On 22 Aug 2025, at 09:14, Andreas Hindborg [off-list ref] wrote:

Use the new `NullTerminatedFormatter` to write the name of a `GenDisk` to
the name buffer. This new formatter automatically adds a trailing null
marker after the written characters, so we don't need to append that at the
call site any longer.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/block/mq/gen_disk.rs   | 12 +++++++-----
rust/kernel/block/mq/raw_writer.rs |  1 +
rust/kernel/str.rs                 |  1 -
3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/rust/kernel/block/mq/gen_disk.rs b/rust/kernel/block/mq/gen_disk.rs
index 679ee1bb2195..20f1d46c774d 100644
--- a/rust/kernel/block/mq/gen_disk.rs
+++ b/rust/kernel/block/mq/gen_disk.rs

@@ -7,9 +7,11 @@

use crate::{
    bindings,
-    block::mq::{raw_writer::RawWriter, Operations, TagSet},
+    block::mq::{Operations, TagSet},
    error::{self, from_err_ptr, Result},
+    prelude::*,
    static_lock_class,
+    str::NullTerminatedFormatter,
    sync::Arc,
};
use core::fmt::{self, Write};

@@ -143,14 +145,14 @@ pub fn build<T: Operations>(
        // SAFETY: `gendisk` is a valid pointer as we initialized it above
        unsafe { (*gendisk).fops = &TABLE };

-        let mut raw_writer = RawWriter::from_array(
+        let mut writer = NullTerminatedFormatter::new(
            // SAFETY: `gendisk` points to a valid and initialized instance. We
            // have exclusive access, since the disk is not added to the VFS
            // yet.
            unsafe { &mut (*gendisk).disk_name },
-        )?;
-        raw_writer.write_fmt(name)?;
-        raw_writer.write_char('\0')?;
+        )
+        .ok_or(EINVAL)?;
+        writer.write_fmt(name)?;

        // SAFETY: `gendisk` points to a valid and initialized instance of
        // `struct gendisk`. `set_capacity` takes a lock to synchronize this

diff --git a/rust/kernel/block/mq/raw_writer.rs b/rust/kernel/block/mq/raw_writer.rs
index 7e2159e4f6a6..0aef55703e71 100644
--- a/rust/kernel/block/mq/raw_writer.rs
+++ b/rust/kernel/block/mq/raw_writer.rs

@@ -24,6 +24,7 @@ fn new(buffer: &'a mut [u8]) -> Result<RawWriter<'a>> {
        Ok(Self { buffer, pos: 0 })
    }

+    #[expect(dead_code)]
    pub(crate) fn from_array<const N: usize>(
        a: &'a mut [crate::ffi::c_char; N],
    ) -> Result<RawWriter<'a>> {

diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index b185262b4851..a3e34f566034 100644
--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs

@@ -886,7 +886,6 @@ pub(crate) struct NullTerminatedFormatter<'a> {

impl<'a> NullTerminatedFormatter<'a> {
    /// Create a new [`Self`] instance.
-    #[expect(dead_code)]
    pub(crate) fn new(buffer: &'a mut [u8]) -> Option<NullTerminatedFormatter<'a>> {
        *(buffer.first_mut()?) = 0;


-- 
2.47.2