4. Unmounting a file system

• A file system cannot be unmounted if something in the system is using one of its files.
• If anything is using the file system to be unmounted there may be VFS inodes from it in the VFS inode cache,
• If the VFS superblock for the mounted file system is dirty, that is it has been modified, then it must be written back to the file system on disk.
• Once it has been written to disk, the memory occupied by the VFS superblock is returned to the kernel's free pool of memory.

[next]