[tip: x86/urgent] fs/resctrl: Restore the rdt_last_cmd_clear() calls after acquiring rdtgroup_mutex

["tip-bot2 for Zeng Heng" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     dd2922dcfaa3296846265e113309e5f7f138839f
Gitweb:        https://git.kernel.org/tip/dd2922dcfaa3296846265e113309e5f7f138839f
Author:        Zeng Heng <zengheng4@huawei.com>
AuthorDate:    Tue, 03 Jun 2025 20:58:28 +08:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Wed, 04 Jun 2025 20:32:55 +02:00

fs/resctrl: Restore the rdt_last_cmd_clear() calls after acquiring rdtgroup_mutex

A lockdep fix removed two rdt_last_cmd_clear() calls that were used to
clear the last_cmd_status buffer but called without holding the required
rdtgroup_mutex.

The impacted resctrl commands are writing to the cpus or cpus_list files
and creating a new monitor or control group. With stale data in the
last_cmd_status buffer the impacted resctrl commands report the stale error
on success, or append its own failure message to the stale error on
failure.

Consequently, restore the rdt_last_cmd_clear() calls after acquiring
rdtgroup_mutex.

Fixes: c8eafe149530 ("x86/resctrl: Fix potential lockdep warning")
Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/all/20250603125828.1590067-1-zengheng4@huawei.com
---
 fs/resctrl/rdtgroup.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index cc37f58..1beb124 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -536,6 +536,8 @@ static ssize_t rdtgroup_cpus_write(struct kernfs_open_file *of,
 		goto unlock;
 	}
 
+	rdt_last_cmd_clear();
+
 	if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED ||
 	    rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
 		ret = -EINVAL;
@@ -3472,6 +3474,8 @@ static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
 		goto out_unlock;
 	}
 
+	rdt_last_cmd_clear();
+
 	/*
 	 * Check that the parent directory for a monitor group is a "mon_groups"
 	 * directory.