[PATCH v5 08/10] fs/resctrl: Add last_cmd_status support for writes to max_threshold_occupancy

[Reinette Chatre]

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@xxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
---
Changes since v1:
- Add Ben's RB tag.

Changes since v2:
- Switch to guard(). (Chenyu)
- Drop Ben's RB tag due to significant code change.

Changes since v4:
- Rebased on top of the "x86,fs/resctrl: Fix long-standing issues" series
  that added locking helpers to info file handlers.
- Add Tony's Reviewed-by tag.
---
 fs/resctrl/rdtgroup.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index a5fe76b0e9eb..0e428d337641 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1300,14 +1300,20 @@ static ssize_t max_threshold_occ_write(struct kernfs_open_file *of,
 	unsigned int bytes;
 	int ret;
 
-	ret = kstrtouint(buf, 0, &bytes);
-	if (ret)
-		return ret;
-
 	if (!info_kn_lock(of->kn))
 		return -ENOENT;
 
+	rdt_last_cmd_clear();
+
+	ret = kstrtouint(buf, 0, &bytes);
+	if (ret) {
+		rdt_last_cmd_puts("max_threshold_occupancy: Invalid input\n");
+		goto out_unlock;
+	}
+
 	if (bytes > resctrl_rmid_realloc_limit) {
+		rdt_last_cmd_printf("max_threshold_occupancy: Exceeds limit (before adjustment) of %u bytes\n",
+				    resctrl_rmid_realloc_limit);
 		ret = -EINVAL;
 		goto out_unlock;
 	}
-- 
2.54.0