfs
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number, zero means "undefined"
	 */
	void (*statfs) (fuse_req_t req, fuse_ino_t ino);

	/**
	 * Set an extended attribute
	 *
	 * Valid replies:
	 *   fuse_reply_err
	 */
	void (*setxattr) (fuse_req_t req, fuse_ino_t ino, const char *name,
			  const char *value, size_t size, int flags);

	/**
	 * Get an extended attribute
	 *
	 * If size is zero, the size of the value should be sent with
	 * fuse_reply_xattr.
	 *
	 * If the size is non-zero, and the value fits in the buffer, the
	 * value should be sent with fuse_reply_buf.
	 *
	 * If the size is too small for the value, the ERANGE error should
	 * be sent.
	 *
	 * Valid replies:
	 *   fuse_reply_buf
	 *   fuse_reply_xattr
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param name of the extended attribute
	 * @param size maximum size of the value to send
	 */
	void (*getxattr) (fuse_req_t req, fuse_ino_t ino, const char *name,
			  size_t size);

	/**
	 * List extended attribute names
	 *
	 * If size is zero, the total size of the attribute list should be
	 * sent with fuse_reply_xattr.
	 *
	 * If the size is non-zero, and the null character separated
	 * attribute list fits in the buffer, the list should be sent with
	 * fuse_reply_buf.
	 *
	 * If the size is too small for the list, the ERANGE error should
	 * be sent.
	 *
	 * Valid replies:
	 *   fuse_reply_buf
	 *   fuse_reply_xattr
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param size maximum size of the list to send
	 */
	void (*listxattr) (fuse_req_t req, fuse_ino_t ino, size_t size);

	/**
	 * Remove an extended attribute
	 *
	 * Valid replies:
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param name of the extended attribute
	 */
	void (*removexattr) (fuse_req_t req, fuse_ino_t ino, const char *name);

	/**
	 * Check file access permissions
	 *
	 * This will be called for the access() system call.  If the
	 * 'default_permissions' mount option is given, this method is not
	 * called.
	 *
	 * This method is not called under Linux kernel versions 2.4.x
	 *
	 * Introduced in version 2.5
	 *
	 * Valid replies:
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param mask requested access mode
	 */
	void (*access) (fuse_req_t req, fuse_ino_t ino, int mask);

	/**
	 * Create and open a file
	 *
	 * If the file does not exist, first create it with the specified
	 * mode, and then open it.
	 *
	 * Open flags (with the exception of O_NOCTTY) are available in
	 * fi->flags.
	 *
	 * Filesystem may store an arbitrary file handle (pointer, index,
	 * etc) in fi->fh, and use this in other all other file operations
	 * (read, write, flush, release, fsync).
	 *
	 * There are also some flags (direct_io, keep_cache) which the
	 * filesystem may set in fi, to change the way the file is opened.
	 * See fuse_file_info structure in <fuse_common.h> for more details.
	 *
	 * If this method is not implemented or under Linux kernel
	 * versions earlier than 2.6.15, the mknod() and open() methods
	 * will be called instead.
	 *
	 * Introduced in version 2.5
	 *
	 * Valid replies:
	 *   fuse_reply_create
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param parent inode number of the parent directory
	 * @param name to create
	 * @param mode file type and mode with which to create the new file
	 * @param fi file information
	 */
	void (*create) (fuse_req_t req, fuse_ino_t parent, const char *name,
			mode_t mode, struct fuse_file_info *fi);

	/**
	 * Test for a POSIX file lock
	 *
	 * Introduced in version 2.6
	 *
	 * Valid replies:
	 *   fuse_reply_lock
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param fi file information
	 * @param lock the region/type to test
	 */
	void (*getlk) (fuse_req_t req, fuse_ino_t ino,
		       struct fuse_file_info *fi, struct flock *lock);

	/**
	 * Acquire, modify or release a POSIX file lock
	 *
	 * For POSIX threads (NPTL) there's a 1-1 relation between pid and
	 * owner, but otherwise this is not always the case.  For checking
	 * lock ownership, 'fi->owner' must be used.  The l_pid field in
	 * 'struct flock' should only be used to fill in this field in
	 * getlk().
	 *
	 * Note: if the locking methods are not implemented, the kernel
	 * will still allow file locking to work locally.  Hence these are
	 * only interesting for network filesystems and similar.
	 *
	 * Introduced in version 2.6
	 *
	 * Valid replies:
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param fi file information
	 * @param lock the region/type to test
	 * @param sleep locking operation may sleep
	 */
	void (*setlk) (fuse_req_t req, fuse_ino_t ino,
		       struct fuse_file_info *fi,
		       struct flock *lock, int sleep);

	/**
	 * Map block index within file to block index within device
	 *
	 * Note: This makes sense only for block device backed filesystems
	 * mounted with the 'blkdev' option
	 *
	 * Introduced in version 2.6
	 *
	 * Valid replies:
	 *   fuse_reply_bmap
	 *   fuse_reply_err
	 *
	 * @param req request handle
	 * @param ino the inode number
	 * @param blocksize unit of block index
	 * @param idx block index within file
	 */
	void (*bmap) (fuse_req_t req, fuse_ino_t ino, size_t blocksize,
		      uint64_t idx);
};

/**
 * Reply with an error code or success
 *
 * Possible requests:
 *   all except forget
 *
 * unlink, rmdir, rename, flush, release, fsync, fsyncdir, setxattr,
 * removexattr and setlk may send a zero code
 *
 * @param req request handle
 * @param err the positive error value, or zero for success
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_err(fuse_req_t req, int err);

/**
 * Don't send reply
 *
 * Possible requests:
 *   forget
 *
 * @param req request handle
 */
void fuse_reply_none(fuse_req_t req);

/**
 * Reply with a directory entry
 *
 * Possible requests:
 *   lookup, mknod, mkdir, symlink, link
 *
 * @param req request handle
 * @param e the entry parameters
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e);

/**
 * Reply with a directory entry and open parameters
 *
 * currently the following members of 'fi' are used:
 *   fh, direct_io, keep_cache
 *
 * Possible requests:
 *   create
 *
 * @param req request handle
 * @param e the entry parameters
 * @param fi file information
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_create(fuse_req_t req, const struct fuse_entry_param *e,
		      const struct fuse_file_info *fi);

/**
 * Reply with attributes
 *
 * Possible requests:
 *   getattr, setattr
 *
 * @param req request handle
 * @param the attributes
 * @param attr_timeout	validity timeout (in seconds) for the attributes
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_attr(fuse_req_t req, const struct stat *attr,
		    double attr_timeout);

/**
 * Reply with the contents of a symbolic link
 *
 * Possible requests:
 *   readlink
 *
 * @param req request handle
 * @param link symbolic link contents
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_readlink(fuse_req_t req, const char *link);

/**
 * Reply with open parameters
 *
 * currently the following members of 'fi' are used:
 *   fh, direct_io, keep_cache
 *
 * Possible requests:
 *   open, opendir
 *
 * @param req request handle
 * @param fi file information
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_open(fuse_req_t req, const struct fuse_file_info *fi);

/**
 * Reply with number of bytes written
 *
 * Possible requests:
 *   write
 *
 * @param req request handle
 * @param count the number of bytes written
 * @return zero for success, -errno for failure to send reply
 */
int fuse_reply_write(fuse_req_t req, size_t count);

/**
 * Reply with data
 *
 * Possible requests:
 *   read, readdir, getxattr, listxattr
 *
 * @param req request handle
 * @param buf buffer containing data
 * @param size the size of data in bytes
 * @return zero for success, -errno for failure to send reply