[pve-devel] [PATCH kernel] cherry-pick fix for problematic CIFS/io_uring interaction

[Friedrich Weber]

On 06/10/2025 11:24, Fiona Ebner wrote:
> When io_uring is used in the same task as CIFS, there might be
> unnecessary reconnects, which QEMU will treat as an IO error.
> 
> This has been a long-standing issue [0] and was partially mitigated by
> qemu-server commit e31762f2 ("fix #4099: disable io_uring for virtual
> disks on CIFS storages"). However, back then it was not clear that
> it's enough to have IO via io_uring and IO via CIFS be present in the
> same task, even if io_uring is not used for CIFS. The issue resurfaced
> when QEMU blockdev mirroring was used with the source side using
> io_uring and the target being CIFS. This was reported by Aaron
> Lauterer and Friedrich Weber. It's also enough to have a VM with two
> disks, one using io_uring and one using CIFS and doing IO on both, to
> trigger the issue.
> 
> Fix the issue by picking up the accepted fix from upstream, i.e.
> kernel commit 00be6f26a2a7 ("smb: client: transport: avoid reconnects
> triggered by pending task work").
> 
> [0]: https://bugzilla.proxmox.com/show_bug.cgi?id=4099
> 
> Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
> ---

I noticed the patch was backported to Ubuntu-6.17.0-14.14 as
0d83d11f144a, and is thus contained in our kernel >= 6.17.9-1.