You've probably picked up a wrong tokudb rpm.
The one from centos74 builder is built without jemalloc, on centos73 — with, on centos7 — with.

So if you use tokudb binary that was not built with jemalloc, dynamic linker will not automatically load it for you. You either need to LD_PRELOAD it (mysqld_safe has a malloc-lib option for it) or disable startup jemalloc check in tokudb. Or use a different tokudb rpm.

can you indicate what changes exactly needs to be applied to mysqld_safe?
Everybody will have the same issue
I think this is another bug. If Tokudb was built without jemalloc, and before this version it was built with jemalloc, then we need to automate the changes so nodboy goes down unexpectedly.
Business cannot afford to go down, for no reason.

Most likely for previous installations/upgrades you were using centos7-amd64 repo. That's the one which our repo configuration tool offers for any CentOS 7, regardless subversions:
https://downloads.mariadb.org/mariadb/repositories/#mirror=netinch&distro=CentOS&distro_release=centos7-amd64--centos7&version=10.2

So, if that's what you probably have in your yum repo configuration.

But now, you had to go straight to downloads, so you've chosen centos74 – logical choice, if that's what you have, but not the same as you had before.
Just use whatever flavor you were previously using (you can double-check it in your repo config).

You guessed it right in all aspects.
So kindly make sure that the next person does no suffer from the same issue, namely, that jemalloc is installed but it needs to be preloaded as well.
I would love to use jemalloc.

tokudb is already in the repository, so upgrading normally should work for the next person with no jemalloc issues.
Very sorry for this, but thanks for the early alert!