[linux-block.git] / io_uring / sqpoll.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Contains the core associated with submission side polling of the SQ
 * ring, offloading submissions from the application to a kernel thread.
 */
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/audit.h>
#include <linux/security.h>
#include <linux/io_uring.h>

#include <uapi/linux/io_uring.h>

#include "io_uring_types.h"
#include "io_uring.h"
#include "sqpoll.h"

#define IORING_SQPOLL_CAP_ENTRIES_VALUE 8

enum {
	IO_SQ_THREAD_SHOULD_STOP = 0,
	IO_SQ_THREAD_SHOULD_PARK,
};

void io_sq_thread_unpark(struct io_sq_data *sqd)
	__releases(&sqd->lock)
{
	WARN_ON_ONCE(sqd->thread == current);

	/*
	 * Do the dance but not conditional clear_bit() because it'd race with
	 * other threads incrementing park_pending and setting the bit.
	 */
	clear_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
	if (atomic_dec_return(&sqd->park_pending))
		set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
	mutex_unlock(&sqd->lock);
}

void io_sq_thread_park(struct io_sq_data *sqd)
	__acquires(&sqd->lock)
{
	WARN_ON_ONCE(sqd->thread == current);

	atomic_inc(&sqd->park_pending);
	set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
	mutex_lock(&sqd->lock);
	if (sqd->thread)
		wake_up_process(sqd->thread);
}

void io_sq_thread_stop(struct io_sq_data *sqd)
{
	WARN_ON_ONCE(sqd->thread == current);
	WARN_ON_ONCE(test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state));

	set_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
	mutex_lock(&sqd->lock);
	if (sqd->thread)
		wake_up_process(sqd->thread);
	mutex_unlock(&sqd->lock);
	wait_for_completion(&sqd->exited);
}

void io_put_sq_data(struct io_sq_data *sqd)
{
	if (refcount_dec_and_test(&sqd->refs)) {
		WARN_ON_ONCE(atomic_read(&sqd->park_pending));

		io_sq_thread_stop(sqd);
		kfree(sqd);
	}
}

static __cold void io_sqd_update_thread_idle(struct io_sq_data *sqd)
{
	struct io_ring_ctx *ctx;
	unsigned sq_thread_idle = 0;

	list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
		sq_thread_idle = max(sq_thread_idle, ctx->sq_thread_idle);
	sqd->sq_thread_idle = sq_thread_idle;
}

void io_sq_thread_finish(struct io_ring_ctx *ctx)
{
	struct io_sq_data *sqd = ctx->sq_data;

	if (sqd) {
		io_sq_thread_park(sqd);
		list_del_init(&ctx->sqd_list);
		io_sqd_update_thread_idle(sqd);
		io_sq_thread_unpark(sqd);

		io_put_sq_data(sqd);
		ctx->sq_data = NULL;
	}
}

static struct io_sq_data *io_attach_sq_data(struct io_uring_params *p)
{
	struct io_ring_ctx *ctx_attach;
	struct io_sq_data *sqd;
	struct fd f;

	f = fdget(p->wq_fd);
	if (!f.file)
		return ERR_PTR(-ENXIO);
	if (!io_is_uring_fops(f.file)) {
		fdput(f);
		return ERR_PTR(-EINVAL);
	}

	ctx_attach = f.file->private_data;
	sqd = ctx_attach->sq_data;
	if (!sqd) {
		fdput(f);
		return ERR_PTR(-EINVAL);
	}
	if (sqd->task_tgid != current->tgid) {
		fdput(f);
		return ERR_PTR(-EPERM);
	}

	refcount_inc(&sqd->refs);
	fdput(f);
	return sqd;
}

static struct io_sq_data *io_get_sq_data(struct io_uring_params *p,
					 bool *attached)
{
	struct io_sq_data *sqd;

	*attached = false;
	if (p->flags & IORING_SETUP_ATTACH_WQ) {
		sqd = io_attach_sq_data(p);
		if (!IS_ERR(sqd)) {
			*attached = true;
			return sqd;
		}
		/* fall through for EPERM case, setup new sqd/task */
		if (PTR_ERR(sqd) != -EPERM)
			return sqd;
	}

	sqd = kzalloc(sizeof(*sqd), GFP_KERNEL);
	if (!sqd)
		return ERR_PTR(-ENOMEM);

	atomic_set(&sqd->park_pending, 0);
	refcount_set(&sqd->refs, 1);
	INIT_LIST_HEAD(&sqd->ctx_list);
	mutex_init(&sqd->lock);
	init_waitqueue_head(&sqd->wait);
	init_completion(&sqd->exited);
	return sqd;
}

static inline bool io_sqd_events_pending(struct io_sq_data *sqd)
{
	return READ_ONCE(sqd->state);
}

static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
{
	unsigned int to_submit;
	int ret = 0;

	to_submit = io_sqring_entries(ctx);
	/* if we're handling multiple rings, cap submit size for fairness */
	if (cap_entries && to_submit > IORING_SQPOLL_CAP_ENTRIES_VALUE)
		to_submit = IORING_SQPOLL_CAP_ENTRIES_VALUE;

	if (!wq_list_empty(&ctx->iopoll_list) || to_submit) {
		const struct cred *creds = NULL;

		if (ctx->sq_creds != current_cred())
			creds = override_creds(ctx->sq_creds);

		mutex_lock(&ctx->uring_lock);
		if (!wq_list_empty(&ctx->iopoll_list))
			io_do_iopoll(ctx, true);

		/*
		 * Don't submit if refs are dying, good for io_uring_register(),
		 * but also it is relied upon by io_ring_exit_work()
		 */
		if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)) &&
		    !(ctx->flags & IORING_SETUP_R_DISABLED))
			ret = io_submit_sqes(ctx, to_submit);
		mutex_unlock(&ctx->uring_lock);

		if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
			wake_up(&ctx->sqo_sq_wait);
		if (creds)
			revert_creds(creds);
	}

	return ret;
}

static bool io_sqd_handle_event(struct io_sq_data *sqd)
{
	bool did_sig = false;
	struct ksignal ksig;

	if (test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) ||
	    signal_pending(current)) {
		mutex_unlock(&sqd->lock);
		if (signal_pending(current))
			did_sig = get_signal(&ksig);
		cond_resched();
		mutex_lock(&sqd->lock);
	}
	return did_sig || test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
}

static int io_sq_thread(void *data)
{
	struct io_sq_data *sqd = data;
	struct io_ring_ctx *ctx;
	unsigned long timeout = 0;
	char buf[TASK_COMM_LEN];
	DEFINE_WAIT(wait);

	snprintf(buf, sizeof(buf), "iou-sqp-%d", sqd->task_pid);
	set_task_comm(current, buf);

	if (sqd->sq_cpu != -1)
		set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu));
	else
		set_cpus_allowed_ptr(current, cpu_online_mask);
	current->flags |= PF_NO_SETAFFINITY;

	audit_alloc_kernel(current);

	mutex_lock(&sqd->lock);
	while (1) {
		bool cap_entries, sqt_spin = false;

		if (io_sqd_events_pending(sqd) || signal_pending(current)) {
			if (io_sqd_handle_event(sqd))
				break;
			timeout = jiffies + sqd->sq_thread_idle;
		}

		cap_entries = !list_is_singular(&sqd->ctx_list);
		list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
			int ret = __io_sq_thread(ctx, cap_entries);

			if (!sqt_spin && (ret > 0 || !wq_list_empty(&ctx->iopoll_list)))
				sqt_spin = true;
		}
		if (io_run_task_work())
			sqt_spin = true;

		if (sqt_spin || !time_after(jiffies, timeout)) {
			cond_resched();
			if (sqt_spin)
				timeout = jiffies + sqd->sq_thread_idle;
			continue;
		}

		prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
		if (!io_sqd_events_pending(sqd) && !task_work_pending(current)) {
			bool needs_sched = true;

			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
				atomic_or(IORING_SQ_NEED_WAKEUP,
						&ctx->rings->sq_flags);
				if ((ctx->flags & IORING_SETUP_IOPOLL) &&
				    !wq_list_empty(&ctx->iopoll_list)) {
					needs_sched = false;
					break;
				}

				/*
				 * Ensure the store of the wakeup flag is not
				 * reordered with the load of the SQ tail
				 */
				smp_mb__after_atomic();

				if (io_sqring_entries(ctx)) {
					needs_sched = false;
					break;
				}
			}

			if (needs_sched) {
				mutex_unlock(&sqd->lock);
				schedule();
				mutex_lock(&sqd->lock);
			}
			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
				atomic_andnot(IORING_SQ_NEED_WAKEUP,
						&ctx->rings->sq_flags);
		}

		finish_wait(&sqd->wait, &wait);
		timeout = jiffies + sqd->sq_thread_idle;
	}

	io_uring_cancel_generic(true, sqd);
	sqd->thread = NULL;
	list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
		atomic_or(IORING_SQ_NEED_WAKEUP, &ctx->rings->sq_flags);
	io_run_task_work();
	mutex_unlock(&sqd->lock);

	audit_free(current);

	complete(&sqd->exited);
	do_exit(0);
}

int io_sqpoll_wait_sq(struct io_ring_ctx *ctx)
{
	DEFINE_WAIT(wait);

	do {
		if (!io_sqring_full(ctx))
			break;
		prepare_to_wait(&ctx->sqo_sq_wait, &wait, TASK_INTERRUPTIBLE);

		if (!io_sqring_full(ctx))
			break;
		schedule();
	} while (!signal_pending(current));

	finish_wait(&ctx->sqo_sq_wait, &wait);
	return 0;
}

__cold int io_sq_offload_create(struct io_ring_ctx *ctx,
				struct io_uring_params *p)
{
	int ret;

	/* Retain compatibility with failing for an invalid attach attempt */
	if ((ctx->flags & (IORING_SETUP_ATTACH_WQ | IORING_SETUP_SQPOLL)) ==
				IORING_SETUP_ATTACH_WQ) {
		struct fd f;

		f = fdget(p->wq_fd);
		if (!f.file)
			return -ENXIO;
		if (!io_is_uring_fops(f.file)) {
			fdput(f);
			return -EINVAL;
		}
		fdput(f);
	}
	if (ctx->flags & IORING_SETUP_SQPOLL) {
		struct task_struct *tsk;
		struct io_sq_data *sqd;
		bool attached;

		ret = security_uring_sqpoll();
		if (ret)
			return ret;

		sqd = io_get_sq_data(p, &attached);
		if (IS_ERR(sqd)) {
			ret = PTR_ERR(sqd);
			goto err;
		}

		ctx->sq_creds = get_current_cred();
		ctx->sq_data = sqd;
		ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
		if (!ctx->sq_thread_idle)
			ctx->sq_thread_idle = HZ;

		io_sq_thread_park(sqd);
		list_add(&ctx->sqd_list, &sqd->ctx_list);
		io_sqd_update_thread_idle(sqd);
		/* don't attach to a dying SQPOLL thread, would be racy */
		ret = (attached && !sqd->thread) ? -ENXIO : 0;
		io_sq_thread_unpark(sqd);

		if (ret < 0)
			goto err;
		if (attached)
			return 0;

		if (p->flags & IORING_SETUP_SQ_AFF) {
			int cpu = p->sq_thread_cpu;

			ret = -EINVAL;
			if (cpu >= nr_cpu_ids || !cpu_online(cpu))
				goto err_sqpoll;
			sqd->sq_cpu = cpu;
		} else {
			sqd->sq_cpu = -1;
		}

		sqd->task_pid = current->pid;
		sqd->task_tgid = current->tgid;
		tsk = create_io_thread(io_sq_thread, sqd, NUMA_NO_NODE);
		if (IS_ERR(tsk)) {
			ret = PTR_ERR(tsk);
			goto err_sqpoll;
		}

		sqd->thread = tsk;
		ret = io_uring_alloc_task_context(tsk, ctx);
		wake_up_new_task(tsk);
		if (ret)
			goto err;
	} else if (p->flags & IORING_SETUP_SQ_AFF) {
		/* Can't have SQ_AFF without SQPOLL */
		ret = -EINVAL;
		goto err;
	}

	return 0;
err_sqpoll:
	complete(&ctx->sq_data->exited);
err:
	io_sq_thread_finish(ctx);
	return ret;
}
Commit	Line	Data
17437f31 JA	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* Contains the core associated with submission side polling of the SQ
	4	* ring, offloading submissions from the application to a kernel thread.
	5	*/
	6	#include <linux/kernel.h>
	7	#include <linux/errno.h>
	8	#include <linux/file.h>
	9	#include <linux/mm.h>
	10	#include <linux/slab.h>
	11	#include <linux/audit.h>
	12	#include <linux/security.h>
	13	#include <linux/io_uring.h>
	14
	15	#include <uapi/linux/io_uring.h>
	16
	17	#include "io_uring_types.h"
	18	#include "io_uring.h"
	19	#include "sqpoll.h"
	20
	21	#define IORING_SQPOLL_CAP_ENTRIES_VALUE 8
	22
	23	enum {
	24	IO_SQ_THREAD_SHOULD_STOP = 0,
	25	IO_SQ_THREAD_SHOULD_PARK,
	26	};
	27
	28	void io_sq_thread_unpark(struct io_sq_data *sqd)
	29	__releases(&sqd->lock)
	30	{
	31	WARN_ON_ONCE(sqd->thread == current);
	32
	33	/*
	34	* Do the dance but not conditional clear_bit() because it'd race with
	35	* other threads incrementing park_pending and setting the bit.
	36	*/
	37	clear_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
	38	if (atomic_dec_return(&sqd->park_pending))
	39	set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
	40	mutex_unlock(&sqd->lock);
	41	}
	42
	43	void io_sq_thread_park(struct io_sq_data *sqd)
	44	__acquires(&sqd->lock)
	45	{
	46	WARN_ON_ONCE(sqd->thread == current);
	47
	48	atomic_inc(&sqd->park_pending);
	49	set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
	50	mutex_lock(&sqd->lock);
	51	if (sqd->thread)
	52	wake_up_process(sqd->thread);
	53	}
	54
	55	void io_sq_thread_stop(struct io_sq_data *sqd)
	56	{
	57	WARN_ON_ONCE(sqd->thread == current);
	58	WARN_ON_ONCE(test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state));
	59
	60	set_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
	61	mutex_lock(&sqd->lock);
	62	if (sqd->thread)
	63	wake_up_process(sqd->thread);
	64	mutex_unlock(&sqd->lock);
65	wait_for_completion(&sqd->exited);
66	}
67
68	void io_put_sq_data(struct io_sq_data *sqd)
69	{
70	if (refcount_dec_and_test(&sqd->refs)) {
71	WARN_ON_ONCE(atomic_read(&sqd->park_pending));
72
73	io_sq_thread_stop(sqd);
74	kfree(sqd);
75	}
76	}
77
78	static __cold void io_sqd_update_thread_idle(struct io_sq_data *sqd)
79	{
80	struct io_ring_ctx *ctx;
81	unsigned sq_thread_idle = 0;
82
83	list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
84	sq_thread_idle = max(sq_thread_idle, ctx->sq_thread_idle);
85	sqd->sq_thread_idle = sq_thread_idle;
86	}
87
88	void io_sq_thread_finish(struct io_ring_ctx *ctx)
89	{
90	struct io_sq_data *sqd = ctx->sq_data;
91
92	if (sqd) {
93	io_sq_thread_park(sqd);
94	list_del_init(&ctx->sqd_list);
95	io_sqd_update_thread_idle(sqd);
96	io_sq_thread_unpark(sqd);
97
98	io_put_sq_data(sqd);
99	ctx->sq_data = NULL;
100	}
101	}
102
103	static struct io_sq_data io_attach_sq_data(struct io_uring_params p)
104	{
105	struct io_ring_ctx *ctx_attach;
106	struct io_sq_data *sqd;
107	struct fd f;
108
109	f = fdget(p->wq_fd);
110	if (!f.file)
111	return ERR_PTR(-ENXIO);
112	if (!io_is_uring_fops(f.file)) {
113	fdput(f);
114	return ERR_PTR(-EINVAL);
115	}
116
117	ctx_attach = f.file->private_data;
118	sqd = ctx_attach->sq_data;
119	if (!sqd) {
120	fdput(f);
121	return ERR_PTR(-EINVAL);
122	}
123	if (sqd->task_tgid != current->tgid) {
124	fdput(f);
125	return ERR_PTR(-EPERM);
126	}
127
128	refcount_inc(&sqd->refs);
129	fdput(f);
130	return sqd;
131	}
132
133	static struct io_sq_data io_get_sq_data(struct io_uring_params p,
134	bool *attached)
135	{
136	struct io_sq_data *sqd;
137
138	*attached = false;
139	if (p->flags & IORING_SETUP_ATTACH_WQ) {
140	sqd = io_attach_sq_data(p);
141	if (!IS_ERR(sqd)) {
142	*attached = true;
143	return sqd;
144	}
145	/* fall through for EPERM case, setup new sqd/task */
146	if (PTR_ERR(sqd) != -EPERM)
147	return sqd;
148	}
149
150	sqd = kzalloc(sizeof(*sqd), GFP_KERNEL);
151	if (!sqd)
152	return ERR_PTR(-ENOMEM);
153
154	atomic_set(&sqd->park_pending, 0);
155	refcount_set(&sqd->refs, 1);
156	INIT_LIST_HEAD(&sqd->ctx_list);
157	mutex_init(&sqd->lock);
158	init_waitqueue_head(&sqd->wait);
159	init_completion(&sqd->exited);
160	return sqd;
161	}
162
163	static inline bool io_sqd_events_pending(struct io_sq_data *sqd)
164	{
165	return READ_ONCE(sqd->state);
166	}
167
168	static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
169	{
170	unsigned int to_submit;
171	int ret = 0;
172
173	to_submit = io_sqring_entries(ctx);
174	/* if we're handling multiple rings, cap submit size for fairness */
175	if (cap_entries && to_submit > IORING_SQPOLL_CAP_ENTRIES_VALUE)
176	to_submit = IORING_SQPOLL_CAP_ENTRIES_VALUE;
177
178	if (!wq_list_empty(&ctx->iopoll_list) \|\| to_submit) {
179	const struct cred *creds = NULL;
180
181	if (ctx->sq_creds != current_cred())
182	creds = override_creds(ctx->sq_creds);
183
184	mutex_lock(&ctx->uring_lock);
185	if (!wq_list_empty(&ctx->iopoll_list))
186	io_do_iopoll(ctx, true);
187
188	/*
189	* Don't submit if refs are dying, good for io_uring_register(),
190	* but also it is relied upon by io_ring_exit_work()
191	*/
192	if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)) &&
193	!(ctx->flags & IORING_SETUP_R_DISABLED))
194	ret = io_submit_sqes(ctx, to_submit);
195	mutex_unlock(&ctx->uring_lock);
196
197	if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
198	wake_up(&ctx->sqo_sq_wait);
199	if (creds)
200	revert_creds(creds);
201	}
202
203	return ret;
204	}
205
206	static bool io_sqd_handle_event(struct io_sq_data *sqd)
207	{
208	bool did_sig = false;
209	struct ksignal ksig;
210
211	if (test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) \|\|
212	signal_pending(current)) {
213	mutex_unlock(&sqd->lock);
214	if (signal_pending(current))
215	did_sig = get_signal(&ksig);
216	cond_resched();
217	mutex_lock(&sqd->lock);
218	}
219	return did_sig \|\| test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
220	}
221
222	static int io_sq_thread(void *data)
223	{
224	struct io_sq_data *sqd = data;
225	struct io_ring_ctx *ctx;
226	unsigned long timeout = 0;
227	char buf[TASK_COMM_LEN];
228	DEFINE_WAIT(wait);
229
230	snprintf(buf, sizeof(buf), "iou-sqp-%d", sqd->task_pid);
231	set_task_comm(current, buf);
232
233	if (sqd->sq_cpu != -1)
234	set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu));
235	else
236	set_cpus_allowed_ptr(current, cpu_online_mask);
237	current->flags \|= PF_NO_SETAFFINITY;
238
239	audit_alloc_kernel(current);
240
241	mutex_lock(&sqd->lock);
242	while (1) {
243	bool cap_entries, sqt_spin = false;
244
245	if (io_sqd_events_pending(sqd) \|\| signal_pending(current)) {
246	if (io_sqd_handle_event(sqd))
247	break;
248	timeout = jiffies + sqd->sq_thread_idle;
249	}
250
251	cap_entries = !list_is_singular(&sqd->ctx_list);
252	list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
253	int ret = __io_sq_thread(ctx, cap_entries);
254
255	if (!sqt_spin && (ret > 0 \|\| !wq_list_empty(&ctx->iopoll_list)))
256	sqt_spin = true;
257	}
258	if (io_run_task_work())
259	sqt_spin = true;
260
261	if (sqt_spin \|\| !time_after(jiffies, timeout)) {
262	cond_resched();
263	if (sqt_spin)
264	timeout = jiffies + sqd->sq_thread_idle;
265	continue;
266	}
267
268	prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
269	if (!io_sqd_events_pending(sqd) && !task_work_pending(current)) {
270	bool needs_sched = true;
271
272	list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
273	atomic_or(IORING_SQ_NEED_WAKEUP,
274	&ctx->rings->sq_flags);
275	if ((ctx->flags & IORING_SETUP_IOPOLL) &&
276	!wq_list_empty(&ctx->iopoll_list)) {
277	needs_sched = false;
278	break;
279	}
280
281	/*
282	* Ensure the store of the wakeup flag is not
283	* reordered with the load of the SQ tail
284	*/
285	smp_mb__after_atomic();
286
287	if (io_sqring_entries(ctx)) {
288	needs_sched = false;
289	break;
290	}
291	}
292
293	if (needs_sched) {
294	mutex_unlock(&sqd->lock);
295	schedule();
296	mutex_lock(&sqd->lock);
297	}
298	list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
299	atomic_andnot(IORING_SQ_NEED_WAKEUP,
300	&ctx->rings->sq_flags);
301	}
302
303	finish_wait(&sqd->wait, &wait);
304	timeout = jiffies + sqd->sq_thread_idle;
305	}
306
307	io_uring_cancel_generic(true, sqd);
308	sqd->thread = NULL;
309	list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
310	atomic_or(IORING_SQ_NEED_WAKEUP, &ctx->rings->sq_flags);
311	io_run_task_work();
312	mutex_unlock(&sqd->lock);
313
314	audit_free(current);
315
316	complete(&sqd->exited);
317	do_exit(0);
318	}
319
320	int io_sqpoll_wait_sq(struct io_ring_ctx *ctx)
321	{
322	DEFINE_WAIT(wait);
323
324	do {
325	if (!io_sqring_full(ctx))
326	break;
327	prepare_to_wait(&ctx->sqo_sq_wait, &wait, TASK_INTERRUPTIBLE);
328
329	if (!io_sqring_full(ctx))
330	break;
331	schedule();
332	} while (!signal_pending(current));
333
334	finish_wait(&ctx->sqo_sq_wait, &wait);
335	return 0;
336	}
337
338	__cold int io_sq_offload_create(struct io_ring_ctx *ctx,
339	struct io_uring_params *p)
340	{
341	int ret;
342
343	/* Retain compatibility with failing for an invalid attach attempt */
344	if ((ctx->flags & (IORING_SETUP_ATTACH_WQ \| IORING_SETUP_SQPOLL)) ==
345	IORING_SETUP_ATTACH_WQ) {
346	struct fd f;
347
348	f = fdget(p->wq_fd);
349	if (!f.file)
350	return -ENXIO;
351	if (!io_is_uring_fops(f.file)) {
352	fdput(f);
353	return -EINVAL;
354	}
355	fdput(f);
356	}
357	if (ctx->flags & IORING_SETUP_SQPOLL) {
358	struct task_struct *tsk;
359	struct io_sq_data *sqd;
360	bool attached;
361
362	ret = security_uring_sqpoll();
363	if (ret)
364	return ret;
365
366	sqd = io_get_sq_data(p, &attached);
367	if (IS_ERR(sqd)) {
368	ret = PTR_ERR(sqd);
369	goto err;
370	}
371
372	ctx->sq_creds = get_current_cred();
373	ctx->sq_data = sqd;
374	ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
375	if (!ctx->sq_thread_idle)
376	ctx->sq_thread_idle = HZ;
377
378	io_sq_thread_park(sqd);
379	list_add(&ctx->sqd_list, &sqd->ctx_list);
380	io_sqd_update_thread_idle(sqd);
381	/* don't attach to a dying SQPOLL thread, would be racy */
382	ret = (attached && !sqd->thread) ? -ENXIO : 0;
383	io_sq_thread_unpark(sqd);
384
385	if (ret < 0)
386	goto err;
387	if (attached)
388	return 0;
389
390	if (p->flags & IORING_SETUP_SQ_AFF) {
391	int cpu = p->sq_thread_cpu;
392
393	ret = -EINVAL;
394	if (cpu >= nr_cpu_ids \|\| !cpu_online(cpu))
395	goto err_sqpoll;
396	sqd->sq_cpu = cpu;
397	} else {
398	sqd->sq_cpu = -1;
399	}
400
401	sqd->task_pid = current->pid;
402	sqd->task_tgid = current->tgid;
403	tsk = create_io_thread(io_sq_thread, sqd, NUMA_NO_NODE);
404	if (IS_ERR(tsk)) {
405	ret = PTR_ERR(tsk);
406	goto err_sqpoll;
407	}
408
409	sqd->thread = tsk;
410	ret = io_uring_alloc_task_context(tsk, ctx);
411	wake_up_new_task(tsk);
412	if (ret)
413	goto err;
414	} else if (p->flags & IORING_SETUP_SQ_AFF) {
415	/* Can't have SQ_AFF without SQPOLL */
416	ret = -EINVAL;
417	goto err;
418	}
419
420	return 0;
421	err_sqpoll:
422	complete(&ctx->sq_data->exited);
423	err:
424	io_sq_thread_finish(ctx);
425	return ret;
426	}