Convergence a.e. and of norms implies that in $L^1$ norm

Suppose $f_n$ is as sequence of functions in $L^1[0,1]$ such that $f_n$ converges pointwise a.e. to $f\in L^1[0,1]$. Suppose also that $\int \vert f_n\vert \rightarrow \int \vert f\vert$. Is it true that $f_n$ converges to $f$ in the $L^1$ norm?


From Javaman's comment below: $|f_n-f|\leqslant |f_n|+|f|$. So DCT applies. Since $f_n\rightarrow f$ a.e. we have $\lim_n\int |f_n-f|=0.$ i.e $\Vert f_n-f\Vert \rightarrow 0.$


Yes you are right. Fatou's lemma can be applied here. As Javaman said, $|f_n-f|\le |f_n|+|f|$ is the key. Then $|f_n|+|f|-|f_n-f|\ge 0$, so Fatou's lemma applies. That is, $$\liminf_{n\to \infty}\int \left(|f_n|+|f|-|f_n-f|\right)\ge \int \liminf_{n\to \infty} \left(|f_n|+|f|-|f_n-f|\right)$$

Hence $$2\int |f|-\limsup_{n\to \infty}\int|f_n-f|\ge 2\int |f|$$

Thus $$\limsup_{n\to \infty}\int|f_n-f|\le 0$$ and we are done.