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VFSCONF(9)		 BSD Kernel Developer's	Manual		    VFSCONF(9)

     vfsconf --	vfs configuration information

     #include <sys/param.h>
     #include <sys/mount.h>

     vfs_register(struct vfsconf *vfc);

     vfs_unregister(struct vfsconf *vfc);

     vfs_modevent(module_t mod,	int type, void *data);

     Each file system type known to the	kernel has a vfsconf structure that
     contains the information required to create a new mount of	that file sys-
     tems 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 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 mount structure
     is	made to	point directly at the vfsconf structure	for the	file system
     type.  The	file system type number	is taken from vfc_typenum which	was
     assigned in 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.

     vfs_register() takes a new	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 vfs_init() function in the file system op-
     erations vector.  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

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

     vfs_modevent() is registered by VFS_SET() to handle the loading and un-
     loading of	file system kernel modules.  In	the case of MOD_LOAD,
     vfs_register() is called.	In the case of MOD_UNLOAD, vfs_unregister() is

     vfs_register() returns 0 if successful; otherwise,	EEXIST is returned in-
     dicating that the file system type	has already been registered.

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

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

     mount(2), vfs_rootmountalloc(9), VFS_SET(9)

     This manual page was written by Chad David	<>.

BSD				 June 16, 2013				   BSD


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