Current code in IdPool::with_capacity rounds the capacity up to BitmapVec::MAX_INLINE_LEN, but BitmapVec::new works fine with values smaller than this and still uses an inline representation. Remove this behaviour.
This allows specifying a real capacity of 0, which was not previously possible. This breaks `grow_request` in this case, so change it to grow to at least `BitmapVec::MAX_INLINE_LEN`, mirroring the capacity floor in `shrink_request`. Signed-off-by: Eliot Courtney <[email protected]> --- rust/kernel/id_pool.rs | 38 ++++++++++++++++++++++++++++++++------ 1 file changed, 32 insertions(+), 6 deletions(-) diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs index 06a4c71c4c6c..4f329249df9d 100644 --- a/rust/kernel/id_pool.rs +++ b/rust/kernel/id_pool.rs @@ -112,13 +112,8 @@ pub fn new() -> Self { } /// Constructs a new [`IdPool`] with space for a specific number of bits. - /// - /// A capacity below [`MAX_INLINE_LEN`] is adjusted to [`MAX_INLINE_LEN`]. - /// - /// [`MAX_INLINE_LEN`]: BitmapVec::MAX_INLINE_LEN #[inline] pub fn with_capacity(num_ids: usize, flags: Flags) -> Result<Self, AllocError> { - let num_ids = usize::max(num_ids, BitmapVec::MAX_INLINE_LEN); let map = BitmapVec::new(num_ids, flags)?; Ok(Self { map }) } @@ -152,6 +147,13 @@ pub fn capacity(&self) -> usize { /// let resizer = alloc_request.realloc(GFP_KERNEL)?; /// pool.shrink(resizer); /// assert_eq!(pool.capacity(), BitmapVec::MAX_INLINE_LEN); + /// + /// // A pool at the `MAX_INLINE_LEN` floor cannot shrink further. + /// assert!(pool.shrink_request().is_none()); + /// + /// // Neither can a pool with a capacity below `MAX_INLINE_LEN`. + /// let small = IdPool::with_capacity(8, GFP_KERNEL)?; + /// assert!(small.shrink_request().is_none()); /// # Ok::<(), AllocError>(()) /// ``` #[inline] @@ -198,12 +200,36 @@ pub fn shrink(&mut self, mut resizer: PoolResizer) { /// Returns a [`ReallocRequest`] for growing this [`IdPool`], if possible. /// + /// Grows to at least [`MAX_INLINE_LEN`]. /// The capacity of an [`IdPool`] cannot be grown above [`MAX_LEN`]. /// + /// [`MAX_INLINE_LEN`]: BitmapVec::MAX_INLINE_LEN /// [`MAX_LEN`]: BitmapVec::MAX_LEN + /// + /// # Examples + /// + /// ``` + /// use kernel::{ + /// alloc::AllocError, + /// bitmap::BitmapVec, + /// id_pool::IdPool, // + /// }; + /// + /// // Grow goes to at least BitmapVec::MAX_INLINE_LEN. + /// let mut pool = IdPool::with_capacity(0, GFP_KERNEL)?; + /// let resizer = pool.grow_request().ok_or(AllocError)?.realloc(GFP_KERNEL)?; + /// pool.grow(resizer); + /// assert_eq!(pool.capacity(), BitmapVec::MAX_INLINE_LEN); + /// + /// // Grow doubles if at least BitmapVec::MAX_INLINE_LEN. + /// let resizer = pool.grow_request().ok_or(AllocError)?.realloc(GFP_KERNEL)?; + /// pool.grow(resizer); + /// assert_eq!(pool.capacity(), 2 * BitmapVec::MAX_INLINE_LEN); + /// # Ok::<(), AllocError>(()) + /// ``` #[inline] pub fn grow_request(&self) -> Option<ReallocRequest> { - let num_ids = self.capacity() * 2; + let num_ids = usize::max(BitmapVec::MAX_INLINE_LEN, self.capacity() * 2); if num_ids > BitmapVec::MAX_LEN { return None; } -- 2.55.0
