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More kernel vfs docco.

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Xref vfs_mount(9) from vfs_mount(9)

Submitted by: Chad David <davidc@acns.ab.ca>
PR: docs/32431
This commit is contained in:
Alfred Perlstein 2001-12-03 00:25:04 +00:00
parent 830681f547
commit ffc0b97fd0
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=87252
8 changed files with 498 additions and 4 deletions
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13
share/man/man9/Makefile
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@ -10,7 +10,7 @@ MAN= BUF_LOCK.9 BUF_LOCKFREE.9 BUF_LOCKINIT.9 BUF_REFCNT.9 \
MD5.9 MODULE_DEPEND.9 MODULE_VERSION.9 \
SYSCALL_MODULE.9 \
VFS.9 VFS_CHECKEXP.9 VFS_FHTOVP.9 VFS_INIT.9 VFS_MOUNT.9 \
VFS_QUOTACTL.9 VFS_ROOT.9 VFS_START.9 VFS_STATFS.9 \
VFS_QUOTACTL.9 VFS_ROOT.9 VFS_SET.9 VFS_START.9 VFS_STATFS.9 \
VFS_SYNC.9 VFS_UNMOUNT.9 VFS_VGET.9 VFS_VPTOFH.9 VOP_ACCESS.9 \
VOP_ACLCHECK.9 VOP_ADVLOCK.9 VOP_ATTRIB.9 VOP_BWRITE.9 \
VOP_CREATE.9 VOP_FSYNC.9 VOP_GETACL.9 VOP_GETEXTATTR.9 \
@ -59,8 +59,12 @@ MAN= BUF_LOCK.9 BUF_LOCKFREE.9 BUF_LOCKINIT.9 BUF_REFCNT.9 \
taskqueue.9 time.9 timeout.9 tvtohz.9 \
ucred.9 uidinfo.9 uio.9 \
vaccess.9 vaccess_acl_posix1e.9 \
vcount.9 vfs_busy.9 vfs_mount.9 vfs_timestamp.9 vfs_unbusy.9 \
vfs_unmountall.9 vget.9 vgone.9 vhold.9 vinvalbuf.9 \
vcount.9 \
vfs_busy.9 vfs_getnewfsid.9 vfs_getvfs.9 \
vfs_mount.9 vfs_mountedon.9 vfs_rootmountalloc.9 \
vfs_timestamp.9 vfs_unbusy.9 vfs_unmountall.9 \
vfsconf.9 \
vget.9 vgone.9 vhold.9 vinvalbuf.9 \
vflush.9 \
vm_page_alloc.9 vm_page_bits.9 vm_page_cache.9 \
vm_page_copy.9 vm_page_deactivate.9 vm_page_dontneed.9 \
@ -189,6 +193,9 @@ MLINKS+=timeout.9 callout_stop.9 timeout.9 callout_reset.9
MLINKS+=uidinfo.9 uihashinit.9 uidinfo.9 uifind.9
MLINKS+=uidinfo.9 uihold.9 uidinfo.9 uifree.9
MLINKS+=uio.9 uiomove.9
MLINKS+=vfsconf.9 vfs_modevent.9
MLINKS+=vfsconf.9 vfs_register.9
MLINKS+=vfsconf.9 vfs_unregister.9
MLINKS+=vgone.9 vgonel.9
MLINKS+=vhold.9 vdrop.9
MLINKS+=vm_page_bits.9 vm_page_set_validclean.9

78
share/man/man9/VFS_SET.9 Normal file
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@ -0,0 +1,78 @@
.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice(s), this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
.\" DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd December 2, 2001
.Dt VFS_SET 9
.Os
.Sh NAME
.Nm VFS_SET
.Nd "setup loadable filesystem vfsconf"
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.Ft void
.Fn VFS_SET "struct vfsops *vfsops" "char *fsname" "int flags"
.Sh DESCRIPTION
.Fn VFS_SET
creates a vfsconf structure for the loadable module with the given vfsops, name and
flags, and declares it by calling
.Fn DECLARE_MODULE
using
.Fn vfs_modevent
as the event handler.
.Sh PSEUDO CODE
.Bd -literal
/*
* fill in the ones we use, and use the vfs_std for the rest.
*/
static struct vfsops myfs_vfsops = {
myfs_mount,
vfs_stdstart,
myfs_unmount,
myfs_root,
vfs_stdquotactl,
myfs_statfs,
vfs_stdsync,
vfs_stdvget,
vfs_stdfhtovp,
vfs_stdcheckexp,
vfs_stdvptofh,
vfs_stdinit,
vfs_stduninit,
vfs_stdextattrctl,
};
VFS_SET(myfs_vfsops, skelfs, 0);
.Ed
.Sh SEE ALSO
.Xr vfsconf 9 ,
.Xr vfs_modevent 9 ,
.Xr DECLARE_MODULE 9
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .

73
share/man/man9/vfs_getnewfsid.9 Normal file
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@ -0,0 +1,73 @@
.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice(s), this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
.\" DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd November 21, 2001
.Dt VFS_GETNEWFSID 9
.Os
.Sh NAME
.Nm vfs_getnewfsid
.Nd "allocate a new fsid"
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.Ft void
.Fn vfs_getnewfsid "struct mount *mp"
.Sh DESCRIPTION
The
.Fn vfs_getnewfsid
function allocates a new filesystem identifier for the mount point given.
Filesystems typically call
.Fn vfs_getnewfsid
in their mount routine in order to acquire a unique id within the system
which can later be used to uniquely identify the filesystem via calls such as
.Fn vfs_getvfs .
.Pp
The actual fsid is made up of two 32 bit integers, that are stored in the statfs
structure of
.Fa mp .
The first integer is unique in the set of mounted filesystems, while the second holds
the filesystem type.
.Bd -literal
typedef struct fsid {
int32_t val[2];
} fsid_t;
.Ed
.Sh PSEUDOCODE
.Bd -literal
xxx_mount(struct mount *mp, char *path, caddr_t data, struct nameidata *ndp, struct thread *td)
{
...
vfs_getnewfsid(mp);
...
}
.Ed
.Sh SEE ALSO
.Xr vfs_getvfs 9
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .

72
share/man/man9/vfs_getvfs.9 Normal file
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@ -0,0 +1,72 @@
.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice(s), this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
.\" DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd November 21, 2001
.Dt VFS_GETVFS 9
.Os
.Sh NAME
.Nm vfs_getvfs
.Nd "returns a mount point given its fsid"
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.Ft struct mount *
.Fn vfs_getvfs "fsid_t *fsid"
.Sh DESCRIPTION
The
.Fn vfs_getvfs
function returns the mount point structure for a filesystem given its filesystem
identifier. The filesystem id should have been allocated by calling
.Fn vfs_getnewfsid ;
otherwise, it will not be found.
.Pp
A major user of
.Fn vfs_getvfs
is NFS, which uses the fsid as part of file handles in order to determine the
filesystem a given RPC is for.
If
.Fn vfs_getvfs
fails to find the mount point related to
.Fa fsid
the filesystem is considered stale.
.Sh RETURN VALUES
If
.Fa fsid
is found the mount point for the id is returned; otherwise,
.Dv NULL
is returned.
.Sh PSEUDOCODE
.Bd -literal
if ((mp = vfs_getvfs(&fhp->fh_fsid)) == NULL) {
error = ESTALE;
goto out;
}
.Ed
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .

3
share/man/man9/vfs_mount.9
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@ -121,7 +121,8 @@ this call relies on a large number of other kernel services
whose errors it returns so this list may not be exhaustive.
.Sh SEE ALSO
.Xr mount 2 ,
.Xr mount 8
.Xr mount 8 ,
.Xr vfs_mount 9
.Pp
.Va vfs.usermount
.Sh AUTHORS

75
share/man/man9/vfs_mountedon.9 Normal file
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@ -0,0 +1,75 @@
.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice(s), this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
.\" DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd November 21, 2001
.Dt VFS_MOUNTEDON 9
.Os
.Sh NAME
.Nm vfs_mountedon
.Nd "check if the vnode belongs to a mounted filesystem"
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Ft int
.Fn vfs_mountedon "struct vnode *vp"
.Sh DESCRIPTION
.Fn vfs_mountedon
inspects the mount structure in
.Fa vp
to determine if it points to a valid mount point.
If the mount is valid the vnode is considered to be busy.
.Pp
A common use of
.Fn vfs_mountedon
it to call it on device vnodes to determine if they are already associated with
a filesystem.
This is done to prevent multiple mounts on the same device.
.Sh RETURN VALUES
.Dv EBUSY
is returned if the vnode has a valid mount point; otherwise, 0 is returned.
.Sh PSEUDOCODE
.Bd -literal
int
ffs_mountfs(devvp, mp, td, malloctype)
register struct vnode *devvp;
struct mount *mp;
struct thread *td;
struct malloc_type *malloctype;
{
...
error = vfs_mountedon(devvp);
if (error)
return (error);
...
}
.Ed
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .

57
share/man/man9/vfs_rootmountalloc.9 Normal file
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@ -0,0 +1,57 @@
.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice(s), this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
.\" DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd November 21, 2001
.Dt VFS_ROOTMOUNTALLOC 9
.Os
.Sh NAME
.Nm vfs_rootmountalloc
.Nd "allocate a root mount structure"
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Ft int
.Fn vfs_rootmountalloc "char *fstypename" "char *devname" "struct mount **mpp"
.Sh DESCRIPTION
.Fn vfs_rootmountalloc
allocates a mount structure initialized from the vfsconf type
that matches
.Fa fstypename .
.Sh RETURN VALUES
If successful 0 is returned and
.Fa mpp
points to the newly allocated mount structure.
.Dv ENODEV
is returned if
.Fa fstypename
is NULL or invalid.
.Sh SEE ALSO
.Xr vfsconf 9
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .

131
share/man/man9/vfsconf.9 Normal file
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@ -0,0 +1,131 @@
.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice(s), this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
.\" DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd November 21, 2001
.Dt VFSCONF 9
.Os
.Sh NAME
.Nm vfsconf
.Nd "vfs configuration information"
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.Ft int
.Fn vfs_register "struct vfsconf *vfc"
.Ft int
.Fn vfs_unregister "struct vfsconf *vfc"
.Ft int
.Fn vfs_modevent "module_t mod" "int type" "void *data"
.Sh DESCRIPTION
Each filesystem type known to the kernel has a vfsconf structure that contains the
information required to create a new mount of that filesystems type.
.Bd -literal
struct vfsconf {
struct vfsops *vfc_vfsops; /* filesystem operations vector */
char vfc_name[MFSNAMELEN]; /* filesystem type name */
int vfc_typenum; /* historic filesystem type number */
int vfc_refcount; /* number mounted of this type */
int vfc_flags; /* permanent flags */
struct vfsconf *vfc_next; /* next in list */
};
.Ed
When a new filesystem is mounted
.Fn vfs_mount
does a lookup of the vfcconf structure by its name, and if it is not already registered,
attempts to load a kernel module for it.
The filesystem 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 vfcconf structure for the
filesystem type.
The filesystem type number is taken from vfs_typenum which was assigned in
.Fn vfs_register ,
and the mount flags are taken from a mask of vfc_flags.
Each time a filesystem of a given type is mounted vfc_refcount is incremented.
.Pp
.Fn vfs_register
takes a new vfsconf structure and adds it to the list of existing filesystems.
If the type has not already been registered it is initialize by calling the
.Fn vfs_init
function in the filesystem operations vector.
.Fn vfs_register
also updates the oid's of any sysctl nodes for this filesystem type
to be the same as the newly assigned type number.
.Pp
.Fn vfs_unregister
unlinks
.Fa vfc
from the list of registered filesystem types if there are currently no mounted instances.
If the
.Fn vfs_uninit
function in the filesystems initialization vector is defined it is called.
.Pp
.Fn vfs_modevent
is registered by
.Fn VFS_SET
to handle the loading and unloading of filesystem kernel modules.
In the case of
.Dv MOD_LOAD
.Fn vfs_register
is called.
In the case of
.Dv MOD_UNLOAD
.Fn vfs_unregister
is called.
.Sh RETURN VALUES
.Fn vfs_register
returns 0 if successful; otherwise,
.Dv EEXIST
is returned indicating that the filesystem type has already been registered.
.Pp
.Fn vfs_unregister
returns 0 if successful.
If no vfsconf entry can be found matching the name in
.Fa vfc ,
.Dv EINVAL
is returned.
If the reference count of mounted instances of the filesystem type is not zero
.Dv EBUSY
is returned.
If
.Fn vfs_uninit
is called any errors it returns will be returned by
.Fn vfs_unregister .
.Pp
.Fn vfs_modevent
returns the result of the call to
.Fn vfs_register
or
.Fn vfs_unregister
whatever the case.
.Sh SEE ALSO
.Xr vfs_rootmountalloc 9 ,
.Xr vfs_mount ,
.Xr VFS_SET 9
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .