fs/iomap.c

   1 /*
   2  * Copyright (C) 2010 Red Hat, Inc.
   3  * Copyright (c) 2016 Christoph Hellwig.
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms and conditions of the GNU General Public License,
   7  * version 2, as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  12  * more details.
  13  */
  14 #include <linux/module.h>
  15 #include <linux/compiler.h>
  16 #include <linux/fs.h>
  17 #include <linux/iomap.h>
  18 #include <linux/uaccess.h>
  19 #include <linux/gfp.h>
  20 #include <linux/mm.h>
  21 #include <linux/swap.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/file.h>
  24 #include <linux/uio.h>
  25 #include <linux/backing-dev.h>
  26 #include <linux/buffer_head.h>
  27 #include <linux/task_io_accounting_ops.h>
  28 #include <linux/dax.h>
  29 #include <linux/sched/signal.h>
  30
  31 #include "internal.h"
  32
  33 /*
  34  * Execute a iomap write on a segment of the mapping that spans a
  35  * contiguous range of pages that have identical block mapping state.
  36  *
  37  * This avoids the need to map pages individually, do individual allocations
  38  * for each page and most importantly avoid the need for filesystem specific
  39  * locking per page. Instead, all the operations are amortised over the entire
  40  * range of pages. It is assumed that the filesystems will lock whatever
  41  * resources they require in the iomap_begin call, and release them in the
  42  * iomap_end call.
  43  */
  44 loff_t
  45 iomap_apply(struct inode *inode, loff_t pos, loff_t length, unsigned flags,
  46                 const struct iomap_ops *ops, void *data, iomap_actor_t actor)
  47 {
  48         struct iomap iomap = { 0 };
  49         loff_t written = 0, ret;
  50
  51         /*
  52          * Need to map a range from start position for length bytes. This can
  53          * span multiple pages - it is only guaranteed to return a range of a
  54          * single type of pages (e.g. all into a hole, all mapped or all
  55          * unwritten). Failure at this point has nothing to undo.
  56          *
  57          * If allocation is required for this range, reserve the space now so
  58          * that the allocation is guaranteed to succeed later on. Once we copy
  59          * the data into the page cache pages, then we cannot fail otherwise we
  60          * expose transient stale data. If the reserve fails, we can safely
  61          * back out at this point as there is nothing to undo.
  62          */
  63         ret = ops->iomap_begin(inode, pos, length, flags, &iomap);
  64         if (ret)
  65                 return ret;
  66         if (WARN_ON(iomap.offset > pos))
  67                 return -EIO;
  68
  69         /*
  70          * Cut down the length to the one actually provided by the filesystem,
  71          * as it might not be able to give us the whole size that we requested.
  72          */
  73         if (iomap.offset + iomap.length < pos + length)
  74                 length = iomap.offset + iomap.length - pos;
  75
  76         /*
  77          * Now that we have guaranteed that the space allocation will succeed.
  78          * we can do the copy-in page by page without having to worry about
  79          * failures exposing transient data.
  80          */
  81         written = actor(inode, pos, length, data, &iomap);
  82
  83         /*
  84          * Now the data has been copied, commit the range we've copied.  This
  85          * should not fail unless the filesystem has had a fatal error.
  86          */
  87         if (ops->iomap_end) {
  88                 ret = ops->iomap_end(inode, pos, length,
  89                                      written > 0 ? written : 0,
  90                                      flags, &iomap);
  91         }
  92
  93         return written ? written : ret;
  94 }
  95
  96 static void
  97 iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
  98 {
  99         loff_t i_size = i_size_read(inode);
 100
 101         /*
 102          * Only truncate newly allocated pages beyoned EOF, even if the
 103          * write started inside the existing inode size.
 104          */
 105         if (pos + len > i_size)
 106                 truncate_pagecache_range(inode, max(pos, i_size), pos + len);
 107 }
 108
 109 static int
 110 iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
 111                 struct page **pagep, struct iomap *iomap)
 112 {
 113         pgoff_t index = pos >> PAGE_SHIFT;
 114         struct page *page;
 115         int status = 0;
 116
 117         BUG_ON(pos + len > iomap->offset + iomap->length);
 118
 119         if (fatal_signal_pending(current))
 120                 return -EINTR;
 121
 122         page = grab_cache_page_write_begin(inode->i_mapping, index, flags);
 123         if (!page)
 124                 return -ENOMEM;
 125
 126         status = __block_write_begin_int(page, pos, len, NULL, iomap);
 127         if (unlikely(status)) {
 128                 unlock_page(page);
 129                 put_page(page);
 130                 page = NULL;
 131
 132                 iomap_write_failed(inode, pos, len);
 133         }
 134
 135         *pagep = page;
 136         return status;
 137 }
 138
 139 static int
 140 iomap_write_end(struct inode *inode, loff_t pos, unsigned len,
 141                 unsigned copied, struct page *page)
 142 {
 143         int ret;
 144
 145         ret = generic_write_end(NULL, inode->i_mapping, pos, len,
 146                         copied, page, NULL);
 147         if (ret < len)
 148                 iomap_write_failed(inode, pos, len);
 149         return ret;
 150 }
 151
 152 static loff_t
 153 iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 154                 struct iomap *iomap)
 155 {
 156         struct iov_iter *i = data;
 157         long status = 0;
 158         ssize_t written = 0;
 159         unsigned int flags = AOP_FLAG_NOFS;
 160
 161         do {
 162                 struct page *page;
 163                 unsigned long offset;   /* Offset into pagecache page */
 164                 unsigned long bytes;    /* Bytes to write to page */
 165                 size_t copied;          /* Bytes copied from user */
 166
 167                 offset = (pos & (PAGE_SIZE - 1));
 168                 bytes = min_t(unsigned long, PAGE_SIZE - offset,
 169                                                 iov_iter_count(i));
 170 again:
 171                 if (bytes > length)
 172                         bytes = length;
 173
 174                 /*
 175                  * Bring in the user page that we will copy from _first_.
 176                  * Otherwise there's a nasty deadlock on copying from the
 177                  * same page as we're writing to, without it being marked
 178                  * up-to-date.
 179                  *
 180                  * Not only is this an optimisation, but it is also required
 181                  * to check that the address is actually valid, when atomic
 182                  * usercopies are used, below.
 183                  */
 184                 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
 185                         status = -EFAULT;
 186                         break;
 187                 }
 188
 189                 status = iomap_write_begin(inode, pos, bytes, flags, &page,
 190                                 iomap);
 191                 if (unlikely(status))
 192                         break;
 193
 194                 if (mapping_writably_mapped(inode->i_mapping))
 195                         flush_dcache_page(page);
 196
 197                 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
 198
 199                 flush_dcache_page(page);
 200
 201                 status = iomap_write_end(inode, pos, bytes, copied, page);
 202                 if (unlikely(status < 0))
 203                         break;
 204                 copied = status;
 205
 206                 cond_resched();
 207
 208                 iov_iter_advance(i, copied);
 209                 if (unlikely(copied == 0)) {
 210                         /*
 211                          * If we were unable to copy any data at all, we must
 212                          * fall back to a single segment length write.
 213                          *
 214                          * If we didn't fallback here, we could livelock
 215                          * because not all segments in the iov can be copied at
 216                          * once without a pagefault.
 217                          */
 218                         bytes = min_t(unsigned long, PAGE_SIZE - offset,
 219                                                 iov_iter_single_seg_count(i));
 220                         goto again;
 221                 }
 222                 pos += copied;
 223                 written += copied;
 224                 length -= copied;
 225
 226                 balance_dirty_pages_ratelimited(inode->i_mapping);
 227         } while (iov_iter_count(i) && length);
 228
 229         return written ? written : status;
 230 }
 231
 232 ssize_t
 233 iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *iter,
 234                 const struct iomap_ops *ops)
 235 {
 236         struct inode *inode = iocb->ki_filp->f_mapping->host;
 237         loff_t pos = iocb->ki_pos, ret = 0, written = 0;
 238
 239         while (iov_iter_count(iter)) {
 240                 ret = iomap_apply(inode, pos, iov_iter_count(iter),
 241                                 IOMAP_WRITE, ops, iter, iomap_write_actor);
 242                 if (ret <= 0)
 243                         break;
 244                 pos += ret;
 245                 written += ret;
 246         }
 247
 248         return written ? written : ret;
 249 }
 250 EXPORT_SYMBOL_GPL(iomap_file_buffered_write);
 251
 252 static struct page *
 253 __iomap_read_page(struct inode *inode, loff_t offset)
 254 {
 255         struct address_space *mapping = inode->i_mapping;
 256         struct page *page;
 257
 258         page = read_mapping_page(mapping, offset >> PAGE_SHIFT, NULL);
 259         if (IS_ERR(page))
 260                 return page;
 261         if (!PageUptodate(page)) {
 262                 put_page(page);
 263                 return ERR_PTR(-EIO);
 264         }
 265         return page;
 266 }
 267
 268 static loff_t
 269 iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 270                 struct iomap *iomap)
 271 {
 272         long status = 0;
 273         ssize_t written = 0;
 274
 275         do {
 276                 struct page *page, *rpage;
 277                 unsigned long offset;   /* Offset into pagecache page */
 278                 unsigned long bytes;    /* Bytes to write to page */
 279
 280                 offset = (pos & (PAGE_SIZE - 1));
 281                 bytes = min_t(unsigned long, PAGE_SIZE - offset, length);
 282
 283                 rpage = __iomap_read_page(inode, pos);
 284                 if (IS_ERR(rpage))
 285                         return PTR_ERR(rpage);
 286
 287                 status = iomap_write_begin(inode, pos, bytes,
 288                                            AOP_FLAG_NOFS, &page, iomap);
 289                 put_page(rpage);
 290                 if (unlikely(status))
 291                         return status;
 292
 293                 WARN_ON_ONCE(!PageUptodate(page));
 294
 295                 status = iomap_write_end(inode, pos, bytes, bytes, page);
 296                 if (unlikely(status <= 0)) {
 297                         if (WARN_ON_ONCE(status == 0))
 298                                 return -EIO;
 299                         return status;
 300                 }
 301
 302                 cond_resched();
 303
 304                 pos += status;
 305                 written += status;
 306                 length -= status;
 307
 308                 balance_dirty_pages_ratelimited(inode->i_mapping);
 309         } while (length);
 310
 311         return written;
 312 }
 313
 314 int
 315 iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
 316                 const struct iomap_ops *ops)
 317 {
 318         loff_t ret;
 319
 320         while (len) {
 321                 ret = iomap_apply(inode, pos, len, IOMAP_WRITE, ops, NULL,
 322                                 iomap_dirty_actor);
 323                 if (ret <= 0)
 324                         return ret;
 325                 pos += ret;
 326                 len -= ret;
 327         }
 328
 329         return 0;
 330 }
 331 EXPORT_SYMBOL_GPL(iomap_file_dirty);
 332
 333 static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
 334                 unsigned bytes, struct iomap *iomap)
 335 {
 336         struct page *page;
 337         int status;
 338
 339         status = iomap_write_begin(inode, pos, bytes, AOP_FLAG_NOFS, &page,
 340                                    iomap);
 341         if (status)
 342                 return status;
 343
 344         zero_user(page, offset, bytes);
 345         mark_page_accessed(page);
 346
 347         return iomap_write_end(inode, pos, bytes, bytes, page);
 348 }
 349
 350 static int iomap_dax_zero(loff_t pos, unsigned offset, unsigned bytes,
 351                 struct iomap *iomap)
 352 {
 353         sector_t sector = iomap->blkno +
 354                 (((pos & ~(PAGE_SIZE - 1)) - iomap->offset) >> 9);
 355
 356         return __dax_zero_page_range(iomap->bdev, iomap->dax_dev, sector,
 357                         offset, bytes);
 358 }
 359
 360 static loff_t
 361 iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
 362                 void *data, struct iomap *iomap)
 363 {
 364         bool *did_zero = data;
 365         loff_t written = 0;
 366         int status;
 367
 368         /* already zeroed?  we're done. */
 369         if (iomap->type == IOMAP_HOLE || iomap->type == IOMAP_UNWRITTEN)
 370                 return count;
 371
 372         do {
 373                 unsigned offset, bytes;
 374
 375                 offset = pos & (PAGE_SIZE - 1); /* Within page */
 376                 bytes = min_t(unsigned, PAGE_SIZE - offset, count);
 377
 378                 if (IS_DAX(inode))
 379                         status = iomap_dax_zero(pos, offset, bytes, iomap);
 380                 else
 381                         status = iomap_zero(inode, pos, offset, bytes, iomap);
 382                 if (status < 0)
 383                         return status;
 384
 385                 pos += bytes;
 386                 count -= bytes;
 387                 written += bytes;
 388                 if (did_zero)
 389                         *did_zero = true;
 390         } while (count > 0);
 391
 392         return written;
 393 }
 394
 395 int
 396 iomap_zero_range(struct inode *inode, loff_t pos, loff_t len, bool *did_zero,
 397                 const struct iomap_ops *ops)
 398 {
 399         loff_t ret;
 400
 401         while (len > 0) {
 402                 ret = iomap_apply(inode, pos, len, IOMAP_ZERO,
 403                                 ops, did_zero, iomap_zero_range_actor);
 404                 if (ret <= 0)
 405                         return ret;
 406
 407                 pos += ret;
 408                 len -= ret;
 409         }
 410
 411         return 0;
 412 }
 413 EXPORT_SYMBOL_GPL(iomap_zero_range);
 414
 415 int
 416 iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero,
 417                 const struct iomap_ops *ops)
 418 {
 419         unsigned int blocksize = i_blocksize(inode);
 420         unsigned int off = pos & (blocksize - 1);
 421
 422         /* Block boundary? Nothing to do */
 423         if (!off)
 424                 return 0;
 425         return iomap_zero_range(inode, pos, blocksize - off, did_zero, ops);
 426 }
 427 EXPORT_SYMBOL_GPL(iomap_truncate_page);
 428
 429 static loff_t
 430 iomap_page_mkwrite_actor(struct inode *inode, loff_t pos, loff_t length,
 431                 void *data, struct iomap *iomap)
 432 {
 433         struct page *page = data;
 434         int ret;
 435
 436         ret = __block_write_begin_int(page, pos, length, NULL, iomap);
 437         if (ret)
 438                 return ret;
 439
 440         block_commit_write(page, 0, length);
 441         return length;
 442 }
 443
 444 int iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops)
 445 {
 446         struct page *page = vmf->page;
 447         struct inode *inode = file_inode(vmf->vma->vm_file);
 448         unsigned long length;
 449         loff_t offset, size;
 450         ssize_t ret;
 451
 452         lock_page(page);
 453         size = i_size_read(inode);
 454         if ((page->mapping != inode->i_mapping) ||
 455             (page_offset(page) > size)) {
 456                 /* We overload EFAULT to mean page got truncated */
 457                 ret = -EFAULT;
 458                 goto out_unlock;
 459         }
 460
 461         /* page is wholly or partially inside EOF */
 462         if (((page->index + 1) << PAGE_SHIFT) > size)
 463                 length = size & ~PAGE_MASK;
 464         else
 465                 length = PAGE_SIZE;
 466
 467         offset = page_offset(page);
 468         while (length > 0) {
 469                 ret = iomap_apply(inode, offset, length,
 470                                 IOMAP_WRITE | IOMAP_FAULT, ops, page,
 471                                 iomap_page_mkwrite_actor);
 472                 if (unlikely(ret <= 0))
 473                         goto out_unlock;
 474                 offset += ret;
 475                 length -= ret;
 476         }
 477
 478         set_page_dirty(page);
 479         wait_for_stable_page(page);
 480         return 0;
 481 out_unlock:
 482         unlock_page(page);
 483         return ret;
 484 }
 485 EXPORT_SYMBOL_GPL(iomap_page_mkwrite);
 486
 487 struct fiemap_ctx {
 488         struct fiemap_extent_info *fi;
 489         struct iomap prev;
 490 };
 491
 492 static int iomap_to_fiemap(struct fiemap_extent_info *fi,
 493                 struct iomap *iomap, u32 flags)
 494 {
 495         switch (iomap->type) {
 496         case IOMAP_HOLE:
 497                 /* skip holes */
 498                 return 0;
 499         case IOMAP_DELALLOC:
 500                 flags |= FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_UNKNOWN;
 501                 break;
 502         case IOMAP_UNWRITTEN:
 503                 flags |= FIEMAP_EXTENT_UNWRITTEN;
 504                 break;
 505         case IOMAP_MAPPED:
 506                 break;
 507         }
 508
 509         if (iomap->flags & IOMAP_F_MERGED)
 510                 flags |= FIEMAP_EXTENT_MERGED;
 511         if (iomap->flags & IOMAP_F_SHARED)
 512                 flags |= FIEMAP_EXTENT_SHARED;
 513
 514         return fiemap_fill_next_extent(fi, iomap->offset,
 515                         iomap->blkno != IOMAP_NULL_BLOCK ? iomap->blkno << 9: 0,
 516                         iomap->length, flags);
 517
 518 }
 519
 520 static loff_t
 521 iomap_fiemap_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 522                 struct iomap *iomap)
 523 {
 524         struct fiemap_ctx *ctx = data;
 525         loff_t ret = length;
 526
 527         if (iomap->type == IOMAP_HOLE)
 528                 return length;
 529
 530         ret = iomap_to_fiemap(ctx->fi, &ctx->prev, 0);
 531         ctx->prev = *iomap;
 532         switch (ret) {
 533         case 0:         /* success */
 534                 return length;
 535         case 1:         /* extent array full */
 536                 return 0;
 537         default:
 538                 return ret;
 539         }
 540 }
 541
 542 int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
 543                 loff_t start, loff_t len, const struct iomap_ops *ops)
 544 {
 545         struct fiemap_ctx ctx;
 546         loff_t ret;
 547
 548         memset(&ctx, 0, sizeof(ctx));
 549         ctx.fi = fi;
 550         ctx.prev.type = IOMAP_HOLE;
 551
 552         ret = fiemap_check_flags(fi, FIEMAP_FLAG_SYNC);
 553         if (ret)
 554                 return ret;
 555
 556         if (fi->fi_flags & FIEMAP_FLAG_SYNC) {
 557                 ret = filemap_write_and_wait(inode->i_mapping);
 558                 if (ret)
 559                         return ret;
 560         }
 561
 562         while (len > 0) {
 563                 ret = iomap_apply(inode, start, len, IOMAP_REPORT, ops, &ctx,
 564                                 iomap_fiemap_actor);
 565                 /* inode with no (attribute) mapping will give ENOENT */
 566                 if (ret == -ENOENT)
 567                         break;
 568                 if (ret < 0)
 569                         return ret;
 570                 if (ret == 0)
 571                         break;
 572
 573                 start += ret;
 574                 len -= ret;
 575         }
 576
 577         if (ctx.prev.type != IOMAP_HOLE) {
 578                 ret = iomap_to_fiemap(fi, &ctx.prev, FIEMAP_EXTENT_LAST);
 579                 if (ret < 0)
 580                         return ret;
 581         }
 582
 583         return 0;
 584 }
 585 EXPORT_SYMBOL_GPL(iomap_fiemap);
 586
 587 /*
 588  * Private flags for iomap_dio, must not overlap with the public ones in
 589  * iomap.h:
 590  */
 591 #define IOMAP_DIO_WRITE         (1 << 30)
 592 #define IOMAP_DIO_DIRTY         (1 << 31)
 593
 594 struct iomap_dio {
 595         struct kiocb            *iocb;
 596         iomap_dio_end_io_t      *end_io;
 597         loff_t                  i_size;
 598         loff_t                  size;
 599         atomic_t                ref;
 600         unsigned                flags;
 601         int                     error;
 602
 603         union {
 604                 /* used during submission and for synchronous completion: */
 605                 struct {
 606                         struct iov_iter         *iter;
 607                         struct task_struct      *waiter;
 608                         struct request_queue    *last_queue;
 609                         blk_qc_t                cookie;
 610                 } submit;
 611
 612                 /* used for aio completion: */
 613                 struct {
 614                         struct work_struct      work;
 615                 } aio;
 616         };
 617 };
 618
 619 static ssize_t iomap_dio_complete(struct iomap_dio *dio)
 620 {
 621         struct kiocb *iocb = dio->iocb;
 622         ssize_t ret;
 623
 624         if (dio->end_io) {
 625                 ret = dio->end_io(iocb,
 626                                 dio->error ? dio->error : dio->size,
 627                                 dio->flags);
 628         } else {
 629                 ret = dio->error;
 630         }
 631
 632         if (likely(!ret)) {
 633                 ret = dio->size;
 634                 /* check for short read */
 635                 if (iocb->ki_pos + ret > dio->i_size &&
 636                     !(dio->flags & IOMAP_DIO_WRITE))
 637                         ret = dio->i_size - iocb->ki_pos;
 638                 iocb->ki_pos += ret;
 639         }
 640
 641         inode_dio_end(file_inode(iocb->ki_filp));
 642         kfree(dio);
 643
 644         return ret;
 645 }
 646
 647 static void iomap_dio_complete_work(struct work_struct *work)
 648 {
 649         struct iomap_dio *dio = container_of(work, struct iomap_dio, aio.work);
 650         struct kiocb *iocb = dio->iocb;
 651         bool is_write = (dio->flags & IOMAP_DIO_WRITE);
 652         ssize_t ret;
 653
 654         ret = iomap_dio_complete(dio);
 655         if (is_write && ret > 0)
 656                 ret = generic_write_sync(iocb, ret);
 657         iocb->ki_complete(iocb, ret, 0);
 658 }
 659
 660 /*
 661  * Set an error in the dio if none is set yet.  We have to use cmpxchg
 662  * as the submission context and the completion context(s) can race to
 663  * update the error.
 664  */
 665 static inline void iomap_dio_set_error(struct iomap_dio *dio, int ret)
 666 {
 667         cmpxchg(&dio->error, 0, ret);
 668 }
 669
 670 static void iomap_dio_bio_end_io(struct bio *bio)
 671 {
 672         struct iomap_dio *dio = bio->bi_private;
 673         bool should_dirty = (dio->flags & IOMAP_DIO_DIRTY);
 674
 675         if (bio->bi_error)
 676                 iomap_dio_set_error(dio, bio->bi_error);
 677
 678         if (atomic_dec_and_test(&dio->ref)) {
 679                 if (is_sync_kiocb(dio->iocb)) {
 680                         struct task_struct *waiter = dio->submit.waiter;
 681
 682                         WRITE_ONCE(dio->submit.waiter, NULL);
 683                         wake_up_process(waiter);
 684                 } else if (dio->flags & IOMAP_DIO_WRITE) {
 685                         struct inode *inode = file_inode(dio->iocb->ki_filp);
 686
 687                         INIT_WORK(&dio->aio.work, iomap_dio_complete_work);
 688                         queue_work(inode->i_sb->s_dio_done_wq, &dio->aio.work);
 689                 } else {
 690                         iomap_dio_complete_work(&dio->aio.work);
 691                 }
 692         }
 693
 694         if (should_dirty) {
 695                 bio_check_pages_dirty(bio);
 696         } else {
 697                 struct bio_vec *bvec;
 698                 int i;
 699
 700                 bio_for_each_segment_all(bvec, bio, i)
 701                         put_page(bvec->bv_page);
 702                 bio_put(bio);
 703         }
 704 }
 705
 706 static blk_qc_t
 707 iomap_dio_zero(struct iomap_dio *dio, struct iomap *iomap, loff_t pos,
 708                 unsigned len)
 709 {
 710         struct page *page = ZERO_PAGE(0);
 711         struct bio *bio;
 712
 713         bio = bio_alloc(GFP_KERNEL, 1);
 714         bio->bi_bdev = iomap->bdev;
 715         bio->bi_iter.bi_sector =
 716                 iomap->blkno + ((pos - iomap->offset) >> 9);
 717         bio->bi_private = dio;
 718         bio->bi_end_io = iomap_dio_bio_end_io;
 719
 720         get_page(page);
 721         if (bio_add_page(bio, page, len, 0) != len)
 722                 BUG();
 723         bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_SYNC | REQ_IDLE);
 724
 725         atomic_inc(&dio->ref);
 726         return submit_bio(bio);
 727 }
 728
 729 static loff_t
 730 iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
 731                 void *data, struct iomap *iomap)
 732 {
 733         struct iomap_dio *dio = data;
 734         unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
 735         unsigned int fs_block_size = i_blocksize(inode), pad;
 736         unsigned int align = iov_iter_alignment(dio->submit.iter);
 737         struct iov_iter iter;
 738         struct bio *bio;
 739         bool need_zeroout = false;
 740         int nr_pages, ret;
 741
 742         if ((pos | length | align) & ((1 << blkbits) - 1))
 743                 return -EINVAL;
 744
 745         switch (iomap->type) {
 746         case IOMAP_HOLE:
 747                 if (WARN_ON_ONCE(dio->flags & IOMAP_DIO_WRITE))
 748                         return -EIO;
 749                 /*FALLTHRU*/
 750         case IOMAP_UNWRITTEN:
 751                 if (!(dio->flags & IOMAP_DIO_WRITE)) {
 752                         iov_iter_zero(length, dio->submit.iter);
 753                         dio->size += length;
 754                         return length;
 755                 }
 756                 dio->flags |= IOMAP_DIO_UNWRITTEN;
 757                 need_zeroout = true;
 758                 break;
 759         case IOMAP_MAPPED:
 760                 if (iomap->flags & IOMAP_F_SHARED)
 761                         dio->flags |= IOMAP_DIO_COW;
 762                 if (iomap->flags & IOMAP_F_NEW)
 763                         need_zeroout = true;
 764                 break;
 765         default:
 766                 WARN_ON_ONCE(1);
 767                 return -EIO;
 768         }
 769
 770         /*
 771          * Operate on a partial iter trimmed to the extent we were called for.
 772          * We'll update the iter in the dio once we're done with this extent.
 773          */
 774         iter = *dio->submit.iter;
 775         iov_iter_truncate(&iter, length);
 776
 777         nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
 778         if (nr_pages <= 0)
 779                 return nr_pages;
 780
 781         if (need_zeroout) {
 782                 /* zero out from the start of the block to the write offset */
 783                 pad = pos & (fs_block_size - 1);
 784                 if (pad)
 785                         iomap_dio_zero(dio, iomap, pos - pad, pad);
 786         }
 787
 788         do {
 789                 if (dio->error)
 790                         return 0;
 791
 792                 bio = bio_alloc(GFP_KERNEL, nr_pages);
 793                 bio->bi_bdev = iomap->bdev;
 794                 bio->bi_iter.bi_sector =
 795                         iomap->blkno + ((pos - iomap->offset) >> 9);
 796                 bio->bi_private = dio;
 797                 bio->bi_end_io = iomap_dio_bio_end_io;
 798
 799                 ret = bio_iov_iter_get_pages(bio, &iter);
 800                 if (unlikely(ret)) {
 801                         bio_put(bio);
 802                         return ret;
 803                 }
 804
 805                 if (dio->flags & IOMAP_DIO_WRITE) {
 806                         bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_SYNC | REQ_IDLE);
 807                         task_io_account_write(bio->bi_iter.bi_size);
 808                 } else {
 809                         bio_set_op_attrs(bio, REQ_OP_READ, 0);
 810                         if (dio->flags & IOMAP_DIO_DIRTY)
 811                                 bio_set_pages_dirty(bio);
 812                 }
 813
 814                 dio->size += bio->bi_iter.bi_size;
 815                 pos += bio->bi_iter.bi_size;
 816
 817                 nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES);
 818
 819                 atomic_inc(&dio->ref);
 820
 821                 dio->submit.last_queue = bdev_get_queue(iomap->bdev);
 822                 dio->submit.cookie = submit_bio(bio);
 823         } while (nr_pages);
 824
 825         if (need_zeroout) {
 826                 /* zero out from the end of the write to the end of the block */
 827                 pad = pos & (fs_block_size - 1);
 828                 if (pad)
 829                         iomap_dio_zero(dio, iomap, pos, fs_block_size - pad);
 830         }
 831
 832         iov_iter_advance(dio->submit.iter, length);
 833         return length;
 834 }
 835
 836 ssize_t
 837 iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 838                 const struct iomap_ops *ops, iomap_dio_end_io_t end_io)
 839 {
 840         struct address_space *mapping = iocb->ki_filp->f_mapping;
 841         struct inode *inode = file_inode(iocb->ki_filp);
 842         size_t count = iov_iter_count(iter);
 843         loff_t pos = iocb->ki_pos, start = pos;
 844         loff_t end = iocb->ki_pos + count - 1, ret = 0;
 845         unsigned int flags = IOMAP_DIRECT;
 846         struct blk_plug plug;
 847         struct iomap_dio *dio;
 848
 849         lockdep_assert_held(&inode->i_rwsem);
 850
 851         if (!count)
 852                 return 0;
 853
 854         dio = kmalloc(sizeof(*dio), GFP_KERNEL);
 855         if (!dio)
 856                 return -ENOMEM;
 857
 858         dio->iocb = iocb;
 859         atomic_set(&dio->ref, 1);
 860         dio->size = 0;
 861         dio->i_size = i_size_read(inode);
 862         dio->end_io = end_io;
 863         dio->error = 0;
 864         dio->flags = 0;
 865
 866         dio->submit.iter = iter;
 867         if (is_sync_kiocb(iocb)) {
 868                 dio->submit.waiter = current;
 869                 dio->submit.cookie = BLK_QC_T_NONE;
 870                 dio->submit.last_queue = NULL;
 871         }
 872
 873         if (iov_iter_rw(iter) == READ) {
 874                 if (pos >= dio->i_size)
 875                         goto out_free_dio;
 876
 877                 if (iter->type == ITER_IOVEC)
 878                         dio->flags |= IOMAP_DIO_DIRTY;
 879         } else {
 880                 dio->flags |= IOMAP_DIO_WRITE;
 881                 flags |= IOMAP_WRITE;
 882         }
 883
 884         ret = filemap_write_and_wait_range(mapping, start, end);
 885         if (ret)
 886                 goto out_free_dio;
 887
 888         ret = invalidate_inode_pages2_range(mapping,
 889                         start >> PAGE_SHIFT, end >> PAGE_SHIFT);
 890         WARN_ON_ONCE(ret);
 891         ret = 0;
 892
 893         inode_dio_begin(inode);
 894
 895         blk_start_plug(&plug);
 896         do {
 897                 ret = iomap_apply(inode, pos, count, flags, ops, dio,
 898                                 iomap_dio_actor);
 899                 if (ret <= 0) {
 900                         /* magic error code to fall back to buffered I/O */
 901                         if (ret == -ENOTBLK)
 902                                 ret = 0;
 903                         break;
 904                 }
 905                 pos += ret;
 906
 907                 if (iov_iter_rw(iter) == READ && pos >= dio->i_size)
 908                         break;
 909         } while ((count = iov_iter_count(iter)) > 0);
 910         blk_finish_plug(&plug);
 911
 912         if (ret < 0)
 913                 iomap_dio_set_error(dio, ret);
 914
 915         if (ret >= 0 && iov_iter_rw(iter) == WRITE && !is_sync_kiocb(iocb) &&
 916                         !inode->i_sb->s_dio_done_wq) {
 917                 ret = sb_init_dio_done_wq(inode->i_sb);
 918                 if (ret < 0)
 919                         iomap_dio_set_error(dio, ret);
 920         }
 921
 922         if (!atomic_dec_and_test(&dio->ref)) {
 923                 if (!is_sync_kiocb(iocb))
 924                         return -EIOCBQUEUED;
 925
 926                 for (;;) {
 927                         set_current_state(TASK_UNINTERRUPTIBLE);
 928                         if (!READ_ONCE(dio->submit.waiter))
 929                                 break;
 930
 931                         if (!(iocb->ki_flags & IOCB_HIPRI) ||
 932                             !dio->submit.last_queue ||
 933                             !blk_mq_poll(dio->submit.last_queue,
 934                                          dio->submit.cookie))
 935                                 io_schedule();
 936                 }
 937                 __set_current_state(TASK_RUNNING);
 938         }
 939
 940         ret = iomap_dio_complete(dio);
 941
 942         /*
 943          * Try again to invalidate clean pages which might have been cached by
 944          * non-direct readahead, or faulted in by get_user_pages() if the source
 945          * of the write was an mmap'ed region of the file we're writing.  Either
 946          * one is a pretty crazy thing to do, so we don't support it 100%.  If
 947          * this invalidation fails, tough, the write still worked...
 948          */
 949         if (iov_iter_rw(iter) == WRITE) {
 950                 int err = invalidate_inode_pages2_range(mapping,
 951                                 start >> PAGE_SHIFT, end >> PAGE_SHIFT);
 952                 WARN_ON_ONCE(err);
 953         }
 954
 955         return ret;
 956
 957 out_free_dio:
 958         kfree(dio);
 959         return ret;
 960 }
 961 EXPORT_SYMBOL_GPL(iomap_dio_rw);