FAILED: patch "[PATCH] cgroup/cpuset: Reset DL migration state on can_attach()" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-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 <[email protected]>.

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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 4a39eda5fdd867fc39f3c039714dd432cee00268
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026051951-scheming-poking-d3a2@gregkh' --subject-prefix 'PATCH 6.6.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 <[email protected]>
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().

index a48901a0416a..3fbf6e7f68c3 100644
@@ -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;
 }

From: Guopeng Zhang <[email protected]>

[ Upstream commit 4a39eda5fdd867fc39f3c039714dd432cee00268 ]

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().

---
 kernel/cgroup/cpuset.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

index 3c466e7427516..633a91709eb54 100644
@@ -2609,16 +2609,13 @@ 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;
-		}
 	}
 
 out_success:

@@ -3458,7 +3455,10 @@ static int cpuset_can_fork(struct task_struct *task, struct css_set *cset)
 	 * 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;
 }

2.53.0