Re: [PATCH] samples: rust: debugfs: fix excessive stack use

Hi Gary,

kernel test robot noticed the following build errors:

[auto build test ERROR on b8809969e1d7a591e0f49dd464a5d04b3cf02ab1]

url:    https://github.com/intel-lab-lkp/linux/commits/Gary-Guo/samples-rust-debugfs-fix-excessive-stack-use/20260717-053803
base:   b8809969e1d7a591e0f49dd464a5d04b3cf02ab1
patch link:    https://lore.kernel.org/r/20260716144144.3665719-1-gary%40kernel.org
patch subject: [PATCH] samples: rust: debugfs: fix excessive stack use
config: x86_64-rhel-9.4-rust (https://download.01.org/0day-ci/archive/20260717/[email protected]/config)
compiler: clang version 22.1.8 (https://github.com/llvm/llvm-project ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)
rustc: rustc 1.96.0 (ac68faa20 2026-05-25)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260717/[email protected]/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/

All errors (new ones prefixed by >>):

   PATH=/opt/cross/clang-22/bin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
   INFO PATH=/opt/cross/rustc-1.96.0-bindgen-0.72.1/cargo/bin:/opt/cross/clang-22/bin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
   /usr/bin/timeout -k 100 12h /usr/bin/make KCFLAGS=\ -fno-crash-diagnostics\ -Wno-error=return-type\ -Wreturn-type\ -funsigned-char\ -Wundef\ -falign-functions=64 W=1 --keep-going LLVM=1 -j384 -C source O=/kbuild/obj/consumer/x86_64-rhel-9.4-rust ARCH=x86_64 SHELL=/bin/bash rustfmtcheck 
   make: Entering directory '/kbuild/src'
   make[1]: Entering directory '/kbuild/obj/consumer/x86_64-rhel-9.4-rust'
   Diff in rust/kernel/cpufreq.rs:792:
        }
    
        /// Driver's `adjust_perf` callback.
   -    fn adjust_perf(_policy: &mut Policy, _min_perf: usize, _target_perf: usize,
   -                   _max_perf: usize, _capacity: usize) {
   +    fn adjust_perf(
   +        _policy: &mut Policy,
   +        _min_perf: usize,
   +        _target_perf: usize,
   +        _max_perf: usize,
   +        _capacity: usize,
   +    ) {
            build_error!(VTABLE_DEFAULT_ERROR)
        }
    
   Diff in rust/kernel/cpufreq.rs:792:
        }
    
        /// Driver's `adjust_perf` callback.
   -    fn adjust_perf(_policy: &mut Policy, _min_perf: usize, _target_perf: usize,
   -                   _max_perf: usize, _capacity: usize) {
   +    fn adjust_perf(
   +        _policy: &mut Policy,
   +        _min_perf: usize,
   +        _target_perf: usize,
   +        _max_perf: usize,
   +        _capacity: usize,
   +    ) {
            build_error!(VTABLE_DEFAULT_ERROR)
        }
    
>> Diff in samples/rust/rust_debugfs_scoped.rs:75:
                GFP_KERNEL,
            )?;
        }
   -    let blob = KBox::pin_init(new_mutex!(pin_init::init_array_from_fn(|_| 0x42)), GFP_KERNEL)?;
   +    let blob = KBox::pin_init(
   +        new_mutex!(pin_init::init_array_from_fn(|_| 0x42)),
   +        GFP_KERNEL,
   +    )?;
    
        let scope = KBox::pin_init(
            mod_data.device_dir.scope(
   make[2]: *** [Makefile:2029: rustfmt] Error 123
   make[2]: Target 'rustfmtcheck' not remade because of errors.
   make[1]: Leaving directory '/kbuild/obj/consumer/x86_64-rhel-9.4-rust'
   make[1]: *** [Makefile:248: __sub-make] Error 2
   make[1]: Target 'rustfmtcheck' not remade because of errors.
   make: *** [Makefile:248: __sub-make] Error 2
   make: Target 'rustfmtcheck' not remade because of errors.
   make: Leaving directory '/kbuild/src'

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