vfs_umount Entry Point

Purpose

Unmounts a virtual file system.

Syntax

int vfs_umount (vfsp, crp)
struct vfs *vfsp;
struct ucred *crp;

Parameters

Description

The vfs_umount entry point is called to unmount a virtual file system. The logical file system performs services independent of the virtual file system that initiate the unmounting. The logical file system services:

• Guarantee the syntax of the uvmount subroutine.
• Perform permission checks:
  • If the vfsp parameter refers to a device mount, then the user must have root user authority to perform the operation.
  • If the vfsp parameter does not refer to a device mount, then the user must have root user authority or write permission in the parent directory of the mounted-over virtual node (v-node), as well as write permission to the file represented by the mounted-over v-node.
• Ensure that the virtual file system being unmounted contains no mount points for other virtual file systems.
• Ensure that the root v-node is not in use except for the mount. The root v-node is also referred to as the mounted v-node.
• Clear the v_mvfsp field in the stub v-node. This prevents lookup operations already in progress from traversing the soon-to-be unmounted mount point.

The logical file system assumes that, if necessary, successful vfs_umount entry point calls free the root v-node. An error return from the vfs_umount entry point causes the mount point to be re-established. A 0 (zero) returned from the vfs_umount entry point indicates the routine was successful and that the vfs structure was released.

Execution Environment

The vfs_umount entry point can be called from the process environment only.

Return Values

Nonzero return values are returned from the /usr/include/sys/errno.h file to indicate failure.

Related Information

The umount subroutine, uvmount subroutine, vmount subroutine.

Virtual File System Overview, Virtual File System Kernel Extensions Overview, Virtual File System Kernel Extensions Overview, Understanding Data Structures and Header Files for Virtual File Systems, Logical File System Overview, Understanding Virtual Nodes (V-nodes) in AIX Kernel Extensions and Device Support Programming Concepts.

List of Virtual File System Operations.