(Re-sending without the log from the older kernel, because the mail hit
the 100000 char limit with that)

Hi,
it seems that in kernels >= 5.15, io_uring and CIFS don't interact
nicely sometimes, leading to IO errors. Unfortunately, my reproducer is
a QEMU VM with a disk on CIFS (original report by one of our users [0]),
but I can try to cook up something simpler if you want.

Bisecting got me to 8ef12efe26c8 ("io_uring: run regular file
completions from task_work") being the first bad commit.

Attached are debug logs taken with Ubuntu's build of 5.18.6. QEMU trace
was taken with '-trace luring*' and CIFS debug log was enabled as
described in [1].

Without CIFS debugging, the error messages in syslog are, for 5.18.6:
> Jun 29 12:41:45 pve702 kernel: [  112.664911] CIFS: VFS: \\192.168.20.241 Error -512 sending data on socket to server
> Jun 29 12:41:46 pve702 kernel: [  112.796227] CIFS: Status code returned 0xc00000d0 STATUS_REQUEST_NOT_ACCEPTED
> Jun 29 12:41:46 pve702 kernel: [  112.796250] CIFS: VFS: \\192.168.20.241 Send error in SessSetup = -5
> Jun 29 12:41:46 pve702 kernel: [  112.797781] CIFS: VFS: \\192.168.20.241 Send error in SessSetup = -11
> Jun 29 12:41:46 pve702 kernel: [  112.798065] CIFS: VFS: \\192.168.20.241 Send error in SessSetup = -11
> Jun 29 12:41:46 pve702 kernel: [  112.813485] CIFS: Status code returned 0xc00000d0 STATUS_REQUEST_NOT_ACCEPTED
> Jun 29 12:41:46 pve702 kernel: [  112.813497] CIFS: VFS: \\192.168.20.241 Send error in SessSetup = -5
> Jun 29 12:41:46 pve702 kernel: [  112.826829] CIFS: Status code returned 0xc00000d0 STATUS_REQUEST_NOT_ACCEPTED
> Jun 29 12:41:46 pve702 kernel: [  112.826837] CIFS: VFS: \\192.168.20.241 Send error in SessSetup = -5
> Jun 29 12:41:46 pve702 kernel: [  112.839369] CIFS: Status code returned 0xc00000d0 STATUS_REQUEST_NOT_ACCEPTED
> Jun 29 12:41:46 pve702 kernel: [  112.839381] CIFS: VFS: \\192.168.20.241 Send error in SessSetup = -5
> Jun 29 12:41:46 pve702 kernel: [  112.851854] CIFS: Status code returned 0xc00000d0 STATUS_REQUEST_NOT_ACCEPTED
> Jun 29 12:41:46 pve702 kernel: [  112.851867] CIFS: VFS: \\192.168.20.241 Send error in SessSetup = -5
> Jun 29 12:41:46 pve702 kernel: [  112.870763] CIFS: Status code returned 0xc00000d0 STATUS_REQUEST_NOT_ACCEPTED
> Jun 29 12:41:46 pve702 kernel: [  112.870777] CIFS: VFS: \\192.168.20.241 Send error in SessSetup = -5

and, for 8ef12efe26c8:
> Jun 29 12:50:35 pve702 kernel: [   92.099496] CIFS: VFS: \\192.168.20.241 Error -512 sending data on socket to server
> Jun 29 12:50:35 pve702 kernel: [   92.110467] CIFS: VFS: \\192.168.20.241 Error -512 sending data on socket to server

If there's any additional information I should provide, just let me know.

[0]: https://forum.proxmox.com/threads/110464/post-475858
[1]:
https://wiki.samba.org/index.php/LinuxCIFS_troubleshooting#Enabling_Debugging