libxfs/xfs_rmap_btree.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (c) 2014 Red Hat, Inc.
   4  * All Rights Reserved.
   5  */
   6 #include "libxfs_priv.h"
   7 #include "xfs_fs.h"
   8 #include "xfs_shared.h"
   9 #include "xfs_format.h"
  10 #include "xfs_log_format.h"
  11 #include "xfs_trans_resv.h"
  12 #include "xfs_sb.h"
  13 #include "xfs_mount.h"
  14 #include "xfs_trans.h"
  15 #include "xfs_alloc.h"
  16 #include "xfs_btree.h"
  17 #include "xfs_btree_staging.h"
  18 #include "xfs_rmap.h"
  19 #include "xfs_rmap_btree.h"
  20 #include "xfs_trace.h"
  21 #include "xfs_ag_resv.h"
  22
  23 /*
  24  * Reverse map btree.
  25  *
  26  * This is a per-ag tree used to track the owner(s) of a given extent. With
  27  * reflink it is possible for there to be multiple owners, which is a departure
  28  * from classic XFS. Owner records for data extents are inserted when the
  29  * extent is mapped and removed when an extent is unmapped.  Owner records for
  30  * all other block types (i.e. metadata) are inserted when an extent is
  31  * allocated and removed when an extent is freed. There can only be one owner
  32  * of a metadata extent, usually an inode or some other metadata structure like
  33  * an AG btree.
  34  *
  35  * The rmap btree is part of the free space management, so blocks for the tree
  36  * are sourced from the agfl. Hence we need transaction reservation support for
  37  * this tree so that the freelist is always large enough. This also impacts on
  38  * the minimum space we need to leave free in the AG.
  39  *
  40  * The tree is ordered by [ag block, owner, offset]. This is a large key size,
  41  * but it is the only way to enforce unique keys when a block can be owned by
  42  * multiple files at any offset. There's no need to order/search by extent
  43  * size for online updating/management of the tree. It is intended that most
  44  * reverse lookups will be to find the owner(s) of a particular block, or to
  45  * try to recover tree and file data from corrupt primary metadata.
  46  */
  47
  48 static struct xfs_btree_cur *
  49 xfs_rmapbt_dup_cursor(
  50         struct xfs_btree_cur    *cur)
  51 {
  52         return xfs_rmapbt_init_cursor(cur->bc_mp, cur->bc_tp,
  53                         cur->bc_ag.agbp, cur->bc_ag.agno);
  54 }
  55
  56 STATIC void
  57 xfs_rmapbt_set_root(
  58         struct xfs_btree_cur    *cur,
  59         union xfs_btree_ptr     *ptr,
  60         int                     inc)
  61 {
  62         struct xfs_buf          *agbp = cur->bc_ag.agbp;
  63         struct xfs_agf          *agf = agbp->b_addr;
  64         xfs_agnumber_t          seqno = be32_to_cpu(agf->agf_seqno);
  65         int                     btnum = cur->bc_btnum;
  66         struct xfs_perag        *pag = xfs_perag_get(cur->bc_mp, seqno);
  67
  68         ASSERT(ptr->s != 0);
  69
  70         agf->agf_roots[btnum] = ptr->s;
  71         be32_add_cpu(&agf->agf_levels[btnum], inc);
  72         pag->pagf_levels[btnum] += inc;
  73         xfs_perag_put(pag);
  74
  75         xfs_alloc_log_agf(cur->bc_tp, agbp, XFS_AGF_ROOTS | XFS_AGF_LEVELS);
  76 }
  77
  78 STATIC int
  79 xfs_rmapbt_alloc_block(
  80         struct xfs_btree_cur    *cur,
  81         union xfs_btree_ptr     *start,
  82         union xfs_btree_ptr     *new,
  83         int                     *stat)
  84 {
  85         struct xfs_buf          *agbp = cur->bc_ag.agbp;
  86         struct xfs_agf          *agf = agbp->b_addr;
  87         int                     error;
  88         xfs_agblock_t           bno;
  89
  90         /* Allocate the new block from the freelist. If we can't, give up.  */
  91         error = xfs_alloc_get_freelist(cur->bc_tp, cur->bc_ag.agbp,
  92                                        &bno, 1);
  93         if (error)
  94                 return error;
  95
  96         trace_xfs_rmapbt_alloc_block(cur->bc_mp, cur->bc_ag.agno,
  97                         bno, 1);
  98         if (bno == NULLAGBLOCK) {
  99                 *stat = 0;
 100                 return 0;
 101         }
 102
 103         xfs_extent_busy_reuse(cur->bc_mp, cur->bc_ag.agno, bno, 1,
 104                         false);
 105
 106         xfs_trans_agbtree_delta(cur->bc_tp, 1);
 107         new->s = cpu_to_be32(bno);
 108         be32_add_cpu(&agf->agf_rmap_blocks, 1);
 109         xfs_alloc_log_agf(cur->bc_tp, agbp, XFS_AGF_RMAP_BLOCKS);
 110
 111         xfs_ag_resv_rmapbt_alloc(cur->bc_mp, cur->bc_ag.agno);
 112
 113         *stat = 1;
 114         return 0;
 115 }
 116
 117 STATIC int
 118 xfs_rmapbt_free_block(
 119         struct xfs_btree_cur    *cur,
 120         struct xfs_buf          *bp)
 121 {
 122         struct xfs_buf          *agbp = cur->bc_ag.agbp;
 123         struct xfs_agf          *agf = agbp->b_addr;
 124         xfs_agblock_t           bno;
 125         int                     error;
 126
 127         bno = xfs_daddr_to_agbno(cur->bc_mp, XFS_BUF_ADDR(bp));
 128         trace_xfs_rmapbt_free_block(cur->bc_mp, cur->bc_ag.agno,
 129                         bno, 1);
 130         be32_add_cpu(&agf->agf_rmap_blocks, -1);
 131         xfs_alloc_log_agf(cur->bc_tp, agbp, XFS_AGF_RMAP_BLOCKS);
 132         error = xfs_alloc_put_freelist(cur->bc_tp, agbp, NULL, bno, 1);
 133         if (error)
 134                 return error;
 135
 136         xfs_extent_busy_insert(cur->bc_tp, be32_to_cpu(agf->agf_seqno), bno, 1,
 137                               XFS_EXTENT_BUSY_SKIP_DISCARD);
 138         xfs_trans_agbtree_delta(cur->bc_tp, -1);
 139
 140         xfs_ag_resv_rmapbt_free(cur->bc_mp, cur->bc_ag.agno);
 141
 142         return 0;
 143 }
 144
 145 STATIC int
 146 xfs_rmapbt_get_minrecs(
 147         struct xfs_btree_cur    *cur,
 148         int                     level)
 149 {
 150         return cur->bc_mp->m_rmap_mnr[level != 0];
 151 }
 152
 153 STATIC int
 154 xfs_rmapbt_get_maxrecs(
 155         struct xfs_btree_cur    *cur,
 156         int                     level)
 157 {
 158         return cur->bc_mp->m_rmap_mxr[level != 0];
 159 }
 160
 161 STATIC void
 162 xfs_rmapbt_init_key_from_rec(
 163         union xfs_btree_key     *key,
 164         union xfs_btree_rec     *rec)
 165 {
 166         key->rmap.rm_startblock = rec->rmap.rm_startblock;
 167         key->rmap.rm_owner = rec->rmap.rm_owner;
 168         key->rmap.rm_offset = rec->rmap.rm_offset;
 169 }
 170
 171 /*
 172  * The high key for a reverse mapping record can be computed by shifting
 173  * the startblock and offset to the highest value that would still map
 174  * to that record.  In practice this means that we add blockcount-1 to
 175  * the startblock for all records, and if the record is for a data/attr
 176  * fork mapping, we add blockcount-1 to the offset too.
 177  */
 178 STATIC void
 179 xfs_rmapbt_init_high_key_from_rec(
 180         union xfs_btree_key     *key,
 181         union xfs_btree_rec     *rec)
 182 {
 183         uint64_t                off;
 184         int                     adj;
 185
 186         adj = be32_to_cpu(rec->rmap.rm_blockcount) - 1;
 187
 188         key->rmap.rm_startblock = rec->rmap.rm_startblock;
 189         be32_add_cpu(&key->rmap.rm_startblock, adj);
 190         key->rmap.rm_owner = rec->rmap.rm_owner;
 191         key->rmap.rm_offset = rec->rmap.rm_offset;
 192         if (XFS_RMAP_NON_INODE_OWNER(be64_to_cpu(rec->rmap.rm_owner)) ||
 193             XFS_RMAP_IS_BMBT_BLOCK(be64_to_cpu(rec->rmap.rm_offset)))
 194                 return;
 195         off = be64_to_cpu(key->rmap.rm_offset);
 196         off = (XFS_RMAP_OFF(off) + adj) | (off & ~XFS_RMAP_OFF_MASK);
 197         key->rmap.rm_offset = cpu_to_be64(off);
 198 }
 199
 200 STATIC void
 201 xfs_rmapbt_init_rec_from_cur(
 202         struct xfs_btree_cur    *cur,
 203         union xfs_btree_rec     *rec)
 204 {
 205         rec->rmap.rm_startblock = cpu_to_be32(cur->bc_rec.r.rm_startblock);
 206         rec->rmap.rm_blockcount = cpu_to_be32(cur->bc_rec.r.rm_blockcount);
 207         rec->rmap.rm_owner = cpu_to_be64(cur->bc_rec.r.rm_owner);
 208         rec->rmap.rm_offset = cpu_to_be64(
 209                         xfs_rmap_irec_offset_pack(&cur->bc_rec.r));
 210 }
 211
 212 STATIC void
 213 xfs_rmapbt_init_ptr_from_cur(
 214         struct xfs_btree_cur    *cur,
 215         union xfs_btree_ptr     *ptr)
 216 {
 217         struct xfs_agf          *agf = cur->bc_ag.agbp->b_addr;
 218
 219         ASSERT(cur->bc_ag.agno == be32_to_cpu(agf->agf_seqno));
 220
 221         ptr->s = agf->agf_roots[cur->bc_btnum];
 222 }
 223
 224 STATIC int64_t
 225 xfs_rmapbt_key_diff(
 226         struct xfs_btree_cur    *cur,
 227         union xfs_btree_key     *key)
 228 {
 229         struct xfs_rmap_irec    *rec = &cur->bc_rec.r;
 230         struct xfs_rmap_key     *kp = &key->rmap;
 231         __u64                   x, y;
 232         int64_t                 d;
 233
 234         d = (int64_t)be32_to_cpu(kp->rm_startblock) - rec->rm_startblock;
 235         if (d)
 236                 return d;
 237
 238         x = be64_to_cpu(kp->rm_owner);
 239         y = rec->rm_owner;
 240         if (x > y)
 241                 return 1;
 242         else if (y > x)
 243                 return -1;
 244
 245         x = XFS_RMAP_OFF(be64_to_cpu(kp->rm_offset));
 246         y = rec->rm_offset;
 247         if (x > y)
 248                 return 1;
 249         else if (y > x)
 250                 return -1;
 251         return 0;
 252 }
 253
 254 STATIC int64_t
 255 xfs_rmapbt_diff_two_keys(
 256         struct xfs_btree_cur    *cur,
 257         union xfs_btree_key     *k1,
 258         union xfs_btree_key     *k2)
 259 {
 260         struct xfs_rmap_key     *kp1 = &k1->rmap;
 261         struct xfs_rmap_key     *kp2 = &k2->rmap;
 262         int64_t                 d;
 263         __u64                   x, y;
 264
 265         d = (int64_t)be32_to_cpu(kp1->rm_startblock) -
 266                        be32_to_cpu(kp2->rm_startblock);
 267         if (d)
 268                 return d;
 269
 270         x = be64_to_cpu(kp1->rm_owner);
 271         y = be64_to_cpu(kp2->rm_owner);
 272         if (x > y)
 273                 return 1;
 274         else if (y > x)
 275                 return -1;
 276
 277         x = XFS_RMAP_OFF(be64_to_cpu(kp1->rm_offset));
 278         y = XFS_RMAP_OFF(be64_to_cpu(kp2->rm_offset));
 279         if (x > y)
 280                 return 1;
 281         else if (y > x)
 282                 return -1;
 283         return 0;
 284 }
 285
 286 static xfs_failaddr_t
 287 xfs_rmapbt_verify(
 288         struct xfs_buf          *bp)
 289 {
 290         struct xfs_mount        *mp = bp->b_mount;
 291         struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);
 292         struct xfs_perag        *pag = bp->b_pag;
 293         xfs_failaddr_t          fa;
 294         unsigned int            level;
 295
 296         /*
 297          * magic number and level verification
 298          *
 299          * During growfs operations, we can't verify the exact level or owner as
 300          * the perag is not fully initialised and hence not attached to the
 301          * buffer.  In this case, check against the maximum tree depth.
 302          *
 303          * Similarly, during log recovery we will have a perag structure
 304          * attached, but the agf information will not yet have been initialised
 305          * from the on disk AGF. Again, we can only check against maximum limits
 306          * in this case.
 307          */
 308         if (!xfs_verify_magic(bp, block->bb_magic))
 309                 return __this_address;
 310
 311         if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
 312                 return __this_address;
 313         fa = xfs_btree_sblock_v5hdr_verify(bp);
 314         if (fa)
 315                 return fa;
 316
 317         level = be16_to_cpu(block->bb_level);
 318         if (pag && pag->pagf_init) {
 319                 if (level >= pag->pagf_levels[XFS_BTNUM_RMAPi])
 320                         return __this_address;
 321         } else if (level >= mp->m_rmap_maxlevels)
 322                 return __this_address;
 323
 324         return xfs_btree_sblock_verify(bp, mp->m_rmap_mxr[level != 0]);
 325 }
 326
 327 static void
 328 xfs_rmapbt_read_verify(
 329         struct xfs_buf  *bp)
 330 {
 331         xfs_failaddr_t  fa;
 332
 333         if (!xfs_btree_sblock_verify_crc(bp))
 334                 xfs_verifier_error(bp, -EFSBADCRC, __this_address);
 335         else {
 336                 fa = xfs_rmapbt_verify(bp);
 337                 if (fa)
 338                         xfs_verifier_error(bp, -EFSCORRUPTED, fa);
 339         }
 340
 341         if (bp->b_error)
 342                 trace_xfs_btree_corrupt(bp, _RET_IP_);
 343 }
 344
 345 static void
 346 xfs_rmapbt_write_verify(
 347         struct xfs_buf  *bp)
 348 {
 349         xfs_failaddr_t  fa;
 350
 351         fa = xfs_rmapbt_verify(bp);
 352         if (fa) {
 353                 trace_xfs_btree_corrupt(bp, _RET_IP_);
 354                 xfs_verifier_error(bp, -EFSCORRUPTED, fa);
 355                 return;
 356         }
 357         xfs_btree_sblock_calc_crc(bp);
 358
 359 }
 360
 361 const struct xfs_buf_ops xfs_rmapbt_buf_ops = {
 362         .name                   = "xfs_rmapbt",
 363         .magic                  = { 0, cpu_to_be32(XFS_RMAP_CRC_MAGIC) },
 364         .verify_read            = xfs_rmapbt_read_verify,
 365         .verify_write           = xfs_rmapbt_write_verify,
 366         .verify_struct          = xfs_rmapbt_verify,
 367 };
 368
 369 STATIC int
 370 xfs_rmapbt_keys_inorder(
 371         struct xfs_btree_cur    *cur,
 372         union xfs_btree_key     *k1,
 373         union xfs_btree_key     *k2)
 374 {
 375         uint32_t                x;
 376         uint32_t                y;
 377         uint64_t                a;
 378         uint64_t                b;
 379
 380         x = be32_to_cpu(k1->rmap.rm_startblock);
 381         y = be32_to_cpu(k2->rmap.rm_startblock);
 382         if (x < y)
 383                 return 1;
 384         else if (x > y)
 385                 return 0;
 386         a = be64_to_cpu(k1->rmap.rm_owner);
 387         b = be64_to_cpu(k2->rmap.rm_owner);
 388         if (a < b)
 389                 return 1;
 390         else if (a > b)
 391                 return 0;
 392         a = XFS_RMAP_OFF(be64_to_cpu(k1->rmap.rm_offset));
 393         b = XFS_RMAP_OFF(be64_to_cpu(k2->rmap.rm_offset));
 394         if (a <= b)
 395                 return 1;
 396         return 0;
 397 }
 398
 399 STATIC int
 400 xfs_rmapbt_recs_inorder(
 401         struct xfs_btree_cur    *cur,
 402         union xfs_btree_rec     *r1,
 403         union xfs_btree_rec     *r2)
 404 {
 405         uint32_t                x;
 406         uint32_t                y;
 407         uint64_t                a;
 408         uint64_t                b;
 409
 410         x = be32_to_cpu(r1->rmap.rm_startblock);
 411         y = be32_to_cpu(r2->rmap.rm_startblock);
 412         if (x < y)
 413                 return 1;
 414         else if (x > y)
 415                 return 0;
 416         a = be64_to_cpu(r1->rmap.rm_owner);
 417         b = be64_to_cpu(r2->rmap.rm_owner);
 418         if (a < b)
 419                 return 1;
 420         else if (a > b)
 421                 return 0;
 422         a = XFS_RMAP_OFF(be64_to_cpu(r1->rmap.rm_offset));
 423         b = XFS_RMAP_OFF(be64_to_cpu(r2->rmap.rm_offset));
 424         if (a <= b)
 425                 return 1;
 426         return 0;
 427 }
 428
 429 static const struct xfs_btree_ops xfs_rmapbt_ops = {
 430         .rec_len                = sizeof(struct xfs_rmap_rec),
 431         .key_len                = 2 * sizeof(struct xfs_rmap_key),
 432
 433         .dup_cursor             = xfs_rmapbt_dup_cursor,
 434         .set_root               = xfs_rmapbt_set_root,
 435         .alloc_block            = xfs_rmapbt_alloc_block,
 436         .free_block             = xfs_rmapbt_free_block,
 437         .get_minrecs            = xfs_rmapbt_get_minrecs,
 438         .get_maxrecs            = xfs_rmapbt_get_maxrecs,
 439         .init_key_from_rec      = xfs_rmapbt_init_key_from_rec,
 440         .init_high_key_from_rec = xfs_rmapbt_init_high_key_from_rec,
 441         .init_rec_from_cur      = xfs_rmapbt_init_rec_from_cur,
 442         .init_ptr_from_cur      = xfs_rmapbt_init_ptr_from_cur,
 443         .key_diff               = xfs_rmapbt_key_diff,
 444         .buf_ops                = &xfs_rmapbt_buf_ops,
 445         .diff_two_keys          = xfs_rmapbt_diff_two_keys,
 446         .keys_inorder           = xfs_rmapbt_keys_inorder,
 447         .recs_inorder           = xfs_rmapbt_recs_inorder,
 448 };
 449
 450 static struct xfs_btree_cur *
 451 xfs_rmapbt_init_common(
 452         struct xfs_mount        *mp,
 453         struct xfs_trans        *tp,
 454         xfs_agnumber_t          agno)
 455 {
 456         struct xfs_btree_cur    *cur;
 457
 458         cur = kmem_zone_zalloc(xfs_btree_cur_zone, KM_NOFS);
 459         cur->bc_tp = tp;
 460         cur->bc_mp = mp;
 461         /* Overlapping btree; 2 keys per pointer. */
 462         cur->bc_btnum = XFS_BTNUM_RMAP;
 463         cur->bc_flags = XFS_BTREE_CRC_BLOCKS | XFS_BTREE_OVERLAPPING;
 464         cur->bc_blocklog = mp->m_sb.sb_blocklog;
 465         cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_rmap_2);
 466         cur->bc_ag.agno = agno;
 467         cur->bc_ops = &xfs_rmapbt_ops;
 468
 469         return cur;
 470 }
 471
 472 /* Create a new reverse mapping btree cursor. */
 473 struct xfs_btree_cur *
 474 xfs_rmapbt_init_cursor(
 475         struct xfs_mount        *mp,
 476         struct xfs_trans        *tp,
 477         struct xfs_buf          *agbp,
 478         xfs_agnumber_t          agno)
 479 {
 480         struct xfs_agf          *agf = agbp->b_addr;
 481         struct xfs_btree_cur    *cur;
 482
 483         cur = xfs_rmapbt_init_common(mp, tp, agno);
 484         cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]);
 485         cur->bc_ag.agbp = agbp;
 486         return cur;
 487 }
 488
 489 /* Create a new reverse mapping btree cursor with a fake root for staging. */
 490 struct xfs_btree_cur *
 491 xfs_rmapbt_stage_cursor(
 492         struct xfs_mount        *mp,
 493         struct xbtree_afakeroot *afake,
 494         xfs_agnumber_t          agno)
 495 {
 496         struct xfs_btree_cur    *cur;
 497
 498         cur = xfs_rmapbt_init_common(mp, NULL, agno);
 499         xfs_btree_stage_afakeroot(cur, afake);
 500         return cur;
 501 }
 502
 503 /*
 504  * Install a new reverse mapping btree root.  Caller is responsible for
 505  * invalidating and freeing the old btree blocks.
 506  */
 507 void
 508 xfs_rmapbt_commit_staged_btree(
 509         struct xfs_btree_cur    *cur,
 510         struct xfs_trans        *tp,
 511         struct xfs_buf          *agbp)
 512 {
 513         struct xfs_agf          *agf = agbp->b_addr;
 514         struct xbtree_afakeroot *afake = cur->bc_ag.afake;
 515
 516         ASSERT(cur->bc_flags & XFS_BTREE_STAGING);
 517
 518         agf->agf_roots[cur->bc_btnum] = cpu_to_be32(afake->af_root);
 519         agf->agf_levels[cur->bc_btnum] = cpu_to_be32(afake->af_levels);
 520         agf->agf_rmap_blocks = cpu_to_be32(afake->af_blocks);
 521         xfs_alloc_log_agf(tp, agbp, XFS_AGF_ROOTS | XFS_AGF_LEVELS |
 522                                     XFS_AGF_RMAP_BLOCKS);
 523         xfs_btree_commit_afakeroot(cur, tp, agbp, &xfs_rmapbt_ops);
 524 }
 525
 526 /*
 527  * Calculate number of records in an rmap btree block.
 528  */
 529 int
 530 xfs_rmapbt_maxrecs(
 531         int                     blocklen,
 532         int                     leaf)
 533 {
 534         blocklen -= XFS_RMAP_BLOCK_LEN;
 535
 536         if (leaf)
 537                 return blocklen / sizeof(struct xfs_rmap_rec);
 538         return blocklen /
 539                 (2 * sizeof(struct xfs_rmap_key) + sizeof(xfs_rmap_ptr_t));
 540 }
 541
 542 /* Compute the maximum height of an rmap btree. */
 543 void
 544 xfs_rmapbt_compute_maxlevels(
 545         struct xfs_mount                *mp)
 546 {
 547         /*
 548          * On a non-reflink filesystem, the maximum number of rmap
 549          * records is the number of blocks in the AG, hence the max
 550          * rmapbt height is log_$maxrecs($agblocks).  However, with
 551          * reflink each AG block can have up to 2^32 (per the refcount
 552          * record format) owners, which means that theoretically we
 553          * could face up to 2^64 rmap records.
 554          *
 555          * That effectively means that the max rmapbt height must be
 556          * XFS_BTREE_MAXLEVELS.  "Fortunately" we'll run out of AG
 557          * blocks to feed the rmapbt long before the rmapbt reaches
 558          * maximum height.  The reflink code uses ag_resv_critical to
 559          * disallow reflinking when less than 10% of the per-AG metadata
 560          * block reservation since the fallback is a regular file copy.
 561          */
 562         if (xfs_sb_version_hasreflink(&mp->m_sb))
 563                 mp->m_rmap_maxlevels = XFS_BTREE_MAXLEVELS;
 564         else
 565                 mp->m_rmap_maxlevels = xfs_btree_compute_maxlevels(
 566                                 mp->m_rmap_mnr, mp->m_sb.sb_agblocks);
 567 }
 568
 569 /* Calculate the refcount btree size for some records. */
 570 xfs_extlen_t
 571 xfs_rmapbt_calc_size(
 572         struct xfs_mount        *mp,
 573         unsigned long long      len)
 574 {
 575         return xfs_btree_calc_size(mp->m_rmap_mnr, len);
 576 }
 577
 578 /*
 579  * Calculate the maximum refcount btree size.
 580  */
 581 xfs_extlen_t
 582 xfs_rmapbt_max_size(
 583         struct xfs_mount        *mp,
 584         xfs_agblock_t           agblocks)
 585 {
 586         /* Bail out if we're uninitialized, which can happen in mkfs. */
 587         if (mp->m_rmap_mxr[0] == 0)
 588                 return 0;
 589
 590         return xfs_rmapbt_calc_size(mp, agblocks);
 591 }
 592
 593 /*
 594  * Figure out how many blocks to reserve and how many are used by this btree.
 595  */
 596 int
 597 xfs_rmapbt_calc_reserves(
 598         struct xfs_mount        *mp,
 599         struct xfs_trans        *tp,
 600         xfs_agnumber_t          agno,
 601         xfs_extlen_t            *ask,
 602         xfs_extlen_t            *used)
 603 {
 604         struct xfs_buf          *agbp;
 605         struct xfs_agf          *agf;
 606         xfs_agblock_t           agblocks;
 607         xfs_extlen_t            tree_len;
 608         int                     error;
 609
 610         if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
 611                 return 0;
 612
 613         error = xfs_alloc_read_agf(mp, tp, agno, 0, &agbp);
 614         if (error)
 615                 return error;
 616
 617         agf = agbp->b_addr;
 618         agblocks = be32_to_cpu(agf->agf_length);
 619         tree_len = be32_to_cpu(agf->agf_rmap_blocks);
 620         xfs_trans_brelse(tp, agbp);
 621
 622         /*
 623          * The log is permanently allocated, so the space it occupies will
 624          * never be available for the kinds of things that would require btree
 625          * expansion.  We therefore can pretend the space isn't there.
 626          */
 627         if (mp->m_sb.sb_logstart &&
 628             XFS_FSB_TO_AGNO(mp, mp->m_sb.sb_logstart) == agno)
 629                 agblocks -= mp->m_sb.sb_logblocks;
 630
 631         /* Reserve 1% of the AG or enough for 1 block per record. */
 632         *ask += max(agblocks / 100, xfs_rmapbt_max_size(mp, agblocks));
 633         *used += tree_len;
 634
 635         return error;
 636 }