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 "alloc_cache.h" 18#include "refs.h" 19#include "napi.h" 20#include "opdef.h" 21#include "kbuf.h" 22#include "poll.h" 23#include "cancel.h" 24 25struct io_poll_update { 26 struct file *file; 27 u64 old_user_data; 28 u64 new_user_data; 29 __poll_t events; 30 bool update_events; 31 bool update_user_data; 32}; 33 34struct io_poll_table { 35 struct poll_table_struct pt; 36 struct io_kiocb *req; 37 int nr_entries; 38 int error; 39 bool owning; 40 /* output value, set only if arm poll returns >0 */ 41 __poll_t result_mask; 42}; 43 44#define IO_POLL_CANCEL_FLAG BIT(31) 45#define IO_POLL_RETRY_FLAG BIT(30) 46#define IO_POLL_REF_MASK GENMASK(29, 0) 47 48/* 49 * We usually have 1-2 refs taken, 128 is more than enough and we want to 50 * maximise the margin between this amount and the moment when it overflows. 51 */ 52#define IO_POLL_REF_BIAS 128 53 54#define IO_WQE_F_DOUBLE 1 55 56static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, 57 void *key); 58 59static inline struct io_kiocb *wqe_to_req(struct wait_queue_entry *wqe) 60{ 61 unsigned long priv = (unsigned long)wqe->private; 62 63 return (struct io_kiocb *)(priv & ~IO_WQE_F_DOUBLE); 64} 65 66static inline bool wqe_is_double(struct wait_queue_entry *wqe) 67{ 68 unsigned long priv = (unsigned long)wqe->private; 69 70 return priv & IO_WQE_F_DOUBLE; 71} 72 73static bool io_poll_get_ownership_slowpath(struct io_kiocb *req) 74{ 75 int v; 76 77 /* 78 * poll_refs are already elevated and we don't have much hope for 79 * grabbing the ownership. Instead of incrementing set a retry flag 80 * to notify the loop that there might have been some change. 81 */ 82 v = atomic_fetch_or(IO_POLL_RETRY_FLAG, &req->poll_refs); 83 if (v & IO_POLL_REF_MASK) 84 return false; 85 return !(atomic_fetch_inc(&req->poll_refs) & IO_POLL_REF_MASK); 86} 87 88/* 89 * If refs part of ->poll_refs (see IO_POLL_REF_MASK) is 0, it's free. We can 90 * bump it and acquire ownership. It's disallowed to modify requests while not 91 * owning it, that prevents from races for enqueueing task_work's and b/w 92 * arming poll and wakeups. 93 */ 94static inline bool io_poll_get_ownership(struct io_kiocb *req) 95{ 96 if (unlikely(atomic_read(&req->poll_refs) >= IO_POLL_REF_BIAS)) 97 return io_poll_get_ownership_slowpath(req); 98 return !(atomic_fetch_inc(&req->poll_refs) & IO_POLL_REF_MASK); 99} 100 101static void io_poll_mark_cancelled(struct io_kiocb *req) 102{ 103 atomic_or(IO_POLL_CANCEL_FLAG, &req->poll_refs); 104} 105 106static struct io_poll *io_poll_get_double(struct io_kiocb *req) 107{ 108 /* pure poll stashes this in ->async_data, poll driven retry elsewhere */ 109 if (req->opcode == IORING_OP_POLL_ADD) 110 return req->async_data; 111 return req->apoll->double_poll; 112} 113 114static struct io_poll *io_poll_get_single(struct io_kiocb *req) 115{ 116 if (req->opcode == IORING_OP_POLL_ADD) 117 return io_kiocb_to_cmd(req, struct io_poll); 118 return &req->apoll->poll; 119} 120 121static void io_poll_req_insert(struct io_kiocb *req) 122{ 123 struct io_hash_table *table = &req->ctx->cancel_table; 124 u32 index = hash_long(req->cqe.user_data, table->hash_bits); 125 struct io_hash_bucket *hb = &table->hbs[index]; 126 127 spin_lock(&hb->lock); 128 hlist_add_head(&req->hash_node, &hb->list); 129 spin_unlock(&hb->lock); 130} 131 132static void io_poll_req_delete(struct io_kiocb *req, struct io_ring_ctx *ctx) 133{ 134 struct io_hash_table *table = &req->ctx->cancel_table; 135 u32 index = hash_long(req->cqe.user_data, table->hash_bits); 136 spinlock_t *lock = &table->hbs[index].lock; 137 138 spin_lock(lock); 139 hash_del(&req->hash_node); 140 spin_unlock(lock); 141} 142 143static void io_poll_req_insert_locked(struct io_kiocb *req) 144{ 145 struct io_hash_table *table = &req->ctx->cancel_table_locked; 146 u32 index = hash_long(req->cqe.user_data, table->hash_bits); 147 148 lockdep_assert_held(&req->ctx->uring_lock); 149 150 hlist_add_head(&req->hash_node, &table->hbs[index].list); 151} 152 153static void io_poll_tw_hash_eject(struct io_kiocb *req, struct io_tw_state *ts) 154{ 155 struct io_ring_ctx *ctx = req->ctx; 156 157 if (req->flags & REQ_F_HASH_LOCKED) { 158 /* 159 * ->cancel_table_locked is protected by ->uring_lock in 160 * contrast to per bucket spinlocks. Likely, tctx_task_work() 161 * already grabbed the mutex for us, but there is a chance it 162 * failed. 163 */ 164 io_tw_lock(ctx, ts); 165 hash_del(&req->hash_node); 166 req->flags &= ~REQ_F_HASH_LOCKED; 167 } else { 168 io_poll_req_delete(req, ctx); 169 } 170} 171 172static void io_init_poll_iocb(struct io_poll *poll, __poll_t events) 173{ 174 poll->head = NULL; 175#define IO_POLL_UNMASK (EPOLLERR|EPOLLHUP|EPOLLNVAL|EPOLLRDHUP) 176 /* mask in events that we always want/need */ 177 poll->events = events | IO_POLL_UNMASK; 178 INIT_LIST_HEAD(&poll->wait.entry); 179 init_waitqueue_func_entry(&poll->wait, io_poll_wake); 180} 181 182static inline void io_poll_remove_entry(struct io_poll *poll) 183{ 184 struct wait_queue_head *head = smp_load_acquire(&poll->head); 185 186 if (head) { 187 spin_lock_irq(&head->lock); 188 list_del_init(&poll->wait.entry); 189 poll->head = NULL; 190 spin_unlock_irq(&head->lock); 191 } 192} 193 194static void io_poll_remove_entries(struct io_kiocb *req) 195{ 196 /* 197 * Nothing to do if neither of those flags are set. Avoid dipping 198 * into the poll/apoll/double cachelines if we can. 199 */ 200 if (!(req->flags & (REQ_F_SINGLE_POLL | REQ_F_DOUBLE_POLL))) 201 return; 202 203 /* 204 * While we hold the waitqueue lock and the waitqueue is nonempty, 205 * wake_up_pollfree() will wait for us. However, taking the waitqueue 206 * lock in the first place can race with the waitqueue being freed. 207 * 208 * We solve this as eventpoll does: by taking advantage of the fact that 209 * all users of wake_up_pollfree() will RCU-delay the actual free. If 210 * we enter rcu_read_lock() and see that the pointer to the queue is 211 * non-NULL, we can then lock it without the memory being freed out from 212 * under us. 213 * 214 * Keep holding rcu_read_lock() as long as we hold the queue lock, in 215 * case the caller deletes the entry from the queue, leaving it empty. 216 * In that case, only RCU prevents the queue memory from being freed. 217 */ 218 rcu_read_lock(); 219 if (req->flags & REQ_F_SINGLE_POLL) 220 io_poll_remove_entry(io_poll_get_single(req)); 221 if (req->flags & REQ_F_DOUBLE_POLL) 222 io_poll_remove_entry(io_poll_get_double(req)); 223 rcu_read_unlock(); 224} 225 226enum { 227 IOU_POLL_DONE = 0, 228 IOU_POLL_NO_ACTION = 1, 229 IOU_POLL_REMOVE_POLL_USE_RES = 2, 230 IOU_POLL_REISSUE = 3, 231 IOU_POLL_REQUEUE = 4, 232}; 233 234static void __io_poll_execute(struct io_kiocb *req, int mask) 235{ 236 unsigned flags = 0; 237 238 io_req_set_res(req, mask, 0); 239 req->io_task_work.func = io_poll_task_func; 240 241 trace_io_uring_task_add(req, mask); 242 243 if (!(req->flags & REQ_F_POLL_NO_LAZY)) 244 flags = IOU_F_TWQ_LAZY_WAKE; 245 __io_req_task_work_add(req, flags); 246} 247 248static inline void io_poll_execute(struct io_kiocb *req, int res) 249{ 250 if (io_poll_get_ownership(req)) 251 __io_poll_execute(req, res); 252} 253 254/* 255 * All poll tw should go through this. Checks for poll events, manages 256 * references, does rewait, etc. 257 * 258 * Returns a negative error on failure. IOU_POLL_NO_ACTION when no action 259 * require, which is either spurious wakeup or multishot CQE is served. 260 * IOU_POLL_DONE when it's done with the request, then the mask is stored in 261 * req->cqe.res. IOU_POLL_REMOVE_POLL_USE_RES indicates to remove multishot 262 * poll and that the result is stored in req->cqe. 263 */ 264static int io_poll_check_events(struct io_kiocb *req, struct io_tw_state *ts) 265{ 266 int v; 267 268 /* req->task == current here, checking PF_EXITING is safe */ 269 if (unlikely(req->task->flags & PF_EXITING)) 270 return -ECANCELED; 271 272 do { 273 v = atomic_read(&req->poll_refs); 274 275 if (unlikely(v != 1)) { 276 /* tw should be the owner and so have some refs */ 277 if (WARN_ON_ONCE(!(v & IO_POLL_REF_MASK))) 278 return IOU_POLL_NO_ACTION; 279 if (v & IO_POLL_CANCEL_FLAG) 280 return -ECANCELED; 281 /* 282 * cqe.res contains only events of the first wake up 283 * and all others are to be lost. Redo vfs_poll() to get 284 * up to date state. 285 */ 286 if ((v & IO_POLL_REF_MASK) != 1) 287 req->cqe.res = 0; 288 289 if (v & IO_POLL_RETRY_FLAG) { 290 req->cqe.res = 0; 291 /* 292 * We won't find new events that came in between 293 * vfs_poll and the ref put unless we clear the 294 * flag in advance. 295 */ 296 atomic_andnot(IO_POLL_RETRY_FLAG, &req->poll_refs); 297 v &= ~IO_POLL_RETRY_FLAG; 298 } 299 } 300 301 /* the mask was stashed in __io_poll_execute */ 302 if (!req->cqe.res) { 303 struct poll_table_struct pt = { ._key = req->apoll_events }; 304 req->cqe.res = vfs_poll(req->file, &pt) & req->apoll_events; 305 /* 306 * We got woken with a mask, but someone else got to 307 * it first. The above vfs_poll() doesn't add us back 308 * to the waitqueue, so if we get nothing back, we 309 * should be safe and attempt a reissue. 310 */ 311 if (unlikely(!req->cqe.res)) { 312 /* Multishot armed need not reissue */ 313 if (!(req->apoll_events & EPOLLONESHOT)) 314 continue; 315 return IOU_POLL_REISSUE; 316 } 317 } 318 if (req->apoll_events & EPOLLONESHOT) 319 return IOU_POLL_DONE; 320 321 /* multishot, just fill a CQE and proceed */ 322 if (!(req->flags & REQ_F_APOLL_MULTISHOT)) { 323 __poll_t mask = mangle_poll(req->cqe.res & 324 req->apoll_events); 325 326 if (!io_req_post_cqe(req, mask, IORING_CQE_F_MORE)) { 327 io_req_set_res(req, mask, 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(v, &req->poll_refs) & IO_POLL_REF_MASK); 349 350 return IOU_POLL_NO_ACTION; 351} 352 353void 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, 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(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, req->cqe.res, 0); 382 io_req_task_complete(req, ts); 383 } else { 384 io_tw_lock(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, ret); 392 } 393} 394 395static 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, 0); 400} 401 402#define IO_ASYNC_POLL_COMMON (EPOLLONESHOT | EPOLLPRI) 403 404static __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, 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(&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 429static 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(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(&poll->wait.entry); 455 poll->head = NULL; 456 if (wqe_is_double(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 */ 467static 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(&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(&head->lock); 487 } 488 rcu_read_unlock(); 489 return !!head; 490} 491 492static 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(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, first->events); 527 if (!io_poll_double_prepare(req)) { 528 /* the request is completing, just back off */ 529 kfree(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(head, &poll->wait); 544 } else { 545 add_wait_queue(head, &poll->wait); 546 } 547} 548 549static 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 (struct io_poll **) &pt->req->async_data); 557} 558 559static 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 565static 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 */ 579static 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(&req->hash_node); 585 io_init_poll_iocb(poll, 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(&req->poll_refs, (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(req->file, &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, 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, 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, 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(&req->poll_refs, 1, 0) != 1) 664 __io_poll_execute(req, 0); 665 } 666 return 0; 667} 668 669static 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(&apoll->poll, pt, head, &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 686static 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 async_poll *apoll; 691 692 if (req->flags & REQ_F_POLLED) { 693 apoll = req->apoll; 694 kfree(apoll->double_poll); 695 } else if (!(issue_flags & IO_URING_F_UNLOCKED)) { 696 apoll = io_alloc_cache_get(&ctx->apoll_cache); 697 if (!apoll) 698 goto alloc_apoll; 699 apoll->poll.retries = APOLL_MAX_RETRY; 700 } else { 701alloc_apoll: 702 apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC); 703 if (unlikely(!apoll)) 704 return NULL; 705 apoll->poll.retries = APOLL_MAX_RETRY; 706 } 707 apoll->double_poll = NULL; 708 req->apoll = apoll; 709 if (unlikely(!--apoll->poll.retries)) 710 return NULL; 711 return apoll; 712} 713 714int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags) 715{ 716 const struct io_issue_def *def = &io_issue_defs[req->opcode]; 717 struct async_poll *apoll; 718 struct io_poll_table ipt; 719 __poll_t mask = POLLPRI | POLLERR | EPOLLET; 720 int ret; 721 722 /* 723 * apoll requests already grab the mutex to complete in the tw handler, 724 * so removal from the mutex-backed hash is free, use it by default. 725 */ 726 req->flags |= REQ_F_HASH_LOCKED; 727 728 if (!def->pollin && !def->pollout) 729 return IO_APOLL_ABORTED; 730 if (!io_file_can_poll(req)) 731 return IO_APOLL_ABORTED; 732 if (!(req->flags & REQ_F_APOLL_MULTISHOT)) 733 mask |= EPOLLONESHOT; 734 735 if (def->pollin) { 736 mask |= EPOLLIN | EPOLLRDNORM; 737 738 /* If reading from MSG_ERRQUEUE using recvmsg, ignore POLLIN */ 739 if (req->flags & REQ_F_CLEAR_POLLIN) 740 mask &= ~EPOLLIN; 741 } else { 742 mask |= EPOLLOUT | EPOLLWRNORM; 743 } 744 if (def->poll_exclusive) 745 mask |= EPOLLEXCLUSIVE; 746 747 apoll = io_req_alloc_apoll(req, issue_flags); 748 if (!apoll) 749 return IO_APOLL_ABORTED; 750 req->flags &= ~(REQ_F_SINGLE_POLL | REQ_F_DOUBLE_POLL); 751 req->flags |= REQ_F_POLLED; 752 ipt.pt._qproc = io_async_queue_proc; 753 754 io_kbuf_recycle(req, issue_flags); 755 756 ret = __io_arm_poll_handler(req, &apoll->poll, &ipt, mask, issue_flags); 757 if (ret) 758 return ret > 0 ? IO_APOLL_READY : IO_APOLL_ABORTED; 759 trace_io_uring_poll_arm(req, mask, apoll->poll.events); 760 return IO_APOLL_OK; 761} 762 763static __cold bool io_poll_remove_all_table(struct task_struct *tsk, 764 struct io_hash_table *table, 765 bool cancel_all) 766{ 767 unsigned nr_buckets = 1U << table->hash_bits; 768 struct hlist_node *tmp; 769 struct io_kiocb *req; 770 bool found = false; 771 int i; 772 773 for (i = 0; i < nr_buckets; i++) { 774 struct io_hash_bucket *hb = &table->hbs[i]; 775 776 spin_lock(&hb->lock); 777 hlist_for_each_entry_safe(req, tmp, &hb->list, hash_node) { 778 if (io_match_task_safe(req, tsk, cancel_all)) { 779 hlist_del_init(&req->hash_node); 780 io_poll_cancel_req(req); 781 found = true; 782 } 783 } 784 spin_unlock(&hb->lock); 785 } 786 return found; 787} 788 789/* 790 * Returns true if we found and killed one or more poll requests 791 */ 792__cold bool io_poll_remove_all(struct io_ring_ctx *ctx, struct task_struct *tsk, 793 bool cancel_all) 794 __must_hold(&ctx->uring_lock) 795{ 796 bool ret; 797 798 ret = io_poll_remove_all_table(tsk, &ctx->cancel_table, cancel_all); 799 ret |= io_poll_remove_all_table(tsk, &ctx->cancel_table_locked, cancel_all); 800 return ret; 801} 802 803static struct io_kiocb *io_poll_find(struct io_ring_ctx *ctx, bool poll_only, 804 struct io_cancel_data *cd, 805 struct io_hash_table *table, 806 struct io_hash_bucket **out_bucket) 807{ 808 struct io_kiocb *req; 809 u32 index = hash_long(cd->data, table->hash_bits); 810 struct io_hash_bucket *hb = &table->hbs[index]; 811 812 *out_bucket = NULL; 813 814 spin_lock(&hb->lock); 815 hlist_for_each_entry(req, &hb->list, hash_node) { 816 if (cd->data != req->cqe.user_data) 817 continue; 818 if (poll_only && req->opcode != IORING_OP_POLL_ADD) 819 continue; 820 if (cd->flags & IORING_ASYNC_CANCEL_ALL) { 821 if (io_cancel_match_sequence(req, cd->seq)) 822 continue; 823 } 824 *out_bucket = hb; 825 return req; 826 } 827 spin_unlock(&hb->lock); 828 return NULL; 829} 830 831static struct io_kiocb *io_poll_file_find(struct io_ring_ctx *ctx, 832 struct io_cancel_data *cd, 833 struct io_hash_table *table, 834 struct io_hash_bucket **out_bucket) 835{ 836 unsigned nr_buckets = 1U << table->hash_bits; 837 struct io_kiocb *req; 838 int i; 839 840 *out_bucket = NULL; 841 842 for (i = 0; i < nr_buckets; i++) { 843 struct io_hash_bucket *hb = &table->hbs[i]; 844 845 spin_lock(&hb->lock); 846 hlist_for_each_entry(req, &hb->list, hash_node) { 847 if (io_cancel_req_match(req, cd)) { 848 *out_bucket = hb; 849 return req; 850 } 851 } 852 spin_unlock(&hb->lock); 853 } 854 return NULL; 855} 856 857static int io_poll_disarm(struct io_kiocb *req) 858{ 859 if (!req) 860 return -ENOENT; 861 if (!io_poll_get_ownership(req)) 862 return -EALREADY; 863 io_poll_remove_entries(req); 864 hash_del(&req->hash_node); 865 return 0; 866} 867 868static int __io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd, 869 struct io_hash_table *table) 870{ 871 struct io_hash_bucket *bucket; 872 struct io_kiocb *req; 873 874 if (cd->flags & (IORING_ASYNC_CANCEL_FD | IORING_ASYNC_CANCEL_OP | 875 IORING_ASYNC_CANCEL_ANY)) 876 req = io_poll_file_find(ctx, cd, table, &bucket); 877 else 878 req = io_poll_find(ctx, false, cd, table, &bucket); 879 880 if (req) 881 io_poll_cancel_req(req); 882 if (bucket) 883 spin_unlock(&bucket->lock); 884 return req ? 0 : -ENOENT; 885} 886 887int io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd, 888 unsigned issue_flags) 889{ 890 int ret; 891 892 ret = __io_poll_cancel(ctx, cd, &ctx->cancel_table); 893 if (ret != -ENOENT) 894 return ret; 895 896 io_ring_submit_lock(ctx, issue_flags); 897 ret = __io_poll_cancel(ctx, cd, &ctx->cancel_table_locked); 898 io_ring_submit_unlock(ctx, issue_flags); 899 return ret; 900} 901 902static __poll_t io_poll_parse_events(const struct io_uring_sqe *sqe, 903 unsigned int flags) 904{ 905 u32 events; 906 907 events = READ_ONCE(sqe->poll32_events); 908#ifdef __BIG_ENDIAN 909 events = swahw32(events); 910#endif 911 if (!(flags & IORING_POLL_ADD_MULTI)) 912 events |= EPOLLONESHOT; 913 if (!(flags & IORING_POLL_ADD_LEVEL)) 914 events |= EPOLLET; 915 return demangle_poll(events) | 916 (events & (EPOLLEXCLUSIVE|EPOLLONESHOT|EPOLLET)); 917} 918 919int io_poll_remove_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) 920{ 921 struct io_poll_update *upd = io_kiocb_to_cmd(req, struct io_poll_update); 922 u32 flags; 923 924 if (sqe->buf_index || sqe->splice_fd_in) 925 return -EINVAL; 926 flags = READ_ONCE(sqe->len); 927 if (flags & ~(IORING_POLL_UPDATE_EVENTS | IORING_POLL_UPDATE_USER_DATA | 928 IORING_POLL_ADD_MULTI)) 929 return -EINVAL; 930 /* meaningless without update */ 931 if (flags == IORING_POLL_ADD_MULTI) 932 return -EINVAL; 933 934 upd->old_user_data = READ_ONCE(sqe->addr); 935 upd->update_events = flags & IORING_POLL_UPDATE_EVENTS; 936 upd->update_user_data = flags & IORING_POLL_UPDATE_USER_DATA; 937 938 upd->new_user_data = READ_ONCE(sqe->off); 939 if (!upd->update_user_data && upd->new_user_data) 940 return -EINVAL; 941 if (upd->update_events) 942 upd->events = io_poll_parse_events(sqe, flags); 943 else if (sqe->poll32_events) 944 return -EINVAL; 945 946 return 0; 947} 948 949int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) 950{ 951 struct io_poll *poll = io_kiocb_to_cmd(req, struct io_poll); 952 u32 flags; 953 954 if (sqe->buf_index || sqe->off || sqe->addr) 955 return -EINVAL; 956 flags = READ_ONCE(sqe->len); 957 if (flags & ~IORING_POLL_ADD_MULTI) 958 return -EINVAL; 959 if ((flags & IORING_POLL_ADD_MULTI) && (req->flags & REQ_F_CQE_SKIP)) 960 return -EINVAL; 961 962 poll->events = io_poll_parse_events(sqe, flags); 963 return 0; 964} 965 966int io_poll_add(struct io_kiocb *req, unsigned int issue_flags) 967{ 968 struct io_poll *poll = io_kiocb_to_cmd(req, struct io_poll); 969 struct io_poll_table ipt; 970 int ret; 971 972 ipt.pt._qproc = io_poll_queue_proc; 973 974 /* 975 * If sqpoll or single issuer, there is no contention for ->uring_lock 976 * and we'll end up holding it in tw handlers anyway. 977 */ 978 if (req->ctx->flags & (IORING_SETUP_SQPOLL|IORING_SETUP_SINGLE_ISSUER)) 979 req->flags |= REQ_F_HASH_LOCKED; 980 981 ret = __io_arm_poll_handler(req, poll, &ipt, poll->events, issue_flags); 982 if (ret > 0) { 983 io_req_set_res(req, ipt.result_mask, 0); 984 return IOU_OK; 985 } 986 return ret ?: IOU_ISSUE_SKIP_COMPLETE; 987} 988 989int io_poll_remove(struct io_kiocb *req, unsigned int issue_flags) 990{ 991 struct io_poll_update *poll_update = io_kiocb_to_cmd(req, struct io_poll_update); 992 struct io_ring_ctx *ctx = req->ctx; 993 struct io_cancel_data cd = { .ctx = ctx, .data = poll_update->old_user_data, }; 994 struct io_hash_bucket *bucket; 995 struct io_kiocb *preq; 996 int ret2, ret = 0; 997 998 io_ring_submit_lock(ctx, issue_flags); 999 preq = io_poll_find(ctx, true, &cd, &ctx->cancel_table, &bucket); 1000 ret2 = io_poll_disarm(preq); 1001 if (bucket) 1002 spin_unlock(&bucket->lock); 1003 if (!ret2) 1004 goto found; 1005 if (ret2 != -ENOENT) { 1006 ret = ret2; 1007 goto out; 1008 } 1009 1010 preq = io_poll_find(ctx, true, &cd, &ctx->cancel_table_locked, &bucket); 1011 ret2 = io_poll_disarm(preq); 1012 if (bucket) 1013 spin_unlock(&bucket->lock); 1014 if (ret2) { 1015 ret = ret2; 1016 goto out; 1017 } 1018 1019found: 1020 if (WARN_ON_ONCE(preq->opcode != IORING_OP_POLL_ADD)) { 1021 ret = -EFAULT; 1022 goto out; 1023 } 1024 1025 if (poll_update->update_events || poll_update->update_user_data) { 1026 /* only mask one event flags, keep behavior flags */ 1027 if (poll_update->update_events) { 1028 struct io_poll *poll = io_kiocb_to_cmd(preq, struct io_poll); 1029 1030 poll->events &= ~0xffff; 1031 poll->events |= poll_update->events & 0xffff; 1032 poll->events |= IO_POLL_UNMASK; 1033 } 1034 if (poll_update->update_user_data) 1035 preq->cqe.user_data = poll_update->new_user_data; 1036 1037 ret2 = io_poll_add(preq, issue_flags & ~IO_URING_F_UNLOCKED); 1038 /* successfully updated, don't complete poll request */ 1039 if (!ret2 || ret2 == -EIOCBQUEUED) 1040 goto out; 1041 } 1042 1043 req_set_fail(preq); 1044 io_req_set_res(preq, -ECANCELED, 0); 1045 preq->io_task_work.func = io_req_task_complete; 1046 io_req_task_work_add(preq); 1047out: 1048 io_ring_submit_unlock(ctx, issue_flags); 1049 if (ret < 0) { 1050 req_set_fail(req); 1051 return ret; 1052 } 1053 /* complete update request, we're done with it */ 1054 io_req_set_res(req, ret, 0); 1055 return IOU_OK; 1056} 1057