freebsd-skq/share/man/man9/VOP_LINK.9

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.\" Copyright (c) 1996 Doug Rabson
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.\" $Id: VOP_LINK.9,v 1.4 1998/03/12 07:31:11 charnier Exp $
.\"
.Dd July 24, 1996
.Os
.Dt VOP_LINK 9
.Sh NAME
.Nm VOP_LINK
.Nd create a new name for a file
.Sh SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <sys/vnode.h>
.Ft int
.Fn VOP_LINK "struct vnode *dvp" "struct vnode *vp" "struct componentname *cnp"
.Sh DESCRIPTION
This links a new name in the specified directory to an existing file.
.Pp
Its arguments are:
.Bl -tag -width 8X
.It Ar dvp
the vnode of the directory
.It Ar vp
the vnode of the file to be linked
.It Ar cnp
pathname information about the file
.El
.Pp
The pathname info must be released on exit.  The directory and 
file vnodes should NOT be released on exit.
.Sh LOCKS
The directory,
.Fa dvp
should be locked on entry.  The caller will unlock and release
it on return so the VOP routine should not.
The file
.Fa vp
should not be locked.
.Sh RETURN VALUES
Zero is returned if the file was linked successfully, otherwise an
error is returned.
.Sh PSEUDOCODE
.Bd -literal
int
vop_link(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
{
    int error = 0;

    if (vp->v_mount != dvp->v_mount) {
	VOP_ABORTOP(dvp, cnp);
	error = EXDEV;
	goto out2;
    }
    if (vp != dvp && (error = VOP_LOCK(vp))) {
	VOP_ABORTOP(dvp, cnp);
	goto out2;
    }

    if (vp would have too many links) {
	VOP_ABORTOP(dvp, cnp);
	error = EMLINK;
	goto out1;
    }

    if (vp is immutable) {
	VOP_ABORTOP(dvp, cnp);
	error = EPERM;
	goto out1;
    }

    /*
     * Increment link count of vp and write back the on-disc version of it.
     */
    ...;

    if (!error) {
	/*
	 * Add the new name to the directory.
	 */
	...;
    }

    free(cnp->cn_pnbuf, M_NAMEI);
out1:
    if (vp != dvp)
	VOP_UNLOCK(vp);
out2:
    vput(dvp);

    return error;
}
.Ed
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EPERM
the file is immutable
.El
.Sh SEE ALSO
.Xr vnode 9
.Sh AUTHORS
This man page was written by
.An Doug Rabson .