linux-kernel - [PATCH v2 02/13] rust: init: simplify from `map_err` to `inspect

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Message-ID: <20240709160615.998336-3-ojeda@kernel.org>
Date: Tue,  9 Jul 2024 18:05:57 +0200
From: Miguel Ojeda <ojeda@...nel.org>
To: Miguel Ojeda <ojeda@...nel.org>,
	Wedson Almeida Filho <wedsonaf@...il.com>,
	Alex Gaynor <alex.gaynor@...il.com>
Cc: Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...sung.com>,
	Alice Ryhl <aliceryhl@...gle.com>,
	rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	patches@...ts.linux.dev
Subject: [PATCH v2 02/13] rust: init: simplify from `map_err` to `inspect_err`

A new complexity lint, `manual_inspect` [1], has been introduced in
the upcoming Rust 1.81 (currently in nightly), which checks for uses of
`map*` which return the original item:

    error:
    --> rust/kernel/init.rs:846:23
        |
    846 |         (self.1)(val).map_err(|e| {
        |                       ^^^^^^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_inspect
        = note: `-D clippy::manual-inspect` implied by `-D warnings`
        = help: to override `-D warnings` add `#[allow(clippy::manual_inspect)]`
    help: try
        |
    846 ~         (self.1)(val).inspect_err(|e| {
    847 |             // SAFETY: `slot` was initialized above.
    848 ~             unsafe { core::ptr::drop_in_place(slot) };
        |

Thus clean them up.

Link: https://rust-lang.github.io/rust-clippy/master/index.html#/manual_inspect [1]
Tested-by: Benno Lossin <benno.lossin@...ton.me>
Tested-by: Andreas Hindborg <a.hindborg@...sung.com>
Signed-off-by: Miguel Ojeda <ojeda@...nel.org>
---
v2:
  - Moved `SAFETY` comment out of the closure, in one of the instances
    only. In the other, it would mean putting two `SAFETY` comments in
    a row, which is even more confusing. Open coding it may be clearer,
    though -- happy to get a patch for that later on (with some docs
    about guidelines for using or avoiding `inspect_*`). (Björn, Benno,
    Alice)

 rust/kernel/init.rs | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index 68605b633e73..495c09ebe3a3 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -843,11 +843,8 @@ unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
         let val = unsafe { &mut *slot };
         // SAFETY: `slot` is considered pinned.
         let val = unsafe { Pin::new_unchecked(val) };
-        (self.1)(val).map_err(|e| {
-            // SAFETY: `slot` was initialized above.
-            unsafe { core::ptr::drop_in_place(slot) };
-            e
-        })
+        // SAFETY: `slot` was initialized above.
+        (self.1)(val).inspect_err(|_| unsafe { core::ptr::drop_in_place(slot) })
     }
 }

@@ -941,11 +938,9 @@ unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
         // SAFETY: All requirements fulfilled since this function is `__init`.
         unsafe { self.0.__pinned_init(slot)? };
         // SAFETY: The above call initialized `slot` and we still have unique access.
-        (self.1)(unsafe { &mut *slot }).map_err(|e| {
+        (self.1)(unsafe { &mut *slot }).inspect_err(|_|
             // SAFETY: `slot` was initialized above.
-            unsafe { core::ptr::drop_in_place(slot) };
-            e
-        })
+            unsafe { core::ptr::drop_in_place(slot) })
     }
 }

--
2.45.2