vop_createvobject(9)

NAME

VOP_CREATEVOBJECT, VOP_DESTROYVOBJECT, VOP_GETVOBJECT - VM

object interaction

SYNOPSIS

#include <sys/param.h>
#include <sys/vnode.h>
int
VOP_CREATEVOBJECT(struct vnode *vp, struct ucred *cred,
        struct thread *td);
int
VOP_DESTROYVOBJECT(struct vnode *vp);
int
VOP_GETVOBJECT(struct vnode *vp, struct vm_object **objpp);

DESCRIPTION

These calls are used to control the association of a VM ob

ject with a
particular vnode.

The arguments specific to these functions are:

vp The vnode of the file.

objpp The VM object being returned, or NULL if the caller

wants to test

for the existence of the VM object).

VFS(9) invokes VOP_CREATEVOBJECT() when it needs to create a

VM object
for the given vnode(9). File system code may pass this call

down to the
underlying file system. This VOP can be called multiple

times, and file
system code should ignore any additional calls, exiting with

a zero
return code.

VOP_DESTROYVOBJECT() is called when a vnode(9) is recycled.

VOP_GETVOBJECT() should be used by all kernel code to get a

VM object.
The returned VM object may belong to a different file system

in the case
of stacked mounts.

VFS(9) has three functions which perform standard operations

by creating
and destroying VM objects. These functions are:

vop_stdcreatevobject(),
vop_stddestroyvobject() and vop_stdgetvobject().

Note: a vnode(9) should be locked on entry and must be left

locked on
exit.

RETURN VALUES

The VOP_CREATEVOBJECT(), VOP_DESTROYVOBJECT() and

VOP_GETVOBJECT

tions return zero on success, or a non-zero value on fail

ure. Zero is
returned on success, otherwise an error is returned.

EXAMPLES

By default, file systems leave VM object handling to the

vop_std*() functions.

SEE ALSO

vnode(9), VOP_GETPAGES(9), VOP_PUTPAGES(9)

AUTHORS

This manual page was written by Boris Popov.

BSD September 10, 2000

BSD