More kernel vfs docco.

Xref vfs_mount(9) from vfs_mount(9)

Submitted by: Chad David <davidc@acns.ab.ca>
PR: docs/32431

8 files changed, 498 insertions, 4 deletions

diff --git a/share/man/man9/Makefile b/share/man/man9/Makefile
index 62fd9ef..d6a13e5 100644
--- a/share/man/man9/Makefile
+++ b/share/man/man9/Makefile
@@ -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
diff --git a/share/man/man9/VFS_SET.9 b/share/man/man9/VFS_SET.9
new file mode 100644
index 0000000..d335d17
--- /dev/null
+++ b/share/man/man9/VFS_SET.9
@@ -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 .
diff --git a/share/man/man9/vfs_getnewfsid.9 b/share/man/man9/vfs_getnewfsid.9
new file mode 100644
index 0000000..b12e027
--- /dev/null
+++ b/share/man/man9/vfs_getnewfsid.9
@@ -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 .
diff --git a/share/man/man9/vfs_getvfs.9 b/share/man/man9/vfs_getvfs.9
new file mode 100644
index 0000000..273d3c9
--- /dev/null
+++ b/share/man/man9/vfs_getvfs.9
@@ -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 .
diff --git a/share/man/man9/vfs_mount.9 b/share/man/man9/vfs_mount.9
index 8370e2a..b964801 100644
--- a/share/man/man9/vfs_mount.9
+++ b/share/man/man9/vfs_mount.9
@@ -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
diff --git a/share/man/man9/vfs_mountedon.9 b/share/man/man9/vfs_mountedon.9
new file mode 100644
index 0000000..e970d67
--- /dev/null
+++ b/share/man/man9/vfs_mountedon.9
@@ -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 .
diff --git a/share/man/man9/vfs_rootmountalloc.9 b/share/man/man9/vfs_rootmountalloc.9
new file mode 100644
index 0000000..559b671
--- /dev/null
+++ b/share/man/man9/vfs_rootmountalloc.9
@@ -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 .
diff --git a/share/man/man9/vfsconf.9 b/share/man/man9/vfsconf.9
new file mode 100644
index 0000000..176e764
--- /dev/null
+++ b/share/man/man9/vfsconf.9
@@ -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 .