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VFSCONF(9) FreeBSD 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
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.
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
mount(2), vfs_rootmountalloc(9), VFS_SET(9)
AUTHORS
This manual page was written by Chad David <davidc@acns.ab.ca>.
FreeBSD 14.0-RELEASE-p6 June 16, 2013 FreeBSD 14.0-RELEASE-p6