ZFS: occationally symlinks are randomly not created under /dev/zvol/ since LTS kernel 5.15.x

As I understand it, OpenZFS has logic that depend on kernel behaviour that was removed from 5.13 and onward.

Related issues reported at MS GitHub:

Linux v5.13 broke zvol_first_open lock retry logic, so open() on a zvol dev node now sometimes fails with errno=ERESTARTSYS in userspace (particularly noticeable in udev)

Missing symlinks in /dev/zvol

Zvols get lost upon host startup and VM shut down

Possible fix in PR:

Linux 5.13 compat: retry zvol_open() when contended