1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2010 Red Hat, Inc. 4 * Copyright (c) 2016-2021 Christoph Hellwig. 5 */ 6 #include <linux/module.h> 7 #include <linux/compiler.h> 8 #include <linux/fs.h> 9 #include <linux/fscrypt.h> 10 #include <linux/pagemap.h> 11 #include <linux/iomap.h> 12 #include <linux/backing-dev.h> 13 #include <linux/uio.h> 14 #include <linux/task_io_accounting_ops.h> 15 #include "trace.h" 16 17 #include "../internal.h" 18 19 /* 20 * Private flags for iomap_dio, must not overlap with the public ones in 21 * iomap.h: 22 */ 23 #define IOMAP_DIO_WRITE_FUA (1 << 28) 24 #define IOMAP_DIO_NEED_SYNC (1 << 29) 25 #define IOMAP_DIO_WRITE (1 << 30) 26 #define IOMAP_DIO_DIRTY (1 << 31) 27 28 struct iomap_dio { 29 struct kiocb *iocb; 30 const struct iomap_dio_ops *dops; 31 loff_t i_size; 32 loff_t size; 33 atomic_t ref; 34 unsigned flags; 35 int error; 36 size_t done_before; 37 bool wait_for_completion; 38 39 union { 40 /* used during submission and for synchronous completion: */ 41 struct { 42 struct iov_iter *iter; 43 struct task_struct *waiter; 44 struct bio *poll_bio; 45 } submit; 46 47 /* used for aio completion: */ 48 struct { 49 struct work_struct work; 50 } aio; 51 }; 52 }; 53 54 static struct bio *iomap_dio_alloc_bio(const struct iomap_iter *iter, 55 struct iomap_dio *dio, unsigned short nr_vecs, blk_opf_t opf) 56 { 57 if (dio->dops && dio->dops->bio_set) 58 return bio_alloc_bioset(iter->iomap.bdev, nr_vecs, opf, 59 GFP_KERNEL, dio->dops->bio_set); 60 return bio_alloc(iter->iomap.bdev, nr_vecs, opf, GFP_KERNEL); 61 } 62 63 static void iomap_dio_submit_bio(const struct iomap_iter *iter, 64 struct iomap_dio *dio, struct bio *bio, loff_t pos) 65 { 66 atomic_inc(&dio->ref); 67 68 /* Sync dio can't be polled reliably */ 69 if ((dio->iocb->ki_flags & IOCB_HIPRI) && !is_sync_kiocb(dio->iocb)) { 70 bio_set_polled(bio, dio->iocb); 71 dio->submit.poll_bio = bio; 72 } 73 74 if (dio->dops && dio->dops->submit_io) 75 dio->dops->submit_io(iter, bio, pos); 76 else 77 submit_bio(bio); 78 } 79 80 ssize_t iomap_dio_complete(struct iomap_dio *dio) 81 { 82 const struct iomap_dio_ops *dops = dio->dops; 83 struct kiocb *iocb = dio->iocb; 84 struct inode *inode = file_inode(iocb->ki_filp); 85 loff_t offset = iocb->ki_pos; 86 ssize_t ret = dio->error; 87 88 if (dops && dops->end_io) 89 ret = dops->end_io(iocb, dio->size, ret, dio->flags); 90 91 if (likely(!ret)) { 92 ret = dio->size; 93 /* check for short read */ 94 if (offset + ret > dio->i_size && 95 !(dio->flags & IOMAP_DIO_WRITE)) 96 ret = dio->i_size - offset; 97 iocb->ki_pos += ret; 98 } 99 100 /* 101 * Try again to invalidate clean pages which might have been cached by 102 * non-direct readahead, or faulted in by get_user_pages() if the source 103 * of the write was an mmap'ed region of the file we're writing. Either 104 * one is a pretty crazy thing to do, so we don't support it 100%. If 105 * this invalidation fails, tough, the write still worked... 106 * 107 * And this page cache invalidation has to be after ->end_io(), as some 108 * filesystems convert unwritten extents to real allocations in 109 * ->end_io() when necessary, otherwise a racing buffer read would cache 110 * zeros from unwritten extents. 111 */ 112 if (!dio->error && dio->size && 113 (dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) { 114 int err; 115 err = invalidate_inode_pages2_range(inode->i_mapping, 116 offset >> PAGE_SHIFT, 117 (offset + dio->size - 1) >> PAGE_SHIFT); 118 if (err) 119 dio_warn_stale_pagecache(iocb->ki_filp); 120 } 121 122 inode_dio_end(file_inode(iocb->ki_filp)); 123 /* 124 * If this is a DSYNC write, make sure we push it to stable storage now 125 * that we've written data. 126 */ 127 if (ret > 0 && (dio->flags & IOMAP_DIO_NEED_SYNC)) 128 ret = generic_write_sync(iocb, ret); 129 130 if (ret > 0) 131 ret += dio->done_before; 132 133 kfree(dio); 134 135 return ret; 136 } 137 EXPORT_SYMBOL_GPL(iomap_dio_complete); 138 139 static void iomap_dio_complete_work(struct work_struct *work) 140 { 141 struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work); 142 struct kiocb *iocb = dio->iocb; 143 144 iocb->ki_complete(iocb, iomap_dio_complete(dio)); 145 } 146 147 /* 148 * Set an error in the dio if none is set yet. We have to use cmpxchg 149 * as the submission context and the completion context(s) can race to 150 * update the error. 151 */ 152 static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret) 153 { 154 cmpxchg(&dio->error, 0, ret); 155 } 156 157 void iomap_dio_bio_end_io(struct bio *bio) 158 { 159 struct iomap_dio *dio = bio->bi_private; 160 bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY); 161 162 if (bio->bi_status) 163 iomap_dio_set_error(dio, blk_status_to_errno(bio->bi_status)); 164 165 if (atomic_dec_and_test(&dio->ref)) { 166 if (dio->wait_for_completion) { 167 struct task_struct *waiter = dio->submit.waiter; 168 WRITE_ONCE(dio->submit.waiter, NULL); 169 blk_wake_io_task(waiter); 170 } else if (dio->flags & IOMAP_DIO_WRITE) { 171 struct inode *inode = file_inode(dio->iocb->ki_filp); 172 173 WRITE_ONCE(dio->iocb->private, NULL); 174 INIT_WORK(&dio->aio.work, iomap_dio_complete_work); 175 queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work); 176 } else { 177 WRITE_ONCE(dio->iocb->private, NULL); 178 iomap_dio_complete_work(&dio->aio.work); 179 } 180 } 181 182 if (should_dirty) { 183 bio_check_pages_dirty(bio); 184 } else { 185 bio_release_pages(bio, false); 186 bio_put(bio); 187 } 188 } 189 EXPORT_SYMBOL_GPL(iomap_dio_bio_end_io); 190 191 static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio, 192 loff_t pos, unsigned len) 193 { 194 struct inode *inode = file_inode(dio->iocb->ki_filp); 195 struct page *page = ZERO_PAGE(0); 196 struct bio *bio; 197 198 bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE); 199 fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits, 200 GFP_KERNEL); 201 bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos); 202 bio->bi_private = dio; 203 bio->bi_end_io = iomap_dio_bio_end_io; 204 205 get_page(page); 206 __bio_add_page(bio, page, len, 0); 207 iomap_dio_submit_bio(iter, dio, bio, pos); 208 } 209 210 /* 211 * Figure out the bio's operation flags from the dio request, the 212 * mapping, and whether or not we want FUA. Note that we can end up 213 * clearing the WRITE_FUA flag in the dio request. 214 */ 215 static inline blk_opf_t iomap_dio_bio_opflags(struct iomap_dio *dio, 216 const struct iomap *iomap, bool use_fua) 217 { 218 blk_opf_t opflags = REQ_SYNC | REQ_IDLE; 219 220 if (!(dio->flags & IOMAP_DIO_WRITE)) { 221 WARN_ON_ONCE(iomap->flags & IOMAP_F_ZONE_APPEND); 222 return REQ_OP_READ; 223 } 224 225 if (iomap->flags & IOMAP_F_ZONE_APPEND) 226 opflags |= REQ_OP_ZONE_APPEND; 227 else 228 opflags |= REQ_OP_WRITE; 229 230 if (use_fua) 231 opflags |= REQ_FUA; 232 else 233 dio->flags &= ~IOMAP_DIO_WRITE_FUA; 234 235 return opflags; 236 } 237 238 static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter, 239 struct iomap_dio *dio) 240 { 241 const struct iomap *iomap = &iter->iomap; 242 struct inode *inode = iter->inode; 243 unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev)); 244 unsigned int fs_block_size = i_blocksize(inode), pad; 245 loff_t length = iomap_length(iter); 246 loff_t pos = iter->pos; 247 blk_opf_t bio_opf; 248 struct bio *bio; 249 bool need_zeroout = false; 250 bool use_fua = false; 251 int nr_pages, ret = 0; 252 size_t copied = 0; 253 size_t orig_count; 254 255 if ((pos | length) & ((1 << blkbits) - 1) || 256 !bdev_iter_is_aligned(iomap->bdev, dio->submit.iter)) 257 return -EINVAL; 258 259 if (iomap->type == IOMAP_UNWRITTEN) { 260 dio->flags |= IOMAP_DIO_UNWRITTEN; 261 need_zeroout = true; 262 } 263 264 if (iomap->flags & IOMAP_F_SHARED) 265 dio->flags |= IOMAP_DIO_COW; 266 267 if (iomap->flags & IOMAP_F_NEW) { 268 need_zeroout = true; 269 } else if (iomap->type == IOMAP_MAPPED) { 270 /* 271 * Use a FUA write if we need datasync semantics, this is a pure 272 * data IO that doesn't require any metadata updates (including 273 * after IO completion such as unwritten extent conversion) and 274 * the underlying device supports FUA. This allows us to avoid 275 * cache flushes on IO completion. 276 */ 277 if (!(iomap->flags & (IOMAP_F_SHARED|IOMAP_F_DIRTY)) && 278 (dio->flags & IOMAP_DIO_WRITE_FUA) && bdev_fua(iomap->bdev)) 279 use_fua = true; 280 } 281 282 /* 283 * Save the original count and trim the iter to just the extent we 284 * are operating on right now. The iter will be re-expanded once 285 * we are done. 286 */ 287 orig_count = iov_iter_count(dio->submit.iter); 288 iov_iter_truncate(dio->submit.iter, length); 289 290 if (!iov_iter_count(dio->submit.iter)) 291 goto out; 292 293 /* 294 * We can only poll for single bio I/Os. 295 */ 296 if (need_zeroout || 297 ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) 298 dio->iocb->ki_flags &= ~IOCB_HIPRI; 299 300 if (need_zeroout) { 301 /* zero out from the start of the block to the write offset */ 302 pad = pos & (fs_block_size - 1); 303 if (pad) 304 iomap_dio_zero(iter, dio, pos - pad, pad); 305 } 306 307 /* 308 * Set the operation flags early so that bio_iov_iter_get_pages 309 * can set up the page vector appropriately for a ZONE_APPEND 310 * operation. 311 */ 312 bio_opf = iomap_dio_bio_opflags(dio, iomap, use_fua); 313 314 nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, BIO_MAX_VECS); 315 do { 316 size_t n; 317 if (dio->error) { 318 iov_iter_revert(dio->submit.iter, copied); 319 copied = ret = 0; 320 goto out; 321 } 322 323 bio = iomap_dio_alloc_bio(iter, dio, nr_pages, bio_opf); 324 fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits, 325 GFP_KERNEL); 326 bio->bi_iter.bi_sector = iomap_sector(iomap, pos); 327 bio->bi_ioprio = dio->iocb->ki_ioprio; 328 bio->bi_private = dio; 329 bio->bi_end_io = iomap_dio_bio_end_io; 330 331 ret = bio_iov_iter_get_pages(bio, dio->submit.iter); 332 if (unlikely(ret)) { 333 /* 334 * We have to stop part way through an IO. We must fall 335 * through to the sub-block tail zeroing here, otherwise 336 * this short IO may expose stale data in the tail of 337 * the block we haven't written data to. 338 */ 339 bio_put(bio); 340 goto zero_tail; 341 } 342 343 n = bio->bi_iter.bi_size; 344 if (dio->flags & IOMAP_DIO_WRITE) { 345 task_io_account_write(n); 346 } else { 347 if (dio->flags & IOMAP_DIO_DIRTY) 348 bio_set_pages_dirty(bio); 349 } 350 351 dio->size += n; 352 copied += n; 353 354 nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter, 355 BIO_MAX_VECS); 356 /* 357 * We can only poll for single bio I/Os. 358 */ 359 if (nr_pages) 360 dio->iocb->ki_flags &= ~IOCB_HIPRI; 361 iomap_dio_submit_bio(iter, dio, bio, pos); 362 pos += n; 363 } while (nr_pages); 364 365 /* 366 * We need to zeroout the tail of a sub-block write if the extent type 367 * requires zeroing or the write extends beyond EOF. If we don't zero 368 * the block tail in the latter case, we can expose stale data via mmap 369 * reads of the EOF block. 370 */ 371 zero_tail: 372 if (need_zeroout || 373 ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode))) { 374 /* zero out from the end of the write to the end of the block */ 375 pad = pos & (fs_block_size - 1); 376 if (pad) 377 iomap_dio_zero(iter, dio, pos, fs_block_size - pad); 378 } 379 out: 380 /* Undo iter limitation to current extent */ 381 iov_iter_reexpand(dio->submit.iter, orig_count - copied); 382 if (copied) 383 return copied; 384 return ret; 385 } 386 387 static loff_t iomap_dio_hole_iter(const struct iomap_iter *iter, 388 struct iomap_dio *dio) 389 { 390 loff_t length = iov_iter_zero(iomap_length(iter), dio->submit.iter); 391 392 dio->size += length; 393 if (!length) 394 return -EFAULT; 395 return length; 396 } 397 398 static loff_t iomap_dio_inline_iter(const struct iomap_iter *iomi, 399 struct iomap_dio *dio) 400 { 401 const struct iomap *iomap = &iomi->iomap; 402 struct iov_iter *iter = dio->submit.iter; 403 void *inline_data = iomap_inline_data(iomap, iomi->pos); 404 loff_t length = iomap_length(iomi); 405 loff_t pos = iomi->pos; 406 size_t copied; 407 408 if (WARN_ON_ONCE(!iomap_inline_data_valid(iomap))) 409 return -EIO; 410 411 if (dio->flags & IOMAP_DIO_WRITE) { 412 loff_t size = iomi->inode->i_size; 413 414 if (pos > size) 415 memset(iomap_inline_data(iomap, size), 0, pos - size); 416 copied = copy_from_iter(inline_data, length, iter); 417 if (copied) { 418 if (pos + copied > size) 419 i_size_write(iomi->inode, pos + copied); 420 mark_inode_dirty(iomi->inode); 421 } 422 } else { 423 copied = copy_to_iter(inline_data, length, iter); 424 } 425 dio->size += copied; 426 if (!copied) 427 return -EFAULT; 428 return copied; 429 } 430 431 static loff_t iomap_dio_iter(const struct iomap_iter *iter, 432 struct iomap_dio *dio) 433 { 434 switch (iter->iomap.type) { 435 case IOMAP_HOLE: 436 if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE)) 437 return -EIO; 438 return iomap_dio_hole_iter(iter, dio); 439 case IOMAP_UNWRITTEN: 440 if (!(dio->flags & IOMAP_DIO_WRITE)) 441 return iomap_dio_hole_iter(iter, dio); 442 return iomap_dio_bio_iter(iter, dio); 443 case IOMAP_MAPPED: 444 return iomap_dio_bio_iter(iter, dio); 445 case IOMAP_INLINE: 446 return iomap_dio_inline_iter(iter, dio); 447 case IOMAP_DELALLOC: 448 /* 449 * DIO is not serialised against mmap() access at all, and so 450 * if the page_mkwrite occurs between the writeback and the 451 * iomap_iter() call in the DIO path, then it will see the 452 * DELALLOC block that the page-mkwrite allocated. 453 */ 454 pr_warn_ratelimited("Direct I/O collision with buffered writes! File: %pD4 Comm: %.20s\n", 455 dio->iocb->ki_filp, current->comm); 456 return -EIO; 457 default: 458 WARN_ON_ONCE(1); 459 return -EIO; 460 } 461 } 462 463 /* 464 * iomap_dio_rw() always completes O_[D]SYNC writes regardless of whether the IO 465 * is being issued as AIO or not. This allows us to optimise pure data writes 466 * to use REQ_FUA rather than requiring generic_write_sync() to issue a 467 * REQ_FLUSH post write. This is slightly tricky because a single request here 468 * can be mapped into multiple disjoint IOs and only a subset of the IOs issued 469 * may be pure data writes. In that case, we still need to do a full data sync 470 * completion. 471 * 472 * When page faults are disabled and @dio_flags includes IOMAP_DIO_PARTIAL, 473 * __iomap_dio_rw can return a partial result if it encounters a non-resident 474 * page in @iter after preparing a transfer. In that case, the non-resident 475 * pages can be faulted in and the request resumed with @done_before set to the 476 * number of bytes previously transferred. The request will then complete with 477 * the correct total number of bytes transferred; this is essential for 478 * completing partial requests asynchronously. 479 * 480 * Returns -ENOTBLK In case of a page invalidation invalidation failure for 481 * writes. The callers needs to fall back to buffered I/O in this case. 482 */ 483 struct iomap_dio * 484 __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, 485 const struct iomap_ops *ops, const struct iomap_dio_ops *dops, 486 unsigned int dio_flags, void *private, size_t done_before) 487 { 488 struct address_space *mapping = iocb->ki_filp->f_mapping; 489 struct inode *inode = file_inode(iocb->ki_filp); 490 struct iomap_iter iomi = { 491 .inode = inode, 492 .pos = iocb->ki_pos, 493 .len = iov_iter_count(iter), 494 .flags = IOMAP_DIRECT, 495 .private = private, 496 }; 497 loff_t end = iomi.pos + iomi.len - 1, ret = 0; 498 bool wait_for_completion = 499 is_sync_kiocb(iocb) || (dio_flags & IOMAP_DIO_FORCE_WAIT); 500 struct blk_plug plug; 501 struct iomap_dio *dio; 502 503 if (!iomi.len) 504 return NULL; 505 506 dio = kmalloc(sizeof(*dio), GFP_KERNEL); 507 if (!dio) 508 return ERR_PTR(-ENOMEM); 509 510 dio->iocb = iocb; 511 atomic_set(&dio->ref, 1); 512 dio->size = 0; 513 dio->i_size = i_size_read(inode); 514 dio->dops = dops; 515 dio->error = 0; 516 dio->flags = 0; 517 dio->done_before = done_before; 518 519 dio->submit.iter = iter; 520 dio->submit.waiter = current; 521 dio->submit.poll_bio = NULL; 522 523 if (iov_iter_rw(iter) == READ) { 524 if (iomi.pos >= dio->i_size) 525 goto out_free_dio; 526 527 if (iocb->ki_flags & IOCB_NOWAIT) { 528 if (filemap_range_needs_writeback(mapping, iomi.pos, 529 end)) { 530 ret = -EAGAIN; 531 goto out_free_dio; 532 } 533 iomi.flags |= IOMAP_NOWAIT; 534 } 535 536 if (user_backed_iter(iter)) 537 dio->flags |= IOMAP_DIO_DIRTY; 538 } else { 539 iomi.flags |= IOMAP_WRITE; 540 dio->flags |= IOMAP_DIO_WRITE; 541 542 if (iocb->ki_flags & IOCB_NOWAIT) { 543 if (filemap_range_has_page(mapping, iomi.pos, end)) { 544 ret = -EAGAIN; 545 goto out_free_dio; 546 } 547 iomi.flags |= IOMAP_NOWAIT; 548 } 549 550 /* for data sync or sync, we need sync completion processing */ 551 if (iocb_is_dsync(iocb) && !(dio_flags & IOMAP_DIO_NOSYNC)) { 552 dio->flags |= IOMAP_DIO_NEED_SYNC; 553 554 /* 555 * For datasync only writes, we optimistically try 556 * using FUA for this IO. Any non-FUA write that 557 * occurs will clear this flag, hence we know before 558 * completion whether a cache flush is necessary. 559 */ 560 if (!(iocb->ki_flags & IOCB_SYNC)) 561 dio->flags |= IOMAP_DIO_WRITE_FUA; 562 } 563 } 564 565 if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) { 566 ret = -EAGAIN; 567 if (iomi.pos >= dio->i_size || 568 iomi.pos + iomi.len > dio->i_size) 569 goto out_free_dio; 570 iomi.flags |= IOMAP_OVERWRITE_ONLY; 571 } 572 573 ret = filemap_write_and_wait_range(mapping, iomi.pos, end); 574 if (ret) 575 goto out_free_dio; 576 577 if (iov_iter_rw(iter) == WRITE) { 578 /* 579 * Try to invalidate cache pages for the range we are writing. 580 * If this invalidation fails, let the caller fall back to 581 * buffered I/O. 582 */ 583 if (invalidate_inode_pages2_range(mapping, 584 iomi.pos >> PAGE_SHIFT, end >> PAGE_SHIFT)) { 585 trace_iomap_dio_invalidate_fail(inode, iomi.pos, 586 iomi.len); 587 ret = -ENOTBLK; 588 goto out_free_dio; 589 } 590 591 if (!wait_for_completion && !inode->i_sb->s_dio_done_wq) { 592 ret = sb_init_dio_done_wq(inode->i_sb); 593 if (ret < 0) 594 goto out_free_dio; 595 } 596 } 597 598 inode_dio_begin(inode); 599 600 blk_start_plug(&plug); 601 while ((ret = iomap_iter(&iomi, ops)) > 0) { 602 iomi.processed = iomap_dio_iter(&iomi, dio); 603 604 /* 605 * We can only poll for single bio I/Os. 606 */ 607 iocb->ki_flags &= ~IOCB_HIPRI; 608 } 609 610 blk_finish_plug(&plug); 611 612 /* 613 * We only report that we've read data up to i_size. 614 * Revert iter to a state corresponding to that as some callers (such 615 * as the splice code) rely on it. 616 */ 617 if (iov_iter_rw(iter) == READ && iomi.pos >= dio->i_size) 618 iov_iter_revert(iter, iomi.pos - dio->i_size); 619 620 if (ret == -EFAULT && dio->size && (dio_flags & IOMAP_DIO_PARTIAL)) { 621 if (!(iocb->ki_flags & IOCB_NOWAIT)) 622 wait_for_completion = true; 623 ret = 0; 624 } 625 626 /* magic error code to fall back to buffered I/O */ 627 if (ret == -ENOTBLK) { 628 wait_for_completion = true; 629 ret = 0; 630 } 631 if (ret < 0) 632 iomap_dio_set_error(dio, ret); 633 634 /* 635 * If all the writes we issued were FUA, we don't need to flush the 636 * cache on IO completion. Clear the sync flag for this case. 637 */ 638 if (dio->flags & IOMAP_DIO_WRITE_FUA) 639 dio->flags &= ~IOMAP_DIO_NEED_SYNC; 640 641 WRITE_ONCE(iocb->private, dio->submit.poll_bio); 642 643 /* 644 * We are about to drop our additional submission reference, which 645 * might be the last reference to the dio. There are three different 646 * ways we can progress here: 647 * 648 * (a) If this is the last reference we will always complete and free 649 * the dio ourselves. 650 * (b) If this is not the last reference, and we serve an asynchronous 651 * iocb, we must never touch the dio after the decrement, the 652 * I/O completion handler will complete and free it. 653 * (c) If this is not the last reference, but we serve a synchronous 654 * iocb, the I/O completion handler will wake us up on the drop 655 * of the final reference, and we will complete and free it here 656 * after we got woken by the I/O completion handler. 657 */ 658 dio->wait_for_completion = wait_for_completion; 659 if (!atomic_dec_and_test(&dio->ref)) { 660 if (!wait_for_completion) 661 return ERR_PTR(-EIOCBQUEUED); 662 663 for (;;) { 664 set_current_state(TASK_UNINTERRUPTIBLE); 665 if (!READ_ONCE(dio->submit.waiter)) 666 break; 667 668 blk_io_schedule(); 669 } 670 __set_current_state(TASK_RUNNING); 671 } 672 673 return dio; 674 675 out_free_dio: 676 kfree(dio); 677 if (ret) 678 return ERR_PTR(ret); 679 return NULL; 680 } 681 EXPORT_SYMBOL_GPL(__iomap_dio_rw); 682 683 ssize_t 684 iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, 685 const struct iomap_ops *ops, const struct iomap_dio_ops *dops, 686 unsigned int dio_flags, void *private, size_t done_before) 687 { 688 struct iomap_dio *dio; 689 690 dio = __iomap_dio_rw(iocb, iter, ops, dops, dio_flags, private, 691 done_before); 692 if (IS_ERR_OR_NULL(dio)) 693 return PTR_ERR_OR_ZERO(dio); 694 return iomap_dio_complete(dio); 695 } 696 EXPORT_SYMBOL_GPL(iomap_dio_rw); 697