vfs_modevent (9)

Leading comments

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 for...

(The comments found at the beginning of the groff file "man9/vfs_modevent.9freebsd".)

NAME

vfsconf - vfs configuration information

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

DESCRIPTION

Each file system type known to the kernel has a Vt 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 Vt 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 Vt mount structure is made to point directly at the Vt vfsconf structure for the file system type. The file system type number is taken from vfc_typenum which was assigned in Fn 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.

Fn vfs_register takes a new Vt 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 Fn vfs_init function in the file system operations vector. Fn 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.

Fn vfs_unregister unlinks Fa vfc from the list of registered file system types if there are currently no mounted instances. If the Fn vfs_uninit function in the file systems initialization vector is defined, it is called.

Fn vfs_modevent is registered by Fn VFS_SET to handle the loading and unloading of file system kernel modules. In the case of MOD_LOAD Fn vfs_register is called. In the case of MOD_UNLOAD Fn vfs_unregister is called.

RETURN VALUES

Fn vfs_register returns 0 if successful; otherwise, Er EEXIST is returned indicating that the file system type has already been registered.

Fn vfs_unregister returns 0 if successful. If no Vt vfsconf entry can be found matching the name in Fa vfc , Er EINVAL is returned. If the reference count of mounted instances of the file system type is not zero, Er EBUSY is returned. If Fn vfs_uninit is called, any errors it returns will be returned by Fn vfs_unregister .

Fn vfs_modevent returns the result of the call to Fn vfs_register or Fn vfs_unregister , whatever the case.

SEE ALSO

mount(2), vfs_rootmountalloc9, VFS_SET9

AUTHORS

This manual page was written by An Chad David Aq davidc@acns.ab.ca .