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add safety comment

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Signed-off-by: Yuchen Liang <yuchen@neon.tech>
This commit is contained in:
Yuchen Liang
2024-08-16 18:06:16 +00:00
parent 253e4d5843
commit ea6f9798c6
1 changed files with 7 additions and 1 deletions
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8
pageserver/src/virtual_file/dio.rs
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@@ -36,6 +36,7 @@ impl IoBufferMut {
pub fn with_capacity_aligned(capacity: usize, align: usize) -> Self {
let layout = Layout::from_size_align(capacity, align).expect("Invalid layout");
// SAFETY: Making an allocation and construct a `Vec` from raw ptr. The memory is manually freed with the same layout.
let buf = unsafe {
let ptr = alloc::alloc(layout);
if ptr.is_null() {
@@ -75,7 +76,7 @@ impl IoBufferMut {
impl Drop for IoBufferMut {
fn drop(&mut self) {
// SAFETY: memory was allocated with std::alloc::alloc
// SAFETY: memory was allocated with std::alloc::alloc with the same layout.
unsafe {
alloc::dealloc(
self.buf.as_ptr() as *mut u8,
@@ -99,6 +100,7 @@ impl DerefMut for IoBufferMut {
}
}
// SAFETY: See [`IoBufferMut::advance_mut`]
unsafe impl bytes::BufMut for IoBufferMut {
#[inline]
fn remaining_mut(&self) -> usize {
@@ -107,6 +109,7 @@ unsafe impl bytes::BufMut for IoBufferMut {
self.capacity() - self.len()
}
// SAFETY: Caller needs to make sure the bytes being advanced past have been initialized.
#[inline]
unsafe fn advance_mut(&mut self, cnt: usize) {
let len = self.len();
@@ -142,6 +145,8 @@ fn panic_advance(idx: usize, len: usize) -> ! {
);
}
// Safety: [`IoBufferMut`] has exclusive ownership of the io buffer,
// and the location remains stable even if [`Self`] is moved.
unsafe impl tokio_epoll_uring::IoBuf for IoBufferMut {
fn stable_ptr(&self) -> *const u8 {
self.buf.as_ptr()
@@ -156,6 +161,7 @@ unsafe impl tokio_epoll_uring::IoBuf for IoBufferMut {
}
}
// SAFETY: See above.
unsafe impl tokio_epoll_uring::IoBufMut for IoBufferMut {
fn stable_mut_ptr(&mut self) -> *mut u8 {
self.buf.as_mut_ptr()