  The current paper considers the boundedness of solutions to the following
quasilinear Keller-Segel model (with logistic source)
$$\left\{\begin{array}{ll} u_t = \nabla\cdot(D(u)\nabla
u)-\chi\nabla\cdot(u\nabla v)+\mu (u-u^2),\quad x\in \Omega, t>0,\\ v_t-\Delta
v = u-v,\quad x\in \Omega, t>0,\\ (D(u)\nabla u-\chi u\cdot \nabla v)\cdot \nu
= \frac{\partial v}{\partial\nu}=0,\quad x\in \partial\Omega, t>0,\\ u(x,0) =
u_0(x),\quad v(x,0) = v_0(x),\ \ x\in \Omega, \end{array}\right.$$ where
$\Omega\subset\mathbb{R}^N(N\geq1)$ is a bounded domain with smooth boundary
$\partial\Omega,$ $\chi>0$ and $\mu\geq0$. We prove that for nonnegative and
suitably smooth initial data $(u_0, v_0)$, if $D(u)\geq C_{D}(u+1)^{m-1}$ for
all $u\geq 0$ with some $C_{D} > 0$ and some
$m>2-\frac{2}{N}\frac{\chi\max\{1,\lambda_0\}}{[\chi\max\{1,\lambda_0\}-\mu]_{+}}$
or $m=2-\frac{2}{N}$ and
$C_D>\frac{C_{GN}(1+\|u_0\|_{L^1(\Omega)})}{3}(2-\frac{2}{N})^2\max\{1,\lambda_0\}\chi$,
the $(KS)$ possesses a global classical solution which is bounded in
$\Omega\times (0,\infty)$, where $C_{GN}$ and $\lambda_0$ are the constants
which are corresponding to the Gagliardo--Nirenberg inequality and the maximal
Sobolev regularity. To our best knowledge, this seems to be the first rigorous
mathematical result which (precisely) gives the relationship between $m$ and
$\frac{\mu}{\chi}$ that yields to the boundedness of the solutions.
