152 lines
4.5 KiB
Groff
152 lines
4.5 KiB
Groff
.\"
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.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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.\" DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd June 16, 2013
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.Dt VFSCONF 9
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.Os
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.Sh NAME
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.Nm vfsconf
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.Nd "vfs configuration information"
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/mount.h
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.Ft int
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.Fn vfs_register "struct vfsconf *vfc"
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.Ft int
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.Fn vfs_unregister "struct vfsconf *vfc"
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.Ft int
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.Fn vfs_modevent "module_t mod" "int type" "void *data"
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.Sh DESCRIPTION
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Each file system type known to the kernel has a
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.Vt vfsconf
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structure that contains the
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information required to create a new mount of that file systems type.
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.Bd -literal
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struct vfsconf {
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struct vfsops *vfc_vfsops; /* file system operations vector */
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char vfc_name[MFSNAMELEN]; /* file system type name */
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int vfc_typenum; /* historic file system type number */
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int vfc_refcount; /* number mounted of this type */
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int vfc_flags; /* permanent flags */
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struct vfsconf *vfc_next; /* next in list */
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};
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.Ed
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.Pp
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When a new file system is mounted,
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.Xr mount 2
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does a lookup of the
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.Vt vfsconf
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structure by its name, and if it is not already registered,
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attempts to load a kernel module for it.
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The file system operations for the new mount point are taken from
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.Va vfc_vfsops ,
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and
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.Va mnt_vfc
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in the
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.Vt mount
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structure is made to point directly at the
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.Vt vfsconf
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structure for the
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file system type.
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The file system type number is taken from
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.Va vfc_typenum
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which was assigned in
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.Fn vfs_register ,
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and the mount flags are taken from a mask of
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.Va vfc_flags .
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Each time a file system of a given type is mounted,
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.Va vfc_refcount
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is incremented.
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.Pp
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.Fn vfs_register
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takes a new
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.Vt vfsconf
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structure and adds it to the list of existing file systems.
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If the type has not already been registered, it is initialized by calling the
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.Fn vfs_init
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function in the file system operations vector.
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.Fn vfs_register
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also updates the oid's of any sysctl nodes for this file system type
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to be the same as the newly assigned type number.
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.Pp
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.Fn vfs_unregister
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unlinks
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.Fa vfc
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from the list of registered file system types if there are currently no mounted instances.
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If the
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.Fn vfs_uninit
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function in the file systems initialization vector is defined, it is called.
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.Pp
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.Fn vfs_modevent
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is registered by
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.Fn VFS_SET
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to handle the loading and unloading of file system kernel modules.
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In the case of
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.Dv MOD_LOAD ,
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.Fn vfs_register
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is called.
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In the case of
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.Dv MOD_UNLOAD ,
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.Fn vfs_unregister
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is called.
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.Sh RETURN VALUES
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.Fn vfs_register
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returns 0 if successful; otherwise,
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.Er EEXIST
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is returned indicating that the file system type has already been registered.
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.Pp
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.Fn vfs_unregister
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returns 0 if successful.
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If no
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.Vt vfsconf
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entry can be found matching the name in
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.Fa vfc ,
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.Er EINVAL
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is returned.
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If the reference count of mounted instances of the file system type is not zero,
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.Er EBUSY
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is returned.
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If
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.Fn vfs_uninit
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is called, any errors it returns will be returned by
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.Fn vfs_unregister .
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.Pp
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.Fn vfs_modevent
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returns the result of the call to
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.Fn vfs_register
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or
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.Fn vfs_unregister ,
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whatever the case.
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.Sh SEE ALSO
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.Xr mount 2 ,
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.Xr vfs_rootmountalloc 9 ,
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.Xr VFS_SET 9
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.Sh AUTHORS
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This manual page was written by
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.An Chad David Aq davidc@acns.ab.ca .
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