io_uring/rw.c

   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/blk-mq.h>
   7 #include <linux/mm.h>
   8 #include <linux/slab.h>
   9 #include <linux/fsnotify.h>
  10 #include <linux/poll.h>
  11 #include <linux/nospec.h>
  12 #include <linux/compat.h>
  13 #include <linux/io_uring/cmd.h>
  14 #include <linux/indirect_call_wrapper.h>
  15
  16 #include <uapi/linux/io_uring.h>
  17
  18 #include "io_uring.h"
  19 #include "opdef.h"
  20 #include "kbuf.h"
  21 #include "rsrc.h"
  22 #include "poll.h"
  23 #include "rw.h"
  24
  25 struct io_rw {
  26         /* NOTE: kiocb has the file as the first member, so don't do it here */
  27         struct kiocb                    kiocb;
  28         u64                             addr;
  29         u32                             len;
  30         rwf_t                           flags;
  31 };
  32
  33 static inline bool io_file_supports_nowait(struct io_kiocb *req)
  34 {
  35         return req->flags & REQ_F_SUPPORT_NOWAIT;
  36 }
  37
  38 #ifdef CONFIG_COMPAT
  39 static int io_iov_compat_buffer_select_prep(struct io_rw *rw)
  40 {
  41         struct compat_iovec __user *uiov;
  42         compat_ssize_t clen;
  43
  44         uiov = u64_to_user_ptr(rw->addr);
  45         if (!access_ok(uiov, sizeof(*uiov)))
  46                 return -EFAULT;
  47         if (__get_user(clen, &uiov->iov_len))
  48                 return -EFAULT;
  49         if (clen < 0)
  50                 return -EINVAL;
  51
  52         rw->len = clen;
  53         return 0;
  54 }
  55 #endif
  56
  57 static int io_iov_buffer_select_prep(struct io_kiocb *req)
  58 {
  59         struct iovec __user *uiov;
  60         struct iovec iov;
  61         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
  62
  63         if (rw->len != 1)
  64                 return -EINVAL;
  65
  66 #ifdef CONFIG_COMPAT
  67         if (req->ctx->compat)
  68                 return io_iov_compat_buffer_select_prep(rw);
  69 #endif
  70
  71         uiov = u64_to_user_ptr(rw->addr);
  72         if (copy_from_user(&iov, uiov, sizeof(*uiov)))
  73                 return -EFAULT;
  74         rw->len = iov.iov_len;
  75         return 0;
  76 }
  77
  78 int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
  79 {
  80         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
  81         unsigned ioprio;
  82         int ret;
  83
  84         rw->kiocb.ki_pos = READ_ONCE(sqe->off);
  85         /* used for fixed read/write too - just read unconditionally */
  86         req->buf_index = READ_ONCE(sqe->buf_index);
  87
  88         ioprio = READ_ONCE(sqe->ioprio);
  89         if (ioprio) {
  90                 ret = ioprio_check_cap(ioprio);
  91                 if (ret)
  92                         return ret;
  93
  94                 rw->kiocb.ki_ioprio = ioprio;
  95         } else {
  96                 rw->kiocb.ki_ioprio = get_current_ioprio();
  97         }
  98         rw->kiocb.dio_complete = NULL;
  99
 100         rw->addr = READ_ONCE(sqe->addr);
 101         rw->len = READ_ONCE(sqe->len);
 102         rw->flags = READ_ONCE(sqe->rw_flags);
 103         return 0;
 104 }
 105
 106 int io_prep_rwv(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 107 {
 108         int ret;
 109
 110         ret = io_prep_rw(req, sqe);
 111         if (unlikely(ret))
 112                 return ret;
 113
 114         /*
 115          * Have to do this validation here, as this is in io_read() rw->len
 116          * might have chanaged due to buffer selection
 117          */
 118         if (req->flags & REQ_F_BUFFER_SELECT)
 119                 return io_iov_buffer_select_prep(req);
 120
 121         return 0;
 122 }
 123
 124 int io_prep_rw_fixed(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 125 {
 126         struct io_ring_ctx *ctx = req->ctx;
 127         u16 index;
 128         int ret;
 129
 130         ret = io_prep_rw(req, sqe);
 131         if (unlikely(ret))
 132                 return ret;
 133
 134         if (unlikely(req->buf_index >= ctx->nr_user_bufs))
 135                 return -EFAULT;
 136         index = array_index_nospec(req->buf_index, ctx->nr_user_bufs);
 137         req->imu = ctx->user_bufs[index];
 138         io_req_set_rsrc_node(req, ctx, 0);
 139         return 0;
 140 }
 141
 142 /*
 143  * Multishot read is prepared just like a normal read/write request, only
 144  * difference is that we set the MULTISHOT flag.
 145  */
 146 int io_read_mshot_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 147 {
 148         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 149         int ret;
 150
 151         /* must be used with provided buffers */
 152         if (!(req->flags & REQ_F_BUFFER_SELECT))
 153                 return -EINVAL;
 154
 155         ret = io_prep_rw(req, sqe);
 156         if (unlikely(ret))
 157                 return ret;
 158
 159         if (rw->addr || rw->len)
 160                 return -EINVAL;
 161
 162         req->flags |= REQ_F_APOLL_MULTISHOT;
 163         return 0;
 164 }
 165
 166 void io_readv_writev_cleanup(struct io_kiocb *req)
 167 {
 168         struct io_async_rw *io = req->async_data;
 169
 170         kfree(io->free_iovec);
 171 }
 172
 173 static inline loff_t *io_kiocb_update_pos(struct io_kiocb *req)
 174 {
 175         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 176
 177         if (rw->kiocb.ki_pos != -1)
 178                 return &rw->kiocb.ki_pos;
 179
 180         if (!(req->file->f_mode & FMODE_STREAM)) {
 181                 req->flags |= REQ_F_CUR_POS;
 182                 rw->kiocb.ki_pos = req->file->f_pos;
 183                 return &rw->kiocb.ki_pos;
 184         }
 185
 186         rw->kiocb.ki_pos = 0;
 187         return NULL;
 188 }
 189
 190 static void io_req_task_queue_reissue(struct io_kiocb *req)
 191 {
 192         req->io_task_work.func = io_queue_iowq;
 193         io_req_task_work_add(req);
 194 }
 195
 196 #ifdef CONFIG_BLOCK
 197 static bool io_resubmit_prep(struct io_kiocb *req)
 198 {
 199         struct io_async_rw *io = req->async_data;
 200
 201         if (!req_has_async_data(req))
 202                 return !io_req_prep_async(req);
 203         iov_iter_restore(&io->s.iter, &io->s.iter_state);
 204         return true;
 205 }
 206
 207 static bool io_rw_should_reissue(struct io_kiocb *req)
 208 {
 209         umode_t mode = file_inode(req->file)->i_mode;
 210         struct io_ring_ctx *ctx = req->ctx;
 211
 212         if (!S_ISBLK(mode) && !S_ISREG(mode))
 213                 return false;
 214         if ((req->flags & REQ_F_NOWAIT) || (io_wq_current_is_worker() &&
 215             !(ctx->flags & IORING_SETUP_IOPOLL)))
 216                 return false;
 217         /*
 218          * If ref is dying, we might be running poll reap from the exit work.
 219          * Don't attempt to reissue from that path, just let it fail with
 220          * -EAGAIN.
 221          */
 222         if (percpu_ref_is_dying(&ctx->refs))
 223                 return false;
 224         /*
 225          * Play it safe and assume not safe to re-import and reissue if we're
 226          * not in the original thread group (or in task context).
 227          */
 228         if (!same_thread_group(req->task, current) || !in_task())
 229                 return false;
 230         return true;
 231 }
 232 #else
 233 static bool io_resubmit_prep(struct io_kiocb *req)
 234 {
 235         return false;
 236 }
 237 static bool io_rw_should_reissue(struct io_kiocb *req)
 238 {
 239         return false;
 240 }
 241 #endif
 242
 243 static void io_req_end_write(struct io_kiocb *req)
 244 {
 245         if (req->flags & REQ_F_ISREG) {
 246                 struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 247
 248                 kiocb_end_write(&rw->kiocb);
 249         }
 250 }
 251
 252 /*
 253  * Trigger the notifications after having done some IO, and finish the write
 254  * accounting, if any.
 255  */
 256 static void io_req_io_end(struct io_kiocb *req)
 257 {
 258         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 259
 260         if (rw->kiocb.ki_flags & IOCB_WRITE) {
 261                 io_req_end_write(req);
 262                 fsnotify_modify(req->file);
 263         } else {
 264                 fsnotify_access(req->file);
 265         }
 266 }
 267
 268 static bool __io_complete_rw_common(struct io_kiocb *req, long res)
 269 {
 270         if (unlikely(res != req->cqe.res)) {
 271                 if ((res == -EAGAIN || res == -EOPNOTSUPP) &&
 272                     io_rw_should_reissue(req)) {
 273                         /*
 274                          * Reissue will start accounting again, finish the
 275                          * current cycle.
 276                          */
 277                         io_req_io_end(req);
 278                         req->flags |= REQ_F_REISSUE | REQ_F_BL_NO_RECYCLE;
 279                         return true;
 280                 }
 281                 req_set_fail(req);
 282                 req->cqe.res = res;
 283         }
 284         return false;
 285 }
 286
 287 static inline int io_fixup_rw_res(struct io_kiocb *req, long res)
 288 {
 289         struct io_async_rw *io = req->async_data;
 290
 291         /* add previously done IO, if any */
 292         if (req_has_async_data(req) && io->bytes_done > 0) {
 293                 if (res < 0)
 294                         res = io->bytes_done;
 295                 else
 296                         res += io->bytes_done;
 297         }
 298         return res;
 299 }
 300
 301 void io_req_rw_complete(struct io_kiocb *req, struct io_tw_state *ts)
 302 {
 303         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 304         struct kiocb *kiocb = &rw->kiocb;
 305
 306         if ((kiocb->ki_flags & IOCB_DIO_CALLER_COMP) && kiocb->dio_complete) {
 307                 long res = kiocb->dio_complete(rw->kiocb.private);
 308
 309                 io_req_set_res(req, io_fixup_rw_res(req, res), 0);
 310         }
 311
 312         io_req_io_end(req);
 313
 314         if (req->flags & (REQ_F_BUFFER_SELECTED|REQ_F_BUFFER_RING)) {
 315                 unsigned issue_flags = ts->locked ? 0 : IO_URING_F_UNLOCKED;
 316
 317                 req->cqe.flags |= io_put_kbuf(req, issue_flags);
 318         }
 319         io_req_task_complete(req, ts);
 320 }
 321
 322 static void io_complete_rw(struct kiocb *kiocb, long res)
 323 {
 324         struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb);
 325         struct io_kiocb *req = cmd_to_io_kiocb(rw);
 326
 327         if (!kiocb->dio_complete || !(kiocb->ki_flags & IOCB_DIO_CALLER_COMP)) {
 328                 if (__io_complete_rw_common(req, res))
 329                         return;
 330                 io_req_set_res(req, io_fixup_rw_res(req, res), 0);
 331         }
 332         req->io_task_work.func = io_req_rw_complete;
 333         __io_req_task_work_add(req, IOU_F_TWQ_LAZY_WAKE);
 334 }
 335
 336 static void io_complete_rw_iopoll(struct kiocb *kiocb, long res)
 337 {
 338         struct io_rw *rw = container_of(kiocb, struct io_rw, kiocb);
 339         struct io_kiocb *req = cmd_to_io_kiocb(rw);
 340
 341         if (kiocb->ki_flags & IOCB_WRITE)
 342                 io_req_end_write(req);
 343         if (unlikely(res != req->cqe.res)) {
 344                 if (res == -EAGAIN && io_rw_should_reissue(req)) {
 345                         req->flags |= REQ_F_REISSUE | REQ_F_BL_NO_RECYCLE;
 346                         return;
 347                 }
 348                 req->cqe.res = res;
 349         }
 350
 351         /* order with io_iopoll_complete() checking ->iopoll_completed */
 352         smp_store_release(&req->iopoll_completed, 1);
 353 }
 354
 355 static inline void io_rw_done(struct kiocb *kiocb, ssize_t ret)
 356 {
 357         /* IO was queued async, completion will happen later */
 358         if (ret == -EIOCBQUEUED)
 359                 return;
 360
 361         /* transform internal restart error codes */
 362         if (unlikely(ret < 0)) {
 363                 switch (ret) {
 364                 case -ERESTARTSYS:
 365                 case -ERESTARTNOINTR:
 366                 case -ERESTARTNOHAND:
 367                 case -ERESTART_RESTARTBLOCK:
 368                         /*
 369                          * We can't just restart the syscall, since previously
 370                          * submitted sqes may already be in progress. Just fail
 371                          * this IO with EINTR.
 372                          */
 373                         ret = -EINTR;
 374                         break;
 375                 }
 376         }
 377
 378         INDIRECT_CALL_2(kiocb->ki_complete, io_complete_rw_iopoll,
 379                         io_complete_rw, kiocb, ret);
 380 }
 381
 382 static int kiocb_done(struct io_kiocb *req, ssize_t ret,
 383                        unsigned int issue_flags)
 384 {
 385         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 386         unsigned final_ret = io_fixup_rw_res(req, ret);
 387
 388         if (ret >= 0 && req->flags & REQ_F_CUR_POS)
 389                 req->file->f_pos = rw->kiocb.ki_pos;
 390         if (ret >= 0 && (rw->kiocb.ki_complete == io_complete_rw)) {
 391                 if (!__io_complete_rw_common(req, ret)) {
 392                         /*
 393                          * Safe to call io_end from here as we're inline
 394                          * from the submission path.
 395                          */
 396                         io_req_io_end(req);
 397                         io_req_set_res(req, final_ret,
 398                                        io_put_kbuf(req, issue_flags));
 399                         return IOU_OK;
 400                 }
 401         } else {
 402                 io_rw_done(&rw->kiocb, ret);
 403         }
 404
 405         if (req->flags & REQ_F_REISSUE) {
 406                 req->flags &= ~REQ_F_REISSUE;
 407                 if (io_resubmit_prep(req))
 408                         io_req_task_queue_reissue(req);
 409                 else
 410                         io_req_task_queue_fail(req, final_ret);
 411         }
 412         return IOU_ISSUE_SKIP_COMPLETE;
 413 }
 414
 415 static struct iovec *__io_import_iovec(int ddir, struct io_kiocb *req,
 416                                        struct io_rw_state *s,
 417                                        unsigned int issue_flags)
 418 {
 419         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 420         struct iov_iter *iter = &s->iter;
 421         u8 opcode = req->opcode;
 422         struct iovec *iovec;
 423         void __user *buf;
 424         size_t sqe_len;
 425         ssize_t ret;
 426
 427         if (opcode == IORING_OP_READ_FIXED || opcode == IORING_OP_WRITE_FIXED) {
 428                 ret = io_import_fixed(ddir, iter, req->imu, rw->addr, rw->len);
 429                 if (ret)
 430                         return ERR_PTR(ret);
 431                 return NULL;
 432         }
 433
 434         buf = u64_to_user_ptr(rw->addr);
 435         sqe_len = rw->len;
 436
 437         if (!io_issue_defs[opcode].vectored || req->flags & REQ_F_BUFFER_SELECT) {
 438                 if (io_do_buffer_select(req)) {
 439                         buf = io_buffer_select(req, &sqe_len, issue_flags);
 440                         if (!buf)
 441                                 return ERR_PTR(-ENOBUFS);
 442                         rw->addr = (unsigned long) buf;
 443                         rw->len = sqe_len;
 444                 }
 445
 446                 ret = import_ubuf(ddir, buf, sqe_len, iter);
 447                 if (ret)
 448                         return ERR_PTR(ret);
 449                 return NULL;
 450         }
 451
 452         iovec = s->fast_iov;
 453         ret = __import_iovec(ddir, buf, sqe_len, UIO_FASTIOV, &iovec, iter,
 454                               req->ctx->compat);
 455         if (unlikely(ret < 0))
 456                 return ERR_PTR(ret);
 457         return iovec;
 458 }
 459
 460 static inline int io_import_iovec(int rw, struct io_kiocb *req,
 461                                   struct iovec **iovec, struct io_rw_state *s,
 462                                   unsigned int issue_flags)
 463 {
 464         *iovec = __io_import_iovec(rw, req, s, issue_flags);
 465         if (IS_ERR(*iovec))
 466                 return PTR_ERR(*iovec);
 467
 468         iov_iter_save_state(&s->iter, &s->iter_state);
 469         return 0;
 470 }
 471
 472 static inline loff_t *io_kiocb_ppos(struct kiocb *kiocb)
 473 {
 474         return (kiocb->ki_filp->f_mode & FMODE_STREAM) ? NULL : &kiocb->ki_pos;
 475 }
 476
 477 /*
 478  * For files that don't have ->read_iter() and ->write_iter(), handle them
 479  * by looping over ->read() or ->write() manually.
 480  */
 481 static ssize_t loop_rw_iter(int ddir, struct io_rw *rw, struct iov_iter *iter)
 482 {
 483         struct kiocb *kiocb = &rw->kiocb;
 484         struct file *file = kiocb->ki_filp;
 485         ssize_t ret = 0;
 486         loff_t *ppos;
 487
 488         /*
 489          * Don't support polled IO through this interface, and we can't
 490          * support non-blocking either. For the latter, this just causes
 491          * the kiocb to be handled from an async context.
 492          */
 493         if (kiocb->ki_flags & IOCB_HIPRI)
 494                 return -EOPNOTSUPP;
 495         if ((kiocb->ki_flags & IOCB_NOWAIT) &&
 496             !(kiocb->ki_filp->f_flags & O_NONBLOCK))
 497                 return -EAGAIN;
 498
 499         ppos = io_kiocb_ppos(kiocb);
 500
 501         while (iov_iter_count(iter)) {
 502                 void __user *addr;
 503                 size_t len;
 504                 ssize_t nr;
 505
 506                 if (iter_is_ubuf(iter)) {
 507                         addr = iter->ubuf + iter->iov_offset;
 508                         len = iov_iter_count(iter);
 509                 } else if (!iov_iter_is_bvec(iter)) {
 510                         addr = iter_iov_addr(iter);
 511                         len = iter_iov_len(iter);
 512                 } else {
 513                         addr = u64_to_user_ptr(rw->addr);
 514                         len = rw->len;
 515                 }
 516
 517                 if (ddir == READ)
 518                         nr = file->f_op->read(file, addr, len, ppos);
 519                 else
 520                         nr = file->f_op->write(file, addr, len, ppos);
 521
 522                 if (nr < 0) {
 523                         if (!ret)
 524                                 ret = nr;
 525                         break;
 526                 }
 527                 ret += nr;
 528                 if (!iov_iter_is_bvec(iter)) {
 529                         iov_iter_advance(iter, nr);
 530                 } else {
 531                         rw->addr += nr;
 532                         rw->len -= nr;
 533                         if (!rw->len)
 534                                 break;
 535                 }
 536                 if (nr != len)
 537                         break;
 538         }
 539
 540         return ret;
 541 }
 542
 543 static void io_req_map_rw(struct io_kiocb *req, const struct iovec *iovec,
 544                           const struct iovec *fast_iov, struct iov_iter *iter)
 545 {
 546         struct io_async_rw *io = req->async_data;
 547
 548         memcpy(&io->s.iter, iter, sizeof(*iter));
 549         io->free_iovec = iovec;
 550         io->bytes_done = 0;
 551         /* can only be fixed buffers, no need to do anything */
 552         if (iov_iter_is_bvec(iter) || iter_is_ubuf(iter))
 553                 return;
 554         if (!iovec) {
 555                 unsigned iov_off = 0;
 556
 557                 io->s.iter.__iov = io->s.fast_iov;
 558                 if (iter->__iov != fast_iov) {
 559                         iov_off = iter_iov(iter) - fast_iov;
 560                         io->s.iter.__iov += iov_off;
 561                 }
 562                 if (io->s.fast_iov != fast_iov)
 563                         memcpy(io->s.fast_iov + iov_off, fast_iov + iov_off,
 564                                sizeof(struct iovec) * iter->nr_segs);
 565         } else {
 566                 req->flags |= REQ_F_NEED_CLEANUP;
 567         }
 568 }
 569
 570 static int io_setup_async_rw(struct io_kiocb *req, const struct iovec *iovec,
 571                              struct io_rw_state *s, bool force)
 572 {
 573         if (!force && !io_cold_defs[req->opcode].prep_async)
 574                 return 0;
 575         /* opcode type doesn't need async data */
 576         if (!io_cold_defs[req->opcode].async_size)
 577                 return 0;
 578         if (!req_has_async_data(req)) {
 579                 struct io_async_rw *iorw;
 580
 581                 if (io_alloc_async_data(req)) {
 582                         kfree(iovec);
 583                         return -ENOMEM;
 584                 }
 585
 586                 io_req_map_rw(req, iovec, s->fast_iov, &s->iter);
 587                 iorw = req->async_data;
 588                 /* we've copied and mapped the iter, ensure state is saved */
 589                 iov_iter_save_state(&iorw->s.iter, &iorw->s.iter_state);
 590         }
 591         return 0;
 592 }
 593
 594 static inline int io_rw_prep_async(struct io_kiocb *req, int rw)
 595 {
 596         struct io_async_rw *iorw = req->async_data;
 597         struct iovec *iov;
 598         int ret;
 599
 600         iorw->bytes_done = 0;
 601         iorw->free_iovec = NULL;
 602
 603         /* submission path, ->uring_lock should already be taken */
 604         ret = io_import_iovec(rw, req, &iov, &iorw->s, 0);
 605         if (unlikely(ret < 0))
 606                 return ret;
 607
 608         if (iov) {
 609                 iorw->free_iovec = iov;
 610                 req->flags |= REQ_F_NEED_CLEANUP;
 611         }
 612
 613         return 0;
 614 }
 615
 616 int io_readv_prep_async(struct io_kiocb *req)
 617 {
 618         return io_rw_prep_async(req, ITER_DEST);
 619 }
 620
 621 int io_writev_prep_async(struct io_kiocb *req)
 622 {
 623         return io_rw_prep_async(req, ITER_SOURCE);
 624 }
 625
 626 /*
 627  * This is our waitqueue callback handler, registered through __folio_lock_async()
 628  * when we initially tried to do the IO with the iocb armed our waitqueue.
 629  * This gets called when the page is unlocked, and we generally expect that to
 630  * happen when the page IO is completed and the page is now uptodate. This will
 631  * queue a task_work based retry of the operation, attempting to copy the data
 632  * again. If the latter fails because the page was NOT uptodate, then we will
 633  * do a thread based blocking retry of the operation. That's the unexpected
 634  * slow path.
 635  */
 636 static int io_async_buf_func(struct wait_queue_entry *wait, unsigned mode,
 637                              int sync, void *arg)
 638 {
 639         struct wait_page_queue *wpq;
 640         struct io_kiocb *req = wait->private;
 641         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 642         struct wait_page_key *key = arg;
 643
 644         wpq = container_of(wait, struct wait_page_queue, wait);
 645
 646         if (!wake_page_match(wpq, key))
 647                 return 0;
 648
 649         rw->kiocb.ki_flags &= ~IOCB_WAITQ;
 650         list_del_init(&wait->entry);
 651         io_req_task_queue(req);
 652         return 1;
 653 }
 654
 655 /*
 656  * This controls whether a given IO request should be armed for async page
 657  * based retry. If we return false here, the request is handed to the async
 658  * worker threads for retry. If we're doing buffered reads on a regular file,
 659  * we prepare a private wait_page_queue entry and retry the operation. This
 660  * will either succeed because the page is now uptodate and unlocked, or it
 661  * will register a callback when the page is unlocked at IO completion. Through
 662  * that callback, io_uring uses task_work to setup a retry of the operation.
 663  * That retry will attempt the buffered read again. The retry will generally
 664  * succeed, or in rare cases where it fails, we then fall back to using the
 665  * async worker threads for a blocking retry.
 666  */
 667 static bool io_rw_should_retry(struct io_kiocb *req)
 668 {
 669         struct io_async_rw *io = req->async_data;
 670         struct wait_page_queue *wait = &io->wpq;
 671         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 672         struct kiocb *kiocb = &rw->kiocb;
 673
 674         /* never retry for NOWAIT, we just complete with -EAGAIN */
 675         if (req->flags & REQ_F_NOWAIT)
 676                 return false;
 677
 678         /* Only for buffered IO */
 679         if (kiocb->ki_flags & (IOCB_DIRECT | IOCB_HIPRI))
 680                 return false;
 681
 682         /*
 683          * just use poll if we can, and don't attempt if the fs doesn't
 684          * support callback based unlocks
 685          */
 686         if (io_file_can_poll(req) || !(req->file->f_mode & FMODE_BUF_RASYNC))
 687                 return false;
 688
 689         wait->wait.func = io_async_buf_func;
 690         wait->wait.private = req;
 691         wait->wait.flags = 0;
 692         INIT_LIST_HEAD(&wait->wait.entry);
 693         kiocb->ki_flags |= IOCB_WAITQ;
 694         kiocb->ki_flags &= ~IOCB_NOWAIT;
 695         kiocb->ki_waitq = wait;
 696         return true;
 697 }
 698
 699 static inline int io_iter_do_read(struct io_rw *rw, struct iov_iter *iter)
 700 {
 701         struct file *file = rw->kiocb.ki_filp;
 702
 703         if (likely(file->f_op->read_iter))
 704                 return call_read_iter(file, &rw->kiocb, iter);
 705         else if (file->f_op->read)
 706                 return loop_rw_iter(READ, rw, iter);
 707         else
 708                 return -EINVAL;
 709 }
 710
 711 static bool need_complete_io(struct io_kiocb *req)
 712 {
 713         return req->flags & REQ_F_ISREG ||
 714                 S_ISBLK(file_inode(req->file)->i_mode);
 715 }
 716
 717 static int io_rw_init_file(struct io_kiocb *req, fmode_t mode)
 718 {
 719         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 720         struct kiocb *kiocb = &rw->kiocb;
 721         struct io_ring_ctx *ctx = req->ctx;
 722         struct file *file = req->file;
 723         int ret;
 724
 725         if (unlikely(!(file->f_mode & mode)))
 726                 return -EBADF;
 727
 728         if (!(req->flags & REQ_F_FIXED_FILE))
 729                 req->flags |= io_file_get_flags(file);
 730
 731         kiocb->ki_flags = file->f_iocb_flags;
 732         ret = kiocb_set_rw_flags(kiocb, rw->flags);
 733         if (unlikely(ret))
 734                 return ret;
 735         kiocb->ki_flags |= IOCB_ALLOC_CACHE;
 736
 737         /*
 738          * If the file is marked O_NONBLOCK, still allow retry for it if it
 739          * supports async. Otherwise it's impossible to use O_NONBLOCK files
 740          * reliably. If not, or it IOCB_NOWAIT is set, don't retry.
 741          */
 742         if ((kiocb->ki_flags & IOCB_NOWAIT) ||
 743             ((file->f_flags & O_NONBLOCK) && !io_file_supports_nowait(req)))
 744                 req->flags |= REQ_F_NOWAIT;
 745
 746         if (ctx->flags & IORING_SETUP_IOPOLL) {
 747                 if (!(kiocb->ki_flags & IOCB_DIRECT) || !file->f_op->iopoll)
 748                         return -EOPNOTSUPP;
 749
 750                 kiocb->private = NULL;
 751                 kiocb->ki_flags |= IOCB_HIPRI;
 752                 kiocb->ki_complete = io_complete_rw_iopoll;
 753                 req->iopoll_completed = 0;
 754         } else {
 755                 if (kiocb->ki_flags & IOCB_HIPRI)
 756                         return -EINVAL;
 757                 kiocb->ki_complete = io_complete_rw;
 758         }
 759
 760         return 0;
 761 }
 762
 763 static int __io_read(struct io_kiocb *req, unsigned int issue_flags)
 764 {
 765         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 766         struct io_rw_state __s, *s = &__s;
 767         struct iovec *iovec;
 768         struct kiocb *kiocb = &rw->kiocb;
 769         bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
 770         struct io_async_rw *io;
 771         ssize_t ret, ret2;
 772         loff_t *ppos;
 773
 774         if (!req_has_async_data(req)) {
 775                 ret = io_import_iovec(ITER_DEST, req, &iovec, s, issue_flags);
 776                 if (unlikely(ret < 0))
 777                         return ret;
 778         } else {
 779                 io = req->async_data;
 780                 s = &io->s;
 781
 782                 /*
 783                  * Safe and required to re-import if we're using provided
 784                  * buffers, as we dropped the selected one before retry.
 785                  */
 786                 if (io_do_buffer_select(req)) {
 787                         ret = io_import_iovec(ITER_DEST, req, &iovec, s, issue_flags);
 788                         if (unlikely(ret < 0))
 789                                 return ret;
 790                 }
 791
 792                 /*
 793                  * We come here from an earlier attempt, restore our state to
 794                  * match in case it doesn't. It's cheap enough that we don't
 795                  * need to make this conditional.
 796                  */
 797                 iov_iter_restore(&s->iter, &s->iter_state);
 798                 iovec = NULL;
 799         }
 800         ret = io_rw_init_file(req, FMODE_READ);
 801         if (unlikely(ret)) {
 802                 kfree(iovec);
 803                 return ret;
 804         }
 805         req->cqe.res = iov_iter_count(&s->iter);
 806
 807         if (force_nonblock) {
 808                 /* If the file doesn't support async, just async punt */
 809                 if (unlikely(!io_file_supports_nowait(req))) {
 810                         ret = io_setup_async_rw(req, iovec, s, true);
 811                         return ret ?: -EAGAIN;
 812                 }
 813                 kiocb->ki_flags |= IOCB_NOWAIT;
 814         } else {
 815                 /* Ensure we clear previously set non-block flag */
 816                 kiocb->ki_flags &= ~IOCB_NOWAIT;
 817         }
 818
 819         ppos = io_kiocb_update_pos(req);
 820
 821         ret = rw_verify_area(READ, req->file, ppos, req->cqe.res);
 822         if (unlikely(ret)) {
 823                 kfree(iovec);
 824                 return ret;
 825         }
 826
 827         ret = io_iter_do_read(rw, &s->iter);
 828
 829         if (ret == -EAGAIN || (req->flags & REQ_F_REISSUE)) {
 830                 req->flags &= ~REQ_F_REISSUE;
 831                 /*
 832                  * If we can poll, just do that. For a vectored read, we'll
 833                  * need to copy state first.
 834                  */
 835                 if (io_file_can_poll(req) && !io_issue_defs[req->opcode].vectored)
 836                         return -EAGAIN;
 837                 /* IOPOLL retry should happen for io-wq threads */
 838                 if (!force_nonblock && !(req->ctx->flags & IORING_SETUP_IOPOLL))
 839                         goto done;
 840                 /* no retry on NONBLOCK nor RWF_NOWAIT */
 841                 if (req->flags & REQ_F_NOWAIT)
 842                         goto done;
 843                 ret = 0;
 844         } else if (ret == -EIOCBQUEUED) {
 845                 if (iovec)
 846                         kfree(iovec);
 847                 return IOU_ISSUE_SKIP_COMPLETE;
 848         } else if (ret == req->cqe.res || ret <= 0 || !force_nonblock ||
 849                    (req->flags & REQ_F_NOWAIT) || !need_complete_io(req)) {
 850                 /* read all, failed, already did sync or don't want to retry */
 851                 goto done;
 852         }
 853
 854         /*
 855          * Don't depend on the iter state matching what was consumed, or being
 856          * untouched in case of error. Restore it and we'll advance it
 857          * manually if we need to.
 858          */
 859         iov_iter_restore(&s->iter, &s->iter_state);
 860
 861         ret2 = io_setup_async_rw(req, iovec, s, true);
 862         iovec = NULL;
 863         if (ret2) {
 864                 ret = ret > 0 ? ret : ret2;
 865                 goto done;
 866         }
 867
 868         io = req->async_data;
 869         s = &io->s;
 870         /*
 871          * Now use our persistent iterator and state, if we aren't already.
 872          * We've restored and mapped the iter to match.
 873          */
 874
 875         do {
 876                 /*
 877                  * We end up here because of a partial read, either from
 878                  * above or inside this loop. Advance the iter by the bytes
 879                  * that were consumed.
 880                  */
 881                 iov_iter_advance(&s->iter, ret);
 882                 if (!iov_iter_count(&s->iter))
 883                         break;
 884                 io->bytes_done += ret;
 885                 iov_iter_save_state(&s->iter, &s->iter_state);
 886
 887                 /* if we can retry, do so with the callbacks armed */
 888                 if (!io_rw_should_retry(req)) {
 889                         kiocb->ki_flags &= ~IOCB_WAITQ;
 890                         return -EAGAIN;
 891                 }
 892
 893                 req->cqe.res = iov_iter_count(&s->iter);
 894                 /*
 895                  * Now retry read with the IOCB_WAITQ parts set in the iocb. If
 896                  * we get -EIOCBQUEUED, then we'll get a notification when the
 897                  * desired page gets unlocked. We can also get a partial read
 898                  * here, and if we do, then just retry at the new offset.
 899                  */
 900                 ret = io_iter_do_read(rw, &s->iter);
 901                 if (ret == -EIOCBQUEUED)
 902                         return IOU_ISSUE_SKIP_COMPLETE;
 903                 /* we got some bytes, but not all. retry. */
 904                 kiocb->ki_flags &= ~IOCB_WAITQ;
 905                 iov_iter_restore(&s->iter, &s->iter_state);
 906         } while (ret > 0);
 907 done:
 908         /* it's faster to check here then delegate to kfree */
 909         if (iovec)
 910                 kfree(iovec);
 911         return ret;
 912 }
 913
 914 int io_read(struct io_kiocb *req, unsigned int issue_flags)
 915 {
 916         int ret;
 917
 918         ret = __io_read(req, issue_flags);
 919         if (ret >= 0)
 920                 return kiocb_done(req, ret, issue_flags);
 921
 922         return ret;
 923 }
 924
 925 int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags)
 926 {
 927         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
 928         unsigned int cflags = 0;
 929         int ret;
 930
 931         /*
 932          * Multishot MUST be used on a pollable file
 933          */
 934         if (!io_file_can_poll(req))
 935                 return -EBADFD;
 936
 937         ret = __io_read(req, issue_flags);
 938
 939         /*
 940          * If the file doesn't support proper NOWAIT, then disable multishot
 941          * and stay in single shot mode.
 942          */
 943         if (!io_file_supports_nowait(req))
 944                 req->flags &= ~REQ_F_APOLL_MULTISHOT;
 945
 946         /*
 947          * If we get -EAGAIN, recycle our buffer and just let normal poll
 948          * handling arm it.
 949          */
 950         if (ret == -EAGAIN) {
 951                 /*
 952                  * Reset rw->len to 0 again to avoid clamping future mshot
 953                  * reads, in case the buffer size varies.
 954                  */
 955                 if (io_kbuf_recycle(req, issue_flags))
 956                         rw->len = 0;
 957                 if (issue_flags & IO_URING_F_MULTISHOT)
 958                         return IOU_ISSUE_SKIP_COMPLETE;
 959                 return -EAGAIN;
 960         }
 961
 962         /*
 963          * Any successful return value will keep the multishot read armed.
 964          */
 965         if (ret > 0 && req->flags & REQ_F_APOLL_MULTISHOT) {
 966                 /*
 967                  * Put our buffer and post a CQE. If we fail to post a CQE, then
 968                  * jump to the termination path. This request is then done.
 969                  */
 970                 cflags = io_put_kbuf(req, issue_flags);
 971                 rw->len = 0; /* similarly to above, reset len to 0 */
 972
 973                 if (io_fill_cqe_req_aux(req,
 974                                         issue_flags & IO_URING_F_COMPLETE_DEFER,
 975                                         ret, cflags | IORING_CQE_F_MORE)) {
 976                         if (issue_flags & IO_URING_F_MULTISHOT) {
 977                                 /*
 978                                  * Force retry, as we might have more data to
 979                                  * be read and otherwise it won't get retried
 980                                  * until (if ever) another poll is triggered.
 981                                  */
 982                                 io_poll_multishot_retry(req);
 983                                 return IOU_ISSUE_SKIP_COMPLETE;
 984                         }
 985                         return -EAGAIN;
 986                 }
 987         }
 988
 989         /*
 990          * Either an error, or we've hit overflow posting the CQE. For any
 991          * multishot request, hitting overflow will terminate it.
 992          */
 993         io_req_set_res(req, ret, cflags);
 994         if (issue_flags & IO_URING_F_MULTISHOT)
 995                 return IOU_STOP_MULTISHOT;
 996         return IOU_OK;
 997 }
 998
 999 int io_write(struct io_kiocb *req, unsigned int issue_flags)
1000 {
1001         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
1002         struct io_rw_state __s, *s = &__s;
1003         struct iovec *iovec;
1004         struct kiocb *kiocb = &rw->kiocb;
1005         bool force_nonblock = issue_flags & IO_URING_F_NONBLOCK;
1006         ssize_t ret, ret2;
1007         loff_t *ppos;
1008
1009         if (!req_has_async_data(req)) {
1010                 ret = io_import_iovec(ITER_SOURCE, req, &iovec, s, issue_flags);
1011                 if (unlikely(ret < 0))
1012                         return ret;
1013         } else {
1014                 struct io_async_rw *io = req->async_data;
1015
1016                 s = &io->s;
1017                 iov_iter_restore(&s->iter, &s->iter_state);
1018                 iovec = NULL;
1019         }
1020         ret = io_rw_init_file(req, FMODE_WRITE);
1021         if (unlikely(ret)) {
1022                 kfree(iovec);
1023                 return ret;
1024         }
1025         req->cqe.res = iov_iter_count(&s->iter);
1026
1027         if (force_nonblock) {
1028                 /* If the file doesn't support async, just async punt */
1029                 if (unlikely(!io_file_supports_nowait(req)))
1030                         goto copy_iov;
1031
1032                 /* File path supports NOWAIT for non-direct_IO only for block devices. */
1033                 if (!(kiocb->ki_flags & IOCB_DIRECT) &&
1034                         !(kiocb->ki_filp->f_mode & FMODE_BUF_WASYNC) &&
1035                         (req->flags & REQ_F_ISREG))
1036                         goto copy_iov;
1037
1038                 kiocb->ki_flags |= IOCB_NOWAIT;
1039         } else {
1040                 /* Ensure we clear previously set non-block flag */
1041                 kiocb->ki_flags &= ~IOCB_NOWAIT;
1042         }
1043
1044         ppos = io_kiocb_update_pos(req);
1045
1046         ret = rw_verify_area(WRITE, req->file, ppos, req->cqe.res);
1047         if (unlikely(ret)) {
1048                 kfree(iovec);
1049                 return ret;
1050         }
1051
1052         if (req->flags & REQ_F_ISREG)
1053                 kiocb_start_write(kiocb);
1054         kiocb->ki_flags |= IOCB_WRITE;
1055
1056         if (likely(req->file->f_op->write_iter))
1057                 ret2 = call_write_iter(req->file, kiocb, &s->iter);
1058         else if (req->file->f_op->write)
1059                 ret2 = loop_rw_iter(WRITE, rw, &s->iter);
1060         else
1061                 ret2 = -EINVAL;
1062
1063         if (req->flags & REQ_F_REISSUE) {
1064                 req->flags &= ~REQ_F_REISSUE;
1065                 ret2 = -EAGAIN;
1066         }
1067
1068         /*
1069          * Raw bdev writes will return -EOPNOTSUPP for IOCB_NOWAIT. Just
1070          * retry them without IOCB_NOWAIT.
1071          */
1072         if (ret2 == -EOPNOTSUPP && (kiocb->ki_flags & IOCB_NOWAIT))
1073                 ret2 = -EAGAIN;
1074         /* no retry on NONBLOCK nor RWF_NOWAIT */
1075         if (ret2 == -EAGAIN && (req->flags & REQ_F_NOWAIT))
1076                 goto done;
1077         if (!force_nonblock || ret2 != -EAGAIN) {
1078                 /* IOPOLL retry should happen for io-wq threads */
1079                 if (ret2 == -EAGAIN && (req->ctx->flags & IORING_SETUP_IOPOLL))
1080                         goto copy_iov;
1081
1082                 if (ret2 != req->cqe.res && ret2 >= 0 && need_complete_io(req)) {
1083                         struct io_async_rw *io;
1084
1085                         trace_io_uring_short_write(req->ctx, kiocb->ki_pos - ret2,
1086                                                 req->cqe.res, ret2);
1087
1088                         /* This is a partial write. The file pos has already been
1089                          * updated, setup the async struct to complete the request
1090                          * in the worker. Also update bytes_done to account for
1091                          * the bytes already written.
1092                          */
1093                         iov_iter_save_state(&s->iter, &s->iter_state);
1094                         ret = io_setup_async_rw(req, iovec, s, true);
1095
1096                         io = req->async_data;
1097                         if (io)
1098                                 io->bytes_done += ret2;
1099
1100                         if (kiocb->ki_flags & IOCB_WRITE)
1101                                 io_req_end_write(req);
1102                         return ret ? ret : -EAGAIN;
1103                 }
1104 done:
1105                 ret = kiocb_done(req, ret2, issue_flags);
1106         } else {
1107 copy_iov:
1108                 iov_iter_restore(&s->iter, &s->iter_state);
1109                 ret = io_setup_async_rw(req, iovec, s, false);
1110                 if (!ret) {
1111                         if (kiocb->ki_flags & IOCB_WRITE)
1112                                 io_req_end_write(req);
1113                         return -EAGAIN;
1114                 }
1115                 return ret;
1116         }
1117         /* it's reportedly faster than delegating the null check to kfree() */
1118         if (iovec)
1119                 kfree(iovec);
1120         return ret;
1121 }
1122
1123 void io_rw_fail(struct io_kiocb *req)
1124 {
1125         int res;
1126
1127         res = io_fixup_rw_res(req, req->cqe.res);
1128         io_req_set_res(req, res, req->cqe.flags);
1129 }
1130
1131 int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
1132 {
1133         struct io_wq_work_node *pos, *start, *prev;
1134         unsigned int poll_flags = 0;
1135         DEFINE_IO_COMP_BATCH(iob);
1136         int nr_events = 0;
1137
1138         /*
1139          * Only spin for completions if we don't have multiple devices hanging
1140          * off our complete list.
1141          */
1142         if (ctx->poll_multi_queue || force_nonspin)
1143                 poll_flags |= BLK_POLL_ONESHOT;
1144
1145         wq_list_for_each(pos, start, &ctx->iopoll_list) {
1146                 struct io_kiocb *req = container_of(pos, struct io_kiocb, comp_list);
1147                 struct file *file = req->file;
1148                 int ret;
1149
1150                 /*
1151                  * Move completed and retryable entries to our local lists.
1152                  * If we find a request that requires polling, break out
1153                  * and complete those lists first, if we have entries there.
1154                  */
1155                 if (READ_ONCE(req->iopoll_completed))
1156                         break;
1157
1158                 if (req->opcode == IORING_OP_URING_CMD) {
1159                         struct io_uring_cmd *ioucmd;
1160
1161                         ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
1162                         ret = file->f_op->uring_cmd_iopoll(ioucmd, &iob,
1163                                                                 poll_flags);
1164                 } else {
1165                         struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
1166
1167                         ret = file->f_op->iopoll(&rw->kiocb, &iob, poll_flags);
1168                 }
1169                 if (unlikely(ret < 0))
1170                         return ret;
1171                 else if (ret)
1172                         poll_flags |= BLK_POLL_ONESHOT;
1173
1174                 /* iopoll may have completed current req */
1175                 if (!rq_list_empty(iob.req_list) ||
1176                     READ_ONCE(req->iopoll_completed))
1177                         break;
1178         }
1179
1180         if (!rq_list_empty(iob.req_list))
1181                 iob.complete(&iob);
1182         else if (!pos)
1183                 return 0;
1184
1185         prev = start;
1186         wq_list_for_each_resume(pos, prev) {
1187                 struct io_kiocb *req = container_of(pos, struct io_kiocb, comp_list);
1188
1189                 /* order with io_complete_rw_iopoll(), e.g. ->result updates */
1190                 if (!smp_load_acquire(&req->iopoll_completed))
1191                         break;
1192                 nr_events++;
1193                 req->cqe.flags = io_put_kbuf(req, 0);
1194         }
1195         if (unlikely(!nr_events))
1196                 return 0;
1197
1198         pos = start ? start->next : ctx->iopoll_list.first;
1199         wq_list_cut(&ctx->iopoll_list, prev, start);
1200
1201         if (WARN_ON_ONCE(!wq_list_empty(&ctx->submit_state.compl_reqs)))
1202                 return 0;
1203         ctx->submit_state.compl_reqs.first = pos;
1204         __io_submit_flush_completions(ctx);
1205         return nr_events;
1206 }