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

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

[Andreas Hindborg]

Hi Jens,

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.

The following changes since commit df2908090cda368b01ff43709f51890076c56157:

  Linux 7.3-rc2 (2026-09-06 15:07:20 -0700)

are available in the Git repository at:

  https://github.com/rust-for-linux/linux.git tags/rust-block-for-v7.4-rc1

for you to fetch changes up to b6cfe408d16ecb68a8b10b0d738669aeaecbde6f:

  rust: block: require `Sync` for `Operations::QueueData` (2026-09-29 11:23:27 +0200)

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
Alvin Sun (4):
      rust: block: mq: use vertical import style
      rust: block: mq: remove redundant imports and format
      rust: block: rnull: use vertical import style
      rust: block: gen_disk: set fops.owner from driver module pointer

Andreas Hindborg (2):
      rust: block: fix `Send` bound for `GenDisk`
      rust: block: require `Sync` for `Operations::QueueData`

Malte Wechter (1):
      rnull: configfs: add power to configfs features

Qingxiao Xu (1):
      rnull: fix geometry store check-then-act across lock scopes

Sophon Z (1):
      rust: block: Fix GenDiskBuilder block size documentation

 drivers/block/rnull/configfs.rs    | 44 +++++++++++++++--------
 drivers/block/rnull/rnull.rs       | 15 +++++---
 rust/kernel/block/mq/gen_disk.rs   | 72 ++++++++++++++++++++------------------
 rust/kernel/block/mq/operations.rs | 16 ++++++---
 rust/kernel/block/mq/request.rs    | 16 ++++++---
 rust/kernel/block/mq/tag_set.rs    | 28 +++++++--------
 6 files changed, 115 insertions(+), 76 deletions(-)
---
base-commit: df2908090cda368b01ff43709f51890076c56157
change-id: 20260929-rust-block-for-v7-4-rc1-b4-6fac377c366c

Best regards,
--  
Andreas Hindborg <a.hindborg@kernel.org>

[PATCH GIT PULL 4/9] rust: block: fix `Send` bound for `GenDisk`

[Andreas Hindborg]

The `Send` implementation for `GenDisk<T>` was conditioned on `T: Send`.
This constrains the wrong type. `T` is the `Operations` implementation,
which is typically a zero-sized marker type that carries no data, so `T:
Send` says nothing about whether the data a `GenDisk` actually owns can be
moved to another thread.

A `GenDisk<T>` owns the queue data `T::QueueData` (stored as the
`gendisk`'s `queuedata` and dropped when the `GenDisk` is dropped) and an
`Arc<TagSet<T>>`. These are the values transferred when a `GenDisk` is sent
across a thread boundary, so the `Send` bound must constrain exactly them.
Bound `T::QueueData: Send` and `Arc<TagSet<T>>: Send` instead.

Fixes: 3253aba3408a ("rust: block: introduce `kernel::block::mq` module")
Cc: stable@vger.kernel.org
Reported-by: Priya Bala Govindasamy <pgovind2@uci.edu>, Dylan Zueck <dzueck@uci.edu>, Yuan Tan <ytan089@ucr.edu>
Closes: https://lore.kernel.org/all/cover.1780633578.git.ytan089@ucr.edu
Signed-off-by: Yuan Tan <ytan089@ucr.edu>
Link: https://msgid.link/20260709100100.604252-1-yuantan098@gmail.com
[ Andreas: Fix tags to make checkpatch happy. Change summary line. ]
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/block/mq/gen_disk.rs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/block/mq/gen_disk.rs b/rust/kernel/block/mq/gen_disk.rs
index 8ec38a7b9815..080dedb5d5d9 100644
--- a/rust/kernel/block/mq/gen_disk.rs
+++ b/rust/kernel/block/mq/gen_disk.rs
@@ -224,8 +224,14 @@ pub struct GenDisk<T: Operations> {
 }
 
 // SAFETY: `GenDisk` is an owned pointer to a `struct gendisk` and an `Arc` to a
-// `TagSet` It is safe to send this to other threads as long as T is Send.
-unsafe impl<T: Operations + Send> Send for GenDisk<T> {}
+// `TagSet`. It is safe to send this to other threads as long as these two are `Send`.
+unsafe impl<T> Send for GenDisk<T>
+where
+    T: Operations,
+    T::QueueData: Send,
+    Arc<TagSet<T>>: Send,
+{
+}
 
 impl<T: Operations> Drop for GenDisk<T> {
     fn drop(&mut self) {

-- 
2.54.0

[PATCH GIT PULL 9/9] rust: block: require `Sync` for `Operations::QueueData`

[Andreas Hindborg]

The queue data installed in a `GenDisk` is stored in the request queue and
handed back to the driver as a shared borrow through the `queue_rq` and
`commit_rqs` callbacks. Both callbacks obtain that borrow via
`ForeignOwnable::borrow` and may execute concurrently on several CPUs,
since the block layer runs one hardware queue per CPU. That means a shared
reference to the same queue data can be live on multiple threads at once,
which is only sound when the referent is `Sync`.

The initial `GenDisk` private data support omitted this bound, so a
driver could install a non-`Sync` type as queue data and then access
it concurrently from multiple CPUs without synchronization. Add a
`Sync` bound to the `QueueData` associated type to rule that out.

Fixes: 90d952fac8ac ("rust: block: add `GenDisk` private data support")
Cc: stable@vger.kernel.org
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://msgid.link/20260608-queue-data-sync-v1-1-0efff051aaf3@kernel.org
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/block/mq/operations.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/kernel/block/mq/operations.rs b/rust/kernel/block/mq/operations.rs
index b9ab0e6102a4..08111d8368eb 100644
--- a/rust/kernel/block/mq/operations.rs
+++ b/rust/kernel/block/mq/operations.rs
@@ -36,7 +36,7 @@
 pub trait Operations: Sized {
     /// Data associated with the `struct request_queue` that is allocated for
     /// the `GenDisk` associated with this `Operations` implementation.
-    type QueueData: ForeignOwnable;
+    type QueueData: ForeignOwnable + Sync;
 
     /// Called by the kernel to queue a request with the driver. If `is_last` is
     /// `false`, the driver is allowed to defer committing the request.

-- 
2.54.0

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

[Jens Axboe]

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!

[1/9] rust: block: mq: use vertical import style
      commit: 020185c5f4a5590267b825dffda05eb5d45dfa5f
[2/9] rust: block: mq: remove redundant imports and format
      commit: 06e75dbe894f260651627c35e0f36536c4894536
[3/9] rust: block: rnull: use vertical import style
      commit: a463f71c492336f9650bae7d7166b66ee87461e9
[4/9] rust: block: fix `Send` bound for `GenDisk`
      commit: e502b667ee70a7fa2a578e7722672ecd4fe0eb81
[5/9] rust: block: gen_disk: set fops.owner from driver module pointer
      commit: 67a11f2e076016f054dc4a4a637d9b37530b7908
[6/9] rust: block: Fix GenDiskBuilder block size documentation
      commit: c595572d0e49c79fcefe8db8e3e4f4e6e1fab734
[7/9] rnull: fix geometry store check-then-act across lock scopes
      commit: 7ac697d4a08f01e7aefdeb1f3e1d6f71b2cdac0d
[8/9] rnull: configfs: add power to configfs features
      commit: 0cd698e89375d0dfc257f9ae978420aa7fe5359d
[9/9] rust: block: require `Sync` for `Operations::QueueData`
      commit: 67b7a2728e4873e64405c5564fe50f7123012b71

Best regards,
-- 
Jens Axboe

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

[Thorsten Leemhuis]

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

Ciao, Thorsten

"""
> error[E0277]: `UnsafeCell<MaybeUninit<blk_mq_tag_set>>` cannot be shared between threads safely
>    --> drivers/block/rnull/configfs.rs:57:18
>     |
>  57 |     type Child = DeviceConfig;
>     |                  ^^^^^^^^^^^^ `UnsafeCell<MaybeUninit<blk_mq_tag_set>>` cannot be shared between threads safely
>     |
>     = help: within `TagSet<NullBlkDevice>`, the trait `Sync` is not implemented for `UnsafeCell<MaybeUninit<blk_mq_tag_set>>`
> note: required because it appears within the type `Opaque<blk_mq_tag_set>`
>    --> rust/kernel/types.rs:332:12
>     |
> 332 | pub struct Opaque<T> {
>     |            ^^^^^^
> note: required because it appears within the type `TagSet<NullBlkDevice>`
>    --> rust/kernel/block/mq/tag_set.rs:32:12
>     |
>  32 | pub struct TagSet<T: Operations> {
>     |            ^^^^^^
>     = note: required for `Arc<TagSet<NullBlkDevice>>` to implement `Send`
>     = note: 1 redundant requirement hidden
>     = note: required for `GenDisk<NullBlkDevice>` to implement `Send`
> note: required because it appears within the type `Option<GenDisk<NullBlkDevice>>`
>    --> /usr/lib/rustlib/src/rust/library/core/src/option.rs:598:10
>     |
> 598 | pub enum Option<T> {
>     |          ^^^^^^
> note: required because it appears within the type `DeviceConfigInner`
>    --> drivers/block/rnull/configfs.rs:130:8
>     |
> 130 | struct DeviceConfigInner {
>     |        ^^^^^^^^^^^^^^^^^
>     = note: required for `Lock<DeviceConfigInner, MutexBackend>` to implement `Send`
> note: required because it appears within the type `DeviceConfig`
>    --> drivers/block/rnull/configfs.rs:124:19
>     |
> 124 | pub(crate) struct DeviceConfig {
>     |                   ^^^^^^^^^^^^
> note: required by a bound in `kernel::configfs::GroupOperations::Child`
>    --> rust/kernel/configfs.rs:518:27
>     |
> 518 |     type Child: 'static + Send;
>     |                           ^^^^ required by this bound in `GroupOperations::Child`
> 
> error[E0277]: `*const blk_mq_ops` cannot be sent between threads safely
>       --> drivers/block/rnull/configfs.rs:57:18
>        |
>     57 |     type Child = DeviceConfig;
>        |                  ^^^^^^^^^^^^ `*const blk_mq_ops` cannot be sent between threads safely
>        |
>        = help: within `TagSet<NullBlkDevice>`, the trait `Send` is not implemented for `*const blk_mq_ops`
> note: required because it appears within the type `blk_mq_tag_set`
>       --> /builddir/build/BUILD/kernel-7.3.0-build/kernel-next-20260930/linux-7.3.0-0.0.next.20260930.545.vanilla.fc46.aarch64/rust/bindings/bindings_generated.rs:105198:12
>        |
> 105198 | pub struct blk_mq_tag_set {
>        |            ^^^^^^^^^^^^^^
> note: required because it appears within the type `MaybeDangling<blk_mq_tag_set>`
>       --> /usr/lib/rustlib/src/rust/library/core/src/mem/maybe_dangling.rs:73:12
>        |
>     73 | pub struct MaybeDangling<P: ?Sized>(P);
> [...]"""

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

[Miguel Ojeda]

On Wed, Sep 30, 2026 at 5:07 PM Thorsten Leemhuis <linux@leemhuis.info> wrote:
>
> 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

Confirmed, I see it e.g. in my arm32 build.

Cheers,
Miguel

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@qq.com/.
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

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

[Andreas Hindborg]

"Gary Guo" <gary@garyguo.net> writes:

> 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@qq.com/.
> So this is more or less a semantic conflict.

I did not consider the interactions of the two trees together. Good
thing we have linux-next.

> 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.

`GenDisk<T>` has a field of type `Arc<TagSet<T>>`, so for `GenDisk` to be
send, so must `Arc<TagSet<T>>`. That `Arc` may be dropped with the
`GenDisk` if it is the last reference.

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

`QueueData` is not involved here. An unconditional implementation is
fine. I submitted a patch here [1], hopefully Jens can pick it soon so
next can be unbroken tomorrow.

Best regards,
Andreas Hindborg

[1] https://lore.kernel.org/r/20260930-tag-set-send-sync-v1-1-51acdb36f4bb@kernel.org