From e5552ce2eab3c1b9e508e8db8315f8caf8916877 Mon Sep 17 00:00:00 2001
From: Vchanger <chenzhen126@huawei.com>
Date: Thu, 3 Jul 2025 17:41:51 +0800
Subject: [PATCH] io_uring: support detach sq thread from its parent

---
 include/linux/cgroup.h        |  1 +
 include/uapi/linux/io_uring.h |  1 +
 io_uring/io_uring.c           |  5 +++++
 kernel/cgroup/cgroup.c        | 20 ++++++++++++++++++++
 4 files changed, 27 insertions(+)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index b7ffef090ea7..e2be80313a1c 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -950,4 +950,5 @@ static inline void cgroup_bpf_put(struct cgroup *cgrp) {}
 void cgroup_move_task_to_root(struct task_struct *tsk);
 #endif
 
+void cgroup_attach_task_cpuset(struct task_struct *target_tsk, struct task_struct *tsk);
 #endif /* _LINUX_CGROUP_H */
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 6481db937002..5ed3b1bc6b98 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -98,6 +98,7 @@ enum {
 #define IORING_SETUP_CLAMP	(1U << 4)	/* clamp SQ/CQ ring sizes */
 #define IORING_SETUP_ATTACH_WQ	(1U << 5)	/* attach to existing wq */
 #define IORING_SETUP_R_DISABLED	(1U << 6)	/* start with ring disabled */
+#define IORING_SETUP_DETACH_SQ_THREAD (1U << 26)  /* Detach SQ poll thread to root cgroup and namespace */
 
 enum {
 	IORING_OP_NOP,
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index fee6459547d9..05265c5609ab 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -8654,6 +8654,11 @@ static int io_sq_offload_create(struct io_ring_ctx *ctx,
 		wake_up_new_task(tsk);
 		if (ret)
 			goto err;
+
+		if (ctx->flags & IORING_SETUP_DETACH_SQ_THREAD) {
+			struct task_struct *root_task = find_task_by_pid_ns(1, &init_pid_ns);
+			cgroup_attach_task_cpuset(root_task, tsk);
+		}
 	} else if (p->flags & IORING_SETUP_SQ_AFF) {
 		/* Can't have SQ_AFF without SQPOLL */
 		ret = -EINVAL;
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 965c05ecf3c6..1dd707037511 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -3003,6 +3003,26 @@ void cgroup_move_task_to_root(struct task_struct *tsk)
 }
 #endif
 
+void cgroup_attach_task_cpuset(struct task_struct *target_tsk, struct task_struct *tsk)
+{
+	struct css_set *css;
+	struct cgroup *cpuset_cgrp;
+	struct cgroup *cpuset_root_cgrp;
+
+	mutex_lock(&cgroup_mutex);
+	cgroup_attach_lock(true);
+
+	spin_lock_irq(&css_set_lock);
+	css = task_css_set(target_tsk);
+	cpuset_cgrp = css->subsys[cpuset_cgrp_id]->cgroup;
+	cpuset_root_cgrp = &cpuset_cgrp->root->cgrp;
+	spin_unlock_irq(&css_set_lock);
+
+	(void)cgroup_attach_task(cpuset_root_cgrp, tsk, false);
+	cgroup_attach_unlock(true);
+	mutex_unlock(&cgroup_mutex);
+}
+
 static void cgroup_print_ss_mask(struct seq_file *seq, u16 ss_mask)
 {
 	struct cgroup_subsys *ss;
-- 
Gitee