fs/ext4/file.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/fs/ext4/file.c
   4  *
   5  * Copyright (C) 1992, 1993, 1994, 1995
   6  * Remy Card ([email protected])
   7  * Laboratoire MASI - Institut Blaise Pascal
   8  * Universite Pierre et Marie Curie (Paris VI)
   9  *
  10  *  from
  11  *
  12  *  linux/fs/minix/file.c
  13  *
  14  *  Copyright (C) 1991, 1992  Linus Torvalds
  15  *
  16  *  ext4 fs regular file handling primitives
  17  *
  18  *  64-bit file support on 64-bit platforms by Jakub Jelinek
  19  *      ([email protected])
  20  */
  21
  22 #include <linux/time.h>
  23 #include <linux/fs.h>
  24 #include <linux/iomap.h>
  25 #include <linux/mount.h>
  26 #include <linux/path.h>
  27 #include <linux/dax.h>
  28 #include <linux/quotaops.h>
  29 #include <linux/pagevec.h>
  30 #include <linux/uio.h>
  31 #include <linux/mman.h>
  32 #include <linux/backing-dev.h>
  33 #include "ext4.h"
  34 #include "ext4_jbd2.h"
  35 #include "xattr.h"
  36 #include "acl.h"
  37 #include "truncate.h"
  38
  39 static bool ext4_dio_supported(struct inode *inode)
  40 {
  41         if (IS_ENABLED(CONFIG_FS_ENCRYPTION) && IS_ENCRYPTED(inode))
  42                 return false;
  43         if (fsverity_active(inode))
  44                 return false;
  45         if (ext4_should_journal_data(inode))
  46                 return false;
  47         if (ext4_has_inline_data(inode))
  48                 return false;
  49         return true;
  50 }
  51
  52 static ssize_t ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to)
  53 {
  54         ssize_t ret;
  55         struct inode *inode = file_inode(iocb->ki_filp);
  56
  57         if (iocb->ki_flags & IOCB_NOWAIT) {
  58                 if (!inode_trylock_shared(inode))
  59                         return -EAGAIN;
  60         } else {
  61                 inode_lock_shared(inode);
  62         }
  63
  64         if (!ext4_dio_supported(inode)) {
  65                 inode_unlock_shared(inode);
  66                 /*
  67                  * Fallback to buffered I/O if the operation being performed on
  68                  * the inode is not supported by direct I/O. The IOCB_DIRECT
  69                  * flag needs to be cleared here in order to ensure that the
  70                  * direct I/O path within generic_file_read_iter() is not
  71                  * taken.
  72                  */
  73                 iocb->ki_flags &= ~IOCB_DIRECT;
  74                 return generic_file_read_iter(iocb, to);
  75         }
  76
  77         ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL,
  78                            is_sync_kiocb(iocb));
  79         inode_unlock_shared(inode);
  80
  81         file_accessed(iocb->ki_filp);
  82         return ret;
  83 }
  84
  85 #ifdef CONFIG_FS_DAX
  86 static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
  87 {
  88         struct inode *inode = file_inode(iocb->ki_filp);
  89         ssize_t ret;
  90
  91         if (iocb->ki_flags & IOCB_NOWAIT) {
  92                 if (!inode_trylock_shared(inode))
  93                         return -EAGAIN;
  94         } else {
  95                 inode_lock_shared(inode);
  96         }
  97         /*
  98          * Recheck under inode lock - at this point we are sure it cannot
  99          * change anymore
 100          */
 101         if (!IS_DAX(inode)) {
 102                 inode_unlock_shared(inode);
 103                 /* Fallback to buffered IO in case we cannot support DAX */
 104                 return generic_file_read_iter(iocb, to);
 105         }
 106         ret = dax_iomap_rw(iocb, to, &ext4_iomap_ops);
 107         inode_unlock_shared(inode);
 108
 109         file_accessed(iocb->ki_filp);
 110         return ret;
 111 }
 112 #endif
 113
 114 static ssize_t ext4_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 115 {
 116         struct inode *inode = file_inode(iocb->ki_filp);
 117
 118         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
 119                 return -EIO;
 120
 121         if (!iov_iter_count(to))
 122                 return 0; /* skip atime */
 123
 124 #ifdef CONFIG_FS_DAX
 125         if (IS_DAX(inode))
 126                 return ext4_dax_read_iter(iocb, to);
 127 #endif
 128         if (iocb->ki_flags & IOCB_DIRECT)
 129                 return ext4_dio_read_iter(iocb, to);
 130
 131         return generic_file_read_iter(iocb, to);
 132 }
 133
 134 /*
 135  * Called when an inode is released. Note that this is different
 136  * from ext4_file_open: open gets called at every open, but release
 137  * gets called only when /all/ the files are closed.
 138  */
 139 static int ext4_release_file(struct inode *inode, struct file *filp)
 140 {
 141         if (ext4_test_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE)) {
 142                 ext4_alloc_da_blocks(inode);
 143                 ext4_clear_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);
 144         }
 145         /* if we are the last writer on the inode, drop the block reservation */
 146         if ((filp->f_mode & FMODE_WRITE) &&
 147                         (atomic_read(&inode->i_writecount) == 1) &&
 148                         !EXT4_I(inode)->i_reserved_data_blocks) {
 149                 down_write(&EXT4_I(inode)->i_data_sem);
 150                 ext4_discard_preallocations(inode, 0);
 151                 up_write(&EXT4_I(inode)->i_data_sem);
 152         }
 153         if (is_dx(inode) && filp->private_data)
 154                 ext4_htree_free_dir_info(filp->private_data);
 155
 156         return 0;
 157 }
 158
 159 /*
 160  * This tests whether the IO in question is block-aligned or not.
 161  * Ext4 utilizes unwritten extents when hole-filling during direct IO, and they
 162  * are converted to written only after the IO is complete.  Until they are
 163  * mapped, these blocks appear as holes, so dio_zero_block() will assume that
 164  * it needs to zero out portions of the start and/or end block.  If 2 AIO
 165  * threads are at work on the same unwritten block, they must be synchronized
 166  * or one thread will zero the other's data, causing corruption.
 167  */
 168 static bool
 169 ext4_unaligned_io(struct inode *inode, struct iov_iter *from, loff_t pos)
 170 {
 171         struct super_block *sb = inode->i_sb;
 172         unsigned long blockmask = sb->s_blocksize - 1;
 173
 174         if ((pos | iov_iter_alignment(from)) & blockmask)
 175                 return true;
 176
 177         return false;
 178 }
 179
 180 static bool
 181 ext4_extending_io(struct inode *inode, loff_t offset, size_t len)
 182 {
 183         if (offset + len > i_size_read(inode) ||
 184             offset + len > EXT4_I(inode)->i_disksize)
 185                 return true;
 186         return false;
 187 }
 188
 189 /* Is IO overwriting allocated and initialized blocks? */
 190 static bool ext4_overwrite_io(struct inode *inode, loff_t pos, loff_t len)
 191 {
 192         struct ext4_map_blocks map;
 193         unsigned int blkbits = inode->i_blkbits;
 194         int err, blklen;
 195
 196         if (pos + len > i_size_read(inode))
 197                 return false;
 198
 199         map.m_lblk = pos >> blkbits;
 200         map.m_len = EXT4_MAX_BLOCKS(len, pos, blkbits);
 201         blklen = map.m_len;
 202
 203         err = ext4_map_blocks(NULL, inode, &map, 0);
 204         /*
 205          * 'err==len' means that all of the blocks have been preallocated,
 206          * regardless of whether they have been initialized or not. To exclude
 207          * unwritten extents, we need to check m_flags.
 208          */
 209         return err == blklen && (map.m_flags & EXT4_MAP_MAPPED);
 210 }
 211
 212 static ssize_t ext4_generic_write_checks(struct kiocb *iocb,
 213                                          struct iov_iter *from)
 214 {
 215         struct inode *inode = file_inode(iocb->ki_filp);
 216         ssize_t ret;
 217
 218         if (unlikely(IS_IMMUTABLE(inode)))
 219                 return -EPERM;
 220
 221         ret = generic_write_checks(iocb, from);
 222         if (ret <= 0)
 223                 return ret;
 224
 225         /*
 226          * If we have encountered a bitmap-format file, the size limit
 227          * is smaller than s_maxbytes, which is for extent-mapped files.
 228          */
 229         if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
 230                 struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 231
 232                 if (iocb->ki_pos >= sbi->s_bitmap_maxbytes)
 233                         return -EFBIG;
 234                 iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
 235         }
 236
 237         return iov_iter_count(from);
 238 }
 239
 240 static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
 241 {
 242         ssize_t ret, count;
 243
 244         count = ext4_generic_write_checks(iocb, from);
 245         if (count <= 0)
 246                 return count;
 247
 248         ret = file_modified(iocb->ki_filp);
 249         if (ret)
 250                 return ret;
 251         return count;
 252 }
 253
 254 static ssize_t ext4_buffered_write_iter(struct kiocb *iocb,
 255                                         struct iov_iter *from)
 256 {
 257         ssize_t ret;
 258         struct inode *inode = file_inode(iocb->ki_filp);
 259
 260         if (iocb->ki_flags & IOCB_NOWAIT)
 261                 return -EOPNOTSUPP;
 262
 263         ext4_fc_start_update(inode);
 264         inode_lock(inode);
 265         ret = ext4_write_checks(iocb, from);
 266         if (ret <= 0)
 267                 goto out;
 268
 269         current->backing_dev_info = inode_to_bdi(inode);
 270         ret = generic_perform_write(iocb->ki_filp, from, iocb->ki_pos);
 271         current->backing_dev_info = NULL;
 272
 273 out:
 274         inode_unlock(inode);
 275         ext4_fc_stop_update(inode);
 276         if (likely(ret > 0)) {
 277                 iocb->ki_pos += ret;
 278                 ret = generic_write_sync(iocb, ret);
 279         }
 280
 281         return ret;
 282 }
 283
 284 static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset,
 285                                            ssize_t written, size_t count)
 286 {
 287         handle_t *handle;
 288         bool truncate = false;
 289         u8 blkbits = inode->i_blkbits;
 290         ext4_lblk_t written_blk, end_blk;
 291         int ret;
 292
 293         /*
 294          * Note that EXT4_I(inode)->i_disksize can get extended up to
 295          * inode->i_size while the I/O was running due to writeback of delalloc
 296          * blocks. But, the code in ext4_iomap_alloc() is careful to use
 297          * zeroed/unwritten extents if this is possible; thus we won't leave
 298          * uninitialized blocks in a file even if we didn't succeed in writing
 299          * as much as we intended.
 300          */
 301         WARN_ON_ONCE(i_size_read(inode) < EXT4_I(inode)->i_disksize);
 302         if (offset + count <= EXT4_I(inode)->i_disksize) {
 303                 /*
 304                  * We need to ensure that the inode is removed from the orphan
 305                  * list if it has been added prematurely, due to writeback of
 306                  * delalloc blocks.
 307                  */
 308                 if (!list_empty(&EXT4_I(inode)->i_orphan) && inode->i_nlink) {
 309                         handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
 310
 311                         if (IS_ERR(handle)) {
 312                                 ext4_orphan_del(NULL, inode);
 313                                 return PTR_ERR(handle);
 314                         }
 315
 316                         ext4_orphan_del(handle, inode);
 317                         ext4_journal_stop(handle);
 318                 }
 319
 320                 return written;
 321         }
 322
 323         if (written < 0)
 324                 goto truncate;
 325
 326         handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
 327         if (IS_ERR(handle)) {
 328                 written = PTR_ERR(handle);
 329                 goto truncate;
 330         }
 331
 332         if (ext4_update_inode_size(inode, offset + written)) {
 333                 ret = ext4_mark_inode_dirty(handle, inode);
 334                 if (unlikely(ret)) {
 335                         written = ret;
 336                         ext4_journal_stop(handle);
 337                         goto truncate;
 338                 }
 339         }
 340
 341         /*
 342          * We may need to truncate allocated but not written blocks beyond EOF.
 343          */
 344         written_blk = ALIGN(offset + written, 1 << blkbits);
 345         end_blk = ALIGN(offset + count, 1 << blkbits);
 346         if (written_blk < end_blk && ext4_can_truncate(inode))
 347                 truncate = true;
 348
 349         /*
 350          * Remove the inode from the orphan list if it has been extended and
 351          * everything went OK.
 352          */
 353         if (!truncate && inode->i_nlink)
 354                 ext4_orphan_del(handle, inode);
 355         ext4_journal_stop(handle);
 356
 357         if (truncate) {
 358 truncate:
 359                 ext4_truncate_failed_write(inode);
 360                 /*
 361                  * If the truncate operation failed early, then the inode may
 362                  * still be on the orphan list. In that case, we need to try
 363                  * remove the inode from the in-memory linked list.
 364                  */
 365                 if (inode->i_nlink)
 366                         ext4_orphan_del(NULL, inode);
 367         }
 368
 369         return written;
 370 }
 371
 372 static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size,
 373                                  int error, unsigned int flags)
 374 {
 375         loff_t offset = iocb->ki_pos;
 376         struct inode *inode = file_inode(iocb->ki_filp);
 377
 378         if (error)
 379                 return error;
 380
 381         if (size && flags & IOMAP_DIO_UNWRITTEN)
 382                 return ext4_convert_unwritten_extents(NULL, inode,
 383                                                       offset, size);
 384
 385         return 0;
 386 }
 387
 388 static const struct iomap_dio_ops ext4_dio_write_ops = {
 389         .end_io = ext4_dio_write_end_io,
 390 };
 391
 392 /*
 393  * The intention here is to start with shared lock acquired then see if any
 394  * condition requires an exclusive inode lock. If yes, then we restart the
 395  * whole operation by releasing the shared lock and acquiring exclusive lock.
 396  *
 397  * - For unaligned_io we never take shared lock as it may cause data corruption
 398  *   when two unaligned IO tries to modify the same block e.g. while zeroing.
 399  *
 400  * - For extending writes case we don't take the shared lock, since it requires
 401  *   updating inode i_disksize and/or orphan handling with exclusive lock.
 402  *
 403  * - shared locking will only be true mostly with overwrites. Otherwise we will
 404  *   switch to exclusive i_rwsem lock.
 405  */
 406 static ssize_t ext4_dio_write_checks(struct kiocb *iocb, struct iov_iter *from,
 407                                      bool *ilock_shared, bool *extend)
 408 {
 409         struct file *file = iocb->ki_filp;
 410         struct inode *inode = file_inode(file);
 411         loff_t offset;
 412         size_t count;
 413         ssize_t ret;
 414
 415 restart:
 416         ret = ext4_generic_write_checks(iocb, from);
 417         if (ret <= 0)
 418                 goto out;
 419
 420         offset = iocb->ki_pos;
 421         count = ret;
 422         if (ext4_extending_io(inode, offset, count))
 423                 *extend = true;
 424         /*
 425          * Determine whether the IO operation will overwrite allocated
 426          * and initialized blocks.
 427          * We need exclusive i_rwsem for changing security info
 428          * in file_modified().
 429          */
 430         if (*ilock_shared && (!IS_NOSEC(inode) || *extend ||
 431              !ext4_overwrite_io(inode, offset, count))) {
 432                 if (iocb->ki_flags & IOCB_NOWAIT) {
 433                         ret = -EAGAIN;
 434                         goto out;
 435                 }
 436                 inode_unlock_shared(inode);
 437                 *ilock_shared = false;
 438                 inode_lock(inode);
 439                 goto restart;
 440         }
 441
 442         ret = file_modified(file);
 443         if (ret < 0)
 444                 goto out;
 445
 446         return count;
 447 out:
 448         if (*ilock_shared)
 449                 inode_unlock_shared(inode);
 450         else
 451                 inode_unlock(inode);
 452         return ret;
 453 }
 454
 455 static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
 456 {
 457         ssize_t ret;
 458         handle_t *handle;
 459         struct inode *inode = file_inode(iocb->ki_filp);
 460         loff_t offset = iocb->ki_pos;
 461         size_t count = iov_iter_count(from);
 462         const struct iomap_ops *iomap_ops = &ext4_iomap_ops;
 463         bool extend = false, unaligned_io = false;
 464         bool ilock_shared = true;
 465
 466         /*
 467          * We initially start with shared inode lock unless it is
 468          * unaligned IO which needs exclusive lock anyways.
 469          */
 470         if (ext4_unaligned_io(inode, from, offset)) {
 471                 unaligned_io = true;
 472                 ilock_shared = false;
 473         }
 474         /*
 475          * Quick check here without any i_rwsem lock to see if it is extending
 476          * IO. A more reliable check is done in ext4_dio_write_checks() with
 477          * proper locking in place.
 478          */
 479         if (offset + count > i_size_read(inode))
 480                 ilock_shared = false;
 481
 482         if (iocb->ki_flags & IOCB_NOWAIT) {
 483                 if (ilock_shared) {
 484                         if (!inode_trylock_shared(inode))
 485                                 return -EAGAIN;
 486                 } else {
 487                         if (!inode_trylock(inode))
 488                                 return -EAGAIN;
 489                 }
 490         } else {
 491                 if (ilock_shared)
 492                         inode_lock_shared(inode);
 493                 else
 494                         inode_lock(inode);
 495         }
 496
 497         /* Fallback to buffered I/O if the inode does not support direct I/O. */
 498         if (!ext4_dio_supported(inode)) {
 499                 if (ilock_shared)
 500                         inode_unlock_shared(inode);
 501                 else
 502                         inode_unlock(inode);
 503                 return ext4_buffered_write_iter(iocb, from);
 504         }
 505
 506         ret = ext4_dio_write_checks(iocb, from, &ilock_shared, &extend);
 507         if (ret <= 0)
 508                 return ret;
 509
 510         /* if we're going to block and IOCB_NOWAIT is set, return -EAGAIN */
 511         if ((iocb->ki_flags & IOCB_NOWAIT) && (unaligned_io || extend)) {
 512                 ret = -EAGAIN;
 513                 goto out;
 514         }
 515
 516         offset = iocb->ki_pos;
 517         count = ret;
 518
 519         /*
 520          * Unaligned direct IO must be serialized among each other as zeroing
 521          * of partial blocks of two competing unaligned IOs can result in data
 522          * corruption.
 523          *
 524          * So we make sure we don't allow any unaligned IO in flight.
 525          * For IOs where we need not wait (like unaligned non-AIO DIO),
 526          * below inode_dio_wait() may anyway become a no-op, since we start
 527          * with exclusive lock.
 528          */
 529         if (unaligned_io)
 530                 inode_dio_wait(inode);
 531
 532         if (extend) {
 533                 handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
 534                 if (IS_ERR(handle)) {
 535                         ret = PTR_ERR(handle);
 536                         goto out;
 537                 }
 538
 539                 ext4_fc_start_update(inode);
 540                 ret = ext4_orphan_add(handle, inode);
 541                 ext4_fc_stop_update(inode);
 542                 if (ret) {
 543                         ext4_journal_stop(handle);
 544                         goto out;
 545                 }
 546
 547                 ext4_journal_stop(handle);
 548         }
 549
 550         if (ilock_shared)
 551                 iomap_ops = &ext4_iomap_overwrite_ops;
 552         ret = iomap_dio_rw(iocb, from, iomap_ops, &ext4_dio_write_ops,
 553                            is_sync_kiocb(iocb) || unaligned_io || extend);
 554         if (ret == -ENOTBLK)
 555                 ret = 0;
 556
 557         if (extend)
 558                 ret = ext4_handle_inode_extension(inode, offset, ret, count);
 559
 560 out:
 561         if (ilock_shared)
 562                 inode_unlock_shared(inode);
 563         else
 564                 inode_unlock(inode);
 565
 566         if (ret >= 0 && iov_iter_count(from)) {
 567                 ssize_t err;
 568                 loff_t endbyte;
 569
 570                 offset = iocb->ki_pos;
 571                 err = ext4_buffered_write_iter(iocb, from);
 572                 if (err < 0)
 573                         return err;
 574
 575                 /*
 576                  * We need to ensure that the pages within the page cache for
 577                  * the range covered by this I/O are written to disk and
 578                  * invalidated. This is in attempt to preserve the expected
 579                  * direct I/O semantics in the case we fallback to buffered I/O
 580                  * to complete off the I/O request.
 581                  */
 582                 ret += err;
 583                 endbyte = offset + err - 1;
 584                 err = filemap_write_and_wait_range(iocb->ki_filp->f_mapping,
 585                                                    offset, endbyte);
 586                 if (!err)
 587                         invalidate_mapping_pages(iocb->ki_filp->f_mapping,
 588                                                  offset >> PAGE_SHIFT,
 589                                                  endbyte >> PAGE_SHIFT);
 590         }
 591
 592         return ret;
 593 }
 594
 595 #ifdef CONFIG_FS_DAX
 596 static ssize_t
 597 ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
 598 {
 599         ssize_t ret;
 600         size_t count;
 601         loff_t offset;
 602         handle_t *handle;
 603         bool extend = false;
 604         struct inode *inode = file_inode(iocb->ki_filp);
 605
 606         if (iocb->ki_flags & IOCB_NOWAIT) {
 607                 if (!inode_trylock(inode))
 608                         return -EAGAIN;
 609         } else {
 610                 inode_lock(inode);
 611         }
 612
 613         ret = ext4_write_checks(iocb, from);
 614         if (ret <= 0)
 615                 goto out;
 616
 617         offset = iocb->ki_pos;
 618         count = iov_iter_count(from);
 619
 620         if (offset + count > EXT4_I(inode)->i_disksize) {
 621                 handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
 622                 if (IS_ERR(handle)) {
 623                         ret = PTR_ERR(handle);
 624                         goto out;
 625                 }
 626
 627                 ret = ext4_orphan_add(handle, inode);
 628                 if (ret) {
 629                         ext4_journal_stop(handle);
 630                         goto out;
 631                 }
 632
 633                 extend = true;
 634                 ext4_journal_stop(handle);
 635         }
 636
 637         ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);
 638
 639         if (extend)
 640                 ret = ext4_handle_inode_extension(inode, offset, ret, count);
 641 out:
 642         inode_unlock(inode);
 643         if (ret > 0)
 644                 ret = generic_write_sync(iocb, ret);
 645         return ret;
 646 }
 647 #endif
 648
 649 static ssize_t
 650 ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 651 {
 652         struct inode *inode = file_inode(iocb->ki_filp);
 653
 654         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
 655                 return -EIO;
 656
 657 #ifdef CONFIG_FS_DAX
 658         if (IS_DAX(inode))
 659                 return ext4_dax_write_iter(iocb, from);
 660 #endif
 661         if (iocb->ki_flags & IOCB_DIRECT)
 662                 return ext4_dio_write_iter(iocb, from);
 663         else
 664                 return ext4_buffered_write_iter(iocb, from);
 665 }
 666
 667 #ifdef CONFIG_FS_DAX
 668 static vm_fault_t ext4_dax_huge_fault(struct vm_fault *vmf,
 669                 enum page_entry_size pe_size)
 670 {
 671         int error = 0;
 672         vm_fault_t result;
 673         int retries = 0;
 674         handle_t *handle = NULL;
 675         struct inode *inode = file_inode(vmf->vma->vm_file);
 676         struct super_block *sb = inode->i_sb;
 677
 678         /*
 679          * We have to distinguish real writes from writes which will result in a
 680          * COW page; COW writes should *not* poke the journal (the file will not
 681          * be changed). Doing so would cause unintended failures when mounted
 682          * read-only.
 683          *
 684          * We check for VM_SHARED rather than vmf->cow_page since the latter is
 685          * unset for pe_size != PE_SIZE_PTE (i.e. only in do_cow_fault); for
 686          * other sizes, dax_iomap_fault will handle splitting / fallback so that
 687          * we eventually come back with a COW page.
 688          */
 689         bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
 690                 (vmf->vma->vm_flags & VM_SHARED);
 691         pfn_t pfn;
 692
 693         if (write) {
 694                 sb_start_pagefault(sb);
 695                 file_update_time(vmf->vma->vm_file);
 696                 down_read(&EXT4_I(inode)->i_mmap_sem);
 697 retry:
 698                 handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
 699                                                EXT4_DATA_TRANS_BLOCKS(sb));
 700                 if (IS_ERR(handle)) {
 701                         up_read(&EXT4_I(inode)->i_mmap_sem);
 702                         sb_end_pagefault(sb);
 703                         return VM_FAULT_SIGBUS;
 704                 }
 705         } else {
 706                 down_read(&EXT4_I(inode)->i_mmap_sem);
 707         }
 708         result = dax_iomap_fault(vmf, pe_size, &pfn, &error, &ext4_iomap_ops);
 709         if (write) {
 710                 ext4_journal_stop(handle);
 711
 712                 if ((result & VM_FAULT_ERROR) && error == -ENOSPC &&
 713                     ext4_should_retry_alloc(sb, &retries))
 714                         goto retry;
 715                 /* Handling synchronous page fault? */
 716                 if (result & VM_FAULT_NEEDDSYNC)
 717                         result = dax_finish_sync_fault(vmf, pe_size, pfn);
 718                 up_read(&EXT4_I(inode)->i_mmap_sem);
 719                 sb_end_pagefault(sb);
 720         } else {
 721                 up_read(&EXT4_I(inode)->i_mmap_sem);
 722         }
 723
 724         return result;
 725 }
 726
 727 static vm_fault_t ext4_dax_fault(struct vm_fault *vmf)
 728 {
 729         return ext4_dax_huge_fault(vmf, PE_SIZE_PTE);
 730 }
 731
 732 static const struct vm_operations_struct ext4_dax_vm_ops = {
 733         .fault          = ext4_dax_fault,
 734         .huge_fault     = ext4_dax_huge_fault,
 735         .page_mkwrite   = ext4_dax_fault,
 736         .pfn_mkwrite    = ext4_dax_fault,
 737 };
 738 #else
 739 #define ext4_dax_vm_ops ext4_file_vm_ops
 740 #endif
 741
 742 static const struct vm_operations_struct ext4_file_vm_ops = {
 743         .fault          = ext4_filemap_fault,
 744         .map_pages      = filemap_map_pages,
 745         .page_mkwrite   = ext4_page_mkwrite,
 746 };
 747
 748 static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
 749 {
 750         struct inode *inode = file->f_mapping->host;
 751         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 752         struct dax_device *dax_dev = sbi->s_daxdev;
 753
 754         if (unlikely(ext4_forced_shutdown(sbi)))
 755                 return -EIO;
 756
 757         /*
 758          * We don't support synchronous mappings for non-DAX files and
 759          * for DAX files if underneath dax_device is not synchronous.
 760          */
 761         if (!daxdev_mapping_supported(vma, dax_dev))
 762                 return -EOPNOTSUPP;
 763
 764         ext4_fc_start_update(inode);
 765         file_accessed(file);
 766         if (IS_DAX(file_inode(file))) {
 767                 vma->vm_ops = &ext4_dax_vm_ops;
 768                 vma->vm_flags |= VM_HUGEPAGE;
 769         } else {
 770                 vma->vm_ops = &ext4_file_vm_ops;
 771         }
 772         ext4_fc_stop_update(inode);
 773         return 0;
 774 }
 775
 776 static int ext4_sample_last_mounted(struct super_block *sb,
 777                                     struct vfsmount *mnt)
 778 {
 779         struct ext4_sb_info *sbi = EXT4_SB(sb);
 780         struct path path;
 781         char buf[64], *cp;
 782         handle_t *handle;
 783         int err;
 784
 785         if (likely(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED))
 786                 return 0;
 787
 788         if (sb_rdonly(sb) || !sb_start_intwrite_trylock(sb))
 789                 return 0;
 790
 791         sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
 792         /*
 793          * Sample where the filesystem has been mounted and
 794          * store it in the superblock for sysadmin convenience
 795          * when trying to sort through large numbers of block
 796          * devices or filesystem images.
 797          */
 798         memset(buf, 0, sizeof(buf));
 799         path.mnt = mnt;
 800         path.dentry = mnt->mnt_root;
 801         cp = d_path(&path, buf, sizeof(buf));
 802         err = 0;
 803         if (IS_ERR(cp))
 804                 goto out;
 805
 806         handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
 807         err = PTR_ERR(handle);
 808         if (IS_ERR(handle))
 809                 goto out;
 810         BUFFER_TRACE(sbi->s_sbh, "get_write_access");
 811         err = ext4_journal_get_write_access(handle, sbi->s_sbh);
 812         if (err)
 813                 goto out_journal;
 814         strlcpy(sbi->s_es->s_last_mounted, cp,
 815                 sizeof(sbi->s_es->s_last_mounted));
 816         ext4_handle_dirty_super(handle, sb);
 817 out_journal:
 818         ext4_journal_stop(handle);
 819 out:
 820         sb_end_intwrite(sb);
 821         return err;
 822 }
 823
 824 static int ext4_file_open(struct inode *inode, struct file *filp)
 825 {
 826         int ret;
 827
 828         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
 829                 return -EIO;
 830
 831         ret = ext4_sample_last_mounted(inode->i_sb, filp->f_path.mnt);
 832         if (ret)
 833                 return ret;
 834
 835         ret = fscrypt_file_open(inode, filp);
 836         if (ret)
 837                 return ret;
 838
 839         ret = fsverity_file_open(inode, filp);
 840         if (ret)
 841                 return ret;
 842
 843         /*
 844          * Set up the jbd2_inode if we are opening the inode for
 845          * writing and the journal is present
 846          */
 847         if (filp->f_mode & FMODE_WRITE) {
 848                 ret = ext4_inode_attach_jinode(inode);
 849                 if (ret < 0)
 850                         return ret;
 851         }
 852
 853         filp->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC;
 854         return dquot_file_open(inode, filp);
 855 }
 856
 857 /*
 858  * ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
 859  * by calling generic_file_llseek_size() with the appropriate maxbytes
 860  * value for each.
 861  */
 862 loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
 863 {
 864         struct inode *inode = file->f_mapping->host;
 865         loff_t maxbytes;
 866
 867         if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
 868                 maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
 869         else
 870                 maxbytes = inode->i_sb->s_maxbytes;
 871
 872         switch (whence) {
 873         default:
 874                 return generic_file_llseek_size(file, offset, whence,
 875                                                 maxbytes, i_size_read(inode));
 876         case SEEK_HOLE:
 877                 inode_lock_shared(inode);
 878                 offset = iomap_seek_hole(inode, offset,
 879                                          &ext4_iomap_report_ops);
 880                 inode_unlock_shared(inode);
 881                 break;
 882         case SEEK_DATA:
 883                 inode_lock_shared(inode);
 884                 offset = iomap_seek_data(inode, offset,
 885                                          &ext4_iomap_report_ops);
 886                 inode_unlock_shared(inode);
 887                 break;
 888         }
 889
 890         if (offset < 0)
 891                 return offset;
 892         return vfs_setpos(file, offset, maxbytes);
 893 }
 894
 895 const struct file_operations ext4_file_operations = {
 896         .llseek         = ext4_llseek,
 897         .read_iter      = ext4_file_read_iter,
 898         .write_iter     = ext4_file_write_iter,
 899         .iopoll         = iomap_dio_iopoll,
 900         .unlocked_ioctl = ext4_ioctl,
 901 #ifdef CONFIG_COMPAT
 902         .compat_ioctl   = ext4_compat_ioctl,
 903 #endif
 904         .mmap           = ext4_file_mmap,
 905         .mmap_supported_flags = MAP_SYNC,
 906         .open           = ext4_file_open,
 907         .release        = ext4_release_file,
 908         .fsync          = ext4_sync_file,
 909         .get_unmapped_area = thp_get_unmapped_area,
 910         .splice_read    = generic_file_splice_read,
 911         .splice_write   = iter_file_splice_write,
 912         .fallocate      = ext4_fallocate,
 913 };
 914
 915 const struct inode_operations ext4_file_inode_operations = {
 916         .setattr        = ext4_setattr,
 917         .getattr        = ext4_file_getattr,
 918         .listxattr      = ext4_listxattr,
 919         .get_acl        = ext4_get_acl,
 920         .set_acl        = ext4_set_acl,
 921         .fiemap         = ext4_fiemap,
 922 };
 923