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CIFS stopped working/is unstable with kernel update to 5.15.0-102.112

Asked by Andreas Besold

Hi,

updated some Ubuntu 22.04 systems to lastest available state this morning, which caused CIFS mounts (from various fileservers) to stop working. Kernel was updated to version 5.15.0-102-generic.

I can mount the shares without problems (mount -t cifs), but then, df for example tells me: df: /mnt: Resource temporarily unavailable.
I'm able to list and browse all the files, but accessing them (even readonly) is very unstable. Sometimes it works and sometimes it just gives me i/o errors.

Switching back to 5.15.0-101-generic or 5.15.0-100-generic solves the problem and everything works again as expected.

Seems like some bug has been implemented in 5.15.0-102-generic...

To reproduce the problem, I started a while loop on one server to write to some file on a specific mounted CIFS share and read it from another one

root@<hostname1>:~# while true; do echo "$(date) hallo" >> /mnt/hallo.txt; sleep 1 ; done
-bash: /mnt/hallo.txt: Input/output error
-bash: /mnt/hallo.txt: Input/output error
^C

root@<hostname2>:~$ tail -f /mnt/hallo.txt
Tue Apr 9 04:10:52 PM CEST 2024 hallo
Tue Apr 9 04:10:53 PM CEST 2024 hallo
Tue Apr 9 04:10:54 PM CEST 2024 hallo
Tue Apr 9 04:10:55 PM CEST 2024 hallo
Tue Apr 9 04:10:56 PM CEST 2024 hallo
Tue Apr 9 04:10:57 PM CEST 2024 hallo
Tue Apr 9 04:10:58 PM CEST 2024 hallo
Tue Apr 9 04:10:59 PM CEST 2024 hallo
Tue Apr 9 04:11:00 PM CEST 2024 hallo
Tue Apr 9 04:11:01 PM CEST 2024 hallo
tail: cannot determine location of '/mnt/hallo.txt'. reverting to polling: Resource temporarily unavailable
Tue Apr 9 04:11:04 PM CEST 2024 hallo
Tue Apr 9 04:11:05 PM CEST 2024 hallo
Tue Apr 9 04:11:06 PM CEST 2024 hallo
Tue Apr 9 04:11:07 PM CEST 2024 hallo
Tue Apr 9 04:11:08 PM CEST 2024 hallo
Tue Apr 9 04:11:09 PM CEST 2024 hallo
Tue Apr 9 04:11:10 PM CEST 2024 hallo

While doing this, both servers tell me, the resource is unavailable

root@<hostname1>:~# df -h /mnt
df: /mnt: Resource temporarily unavailable

root@<hostname2>:~$ df -h /mnt
df: /mnt: Resource temporarily unavailable

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Revision history for this message
actionparsnip (andrew-woodhead666) said : 		#1

I suggest you report a bug. Mark it as a regression

Revision history for this message
Benjamin Richner (benri) said (last edit ): 		#2

Can confirm. I just upgraded to the exact same kernel and the same happened to me. Random but aggressive CIFS outage, Dolphin is confused and doesn't show half the files. Tail fails immediately:

```
foo@mainpc:/media/nasdata1$ tail -f test.txt
TEST
tail: cannot determine location of 'test.txt'. reverting to polling: Resource temporarily unavailable
^C
foo@mainpc:/media/nasdata1$ tail -f test.txt
TEST
tail: cannot determine location of 'test.txt'. reverting to polling: Resource temporarily unavailable
^C
foo@mainpc:/media/nasdata1$ tail -f test.txt
TEST
tail: cannot determine location of 'test.txt'. reverting to polling: Resource temporarily unavailable
^C
foo@mainpc:/media/nasdata1$ tail -f test.txt
TEST
tail: cannot determine location of 'test.txt'. reverting to polling: Resource temporarily unavailable
^C
```

My network share is basically unusable. I can supply log files or help analyse it if required, but I believe that this kernel update needs to be rolled back ASAP, this is one of the severest regressions I've seen on stable Ubuntu LTS.

Now I'm back on `5.15.0-100.110` which I had previously. CIFS works perfectly well on the older kernel.

Revision history for this message
Andreas Besold (absld) said : 		#3

Thanks Benjamin for your input. I created a bug ticket from this question

Revision history for this message
Dick Shouldis (bobnwieve) said : 		#4

Confirming this bug as well. Current workaround was to downgrade to 5.15.0-101-generic and it worked just as it was previously. For any other newbs like me here's a helpful article on downgrading: https://zrruziev.medium.com/how-to-change-linux-kernel-version-2e9d6973d3fe

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