Understanding Virtual Nodes (V-nodes)

A virtual node (v-node) represents access to an object within a virtual file system. V-nodes are used only to translate a path name into a generic node (g-node).

For more information on g-nodes, see Understanding Generic I-nodes (G-nodes).

A v-node is either created or used again for every reference made to a file by path name. When a user attempts to open or create a file, if the VFS containing the file already has a v-node representing that file, a use count in the v-node is incremented and the existing v-node is used. Otherwise, a new v-node is created.

Every path name known to the logical file system can be associated with, at most, one file system object. However, each file system object can have several names. Multiple names appear in the following cases:

• The object can appear in multiple virtual file systems. This can happen if the object (or an ancestor) is mounted in different virtual file systems using a local file-over-file or directory-over-directory mount.
• The object does not have a unique name within the virtual file system. (The file system implementation can provide synonyms. For example, the use of links causes files to have more than one name. However, opens of synonymous paths do not cause multiple v-nodes to be created.)