sched_ext: Move sources under kernel/sched/ext/

The sched_ext sources had grown to ten ext* files directly under
kernel/sched/. Move them into a new kernel/sched/ext/ subdirectory and drop
the now-redundant ext_ prefix. ext.c/h keep their names.

  kernel/sched/ext.{c,h}       -> kernel/sched/ext/ext.{c,h}
  kernel/sched/ext_internal.h  -> kernel/sched/ext/internal.h
  kernel/sched/ext_types.h     -> kernel/sched/ext/types.h
  kernel/sched/ext_idle.{c,h}  -> kernel/sched/ext/idle.{c,h}
  kernel/sched/ext_cid.{c,h}   -> kernel/sched/ext/cid.{c,h}
  kernel/sched/ext_arena.{c,h} -> kernel/sched/ext/arena.{c,h}

The include paths in build_policy.c and sched.h, the MAINTAINERS glob, and a
few documentation and comment references are updated to match. No code or
symbol changes.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/sched/build_policy.c

@@ -61,15 +61,15 @@
 # include <linux/btf_ids.h>
 # include <linux/find.h>
 # include <linux/genalloc.h>
-# include "ext_types.h"
-# include "ext_internal.h"
-# include "ext_cid.h"
-# include "ext_arena.h"
-# include "ext_idle.h"
-# include "ext.c"
-# include "ext_cid.c"
-# include "ext_arena.c"
-# include "ext_idle.c"
+# include "ext/types.h"
+# include "ext/internal.h"
+# include "ext/cid.h"
+# include "ext/arena.h"
+# include "ext/idle.h"
+# include "ext/ext.c"
+# include "ext/cid.c"
+# include "ext/arena.c"
+# include "ext/idle.c"
 #endif
 
 #include "syscalls.c"

kernel/sched/ext/cid.c

@@ -71,7 +71,7 @@ static s32 scx_cid_arrays_alloc(void)
  * scx_cid_init - build the cid mapping
  * @sch: the scx_sched being initialized; used as the scx_error() target
  *
- * See "Topological CPU IDs" in ext_cid.h for the model. Walk online cpus by
+ * See "Topological CPU IDs" in cid.h for the model. Walk online cpus by
  * intersection at each level (parent_scratch & this_level_mask), which keeps
  * containment correct by construction and naturally splits a physical LLC
  * straddling two NUMA nodes into two LLC units. The caller must hold

kernel/sched/ext/cid.h

@@ -43,7 +43,7 @@ struct scx_sched;
  * possible-but-not-online cpus and carries all-(-1) topo info (see
  * scx_cid_topo); callers detect it via the -1 sentinels.
  *
- * See the comment above the table definitions in ext_cid.c for the
+ * See the comment above the table definitions in cid.c for the
  * memory-ordering and visibility contract.
  */
 extern s16 *scx_cid_to_cpu_tbl;

kernel/sched/ext/ext.c

@@ -513,7 +513,7 @@ do {										\
 } while (0)
 
 /*
- * Flipped on enable per sch->is_cid_type. Declared in ext_internal.h so
+ * Flipped on enable per sch->is_cid_type. Declared in internal.h so
  * subsystem inlines can read it.
  */
 DEFINE_STATIC_KEY_FALSE(__scx_is_cid_type);
@@ -608,7 +608,7 @@ do {										\
  * @cpumask: new cpumask
  *
  * For cid-form schedulers, translate @cpumask to a cmask via the per-cpu
- * scratch in ext_cid.c and dispatch through the ops_cid union view. Caller
+ * scratch in cid.c and dispatch through the ops_cid union view. Caller
  * must hold @rq's rq lock so this_cpu_ptr is stable across the call.
  */
 static inline void scx_call_op_set_cpumask(struct scx_sched *sch, struct rq *rq,

kernel/sched/sched.h

@@ -4211,6 +4211,6 @@ DEFINE_CLASS(sched_change, struct sched_change_ctx *,
 
 DEFINE_CLASS_IS_UNCONDITIONAL(sched_change)
 
-#include "ext.h"
+#include "ext/ext.h"
 
 #endif /* _KERNEL_SCHED_SCHED_H */