Manual Pages  — VFSCONF

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 operations 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 number.

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 called.

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