Function fdinit

freebsd/kern/kern_descrip.c:2124–2165

* Build a new filedesc structure from another. * * If fdp is not NULL, return with it shared locked. */

 * If fdp is not NULL, return with it shared locked.
 */
struct filedesc *
fdinit(struct filedesc *fdp, bool prepfiles, int *lastfile)
{
	struct filedesc0 *newfdp0;
	struct filedesc *newfdp;

	if (prepfiles)
		MPASS(lastfile != NULL);
	else
		MPASS(lastfile == NULL);

	newfdp0 = uma_zalloc(filedesc0_zone, M_WAITOK | M_ZERO);
	newfdp = &newfdp0->fd_fd;

	/* Create the file descriptor table. */
	FILEDESC_LOCK_INIT(newfdp);
	refcount_init(&newfdp->fd_refcnt, 1);
	refcount_init(&newfdp->fd_holdcnt, 1);
	newfdp->fd_map = newfdp0->fd_dmap;
	newfdp->fd_files = (struct fdescenttbl *)&newfdp0->fd_dfiles;
	newfdp->fd_files->fdt_nfiles = NDFILE;

	if (fdp == NULL)
		return (newfdp);

	FILEDESC_SLOCK(fdp);
	if (!prepfiles) {
		FILEDESC_SUNLOCK(fdp);
		return (newfdp);
	}

	for (;;) {
		*lastfile = fdlastfile(fdp);
		if (*lastfile < newfdp->fd_nfiles)
			break;
		FILEDESC_SUNLOCK(fdp);
		fdgrowtable(newfdp, *lastfile + 1);
		FILEDESC_SLOCK(fdp);
	}

	return (newfdp);
}

/*
 * Build a pwddesc structure from another.