Re: [PATCH] cpuset: introduce non-blocking cpuset.mems setting option

[kernel test robot <lkp@intel.com>]

Hi Zhongkun,

kernel test robot noticed the following build warnings:

[auto build test WARNING on tj-cgroup/for-next]
[also build test WARNING on linus/master v6.15-rc7 next-20250516]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Zhongkun-He/cpuset-introduce-non-blocking-cpuset-mems-setting-option/20250520-111737
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git for-next
patch link:    https://lore.kernel.org/r/20250520031552.1931598-1-hezhongkun.hzk%40bytedance.com
patch subject: [PATCH] cpuset: introduce non-blocking cpuset.mems setting option
config: s390-randconfig-002-20250520 (https://download.01.org/0day-ci/archive/20250520/202505202112.tmU9BTzA-lkp@intel.com/config)
compiler: clang version 21.0.0git (https://github.com/llvm/llvm-project f819f46284f2a79790038e1f6649172789734ae8)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250520/202505202112.tmU9BTzA-lkp@intel.com/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 <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202505202112.tmU9BTzA-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/cgroup/cpuset.c:3246:3: warning: label followed by a declaration is a C23 extension [-Wc23-extensions]
    3246 |                 bool skip_migrate_once = false;
         |                 ^
   1 warning generated.


vim +3246 kernel/cgroup/cpuset.c

  3215	
  3216	/*
  3217	 * Common handling for a write to a "cpus" or "mems" file.
  3218	 */
  3219	ssize_t cpuset_write_resmask(struct kernfs_open_file *of,
  3220					    char *buf, size_t nbytes, loff_t off)
  3221	{
  3222		struct cpuset *cs = css_cs(of_css(of));
  3223		struct cpuset *trialcs;
  3224		int retval = -ENODEV;
  3225	
  3226		buf = strstrip(buf);
  3227		cpus_read_lock();
  3228		mutex_lock(&cpuset_mutex);
  3229		if (!is_cpuset_online(cs))
  3230			goto out_unlock;
  3231	
  3232		trialcs = alloc_trial_cpuset(cs);
  3233		if (!trialcs) {
  3234			retval = -ENOMEM;
  3235			goto out_unlock;
  3236		}
  3237	
  3238		switch (of_cft(of)->private) {
  3239		case FILE_CPULIST:
  3240			retval = update_cpumask(cs, trialcs, buf);
  3241			break;
  3242		case FILE_EXCLUSIVE_CPULIST:
  3243			retval = update_exclusive_cpumask(cs, trialcs, buf);
  3244			break;
  3245		case FILE_MEMLIST:
> 3246			bool skip_migrate_once = false;
  3247	
  3248			if ((of->file->f_flags & O_NONBLOCK) &&
  3249				is_memory_migrate(cs) &&
  3250				!cpuset_update_flag(CS_MEMORY_MIGRATE, cs, 0))
  3251				skip_migrate_once = true;
  3252	
  3253			retval = update_nodemask(cs, trialcs, buf);
  3254	
  3255			/* Restore the migrate flag */
  3256			if (skip_migrate_once)
  3257				cpuset_update_flag(CS_MEMORY_MIGRATE, cs, 1);
  3258			break;
  3259		default:
  3260			retval = -EINVAL;
  3261			break;
  3262		}
  3263	
  3264		free_cpuset(trialcs);
  3265		if (force_sd_rebuild)
  3266			rebuild_sched_domains_locked();
  3267	out_unlock:
  3268		mutex_unlock(&cpuset_mutex);
  3269		cpus_read_unlock();
  3270		flush_workqueue(cpuset_migrate_mm_wq);
  3271		return retval ?: nbytes;
  3272	}
  3273	

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