From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BC1E02EFD87; Tue, 2 Sep 2025 09:56:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756806987; cv=none; b=mHgvsmjYVz1n2usyE2H1MSZ70gdm5BT0lJdCpY/iWEY3U71ikh0j82WbylR/oB8TcsjTj0fbIEHUCo7Hm+4mnkMm9dA3p5TcupVBSa698khwLBWioAwqF51r1N3Ryvx0Vm/ZJV+/SMs9gSv0ZHWIHklszdrxemUuW5e/Ddu3CRE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756806987; c=relaxed/simple; bh=FG1VNwc+aiZdHMw5FUZZPe+D7cA4Ib1P36m8f0+W2JQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=FrRZ/NCpzj241+ti/wNumseXUzDCyV+hpOeovaSjZ3CljOMuHKS5NOKtCb6hhnTLdFUjvayoz0G4JiCKoGCoH357kUcuSe7m+SAqvxBabon3CC95hG33T2KdOeGkI2vGv1Bn3a797WAyNaTJUTOO6dmT+jLZmxDz50lPaUO9fHA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=vJuECx3d; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="vJuECx3d" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8D88C4CEED; Tue, 2 Sep 2025 09:56:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756806987; bh=FG1VNwc+aiZdHMw5FUZZPe+D7cA4Ib1P36m8f0+W2JQ=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=vJuECx3dCr4a7/qbQmBFw+0OUSS1NXQczQSBoFPR55eoGs9Zd62C6u8ahtjZB6eYp HaWN++6JDqB0peOpKm3fqIl1ka77aoVY61O21ROqhP8vu2piw00pIe0ZmNi0HjMCQt CSIHNzuImkKzKNZiTFx71y4u/S269ltgfHDIs9iEhbj4hy54TWYS3Z16HF3Gt5K7ip zGzl7pYEOQVMX7lCymGcCFdlBYeR27V0KWaNRBYPWq6fIR6quIaKPXV1uxdWi3zuGl nXT3rushQKWjMmfvwgZvj6uvJEhBvmNbmRyYSYxIi2Vx04glu5xnLyJQxrdVTIP4NS +7I6sE0rNLUug== From: Andreas Hindborg Date: Tue, 02 Sep 2025 11:55:08 +0200 Subject: [PATCH v7 14/17] rust: block: add `GenDisk` private data support Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250902-rnull-up-v6-16-v7-14-b5212cc89b98@kernel.org> References: <20250902-rnull-up-v6-16-v7-0-b5212cc89b98@kernel.org> In-Reply-To: <20250902-rnull-up-v6-16-v7-0-b5212cc89b98@kernel.org> To: Boqun Feng , Miguel Ojeda , Alex Gaynor , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Alice Ryhl , Trevor Gross , Danilo Krummrich , Jens Axboe , Breno Leitao Cc: linux-block@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Andreas Hindborg , Daniel Almeida X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=10628; i=a.hindborg@kernel.org; h=from:subject:message-id; bh=FG1VNwc+aiZdHMw5FUZZPe+D7cA4Ib1P36m8f0+W2JQ=; b=owEBbQKS/ZANAwAIAeG4Gj55KGN3AcsmYgBotr8G8wb9KKgOQLGn2/x++mr6TpgZ0WJ+EdXVe mz3jtKUZW6JAjMEAAEIAB0WIQQSwflHVr98KhXWwBLhuBo+eShjdwUCaLa/BgAKCRDhuBo+eShj d3aFEACqelXfSm+/5FD7zFN0QWX+wxxKKLSFqdhRZTFoRkdq3W49nQFOQQya4ogkGyHvVjEFPPB gvz56+AhMuMU1fK9HWPafiXACoXHMt088aSPyH6D+ax2MR4Cs0LcmKp7mYiji7+aLlboAbA+w6x UT55sivXrULEv85Fmk2TVQjyWYfQ9PEHp8aBZKxEVU4gIe03/Nfqe1HS0VG04C0yubr4lkkDg6K j8cDo1nPTJbvW9f0g7nDpzhS40fE1NwWMT679mCto78kKbNZNUsJbVdMhtLvnHH92COWBuFjdwX zFa9pngpoYKagjXECJnOvl1N7VjIEdHZvYyydJpl+lpvrFKVrZMA2cjLArCjrVc6OfwzPF6Ooab YY5XWmeSHUi/pX4Rcl9BhU/4b9MLQKuv/1K9v4DsPY1qVlXMThvDOM8RkEADT1OUnkr0a+Wbprr p2BTSgYPQLFcvXcPA2GYSsyKOije9ZV2RtfSHGpM4RrNkvTYaQmfyrwQubmn2gXlatYD/OjakvV 14YLElpfKEJcuWhncpOVrlwozis7wW+qBFPLodnO6j6IWurKbeQGhVTr2h8gAyas9er417l+Nuu 2WoLhBvPPqhd7vB5YHiT+EYg/lQBaYm8qEtUjX+ynI3Zg5OO+N/jimfcjImjfgiQKv3q5U7H8uO WkwKVQQj61U0PJg== X-Developer-Key: i=a.hindborg@kernel.org; a=openpgp; fpr=3108C10F46872E248D1FB221376EB100563EF7A7 Allow users of the rust block device driver API to install private data in the `GenDisk` structure. Reviewed-by: Alice Ryhl Reviewed-by: Daniel Almeida Signed-off-by: Andreas Hindborg --- drivers/block/rnull/rnull.rs | 8 ++++--- rust/kernel/block/mq.rs | 7 +++--- rust/kernel/block/mq/gen_disk.rs | 32 ++++++++++++++++++++++---- rust/kernel/block/mq/operations.rs | 46 ++++++++++++++++++++++++++++++-------- 4 files changed, 74 insertions(+), 19 deletions(-) diff --git a/drivers/block/rnull/rnull.rs b/drivers/block/rnull/rnull.rs index 8690ff5f974f..8255236bc550 100644 --- a/drivers/block/rnull/rnull.rs +++ b/drivers/block/rnull/rnull.rs @@ -61,14 +61,16 @@ fn new( .logical_block_size(block_size)? .physical_block_size(block_size)? .rotational(rotational) - .build(fmt!("{}", name.to_str()?), tagset) + .build(fmt!("{}", name.to_str()?), tagset, ()) } } #[vtable] impl Operations for NullBlkDevice { + type QueueData = (); + #[inline(always)] - fn queue_rq(rq: ARef>, _is_last: bool) -> Result { + fn queue_rq(_queue_data: (), rq: ARef>, _is_last: bool) -> Result { mq::Request::end_ok(rq) .map_err(|_e| kernel::error::code::EIO) // We take no refcounts on the request, so we expect to be able to @@ -79,5 +81,5 @@ fn queue_rq(rq: ARef>, _is_last: bool) -> Result { Ok(()) } - fn commit_rqs() {} + fn commit_rqs(_queue_data: ()) {} } diff --git a/rust/kernel/block/mq.rs b/rust/kernel/block/mq.rs index 98fa0d6bc8f7..6e546f4f3d1c 100644 --- a/rust/kernel/block/mq.rs +++ b/rust/kernel/block/mq.rs @@ -69,20 +69,21 @@ //! //! #[vtable] //! impl Operations for MyBlkDevice { +//! type QueueData = (); //! -//! fn queue_rq(rq: ARef>, _is_last: bool) -> Result { +//! fn queue_rq(_queue_data: (), rq: ARef>, _is_last: bool) -> Result { //! Request::end_ok(rq); //! Ok(()) //! } //! -//! fn commit_rqs() {} +//! fn commit_rqs(_queue_data: ()) {} //! } //! //! let tagset: Arc> = //! Arc::pin_init(TagSet::new(1, 256, 1), flags::GFP_KERNEL)?; //! let mut disk = gen_disk::GenDiskBuilder::new() //! .capacity_sectors(4096) -//! .build(format_args!("myblk"), tagset)?; +//! .build(format_args!("myblk"), tagset, ())?; //! //! # Ok::<(), kernel::error::Error>(()) //! ``` diff --git a/rust/kernel/block/mq/gen_disk.rs b/rust/kernel/block/mq/gen_disk.rs index 6b1b846874db..46ec80269970 100644 --- a/rust/kernel/block/mq/gen_disk.rs +++ b/rust/kernel/block/mq/gen_disk.rs @@ -13,6 +13,7 @@ static_lock_class, str::NullTerminatedFormatter, sync::Arc, + types::{ForeignOwnable, ScopeGuard}, }; use core::fmt::{self, Write}; @@ -98,7 +99,14 @@ pub fn build( self, name: fmt::Arguments<'_>, tagset: Arc>, + queue_data: T::QueueData, ) -> Result> { + let data = queue_data.into_foreign(); + let recover_data = ScopeGuard::new(|| { + // SAFETY: T::QueueData was created by the call to `into_foreign()` above + drop(unsafe { T::QueueData::from_foreign(data) }); + }); + // SAFETY: `bindings::queue_limits` contain only fields that are valid when zeroed. let mut lim: bindings::queue_limits = unsafe { core::mem::zeroed() }; @@ -113,7 +121,7 @@ pub fn build( bindings::__blk_mq_alloc_disk( tagset.raw_tag_set(), &mut lim, - core::ptr::null_mut(), + data, static_lock_class!().as_ptr(), ) })?; @@ -167,8 +175,12 @@ pub fn build( }, )?; + recover_data.dismiss(); + // INVARIANT: `gendisk` was initialized above. // INVARIANT: `gendisk` was added to the VFS via `device_add_disk` above. + // INVARIANT: `gendisk.queue.queue_data` is set to `data` in the call to + // `__blk_mq_alloc_disk` above. Ok(GenDisk { _tagset: tagset, gendisk, @@ -180,9 +192,10 @@ pub fn build( /// /// # Invariants /// -/// - `gendisk` must always point to an initialized and valid `struct gendisk`. -/// - `gendisk` was added to the VFS through a call to -/// `bindings::device_add_disk`. +/// - `gendisk` must always point to an initialized and valid `struct gendisk`. +/// - `gendisk` was added to the VFS through a call to +/// `bindings::device_add_disk`. +/// - `self.gendisk.queue.queuedata` is initialized by a call to `ForeignOwnable::into_foreign`. pub struct GenDisk { _tagset: Arc>, gendisk: *mut bindings::gendisk, @@ -194,9 +207,20 @@ unsafe impl Send for GenDisk {} impl Drop for GenDisk { fn drop(&mut self) { + // SAFETY: By type invariant of `Self`, `self.gendisk` points to a valid + // and initialized instance of `struct gendisk`, and, `queuedata` was + // initialized with the result of a call to + // `ForeignOwnable::into_foreign`. + let queue_data = unsafe { (*(*self.gendisk).queue).queuedata }; + // SAFETY: By type invariant, `self.gendisk` points to a valid and // initialized instance of `struct gendisk`, and it was previously added // to the VFS. unsafe { bindings::del_gendisk(self.gendisk) }; + + // SAFETY: `queue.queuedata` was created by `GenDiskBuilder::build` with + // a call to `ForeignOwnable::into_foreign` to create `queuedata`. + // `ForeignOwnable::from_foreign` is only called here. + drop(unsafe { T::QueueData::from_foreign(queue_data) }); } } diff --git a/rust/kernel/block/mq/operations.rs b/rust/kernel/block/mq/operations.rs index c2b98f507bcb..9e31d24e1164 100644 --- a/rust/kernel/block/mq/operations.rs +++ b/rust/kernel/block/mq/operations.rs @@ -6,14 +6,15 @@ use crate::{ bindings, - block::mq::request::RequestDataWrapper, - block::mq::Request, + block::mq::{request::RequestDataWrapper, Request}, error::{from_result, Result}, prelude::*, - types::ARef, + types::{ARef, ForeignOwnable}, }; use core::{marker::PhantomData, sync::atomic::AtomicU64, sync::atomic::Ordering}; +type ForeignBorrowed<'a, T> = ::Borrowed<'a>; + /// Implement this trait to interface blk-mq as block devices. /// /// To implement a block device driver, implement this trait as described in the @@ -26,12 +27,20 @@ /// [module level documentation]: kernel::block::mq #[macros::vtable] 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; + /// 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. - fn queue_rq(rq: ARef>, is_last: bool) -> Result; + fn queue_rq( + queue_data: ForeignBorrowed<'_, Self::QueueData>, + rq: ARef>, + is_last: bool, + ) -> Result; /// Called by the kernel to indicate that queued requests should be submitted. - fn commit_rqs(); + fn commit_rqs(queue_data: ForeignBorrowed<'_, Self::QueueData>); /// Called by the kernel to poll the device for completed requests. Only /// used for poll queues. @@ -70,7 +79,7 @@ impl OperationsVTable { /// promise to not access the request until the driver calls /// `bindings::blk_mq_end_request` for the request. unsafe extern "C" fn queue_rq_callback( - _hctx: *mut bindings::blk_mq_hw_ctx, + hctx: *mut bindings::blk_mq_hw_ctx, bd: *const bindings::blk_mq_queue_data, ) -> bindings::blk_status_t { // SAFETY: `bd.rq` is valid as required by the safety requirement for @@ -88,10 +97,20 @@ impl OperationsVTable { // reference counted by `ARef` until then. let rq = unsafe { Request::aref_from_raw((*bd).rq) }; + // SAFETY: `hctx` is valid as required by this function. + let queue_data = unsafe { (*(*hctx).queue).queuedata }; + + // SAFETY: `queue.queuedata` was created by `GenDiskBuilder::build` with + // a call to `ForeignOwnable::into_foreign` to create `queuedata`. + // `ForeignOwnable::from_foreign` is only called when the tagset is + // dropped, which happens after we are dropped. + let queue_data = unsafe { T::QueueData::borrow(queue_data) }; + // SAFETY: We have exclusive access and we just set the refcount above. unsafe { Request::start_unchecked(&rq) }; let ret = T::queue_rq( + queue_data, rq, // SAFETY: `bd` is valid as required by the safety requirement for // this function. @@ -110,9 +129,18 @@ impl OperationsVTable { /// /// # Safety /// - /// This function may only be called by blk-mq C infrastructure. - unsafe extern "C" fn commit_rqs_callback(_hctx: *mut bindings::blk_mq_hw_ctx) { - T::commit_rqs() + /// This function may only be called by blk-mq C infrastructure. The caller + /// must ensure that `hctx` is valid. + unsafe extern "C" fn commit_rqs_callback(hctx: *mut bindings::blk_mq_hw_ctx) { + // SAFETY: `hctx` is valid as required by this function. + let queue_data = unsafe { (*(*hctx).queue).queuedata }; + + // SAFETY: `queue.queuedata` was created by `GenDisk::try_new()` with a + // call to `ForeignOwnable::into_foreign()` to create `queuedata`. + // `ForeignOwnable::from_foreign()` is only called when the tagset is + // dropped, which happens after we are dropped. + let queue_data = unsafe { T::QueueData::borrow(queue_data) }; + T::commit_rqs(queue_data) } /// This function is called by the C kernel. It is not currently -- 2.47.2