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Adds F: to existing MAINTAINERS section BITMAP API BINDINGS [RUST]. Suggested-by: Alice Ryhl Suggested-by: Yury Norov Signed-off-by: Burak Emir --- 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 1cd25139cc58..fcc56f7d7f16 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4031,6 +4031,7 @@ 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 2396ca1cf8fb..1d96fb915917 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); 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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 Suggested-by: Yury Norov Signed-off-by: Burak Emir --- 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 fcc56f7d7f16..11bc11945838 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4048,6 +4048,11 @@ 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..1fe9e3b23a39 --- /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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Thu, 27 Mar 2025 09:16:37 -0700 (PDT) Date: Thu, 27 Mar 2025 16:16:13 +0000 In-Reply-To: <20250327161617.117748-1-bqe@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250327161617.117748-1-bqe@google.com> X-Mailer: git-send-email 2.49.0.395.g12beb8f557-goog Message-ID: <20250327161617.117748-4-bqe@google.com> Subject: [PATCH v6 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. Atomic variants set_bit_atomic and clear_bit_atomic are provided. For these, absence of data races is ensured by the Rust type system: all non-atomic operations require a &mut reference which amounts to exclusive access. 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 Suggested-by: Yury Norov Signed-off-by: Burak Emir --- MAINTAINERS | 7 + rust/kernel/bitmap.rs | 306 ++++++++++++++++++++++++++++++++++++++++++ rust/kernel/lib.rs | 1 + 3 files changed, 314 insertions(+) create mode 100644 rust/kernel/bitmap.rs diff --git a/MAINTAINERS b/MAINTAINERS index 11bc11945838..efb0d367dea2 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4034,6 +4034,13 @@ 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..2622af3af1ec --- /dev/null +++ b/rust/kernel/bitmap.rs @@ -0,0 +1,306 @@ +// 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` 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`. + 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`]. + /// + /// Fails with [`AllocError`] when the [`Bitmap`] could not be allocat= ed. This + /// includes the case when `nbits` is greater than `i32::MAX`. + #[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 > i32::MAX.try_into().unwrap() { + return Err(AllocError); + } + let nbits_u32 =3D u32::try_from(nbits).unwrap(); + // SAFETY: `bindings::BITS_PER_LONG < nbits` and `nbits <=3D i32::= MAX`. + let ptr =3D unsafe { bindings::bitmap_zalloc(nbits_u32, flags.as_r= aw()) }; + let ptr =3D NonNull::new(ptr).ok_or(AllocError)?; + // INVARIANT: `ptr` returned by C `bitmap_zalloc` and `nbits` chec= ked. + return Ok(Bitmap { + repr: BitmapRepr { ptr }, + nbits, + }); + } + + /// 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. + /// + /// WARNING: this is a relaxed atomic operation (no implied memory bar= riers). + /// + /// # 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 there cannot be any data r= aces + // because all non-atomic operations require exclusive access thro= ugh + // a &mut reference. + unsafe { bindings::set_bit(index as u32, self.as_ptr() as *mut usi= ze) }; + } + + /// Clear `index` bit. + /// + /// # 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 `index` bit, atomically. + /// + /// WARNING: this is a relaxed atomic operation (no implied memory bar= riers). + /// + /// # 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 there cannot be any data r= aces + // because all non-atomic operations require exclusive access thro= ugh + // a &mut reference. + 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 set bit. + /// + /// # 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: access is within bounds. + 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, + "`start` must be < {}, was {}", + self.nbits, + start + ); + + // SAFETY: access is within bounds. + let index =3D unsafe { bindings::_find_next_zero_bit(self.as_ptr()= , self.nbits, start) }; + if index =3D=3D self.nbits { + None + } else { + Some(index) + } + } +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 7697c60b2d1a..c82b23236056 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -36,6 +36,7 @@ pub use ffi; 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AJvYcCVII16f/CA7IW3VKRTrklMQtdL+TjSD2Xt2YmcZUPS/ezw5vGTTyYBnOFPszM+xyMQWLLFuZyBTiry4Z6M=@vger.kernel.org X-Gm-Message-State: AOJu0YyLBOI2NWSfWd0FPOpfetx6DOKGA2upN8QJw1Wd48XU+yxMFXmr mNxJ9x50SXt9BhQcqGDw3JkQXvKecjV+6hj0jB3O+YV846dS75yZNN/SbeGW3Hfqog== X-Google-Smtp-Source: AGHT+IGMNNLBeGoFDGM/YN3dohqRU/VHAkNClOFV3WlHWzboKThygC1+BFMBGcJLJZuE8N9hNGiNS+c= X-Received: from wmdd9.prod.google.com ([2002:a05:600c:a209:b0:43d:896f:72e5]) (user=bqe job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:40e0:b0:399:7f43:b3a4 with SMTP id ffacd0b85a97d-39ad1748dc1mr3646412f8f.24.1743092200090; Thu, 27 Mar 2025 09:16:40 -0700 (PDT) Date: Thu, 27 Mar 2025 16:16:14 +0000 In-Reply-To: <20250327161617.117748-1-bqe@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250327161617.117748-1-bqe@google.com> X-Mailer: git-send-email 2.49.0.395.g12beb8f557-goog Message-ID: <20250327161617.117748-5-bqe@google.com> Subject: [PATCH v6 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 Suggested-by: Yury Norov Signed-off-by: Burak Emir --- 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 efb0d367dea2..13bc1c695858 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -4040,6 +4040,7 @@ 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 c82b23236056..fc19d97f7b9b 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