[PATCH v2] sched_ext: Fix stale errno in scx_sub_enable_workfn()

[Cui Jian <cjian720@163.com>]

The nesting depth check and the cgroup online check in
scx_sub_enable_workfn() reach err_disable without setting ret, so
the fallback error added by commit db4e9defd2e8 ("sched_ext: Record
an error on errno-only sub-enable failure") reports
"scx_sub_enable() failed (0)".

This is currently harmless because both paths record their own
scx_error() first and the first error wins, but it leaves the
fallback broken for these paths. Set -EINVAL and -ENODEV there
so the fallback always reports a real errno.

v2: The validate_ops() path from v1 is already fixed in for-7.3
    (sub.c already has ret = scx_validate_ops()), so only the two
    remaining paths are addressed.

Signed-off-by: Cui Jian <cjian720@163.com>
---
 kernel/sched/ext/sub.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/ext/sub.c b/kernel/sched/ext/sub.c
index d7842a609d96..6da6c91e4287 100644
--- a/kernel/sched/ext/sub.c
+++ b/kernel/sched/ext/sub.c
@@ -1331,6 +1331,7 @@ void scx_sub_enable_workfn(struct kthread_work *work)
 	if (sch->level >= SCX_SUB_MAX_DEPTH) {
 		scx_error(sch, "max nesting depth %d violated",
 			  SCX_SUB_MAX_DEPTH);
+		ret = -EINVAL;
 		goto err_disable;
 	}
 
@@ -1378,6 +1379,7 @@ void scx_sub_enable_workfn(struct kthread_work *work)
 	set_cgroup_sched(sch_cgroup(sch), sch);
 	if (!(cgrp->self.flags & CSS_ONLINE)) {
 		scx_error(sch, "cgroup is not online");
+		ret = -ENODEV;
 		goto err_unlock_and_disable;
 	}
 
-- 
2.34.1