A virtual file system (VFS) is an abstraction layer on top of a more concrete file system. The purpose of a VFS is to allow client applications to access different types of concrete file systems uniformly. A VFS can, for example, be used to access local and network storage devices transparently without the client application noticing the difference.
When a user program requests a file, i.e., fopen("0:/foo.txt", "r"), the kernel will parse the path and find the disk number and the file name. Then, the kernel will find the file system driver for the disk and call the driver's fopen function. The driver will read the file system header and find the file. The driver will then return a file descriptor to the kernel. The kernel will then return the file descriptor to the user program.
File descriptors are just integers. The kernel maintains a table of file descriptors and the corresponding file system driver. When the user program calls fread, the kernel will find the file system driver from the table and call the driver's fread function.
- Core functionality commit
- Structures commit
- FAT16 resolver function commit
- VFS fopen function commit
- FAT16 fopen function commit
- VFS fread function commit
- FAT16 fread function commit
- VFS fseek function commit
- FAT16 fseek function commit
- VFS/FAT16 fstat function commit
- VFS/FAT16 fclose function commit