mm/damon/sysfs: remove damon_sysfs_cmd_request code from damon_sysfs_handle_cmd()

damon_sysfs_handle_cmd() handles user requests that it can directly handle
on its own.  For requests that need to be handled from damon_callback
hooks, it uses DAMON sysfs interface's own synchronous damon_callback
hooks management mechanism, namely damon_sysfs_cmd_request.  Now all user
requests are handled without damon_callback hooks, so
damon_sysfs_cmd_request client code in damon_sysfs_andle_cmd() does
nothing in real.  Remove the unnecessary code.

Link: https://lkml.kernel.org/r/20250306175908.66300-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: sjp38

mm/damon/sysfs.c

@@ -1715,8 +1715,6 @@ static int damon_sysfs_update_schemes_tried_regions(
 static int damon_sysfs_handle_cmd(enum damon_sysfs_cmd cmd,
 		struct damon_sysfs_kdamond *kdamond)
 {
-	bool need_wait = true;
-
 	switch (cmd) {
 	case DAMON_SYSFS_CMD_ON:
 		return damon_sysfs_turn_damon_on(kdamond);
@@ -1747,38 +1745,8 @@ static int damon_sysfs_handle_cmd(enum damon_sysfs_cmd cmd,
 		return damon_sysfs_damon_call(
 				damon_sysfs_upd_tuned_intervals, kdamond);
 	default:
-		break;
-	}
-
-	/* Pass the command to DAMON callback for safe DAMON context access */
-	if (damon_sysfs_cmd_request.kdamond)
-		return -EBUSY;
-	if (!damon_sysfs_kdamond_running(kdamond))
 		return -EINVAL;
-	damon_sysfs_cmd_request.cmd = cmd;
-	damon_sysfs_cmd_request.kdamond = kdamond;
-
-	/*
-	 * wait until damon_sysfs_cmd_request_callback() handles the request
-	 * from kdamond context
-	 */
-	mutex_unlock(&damon_sysfs_lock);
-	while (need_wait) {
-		schedule_timeout_idle(msecs_to_jiffies(100));
-		if (!mutex_trylock(&damon_sysfs_lock))
-			continue;
-		if (!damon_sysfs_cmd_request.kdamond) {
-			/* damon_sysfs_cmd_request_callback() handled */
-			need_wait = false;
-		} else if (!damon_sysfs_kdamond_running(kdamond)) {
-			/* kdamond has already finished */
-			need_wait = false;
-			damon_sysfs_cmd_request.kdamond = NULL;
-		}
-		mutex_unlock(&damon_sysfs_lock);
 	}
-	mutex_lock(&damon_sysfs_lock);
-	return 0;
 }
 
 static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,