** Changed in: linux (Ubuntu Jammy)
Status: In Progress => Fix Committed
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https://bugs.launchpad.net/bugs/2056143
Title:
block/loop: No longer allows to create partitions
Status in linux package in Ubuntu:
Invalid
Status in linux source package in Jammy:
Fix Committed
Bug description:
== SRU Justification ==
-- Impact --
In 22.04/Jammy with the GA 5.15 kernel there was an upstream change
preventing partition table operations when GENHD_FL_NO_PART is set.
1a721de8489f "block: don't add or resize partition on the disk with
GENHD_FL_NO_PART"
Beside of changing return codes and breaking some user-space that way this
also causes loop block devices to no longer be able to have partitions manually
created. This is because the loop block driver uses GENHD_FL_NO_PART to prevent
active partition scans.
-- Fix --
This was changed in 5.19 (and thus Mantic is not affected) by introducing a
separate flag to prevent those scans:
b9684a71fca7 "block, loop: support partitions without scanning"
The fix depends on a larger rewrite so it cannot be simply picked. The
biggest change from the original is moving the check for the new flag into a
helper function in genhd.h which checks whether a disk should be scanned for
partitions. That function was dropped with the upstream rewrite and checking
moved into the loop driver directly. But it felt like adjusting the helper was
the better approach.
Note: The upstream patch has a follow-up change submitted:
748008e1da92 "block: don't add partitions if GD_SUPPRESS_PART_SCAN is set"
We do _NOT_ need that in Jammy/5.15 because block/partitions/core.c:
blk_add_partitions() checks disk_part_scan_enabled() which was where we added
the check for the backport instead of modifying disk_scan_partitions() directly.
-- Testcase --
$ fallocate -l 1G /tmp/blob
$ LOOPDEV=$(sudo losetup --find --show /tmp/blob)
$ sudo /usr/sbin/parted -s -m -a optimal $LOOPDEV -- unit KiB mklabel gpt
mkpart primary 0% 100%
-- Regression Potential --
If things go wrong it might be other devices which no longer get scanned
automatically or other issues with the loop block driver.
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