[PATCH 04/16] sched_ext: Relocate cpu_acquire/cpu_release to end of struct sched_ext_ops

[Tejun Heo <tj@kernel.org>]

cpu_acquire and cpu_release are deprecated and slated for removal. Move
their declarations to the end of struct sched_ext_ops so an upcoming
cid-form struct (sched_ext_ops_cid) can omit them entirely without
disturbing the offsets of the shared fields.

Switch the two SCX_HAS_OP() callers for these ops to direct field checks
since the relocated ops sit outside the SCX_OPI_END range covered by the
has_op bitmap.

scx_kf_allow_flags[] auto-sizes to the highest used SCX_OP_IDX, so
SCX_OP_IDX(cpu_release) moving to a higher index just enlarges the
sparse array; the lookup logic is unchanged.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext.c          |  4 +--
 kernel/sched/ext_internal.h | 54 ++++++++++++++++++++++---------------
 2 files changed, 34 insertions(+), 24 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 9e802d73f205..74e4271e44e9 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -2813,7 +2813,7 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
 		 * core. This callback complements ->cpu_release(), which is
 		 * emitted in switch_class().
 		 */
-		if (SCX_HAS_OP(sch, cpu_acquire))
+		if (sch->ops.cpu_acquire)
 			SCX_CALL_OP(sch, cpu_acquire, rq, cpu, NULL);
 		rq->scx.cpu_released = false;
 	}
@@ -2959,7 +2959,7 @@ static void switch_class(struct rq *rq, struct task_struct *next)
 	 *  next time that balance_one() is invoked.
 	 */
 	if (!rq->scx.cpu_released) {
-		if (SCX_HAS_OP(sch, cpu_release)) {
+		if (sch->ops.cpu_release) {
 			struct scx_cpu_release_args args = {
 				.reason = preempt_reason_from_class(next_class),
 				.task = next,
diff --git a/kernel/sched/ext_internal.h b/kernel/sched/ext_internal.h
index 350b84876b2a..1d73fcc19aaf 100644
--- a/kernel/sched/ext_internal.h
+++ b/kernel/sched/ext_internal.h
@@ -555,28 +555,6 @@ struct sched_ext_ops {
 	 */
 	void (*update_idle)(s32 cpu, bool idle);
 
-	/**
-	 * @cpu_acquire: A CPU is becoming available to the BPF scheduler
-	 * @cpu: The CPU being acquired by the BPF scheduler.
-	 * @args: Acquire arguments, see the struct definition.
-	 *
-	 * A CPU that was previously released from the BPF scheduler is now once
-	 * again under its control.
-	 */
-	void (*cpu_acquire)(s32 cpu, struct scx_cpu_acquire_args *args);
-
-	/**
-	 * @cpu_release: A CPU is taken away from the BPF scheduler
-	 * @cpu: The CPU being released by the BPF scheduler.
-	 * @args: Release arguments, see the struct definition.
-	 *
-	 * The specified CPU is no longer under the control of the BPF
-	 * scheduler. This could be because it was preempted by a higher
-	 * priority sched_class, though there may be other reasons as well. The
-	 * caller should consult @args->reason to determine the cause.
-	 */
-	void (*cpu_release)(s32 cpu, struct scx_cpu_release_args *args);
-
 	/**
 	 * @init_task: Initialize a task to run in a BPF scheduler
 	 * @p: task to initialize for BPF scheduling
@@ -867,6 +845,38 @@ struct sched_ext_ops {
 
 	/* internal use only, must be NULL */
 	void __rcu *priv;
+
+	/*
+	 * Deprecated callbacks. Kept at the end of the struct so the cid-form
+	 * struct (sched_ext_ops_cid) can omit them without affecting the
+	 * shared field offsets. Use SCX_ENQ_IMMED instead. Sitting past
+	 * SCX_OPI_END means has_op doesn't cover them, so SCX_HAS_OP() cannot
+	 * be used; callers must test sch->ops.cpu_acquire / cpu_release
+	 * directly.
+	 */
+
+	/**
+	 * @cpu_acquire: A CPU is becoming available to the BPF scheduler
+	 * @cpu: The CPU being acquired by the BPF scheduler.
+	 * @args: Acquire arguments, see the struct definition.
+	 *
+	 * A CPU that was previously released from the BPF scheduler is now once
+	 * again under its control. Deprecated; use SCX_ENQ_IMMED instead.
+	 */
+	void (*cpu_acquire)(s32 cpu, struct scx_cpu_acquire_args *args);
+
+	/**
+	 * @cpu_release: A CPU is taken away from the BPF scheduler
+	 * @cpu: The CPU being released by the BPF scheduler.
+	 * @args: Release arguments, see the struct definition.
+	 *
+	 * The specified CPU is no longer under the control of the BPF
+	 * scheduler. This could be because it was preempted by a higher
+	 * priority sched_class, though there may be other reasons as well. The
+	 * caller should consult @args->reason to determine the cause.
+	 * Deprecated; use SCX_ENQ_IMMED instead.
+	 */
+	void (*cpu_release)(s32 cpu, struct scx_cpu_release_args *args);
 };
 
 enum scx_opi {
-- 
2.53.0