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 systems type.

struct vfsconf {

struct vfsops *vfc_vfsops; /* file system oper

ations 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 reg

istered,
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 tak

en 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 de

fined, 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 VALUES

vfs_register() returns 0 if successful; otherwise, EEXIST is

returned
indicating that the file system type has already been regis

tered.

vfs_unregister() returns 0 if successful. If no vfsconf en

try 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 ALSO

vfs_mount(9), vfs_rootmountalloc(9), VFS_SET(9)

AUTHORS

This manual page was written by Chad David <davidc@ac

ns.ab.ca>.

BSD November 21, 2001

BSD