230 lines
5.2 KiB
Groff
230 lines
5.2 KiB
Groff
.\" $Id: getvfsent.3,v 1.12 1998/05/25 21:42:51 steve Exp $
|
|
.\" Written by Garrett A. Wollman, September 1994.
|
|
.\" This manual page is in the public domain.
|
|
.\"
|
|
.Dd September 24, 1994
|
|
.Dt GETVFSBYNAME 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm getvfsbyname ,
|
|
.Nm getvfsbytype ,
|
|
.Nm getvfsent ,
|
|
.Nm setvfsent ,
|
|
.Nm endvfsent ,
|
|
.Nm vfsisloadable ,
|
|
.Nm vfsload
|
|
.Nd manage virtual filesystem modules
|
|
.Sh SYNOPSIS
|
|
.Fd #include <sys/param.h>
|
|
.Fd #include <sys/mount.h>
|
|
.Fd #undef getvfsbyname
|
|
.Ft struct ovfsconf *
|
|
.Fn getvfsbyname "const char *name"
|
|
.Ft struct ovfsconf *
|
|
.Fn getvfsbytype "int type"
|
|
.Ft struct ovfsconf *
|
|
.Fn getvfsent "void"
|
|
.Ft void
|
|
.Fn setvfsent "int cachelist"
|
|
.Ft void
|
|
.Fn endvfsent "void"
|
|
.Ft int
|
|
.Fn vfsisloadable "const char *name"
|
|
.Ft int
|
|
.Fn vfsload "const char *name"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn getvfsbyname ,
|
|
.Fn getvfsbytype ,
|
|
and
|
|
.Fn getvfsent
|
|
functions provide convenient access to a list of installed virtual
|
|
filesystem modules managed by the kernel.
|
|
.Fn getvfsbyname
|
|
and
|
|
.Fn getvfsbytype
|
|
provide direct access to a single filesystem's information;
|
|
.Fn getvfsent
|
|
steps through the list of filesystems one at a time. All three
|
|
functions return a null pointer when no data is available. The fields
|
|
in a
|
|
.Dq Li struct ovfsconf
|
|
are as follows:
|
|
.Pp
|
|
.Bl -tag -compact -width vfc_refcount
|
|
.It vfc_name
|
|
the name of the filesystem
|
|
.It vfc_index
|
|
the filesystem type number assigned by the kernel and used in calls to
|
|
.Xr mount 2
|
|
.It vfc_refcount
|
|
the number of references to this filesystem
|
|
(usually the number of mounts, but one greater for filesystems which
|
|
cannot be unloaded or which are statically linked into the kernel)
|
|
.It vfc_flags
|
|
flag bits, of which none are currently defined
|
|
.El
|
|
.Pp
|
|
The
|
|
.Fn setvfsent
|
|
and
|
|
.Fn endvfsent
|
|
functions are used to control caching of the filesystem list, which is
|
|
obtained in toto from the kernel via
|
|
.Xr sysctl 3 .
|
|
If the
|
|
.Fa cachelist
|
|
parameter to
|
|
.Fn setvfsent
|
|
is non-zero, the list will be retrieved only once, upon the first call
|
|
to one of the retrieval functions, until
|
|
.Fn endvfsent
|
|
is called to clear the cache. In general,
|
|
.Fn setvfsent 1
|
|
should be called by programs using the
|
|
.Fn getvfsent
|
|
function, and
|
|
.Fn setvfsent 0
|
|
(which is also the default state)
|
|
should be called by programs using the
|
|
.Fn vfsload
|
|
function.
|
|
.Pp
|
|
The
|
|
.Fn vfsisloadable
|
|
function returns a non-zero value if a later call to
|
|
.Fn vfsload name
|
|
is likely to succeed. We say ``likely'' because the conditions
|
|
checked by
|
|
.Fn vfsisloadable
|
|
are only a small subset of the conditions necessary for
|
|
.Fn vfsload
|
|
to succeed. In particular,
|
|
.Fn vfsisloadable
|
|
checks that
|
|
.Pa /dev/lkm
|
|
is present and can be opened for writing, and that
|
|
.Pa Ns Fa name Ns _mod.o
|
|
can be found in one of the directories designated for LKMs.
|
|
.Pp
|
|
The
|
|
.Fn vfsload
|
|
function attempts to load a kernel module implementing filesystem
|
|
.Fa name .
|
|
It returns zero if the filesystem module was successfully located and
|
|
loaded, or non-zero otherwise. It should only be called in the
|
|
following circumstances:
|
|
.Bl -enum
|
|
.It
|
|
.Fn getvfsbyname name
|
|
has been called and returned a null pointer.
|
|
.It
|
|
.Fn vfsisloadable name
|
|
has been called and returned a non-zero value.
|
|
.It
|
|
sufficient temporary file space is available
|
|
.Em and writable
|
|
in one of
|
|
.No Ns \&${ Ns Ev TMPDIR Ns \&} ,
|
|
.Pa /var/tmp ,
|
|
or
|
|
.Pa /tmp .
|
|
.El
|
|
.Pp
|
|
Here is an example, taken from the source to
|
|
.Xr mount_cd9660 8 :
|
|
.Bd -literal -offset indent
|
|
|
|
struct ovfsconf *vfc;
|
|
int error;
|
|
|
|
/* setup code here */
|
|
|
|
error = getvfsbyname("cd9660", &vfc);
|
|
if (error && vfsisloadable("cd9660")) {
|
|
if (vfsload("cd9660"))
|
|
err(EX_OSERR, "vfsload(cd9660)");
|
|
endvfsent(); /* flush cache */
|
|
error = getvfsbyname("cd9660", &vfc);
|
|
}
|
|
if (error)
|
|
errx(1, "cd9660 filesystem is not available");
|
|
|
|
if (mount(vfc.vfc_name, dir, mntflags, &args) < 0)
|
|
err(1, NULL);
|
|
|
|
.Ed
|
|
.Sh RETURN VALUES
|
|
The
|
|
.Fn getvfsbyname ,
|
|
.Fn getvfsbytype ,
|
|
and
|
|
.Fn getvfsent
|
|
routines all return a pointer to the same static data structure when
|
|
they succeed, and return a null pointer when they fail. On failure,
|
|
.Va errno
|
|
may be set to one of the values documented for
|
|
.Xr sysctl 3
|
|
or
|
|
.Xr malloc 3 ,
|
|
if a failure of that function was the cause; otherwise
|
|
.Va errno
|
|
will be unmodified.
|
|
.Pp
|
|
The
|
|
.Fn vfsload
|
|
function returns a non-zero value on failure, or zero on success. If
|
|
.Fn vfsload
|
|
fails,
|
|
.Va errno
|
|
may be set to one of the values documented for
|
|
.Xr fork 2 ,
|
|
.Xr waitpid 2 ,
|
|
.Xr chdir 2 ,
|
|
or
|
|
.Xr execlp 3 ,
|
|
or the return status of the
|
|
.Xr modload 8
|
|
program, which is not currently particularly useful but eventually
|
|
will be. In addition, if
|
|
.Xr modload 8
|
|
exits on a signal,
|
|
.Fn vfsload
|
|
will fail and set
|
|
.Va errno
|
|
to
|
|
.Er EINVAL .
|
|
.Sh ENVIRONMENT
|
|
.Bl -tag -compact -width TMPDIRx
|
|
.It Ev TMPDIR
|
|
location for temporary file created by
|
|
.Xr modload 8
|
|
on behalf of
|
|
.Fn vfsload .
|
|
.It Ev LKMDIR
|
|
alternate directory for
|
|
.Fn vfsisloadable
|
|
and
|
|
.Fn vfsload
|
|
to search for loadable modules.
|
|
.Sh SEE ALSO
|
|
.Xr mount 2 ,
|
|
.Xr modload 8 ,
|
|
.Xr mount 8
|
|
.Sh BUGS
|
|
The return value of the
|
|
.Xr modload 8
|
|
command isn't particularly useful when interpreted as an
|
|
.Va errno
|
|
value (or anything else, for that matter).
|
|
.Sh AUTHORS
|
|
The loadable filesystem support was written by
|
|
.An Garrett A. Wollman ,
|
|
based on generic loadable kernel module support by
|
|
.An Terry Lambert .
|
|
.Sh HISTORY
|
|
The
|
|
.Fn getvfsbyname
|
|
family of functions first appeared in
|
|
.Fx 2.0 .
|