Arch Linux

Description:
Since kernel 5.6.8 the handling of loop devices seems to be partially broken - after setting up a loop device kernel complain about failing to read its partition table and the loop device is loaded as unpartitioned, which is incorrect. Also happens on 5.6.10 from testing.

I did a few tests on 5.7.0 (provided by Fedora Rawhide ATM) and the handling seems to be back, even though kernel still complains (which isn't reassuring).

Additional info:
* package version(s)
linux 5.6.8.arch1-1 (core)
linux 5.6.10.arch1-1 (testing)

Steps to reproduce (linux 5.6.10.arch1-1):
# dd if=/dev/zero of=/disk.img bs=1M count=100
# losetup --show -P -f /disk.img
/dev/loop0
# printf ",10M\n,\n" | sfdisk /dev/loop0
...
Device Boot Start End Sectors Size Id Type
/dev/loop0p1 2048 22527 20480 10M 83 Linux
/dev/loop0p2 22528 204799 182272 89M 83 Linux

The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
# dmesg | tail
...
[ 606.892705] loop_reread_partitions: partition scan of loop1 (/disk.img) failed (rc=-16)
[ 611.236442] __loop_clr_fd: partition scan of loop0 failed (rc=-16)
[ 611.985511] loop_reread_partitions: partition scan of loop0 (/disk.img) failed (rc=-16)
[ 630.835052] loop0: p1 p2
# losetup -d /dev/loop0
# losetup --show -P -f /disk.img
/dev/loop0
# lsblk /dev/loop0
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
loop0 7:0 0 100M 0 loop
# dmesg | tail
...
[ 695.772141] loop_reread_partitions: partition scan of loop0 (/disk.img) failed (rc=-16)
# blockdev --rereadpt /dev/loop0
# lsblk /dev/loop0
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
loop0 7:0 0 100M 0 loop
├─loop0p1 259:0 0 10M 0 part
└─loop0p2 259:1 0 89M 0 part