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 (card@masi.ibp.fr)
   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  *      (jj@sunsite.ms.mff.cuni.cz)
  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         inode_lock(inode);
 264         ret = ext4_write_checks(iocb, from);
 265         if (ret <= 0)
 266                 goto out;
 267
 268         current->backing_dev_info = inode_to_bdi(inode);
 269         ret = generic_perform_write(iocb->ki_filp, from, iocb->ki_pos);
 270         current->backing_dev_info = NULL;
 271
 272 out:
 273         inode_unlock(inode);
 274         if (likely(ret > 0)) {
 275                 iocb->ki_pos += ret;
 276                 ret = generic_write_sync(iocb, ret);
 277         }
 278
 279         return ret;
 280 }
 281
 282 static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset,
 283                                            ssize_t written, size_t count)
 284 {
 285         handle_t *handle;
 286         bool truncate = false;
 287         u8 blkbits = inode->i_blkbits;
 288         ext4_lblk_t written_blk, end_blk;
 289         int ret;
 290
 291         /*
 292          * Note that EXT4_I(inode)->i_disksize can get extended up to
 293          * inode->i_size while the I/O was running due to writeback of delalloc
 294          * blocks. But, the code in ext4_iomap_alloc() is careful to use
 295          * zeroed/unwritten extents if this is possible; thus we won't leave
 296          * uninitialized blocks in a file even if we didn't succeed in writing
 297          * as much as we intended.
 298          */
 299         WARN_ON_ONCE(i_size_read(inode) < EXT4_I(inode)->i_disksize);
 300         if (offset + count <= EXT4_I(inode)->i_disksize) {
 301                 /*
 302                  * We need to ensure that the inode is removed from the orphan
 303                  * list if it has been added prematurely, due to writeback of
 304                  * delalloc blocks.
 305                  */
 306                 if (!list_empty(&EXT4_I(inode)->i_orphan) && inode->i_nlink) {
 307                         handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
 308
 309                         if (IS_ERR(handle)) {
 310                                 ext4_orphan_del(NULL, inode);
 311                                 return PTR_ERR(handle);
 312                         }
 313
 314                         ext4_orphan_del(handle, inode);
 315                         ext4_journal_stop(handle);
 316                 }
 317
 318                 return written;
 319         }
 320
 321         if (written < 0)
 322                 goto truncate;
 323
 324         handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
 325         if (IS_ERR(handle)) {
 326                 written = PTR_ERR(handle);
 327                 goto truncate;
 328         }
 329
 330         if (ext4_update_inode_size(inode, offset + written)) {
 331                 ret = ext4_mark_inode_dirty(handle, inode);
 332                 if (unlikely(ret)) {
 333                         written = ret;
 334                         ext4_journal_stop(handle);
 335                         goto truncate;
 336                 }
 337         }
 338
 339         /*
 340          * We may need to truncate allocated but not written blocks beyond EOF.
 341          */
 342         written_blk = ALIGN(offset + written, 1 << blkbits);
 343         end_blk = ALIGN(offset + count, 1 << blkbits);
 344         if (written_blk < end_blk && ext4_can_truncate(inode))
 345                 truncate = true;
 346
 347         /*
 348          * Remove the inode from the orphan list if it has been extended and
 349          * everything went OK.
 350          */
 351         if (!truncate && inode->i_nlink)
 352                 ext4_orphan_del(handle, inode);
 353         ext4_journal_stop(handle);
 354
 355         if (truncate) {
 356 truncate:
 357                 ext4_truncate_failed_write(inode);
 358                 /*
 359                  * If the truncate operation failed early, then the inode may
 360                  * still be on the orphan list. In that case, we need to try
 361                  * remove the inode from the in-memory linked list.
 362                  */
 363                 if (inode->i_nlink)
 364                         ext4_orphan_del(NULL, inode);
 365         }
 366
 367         return written;
 368 }
 369
 370 static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size,
 371                                  int error, unsigned int flags)
 372 {
 373         loff_t offset = iocb->ki_pos;
 374         struct inode *inode = file_inode(iocb->ki_filp);
 375
 376         if (error)
 377                 return error;
 378
 379         if (size && flags & IOMAP_DIO_UNWRITTEN)
 380                 return ext4_convert_unwritten_extents(NULL, inode,
 381                                                       offset, size);
 382
 383         return 0;
 384 }
 385
 386 static const struct iomap_dio_ops ext4_dio_write_ops = {
 387         .end_io = ext4_dio_write_end_io,
 388 };
 389
 390 /*
 391  * The intention here is to start with shared lock acquired then see if any
 392  * condition requires an exclusive inode lock. If yes, then we restart the
 393  * whole operation by releasing the shared lock and acquiring exclusive lock.
 394  *
 395  * - For unaligned_io we never take shared lock as it may cause data corruption
 396  *   when two unaligned IO tries to modify the same block e.g. while zeroing.
 397  *
 398  * - For extending writes case we don't take the shared lock, since it requires
 399  *   updating inode i_disksize and/or orphan handling with exclusive lock.
 400  *
 401  * - shared locking will only be true mostly with overwrites. Otherwise we will
 402  *   switch to exclusive i_rwsem lock.
 403  */
 404 static ssize_t ext4_dio_write_checks(struct kiocb *iocb, struct iov_iter *from,
 405                                      bool *ilock_shared, bool *extend)
 406 {
 407         struct file *file = iocb->ki_filp;
 408         struct inode *inode = file_inode(file);
 409         loff_t offset;
 410         size_t count;
 411         ssize_t ret;
 412
 413 restart:
 414         ret = ext4_generic_write_checks(iocb, from);
 415         if (ret <= 0)
 416                 goto out;
 417
 418         offset = iocb->ki_pos;
 419         count = ret;
 420         if (ext4_extending_io(inode, offset, count))
 421                 *extend = true;
 422         /*
 423          * Determine whether the IO operation will overwrite allocated
 424          * and initialized blocks.
 425          * We need exclusive i_rwsem for changing security info
 426          * in file_modified().
 427          */
 428         if (*ilock_shared && (!IS_NOSEC(inode) || *extend ||
 429              !ext4_overwrite_io(inode, offset, count))) {
 430                 if (iocb->ki_flags & IOCB_NOWAIT) {
 431                         ret = -EAGAIN;
 432                         goto out;
 433                 }
 434                 inode_unlock_shared(inode);
 435                 *ilock_shared = false;
 436                 inode_lock(inode);
 437                 goto restart;
 438         }
 439
 440         ret = file_modified(file);
 441         if (ret < 0)
 442                 goto out;
 443
 444         return count;
 445 out:
 446         if (*ilock_shared)
 447                 inode_unlock_shared(inode);
 448         else
 449                 inode_unlock(inode);
 450         return ret;
 451 }
 452
 453 static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
 454 {
 455         ssize_t ret;
 456         handle_t *handle;
 457         struct inode *inode = file_inode(iocb->ki_filp);
 458         loff_t offset = iocb->ki_pos;
 459         size_t count = iov_iter_count(from);
 460         const struct iomap_ops *iomap_ops = &ext4_iomap_ops;
 461         bool extend = false, unaligned_io = false;
 462         bool ilock_shared = true;
 463
 464         /*
 465          * We initially start with shared inode lock unless it is
 466          * unaligned IO which needs exclusive lock anyways.
 467          */
 468         if (ext4_unaligned_io(inode, from, offset)) {
 469                 unaligned_io = true;
 470                 ilock_shared = false;
 471         }
 472         /*
 473          * Quick check here without any i_rwsem lock to see if it is extending
 474          * IO. A more reliable check is done in ext4_dio_write_checks() with
 475          * proper locking in place.
 476          */
 477         if (offset + count > i_size_read(inode))
 478                 ilock_shared = false;
 479
 480         if (iocb->ki_flags & IOCB_NOWAIT) {
 481                 if (ilock_shared) {
 482                         if (!inode_trylock_shared(inode))
 483                                 return -EAGAIN;
 484                 } else {
 485                         if (!inode_trylock(inode))
 486                                 return -EAGAIN;
 487                 }
 488         } else {
 489                 if (ilock_shared)
 490                         inode_lock_shared(inode);
 491                 else
 492                         inode_lock(inode);
 493         }
 494
 495         /* Fallback to buffered I/O if the inode does not support direct I/O. */
 496         if (!ext4_dio_supported(inode)) {
 497                 if (ilock_shared)
 498                         inode_unlock_shared(inode);
 499                 else
 500                         inode_unlock(inode);
 501                 return ext4_buffered_write_iter(iocb, from);
 502         }
 503
 504         ret = ext4_dio_write_checks(iocb, from, &ilock_shared, &extend);
 505         if (ret <= 0)
 506                 return ret;
 507
 508         /* if we're going to block and IOCB_NOWAIT is set, return -EAGAIN */
 509         if ((iocb->ki_flags & IOCB_NOWAIT) && (unaligned_io || extend)) {
 510                 ret = -EAGAIN;
 511                 goto out;
 512         }
 513
 514         offset = iocb->ki_pos;
 515         count = ret;
 516
 517         /*
 518          * Unaligned direct IO must be serialized among each other as zeroing
 519          * of partial blocks of two competing unaligned IOs can result in data
 520          * corruption.
 521          *
 522          * So we make sure we don't allow any unaligned IO in flight.
 523          * For IOs where we need not wait (like unaligned non-AIO DIO),
 524          * below inode_dio_wait() may anyway become a no-op, since we start
 525          * with exclusive lock.
 526          */
 527         if (unaligned_io)
 528                 inode_dio_wait(inode);
 529
 530         if (extend) {
 531                 handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
 532                 if (IS_ERR(handle)) {
 533                         ret = PTR_ERR(handle);
 534                         goto out;
 535                 }
 536
 537                 ret = ext4_orphan_add(handle, inode);
 538                 if (ret) {
 539                         ext4_journal_stop(handle);
 540                         goto out;
 541                 }
 542
 543                 ext4_journal_stop(handle);
 544         }
 545
 546         if (ilock_shared)
 547                 iomap_ops = &ext4_iomap_overwrite_ops;
 548         ret = iomap_dio_rw(iocb, from, iomap_ops, &ext4_dio_write_ops,
 549                            is_sync_kiocb(iocb) || unaligned_io || extend);
 550         if (ret == -ENOTBLK)
 551                 ret = 0;
 552
 553         if (extend)
 554                 ret = ext4_handle_inode_extension(inode, offset, ret, count);
 555
 556 out:
 557         if (ilock_shared)
 558                 inode_unlock_shared(inode);
 559         else
 560                 inode_unlock(inode);
 561
 562         if (ret >= 0 && iov_iter_count(from)) {
 563                 ssize_t err;
 564                 loff_t endbyte;
 565
 566                 offset = iocb->ki_pos;
 567                 err = ext4_buffered_write_iter(iocb, from);
 568                 if (err < 0)
 569                         return err;
 570
 571                 /*
 572                  * We need to ensure that the pages within the page cache for
 573                  * the range covered by this I/O are written to disk and
 574                  * invalidated. This is in attempt to preserve the expected
 575                  * direct I/O semantics in the case we fallback to buffered I/O
 576                  * to complete off the I/O request.
 577                  */
 578                 ret += err;
 579                 endbyte = offset + err - 1;
 580                 err = filemap_write_and_wait_range(iocb->ki_filp->f_mapping,
 581                                                    offset, endbyte);
 582                 if (!err)
 583                         invalidate_mapping_pages(iocb->ki_filp->f_mapping,
 584                                                  offset >> PAGE_SHIFT,
 585                                                  endbyte >> PAGE_SHIFT);
 586         }
 587
 588         return ret;
 589 }
 590
 591 #ifdef CONFIG_FS_DAX
 592 static ssize_t
 593 ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
 594 {
 595         ssize_t ret;
 596         size_t count;
 597         loff_t offset;
 598         handle_t *handle;
 599         bool extend = false;
 600         struct inode *inode = file_inode(iocb->ki_filp);
 601
 602         if (iocb->ki_flags & IOCB_NOWAIT) {
 603                 if (!inode_trylock(inode))
 604                         return -EAGAIN;
 605         } else {
 606                 inode_lock(inode);
 607         }
 608
 609         ret = ext4_write_checks(iocb, from);
 610         if (ret <= 0)
 611                 goto out;
 612
 613         offset = iocb->ki_pos;
 614         count = iov_iter_count(from);
 615
 616         if (offset + count > EXT4_I(inode)->i_disksize) {
 617                 handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
 618                 if (IS_ERR(handle)) {
 619                         ret = PTR_ERR(handle);
 620                         goto out;
 621                 }
 622
 623                 ret = ext4_orphan_add(handle, inode);
 624                 if (ret) {
 625                         ext4_journal_stop(handle);
 626                         goto out;
 627                 }
 628
 629                 extend = true;
 630                 ext4_journal_stop(handle);
 631         }
 632
 633         ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);
 634
 635         if (extend)
 636                 ret = ext4_handle_inode_extension(inode, offset, ret, count);
 637 out:
 638         inode_unlock(inode);
 639         if (ret > 0)
 640                 ret = generic_write_sync(iocb, ret);
 641         return ret;
 642 }
 643 #endif
 644
 645 static ssize_t
 646 ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 647 {
 648         struct inode *inode = file_inode(iocb->ki_filp);
 649
 650         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
 651                 return -EIO;
 652
 653 #ifdef CONFIG_FS_DAX
 654         if (IS_DAX(inode))
 655                 return ext4_dax_write_iter(iocb, from);
 656 #endif
 657         if (iocb->ki_flags & IOCB_DIRECT)
 658                 return ext4_dio_write_iter(iocb, from);
 659
 660         return ext4_buffered_write_iter(iocb, from);
 661 }
 662
 663 #ifdef CONFIG_FS_DAX
 664 static vm_fault_t ext4_dax_huge_fault(struct vm_fault *vmf,
 665                 enum page_entry_size pe_size)
 666 {
 667         int error = 0;
 668         vm_fault_t result;
 669         int retries = 0;
 670         handle_t *handle = NULL;
 671         struct inode *inode = file_inode(vmf->vma->vm_file);
 672         struct super_block *sb = inode->i_sb;
 673
 674         /*
 675          * We have to distinguish real writes from writes which will result in a
 676          * COW page; COW writes should *not* poke the journal (the file will not
 677          * be changed). Doing so would cause unintended failures when mounted
 678          * read-only.
 679          *
 680          * We check for VM_SHARED rather than vmf->cow_page since the latter is
 681          * unset for pe_size != PE_SIZE_PTE (i.e. only in do_cow_fault); for
 682          * other sizes, dax_iomap_fault will handle splitting / fallback so that
 683          * we eventually come back with a COW page.
 684          */
 685         bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
 686                 (vmf->vma->vm_flags & VM_SHARED);
 687         pfn_t pfn;
 688
 689         if (write) {
 690                 sb_start_pagefault(sb);
 691                 file_update_time(vmf->vma->vm_file);
 692                 down_read(&EXT4_I(inode)->i_mmap_sem);
 693 retry:
 694                 handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
 695                                                EXT4_DATA_TRANS_BLOCKS(sb));
 696                 if (IS_ERR(handle)) {
 697                         up_read(&EXT4_I(inode)->i_mmap_sem);
 698                         sb_end_pagefault(sb);
 699                         return VM_FAULT_SIGBUS;
 700                 }
 701         } else {
 702                 down_read(&EXT4_I(inode)->i_mmap_sem);
 703         }
 704         result = dax_iomap_fault(vmf, pe_size, &pfn, &error, &ext4_iomap_ops);
 705         if (write) {
 706                 ext4_journal_stop(handle);
 707
 708                 if ((result & VM_FAULT_ERROR) && error == -ENOSPC &&
 709                     ext4_should_retry_alloc(sb, &retries))
 710                         goto retry;
 711                 /* Handling synchronous page fault? */
 712                 if (result & VM_FAULT_NEEDDSYNC)
 713                         result = dax_finish_sync_fault(vmf, pe_size, pfn);
 714                 up_read(&EXT4_I(inode)->i_mmap_sem);
 715                 sb_end_pagefault(sb);
 716         } else {
 717                 up_read(&EXT4_I(inode)->i_mmap_sem);
 718         }
 719
 720         return result;
 721 }
 722
 723 static vm_fault_t ext4_dax_fault(struct vm_fault *vmf)
 724 {
 725         return ext4_dax_huge_fault(vmf, PE_SIZE_PTE);
 726 }
 727
 728 static const struct vm_operations_struct ext4_dax_vm_ops = {
 729         .fault          = ext4_dax_fault,
 730         .huge_fault     = ext4_dax_huge_fault,
 731         .page_mkwrite   = ext4_dax_fault,
 732         .pfn_mkwrite    = ext4_dax_fault,
 733 };
 734 #else
 735 #define ext4_dax_vm_ops ext4_file_vm_ops
 736 #endif
 737
 738 static const struct vm_operations_struct ext4_file_vm_ops = {
 739         .fault          = ext4_filemap_fault,
 740         .map_pages      = filemap_map_pages,
 741         .page_mkwrite   = ext4_page_mkwrite,
 742 };
 743
 744 static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
 745 {
 746         struct inode *inode = file->f_mapping->host;
 747         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 748         struct dax_device *dax_dev = sbi->s_daxdev;
 749
 750         if (unlikely(ext4_forced_shutdown(sbi)))
 751                 return -EIO;
 752
 753         /*
 754          * We don't support synchronous mappings for non-DAX files and
 755          * for DAX files if underneath dax_device is not synchronous.
 756          */
 757         if (!daxdev_mapping_supported(vma, dax_dev))
 758                 return -EOPNOTSUPP;
 759
 760         file_accessed(file);
 761         if (IS_DAX(file_inode(file))) {
 762                 vma->vm_ops = &ext4_dax_vm_ops;
 763                 vma->vm_flags |= VM_HUGEPAGE;
 764         } else {
 765                 vma->vm_ops = &ext4_file_vm_ops;
 766         }
 767         return 0;
 768 }
 769
 770 static int ext4_sample_last_mounted(struct super_block *sb,
 771                                     struct vfsmount *mnt)
 772 {
 773         struct ext4_sb_info *sbi = EXT4_SB(sb);
 774         struct path path;
 775         char buf[64], *cp;
 776         handle_t *handle;
 777         int err;
 778
 779         if (likely(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED))
 780                 return 0;
 781
 782         if (sb_rdonly(sb) || !sb_start_intwrite_trylock(sb))
 783                 return 0;
 784
 785         sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
 786         /*
 787          * Sample where the filesystem has been mounted and
 788          * store it in the superblock for sysadmin convenience
 789          * when trying to sort through large numbers of block
 790          * devices or filesystem images.
 791          */
 792         memset(buf, 0, sizeof(buf));
 793         path.mnt = mnt;
 794         path.dentry = mnt->mnt_root;
 795         cp = d_path(&path, buf, sizeof(buf));
 796         err = 0;
 797         if (IS_ERR(cp))
 798                 goto out;
 799
 800         handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
 801         err = PTR_ERR(handle);
 802         if (IS_ERR(handle))
 803                 goto out;
 804         BUFFER_TRACE(sbi->s_sbh, "get_write_access");
 805         err = ext4_journal_get_write_access(handle, sbi->s_sbh);
 806         if (err)
 807                 goto out_journal;
 808         strlcpy(sbi->s_es->s_last_mounted, cp,
 809                 sizeof(sbi->s_es->s_last_mounted));
 810         ext4_handle_dirty_super(handle, sb);
 811 out_journal:
 812         ext4_journal_stop(handle);
 813 out:
 814         sb_end_intwrite(sb);
 815         return err;
 816 }
 817
 818 static int ext4_file_open(struct inode *inode, struct file *filp)
 819 {
 820         int ret;
 821
 822         if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
 823                 return -EIO;
 824
 825         ret = ext4_sample_last_mounted(inode->i_sb, filp->f_path.mnt);
 826         if (ret)
 827                 return ret;
 828
 829         ret = fscrypt_file_open(inode, filp);
 830         if (ret)
 831                 return ret;
 832
 833         ret = fsverity_file_open(inode, filp);
 834         if (ret)
 835                 return ret;
 836
 837         /*
 838          * Set up the jbd2_inode if we are opening the inode for
 839          * writing and the journal is present
 840          */
 841         if (filp->f_mode & FMODE_WRITE) {
 842                 ret = ext4_inode_attach_jinode(inode);
 843                 if (ret < 0)
 844                         return ret;
 845         }
 846
 847         filp->f_mode |= FMODE_NOWAIT;
 848         return dquot_file_open(inode, filp);
 849 }
 850
 851 /*
 852  * ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
 853  * by calling generic_file_llseek_size() with the appropriate maxbytes
 854  * value for each.
 855  */
 856 loff_t ext4_llseek(struct file *file, loff_t offset, int whence)
 857 {
 858         struct inode *inode = file->f_mapping->host;
 859         loff_t maxbytes;
 860
 861         if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
 862                 maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
 863         else
 864                 maxbytes = inode->i_sb->s_maxbytes;
 865
 866         switch (whence) {
 867         default:
 868                 return generic_file_llseek_size(file, offset, whence,
 869                                                 maxbytes, i_size_read(inode));
 870         case SEEK_HOLE:
 871                 inode_lock_shared(inode);
 872                 offset = iomap_seek_hole(inode, offset,
 873                                          &ext4_iomap_report_ops);
 874                 inode_unlock_shared(inode);
 875                 break;
 876         case SEEK_DATA:
 877                 inode_lock_shared(inode);
 878                 offset = iomap_seek_data(inode, offset,
 879                                          &ext4_iomap_report_ops);
 880                 inode_unlock_shared(inode);
 881                 break;
 882         }
 883
 884         if (offset < 0)
 885                 return offset;
 886         return vfs_setpos(file, offset, maxbytes);
 887 }
 888
 889 const struct file_operations ext4_file_operations = {
 890         .llseek         = ext4_llseek,
 891         .read_iter      = ext4_file_read_iter,
 892         .write_iter     = ext4_file_write_iter,
 893         .iopoll         = iomap_dio_iopoll,
 894         .unlocked_ioctl = ext4_ioctl,
 895 #ifdef CONFIG_COMPAT
 896         .compat_ioctl   = ext4_compat_ioctl,
 897 #endif
 898         .mmap           = ext4_file_mmap,
 899         .mmap_supported_flags = MAP_SYNC,
 900         .open           = ext4_file_open,
 901         .release        = ext4_release_file,
 902         .fsync          = ext4_sync_file,
 903         .get_unmapped_area = thp_get_unmapped_area,
 904         .splice_read    = generic_file_splice_read,
 905         .splice_write   = iter_file_splice_write,
 906         .fallocate      = ext4_fallocate,
 907 };
 908
 909 const struct inode_operations ext4_file_inode_operations = {
 910         .setattr        = ext4_setattr,
 911         .getattr        = ext4_file_getattr,
 912         .listxattr      = ext4_listxattr,
 913         .get_acl        = ext4_get_acl,
 914         .set_acl        = ext4_set_acl,
 915         .fiemap         = ext4_fiemap,
 916 };
 917