Abstract: A permission check method is disclosed. A node receives an operation request, the operation request includes a target identifier. The node determines an operation permission of the operation request based on a file ACL of the target identifier and a file user identifier associated with the operation request, and determines a permission check result based on the operation permission of the operation request and a target operation type included in the operation request.

Abstract: A data access method includes receiving a file creation request, where the file creation request carries a first file name and a first file identifier of a parent directory of a first file; obtaining metadata of the parent directory that is of the first file and that corresponds to the first file identifier; creating the first file in the parent directory based on the metadata of the parent directory of the first file, and allocating a second file identifier to the first file, where the first file is a file or a directory in the directory tree; and recording a correspondence between the second file identifier and the first file name into a file index table.

Abstract: A data access method in a file system comprises receiving a data access request including an identifier of a to-be-accessed node, obtaining access permission for the to-be-accessed node based on the identifier of the to-be-accessed node, wherein when a permission version number of the to-be-accessed node is not the latest in permission version numbers of all nodes indicated by path information of the to-be-accessed node in a file system, the access permission for the to-be-accessed node inherits a permission record corresponding to a parent node that is of the to-be-accessed node and that has a latest permission version number, and performing authentication based on the access permission for the to-be-accessed node, and accessing data of the to-be-accessed node after the authentication succeeds.

Abstract: A data access method in a file system comprises receiving a data access request including an identifier of a to-be-accessed node, obtaining access permission for the to-be-accessed node based on the identifier of the to-be-accessed node, wherein when a permission version number of the to-be-accessed node is not the latest in permission version numbers of all nodes indicated by path information of the to-be-accessed node in a file system, the access permission for the to-be-accessed node inherits a permission record corresponding to a parent node that is of the to-be-accessed node and that has a latest permission version number, and performing authentication based on the access permission for the to-be-accessed node, and accessing data of the to-be-accessed node after the authentication succeeds.

Abstract: The invention provides an optical phase device, method and system. The optical phase device consists of a transparent dielectric substrate, a multilayer stack of dielectrics and a buffer layer. The refractive index of the transparent dielectric substrate, the multilayer stack of dielectrics and the buffer layer are all larger than that of the external medium. For the wavelength of the incident beam, the optical phase device has a phase variation in the angular range [?, ?] and the critical angle for total reflection on the interface between the buffer layer and the external medium adjacent to the buffer layer is ?, ?<?. The optical device has both low loss and large phase variation, which leads to a large Goos-Hanchen shift. As a dispersion compensation component, it can produce larger, tunable dispersions, and different dispersion compensations can be obtained by adjusting the operating angle or parameters in the structure.