kernel/fs/xfs/xfs_attr_list.c

   1 /*
   2  * Copyright (c) 2000-2005 Silicon Graphics, Inc.
   3  * Copyright (c) 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_format.h"
  22 #include "xfs_log_format.h"
  23 #include "xfs_trans_resv.h"
  24 #include "xfs_bit.h"
  25 #include "xfs_mount.h"
  26 #include "xfs_da_format.h"
  27 #include "xfs_da_btree.h"
  28 #include "xfs_inode.h"
  29 #include "xfs_trans.h"
  30 #include "xfs_inode_item.h"
  31 #include "xfs_bmap.h"
  32 #include "xfs_attr.h"
  33 #include "xfs_attr_sf.h"
  34 #include "xfs_attr_remote.h"
  35 #include "xfs_attr_leaf.h"
  36 #include "xfs_error.h"
  37 #include "xfs_trace.h"
  38 #include "xfs_buf_item.h"
  39 #include "xfs_cksum.h"
  40 #include "xfs_dir2.h"
  41
  42 STATIC int
  43 xfs_attr_shortform_compare(const void *a, const void *b)
  44 {
  45         xfs_attr_sf_sort_t *sa, *sb;
  46
  47         sa = (xfs_attr_sf_sort_t *)a;
  48         sb = (xfs_attr_sf_sort_t *)b;
  49         if (sa->hash < sb->hash) {
  50                 return -1;
  51         } else if (sa->hash > sb->hash) {
  52                 return 1;
  53         } else {
  54                 return sa->entno - sb->entno;
  55         }
  56 }
  57
  58 #define XFS_ISRESET_CURSOR(cursor) \
  59         (!((cursor)->initted) && !((cursor)->hashval) && \
  60          !((cursor)->blkno) && !((cursor)->offset))
  61 /*
  62  * Copy out entries of shortform attribute lists for attr_list().
  63  * Shortform attribute lists are not stored in hashval sorted order.
  64  * If the output buffer is not large enough to hold them all, then we
  65  * we have to calculate each entries' hashvalue and sort them before
  66  * we can begin returning them to the user.
  67  */
  68 int
  69 xfs_attr_shortform_list(xfs_attr_list_context_t *context)
  70 {
  71         attrlist_cursor_kern_t *cursor;
  72         xfs_attr_sf_sort_t *sbuf, *sbp;
  73         xfs_attr_shortform_t *sf;
  74         xfs_attr_sf_entry_t *sfe;
  75         xfs_inode_t *dp;
  76         int sbsize, nsbuf, count, i;
  77         int error;
  78
  79         ASSERT(context != NULL);
  80         dp = context->dp;
  81         ASSERT(dp != NULL);
  82         ASSERT(dp->i_afp != NULL);
  83         sf = (xfs_attr_shortform_t *)dp->i_afp->if_u1.if_data;
  84         ASSERT(sf != NULL);
  85         if (!sf->hdr.count)
  86                 return 0;
  87         cursor = context->cursor;
  88         ASSERT(cursor != NULL);
  89
  90         trace_xfs_attr_list_sf(context);
  91
  92         /*
  93          * If the buffer is large enough and the cursor is at the start,
  94          * do not bother with sorting since we will return everything in
  95          * one buffer and another call using the cursor won't need to be
  96          * made.
  97          * Note the generous fudge factor of 16 overhead bytes per entry.
  98          * If bufsize is zero then put_listent must be a search function
  99          * and can just scan through what we have.
 100          */
 101         if (context->bufsize == 0 ||
 102             (XFS_ISRESET_CURSOR(cursor) &&
 103              (dp->i_afp->if_bytes + sf->hdr.count * 16) < context->bufsize)) {
 104                 for (i = 0, sfe = &sf->list[0]; i < sf->hdr.count; i++) {
 105                         error = context->put_listent(context,
 106                                            sfe->flags,
 107                                            sfe->nameval,
 108                                            (int)sfe->namelen,
 109                                            (int)sfe->valuelen,
 110                                            &sfe->nameval[sfe->namelen]);
 111
 112                         /*
 113                          * Either search callback finished early or
 114                          * didn't fit it all in the buffer after all.
 115                          */
 116                         if (context->seen_enough)
 117                                 break;
 118
 119                         if (error)
 120                                 return error;
 121                         sfe = XFS_ATTR_SF_NEXTENTRY(sfe);
 122                 }
 123                 trace_xfs_attr_list_sf_all(context);
 124                 return 0;
 125         }
 126
 127         /* do no more for a search callback */
 128         if (context->bufsize == 0)
 129                 return 0;
 130
 131         /*
 132          * It didn't all fit, so we have to sort everything on hashval.
 133          */
 134         sbsize = sf->hdr.count * sizeof(*sbuf);
 135         sbp = sbuf = kmem_alloc(sbsize, KM_SLEEP | KM_NOFS);
 136
 137         /*
 138          * Scan the attribute list for the rest of the entries, storing
 139          * the relevant info from only those that match into a buffer.
 140          */
 141         nsbuf = 0;
 142         for (i = 0, sfe = &sf->list[0]; i < sf->hdr.count; i++) {
 143                 if (unlikely(
 144                     ((char *)sfe < (char *)sf) ||
 145                     ((char *)sfe >= ((char *)sf + dp->i_afp->if_bytes)))) {
 146                         XFS_CORRUPTION_ERROR("xfs_attr_shortform_list",
 147                                              XFS_ERRLEVEL_LOW,
 148                                              context->dp->i_mount, sfe);
 149                         kmem_free(sbuf);
 150                         return -EFSCORRUPTED;
 151                 }
 152
 153                 sbp->entno = i;
 154                 sbp->hash = xfs_da_hashname(sfe->nameval, sfe->namelen);
 155                 sbp->name = sfe->nameval;
 156                 sbp->namelen = sfe->namelen;
 157                 /* These are bytes, and both on-disk, don't endian-flip */
 158                 sbp->valuelen = sfe->valuelen;
 159                 sbp->flags = sfe->flags;
 160                 sfe = XFS_ATTR_SF_NEXTENTRY(sfe);
 161                 sbp++;
 162                 nsbuf++;
 163         }
 164
 165         /*
 166          * Sort the entries on hash then entno.
 167          */
 168         xfs_sort(sbuf, nsbuf, sizeof(*sbuf), xfs_attr_shortform_compare);
 169
 170         /*
 171          * Re-find our place IN THE SORTED LIST.
 172          */
 173         count = 0;
 174         cursor->initted = 1;
 175         cursor->blkno = 0;
 176         for (sbp = sbuf, i = 0; i < nsbuf; i++, sbp++) {
 177                 if (sbp->hash == cursor->hashval) {
 178                         if (cursor->offset == count) {
 179                                 break;
 180                         }
 181                         count++;
 182                 } else if (sbp->hash > cursor->hashval) {
 183                         break;
 184                 }
 185         }
 186         if (i == nsbuf) {
 187                 kmem_free(sbuf);
 188                 return 0;
 189         }
 190
 191         /*
 192          * Loop putting entries into the user buffer.
 193          */
 194         for ( ; i < nsbuf; i++, sbp++) {
 195                 if (cursor->hashval != sbp->hash) {
 196                         cursor->hashval = sbp->hash;
 197                         cursor->offset = 0;
 198                 }
 199                 error = context->put_listent(context,
 200                                         sbp->flags,
 201                                         sbp->name,
 202                                         sbp->namelen,
 203                                         sbp->valuelen,
 204                                         &sbp->name[sbp->namelen]);
 205                 if (error) {
 206                         kmem_free(sbuf);
 207                         return error;
 208                 }
 209                 if (context->seen_enough)
 210                         break;
 211                 cursor->offset++;
 212         }
 213
 214         kmem_free(sbuf);
 215         return 0;
 216 }
 217
 218 STATIC int
 219 xfs_attr_node_list(xfs_attr_list_context_t *context)
 220 {
 221         attrlist_cursor_kern_t *cursor;
 222         xfs_attr_leafblock_t *leaf;
 223         xfs_da_intnode_t *node;
 224         struct xfs_attr3_icleaf_hdr leafhdr;
 225         struct xfs_da3_icnode_hdr nodehdr;
 226         struct xfs_da_node_entry *btree;
 227         int error, i;
 228         struct xfs_buf *bp;
 229         struct xfs_inode        *dp = context->dp;
 230         struct xfs_mount        *mp = dp->i_mount;
 231
 232         trace_xfs_attr_node_list(context);
 233
 234         cursor = context->cursor;
 235         cursor->initted = 1;
 236
 237         /*
 238          * Do all sorts of validation on the passed-in cursor structure.
 239          * If anything is amiss, ignore the cursor and look up the hashval
 240          * starting from the btree root.
 241          */
 242         bp = NULL;
 243         if (cursor->blkno > 0) {
 244                 error = xfs_da3_node_read(NULL, dp, cursor->blkno, -1,
 245                                               &bp, XFS_ATTR_FORK);
 246                 if ((error != 0) && (error != -EFSCORRUPTED))
 247                         return error;
 248                 if (bp) {
 249                         struct xfs_attr_leaf_entry *entries;
 250
 251                         node = bp->b_addr;
 252                         switch (be16_to_cpu(node->hdr.info.magic)) {
 253                         case XFS_DA_NODE_MAGIC:
 254                         case XFS_DA3_NODE_MAGIC:
 255                                 trace_xfs_attr_list_wrong_blk(context);
 256                                 xfs_trans_brelse(NULL, bp);
 257                                 bp = NULL;
 258                                 break;
 259                         case XFS_ATTR_LEAF_MAGIC:
 260                         case XFS_ATTR3_LEAF_MAGIC:
 261                                 leaf = bp->b_addr;
 262                                 xfs_attr3_leaf_hdr_from_disk(mp->m_attr_geo,
 263                                                              &leafhdr, leaf);
 264                                 entries = xfs_attr3_leaf_entryp(leaf);
 265                                 if (cursor->hashval > be32_to_cpu(
 266                                                 entries[leafhdr.count - 1].hashval)) {
 267                                         trace_xfs_attr_list_wrong_blk(context);
 268                                         xfs_trans_brelse(NULL, bp);
 269                                         bp = NULL;
 270                                 } else if (cursor->hashval <= be32_to_cpu(
 271                                                 entries[0].hashval)) {
 272                                         trace_xfs_attr_list_wrong_blk(context);
 273                                         xfs_trans_brelse(NULL, bp);
 274                                         bp = NULL;
 275                                 }
 276                                 break;
 277                         default:
 278                                 trace_xfs_attr_list_wrong_blk(context);
 279                                 xfs_trans_brelse(NULL, bp);
 280                                 bp = NULL;
 281                         }
 282                 }
 283         }
 284
 285         /*
 286          * We did not find what we expected given the cursor's contents,
 287          * so we start from the top and work down based on the hash value.
 288          * Note that start of node block is same as start of leaf block.
 289          */
 290         if (bp == NULL) {
 291                 cursor->blkno = 0;
 292                 for (;;) {
 293                         __uint16_t magic;
 294
 295                         error = xfs_da3_node_read(NULL, dp,
 296                                                       cursor->blkno, -1, &bp,
 297                                                       XFS_ATTR_FORK);
 298                         if (error)
 299                                 return error;
 300                         node = bp->b_addr;
 301                         magic = be16_to_cpu(node->hdr.info.magic);
 302                         if (magic == XFS_ATTR_LEAF_MAGIC ||
 303                             magic == XFS_ATTR3_LEAF_MAGIC)
 304                                 break;
 305                         if (magic != XFS_DA_NODE_MAGIC &&
 306                             magic != XFS_DA3_NODE_MAGIC) {
 307                                 XFS_CORRUPTION_ERROR("xfs_attr_node_list(3)",
 308                                                      XFS_ERRLEVEL_LOW,
 309                                                      context->dp->i_mount,
 310                                                      node);
 311                                 xfs_trans_brelse(NULL, bp);
 312                                 return -EFSCORRUPTED;
 313                         }
 314
 315                         dp->d_ops->node_hdr_from_disk(&nodehdr, node);
 316                         btree = dp->d_ops->node_tree_p(node);
 317                         for (i = 0; i < nodehdr.count; btree++, i++) {
 318                                 if (cursor->hashval
 319                                                 <= be32_to_cpu(btree->hashval)) {
 320                                         cursor->blkno = be32_to_cpu(btree->before);
 321                                         trace_xfs_attr_list_node_descend(context,
 322                                                                          btree);
 323                                         break;
 324                                 }
 325                         }
 326                         if (i == nodehdr.count) {
 327                                 xfs_trans_brelse(NULL, bp);
 328                                 return 0;
 329                         }
 330                         xfs_trans_brelse(NULL, bp);
 331                 }
 332         }
 333         ASSERT(bp != NULL);
 334
 335         /*
 336          * Roll upward through the blocks, processing each leaf block in
 337          * order.  As long as there is space in the result buffer, keep
 338          * adding the information.
 339          */
 340         for (;;) {
 341                 leaf = bp->b_addr;
 342                 error = xfs_attr3_leaf_list_int(bp, context);
 343                 if (error) {
 344                         xfs_trans_brelse(NULL, bp);
 345                         return error;
 346                 }
 347                 xfs_attr3_leaf_hdr_from_disk(mp->m_attr_geo, &leafhdr, leaf);
 348                 if (context->seen_enough || leafhdr.forw == 0)
 349                         break;
 350                 cursor->blkno = leafhdr.forw;
 351                 xfs_trans_brelse(NULL, bp);
 352                 error = xfs_attr3_leaf_read(NULL, dp, cursor->blkno, -1, &bp);
 353                 if (error)
 354                         return error;
 355         }
 356         xfs_trans_brelse(NULL, bp);
 357         return 0;
 358 }
 359
 360 /*
 361  * Copy out attribute list entries for attr_list(), for leaf attribute lists.
 362  */
 363 int
 364 xfs_attr3_leaf_list_int(
 365         struct xfs_buf                  *bp,
 366         struct xfs_attr_list_context    *context)
 367 {
 368         struct attrlist_cursor_kern     *cursor;
 369         struct xfs_attr_leafblock       *leaf;
 370         struct xfs_attr3_icleaf_hdr     ichdr;
 371         struct xfs_attr_leaf_entry      *entries;
 372         struct xfs_attr_leaf_entry      *entry;
 373         int                             retval;
 374         int                             i;
 375         struct xfs_mount                *mp = context->dp->i_mount;
 376
 377         trace_xfs_attr_list_leaf(context);
 378
 379         leaf = bp->b_addr;
 380         xfs_attr3_leaf_hdr_from_disk(mp->m_attr_geo, &ichdr, leaf);
 381         entries = xfs_attr3_leaf_entryp(leaf);
 382
 383         cursor = context->cursor;
 384         cursor->initted = 1;
 385
 386         /*
 387          * Re-find our place in the leaf block if this is a new syscall.
 388          */
 389         if (context->resynch) {
 390                 entry = &entries[0];
 391                 for (i = 0; i < ichdr.count; entry++, i++) {
 392                         if (be32_to_cpu(entry->hashval) == cursor->hashval) {
 393                                 if (cursor->offset == context->dupcnt) {
 394                                         context->dupcnt = 0;
 395                                         break;
 396                                 }
 397                                 context->dupcnt++;
 398                         } else if (be32_to_cpu(entry->hashval) >
 399                                         cursor->hashval) {
 400                                 context->dupcnt = 0;
 401                                 break;
 402                         }
 403                 }
 404                 if (i == ichdr.count) {
 405                         trace_xfs_attr_list_notfound(context);
 406                         return 0;
 407                 }
 408         } else {
 409                 entry = &entries[0];
 410                 i = 0;
 411         }
 412         context->resynch = 0;
 413
 414         /*
 415          * We have found our place, start copying out the new attributes.
 416          */
 417         retval = 0;
 418         for (; i < ichdr.count; entry++, i++) {
 419                 if (be32_to_cpu(entry->hashval) != cursor->hashval) {
 420                         cursor->hashval = be32_to_cpu(entry->hashval);
 421                         cursor->offset = 0;
 422                 }
 423
 424                 if (entry->flags & XFS_ATTR_INCOMPLETE)
 425                         continue;               /* skip incomplete entries */
 426
 427                 if (entry->flags & XFS_ATTR_LOCAL) {
 428                         xfs_attr_leaf_name_local_t *name_loc =
 429                                 xfs_attr3_leaf_name_local(leaf, i);
 430
 431                         retval = context->put_listent(context,
 432                                                 entry->flags,
 433                                                 name_loc->nameval,
 434                                                 (int)name_loc->namelen,
 435                                                 be16_to_cpu(name_loc->valuelen),
 436                                                 &name_loc->nameval[name_loc->namelen]);
 437                         if (retval)
 438                                 return retval;
 439                 } else {
 440                         xfs_attr_leaf_name_remote_t *name_rmt =
 441                                 xfs_attr3_leaf_name_remote(leaf, i);
 442
 443                         int valuelen = be32_to_cpu(name_rmt->valuelen);
 444
 445                         if (context->put_value) {
 446                                 xfs_da_args_t args;
 447
 448                                 memset((char *)&args, 0, sizeof(args));
 449                                 args.geo = context->dp->i_mount->m_attr_geo;
 450                                 args.dp = context->dp;
 451                                 args.whichfork = XFS_ATTR_FORK;
 452                                 args.valuelen = valuelen;
 453                                 args.rmtvaluelen = valuelen;
 454                                 args.value = kmem_alloc(valuelen, KM_SLEEP | KM_NOFS);
 455                                 args.rmtblkno = be32_to_cpu(name_rmt->valueblk);
 456                                 args.rmtblkcnt = xfs_attr3_rmt_blocks(
 457                                                         args.dp->i_mount, valuelen);
 458                                 retval = xfs_attr_rmtval_get(&args);
 459                                 if (!retval)
 460                                         retval = context->put_listent(context,
 461                                                         entry->flags,
 462                                                         name_rmt->name,
 463                                                         (int)name_rmt->namelen,
 464                                                         valuelen,
 465                                                         args.value);
 466                                 kmem_free(args.value);
 467                         } else {
 468                                 retval = context->put_listent(context,
 469                                                 entry->flags,
 470                                                 name_rmt->name,
 471                                                 (int)name_rmt->namelen,
 472                                                 valuelen,
 473                                                 NULL);
 474                         }
 475                         if (retval)
 476                                 return retval;
 477                 }
 478                 if (context->seen_enough)
 479                         break;
 480                 cursor->offset++;
 481         }
 482         trace_xfs_attr_list_leaf_end(context);
 483         return retval;
 484 }
 485
 486 /*
 487  * Copy out attribute entries for attr_list(), for leaf attribute lists.
 488  */
 489 STATIC int
 490 xfs_attr_leaf_list(xfs_attr_list_context_t *context)
 491 {
 492         int error;
 493         struct xfs_buf *bp;
 494
 495         trace_xfs_attr_leaf_list(context);
 496
 497         context->cursor->blkno = 0;
 498         error = xfs_attr3_leaf_read(NULL, context->dp, 0, -1, &bp);
 499         if (error)
 500                 return error;
 501
 502         error = xfs_attr3_leaf_list_int(bp, context);
 503         xfs_trans_brelse(NULL, bp);
 504         return error;
 505 }
 506
 507 int
 508 xfs_attr_list_int(
 509         xfs_attr_list_context_t *context)
 510 {
 511         int error;
 512         xfs_inode_t *dp = context->dp;
 513         uint            lock_mode;
 514
 515         XFS_STATS_INC(dp->i_mount, xs_attr_list);
 516
 517         if (XFS_FORCED_SHUTDOWN(dp->i_mount))
 518                 return -EIO;
 519
 520         /*
 521          * Decide on what work routines to call based on the inode size.
 522          */
 523         lock_mode = xfs_ilock_attr_map_shared(dp);
 524         if (!xfs_inode_hasattr(dp)) {
 525                 error = 0;
 526         } else if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL) {
 527                 error = xfs_attr_shortform_list(context);
 528         } else if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
 529                 error = xfs_attr_leaf_list(context);
 530         } else {
 531                 error = xfs_attr_node_list(context);
 532         }
 533         xfs_iunlock(dp, lock_mode);
 534         return error;
 535 }
 536
 537 #define ATTR_ENTBASESIZE                /* minimum bytes used by an attr */ \
 538         (((struct attrlist_ent *) 0)->a_name - (char *) 0)
 539 #define ATTR_ENTSIZE(namelen)           /* actual bytes used by an attr */ \
 540         ((ATTR_ENTBASESIZE + (namelen) + 1 + sizeof(u_int32_t)-1) \
 541          & ~(sizeof(u_int32_t)-1))
 542
 543 /*
 544  * Format an attribute and copy it out to the user's buffer.
 545  * Take care to check values and protect against them changing later,
 546  * we may be reading them directly out of a user buffer.
 547  */
 548 STATIC int
 549 xfs_attr_put_listent(
 550         xfs_attr_list_context_t *context,
 551         int             flags,
 552         unsigned char   *name,
 553         int             namelen,
 554         int             valuelen,
 555         unsigned char   *value)
 556 {
 557         struct attrlist *alist = (struct attrlist *)context->alist;
 558         attrlist_ent_t *aep;
 559         int arraytop;
 560
 561         ASSERT(!(context->flags & ATTR_KERNOVAL));
 562         ASSERT(context->count >= 0);
 563         ASSERT(context->count < (ATTR_MAX_VALUELEN/8));
 564         ASSERT(context->firstu >= sizeof(*alist));
 565         ASSERT(context->firstu <= context->bufsize);
 566
 567         /*
 568          * Only list entries in the right namespace.
 569          */
 570         if (((context->flags & ATTR_SECURE) == 0) !=
 571             ((flags & XFS_ATTR_SECURE) == 0))
 572                 return 0;
 573         if (((context->flags & ATTR_ROOT) == 0) !=
 574             ((flags & XFS_ATTR_ROOT) == 0))
 575                 return 0;
 576
 577         arraytop = sizeof(*alist) +
 578                         context->count * sizeof(alist->al_offset[0]);
 579         context->firstu -= ATTR_ENTSIZE(namelen);
 580         if (context->firstu < arraytop) {
 581                 trace_xfs_attr_list_full(context);
 582                 alist->al_more = 1;
 583                 context->seen_enough = 1;
 584                 return 1;
 585         }
 586
 587         aep = (attrlist_ent_t *)&context->alist[context->firstu];
 588         aep->a_valuelen = valuelen;
 589         memcpy(aep->a_name, name, namelen);
 590         aep->a_name[namelen] = 0;
 591         alist->al_offset[context->count++] = context->firstu;
 592         alist->al_count = context->count;
 593         trace_xfs_attr_list_add(context);
 594         return 0;
 595 }
 596
 597 /*
 598  * Generate a list of extended attribute names and optionally
 599  * also value lengths.  Positive return value follows the XFS
 600  * convention of being an error, zero or negative return code
 601  * is the length of the buffer returned (negated), indicating
 602  * success.
 603  */
 604 int
 605 xfs_attr_list(
 606         xfs_inode_t     *dp,
 607         char            *buffer,
 608         int             bufsize,
 609         int             flags,
 610         attrlist_cursor_kern_t *cursor)
 611 {
 612         xfs_attr_list_context_t context;
 613         struct attrlist *alist;
 614         int error;
 615
 616         /*
 617          * Validate the cursor.
 618          */
 619         if (cursor->pad1 || cursor->pad2)
 620                 return -EINVAL;
 621         if ((cursor->initted == 0) &&
 622             (cursor->hashval || cursor->blkno || cursor->offset))
 623                 return -EINVAL;
 624
 625         /*
 626          * Check for a properly aligned buffer.
 627          */
 628         if (((long)buffer) & (sizeof(int)-1))
 629                 return -EFAULT;
 630         if (flags & ATTR_KERNOVAL)
 631                 bufsize = 0;
 632
 633         /*
 634          * Initialize the output buffer.
 635          */
 636         memset(&context, 0, sizeof(context));
 637         context.dp = dp;
 638         context.cursor = cursor;
 639         context.resynch = 1;
 640         context.flags = flags;
 641         context.alist = buffer;
 642         context.bufsize = (bufsize & ~(sizeof(int)-1));  /* align */
 643         context.firstu = context.bufsize;
 644         context.put_listent = xfs_attr_put_listent;
 645
 646         alist = (struct attrlist *)context.alist;
 647         alist->al_count = 0;
 648         alist->al_more = 0;
 649         alist->al_offset[0] = context.bufsize;
 650
 651         error = xfs_attr_list_int(&context);
 652         ASSERT(error <= 0);
 653         return error;
 654 }