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