mm/damon/sysfs: simplify the judgement whether kdamonds are busy

It is unnecessary to get the number of the running kdamond to judge
whether kdamonds are busy. Here we can use the
damon_sysfs_kdamond_running() helper and return -EBUSY directly when
finding a running kdamond. Meanwhile, merging with the judgement that a
kdamond has current sysfs command callback request to make the code more
clear.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Kaixu Xia <[e-mail]>
Reviewed-by: SeongJae Park <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

mm/damon/sysfs.c

···
 	kdamonds->kdamonds_arr = NULL;
 }
 
-static int damon_sysfs_nr_running_ctxs(struct damon_sysfs_kdamond **kdamonds,
+static bool damon_sysfs_kdamonds_busy(struct damon_sysfs_kdamond **kdamonds,
 		int nr_kdamonds)
 {
-	int nr_running_ctxs = 0;
 	int i;
 
 	for (i = 0; i < nr_kdamonds; i++) {
-		struct damon_ctx *ctx = kdamonds[i]->damon_ctx;
-
-		if (!ctx)
-			continue;
-		mutex_lock(&ctx->kdamond_lock);
-		if (ctx->kdamond)
-			nr_running_ctxs++;
-		mutex_unlock(&ctx->kdamond_lock);
+		if (damon_sysfs_kdamond_running(kdamonds[i]) ||
+		    damon_sysfs_cmd_request.kdamond == kdamonds[i])
+			return true;
 	}
-	return nr_running_ctxs;
+
+	return false;
 }
 
 static int damon_sysfs_kdamonds_add_dirs(struct damon_sysfs_kdamonds *kdamonds,
···
 	struct damon_sysfs_kdamond **kdamonds_arr, *kdamond;
 	int err, i;
 
-	if (damon_sysfs_nr_running_ctxs(kdamonds->kdamonds_arr, kdamonds->nr))
+	if (damon_sysfs_kdamonds_busy(kdamonds->kdamonds_arr, kdamonds->nr))
 		return -EBUSY;
-
-	for (i = 0; i < kdamonds->nr; i++) {
-		if (damon_sysfs_cmd_request.kdamond ==
-				kdamonds->kdamonds_arr[i])
-			return -EBUSY;
-	}
 
 	damon_sysfs_kdamonds_rm_dirs(kdamonds);
 	if (!nr_kdamonds)