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_dir2.h"
  27 #include "xfs_alloc.h"
  28 #include "xfs_dmapi.h"
  29 #include "xfs_quota.h"
  30 #include "xfs_mount.h"
  31 #include "xfs_bmap_btree.h"
  32 #include "xfs_alloc_btree.h"
  33 #include "xfs_ialloc_btree.h"
  34 #include "xfs_dir2_sf.h"
  35 #include "xfs_attr_sf.h"
  36 #include "xfs_dinode.h"
  37 #include "xfs_inode.h"
  38 #include "xfs_ialloc.h"
  39 #include "xfs_btree.h"
  40 #include "xfs_bmap.h"
  41 #include "xfs_rtalloc.h"
  42 #include "xfs_error.h"
  43 #include "xfs_itable.h"
  44 #include "xfs_rw.h"
  45 #include "xfs_attr.h"
  46 #include "xfs_buf_item.h"
  47 #include "xfs_trans_space.h"
  48 #include "xfs_utils.h"
  49 #include "xfs_iomap.h"
  50 #include "xfs_trace.h"
  51
  52
  53 #define XFS_WRITEIO_ALIGN(mp,off)       (((off) >> mp->m_writeio_log) \
  54                                                 << mp->m_writeio_log)
  55 #define XFS_STRAT_WRITE_IMAPS   2
  56 #define XFS_WRITE_IMAPS         XFS_BMAP_MAX_NMAP
  57
  58 STATIC int xfs_iomap_write_direct(struct xfs_inode *, xfs_off_t, size_t,
  59                                   int, struct xfs_bmbt_irec *, int *);
  60 STATIC int xfs_iomap_write_delay(struct xfs_inode *, xfs_off_t, size_t, int,
  61                                  struct xfs_bmbt_irec *, int *);
  62 STATIC int xfs_iomap_write_allocate(struct xfs_inode *, xfs_off_t, size_t,
  63                                 struct xfs_bmbt_irec *, int *);
  64
  65 int
  66 xfs_iomap(
  67         struct xfs_inode        *ip,
  68         xfs_off_t               offset,
  69         ssize_t                 count,
  70         int                     flags,
  71         struct xfs_bmbt_irec    *imap,
  72         int                     *nimaps,
  73         int                     *new)
  74 {
  75         struct xfs_mount        *mp = ip->i_mount;
  76         xfs_fileoff_t           offset_fsb, end_fsb;
  77         int                     error = 0;
  78         int                     lockmode = 0;
  79         int                     bmapi_flags = 0;
  80
  81         ASSERT((ip->i_d.di_mode & S_IFMT) == S_IFREG);
  82
  83         *new = 0;
  84
  85         if (XFS_FORCED_SHUTDOWN(mp))
  86                 return XFS_ERROR(EIO);
  87
  88         trace_xfs_iomap_enter(ip, offset, count, flags, NULL);
  89
  90         switch (flags & (BMAPI_READ | BMAPI_WRITE | BMAPI_ALLOCATE)) {
  91         case BMAPI_READ:
  92                 lockmode = xfs_ilock_map_shared(ip);
  93                 bmapi_flags = XFS_BMAPI_ENTIRE;
  94                 break;
  95         case BMAPI_WRITE:
  96                 lockmode = XFS_ILOCK_EXCL;
  97                 if (flags & BMAPI_IGNSTATE)
  98                         bmapi_flags |= XFS_BMAPI_IGSTATE|XFS_BMAPI_ENTIRE;
  99                 xfs_ilock(ip, lockmode);
 100                 break;
 101         case BMAPI_ALLOCATE:
 102                 lockmode = XFS_ILOCK_SHARED;
 103                 bmapi_flags = XFS_BMAPI_ENTIRE;
 104
 105                 /* Attempt non-blocking lock */
 106                 if (flags & BMAPI_TRYLOCK) {
 107                         if (!xfs_ilock_nowait(ip, lockmode))
 108                                 return XFS_ERROR(EAGAIN);
 109                 } else {
 110                         xfs_ilock(ip, lockmode);
 111                 }
 112                 break;
 113         default:
 114                 BUG();
 115         }
 116
 117         ASSERT(offset <= mp->m_maxioffset);
 118         if ((xfs_fsize_t)offset + count > mp->m_maxioffset)
 119                 count = mp->m_maxioffset - offset;
 120         end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
 121         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 122
 123         error = xfs_bmapi(NULL, ip, offset_fsb,
 124                         (xfs_filblks_t)(end_fsb - offset_fsb),
 125                         bmapi_flags,  NULL, 0, imap,
 126                         nimaps, NULL, NULL);
 127
 128         if (error)
 129                 goto out;
 130
 131         switch (flags & (BMAPI_WRITE|BMAPI_ALLOCATE)) {
 132         case BMAPI_WRITE:
 133                 /* If we found an extent, return it */
 134                 if (*nimaps &&
 135                     (imap->br_startblock != HOLESTARTBLOCK) &&
 136                     (imap->br_startblock != DELAYSTARTBLOCK)) {
 137                         trace_xfs_iomap_found(ip, offset, count, flags, imap);
 138                         break;
 139                 }
 140
 141                 if (flags & (BMAPI_DIRECT|BMAPI_MMAP)) {
 142                         error = xfs_iomap_write_direct(ip, offset, count, flags,
 143                                                        imap, nimaps);
 144                 } else {
 145                         error = xfs_iomap_write_delay(ip, offset, count, flags,
 146                                                       imap, nimaps);
 147                 }
 148                 if (!error) {
 149                         trace_xfs_iomap_alloc(ip, offset, count, flags, imap);
 150                 }
 151                 *new = 1;
 152                 break;
 153         case BMAPI_ALLOCATE:
 154                 /* If we found an extent, return it */
 155                 xfs_iunlock(ip, lockmode);
 156                 lockmode = 0;
 157
 158                 if (*nimaps && !isnullstartblock(imap->br_startblock)) {
 159                         trace_xfs_iomap_found(ip, offset, count, flags, imap);
 160                         break;
 161                 }
 162
 163                 error = xfs_iomap_write_allocate(ip, offset, count,
 164                                                  imap, nimaps);
 165                 break;
 166         }
 167
 168         ASSERT(*nimaps <= 1);
 169
 170 out:
 171         if (lockmode)
 172                 xfs_iunlock(ip, lockmode);
 173         return XFS_ERROR(error);
 174 }
 175
 176 STATIC int
 177 xfs_iomap_eof_align_last_fsb(
 178         xfs_mount_t     *mp,
 179         xfs_inode_t     *ip,
 180         xfs_extlen_t    extsize,
 181         xfs_fileoff_t   *last_fsb)
 182 {
 183         xfs_fileoff_t   new_last_fsb = 0;
 184         xfs_extlen_t    align;
 185         int             eof, error;
 186
 187         if (XFS_IS_REALTIME_INODE(ip))
 188                 ;
 189         /*
 190          * If mounted with the "-o swalloc" option, roundup the allocation
 191          * request to a stripe width boundary if the file size is >=
 192          * stripe width and we are allocating past the allocation eof.
 193          */
 194         else if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC) &&
 195                 (ip->i_size >= XFS_FSB_TO_B(mp, mp->m_swidth)))
 196                 new_last_fsb = roundup_64(*last_fsb, mp->m_swidth);
 197         /*
 198          * Roundup the allocation request to a stripe unit (m_dalign) boundary
 199          * if the file size is >= stripe unit size, and we are allocating past
 200          * the allocation eof.
 201          */
 202         else if (mp->m_dalign && (ip->i_size >= XFS_FSB_TO_B(mp, mp->m_dalign)))
 203                 new_last_fsb = roundup_64(*last_fsb, mp->m_dalign);
 204
 205         /*
 206          * Always round up the allocation request to an extent boundary
 207          * (when file on a real-time subvolume or has di_extsize hint).
 208          */
 209         if (extsize) {
 210                 if (new_last_fsb)
 211                         align = roundup_64(new_last_fsb, extsize);
 212                 else
 213                         align = extsize;
 214                 new_last_fsb = roundup_64(*last_fsb, align);
 215         }
 216
 217         if (new_last_fsb) {
 218                 error = xfs_bmap_eof(ip, new_last_fsb, XFS_DATA_FORK, &eof);
 219                 if (error)
 220                         return error;
 221                 if (eof)
 222                         *last_fsb = new_last_fsb;
 223         }
 224         return 0;
 225 }
 226
 227 STATIC int
 228 xfs_cmn_err_fsblock_zero(
 229         xfs_inode_t     *ip,
 230         xfs_bmbt_irec_t *imap)
 231 {
 232         xfs_cmn_err(XFS_PTAG_FSBLOCK_ZERO, CE_ALERT, ip->i_mount,
 233                         "Access to block zero in inode %llu "
 234                         "start_block: %llx start_off: %llx "
 235                         "blkcnt: %llx extent-state: %x\n",
 236                 (unsigned long long)ip->i_ino,
 237                 (unsigned long long)imap->br_startblock,
 238                 (unsigned long long)imap->br_startoff,
 239                 (unsigned long long)imap->br_blockcount,
 240                 imap->br_state);
 241         return EFSCORRUPTED;
 242 }
 243
 244 STATIC int
 245 xfs_iomap_write_direct(
 246         xfs_inode_t     *ip,
 247         xfs_off_t       offset,
 248         size_t          count,
 249         int             flags,
 250         xfs_bmbt_irec_t *ret_imap,
 251         int             *nmaps)
 252 {
 253         xfs_mount_t     *mp = ip->i_mount;
 254         xfs_fileoff_t   offset_fsb;
 255         xfs_fileoff_t   last_fsb;
 256         xfs_filblks_t   count_fsb, resaligned;
 257         xfs_fsblock_t   firstfsb;
 258         xfs_extlen_t    extsz, temp;
 259         int             nimaps;
 260         int             bmapi_flag;
 261         int             quota_flag;
 262         int             rt;
 263         xfs_trans_t     *tp;
 264         xfs_bmbt_irec_t imap;
 265         xfs_bmap_free_t free_list;
 266         uint            qblocks, resblks, resrtextents;
 267         int             committed;
 268         int             error;
 269
 270         /*
 271          * Make sure that the dquots are there. This doesn't hold
 272          * the ilock across a disk read.
 273          */
 274         error = xfs_qm_dqattach_locked(ip, 0);
 275         if (error)
 276                 return XFS_ERROR(error);
 277
 278         rt = XFS_IS_REALTIME_INODE(ip);
 279         extsz = xfs_get_extsz_hint(ip);
 280
 281         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 282         last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));
 283         if ((offset + count) > ip->i_size) {
 284                 error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
 285                 if (error)
 286                         goto error_out;
 287         } else {
 288                 if (*nmaps && (ret_imap->br_startblock == HOLESTARTBLOCK))
 289                         last_fsb = MIN(last_fsb, (xfs_fileoff_t)
 290                                         ret_imap->br_blockcount +
 291                                         ret_imap->br_startoff);
 292         }
 293         count_fsb = last_fsb - offset_fsb;
 294         ASSERT(count_fsb > 0);
 295
 296         resaligned = count_fsb;
 297         if (unlikely(extsz)) {
 298                 if ((temp = do_mod(offset_fsb, extsz)))
 299                         resaligned += temp;
 300                 if ((temp = do_mod(resaligned, extsz)))
 301                         resaligned += extsz - temp;
 302         }
 303
 304         if (unlikely(rt)) {
 305                 resrtextents = qblocks = resaligned;
 306                 resrtextents /= mp->m_sb.sb_rextsize;
 307                 resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
 308                 quota_flag = XFS_QMOPT_RES_RTBLKS;
 309         } else {
 310                 resrtextents = 0;
 311                 resblks = qblocks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
 312                 quota_flag = XFS_QMOPT_RES_REGBLKS;
 313         }
 314
 315         /*
 316          * Allocate and setup the transaction
 317          */
 318         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 319         tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);
 320         error = xfs_trans_reserve(tp, resblks,
 321                         XFS_WRITE_LOG_RES(mp), resrtextents,
 322                         XFS_TRANS_PERM_LOG_RES,
 323                         XFS_WRITE_LOG_COUNT);
 324         /*
 325          * Check for running out of space, note: need lock to return
 326          */
 327         if (error)
 328                 xfs_trans_cancel(tp, 0);
 329         xfs_ilock(ip, XFS_ILOCK_EXCL);
 330         if (error)
 331                 goto error_out;
 332
 333         error = xfs_trans_reserve_quota_nblks(tp, ip, qblocks, 0, quota_flag);
 334         if (error)
 335                 goto error1;
 336
 337         xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
 338         xfs_trans_ihold(tp, ip);
 339
 340         bmapi_flag = XFS_BMAPI_WRITE;
 341         if ((flags & BMAPI_DIRECT) && (offset < ip->i_size || extsz))
 342                 bmapi_flag |= XFS_BMAPI_PREALLOC;
 343
 344         /*
 345          * Issue the xfs_bmapi() call to allocate the blocks
 346          */
 347         xfs_bmap_init(&free_list, &firstfsb);
 348         nimaps = 1;
 349         error = xfs_bmapi(tp, ip, offset_fsb, count_fsb, bmapi_flag,
 350                 &firstfsb, 0, &imap, &nimaps, &free_list, NULL);
 351         if (error)
 352                 goto error0;
 353
 354         /*
 355          * Complete the transaction
 356          */
 357         error = xfs_bmap_finish(&tp, &free_list, &committed);
 358         if (error)
 359                 goto error0;
 360         error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
 361         if (error)
 362                 goto error_out;
 363
 364         /*
 365          * Copy any maps to caller's array and return any error.
 366          */
 367         if (nimaps == 0) {
 368                 error = ENOSPC;
 369                 goto error_out;
 370         }
 371
 372         if (!(imap.br_startblock || XFS_IS_REALTIME_INODE(ip))) {
 373                 error = xfs_cmn_err_fsblock_zero(ip, &imap);
 374                 goto error_out;
 375         }
 376
 377         *ret_imap = imap;
 378         *nmaps = 1;
 379         return 0;
 380
 381 error0: /* Cancel bmap, unlock inode, unreserve quota blocks, cancel trans */
 382         xfs_bmap_cancel(&free_list);
 383         xfs_trans_unreserve_quota_nblks(tp, ip, qblocks, 0, quota_flag);
 384
 385 error1: /* Just cancel transaction */
 386         xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT);
 387         *nmaps = 0;     /* nothing set-up here */
 388
 389 error_out:
 390         return XFS_ERROR(error);
 391 }
 392
 393 /*
 394  * If the caller is doing a write at the end of the file, then extend the
 395  * allocation out to the file system's write iosize.  We clean up any extra
 396  * space left over when the file is closed in xfs_inactive().
 397  */
 398 STATIC int
 399 xfs_iomap_eof_want_preallocate(
 400         xfs_mount_t     *mp,
 401         xfs_inode_t     *ip,
 402         xfs_off_t       offset,
 403         size_t          count,
 404         int             ioflag,
 405         xfs_bmbt_irec_t *imap,
 406         int             nimaps,
 407         int             *prealloc)
 408 {
 409         xfs_fileoff_t   start_fsb;
 410         xfs_filblks_t   count_fsb;
 411         xfs_fsblock_t   firstblock;
 412         int             n, error, imaps;
 413
 414         *prealloc = 0;
 415         if ((offset + count) <= ip->i_size)
 416                 return 0;
 417
 418         /*
 419          * If there are any real blocks past eof, then don't
 420          * do any speculative allocation.
 421          */
 422         start_fsb = XFS_B_TO_FSBT(mp, ((xfs_ufsize_t)(offset + count - 1)));
 423         count_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_MAXIOFFSET(mp));
 424         while (count_fsb > 0) {
 425                 imaps = nimaps;
 426                 firstblock = NULLFSBLOCK;
 427                 error = xfs_bmapi(NULL, ip, start_fsb, count_fsb, 0,
 428                                   &firstblock, 0, imap, &imaps, NULL, NULL);
 429                 if (error)
 430                         return error;
 431                 for (n = 0; n < imaps; n++) {
 432                         if ((imap[n].br_startblock != HOLESTARTBLOCK) &&
 433                             (imap[n].br_startblock != DELAYSTARTBLOCK))
 434                                 return 0;
 435                         start_fsb += imap[n].br_blockcount;
 436                         count_fsb -= imap[n].br_blockcount;
 437                 }
 438         }
 439         *prealloc = 1;
 440         return 0;
 441 }
 442
 443 STATIC int
 444 xfs_iomap_write_delay(
 445         xfs_inode_t     *ip,
 446         xfs_off_t       offset,
 447         size_t          count,
 448         int             ioflag,
 449         xfs_bmbt_irec_t *ret_imap,
 450         int             *nmaps)
 451 {
 452         xfs_mount_t     *mp = ip->i_mount;
 453         xfs_fileoff_t   offset_fsb;
 454         xfs_fileoff_t   last_fsb;
 455         xfs_off_t       aligned_offset;
 456         xfs_fileoff_t   ioalign;
 457         xfs_fsblock_t   firstblock;
 458         xfs_extlen_t    extsz;
 459         int             nimaps;
 460         xfs_bmbt_irec_t imap[XFS_WRITE_IMAPS];
 461         int             prealloc, flushed = 0;
 462         int             error;
 463
 464         ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
 465
 466         /*
 467          * Make sure that the dquots are there. This doesn't hold
 468          * the ilock across a disk read.
 469          */
 470         error = xfs_qm_dqattach_locked(ip, 0);
 471         if (error)
 472                 return XFS_ERROR(error);
 473
 474         extsz = xfs_get_extsz_hint(ip);
 475         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 476
 477         error = xfs_iomap_eof_want_preallocate(mp, ip, offset, count,
 478                                 ioflag, imap, XFS_WRITE_IMAPS, &prealloc);
 479         if (error)
 480                 return error;
 481
 482 retry:
 483         if (prealloc) {
 484                 aligned_offset = XFS_WRITEIO_ALIGN(mp, (offset + count - 1));
 485                 ioalign = XFS_B_TO_FSBT(mp, aligned_offset);
 486                 last_fsb = ioalign + mp->m_writeio_blocks;
 487         } else {
 488                 last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));
 489         }
 490
 491         if (prealloc || extsz) {
 492                 error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
 493                 if (error)
 494                         return error;
 495         }
 496
 497         nimaps = XFS_WRITE_IMAPS;
 498         firstblock = NULLFSBLOCK;
 499         error = xfs_bmapi(NULL, ip, offset_fsb,
 500                           (xfs_filblks_t)(last_fsb - offset_fsb),
 501                           XFS_BMAPI_DELAY | XFS_BMAPI_WRITE |
 502                           XFS_BMAPI_ENTIRE, &firstblock, 1, imap,
 503                           &nimaps, NULL, NULL);
 504         if (error && (error != ENOSPC))
 505                 return XFS_ERROR(error);
 506
 507         /*
 508          * If bmapi returned us nothing, and if we didn't get back EDQUOT,
 509          * then we must have run out of space - flush all other inodes with
 510          * delalloc blocks and retry without EOF preallocation.
 511          */
 512         if (nimaps == 0) {
 513                 trace_xfs_delalloc_enospc(ip, offset, count);
 514                 if (flushed)
 515                         return XFS_ERROR(ENOSPC);
 516
 517                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 518                 xfs_flush_inodes(ip);
 519                 xfs_ilock(ip, XFS_ILOCK_EXCL);
 520
 521                 flushed = 1;
 522                 error = 0;
 523                 prealloc = 0;
 524                 goto retry;
 525         }
 526
 527         if (!(imap[0].br_startblock || XFS_IS_REALTIME_INODE(ip)))
 528                 return xfs_cmn_err_fsblock_zero(ip, &imap[0]);
 529
 530         *ret_imap = imap[0];
 531         *nmaps = 1;
 532
 533         return 0;
 534 }
 535
 536 /*
 537  * Pass in a delayed allocate extent, convert it to real extents;
 538  * return to the caller the extent we create which maps on top of
 539  * the originating callers request.
 540  *
 541  * Called without a lock on the inode.
 542  *
 543  * We no longer bother to look at the incoming map - all we have to
 544  * guarantee is that whatever we allocate fills the required range.
 545  */
 546 STATIC int
 547 xfs_iomap_write_allocate(
 548         xfs_inode_t     *ip,
 549         xfs_off_t       offset,
 550         size_t          count,
 551         xfs_bmbt_irec_t *map,
 552         int             *retmap)
 553 {
 554         xfs_mount_t     *mp = ip->i_mount;
 555         xfs_fileoff_t   offset_fsb, last_block;
 556         xfs_fileoff_t   end_fsb, map_start_fsb;
 557         xfs_fsblock_t   first_block;
 558         xfs_bmap_free_t free_list;
 559         xfs_filblks_t   count_fsb;
 560         xfs_bmbt_irec_t imap;
 561         xfs_trans_t     *tp;
 562         int             nimaps, committed;
 563         int             error = 0;
 564         int             nres;
 565
 566         *retmap = 0;
 567
 568         /*
 569          * Make sure that the dquots are there.
 570          */
 571         error = xfs_qm_dqattach(ip, 0);
 572         if (error)
 573                 return XFS_ERROR(error);
 574
 575         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 576         count_fsb = map->br_blockcount;
 577         map_start_fsb = map->br_startoff;
 578
 579         XFS_STATS_ADD(xs_xstrat_bytes, XFS_FSB_TO_B(mp, count_fsb));
 580
 581         while (count_fsb != 0) {
 582                 /*
 583                  * Set up a transaction with which to allocate the
 584                  * backing store for the file.  Do allocations in a
 585                  * loop until we get some space in the range we are
 586                  * interested in.  The other space that might be allocated
 587                  * is in the delayed allocation extent on which we sit
 588                  * but before our buffer starts.
 589                  */
 590
 591                 nimaps = 0;
 592                 while (nimaps == 0) {
 593                         tp = xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE);
 594                         tp->t_flags |= XFS_TRANS_RESERVE;
 595                         nres = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
 596                         error = xfs_trans_reserve(tp, nres,
 597                                         XFS_WRITE_LOG_RES(mp),
 598                                         0, XFS_TRANS_PERM_LOG_RES,
 599                                         XFS_WRITE_LOG_COUNT);
 600                         if (error) {
 601                                 xfs_trans_cancel(tp, 0);
 602                                 return XFS_ERROR(error);
 603                         }
 604                         xfs_ilock(ip, XFS_ILOCK_EXCL);
 605                         xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
 606                         xfs_trans_ihold(tp, ip);
 607
 608                         xfs_bmap_init(&free_list, &first_block);
 609
 610                         /*
 611                          * it is possible that the extents have changed since
 612                          * we did the read call as we dropped the ilock for a
 613                          * while. We have to be careful about truncates or hole
 614                          * punchs here - we are not allowed to allocate
 615                          * non-delalloc blocks here.
 616                          *
 617                          * The only protection against truncation is the pages
 618                          * for the range we are being asked to convert are
 619                          * locked and hence a truncate will block on them
 620                          * first.
 621                          *
 622                          * As a result, if we go beyond the range we really
 623                          * need and hit an delalloc extent boundary followed by
 624                          * a hole while we have excess blocks in the map, we
 625                          * will fill the hole incorrectly and overrun the
 626                          * transaction reservation.
 627                          *
 628                          * Using a single map prevents this as we are forced to
 629                          * check each map we look for overlap with the desired
 630                          * range and abort as soon as we find it. Also, given
 631                          * that we only return a single map, having one beyond
 632                          * what we can return is probably a bit silly.
 633                          *
 634                          * We also need to check that we don't go beyond EOF;
 635                          * this is a truncate optimisation as a truncate sets
 636                          * the new file size before block on the pages we
 637                          * currently have locked under writeback. Because they
 638                          * are about to be tossed, we don't need to write them
 639                          * back....
 640                          */
 641                         nimaps = 1;
 642                         end_fsb = XFS_B_TO_FSB(mp, ip->i_size);
 643                         error = xfs_bmap_last_offset(NULL, ip, &last_block,
 644                                                         XFS_DATA_FORK);
 645                         if (error)
 646                                 goto trans_cancel;
 647
 648                         last_block = XFS_FILEOFF_MAX(last_block, end_fsb);
 649                         if ((map_start_fsb + count_fsb) > last_block) {
 650                                 count_fsb = last_block - map_start_fsb;
 651                                 if (count_fsb == 0) {
 652                                         error = EAGAIN;
 653                                         goto trans_cancel;
 654                                 }
 655                         }
 656
 657                         /* Go get the actual blocks */
 658                         error = xfs_bmapi(tp, ip, map_start_fsb, count_fsb,
 659                                         XFS_BMAPI_WRITE, &first_block, 1,
 660                                         &imap, &nimaps, &free_list, NULL);
 661                         if (error)
 662                                 goto trans_cancel;
 663
 664                         error = xfs_bmap_finish(&tp, &free_list, &committed);
 665                         if (error)
 666                                 goto trans_cancel;
 667
 668                         error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
 669                         if (error)
 670                                 goto error0;
 671
 672                         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 673                 }
 674
 675                 /*
 676                  * See if we were able to allocate an extent that
 677                  * covers at least part of the callers request
 678                  */
 679                 if (!(imap.br_startblock || XFS_IS_REALTIME_INODE(ip)))
 680                         return xfs_cmn_err_fsblock_zero(ip, &imap);
 681
 682                 if ((offset_fsb >= imap.br_startoff) &&
 683                     (offset_fsb < (imap.br_startoff +
 684                                    imap.br_blockcount))) {
 685                         *map = imap;
 686                         *retmap = 1;
 687                         XFS_STATS_INC(xs_xstrat_quick);
 688                         return 0;
 689                 }
 690
 691                 /*
 692                  * So far we have not mapped the requested part of the
 693                  * file, just surrounding data, try again.
 694                  */
 695                 count_fsb -= imap.br_blockcount;
 696                 map_start_fsb = imap.br_startoff + imap.br_blockcount;
 697         }
 698
 699 trans_cancel:
 700         xfs_bmap_cancel(&free_list);
 701         xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT);
 702 error0:
 703         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 704         return XFS_ERROR(error);
 705 }
 706
 707 int
 708 xfs_iomap_write_unwritten(
 709         xfs_inode_t     *ip,
 710         xfs_off_t       offset,
 711         size_t          count)
 712 {
 713         xfs_mount_t     *mp = ip->i_mount;
 714         xfs_fileoff_t   offset_fsb;
 715         xfs_filblks_t   count_fsb;
 716         xfs_filblks_t   numblks_fsb;
 717         xfs_fsblock_t   firstfsb;
 718         int             nimaps;
 719         xfs_trans_t     *tp;
 720         xfs_bmbt_irec_t imap;
 721         xfs_bmap_free_t free_list;
 722         uint            resblks;
 723         int             committed;
 724         int             error;
 725
 726         trace_xfs_unwritten_convert(ip, offset, count);
 727
 728         offset_fsb = XFS_B_TO_FSBT(mp, offset);
 729         count_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
 730         count_fsb = (xfs_filblks_t)(count_fsb - offset_fsb);
 731
 732         /*
 733          * Reserve enough blocks in this transaction for two complete extent
 734          * btree splits.  We may be converting the middle part of an unwritten
 735          * extent and in this case we will insert two new extents in the btree
 736          * each of which could cause a full split.
 737          *
 738          * This reservation amount will be used in the first call to
 739          * xfs_bmbt_split() to select an AG with enough space to satisfy the
 740          * rest of the operation.
 741          */
 742         resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
 743
 744         do {
 745                 /*
 746                  * set up a transaction to convert the range of extents
 747                  * from unwritten to real. Do allocations in a loop until
 748                  * we have covered the range passed in.
 749                  *
 750                  * Note that we open code the transaction allocation here
 751                  * to pass KM_NOFS--we can't risk to recursing back into
 752                  * the filesystem here as we might be asked to write out
 753                  * the same inode that we complete here and might deadlock
 754                  * on the iolock.
 755                  */
 756                 xfs_wait_for_freeze(mp, SB_FREEZE_TRANS);
 757                 tp = _xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE, KM_NOFS);
 758                 tp->t_flags |= XFS_TRANS_RESERVE;
 759                 error = xfs_trans_reserve(tp, resblks,
 760                                 XFS_WRITE_LOG_RES(mp), 0,
 761                                 XFS_TRANS_PERM_LOG_RES,
 762                                 XFS_WRITE_LOG_COUNT);
 763                 if (error) {
 764                         xfs_trans_cancel(tp, 0);
 765                         return XFS_ERROR(error);
 766                 }
 767
 768                 xfs_ilock(ip, XFS_ILOCK_EXCL);
 769                 xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
 770                 xfs_trans_ihold(tp, ip);
 771
 772                 /*
 773                  * Modify the unwritten extent state of the buffer.
 774                  */
 775                 xfs_bmap_init(&free_list, &firstfsb);
 776                 nimaps = 1;
 777                 error = xfs_bmapi(tp, ip, offset_fsb, count_fsb,
 778                                   XFS_BMAPI_WRITE|XFS_BMAPI_CONVERT, &firstfsb,
 779                                   1, &imap, &nimaps, &free_list, NULL);
 780                 if (error)
 781                         goto error_on_bmapi_transaction;
 782
 783                 error = xfs_bmap_finish(&(tp), &(free_list), &committed);
 784                 if (error)
 785                         goto error_on_bmapi_transaction;
 786
 787                 error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
 788                 xfs_iunlock(ip, XFS_ILOCK_EXCL);
 789                 if (error)
 790                         return XFS_ERROR(error);
 791
 792                 if (!(imap.br_startblock || XFS_IS_REALTIME_INODE(ip)))
 793                         return xfs_cmn_err_fsblock_zero(ip, &imap);
 794
 795                 if ((numblks_fsb = imap.br_blockcount) == 0) {
 796                         /*
 797                          * The numblks_fsb value should always get
 798                          * smaller, otherwise the loop is stuck.
 799                          */
 800                         ASSERT(imap.br_blockcount);
 801                         break;
 802                 }
 803                 offset_fsb += numblks_fsb;
 804                 count_fsb -= numblks_fsb;
 805         } while (count_fsb > 0);
 806
 807         return 0;
 808
 809 error_on_bmapi_transaction:
 810         xfs_bmap_cancel(&free_list);
 811         xfs_trans_cancel(tp, (XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT));
 812         xfs_iunlock(ip, XFS_ILOCK_EXCL);
 813         return XFS_ERROR(error);
 814 }