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Adds F: to existing MAINTAINERS section BITMAP API BINDINGS [RUST]. Suggested-by: Alice Ryhl Signed-off-by: Burak Emir Suggested-by: Yury Norov --- MAINTAINERS | 1 + rust/bindings/bindings_helper.h | 1 + rust/helpers/bitmap.c | 9 +++++++++ rust/helpers/helpers.c | 1 + 4 files changed, 12 insertions(+) create mode 100644 rust/helpers/bitmap.c diff --git a/MAINTAINERS b/MAINTAINERS index ebf7fa9a814d..52fc47a28b4c 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4111,6 +4111,7 @@ F: tools/lib/find_bit.c BITMAP API BINDINGS [RUST] M: Yury Norov S: Maintained +F: rust/helpers/bitmap.c F: rust/helpers/cpumask.c =20 BITOPS API diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helpe= r.h index fcefe3068a28..4f9374c2d7e5 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -7,6 +7,7 @@ */ =20 #include +#include #include #include #include diff --git a/rust/helpers/bitmap.c b/rust/helpers/bitmap.c new file mode 100644 index 000000000000..a50e2f082e47 --- /dev/null +++ b/rust/helpers/bitmap.c @@ -0,0 +1,9 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +void rust_helper_bitmap_copy_and_extend(unsigned long *to, const unsigned = long *from, + unsigned int count, unsigned int size) +{ + bitmap_copy_and_extend(to, from, count, size); +} diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index e1c21eba9b15..d4a60f1d6cc4 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -7,6 +7,7 @@ * Sorted alphabetically. */ =20 +#include "bitmap.c" #include "blk.c" #include "bug.c" #include "build_assert.c" --=20 2.49.0.395.g12beb8f557-goog From nobody Wed Dec 17 10:22:33 2025 Received: from mail-wr1-f73.google.com (mail-wr1-f73.google.com [209.85.221.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B4D8522370A for ; Fri, 21 Mar 2025 11:15:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742555747; cv=none; b=L1W+GnbxntEpwwvxBVuHjG+eUM9GIWFMv8foXLm/oGZ0OuuZvfzdcTUBhovXJMCSbhDevcQtX4aAdxQx0mvmo8ETUGvQKz6PAE2YuNLyhfyECmk/nPTKhhcmU0CZTqFaMJD+CR1y/tScIb7icKLZjl5BzSinaCBdFDVg0GDJqaw= ARC-Message-Signature: i=1; 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AJvYcCWKAU5YasaKhVGME4aH0vSlA1OzojC6ikyfzUDRswSxDiWD9x5pYnXvZ5PzCUR29RFrjrfnqaXdQSXdTZI=@vger.kernel.org X-Gm-Message-State: AOJu0Yz4ta7RdJLXy7s62luWfrVrdWSFLmRo3kKs5VrG1uj2+o9Gw03b d9gSlIbLbUQ7Fs8FG6v/pdQg8iu2B7QMQUNm6lBp88XRKUOYbwIehfHjWbaTySxmvw== X-Google-Smtp-Source: AGHT+IFjWEPxXxy0axKgC1Qsy0TWOjbtL4nGbIrKrKA70O1rBQtPabD4KPuVGaJzQTHJOIgnvHOsYjs= X-Received: from wmbeq10.prod.google.com ([2002:a05:600c:848a:b0:43c:ef7b:ffac]) (user=bqe job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:4014:b0:399:7f2b:8531 with SMTP id ffacd0b85a97d-3997f92dad8mr2642504f8f.38.1742555744131; Fri, 21 Mar 2025 04:15:44 -0700 (PDT) Date: Fri, 21 Mar 2025 11:15:30 +0000 In-Reply-To: <20250321111535.3740332-1-bqe@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250321111535.3740332-1-bqe@google.com> X-Mailer: git-send-email 2.49.0.395.g12beb8f557-goog Message-ID: <20250321111535.3740332-3-bqe@google.com> Subject: [PATCH v5 2/4] rust: add bindings for bitops.h From: Burak Emir To: Yury Norov Cc: Burak Emir , Rasmus Villemoes , Viresh Kumar , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , "=?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?=" , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Makes atomic set_bit and clear_bit inline functions as well as the non-atomic variants __set_bit and __clear_bit available to Rust. Adds a new MAINTAINERS section BITOPS API BINDINGS [RUST]. Suggested-by: Alice Ryhl Signed-off-by: Burak Emir Suggested-by: Yury Norov --- MAINTAINERS | 5 +++++ rust/helpers/bitops.c | 23 +++++++++++++++++++++++ rust/helpers/helpers.c | 1 + 3 files changed, 29 insertions(+) create mode 100644 rust/helpers/bitops.c diff --git a/MAINTAINERS b/MAINTAINERS index 52fc47a28b4c..7cd15c25a43c 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4128,6 +4128,11 @@ F: include/linux/bitops.h F: lib/test_bitops.c F: tools/*/bitops* =20 +BITOPS API BINDINGS [RUST] +M: Yury Norov +S: Maintained +F: rust/helpers/bitops.c + BLINKM RGB LED DRIVER M: Jan-Simon Moeller S: Maintained diff --git a/rust/helpers/bitops.c b/rust/helpers/bitops.c new file mode 100644 index 000000000000..2eaab292db4f --- /dev/null +++ b/rust/helpers/bitops.c @@ -0,0 +1,23 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +void rust_helper___set_bit(unsigned int nr, unsigned long *addr) +{ + __set_bit(nr, addr); +} + +void rust_helper___clear_bit(unsigned int nr, unsigned long *addr) +{ + __clear_bit(nr, addr); 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Fri, 21 Mar 2025 04:15:46 -0700 (PDT) Date: Fri, 21 Mar 2025 11:15:31 +0000 In-Reply-To: <20250321111535.3740332-1-bqe@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250321111535.3740332-1-bqe@google.com> X-Mailer: git-send-email 2.49.0.395.g12beb8f557-goog Message-ID: <20250321111535.3740332-4-bqe@google.com> Subject: [PATCH v5 3/4] rust: add bitmap API. From: Burak Emir To: Yury Norov Cc: Burak Emir , Rasmus Villemoes , Viresh Kumar , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , "=?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?=" , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Provides an abstraction for C bitmap API and bitops operations. Includes enough to implement a Binder data structure that was introduced in commit 15d9da3f818c ("binder: use bitmap for faster descriptor lookup"), namely drivers/android/dbitmap.h. The implementation is optimized to represent the bitmap inline if it would take the space of a pointer. This saves allocations. We offer a safe API through bounds checks which panic if violated. We use the `usize` type for sizes and indices into the bitmap, because Rust generally always uses that type for indices and lengths and it will be more convenient if the API accepts that type. This means that we need to perform some casts to/from u32 and usize, since the C headers use unsigned int instead of size_t/unsigned long for these numbers in some places. Adds new MAINTAINERS section BITMAP API [RUST]. Suggested-by: Alice Ryhl Signed-off-by: Burak Emir Suggested-by: Yury Norov --- MAINTAINERS | 7 + rust/kernel/bitmap.rs | 293 ++++++++++++++++++++++++++++++++++++++++++ rust/kernel/lib.rs | 1 + 3 files changed, 301 insertions(+) create mode 100644 rust/kernel/bitmap.rs diff --git a/MAINTAINERS b/MAINTAINERS index 7cd15c25a43c..bc8f05431689 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4114,6 +4114,13 @@ S: Maintained F: rust/helpers/bitmap.c F: rust/helpers/cpumask.c =20 +BITMAP API [RUST] +M: Alice Ryhl +M: Burak Emir +R: Yury Norov +S: Maintained +F: rust/kernel/bitmap.rs + BITOPS API M: Yury Norov R: Rasmus Villemoes diff --git a/rust/kernel/bitmap.rs b/rust/kernel/bitmap.rs new file mode 100644 index 000000000000..118dceaf2b4b --- /dev/null +++ b/rust/kernel/bitmap.rs @@ -0,0 +1,293 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2025 Google LLC. + +//! Rust API for bitmap. +//! +//! C headers: [`include/linux/bitmap.h`](srctree/include/linux/bitmap.h). + +use crate::alloc::{AllocError, Flags}; +use crate::bindings; +use core::ptr::NonNull; + +/// Holds either a pointer to array of `unsigned long` or a small bitmap. +#[repr(C)] +union BitmapRepr { + bitmap: usize, + ptr: NonNull +} + +/// Represents a bitmap. +/// +/// Wraps underlying C bitmap API. +/// +/// # Examples +/// +/// Basic usage +/// +/// ``` +/// use kernel::alloc::flags::GFP_KERNEL; +/// use kernel::bitmap::Bitmap; +/// +/// let mut b =3D Bitmap::new(16, GFP_KERNEL)?; +/// assert_eq!(16, b.len()); +/// for i in 0..16 { +/// if i % 4 =3D=3D 0 { +/// b.set_bit(i); +/// } +/// } +/// assert_eq!(Some(1), b.next_zero_bit(0)); +/// assert_eq!(Some(5), b.next_zero_bit(5)); +/// assert_eq!(Some(12), b.last_bit()); +/// # Ok::<(), Error>(()) +/// ``` +/// +/// Requesting too large values results in [`AllocError`] +/// +/// ``` +/// use kernel::alloc::flags::GFP_KERNEL; +/// use kernel::bitmap::Bitmap; +/// assert!(Bitmap::new(1 << 31, GFP_KERNEL).is_err()); +/// ``` +/// +/// # Invariants +/// +/// * `nbits` is `<=3D i32::MAX - 1` and never changes. +/// * if `nbits <=3D bindings::BITS_PER_LONG`, then `repr` is a bitmap. +/// * otherwise, `repr` holds a non-null pointer that was obtained from a +/// successful call to `bitmap_zalloc` and holds the address of an initi= alized +/// array of `unsigned long` that is large enough to hold `nbits` bits. +pub struct Bitmap { + /// Representation of bitmap. + repr: BitmapRepr, + /// Length of this bitmap. Must be `<=3D i32::MAX - 1`. + nbits: usize, +} + +impl Drop for Bitmap { + fn drop(&mut self) { + if self.nbits <=3D bindings::BITS_PER_LONG as _ { + return + } + // SAFETY: `self.ptr` was returned by the C `bitmap_zalloc`. + // + // INVARIANT: there is no other use of the `self.ptr` after this + // call and the value is being dropped so the broken invariant is + // not observable on function exit. + unsafe { bindings::bitmap_free(self.as_mut_ptr()) }; + } +} + +impl Bitmap { + /// Constructs a new [`Bitmap`]. + /// + /// If the length `nbits` is small enough to admit inline representati= on, this + /// implementation does not allocate. + /// + /// Fails with [`AllocError`] when the [`Bitmap`] could not be allocat= ed. This + /// includes the case when `nbits` is greater than `i32::MAX - 1`. + #[inline] + pub fn new(nbits: usize, flags: Flags) -> Result { + if nbits <=3D bindings::BITS_PER_LONG as _ { + return Ok(Bitmap { repr: BitmapRepr { bitmap: 0 }, nbits }); + } + if nbits <=3D i32::MAX.try_into().unwrap() { + let nbits_u32 =3D u32::try_from(nbits).unwrap(); + // SAFETY: `nbits <=3D i32::MAX - 1` and the C function handle= s `nbits =3D=3D 0`. + let ptr =3D unsafe { bindings::bitmap_zalloc(nbits_u32, flags.= as_raw()) }; + let ptr =3D NonNull::new(ptr).ok_or(AllocError)?; + // INVARIANT: `ptr` returned by C `bitmap_zalloc` and `nbits` = checked. + return Ok(Bitmap { + repr: BitmapRepr { ptr }, + nbits, + }); + } + Err(AllocError) + } + + /// Returns length of this [`Bitmap`]. + #[inline] + pub fn len(&self) -> usize { + self.nbits + } + + /// Returns a mutable raw pointer to the backing [`Bitmap`]. + #[inline] + fn as_mut_ptr(&mut self) -> *mut usize { + if self.nbits <=3D bindings::BITS_PER_LONG as _ { + // SAFETY: Bitmap is represented inline. + unsafe { core::ptr::addr_of_mut!(self.repr.bitmap) } + } else { + // SAFETY: Bitmap is represented as array of `unsigned long`. + unsafe { self.repr.ptr.as_mut() } + } + } + + /// Returns a raw pointer to the backing [`Bitmap`]. + #[inline] + fn as_ptr(&self) -> *const usize { + if self.nbits <=3D bindings::BITS_PER_LONG as _ { + // SAFETY: Bitmap is represented inline. + unsafe { core::ptr::addr_of!(self.repr.bitmap) } + } else { + // SAFETY: Bitmap is represented as array of `unsigned long`. + unsafe { self.repr.ptr.as_ptr() } + } + } + + /// Set bit with index `index`. + /// + /// # Panics + /// + /// Panics if `index` is greater than or equal to `self.nbits`. + #[inline] + pub fn set_bit(&mut self, index: usize) { + assert!( + index < self.nbits, + "Bit `index` must be < {}, was {}", + self.nbits, + index + ); + // SAFETY: Bit `index` is within bounds. + unsafe { bindings::__set_bit(index as u32, self.as_mut_ptr()) }; + } + + /// Set bit with index `index`, atomically. + /// + /// # Panics + /// + /// Panics if `index` is greater than or equal to `self.nbits`. + #[inline] + pub fn set_bit_atomic(&self, index: usize) { + assert!( + index < self.nbits, + "Bit `index` must be < {}, was {}", + self.nbits, + index + ); + // SAFETY: `index` is within bounds and `set_bit` is atomic. + unsafe { bindings::set_bit(index as u32, self.as_ptr() as *mut usi= ze) }; + } + + /// Clear bit with index `index`. + /// + /// # Panics + /// + /// Panics if `index` is greater than or equal to `self.nbits`. + #[inline] + pub fn clear_bit(&mut self, index: usize) { + assert!( + index < self.nbits, + "Bit `index` must be < {}, was {}", + self.nbits, + index + ); + // SAFETY: `index` is within bounds. + unsafe { bindings::__clear_bit(index as u32, self.as_mut_ptr()) }; + } + + /// Clear bit with index `index`, atomically. + /// + /// # Panics + /// + /// Panics if `index` is greater than or equal to `self.nbits`. + #[inline] + pub fn clear_bit_atomic(&self, index: usize) { + assert!( + index < self.nbits, + "Bit `index` must be < {}, was {}", + self.nbits, + index + ); + // SAFETY: `index` is within bounds and `clear_bit` is atomic. + unsafe { bindings::clear_bit(index as u32, self.as_ptr() as *mut u= size) }; + } + + /// Copy `src` into this [`Bitmap`] and set any remaining bits to zero. + /// + /// # Examples + /// + /// ``` + /// use kernel::alloc::{AllocError, flags::GFP_KERNEL}; + /// use kernel::bitmap::Bitmap; + /// + /// let mut long_bitmap =3D Bitmap::new(256, GFP_KERNEL)?; + /// assert_eq!(None, long_bitmap.last_bit()); + /// let mut short_bitmap =3D Bitmap::new(16, GFP_KERNEL)?; + /// short_bitmap.set_bit(7); + /// + /// long_bitmap.copy_and_extend(&short_bitmap); + /// assert_eq!(Some(7), long_bitmap.last_bit()); + /// + /// long_bitmap.clear_bit(7); + /// assert_eq!(None, long_bitmap.last_bit()); + /// + /// # Ok::<(), AllocError>(()) + /// ``` + #[inline] + pub fn copy_and_extend(&mut self, src: &Bitmap) { + let len =3D core::cmp::min(src.nbits, self.nbits); + // SAFETY: access to `self` and `src` is within bounds. + unsafe { + bindings::bitmap_copy_and_extend( + self.as_mut_ptr(), + src.as_ptr(), + len as u32, + self.nbits as u32, + ) + }; + } + + /// Finds last bit that is set. + /// + /// # Examples + /// + /// ``` + /// use kernel::alloc::{AllocError, flags::GFP_KERNEL}; + /// use kernel::bitmap::Bitmap; + /// + /// let bitmap =3D Bitmap::new(64, GFP_KERNEL)?; + /// match bitmap.last_bit() { + /// Some(idx) =3D> { + /// pr_info!("The last bit has index {idx}.\n"); + /// } + /// None =3D> { + /// pr_info!("All bits in this bitmap are 0.\n"); + /// } + /// } + /// # Ok::<(), AllocError>(()) + /// ``` + #[inline] + pub fn last_bit(&self) -> Option { + // SAFETY: `nbits =3D=3D 0` is supported and access is within boun= ds. + let index =3D unsafe { bindings::_find_last_bit(self.as_ptr(), sel= f.nbits) }; + if index =3D=3D self.nbits { + None + } else { + Some(index) + } + } + + /// Finds next zero bit, starting from `start`. + /// + /// # Panics + /// + /// Panics if `index` is greater than or equal to `self.nbits`. + #[inline] + pub fn next_zero_bit(&self, start: usize) -> Option { + assert!( + start < self.nbits, + "Offset `start` must be < {}, was {}", + self.nbits, + start + ); 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Fri, 21 Mar 2025 04:15:49 -0700 (PDT) Date: Fri, 21 Mar 2025 11:15:32 +0000 In-Reply-To: <20250321111535.3740332-1-bqe@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250321111535.3740332-1-bqe@google.com> X-Mailer: git-send-email 2.49.0.395.g12beb8f557-goog Message-ID: <20250321111535.3740332-5-bqe@google.com> Subject: [PATCH v5 4/4] rust: add dynamic ID pool abstraction for bitmap From: Burak Emir To: Yury Norov Cc: Burak Emir , Rasmus Villemoes , Viresh Kumar , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , "=?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?=" , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This is a port of the Binder data structure introduced in commit 15d9da3f818c ("binder: use bitmap for faster descriptor lookup") to Rust. Like drivers/android/dbitmap.h, the ID pool abstraction lets clients acquire and release IDs. The implementation uses a bitmap to know what IDs are in use, and gives clients fine-grained control over the time of allocation. This fine-grained control is needed in the Android Binder. We provide an example that release a spinlock for allocation and unit tests (rustdoc examples). The implementation is not aware that the underlying Bitmap abstraction handles lengths below BITS_PER_LONG without allocation. Suggested-by: Alice Ryhl Signed-off-by: Burak Emir Suggested-by: Yury Norov --- MAINTAINERS | 1 + rust/kernel/id_pool.rs | 201 +++++++++++++++++++++++++++++++++++++++++ rust/kernel/lib.rs | 1 + 3 files changed, 203 insertions(+) create mode 100644 rust/kernel/id_pool.rs diff --git a/MAINTAINERS b/MAINTAINERS index bc8f05431689..61ac5da0dfbf 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4120,6 +4120,7 @@ M: Burak Emir R: Yury Norov S: Maintained F: rust/kernel/bitmap.rs +F: rust/kernel/id_pool.rs =20 BITOPS API M: Yury Norov diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs new file mode 100644 index 000000000000..8f07526bb580 --- /dev/null +++ b/rust/kernel/id_pool.rs @@ -0,0 +1,201 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2025 Google LLC. + +//! Rust API for an ID pool backed by a `Bitmap`. + +use crate::alloc::{AllocError, Flags}; +use crate::bitmap::Bitmap; + +/// Represents a dynamic ID pool backed by a `Bitmap`. +/// +/// Clients acquire and release IDs from zero bits in a bitmap. +/// +/// The ID pool can grow or shrink as needed. It has been designed +/// to support the scenario where users need to control the time +/// of allocation of a new backing bitmap, which may require release +/// of locks. +/// These operations then, are verified to determine if the grow or +/// shrink is sill valid. +/// +/// # Examples +/// +/// Basic usage +/// +/// ``` +/// use kernel::alloc::{AllocError, flags::GFP_KERNEL}; +/// use kernel::id_pool::IdPool; +/// +/// let mut pool =3D IdPool::new(64, GFP_KERNEL)?; +/// for i in 0..64 { +/// assert_eq!(i, pool.acquire_next_id(i).ok_or(ENOSPC)?); +/// } +/// +/// pool.release_id(23); +/// assert_eq!(23, pool.acquire_next_id(0).ok_or(ENOSPC)?); +/// +/// assert_eq!(None, pool.acquire_next_id(0)); // time to realloc. +/// let resizer =3D pool.grow_alloc().alloc(GFP_KERNEL)?; +/// pool.grow(resizer); +/// +/// assert_eq!(pool.acquire_next_id(0), Some(64)); +/// # Ok::<(), Error>(()) +/// ``` +/// +/// Releasing spinlock to grow the pool +/// +/// ```no_run +/// use kernel::alloc::{AllocError, flags::GFP_KERNEL}; +/// use kernel::sync::{new_spinlock, SpinLock}; +/// use kernel::id_pool::IdPool; +/// +/// fn get_id_maybe_alloc(guarded_pool: &SpinLock) -> Result { +/// let mut pool =3D guarded_pool.lock(); +/// loop { +/// match pool.acquire_next_id(0) { +/// Some(index) =3D> return Ok(index), +/// None =3D> { +/// let alloc_request =3D pool.grow_alloc(); +/// drop(pool); +/// let resizer =3D alloc_request.alloc(GFP_KERNEL)?; +/// pool =3D guarded_pool.lock(); +/// pool.grow(resizer) +/// } +/// } +/// } +/// } +/// ``` +pub struct IdPool { + map: Bitmap, +} + +/// Returned when the `IdPool` should change size. +pub struct AllocRequest { + nbits: usize, +} + +/// Contains an allocated `Bitmap` for resizing `IdPool`. +pub struct PoolResizer { + new: Bitmap, +} + +impl AllocRequest { + /// Allocates a new `Bitmap` for `IdPool`. + pub fn alloc(&self, flags: Flags) -> Result { + let new =3D Bitmap::new(self.nbits, flags)?; + Ok(PoolResizer { new }) + } +} + +impl IdPool { + /// Constructs a new `[IdPool]`. + #[inline] + pub fn new(nbits: usize, flags: Flags) -> Result { + let map =3D Bitmap::new(nbits, flags)?; + Ok(Self { map }) + } + + /// Returns how many IDs this pool can currently have. + #[inline] + pub fn len(&self) -> usize { + self.map.len() + } + + /// Returns an [`AllocRequest`] if the [`IdPool`] can be shrunk, [`Non= e`] otherwise. + /// + /// # Examples + /// + /// ``` + /// use kernel::alloc::{AllocError, flags::GFP_KERNEL}; + /// use kernel::id_pool::{AllocRequest, IdPool}; + /// + /// let mut pool =3D IdPool::new(1024, GFP_KERNEL)?; + /// let alloc_request =3D pool.shrink_alloc().ok_or(AllocError)?; + /// let resizer =3D alloc_request.alloc(GFP_KERNEL)?; + /// pool.shrink(resizer); + /// assert_eq!(pool.len(), kernel::bindings::BITS_PER_LONG as usize); + /// # Ok::<(), AllocError>(()) + /// ``` + #[inline] + pub fn shrink_alloc(&self) -> Option { + let len =3D self.map.len(); + if len <=3D bindings::BITS_PER_LONG as usize { + return None; + } + /* + * Determine if the bitmap can shrink based on the position of + * its last set bit. If the bit is within the first quarter of + * the bitmap then shrinking is possible. In this case, the + * bitmap should shrink to half its current size. + */ + match self.map.last_bit() { + Some(bit) =3D> { + if bit < (len >> 2) { + Some(AllocRequest { nbits: len >> 1 }) + } else { + None + } + } + None =3D> Some(AllocRequest { + nbits: bindings::BITS_PER_LONG as usize, + }), + } + } + + /// Shrinks pool by using a new `Bitmap`, if still possible. + #[inline] + pub fn shrink(&mut self, mut resizer: PoolResizer) { + // Verify that shrinking is still possible. The `resizer` + // bitmap might have been allocated without locks, so this call + // could now be outdated. In this case, drop `resizer` and move on. + if let Some(AllocRequest { nbits }) =3D self.shrink_alloc() { + if nbits <=3D resizer.new.len() { + resizer.new.copy_and_extend(&self.map); + self.map =3D resizer.new; + return; + } + } + } + + /// Returns an `AllocRequest` for growing this `IdPool`. + #[inline] + pub fn grow_alloc(&self) -> AllocRequest { + AllocRequest { + nbits: self.map.len() << 1, + } + } + + /// Grows pool by using a new `Bitmap`, if still necessary. + #[inline] + pub fn grow(&mut self, mut resizer: PoolResizer) { + // `resizer` bitmap might have been allocated without locks, + // so this call could now be outdated. In this case, drop + // `resizer` and move on. + if resizer.new.len() <=3D self.map.len() { + return; + } + + resizer.new.copy_and_extend(&self.map); + self.map =3D resizer.new; + } + + /// Acquires a new ID by finding and setting the next zero bit in the + /// bitmap. Upon success, returns its index. Otherwise, returns `None` + /// to indicate that a `grow_alloc` is needed. + #[inline] + pub fn acquire_next_id(&mut self, offset: usize) -> Option { + match self.map.next_zero_bit(offset) { + res @ Some(nr) =3D> { + self.map.set_bit(nr); + res + } + None =3D> None, + } + } + + /// Releases an ID. + #[inline] + pub fn release_id(&mut self, id: usize) { + self.map.clear_bit(id); + } +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 9f675c0841e6..d77a27bee388 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -51,6 +51,7 @@ #[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)] pub mod firmware; pub mod fs; +pub mod id_pool; pub mod init; pub mod io; pub mod ioctl; --=20 2.49.0.395.g12beb8f557-goog