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 "napi.h" |
19 | #include "opdef.h" |
20 | #include "kbuf.h" |
21 | #include "poll.h" |
22 | #include "cancel.h" |
23 | |
24 | struct io_poll_update { |
25 | struct file *file; |
26 | u64 old_user_data; |
27 | u64 new_user_data; |
28 | __poll_t events; |
29 | bool update_events; |
30 | bool update_user_data; |
31 | }; |
32 | |
33 | struct io_poll_table { |
34 | struct poll_table_struct pt; |
35 | struct io_kiocb *req; |
36 | int nr_entries; |
37 | int error; |
38 | bool owning; |
39 | /* output value, set only if arm poll returns >0 */ |
40 | __poll_t result_mask; |
41 | }; |
42 | |
43 | #define IO_POLL_CANCEL_FLAG BIT(31) |
44 | #define IO_POLL_RETRY_FLAG BIT(30) |
45 | #define IO_POLL_REF_MASK GENMASK(29, 0) |
46 | |
47 | /* |
48 | * We usually have 1-2 refs taken, 128 is more than enough and we want to |
49 | * maximise the margin between this amount and the moment when it overflows. |
50 | */ |
51 | #define IO_POLL_REF_BIAS 128 |
52 | |
53 | #define IO_WQE_F_DOUBLE 1 |
54 | |
55 | static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, |
56 | void *key); |
57 | |
58 | static inline struct io_kiocb *wqe_to_req(struct wait_queue_entry *wqe) |
59 | { |
60 | unsigned long priv = (unsigned long)wqe->private; |
61 | |
62 | return (struct io_kiocb *)(priv & ~IO_WQE_F_DOUBLE); |
63 | } |
64 | |
65 | static inline bool wqe_is_double(struct wait_queue_entry *wqe) |
66 | { |
67 | unsigned long priv = (unsigned long)wqe->private; |
68 | |
69 | return priv & IO_WQE_F_DOUBLE; |
70 | } |
71 | |
72 | static bool io_poll_get_ownership_slowpath(struct io_kiocb *req) |
73 | { |
74 | int v; |
75 | |
76 | /* |
77 | * poll_refs are already elevated and we don't have much hope for |
78 | * grabbing the ownership. Instead of incrementing set a retry flag |
79 | * to notify the loop that there might have been some change. |
80 | */ |
81 | v = atomic_fetch_or(IO_POLL_RETRY_FLAG, v: &req->poll_refs); |
82 | if (v & IO_POLL_REF_MASK) |
83 | return false; |
84 | return !(atomic_fetch_inc(v: &req->poll_refs) & IO_POLL_REF_MASK); |
85 | } |
86 | |
87 | /* |
88 | * If refs part of ->poll_refs (see IO_POLL_REF_MASK) is 0, it's free. We can |
89 | * bump it and acquire ownership. It's disallowed to modify requests while not |
90 | * owning it, that prevents from races for enqueueing task_work's and b/w |
91 | * arming poll and wakeups. |
92 | */ |
93 | static inline bool io_poll_get_ownership(struct io_kiocb *req) |
94 | { |
95 | if (unlikely(atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS)) |
96 | return io_poll_get_ownership_slowpath(req); |
97 | return !(atomic_fetch_inc(v: &req->poll_refs) & IO_POLL_REF_MASK); |
98 | } |
99 | |
100 | static void io_poll_mark_cancelled(struct io_kiocb *req) |
101 | { |
102 | atomic_or(IO_POLL_CANCEL_FLAG, v: &req->poll_refs); |
103 | } |
104 | |
105 | static struct io_poll *io_poll_get_double(struct io_kiocb *req) |
106 | { |
107 | /* pure poll stashes this in ->async_data, poll driven retry elsewhere */ |
108 | if (req->opcode == IORING_OP_POLL_ADD) |
109 | return req->async_data; |
110 | return req->apoll->double_poll; |
111 | } |
112 | |
113 | static struct io_poll *io_poll_get_single(struct io_kiocb *req) |
114 | { |
115 | if (req->opcode == IORING_OP_POLL_ADD) |
116 | return io_kiocb_to_cmd(req, struct io_poll); |
117 | return &req->apoll->poll; |
118 | } |
119 | |
120 | static void io_poll_req_insert(struct io_kiocb *req) |
121 | { |
122 | struct io_hash_table *table = &req->ctx->cancel_table; |
123 | u32 index = hash_long(req->cqe.user_data, table->hash_bits); |
124 | struct io_hash_bucket *hb = &table->hbs[index]; |
125 | |
126 | spin_lock(lock: &hb->lock); |
127 | hlist_add_head(n: &req->hash_node, h: &hb->list); |
128 | spin_unlock(lock: &hb->lock); |
129 | } |
130 | |
131 | static void io_poll_req_delete(struct io_kiocb *req, struct io_ring_ctx *ctx) |
132 | { |
133 | struct io_hash_table *table = &req->ctx->cancel_table; |
134 | u32 index = hash_long(req->cqe.user_data, table->hash_bits); |
135 | spinlock_t *lock = &table->hbs[index].lock; |
136 | |
137 | spin_lock(lock); |
138 | hash_del(node: &req->hash_node); |
139 | spin_unlock(lock); |
140 | } |
141 | |
142 | static void io_poll_req_insert_locked(struct io_kiocb *req) |
143 | { |
144 | struct io_hash_table *table = &req->ctx->cancel_table_locked; |
145 | u32 index = hash_long(req->cqe.user_data, table->hash_bits); |
146 | |
147 | lockdep_assert_held(&req->ctx->uring_lock); |
148 | |
149 | hlist_add_head(n: &req->hash_node, h: &table->hbs[index].list); |
150 | } |
151 | |
152 | static void io_poll_tw_hash_eject(struct io_kiocb *req, struct io_tw_state *ts) |
153 | { |
154 | struct io_ring_ctx *ctx = req->ctx; |
155 | |
156 | if (req->flags & REQ_F_HASH_LOCKED) { |
157 | /* |
158 | * ->cancel_table_locked is protected by ->uring_lock in |
159 | * contrast to per bucket spinlocks. Likely, tctx_task_work() |
160 | * already grabbed the mutex for us, but there is a chance it |
161 | * failed. |
162 | */ |
163 | io_tw_lock(ctx, ts); |
164 | hash_del(node: &req->hash_node); |
165 | req->flags &= ~REQ_F_HASH_LOCKED; |
166 | } else { |
167 | io_poll_req_delete(req, ctx); |
168 | } |
169 | } |
170 | |
171 | static void io_init_poll_iocb(struct io_poll *poll, __poll_t events) |
172 | { |
173 | poll->head = NULL; |
174 | #define IO_POLL_UNMASK (EPOLLERR|EPOLLHUP|EPOLLNVAL|EPOLLRDHUP) |
175 | /* mask in events that we always want/need */ |
176 | poll->events = events | IO_POLL_UNMASK; |
177 | INIT_LIST_HEAD(list: &poll->wait.entry); |
178 | init_waitqueue_func_entry(wq_entry: &poll->wait, func: io_poll_wake); |
179 | } |
180 | |
181 | static inline void io_poll_remove_entry(struct io_poll *poll) |
182 | { |
183 | struct wait_queue_head *head = smp_load_acquire(&poll->head); |
184 | |
185 | if (head) { |
186 | spin_lock_irq(lock: &head->lock); |
187 | list_del_init(entry: &poll->wait.entry); |
188 | poll->head = NULL; |
189 | spin_unlock_irq(lock: &head->lock); |
190 | } |
191 | } |
192 | |
193 | static void io_poll_remove_entries(struct io_kiocb *req) |
194 | { |
195 | /* |
196 | * Nothing to do if neither of those flags are set. Avoid dipping |
197 | * into the poll/apoll/double cachelines if we can. |
198 | */ |
199 | if (!(req->flags & (REQ_F_SINGLE_POLL | REQ_F_DOUBLE_POLL))) |
200 | return; |
201 | |
202 | /* |
203 | * While we hold the waitqueue lock and the waitqueue is nonempty, |
204 | * wake_up_pollfree() will wait for us. However, taking the waitqueue |
205 | * lock in the first place can race with the waitqueue being freed. |
206 | * |
207 | * We solve this as eventpoll does: by taking advantage of the fact that |
208 | * all users of wake_up_pollfree() will RCU-delay the actual free. If |
209 | * we enter rcu_read_lock() and see that the pointer to the queue is |
210 | * non-NULL, we can then lock it without the memory being freed out from |
211 | * under us. |
212 | * |
213 | * Keep holding rcu_read_lock() as long as we hold the queue lock, in |
214 | * case the caller deletes the entry from the queue, leaving it empty. |
215 | * In that case, only RCU prevents the queue memory from being freed. |
216 | */ |
217 | rcu_read_lock(); |
218 | if (req->flags & REQ_F_SINGLE_POLL) |
219 | io_poll_remove_entry(poll: io_poll_get_single(req)); |
220 | if (req->flags & REQ_F_DOUBLE_POLL) |
221 | io_poll_remove_entry(poll: io_poll_get_double(req)); |
222 | rcu_read_unlock(); |
223 | } |
224 | |
225 | enum { |
226 | IOU_POLL_DONE = 0, |
227 | IOU_POLL_NO_ACTION = 1, |
228 | IOU_POLL_REMOVE_POLL_USE_RES = 2, |
229 | IOU_POLL_REISSUE = 3, |
230 | IOU_POLL_REQUEUE = 4, |
231 | }; |
232 | |
233 | static void __io_poll_execute(struct io_kiocb *req, int mask) |
234 | { |
235 | unsigned flags = 0; |
236 | |
237 | io_req_set_res(req, res: mask, cflags: 0); |
238 | req->io_task_work.func = io_poll_task_func; |
239 | |
240 | trace_io_uring_task_add(req, mask); |
241 | |
242 | if (!(req->flags & REQ_F_POLL_NO_LAZY)) |
243 | flags = IOU_F_TWQ_LAZY_WAKE; |
244 | __io_req_task_work_add(req, flags); |
245 | } |
246 | |
247 | static inline void io_poll_execute(struct io_kiocb *req, int res) |
248 | { |
249 | if (io_poll_get_ownership(req)) |
250 | __io_poll_execute(req, mask: res); |
251 | } |
252 | |
253 | /* |
254 | * All poll tw should go through this. Checks for poll events, manages |
255 | * references, does rewait, etc. |
256 | * |
257 | * Returns a negative error on failure. IOU_POLL_NO_ACTION when no action |
258 | * require, which is either spurious wakeup or multishot CQE is served. |
259 | * IOU_POLL_DONE when it's done with the request, then the mask is stored in |
260 | * req->cqe.res. IOU_POLL_REMOVE_POLL_USE_RES indicates to remove multishot |
261 | * poll and that the result is stored in req->cqe. |
262 | */ |
263 | static int io_poll_check_events(struct io_kiocb *req, struct io_tw_state *ts) |
264 | { |
265 | int v; |
266 | |
267 | /* req->task == current here, checking PF_EXITING is safe */ |
268 | if (unlikely(req->task->flags & PF_EXITING)) |
269 | return -ECANCELED; |
270 | |
271 | do { |
272 | v = atomic_read(v: &req->poll_refs); |
273 | |
274 | if (unlikely(v != 1)) { |
275 | /* tw should be the owner and so have some refs */ |
276 | if (WARN_ON_ONCE(!(v & IO_POLL_REF_MASK))) |
277 | return IOU_POLL_NO_ACTION; |
278 | if (v & IO_POLL_CANCEL_FLAG) |
279 | return -ECANCELED; |
280 | /* |
281 | * cqe.res contains only events of the first wake up |
282 | * and all others are to be lost. Redo vfs_poll() to get |
283 | * up to date state. |
284 | */ |
285 | if ((v & IO_POLL_REF_MASK) != 1) |
286 | req->cqe.res = 0; |
287 | |
288 | if (v & IO_POLL_RETRY_FLAG) { |
289 | req->cqe.res = 0; |
290 | /* |
291 | * We won't find new events that came in between |
292 | * vfs_poll and the ref put unless we clear the |
293 | * flag in advance. |
294 | */ |
295 | atomic_andnot(IO_POLL_RETRY_FLAG, v: &req->poll_refs); |
296 | v &= ~IO_POLL_RETRY_FLAG; |
297 | } |
298 | } |
299 | |
300 | /* the mask was stashed in __io_poll_execute */ |
301 | if (!req->cqe.res) { |
302 | struct poll_table_struct pt = { ._key = req->apoll_events }; |
303 | req->cqe.res = vfs_poll(file: req->file, pt: &pt) & req->apoll_events; |
304 | /* |
305 | * We got woken with a mask, but someone else got to |
306 | * it first. The above vfs_poll() doesn't add us back |
307 | * to the waitqueue, so if we get nothing back, we |
308 | * should be safe and attempt a reissue. |
309 | */ |
310 | if (unlikely(!req->cqe.res)) { |
311 | /* Multishot armed need not reissue */ |
312 | if (!(req->apoll_events & EPOLLONESHOT)) |
313 | continue; |
314 | return IOU_POLL_REISSUE; |
315 | } |
316 | } |
317 | if (req->apoll_events & EPOLLONESHOT) |
318 | return IOU_POLL_DONE; |
319 | |
320 | /* multishot, just fill a CQE and proceed */ |
321 | if (!(req->flags & REQ_F_APOLL_MULTISHOT)) { |
322 | __poll_t mask = mangle_poll(val: req->cqe.res & |
323 | req->apoll_events); |
324 | |
325 | if (!io_fill_cqe_req_aux(req, defer: ts->locked, res: mask, |
326 | IORING_CQE_F_MORE)) { |
327 | io_req_set_res(req, res: mask, cflags: 0); |
328 | return IOU_POLL_REMOVE_POLL_USE_RES; |
329 | } |
330 | } else { |
331 | int ret = io_poll_issue(req, ts); |
332 | if (ret == IOU_STOP_MULTISHOT) |
333 | return IOU_POLL_REMOVE_POLL_USE_RES; |
334 | else if (ret == IOU_REQUEUE) |
335 | return IOU_POLL_REQUEUE; |
336 | if (ret < 0) |
337 | return ret; |
338 | } |
339 | |
340 | /* force the next iteration to vfs_poll() */ |
341 | req->cqe.res = 0; |
342 | |
343 | /* |
344 | * Release all references, retry if someone tried to restart |
345 | * task_work while we were executing it. |
346 | */ |
347 | v &= IO_POLL_REF_MASK; |
348 | } while (atomic_sub_return(i: v, v: &req->poll_refs) & IO_POLL_REF_MASK); |
349 | |
350 | return IOU_POLL_NO_ACTION; |
351 | } |
352 | |
353 | void io_poll_task_func(struct io_kiocb *req, struct io_tw_state *ts) |
354 | { |
355 | int ret; |
356 | |
357 | ret = io_poll_check_events(req, ts); |
358 | if (ret == IOU_POLL_NO_ACTION) { |
359 | return; |
360 | } else if (ret == IOU_POLL_REQUEUE) { |
361 | __io_poll_execute(req, mask: 0); |
362 | return; |
363 | } |
364 | io_poll_remove_entries(req); |
365 | io_poll_tw_hash_eject(req, ts); |
366 | |
367 | if (req->opcode == IORING_OP_POLL_ADD) { |
368 | if (ret == IOU_POLL_DONE) { |
369 | struct io_poll *poll; |
370 | |
371 | poll = io_kiocb_to_cmd(req, struct io_poll); |
372 | req->cqe.res = mangle_poll(val: req->cqe.res & poll->events); |
373 | } else if (ret == IOU_POLL_REISSUE) { |
374 | io_req_task_submit(req, ts); |
375 | return; |
376 | } else if (ret != IOU_POLL_REMOVE_POLL_USE_RES) { |
377 | req->cqe.res = ret; |
378 | req_set_fail(req); |
379 | } |
380 | |
381 | io_req_set_res(req, res: req->cqe.res, cflags: 0); |
382 | io_req_task_complete(req, ts); |
383 | } else { |
384 | io_tw_lock(ctx: req->ctx, ts); |
385 | |
386 | if (ret == IOU_POLL_REMOVE_POLL_USE_RES) |
387 | io_req_task_complete(req, ts); |
388 | else if (ret == IOU_POLL_DONE || ret == IOU_POLL_REISSUE) |
389 | io_req_task_submit(req, ts); |
390 | else |
391 | io_req_defer_failed(req, res: ret); |
392 | } |
393 | } |
394 | |
395 | static void io_poll_cancel_req(struct io_kiocb *req) |
396 | { |
397 | io_poll_mark_cancelled(req); |
398 | /* kick tw, which should complete the request */ |
399 | io_poll_execute(req, res: 0); |
400 | } |
401 | |
402 | #define IO_ASYNC_POLL_COMMON (EPOLLONESHOT | EPOLLPRI) |
403 | |
404 | static __cold int io_pollfree_wake(struct io_kiocb *req, struct io_poll *poll) |
405 | { |
406 | io_poll_mark_cancelled(req); |
407 | /* we have to kick tw in case it's not already */ |
408 | io_poll_execute(req, res: 0); |
409 | |
410 | /* |
411 | * If the waitqueue is being freed early but someone is already |
412 | * holds ownership over it, we have to tear down the request as |
413 | * best we can. That means immediately removing the request from |
414 | * its waitqueue and preventing all further accesses to the |
415 | * waitqueue via the request. |
416 | */ |
417 | list_del_init(entry: &poll->wait.entry); |
418 | |
419 | /* |
420 | * Careful: this *must* be the last step, since as soon |
421 | * as req->head is NULL'ed out, the request can be |
422 | * completed and freed, since aio_poll_complete_work() |
423 | * will no longer need to take the waitqueue lock. |
424 | */ |
425 | smp_store_release(&poll->head, NULL); |
426 | return 1; |
427 | } |
428 | |
429 | static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, |
430 | void *key) |
431 | { |
432 | struct io_kiocb *req = wqe_to_req(wqe: wait); |
433 | struct io_poll *poll = container_of(wait, struct io_poll, wait); |
434 | __poll_t mask = key_to_poll(key); |
435 | |
436 | if (unlikely(mask & POLLFREE)) |
437 | return io_pollfree_wake(req, poll); |
438 | |
439 | /* for instances that support it check for an event match first */ |
440 | if (mask && !(mask & (poll->events & ~IO_ASYNC_POLL_COMMON))) |
441 | return 0; |
442 | |
443 | if (io_poll_get_ownership(req)) { |
444 | /* |
445 | * If we trigger a multishot poll off our own wakeup path, |
446 | * disable multishot as there is a circular dependency between |
447 | * CQ posting and triggering the event. |
448 | */ |
449 | if (mask & EPOLL_URING_WAKE) |
450 | poll->events |= EPOLLONESHOT; |
451 | |
452 | /* optional, saves extra locking for removal in tw handler */ |
453 | if (mask && poll->events & EPOLLONESHOT) { |
454 | list_del_init(entry: &poll->wait.entry); |
455 | poll->head = NULL; |
456 | if (wqe_is_double(wqe: wait)) |
457 | req->flags &= ~REQ_F_DOUBLE_POLL; |
458 | else |
459 | req->flags &= ~REQ_F_SINGLE_POLL; |
460 | } |
461 | __io_poll_execute(req, mask); |
462 | } |
463 | return 1; |
464 | } |
465 | |
466 | /* fails only when polling is already completing by the first entry */ |
467 | static bool io_poll_double_prepare(struct io_kiocb *req) |
468 | { |
469 | struct wait_queue_head *head; |
470 | struct io_poll *poll = io_poll_get_single(req); |
471 | |
472 | /* head is RCU protected, see io_poll_remove_entries() comments */ |
473 | rcu_read_lock(); |
474 | head = smp_load_acquire(&poll->head); |
475 | /* |
476 | * poll arm might not hold ownership and so race for req->flags with |
477 | * io_poll_wake(). There is only one poll entry queued, serialise with |
478 | * it by taking its head lock. As we're still arming the tw hanlder |
479 | * is not going to be run, so there are no races with it. |
480 | */ |
481 | if (head) { |
482 | spin_lock_irq(lock: &head->lock); |
483 | req->flags |= REQ_F_DOUBLE_POLL; |
484 | if (req->opcode == IORING_OP_POLL_ADD) |
485 | req->flags |= REQ_F_ASYNC_DATA; |
486 | spin_unlock_irq(lock: &head->lock); |
487 | } |
488 | rcu_read_unlock(); |
489 | return !!head; |
490 | } |
491 | |
492 | static void __io_queue_proc(struct io_poll *poll, struct io_poll_table *pt, |
493 | struct wait_queue_head *head, |
494 | struct io_poll **poll_ptr) |
495 | { |
496 | struct io_kiocb *req = pt->req; |
497 | unsigned long wqe_private = (unsigned long) req; |
498 | |
499 | /* |
500 | * The file being polled uses multiple waitqueues for poll handling |
501 | * (e.g. one for read, one for write). Setup a separate io_poll |
502 | * if this happens. |
503 | */ |
504 | if (unlikely(pt->nr_entries)) { |
505 | struct io_poll *first = poll; |
506 | |
507 | /* double add on the same waitqueue head, ignore */ |
508 | if (first->head == head) |
509 | return; |
510 | /* already have a 2nd entry, fail a third attempt */ |
511 | if (*poll_ptr) { |
512 | if ((*poll_ptr)->head == head) |
513 | return; |
514 | pt->error = -EINVAL; |
515 | return; |
516 | } |
517 | |
518 | poll = kmalloc(size: sizeof(*poll), GFP_ATOMIC); |
519 | if (!poll) { |
520 | pt->error = -ENOMEM; |
521 | return; |
522 | } |
523 | |
524 | /* mark as double wq entry */ |
525 | wqe_private |= IO_WQE_F_DOUBLE; |
526 | io_init_poll_iocb(poll, events: first->events); |
527 | if (!io_poll_double_prepare(req)) { |
528 | /* the request is completing, just back off */ |
529 | kfree(objp: poll); |
530 | return; |
531 | } |
532 | *poll_ptr = poll; |
533 | } else { |
534 | /* fine to modify, there is no poll queued to race with us */ |
535 | req->flags |= REQ_F_SINGLE_POLL; |
536 | } |
537 | |
538 | pt->nr_entries++; |
539 | poll->head = head; |
540 | poll->wait.private = (void *) wqe_private; |
541 | |
542 | if (poll->events & EPOLLEXCLUSIVE) { |
543 | add_wait_queue_exclusive(wq_head: head, wq_entry: &poll->wait); |
544 | } else { |
545 | add_wait_queue(wq_head: head, wq_entry: &poll->wait); |
546 | } |
547 | } |
548 | |
549 | static void io_poll_queue_proc(struct file *file, struct wait_queue_head *head, |
550 | struct poll_table_struct *p) |
551 | { |
552 | struct io_poll_table *pt = container_of(p, struct io_poll_table, pt); |
553 | struct io_poll *poll = io_kiocb_to_cmd(pt->req, struct io_poll); |
554 | |
555 | __io_queue_proc(poll, pt, head, |
556 | poll_ptr: (struct io_poll **) &pt->req->async_data); |
557 | } |
558 | |
559 | static bool io_poll_can_finish_inline(struct io_kiocb *req, |
560 | struct io_poll_table *pt) |
561 | { |
562 | return pt->owning || io_poll_get_ownership(req); |
563 | } |
564 | |
565 | static void io_poll_add_hash(struct io_kiocb *req) |
566 | { |
567 | if (req->flags & REQ_F_HASH_LOCKED) |
568 | io_poll_req_insert_locked(req); |
569 | else |
570 | io_poll_req_insert(req); |
571 | } |
572 | |
573 | /* |
574 | * Returns 0 when it's handed over for polling. The caller owns the requests if |
575 | * it returns non-zero, but otherwise should not touch it. Negative values |
576 | * contain an error code. When the result is >0, the polling has completed |
577 | * inline and ipt.result_mask is set to the mask. |
578 | */ |
579 | static int __io_arm_poll_handler(struct io_kiocb *req, |
580 | struct io_poll *poll, |
581 | struct io_poll_table *ipt, __poll_t mask, |
582 | unsigned issue_flags) |
583 | { |
584 | INIT_HLIST_NODE(h: &req->hash_node); |
585 | io_init_poll_iocb(poll, events: mask); |
586 | poll->file = req->file; |
587 | req->apoll_events = poll->events; |
588 | |
589 | ipt->pt._key = mask; |
590 | ipt->req = req; |
591 | ipt->error = 0; |
592 | ipt->nr_entries = 0; |
593 | /* |
594 | * Polling is either completed here or via task_work, so if we're in the |
595 | * task context we're naturally serialised with tw by merit of running |
596 | * the same task. When it's io-wq, take the ownership to prevent tw |
597 | * from running. However, when we're in the task context, skip taking |
598 | * it as an optimisation. |
599 | * |
600 | * Note: even though the request won't be completed/freed, without |
601 | * ownership we still can race with io_poll_wake(). |
602 | * io_poll_can_finish_inline() tries to deal with that. |
603 | */ |
604 | ipt->owning = issue_flags & IO_URING_F_UNLOCKED; |
605 | atomic_set(v: &req->poll_refs, i: (int)ipt->owning); |
606 | |
607 | /* io-wq doesn't hold uring_lock */ |
608 | if (issue_flags & IO_URING_F_UNLOCKED) |
609 | req->flags &= ~REQ_F_HASH_LOCKED; |
610 | |
611 | |
612 | /* |
613 | * Exclusive waits may only wake a limited amount of entries |
614 | * rather than all of them, this may interfere with lazy |
615 | * wake if someone does wait(events > 1). Ensure we don't do |
616 | * lazy wake for those, as we need to process each one as they |
617 | * come in. |
618 | */ |
619 | if (poll->events & EPOLLEXCLUSIVE) |
620 | req->flags |= REQ_F_POLL_NO_LAZY; |
621 | |
622 | mask = vfs_poll(file: req->file, pt: &ipt->pt) & poll->events; |
623 | |
624 | if (unlikely(ipt->error || !ipt->nr_entries)) { |
625 | io_poll_remove_entries(req); |
626 | |
627 | if (!io_poll_can_finish_inline(req, pt: ipt)) { |
628 | io_poll_mark_cancelled(req); |
629 | return 0; |
630 | } else if (mask && (poll->events & EPOLLET)) { |
631 | ipt->result_mask = mask; |
632 | return 1; |
633 | } |
634 | return ipt->error ?: -EINVAL; |
635 | } |
636 | |
637 | if (mask && |
638 | ((poll->events & (EPOLLET|EPOLLONESHOT)) == (EPOLLET|EPOLLONESHOT))) { |
639 | if (!io_poll_can_finish_inline(req, pt: ipt)) { |
640 | io_poll_add_hash(req); |
641 | return 0; |
642 | } |
643 | io_poll_remove_entries(req); |
644 | ipt->result_mask = mask; |
645 | /* no one else has access to the req, forget about the ref */ |
646 | return 1; |
647 | } |
648 | |
649 | io_poll_add_hash(req); |
650 | |
651 | if (mask && (poll->events & EPOLLET) && |
652 | io_poll_can_finish_inline(req, pt: ipt)) { |
653 | __io_poll_execute(req, mask); |
654 | return 0; |
655 | } |
656 | io_napi_add(req); |
657 | |
658 | if (ipt->owning) { |
659 | /* |
660 | * Try to release ownership. If we see a change of state, e.g. |
661 | * poll was waken up, queue up a tw, it'll deal with it. |
662 | */ |
663 | if (atomic_cmpxchg(v: &req->poll_refs, old: 1, new: 0) != 1) |
664 | __io_poll_execute(req, mask: 0); |
665 | } |
666 | return 0; |
667 | } |
668 | |
669 | static void io_async_queue_proc(struct file *file, struct wait_queue_head *head, |
670 | struct poll_table_struct *p) |
671 | { |
672 | struct io_poll_table *pt = container_of(p, struct io_poll_table, pt); |
673 | struct async_poll *apoll = pt->req->apoll; |
674 | |
675 | __io_queue_proc(poll: &apoll->poll, pt, head, poll_ptr: &apoll->double_poll); |
676 | } |
677 | |
678 | /* |
679 | * We can't reliably detect loops in repeated poll triggers and issue |
680 | * subsequently failing. But rather than fail these immediately, allow a |
681 | * certain amount of retries before we give up. Given that this condition |
682 | * should _rarely_ trigger even once, we should be fine with a larger value. |
683 | */ |
684 | #define APOLL_MAX_RETRY 128 |
685 | |
686 | static struct async_poll *io_req_alloc_apoll(struct io_kiocb *req, |
687 | unsigned issue_flags) |
688 | { |
689 | struct io_ring_ctx *ctx = req->ctx; |
690 | struct io_cache_entry *entry; |
691 | struct async_poll *apoll; |
692 | |
693 | if (req->flags & REQ_F_POLLED) { |
694 | apoll = req->apoll; |
695 | kfree(objp: apoll->double_poll); |
696 | } else if (!(issue_flags & IO_URING_F_UNLOCKED)) { |
697 | entry = io_alloc_cache_get(cache: &ctx->apoll_cache); |
698 | if (entry == NULL) |
699 | goto alloc_apoll; |
700 | apoll = container_of(entry, struct async_poll, cache); |
701 | apoll->poll.retries = APOLL_MAX_RETRY; |
702 | } else { |
703 | alloc_apoll: |
704 | apoll = kmalloc(size: sizeof(*apoll), GFP_ATOMIC); |
705 | if (unlikely(!apoll)) |
706 | return NULL; |
707 | apoll->poll.retries = APOLL_MAX_RETRY; |
708 | } |
709 | apoll->double_poll = NULL; |
710 | req->apoll = apoll; |
711 | if (unlikely(!--apoll->poll.retries)) |
712 | return NULL; |
713 | return apoll; |
714 | } |
715 | |
716 | int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags) |
717 | { |
718 | const struct io_issue_def *def = &io_issue_defs[req->opcode]; |
719 | struct async_poll *apoll; |
720 | struct io_poll_table ipt; |
721 | __poll_t mask = POLLPRI | POLLERR | EPOLLET; |
722 | int ret; |
723 | |
724 | /* |
725 | * apoll requests already grab the mutex to complete in the tw handler, |
726 | * so removal from the mutex-backed hash is free, use it by default. |
727 | */ |
728 | req->flags |= REQ_F_HASH_LOCKED; |
729 | |
730 | if (!def->pollin && !def->pollout) |
731 | return IO_APOLL_ABORTED; |
732 | if (!io_file_can_poll(req)) |
733 | return IO_APOLL_ABORTED; |
734 | if (!(req->flags & REQ_F_APOLL_MULTISHOT)) |
735 | mask |= EPOLLONESHOT; |
736 | |
737 | if (def->pollin) { |
738 | mask |= EPOLLIN | EPOLLRDNORM; |
739 | |
740 | /* If reading from MSG_ERRQUEUE using recvmsg, ignore POLLIN */ |
741 | if (req->flags & REQ_F_CLEAR_POLLIN) |
742 | mask &= ~EPOLLIN; |
743 | } else { |
744 | mask |= EPOLLOUT | EPOLLWRNORM; |
745 | } |
746 | if (def->poll_exclusive) |
747 | mask |= EPOLLEXCLUSIVE; |
748 | |
749 | apoll = io_req_alloc_apoll(req, issue_flags); |
750 | if (!apoll) |
751 | return IO_APOLL_ABORTED; |
752 | req->flags &= ~(REQ_F_SINGLE_POLL | REQ_F_DOUBLE_POLL); |
753 | req->flags |= REQ_F_POLLED; |
754 | ipt.pt._qproc = io_async_queue_proc; |
755 | |
756 | io_kbuf_recycle(req, issue_flags); |
757 | |
758 | ret = __io_arm_poll_handler(req, poll: &apoll->poll, ipt: &ipt, mask, issue_flags); |
759 | if (ret) |
760 | return ret > 0 ? IO_APOLL_READY : IO_APOLL_ABORTED; |
761 | trace_io_uring_poll_arm(req, mask, events: apoll->poll.events); |
762 | return IO_APOLL_OK; |
763 | } |
764 | |
765 | static __cold bool io_poll_remove_all_table(struct task_struct *tsk, |
766 | struct io_hash_table *table, |
767 | bool cancel_all) |
768 | { |
769 | unsigned nr_buckets = 1U << table->hash_bits; |
770 | struct hlist_node *tmp; |
771 | struct io_kiocb *req; |
772 | bool found = false; |
773 | int i; |
774 | |
775 | for (i = 0; i < nr_buckets; i++) { |
776 | struct io_hash_bucket *hb = &table->hbs[i]; |
777 | |
778 | spin_lock(lock: &hb->lock); |
779 | hlist_for_each_entry_safe(req, tmp, &hb->list, hash_node) { |
780 | if (io_match_task_safe(head: req, task: tsk, cancel_all)) { |
781 | hlist_del_init(n: &req->hash_node); |
782 | io_poll_cancel_req(req); |
783 | found = true; |
784 | } |
785 | } |
786 | spin_unlock(lock: &hb->lock); |
787 | } |
788 | return found; |
789 | } |
790 | |
791 | /* |
792 | * Returns true if we found and killed one or more poll requests |
793 | */ |
794 | __cold bool io_poll_remove_all(struct io_ring_ctx *ctx, struct task_struct *tsk, |
795 | bool cancel_all) |
796 | __must_hold(&ctx->uring_lock) |
797 | { |
798 | bool ret; |
799 | |
800 | ret = io_poll_remove_all_table(tsk, table: &ctx->cancel_table, cancel_all); |
801 | ret |= io_poll_remove_all_table(tsk, table: &ctx->cancel_table_locked, cancel_all); |
802 | return ret; |
803 | } |
804 | |
805 | static struct io_kiocb *io_poll_find(struct io_ring_ctx *ctx, bool poll_only, |
806 | struct io_cancel_data *cd, |
807 | struct io_hash_table *table, |
808 | struct io_hash_bucket **out_bucket) |
809 | { |
810 | struct io_kiocb *req; |
811 | u32 index = hash_long(cd->data, table->hash_bits); |
812 | struct io_hash_bucket *hb = &table->hbs[index]; |
813 | |
814 | *out_bucket = NULL; |
815 | |
816 | spin_lock(lock: &hb->lock); |
817 | hlist_for_each_entry(req, &hb->list, hash_node) { |
818 | if (cd->data != req->cqe.user_data) |
819 | continue; |
820 | if (poll_only && req->opcode != IORING_OP_POLL_ADD) |
821 | continue; |
822 | if (cd->flags & IORING_ASYNC_CANCEL_ALL) { |
823 | if (io_cancel_match_sequence(req, sequence: cd->seq)) |
824 | continue; |
825 | } |
826 | *out_bucket = hb; |
827 | return req; |
828 | } |
829 | spin_unlock(lock: &hb->lock); |
830 | return NULL; |
831 | } |
832 | |
833 | static struct io_kiocb *io_poll_file_find(struct io_ring_ctx *ctx, |
834 | struct io_cancel_data *cd, |
835 | struct io_hash_table *table, |
836 | struct io_hash_bucket **out_bucket) |
837 | { |
838 | unsigned nr_buckets = 1U << table->hash_bits; |
839 | struct io_kiocb *req; |
840 | int i; |
841 | |
842 | *out_bucket = NULL; |
843 | |
844 | for (i = 0; i < nr_buckets; i++) { |
845 | struct io_hash_bucket *hb = &table->hbs[i]; |
846 | |
847 | spin_lock(lock: &hb->lock); |
848 | hlist_for_each_entry(req, &hb->list, hash_node) { |
849 | if (io_cancel_req_match(req, cd)) { |
850 | *out_bucket = hb; |
851 | return req; |
852 | } |
853 | } |
854 | spin_unlock(lock: &hb->lock); |
855 | } |
856 | return NULL; |
857 | } |
858 | |
859 | static int io_poll_disarm(struct io_kiocb *req) |
860 | { |
861 | if (!req) |
862 | return -ENOENT; |
863 | if (!io_poll_get_ownership(req)) |
864 | return -EALREADY; |
865 | io_poll_remove_entries(req); |
866 | hash_del(node: &req->hash_node); |
867 | return 0; |
868 | } |
869 | |
870 | static int __io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd, |
871 | struct io_hash_table *table) |
872 | { |
873 | struct io_hash_bucket *bucket; |
874 | struct io_kiocb *req; |
875 | |
876 | if (cd->flags & (IORING_ASYNC_CANCEL_FD | IORING_ASYNC_CANCEL_OP | |
877 | IORING_ASYNC_CANCEL_ANY)) |
878 | req = io_poll_file_find(ctx, cd, table, out_bucket: &bucket); |
879 | else |
880 | req = io_poll_find(ctx, poll_only: false, cd, table, out_bucket: &bucket); |
881 | |
882 | if (req) |
883 | io_poll_cancel_req(req); |
884 | if (bucket) |
885 | spin_unlock(lock: &bucket->lock); |
886 | return req ? 0 : -ENOENT; |
887 | } |
888 | |
889 | int io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd, |
890 | unsigned issue_flags) |
891 | { |
892 | int ret; |
893 | |
894 | ret = __io_poll_cancel(ctx, cd, table: &ctx->cancel_table); |
895 | if (ret != -ENOENT) |
896 | return ret; |
897 | |
898 | io_ring_submit_lock(ctx, issue_flags); |
899 | ret = __io_poll_cancel(ctx, cd, table: &ctx->cancel_table_locked); |
900 | io_ring_submit_unlock(ctx, issue_flags); |
901 | return ret; |
902 | } |
903 | |
904 | static __poll_t io_poll_parse_events(const struct io_uring_sqe *sqe, |
905 | unsigned int flags) |
906 | { |
907 | u32 events; |
908 | |
909 | events = READ_ONCE(sqe->poll32_events); |
910 | #ifdef __BIG_ENDIAN |
911 | events = swahw32(events); |
912 | #endif |
913 | if (!(flags & IORING_POLL_ADD_MULTI)) |
914 | events |= EPOLLONESHOT; |
915 | if (!(flags & IORING_POLL_ADD_LEVEL)) |
916 | events |= EPOLLET; |
917 | return demangle_poll(val: events) | |
918 | (events & (EPOLLEXCLUSIVE|EPOLLONESHOT|EPOLLET)); |
919 | } |
920 | |
921 | int io_poll_remove_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) |
922 | { |
923 | struct io_poll_update *upd = io_kiocb_to_cmd(req, struct io_poll_update); |
924 | u32 flags; |
925 | |
926 | if (sqe->buf_index || sqe->splice_fd_in) |
927 | return -EINVAL; |
928 | flags = READ_ONCE(sqe->len); |
929 | if (flags & ~(IORING_POLL_UPDATE_EVENTS | IORING_POLL_UPDATE_USER_DATA | |
930 | IORING_POLL_ADD_MULTI)) |
931 | return -EINVAL; |
932 | /* meaningless without update */ |
933 | if (flags == IORING_POLL_ADD_MULTI) |
934 | return -EINVAL; |
935 | |
936 | upd->old_user_data = READ_ONCE(sqe->addr); |
937 | upd->update_events = flags & IORING_POLL_UPDATE_EVENTS; |
938 | upd->update_user_data = flags & IORING_POLL_UPDATE_USER_DATA; |
939 | |
940 | upd->new_user_data = READ_ONCE(sqe->off); |
941 | if (!upd->update_user_data && upd->new_user_data) |
942 | return -EINVAL; |
943 | if (upd->update_events) |
944 | upd->events = io_poll_parse_events(sqe, flags); |
945 | else if (sqe->poll32_events) |
946 | return -EINVAL; |
947 | |
948 | return 0; |
949 | } |
950 | |
951 | int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) |
952 | { |
953 | struct io_poll *poll = io_kiocb_to_cmd(req, struct io_poll); |
954 | u32 flags; |
955 | |
956 | if (sqe->buf_index || sqe->off || sqe->addr) |
957 | return -EINVAL; |
958 | flags = READ_ONCE(sqe->len); |
959 | if (flags & ~IORING_POLL_ADD_MULTI) |
960 | return -EINVAL; |
961 | if ((flags & IORING_POLL_ADD_MULTI) && (req->flags & REQ_F_CQE_SKIP)) |
962 | return -EINVAL; |
963 | |
964 | poll->events = io_poll_parse_events(sqe, flags); |
965 | return 0; |
966 | } |
967 | |
968 | int io_poll_add(struct io_kiocb *req, unsigned int issue_flags) |
969 | { |
970 | struct io_poll *poll = io_kiocb_to_cmd(req, struct io_poll); |
971 | struct io_poll_table ipt; |
972 | int ret; |
973 | |
974 | ipt.pt._qproc = io_poll_queue_proc; |
975 | |
976 | /* |
977 | * If sqpoll or single issuer, there is no contention for ->uring_lock |
978 | * and we'll end up holding it in tw handlers anyway. |
979 | */ |
980 | if (req->ctx->flags & (IORING_SETUP_SQPOLL|IORING_SETUP_SINGLE_ISSUER)) |
981 | req->flags |= REQ_F_HASH_LOCKED; |
982 | |
983 | ret = __io_arm_poll_handler(req, poll, ipt: &ipt, mask: poll->events, issue_flags); |
984 | if (ret > 0) { |
985 | io_req_set_res(req, res: ipt.result_mask, cflags: 0); |
986 | return IOU_OK; |
987 | } |
988 | return ret ?: IOU_ISSUE_SKIP_COMPLETE; |
989 | } |
990 | |
991 | int io_poll_remove(struct io_kiocb *req, unsigned int issue_flags) |
992 | { |
993 | struct io_poll_update *poll_update = io_kiocb_to_cmd(req, struct io_poll_update); |
994 | struct io_ring_ctx *ctx = req->ctx; |
995 | struct io_cancel_data cd = { .ctx = ctx, .data = poll_update->old_user_data, }; |
996 | struct io_hash_bucket *bucket; |
997 | struct io_kiocb *preq; |
998 | int ret2, ret = 0; |
999 | |
1000 | io_ring_submit_lock(ctx, issue_flags); |
1001 | preq = io_poll_find(ctx, poll_only: true, cd: &cd, table: &ctx->cancel_table, out_bucket: &bucket); |
1002 | ret2 = io_poll_disarm(req: preq); |
1003 | if (bucket) |
1004 | spin_unlock(lock: &bucket->lock); |
1005 | if (!ret2) |
1006 | goto found; |
1007 | if (ret2 != -ENOENT) { |
1008 | ret = ret2; |
1009 | goto out; |
1010 | } |
1011 | |
1012 | preq = io_poll_find(ctx, poll_only: true, cd: &cd, table: &ctx->cancel_table_locked, out_bucket: &bucket); |
1013 | ret2 = io_poll_disarm(req: preq); |
1014 | if (bucket) |
1015 | spin_unlock(lock: &bucket->lock); |
1016 | if (ret2) { |
1017 | ret = ret2; |
1018 | goto out; |
1019 | } |
1020 | |
1021 | found: |
1022 | if (WARN_ON_ONCE(preq->opcode != IORING_OP_POLL_ADD)) { |
1023 | ret = -EFAULT; |
1024 | goto out; |
1025 | } |
1026 | |
1027 | if (poll_update->update_events || poll_update->update_user_data) { |
1028 | /* only mask one event flags, keep behavior flags */ |
1029 | if (poll_update->update_events) { |
1030 | struct io_poll *poll = io_kiocb_to_cmd(preq, struct io_poll); |
1031 | |
1032 | poll->events &= ~0xffff; |
1033 | poll->events |= poll_update->events & 0xffff; |
1034 | poll->events |= IO_POLL_UNMASK; |
1035 | } |
1036 | if (poll_update->update_user_data) |
1037 | preq->cqe.user_data = poll_update->new_user_data; |
1038 | |
1039 | ret2 = io_poll_add(req: preq, issue_flags: issue_flags & ~IO_URING_F_UNLOCKED); |
1040 | /* successfully updated, don't complete poll request */ |
1041 | if (!ret2 || ret2 == -EIOCBQUEUED) |
1042 | goto out; |
1043 | } |
1044 | |
1045 | req_set_fail(req: preq); |
1046 | io_req_set_res(req: preq, res: -ECANCELED, cflags: 0); |
1047 | preq->io_task_work.func = io_req_task_complete; |
1048 | io_req_task_work_add(req: preq); |
1049 | out: |
1050 | io_ring_submit_unlock(ctx, issue_flags); |
1051 | if (ret < 0) { |
1052 | req_set_fail(req); |
1053 | return ret; |
1054 | } |
1055 | /* complete update request, we're done with it */ |
1056 | io_req_set_res(req, res: ret, cflags: 0); |
1057 | return IOU_OK; |
1058 | } |
1059 | |
1060 | void io_apoll_cache_free(struct io_cache_entry *entry) |
1061 | { |
1062 | kfree(container_of(entry, struct async_poll, cache)); |
1063 | } |
1064 | |