Re: [ammarfaizi2-block:af/dev.btrfs 10/11] fs/btrfs/super.c:352:19: error: array type 'cpumask_var_t' (aka 'struct cpumask[1]') is not assignable

[Ammar Faizi <ammarfaizi2@gnuweeb.org>]

On Sat, Feb 25, 2023 at 03:23:48PM +0800, kernel test robot wrote: 
> >> fs/btrfs/super.c:352:19: error: array type 'cpumask_var_t' (aka 'struct cpumask[1]') is not assignable
>            info->wq_cpu_set = mask;
>            ~~~~~~~~~~~~~~~~ ^
>    1 error generated.

Oh, it is because cpumask_var_t is defined as a different type,
depending on CONFIG_CPUMASK_OFFSTACK.

When CONFIG_CPUMASK_OFFSTACK=y

   typedef struct cpumask *cpumask_var_t;

When CONFIG_CPUMASK_OFFSTACK is not set:

   typedef struct cpumask cpumask_var_t[1];

Let's avoid that temporary variable. The fix below...

---
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 47b9e38d6a6313a1..f2e064ba0534a39c 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -323,7 +323,6 @@ static void wq_cpu_set_fix_cpulist(char *set)
 
 static int parse_wq_cpu_set(struct btrfs_fs_info *info, const char *set)
 {
-	cpumask_var_t mask;
 	char *set_copy;
 	int ret;
 
@@ -331,31 +330,30 @@ static int parse_wq_cpu_set(struct btrfs_fs_info *info, const char *set)
 	if (!set_copy)
 		return -ENOMEM;
 
-	if (!alloc_cpumask_var(&mask, GFP_KERNEL)) {
+	if (!alloc_cpumask_var(&info->wq_cpu_set, GFP_KERNEL)) {
 		ret = -ENOMEM;
 		goto out_fail;
 	}
 
 	wq_cpu_set_fix_cpulist(set_copy);
-	ret = cpulist_parse(set_copy, mask);
+	ret = cpulist_parse(set_copy, info->wq_cpu_set);
 	if (ret) {
 		btrfs_err(info, "failed to parse wq_cpu_set: %d", ret);
 		goto out_fail_cpu;
 	}
 
-	if (cpumask_empty(mask)) {
+	if (cpumask_empty(info->wq_cpu_set)) {
 		ret = -EINVAL;
 		btrfs_err(info, "wq_cpu_set cannot be empty");
 		goto out_fail_cpu;
 	}
 
-	info->wq_cpu_set = mask;
 	info->wq_cpu_set_str = set_copy;
 	btrfs_set_and_info(info, WQ_CPU_SET, "using wq_cpu_set=%s", set_copy);
 	return 0;
 
 out_fail_cpu:
-	free_cpumask_var(mask);
+	free_cpumask_var(info->wq_cpu_set);
 out_fail:
 	kfree(set_copy);
 	return ret;


-- 
Ammar Faizi