Subject: FAILED: patch "[PATCH] cgroup/cpuset: Reset DL migration state on can_attach()" failed to apply to 6.18-stable tree
To: zhangguopeng@kylinos.cn,chenridong@huaweicloud.com,longman@redhat.com,tj@kernel.org
Cc: <stable@vger.kernel.org>
From: <gregkh@linuxfoundation.org>
Date: Tue, 19 May 2026 12:18:50 +0200
Message-ID: <2026051950-charbroil-unbutton-3311@gregkh>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=ANSI_X3.4-1968
Content-Transfer-Encoding: 8bit


The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 4a39eda5fdd867fc39f3c039714dd432cee00268
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026051950-charbroil-unbutton-3311@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^..

Possible dependencies:


thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 4a39eda5fdd867fc39f3c039714dd432cee00268 Mon Sep 17 00:00:00 2001
From: Guopeng Zhang <zhangguopeng@kylinos.cn>
Date: Sat, 9 May 2026 18:20:30 +0800
Subject: [PATCH] cgroup/cpuset: Reset DL migration state on can_attach()
 failure

cpuset_can_attach() accumulates temporary SCHED_DEADLINE migration
state in the destination cpuset while walking the taskset.

If a later task_can_attach() or security_task_setscheduler() check
fails, cgroup_migrate_execute() treats cpuset as the failing subsystem
and does not call cpuset_cancel_attach() for it. The partially
accumulated state is then left behind and can be consumed by a later
attach, corrupting cpuset DL task accounting and pending DL bandwidth
accounting.

Reset the pending DL migration state from the common error exit when
ret is non-zero. Successful can_attach() keeps the state for
cpuset_attach() or cpuset_cancel_attach().

Fixes: 2ef269ef1ac0 ("cgroup/cpuset: Free DL BW in case can_attach() fails")
Cc: stable@vger.kernel.org # v6.10+
Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Chen Ridong <chenridong@huaweicloud.com>
Reviewed-by: Waiman Long <longman@redhat.com>

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index a48901a0416a..3fbf6e7f68c3 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3050,16 +3050,13 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
 		int cpu = cpumask_any_and(cpu_active_mask, cs->effective_cpus);
 
 		if (unlikely(cpu >= nr_cpu_ids)) {
-			reset_migrate_dl_data(cs);
 			ret = -EINVAL;
 			goto out_unlock;
 		}
 
 		ret = dl_bw_alloc(cpu, cs->sum_migrate_dl_bw);
-		if (ret) {
-			reset_migrate_dl_data(cs);
+		if (ret)
 			goto out_unlock;
-		}
 
 		cs->dl_bw_cpu = cpu;
 	}
@@ -3070,7 +3067,10 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
 	 * changes which zero cpus/mems_allowed.
 	 */
 	cs->attach_in_progress++;
+
 out_unlock:
+	if (ret)
+		reset_migrate_dl_data(cs);
 	mutex_unlock(&cpuset_mutex);
 	return ret;
 }