| Message ID | 20250416-ptr-as-ptr-v9-2-18ec29b1b1f3@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | rust: reduce `as` casts, enable related lints | expand |
On Wed, Apr 16, 2025 at 01:36:06PM -0400, Tamir Duberstein wrote: > In Rust 1.72.0, Clippy introduced the `ptr_cast_constness` lint [1]: > > > Though `as` casts between raw pointers are not terrible, > > `pointer::cast_mut` and `pointer::cast_const` are safer because they > > cannot accidentally cast the pointer to another type. > > There are only 2 affected sites: > - `*mut T as *const U as *mut U` becomes `(*mut T).cast()` > - `&self as *const Self as *mut Self` becomes > `core::ptr::from_ref(self).cast_mut()`. > > Apply these changes and enable the lint -- no functional change > intended. > > Link: https://rust-lang.github.io/rust-clippy/master/index.html#ptr_cast_constness [1] > Reviewed-by: Benno Lossin <benno.lossin@proton.me> > Signed-off-by: Tamir Duberstein <tamird@gmail.com> > --- > Makefile | 1 + > rust/kernel/block/mq/request.rs | 4 ++-- > rust/kernel/dma.rs | 2 +- > 3 files changed, 4 insertions(+), 3 deletions(-) > > diff --git a/Makefile b/Makefile > index 5d2931344490..7b85b2a8d371 100644 > --- a/Makefile > +++ b/Makefile > @@ -481,6 +481,7 @@ export rust_common_flags := --edition=2021 \ > -Aclippy::needless_lifetimes \ > -Wclippy::no_mangle_with_rust_abi \ > -Wclippy::ptr_as_ptr \ > + -Wclippy::ptr_cast_constness \ > -Wclippy::undocumented_unsafe_blocks \ > -Wclippy::unnecessary_safety_comment \ > -Wclippy::unnecessary_safety_doc \ > diff --git a/rust/kernel/block/mq/request.rs b/rust/kernel/block/mq/request.rs > index 4a5b7ec914ef..af5c9ac94f36 100644 > --- a/rust/kernel/block/mq/request.rs > +++ b/rust/kernel/block/mq/request.rs > @@ -69,7 +69,7 @@ pub(crate) unsafe fn aref_from_raw(ptr: *mut bindings::request) -> ARef<Self> { > // INVARIANT: By the safety requirements of this function, invariants are upheld. > // SAFETY: By the safety requirement of this function, we own a > // reference count that we can pass to `ARef`. > - unsafe { ARef::from_raw(NonNull::new_unchecked(ptr as *const Self as *mut Self)) } > + unsafe { ARef::from_raw(NonNull::new_unchecked(ptr.cast())) } > } > > /// Notify the block layer that a request is going to be processed now. > @@ -155,7 +155,7 @@ pub(crate) fn wrapper_ref(&self) -> &RequestDataWrapper { > // the private data associated with this request is initialized and > // valid. The existence of `&self` guarantees that the private data is > // valid as a shared reference. > - unsafe { Self::wrapper_ptr(self as *const Self as *mut Self).as_ref() } > + unsafe { Self::wrapper_ptr(core::ptr::from_ref(self).cast_mut()).as_ref() } > } > } > > diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs > index f395d1a6fe48..43ecf3c2e860 100644 > --- a/rust/kernel/dma.rs > +++ b/rust/kernel/dma.rs > @@ -186,7 +186,7 @@ pub fn alloc_attrs( > dev: dev.into(), > dma_handle, > count, > - cpu_addr: ret.cast(), > + cpu_addr: ret.cast::<T>(), Is this change necessary? The rest looks good to me. Regards, Boqun > dma_attrs, > }) > } > > -- > 2.49.0 >
On Thu, Apr 17, 2025 at 1:12 PM Boqun Feng <boqun.feng@gmail.com> wrote: > > On Wed, Apr 16, 2025 at 01:36:06PM -0400, Tamir Duberstein wrote: > > In Rust 1.72.0, Clippy introduced the `ptr_cast_constness` lint [1]: > > > > > Though `as` casts between raw pointers are not terrible, > > > `pointer::cast_mut` and `pointer::cast_const` are safer because they > > > cannot accidentally cast the pointer to another type. > > > > There are only 2 affected sites: > > - `*mut T as *const U as *mut U` becomes `(*mut T).cast()` > > - `&self as *const Self as *mut Self` becomes > > `core::ptr::from_ref(self).cast_mut()`. > > > > Apply these changes and enable the lint -- no functional change > > intended. > > > > Link: https://rust-lang.github.io/rust-clippy/master/index.html#ptr_cast_constness [1] > > Reviewed-by: Benno Lossin <benno.lossin@proton.me> > > Signed-off-by: Tamir Duberstein <tamird@gmail.com> > > --- > > Makefile | 1 + > > rust/kernel/block/mq/request.rs | 4 ++-- > > rust/kernel/dma.rs | 2 +- > > 3 files changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/Makefile b/Makefile > > index 5d2931344490..7b85b2a8d371 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -481,6 +481,7 @@ export rust_common_flags := --edition=2021 \ > > -Aclippy::needless_lifetimes \ > > -Wclippy::no_mangle_with_rust_abi \ > > -Wclippy::ptr_as_ptr \ > > + -Wclippy::ptr_cast_constness \ > > -Wclippy::undocumented_unsafe_blocks \ > > -Wclippy::unnecessary_safety_comment \ > > -Wclippy::unnecessary_safety_doc \ > > diff --git a/rust/kernel/block/mq/request.rs b/rust/kernel/block/mq/request.rs > > index 4a5b7ec914ef..af5c9ac94f36 100644 > > --- a/rust/kernel/block/mq/request.rs > > +++ b/rust/kernel/block/mq/request.rs > > @@ -69,7 +69,7 @@ pub(crate) unsafe fn aref_from_raw(ptr: *mut bindings::request) -> ARef<Self> { > > // INVARIANT: By the safety requirements of this function, invariants are upheld. > > // SAFETY: By the safety requirement of this function, we own a > > // reference count that we can pass to `ARef`. > > - unsafe { ARef::from_raw(NonNull::new_unchecked(ptr as *const Self as *mut Self)) } > > + unsafe { ARef::from_raw(NonNull::new_unchecked(ptr.cast())) } > > } > > > > /// Notify the block layer that a request is going to be processed now. > > @@ -155,7 +155,7 @@ pub(crate) fn wrapper_ref(&self) -> &RequestDataWrapper { > > // the private data associated with this request is initialized and > > // valid. The existence of `&self` guarantees that the private data is > > // valid as a shared reference. > > - unsafe { Self::wrapper_ptr(self as *const Self as *mut Self).as_ref() } > > + unsafe { Self::wrapper_ptr(core::ptr::from_ref(self).cast_mut()).as_ref() } > > } > > } > > > > diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs > > index f395d1a6fe48..43ecf3c2e860 100644 > > --- a/rust/kernel/dma.rs > > +++ b/rust/kernel/dma.rs > > @@ -186,7 +186,7 @@ pub fn alloc_attrs( > > dev: dev.into(), > > dma_handle, > > count, > > - cpu_addr: ret.cast(), > > + cpu_addr: ret.cast::<T>(), > > Is this change necessary? The rest looks good to me. Ah, it belongs in the preceding patch. I'll fix that on the next spin.
diff --git a/Makefile b/Makefile index 5d2931344490..7b85b2a8d371 100644 --- a/Makefile +++ b/Makefile @@ -481,6 +481,7 @@ export rust_common_flags := --edition=2021 \ -Aclippy::needless_lifetimes \ -Wclippy::no_mangle_with_rust_abi \ -Wclippy::ptr_as_ptr \ + -Wclippy::ptr_cast_constness \ -Wclippy::undocumented_unsafe_blocks \ -Wclippy::unnecessary_safety_comment \ -Wclippy::unnecessary_safety_doc \ diff --git a/rust/kernel/block/mq/request.rs b/rust/kernel/block/mq/request.rs index 4a5b7ec914ef..af5c9ac94f36 100644 --- a/rust/kernel/block/mq/request.rs +++ b/rust/kernel/block/mq/request.rs @@ -69,7 +69,7 @@ pub(crate) unsafe fn aref_from_raw(ptr: *mut bindings::request) -> ARef<Self> { // INVARIANT: By the safety requirements of this function, invariants are upheld. // SAFETY: By the safety requirement of this function, we own a // reference count that we can pass to `ARef`. - unsafe { ARef::from_raw(NonNull::new_unchecked(ptr as *const Self as *mut Self)) } + unsafe { ARef::from_raw(NonNull::new_unchecked(ptr.cast())) } } /// Notify the block layer that a request is going to be processed now. @@ -155,7 +155,7 @@ pub(crate) fn wrapper_ref(&self) -> &RequestDataWrapper { // the private data associated with this request is initialized and // valid. The existence of `&self` guarantees that the private data is // valid as a shared reference. - unsafe { Self::wrapper_ptr(self as *const Self as *mut Self).as_ref() } + unsafe { Self::wrapper_ptr(core::ptr::from_ref(self).cast_mut()).as_ref() } } } diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs index f395d1a6fe48..43ecf3c2e860 100644 --- a/rust/kernel/dma.rs +++ b/rust/kernel/dma.rs @@ -186,7 +186,7 @@ pub fn alloc_attrs( dev: dev.into(), dma_handle, count, - cpu_addr: ret.cast(), + cpu_addr: ret.cast::<T>(), dma_attrs, }) }