linux-kernel - [PATCH v5 4/6] rust: id_pool: do not supply starting capacity

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Message-ID: <20251112-binder-bitmap-v5-4-8b9d7c7eca82@google.com>
Date: Wed, 12 Nov 2025 12:47:22 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Yury Norov <yury.norov@...il.com>
Cc: "Arve Hjønnevåg" <arve@...roid.com>, Todd Kjos <tkjos@...roid.com>, 
	Martijn Coenen <maco@...roid.com>, Joel Fernandes <joelagnelf@...dia.com>, 
	Christian Brauner <brauner@...nel.org>, Carlos Llamas <cmllamas@...gle.com>, 
	Suren Baghdasaryan <surenb@...gle.com>, Burak Emir <bqe@...gle.com>, Miguel Ojeda <ojeda@...nel.org>, 
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Alice Ryhl <aliceryhl@...gle.com>
Subject: [PATCH v5 4/6] rust: id_pool: do not supply starting capacity

Rust Binder wants to use inline bitmaps whenever possible to avoid
allocations, so introduce a constructor for an IdPool with arbitrary
capacity that stores the bitmap inline.

The existing constructor could be renamed to with_capacity() to match
constructors for other similar types, but it is removed as there is
currently no user for it.

Acked-by: Yury Norov (NVIDIA) <yury.norov@...il.com>
Reviewed-by: Burak Emir <bqe@...gle.com>
Reviewed-by: Danilo Krummrich <dakr@...nel.org>
Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
 rust/kernel/id_pool.rs | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs
index 90836b05c6155f98ab8393c8291749f408dbd4da..dc856fc68f4cf38971332f15e63440f27868a3b6 100644
--- a/rust/kernel/id_pool.rs
+++ b/rust/kernel/id_pool.rs
@@ -93,6 +93,18 @@ pub fn realloc(&self, flags: Flags) -> Result<PoolResizer, AllocError> {
 }
 
 impl IdPool {
+    /// Constructs a new [`IdPool`].
+    ///
+    /// The pool will have a capacity of [`NO_ALLOC_MAX_LEN`].
+    ///
+    /// [`NO_ALLOC_MAX_LEN`]: BitmapVec::NO_ALLOC_MAX_LEN
+    #[inline]
+    pub fn new() -> Self {
+        Self {
+            map: BitmapVec::new_inline(),
+        }
+    }
+
     /// Constructs a new [`IdPool`] with space for a specific number of bits.
     ///
     /// A capacity below [`MAX_INLINE_LEN`] is adjusted to [`MAX_INLINE_LEN`].
@@ -223,3 +235,10 @@ pub fn release_id(&mut self, id: usize) {
         self.map.clear_bit(id);
     }
 }
+
+impl Default for IdPool {
+    #[inline]
+    fn default() -> Self {
+        Self::new()
+    }
+}

-- 
2.51.2.1041.gc1ab5b90ca-goog