fs/xfs/xfs_iomap.c

   1 /*
   2  * Copyright (c) 2000-2006 Silicon Graphics, Inc.
   3  * All Rights Reserved.
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License as
   7  * published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it would be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write the Free Software Foundation,
  16  * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  17  */
  18 #include "xfs.h"
  19 #include "xfs_fs.h"
  20 #include "xfs_bit.h"
  21 #include "xfs_log.h"
  22 #include "xfs_inum.h"
  23 #include "xfs_trans.h"
  24 #include "xfs_sb.h"
  25 #include "xfs_ag.h"
  26 #include "xfs_alloc.h"
  27 #include "xfs_quota.h"
  28 #include "xfs_mount.h"
  29 #include "xfs_bmap_btree.h"
  30 #include "xfs_alloc_btree.h"
  31 #include "xfs_ialloc_btree.h"
  32 #include "xfs_dinode.h"
  33 #include "xfs_inode.h"
  34 #include "xfs_inode_item.h"
  35 #include "xfs_btree.h"
  36 #include "xfs_bmap.h"
  37 #include "xfs_rtalloc.h"
  38 #include "xfs_error.h"
  39 #include "xfs_itable.h"
  40 #include "xfs_rw.h"
  41 #include "xfs_attr.h"
  42 #include "xfs_buf_item.h"
  43 #include "xfs_trans_space.h"
  44 #include "xfs_utils.h"
  45 #include "xfs_iomap.h"
  46 #include "xfs_trace.h"
  47
  48
  49 #define XFS_WRITEIO_ALIGN(mp,off)       (((off) >> mp->m_writeio_log) \
  50                                                 << mp->m_writeio_log)
  51 #define XFS_WRITE_IMAPS         XFS_BMAP_MAX_NMAP
  52
  53 STATIC int
  54 xfs_iomap_eof_align_last_fsb(
  55         xfs_mount_t     *mp,
  56         xfs_inode_t     *ip,
  57         xfs_extlen_t    extsize,
  58         xfs_fileoff_t   *last_fsb)
  59 {
  60         xfs_fileoff_t   new_last_fsb = 0;
  61         xfs_extlen_t    align = 0;
  62         int             eof, error;
  63
  64         if (!XFS_IS_REALTIME_INODE(ip)) {
  65                 /*
  66                  * Round up the allocation request to a stripe unit
  67                  * (m_dalign) boundary if the file size is >= stripe unit
  68                  * size, and we are allocating past the allocation eof.
  69                  *
  70                  * If mounted with the "-o swalloc" option the alignment is
  71                  * increased from the strip unit size to the stripe width.
  72                  */
  73                 if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC))
  74                         align = mp->m_swidth;
  75                 else if (mp->m_dalign)
  76                         align = mp->m_dalign;
  77
  78                 if (align && XFS_ISIZE(ip) >= XFS_FSB_TO_B(mp, align))
  79                         new_last_fsb = roundup_64(*last_fsb, align);
  80         }
  81
  82         /*
  83          * Always round up the allocation request to an extent boundary
  84          * (when file on a real-time subvolume or has di_extsize hint).
  85          */
  86         if (extsize) {
  87                 if (new_last_fsb)
  88                         align = roundup_64(new_last_fsb, extsize);
  89                 else
  90                         align = extsize;
  91                 new_last_fsb = roundup_64(*last_fsb, align);
  92         }
  93
  94         if (new_last_fsb) {
  95                 error = xfs_bmap_eof(ip, new_last_fsb, XFS_DATA_FORK, &eof);
  96                 if (error)
  97                         return error;
  98                 if (eof)
  99                         *last_fsb = new_last_fsb;
 100         }
 101         return 0;
 102 }
 103
 104 STATIC int
 105 xfs_alert_fsblock_zero(
 106         xfs_inode_t     *ip,
 107         xfs_bmbt_irec_t *imap)
 108 {
 109         xfs_alert_tag(ip->i_mount, XFS_PTAG_FSBLOCK_ZERO,
 110                         "Access to block zero in inode %llu "
 111                         "start_block: %llx start_off: %llx "
 112                         "blkcnt: %llx extent-state: %x\n",
 113                 (unsigned long long)ip->i_ino,
 114                 (unsigned long long)imap->br_startblock,
 115                 (unsigned long long)imap->br_startoff,
 116                 (unsigned long long)imap->br_blockcount,
 117                 imap->br_state);
 118         return EFSCORRUPTED;
 119 }
 120
 121 int
 122 xfs_iomap_write_direct(
 123         xfs_inode_t     *ip,
 124         xfs_off_t       offset,
 125         size_t          count,
 126         xfs_bmbt_irec_t *imap,
 127         int             nmaps)
 128 {
 129         xfs_mount_t     *mp = ip->i_mount;
 130         xfs_fileoff_t   offset_fsb;
 131         xfs_fileoff_t   last_fsb;
 132         xfs_filblks_t   count_fsb, resaligned;
 133         xfs_fsblock_t   firstfsb;
 134         xfs_extlen_t    extsz, temp;
 135         int             nimaps;
 136         int             bmapi_flag;
 137         int             quota_flag;
 138         int             rt;
 139         xfs_trans_t     *tp;
 140         xfs_bmap_free_t free_list;
 141         uint            qblocks, resblks, resrtextents;
 142         int             committed;
 143         int             error;
 144
 145         /*
 146          * Make sure that the dquots are there. This doesn't hold
 147          * the ilock across a disk read.
 148          */
 149         error = xfs_qm_dqattach_locked(ip, 0);
 150         if (error)
 151                 return XFS_ERROR(error);
 152
 153         rt = XFS_IS_REALTIME_INODE(ip);
 154         extsz = xfs_get_extsz_hint(ip);
 155
 156         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 157         last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));
 158         if ((offset + count) > XFS_ISIZE(ip)) {
 159                 error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
 160                 if (error)
 161                         goto error_out;
 162         } else {
 163                 if (nmaps && (imap->br_startblock == HOLESTARTBLOCK))
 164                         last_fsb = MIN(last_fsb, (xfs_fileoff_t)
 165                                         imap->br_blockcount +
 166                                         imap->br_startoff);
 167         }
 168         count_fsb = last_fsb - offset_fsb;
 169         ASSERT(count_fsb > 0);
 170
 171         resaligned = count_fsb;
 172         if (unlikely(extsz)) {
 173                 if ((temp = do_mod(offset_fsb, extsz)))
 174                         resaligned += temp;
 175                 if ((temp = do_mod(resaligned, extsz)))
 176                         resaligned += extsz - temp;
 177         }
 178
 179         if (unlikely(rt)) {
 180                 resrtextents = qblocks = resaligned;
 181                 resrtextents /= mp->m_sb.sb_rextsize;
 182                 resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
 183                 quota_flag = XFS_QMOPT_RES_RTBLKS;
 184         } else {
 185                 resrtextents = 0;
 186                 resblks = qblocks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
 187                 quota_flag = XFS_QMOPT_RES_REGBLKS;
 188         }
 189
 190         /*
 191          * Allocate and setup the transaction
 192          */
 193         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 194         tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);
 195         error = xfs_trans_reserve(tp, resblks,
 196                         XFS_WRITE_LOG_RES(mp), resrtextents,
 197                         XFS_TRANS_PERM_LOG_RES,
 198                         XFS_WRITE_LOG_COUNT);
 199         /*
 200          * Check for running out of space, note: need lock to return
 201          */
 202         if (error)
 203                 xfs_trans_cancel(tp, 0);
 204         xfs_ilock(ip, XFS_ILOCK_EXCL);
 205         if (error)
 206                 goto error_out;
 207
 208         error = xfs_trans_reserve_quota_nblks(tp, ip, qblocks, 0, quota_flag);
 209         if (error)
 210                 goto error1;
 211
 212         xfs_trans_ijoin(tp, ip, 0);
 213
 214         bmapi_flag = 0;
 215         if (offset < XFS_ISIZE(ip) || extsz)
 216                 bmapi_flag |= XFS_BMAPI_PREALLOC;
 217
 218         /*
 219          * From this point onwards we overwrite the imap pointer that the
 220          * caller gave to us.
 221          */
 222         xfs_bmap_init(&free_list, &firstfsb);
 223         nimaps = 1;
 224         error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb, bmapi_flag,
 225                                 &firstfsb, 0, imap, &nimaps, &free_list);
 226         if (error)
 227                 goto error0;
 228
 229         /*
 230          * Complete the transaction
 231          */
 232         error = xfs_bmap_finish(&tp, &free_list, &committed);
 233         if (error)
 234                 goto error0;
 235         error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
 236         if (error)
 237                 goto error_out;
 238
 239         /*
 240          * Copy any maps to caller's array and return any error.
 241          */
 242         if (nimaps == 0) {
 243                 error = ENOSPC;
 244                 goto error_out;
 245         }
 246
 247         if (!(imap->br_startblock || XFS_IS_REALTIME_INODE(ip))) {
 248                 error = xfs_alert_fsblock_zero(ip, imap);
 249                 goto error_out;
 250         }
 251
 252         return 0;
 253
 254 error0: /* Cancel bmap, unlock inode, unreserve quota blocks, cancel trans */
 255         xfs_bmap_cancel(&free_list);
 256         xfs_trans_unreserve_quota_nblks(tp, ip, qblocks, 0, quota_flag);
 257
 258 error1: /* Just cancel transaction */
 259         xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT);
 260
 261 error_out:
 262         return XFS_ERROR(error);
 263 }
 264
 265 /*
 266  * If the caller is doing a write at the end of the file, then extend the
 267  * allocation out to the file system's write iosize.  We clean up any extra
 268  * space left over when the file is closed in xfs_inactive().
 269  *
 270  * If we find we already have delalloc preallocation beyond EOF, don't do more
 271  * preallocation as it it not needed.
 272  */
 273 STATIC int
 274 xfs_iomap_eof_want_preallocate(
 275         xfs_mount_t     *mp,
 276         xfs_inode_t     *ip,
 277         xfs_off_t       offset,
 278         size_t          count,
 279         xfs_bmbt_irec_t *imap,
 280         int             nimaps,
 281         int             *prealloc)
 282 {
 283         xfs_fileoff_t   start_fsb;
 284         xfs_filblks_t   count_fsb;
 285         xfs_fsblock_t   firstblock;
 286         int             n, error, imaps;
 287         int             found_delalloc = 0;
 288
 289         *prealloc = 0;
 290         if (offset + count <= XFS_ISIZE(ip))
 291                 return 0;
 292
 293         /*
 294          * If there are any real blocks past eof, then don't
 295          * do any speculative allocation.
 296          */
 297         start_fsb = XFS_B_TO_FSBT(mp, ((xfs_ufsize_t)(offset + count - 1)));
 298         count_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_MAXIOFFSET(mp));
 299         while (count_fsb > 0) {
 300                 imaps = nimaps;
 301                 firstblock = NULLFSBLOCK;
 302                 error = xfs_bmapi_read(ip, start_fsb, count_fsb, imap, &imaps,
 303                                        0);
 304                 if (error)
 305                         return error;
 306                 for (n = 0; n < imaps; n++) {
 307                         if ((imap[n].br_startblock != HOLESTARTBLOCK) &&
 308                             (imap[n].br_startblock != DELAYSTARTBLOCK))
 309                                 return 0;
 310                         start_fsb += imap[n].br_blockcount;
 311                         count_fsb -= imap[n].br_blockcount;
 312
 313                         if (imap[n].br_startblock == DELAYSTARTBLOCK)
 314                                 found_delalloc = 1;
 315                 }
 316         }
 317         if (!found_delalloc)
 318                 *prealloc = 1;
 319         return 0;
 320 }
 321
 322 /*
 323  * If we don't have a user specified preallocation size, dynamically increase
 324  * the preallocation size as the size of the file grows. Cap the maximum size
 325  * at a single extent or less if the filesystem is near full. The closer the
 326  * filesystem is to full, the smaller the maximum prealocation.
 327  */
 328 STATIC xfs_fsblock_t
 329 xfs_iomap_prealloc_size(
 330         struct xfs_mount        *mp,
 331         struct xfs_inode        *ip)
 332 {
 333         xfs_fsblock_t           alloc_blocks = 0;
 334
 335         if (!(mp->m_flags & XFS_MOUNT_DFLT_IOSIZE)) {
 336                 int shift = 0;
 337                 int64_t freesp;
 338
 339                 /*
 340                  * rounddown_pow_of_two() returns an undefined result
 341                  * if we pass in alloc_blocks = 0. Hence the "+ 1" to
 342                  * ensure we always pass in a non-zero value.
 343                  */
 344                 alloc_blocks = XFS_B_TO_FSB(mp, XFS_ISIZE(ip)) + 1;
 345                 alloc_blocks = XFS_FILEOFF_MIN(MAXEXTLEN,
 346                                         rounddown_pow_of_two(alloc_blocks));
 347
 348                 xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
 349                 freesp = mp->m_sb.sb_fdblocks;
 350                 if (freesp < mp->m_low_space[XFS_LOWSP_5_PCNT]) {
 351                         shift = 2;
 352                         if (freesp < mp->m_low_space[XFS_LOWSP_4_PCNT])
 353                                 shift++;
 354                         if (freesp < mp->m_low_space[XFS_LOWSP_3_PCNT])
 355                                 shift++;
 356                         if (freesp < mp->m_low_space[XFS_LOWSP_2_PCNT])
 357                                 shift++;
 358                         if (freesp < mp->m_low_space[XFS_LOWSP_1_PCNT])
 359                                 shift++;
 360                 }
 361                 if (shift)
 362                         alloc_blocks >>= shift;
 363         }
 364
 365         if (alloc_blocks < mp->m_writeio_blocks)
 366                 alloc_blocks = mp->m_writeio_blocks;
 367
 368         return alloc_blocks;
 369 }
 370
 371 int
 372 xfs_iomap_write_delay(
 373         xfs_inode_t     *ip,
 374         xfs_off_t       offset,
 375         size_t          count,
 376         xfs_bmbt_irec_t *ret_imap)
 377 {
 378         xfs_mount_t     *mp = ip->i_mount;
 379         xfs_fileoff_t   offset_fsb;
 380         xfs_fileoff_t   last_fsb;
 381         xfs_off_t       aligned_offset;
 382         xfs_fileoff_t   ioalign;
 383         xfs_extlen_t    extsz;
 384         int             nimaps;
 385         xfs_bmbt_irec_t imap[XFS_WRITE_IMAPS];
 386         int             prealloc, flushed = 0;
 387         int             error;
 388
 389         ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
 390
 391         /*
 392          * Make sure that the dquots are there. This doesn't hold
 393          * the ilock across a disk read.
 394          */
 395         error = xfs_qm_dqattach_locked(ip, 0);
 396         if (error)
 397                 return XFS_ERROR(error);
 398
 399         extsz = xfs_get_extsz_hint(ip);
 400         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 401
 402
 403         error = xfs_iomap_eof_want_preallocate(mp, ip, offset, count,
 404                                 imap, XFS_WRITE_IMAPS, &prealloc);
 405         if (error)
 406                 return error;
 407
 408 retry:
 409         if (prealloc) {
 410                 xfs_fsblock_t   alloc_blocks = xfs_iomap_prealloc_size(mp, ip);
 411
 412                 aligned_offset = XFS_WRITEIO_ALIGN(mp, (offset + count - 1));
 413                 ioalign = XFS_B_TO_FSBT(mp, aligned_offset);
 414                 last_fsb = ioalign + alloc_blocks;
 415         } else {
 416                 last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));
 417         }
 418
 419         if (prealloc || extsz) {
 420                 error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
 421                 if (error)
 422                         return error;
 423         }
 424
 425         nimaps = XFS_WRITE_IMAPS;
 426         error = xfs_bmapi_delay(ip, offset_fsb, last_fsb - offset_fsb,
 427                                 imap, &nimaps, XFS_BMAPI_ENTIRE);
 428         switch (error) {
 429         case 0:
 430         case ENOSPC:
 431         case EDQUOT:
 432                 break;
 433         default:
 434                 return XFS_ERROR(error);
 435         }
 436
 437         /*
 438          * If bmapi returned us nothing, we got either ENOSPC or EDQUOT.  For
 439          * ENOSPC, * flush all other inodes with delalloc blocks to free up
 440          * some of the excess reserved metadata space. For both cases, retry
 441          * without EOF preallocation.
 442          */
 443         if (nimaps == 0) {
 444                 trace_xfs_delalloc_enospc(ip, offset, count);
 445                 if (flushed)
 446                         return XFS_ERROR(error ? error : ENOSPC);
 447
 448                 if (error == ENOSPC) {
 449                         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 450                         xfs_flush_inodes(ip);
 451                         xfs_ilock(ip, XFS_ILOCK_EXCL);
 452                 }
 453
 454                 flushed = 1;
 455                 error = 0;
 456                 prealloc = 0;
 457                 goto retry;
 458         }
 459
 460         if (!(imap[0].br_startblock || XFS_IS_REALTIME_INODE(ip)))
 461                 return xfs_alert_fsblock_zero(ip, &imap[0]);
 462
 463         *ret_imap = imap[0];
 464         return 0;
 465 }
 466
 467 /*
 468  * Pass in a delayed allocate extent, convert it to real extents;
 469  * return to the caller the extent we create which maps on top of
 470  * the originating callers request.
 471  *
 472  * Called without a lock on the inode.
 473  *
 474  * We no longer bother to look at the incoming map - all we have to
 475  * guarantee is that whatever we allocate fills the required range.
 476  */
 477 int
 478 xfs_iomap_write_allocate(
 479         xfs_inode_t     *ip,
 480         xfs_off_t       offset,
 481         size_t          count,
 482         xfs_bmbt_irec_t *imap)
 483 {
 484         xfs_mount_t     *mp = ip->i_mount;
 485         xfs_fileoff_t   offset_fsb, last_block;
 486         xfs_fileoff_t   end_fsb, map_start_fsb;
 487         xfs_fsblock_t   first_block;
 488         xfs_bmap_free_t free_list;
 489         xfs_filblks_t   count_fsb;
 490         xfs_trans_t     *tp;
 491         int             nimaps, committed;
 492         int             error = 0;
 493         int             nres;
 494
 495         /*
 496          * Make sure that the dquots are there.
 497          */
 498         error = xfs_qm_dqattach(ip, 0);
 499         if (error)
 500                 return XFS_ERROR(error);
 501
 502         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 503         count_fsb = imap->br_blockcount;
 504         map_start_fsb = imap->br_startoff;
 505
 506         XFS_STATS_ADD(xs_xstrat_bytes, XFS_FSB_TO_B(mp, count_fsb));
 507
 508         while (count_fsb != 0) {
 509                 /*
 510                  * Set up a transaction with which to allocate the
 511                  * backing store for the file.  Do allocations in a
 512                  * loop until we get some space in the range we are
 513                  * interested in.  The other space that might be allocated
 514                  * is in the delayed allocation extent on which we sit
 515                  * but before our buffer starts.
 516                  */
 517
 518                 nimaps = 0;
 519                 while (nimaps == 0) {
 520                         tp = xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE);
 521                         tp->t_flags |= XFS_TRANS_RESERVE;
 522                         nres = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
 523                         error = xfs_trans_reserve(tp, nres,
 524                                         XFS_WRITE_LOG_RES(mp),
 525                                         0, XFS_TRANS_PERM_LOG_RES,
 526                                         XFS_WRITE_LOG_COUNT);
 527                         if (error) {
 528                                 xfs_trans_cancel(tp, 0);
 529                                 return XFS_ERROR(error);
 530                         }
 531                         xfs_ilock(ip, XFS_ILOCK_EXCL);
 532                         xfs_trans_ijoin(tp, ip, 0);
 533
 534                         xfs_bmap_init(&free_list, &first_block);
 535
 536                         /*
 537                          * it is possible that the extents have changed since
 538                          * we did the read call as we dropped the ilock for a
 539                          * while. We have to be careful about truncates or hole
 540                          * punchs here - we are not allowed to allocate
 541                          * non-delalloc blocks here.
 542                          *
 543                          * The only protection against truncation is the pages
 544                          * for the range we are being asked to convert are
 545                          * locked and hence a truncate will block on them
 546                          * first.
 547                          *
 548                          * As a result, if we go beyond the range we really
 549                          * need and hit an delalloc extent boundary followed by
 550                          * a hole while we have excess blocks in the map, we
 551                          * will fill the hole incorrectly and overrun the
 552                          * transaction reservation.
 553                          *
 554                          * Using a single map prevents this as we are forced to
 555                          * check each map we look for overlap with the desired
 556                          * range and abort as soon as we find it. Also, given
 557                          * that we only return a single map, having one beyond
 558                          * what we can return is probably a bit silly.
 559                          *
 560                          * We also need to check that we don't go beyond EOF;
 561                          * this is a truncate optimisation as a truncate sets
 562                          * the new file size before block on the pages we
 563                          * currently have locked under writeback. Because they
 564                          * are about to be tossed, we don't need to write them
 565                          * back....
 566                          */
 567                         nimaps = 1;
 568                         end_fsb = XFS_B_TO_FSB(mp, XFS_ISIZE(ip));
 569                         error = xfs_bmap_last_offset(NULL, ip, &last_block,
 570                                                         XFS_DATA_FORK);
 571                         if (error)
 572                                 goto trans_cancel;
 573
 574                         last_block = XFS_FILEOFF_MAX(last_block, end_fsb);
 575                         if ((map_start_fsb + count_fsb) > last_block) {
 576                                 count_fsb = last_block - map_start_fsb;
 577                                 if (count_fsb == 0) {
 578                                         error = EAGAIN;
 579                                         goto trans_cancel;
 580                                 }
 581                         }
 582
 583                         /*
 584                          * From this point onwards we overwrite the imap
 585                          * pointer that the caller gave to us.
 586                          */
 587                         error = xfs_bmapi_write(tp, ip, map_start_fsb,
 588                                                 count_fsb, 0, &first_block, 1,
 589                                                 imap, &nimaps, &free_list);
 590                         if (error)
 591                                 goto trans_cancel;
 592
 593                         error = xfs_bmap_finish(&tp, &free_list, &committed);
 594                         if (error)
 595                                 goto trans_cancel;
 596
 597                         error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
 598                         if (error)
 599                                 goto error0;
 600
 601                         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 602                 }
 603
 604                 /*
 605                  * See if we were able to allocate an extent that
 606                  * covers at least part of the callers request
 607                  */
 608                 if (!(imap->br_startblock || XFS_IS_REALTIME_INODE(ip)))
 609                         return xfs_alert_fsblock_zero(ip, imap);
 610
 611                 if ((offset_fsb >= imap->br_startoff) &&
 612                     (offset_fsb < (imap->br_startoff +
 613                                    imap->br_blockcount))) {
 614                         XFS_STATS_INC(xs_xstrat_quick);
 615                         return 0;
 616                 }
 617
 618                 /*
 619                  * So far we have not mapped the requested part of the
 620                  * file, just surrounding data, try again.
 621                  */
 622                 count_fsb -= imap->br_blockcount;
 623                 map_start_fsb = imap->br_startoff + imap->br_blockcount;
 624         }
 625
 626 trans_cancel:
 627         xfs_bmap_cancel(&free_list);
 628         xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT);
 629 error0:
 630         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 631         return XFS_ERROR(error);
 632 }
 633
 634 int
 635 xfs_iomap_write_unwritten(
 636         xfs_inode_t     *ip,
 637         xfs_off_t       offset,
 638         size_t          count)
 639 {
 640         xfs_mount_t     *mp = ip->i_mount;
 641         xfs_fileoff_t   offset_fsb;
 642         xfs_filblks_t   count_fsb;
 643         xfs_filblks_t   numblks_fsb;
 644         xfs_fsblock_t   firstfsb;
 645         int             nimaps;
 646         xfs_trans_t     *tp;
 647         xfs_bmbt_irec_t imap;
 648         xfs_bmap_free_t free_list;
 649         xfs_fsize_t     i_size;
 650         uint            resblks;
 651         int             committed;
 652         int             error;
 653
 654         trace_xfs_unwritten_convert(ip, offset, count);
 655
 656         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 657         count_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
 658         count_fsb = (xfs_filblks_t)(count_fsb - offset_fsb);
 659
 660         /*
 661          * Reserve enough blocks in this transaction for two complete extent
 662          * btree splits.  We may be converting the middle part of an unwritten
 663          * extent and in this case we will insert two new extents in the btree
 664          * each of which could cause a full split.
 665          *
 666          * This reservation amount will be used in the first call to
 667          * xfs_bmbt_split() to select an AG with enough space to satisfy the
 668          * rest of the operation.
 669          */
 670         resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
 671
 672         do {
 673                 /*
 674                  * set up a transaction to convert the range of extents
 675                  * from unwritten to real. Do allocations in a loop until
 676                  * we have covered the range passed in.
 677                  *
 678                  * Note that we open code the transaction allocation here
 679                  * to pass KM_NOFS--we can't risk to recursing back into
 680                  * the filesystem here as we might be asked to write out
 681                  * the same inode that we complete here and might deadlock
 682                  * on the iolock.
 683                  */
 684                 xfs_wait_for_freeze(mp, SB_FREEZE_TRANS);
 685                 tp = _xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE, KM_NOFS);
 686                 tp->t_flags |= XFS_TRANS_RESERVE;
 687                 error = xfs_trans_reserve(tp, resblks,
 688                                 XFS_WRITE_LOG_RES(mp), 0,
 689                                 XFS_TRANS_PERM_LOG_RES,
 690                                 XFS_WRITE_LOG_COUNT);
 691                 if (error) {
 692                         xfs_trans_cancel(tp, 0);
 693                         return XFS_ERROR(error);
 694                 }
 695
 696                 xfs_ilock(ip, XFS_ILOCK_EXCL);
 697                 xfs_trans_ijoin(tp, ip, 0);
 698
 699                 /*
 700                  * Modify the unwritten extent state of the buffer.
 701                  */
 702                 xfs_bmap_init(&free_list, &firstfsb);
 703                 nimaps = 1;
 704                 error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,
 705                                   XFS_BMAPI_CONVERT, &firstfsb,
 706                                   1, &imap, &nimaps, &free_list);
 707                 if (error)
 708                         goto error_on_bmapi_transaction;
 709
 710                 /*
 711                  * Log the updated inode size as we go.  We have to be careful
 712                  * to only log it up to the actual write offset if it is
 713                  * halfway into a block.
 714                  */
 715                 i_size = XFS_FSB_TO_B(mp, offset_fsb + count_fsb);
 716                 if (i_size > offset + count)
 717                         i_size = offset + count;
 718
 719                 i_size = xfs_new_eof(ip, i_size);
 720                 if (i_size) {
 721                         ip->i_d.di_size = i_size;
 722                         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 723                 }
 724
 725                 error = xfs_bmap_finish(&tp, &free_list, &committed);
 726                 if (error)
 727                         goto error_on_bmapi_transaction;
 728
 729                 error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
 730                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 731                 if (error)
 732                         return XFS_ERROR(error);
 733
 734                 if (!(imap.br_startblock || XFS_IS_REALTIME_INODE(ip)))
 735                         return xfs_alert_fsblock_zero(ip, &imap);
 736
 737                 if ((numblks_fsb = imap.br_blockcount) == 0) {
 738                         /*
 739                          * The numblks_fsb value should always get
 740                          * smaller, otherwise the loop is stuck.
 741                          */
 742                         ASSERT(imap.br_blockcount);
 743                         break;
 744                 }
 745                 offset_fsb += numblks_fsb;
 746                 count_fsb -= numblks_fsb;
 747         } while (count_fsb > 0);
 748
 749         return 0;
 750
 751 error_on_bmapi_transaction:
 752         xfs_bmap_cancel(&free_list);
 753         xfs_trans_cancel(tp, (XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT));
 754         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 755         return XFS_ERROR(error);
 756 }