Re: [PATCH 3/3] iotests/graph-changes-while-io: New test

[Eric Blake]

On Tue, Feb 15, 2022 at 02:57:27PM +0100, Hanna Reitz wrote:
> Test the following scenario:
> 1. Some block node (null-co) attached to a user (here: NBD server) that
>    performs I/O and keeps the node in an I/O thread
> 2. Repeatedly run blockdev-add/blockdev-del to add/remove an overlay
>    to/from that node
> 
> Each blockdev-add triggers bdrv_refresh_limits(), and because
> blockdev-add runs in the main thread, it does not stop the I/O requests.
> I/O can thus happen while the limits are refreshed, and when such a
> request sees a temporarily invalid block limit (e.g. alignment is 0),
> this may easily crash qemu (or the storage daemon in this case).
> 
> The block layer needs to ensure that I/O requests to a node are paused
> while that node's BlockLimits are refreshed.
> 
> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
> ---
>  .../qemu-iotests/tests/graph-changes-while-io | 91 +++++++++++++++++++
>  .../tests/graph-changes-while-io.out          |  5 +
>  2 files changed, 96 insertions(+)
>  create mode 100755 tests/qemu-iotests/tests/graph-changes-while-io
>  create mode 100644 tests/qemu-iotests/tests/graph-changes-while-io.out

Reviewed-by: Eric Blake <eblake@redhat.com>

Since we found this with the help of NBD, should I be considering this
series for my NBD queue, or is there a better block-related maintainer
queue that it should go through?

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org