Virtual File System (VFS) Kernel Services
The Virtual File System (VFS) kernel services are provided as fundamental building blocks for use when writing a virtual file system.
These services present a standard interface for such functions as configuring file systems, creating and freeing v-nodes, and looking up path names.
Most functions involved in the writing of a file system are specific to that file system type. But a limited number of functions must be performed in a consistent manner across the various file system types to enable the logical file system to operate independently of the file system type.
The VFS kernel services are:
| Item | Description |
|---|---|
| common_reclock | Implements a generic interface to the record locking functions. |
| fidtovp | Maps a file system structure to a file ID. |
| gfsadd | Adds a file system type to the gfs table. |
| gfsdel | Removes a file system type from the gfs table. |
| vfs_hold | Holds a vfs structure and increments the structure's use count. |
| vfs_unhold | Releases a vfs structure and decrements the structure's use count. |
| vfsrele | Releases all resources associated with a virtual file system. |
| vfs_search | Searches the vfs list. |
| vn_free | Frees a v-node previously allocated by the vn_get kernel service. |
| vn_get | Allocates a virtual node and associates it with the designated virtual file system. |
| lookupvp | Retrieves the v-node that corresponds to the named path. |