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 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,
mount(2) 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 VALUES
vfs_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 ALSO
AUTHORS
This manual page was written by Chad David <davidc@acns.ab.ca>.