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_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_mount.h"
  28 #include "xfs_da_btree.h"
  29 #include "xfs_bmap_btree.h"
  30 #include "xfs_alloc_btree.h"
  31 #include "xfs_ialloc_btree.h"
  32 #include "xfs_alloc.h"
  33 #include "xfs_btree.h"
  34 #include "xfs_attr_sf.h"
  35 #include "xfs_attr_remote.h"
  36 #include "xfs_dinode.h"
  37 #include "xfs_inode.h"
  38 #include "xfs_inode_item.h"
  39 #include "xfs_bmap.h"
  40 #include "xfs_attr.h"
  41 #include "xfs_attr_leaf.h"
  42 #include "xfs_error.h"
  43 #include "xfs_trace.h"
  44 #include "xfs_buf_item.h"
  45 #include "xfs_cksum.h"
  46
  47 STATIC int
  48 xfs_attr_shortform_compare(const void *a, const void *b)
  49 {
  50         xfs_attr_sf_sort_t *sa, *sb;
  51
  52         sa = (xfs_attr_sf_sort_t *)a;
  53         sb = (xfs_attr_sf_sort_t *)b;
  54         if (sa->hash < sb->hash) {
  55                 return(-1);
  56         } else if (sa->hash > sb->hash) {
  57                 return(1);
  58         } else {
  59                 return(sa->entno - sb->entno);
  60         }
  61 }
  62
  63 #define XFS_ISRESET_CURSOR(cursor) \
  64         (!((cursor)->initted) && !((cursor)->hashval) && \
  65          !((cursor)->blkno) && !((cursor)->offset))
  66 /*
  67  * Copy out entries of shortform attribute lists for attr_list().
  68  * Shortform attribute lists are not stored in hashval sorted order.
  69  * If the output buffer is not large enough to hold them all, then we
  70  * we have to calculate each entries' hashvalue and sort them before
  71  * we can begin returning them to the user.
  72  */
  73 int
  74 xfs_attr_shortform_list(xfs_attr_list_context_t *context)
  75 {
  76         attrlist_cursor_kern_t *cursor;
  77         xfs_attr_sf_sort_t *sbuf, *sbp;
  78         xfs_attr_shortform_t *sf;
  79         xfs_attr_sf_entry_t *sfe;
  80         xfs_inode_t *dp;
  81         int sbsize, nsbuf, count, i;
  82         int error;
  83
  84         ASSERT(context != NULL);
  85         dp = context->dp;
  86         ASSERT(dp != NULL);
  87         ASSERT(dp->i_afp != NULL);
  88         sf = (xfs_attr_shortform_t *)dp->i_afp->if_u1.if_data;
  89         ASSERT(sf != NULL);
  90         if (!sf->hdr.count)
  91                 return(0);
  92         cursor = context->cursor;
  93         ASSERT(cursor != NULL);
  94
  95         trace_xfs_attr_list_sf(context);
  96
  97         /*
  98          * If the buffer is large enough and the cursor is at the start,
  99          * do not bother with sorting since we will return everything in
 100          * one buffer and another call using the cursor won't need to be
 101          * made.
 102          * Note the generous fudge factor of 16 overhead bytes per entry.
 103          * If bufsize is zero then put_listent must be a search function
 104          * and can just scan through what we have.
 105          */
 106         if (context->bufsize == 0 ||
 107             (XFS_ISRESET_CURSOR(cursor) &&
 108              (dp->i_afp->if_bytes + sf->hdr.count * 16) < context->bufsize)) {
 109                 for (i = 0, sfe = &sf->list[0]; i < sf->hdr.count; i++) {
 110                         error = context->put_listent(context,
 111                                            sfe->flags,
 112                                            sfe->nameval,
 113                                            (int)sfe->namelen,
 114                                            (int)sfe->valuelen,
 115                                            &sfe->nameval[sfe->namelen]);
 116
 117                         /*
 118                          * Either search callback finished early or
 119                          * didn't fit it all in the buffer after all.
 120                          */
 121                         if (context->seen_enough)
 122                                 break;
 123
 124                         if (error)
 125                                 return error;
 126                         sfe = XFS_ATTR_SF_NEXTENTRY(sfe);
 127                 }
 128                 trace_xfs_attr_list_sf_all(context);
 129                 return(0);
 130         }
 131
 132         /* do no more for a search callback */
 133         if (context->bufsize == 0)
 134                 return 0;
 135
 136         /*
 137          * It didn't all fit, so we have to sort everything on hashval.
 138          */
 139         sbsize = sf->hdr.count * sizeof(*sbuf);
 140         sbp = sbuf = kmem_alloc(sbsize, KM_SLEEP | KM_NOFS);
 141
 142         /*
 143          * Scan the attribute list for the rest of the entries, storing
 144          * the relevant info from only those that match into a buffer.
 145          */
 146         nsbuf = 0;
 147         for (i = 0, sfe = &sf->list[0]; i < sf->hdr.count; i++) {
 148                 if (unlikely(
 149                     ((char *)sfe < (char *)sf) ||
 150                     ((char *)sfe >= ((char *)sf + dp->i_afp->if_bytes)))) {
 151                         XFS_CORRUPTION_ERROR("xfs_attr_shortform_list",
 152                                              XFS_ERRLEVEL_LOW,
 153                                              context->dp->i_mount, sfe);
 154                         kmem_free(sbuf);
 155                         return XFS_ERROR(EFSCORRUPTED);
 156                 }
 157
 158                 sbp->entno = i;
 159                 sbp->hash = xfs_da_hashname(sfe->nameval, sfe->namelen);
 160                 sbp->name = sfe->nameval;
 161                 sbp->namelen = sfe->namelen;
 162                 /* These are bytes, and both on-disk, don't endian-flip */
 163                 sbp->valuelen = sfe->valuelen;
 164                 sbp->flags = sfe->flags;
 165                 sfe = XFS_ATTR_SF_NEXTENTRY(sfe);
 166                 sbp++;
 167                 nsbuf++;
 168         }
 169
 170         /*
 171          * Sort the entries on hash then entno.
 172          */
 173         xfs_sort(sbuf, nsbuf, sizeof(*sbuf), xfs_attr_shortform_compare);
 174
 175         /*
 176          * Re-find our place IN THE SORTED LIST.
 177          */
 178         count = 0;
 179         cursor->initted = 1;
 180         cursor->blkno = 0;
 181         for (sbp = sbuf, i = 0; i < nsbuf; i++, sbp++) {
 182                 if (sbp->hash == cursor->hashval) {
 183                         if (cursor->offset == count) {
 184                                 break;
 185                         }
 186                         count++;
 187                 } else if (sbp->hash > cursor->hashval) {
 188                         break;
 189                 }
 190         }
 191         if (i == nsbuf) {
 192                 kmem_free(sbuf);
 193                 return(0);
 194         }
 195
 196         /*
 197          * Loop putting entries into the user buffer.
 198          */
 199         for ( ; i < nsbuf; i++, sbp++) {
 200                 if (cursor->hashval != sbp->hash) {
 201                         cursor->hashval = sbp->hash;
 202                         cursor->offset = 0;
 203                 }
 204                 error = context->put_listent(context,
 205                                         sbp->flags,
 206                                         sbp->name,
 207                                         sbp->namelen,
 208                                         sbp->valuelen,
 209                                         &sbp->name[sbp->namelen]);
 210                 if (error)
 211                         return error;
 212                 if (context->seen_enough)
 213                         break;
 214                 cursor->offset++;
 215         }
 216
 217         kmem_free(sbuf);
 218         return(0);
 219 }
 220
 221 STATIC int
 222 xfs_attr_node_list(xfs_attr_list_context_t *context)
 223 {
 224         attrlist_cursor_kern_t *cursor;
 225         xfs_attr_leafblock_t *leaf;
 226         xfs_da_intnode_t *node;
 227         struct xfs_attr3_icleaf_hdr leafhdr;
 228         struct xfs_da3_icnode_hdr nodehdr;
 229         struct xfs_da_node_entry *btree;
 230         int error, i;
 231         struct xfs_buf *bp;
 232
 233         trace_xfs_attr_node_list(context);
 234
 235         cursor = context->cursor;
 236         cursor->initted = 1;
 237
 238         /*
 239          * Do all sorts of validation on the passed-in cursor structure.
 240          * If anything is amiss, ignore the cursor and look up the hashval
 241          * starting from the btree root.
 242          */
 243         bp = NULL;
 244         if (cursor->blkno > 0) {
 245                 error = xfs_da3_node_read(NULL, context->dp, cursor->blkno, -1,
 246                                               &bp, XFS_ATTR_FORK);
 247                 if ((error != 0) && (error != EFSCORRUPTED))
 248                         return(error);
 249                 if (bp) {
 250                         struct xfs_attr_leaf_entry *entries;
 251
 252                         node = bp->b_addr;
 253                         switch (be16_to_cpu(node->hdr.info.magic)) {
 254                         case XFS_DA_NODE_MAGIC:
 255                         case XFS_DA3_NODE_MAGIC:
 256                                 trace_xfs_attr_list_wrong_blk(context);
 257                                 xfs_trans_brelse(NULL, bp);
 258                                 bp = NULL;
 259                                 break;
 260                         case XFS_ATTR_LEAF_MAGIC:
 261                         case XFS_ATTR3_LEAF_MAGIC:
 262                                 leaf = bp->b_addr;
 263                                 xfs_attr3_leaf_hdr_from_disk(&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, context->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 XFS_ERROR(EFSCORRUPTED);
 313                         }
 314
 315                         xfs_da3_node_hdr_from_disk(&nodehdr, node);
 316                         btree = xfs_da3_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(&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, context->dp, cursor->blkno, -1,
 353                                            &bp);
 354                 if (error)
 355                         return error;
 356         }
 357         xfs_trans_brelse(NULL, bp);
 358         return 0;
 359 }
 360
 361 /*
 362  * Copy out attribute list entries for attr_list(), for leaf attribute lists.
 363  */
 364 int
 365 xfs_attr3_leaf_list_int(
 366         struct xfs_buf                  *bp,
 367         struct xfs_attr_list_context    *context)
 368 {
 369         struct attrlist_cursor_kern     *cursor;
 370         struct xfs_attr_leafblock       *leaf;
 371         struct xfs_attr3_icleaf_hdr     ichdr;
 372         struct xfs_attr_leaf_entry      *entries;
 373         struct xfs_attr_leaf_entry      *entry;
 374         int                             retval;
 375         int                             i;
 376
 377         trace_xfs_attr_list_leaf(context);
 378
 379         leaf = bp->b_addr;
 380         xfs_attr3_leaf_hdr_from_disk(&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.dp = context->dp;
 450                                 args.whichfork = XFS_ATTR_FORK;
 451                                 args.valuelen = valuelen;
 452                                 args.value = kmem_alloc(valuelen, KM_SLEEP | KM_NOFS);
 453                                 args.rmtblkno = be32_to_cpu(name_rmt->valueblk);
 454                                 args.rmtblkcnt = xfs_attr3_rmt_blocks(
 455                                                         args.dp->i_mount, valuelen);
 456                                 retval = xfs_attr_rmtval_get(&args);
 457                                 if (retval)
 458                                         return retval;
 459                                 retval = context->put_listent(context,
 460                                                 entry->flags,
 461                                                 name_rmt->name,
 462                                                 (int)name_rmt->namelen,
 463                                                 valuelen,
 464                                                 args.value);
 465                                 kmem_free(args.value);
 466                         } else {
 467                                 retval = context->put_listent(context,
 468                                                 entry->flags,
 469                                                 name_rmt->name,
 470                                                 (int)name_rmt->namelen,
 471                                                 valuelen,
 472                                                 NULL);
 473                         }
 474                         if (retval)
 475                                 return retval;
 476                 }
 477                 if (context->seen_enough)
 478                         break;
 479                 cursor->offset++;
 480         }
 481         trace_xfs_attr_list_leaf_end(context);
 482         return retval;
 483 }
 484
 485 /*
 486  * Copy out attribute entries for attr_list(), for leaf attribute lists.
 487  */
 488 STATIC int
 489 xfs_attr_leaf_list(xfs_attr_list_context_t *context)
 490 {
 491         int error;
 492         struct xfs_buf *bp;
 493
 494         trace_xfs_attr_leaf_list(context);
 495
 496         context->cursor->blkno = 0;
 497         error = xfs_attr3_leaf_read(NULL, context->dp, 0, -1, &bp);
 498         if (error)
 499                 return XFS_ERROR(error);
 500
 501         error = xfs_attr3_leaf_list_int(bp, context);
 502         xfs_trans_brelse(NULL, bp);
 503         return XFS_ERROR(error);
 504 }
 505
 506 int
 507 xfs_attr_list_int(
 508         xfs_attr_list_context_t *context)
 509 {
 510         int error;
 511         xfs_inode_t *dp = context->dp;
 512
 513         XFS_STATS_INC(xs_attr_list);
 514
 515         if (XFS_FORCED_SHUTDOWN(dp->i_mount))
 516                 return EIO;
 517
 518         xfs_ilock(dp, XFS_ILOCK_SHARED);
 519
 520         /*
 521          * Decide on what work routines to call based on the inode size.
 522          */
 523         if (!xfs_inode_hasattr(dp)) {
 524                 error = 0;
 525         } else if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL) {
 526                 error = xfs_attr_shortform_list(context);
 527         } else if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
 528                 error = xfs_attr_leaf_list(context);
 529         } else {
 530                 error = xfs_attr_node_list(context);
 531         }
 532
 533         xfs_iunlock(dp, XFS_ILOCK_SHARED);
 534
 535         return error;
 536 }
 537
 538 #define ATTR_ENTBASESIZE                /* minimum bytes used by an attr */ \
 539         (((struct attrlist_ent *) 0)->a_name - (char *) 0)
 540 #define ATTR_ENTSIZE(namelen)           /* actual bytes used by an attr */ \
 541         ((ATTR_ENTBASESIZE + (namelen) + 1 + sizeof(u_int32_t)-1) \
 542          & ~(sizeof(u_int32_t)-1))
 543
 544 /*
 545  * Format an attribute and copy it out to the user's buffer.
 546  * Take care to check values and protect against them changing later,
 547  * we may be reading them directly out of a user buffer.
 548  */
 549 STATIC int
 550 xfs_attr_put_listent(
 551         xfs_attr_list_context_t *context,
 552         int             flags,
 553         unsigned char   *name,
 554         int             namelen,
 555         int             valuelen,
 556         unsigned char   *value)
 557 {
 558         struct attrlist *alist = (struct attrlist *)context->alist;
 559         attrlist_ent_t *aep;
 560         int arraytop;
 561
 562         ASSERT(!(context->flags & ATTR_KERNOVAL));
 563         ASSERT(context->count >= 0);
 564         ASSERT(context->count < (ATTR_MAX_VALUELEN/8));
 565         ASSERT(context->firstu >= sizeof(*alist));
 566         ASSERT(context->firstu <= context->bufsize);
 567
 568         /*
 569          * Only list entries in the right namespace.
 570          */
 571         if (((context->flags & ATTR_SECURE) == 0) !=
 572             ((flags & XFS_ATTR_SECURE) == 0))
 573                 return 0;
 574         if (((context->flags & ATTR_ROOT) == 0) !=
 575             ((flags & XFS_ATTR_ROOT) == 0))
 576                 return 0;
 577
 578         arraytop = sizeof(*alist) +
 579                         context->count * sizeof(alist->al_offset[0]);
 580         context->firstu -= ATTR_ENTSIZE(namelen);
 581         if (context->firstu < arraytop) {
 582                 trace_xfs_attr_list_full(context);
 583                 alist->al_more = 1;
 584                 context->seen_enough = 1;
 585                 return 1;
 586         }
 587
 588         aep = (attrlist_ent_t *)&context->alist[context->firstu];
 589         aep->a_valuelen = valuelen;
 590         memcpy(aep->a_name, name, namelen);
 591         aep->a_name[namelen] = 0;
 592         alist->al_offset[context->count++] = context->firstu;
 593         alist->al_count = context->count;
 594         trace_xfs_attr_list_add(context);
 595         return 0;
 596 }
 597
 598 /*
 599  * Generate a list of extended attribute names and optionally
 600  * also value lengths.  Positive return value follows the XFS
 601  * convention of being an error, zero or negative return code
 602  * is the length of the buffer returned (negated), indicating
 603  * success.
 604  */
 605 int
 606 xfs_attr_list(
 607         xfs_inode_t     *dp,
 608         char            *buffer,
 609         int             bufsize,
 610         int             flags,
 611         attrlist_cursor_kern_t *cursor)
 612 {
 613         xfs_attr_list_context_t context;
 614         struct attrlist *alist;
 615         int error;
 616
 617         /*
 618          * Validate the cursor.
 619          */
 620         if (cursor->pad1 || cursor->pad2)
 621                 return(XFS_ERROR(EINVAL));
 622         if ((cursor->initted == 0) &&
 623             (cursor->hashval || cursor->blkno || cursor->offset))
 624                 return XFS_ERROR(EINVAL);
 625
 626         /*
 627          * Check for a properly aligned buffer.
 628          */
 629         if (((long)buffer) & (sizeof(int)-1))
 630                 return XFS_ERROR(EFAULT);
 631         if (flags & ATTR_KERNOVAL)
 632                 bufsize = 0;
 633
 634         /*
 635          * Initialize the output buffer.
 636          */
 637         memset(&context, 0, sizeof(context));
 638         context.dp = dp;
 639         context.cursor = cursor;
 640         context.resynch = 1;
 641         context.flags = flags;
 642         context.alist = buffer;
 643         context.bufsize = (bufsize & ~(sizeof(int)-1));  /* align */
 644         context.firstu = context.bufsize;
 645         context.put_listent = xfs_attr_put_listent;
 646
 647         alist = (struct attrlist *)context.alist;
 648         alist->al_count = 0;
 649         alist->al_more = 0;
 650         alist->al_offset[0] = context.bufsize;
 651
 652         error = xfs_attr_list_int(&context);
 653         ASSERT(error >= 0);
 654         return error;
 655 }