[PATCH] cgroup: Simplify cgroup_disable loop given limited count

[PATCH] cgroup: Simplify cgroup_disable loop given limited count

[Zhen Ni]

This patch refactors the cgroup_disable loop in cgroup_disable() to
leverage the fact that OPT_FEATURE_COUNT can only be 0 or 1, making
the loop structure unnecessary complex.

Key insights:
- OPT_FEATURE_COUNT is defined as an enum value that is either:
  * 0 when CONFIG_PSI is disabled (no optional features)
  * 1 when CONFIG_PSI is enabled (only "pressure" feature)
- Therefore, the loop will either:
  * Run 0 times (when no features exist)
  * Run exactly 1 time (when only one feature exists)

Performance considerations:
- The change has no performance impact since the loop runs at most once

Signed-off-by: Zhen Ni <zhen.ni@easystack.cn>
---
 kernel/cgroup/cgroup.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index a723b7dc6e4e..71059b61b341 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -6895,11 +6895,11 @@ static int __init cgroup_disable(char *str)
 		}
 
 		for (i = 0; i < OPT_FEATURE_COUNT; i++) {
-			if (strcmp(token, cgroup_opt_feature_names[i]))
-				continue;
-			cgroup_feature_disable_mask |= 1 << i;
-			pr_info("Disabling %s control group feature\n",
-				cgroup_opt_feature_names[i]);
+			if (!strcmp(token, cgroup_opt_feature_names[i])) {
+				cgroup_feature_disable_mask |= 1 << i;
+				pr_info("Disabling %s control group feature\n",
+					cgroup_opt_feature_names[i]);
+			}
 			break;
 		}
 	}
-- 
2.20.1

Re: [PATCH] cgroup: Simplify cgroup_disable loop given limited count

[Michal Koutný]

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On Wed, Jul 30, 2025 at 04:10:15PM +0800, Zhen Ni <zhen.ni@easystack.cn> wrote:
> This patch refactors the cgroup_disable loop in cgroup_disable() to
> leverage the fact that OPT_FEATURE_COUNT can only be 0 or 1, making
> the loop structure unnecessary complex.

(The complexity measure here is subjective.)
But this rework would make the parsing subtly broken when enum
cgroup_opt_features is expandded in the future, it should be generic not
crafted for a particular value.

Michal

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