ACK: [PATCH 0/1][H] Fix disk hot removal regression in s390x under kvm

[Colin Ian King]

On 21/04/2021 13:43, Seth Forshee wrote:
> BugLink: https://bugs.launchpad.net/bugs/1925211
> 
> [Impact]
> 
> Hot removal of disks under kvm on s390 does not result in the kernel
> removing the block device, which can lead to hung tasks and other
> issues.
> 
> [Fix]
> 
> A bisect identified commit 8cc0dcfdc1c0 "s390/cio: remove pm support
> from ccw bus driver" as introducing the regression. Reverting this patch
> fixed the problem in testing.
> 
> [Test Plan]
> 
> See steps to reproduce the bug in the original description below. To
> test, execute these steps and confirm that the block device gets removed
> as expected.
> 
> [Where problems could occur]
> 
> The fix is a revert of the changes which introduced this regression. The
> original commit was a removal of supposedly unused code, but it seems a
> mistake was made in the logic around unregistering of disks. Reverting
> the changes could have potential to introduce bugs related to other virt
> devices, especially if it interacts badly with subsequent driver
> changes. However, the patch reverted cleanly, and reverting restores the
> code to the state which has been working well in previous kernels and
> seems like the lowest risk option until a proper fix is available
> upstream.
> 
> ---
> 
> Seth Forshee (1):
>   UBUNTU: SAUCE: Revert "s390/cio: remove pm support from ccw bus
>     driver"
> 
>  arch/s390/include/asm/ccwdev.h |  10 ++
>  drivers/s390/cio/cmf.c         |   5 +
>  drivers/s390/cio/device.c      | 247 ++++++++++++++++++++++++++++++++-
>  drivers/s390/cio/device.h      |   1 +
>  drivers/s390/cio/device_fsm.c  |   6 +
>  drivers/s390/cio/io_sch.h      |   1 +
>  6 files changed, 268 insertions(+), 2 deletions(-)
> 
> 

Yep, seems good to me.

Acked-by: Colin Ian King <colin.king at canonical.com>