VFSCONF(9) BSD Kernel Developer's Manual VFSCONF(9)NAME
vfsconf — vfs configuration information
SYNOPSIS
#include <sys/param.h>
#include <sys/mount.h>
int
vfs_register(struct vfsconf *vfc);
int
vfs_unregister(struct vfsconf *vfc);
int
vfs_modevent(module_t mod, int type, void *data);
DESCRIPTION
Each file system type known to the kernel has a vfsconf structure that
contains the information required to create a new mount of that file sys‐
tems type.
struct vfsconf {
struct vfsops *vfc_vfsops; /* file system operations vector */
char vfc_name[MFSNAMELEN]; /* file system type name */
int vfc_typenum; /* historic file system type number */
int vfc_refcount; /* number mounted of this type */
int vfc_flags; /* permanent flags */
struct vfsconf *vfc_next; /* next in list */
};
When a new file system is mounted, vfs_mount(9) does a lookup of the
vfsconf structure by its name, and if it is not already registered,
attempts to load a kernel module for it. The file system operations for
the new mount point are taken from vfc_vfsops, and mnt_vfc in the mount
structure is made to point directly at the vfsconf structure for the file
system type. The file system type number is taken from vfc_typenum which
was assigned in vfs_register(), and the mount flags are taken from a mask
of vfc_flags. Each time a file system of a given type is mounted,
vfc_refcount is incremented.
vfs_register() takes a new vfsconf structure and adds it to the list of
existing file systems. If the type has not already been registered, it
is initialized by calling the vfs_init() function in the file system
operations vector. vfs_register() also updates the oid's of any sysctl
nodes for this file system type to be the same as the newly assigned type
number.
vfs_unregister() unlinks vfc from the list of registered file system
types if there are currently no mounted instances. If the vfs_uninit()
function in the file systems initialization vector is defined, it is
called.
vfs_modevent() is registered by VFS_SET() to handle the loading and
unloading of file system kernel modules. In the case of MOD_LOAD,
vfs_register() is called. In the case of MOD_UNLOAD, vfs_unregister() is
called.
RETURN VALUESvfs_register() returns 0 if successful; otherwise, EEXIST is returned
indicating that the file system type has already been registered.
vfs_unregister() returns 0 if successful. If no vfsconf entry can be
found matching the name in vfc, EINVAL is returned. If the reference
count of mounted instances of the file system type is not zero, EBUSY is
returned. If vfs_uninit() is called, any errors it returns will be
returned by vfs_unregister().
vfs_modevent() returns the result of the call to vfs_register() or
vfs_unregister(), whatever the case.
SEE ALSOvfs_mount(9), vfs_rootmountalloc(9), VFS_SET(9)AUTHORS
This manual page was written by Chad David ⟨davidc@acns.ab.ca⟩.
BSD November 21, 2001 BSD
