Function cache_fplookup_final_modifying

freebsd/kern/vfs_cache.c:4202–4391

* They want to possibly modify the state of the namecache. */

 * They want to possibly modify the state of the namecache.
 */
static int __noinline
cache_fplookup_final_modifying(struct cache_fpl *fpl)
{
	struct nameidata *ndp;
	struct componentname *cnp;
	enum vgetstate dvs;
	struct vnode *dvp, *tvp;
	struct mount *mp;
	seqc_t dvp_seqc;
	int error;
	bool docache;

	ndp = fpl->ndp;
	cnp = fpl->cnp;
	dvp = fpl->dvp;
	dvp_seqc = fpl->dvp_seqc;

	MPASS(*(cnp->cn_nameptr) != '/');
	MPASS(cache_fpl_islastcn(ndp));
	if ((cnp->cn_flags & LOCKPARENT) == 0)
		MPASS((cnp->cn_flags & WANTPARENT) != 0);
	MPASS((cnp->cn_flags & TRAILINGSLASH) == 0);
	MPASS(cnp->cn_nameiop == CREATE || cnp->cn_nameiop == DELETE ||
	    cnp->cn_nameiop == RENAME);
	MPASS((cnp->cn_flags & MAKEENTRY) == 0);
	MPASS((cnp->cn_flags & ISDOTDOT) == 0);

	docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
	if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)
		docache = false;

	/*
	 * Regular lookup nulifies the slash, which we don't do here.
	 * Don't take chances with filesystem routines seeing it for
	 * the last entry.
	 */
	if (cache_fpl_istrailingslash(fpl)) {
		return (cache_fpl_partial(fpl));
	}

	mp = atomic_load_ptr(&dvp->v_mount);
	if (__predict_false(mp == NULL)) {
		return (cache_fpl_aborted(fpl));
	}

	if (__predict_false(mp->mnt_flag & MNT_RDONLY)) {
		cache_fpl_smr_exit(fpl);
		/*
		 * Original code keeps not checking for CREATE which
		 * might be a bug. For now let the old lookup decide.
		 */
		if (cnp->cn_nameiop == CREATE) {
			return (cache_fpl_aborted(fpl));
		}
		return (cache_fpl_handled_error(fpl, EROFS));
	}

	if (fpl->tvp != NULL && (cnp->cn_flags & FAILIFEXISTS) != 0) {