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