I have a usb disk image on file with several partitions on it.
Normally I would run:
  losetup -P -f --show usb.img
and such command would attach the file usb.img to a loop device (/dev/loop0)
and it would create also the devices /dev/loop0p1, /dev/loop0p<n> for each
partition in the image file.
Such command works in 15.1 but fails in 15.2. dmesg shows:
  loop_reread_partitions: partition scan of loop0 (usb.img) failed (rc=-16)
Instead with the latest kernelstable installed losetup -P works as expected.
I have found this 5.6.11 commit:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.6.y&id=17d02cdd39c9c58d890214f92b9899d600ecc087
I have applied such modification to the kernel 5.3.18-lp152.19 of 15.2 and I
can confirm that such commit fixes the problem.