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.h"
18#include "napi.h"
19#include "sqpoll.h"
20
21#define IORING_SQPOLL_CAP_ENTRIES_VALUE 8
22#define IORING_TW_CAP_ENTRIES_VALUE	8
23
24enum {
25	IO_SQ_THREAD_SHOULD_STOP = 0,
26	IO_SQ_THREAD_SHOULD_PARK,
27};
28
29void io_sq_thread_unpark(struct io_sq_data *sqd)
30	__releases(&sqd->lock)
31{
32	WARN_ON_ONCE(sqd->thread == current);
33
34	/*
35	 * Do the dance but not conditional clear_bit() because it'd race with
36	 * other threads incrementing park_pending and setting the bit.
37	 */
38	clear_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
39	if (atomic_dec_return(&sqd->park_pending))
40		set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
41	mutex_unlock(&sqd->lock);
42}
43
44void io_sq_thread_park(struct io_sq_data *sqd)
45	__acquires(&sqd->lock)
46{
47	WARN_ON_ONCE(sqd->thread == current);
48
49	atomic_inc(&sqd->park_pending);
50	set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
51	mutex_lock(&sqd->lock);
52	if (sqd->thread)
53		wake_up_process(sqd->thread);
54}
55
56void io_sq_thread_stop(struct io_sq_data *sqd)
57{
58	WARN_ON_ONCE(sqd->thread == current);
59	WARN_ON_ONCE(test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state));
60
61	set_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
62	mutex_lock(&sqd->lock);
63	if (sqd->thread)
64		wake_up_process(sqd->thread);
65	mutex_unlock(&sqd->lock);
66	wait_for_completion(&sqd->exited);
67}
68
69void io_put_sq_data(struct io_sq_data *sqd)
70{
71	if (refcount_dec_and_test(&sqd->refs)) {
72		WARN_ON_ONCE(atomic_read(&sqd->park_pending));
73
74		io_sq_thread_stop(sqd);
75		kfree(sqd);
76	}
77}
78
79static __cold void io_sqd_update_thread_idle(struct io_sq_data *sqd)
80{
81	struct io_ring_ctx *ctx;
82	unsigned sq_thread_idle = 0;
83
84	list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
85		sq_thread_idle = max(sq_thread_idle, ctx->sq_thread_idle);
86	sqd->sq_thread_idle = sq_thread_idle;
87}
88
89void io_sq_thread_finish(struct io_ring_ctx *ctx)
90{
91	struct io_sq_data *sqd = ctx->sq_data;
92
93	if (sqd) {
94		io_sq_thread_park(sqd);
95		list_del_init(&ctx->sqd_list);
96		io_sqd_update_thread_idle(sqd);
97		io_sq_thread_unpark(sqd);
98
99		io_put_sq_data(sqd);
100		ctx->sq_data = NULL;
101	}
102}
103
104static struct io_sq_data *io_attach_sq_data(struct io_uring_params *p)
105{
106	struct io_ring_ctx *ctx_attach;
107	struct io_sq_data *sqd;
108	struct fd f;
109
110	f = fdget(p->wq_fd);
111	if (!f.file)
112		return ERR_PTR(-ENXIO);
113	if (!io_is_uring_fops(f.file)) {
114		fdput(f);
115		return ERR_PTR(-EINVAL);
116	}
117
118	ctx_attach = f.file->private_data;
119	sqd = ctx_attach->sq_data;
120	if (!sqd) {
121		fdput(f);
122		return ERR_PTR(-EINVAL);
123	}
124	if (sqd->task_tgid != current->tgid) {
125		fdput(f);
126		return ERR_PTR(-EPERM);
127	}
128
129	refcount_inc(&sqd->refs);
130	fdput(f);
131	return sqd;
132}
133
134static struct io_sq_data *io_get_sq_data(struct io_uring_params *p,
135					 bool *attached)
136{
137	struct io_sq_data *sqd;
138
139	*attached = false;
140	if (p->flags & IORING_SETUP_ATTACH_WQ) {
141		sqd = io_attach_sq_data(p);
142		if (!IS_ERR(sqd)) {
143			*attached = true;
144			return sqd;
145		}
146		/* fall through for EPERM case, setup new sqd/task */
147		if (PTR_ERR(sqd) != -EPERM)
148			return sqd;
149	}
150
151	sqd = kzalloc(sizeof(*sqd), GFP_KERNEL);
152	if (!sqd)
153		return ERR_PTR(-ENOMEM);
154
155	atomic_set(&sqd->park_pending, 0);
156	refcount_set(&sqd->refs, 1);
157	INIT_LIST_HEAD(&sqd->ctx_list);
158	mutex_init(&sqd->lock);
159	init_waitqueue_head(&sqd->wait);
160	init_completion(&sqd->exited);
161	return sqd;
162}
163
164static inline bool io_sqd_events_pending(struct io_sq_data *sqd)
165{
166	return READ_ONCE(sqd->state);
167}
168
169static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
170{
171	unsigned int to_submit;
172	int ret = 0;
173
174	to_submit = io_sqring_entries(ctx);
175	/* if we're handling multiple rings, cap submit size for fairness */
176	if (cap_entries && to_submit > IORING_SQPOLL_CAP_ENTRIES_VALUE)
177		to_submit = IORING_SQPOLL_CAP_ENTRIES_VALUE;
178
179	if (!wq_list_empty(&ctx->iopoll_list) || to_submit) {
180		const struct cred *creds = NULL;
181
182		if (ctx->sq_creds != current_cred())
183			creds = override_creds(ctx->sq_creds);
184
185		mutex_lock(&ctx->uring_lock);
186		if (!wq_list_empty(&ctx->iopoll_list))
187			io_do_iopoll(ctx, true);
188
189		/*
190		 * Don't submit if refs are dying, good for io_uring_register(),
191		 * but also it is relied upon by io_ring_exit_work()
192		 */
193		if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)) &&
194		    !(ctx->flags & IORING_SETUP_R_DISABLED))
195			ret = io_submit_sqes(ctx, to_submit);
196		mutex_unlock(&ctx->uring_lock);
197
198		if (io_napi(ctx))
199			ret += io_napi_sqpoll_busy_poll(ctx);
200
201		if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
202			wake_up(&ctx->sqo_sq_wait);
203		if (creds)
204			revert_creds(creds);
205	}
206
207	return ret;
208}
209
210static bool io_sqd_handle_event(struct io_sq_data *sqd)
211{
212	bool did_sig = false;
213	struct ksignal ksig;
214
215	if (test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) ||
216	    signal_pending(current)) {
217		mutex_unlock(&sqd->lock);
218		if (signal_pending(current))
219			did_sig = get_signal(&ksig);
220		cond_resched();
221		mutex_lock(&sqd->lock);
222		sqd->sq_cpu = raw_smp_processor_id();
223	}
224	return did_sig || test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
225}
226
227/*
228 * Run task_work, processing the retry_list first. The retry_list holds
229 * entries that we passed on in the previous run, if we had more task_work
230 * than we were asked to process. Newly queued task_work isn't run until the
231 * retry list has been fully processed.
232 */
233static unsigned int io_sq_tw(struct llist_node **retry_list, int max_entries)
234{
235	struct io_uring_task *tctx = current->io_uring;
236	unsigned int count = 0;
237
238	if (*retry_list) {
239		*retry_list = io_handle_tw_list(*retry_list, &count, max_entries);
240		if (count >= max_entries)
241			return count;
242		max_entries -= count;
243	}
244
245	*retry_list = tctx_task_work_run(tctx, max_entries, &count);
246	return count;
247}
248
249static bool io_sq_tw_pending(struct llist_node *retry_list)
250{
251	struct io_uring_task *tctx = current->io_uring;
252
253	return retry_list || !llist_empty(&tctx->task_list);
254}
255
256static void io_sq_update_worktime(struct io_sq_data *sqd, struct rusage *start)
257{
258	struct rusage end;
259
260	getrusage(current, RUSAGE_SELF, &end);
261	end.ru_stime.tv_sec -= start->ru_stime.tv_sec;
262	end.ru_stime.tv_usec -= start->ru_stime.tv_usec;
263
264	sqd->work_time += end.ru_stime.tv_usec + end.ru_stime.tv_sec * 1000000;
265}
266
267static int io_sq_thread(void *data)
268{
269	struct llist_node *retry_list = NULL;
270	struct io_sq_data *sqd = data;
271	struct io_ring_ctx *ctx;
272	struct rusage start;
273	unsigned long timeout = 0;
274	char buf[TASK_COMM_LEN];
275	DEFINE_WAIT(wait);
276
277	/* offload context creation failed, just exit */
278	if (!current->io_uring)
279		goto err_out;
280
281	snprintf(buf, sizeof(buf), "iou-sqp-%d", sqd->task_pid);
282	set_task_comm(current, buf);
283
284	/* reset to our pid after we've set task_comm, for fdinfo */
285	sqd->task_pid = current->pid;
286
287	if (sqd->sq_cpu != -1) {
288		set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu));
289	} else {
290		set_cpus_allowed_ptr(current, cpu_online_mask);
291		sqd->sq_cpu = raw_smp_processor_id();
292	}
293
294	mutex_lock(&sqd->lock);
295	while (1) {
296		bool cap_entries, sqt_spin = false;
297
298		if (io_sqd_events_pending(sqd) || signal_pending(current)) {
299			if (io_sqd_handle_event(sqd))
300				break;
301			timeout = jiffies + sqd->sq_thread_idle;
302		}
303
304		cap_entries = !list_is_singular(&sqd->ctx_list);
305		getrusage(current, RUSAGE_SELF, &start);
306		list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
307			int ret = __io_sq_thread(ctx, cap_entries);
308
309			if (!sqt_spin && (ret > 0 || !wq_list_empty(&ctx->iopoll_list)))
310				sqt_spin = true;
311		}
312		if (io_sq_tw(&retry_list, IORING_TW_CAP_ENTRIES_VALUE))
313			sqt_spin = true;
314
315		if (sqt_spin || !time_after(jiffies, timeout)) {
316			if (sqt_spin) {
317				io_sq_update_worktime(sqd, &start);
318				timeout = jiffies + sqd->sq_thread_idle;
319			}
320			if (unlikely(need_resched())) {
321				mutex_unlock(&sqd->lock);
322				cond_resched();
323				mutex_lock(&sqd->lock);
324				sqd->sq_cpu = raw_smp_processor_id();
325			}
326			continue;
327		}
328
329		prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
330		if (!io_sqd_events_pending(sqd) && !io_sq_tw_pending(retry_list)) {
331			bool needs_sched = true;
332
333			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
334				atomic_or(IORING_SQ_NEED_WAKEUP,
335						&ctx->rings->sq_flags);
336				if ((ctx->flags & IORING_SETUP_IOPOLL) &&
337				    !wq_list_empty(&ctx->iopoll_list)) {
338					needs_sched = false;
339					break;
340				}
341
342				/*
343				 * Ensure the store of the wakeup flag is not
344				 * reordered with the load of the SQ tail
345				 */
346				smp_mb__after_atomic();
347
348				if (io_sqring_entries(ctx)) {
349					needs_sched = false;
350					break;
351				}
352			}
353
354			if (needs_sched) {
355				mutex_unlock(&sqd->lock);
356				schedule();
357				mutex_lock(&sqd->lock);
358				sqd->sq_cpu = raw_smp_processor_id();
359			}
360			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
361				atomic_andnot(IORING_SQ_NEED_WAKEUP,
362						&ctx->rings->sq_flags);
363		}
364
365		finish_wait(&sqd->wait, &wait);
366		timeout = jiffies + sqd->sq_thread_idle;
367	}
368
369	if (retry_list)
370		io_sq_tw(&retry_list, UINT_MAX);
371
372	io_uring_cancel_generic(true, sqd);
373	sqd->thread = NULL;
374	list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
375		atomic_or(IORING_SQ_NEED_WAKEUP, &ctx->rings->sq_flags);
376	io_run_task_work();
377	mutex_unlock(&sqd->lock);
378err_out:
379	complete(&sqd->exited);
380	do_exit(0);
381}
382
383void io_sqpoll_wait_sq(struct io_ring_ctx *ctx)
384{
385	DEFINE_WAIT(wait);
386
387	do {
388		if (!io_sqring_full(ctx))
389			break;
390		prepare_to_wait(&ctx->sqo_sq_wait, &wait, TASK_INTERRUPTIBLE);
391
392		if (!io_sqring_full(ctx))
393			break;
394		schedule();
395	} while (!signal_pending(current));
396
397	finish_wait(&ctx->sqo_sq_wait, &wait);
398}
399
400__cold int io_sq_offload_create(struct io_ring_ctx *ctx,
401				struct io_uring_params *p)
402{
403	int ret;
404
405	/* Retain compatibility with failing for an invalid attach attempt */
406	if ((ctx->flags & (IORING_SETUP_ATTACH_WQ | IORING_SETUP_SQPOLL)) ==
407				IORING_SETUP_ATTACH_WQ) {
408		struct fd f;
409
410		f = fdget(p->wq_fd);
411		if (!f.file)
412			return -ENXIO;
413		if (!io_is_uring_fops(f.file)) {
414			fdput(f);
415			return -EINVAL;
416		}
417		fdput(f);
418	}
419	if (ctx->flags & IORING_SETUP_SQPOLL) {
420		struct task_struct *tsk;
421		struct io_sq_data *sqd;
422		bool attached;
423
424		ret = security_uring_sqpoll();
425		if (ret)
426			return ret;
427
428		sqd = io_get_sq_data(p, &attached);
429		if (IS_ERR(sqd)) {
430			ret = PTR_ERR(sqd);
431			goto err;
432		}
433
434		ctx->sq_creds = get_current_cred();
435		ctx->sq_data = sqd;
436		ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
437		if (!ctx->sq_thread_idle)
438			ctx->sq_thread_idle = HZ;
439
440		io_sq_thread_park(sqd);
441		list_add(&ctx->sqd_list, &sqd->ctx_list);
442		io_sqd_update_thread_idle(sqd);
443		/* don't attach to a dying SQPOLL thread, would be racy */
444		ret = (attached && !sqd->thread) ? -ENXIO : 0;
445		io_sq_thread_unpark(sqd);
446
447		if (ret < 0)
448			goto err;
449		if (attached)
450			return 0;
451
452		if (p->flags & IORING_SETUP_SQ_AFF) {
453			int cpu = p->sq_thread_cpu;
454
455			ret = -EINVAL;
456			if (cpu >= nr_cpu_ids || !cpu_online(cpu))
457				goto err_sqpoll;
458			sqd->sq_cpu = cpu;
459		} else {
460			sqd->sq_cpu = -1;
461		}
462
463		sqd->task_pid = current->pid;
464		sqd->task_tgid = current->tgid;
465		tsk = create_io_thread(io_sq_thread, sqd, NUMA_NO_NODE);
466		if (IS_ERR(tsk)) {
467			ret = PTR_ERR(tsk);
468			goto err_sqpoll;
469		}
470
471		sqd->thread = tsk;
472		ret = io_uring_alloc_task_context(tsk, ctx);
473		wake_up_new_task(tsk);
474		if (ret)
475			goto err;
476	} else if (p->flags & IORING_SETUP_SQ_AFF) {
477		/* Can't have SQ_AFF without SQPOLL */
478		ret = -EINVAL;
479		goto err;
480	}
481
482	return 0;
483err_sqpoll:
484	complete(&ctx->sq_data->exited);
485err:
486	io_sq_thread_finish(ctx);
487	return ret;
488}
489
490__cold int io_sqpoll_wq_cpu_affinity(struct io_ring_ctx *ctx,
491				     cpumask_var_t mask)
492{
493	struct io_sq_data *sqd = ctx->sq_data;
494	int ret = -EINVAL;
495
496	if (sqd) {
497		io_sq_thread_park(sqd);
498		/* Don't set affinity for a dying thread */
499		if (sqd->thread)
500			ret = io_wq_cpu_affinity(sqd->thread->io_uring, mask);
501		io_sq_thread_unpark(sqd);
502	}
503
504	return ret;
505}
506