rust: file: improve safety comments

Some of the safety comments in `LocalFile`'s methods incorrectly refer to
the `File` type instead of `LocalFile`, so fix them to use the correct
type.

Also add missing Markdown code spans around lifetimes in the safety
comments, i.e. change 'a to `'a`.

Link: #1165
Signed-off-by: Pekka Ristola <pekkarr@protonmail.com>
Link: https://lore.kernel.org/20250527204636.12573-2-pekkarr@protonmail.com
Reviewed-by: Benno Lossin <lossin@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: pekkarr

rust/kernel/fs/file.rs

@@ -225,7 +225,7 @@ pub struct LocalFile {
 }
 
 // SAFETY: The type invariants guarantee that `LocalFile` is always ref-counted. This implementation
-// makes `ARef<File>` own a normal refcount.
+// makes `ARef<LocalFile>` own a normal refcount.
 unsafe impl AlwaysRefCounted for LocalFile {
     #[inline]
     fn inc_ref(&self) {
@@ -236,7 +236,8 @@ unsafe impl AlwaysRefCounted for LocalFile {
     #[inline]
     unsafe fn dec_ref(obj: ptr::NonNull<LocalFile>) {
         // SAFETY: To call this method, the caller passes us ownership of a normal refcount, so we
-        // may drop it. The cast is okay since `File` has the same representation as `struct file`.
+        // may drop it. The cast is okay since `LocalFile` has the same representation as
+        // `struct file`.
         unsafe { bindings::fput(obj.cast().as_ptr()) }
     }
 }
@@ -274,7 +275,7 @@ impl LocalFile {
     #[inline]
     pub unsafe fn from_raw_file<'a>(ptr: *const bindings::file) -> &'a LocalFile {
         // SAFETY: The caller guarantees that the pointer is not dangling and stays valid for the
-        // duration of 'a. The cast is okay because `File` is `repr(transparent)`.
+        // duration of `'a`. The cast is okay because `LocalFile` is `repr(transparent)`.
         //
         // INVARIANT: The caller guarantees that there are no problematic `fdget_pos` calls.
         unsafe { &*ptr.cast() }
@@ -348,7 +349,7 @@ impl File {
     #[inline]
     pub unsafe fn from_raw_file<'a>(ptr: *const bindings::file) -> &'a File {
         // SAFETY: The caller guarantees that the pointer is not dangling and stays valid for the
-        // duration of 'a. The cast is okay because `File` is `repr(transparent)`.
+        // duration of `'a`. The cast is okay because `File` is `repr(transparent)`.
         //
         // INVARIANT: The caller guarantees that there are no problematic `fdget_pos` calls.
         unsafe { &*ptr.cast() }