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¶
mount(2),
vfs_rootmountalloc(9),
VFS_SET(9)
AUTHORS¶
This manual page was written by
Chad David
⟨davidc@acns.ab.ca⟩.