Description
System information
| Type | Version/Name |
|---|---|
| Distribution Name | Unraid |
| Distribution Version | 7.1.0-rc.2 |
| Kernel Version | 6.12.25 |
| Architecture | x86_64 |
| OpenZFS Version | 2.3.1 |
Describe the problem you're observing
This looks more like a kernel issue to me, but if I report it there I expect them to say that ZFS is not supported, so thought of reporting it here first to see what you think.
After updating the kernel from 6.12.24 to 6.12.25, loopbacks on a ZFS volume hang
Describe how to reproduce the problem
Create a new loopback image on a zfs volume, can be a single device zfs volume, format the loopback device xfs, attempt to mount it and it hangs:
root@test2:~# dd if=/dev/zero of=/mnt/tank/image bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.219488 s, 4.9 GB/s
root@test2:~# losetup /dev/loop2 /mnt/tank/image
root@test2:~# mkfs.xfs /dev/loop2
meta-data=/dev/loop2 isize=512 agcount=4, agsize=65536 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=1, sparse=1, rmapbt=1
= reflink=1 bigtime=1 inobtcount=1 nrext64=1
= exchange=0 metadir=0
data = bsize=4096 blocks=262144, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0, ftype=1, parent=0
log =internal log bsize=4096 blocks=16384, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
= rgcount=0 rgsize=0 extents
Discarding blocks...Done.
root@test2:~# mkdir /x
root@test2:~# mount /dev/loop2 /x
There are no panic/crashes logged, it stops here:
Apr 27 11:25:24 test2 kernel: loop2: detected capacity change from 0 to 2097152
Apr 27 11:26:04 test2 kernel: XFS (loop2): Mounting V5 Filesystem a6d3b0f6-ef7f-4e97-a665-e19a7b1074d2
Top shows that process using 100% CPU, it cannot be killed, and the server needs a hard reboot to recover:
top - 11:28:35 up 14 min, 0 users, load average: 1.98, 0.96, 0.43
Tasks: 252 total, 2 running, 249 sleep, 1 d-sleep, 0 stopped, 0 zombie
%Cpu(s): 1.5 us, 26.3 sy, 0.0 ni, 72.1 id, 0.1 wa, 0.0 hi, 0.1 si, 0.0 st
MiB Mem : 31932.4 total, 30148.2 free, 952.7 used, 1351.2 buff/cache
MiB Swap: 0.0 total, 0.0 free, 0.0 used. 30979.7 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
449 root 20 0 0 0 0 R 100.0 0.0 2:30.51 kworker/u16:5+loop2
P.S. if I format the loopback device btrfs, it doesn't hang on mount, but it does immediately after some i/o, reverting the kernel to 6.12.24 resolves the issue, if any other info is needed, please let me know.
Thanks.