1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/kernel.h>
3 #include <linux/errno.h>
4 #include <linux/fs.h>
5 #include <linux/file.h>
6 #include <linux/mm.h>
7 #include <linux/slab.h>
8 #include <linux/poll.h>
9 #include <linux/hashtable.h>
10 #include <linux/io_uring.h>
11
12 #include <trace/events/io_uring.h>
13
14 #include <uapi/linux/io_uring.h>
15
16 #include "io_uring.h"
17 #include "refs.h"
18 #include "opdef.h"
19 #include "kbuf.h"
20 #include "poll.h"
21 #include "cancel.h"
22
23 struct io_poll_update {
24 struct file *file;
25 u64 old_user_data;
26 u64 new_user_data;
27 __poll_t events;
28 bool update_events;
29 bool update_user_data;
30 };
31
32 struct io_poll_table {
33 struct poll_table_struct pt;
34 struct io_kiocb *req;
35 int nr_entries;
36 int error;
37 bool owning;
38 /* output value, set only if arm poll returns >0 */
39 __poll_t result_mask;
40 };
41
42 #define IO_POLL_CANCEL_FLAG BIT(31)
43 #define IO_POLL_RETRY_FLAG BIT(30)
44 #define IO_POLL_REF_MASK GENMASK(29, 0)
45
46 /*
47 * We usually have 1-2 refs taken, 128 is more than enough and we want to
48 * maximise the margin between this amount and the moment when it overflows.
49 */
50 #define IO_POLL_REF_BIAS 128
51
52 #define IO_WQE_F_DOUBLE 1
53
wqe_to_req(struct wait_queue_entry * wqe)54 static inline struct io_kiocb *wqe_to_req(struct wait_queue_entry *wqe)
55 {
56 unsigned long priv = (unsigned long)wqe->private;
57
58 return (struct io_kiocb *)(priv & ~IO_WQE_F_DOUBLE);
59 }
60
wqe_is_double(struct wait_queue_entry * wqe)61 static inline bool wqe_is_double(struct wait_queue_entry *wqe)
62 {
63 unsigned long priv = (unsigned long)wqe->private;
64
65 return priv & IO_WQE_F_DOUBLE;
66 }
67
io_poll_get_ownership_slowpath(struct io_kiocb * req)68 static bool io_poll_get_ownership_slowpath(struct io_kiocb *req)
69 {
70 int v;
71
72 /*
73 * poll_refs are already elevated and we don't have much hope for
74 * grabbing the ownership. Instead of incrementing set a retry flag
75 * to notify the loop that there might have been some change.
76 */
77 v = atomic_fetch_or(IO_POLL_RETRY_FLAG, &req->poll_refs);
78 if (v & IO_POLL_REF_MASK)
79 return false;
80 return !(atomic_fetch_inc(&req->poll_refs) & IO_POLL_REF_MASK);
81 }
82
83 /*
84 * If refs part of ->poll_refs (see IO_POLL_REF_MASK) is 0, it's free. We can
85 * bump it and acquire ownership. It's disallowed to modify requests while not
86 * owning it, that prevents from races for enqueueing task_work's and b/w
87 * arming poll and wakeups.
88 */
io_poll_get_ownership(struct io_kiocb * req)89 static inline bool io_poll_get_ownership(struct io_kiocb *req)
90 {
91 if (unlikely(atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS))
92 return io_poll_get_ownership_slowpath(req);
93 return !(atomic_fetch_inc(&req->poll_refs) & IO_POLL_REF_MASK);
94 }
95
io_poll_mark_cancelled(struct io_kiocb * req)96 static void io_poll_mark_cancelled(struct io_kiocb *req)
97 {
98 atomic_or(IO_POLL_CANCEL_FLAG, &req->poll_refs);
99 }
100
io_poll_get_double(struct io_kiocb * req)101 static struct io_poll *io_poll_get_double(struct io_kiocb *req)
102 {
103 /* pure poll stashes this in ->async_data, poll driven retry elsewhere */
104 if (req->opcode == IORING_OP_POLL_ADD)
105 return req->async_data;
106 return req->apoll->double_poll;
107 }
108
io_poll_get_single(struct io_kiocb * req)109 static struct io_poll *io_poll_get_single(struct io_kiocb *req)
110 {
111 if (req->opcode == IORING_OP_POLL_ADD)
112 return io_kiocb_to_cmd(req, struct io_poll);
113 return &req->apoll->poll;
114 }
115
io_poll_req_insert(struct io_kiocb * req)116 static void io_poll_req_insert(struct io_kiocb *req)
117 {
118 struct io_hash_table *table = &req->ctx->cancel_table;
119 u32 index = hash_long(req->cqe.user_data, table->hash_bits);
120 struct io_hash_bucket *hb = &table->hbs[index];
121
122 spin_lock(&hb->lock);
123 hlist_add_head(&req->hash_node, &hb->list);
124 spin_unlock(&hb->lock);
125 }
126
io_poll_req_delete(struct io_kiocb * req,struct io_ring_ctx * ctx)127 static void io_poll_req_delete(struct io_kiocb *req, struct io_ring_ctx *ctx)
128 {
129 struct io_hash_table *table = &req->ctx->cancel_table;
130 u32 index = hash_long(req->cqe.user_data, table->hash_bits);
131 spinlock_t *lock = &table->hbs[index].lock;
132
133 spin_lock(lock);
134 hash_del(&req->hash_node);
135 spin_unlock(lock);
136 }
137
io_poll_req_insert_locked(struct io_kiocb * req)138 static void io_poll_req_insert_locked(struct io_kiocb *req)
139 {
140 struct io_hash_table *table = &req->ctx->cancel_table_locked;
141 u32 index = hash_long(req->cqe.user_data, table->hash_bits);
142
143 lockdep_assert_held(&req->ctx->uring_lock);
144
145 hlist_add_head(&req->hash_node, &table->hbs[index].list);
146 }
147
io_poll_tw_hash_eject(struct io_kiocb * req,bool * locked)148 static void io_poll_tw_hash_eject(struct io_kiocb *req, bool *locked)
149 {
150 struct io_ring_ctx *ctx = req->ctx;
151
152 if (req->flags & REQ_F_HASH_LOCKED) {
153 /*
154 * ->cancel_table_locked is protected by ->uring_lock in
155 * contrast to per bucket spinlocks. Likely, tctx_task_work()
156 * already grabbed the mutex for us, but there is a chance it
157 * failed.
158 */
159 io_tw_lock(ctx, locked);
160 hash_del(&req->hash_node);
161 req->flags &= ~REQ_F_HASH_LOCKED;
162 } else {
163 io_poll_req_delete(req, ctx);
164 }
165 }
166
io_init_poll_iocb(struct io_poll * poll,__poll_t events,wait_queue_func_t wake_func)167 static void io_init_poll_iocb(struct io_poll *poll, __poll_t events,
168 wait_queue_func_t wake_func)
169 {
170 poll->head = NULL;
171 #define IO_POLL_UNMASK (EPOLLERR|EPOLLHUP|EPOLLNVAL|EPOLLRDHUP)
172 /* mask in events that we always want/need */
173 poll->events = events | IO_POLL_UNMASK;
174 INIT_LIST_HEAD(&poll->wait.entry);
175 init_waitqueue_func_entry(&poll->wait, wake_func);
176 }
177
io_poll_remove_entry(struct io_poll * poll)178 static inline void io_poll_remove_entry(struct io_poll *poll)
179 {
180 struct wait_queue_head *head = smp_load_acquire(&poll->head);
181
182 if (head) {
183 spin_lock_irq(&head->lock);
184 list_del_init(&poll->wait.entry);
185 poll->head = NULL;
186 spin_unlock_irq(&head->lock);
187 }
188 }
189
io_poll_remove_entries(struct io_kiocb * req)190 static void io_poll_remove_entries(struct io_kiocb *req)
191 {
192 /*
193 * Nothing to do if neither of those flags are set. Avoid dipping
194 * into the poll/apoll/double cachelines if we can.
195 */
196 if (!(req->flags & (REQ_F_SINGLE_POLL | REQ_F_DOUBLE_POLL)))
197 return;
198
199 /*
200 * While we hold the waitqueue lock and the waitqueue is nonempty,
201 * wake_up_pollfree() will wait for us. However, taking the waitqueue
202 * lock in the first place can race with the waitqueue being freed.
203 *
204 * We solve this as eventpoll does: by taking advantage of the fact that
205 * all users of wake_up_pollfree() will RCU-delay the actual free. If
206 * we enter rcu_read_lock() and see that the pointer to the queue is
207 * non-NULL, we can then lock it without the memory being freed out from
208 * under us.
209 *
210 * Keep holding rcu_read_lock() as long as we hold the queue lock, in
211 * case the caller deletes the entry from the queue, leaving it empty.
212 * In that case, only RCU prevents the queue memory from being freed.
213 */
214 rcu_read_lock();
215 if (req->flags & REQ_F_SINGLE_POLL)
216 io_poll_remove_entry(io_poll_get_single(req));
217 if (req->flags & REQ_F_DOUBLE_POLL)
218 io_poll_remove_entry(io_poll_get_double(req));
219 rcu_read_unlock();
220 }
221
222 enum {
223 IOU_POLL_DONE = 0,
224 IOU_POLL_NO_ACTION = 1,
225 IOU_POLL_REMOVE_POLL_USE_RES = 2,
226 IOU_POLL_REISSUE = 3,
227 };
228
229 /*
230 * All poll tw should go through this. Checks for poll events, manages
231 * references, does rewait, etc.
232 *
233 * Returns a negative error on failure. IOU_POLL_NO_ACTION when no action
234 * require, which is either spurious wakeup or multishot CQE is served.
235 * IOU_POLL_DONE when it's done with the request, then the mask is stored in
236 * req->cqe.res. IOU_POLL_REMOVE_POLL_USE_RES indicates to remove multishot
237 * poll and that the result is stored in req->cqe.
238 */
io_poll_check_events(struct io_kiocb * req,bool * locked)239 static int io_poll_check_events(struct io_kiocb *req, bool *locked)
240 {
241 struct io_ring_ctx *ctx = req->ctx;
242 int v;
243
244 /* req->task == current here, checking PF_EXITING is safe */
245 if (unlikely(req->task->flags & PF_EXITING))
246 return -ECANCELED;
247
248 do {
249 v = atomic_read(&req->poll_refs);
250
251 /* tw handler should be the owner, and so have some references */
252 if (WARN_ON_ONCE(!(v & IO_POLL_REF_MASK)))
253 return IOU_POLL_DONE;
254 if (v & IO_POLL_CANCEL_FLAG)
255 return -ECANCELED;
256 /*
257 * cqe.res contains only events of the first wake up
258 * and all others are be lost. Redo vfs_poll() to get
259 * up to date state.
260 */
261 if ((v & IO_POLL_REF_MASK) != 1)
262 req->cqe.res = 0;
263 if (v & IO_POLL_RETRY_FLAG) {
264 req->cqe.res = 0;
265 /*
266 * We won't find new events that came in between
267 * vfs_poll and the ref put unless we clear the flag
268 * in advance.
269 */
270 atomic_andnot(IO_POLL_RETRY_FLAG, &req->poll_refs);
271 v &= ~IO_POLL_RETRY_FLAG;
272 }
273
274 /* the mask was stashed in __io_poll_execute */
275 if (!req->cqe.res) {
276 struct poll_table_struct pt = { ._key = req->apoll_events };
277 req->cqe.res = vfs_poll(req->file, &pt) & req->apoll_events;
278 /*
279 * We got woken with a mask, but someone else got to
280 * it first. The above vfs_poll() doesn't add us back
281 * to the waitqueue, so if we get nothing back, we
282 * should be safe and attempt a reissue.
283 */
284 if (unlikely(!req->cqe.res)) {
285 /* Multishot armed need not reissue */
286 if (!(req->apoll_events & EPOLLONESHOT))
287 continue;
288 return IOU_POLL_REISSUE;
289 }
290 }
291 if (req->apoll_events & EPOLLONESHOT)
292 return IOU_POLL_DONE;
293 if (io_is_uring_fops(req->file))
294 return IOU_POLL_DONE;
295
296 /* multishot, just fill a CQE and proceed */
297 if (!(req->flags & REQ_F_APOLL_MULTISHOT)) {
298 __poll_t mask = mangle_poll(req->cqe.res &
299 req->apoll_events);
300
301 if (!io_post_aux_cqe(ctx, req->cqe.user_data,
302 mask, IORING_CQE_F_MORE, false)) {
303 io_req_set_res(req, mask, 0);
304 return IOU_POLL_REMOVE_POLL_USE_RES;
305 }
306 } else {
307 int ret = io_poll_issue(req, locked);
308 if (ret == IOU_STOP_MULTISHOT)
309 return IOU_POLL_REMOVE_POLL_USE_RES;
310 if (ret < 0)
311 return ret;
312 }
313
314 /* force the next iteration to vfs_poll() */
315 req->cqe.res = 0;
316
317 /*
318 * Release all references, retry if someone tried to restart
319 * task_work while we were executing it.
320 */
321 } while (atomic_sub_return(v & IO_POLL_REF_MASK, &req->poll_refs) &
322 IO_POLL_REF_MASK);
323
324 return IOU_POLL_NO_ACTION;
325 }
326
io_poll_task_func(struct io_kiocb * req,bool * locked)327 static void io_poll_task_func(struct io_kiocb *req, bool *locked)
328 {
329 int ret;
330
331 ret = io_poll_check_events(req, locked);
332 if (ret == IOU_POLL_NO_ACTION)
333 return;
334
335 if (ret == IOU_POLL_DONE) {
336 struct io_poll *poll = io_kiocb_to_cmd(req, struct io_poll);
337 req->cqe.res = mangle_poll(req->cqe.res & poll->events);
338 } else if (ret == IOU_POLL_REISSUE) {
339 io_poll_remove_entries(req);
340 io_poll_tw_hash_eject(req, locked);
341 io_req_task_submit(req, locked);
342 return;
343 } else if (ret != IOU_POLL_REMOVE_POLL_USE_RES) {
344 req->cqe.res = ret;
345 req_set_fail(req);
346 }
347
348 io_poll_remove_entries(req);
349 io_poll_tw_hash_eject(req, locked);
350
351 io_req_set_res(req, req->cqe.res, 0);
352 io_req_task_complete(req, locked);
353 }
354
io_apoll_task_func(struct io_kiocb * req,bool * locked)355 static void io_apoll_task_func(struct io_kiocb *req, bool *locked)
356 {
357 int ret;
358
359 ret = io_poll_check_events(req, locked);
360 if (ret == IOU_POLL_NO_ACTION)
361 return;
362
363 io_poll_remove_entries(req);
364 io_poll_tw_hash_eject(req, locked);
365
366 if (ret == IOU_POLL_REMOVE_POLL_USE_RES)
367 io_req_complete_post(req);
368 else if (ret == IOU_POLL_DONE || ret == IOU_POLL_REISSUE)
369 io_req_task_submit(req, locked);
370 else
371 io_req_complete_failed(req, ret);
372 }
373
__io_poll_execute(struct io_kiocb * req,int mask)374 static void __io_poll_execute(struct io_kiocb *req, int mask)
375 {
376 io_req_set_res(req, mask, 0);
377 /*
378 * This is useful for poll that is armed on behalf of another
379 * request, and where the wakeup path could be on a different
380 * CPU. We want to avoid pulling in req->apoll->events for that
381 * case.
382 */
383 if (req->opcode == IORING_OP_POLL_ADD)
384 req->io_task_work.func = io_poll_task_func;
385 else
386 req->io_task_work.func = io_apoll_task_func;
387
388 trace_io_uring_task_add(req, mask);
389 io_req_task_work_add(req);
390 }
391
io_poll_execute(struct io_kiocb * req,int res)392 static inline void io_poll_execute(struct io_kiocb *req, int res)
393 {
394 if (io_poll_get_ownership(req))
395 __io_poll_execute(req, res);
396 }
397
io_poll_cancel_req(struct io_kiocb * req)398 static void io_poll_cancel_req(struct io_kiocb *req)
399 {
400 io_poll_mark_cancelled(req);
401 /* kick tw, which should complete the request */
402 io_poll_execute(req, 0);
403 }
404
405 #define IO_ASYNC_POLL_COMMON (EPOLLONESHOT | EPOLLPRI)
406
io_pollfree_wake(struct io_kiocb * req,struct io_poll * poll)407 static __cold int io_pollfree_wake(struct io_kiocb *req, struct io_poll *poll)
408 {
409 io_poll_mark_cancelled(req);
410 /* we have to kick tw in case it's not already */
411 io_poll_execute(req, 0);
412
413 /*
414 * If the waitqueue is being freed early but someone is already
415 * holds ownership over it, we have to tear down the request as
416 * best we can. That means immediately removing the request from
417 * its waitqueue and preventing all further accesses to the
418 * waitqueue via the request.
419 */
420 list_del_init(&poll->wait.entry);
421
422 /*
423 * Careful: this *must* be the last step, since as soon
424 * as req->head is NULL'ed out, the request can be
425 * completed and freed, since aio_poll_complete_work()
426 * will no longer need to take the waitqueue lock.
427 */
428 smp_store_release(&poll->head, NULL);
429 return 1;
430 }
431
io_poll_wake(struct wait_queue_entry * wait,unsigned mode,int sync,void * key)432 static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
433 void *key)
434 {
435 struct io_kiocb *req = wqe_to_req(wait);
436 struct io_poll *poll = container_of(wait, struct io_poll, wait);
437 __poll_t mask = key_to_poll(key);
438
439 if (unlikely(mask & POLLFREE))
440 return io_pollfree_wake(req, poll);
441
442 /* for instances that support it check for an event match first */
443 if (mask && !(mask & (poll->events & ~IO_ASYNC_POLL_COMMON)))
444 return 0;
445
446 if (io_poll_get_ownership(req)) {
447 /*
448 * If we trigger a multishot poll off our own wakeup path,
449 * disable multishot as there is a circular dependency between
450 * CQ posting and triggering the event.
451 */
452 if (mask & EPOLL_URING_WAKE)
453 poll->events |= EPOLLONESHOT;
454
455 /* optional, saves extra locking for removal in tw handler */
456 if (mask && poll->events & EPOLLONESHOT) {
457 list_del_init(&poll->wait.entry);
458 poll->head = NULL;
459 if (wqe_is_double(wait))
460 req->flags &= ~REQ_F_DOUBLE_POLL;
461 else
462 req->flags &= ~REQ_F_SINGLE_POLL;
463 }
464 __io_poll_execute(req, mask);
465 }
466 return 1;
467 }
468
469 /* fails only when polling is already completing by the first entry */
io_poll_double_prepare(struct io_kiocb * req)470 static bool io_poll_double_prepare(struct io_kiocb *req)
471 {
472 struct wait_queue_head *head;
473 struct io_poll *poll = io_poll_get_single(req);
474
475 /* head is RCU protected, see io_poll_remove_entries() comments */
476 rcu_read_lock();
477 head = smp_load_acquire(&poll->head);
478 /*
479 * poll arm might not hold ownership and so race for req->flags with
480 * io_poll_wake(). There is only one poll entry queued, serialise with
481 * it by taking its head lock. As we're still arming the tw hanlder
482 * is not going to be run, so there are no races with it.
483 */
484 if (head) {
485 spin_lock_irq(&head->lock);
486 req->flags |= REQ_F_DOUBLE_POLL;
487 if (req->opcode == IORING_OP_POLL_ADD)
488 req->flags |= REQ_F_ASYNC_DATA;
489 spin_unlock_irq(&head->lock);
490 }
491 rcu_read_unlock();
492 return !!head;
493 }
494
__io_queue_proc(struct io_poll * poll,struct io_poll_table * pt,struct wait_queue_head * head,struct io_poll ** poll_ptr)495 static void __io_queue_proc(struct io_poll *poll, struct io_poll_table *pt,
496 struct wait_queue_head *head,
497 struct io_poll **poll_ptr)
498 {
499 struct io_kiocb *req = pt->req;
500 unsigned long wqe_private = (unsigned long) req;
501
502 /*
503 * The file being polled uses multiple waitqueues for poll handling
504 * (e.g. one for read, one for write). Setup a separate io_poll
505 * if this happens.
506 */
507 if (unlikely(pt->nr_entries)) {
508 struct io_poll *first = poll;
509
510 /* double add on the same waitqueue head, ignore */
511 if (first->head == head)
512 return;
513 /* already have a 2nd entry, fail a third attempt */
514 if (*poll_ptr) {
515 if ((*poll_ptr)->head == head)
516 return;
517 pt->error = -EINVAL;
518 return;
519 }
520
521 poll = kmalloc(sizeof(*poll), GFP_ATOMIC);
522 if (!poll) {
523 pt->error = -ENOMEM;
524 return;
525 }
526
527 /* mark as double wq entry */
528 wqe_private |= IO_WQE_F_DOUBLE;
529 io_init_poll_iocb(poll, first->events, first->wait.func);
530 if (!io_poll_double_prepare(req)) {
531 /* the request is completing, just back off */
532 kfree(poll);
533 return;
534 }
535 *poll_ptr = poll;
536 } else {
537 /* fine to modify, there is no poll queued to race with us */
538 req->flags |= REQ_F_SINGLE_POLL;
539 }
540
541 pt->nr_entries++;
542 poll->head = head;
543 poll->wait.private = (void *) wqe_private;
544
545 if (poll->events & EPOLLEXCLUSIVE)
546 add_wait_queue_exclusive(head, &poll->wait);
547 else
548 add_wait_queue(head, &poll->wait);
549 }
550
io_poll_queue_proc(struct file * file,struct wait_queue_head * head,struct poll_table_struct * p)551 static void io_poll_queue_proc(struct file *file, struct wait_queue_head *head,
552 struct poll_table_struct *p)
553 {
554 struct io_poll_table *pt = container_of(p, struct io_poll_table, pt);
555 struct io_poll *poll = io_kiocb_to_cmd(pt->req, struct io_poll);
556
557 __io_queue_proc(poll, pt, head,
558 (struct io_poll **) &pt->req->async_data);
559 }
560
io_poll_can_finish_inline(struct io_kiocb * req,struct io_poll_table * pt)561 static bool io_poll_can_finish_inline(struct io_kiocb *req,
562 struct io_poll_table *pt)
563 {
564 return pt->owning || io_poll_get_ownership(req);
565 }
566
io_poll_add_hash(struct io_kiocb * req)567 static void io_poll_add_hash(struct io_kiocb *req)
568 {
569 if (req->flags & REQ_F_HASH_LOCKED)
570 io_poll_req_insert_locked(req);
571 else
572 io_poll_req_insert(req);
573 }
574
575 /*
576 * Returns 0 when it's handed over for polling. The caller owns the requests if
577 * it returns non-zero, but otherwise should not touch it. Negative values
578 * contain an error code. When the result is >0, the polling has completed
579 * inline and ipt.result_mask is set to the mask.
580 */
__io_arm_poll_handler(struct io_kiocb * req,struct io_poll * poll,struct io_poll_table * ipt,__poll_t mask,unsigned issue_flags)581 static int __io_arm_poll_handler(struct io_kiocb *req,
582 struct io_poll *poll,
583 struct io_poll_table *ipt, __poll_t mask,
584 unsigned issue_flags)
585 {
586 struct io_ring_ctx *ctx = req->ctx;
587
588 INIT_HLIST_NODE(&req->hash_node);
589 req->work.cancel_seq = atomic_read(&ctx->cancel_seq);
590 io_init_poll_iocb(poll, mask, io_poll_wake);
591 poll->file = req->file;
592 req->apoll_events = poll->events;
593
594 ipt->pt._key = mask;
595 ipt->req = req;
596 ipt->error = 0;
597 ipt->nr_entries = 0;
598 /*
599 * Polling is either completed here or via task_work, so if we're in the
600 * task context we're naturally serialised with tw by merit of running
601 * the same task. When it's io-wq, take the ownership to prevent tw
602 * from running. However, when we're in the task context, skip taking
603 * it as an optimisation.
604 *
605 * Note: even though the request won't be completed/freed, without
606 * ownership we still can race with io_poll_wake().
607 * io_poll_can_finish_inline() tries to deal with that.
608 */
609 ipt->owning = issue_flags & IO_URING_F_UNLOCKED;
610 atomic_set(&req->poll_refs, (int)ipt->owning);
611
612 /* io-wq doesn't hold uring_lock */
613 if (issue_flags & IO_URING_F_UNLOCKED)
614 req->flags &= ~REQ_F_HASH_LOCKED;
615
616 mask = vfs_poll(req->file, &ipt->pt) & poll->events;
617
618 if (unlikely(ipt->error || !ipt->nr_entries)) {
619 io_poll_remove_entries(req);
620
621 if (!io_poll_can_finish_inline(req, ipt)) {
622 io_poll_mark_cancelled(req);
623 return 0;
624 } else if (mask && (poll->events & EPOLLET)) {
625 ipt->result_mask = mask;
626 return 1;
627 }
628 return ipt->error ?: -EINVAL;
629 }
630
631 if (mask &&
632 ((poll->events & (EPOLLET|EPOLLONESHOT)) == (EPOLLET|EPOLLONESHOT))) {
633 if (!io_poll_can_finish_inline(req, ipt)) {
634 io_poll_add_hash(req);
635 return 0;
636 }
637 io_poll_remove_entries(req);
638 ipt->result_mask = mask;
639 /* no one else has access to the req, forget about the ref */
640 return 1;
641 }
642
643 io_poll_add_hash(req);
644
645 if (mask && (poll->events & EPOLLET) &&
646 io_poll_can_finish_inline(req, ipt)) {
647 __io_poll_execute(req, mask);
648 return 0;
649 }
650
651 if (ipt->owning) {
652 /*
653 * Try to release ownership. If we see a change of state, e.g.
654 * poll was waken up, queue up a tw, it'll deal with it.
655 */
656 if (atomic_cmpxchg(&req->poll_refs, 1, 0) != 1)
657 __io_poll_execute(req, 0);
658 }
659 return 0;
660 }
661
io_async_queue_proc(struct file * file,struct wait_queue_head * head,struct poll_table_struct * p)662 static void io_async_queue_proc(struct file *file, struct wait_queue_head *head,
663 struct poll_table_struct *p)
664 {
665 struct io_poll_table *pt = container_of(p, struct io_poll_table, pt);
666 struct async_poll *apoll = pt->req->apoll;
667
668 __io_queue_proc(&apoll->poll, pt, head, &apoll->double_poll);
669 }
670
io_req_alloc_apoll(struct io_kiocb * req,unsigned issue_flags)671 static struct async_poll *io_req_alloc_apoll(struct io_kiocb *req,
672 unsigned issue_flags)
673 {
674 struct io_ring_ctx *ctx = req->ctx;
675 struct io_cache_entry *entry;
676 struct async_poll *apoll;
677
678 if (req->flags & REQ_F_POLLED) {
679 apoll = req->apoll;
680 kfree(apoll->double_poll);
681 } else if (!(issue_flags & IO_URING_F_UNLOCKED) &&
682 (entry = io_alloc_cache_get(&ctx->apoll_cache)) != NULL) {
683 apoll = container_of(entry, struct async_poll, cache);
684 } else {
685 apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);
686 if (unlikely(!apoll))
687 return NULL;
688 }
689 apoll->double_poll = NULL;
690 req->apoll = apoll;
691 return apoll;
692 }
693
io_arm_poll_handler(struct io_kiocb * req,unsigned issue_flags)694 int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags)
695 {
696 const struct io_op_def *def = &io_op_defs[req->opcode];
697 struct async_poll *apoll;
698 struct io_poll_table ipt;
699 __poll_t mask = POLLPRI | POLLERR | EPOLLET;
700 int ret;
701
702 /*
703 * apoll requests already grab the mutex to complete in the tw handler,
704 * so removal from the mutex-backed hash is free, use it by default.
705 */
706 req->flags |= REQ_F_HASH_LOCKED;
707
708 if (!def->pollin && !def->pollout)
709 return IO_APOLL_ABORTED;
710 if (!file_can_poll(req->file))
711 return IO_APOLL_ABORTED;
712 if ((req->flags & (REQ_F_POLLED|REQ_F_PARTIAL_IO)) == REQ_F_POLLED)
713 return IO_APOLL_ABORTED;
714 if (!(req->flags & REQ_F_APOLL_MULTISHOT))
715 mask |= EPOLLONESHOT;
716
717 if (def->pollin) {
718 mask |= EPOLLIN | EPOLLRDNORM;
719
720 /* If reading from MSG_ERRQUEUE using recvmsg, ignore POLLIN */
721 if (req->flags & REQ_F_CLEAR_POLLIN)
722 mask &= ~EPOLLIN;
723 } else {
724 mask |= EPOLLOUT | EPOLLWRNORM;
725 }
726 if (def->poll_exclusive)
727 mask |= EPOLLEXCLUSIVE;
728
729 apoll = io_req_alloc_apoll(req, issue_flags);
730 if (!apoll)
731 return IO_APOLL_ABORTED;
732 req->flags |= REQ_F_POLLED;
733 ipt.pt._qproc = io_async_queue_proc;
734
735 io_kbuf_recycle(req, issue_flags);
736
737 ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask, issue_flags);
738 if (ret)
739 return ret > 0 ? IO_APOLL_READY : IO_APOLL_ABORTED;
740 trace_io_uring_poll_arm(req, mask, apoll->poll.events);
741 return IO_APOLL_OK;
742 }
743
io_poll_remove_all_table(struct task_struct * tsk,struct io_hash_table * table,bool cancel_all)744 static __cold bool io_poll_remove_all_table(struct task_struct *tsk,
745 struct io_hash_table *table,
746 bool cancel_all)
747 {
748 unsigned nr_buckets = 1U << table->hash_bits;
749 struct hlist_node *tmp;
750 struct io_kiocb *req;
751 bool found = false;
752 int i;
753
754 for (i = 0; i < nr_buckets; i++) {
755 struct io_hash_bucket *hb = &table->hbs[i];
756
757 spin_lock(&hb->lock);
758 hlist_for_each_entry_safe(req, tmp, &hb->list, hash_node) {
759 if (io_match_task_safe(req, tsk, cancel_all)) {
760 hlist_del_init(&req->hash_node);
761 io_poll_cancel_req(req);
762 found = true;
763 }
764 }
765 spin_unlock(&hb->lock);
766 }
767 return found;
768 }
769
770 /*
771 * Returns true if we found and killed one or more poll requests
772 */
io_poll_remove_all(struct io_ring_ctx * ctx,struct task_struct * tsk,bool cancel_all)773 __cold bool io_poll_remove_all(struct io_ring_ctx *ctx, struct task_struct *tsk,
774 bool cancel_all)
775 __must_hold(&ctx->uring_lock)
776 {
777 bool ret;
778
779 ret = io_poll_remove_all_table(tsk, &ctx->cancel_table, cancel_all);
780 ret |= io_poll_remove_all_table(tsk, &ctx->cancel_table_locked, cancel_all);
781 return ret;
782 }
783
io_poll_find(struct io_ring_ctx * ctx,bool poll_only,struct io_cancel_data * cd,struct io_hash_table * table,struct io_hash_bucket ** out_bucket)784 static struct io_kiocb *io_poll_find(struct io_ring_ctx *ctx, bool poll_only,
785 struct io_cancel_data *cd,
786 struct io_hash_table *table,
787 struct io_hash_bucket **out_bucket)
788 {
789 struct io_kiocb *req;
790 u32 index = hash_long(cd->data, table->hash_bits);
791 struct io_hash_bucket *hb = &table->hbs[index];
792
793 *out_bucket = NULL;
794
795 spin_lock(&hb->lock);
796 hlist_for_each_entry(req, &hb->list, hash_node) {
797 if (cd->data != req->cqe.user_data)
798 continue;
799 if (poll_only && req->opcode != IORING_OP_POLL_ADD)
800 continue;
801 if (cd->flags & IORING_ASYNC_CANCEL_ALL) {
802 if (cd->seq == req->work.cancel_seq)
803 continue;
804 req->work.cancel_seq = cd->seq;
805 }
806 *out_bucket = hb;
807 return req;
808 }
809 spin_unlock(&hb->lock);
810 return NULL;
811 }
812
io_poll_file_find(struct io_ring_ctx * ctx,struct io_cancel_data * cd,struct io_hash_table * table,struct io_hash_bucket ** out_bucket)813 static struct io_kiocb *io_poll_file_find(struct io_ring_ctx *ctx,
814 struct io_cancel_data *cd,
815 struct io_hash_table *table,
816 struct io_hash_bucket **out_bucket)
817 {
818 unsigned nr_buckets = 1U << table->hash_bits;
819 struct io_kiocb *req;
820 int i;
821
822 *out_bucket = NULL;
823
824 for (i = 0; i < nr_buckets; i++) {
825 struct io_hash_bucket *hb = &table->hbs[i];
826
827 spin_lock(&hb->lock);
828 hlist_for_each_entry(req, &hb->list, hash_node) {
829 if (!(cd->flags & IORING_ASYNC_CANCEL_ANY) &&
830 req->file != cd->file)
831 continue;
832 if (cd->seq == req->work.cancel_seq)
833 continue;
834 req->work.cancel_seq = cd->seq;
835 *out_bucket = hb;
836 return req;
837 }
838 spin_unlock(&hb->lock);
839 }
840 return NULL;
841 }
842
io_poll_disarm(struct io_kiocb * req)843 static int io_poll_disarm(struct io_kiocb *req)
844 {
845 if (!req)
846 return -ENOENT;
847 if (!io_poll_get_ownership(req))
848 return -EALREADY;
849 io_poll_remove_entries(req);
850 hash_del(&req->hash_node);
851 return 0;
852 }
853
__io_poll_cancel(struct io_ring_ctx * ctx,struct io_cancel_data * cd,struct io_hash_table * table)854 static int __io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
855 struct io_hash_table *table)
856 {
857 struct io_hash_bucket *bucket;
858 struct io_kiocb *req;
859
860 if (cd->flags & (IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_ANY))
861 req = io_poll_file_find(ctx, cd, table, &bucket);
862 else
863 req = io_poll_find(ctx, false, cd, table, &bucket);
864
865 if (req)
866 io_poll_cancel_req(req);
867 if (bucket)
868 spin_unlock(&bucket->lock);
869 return req ? 0 : -ENOENT;
870 }
871
io_poll_cancel(struct io_ring_ctx * ctx,struct io_cancel_data * cd,unsigned issue_flags)872 int io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
873 unsigned issue_flags)
874 {
875 int ret;
876
877 ret = __io_poll_cancel(ctx, cd, &ctx->cancel_table);
878 if (ret != -ENOENT)
879 return ret;
880
881 io_ring_submit_lock(ctx, issue_flags);
882 ret = __io_poll_cancel(ctx, cd, &ctx->cancel_table_locked);
883 io_ring_submit_unlock(ctx, issue_flags);
884 return ret;
885 }
886
io_poll_parse_events(const struct io_uring_sqe * sqe,unsigned int flags)887 static __poll_t io_poll_parse_events(const struct io_uring_sqe *sqe,
888 unsigned int flags)
889 {
890 u32 events;
891
892 events = READ_ONCE(sqe->poll32_events);
893 #ifdef __BIG_ENDIAN
894 events = swahw32(events);
895 #endif
896 if (!(flags & IORING_POLL_ADD_MULTI))
897 events |= EPOLLONESHOT;
898 if (!(flags & IORING_POLL_ADD_LEVEL))
899 events |= EPOLLET;
900 return demangle_poll(events) |
901 (events & (EPOLLEXCLUSIVE|EPOLLONESHOT|EPOLLET));
902 }
903
io_poll_remove_prep(struct io_kiocb * req,const struct io_uring_sqe * sqe)904 int io_poll_remove_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
905 {
906 struct io_poll_update *upd = io_kiocb_to_cmd(req, struct io_poll_update);
907 u32 flags;
908
909 if (sqe->buf_index || sqe->splice_fd_in)
910 return -EINVAL;
911 flags = READ_ONCE(sqe->len);
912 if (flags & ~(IORING_POLL_UPDATE_EVENTS | IORING_POLL_UPDATE_USER_DATA |
913 IORING_POLL_ADD_MULTI))
914 return -EINVAL;
915 /* meaningless without update */
916 if (flags == IORING_POLL_ADD_MULTI)
917 return -EINVAL;
918
919 upd->old_user_data = READ_ONCE(sqe->addr);
920 upd->update_events = flags & IORING_POLL_UPDATE_EVENTS;
921 upd->update_user_data = flags & IORING_POLL_UPDATE_USER_DATA;
922
923 upd->new_user_data = READ_ONCE(sqe->off);
924 if (!upd->update_user_data && upd->new_user_data)
925 return -EINVAL;
926 if (upd->update_events)
927 upd->events = io_poll_parse_events(sqe, flags);
928 else if (sqe->poll32_events)
929 return -EINVAL;
930
931 return 0;
932 }
933
io_poll_add_prep(struct io_kiocb * req,const struct io_uring_sqe * sqe)934 int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
935 {
936 struct io_poll *poll = io_kiocb_to_cmd(req, struct io_poll);
937 u32 flags;
938
939 if (sqe->buf_index || sqe->off || sqe->addr)
940 return -EINVAL;
941 flags = READ_ONCE(sqe->len);
942 if (flags & ~IORING_POLL_ADD_MULTI)
943 return -EINVAL;
944 if ((flags & IORING_POLL_ADD_MULTI) && (req->flags & REQ_F_CQE_SKIP))
945 return -EINVAL;
946
947 poll->events = io_poll_parse_events(sqe, flags);
948 return 0;
949 }
950
io_poll_add(struct io_kiocb * req,unsigned int issue_flags)951 int io_poll_add(struct io_kiocb *req, unsigned int issue_flags)
952 {
953 struct io_poll *poll = io_kiocb_to_cmd(req, struct io_poll);
954 struct io_poll_table ipt;
955 int ret;
956
957 ipt.pt._qproc = io_poll_queue_proc;
958
959 /*
960 * If sqpoll or single issuer, there is no contention for ->uring_lock
961 * and we'll end up holding it in tw handlers anyway.
962 */
963 if (req->ctx->flags & (IORING_SETUP_SQPOLL|IORING_SETUP_SINGLE_ISSUER))
964 req->flags |= REQ_F_HASH_LOCKED;
965
966 ret = __io_arm_poll_handler(req, poll, &ipt, poll->events, issue_flags);
967 if (ret > 0) {
968 io_req_set_res(req, ipt.result_mask, 0);
969 return IOU_OK;
970 }
971 return ret ?: IOU_ISSUE_SKIP_COMPLETE;
972 }
973
io_poll_remove(struct io_kiocb * req,unsigned int issue_flags)974 int io_poll_remove(struct io_kiocb *req, unsigned int issue_flags)
975 {
976 struct io_poll_update *poll_update = io_kiocb_to_cmd(req, struct io_poll_update);
977 struct io_cancel_data cd = { .data = poll_update->old_user_data, };
978 struct io_ring_ctx *ctx = req->ctx;
979 struct io_hash_bucket *bucket;
980 struct io_kiocb *preq;
981 int ret2, ret = 0;
982 bool locked;
983
984 preq = io_poll_find(ctx, true, &cd, &ctx->cancel_table, &bucket);
985 ret2 = io_poll_disarm(preq);
986 if (bucket)
987 spin_unlock(&bucket->lock);
988 if (!ret2)
989 goto found;
990 if (ret2 != -ENOENT) {
991 ret = ret2;
992 goto out;
993 }
994
995 io_ring_submit_lock(ctx, issue_flags);
996 preq = io_poll_find(ctx, true, &cd, &ctx->cancel_table_locked, &bucket);
997 ret2 = io_poll_disarm(preq);
998 if (bucket)
999 spin_unlock(&bucket->lock);
1000 io_ring_submit_unlock(ctx, issue_flags);
1001 if (ret2) {
1002 ret = ret2;
1003 goto out;
1004 }
1005
1006 found:
1007 if (WARN_ON_ONCE(preq->opcode != IORING_OP_POLL_ADD)) {
1008 ret = -EFAULT;
1009 goto out;
1010 }
1011
1012 if (poll_update->update_events || poll_update->update_user_data) {
1013 /* only mask one event flags, keep behavior flags */
1014 if (poll_update->update_events) {
1015 struct io_poll *poll = io_kiocb_to_cmd(preq, struct io_poll);
1016
1017 poll->events &= ~0xffff;
1018 poll->events |= poll_update->events & 0xffff;
1019 poll->events |= IO_POLL_UNMASK;
1020 }
1021 if (poll_update->update_user_data)
1022 preq->cqe.user_data = poll_update->new_user_data;
1023
1024 ret2 = io_poll_add(preq, issue_flags);
1025 /* successfully updated, don't complete poll request */
1026 if (!ret2 || ret2 == -EIOCBQUEUED)
1027 goto out;
1028 }
1029
1030 req_set_fail(preq);
1031 io_req_set_res(preq, -ECANCELED, 0);
1032 locked = !(issue_flags & IO_URING_F_UNLOCKED);
1033 io_req_task_complete(preq, &locked);
1034 out:
1035 if (ret < 0) {
1036 req_set_fail(req);
1037 return ret;
1038 }
1039 /* complete update request, we're done with it */
1040 io_req_set_res(req, ret, 0);
1041 return IOU_OK;
1042 }
1043
io_apoll_cache_free(struct io_cache_entry * entry)1044 void io_apoll_cache_free(struct io_cache_entry *entry)
1045 {
1046 kfree(container_of(entry, struct async_poll, cache));
1047 }
1048