Function vn_fullpath_dir

freebsd/kern/vfs_cache.c:3104–3207

* Resolve a directory to a pathname. * * The name of the directory can always be found in the namecache or fetched * from the filesystem. There is also guaranteed to be only one parent, meaning * we can just follow vnodes up until we find the root. * * The vnode must be referenced. */

 * The vnode must be referenced.
 */
static int
vn_fullpath_dir(struct vnode *vp, struct vnode *rdir, char *buf, char **retbuf,
    size_t *len, size_t addend)
{
#ifdef KDTRACE_HOOKS
	struct vnode *startvp = vp;
#endif
	struct vnode *vp1;
	size_t buflen;
	int error;
	bool slash_prefixed;

	VNPASS(vp->v_type == VDIR || VN_IS_DOOMED(vp), vp);
	VNPASS(vp->v_usecount > 0, vp);

	buflen = *len;

	slash_prefixed = true;
	if (addend == 0) {
		MPASS(*len >= 2);
		buflen--;
		buf[buflen] = '\0';
		slash_prefixed = false;
	}

	error = 0;

	SDT_PROBE1(vfs, namecache, fullpath, entry, vp);
	counter_u64_add(numfullpathcalls, 1);
	while (vp != rdir && vp != rootvnode) {
		/*
		 * The vp vnode must be already fully constructed,
		 * since it is either found in namecache or obtained
		 * from VOP_VPTOCNP().  We may test for VV_ROOT safely
		 * without obtaining the vnode lock.
		 */
		if ((vp->v_vflag & VV_ROOT) != 0) {
			vn_lock(vp, LK_RETRY | LK_SHARED);

			/*
			 * With the vnode locked, check for races with
			 * unmount, forced or not.  Note that we
			 * already verified that vp is not equal to
			 * the root vnode, which means that
			 * mnt_vnodecovered can be NULL only for the
			 * case of unmount.
			 */
			if (VN_IS_DOOMED(vp) ||
			    (vp1 = vp->v_mount->mnt_vnodecovered) == NULL ||
			    vp1->v_mountedhere != vp->v_mount) {
				vput(vp);
				error = ENOENT;
				SDT_PROBE3(vfs, namecache, fullpath, return,
				    error, vp, NULL);
				break;
			}

			vref(vp1);