Function vfs_notify_upper

freebsd/kern/vfs_subr.c:3873–3922

* Notify upper mounts about reclaimed or unlinked vnode. */

 * Notify upper mounts about reclaimed or unlinked vnode.
 */
void
vfs_notify_upper(struct vnode *vp, int event)
{
	static struct vfsops vgonel_vfsops = {
		.vfs_reclaim_lowervp = notify_lowervp_vfs_dummy,
		.vfs_unlink_lowervp = notify_lowervp_vfs_dummy,
	};
	struct mount *mp, *ump, *mmp;

	mp = vp->v_mount;
	if (mp == NULL)
		return;
	if (TAILQ_EMPTY(&mp->mnt_uppers))
		return;

	mmp = malloc(sizeof(struct mount), M_TEMP, M_WAITOK | M_ZERO);
	mmp->mnt_op = &vgonel_vfsops;
	mmp->mnt_kern_flag |= MNTK_MARKER;
	MNT_ILOCK(mp);
	mp->mnt_kern_flag |= MNTK_VGONE_UPPER;
	for (ump = TAILQ_FIRST(&mp->mnt_uppers); ump != NULL;) {
		if ((ump->mnt_kern_flag & MNTK_MARKER) != 0) {
			ump = TAILQ_NEXT(ump, mnt_upper_link);
			continue;
		}
		TAILQ_INSERT_AFTER(&mp->mnt_uppers, ump, mmp, mnt_upper_link);
		MNT_IUNLOCK(mp);
		switch (event) {
		case VFS_NOTIFY_UPPER_RECLAIM:
			VFS_RECLAIM_LOWERVP(ump, vp);
			break;
		case VFS_NOTIFY_UPPER_UNLINK:
			VFS_UNLINK_LOWERVP(ump, vp);
			break;
		default:
			KASSERT(0, ("invalid event %d", event));
			break;
		}
		MNT_ILOCK(mp);
		ump = TAILQ_NEXT(mmp, mnt_upper_link);
		TAILQ_REMOVE(&mp->mnt_uppers, mmp, mnt_upper_link);
	}
	free(mmp, M_TEMP);
	mp->mnt_kern_flag &= ~MNTK_VGONE_UPPER;
	if ((mp->mnt_kern_flag & MNTK_VGONE_WAITER) != 0) {
		mp->mnt_kern_flag &= ~MNTK_VGONE_WAITER;
		wakeup(&mp->mnt_uppers);
	}
	MNT_IUNLOCK(mp);
}

/*
 * vgone, with the vp interlock held.