root/fs/xfs/xfs_iomap.c

DEFINITIONS

1. xfs_alert_fsblock_zero
2. xfs_bmbt_to_iomap
3. xfs_hole_to_iomap
4. xfs_eof_alignment
5. xfs_iomap_eof_align_last_fsb
6. xfs_iomap_write_direct
7. xfs_quota_need_throttle
8. xfs_quota_calc_throttle
9. xfs_iomap_prealloc_size
10. xfs_file_iomap_begin_delay
11. xfs_iomap_write_unwritten
12. imap_needs_alloc
13. needs_cow_for_zeroing
14. xfs_ilock_for_iomap
15. xfs_file_iomap_begin
16. xfs_file_iomap_end_delalloc
17. xfs_file_iomap_end
18. xfs_seek_iomap_begin
19. xfs_xattr_iomap_begin

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (c) 2000-2006 Silicon Graphics, Inc.
   4  * Copyright (c) 2016-2018 Christoph Hellwig.
   5  * All Rights Reserved.
   6  */
   7 #include "xfs.h"
   8 #include "xfs_fs.h"
   9 #include "xfs_shared.h"
  10 #include "xfs_format.h"
  11 #include "xfs_log_format.h"
  12 #include "xfs_trans_resv.h"
  13 #include "xfs_mount.h"
  14 #include "xfs_inode.h"
  15 #include "xfs_btree.h"
  16 #include "xfs_bmap_btree.h"
  17 #include "xfs_bmap.h"
  18 #include "xfs_bmap_util.h"
  19 #include "xfs_errortag.h"
  20 #include "xfs_error.h"
  21 #include "xfs_trans.h"
  22 #include "xfs_trans_space.h"
  23 #include "xfs_inode_item.h"
  24 #include "xfs_iomap.h"
  25 #include "xfs_trace.h"
  26 #include "xfs_quota.h"
  27 #include "xfs_dquot_item.h"
  28 #include "xfs_dquot.h"
  29 #include "xfs_reflink.h"
  30 
  31 
  32 #define XFS_WRITEIO_ALIGN(mp,off)       (((off) >> mp->m_writeio_log) \
  33                                                 << mp->m_writeio_log)
  34 
  35 static int
  36 xfs_alert_fsblock_zero(
  37         xfs_inode_t     *ip,
  38         xfs_bmbt_irec_t *imap)
  39 {
  40         xfs_alert_tag(ip->i_mount, XFS_PTAG_FSBLOCK_ZERO,
  41                         "Access to block zero in inode %llu "
  42                         "start_block: %llx start_off: %llx "
  43                         "blkcnt: %llx extent-state: %x",
  44                 (unsigned long long)ip->i_ino,
  45                 (unsigned long long)imap->br_startblock,
  46                 (unsigned long long)imap->br_startoff,
  47                 (unsigned long long)imap->br_blockcount,
  48                 imap->br_state);
  49         return -EFSCORRUPTED;
  50 }
  51 
  52 int
  53 xfs_bmbt_to_iomap(
  54         struct xfs_inode        *ip,
  55         struct iomap            *iomap,
  56         struct xfs_bmbt_irec    *imap,
  57         bool                    shared)
  58 {
  59         struct xfs_mount        *mp = ip->i_mount;
  60 
  61         if (unlikely(!xfs_valid_startblock(ip, imap->br_startblock)))
  62                 return xfs_alert_fsblock_zero(ip, imap);
  63 
  64         if (imap->br_startblock == HOLESTARTBLOCK) {
  65                 iomap->addr = IOMAP_NULL_ADDR;
  66                 iomap->type = IOMAP_HOLE;
  67         } else if (imap->br_startblock == DELAYSTARTBLOCK ||
  68                    isnullstartblock(imap->br_startblock)) {
  69                 iomap->addr = IOMAP_NULL_ADDR;
  70                 iomap->type = IOMAP_DELALLOC;
  71         } else {
  72                 iomap->addr = BBTOB(xfs_fsb_to_db(ip, imap->br_startblock));
  73                 if (imap->br_state == XFS_EXT_UNWRITTEN)
  74                         iomap->type = IOMAP_UNWRITTEN;
  75                 else
  76                         iomap->type = IOMAP_MAPPED;
  77         }
  78         iomap->offset = XFS_FSB_TO_B(mp, imap->br_startoff);
  79         iomap->length = XFS_FSB_TO_B(mp, imap->br_blockcount);
  80         iomap->bdev = xfs_find_bdev_for_inode(VFS_I(ip));
  81         iomap->dax_dev = xfs_find_daxdev_for_inode(VFS_I(ip));
  82 
  83         if (xfs_ipincount(ip) &&
  84             (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
  85                 iomap->flags |= IOMAP_F_DIRTY;
  86         if (shared)
  87                 iomap->flags |= IOMAP_F_SHARED;
  88         return 0;
  89 }
  90 
  91 static void
  92 xfs_hole_to_iomap(
  93         struct xfs_inode        *ip,
  94         struct iomap            *iomap,
  95         xfs_fileoff_t           offset_fsb,
  96         xfs_fileoff_t           end_fsb)
  97 {
  98         iomap->addr = IOMAP_NULL_ADDR;
  99         iomap->type = IOMAP_HOLE;
 100         iomap->offset = XFS_FSB_TO_B(ip->i_mount, offset_fsb);
 101         iomap->length = XFS_FSB_TO_B(ip->i_mount, end_fsb - offset_fsb);
 102         iomap->bdev = xfs_find_bdev_for_inode(VFS_I(ip));
 103         iomap->dax_dev = xfs_find_daxdev_for_inode(VFS_I(ip));
 104 }
 105 
 106 xfs_extlen_t
 107 xfs_eof_alignment(
 108         struct xfs_inode        *ip,
 109         xfs_extlen_t            extsize)
 110 {
 111         struct xfs_mount        *mp = ip->i_mount;
 112         xfs_extlen_t            align = 0;
 113 
 114         if (!XFS_IS_REALTIME_INODE(ip)) {
 115                 /*
 116                  * Round up the allocation request to a stripe unit
 117                  * (m_dalign) boundary if the file size is >= stripe unit
 118                  * size, and we are allocating past the allocation eof.
 119                  *
 120                  * If mounted with the "-o swalloc" option the alignment is
 121                  * increased from the strip unit size to the stripe width.
 122                  */
 123                 if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC))
 124                         align = mp->m_swidth;
 125                 else if (mp->m_dalign)
 126                         align = mp->m_dalign;
 127 
 128                 if (align && XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, align))
 129                         align = 0;
 130         }
 131 
 132         /*
 133          * Always round up the allocation request to an extent boundary
 134          * (when file on a real-time subvolume or has di_extsize hint).
 135          */
 136         if (extsize) {
 137                 if (align)
 138                         align = roundup_64(align, extsize);
 139                 else
 140                         align = extsize;
 141         }
 142 
 143         return align;
 144 }
 145 
 146 STATIC int
 147 xfs_iomap_eof_align_last_fsb(
 148         struct xfs_inode        *ip,
 149         xfs_extlen_t            extsize,
 150         xfs_fileoff_t           *last_fsb)
 151 {
 152         xfs_extlen_t            align = xfs_eof_alignment(ip, extsize);
 153 
 154         if (align) {
 155                 xfs_fileoff_t   new_last_fsb = roundup_64(*last_fsb, align);
 156                 int             eof, error;
 157 
 158                 error = xfs_bmap_eof(ip, new_last_fsb, XFS_DATA_FORK, &eof);
 159                 if (error)
 160                         return error;
 161                 if (eof)
 162                         *last_fsb = new_last_fsb;
 163         }
 164         return 0;
 165 }
 166 
 167 int
 168 xfs_iomap_write_direct(
 169         xfs_inode_t     *ip,
 170         xfs_off_t       offset,
 171         size_t          count,
 172         xfs_bmbt_irec_t *imap,
 173         int             nmaps)
 174 {
 175         xfs_mount_t     *mp = ip->i_mount;
 176         xfs_fileoff_t   offset_fsb;
 177         xfs_fileoff_t   last_fsb;
 178         xfs_filblks_t   count_fsb, resaligned;
 179         xfs_extlen_t    extsz;
 180         int             nimaps;
 181         int             quota_flag;
 182         int             rt;
 183         xfs_trans_t     *tp;
 184         uint            qblocks, resblks, resrtextents;
 185         int             error;
 186         int             lockmode;
 187         int             bmapi_flags = XFS_BMAPI_PREALLOC;
 188         uint            tflags = 0;
 189 
 190         rt = XFS_IS_REALTIME_INODE(ip);
 191         extsz = xfs_get_extsz_hint(ip);
 192         lockmode = XFS_ILOCK_SHARED;    /* locked by caller */
 193 
 194         ASSERT(xfs_isilocked(ip, lockmode));
 195 
 196         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 197         last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));
 198         if ((offset + count) > XFS_ISIZE(ip)) {
 199                 /*
 200                  * Assert that the in-core extent list is present since this can
 201                  * call xfs_iread_extents() and we only have the ilock shared.
 202                  * This should be safe because the lock was held around a bmapi
 203                  * call in the caller and we only need it to access the in-core
 204                  * list.
 205                  */
 206                 ASSERT(XFS_IFORK_PTR(ip, XFS_DATA_FORK)->if_flags &
 207                                                                 XFS_IFEXTENTS);
 208                 error = xfs_iomap_eof_align_last_fsb(ip, extsz, &last_fsb);
 209                 if (error)
 210                         goto out_unlock;
 211         } else {
 212                 if (nmaps && (imap->br_startblock == HOLESTARTBLOCK))
 213                         last_fsb = min(last_fsb, (xfs_fileoff_t)
 214                                         imap->br_blockcount +
 215                                         imap->br_startoff);
 216         }
 217         count_fsb = last_fsb - offset_fsb;
 218         ASSERT(count_fsb > 0);
 219         resaligned = xfs_aligned_fsb_count(offset_fsb, count_fsb, extsz);
 220 
 221         if (unlikely(rt)) {
 222                 resrtextents = qblocks = resaligned;
 223                 resrtextents /= mp->m_sb.sb_rextsize;
 224                 resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
 225                 quota_flag = XFS_QMOPT_RES_RTBLKS;
 226         } else {
 227                 resrtextents = 0;
 228                 resblks = qblocks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
 229                 quota_flag = XFS_QMOPT_RES_REGBLKS;
 230         }
 231 
 232         /*
 233          * Drop the shared lock acquired by the caller, attach the dquot if
 234          * necessary and move on to transaction setup.
 235          */
 236         xfs_iunlock(ip, lockmode);
 237         error = xfs_qm_dqattach(ip);
 238         if (error)
 239                 return error;
 240 
 241         /*
 242          * For DAX, we do not allocate unwritten extents, but instead we zero
 243          * the block before we commit the transaction.  Ideally we'd like to do
 244          * this outside the transaction context, but if we commit and then crash
 245          * we may not have zeroed the blocks and this will be exposed on
 246          * recovery of the allocation. Hence we must zero before commit.
 247          *
 248          * Further, if we are mapping unwritten extents here, we need to zero
 249          * and convert them to written so that we don't need an unwritten extent
 250          * callback for DAX. This also means that we need to be able to dip into
 251          * the reserve block pool for bmbt block allocation if there is no space
 252          * left but we need to do unwritten extent conversion.
 253          */
 254         if (IS_DAX(VFS_I(ip))) {
 255                 bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;
 256                 if (imap->br_state == XFS_EXT_UNWRITTEN) {
 257                         tflags |= XFS_TRANS_RESERVE;
 258                         resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
 259                 }
 260         }
 261         error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, resrtextents,
 262                         tflags, &tp);
 263         if (error)
 264                 return error;
 265 
 266         lockmode = XFS_ILOCK_EXCL;
 267         xfs_ilock(ip, lockmode);
 268 
 269         error = xfs_trans_reserve_quota_nblks(tp, ip, qblocks, 0, quota_flag);
 270         if (error)
 271                 goto out_trans_cancel;
 272 
 273         xfs_trans_ijoin(tp, ip, 0);
 274 
 275         /*
 276          * From this point onwards we overwrite the imap pointer that the
 277          * caller gave to us.
 278          */
 279         nimaps = 1;
 280         error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,
 281                                 bmapi_flags, resblks, imap, &nimaps);
 282         if (error)
 283                 goto out_res_cancel;
 284 
 285         /*
 286          * Complete the transaction
 287          */
 288         error = xfs_trans_commit(tp);
 289         if (error)
 290                 goto out_unlock;
 291 
 292         /*
 293          * Copy any maps to caller's array and return any error.
 294          */
 295         if (nimaps == 0) {
 296                 error = -ENOSPC;
 297                 goto out_unlock;
 298         }
 299 
 300         if (unlikely(!xfs_valid_startblock(ip, imap->br_startblock)))
 301                 error = xfs_alert_fsblock_zero(ip, imap);
 302 
 303 out_unlock:
 304         xfs_iunlock(ip, lockmode);
 305         return error;
 306 
 307 out_res_cancel:
 308         xfs_trans_unreserve_quota_nblks(tp, ip, (long)qblocks, 0, quota_flag);
 309 out_trans_cancel:
 310         xfs_trans_cancel(tp);
 311         goto out_unlock;
 312 }
 313 
 314 STATIC bool
 315 xfs_quota_need_throttle(
 316         struct xfs_inode *ip,
 317         int type,
 318         xfs_fsblock_t alloc_blocks)
 319 {
 320         struct xfs_dquot *dq = xfs_inode_dquot(ip, type);
 321 
 322         if (!dq || !xfs_this_quota_on(ip->i_mount, type))
 323                 return false;
 324 
 325         /* no hi watermark, no throttle */
 326         if (!dq->q_prealloc_hi_wmark)
 327                 return false;
 328 
 329         /* under the lo watermark, no throttle */
 330         if (dq->q_res_bcount + alloc_blocks < dq->q_prealloc_lo_wmark)
 331                 return false;
 332 
 333         return true;
 334 }
 335 
 336 STATIC void
 337 xfs_quota_calc_throttle(
 338         struct xfs_inode *ip,
 339         int type,
 340         xfs_fsblock_t *qblocks,
 341         int *qshift,
 342         int64_t *qfreesp)
 343 {
 344         int64_t freesp;
 345         int shift = 0;
 346         struct xfs_dquot *dq = xfs_inode_dquot(ip, type);
 347 
 348         /* no dq, or over hi wmark, squash the prealloc completely */
 349         if (!dq || dq->q_res_bcount >= dq->q_prealloc_hi_wmark) {
 350                 *qblocks = 0;
 351                 *qfreesp = 0;
 352                 return;
 353         }
 354 
 355         freesp = dq->q_prealloc_hi_wmark - dq->q_res_bcount;
 356         if (freesp < dq->q_low_space[XFS_QLOWSP_5_PCNT]) {
 357                 shift = 2;
 358                 if (freesp < dq->q_low_space[XFS_QLOWSP_3_PCNT])
 359                         shift += 2;
 360                 if (freesp < dq->q_low_space[XFS_QLOWSP_1_PCNT])
 361                         shift += 2;
 362         }
 363 
 364         if (freesp < *qfreesp)
 365                 *qfreesp = freesp;
 366 
 367         /* only overwrite the throttle values if we are more aggressive */
 368         if ((freesp >> shift) < (*qblocks >> *qshift)) {
 369                 *qblocks = freesp;
 370                 *qshift = shift;
 371         }
 372 }
 373 
 374 /*
 375  * If we are doing a write at the end of the file and there are no allocations
 376  * past this one, then extend the allocation out to the file system's write
 377  * iosize.
 378  *
 379  * If we don't have a user specified preallocation size, dynamically increase
 380  * the preallocation size as the size of the file grows.  Cap the maximum size
 381  * at a single extent or less if the filesystem is near full. The closer the
 382  * filesystem is to full, the smaller the maximum prealocation.
 383  *
 384  * As an exception we don't do any preallocation at all if the file is smaller
 385  * than the minimum preallocation and we are using the default dynamic
 386  * preallocation scheme, as it is likely this is the only write to the file that
 387  * is going to be done.
 388  *
 389  * We clean up any extra space left over when the file is closed in
 390  * xfs_inactive().
 391  */
 392 STATIC xfs_fsblock_t
 393 xfs_iomap_prealloc_size(
 394         struct xfs_inode        *ip,
 395         int                     whichfork,
 396         loff_t                  offset,
 397         loff_t                  count,
 398         struct xfs_iext_cursor  *icur)
 399 {
 400         struct xfs_mount        *mp = ip->i_mount;
 401         struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
 402         xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
 403         struct xfs_bmbt_irec    prev;
 404         int                     shift = 0;
 405         int64_t                 freesp;
 406         xfs_fsblock_t           qblocks;
 407         int                     qshift = 0;
 408         xfs_fsblock_t           alloc_blocks = 0;
 409 
 410         if (offset + count <= XFS_ISIZE(ip))
 411                 return 0;
 412 
 413         if (!(mp->m_flags & XFS_MOUNT_DFLT_IOSIZE) &&
 414             (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_writeio_blocks)))
 415                 return 0;
 416 
 417         /*
 418          * If an explicit allocsize is set, the file is small, or we
 419          * are writing behind a hole, then use the minimum prealloc:
 420          */
 421         if ((mp->m_flags & XFS_MOUNT_DFLT_IOSIZE) ||
 422             XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign) ||
 423             !xfs_iext_peek_prev_extent(ifp, icur, &prev) ||
 424             prev.br_startoff + prev.br_blockcount < offset_fsb)
 425                 return mp->m_writeio_blocks;
 426 
 427         /*
 428          * Determine the initial size of the preallocation. We are beyond the
 429          * current EOF here, but we need to take into account whether this is
 430          * a sparse write or an extending write when determining the
 431          * preallocation size.  Hence we need to look up the extent that ends
 432          * at the current write offset and use the result to determine the
 433          * preallocation size.
 434          *
 435          * If the extent is a hole, then preallocation is essentially disabled.
 436          * Otherwise we take the size of the preceding data extent as the basis
 437          * for the preallocation size. If the size of the extent is greater than
 438          * half the maximum extent length, then use the current offset as the
 439          * basis. This ensures that for large files the preallocation size
 440          * always extends to MAXEXTLEN rather than falling short due to things
 441          * like stripe unit/width alignment of real extents.
 442          */
 443         if (prev.br_blockcount <= (MAXEXTLEN >> 1))
 444                 alloc_blocks = prev.br_blockcount << 1;
 445         else
 446                 alloc_blocks = XFS_B_TO_FSB(mp, offset);
 447         if (!alloc_blocks)
 448                 goto check_writeio;
 449         qblocks = alloc_blocks;
 450 
 451         /*
 452          * MAXEXTLEN is not a power of two value but we round the prealloc down
 453          * to the nearest power of two value after throttling. To prevent the
 454          * round down from unconditionally reducing the maximum supported prealloc
 455          * size, we round up first, apply appropriate throttling, round down and
 456          * cap the value to MAXEXTLEN.
 457          */
 458         alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(MAXEXTLEN),
 459                                        alloc_blocks);
 460 
 461         freesp = percpu_counter_read_positive(&mp->m_fdblocks);
 462         if (freesp < mp->m_low_space[XFS_LOWSP_5_PCNT]) {
 463                 shift = 2;
 464                 if (freesp < mp->m_low_space[XFS_LOWSP_4_PCNT])
 465                         shift++;
 466                 if (freesp < mp->m_low_space[XFS_LOWSP_3_PCNT])
 467                         shift++;
 468                 if (freesp < mp->m_low_space[XFS_LOWSP_2_PCNT])
 469                         shift++;
 470                 if (freesp < mp->m_low_space[XFS_LOWSP_1_PCNT])
 471                         shift++;
 472         }
 473 
 474         /*
 475          * Check each quota to cap the prealloc size, provide a shift value to
 476          * throttle with and adjust amount of available space.
 477          */
 478         if (xfs_quota_need_throttle(ip, XFS_DQ_USER, alloc_blocks))
 479                 xfs_quota_calc_throttle(ip, XFS_DQ_USER, &qblocks, &qshift,
 480                                         &freesp);
 481         if (xfs_quota_need_throttle(ip, XFS_DQ_GROUP, alloc_blocks))
 482                 xfs_quota_calc_throttle(ip, XFS_DQ_GROUP, &qblocks, &qshift,
 483                                         &freesp);
 484         if (xfs_quota_need_throttle(ip, XFS_DQ_PROJ, alloc_blocks))
 485                 xfs_quota_calc_throttle(ip, XFS_DQ_PROJ, &qblocks, &qshift,
 486                                         &freesp);
 487 
 488         /*
 489          * The final prealloc size is set to the minimum of free space available
 490          * in each of the quotas and the overall filesystem.
 491          *
 492          * The shift throttle value is set to the maximum value as determined by
 493          * the global low free space values and per-quota low free space values.
 494          */
 495         alloc_blocks = min(alloc_blocks, qblocks);
 496         shift = max(shift, qshift);
 497 
 498         if (shift)
 499                 alloc_blocks >>= shift;
 500         /*
 501          * rounddown_pow_of_two() returns an undefined result if we pass in
 502          * alloc_blocks = 0.
 503          */
 504         if (alloc_blocks)
 505                 alloc_blocks = rounddown_pow_of_two(alloc_blocks);
 506         if (alloc_blocks > MAXEXTLEN)
 507                 alloc_blocks = MAXEXTLEN;
 508 
 509         /*
 510          * If we are still trying to allocate more space than is
 511          * available, squash the prealloc hard. This can happen if we
 512          * have a large file on a small filesystem and the above
 513          * lowspace thresholds are smaller than MAXEXTLEN.
 514          */
 515         while (alloc_blocks && alloc_blocks >= freesp)
 516                 alloc_blocks >>= 4;
 517 check_writeio:
 518         if (alloc_blocks < mp->m_writeio_blocks)
 519                 alloc_blocks = mp->m_writeio_blocks;
 520         trace_xfs_iomap_prealloc_size(ip, alloc_blocks, shift,
 521                                       mp->m_writeio_blocks);
 522         return alloc_blocks;
 523 }
 524 
 525 static int
 526 xfs_file_iomap_begin_delay(
 527         struct inode            *inode,
 528         loff_t                  offset,
 529         loff_t                  count,
 530         unsigned                flags,
 531         struct iomap            *iomap)
 532 {
 533         struct xfs_inode        *ip = XFS_I(inode);
 534         struct xfs_mount        *mp = ip->i_mount;
 535         xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
 536         xfs_fileoff_t           maxbytes_fsb =
 537                 XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
 538         xfs_fileoff_t           end_fsb;
 539         struct xfs_bmbt_irec    imap, cmap;
 540         struct xfs_iext_cursor  icur, ccur;
 541         xfs_fsblock_t           prealloc_blocks = 0;
 542         bool                    eof = false, cow_eof = false, shared = false;
 543         int                     whichfork = XFS_DATA_FORK;
 544         int                     error = 0;
 545 
 546         ASSERT(!XFS_IS_REALTIME_INODE(ip));
 547         ASSERT(!xfs_get_extsz_hint(ip));
 548 
 549         xfs_ilock(ip, XFS_ILOCK_EXCL);
 550 
 551         if (unlikely(XFS_TEST_ERROR(
 552             (XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_EXTENTS &&
 553              XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_BTREE),
 554              mp, XFS_ERRTAG_BMAPIFORMAT))) {
 555                 XFS_ERROR_REPORT(__func__, XFS_ERRLEVEL_LOW, mp);
 556                 error = -EFSCORRUPTED;
 557                 goto out_unlock;
 558         }
 559 
 560         XFS_STATS_INC(mp, xs_blk_mapw);
 561 
 562         if (!(ip->i_df.if_flags & XFS_IFEXTENTS)) {
 563                 error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
 564                 if (error)
 565                         goto out_unlock;
 566         }
 567 
 568         end_fsb = min(XFS_B_TO_FSB(mp, offset + count), maxbytes_fsb);
 569 
 570         /*
 571          * Search the data fork fork first to look up our source mapping.  We
 572          * always need the data fork map, as we have to return it to the
 573          * iomap code so that the higher level write code can read data in to
 574          * perform read-modify-write cycles for unaligned writes.
 575          */
 576         eof = !xfs_iext_lookup_extent(ip, &ip->i_df, offset_fsb, &icur, &imap);
 577         if (eof)
 578                 imap.br_startoff = end_fsb; /* fake hole until the end */
 579 
 580         /* We never need to allocate blocks for zeroing a hole. */
 581         if ((flags & IOMAP_ZERO) && imap.br_startoff > offset_fsb) {
 582                 xfs_hole_to_iomap(ip, iomap, offset_fsb, imap.br_startoff);
 583                 goto out_unlock;
 584         }
 585 
 586         /*
 587          * Search the COW fork extent list even if we did not find a data fork
 588          * extent.  This serves two purposes: first this implements the
 589          * speculative preallocation using cowextsize, so that we also unshare
 590          * block adjacent to shared blocks instead of just the shared blocks
 591          * themselves.  Second the lookup in the extent list is generally faster
 592          * than going out to the shared extent tree.
 593          */
 594         if (xfs_is_cow_inode(ip)) {
 595                 if (!ip->i_cowfp) {
 596                         ASSERT(!xfs_is_reflink_inode(ip));
 597                         xfs_ifork_init_cow(ip);
 598                 }
 599                 cow_eof = !xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb,
 600                                 &ccur, &cmap);
 601                 if (!cow_eof && cmap.br_startoff <= offset_fsb) {
 602                         trace_xfs_reflink_cow_found(ip, &cmap);
 603                         whichfork = XFS_COW_FORK;
 604                         goto done;
 605                 }
 606         }
 607 
 608         if (imap.br_startoff <= offset_fsb) {
 609                 /*
 610                  * For reflink files we may need a delalloc reservation when
 611                  * overwriting shared extents.   This includes zeroing of
 612                  * existing extents that contain data.
 613                  */
 614                 if (!xfs_is_cow_inode(ip) ||
 615                     ((flags & IOMAP_ZERO) && imap.br_state != XFS_EXT_NORM)) {
 616                         trace_xfs_iomap_found(ip, offset, count, XFS_DATA_FORK,
 617                                         &imap);
 618                         goto done;
 619                 }
 620 
 621                 xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb);
 622 
 623                 /* Trim the mapping to the nearest shared extent boundary. */
 624                 error = xfs_inode_need_cow(ip, &imap, &shared);
 625                 if (error)
 626                         goto out_unlock;
 627 
 628                 /* Not shared?  Just report the (potentially capped) extent. */
 629                 if (!shared) {
 630                         trace_xfs_iomap_found(ip, offset, count, XFS_DATA_FORK,
 631                                         &imap);
 632                         goto done;
 633                 }
 634 
 635                 /*
 636                  * Fork all the shared blocks from our write offset until the
 637                  * end of the extent.
 638                  */
 639                 whichfork = XFS_COW_FORK;
 640                 end_fsb = imap.br_startoff + imap.br_blockcount;
 641         } else {
 642                 /*
 643                  * We cap the maximum length we map here to MAX_WRITEBACK_PAGES
 644                  * pages to keep the chunks of work done where somewhat
 645                  * symmetric with the work writeback does.  This is a completely
 646                  * arbitrary number pulled out of thin air.
 647                  *
 648                  * Note that the values needs to be less than 32-bits wide until
 649                  * the lower level functions are updated.
 650                  */
 651                 count = min_t(loff_t, count, 1024 * PAGE_SIZE);
 652                 end_fsb = min(XFS_B_TO_FSB(mp, offset + count), maxbytes_fsb);
 653 
 654                 if (xfs_is_always_cow_inode(ip))
 655                         whichfork = XFS_COW_FORK;
 656         }
 657 
 658         error = xfs_qm_dqattach_locked(ip, false);
 659         if (error)
 660                 goto out_unlock;
 661 
 662         if (eof) {
 663                 prealloc_blocks = xfs_iomap_prealloc_size(ip, whichfork, offset,
 664                                 count, &icur);
 665                 if (prealloc_blocks) {
 666                         xfs_extlen_t    align;
 667                         xfs_off_t       end_offset;
 668                         xfs_fileoff_t   p_end_fsb;
 669 
 670                         end_offset = XFS_WRITEIO_ALIGN(mp, offset + count - 1);
 671                         p_end_fsb = XFS_B_TO_FSBT(mp, end_offset) +
 672                                         prealloc_blocks;
 673 
 674                         align = xfs_eof_alignment(ip, 0);
 675                         if (align)
 676                                 p_end_fsb = roundup_64(p_end_fsb, align);
 677 
 678                         p_end_fsb = min(p_end_fsb, maxbytes_fsb);
 679                         ASSERT(p_end_fsb > offset_fsb);
 680                         prealloc_blocks = p_end_fsb - end_fsb;
 681                 }
 682         }
 683 
 684 retry:
 685         error = xfs_bmapi_reserve_delalloc(ip, whichfork, offset_fsb,
 686                         end_fsb - offset_fsb, prealloc_blocks,
 687                         whichfork == XFS_DATA_FORK ? &imap : &cmap,
 688                         whichfork == XFS_DATA_FORK ? &icur : &ccur,
 689                         whichfork == XFS_DATA_FORK ? eof : cow_eof);
 690         switch (error) {
 691         case 0:
 692                 break;
 693         case -ENOSPC:
 694         case -EDQUOT:
 695                 /* retry without any preallocation */
 696                 trace_xfs_delalloc_enospc(ip, offset, count);
 697                 if (prealloc_blocks) {
 698                         prealloc_blocks = 0;
 699                         goto retry;
 700                 }
 701                 /*FALLTHRU*/
 702         default:
 703                 goto out_unlock;
 704         }
 705 
 706         /*
 707          * Flag newly allocated delalloc blocks with IOMAP_F_NEW so we punch
 708          * them out if the write happens to fail.
 709          */
 710         iomap->flags |= IOMAP_F_NEW;
 711         trace_xfs_iomap_alloc(ip, offset, count, whichfork,
 712                         whichfork == XFS_DATA_FORK ? &imap : &cmap);
 713 done:
 714         if (whichfork == XFS_COW_FORK) {
 715                 if (imap.br_startoff > offset_fsb) {
 716                         xfs_trim_extent(&cmap, offset_fsb,
 717                                         imap.br_startoff - offset_fsb);
 718                         error = xfs_bmbt_to_iomap(ip, iomap, &cmap, true);
 719                         goto out_unlock;
 720                 }
 721                 /* ensure we only report blocks we have a reservation for */
 722                 xfs_trim_extent(&imap, cmap.br_startoff, cmap.br_blockcount);
 723                 shared = true;
 724         }
 725         error = xfs_bmbt_to_iomap(ip, iomap, &imap, shared);
 726 out_unlock:
 727         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 728         return error;
 729 }
 730 
 731 int
 732 xfs_iomap_write_unwritten(
 733         xfs_inode_t     *ip,
 734         xfs_off_t       offset,
 735         xfs_off_t       count,
 736         bool            update_isize)
 737 {
 738         xfs_mount_t     *mp = ip->i_mount;
 739         xfs_fileoff_t   offset_fsb;
 740         xfs_filblks_t   count_fsb;
 741         xfs_filblks_t   numblks_fsb;
 742         int             nimaps;
 743         xfs_trans_t     *tp;
 744         xfs_bmbt_irec_t imap;
 745         struct inode    *inode = VFS_I(ip);
 746         xfs_fsize_t     i_size;
 747         uint            resblks;
 748         int             error;
 749 
 750         trace_xfs_unwritten_convert(ip, offset, count);
 751 
 752         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 753         count_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
 754         count_fsb = (xfs_filblks_t)(count_fsb - offset_fsb);
 755 
 756         /*
 757          * Reserve enough blocks in this transaction for two complete extent
 758          * btree splits.  We may be converting the middle part of an unwritten
 759          * extent and in this case we will insert two new extents in the btree
 760          * each of which could cause a full split.
 761          *
 762          * This reservation amount will be used in the first call to
 763          * xfs_bmbt_split() to select an AG with enough space to satisfy the
 764          * rest of the operation.
 765          */
 766         resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
 767 
 768         do {
 769                 /*
 770                  * Set up a transaction to convert the range of extents
 771                  * from unwritten to real. Do allocations in a loop until
 772                  * we have covered the range passed in.
 773                  *
 774                  * Note that we can't risk to recursing back into the filesystem
 775                  * here as we might be asked to write out the same inode that we
 776                  * complete here and might deadlock on the iolock.
 777                  */
 778                 error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
 779                                 XFS_TRANS_RESERVE, &tp);
 780                 if (error)
 781                         return error;
 782 
 783                 xfs_ilock(ip, XFS_ILOCK_EXCL);
 784                 xfs_trans_ijoin(tp, ip, 0);
 785 
 786                 /*
 787                  * Modify the unwritten extent state of the buffer.
 788                  */
 789                 nimaps = 1;
 790                 error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,
 791                                         XFS_BMAPI_CONVERT, resblks, &imap,
 792                                         &nimaps);
 793                 if (error)
 794                         goto error_on_bmapi_transaction;
 795 
 796                 /*
 797                  * Log the updated inode size as we go.  We have to be careful
 798                  * to only log it up to the actual write offset if it is
 799                  * halfway into a block.
 800                  */
 801                 i_size = XFS_FSB_TO_B(mp, offset_fsb + count_fsb);
 802                 if (i_size > offset + count)
 803                         i_size = offset + count;
 804                 if (update_isize && i_size > i_size_read(inode))
 805                         i_size_write(inode, i_size);
 806                 i_size = xfs_new_eof(ip, i_size);
 807                 if (i_size) {
 808                         ip->i_d.di_size = i_size;
 809                         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 810                 }
 811 
 812                 error = xfs_trans_commit(tp);
 813                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 814                 if (error)
 815                         return error;
 816 
 817                 if (unlikely(!xfs_valid_startblock(ip, imap.br_startblock)))
 818                         return xfs_alert_fsblock_zero(ip, &imap);
 819 
 820                 if ((numblks_fsb = imap.br_blockcount) == 0) {
 821                         /*
 822                          * The numblks_fsb value should always get
 823                          * smaller, otherwise the loop is stuck.
 824                          */
 825                         ASSERT(imap.br_blockcount);
 826                         break;
 827                 }
 828                 offset_fsb += numblks_fsb;
 829                 count_fsb -= numblks_fsb;
 830         } while (count_fsb > 0);
 831 
 832         return 0;
 833 
 834 error_on_bmapi_transaction:
 835         xfs_trans_cancel(tp);
 836         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 837         return error;
 838 }
 839 
 840 static inline bool
 841 imap_needs_alloc(
 842         struct inode            *inode,
 843         struct xfs_bmbt_irec    *imap,
 844         int                     nimaps)
 845 {
 846         return !nimaps ||
 847                 imap->br_startblock == HOLESTARTBLOCK ||
 848                 imap->br_startblock == DELAYSTARTBLOCK ||
 849                 (IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN);
 850 }
 851 
 852 static inline bool
 853 needs_cow_for_zeroing(
 854         struct xfs_bmbt_irec    *imap,
 855         int                     nimaps)
 856 {
 857         return nimaps &&
 858                 imap->br_startblock != HOLESTARTBLOCK &&
 859                 imap->br_state != XFS_EXT_UNWRITTEN;
 860 }
 861 
 862 static int
 863 xfs_ilock_for_iomap(
 864         struct xfs_inode        *ip,
 865         unsigned                flags,
 866         unsigned                *lockmode)
 867 {
 868         unsigned                mode = XFS_ILOCK_SHARED;
 869         bool                    is_write = flags & (IOMAP_WRITE | IOMAP_ZERO);
 870 
 871         /*
 872          * COW writes may allocate delalloc space or convert unwritten COW
 873          * extents, so we need to make sure to take the lock exclusively here.
 874          */
 875         if (xfs_is_cow_inode(ip) && is_write) {
 876                 /*
 877                  * FIXME: It could still overwrite on unshared extents and not
 878                  * need allocation.
 879                  */
 880                 if (flags & IOMAP_NOWAIT)
 881                         return -EAGAIN;
 882                 mode = XFS_ILOCK_EXCL;
 883         }
 884 
 885         /*
 886          * Extents not yet cached requires exclusive access, don't block.  This
 887          * is an opencoded xfs_ilock_data_map_shared() call but with
 888          * non-blocking behaviour.
 889          */
 890         if (!(ip->i_df.if_flags & XFS_IFEXTENTS)) {
 891                 if (flags & IOMAP_NOWAIT)
 892                         return -EAGAIN;
 893                 mode = XFS_ILOCK_EXCL;
 894         }
 895 
 896 relock:
 897         if (flags & IOMAP_NOWAIT) {
 898                 if (!xfs_ilock_nowait(ip, mode))
 899                         return -EAGAIN;
 900         } else {
 901                 xfs_ilock(ip, mode);
 902         }
 903 
 904         /*
 905          * The reflink iflag could have changed since the earlier unlocked
 906          * check, so if we got ILOCK_SHARED for a write and but we're now a
 907          * reflink inode we have to switch to ILOCK_EXCL and relock.
 908          */
 909         if (mode == XFS_ILOCK_SHARED && is_write && xfs_is_cow_inode(ip)) {
 910                 xfs_iunlock(ip, mode);
 911                 mode = XFS_ILOCK_EXCL;
 912                 goto relock;
 913         }
 914 
 915         *lockmode = mode;
 916         return 0;
 917 }
 918 
 919 static int
 920 xfs_file_iomap_begin(
 921         struct inode            *inode,
 922         loff_t                  offset,
 923         loff_t                  length,
 924         unsigned                flags,
 925         struct iomap            *iomap)
 926 {
 927         struct xfs_inode        *ip = XFS_I(inode);
 928         struct xfs_mount        *mp = ip->i_mount;
 929         struct xfs_bmbt_irec    imap;
 930         xfs_fileoff_t           offset_fsb, end_fsb;
 931         int                     nimaps = 1, error = 0;
 932         bool                    shared = false;
 933         unsigned                lockmode;
 934 
 935         if (XFS_FORCED_SHUTDOWN(mp))
 936                 return -EIO;
 937 
 938         if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && !(flags & IOMAP_DIRECT) &&
 939                         !IS_DAX(inode) && !xfs_get_extsz_hint(ip)) {
 940                 /* Reserve delalloc blocks for regular writeback. */
 941                 return xfs_file_iomap_begin_delay(inode, offset, length, flags,
 942                                 iomap);
 943         }
 944 
 945         /*
 946          * Lock the inode in the manner required for the specified operation and
 947          * check for as many conditions that would result in blocking as
 948          * possible. This removes most of the non-blocking checks from the
 949          * mapping code below.
 950          */
 951         error = xfs_ilock_for_iomap(ip, flags, &lockmode);
 952         if (error)
 953                 return error;
 954 
 955         ASSERT(offset <= mp->m_super->s_maxbytes);
 956         if (offset > mp->m_super->s_maxbytes - length)
 957                 length = mp->m_super->s_maxbytes - offset;
 958         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 959         end_fsb = XFS_B_TO_FSB(mp, offset + length);
 960 
 961         error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
 962                                &nimaps, 0);
 963         if (error)
 964                 goto out_unlock;
 965 
 966         if (flags & IOMAP_REPORT) {
 967                 /* Trim the mapping to the nearest shared extent boundary. */
 968                 error = xfs_reflink_trim_around_shared(ip, &imap, &shared);
 969                 if (error)
 970                         goto out_unlock;
 971         }
 972 
 973         /* Non-modifying mapping requested, so we are done */
 974         if (!(flags & (IOMAP_WRITE | IOMAP_ZERO)))
 975                 goto out_found;
 976 
 977         /*
 978          * Break shared extents if necessary. Checks for non-blocking IO have
 979          * been done up front, so we don't need to do them here.
 980          */
 981         if (xfs_is_cow_inode(ip)) {
 982                 struct xfs_bmbt_irec    cmap;
 983                 bool                    directio = (flags & IOMAP_DIRECT);
 984 
 985                 /* if zeroing doesn't need COW allocation, then we are done. */
 986                 if ((flags & IOMAP_ZERO) &&
 987                     !needs_cow_for_zeroing(&imap, nimaps))
 988                         goto out_found;
 989 
 990                 /* may drop and re-acquire the ilock */
 991                 cmap = imap;
 992                 error = xfs_reflink_allocate_cow(ip, &cmap, &shared, &lockmode,
 993                                 directio);
 994                 if (error)
 995                         goto out_unlock;
 996 
 997                 /*
 998                  * For buffered writes we need to report the address of the
 999                  * previous block (if there was any) so that the higher level
1000                  * write code can perform read-modify-write operations; we
1001                  * won't need the CoW fork mapping until writeback.  For direct
1002                  * I/O, which must be block aligned, we need to report the
1003                  * newly allocated address.  If the data fork has a hole, copy
1004                  * the COW fork mapping to avoid allocating to the data fork.
1005                  */
1006                 if (directio || imap.br_startblock == HOLESTARTBLOCK)
1007                         imap = cmap;
1008 
1009                 end_fsb = imap.br_startoff + imap.br_blockcount;
1010                 length = XFS_FSB_TO_B(mp, end_fsb) - offset;
1011         }
1012 
1013         /* Don't need to allocate over holes when doing zeroing operations. */
1014         if (flags & IOMAP_ZERO)
1015                 goto out_found;
1016 
1017         if (!imap_needs_alloc(inode, &imap, nimaps))
1018                 goto out_found;
1019 
1020         /* If nowait is set bail since we are going to make allocations. */
1021         if (flags & IOMAP_NOWAIT) {
1022                 error = -EAGAIN;
1023                 goto out_unlock;
1024         }
1025 
1026         /*
1027          * We cap the maximum length we map to a sane size  to keep the chunks
1028          * of work done where somewhat symmetric with the work writeback does.
1029          * This is a completely arbitrary number pulled out of thin air as a
1030          * best guess for initial testing.
1031          *
1032          * Note that the values needs to be less than 32-bits wide until the
1033          * lower level functions are updated.
1034          */
1035         length = min_t(loff_t, length, 1024 * PAGE_SIZE);
1036 
1037         /*
1038          * xfs_iomap_write_direct() expects the shared lock. It is unlocked on
1039          * return.
1040          */
1041         if (lockmode == XFS_ILOCK_EXCL)
1042                 xfs_ilock_demote(ip, lockmode);
1043         error = xfs_iomap_write_direct(ip, offset, length, &imap,
1044                         nimaps);
1045         if (error)
1046                 return error;
1047 
1048         iomap->flags |= IOMAP_F_NEW;
1049         trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap);
1050 
1051 out_finish:
1052         return xfs_bmbt_to_iomap(ip, iomap, &imap, shared);
1053 
1054 out_found:
1055         ASSERT(nimaps);
1056         xfs_iunlock(ip, lockmode);
1057         trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap);
1058         goto out_finish;
1059 
1060 out_unlock:
1061         xfs_iunlock(ip, lockmode);
1062         return error;
1063 }
1064 
1065 static int
1066 xfs_file_iomap_end_delalloc(
1067         struct xfs_inode        *ip,
1068         loff_t                  offset,
1069         loff_t                  length,
1070         ssize_t                 written,
1071         struct iomap            *iomap)
1072 {
1073         struct xfs_mount        *mp = ip->i_mount;
1074         xfs_fileoff_t           start_fsb;
1075         xfs_fileoff_t           end_fsb;
1076         int                     error = 0;
1077 
1078         /*
1079          * Behave as if the write failed if drop writes is enabled. Set the NEW
1080          * flag to force delalloc cleanup.
1081          */
1082         if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_DROP_WRITES)) {
1083                 iomap->flags |= IOMAP_F_NEW;
1084                 written = 0;
1085         }
1086 
1087         /*
1088          * start_fsb refers to the first unused block after a short write. If
1089          * nothing was written, round offset down to point at the first block in
1090          * the range.
1091          */
1092         if (unlikely(!written))
1093                 start_fsb = XFS_B_TO_FSBT(mp, offset);
1094         else
1095                 start_fsb = XFS_B_TO_FSB(mp, offset + written);
1096         end_fsb = XFS_B_TO_FSB(mp, offset + length);
1097 
1098         /*
1099          * Trim delalloc blocks if they were allocated by this write and we
1100          * didn't manage to write the whole range.
1101          *
1102          * We don't need to care about racing delalloc as we hold i_mutex
1103          * across the reserve/allocate/unreserve calls. If there are delalloc
1104          * blocks in the range, they are ours.
1105          */
1106         if ((iomap->flags & IOMAP_F_NEW) && start_fsb < end_fsb) {
1107                 truncate_pagecache_range(VFS_I(ip), XFS_FSB_TO_B(mp, start_fsb),
1108                                          XFS_FSB_TO_B(mp, end_fsb) - 1);
1109 
1110                 error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
1111                                                end_fsb - start_fsb);
1112                 if (error && !XFS_FORCED_SHUTDOWN(mp)) {
1113                         xfs_alert(mp, "%s: unable to clean up ino %lld",
1114                                 __func__, ip->i_ino);
1115                         return error;
1116                 }
1117         }
1118 
1119         return 0;
1120 }
1121 
1122 static int
1123 xfs_file_iomap_end(
1124         struct inode            *inode,
1125         loff_t                  offset,
1126         loff_t                  length,
1127         ssize_t                 written,
1128         unsigned                flags,
1129         struct iomap            *iomap)
1130 {
1131         if ((flags & IOMAP_WRITE) && iomap->type == IOMAP_DELALLOC)
1132                 return xfs_file_iomap_end_delalloc(XFS_I(inode), offset,
1133                                 length, written, iomap);
1134         return 0;
1135 }
1136 
1137 const struct iomap_ops xfs_iomap_ops = {
1138         .iomap_begin            = xfs_file_iomap_begin,
1139         .iomap_end              = xfs_file_iomap_end,
1140 };
1141 
1142 static int
1143 xfs_seek_iomap_begin(
1144         struct inode            *inode,
1145         loff_t                  offset,
1146         loff_t                  length,
1147         unsigned                flags,
1148         struct iomap            *iomap)
1149 {
1150         struct xfs_inode        *ip = XFS_I(inode);
1151         struct xfs_mount        *mp = ip->i_mount;
1152         xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
1153         xfs_fileoff_t           end_fsb = XFS_B_TO_FSB(mp, offset + length);
1154         xfs_fileoff_t           cow_fsb = NULLFILEOFF, data_fsb = NULLFILEOFF;
1155         struct xfs_iext_cursor  icur;
1156         struct xfs_bmbt_irec    imap, cmap;
1157         int                     error = 0;
1158         unsigned                lockmode;
1159 
1160         if (XFS_FORCED_SHUTDOWN(mp))
1161                 return -EIO;
1162 
1163         lockmode = xfs_ilock_data_map_shared(ip);
1164         if (!(ip->i_df.if_flags & XFS_IFEXTENTS)) {
1165                 error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
1166                 if (error)
1167                         goto out_unlock;
1168         }
1169 
1170         if (xfs_iext_lookup_extent(ip, &ip->i_df, offset_fsb, &icur, &imap)) {
1171                 /*
1172                  * If we found a data extent we are done.
1173                  */
1174                 if (imap.br_startoff <= offset_fsb)
1175                         goto done;
1176                 data_fsb = imap.br_startoff;
1177         } else {
1178                 /*
1179                  * Fake a hole until the end of the file.
1180                  */
1181                 data_fsb = min(XFS_B_TO_FSB(mp, offset + length),
1182                                XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes));
1183         }
1184 
1185         /*
1186          * If a COW fork extent covers the hole, report it - capped to the next
1187          * data fork extent:
1188          */
1189         if (xfs_inode_has_cow_data(ip) &&
1190             xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &cmap))
1191                 cow_fsb = cmap.br_startoff;
1192         if (cow_fsb != NULLFILEOFF && cow_fsb <= offset_fsb) {
1193                 if (data_fsb < cow_fsb + cmap.br_blockcount)
1194                         end_fsb = min(end_fsb, data_fsb);
1195                 xfs_trim_extent(&cmap, offset_fsb, end_fsb);
1196                 error = xfs_bmbt_to_iomap(ip, iomap, &cmap, true);
1197                 /*
1198                  * This is a COW extent, so we must probe the page cache
1199                  * because there could be dirty page cache being backed
1200                  * by this extent.
1201                  */
1202                 iomap->type = IOMAP_UNWRITTEN;
1203                 goto out_unlock;
1204         }
1205 
1206         /*
1207          * Else report a hole, capped to the next found data or COW extent.
1208          */
1209         if (cow_fsb != NULLFILEOFF && cow_fsb < data_fsb)
1210                 imap.br_blockcount = cow_fsb - offset_fsb;
1211         else
1212                 imap.br_blockcount = data_fsb - offset_fsb;
1213         imap.br_startoff = offset_fsb;
1214         imap.br_startblock = HOLESTARTBLOCK;
1215         imap.br_state = XFS_EXT_NORM;
1216 done:
1217         xfs_trim_extent(&imap, offset_fsb, end_fsb);
1218         error = xfs_bmbt_to_iomap(ip, iomap, &imap, false);
1219 out_unlock:
1220         xfs_iunlock(ip, lockmode);
1221         return error;
1222 }
1223 
1224 const struct iomap_ops xfs_seek_iomap_ops = {
1225         .iomap_begin            = xfs_seek_iomap_begin,
1226 };
1227 
1228 static int
1229 xfs_xattr_iomap_begin(
1230         struct inode            *inode,
1231         loff_t                  offset,
1232         loff_t                  length,
1233         unsigned                flags,
1234         struct iomap            *iomap)
1235 {
1236         struct xfs_inode        *ip = XFS_I(inode);
1237         struct xfs_mount        *mp = ip->i_mount;
1238         xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
1239         xfs_fileoff_t           end_fsb = XFS_B_TO_FSB(mp, offset + length);
1240         struct xfs_bmbt_irec    imap;
1241         int                     nimaps = 1, error = 0;
1242         unsigned                lockmode;
1243 
1244         if (XFS_FORCED_SHUTDOWN(mp))
1245                 return -EIO;
1246 
1247         lockmode = xfs_ilock_attr_map_shared(ip);
1248 
1249         /* if there are no attribute fork or extents, return ENOENT */
1250         if (!XFS_IFORK_Q(ip) || !ip->i_d.di_anextents) {
1251                 error = -ENOENT;
1252                 goto out_unlock;
1253         }
1254 
1255         ASSERT(ip->i_d.di_aformat != XFS_DINODE_FMT_LOCAL);
1256         error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
1257                                &nimaps, XFS_BMAPI_ATTRFORK);
1258 out_unlock:
1259         xfs_iunlock(ip, lockmode);
1260 
1261         if (error)
1262                 return error;
1263         ASSERT(nimaps);
1264         return xfs_bmbt_to_iomap(ip, iomap, &imap, false);
1265 }
1266 
1267 const struct iomap_ops xfs_xattr_iomap_ops = {
1268         .iomap_begin            = xfs_xattr_iomap_begin,
1269 };