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 24struct 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 33struct 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 55static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, 56 void *key); 57 58static 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 65static 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 72static 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, &req->poll_refs); 82 if (v & IO_POLL_REF_MASK) 83 return false; 84 return !(atomic_fetch_inc(&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 */ 93static 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(&req->poll_refs) & IO_POLL_REF_MASK); 98} 99 100static void io_poll_mark_cancelled(struct io_kiocb *req) 101{ 102 atomic_or(IO_POLL_CANCEL_FLAG, &req->poll_refs); 103} 104 105static 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 113static 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 120static 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(&hb->lock); 127 hlist_add_head(&req->hash_node, &hb->list); 128 spin_unlock(&hb->lock); 129} 130 131static 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(&req->hash_node); 139 spin_unlock(lock); 140} 141 142static 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(&req->hash_node, &table->hbs[index].list); 150} 151 152static 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(&req->hash_node); 165 req->flags &= ~REQ_F_HASH_LOCKED; 166 } else { 167 io_poll_req_delete(req, ctx); 168 } 169} 170 171static 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(&poll->wait.entry); 178 init_waitqueue_func_entry(&poll->wait, io_poll_wake); 179} 180 181static 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(&head->lock); 187 list_del_init(&poll->wait.entry); 188 poll->head = NULL; 189 spin_unlock_irq(&head->lock); 190 } 191} 192 193static 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(io_poll_get_single(req)); 220 if (req->flags & REQ_F_DOUBLE_POLL) 221 io_poll_remove_entry(io_poll_get_double(req)); 222 rcu_read_unlock(); 223} 224 225enum { 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 233static void __io_poll_execute(struct io_kiocb *req, int mask) 234{ 235 unsigned flags = 0; 236 237 io_req_set_res(req, mask, 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 247static inline void io_poll_execute(struct io_kiocb *req, int res) 248{ 249 if (io_poll_get_ownership(req)) 250 __io_poll_execute(req, 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 */ 263static 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(&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, &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(req->file, &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(req->cqe.res & 323 req->apoll_events); 324 325 if (!io_fill_cqe_req_aux(req, ts->locked, mask, 326 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 io_cache_entry *entry; 691 struct async_poll *apoll; 692 693 if (req->flags & REQ_F_POLLED) { 694 apoll = req->apoll; 695 kfree(apoll->double_poll); 696 } else if (!(issue_flags & IO_URING_F_UNLOCKED)) { 697 entry = io_alloc_cache_get(&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 { 703alloc_apoll: 704 apoll = kmalloc(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 716int 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, &apoll->poll, &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, apoll->poll.events); 762 return IO_APOLL_OK; 763} 764 765static __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(&hb->lock); 779 hlist_for_each_entry_safe(req, tmp, &hb->list, hash_node) { 780 if (io_match_task_safe(req, tsk, cancel_all)) { 781 hlist_del_init(&req->hash_node); 782 io_poll_cancel_req(req); 783 found = true; 784 } 785 } 786 spin_unlock(&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, &ctx->cancel_table, cancel_all); 801 ret |= io_poll_remove_all_table(tsk, &ctx->cancel_table_locked, cancel_all); 802 return ret; 803} 804 805static 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(&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, cd->seq)) 824 continue; 825 } 826 *out_bucket = hb; 827 return req; 828 } 829 spin_unlock(&hb->lock); 830 return NULL; 831} 832 833static 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(&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(&hb->lock); 855 } 856 return NULL; 857} 858 859static 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(&req->hash_node); 867 return 0; 868} 869 870static 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, &bucket); 879 else 880 req = io_poll_find(ctx, false, cd, table, &bucket); 881 882 if (req) 883 io_poll_cancel_req(req); 884 if (bucket) 885 spin_unlock(&bucket->lock); 886 return req ? 0 : -ENOENT; 887} 888 889int 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, &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, &ctx->cancel_table_locked); 900 io_ring_submit_unlock(ctx, issue_flags); 901 return ret; 902} 903 904static __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(events) | 918 (events & (EPOLLEXCLUSIVE|EPOLLONESHOT|EPOLLET)); 919} 920 921int 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 951int 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 968int 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, poll->events, issue_flags); 984 if (ret > 0) { 985 io_req_set_res(req, ipt.result_mask, 0); 986 return IOU_OK; 987 } 988 return ret ?: IOU_ISSUE_SKIP_COMPLETE; 989} 990 991int 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, true, &cd, &ctx->cancel_table, &bucket); 1002 ret2 = io_poll_disarm(preq); 1003 if (bucket) 1004 spin_unlock(&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, true, &cd, &ctx->cancel_table_locked, &bucket); 1013 ret2 = io_poll_disarm(preq); 1014 if (bucket) 1015 spin_unlock(&bucket->lock); 1016 if (ret2) { 1017 ret = ret2; 1018 goto out; 1019 } 1020 1021found: 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(preq, 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(preq); 1046 io_req_set_res(preq, -ECANCELED, 0); 1047 preq->io_task_work.func = io_req_task_complete; 1048 io_req_task_work_add(preq); 1049out: 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, ret, 0); 1057 return IOU_OK; 1058} 1059 1060void io_apoll_cache_free(struct io_cache_entry *entry) 1061{ 1062 kfree(container_of(entry, struct async_poll, cache)); 1063} 1064