TL;DR: Regression in 3cef9aa17bf7dac59095b6972454c049a5fe97c0 confirmed. Cyril Brulebois <[email protected]> (2026-07-04): > Looking at the changes between v6.12.90 and v6.12.94, the following one > seems pretty plausible: > > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3cef9aa17bf7dac59095b6972454c049a5fe97c0 > > backported from: > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=267ec4d7223a783f029a980f41b93c39b17996da > > From a quick look at loop.c in v6.12.94, the code mentioned in the > commit message looks like it's in place, so if the regression is > confirmed to come from this commit (which I'm not certain of yet), it > shouldn't be caused by assumptions valid in the master branch but not in > the stable branch. > > Next steps for me (in no particular order): > - find a minimal reproducer; > - check what happens with a recent mainline kernel (e.g. > 7.0.12-2~bpo13+1); > - check what happens with v6.12.94 once that commit is reverted.
Building a 6.12.94-2 version with just that patch reverted, deploying
the resulting linux-image-6.12.94+deb13.1-amd64-unsigned package, and
building a system image leaves the system in a consistent state again:
root@iot-isobuilder-54:~# find /sys/ -name loop0'*'|sort
/sys/block/loop0
/sys/class/block/loop0
/sys/devices/virtual/block/loop0
/sys/kernel/debug/block/loop0
(i.e. no more extraneous loop0pX.)
Toying with a fresh file doesn't bring back remnants from the image
build:
root@iot-isobuilder-54:~# fallocate -l 1G foo.img
root@iot-isobuilder-54:~# kpartx -asv foo.img
root@iot-isobuilder-54:~# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
loop0 7:0 0 1G 0 loop
sda 8:0 0 20G 0 disk
├─sda1 8:1 0 18.9G 0 part /
├─sda2 8:2 0 1K 0 part
└─sda5 8:5 0 1.1G 0 part [SWAP]
Cleaning this up, and partitioning also gives the expected brand new
partitions (2 × ~500M):
root@iot-isobuilder-54:~# kpartx -dsv foo.img
loop deleted : /dev/loop0
root@iot-isobuilder-54:~# fdisk /dev/foo.img
[…]
root@iot-isobuilder-54:~# kpartx -asv foo.img
add map loop0p1 (253:2): 0 1024000 linear 7:0 2048
add map loop0p2 (253:3): 0 1071104 linear 7:0 1026048
root@iot-isobuilder-54:~# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
loop0 7:0 0 1G 0 loop
├─loop0p1 253:0 0 500M 0 part
└─loop0p2 253:1 0 523M 0 part
sda 8:0 0 20G 0 disk
├─sda1 8:1 0 18.9G 0 part /
├─sda2 8:2 0 1K 0 part
└─sda5 8:5 0 1.1G 0 part [SWAP]
And finally, a second system image build succeeds again, as there are no
duplicates that trigger the safeguard's exit condition.
Cheers,
--
Cyril Brulebois ([email protected]) <https://debamax.com/>
D-I release manager -- Release team member -- Freelance Consultant
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