fs/xfs/xfs_symlink.c

   1 /*
   2  * Copyright (c) 2000-2006 Silicon Graphics, Inc.
   3  * Copyright (c) 2012-2013 Red Hat, Inc.
   4  * All rights reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it would be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write the Free Software Foundation,
  17  * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  18  */
  19 #include "xfs.h"
  20 #include "xfs_fs.h"
  21 #include "xfs_types.h"
  22 #include "xfs_bit.h"
  23 #include "xfs_log.h"
  24 #include "xfs_trans.h"
  25 #include "xfs_sb.h"
  26 #include "xfs_ag.h"
  27 #include "xfs_dir2.h"
  28 #include "xfs_mount.h"
  29 #include "xfs_da_btree.h"
  30 #include "xfs_bmap_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_itable.h"
  36 #include "xfs_ialloc.h"
  37 #include "xfs_alloc.h"
  38 #include "xfs_bmap.h"
  39 #include "xfs_error.h"
  40 #include "xfs_quota.h"
  41 #include "xfs_utils.h"
  42 #include "xfs_trans_space.h"
  43 #include "xfs_log_priv.h"
  44 #include "xfs_trace.h"
  45 #include "xfs_symlink.h"
  46 #include "xfs_cksum.h"
  47 #include "xfs_buf_item.h"
  48
  49
  50 /*
  51  * Each contiguous block has a header, so it is not just a simple pathlen
  52  * to FSB conversion.
  53  */
  54 int
  55 xfs_symlink_blocks(
  56         struct xfs_mount *mp,
  57         int             pathlen)
  58 {
  59         int buflen = XFS_SYMLINK_BUF_SPACE(mp, mp->m_sb.sb_blocksize);
  60
  61         return (pathlen + buflen - 1) / buflen;
  62 }
  63
  64 static int
  65 xfs_symlink_hdr_set(
  66         struct xfs_mount        *mp,
  67         xfs_ino_t               ino,
  68         uint32_t                offset,
  69         uint32_t                size,
  70         struct xfs_buf          *bp)
  71 {
  72         struct xfs_dsymlink_hdr *dsl = bp->b_addr;
  73
  74         if (!xfs_sb_version_hascrc(&mp->m_sb))
  75                 return 0;
  76
  77         dsl->sl_magic = cpu_to_be32(XFS_SYMLINK_MAGIC);
  78         dsl->sl_offset = cpu_to_be32(offset);
  79         dsl->sl_bytes = cpu_to_be32(size);
  80         uuid_copy(&dsl->sl_uuid, &mp->m_sb.sb_uuid);
  81         dsl->sl_owner = cpu_to_be64(ino);
  82         dsl->sl_blkno = cpu_to_be64(bp->b_bn);
  83         bp->b_ops = &xfs_symlink_buf_ops;
  84
  85         return sizeof(struct xfs_dsymlink_hdr);
  86 }
  87
  88 /*
  89  * Checking of the symlink header is split into two parts. the verifier does
  90  * CRC, location and bounds checking, the unpacking function checks the path
  91  * parameters and owner.
  92  */
  93 bool
  94 xfs_symlink_hdr_ok(
  95         struct xfs_mount        *mp,
  96         xfs_ino_t               ino,
  97         uint32_t                offset,
  98         uint32_t                size,
  99         struct xfs_buf          *bp)
 100 {
 101         struct xfs_dsymlink_hdr *dsl = bp->b_addr;
 102
 103         if (offset != be32_to_cpu(dsl->sl_offset))
 104                 return false;
 105         if (size != be32_to_cpu(dsl->sl_bytes))
 106                 return false;
 107         if (ino != be64_to_cpu(dsl->sl_owner))
 108                 return false;
 109
 110         /* ok */
 111         return true;
 112 }
 113
 114 static bool
 115 xfs_symlink_verify(
 116         struct xfs_buf          *bp)
 117 {
 118         struct xfs_mount        *mp = bp->b_target->bt_mount;
 119         struct xfs_dsymlink_hdr *dsl = bp->b_addr;
 120
 121         if (!xfs_sb_version_hascrc(&mp->m_sb))
 122                 return false;
 123         if (dsl->sl_magic != cpu_to_be32(XFS_SYMLINK_MAGIC))
 124                 return false;
 125         if (!uuid_equal(&dsl->sl_uuid, &mp->m_sb.sb_uuid))
 126                 return false;
 127         if (bp->b_bn != be64_to_cpu(dsl->sl_blkno))
 128                 return false;
 129         if (be32_to_cpu(dsl->sl_offset) +
 130                                 be32_to_cpu(dsl->sl_bytes) >= MAXPATHLEN)
 131                 return false;
 132         if (dsl->sl_owner == 0)
 133                 return false;
 134
 135         return true;
 136 }
 137
 138 static void
 139 xfs_symlink_read_verify(
 140         struct xfs_buf  *bp)
 141 {
 142         struct xfs_mount *mp = bp->b_target->bt_mount;
 143
 144         /* no verification of non-crc buffers */
 145         if (!xfs_sb_version_hascrc(&mp->m_sb))
 146                 return;
 147
 148         if (!xfs_verify_cksum(bp->b_addr, BBTOB(bp->b_length),
 149                                   offsetof(struct xfs_dsymlink_hdr, sl_crc)) ||
 150             !xfs_symlink_verify(bp)) {
 151                 XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
 152                 xfs_buf_ioerror(bp, EFSCORRUPTED);
 153         }
 154 }
 155
 156 static void
 157 xfs_symlink_write_verify(
 158         struct xfs_buf  *bp)
 159 {
 160         struct xfs_mount *mp = bp->b_target->bt_mount;
 161         struct xfs_buf_log_item *bip = bp->b_fspriv;
 162
 163         /* no verification of non-crc buffers */
 164         if (!xfs_sb_version_hascrc(&mp->m_sb))
 165                 return;
 166
 167         if (!xfs_symlink_verify(bp)) {
 168                 XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
 169                 xfs_buf_ioerror(bp, EFSCORRUPTED);
 170                 return;
 171         }
 172
 173         if (bip) {
 174                 struct xfs_dsymlink_hdr *dsl = bp->b_addr;
 175                 dsl->sl_lsn = cpu_to_be64(bip->bli_item.li_lsn);
 176         }
 177         xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length),
 178                          offsetof(struct xfs_dsymlink_hdr, sl_crc));
 179 }
 180
 181 const struct xfs_buf_ops xfs_symlink_buf_ops = {
 182         .verify_read = xfs_symlink_read_verify,
 183         .verify_write = xfs_symlink_write_verify,
 184 };
 185
 186 void
 187 xfs_symlink_local_to_remote(
 188         struct xfs_trans        *tp,
 189         struct xfs_buf          *bp,
 190         struct xfs_inode        *ip,
 191         struct xfs_ifork        *ifp)
 192 {
 193         struct xfs_mount        *mp = ip->i_mount;
 194         char                    *buf;
 195
 196         if (!xfs_sb_version_hascrc(&mp->m_sb)) {
 197                 bp->b_ops = NULL;
 198                 memcpy(bp->b_addr, ifp->if_u1.if_data, ifp->if_bytes);
 199                 return;
 200         }
 201
 202         /*
 203          * As this symlink fits in an inode literal area, it must also fit in
 204          * the smallest buffer the filesystem supports.
 205          */
 206         ASSERT(BBTOB(bp->b_length) >=
 207                         ifp->if_bytes + sizeof(struct xfs_dsymlink_hdr));
 208
 209         bp->b_ops = &xfs_symlink_buf_ops;
 210
 211         buf = bp->b_addr;
 212         buf += xfs_symlink_hdr_set(mp, ip->i_ino, 0, ifp->if_bytes, bp);
 213         memcpy(buf, ifp->if_u1.if_data, ifp->if_bytes);
 214 }
 215
 216 /* ----- Kernel only functions below ----- */
 217 STATIC int
 218 xfs_readlink_bmap(
 219         struct xfs_inode        *ip,
 220         char                    *link)
 221 {
 222         struct xfs_mount        *mp = ip->i_mount;
 223         struct xfs_bmbt_irec    mval[XFS_SYMLINK_MAPS];
 224         struct xfs_buf          *bp;
 225         xfs_daddr_t             d;
 226         char                    *cur_chunk;
 227         int                     pathlen = ip->i_d.di_size;
 228         int                     nmaps = XFS_SYMLINK_MAPS;
 229         int                     byte_cnt;
 230         int                     n;
 231         int                     error = 0;
 232         int                     fsblocks = 0;
 233         int                     offset;
 234
 235         fsblocks = xfs_symlink_blocks(mp, pathlen);
 236         error = xfs_bmapi_read(ip, 0, fsblocks, mval, &nmaps, 0);
 237         if (error)
 238                 goto out;
 239
 240         offset = 0;
 241         for (n = 0; n < nmaps; n++) {
 242                 d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
 243                 byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
 244
 245                 bp = xfs_buf_read(mp->m_ddev_targp, d, BTOBB(byte_cnt), 0,
 246                                   &xfs_symlink_buf_ops);
 247                 if (!bp)
 248                         return XFS_ERROR(ENOMEM);
 249                 error = bp->b_error;
 250                 if (error) {
 251                         xfs_buf_ioerror_alert(bp, __func__);
 252                         xfs_buf_relse(bp);
 253                         goto out;
 254                 }
 255                 byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
 256                 if (pathlen < byte_cnt)
 257                         byte_cnt = pathlen;
 258
 259                 cur_chunk = bp->b_addr;
 260                 if (xfs_sb_version_hascrc(&mp->m_sb)) {
 261                         if (!xfs_symlink_hdr_ok(mp, ip->i_ino, offset,
 262                                                         byte_cnt, bp)) {
 263                                 error = EFSCORRUPTED;
 264                                 xfs_alert(mp,
 265 "symlink header does not match required off/len/owner (0x%x/Ox%x,0x%llx)",
 266                                         offset, byte_cnt, ip->i_ino);
 267                                 xfs_buf_relse(bp);
 268                                 goto out;
 269
 270                         }
 271
 272                         cur_chunk += sizeof(struct xfs_dsymlink_hdr);
 273                 }
 274
 275                 memcpy(link + offset, bp->b_addr, byte_cnt);
 276
 277                 pathlen -= byte_cnt;
 278                 offset += byte_cnt;
 279
 280                 xfs_buf_relse(bp);
 281         }
 282         ASSERT(pathlen == 0);
 283
 284         link[ip->i_d.di_size] = '\0';
 285         error = 0;
 286
 287  out:
 288         return error;
 289 }
 290
 291 int
 292 xfs_readlink(
 293         struct xfs_inode *ip,
 294         char            *link)
 295 {
 296         struct xfs_mount *mp = ip->i_mount;
 297         xfs_fsize_t     pathlen;
 298         int             error = 0;
 299
 300         trace_xfs_readlink(ip);
 301
 302         if (XFS_FORCED_SHUTDOWN(mp))
 303                 return XFS_ERROR(EIO);
 304
 305         xfs_ilock(ip, XFS_ILOCK_SHARED);
 306
 307         pathlen = ip->i_d.di_size;
 308         if (!pathlen)
 309                 goto out;
 310
 311         if (pathlen < 0 || pathlen > MAXPATHLEN) {
 312                 xfs_alert(mp, "%s: inode (%llu) bad symlink length (%lld)",
 313                          __func__, (unsigned long long) ip->i_ino,
 314                          (long long) pathlen);
 315                 ASSERT(0);
 316                 error = XFS_ERROR(EFSCORRUPTED);
 317                 goto out;
 318         }
 319
 320
 321         if (ip->i_df.if_flags & XFS_IFINLINE) {
 322                 memcpy(link, ip->i_df.if_u1.if_data, pathlen);
 323                 link[pathlen] = '\0';
 324         } else {
 325                 error = xfs_readlink_bmap(ip, link);
 326         }
 327
 328  out:
 329         xfs_iunlock(ip, XFS_ILOCK_SHARED);
 330         return error;
 331 }
 332
 333 int
 334 xfs_symlink(
 335         struct xfs_inode        *dp,
 336         struct xfs_name         *link_name,
 337         const char              *target_path,
 338         umode_t                 mode,
 339         struct xfs_inode        **ipp)
 340 {
 341         struct xfs_mount        *mp = dp->i_mount;
 342         struct xfs_trans        *tp = NULL;
 343         struct xfs_inode        *ip = NULL;
 344         int                     error = 0;
 345         int                     pathlen;
 346         struct xfs_bmap_free    free_list;
 347         xfs_fsblock_t           first_block;
 348         bool                    unlock_dp_on_error = false;
 349         uint                    cancel_flags;
 350         int                     committed;
 351         xfs_fileoff_t           first_fsb;
 352         xfs_filblks_t           fs_blocks;
 353         int                     nmaps;
 354         struct xfs_bmbt_irec    mval[XFS_SYMLINK_MAPS];
 355         xfs_daddr_t             d;
 356         const char              *cur_chunk;
 357         int                     byte_cnt;
 358         int                     n;
 359         xfs_buf_t               *bp;
 360         prid_t                  prid;
 361         struct xfs_dquot        *udqp, *gdqp;
 362         uint                    resblks;
 363
 364         *ipp = NULL;
 365
 366         trace_xfs_symlink(dp, link_name);
 367
 368         if (XFS_FORCED_SHUTDOWN(mp))
 369                 return XFS_ERROR(EIO);
 370
 371         /*
 372          * Check component lengths of the target path name.
 373          */
 374         pathlen = strlen(target_path);
 375         if (pathlen >= MAXPATHLEN)      /* total string too long */
 376                 return XFS_ERROR(ENAMETOOLONG);
 377
 378         udqp = gdqp = NULL;
 379         if (dp->i_d.di_flags & XFS_DIFLAG_PROJINHERIT)
 380                 prid = xfs_get_projid(dp);
 381         else
 382                 prid = XFS_PROJID_DEFAULT;
 383
 384         /*
 385          * Make sure that we have allocated dquot(s) on disk.
 386          */
 387         error = xfs_qm_vop_dqalloc(dp, current_fsuid(), current_fsgid(), prid,
 388                         XFS_QMOPT_QUOTALL | XFS_QMOPT_INHERIT, &udqp, &gdqp);
 389         if (error)
 390                 goto std_return;
 391
 392         tp = xfs_trans_alloc(mp, XFS_TRANS_SYMLINK);
 393         cancel_flags = XFS_TRANS_RELEASE_LOG_RES;
 394         /*
 395          * The symlink will fit into the inode data fork?
 396          * There can't be any attributes so we get the whole variable part.
 397          */
 398         if (pathlen <= XFS_LITINO(mp, dp->i_d.di_version))
 399                 fs_blocks = 0;
 400         else
 401                 fs_blocks = xfs_symlink_blocks(mp, pathlen);
 402         resblks = XFS_SYMLINK_SPACE_RES(mp, link_name->len, fs_blocks);
 403         error = xfs_trans_reserve(tp, resblks, XFS_SYMLINK_LOG_RES(mp), 0,
 404                         XFS_TRANS_PERM_LOG_RES, XFS_SYMLINK_LOG_COUNT);
 405         if (error == ENOSPC && fs_blocks == 0) {
 406                 resblks = 0;
 407                 error = xfs_trans_reserve(tp, 0, XFS_SYMLINK_LOG_RES(mp), 0,
 408                                 XFS_TRANS_PERM_LOG_RES, XFS_SYMLINK_LOG_COUNT);
 409         }
 410         if (error) {
 411                 cancel_flags = 0;
 412                 goto error_return;
 413         }
 414
 415         xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
 416         unlock_dp_on_error = true;
 417
 418         /*
 419          * Check whether the directory allows new symlinks or not.
 420          */
 421         if (dp->i_d.di_flags & XFS_DIFLAG_NOSYMLINKS) {
 422                 error = XFS_ERROR(EPERM);
 423                 goto error_return;
 424         }
 425
 426         /*
 427          * Reserve disk quota : blocks and inode.
 428          */
 429         error = xfs_trans_reserve_quota(tp, mp, udqp, gdqp, resblks, 1, 0);
 430         if (error)
 431                 goto error_return;
 432
 433         /*
 434          * Check for ability to enter directory entry, if no space reserved.
 435          */
 436         error = xfs_dir_canenter(tp, dp, link_name, resblks);
 437         if (error)
 438                 goto error_return;
 439         /*
 440          * Initialize the bmap freelist prior to calling either
 441          * bmapi or the directory create code.
 442          */
 443         xfs_bmap_init(&free_list, &first_block);
 444
 445         /*
 446          * Allocate an inode for the symlink.
 447          */
 448         error = xfs_dir_ialloc(&tp, dp, S_IFLNK | (mode & ~S_IFMT), 1, 0,
 449                                prid, resblks > 0, &ip, NULL);
 450         if (error) {
 451                 if (error == ENOSPC)
 452                         goto error_return;
 453                 goto error1;
 454         }
 455
 456         /*
 457          * An error after we've joined dp to the transaction will result in the
 458          * transaction cancel unlocking dp so don't do it explicitly in the
 459          * error path.
 460          */
 461         xfs_trans_ijoin(tp, dp, XFS_ILOCK_EXCL);
 462         unlock_dp_on_error = false;
 463
 464         /*
 465          * Also attach the dquot(s) to it, if applicable.
 466          */
 467         xfs_qm_vop_create_dqattach(tp, ip, udqp, gdqp);
 468
 469         if (resblks)
 470                 resblks -= XFS_IALLOC_SPACE_RES(mp);
 471         /*
 472          * If the symlink will fit into the inode, write it inline.
 473          */
 474         if (pathlen <= XFS_IFORK_DSIZE(ip)) {
 475                 xfs_idata_realloc(ip, pathlen, XFS_DATA_FORK);
 476                 memcpy(ip->i_df.if_u1.if_data, target_path, pathlen);
 477                 ip->i_d.di_size = pathlen;
 478
 479                 /*
 480                  * The inode was initially created in extent format.
 481                  */
 482                 ip->i_df.if_flags &= ~(XFS_IFEXTENTS | XFS_IFBROOT);
 483                 ip->i_df.if_flags |= XFS_IFINLINE;
 484
 485                 ip->i_d.di_format = XFS_DINODE_FMT_LOCAL;
 486                 xfs_trans_log_inode(tp, ip, XFS_ILOG_DDATA | XFS_ILOG_CORE);
 487
 488         } else {
 489                 int     offset;
 490
 491                 first_fsb = 0;
 492                 nmaps = XFS_SYMLINK_MAPS;
 493
 494                 error = xfs_bmapi_write(tp, ip, first_fsb, fs_blocks,
 495                                   XFS_BMAPI_METADATA, &first_block, resblks,
 496                                   mval, &nmaps, &free_list);
 497                 if (error)
 498                         goto error2;
 499
 500                 if (resblks)
 501                         resblks -= fs_blocks;
 502                 ip->i_d.di_size = pathlen;
 503                 xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 504
 505                 cur_chunk = target_path;
 506                 offset = 0;
 507                 for (n = 0; n < nmaps; n++) {
 508                         char    *buf;
 509
 510                         d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
 511                         byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
 512                         bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
 513                                                BTOBB(byte_cnt), 0);
 514                         if (!bp) {
 515                                 error = ENOMEM;
 516                                 goto error2;
 517                         }
 518                         bp->b_ops = &xfs_symlink_buf_ops;
 519
 520                         byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
 521                         byte_cnt = min(byte_cnt, pathlen);
 522
 523                         buf = bp->b_addr;
 524                         buf += xfs_symlink_hdr_set(mp, ip->i_ino, offset,
 525                                                    byte_cnt, bp);
 526
 527                         memcpy(buf, cur_chunk, byte_cnt);
 528
 529                         cur_chunk += byte_cnt;
 530                         pathlen -= byte_cnt;
 531                         offset += byte_cnt;
 532
 533                         xfs_trans_log_buf(tp, bp, 0, (buf + byte_cnt - 1) -
 534                                                         (char *)bp->b_addr);
 535                 }
 536                 ASSERT(pathlen == 0);
 537         }
 538
 539         /*
 540          * Create the directory entry for the symlink.
 541          */
 542         error = xfs_dir_createname(tp, dp, link_name, ip->i_ino,
 543                                         &first_block, &free_list, resblks);
 544         if (error)
 545                 goto error2;
 546         xfs_trans_ichgtime(tp, dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
 547         xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
 548
 549         /*
 550          * If this is a synchronous mount, make sure that the
 551          * symlink transaction goes to disk before returning to
 552          * the user.
 553          */
 554         if (mp->m_flags & (XFS_MOUNT_WSYNC|XFS_MOUNT_DIRSYNC)) {
 555                 xfs_trans_set_sync(tp);
 556         }
 557
 558         error = xfs_bmap_finish(&tp, &free_list, &committed);
 559         if (error) {
 560                 goto error2;
 561         }
 562         error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
 563         xfs_qm_dqrele(udqp);
 564         xfs_qm_dqrele(gdqp);
 565
 566         *ipp = ip;
 567         return 0;
 568
 569  error2:
 570         IRELE(ip);
 571  error1:
 572         xfs_bmap_cancel(&free_list);
 573         cancel_flags |= XFS_TRANS_ABORT;
 574  error_return:
 575         xfs_trans_cancel(tp, cancel_flags);
 576         xfs_qm_dqrele(udqp);
 577         xfs_qm_dqrele(gdqp);
 578
 579         if (unlock_dp_on_error)
 580                 xfs_iunlock(dp, XFS_ILOCK_EXCL);
 581  std_return:
 582         return error;
 583 }
 584
 585 /*
 586  * Free a symlink that has blocks associated with it.
 587  */
 588 int
 589 xfs_inactive_symlink_rmt(
 590         xfs_inode_t     *ip,
 591         xfs_trans_t     **tpp)
 592 {
 593         xfs_buf_t       *bp;
 594         int             committed;
 595         int             done;
 596         int             error;
 597         xfs_fsblock_t   first_block;
 598         xfs_bmap_free_t free_list;
 599         int             i;
 600         xfs_mount_t     *mp;
 601         xfs_bmbt_irec_t mval[XFS_SYMLINK_MAPS];
 602         int             nmaps;
 603         xfs_trans_t     *ntp;
 604         int             size;
 605         xfs_trans_t     *tp;
 606
 607         tp = *tpp;
 608         mp = ip->i_mount;
 609         ASSERT(ip->i_d.di_size > XFS_IFORK_DSIZE(ip));
 610         /*
 611          * We're freeing a symlink that has some
 612          * blocks allocated to it.  Free the
 613          * blocks here.  We know that we've got
 614          * either 1 or 2 extents and that we can
 615          * free them all in one bunmapi call.
 616          */
 617         ASSERT(ip->i_d.di_nextents > 0 && ip->i_d.di_nextents <= 2);
 618
 619         /*
 620          * Lock the inode, fix the size, and join it to the transaction.
 621          * Hold it so in the normal path, we still have it locked for
 622          * the second transaction.  In the error paths we need it
 623          * held so the cancel won't rele it, see below.
 624          */
 625         size = (int)ip->i_d.di_size;
 626         ip->i_d.di_size = 0;
 627         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 628         /*
 629          * Find the block(s) so we can inval and unmap them.
 630          */
 631         done = 0;
 632         xfs_bmap_init(&free_list, &first_block);
 633         nmaps = ARRAY_SIZE(mval);
 634         error = xfs_bmapi_read(ip, 0, xfs_symlink_blocks(mp, size),
 635                                 mval, &nmaps, 0);
 636         if (error)
 637                 goto error0;
 638         /*
 639          * Invalidate the block(s). No validation is done.
 640          */
 641         for (i = 0; i < nmaps; i++) {
 642                 bp = xfs_trans_get_buf(tp, mp->m_ddev_targp,
 643                         XFS_FSB_TO_DADDR(mp, mval[i].br_startblock),
 644                         XFS_FSB_TO_BB(mp, mval[i].br_blockcount), 0);
 645                 if (!bp) {
 646                         error = ENOMEM;
 647                         goto error1;
 648                 }
 649                 xfs_trans_binval(tp, bp);
 650         }
 651         /*
 652          * Unmap the dead block(s) to the free_list.
 653          */
 654         if ((error = xfs_bunmapi(tp, ip, 0, size, XFS_BMAPI_METADATA, nmaps,
 655                         &first_block, &free_list, &done)))
 656                 goto error1;
 657         ASSERT(done);
 658         /*
 659          * Commit the first transaction.  This logs the EFI and the inode.
 660          */
 661         if ((error = xfs_bmap_finish(&tp, &free_list, &committed)))
 662                 goto error1;
 663         /*
 664          * The transaction must have been committed, since there were
 665          * actually extents freed by xfs_bunmapi.  See xfs_bmap_finish.
 666          * The new tp has the extent freeing and EFDs.
 667          */
 668         ASSERT(committed);
 669         /*
 670          * The first xact was committed, so add the inode to the new one.
 671          * Mark it dirty so it will be logged and moved forward in the log as
 672          * part of every commit.
 673          */
 674         xfs_trans_ijoin(tp, ip, 0);
 675         xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 676         /*
 677          * Get a new, empty transaction to return to our caller.
 678          */
 679         ntp = xfs_trans_dup(tp);
 680         /*
 681          * Commit the transaction containing extent freeing and EFDs.
 682          * If we get an error on the commit here or on the reserve below,
 683          * we need to unlock the inode since the new transaction doesn't
 684          * have the inode attached.
 685          */
 686         error = xfs_trans_commit(tp, 0);
 687         tp = ntp;
 688         if (error) {
 689                 ASSERT(XFS_FORCED_SHUTDOWN(mp));
 690                 goto error0;
 691         }
 692         /*
 693          * transaction commit worked ok so we can drop the extra ticket
 694          * reference that we gained in xfs_trans_dup()
 695          */
 696         xfs_log_ticket_put(tp->t_ticket);
 697
 698         /*
 699          * Remove the memory for extent descriptions (just bookkeeping).
 700          */
 701         if (ip->i_df.if_bytes)
 702                 xfs_idata_realloc(ip, -ip->i_df.if_bytes, XFS_DATA_FORK);
 703         ASSERT(ip->i_df.if_bytes == 0);
 704         /*
 705          * Put an itruncate log reservation in the new transaction
 706          * for our caller.
 707          */
 708         if ((error = xfs_trans_reserve(tp, 0, XFS_ITRUNCATE_LOG_RES(mp), 0,
 709                         XFS_TRANS_PERM_LOG_RES, XFS_ITRUNCATE_LOG_COUNT))) {
 710                 ASSERT(XFS_FORCED_SHUTDOWN(mp));
 711                 goto error0;
 712         }
 713
 714         xfs_trans_ijoin(tp, ip, 0);
 715         *tpp = tp;
 716         return 0;
 717
 718  error1:
 719         xfs_bmap_cancel(&free_list);
 720  error0:
 721         return error;
 722 }