info/last_cmd_status is intended to contain more information if a write to
any resctrl file fails. Writes to max_threshold_occupancy did not receive
last_cmd_status support during initial last_cmd_status enabling. Add it now.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---
 fs/resctrl/rdtgroup.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 3c9508fc558d..933f6ae26d59 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1238,16 +1238,27 @@ static ssize_t max_threshold_occ_write(struct kernfs_open_file *of,
 	unsigned int bytes;
 	int ret;
 
+	mutex_lock(&rdtgroup_mutex);
+	rdt_last_cmd_clear();
+
 	ret = kstrtouint(buf, 0, &bytes);
-	if (ret)
-		return ret;
+	if (ret) {
+		rdt_last_cmd_puts("Invalid input\n");
+		goto out_unlock;
+	}
 
-	if (bytes > resctrl_rmid_realloc_limit)
-		return -EINVAL;
+	if (bytes > resctrl_rmid_realloc_limit) {
+		rdt_last_cmd_printf("Exceeds limit (before adjustment) of %u bytes\n",
+				    resctrl_rmid_realloc_limit);
+		ret = -EINVAL;
+		goto out_unlock;
+	}
 
 	resctrl_rmid_realloc_threshold = resctrl_arch_round_mon_val(bytes);
 
-	return nbytes;
+out_unlock:
+	mutex_unlock(&rdtgroup_mutex);
+	return ret ?: nbytes;
 }
 
 /*
-- 
2.50.1