Re: [GIT PULL PATCH 0/9] Rust changes for v7.4-rc1

[Gary Guo]

On Wed Sep 30, 2026 at 4:06 PM BST, Thorsten Leemhuis wrote:
> On 9/29/26 13:47, Jens Axboe wrote:
>> On Tue, 29 Sep 2026 11:33:58 +0200, Andreas Hindborg wrote:
>>> I have a number of Rust block layer patches I would ask you to pick for
>>> v7.4. I have collected them into a patch series as well as a pull request
>>> so you can use whatever is easier.
>>>
>>> The changes cover
>>>
>>>  - Style and formatting changes.
>>>  - Documentation fixes.
>>>  - Fixes for missing trait bounds that can cause API unsoundness.
>>>  - A change to set the owner of the file operations vtable in `GenDisk`.
>>>  - Two bug fixes for the rnull driver.
>>>
>>> [...]
>> 
>> Applied, thanks!
>>  [...]
>
> This series showed up in next today and broke the build for me on
> various Fedora releases for aarch64 and x86_64; reverting this series
> fixed that from a quick build test limited to drivers/block/rnull/
>
> The full error msg is quote long, find the top of it below. Full log:
> https://download.copr.fedorainfracloud.org/results/@kernel-vanilla/next/fedora-rawhide-aarch64/11055137-next-next-all/builder-live.log.gz

The `Child: Send` bound is introduced in configfs:
https://lore.kernel.org/all/tencent_05937A22D2DA2BAE808EF19E491AA109BC09@xxxxxx/.
So this is more or less a semantic conflict.

However, the fundamental issue is that TagSet never implements Send/Sync, which
means that "rust: block: fix `Send` bound for `GenDisk`" will unconditionally
strip away the Send implementation, which is problematic.

Something like this should fix the issue:

    unsafe impl<T: Operations<QueueData: Send>> Send for TagSet<T> {}
    unsafe impl<T: Operations<QueueData: Send>> Sync for TagSet<T> {}

That said, I am not sure why the GenDisk need to carry `Arc<TagSet<T>>: Send`
bound in the first place. Removing it should also fix the issue.

Also, the `QueueData: Send` bound should be part of the `Operations` trait and
not carried around everywhere.

Best,
Gary