From: Tamir Duberstein Date: Tue, 18 Mar 2025 14:52:42 +0000 (-0400) Subject: rust: alloc: use `spare_capacity_mut` to reduce unsafe X-Git-Tag: v6.16-rc1~45^2~33^2~12 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=c3152988c047a7b6abb10d4dc5e24fafbabe8b7e;p=linux-block.git rust: alloc: use `spare_capacity_mut` to reduce unsafe Use `spare_capacity_mut` in the implementation of `push` to reduce the use of `unsafe`. Both methods were added in commit 2aac4cd7dae3 ("rust: alloc: implement kernel `Vec` type"). Reviewed-by: Alice Ryhl Reviewed-by: Benno Lossin Link: https://lore.kernel.org/r/20250318-vec-push-use-spare-v3-1-68741671d1af@gmail.com Signed-off-by: Tamir Duberstein Signed-off-by: Danilo Krummrich --- diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs index 7ebec5c4a277..6ac8756989e5 100644 --- a/rust/kernel/alloc/kvec.rs +++ b/rust/kernel/alloc/kvec.rs @@ -288,15 +288,10 @@ where pub fn push(&mut self, v: T, flags: Flags) -> Result<(), AllocError> { self.reserve(1, flags)?; - // SAFETY: - // - `self.len` is smaller than `self.capacity` and hence, the resulting pointer is - // guaranteed to be part of the same allocated object. - // - `self.len` can not overflow `isize`. - let ptr = unsafe { self.as_mut_ptr().add(self.len) }; + let spare = self.spare_capacity_mut(); - // SAFETY: - // - `ptr` is properly aligned and valid for writes. - unsafe { core::ptr::write(ptr, v) }; + // SAFETY: The call to `reserve` was successful so the spare capacity is at least 1. + unsafe { spare.get_unchecked_mut(0) }.write(v); // SAFETY: We just initialised the first spare entry, so it is safe to increase the length // by 1. We also know that the new length is <= capacity because of the previous call to