PANIC at vdev_raidz.c:4579:spa_raidz_expand_thread()

[tonyhutter]

System information

Type	Version/Name
Distribution Name	Fedora
Distribution Version	40
Kernel Version	6.9
Architecture	x86-64
OpenZFS Version	(private branch equivalent to c8184d7)

Describe the problem you're observing

While testing out the new "run ZTS on a VM in a github runner" #15838, I saw this:

    KILLED raidz/raidz_expand_004_pos (expected PASS)

I noticed this assertion in the console logs:

[ 8738.776195] ZTS run /usr/share/zfs/zfs-tests/tests/functional/raidz/raidz_expand_002_pos
[ 8933.574782] ZTS run /usr/share/zfs/zfs-tests/tests/functional/raidz/raidz_expand_003_neg
[ 8974.221424] ZTS run /usr/share/zfs/zfs-tests/tests/functional/raidz/raidz_expand_003_pos
[ 9152.974374] ZTS run /usr/share/zfs/zfs-tests/tests/functional/raidz/raidz_expand_004_pos
[ 9248.195333] VERIFY3(vre->vre_failed_offset == UINT64_MAX) failed (838860288 == 18446744073709551615)
[ 9248.200161] PANIC at vdev_raidz.c:4579:spa_raidz_expand_thread()              
[ 9248.205327] Showing stack for process 729410                                  
[ 9248.207356] CPU: 3 PID: 729410 Comm: raidz_expand Tainted: P           OE      6.9.12-200.fc40.x86_64 #1
[ 9248.213673] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 9248.220180] Call Trace:                                                       
[ 9248.221461]  <TASK>                                                           
[ 9248.222396]  dump_stack_lvl+0x5d/0x80                                         
[ 9248.224322]  spl_panic+0xf4/0x10b [spl]                                       
[ 9248.226655]  ? srso_alias_return_thunk+0x5/0xfbef5                            
[ 9248.229067]  ? srso_alias_return_thunk+0x5/0xfbef5                            
[ 9248.231569]  spa_raidz_expand_thread+0x8e6/0x960 [zfs]                        
[ 9248.238817]  ? __pfx_thread_generic_wrapper+0x10/0x10 [spl]                   
[ 9248.241729]  zthr_procedure+0x96/0x260 [zfs]                                  
[ 9248.244819]  ? __pfx_zthr_procedure+0x10/0x10 [zfs]                           
[ 9248.247882]  thread_generic_wrapper+0x66/0x90 [spl]                           
[ 9248.249875]  kthread+0xd2/0x100                                               
[ 9248.251239]  ? __pfx_kthread+0x10/0x10                                        
[ 9248.253439]  ret_from_fork+0x34/0x50                                          
[ 9248.254611]  ? __pfx_kthread+0x10/0x10                                        
[ 9248.257311]  ret_from_fork_asm+0x1a/0x30                                      
[ 9248.260032]  </TASK>                                                          
[10353.165221] ZTS run /usr/share/zfs/zfs-tests/callbacks/zfs_failsafe           
[10353.250670] ZTS run /usr/share/zfs/zfs-tests/tests/functional/raidz/raidz_expand_005_pos
[11553.347107] ZTS run /usr/share/zfs/zfs-tests/callbacks/zfs_failsafe           
[11553.422116] ZTS run /usr/share/zfs/zfs-tests/tests/functional/raidz/raidz_expand_006_neg

Test run
https://github.com/tonyhutter/zfs/actions/runs/10221662252/job/28284669082

Full logs:
https://github.com/tonyhutter/zfs/actions/runs/10221662252/artifacts/1771261530

Describe how to reproduce the problem

Include any warning/errors/backtraces from the system logs