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AIX Version 4.3 Kernel Extensions and Device Support Programming Concepts

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:

common_relock Implements a generic interface to the byte range 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.

Related Information

Understanding the Virtual File System Interface.

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