fs/iomap/direct-io.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2010 Red Hat, Inc.
   4  * Copyright (c) 2016-2018 Christoph Hellwig.
   5  */
   6 #include <linux/module.h>
   7 #include <linux/compiler.h>
   8 #include <linux/fs.h>
   9 #include <linux/iomap.h>
  10 #include <linux/backing-dev.h>
  11 #include <linux/uio.h>
  12 #include <linux/task_io_accounting_ops.h>
  13 #include "trace.h"
  14
  15 #include "../internal.h"
  16
  17 /*
  18  * Private flags for iomap_dio, must not overlap with the public ones in
  19  * iomap.h:
  20  */
  21 #define IOMAP_DIO_WRITE_FUA     (1 << 28)
  22 #define IOMAP_DIO_NEED_SYNC     (1 << 29)
  23 #define IOMAP_DIO_WRITE         (1 << 30)
  24 #define IOMAP_DIO_DIRTY         (1 << 31)
  25
  26 struct iomap_dio {
  27         struct kiocb            *iocb;
  28         const struct iomap_dio_ops *dops;
  29         loff_t                  i_size;
  30         loff_t                  size;
  31         atomic_t                ref;
  32         unsigned                flags;
  33         int                     error;
  34         bool                    wait_for_completion;
  35
  36         union {
  37                 /* used during submission and for synchronous completion: */
  38                 struct {
  39                         struct iov_iter         *iter;
  40                         struct task_struct      *waiter;
  41                         struct request_queue    *last_queue;
  42                         blk_qc_t                cookie;
  43                 } submit;
  44
  45                 /* used for aio completion: */
  46                 struct {
  47                         struct work_struct      work;
  48                 } aio;
  49         };
  50 };
  51
  52 int iomap_dio_iopoll(struct kiocb *kiocb, bool spin)
  53 {
  54         struct request_queue *q = READ_ONCE(kiocb->private);
  55
  56         if (!q)
  57                 return 0;
  58         return blk_poll(q, READ_ONCE(kiocb->ki_cookie), spin);
  59 }
  60 EXPORT_SYMBOL_GPL(iomap_dio_iopoll);
  61
  62 static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
  63                 struct bio *bio, loff_t pos)
  64 {
  65         atomic_inc(&dio->ref);
  66
  67         if (dio->iocb->ki_flags & IOCB_HIPRI)
  68                 bio_set_polled(bio, dio->iocb);
  69
  70         dio->submit.last_queue = bdev_get_queue(iomap->bdev);
  71         if (dio->dops && dio->dops->submit_io)
  72                 dio->submit.cookie = dio->dops->submit_io(
  73                                 file_inode(dio->iocb->ki_filp),
  74                                 iomap, bio, pos);
  75         else
  76                 dio->submit.cookie = submit_bio(bio);
  77 }
  78
  79 ssize_t iomap_dio_complete(struct iomap_dio *dio)
  80 {
  81         const struct iomap_dio_ops *dops = dio->dops;
  82         struct kiocb *iocb = dio->iocb;
  83         struct inode *inode = file_inode(iocb->ki_filp);
  84         loff_t offset = iocb->ki_pos;
  85         ssize_t ret = dio->error;
  86
  87         if (dops && dops->end_io)
  88                 ret = dops->end_io(iocb, dio->size, ret, dio->flags);
  89
  90         if (likely(!ret)) {
  91                 ret = dio->size;
  92                 /* check for short read */
  93                 if (offset + ret > dio->i_size &&
  94                     !(dio->flags & IOMAP_DIO_WRITE))
  95                         ret = dio->i_size - offset;
  96                 iocb->ki_pos += ret;
  97         }
  98
  99         /*
 100          * Try again to invalidate clean pages which might have been cached by
 101          * non-direct readahead, or faulted in by get_user_pages() if the source
 102          * of the write was an mmap'ed region of the file we're writing.  Either
 103          * one is a pretty crazy thing to do, so we don't support it 100%.  If
 104          * this invalidation fails, tough, the write still worked...
 105          *
 106          * And this page cache invalidation has to be after ->end_io(), as some
 107          * filesystems convert unwritten extents to real allocations in
 108          * ->end_io() when necessary, otherwise a racing buffer read would cache
 109          * zeros from unwritten extents.
 110          */
 111         if (!dio->error && dio->size &&
 112             (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
 113                 int err;
 114                 err = invalidate_inode_pages2_range(inode->i_mapping,
 115                                 offset >> PAGE_SHIFT,
 116                                 (offset + dio->size - 1) >> PAGE_SHIFT);
 117                 if (err)
 118                         dio_warn_stale_pagecache(iocb->ki_filp);
 119         }
 120
 121         inode_dio_end(file_inode(iocb->ki_filp));
 122         /*
 123          * If this is a DSYNC write, make sure we push it to stable storage now
 124          * that we've written data.
 125          */
 126         if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC))
 127                 ret = generic_write_sync(iocb, ret);
 128
 129         kfree(dio);
 130
 131         return ret;
 132 }
 133 EXPORT_SYMBOL_GPL(iomap_dio_complete);
 134
 135 static void iomap_dio_complete_work(struct work_struct *work)
 136 {
 137         struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
 138         struct kiocb *iocb = dio->iocb;
 139
 140         iocb->ki_complete(iocb, iomap_dio_complete(dio), 0);
 141 }
 142
 143 /*
 144  * Set an error in the dio if none is set yet.  We have to use cmpxchg
 145  * as the submission context and the completion context(s) can race to
 146  * update the error.
 147  */
 148 static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
 149 {
 150         cmpxchg(&dio->error, 0, ret);
 151 }
 152
 153 static void iomap_dio_bio_end_io(struct bio *bio)
 154 {
 155         struct iomap_dio *dio = bio->bi_private;
 156         bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
 157
 158         if (bio->bi_status)
 159                 iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status));
 160
 161         if (atomic_dec_and_test(&dio->ref)) {
 162                 if (dio->wait_for_completion) {
 163                         struct task_struct *waiter = dio->submit.waiter;
 164                         WRITE_ONCE(dio->submit.waiter, NULL);
 165                         blk_wake_io_task(waiter);
 166                 } else if (dio->flags & IOMAP_DIO_WRITE) {
 167                         struct inode *inode = file_inode(dio->iocb->ki_filp);
 168
 169                         INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
 170                         queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
 171                 } else {
 172                         iomap_dio_complete_work(&dio->aio.work);
 173                 }
 174         }
 175
 176         if (should_dirty) {
 177                 bio_check_pages_dirty(bio);
 178         } else {
 179                 bio_release_pages(bio, false);
 180                 bio_put(bio);
 181         }
 182 }
 183
 184 static void
 185 iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
 186                 unsigned len)
 187 {
 188         struct page *page = ZERO_PAGE(0);
 189         int flags = REQ_SYNC | REQ_IDLE;
 190         struct bio *bio;
 191
 192         bio = bio_alloc(GFP_KERNEL, 1);
 193         bio_set_dev(bio, iomap->bdev);
 194         bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
 195         bio->bi_private = dio;
 196         bio->bi_end_io = iomap_dio_bio_end_io;
 197
 198         get_page(page);
 199         __bio_add_page(bio, page, len, 0);
 200         bio_set_op_attrs(bio, REQ_OP_WRITE, flags);
 201         iomap_dio_submit_bio(dio, iomap, bio, pos);
 202 }
 203
 204 /*
 205  * Figure out the bio's operation flags from the dio request, the
 206  * mapping, and whether or not we want FUA.  Note that we can end up
 207  * clearing the WRITE_FUA flag in the dio request.
 208  */
 209 static inline unsigned int
 210 iomap_dio_bio_opflags(struct iomap_dio *dio, struct iomap *iomap, bool use_fua)
 211 {
 212         unsigned int opflags = REQ_SYNC | REQ_IDLE;
 213
 214         if (!(dio->flags & IOMAP_DIO_WRITE)) {
 215                 WARN_ON_ONCE(iomap->flags & IOMAP_F_ZONE_APPEND);
 216                 return REQ_OP_READ;
 217         }
 218
 219         if (iomap->flags & IOMAP_F_ZONE_APPEND)
 220                 opflags |= REQ_OP_ZONE_APPEND;
 221         else
 222                 opflags |= REQ_OP_WRITE;
 223
 224         if (use_fua)
 225                 opflags |= REQ_FUA;
 226         else
 227                 dio->flags &= ~IOMAP_DIO_WRITE_FUA;
 228
 229         return opflags;
 230 }
 231
 232 static loff_t
 233 iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
 234                 struct iomap_dio *dio, struct iomap *iomap)
 235 {
 236         unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
 237         unsigned int fs_block_size = i_blocksize(inode), pad;
 238         unsigned int align = iov_iter_alignment(dio->submit.iter);
 239         unsigned int bio_opf;
 240         struct bio *bio;
 241         bool need_zeroout = false;
 242         bool use_fua = false;
 243         int nr_pages, ret = 0;
 244         size_t copied = 0;
 245         size_t orig_count;
 246
 247         if ((pos | length | align) & ((1 << blkbits) - 1))
 248                 return -EINVAL;
 249
 250         if (iomap->type == IOMAP_UNWRITTEN) {
 251                 dio->flags |= IOMAP_DIO_UNWRITTEN;
 252                 need_zeroout = true;
 253         }
 254
 255         if (iomap->flags & IOMAP_F_SHARED)
 256                 dio->flags |= IOMAP_DIO_COW;
 257
 258         if (iomap->flags & IOMAP_F_NEW) {
 259                 need_zeroout = true;
 260         } else if (iomap->type == IOMAP_MAPPED) {
 261                 /*
 262                  * Use a FUA write if we need datasync semantics, this is a pure
 263                  * data IO that doesn't require any metadata updates (including
 264                  * after IO completion such as unwritten extent conversion) and
 265                  * the underlying device supports FUA. This allows us to avoid
 266                  * cache flushes on IO completion.
 267                  */
 268                 if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) &&
 269                     (dio->flags & IOMAP_DIO_WRITE_FUA) &&
 270                     blk_queue_fua(bdev_get_queue(iomap->bdev)))
 271                         use_fua = true;
 272         }
 273
 274         /*
 275          * Save the original count and trim the iter to just the extent we
 276          * are operating on right now.  The iter will be re-expanded once
 277          * we are done.
 278          */
 279         orig_count = iov_iter_count(dio->submit.iter);
 280         iov_iter_truncate(dio->submit.iter, length);
 281
 282         if (!iov_iter_count(dio->submit.iter))
 283                 goto out;
 284
 285         if (need_zeroout) {
 286                 /* zero out from the start of the block to the write offset */
 287                 pad = pos & (fs_block_size - 1);
 288                 if (pad)
 289                         iomap_dio_zero(dio, iomap, pos - pad, pad);
 290         }
 291
 292         /*
 293          * Set the operation flags early so that bio_iov_iter_get_pages
 294          * can set up the page vector appropriately for a ZONE_APPEND
 295          * operation.
 296          */
 297         bio_opf = iomap_dio_bio_opflags(dio, iomap, use_fua);
 298
 299         nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, BIO_MAX_PAGES);
 300         do {
 301                 size_t n;
 302                 if (dio->error) {
 303                         iov_iter_revert(dio->submit.iter, copied);
 304                         copied = ret = 0;
 305                         goto out;
 306                 }
 307
 308                 bio = bio_alloc(GFP_KERNEL, nr_pages);
 309                 bio_set_dev(bio, iomap->bdev);
 310                 bio->bi_iter.bi_sector = iomap_sector(iomap, pos);
 311                 bio->bi_write_hint = dio->iocb->ki_hint;
 312                 bio->bi_ioprio = dio->iocb->ki_ioprio;
 313                 bio->bi_private = dio;
 314                 bio->bi_end_io = iomap_dio_bio_end_io;
 315                 bio->bi_opf = bio_opf;
 316
 317                 ret = bio_iov_iter_get_pages(bio, dio->submit.iter);
 318                 if (unlikely(ret)) {
 319                         /*
 320                          * We have to stop part way through an IO. We must fall
 321                          * through to the sub-block tail zeroing here, otherwise
 322                          * this short IO may expose stale data in the tail of
 323                          * the block we haven't written data to.
 324                          */
 325                         bio_put(bio);
 326                         goto zero_tail;
 327                 }
 328
 329                 n = bio->bi_iter.bi_size;
 330                 if (dio->flags & IOMAP_DIO_WRITE) {
 331                         task_io_account_write(n);
 332                 } else {
 333                         if (dio->flags & IOMAP_DIO_DIRTY)
 334                                 bio_set_pages_dirty(bio);
 335                 }
 336
 337                 dio->size += n;
 338                 copied += n;
 339
 340                 nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter,
 341                                                  BIO_MAX_PAGES);
 342                 iomap_dio_submit_bio(dio, iomap, bio, pos);
 343                 pos += n;
 344         } while (nr_pages);
 345
 346         /*
 347          * We need to zeroout the tail of a sub-block write if the extent type
 348          * requires zeroing or the write extends beyond EOF. If we don't zero
 349          * the block tail in the latter case, we can expose stale data via mmap
 350          * reads of the EOF block.
 351          */
 352 zero_tail:
 353         if (need_zeroout ||
 354             ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) {
 355                 /* zero out from the end of the write to the end of the block */
 356                 pad = pos & (fs_block_size - 1);
 357                 if (pad)
 358                         iomap_dio_zero(dio, iomap, pos, fs_block_size - pad);
 359         }
 360 out:
 361         /* Undo iter limitation to current extent */
 362         iov_iter_reexpand(dio->submit.iter, orig_count - copied);
 363         if (copied)
 364                 return copied;
 365         return ret;
 366 }
 367
 368 static loff_t
 369 iomap_dio_hole_actor(loff_t length, struct iomap_dio *dio)
 370 {
 371         length = iov_iter_zero(length, dio->submit.iter);
 372         dio->size += length;
 373         return length;
 374 }
 375
 376 static loff_t
 377 iomap_dio_inline_actor(struct inode *inode, loff_t pos, loff_t length,
 378                 struct iomap_dio *dio, struct iomap *iomap)
 379 {
 380         struct iov_iter *iter = dio->submit.iter;
 381         size_t copied;
 382
 383         BUG_ON(pos + length > PAGE_SIZE - offset_in_page(iomap->inline_data));
 384
 385         if (dio->flags & IOMAP_DIO_WRITE) {
 386                 loff_t size = inode->i_size;
 387
 388                 if (pos > size)
 389                         memset(iomap->inline_data + size, 0, pos - size);
 390                 copied = copy_from_iter(iomap->inline_data + pos, length, iter);
 391                 if (copied) {
 392                         if (pos + copied > size)
 393                                 i_size_write(inode, pos + copied);
 394                         mark_inode_dirty(inode);
 395                 }
 396         } else {
 397                 copied = copy_to_iter(iomap->inline_data + pos, length, iter);
 398         }
 399         dio->size += copied;
 400         return copied;
 401 }
 402
 403 static loff_t
 404 iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
 405                 void *data, struct iomap *iomap, struct iomap *srcmap)
 406 {
 407         struct iomap_dio *dio = data;
 408
 409         switch (iomap->type) {
 410         case IOMAP_HOLE:
 411                 if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
 412                         return -EIO;
 413                 return iomap_dio_hole_actor(length, dio);
 414         case IOMAP_UNWRITTEN:
 415                 if (!(dio->flags & IOMAP_DIO_WRITE))
 416                         return iomap_dio_hole_actor(length, dio);
 417                 return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
 418         case IOMAP_MAPPED:
 419                 return iomap_dio_bio_actor(inode, pos, length, dio, iomap);
 420         case IOMAP_INLINE:
 421                 return iomap_dio_inline_actor(inode, pos, length, dio, iomap);
 422         case IOMAP_DELALLOC:
 423                 /*
 424                  * DIO is not serialised against mmap() access at all, and so
 425                  * if the page_mkwrite occurs between the writeback and the
 426                  * iomap_apply() call in the DIO path, then it will see the
 427                  * DELALLOC block that the page-mkwrite allocated.
 428                  */
 429                 pr_warn_ratelimited("Direct I/O collision with buffered writes! File: %pD4 Comm: %.20s\n",
 430                                     dio->iocb->ki_filp, current->comm);
 431                 return -EIO;
 432         default:
 433                 WARN_ON_ONCE(1);
 434                 return -EIO;
 435         }
 436 }
 437
 438 /*
 439  * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO
 440  * is being issued as AIO or not.  This allows us to optimise pure data writes
 441  * to use REQ_FUA rather than requiring generic_write_sync() to issue a
 442  * REQ_FLUSH post write. This is slightly tricky because a single request here
 443  * can be mapped into multiple disjoint IOs and only a subset of the IOs issued
 444  * may be pure data writes. In that case, we still need to do a full data sync
 445  * completion.
 446  *
 447  * Returns -ENOTBLK In case of a page invalidation invalidation failure for
 448  * writes.  The callers needs to fall back to buffered I/O in this case.
 449  */
 450 struct iomap_dio *
 451 __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 452                 const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
 453                 unsigned int dio_flags)
 454 {
 455         struct address_space *mapping = iocb->ki_filp->f_mapping;
 456         struct inode *inode = file_inode(iocb->ki_filp);
 457         size_t count = iov_iter_count(iter);
 458         loff_t pos = iocb->ki_pos;
 459         loff_t end = iocb->ki_pos + count - 1, ret = 0;
 460         bool wait_for_completion =
 461                 is_sync_kiocb(iocb) || (dio_flags & IOMAP_DIO_FORCE_WAIT);
 462         unsigned int iomap_flags = IOMAP_DIRECT;
 463         struct blk_plug plug;
 464         struct iomap_dio *dio;
 465
 466         if (!count)
 467                 return NULL;
 468
 469         dio = kmalloc(sizeof(*dio), GFP_KERNEL);
 470         if (!dio)
 471                 return ERR_PTR(-ENOMEM);
 472
 473         dio->iocb = iocb;
 474         atomic_set(&dio->ref, 1);
 475         dio->size = 0;
 476         dio->i_size = i_size_read(inode);
 477         dio->dops = dops;
 478         dio->error = 0;
 479         dio->flags = 0;
 480
 481         dio->submit.iter = iter;
 482         dio->submit.waiter = current;
 483         dio->submit.cookie = BLK_QC_T_NONE;
 484         dio->submit.last_queue = NULL;
 485
 486         if (iov_iter_rw(iter) == READ) {
 487                 if (pos >= dio->i_size)
 488                         goto out_free_dio;
 489
 490                 if (iter_is_iovec(iter))
 491                         dio->flags |= IOMAP_DIO_DIRTY;
 492         } else {
 493                 iomap_flags |= IOMAP_WRITE;
 494                 dio->flags |= IOMAP_DIO_WRITE;
 495
 496                 /* for data sync or sync, we need sync completion processing */
 497                 if (iocb->ki_flags & IOCB_DSYNC)
 498                         dio->flags |= IOMAP_DIO_NEED_SYNC;
 499
 500                 /*
 501                  * For datasync only writes, we optimistically try using FUA for
 502                  * this IO.  Any non-FUA write that occurs will clear this flag,
 503                  * hence we know before completion whether a cache flush is
 504                  * necessary.
 505                  */
 506                 if ((iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC)) == IOCB_DSYNC)
 507                         dio->flags |= IOMAP_DIO_WRITE_FUA;
 508         }
 509
 510         if (iocb->ki_flags & IOCB_NOWAIT) {
 511                 if (filemap_range_has_page(mapping, pos, end)) {
 512                         ret = -EAGAIN;
 513                         goto out_free_dio;
 514                 }
 515                 iomap_flags |= IOMAP_NOWAIT;
 516         }
 517
 518         if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
 519                 ret = -EAGAIN;
 520                 if (pos >= dio->i_size || pos + count > dio->i_size)
 521                         goto out_free_dio;
 522                 iomap_flags |= IOMAP_OVERWRITE_ONLY;
 523         }
 524
 525         ret = filemap_write_and_wait_range(mapping, pos, end);
 526         if (ret)
 527                 goto out_free_dio;
 528
 529         if (iov_iter_rw(iter) == WRITE) {
 530                 /*
 531                  * Try to invalidate cache pages for the range we are writing.
 532                  * If this invalidation fails, let the caller fall back to
 533                  * buffered I/O.
 534                  */
 535                 if (invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
 536                                 end >> PAGE_SHIFT)) {
 537                         trace_iomap_dio_invalidate_fail(inode, pos, count);
 538                         ret = -ENOTBLK;
 539                         goto out_free_dio;
 540                 }
 541
 542                 if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) {
 543                         ret = sb_init_dio_done_wq(inode->i_sb);
 544                         if (ret < 0)
 545                                 goto out_free_dio;
 546                 }
 547         }
 548
 549         inode_dio_begin(inode);
 550
 551         blk_start_plug(&plug);
 552         do {
 553                 ret = iomap_apply(inode, pos, count, iomap_flags, ops, dio,
 554                                 iomap_dio_actor);
 555                 if (ret <= 0) {
 556                         /* magic error code to fall back to buffered I/O */
 557                         if (ret == -ENOTBLK) {
 558                                 wait_for_completion = true;
 559                                 ret = 0;
 560                         }
 561                         break;
 562                 }
 563                 pos += ret;
 564
 565                 if (iov_iter_rw(iter) == READ && pos >= dio->i_size) {
 566                         /*
 567                          * We only report that we've read data up to i_size.
 568                          * Revert iter to a state corresponding to that as
 569                          * some callers (such as splice code) rely on it.
 570                          */
 571                         iov_iter_revert(iter, pos - dio->i_size);
 572                         break;
 573                 }
 574         } while ((count = iov_iter_count(iter)) > 0);
 575         blk_finish_plug(&plug);
 576
 577         if (ret < 0)
 578                 iomap_dio_set_error(dio, ret);
 579
 580         /*
 581          * If all the writes we issued were FUA, we don't need to flush the
 582          * cache on IO completion. Clear the sync flag for this case.
 583          */
 584         if (dio->flags & IOMAP_DIO_WRITE_FUA)
 585                 dio->flags &= ~IOMAP_DIO_NEED_SYNC;
 586
 587         WRITE_ONCE(iocb->ki_cookie, dio->submit.cookie);
 588         WRITE_ONCE(iocb->private, dio->submit.last_queue);
 589
 590         /*
 591          * We are about to drop our additional submission reference, which
 592          * might be the last reference to the dio.  There are three different
 593          * ways we can progress here:
 594          *
 595          *  (a) If this is the last reference we will always complete and free
 596          *      the dio ourselves.
 597          *  (b) If this is not the last reference, and we serve an asynchronous
 598          *      iocb, we must never touch the dio after the decrement, the
 599          *      I/O completion handler will complete and free it.
 600          *  (c) If this is not the last reference, but we serve a synchronous
 601          *      iocb, the I/O completion handler will wake us up on the drop
 602          *      of the final reference, and we will complete and free it here
 603          *      after we got woken by the I/O completion handler.
 604          */
 605         dio->wait_for_completion = wait_for_completion;
 606         if (!atomic_dec_and_test(&dio->ref)) {
 607                 if (!wait_for_completion)
 608                         return ERR_PTR(-EIOCBQUEUED);
 609
 610                 for (;;) {
 611                         set_current_state(TASK_UNINTERRUPTIBLE);
 612                         if (!READ_ONCE(dio->submit.waiter))
 613                                 break;
 614
 615                         if (!(iocb->ki_flags & IOCB_HIPRI) ||
 616                             !dio->submit.last_queue ||
 617                             !blk_poll(dio->submit.last_queue,
 618                                          dio->submit.cookie, true))
 619                                 blk_io_schedule();
 620                 }
 621                 __set_current_state(TASK_RUNNING);
 622         }
 623
 624         return dio;
 625
 626 out_free_dio:
 627         kfree(dio);
 628         if (ret)
 629                 return ERR_PTR(ret);
 630         return NULL;
 631 }
 632 EXPORT_SYMBOL_GPL(__iomap_dio_rw);
 633
 634 ssize_t
 635 iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 636                 const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
 637                 unsigned int dio_flags)
 638 {
 639         struct iomap_dio *dio;
 640
 641         dio = __iomap_dio_rw(iocb, iter, ops, dops, dio_flags);
 642         if (IS_ERR_OR_NULL(dio))
 643                 return PTR_ERR_OR_ZERO(dio);
 644         return iomap_dio_complete(dio);
 645 }
 646 EXPORT_SYMBOL_GPL(iomap_dio_rw);