issue #14223: fix generation of kernel uevents for snapshot rename on linux

[JKDingwall]

zvol_rename_minors() needs to be given the full path not just the snapshot name. Use code removed in a0bd735 as a guide to providing the necessary values.

Closes #14223

Motivation and Context

Renaming a snapshot zfs rename zpool/volume@snap1 zpool/volume@snap2 should result in the udev generated link for /dev/zvol/zpool/volume@snap1 being removed and a new /dev/zvol/zpool/volume@snap2 being created. Without this then trying to access the snapshot content via the old name results in ENOENT and the new name is not present.

#14223

Description

The change here ensures that the full path to the snapshot is provided to zvol_rename_minors() and not just the plain snapshot name.

How Has This Been Tested?

The kernel module has been rebuilt on the test system with this change and the behaviour of the rename is now as expected, the old link is removed and a new link exists. Content of the snapshot is available via the new link.

make deb has also been executed and the full set of packages has been used to rebuild a virtual machine disk image. The image has been booted and no regressions have been noted.

# modinfo zfs | grep version
version:        2.2.6-7_ge638f31346
srcversion:     A2EB6FF13910945DA37E614
vermagic:       6.8.0-40-generic SMP preempt mod_unload modversions 

# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 22.04.4 LTS
Release:        22.04
Codename:       jammy

# uname -a
Linux hostname 6.8.0-40-generic #40~22.04.1 SMP PREEMPT_DYNAMIC Tue Jul 30 17:51:21 UTC  x86_64 x86_64 x86_64 GNU/Linux

I am not a FreeBSD user so I'm unsure if there was an issue on that platform or how this code may affect it.

N/A.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[behlendorf]

Looks good, thanks for running this down. Let's just make sure to also update at least one of the functional/cli_root/zfs_rename/ test cases to verify the link is update for renamed volume snapshots.

[JKDingwall]

@behlendorf I've had a look around the tests and wondered if function/zvol/... might be a more appropriate area as there a lots of tests here using blockdev_missing and blockdev_exists which is the important thing to check, under cli_root there is no use at all. Since snapdev=visible is also required perhaps it's ok to test the rename here?

diff --git a/tests/zfs-tests/tests/functional/zvol/zvol_misc/zvol_misc_snapdev.ksh b/tests/zfs-tests/tests/functional/zvol/zvol_misc/zvol_misc_snapdev.ksh
index 1fc2d2780..3d229dccd 100755
--- a/tests/zfs-tests/tests/functional/zvol/zvol_misc/zvol_misc_snapdev.ksh
+++ b/tests/zfs-tests/tests/functional/zvol/zvol_misc/zvol_misc_snapdev.ksh
@@ -118,4 +118,15 @@ verify_inherited 'snapdev' 'hidden' $SUBZVOL $VOLFS
 blockdev_missing $SUBSNAPDEV
 blockdev_exists $SNAPDEV
 
+# 4. Verify "rename" is correctly reflected when "snapdev=visible"
+# 4.1 First create a snapshot and verify the device is present
+log_must zfs snapshot $SNAP
+log_must zfs set snapdev=visible $ZVOL
+blockdev_exists $SNAPDEV
+# 4.2 rename the snapshot and verify the devices are updated
+log_must zfs rename $SNAP $SNAP-new
+blockdev_missing $SNAPDEV
+blockdev_exists $SNAPDEV-new
+log_must zfs destroy $SNAP-new
+
 log_pass "ZFS volume property 'snapdev' works as expected"

[behlendorf]

@JKDingwall sure that'd be fine. It does look like it would fit in better there.

[JKDingwall]

The test failures appear to be in a different area to this change so I think it is all in order now.

[behlendorf]

Looks good. The couple of failures observed are all unrelated known test issues.