fix clippy

Signed-off-by: Yuchen Liang <yuchen@neon.tech>

pageserver/src/virtual_file/owned_buffers_io/aligned_buffer/buffer.rs

@@ -35,6 +35,7 @@ impl<A: Alignment> AlignedBuffer<A> {
 
     #[inline]
     fn as_ptr(&self) -> *const u8 {
+        // SAFETY: `self.range.start` is guaranteed to be within [0, self.len()).
         unsafe { self.raw.as_ptr().add(self.range.start) }
     }
 
@@ -93,6 +94,7 @@ impl<A: Alignment> PartialEq<[u8]> for AlignedBuffer<A> {
     }
 }
 
+/// SAFETY: the underlying buffer references a stable memory region.
 unsafe impl<A: Alignment> tokio_epoll_uring::IoBuf for AlignedBuffer<A> {
     fn stable_ptr(&self) -> *const u8 {
         self.as_ptr()

pageserver/src/virtual_file/owned_buffers_io/aligned_buffer/buffer_mut.rs

@@ -38,7 +38,7 @@ impl<const A: usize> AlignedBufferMut<ConstAlign<A>> {
         use bytes::BufMut;
         let mut buf = Self::with_capacity(capacity);
         buf.put_bytes(0, capacity);
-        // `put_bytes` filled the entire buffer.
+        // SAFETY: `put_bytes` filled the entire buffer.
         unsafe { buf.set_len(capacity) };
         buf
     }

pageserver/src/virtual_file/owned_buffers_io/aligned_buffer/slice.rs

@@ -35,6 +35,6 @@ impl<'a, const N: usize, A: Alignment> DerefMut for AlignedSlice<'a, N, A> {
 
 impl<'a, const N: usize, A: Alignment> AsRef<[u8; N]> for AlignedSlice<'a, N, A> {
     fn as_ref(&self) -> &[u8; N] {
-        &self.buf
+        self.buf
     }
 }